1. The document describes a study that developed a procedure to synthesize strontium titanate (SrTiO3) paste as an alternative to titanium dioxide (TiO2) for use in dye-sensitized solar cells (DSSCs). SrTiO3 nanoparticles were successfully synthesized via a vapor diffusion method and characterized.
2. DSSCs were fabricated using the SrTiO3 paste and tested with varying numbers of atomic layer deposition cycles of alumina coating on the SrTiO3. The SrTiO3 DSSCs achieved comparable open circuit voltages to TiO2 DSSCs when coated with two cycles of alumina, demonstrating that alumina coating hinders electron recombination.
3. Additional alumina coating
Thermoluminescence in Pure and Nd+3 + K+ Doped Lead Germanate Single CrystalsAI Publications
Pure lead germanate was grown by Zochralski’stechnique.Nd+3 + K+ doped lead germanate was grown for comparative studies. Thermoluminescence studies were conducted on pure lead germanate and Nd+3 + K+ doped lead germanate. Thermoluminescence in pure lead germanate single crystals (LG) and Nd+3 + K+ doped lead germanate single crystals (DDLG) has been measured in terms of photomultiplier output current on Thermoluminescence Set Up. Thermoluminescence studies of LG revealed an increasing trend of Thermoluminescence output, with increasing temperature and sharp consistent maxima at 50°C and 100°C. TL studies of DDLG revealed a decreasing trend of Thermoluminescence output, with increasing temperature and a sharp consistent peak at 100°C and 120°C. It was further noted that doping increased Thermoluminescence output. Thermoluminescence in ferroelectric lead germanate was attributed to change in polarization with change in temperature and creation of defect states.
Slides of my first invited talk at a conference, the ALD 2005 conference in San Jose 2005, about ALD modelling. ALD is fantastic, but fantastic is not perfect :)
---
R. L. Puurunen, Atomic-scale modelling of atomic layer deposition processes, American Vacuum Society Topical Conference on Atomic Layer Deposition (ALD 2005), San Jose, California, August 8-10, 2005. Invited talk.
Thermoluminescence in Pure and Nd+3 + K+ Doped Lead Germanate Single CrystalsAI Publications
Pure lead germanate was grown by Zochralski’stechnique.Nd+3 + K+ doped lead germanate was grown for comparative studies. Thermoluminescence studies were conducted on pure lead germanate and Nd+3 + K+ doped lead germanate. Thermoluminescence in pure lead germanate single crystals (LG) and Nd+3 + K+ doped lead germanate single crystals (DDLG) has been measured in terms of photomultiplier output current on Thermoluminescence Set Up. Thermoluminescence studies of LG revealed an increasing trend of Thermoluminescence output, with increasing temperature and sharp consistent maxima at 50°C and 100°C. TL studies of DDLG revealed a decreasing trend of Thermoluminescence output, with increasing temperature and a sharp consistent peak at 100°C and 120°C. It was further noted that doping increased Thermoluminescence output. Thermoluminescence in ferroelectric lead germanate was attributed to change in polarization with change in temperature and creation of defect states.
Slides of my first invited talk at a conference, the ALD 2005 conference in San Jose 2005, about ALD modelling. ALD is fantastic, but fantastic is not perfect :)
---
R. L. Puurunen, Atomic-scale modelling of atomic layer deposition processes, American Vacuum Society Topical Conference on Atomic Layer Deposition (ALD 2005), San Jose, California, August 8-10, 2005. Invited talk.
Images and data in the presentation are subject to copyright. Please contact redhwanm(at)mcmaster(dot)ca for permission if you want to use any of its contents.
Newly designed 3D highly ordered macro/mesoporous multifunctional La1–xCexCoO3 nanohybrid frameworks with a 2D hexagonal mesostructure were fabricated via facile meso-molding in a three-dimensionally macroporous perovskite (MTMP) route. The nanohybrid framework exhibited excellent catalytic activity for methane combustion, which derived from the MTMP providing a larger surface area and pore volume, uniform pore sizes, higher accessible surface oxygen concentration, better low-temperature reducibility, and a unique nanovoid 3D structure.
Visit our website, http://www.pcrg.unsw.edu.au , for the latest news, publications, and research from our group.
