Agile nanostructure architectures and smart combinations of
semiconducting metal oxide materials are key features of
high-performing dye-sensitized solar cells (DSSCs). Herein,
we synthesize mesoporous solid nanospheres of ZnO–TiO2
with type-II heterojunction and use these as an efficient photoanode material for excellent photoconversion. These polydisperse aggregates doped with 1%, 5%, and 10% of ZnO
exhibit improved solar cell performance with respect to pristine TiO2 under AM 1.5 G. The 1% ZnO doped TiO2 nanosphere possess high specific surface area (84.23 m2
g
@1
) as
a photoanode and shows high photoconversion efficiency of
about 8.07% with ca. 18% improvement in the photocurrent
density (Jsc) compare to TiO2 nanosphere. The improved
solar cell performance (Dh=40%) of ZnO decorated TiO2
nanospheres is ascribed to type-II heterojunction of ZnO–
TiO2
, that reduces the electron recombination and synergistically enhances the electron mobility and charge collection
capability
Optical studies of nano structured la-doped zn o prepared by combustion methodScience Padayatchi
Coral-shaped zinc oxide (ZnO) nanostructures were successfully synthesized via a combustion method using glycine as a fuel and zinc nitrate and lanthanum nitrate as precursors. Transmission electron microscopy showed the ZnO to have a coral shape with pore sizes of 10-50 nm and grain size of around 15 nm. X-ray diffraction analysis confirmed the hexagonal wurtzite crystal structure of both pure and lanthanum-doped ZnO. The lattice parameters increased with increasing lanthanum concentration, indicating incorporation of lanthanum ions into the ZnO lattice. Ultraviolet-visible spectroscopy showed the band gap increased and absorbance decreased in the near UV region with higher lanthanum doping
The document summarizes research on nano-structured lanthanum (La)-doped zinc oxide (ZnO) prepared using a combustion method. Coral-shaped ZnO nanostructures with pore sizes of 10-50 nm were successfully synthesized. Transmission electron microscopy showed the coral shape and porous nature increased with higher La doping concentrations. X-ray diffraction analysis confirmed the wurtzite structure was maintained with La doping. Optical studies showed absorbance decreased and band gap increased with higher La doping levels. Photoluminescence intensity also increased with La concentration. The research demonstrated La doping altered the structural and optical properties of ZnO nanostructures prepared via a facile combustion process.
The document summarizes research on nano-structured lanthanum (La)-doped zinc oxide (ZnO) prepared using a combustion method. Coral-shaped ZnO nanostructures with pore sizes of 10-50 nm were successfully synthesized. Transmission electron microscopy showed the coral shape and porous nature increased with higher La doping concentrations. X-ray diffraction analysis confirmed the wurtzite structure of pure and doped ZnO. Optical studies showed absorbance in the UV region decreased and band gap increased with higher La doping levels. Photoluminescence spectra exhibited La characteristic emission and a shift in emission with doping. The La-doped ZnO nanostructures showed potential for applications in chemical sensing,
Fabrication of zn o nanorod modified ITOViolet Flower
This document discusses the fabrication and characterization of zinc oxide (ZnO) nanorod arrays deposited on indium tin oxide (ITO) glass substrates via chemical bath deposition. Key points:
- ZnO nanorods were grown on ITO-coated glass by immersing the substrates in solutions containing zinc nitrate and hexamethylenetetramine at 80°C for varying times.
- Scanning electron microscopy images showed the diameter of the ZnO nanorods increased with higher solution concentration and longer growth time.
- X-ray diffraction analysis identified the crystal structure of the ZnO nanorods. Electrochemical measurements including cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the electron transfer properties of
IRJET - Comparative Study on the Structural and Optical Characterization of Z...IRJET Journal
This document reports on a comparative study of the structural and optical characterization of zinc sulfide (ZnS) and zinc oxide (ZnO) nanoparticles. ZnS nanoparticles were prepared via chemical precipitation using zinc chloride, sodium sulfide, and mercaptoethanol as a capping agent. ZnO nanoparticles were prepared using zinc acetate, ammonia, and thiourea as a capping agent. X-ray diffraction and scanning electron microscopy were used to characterize particle size and structure. Absorption spectra showed a blue shift with decreasing particle size due to quantum confinement. Photoluminescence spectra were also studied. The results show ZnS particles were 2-7nm and ZnO particles were 50-60nm. Both
1) Tin oxide nanostructures were synthesized via a hydrothermal process to optimize their morphology for use as photoanodes in dye-sensitized solar cells.
2) Samples synthesized at different temperatures resulted in different nanostructure morphologies. The sample synthesized at 200°C showed an optimal mixture of tin oxide nanoparticles and hollow nanospheres.
3) When used as a photoanode, the optimized tin oxide nanostructures synthesized at 200°C achieved the highest photovoltaic conversion efficiency of 7.5%, the highest reported for pristine tin oxide at the time.
Potentiostatic Deposition of ZnO Nanowires: Effect of Applied Potential and Z...IJRES Journal
In this work we report on potentiostatic deposition of Zinc oxide (ZnO) nanowires on fluorine-doped tin oxide (FTO) covered glass substrates from electroreduction of molecular oxygen. The influence of applied deposition potential, and the concentrations of zinc precursor (ZnCl2) on the properties of ZnO nanowires was investigated.SEM results revealed that ZnO nanowires electrodeposited at applied potential -0.85Vhave high density and good alignment. The diameters and densities of the electrodeposited ZnO nanowires are strongly dependent on the zinc ion concentrations and well aligned nanowires with uniform diameter can be obtained when the concentration of zinc ions is between 0.5 mM and 1 mM.
Optical studies of nano structured la-doped zn o prepared by combustion methodsunilove
This document summarizes research on the optical properties of lanthanum-doped zinc oxide (ZnO) nanostructures prepared using a combustion synthesis method. Coral-shaped ZnO nanostructures with an average grain size of 15 nm were successfully synthesized. Transmission electron microscopy images showed the nanostructures were porous with pore sizes of 10-50 nm. X-ray diffraction analysis confirmed the wurtzite crystal structure of both pure and lanthanum-doped ZnO. The addition of lanthanum altered the structural and optical properties of ZnO. Ultraviolet-visible spectroscopy showed the band gap of ZnO increased with higher lanthanum concentration. Photoluminescence spectra exhibited increased violet emission intensity correlated
Optical studies of nano structured la-doped zn o prepared by combustion methodScience Padayatchi
Coral-shaped zinc oxide (ZnO) nanostructures were successfully synthesized via a combustion method using glycine as a fuel and zinc nitrate and lanthanum nitrate as precursors. Transmission electron microscopy showed the ZnO to have a coral shape with pore sizes of 10-50 nm and grain size of around 15 nm. X-ray diffraction analysis confirmed the hexagonal wurtzite crystal structure of both pure and lanthanum-doped ZnO. The lattice parameters increased with increasing lanthanum concentration, indicating incorporation of lanthanum ions into the ZnO lattice. Ultraviolet-visible spectroscopy showed the band gap increased and absorbance decreased in the near UV region with higher lanthanum doping
The document summarizes research on nano-structured lanthanum (La)-doped zinc oxide (ZnO) prepared using a combustion method. Coral-shaped ZnO nanostructures with pore sizes of 10-50 nm were successfully synthesized. Transmission electron microscopy showed the coral shape and porous nature increased with higher La doping concentrations. X-ray diffraction analysis confirmed the wurtzite structure was maintained with La doping. Optical studies showed absorbance decreased and band gap increased with higher La doping levels. Photoluminescence intensity also increased with La concentration. The research demonstrated La doping altered the structural and optical properties of ZnO nanostructures prepared via a facile combustion process.
The document summarizes research on nano-structured lanthanum (La)-doped zinc oxide (ZnO) prepared using a combustion method. Coral-shaped ZnO nanostructures with pore sizes of 10-50 nm were successfully synthesized. Transmission electron microscopy showed the coral shape and porous nature increased with higher La doping concentrations. X-ray diffraction analysis confirmed the wurtzite structure of pure and doped ZnO. Optical studies showed absorbance in the UV region decreased and band gap increased with higher La doping levels. Photoluminescence spectra exhibited La characteristic emission and a shift in emission with doping. The La-doped ZnO nanostructures showed potential for applications in chemical sensing,
Fabrication of zn o nanorod modified ITOViolet Flower
This document discusses the fabrication and characterization of zinc oxide (ZnO) nanorod arrays deposited on indium tin oxide (ITO) glass substrates via chemical bath deposition. Key points:
- ZnO nanorods were grown on ITO-coated glass by immersing the substrates in solutions containing zinc nitrate and hexamethylenetetramine at 80°C for varying times.
- Scanning electron microscopy images showed the diameter of the ZnO nanorods increased with higher solution concentration and longer growth time.
- X-ray diffraction analysis identified the crystal structure of the ZnO nanorods. Electrochemical measurements including cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the electron transfer properties of
IRJET - Comparative Study on the Structural and Optical Characterization of Z...IRJET Journal
This document reports on a comparative study of the structural and optical characterization of zinc sulfide (ZnS) and zinc oxide (ZnO) nanoparticles. ZnS nanoparticles were prepared via chemical precipitation using zinc chloride, sodium sulfide, and mercaptoethanol as a capping agent. ZnO nanoparticles were prepared using zinc acetate, ammonia, and thiourea as a capping agent. X-ray diffraction and scanning electron microscopy were used to characterize particle size and structure. Absorption spectra showed a blue shift with decreasing particle size due to quantum confinement. Photoluminescence spectra were also studied. The results show ZnS particles were 2-7nm and ZnO particles were 50-60nm. Both
1) Tin oxide nanostructures were synthesized via a hydrothermal process to optimize their morphology for use as photoanodes in dye-sensitized solar cells.
2) Samples synthesized at different temperatures resulted in different nanostructure morphologies. The sample synthesized at 200°C showed an optimal mixture of tin oxide nanoparticles and hollow nanospheres.
3) When used as a photoanode, the optimized tin oxide nanostructures synthesized at 200°C achieved the highest photovoltaic conversion efficiency of 7.5%, the highest reported for pristine tin oxide at the time.
Potentiostatic Deposition of ZnO Nanowires: Effect of Applied Potential and Z...IJRES Journal
In this work we report on potentiostatic deposition of Zinc oxide (ZnO) nanowires on fluorine-doped tin oxide (FTO) covered glass substrates from electroreduction of molecular oxygen. The influence of applied deposition potential, and the concentrations of zinc precursor (ZnCl2) on the properties of ZnO nanowires was investigated.SEM results revealed that ZnO nanowires electrodeposited at applied potential -0.85Vhave high density and good alignment. The diameters and densities of the electrodeposited ZnO nanowires are strongly dependent on the zinc ion concentrations and well aligned nanowires with uniform diameter can be obtained when the concentration of zinc ions is between 0.5 mM and 1 mM.