Growth and Characterization of Barium doped Potassium Hydrogen Phthalate Sing...IJERA Editor
The Non Linear Optical materials have acquired new significance with the advent of a large number of devices
utilizing solid state Laser sources. Potassium Hydrogen Phthalate one of the Non Linear Optical material having
superior non linear optical properties has been exploited for variety of application. In the present work, KHP
single crystals were grown by slow evaporation technique with Barium metal ion as a dopant. The grown
crystals were subjected to powder XRD analysis and the result shows that the Ba2+ ions does not alter the crystal
structure, but it enter into the crystal lattice of pure KHP. The optical transparency of the grown crystal was
studied by UV-Visible spectroscopy, the molecular structure was confirmed by FTIR analysis and its thermal
stability by TG/DTA analysis. The improved SHG efficiency of barium doped Potassium Hydrogen Phthalate
crystal could enhance the nonlinearity behaviour. In addition to this, the electrical parameter such as dielectric
constant was studied in detail.
Au-Pd Supported on 3D Hybrid Strontium-Substituted Lanthanum Manganite Perovs...Hamid Arandiyan
Bimetallic Au–Pd nanoparticles dispersed on a nanohybrid three-dimensionally ordered macroporous (3DOM) perovskite support exhibit a synergy for catalytic methane oxidation. The large support surface area, high Au–Pd dispersion, strong noble metal–support interaction, and an enrichment of adsorbed oxygen species (invoked by the Au inclusion) combine to boost catalytic performance.
Visit our website, http://www.pcrg.unsw.edu.au , for the latest news, publications, and research from our group.
The Controlled Disassembly of Mesostructured Perovskites Hamid Arandiyan
Versatile superstructures composed of nanoparticles have recently been prepared using various disassembly methods. However, little information is known on how the structural disassembly influences the catalytic performance of the materials. Here we show how the disassembly of an ordered porous La0.6Sr0.4MnO3 perovskite array, to give hexapod mesostructured nanoparticles, exposes a new crystal facet which is more active for catalytic methane combustion.
https://www.nature.com/articles/ncomms15553
Visit our website, http://www.pcrg.unsw.edu.au , for the latest news, publications, and research from our group.
Vapor Deposition of Semiconducting Phosphorus Allotropes into TiO2 Nanotube A...Pawan Kumar
Recent evidence of exponential environmental degradation will demand a drastic shift in research and development toward exploiting alternative energy resources such as solar energy. Here, we report the successful low-cost and easily accessible synthesis of hybrid semiconductor@TiO2 nanotube photocatalysts. In order to realize its maximum potential in harvesting photons in the visible-light range, TiO2 nanotubes have been loaded with earth-abundant, low-band-gap fibrous red and black phosphorus (P). Scanning electron microscopy– and scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron microscopy, and UV–vis measurements have been performed, substantiating the deposition of fibrous red and black P on top and inside the cavities of 100-μm-long electrochemically fabricated nanotubes. The nanotubular morphology of titania and a vapor-transport technique are utilized to form heterojunctions of P and TiO2. Compared to pristine anatase 3.2 eV TiO2 nanotubes, the creation of heterojunctions in the hybrid material resulted in 1.5–2.1 eV photoelectrocatalysts. An enhanced photoelectrochemical water-splitting performance under visible light compared with the individual components resulted for the P@TiO2 hybrids. This feature is due to synergistically improved charge separation in the heterojunction and more effective visible-light absorption. The electronic band structure and charge-carrier dynamics are investigated in detail using ultraviolet photoelectron spectroscopy and Kelvin probe force microscopy to elucidate the charge-separation mechanism. A Fermi-level alignment in P@TiO2 heterojunctions leads to a more reductive flat-band potential and a deeper valence band compared to pristine P and thus facilitates a better water-splitting performance. Our results demonstrate effective conversion efficiencies for the nanostructured hybrids, which may enable future applications in optoelectronic applications such as photodetectors, photovoltaics, photoelectrochemical catalysts, and sensors.
Synthesis Of Nanostructured TiO2 Thin Films By Pulsed Laser Deposition (PLD) ...sarmad
Sarmad Sabih Al-Obaidi
Ali Ahmed Yousif
Abstract
In this work, nanostructured TiO2 thin films were grown by pulsed laser deposition (PLD) technique on glass substrates. TiO2 thin films then were annealed at 400-600 °C in air for a period of 2 hours. Effect of annealing on the structural and morphological were studied. Many growth parameters have been considered to specify the optimum conditions, namely substrate temperature (300 °C), oxygen pressure (10-2 Torr), laser fluence energy density (0.4 J/cm2), using double frequency Q-switching Nd:YAG laser beam (wavelength 532nm), repetition rate (1-6 Hz) and the pulse duration of 10 ns. The results of the X-ray test show that all nanostructures tetragonal are polycrystalline. These results show that grain size increase from 19.5 nm to 29.5 with the increase of annealing temperature. The XRD results also reveal that the deposited thin film, annealed at 400 °C of TiO2 have anatase phase. Thin films annealed at 500 °C and 600 °C have mixed anatase and rutile phases. Full Width at Half Maximum (FWHM) values of the (101) peaks of these films decrease from 0.450° to 0.301° with the increase of annealing temperature. Surface morphology of the thin films have been studied by using atomic force microscopes (AFM). AFM measurements confirmed that the films have good crystalline and homogeneous surface. The Root Mean Square (RMS) value of thin films surface roughness are increased with the increase of annealing temperature.
الخلاصة
على (PLD) النانویة بوساطة تقنیة ترسیب اللیزر النبضي (TiO في ھذا البحث، تم انماء أغشیة اوكسید التیتانیوم ( 2
الرقیقة من 400 الى 600 درجة مئویة في الھواء مدة ساعتین . ودرس تأثیر TiO قواعد زجاجیة. ومن ثم لدنت أغشیة 2
التلدین في الخصائص التركیبیة والطبوغرافیة. عوامل عدیدة لأنماء الأغشیة اخذت بنظر الاعتبار لتحدید الحالة المثلى مثل
0.4 ) باستخدام J/cm 10-2 ) ،كثافة طاقة الفیض اللیزري( 2 Torr) 300 ) ،ضغط الأوكسجین ºC) درجة حرارة القاعدة
532 بمعدل تكراریة - 1 nm التردد المضاعف للیزر النیدیمیوم- یاك الذي یعمل بتقنیة عامل النوعیة عند الطول الموجي
6 ھرتز) وامد نبضة 10 نانوثانیة. تظُھر نتائج فحوصات الأشعة السینیة أن جمیع التراكیب النانویة رباعیة متعددة )
التبلور. وان ھذه النتائج تظھر زیادة في حجم الحبیبات من 19.5 نانومتر الى 29.5 نانومترمع زیادة درجة حرارة التلدین.
نتائج الأشعة السینیة اظھرت ایضا ان الغشاء المرسب والملدن في 400 درجة مئویة لثنائي اوكسید
Effect of Annealing on the Structural and Optical Properties of Nanostr...sarmad
Effect of Annealing on the Structural and Optical Properties of Nanostructured TiO2 Films Prepared By PLD. تأثير التلدين على الخواص التركيبية والبصرية لأغشية أوكسيد التيتانيوم (TiO2) ذات التراكيب النانوية المحضرة بتقنية ترسيب الليزر النبضي (PLD)
Synthesis, characterization and electrocatalytic activity of silver nanorods ...kutty79
This paper describes a simple method of synthesizing silver nanorods using the polyol process, where propylene glycol serves both as a reducing
agent and as a solvent in the presence of a capping reagent such as polyvinylpyrrolidone (PVP). The diameter and length of silver nanorods could be
controlled by changing the AgNO3/PVP ratio. The end-to-end assembly of the silver nanorods was found. The silver nanorods were characterized by
using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and absorption spectroscopy. The catalytic activity of a
glassy carbon electrode with Ag nanorods exhibits extraordinary electrocatalytic activities towards the electro-reduction of benzyl chloride.
Images and data in the presentation are subject to copyright. Please contact redhwanm(at)mcmaster(dot)ca for permission if you want to use any of its contents.