Optical studies of nano structured la-doped zn o prepared by combustion methodsunilove
This document summarizes research on the optical properties of lanthanum-doped zinc oxide (ZnO) nanostructures prepared using a combustion synthesis method. Coral-shaped ZnO nanostructures with an average grain size of 15 nm were successfully synthesized. Transmission electron microscopy images showed the nanostructures were porous with pore sizes of 10-50 nm. X-ray diffraction analysis confirmed the wurtzite crystal structure of both pure and lanthanum-doped ZnO. The addition of lanthanum altered the structural and optical properties of ZnO. Ultraviolet-visible spectroscopy showed the band gap of ZnO increased with higher lanthanum concentration. Photoluminescence spectra exhibited increased violet emission intensity correlated
Optical studies of nano structured la-doped zn o prepared by combustion methodsuresh800
This document summarizes research on the optical properties of lanthanum-doped zinc oxide (ZnO) nanostructures prepared using a combustion synthesis method. Coral-shaped ZnO nanostructures with an average grain size of 15 nm were successfully synthesized. Transmission electron microscopy showed the nanostructures were porous with pore sizes of 10-50 nm. X-ray diffraction analysis confirmed the wurtzite crystal structure of both pure and lanthanum-doped ZnO. Doping with lanthanum altered the structural and optical properties of ZnO. Ultraviolet-visible spectroscopy showed the band gap of ZnO increased with higher lanthanum concentration. Photoluminescence spectra exhibited lanthanum characteristic emission and a
Effect of Sn Doping on Structural and Electrical Properties of ZnO Thin Films...journal ijrtem
Abstract: Un-doped and tin (Sn) doped ZnO films were deposited on heated glass substrates by chemical spray pyrolysis method
(CSP). The effect of Sn concentration on the structural, surface morphological and electrical properties of the SnO2 films was
investigated. XRD analyses showed that the obtained films are polycrystalline in nature with hexagonal structure with preferred
orientation of (101). Doping with tin (Sn) causes increase in the grain size. Atomic force microscopy images showed that the root
mean square of the average surface roughness's varied from (1.48 to 3.58) as dopant concentration increased from 0 to 5 wt.%. The
electrical properties of the Sn ZnO films were strongly influenced by doping concentration. The electrical resistance of the films was
sharply decreased as dopant concentration increased.
Keywords: (ZnO) thin films, Sn Doping, Structural and electrical Properties
Photocatalytic degradation of some organic dyes under solar light irradiation...Iranian Chemical Society
Nanoparticles of the ZnO and TiO2 were synthesized and the physicochemical properties of the compounds were characterized by IR, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD patterns of the ZnO and TiO2 nanoparticles could be indexed to hexagonal and rutile phase, respectively. Aggregated nanoparticles of ZnO and TiO2 with spherical-like shapes were observed with particle diameter in the range of 80-100 nm. These nanoparticles were used for photocatalytic degradation of various dyes, Rhodamine B (RhB), Methylene blue (MB) and Acridine orange (AO) under solar light irradiation at room temperature. Effect of the amount of catalyst on the rate of photodegradation was investigated. In general, because ZnO is unstable, due to incongruous dissolution to yield Zn(OH)2 on the ZnO particle surfaces and thus leading to catalyst inactivation,the catalytic activity of the system for photodegradation of dyes decreased dramatically when TiO2 was replaced by ZnO.
This document summarizes research on the electrodeposition of zinc selenide (ZnSe) thin films at varying deposition periods and pH levels. X-ray diffraction analysis showed the films had a cubic structure. Optical analysis found the band gap decreased from 2.7eV to 1.9eV as pH decreased from 2.1 to 1.8. Transmittance was 46-84% in the visible region and increased slightly with higher pH. Structural analysis via XRD confirmed the preferred orientation was along the (111) plane and lattice constant was 5.667 angstroms.
Study the effect of nickel and aluminium doped ZnO photoanode in DSSCTELKOMNIKA JOURNAL
1. The document studies the effect of doping zinc oxide (ZnO) photoanodes in dye-sensitized solar cells (DSSCs) with nickel and aluminium through simulation. Aluminium-doped ZnO (ZnO:Al) and nickel-doped ZnO (ZnO:Ni) photoanodes demonstrated better cell performance than pure ZnO due to enhanced physical properties from the dopants.
2. A power conversion efficiency of 3.96% was achieved for a 3 mol% ZnO:Al photoanode through optimization of parameters like thickness, doping concentration, temperature and defect density. Similarly, ZnO:Ni photoanodes of 4-6 mol% concentration
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Band gap engineering of indium zinc oxide by nitrogen incorporationYahaya Balarabe
The document summarizes research on engineering the band gap of indium zinc oxide (IZO) films through nitrogen incorporation. Nitrogen was incorporated into IZO films deposited by RF reactive magnetron sputtering by varying the ratio of N2/Ar gas fluxes during deposition. Increasing nitrogen content in the films, as measured by EDX, narrowed the band gap from 3.5 eV to 2.5 eV. For high nitrogen content, XRD showed the formation of crystalline InN phases in addition to the original In2O3 matrix. The lowest film resistivity was 3.8 × 10-4 Ω·cm with a carrier concentration of 5.1 × 1020 cm-3.
Photo Physical Investigation on Mg / Sn Doped ZnO Nanoparticles for Gas Sensi...IRJET Journal
This document summarizes research on Mg and Sn doped zinc oxide (ZnO) nanoparticles synthesized by microwave irradiation for gas sensing applications. Key points:
- Mg and Sn doped ZnO nanoparticles were successfully synthesized and characterized through various techniques to study their structural, chemical, optical and morphological properties.
- XRD analysis showed the nanoparticles had good crystallinity and the dopants were well dispersed in the ZnO lattice. FTIR showed peaks corresponding to Zn-O, Mg-O and Sn-O bonds.
- UV-Vis analysis indicated the band gap was increased with doping due to excess oxygen vacancies. PL studies examined the emission behavior.
- SEM images showed the nanoparticles had
Influence of concentration on the structural, optical and electrical properti...iosrjce
IOSR Journal of Applied Physics (IOSR-JAP) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Photocatalytic Degradation of Azo Dye (Methyl Red) In Water under Visible Lig...IJEAB
Commercial TiO2 (P25) co-doped with bimetallic silver and nickel nanoparticles (Ag-Ni/TiO2) was prepared by g-irradiation method. The properties of Ag-Ni/TiO2 were characterized by X-Ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), energy dispersive X-ray spectroscopy techniques (EDX) and surface area measurement by Brunauer-Emmett-Teller (BET) method. The size of silver and nickel nanoparticles was determined by TEM to be of 1-2 nm.The photo-catalytic degradation of azo dye methyl red in the aqueous suspensions of TiO2 and Ag-Ni/TiO2 under visible light was carried out to evaluate the photo-catalytic activity. Results showed that Ag-Ni/TiO2 was found to enhance photo-degradation efficiency of azo dye metyl red compared to commercial TiO2. The results showed that Ag 3% (w/w) and Ni 1.5% (w/w) co-doped TiO2 had the highest photoactivity among all studied samples under visible light. Thus, g-irradiation method can be suitably applied to prepare photo-catalyst of Ag-Ni/TiO2with highly photocatalytic activity.
Fabrication, Structural and Optical Properties of Ni and Cr Doped ZnO Nanocom...IRJET Journal
This document summarizes research on the fabrication, structural, optical, and photocatalytic properties of undoped and Ni, Cr co-daped ZnO nanocomposites. The nanocomposites were synthesized via a facile precipitation method. X-ray diffraction analysis showed the nanocomposites crystallized in the hexagonal wurtzite structure without impurities. Scanning electron microscopy revealed the nanoparticles were uniformly distributed and spherical in shape, ranging in size from 25-44 nm. Ultraviolet-visible spectroscopy showed the optical bandgap decreased from 3.19 eV to 2.99 eV with doping, which is desirable for photocatalytic and optoelectronic applications. Photoluminescence spectroscopy
This document discusses the performance of dye-sensitized solar cells that use different types of titanium dioxide photoelectrodes. Nanocrystalline and nanotube anatase TiO2 photoelectrodes were fabricated using a hydrothermal technique and their morphological characteristics were analyzed using scanning electron microscopy. The nanotube-based dye-sensitized solar cell was found to have a higher efficiency of 7.28% compared to the 6.6% efficiency of the nanocrystalline anatase-based cell, as measured by current density-voltage curves and incident photon to current conversion efficiency spectra. The nanotube structure allows for illumination from both the front and back sides.
Structural and FTIR Studies of Pure and Zinc Doped SNO2NanoParticlesmsejjournal
Pure and zinc-doped tin oxide nanoparticles were synthesized by the chemical co-precipitation method.The structural studies were carried out by X-Ray Diffraction pattern. XRD pattern reveals the tetragonal
rutile structure of tin oxide nanoparticles. Fourier Transform Infrared Spectroscopy studies were used to identify the chemical information of pure and zinc-doped tin oxide nanoparticles. The crystallite size of pure tin oxide nanoparticles is 9 nm obtained from the X-ray diffraction pattern. The Zn ions are incorporated into the tin ions. It is suitable candidate for gas sensor applications.
STRUCTURAL AND FTIR STUDIES OF PURE AND ZINC DOPED SNO2NANOPARTICLESmsejjournal
Pure and zinc-doped tin oxide nanoparticles were synthesized by the chemical co-precipitation method.
The structural studies were carried out by X-Ray Diffraction pattern. XRD pattern reveals the tetragonal
rutile structure of tin oxide nanoparticles. Fourier Transform Infrared Spectroscopy studies were used to
identify the chemical information of pure and zinc-doped tin oxide nanoparticles. The crystallite size of
pure tin oxide nanoparticles is 9 nm obtained from the X-ray diffraction pattern. The Zn ions are
incorporated into the tin ions. It is suitable candidate for gas sensor applications.
Advances in Materials Science and Engineering: An International Journal (MSEJ)msejjournal
Pure and zinc-doped tin oxide nanoparticles were synthesized by the chemical co-precipitation method.
The structural studies were carried out by X-Ray Diffraction pattern. XRD pattern reveals the tetragonal
rutile structure of tin oxide nanoparticles. Fourier Transform Infrared Spectroscopy studies were used to
identify the chemical information of pure and zinc-doped tin oxide nanoparticles. The crystallite size of
pure tin oxide nanoparticles is 9 nm obtained from the X-ray diffraction pattern. The Zn ions are
incorporated into the tin ions. It is suitable candidate for gas sensor applications.
Hanle Effect Measurements of Spin Lifetime in Zn0.4Cd0.6Se Epilayers Grown on...Oleg Maksimov
This document summarizes a study that used the Hanle effect to measure spin lifetimes in ZnCdSe epilayers grown on InP substrates with varying n-doping levels. Four samples were studied: three Zn0.4Cd0.6Se samples with carrier densities of 8.0×1016 cm-3, 4.3×1017 cm-3, and 1.1×1018 cm-3, as well as an undoped Zn0.5Cd0.5Se sample. Measurements showed that spin lifetime varied non-monotonically with carrier density, reaching a maximum of ~10.5 ns for the sample near the metal-insulator transition.
Preparation and Properties of Nanocrystalline Zinc Oxide Thin Filmsijtsrd
Metal oxide is highly important material which possesses many unique optical and electrical properties for applications in many areas such as Solar cells, Gas sensors and so on. With the development of research and applications of Metal oxide thin films, research results are verified that the morphology of Metal oxide thin films are plays an important role in applications of these films. Variety of morphologies, complex structure has been developed by physical or chemical methods. However the work on controlled growth of these films is still in developing state. Therefore in present work we deposited ZnS and ZnO metal oxides thin films on different substrates by Chemical Bath Deposition Technique. Structural, Surface Morphology and Optical properties of as deposited films were investigated by XRD, SEM, and UV VIS Spectrophotometer. The band gap is also calculated from the equation relating absorption co efficient to wavelength. The band gap indicates the film is transmitting within the visible range and the band gaps changes because of the grain size of the films. We also observed that, the change in preparative parameters affects the deposition rate of thin films. From the observation, it is clear that the growth rate increases as the deposition temperature, increases. S. S. Kawar "Preparation and Properties of Nanocrystalline Zinc Oxide Thin Films" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-4 , June 2020, URL: https://www.ijtsrd.com/papers/ijtsrd31623.pdf Paper Url :https://www.ijtsrd.com/physics/nanotechnology/31623/preparation-and-properties-of-nanocrystalline-zinc-oxide-thin-films/s-s-kawar
This document summarizes research on conducting aluminum-doped zinc oxide films deposited at low temperature using an electrochemical deposition method. ZnO films doped with various molar ratios of aluminum nitrate and zinc nitrate were deposited at 70°C using a three-electrode setup. X-ray diffraction analysis showed the successful doping of aluminum into the crystal structure of ZnO without secondary phase formation. Electrical resistivity measurements found the lowest resistivity for a composition ratio of 7:3. Optical characterization showed over 90% transmittance and band gap widening with different aluminum compositions due to incorporation into the ZnO crystal structure.
Arrays of TiO2 nanorods embedded with fluorine doped carbon nitride quantum d...Pawan Kumar
Graphenic semiconductors such as carbon nitride are attracting increasing attention as photocatalysts due to their chemical stability, visible light absorption and excellent electronic properties. The photocatalytic activity of nanostructured TiO2 catalysts is constrained by the wide bandgap and concomitant low visible light responsivity of TiO2. In this context we present the formation of new fluorine doped carbon nitride quantum dots (CNFQDs) by solid state reaction and the subsequent examination of their heterojunctions with TiO2 for photoelectrochemical water splitting. Arrays of rutile phase TiO2 nanorods embedded with CNFQDs were synthesized by a simple in situ hydrothermal approach and the resulting nanomaterials were found to exhibit strong visible light absorption. The energetics at the heterojunction were favorable for efficient electron transfer from CNFQDs to TiO2 under visible light irradiation and …
Water-splitting photoelectrodes consisting of heterojunctions of carbon nitri...Devika Laishram
Quinary and senary non-stoichiometric double perovskites such as Ba2Ca0.66Nb1.34−xFexO6−δ
(BCNF) have been utilized for gas sensing, solid oxide fuel cells and thermochemical CO2
reduction. Herein, we examined their potential as narrow bandgap semiconductors for use in solar
energy harvesting. A cobalt co-doped BCNF, Ba2Ca0.66Nb0.68Fe0.33Co0.33O6−δ (BCNFCo),
exhibited an optical absorption edge at ∼800 nm, p-type conduction and a distinct photoresponse
up to 640 nm while demonstrating high thermochemical stability. A nanocomposite of BCNFCo
and g-C3N4 (CN) was prepared via a facile solvent-assisted exfoliation/blending approach using
dichlorobenzene and glycerol at a moderate temperature. The exfoliation of g-C3N4 followed by
wrapping on perovskite established an effective heterojunction between the materials for charge
separation. The conjugated 2D sheets of CN enabled better charge migration resulting in increased
photoelectrochemical performance. A blend composed of 40 wt% perovskites and CN performed
optimally, whilst achieving a photocurrent density as high as 1.5 mA cm−2 for sunlight-driven
water-splitting with a Faradaic efficiency as high as ∼88%.
This document is from the website www.entechnol.de dated 3/2017. It discusses an article titled "Zinc Oxide–Titania Heterojunction-based Solid Nanospheres as Photoanodes for Electron-Trapping in Dye-Sensitized Solar Cells" which examines using zinc oxide-titania heterojunction solid nanospheres as photoanodes to trap electrons in dye-sensitized solar cells.
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Optical studies of nano structured la-doped zn o prepared by combustion methodsuresh800
This document summarizes research on the optical properties of lanthanum-doped zinc oxide (ZnO) nanostructures prepared using a combustion synthesis method. Coral-shaped ZnO nanostructures with an average grain size of 15 nm were successfully synthesized. Transmission electron microscopy showed the nanostructures were porous with pore sizes of 10-50 nm. X-ray diffraction analysis confirmed the wurtzite crystal structure of both pure and lanthanum-doped ZnO. Doping with lanthanum altered the structural and optical properties of ZnO. Ultraviolet-visible spectroscopy showed the band gap of ZnO increased with higher lanthanum concentration. Photoluminescence spectra exhibited lanthanum characteristic emission and a
Effect of Sn Doping on Structural and Electrical Properties of ZnO Thin Films...journal ijrtem
Abstract: Un-doped and tin (Sn) doped ZnO films were deposited on heated glass substrates by chemical spray pyrolysis method
(CSP). The effect of Sn concentration on the structural, surface morphological and electrical properties of the SnO2 films was
investigated. XRD analyses showed that the obtained films are polycrystalline in nature with hexagonal structure with preferred
orientation of (101). Doping with tin (Sn) causes increase in the grain size. Atomic force microscopy images showed that the root
mean square of the average surface roughness's varied from (1.48 to 3.58) as dopant concentration increased from 0 to 5 wt.%. The
electrical properties of the Sn ZnO films were strongly influenced by doping concentration. The electrical resistance of the films was
sharply decreased as dopant concentration increased.
Keywords: (ZnO) thin films, Sn Doping, Structural and electrical Properties
Photocatalytic degradation of some organic dyes under solar light irradiation...Iranian Chemical Society
Nanoparticles of the ZnO and TiO2 were synthesized and the physicochemical properties of the compounds were characterized by IR, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD patterns of the ZnO and TiO2 nanoparticles could be indexed to hexagonal and rutile phase, respectively. Aggregated nanoparticles of ZnO and TiO2 with spherical-like shapes were observed with particle diameter in the range of 80-100 nm. These nanoparticles were used for photocatalytic degradation of various dyes, Rhodamine B (RhB), Methylene blue (MB) and Acridine orange (AO) under solar light irradiation at room temperature. Effect of the amount of catalyst on the rate of photodegradation was investigated. In general, because ZnO is unstable, due to incongruous dissolution to yield Zn(OH)2 on the ZnO particle surfaces and thus leading to catalyst inactivation,the catalytic activity of the system for photodegradation of dyes decreased dramatically when TiO2 was replaced by ZnO.
This document summarizes research on the electrodeposition of zinc selenide (ZnSe) thin films at varying deposition periods and pH levels. X-ray diffraction analysis showed the films had a cubic structure. Optical analysis found the band gap decreased from 2.7eV to 1.9eV as pH decreased from 2.1 to 1.8. Transmittance was 46-84% in the visible region and increased slightly with higher pH. Structural analysis via XRD confirmed the preferred orientation was along the (111) plane and lattice constant was 5.667 angstroms.
Study the effect of nickel and aluminium doped ZnO photoanode in DSSCTELKOMNIKA JOURNAL
1. The document studies the effect of doping zinc oxide (ZnO) photoanodes in dye-sensitized solar cells (DSSCs) with nickel and aluminium through simulation. Aluminium-doped ZnO (ZnO:Al) and nickel-doped ZnO (ZnO:Ni) photoanodes demonstrated better cell performance than pure ZnO due to enhanced physical properties from the dopants.
2. A power conversion efficiency of 3.96% was achieved for a 3 mol% ZnO:Al photoanode through optimization of parameters like thickness, doping concentration, temperature and defect density. Similarly, ZnO:Ni photoanodes of 4-6 mol% concentration
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Band gap engineering of indium zinc oxide by nitrogen incorporationYahaya Balarabe
The document summarizes research on engineering the band gap of indium zinc oxide (IZO) films through nitrogen incorporation. Nitrogen was incorporated into IZO films deposited by RF reactive magnetron sputtering by varying the ratio of N2/Ar gas fluxes during deposition. Increasing nitrogen content in the films, as measured by EDX, narrowed the band gap from 3.5 eV to 2.5 eV. For high nitrogen content, XRD showed the formation of crystalline InN phases in addition to the original In2O3 matrix. The lowest film resistivity was 3.8 × 10-4 Ω·cm with a carrier concentration of 5.1 × 1020 cm-3.
Photo Physical Investigation on Mg / Sn Doped ZnO Nanoparticles for Gas Sensi...IRJET Journal
This document summarizes research on Mg and Sn doped zinc oxide (ZnO) nanoparticles synthesized by microwave irradiation for gas sensing applications. Key points:
- Mg and Sn doped ZnO nanoparticles were successfully synthesized and characterized through various techniques to study their structural, chemical, optical and morphological properties.
- XRD analysis showed the nanoparticles had good crystallinity and the dopants were well dispersed in the ZnO lattice. FTIR showed peaks corresponding to Zn-O, Mg-O and Sn-O bonds.
- UV-Vis analysis indicated the band gap was increased with doping due to excess oxygen vacancies. PL studies examined the emission behavior.
- SEM images showed the nanoparticles had
Influence of concentration on the structural, optical and electrical properti...iosrjce
IOSR Journal of Applied Physics (IOSR-JAP) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Photocatalytic Degradation of Azo Dye (Methyl Red) In Water under Visible Lig...IJEAB
Commercial TiO2 (P25) co-doped with bimetallic silver and nickel nanoparticles (Ag-Ni/TiO2) was prepared by g-irradiation method. The properties of Ag-Ni/TiO2 were characterized by X-Ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), energy dispersive X-ray spectroscopy techniques (EDX) and surface area measurement by Brunauer-Emmett-Teller (BET) method. The size of silver and nickel nanoparticles was determined by TEM to be of 1-2 nm.The photo-catalytic degradation of azo dye methyl red in the aqueous suspensions of TiO2 and Ag-Ni/TiO2 under visible light was carried out to evaluate the photo-catalytic activity. Results showed that Ag-Ni/TiO2 was found to enhance photo-degradation efficiency of azo dye metyl red compared to commercial TiO2. The results showed that Ag 3% (w/w) and Ni 1.5% (w/w) co-doped TiO2 had the highest photoactivity among all studied samples under visible light. Thus, g-irradiation method can be suitably applied to prepare photo-catalyst of Ag-Ni/TiO2with highly photocatalytic activity.