Newly designed 3D highly ordered macro/mesoporous multifunctional La1–xCexCoO3 nanohybrid frameworks with a 2D hexagonal mesostructure were fabricated via facile meso-molding in a three-dimensionally macroporous perovskite (MTMP) route. The nanohybrid framework exhibited excellent catalytic activity for methane combustion, which derived from the MTMP providing a larger surface area and pore volume, uniform pore sizes, higher accessible surface oxygen concentration, better low-temperature reducibility, and a unique nanovoid 3D structure.
Visit our website, http://www.pcrg.unsw.edu.au , for the latest news, publications, and research from our group.
Growth and Characterization of Barium doped Potassium Hydrogen Phthalate Sing...IJERA Editor
The Non Linear Optical materials have acquired new significance with the advent of a large number of devices
utilizing solid state Laser sources. Potassium Hydrogen Phthalate one of the Non Linear Optical material having
superior non linear optical properties has been exploited for variety of application. In the present work, KHP
single crystals were grown by slow evaporation technique with Barium metal ion as a dopant. The grown
crystals were subjected to powder XRD analysis and the result shows that the Ba2+ ions does not alter the crystal
structure, but it enter into the crystal lattice of pure KHP. The optical transparency of the grown crystal was
studied by UV-Visible spectroscopy, the molecular structure was confirmed by FTIR analysis and its thermal
stability by TG/DTA analysis. The improved SHG efficiency of barium doped Potassium Hydrogen Phthalate
crystal could enhance the nonlinearity behaviour. In addition to this, the electrical parameter such as dielectric
constant was studied in detail.
Au-Pd Supported on 3D Hybrid Strontium-Substituted Lanthanum Manganite Perovs...Hamid Arandiyan
Bimetallic Au–Pd nanoparticles dispersed on a nanohybrid three-dimensionally ordered macroporous (3DOM) perovskite support exhibit a synergy for catalytic methane oxidation. The large support surface area, high Au–Pd dispersion, strong noble metal–support interaction, and an enrichment of adsorbed oxygen species (invoked by the Au inclusion) combine to boost catalytic performance.
Visit our website, http://www.pcrg.unsw.edu.au , for the latest news, publications, and research from our group.
The Controlled Disassembly of Mesostructured Perovskites Hamid Arandiyan
Versatile superstructures composed of nanoparticles have recently been prepared using various disassembly methods. However, little information is known on how the structural disassembly influences the catalytic performance of the materials. Here we show how the disassembly of an ordered porous La0.6Sr0.4MnO3 perovskite array, to give hexapod mesostructured nanoparticles, exposes a new crystal facet which is more active for catalytic methane combustion.
https://www.nature.com/articles/ncomms15553
Visit our website, http://www.pcrg.unsw.edu.au , for the latest news, publications, and research from our group.
Vapor Deposition of Semiconducting Phosphorus Allotropes into TiO2 Nanotube A...Pawan Kumar
Recent evidence of exponential environmental degradation will demand a drastic shift in research and development toward exploiting alternative energy resources such as solar energy. Here, we report the successful low-cost and easily accessible synthesis of hybrid semiconductor@TiO2 nanotube photocatalysts. In order to realize its maximum potential in harvesting photons in the visible-light range, TiO2 nanotubes have been loaded with earth-abundant, low-band-gap fibrous red and black phosphorus (P). Scanning electron microscopy– and scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron microscopy, and UV–vis measurements have been performed, substantiating the deposition of fibrous red and black P on top and inside the cavities of 100-μm-long electrochemically fabricated nanotubes. The nanotubular morphology of titania and a vapor-transport technique are utilized to form heterojunctions of P and TiO2. Compared to pristine anatase 3.2 eV TiO2 nanotubes, the creation of heterojunctions in the hybrid material resulted in 1.5–2.1 eV photoelectrocatalysts. An enhanced photoelectrochemical water-splitting performance under visible light compared with the individual components resulted for the P@TiO2 hybrids. This feature is due to synergistically improved charge separation in the heterojunction and more effective visible-light absorption. The electronic band structure and charge-carrier dynamics are investigated in detail using ultraviolet photoelectron spectroscopy and Kelvin probe force microscopy to elucidate the charge-separation mechanism. A Fermi-level alignment in P@TiO2 heterojunctions leads to a more reductive flat-band potential and a deeper valence band compared to pristine P and thus facilitates a better water-splitting performance. Our results demonstrate effective conversion efficiencies for the nanostructured hybrids, which may enable future applications in optoelectronic applications such as photodetectors, photovoltaics, photoelectrochemical catalysts, and sensors.