Fabrication, Structural and Optical Properties of Ni and Cr Doped ZnO Nanocom...IRJET Journal
This document summarizes research on the fabrication, structural, optical, and photocatalytic properties of undoped and Ni, Cr co-daped ZnO nanocomposites. The nanocomposites were synthesized via a facile precipitation method. X-ray diffraction analysis showed the nanocomposites crystallized in the hexagonal wurtzite structure without impurities. Scanning electron microscopy revealed the nanoparticles were uniformly distributed and spherical in shape, ranging in size from 25-44 nm. Ultraviolet-visible spectroscopy showed the optical bandgap decreased from 3.19 eV to 2.99 eV with doping, which is desirable for photocatalytic and optoelectronic applications. Photoluminescence spectroscopy
This document discusses the performance of dye-sensitized solar cells that use different types of titanium dioxide photoelectrodes. Nanocrystalline and nanotube anatase TiO2 photoelectrodes were fabricated using a hydrothermal technique and their morphological characteristics were analyzed using scanning electron microscopy. The nanotube-based dye-sensitized solar cell was found to have a higher efficiency of 7.28% compared to the 6.6% efficiency of the nanocrystalline anatase-based cell, as measured by current density-voltage curves and incident photon to current conversion efficiency spectra. The nanotube structure allows for illumination from both the front and back sides.
Structural and FTIR Studies of Pure and Zinc Doped SNO2NanoParticlesmsejjournal
Pure and zinc-doped tin oxide nanoparticles were synthesized by the chemical co-precipitation method.The structural studies were carried out by X-Ray Diffraction pattern. XRD pattern reveals the tetragonal
rutile structure of tin oxide nanoparticles. Fourier Transform Infrared Spectroscopy studies were used to identify the chemical information of pure and zinc-doped tin oxide nanoparticles. The crystallite size of pure tin oxide nanoparticles is 9 nm obtained from the X-ray diffraction pattern. The Zn ions are incorporated into the tin ions. It is suitable candidate for gas sensor applications.
STRUCTURAL AND FTIR STUDIES OF PURE AND ZINC DOPED SNO2NANOPARTICLESmsejjournal
Pure and zinc-doped tin oxide nanoparticles were synthesized by the chemical co-precipitation method.
The structural studies were carried out by X-Ray Diffraction pattern. XRD pattern reveals the tetragonal
rutile structure of tin oxide nanoparticles. Fourier Transform Infrared Spectroscopy studies were used to
identify the chemical information of pure and zinc-doped tin oxide nanoparticles. The crystallite size of
pure tin oxide nanoparticles is 9 nm obtained from the X-ray diffraction pattern. The Zn ions are
incorporated into the tin ions. It is suitable candidate for gas sensor applications.
Advances in Materials Science and Engineering: An International Journal (MSEJ)msejjournal
Pure and zinc-doped tin oxide nanoparticles were synthesized by the chemical co-precipitation method.
The structural studies were carried out by X-Ray Diffraction pattern. XRD pattern reveals the tetragonal
rutile structure of tin oxide nanoparticles. Fourier Transform Infrared Spectroscopy studies were used to
identify the chemical information of pure and zinc-doped tin oxide nanoparticles. The crystallite size of
pure tin oxide nanoparticles is 9 nm obtained from the X-ray diffraction pattern. The Zn ions are
incorporated into the tin ions. It is suitable candidate for gas sensor applications.
Hanle Effect Measurements of Spin Lifetime in Zn0.4Cd0.6Se Epilayers Grown on...Oleg Maksimov
This document summarizes a study that used the Hanle effect to measure spin lifetimes in ZnCdSe epilayers grown on InP substrates with varying n-doping levels. Four samples were studied: three Zn0.4Cd0.6Se samples with carrier densities of 8.0×1016 cm-3, 4.3×1017 cm-3, and 1.1×1018 cm-3, as well as an undoped Zn0.5Cd0.5Se sample. Measurements showed that spin lifetime varied non-monotonically with carrier density, reaching a maximum of ~10.5 ns for the sample near the metal-insulator transition.
Preparation and Properties of Nanocrystalline Zinc Oxide Thin Filmsijtsrd
Metal oxide is highly important material which possesses many unique optical and electrical properties for applications in many areas such as Solar cells, Gas sensors and so on. With the development of research and applications of Metal oxide thin films, research results are verified that the morphology of Metal oxide thin films are plays an important role in applications of these films. Variety of morphologies, complex structure has been developed by physical or chemical methods. However the work on controlled growth of these films is still in developing state. Therefore in present work we deposited ZnS and ZnO metal oxides thin films on different substrates by Chemical Bath Deposition Technique. Structural, Surface Morphology and Optical properties of as deposited films were investigated by XRD, SEM, and UV VIS Spectrophotometer. The band gap is also calculated from the equation relating absorption co efficient to wavelength. The band gap indicates the film is transmitting within the visible range and the band gaps changes because of the grain size of the films. We also observed that, the change in preparative parameters affects the deposition rate of thin films. From the observation, it is clear that the growth rate increases as the deposition temperature, increases. S. S. Kawar "Preparation and Properties of Nanocrystalline Zinc Oxide Thin Films" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-4 , June 2020, URL: https://www.ijtsrd.com/papers/ijtsrd31623.pdf Paper Url :https://www.ijtsrd.com/physics/nanotechnology/31623/preparation-and-properties-of-nanocrystalline-zinc-oxide-thin-films/s-s-kawar
This document summarizes research on conducting aluminum-doped zinc oxide films deposited at low temperature using an electrochemical deposition method. ZnO films doped with various molar ratios of aluminum nitrate and zinc nitrate were deposited at 70°C using a three-electrode setup. X-ray diffraction analysis showed the successful doping of aluminum into the crystal structure of ZnO without secondary phase formation. Electrical resistivity measurements found the lowest resistivity for a composition ratio of 7:3. Optical characterization showed over 90% transmittance and band gap widening with different aluminum compositions due to incorporation into the ZnO crystal structure.
Arrays of TiO2 nanorods embedded with fluorine doped carbon nitride quantum d...Pawan Kumar
Graphenic semiconductors such as carbon nitride are attracting increasing attention as photocatalysts due to their chemical stability, visible light absorption and excellent electronic properties. The photocatalytic activity of nanostructured TiO2 catalysts is constrained by the wide bandgap and concomitant low visible light responsivity of TiO2. In this context we present the formation of new fluorine doped carbon nitride quantum dots (CNFQDs) by solid state reaction and the subsequent examination of their heterojunctions with TiO2 for photoelectrochemical water splitting. Arrays of rutile phase TiO2 nanorods embedded with CNFQDs were synthesized by a simple in situ hydrothermal approach and the resulting nanomaterials were found to exhibit strong visible light absorption. The energetics at the heterojunction were favorable for efficient electron transfer from CNFQDs to TiO2 under visible light irradiation and …
Similar to Zinc Oxide–Titania Heterojunction-based Solid Nanospheres as Photoanodes for Electron-Trapping in Dye-Sensitized Solar Cells (20)
Water-splitting photoelectrodes consisting of heterojunctions of carbon nitri...Devika Laishram
Quinary and senary non-stoichiometric double perovskites such as Ba2Ca0.66Nb1.34−xFexO6−δ
(BCNF) have been utilized for gas sensing, solid oxide fuel cells and thermochemical CO2
reduction. Herein, we examined their potential as narrow bandgap semiconductors for use in solar
energy harvesting. A cobalt co-doped BCNF, Ba2Ca0.66Nb0.68Fe0.33Co0.33O6−δ (BCNFCo),
exhibited an optical absorption edge at ∼800 nm, p-type conduction and a distinct photoresponse
up to 640 nm while demonstrating high thermochemical stability. A nanocomposite of BCNFCo
and g-C3N4 (CN) was prepared via a facile solvent-assisted exfoliation/blending approach using
dichlorobenzene and glycerol at a moderate temperature. The exfoliation of g-C3N4 followed by
wrapping on perovskite established an effective heterojunction between the materials for charge
separation. The conjugated 2D sheets of CN enabled better charge migration resulting in increased
photoelectrochemical performance. A blend composed of 40 wt% perovskites and CN performed
optimally, whilst achieving a photocurrent density as high as 1.5 mA cm−2 for sunlight-driven
water-splitting with a Faradaic efficiency as high as ∼88%.
This document is from the website www.entechnol.de dated 3/2017. It discusses an article titled "Zinc Oxide–Titania Heterojunction-based Solid Nanospheres as Photoanodes for Electron-Trapping in Dye-Sensitized Solar Cells" which examines using zinc oxide-titania heterojunction solid nanospheres as photoanodes to trap electrons in dye-sensitized solar cells.
Nickel and cobalt transfigured natural clay: a green catalyst for low-tempera...Devika Laishram
Soot particulates in engine exhausts pose a severe threat to the environment and human health – causing cancer, affecting the heart and lungs and drives metal processes. This study proposes a practical,
real-world application of transition metal modified natural clay as an environmentally benign, low-cost,
green catalyst for soot oxidation. Ni and Co (NC-Clay) incorporated natural clay catalysts were prepared
by a simple wet impregnation method and meticulously characterized by different characterization
techniques. The catalyst exhibited higher H2 absorption at a lower temperature with similar trends as
observed in O2 TPD that indicated a remarkable redox property, which is useful for applications as a
catalyst in soot oxidation. Excellent catalytic activity with a very low T50 of 358 1C was observed and can
be accredited to the improved surface oxygen vacancies and thermal stability by the metal modification
of clay
Recent advances in ultra-low temperature (sub-zero to 100 8C) synthesis, mech...Devika Laishram
The development of titania (TiO2) nanomaterials for next-generation photonic, optoelectronic, and
catalytic applications necessitates a facile and cost-effective synthetic methodology for precisely tuning
the composition, phase, and morphology at nanometer scales. In this review, an attempt has been made
to comprehend the progress of the emerging and rapidly developing synthesis methods evolved for the
low-temperature synthesis of titania with a particular emphasis on sub-zero temperature. Insights and
understandings of how the temperature affects the characteristic surface properties and morphology of
titania, along with a detailed discussion on the material characteristics for various technological device
applications are dealt with various methods of analysis. Furthermore, the temperature-dependent
morphological (0D–3D) and structural changes and their impact on different energy-harvesting and
storage and water remediation applications are elucidated. Thus, this review specifically opens the
understanding of different TiO2 polymorph syntheses and their physiochemical comprehension for
advanced technological device performance enhancements
Engineered ZnO-TiO2 Nanospheres for High Performing Membrane Assimilated Phot...Devika Laishram
This paper is a study of ZnO doped TiO2 in various percentages
ranging from 0% (undoped) up to 10%. The effect of doping
was observed via the change in morphological, optical,
electrical and physical properties of ZnO-TiO2 nanospheres.
Hydrothermally grown nanospheres are used for removing
contaminants photo-catalytically from waste water and also as
photoanodes in dye-sensitized solar cells (DSSCs) with graphene as counter electrode. Of the many approaches that have
been explored for purification of contaminated water, this work
presents designing of an environmental friendly solution, based
on easily available filter paper membrane and incorporating it
with the synthesized catalyst for photodegradation of the
harmful toxic substances. These reusable membranes assist in
the photodegradation process by creating room for better
light-catalyst-dye interaction via large surface sites. The spherically structured heterojunction of ZnO-TiO2 generates excitons
that oxidize methyl orange (MO) and reduce harmful Cr(VI) to
non-toxic Cr(III) with high efficacy. Additionally, the agile
nanostructures were employed as efficient photoanode material by fabricating dye sensitized solar cells with graphene as
counter electrode.
HfO2 nanodots incorporated in TiO2 and its hydrogenation for high performance...Devika Laishram
Black titania (H-TiO2) as a photoanode material has attracted huge attention due to its extremely high
optical absorption in the visible region. Herein, black TiO2 doped with HfO2 shows 45.7% higher photoconversion efficiency than H-TiO2 under identically similar conditions. The incorporation of HfO2
nanodots increased the optical scattering in H-TiO2 only when it underwent hydrogenation along with
TiO2. Hafnia-doped TiO2 (HfO2/TiO2) is synthesized by a combination of simple sol–gel and
hydrothermal method followed by thermal annealing under controlled hydrogen atmosphere. The
hydrogenated H-(TiO2/HfO2) exhibited very high optical absorption but slightly lower than H-TiO2 due
to light scattering by HfO2 nanodots. We observed a sharp decrease in optical band gap of TiO2/HfO2
from 3.2 to 2.4 eV up on hydrogen annealing, which is important in solar applications as demonstrated
by the fabrication of high efficiency dye sensitized solar cells (DSSC)
High-performance dye-sensitized solar cell using dimensionally controlled tit...Devika Laishram
The subject of the current study is a concoct of anatase and rutile mixed phase titania synthesized at 40 C and
10 C. At these sub-zero temperatures, highly crystalline, phase-oriented nanostructured titania were formed.
At 40 C, nanocrystals of TiO2 consist of the anatase phase while nanorods dominated by the rutile phase form
at 10 C. These samples are remarkable photoanode materials with excellent photon scattering ability in dyesensitized solar cells (DSSCs). On performance optimization of DSSCs, a composition of 0.5 wt% TiO2 (prepared
at 40 C) and P25 improved the photon harvesting by providing a large number of sites for interaction, resulting
in a high photocurrent of 18.46 mA cm2 and 8.6% photoconversion efficiency.
Recent Progress in Synthesis of Nano- and Atomic-Sized CatalystsDevika Laishram
Well-defined nano-and atomic-sized heterogeneous catalysts with extremely high
catalytic activities and unique selectivities show promise in addressing the critical
energy- and environment-related challenges of this century. The exceptional
properties of these catalysts, such as their electronic and geometric structures and
the effective interactions between metals and supports, give rise to unprecedented
catalytic efficiency over that of conventional catalysts. The facile prospects for
tuning the active sites of these catalysts pave the way to optimizing their activities,
selectivities, and stabilities, thus offering extensive application possibilities in
significant industry-related catalytic reactions. A prerequisite for synthesizing
nano- and atomic-sized catalyst is to prepare extremely disperse nano- and
subnanoscale atoms on suitable supports. This book chapter summarizes various
synthesis methods employed to synthesize nano- and atomic-scale catalysts.
State of the Art in the Characterization of Nano- and Atomic-Scale CatalystsDevika Laishram
Nanometer and subnanometer particles and films are becoming an essential and
integral part of new technologies and inventions in different areas. Some of the
most common areas include the microelectronic industry, magnetic recordings,
photovoltaic applications, and optical coatings. Because of the ultrasmall size at
atomic levels, the effect of quantum size becomes prominent, and the sensitivity
of size is defined even by a difference of a single atom. Additionally, the effect
is of utmost importance as the single-atom catalysts are far more advantageous
than conventional catalysts as they tend to anchor easily because of their low
coordination. Also, the presence of a single-atom catalyst in reactions creates
efficient charge transfer as it forms a strong interaction with the support.
Furthermore, catalysts in the subnanometer regime exhibit different electronic
states and adsorption capabilities compared to traditional catalysts. Therefore, to
fully appreciate the subnanometer catalysis reactions, it is essential to study the
means of characterizing the prepared subnano catalysts,
Solution Processed Hafnia Nanoaggregates: Influence of Surface Oxygen on Cata...Devika Laishram
Hafnium dioxide (HfO2) nanoaggregates are
synthesized by sol−gel and hydrothermal routes followed by
hydrogen annealing at different time durations. The proposed
study aims to explore the effect of hydrogen annealing time on
the properties of HfO2 and also envisage the catalytic soot
oxidation using HfO2 nanoaggregates. It is observed that
annealing under a hydrogen atmosphere brought about
substantial changes in certain attributes such as chemical and
textural properties with marginal changes in some other
properties like optical activity and band gap. The pristine
HfO2 without hydrogen annealing showed a lower ignition
temperature, whereas hydrogen annealed HfO2 for 2 h showed
the best catalytic performance characterized by the soot
combustion temperature (T50) in contrast to samples prepared at longer duration because of the higher surface adsorbed
oxygen species in its widely distributed pores.
Nitrogen-Enriched Carbon Nanobubbles and Nanospheres for Applications in Ener...Devika Laishram
Multifunctional carbon nanomaterials have attracted remarkable consideration for use in various energy
conversion and storage devices because of their ultrahigh specific
surface area, unique morphology, and excellent electrochemical
properties. Herein, we report the synthesis of highly uniform and
ordered nitrogen-enriched carbon nanospheres (CS) and nanobubbles (CNB) by a modified Stöber reaction using resorcinol and
formaldehyde in the presence of ethylenediamine as a nitrogen
source. A comparative study of the prepared CS and CNB
nanomaterials is presented here with potential use in a wide variety
of applications involving large surface area and electrical
conductivity. As counter electrode materials in solar cells, CNB and CS showed enhanced photoelectrochemical activity for
catalytically reducing I3
− to I− and improved capacitive behavior with a low charge transfer resistance and remarkable power
conversion efficiency (PCE) of 10.40% with improved Jsc (20.20 mA/cm2
) and Voc (0.73 V). The enhanced performance of the
fabricated photoelectrochemical cell is due to the excellent point contact and good conductivity that offered better charge
transportation of electrons with minimum recombination. The enhanced adsorption upon increasing the pressure without an
apparent saturation level signified the large CO2 adsorption with 2 mmol/g for the CS. Additionally, the rectangular-shaped CV
curve indicated the double-layer capacitive behavior, good electrochemical reversibility, and high-power characteristics, prerequisites
for supercapacitor application. This study probes the practical possibility of nitrogen-enriched carbon nanostructures as a
multifunctional material for prospective applications.
Boosting Photocatalytic Activity Using Carbon Nitride Based 2D/2D van der Waa...Devika Laishram
The surging demand for energy and staggering pollutants in the
environment have geared the scientific community to explore sustainable
pathways that are economically feasible and environmentally compelling. In this
context, harnessing solar energy using semiconductor materials to generate
charge pairs to drive photoredox reactions has been envisioned as a futuristic
approach. Numerous inorganic crystals with promising nanoregime properties
investigated in the past decade have yet to demonstrate practical application due
to limited photon absorption and sluggish charge separation kinetics. Twodimensional semiconductors with tunable optical and electronic properties and
quasi-resistance-free lateral charge transfer mechanisms have shown great
promise in photocatalysis. Polymeric graphitic carbon nitride (g-C3N4) is
among the most promising candidates due to fine-tuned band edges and the
feasibility of optimizing the optical properties via materials genomics.
Constructing a two-dimensional (2D)/2D van der Waals (vdW) heterojunction
by allies of 2D carbon nitride sheets and other 2D semiconductors has demonstrated enhanced charge separation with improved
visible photon absorption, and the performance is not restricted by the lattice matching of constituting materials. With the advent of
new 2D semiconductors over the recent past, the 2D/2D heterojunction assemblies are gaining momentum to design high
performance photocatalysts for numerous applications. This review aims to highlight recent advancements and key understanding in
carbon nitride based 2D/2D heterojunctions and their applications in photocatalysis, including small molecules activation,
conversion, and degradations. We conclude with a forward-looking perspective discussing the key challenges and opportunity areas
Multifunctional materials for clean energy conversionDevika Laishram
With the rapid depletion of fossil fuels, rising environmental concerns,
and population growth, it is inevitable to develop clean energy technologies
to power our future society [1e4]. These energy conversion and storage
technologies are anticipated to be sustainable and also capable of meeting
our long-term energy needs. During the past few years, extensive research
interests have been devoted to the advancement of energy conversion devices, as they play a crucial role in the prosperity and economic growth of
a country. Particularly, the energy conversion technologies such as solar
and fuel cells have proved to be highly reliable and can offer clean and sustainable energy at affordable rate [5e8]. However, the performance potential of these devices, such as output voltage, conversion efficiency, and
stability, are greatly relied on the materials used. The energy conversion process comprises physical and/or chemical reactions at th
Surface fluorination of α-Fe2O3 using selectfluor for enhancement in photoele...Devika Laishram
Fluorinated α-Fe2O3 nanostructures are synthesized via a facile hydrothermal route using Selectfluor™ (F-TEDA)
as a fluorinating as well as growth directing agent. The addition of incrementally increasing amount of F-TEDA
to Fe precursor under hydrothermal conditions resulted in preferential growth of α-Fe2O3 along (110) orientation with respect to (104) direction by ~ 35%, the former being important for enhanced charge transport.
On increasing fluorination, the heirarchical dendritic-type α-Fe2O3 changes to a snow-flake type structure (FTEDA-20%) anisotropically growing along the six directions however, at higher F-TEDA concentrations (≥
30%), loosely held particulate aggregates are seen to be formed. The X-Ray Photoelectron Spectroscopy (XPS)
suggest the maximum fluorinarion of α-Fe2O3 at 1.21 at% in 30% F-TEDA. Further, optical absorption studies
reveal reduction in optical band gap from 2.10 eV in case of pristine to 1.95 eV for fluorinated α-Fe2O3. A
photoanode made by taking 20% fluorinated α-Fe2O3 in a ratio of 10:90 with respect to TiO2 (P-25) showed
improved performance in dye sensitized solar cells with an increase in efficiency by ~16% in comparision to that
of pristine Fe2O3 and TiO2. Furthermore, anode consisting of thin films of fluorinated α-Fe2O3 on FTO also
exhibit enhanced current density on illumination of ~100 W/m2
. The increase in photoelectrochemical activity
seems to be due to the combination of two factors namely preferential growth of α-Fe2O3 along (110) direction
resulting in an improved charge transfer efficiency and reduced recombination losses due to the presence of
fluorine.