Synthesis Of Nanostructured TiO2 Thin Films By Pulsed Laser Deposition (PLD) ...sarmad
Sarmad Sabih Al-Obaidi
Ali Ahmed Yousif
Abstract
In this work, nanostructured TiO2 thin films were grown by pulsed laser deposition (PLD) technique on glass substrates. TiO2 thin films then were annealed at 400-600 °C in air for a period of 2 hours. Effect of annealing on the structural and morphological were studied. Many growth parameters have been considered to specify the optimum conditions, namely substrate temperature (300 °C), oxygen pressure (10-2 Torr), laser fluence energy density (0.4 J/cm2), using double frequency Q-switching Nd:YAG laser beam (wavelength 532nm), repetition rate (1-6 Hz) and the pulse duration of 10 ns. The results of the X-ray test show that all nanostructures tetragonal are polycrystalline. These results show that grain size increase from 19.5 nm to 29.5 with the increase of annealing temperature. The XRD results also reveal that the deposited thin film, annealed at 400 °C of TiO2 have anatase phase. Thin films annealed at 500 °C and 600 °C have mixed anatase and rutile phases. Full Width at Half Maximum (FWHM) values of the (101) peaks of these films decrease from 0.450° to 0.301° with the increase of annealing temperature. Surface morphology of the thin films have been studied by using atomic force microscopes (AFM). AFM measurements confirmed that the films have good crystalline and homogeneous surface. The Root Mean Square (RMS) value of thin films surface roughness are increased with the increase of annealing temperature.
الخلاصة
على (PLD) النانویة بوساطة تقنیة ترسیب اللیزر النبضي (TiO في ھذا البحث، تم انماء أغشیة اوكسید التیتانیوم ( 2
الرقیقة من 400 الى 600 درجة مئویة في الھواء مدة ساعتین . ودرس تأثیر TiO قواعد زجاجیة. ومن ثم لدنت أغشیة 2
التلدین في الخصائص التركیبیة والطبوغرافیة. عوامل عدیدة لأنماء الأغشیة اخذت بنظر الاعتبار لتحدید الحالة المثلى مثل
0.4 ) باستخدام J/cm 10-2 ) ،كثافة طاقة الفیض اللیزري( 2 Torr) 300 ) ،ضغط الأوكسجین ºC) درجة حرارة القاعدة
532 بمعدل تكراریة - 1 nm التردد المضاعف للیزر النیدیمیوم- یاك الذي یعمل بتقنیة عامل النوعیة عند الطول الموجي
6 ھرتز) وامد نبضة 10 نانوثانیة. تظُھر نتائج فحوصات الأشعة السینیة أن جمیع التراكیب النانویة رباعیة متعددة )
التبلور. وان ھذه النتائج تظھر زیادة في حجم الحبیبات من 19.5 نانومتر الى 29.5 نانومترمع زیادة درجة حرارة التلدین.
نتائج الأشعة السینیة اظھرت ایضا ان الغشاء المرسب والملدن في 400 درجة مئویة لثنائي اوكسید
Effect of Annealing on the Structural and Optical Properties of Nanostr...sarmad
Effect of Annealing on the Structural and Optical Properties of Nanostructured TiO2 Films Prepared By PLD. تأثير التلدين على الخواص التركيبية والبصرية لأغشية أوكسيد التيتانيوم (TiO2) ذات التراكيب النانوية المحضرة بتقنية ترسيب الليزر النبضي (PLD)
Synthesis, characterization and electrocatalytic activity of silver nanorods ...kutty79
This paper describes a simple method of synthesizing silver nanorods using the polyol process, where propylene glycol serves both as a reducing
agent and as a solvent in the presence of a capping reagent such as polyvinylpyrrolidone (PVP). The diameter and length of silver nanorods could be
controlled by changing the AgNO3/PVP ratio. The end-to-end assembly of the silver nanorods was found. The silver nanorods were characterized by
using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and absorption spectroscopy. The catalytic activity of a
glassy carbon electrode with Ag nanorods exhibits extraordinary electrocatalytic activities towards the electro-reduction of benzyl chloride.