On the study of phase and dimensionally controlled titania nanostructures syn...Devika Laishram
The present studies are about surfactant free simple synthesis for titania (TiO2) nanostructures, by which morphology and phase can be tuned through temperature variation. The formation of oval shaped nanocrystals
and nanorods at different temperatures are attributed to the phase transformation between anatase and rutile
by one-step chemical reaction involving titanium tetraisopropoxide and aqueous ethyl alcohol. Categorically,
two different morphologies of TiO2 were observed with respect to variation in temperature with nanorods
formation at −20 °C and −10 °C and oval shape formation at −40 °C and −30 °C with higher surface area.
Crystalline nature and size of nano-TiO2 were determined by transmission electron microscopy (TEM) and
X-ray diffraction (XRD). The energy gap of TiO2 nanoparticles were determined by optical absorption measurement and found to be in the range of ~2.92 to 3.02 eV with an indirect band nature.
Air- and water-stable halide perovskite nanocrystals protected with nearly-m...Devika Laishram
Halide perovskites are exciting candidates for broad-spectrum photocatalysts but have the problem of ambient
stability. Protective shells of oxides and polymers around halide perovskite nano- and micro-crystals provide a
measure of chemical and photochemical resilience but the photocatalytic performance of perovskites is
compromised due to low electron mobility in amorphous oxide or polymer shells and rapid charge carrier
recombination on the surface. Herein an in situ surface passivation and stabilization of CsPbBr3 nanocrystals was
achieved using monolayered graphenic carbon nitride (CNM). Extensive characterization of carbon nitride
protected CsPbBr3 nanocrystals (CNMBr) indicated spherical CsPbBr3 nanoparticles encased in a few nm thick gC3N4 sheets facilitating better charge separation via percolation/tunneling of charges on conductive 2D nanosheets. The CNMBr core-shell nanocrystals demonstrated enhanced photoelectrochemical water splitting performance and photocurrent reaching up to 1.55 mA cm− 2
. The CNMBr catalyst was successfully deployed for CO2
photoreduction giving carbon monoxide and methane as the reaction products.
Heterostructured HfO2/TiO2 spherical nanoparticles for visible photocatalytic...Devika Laishram
Photocatalytic activity of low band gap hydrogenated HfO2 doped TiO2 (H-HfO2/TiO2), HfO2 doped TiO2
(HfO2/TiO2) and TiO2 (pristine) were investigated by photocatalytic degradation of five different industrial dyes. The current study envisages the effect of doping hydrogen and HfO2 up on TiO2 for photocatalytic degradation of different chemically structured dyes. Methylene Blue attains fast degradation
efficiency of 90%, within 10 min of the reaction due to high photocatalytic adsorption and degradation
over the rough TiO2 surface. Effect of pH on dye degradation is observed, leading to disintegration and
mineralization.
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Leonel Morgado
Current descriptions of immersive learning cases are often difficult or impossible to compare. This is due to a myriad of different options on what details to include, which aspects are relevant, and on the descriptive approaches employed. Also, these aspects often combine very specific details with more general guidelines or indicate intents and rationales without clarifying their implementation. In this paper we provide a method to describe immersive learning cases that is structured to enable comparisons, yet flexible enough to allow researchers and practitioners to decide which aspects to include. This method leverages a taxonomy that classifies educational aspects at three levels (uses, practices, and strategies) and then utilizes two frameworks, the Immersive Learning Brain and the Immersion Cube, to enable a structured description and interpretation of immersive learning cases. The method is then demonstrated on a published immersive learning case on training for wind turbine maintenance using virtual reality. Applying the method results in a structured artifact, the Immersive Learning Case Sheet, that tags the case with its proximal uses, practices, and strategies, and refines the free text case description to ensure that matching details are included. This contribution is thus a case description method in support of future comparative research of immersive learning cases. We then discuss how the resulting description and interpretation can be leveraged to change immersion learning cases, by enriching them (considering low-effort changes or additions) or innovating (exploring more challenging avenues of transformation). The method holds significant promise to support better-grounded research in immersive learning.
PPT on Direct Seeded Rice presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
(June 12, 2024) Webinar: Development of PET theranostics targeting the molecu...Scintica Instrumentation
Targeting Hsp90 and its pathogen Orthologs with Tethered Inhibitors as a Diagnostic and Therapeutic Strategy for cancer and infectious diseases with Dr. Timothy Haystead.
Authoring a personal GPT for your research and practice: How we created the Q...Leonel Morgado
Thematic analysis in qualitative research is a time-consuming and systematic task, typically done using teams. Team members must ground their activities on common understandings of the major concepts underlying the thematic analysis, and define criteria for its development. However, conceptual misunderstandings, equivocations, and lack of adherence to criteria are challenges to the quality and speed of this process. Given the distributed and uncertain nature of this process, we wondered if the tasks in thematic analysis could be supported by readily available artificial intelligence chatbots. Our early efforts point to potential benefits: not just saving time in the coding process but better adherence to criteria and grounding, by increasing triangulation between humans and artificial intelligence. This tutorial will provide a description and demonstration of the process we followed, as two academic researchers, to develop a custom ChatGPT to assist with qualitative coding in the thematic data analysis process of immersive learning accounts in a survey of the academic literature: QUAL-E Immersive Learning Thematic Analysis Helper. In the hands-on time, participants will try out QUAL-E and develop their ideas for their own qualitative coding ChatGPT. Participants that have the paid ChatGPT Plus subscription can create a draft of their assistants. The organizers will provide course materials and slide deck that participants will be able to utilize to continue development of their custom GPT. The paid subscription to ChatGPT Plus is not required to participate in this workshop, just for trying out personal GPTs during it.
Current Ms word generated power point presentation covers major details about the micronuclei test. It's significance and assays to conduct it. It is used to detect the micronuclei formation inside the cells of nearly every multicellular organism. It's formation takes place during chromosomal sepration at metaphase.
Immersive Learning That Works: Research Grounding and Paths ForwardLeonel Morgado
We will metaverse into the essence of immersive learning, into its three dimensions and conceptual models. This approach encompasses elements from teaching methodologies to social involvement, through organizational concerns and technologies. Challenging the perception of learning as knowledge transfer, we introduce a 'Uses, Practices & Strategies' model operationalized by the 'Immersive Learning Brain' and ‘Immersion Cube’ frameworks. This approach offers a comprehensive guide through the intricacies of immersive educational experiences and spotlighting research frontiers, along the immersion dimensions of system, narrative, and agency. Our discourse extends to stakeholders beyond the academic sphere, addressing the interests of technologists, instructional designers, and policymakers. We span various contexts, from formal education to organizational transformation to the new horizon of an AI-pervasive society. This keynote aims to unite the iLRN community in a collaborative journey towards a future where immersive learning research and practice coalesce, paving the way for innovative educational research and practice landscapes.
The technology uses reclaimed CO₂ as the dyeing medium in a closed loop process. When pressurized, CO₂ becomes supercritical (SC-CO₂). In this state CO₂ has a very high solvent power, allowing the dye to dissolve easily.
When I was asked to give a companion lecture in support of ‘The Philosophy of Science’ (https://shorturl.at/4pUXz) I decided not to walk through the detail of the many methodologies in order of use. Instead, I chose to employ a long standing, and ongoing, scientific development as an exemplar. And so, I chose the ever evolving story of Thermodynamics as a scientific investigation at its best.
Conducted over a period of >200 years, Thermodynamics R&D, and application, benefitted from the highest levels of professionalism, collaboration, and technical thoroughness. New layers of application, methodology, and practice were made possible by the progressive advance of technology. In turn, this has seen measurement and modelling accuracy continually improved at a micro and macro level.
Perhaps most importantly, Thermodynamics rapidly became a primary tool in the advance of applied science/engineering/technology, spanning micro-tech, to aerospace and cosmology. I can think of no better a story to illustrate the breadth of scientific methodologies and applications at their best.
Sexuality - Issues, Attitude and Behaviour - Applied Social Psychology - Psyc...PsychoTech Services
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The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
The binding of cosmological structures by massless topological defects
Zinc Oxide–Titania Heterojunction-based Solid Nanospheres as Photoanodes for Electron-Trapping in Dye-Sensitized Solar Cells
1. DOI: 10.1002/ente.201600357
Zinc Oxide–Titania Heterojunction-based Solid
Nanospheres as Photoanodes for Electron-Trapping in
Dye-Sensitized Solar Cells
Kiran P. Shejale, Devika Laishram, Ritu Gupta,* and Rakesh K. Sharma*[a]
Introduction
Titania and zinc oxide are the most-explored metal oxide
semiconductors and are extensively used in a variety of ap-
plications such as environmental detoxification, sensing, solar
cells, and photocatalysis.[1–3]
Over the past few decades, com-
posites,[4]
layered structures,[5]
doping,[6]
and various nano-
morphologies[7–9]
of TiO2/ZnO have been extensively studied.
Despite the wide range of uses of TiO2/ZnO composites,
drawbacks such as charge recombination, low surface areas,
and poor electron transport make their application diffi-
cult.[10,11]
Generating a highly porous surface for the electron
trapping by preparing heterojunctions of ZnO and TiO2 sem-
iconductors is an efficient way to solve these issues, but limit-
ed efforts have been made to enhance poor electron trans-
port owing to a nonfunctional interface at the heterojunc-
tion.[12–16]
A good heterojunction should have matching band
levels for high electron mobility and a conductive interface.[1]
A heterojunction of TiO2 and ZnO with similar band struc-
ture usually forms a II-type heterojunction with high mobili-
ty, due to improved charge isolation compared to the pure
oxides, and reduces recombination during charge separation.
Titanium-doped ZnO has been reported to show high con-
ductivity and high surface area, which are important for elec-
tron trapping.[17]
ZnO has a higher electron mobility (205–
300 cm2
Vs@1
) than TiO2 (10@5
cm2
Vs@1
)[18,19]
and thus ZnO–
TiO2 heterojunction with appropriate architectures and opti-
mal doping can facilitate electron trapping.
Various architectures of both oxides, in the form of nano-
tubes, nanowires, clusters, hollow spheres, core–shell struc-
tures, and 3D hybrid arrays, have been explored for en-
hanced charge transport.[20–23]
Unfortunately, detrapping due
to random electrical paths, surface states, and in some cases
defects hinders their application in dye-sensitized solar cells
(DSSCs). Compared to other architectures the solid nano-
sphere structure reported for the first time in this study is ex-
hibits a higher internal surface area, enhanced light scatter-
ing ability, and more sites for dye anchoring. The highly
porous, micrometer-sized volume spheres significantly en-
hance the total surface area of the film.[24]
To understand the
role of the heterojunction, DSSCs are employed as a simple
and quick method. Attempts have been made towards ex-
ploring combinations of TiO2 and ZnO as photoanode mate-
rials in DSSCs where explicit structural and morphology de-
termines the photoconversion efficiency of the cell (literature
on ZnO–TiO2 architectures used in DSSC is summarized in
detail in Supporting Information, Table S2).[25,26]
.
Herein, we report the synthesis of a novel ZnO–TiO2 het-
erojunction of solid nanospheres decorated with different
percentages of ZnO. The solid nanospheres are synthesized
by an environmentally friendly and facile route. These meso-
porous structures are comprised of polydisperse aggregates
of both oxides, and possess type-II heterojunctions. The
ZnO–TiO2 heterojunction architecture can separate electrons
and holes and provide more electron-trapping sites. The
high-specific-surface-area solid nanospheres used as photoa-
node material in the DSSC can trap more light by facilitating
a higher number of sites for dye attachment. In addition,
these heterojunctions have potential to show increment in
the electron trapping, as a result, charge recombination is
Agile nanostructure architectures and smart combinations of
semiconducting metal oxide materials are key features of
high-performing dye-sensitized solar cells (DSSCs). Herein,
we synthesize mesoporous solid nanospheres of ZnO–TiO2
with type-II heterojunction and use these as an efficient pho-
toanode material for excellent photoconversion. These poly-
disperse aggregates doped with 1%, 5%, and 10% of ZnO
exhibit improved solar cell performance with respect to pris-
tine TiO2 under AM 1.5 G. The 1% ZnO doped TiO2 nano-
sphere possess high specific surface area (84.23 m2
g@1
) as
a photoanode and shows high photoconversion efficiency of
about 8.07% with ca. 18% improvement in the photocurrent
density (Jsc) compare to TiO2 nanosphere. The improved
solar cell performance (Dh=40%) of ZnO decorated TiO2
nanospheres is ascribed to type-II heterojunction of ZnO–
TiO2, that reduces the electron recombination and synergisti-
cally enhances the electron mobility and charge collection
capability.
[a] K. P. Shejale, D. Laishram, Dr. R. Gupta, Dr. R. K. Sharma
Department of Chemistry
Indian Institute of Technology Jodhpur
Jodhpur, Rajasthan 342011 (India)
E-mail: ritu@iitj.ac.in
rks@iitj.ac.in
Supporting Information for this article can be found under http://
dx.doi.org/10.1002/ente.201600357.
Energy Technol. 2017, 5, 489 – 494 T 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 489
2. suppressed and the performance of the DSSC is greatly en-
hanced.
Results and Discussion
The 0, 1, 5, and 10% ZnO doped TiO2 solid nanospheres
were synthesized by a solvothermal crystallization reaction.
Firstly, TiO2 precursor beads were synthesized by hydrolysis
of titanium tetra-isopropoxide followed by addition of differ-
ent amount of zinc acetate dihydrate-precursor during the
solvothermal reaction, resulting in a hybrid nanostructure of
ZnO–TiO2 solid nanospheres. In X-ray diffraction (XRD)
analysis (shown in Figure 1), all the diffraction peaks corre-
late with anatase-phase TiO2 (Joint Committee on Powder
Diffraction Standards (JCPDS) file 21-1272). However, the
crystallinity of the TiO2 solid nanospheres improves with the
percentage of ZnO, and resulted in a relatively higher peak
intensity.[27]
The average crystalline size for TiO2 solid nano-
spheres was calculated, using the Debye–Scherrer equa-
tion,[28]
as ca. 12 nm, which increased to ca. 22 nm for 10%
ZnO doping as shown in the inset of Figure 1, left.
X-ray photoelectron spectroscopy (XPS) was carried out
to analyze the chemical composition and oxide species of the
ZnO-doped TiO2 solid nanospheres. The full-range spectra
show the presence of Ti2p, O1s, and Zn2p as shown in
Figure 2a and respective binding energy values are summar-
ized in Table 1. The spin–orbit components of Zn2p3/2 and
Zn2p1/2 shows binding energy values at around 1021 and
1044 eV respectively, and the splitting of 23 eV indicates that
zinc ions exist mainly as Zn2+
due to the formation of ZnO
(Figure 2b).[29,30]
The intensity of the Zn2p peak increases up
on increasing ZnO %, however, the peak position of Zn2p
exhibits a notable shift by ca. 0.5 eV towards higher binding
energy (BE) value upon introduction of ZnO. This clearly in-
dicates that Zn2+
persists more in the solid nanosphere lat-
tice rather than undergoing phase separation. The Ti2p spec-
tra are similar to typical Ti4+
in the form of TiO2.[31]
The
effect of ZnO on the Ti2p spectrum is visible by the shifting
of the Ti2p peak by 0.2 eV to lower BE values, as shown in
Figure 2c. The cause of this BE difference may be the inter-
face between ZnO and TiO2 nanoparticles. The broadness of
the O1s spectra (Figure 2d) indicates the presence of several
types of oxygen species, with O2@
appearing at 530 eV and
OH@
species at 531 eV. In all samples, the Zn/Ti atomic ratio
was less than 1 (Table 1), which suggests a random distribu-
tion of ZnO all over the TiO2 solid nanospheres.[32]
The O1s
peak of ZnO–TiO2 solid nanosphere shifts due to Zn@O@Ti
complex bond formation at the interface.
Figure 3 shows the influence of the amount of ZnO (wt%)
on the structure and surface morphology of TiO2 solid nano-
spheres. The field-emission scanning electron microscopy
(FESEM) images in Figure 3a–d illustrate the porous nature
of these nanostructures, formed by the aggregation of the
nanocrystallites of TiO2 and ZnO. The porosity is greatly in-
fluenced by ZnO doping. With increasing amounts of ZnO,
the TiO2 solid nanospheres begin to disintegrate, with a de-
crease in average sphere size from 600:20 to 200:30 nm.
The detailed structure of the solid nanospheres was investi-
gated by transmission electron microscopy (TEM) images as
shown in Figure 3e–h. Interestingly, the solid spheres are no
longer packed with monodisperse nanocrystallites, however,
these consist of polydisperse aggregates. Moreover, there is
a gradual increase in crystallite size of TiO2 with increasing
Figure 1. XRD patterns of the TiO2 doped with ZnO of varying weight percent-
age (0%, 1%, 5% and 10%). The inset on right side shows the respective
(101) peak used for fitting and particle size calculation.
Figure 2. a) Full range XPS survey spectra, high resolution spectra of
b) Zn2p, c) Ti2p and d) O1s of TiO2 solid nanospheres with different ZnO
doping.
Table 1. The surface analysis parameters and atomic ratios calculated
from XPS spectra.
Amount of ZnO
in TiO2 [%]
Binding energy [eV] at%
Zn Zn Ti Ti O1s O1s Zn/Ti
2p3/2 2p1/2 2p3/2 2p1/2 (O2@
) (OH@
)
0 – – 458.6 464.4 530 532.2 –
1 1022.1 1045.2 458.6 464.4 530 530 0.04
5 1021.6 1044.8 458.4 464.2 529.7 531.8 0.14
10 1021.5 1044.7 458.4 464.2 529.6 531.7 0.2
Energy Technol. 2017, 5, 489 – 494 T 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 490
3. ZnO resulting in smaller pores at the surface of the solid
sphere.
A typical TEM image of 5% ZnO in TiO2 sample was
chosen for detailed TEM studies as shown in Figure 4a. The
HRTEM image (Figure 4b) is taken from a selected area
marked in Figure 4a which shows lattice planes with two dif-
ferent d-spacings. The d-spacing of 0.35 nm corresponds to
(101) anatase TiO2 while the other value of 0.26 nm matches
well with the (002) wurtzite structure of ZnO.
No transitional layer was found at the interface between
the ZnO and TiO2 and the distinct boundary of nanocrystals,
which indicates that these solid nanospheres are a mix of
both nanostructures. In the electron diffraction (ED) pattern,
only anatase TiO2 is visible (Figure 4c) and ZnO is absent
due to the lower weight percentage of ZnO. Figure 4d–f con-
firms the compositional homogeneity of the solid nano-
spheres by the random distribution of elements Ti, Zn, and
O. Electron dispersive X-ray (EDX) spectra are shown in
Figure S1 (Supporting Information) and the elemental distri-
bution is summarized by bargraph in Figure 4g. The atomic
percentage of zinc gradually increases from 0 to 3.09%, with
increasing amounts of ZnO doping. The mismatch between
doping amount and atomic percentage controls the growth
behavior of ZnO/TiO2 solid nanosphere.[33]
The zinc ions
have a tendency to segregate into anatase TiO2 crystal lattice
only if their doping concentration (atomic) is <0.1%. This is
a result of a significant difference in charge and atomic prop-
erties between titanium and zinc ions which apparently hin-
ders the incorporation of Zn ions into TiO2 lattice. This leads
to a mismatch between the actual weight percentage and pre-
cursor doping percentage resulting in the heterojunction
crystallite formation of ZnO–TiO2 solid nanospheres.[34]
The adsorption–desorption isotherms of the ZnO-doped
TiO2 solid nanosphere are shown in Figure 5a. The shape of
the curve corresponds to a type-IV isotherm which is charac-
teristic of the mesoporous structure and the observed hyste-
resis suggests the presence of small pores, as observed loops
were not shifted to a high relative pressure.[35]
The specific
surface area obtained from Brunauer–Emmett–Teller (BET)
analysis shows a gradual but linear decrease from
95.23 m2
g@1
to 63 m2
g@1
(Figure 5b), however, the overall
surface area is still higher in comparison to P25
(51 m2
g@1
).[36]
The average pore size was calculated by Bar-
rett–Joyner–Halenda (BJH) analysis for different doping per-
centages and their distribution is shown in the inset of Fig-
ure 5a. Most interestingly, the average pore volume increases
for 1% doping of ZnO in TiO2 while it decremented step-
wise at higher doping levels. This deviation from a decreasing
trend is observed because the size of the pores formed in the
TiO2 solid nanospheres are about the size of the ZnO aggre-
gates.[37]
The average pore size decreases on increasing ZnO
content beyond 1%. This may be due to the bigger grain size
for higher ZnO percentages, as shown by the TEM images in
Figure 3. The UV-vis diffuse reflectance spectra in the wide
spectral range of 250–700 nm for TiO2 solid nanospheres
with different ZnO% are shown in Figure S2 (Supporting In-
formation). The spectra show a decrease in reflectance upon
increasing ZnO%. The decrease in reflectance is slightly
higher (DR~2%) for 1% doped ZnO as compared to 5%
and 10% doped ZnO-TiO2 samples, resulting in enhance-
ment in light scattering for 1% ZnO. The 1% ZnO/TiO2
solid nanospheres scatter visible light more efficiently as
compared to the TiO2 nanospheres alone because the aver-
Figure 3. a–d) FESEM images and e–h) TEM images of TiO2 solid nanosphere doped with ZnO of 0%, 1%, 5% and 10% by weight respectively.
Figure 4. a) TEM image, b) HRTEM image and c) ED pattern of TiO2 solid
nanosphere with 5% ZnO doping. d–f) EDS maps of Ti K (red), Zn K
(yellow) and O K (green). g) Bar graph displaying atomic percentages for dif-
ferent ZnO doping levels.
Energy Technol. 2017, 5, 489 – 494 T 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 491
4. age size is of the order of the wavelength of light. The dense-
ly packed solid nanospheres of both oxides can result in mul-
tiple scattering of light owing to their random distribu-
tion.[38,39]
The ZnO-doped TiO2 solid nanosphere films were used as
photoanode layer in DSSCs fabricated as detailed in the Ex-
perimental Section.[40]
The ZnO-doped TiO2 solid nano-
sphere material was screen printed in the form of a paste
and annealed resulting in a photoanode with thickness of ca.
15 mm. The current density versus voltage (J–V) curves for
DSSC devices fabricated using TiO2 doped with ZnO of
varying weight percentages are shown in Figure 6a. The per-
formance parameters along with the dye loading amount on
various photoanodes are summarized in Table 2. The effect
of ZnO on the photovoltaic properties of TiO2 can be quanti-
tatively shown by the bar graph in Figure 6b. The 1% ZnO
cell shows the highest Jsc up to 18.96 mAcm@2
compared to
14.88, 15.63, and 15.22 mAcm@2
for 0%, 5% and 10%
doped cells. As the 1% showed maximum efficiency, we con-
sidered it important to examine the efficiencies of solar cells
with ZnO between 1% and 5%. The 2% and 3% ZnO-
doped TiO2-based DSSC exhibited JSC of 17.73, and
16.22 mAcm@2
respectively (see Supporting Information, Fig-
ure S5) which is expected and in accordance with the trend
as shown in Figure 6. The enhancement in photocurrent den-
sity for 1% ZnO–TiO2-based DSSCs increases the overall ef-
ficiency. Usually, a high photocurrent is an evidence of better
dye loading. This predominatly increases the light-harvesting
capability of the ZnO–TiO2-based photoanode material.[41]
The dye loading capability of the photoanode was deter-
mined by the dye desorption using 10 mM NaOH solution,
and the amount was calculated from the absorbance spectra
shown in Figure S3 (Supporting Information). On ZnO
doping, the increase in dye loading was lower (~21%) than
the expected value based on efficiency (Dh~40%), however,
the light harvesting capability is improved, which improves
the overall efficiency.
Figure 5. a) N2 adsorption-desorption BET isotherm of TiO2 solid nano-
spheres with different ZnO doping. b) Effect of varying ZnO doping level on
surface area and average pore size.
Figure 6. a) J–V characteristics of DSSC with photoanode based on TiO2 solid nanospheres with different ZnO doping. b) Bar graph displaying photovoltaic pa-
rameters obtained for different DSSC devices fabricated by varying the ZnO doping levels. c) Nyquist plots and equivalent circuit (inset) of ZnO-TiO2 solid
nanosphere with various percentages of ZnO as photoanode in DSSC.
Table 2. Photovoltaic properties of dye-sensitized solar cells based on
ZnO-doped TiO2 solid nanospheres.[a]
Amount of ZnO
in TiO2 [%]
Average pore
size [nm]
N719 dye loading
[nMcm@2
]
JSC
[mAcm@2
]
VOC
[V]
FF
[%]
h
[%]
0 0.55 2.52 14.88 0.68 56 5.78
1 0.57 3.2 18.96 0.70 60 8.07
5 0.46 2.65 15.63 0.71 64 7.11
10 0.38 2.64 15.22 0.74 60 6.68
[a] Jsc, Voc, FF, and h are the short-circuit photocurrent density, open-circuit
potential, fill factor, and photoconversion efficiency, respectively. The solar
cell measurements were carried out under 1 sun illumination.
Energy Technol. 2017, 5, 489 – 494 T 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 492
5. The electron transport in ZnO-doped TiO2 seems to be fa-
vorable, as seen from the lower electrode resistance (Fig-
ure 6c) and increase in the electron carrier density up to
47% with increasing ZnO% (summarized in the Supporting
Information, Table S1). The charge resistance at their inter-
face (Rct) increases with increasing ZnO, however the value
for 1% ZnO is comparatively minimal (~13.88 W) as derived
from the second semicircle and by fitting a Nyquist plot with
equivalent circuit as shown in Figure 6c. Because the con-
duction band of ZnO formed by the s orbital provides a sig-
nificantly smaller me (effective electron mass) compared to
the higher me corresponding to the d orbital of TiO2 conduc-
tion band, ZnO-doped TiO2 has more electron mobility than
TiO2.[20–23,42]
The enhancement in electron transport (ca.
32%) as shown in Table S1 (Supporting Information) im-
proves the photocurrent density, along with photovoltage
and fill factor, resulting in an increase in the photoconversion
efficiency of the DSSC device. For ZnO% <1 the photocur-
rent density is relatively lower, which can be attributed to
the difference in crystallite size up to 10 nm and lower pore
size of the nanosphere as shown in Table 2. This also reveals
the reduced anchoring sites for N719 dye molecules, further
inhibiting the photocurrent density in 5% and 10% nano-
spheres. Although both photocurrent density and efficiency
deteriorated at higher doping percentage, the open-circuit
voltage clearly shows enhancement up to 0.74 V (shown in
Figure 6b). The higher open circuit voltage is the result of
a lower recombination rate at electrolyte interfaces. Both
ZnO and TiO2 exhibit similar band structures, as shown in
the Supporting Information, Figure S4. The incorporation of
ZnO in TiO2 makes energy at conduction band (Ecb) of ZnO
more prominent, which easily transfers electrons to the Ecb
of TiO2 rather than the electrolyte species.[42]
The path length
is lowered at an optimized doping of 1% ZnO that further
reduces the recombination rate at the electrolyte.
Conclusions
A polydisperse aggregate structure of ZnO–TiO2 nano-
spheres is demonstrated to be an excellent photoanode mate-
rial. The anatase TiO2 solid nanospheres decorated with dif-
ferent percentages of ZnO are synthesized by a hydrated-
salt-assisted hydrothermal method. The aggregate structure
leads to good light-scattering properties along with a surface
area appropriate for electron trapping. The heterojunction
spheres exhibit higher photocurrent density, up to
18.96 mAcm@2
, which is due to spherical architecture increas-
ing the number anchoring sites for dye molecules with en-
hanced scattering effect. With 1% ZnO, solid nanospheres
the maximum photoconversion efficiency was about 8.07%.
An enhancement of open-circuit voltage was observed for
the ZnO decoration, also. These improvements are attributed
to enhanced electron transport efficiency and lower recombi-
nation with a better light-harvesting structure.
Experimental Section
Synthesis of photoanode material
All chemicals used in this synthesis were procured commercially
and used without further purification. In a typical synthesis of
the ZnO-TiO2 solid nanosphere, 1.97 g of hexadecylamine
(HDA) was added to 200 mL absolute ethanol, 0.8 mL of 0.1 M
KCl, and then the solution was vigorously stirred to dissolve
HDA completely. Next, 4 mL of titanium tetra-isopropoxide
(TTIP) was added dropwise. For doping, 1%, 5%, and 10 wt%
of ZnOTTIP was mixed followed by sonication for 10 min. The
mixture was kept static overnight and then filtered. The filtrate
was washed with distilled water and absolute ethanol several
times followed by drying in air at room temperature to obtain
a powder. A portion of the above powder (0.8 g) was dispersed
in 10 mL absolute ethanol having 0.45 M liquid ammonia and
transferred to a Teflon-lined autoclave (20 mL). It was kept in an
oven at 1808C for 16 h for complete reaction. The filtrate was
collected by washing with distilled water and ethanol and air an-
nealed at 5008C for 2 h.
Fabrication of dye-sensitized solar cells (DSSCs)
All solar cells were fabricated according to a typical procedure
as mentioned in our previous study.[34]
Briefly, ZnO–TiO2 solid
nanospheres and TiO2 (P25) powders were mixed in 4:6 ratio in
the form of a paste and uniformly grinded with ethyl cellulose in
a-terpinol and ethanol (wt% ratio: 2.7:1:3.38). The paste
(25 mg) was screen printed onto the FTO substrates and dried at
1208C for 6 min and repeatedly printed 5 times to increase the
layer thickness. The electrodes were sintered at 4508C for 30 min
in the air resulting in film of ~15 mm thickness. The platinum sol
was deposited onto the FTO counter electrode and then calcined
at 4508C for 30 min. The photoanodes were soaked in 0.5 mM
N719 dye solution for 18 hrs. Finally, the soaked photoanodes
along with platinum counter electrode were assembled using
a Surlyn spacer and Iodolyte Z 50 (Solaronix) as the electrolyte,
resulting in a sandwich structure.
Characterization
Powder X-ray diffraction (Bruker D8 Advance diffractometer
equipped with 1.54 c wavelength Cu Ka radiation) was used for
the structure and phase identification. The morphology was ex-
amined by field emission scanning electron microscopy
(FESEM) and high-resolution transmission electron microscopy
(HRTEM) equipped (Technai G2 T20 ST) with energy-disper-
sive X-ray spectroscopy (Burker X-100). Surface composition
and chemical states were measured with an Omicron nanotech-
nology (Oxford instruments) X-ray photoelectron spectroscopy
(XPS) instrument equipped with monochromatic Al Ka radia-
tion. Specific surface area was analyzed by N2 adsorption–de-
sorption isotherms (Quntachrome autosorb iQ3). The diffuse re-
flectance spectra were investigated using a UV-visible spectro-
photometer (Varian Cary 4000) over a wavelength range of 200–
800 nm. N719 dye loading amount on the photoanode was calcu-
lated by dye desorption from the photoanode which was washed
using 6 mL of 10 mM NaOH in distilled water. The photovoltaic
performance and electrochemical impedance spectroscopy (EIS)
were measured using electrochemical workstation CHI660E-CH
Instruments Inc. PET Photo Emission Tech SS50AAA solar sim-
ulator was used as a light source to get one sun irradiation. Elec-
Energy Technol. 2017, 5, 489 – 494 T 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 493
6. trochemical impedance of the cells was studies in the range of
1 Hz to 0.1 MHz.
Acknowledgements
The authors acknowledge financial support from the Depart-
ment of Science and Technology (SR/FT/CS-144/2011), Govt.
of India, and the Indo-Portuguese Program of Corporation in
Science and Technology (INT/Portugal/PO2/2013). We also
acknowledge the Material Research Centre, MNIT Jaipur,
India for providing TEM Characterization facility.
Keywords: dye-seinsitized solar cells · metal oxides ·
heterojunctions · titania · zinc oxide
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Received: June 8, 2016
Revised: August 1, 2016
Published online on September 6, 2016
Energy Technol. 2017, 5, 489 – 494 T 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 494