Fabrication of high performance gas sensors from ultrathin films of platinum ...MarkMcCrystall
I completed my final year project with Professor Georg Duesberg's group at the Universität der Bundeswehr, München. I successfully fabricated simple chemoresistive gas sensors from thin films of platinum diselenide and demonstrated their sensitivity to both nitrogen dioxide and ammonia.
Synthesis and Characterization of Silica-Nickel Nanocomposite through sol-gel...IJRES Journal
The optimum combination of experimental variables- temperature, time of heat treatment under nitrogen atmosphere and amount of Ni-salt was delineated to find the maximum yield of nanophase Ni in the silica gel matrix. The size of Ni in the silica gel was found in the range 35 and 61nm. In the last two decades synthesis, characterization and understanding a material with lower dimensions have become the most interesting area of research due to their novel properties and potential applications in different fields. :
Synthesis and Characterization Studies of Solvothermally Synthesized Undoped ...IJERA Editor
Nanocrystalline TiO2 was investigated by solvothermal synthetic method using toluene as a solvent. Titanium tetra isopropoxide (TTIP) was used as a precursor, which was decomposed at high temperature and precipitated in toluene. Subsequently, the solution was thermally treated at 250C for five hours in stainless steel autoclave. Amorphous Nano TiO2 was formed. When these amorphous Nano TiO2 was calcinated to 550 C anatase Nano TiO2 crystalline with particle size <20 nm was formed. These amorphous and anatase phase Nano TiO2 was characterized by Powder X-ray diffraction (PXRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and Photoluminescence (PL) studies and the results were discussed.
A perovskite solar cell is a type of solar cell which includes a perovskite structured compound, most commonly a hybrid organic-inorganic lead or tin halide-based material, as the light-harvesting active layer.
In this work, we synthesized and characterized mesoporous thin fims
of SiO 2 and NiTiO3 structured by a surfactant called Brij58. These fims
were fabricated by the method of dip coating and the best conditions for
well-structured thin fims were investigated as a function of surfactant
concentration and diffrent types of substrates. These fims have been
characterized by X-ray reflctivity which was calculated using the matrix
formalism. We demonstrated that the silicon substrate had a great effct
on the structure and porosity of the fabricated fims for both SiO2 and
NiTiO3. Furthermore, we found that mesoporosity has been increased
as a function of the surfactant concentration in the solution. This experimental procedure allows also to produce NiTiO3 powders which have
been characterized by X-ray diffaction. The XRD coupled to the crystallographic software “Maud”shows that the samples are constituted by 98,
2% NiTiO 3 powders.
— CdTe quantum dots (QDs)/Poly (diallyldimethylammonium chloride) (PDDA) multilayer films (QDMF) have been self-assembled by layer-by-layer (LBL) technique. CdTe quantum dots (QDs) were synthesized by using Te, NaBH 4 , and CdCl 2 as precursors and mercaptopropionic acid (MPA) as stabilizer. The as-prepared composites were characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), UV-vis adsorption spectrum(UV-vis), and Fluorescence spectrum(FS), respectively. It was shown that the self-assembled QDMF in this study could be used as gaseous sensors for detecting organic gases, such as ammonia, acetone, methanol and formaldehyde. The quenching mechanism of CdTe QDs multilayer films by formaldehyde was studied in detail and The detection limit was 10-236ppm.
Octahedral rhenium K4[Re6S8(CN)6] and Cu(OH)2cluster modifiedTiO2for the phot...Pawan Kumar
tOctahedral hexacyano rhenium K4[Re6S8(CN)6] cluster complexes were grafted onto photoactive Cu(OH)2cluster modified TiO2{Cu(OH)2/TiO2} support. The rhenium and copper cluster modified TiO2photocata-lyst combines the advantages of heterogeneous catalyst (facile recovery, recycling ability of the catalyst)with the reactivity, selectivity of the soluble molecular catalyst. The synthesized heterogeneous cata-lyst was found to be highly efficient photoredox catalyst for the reduction of CO2under visible lightirradiation. Methanol was found to be the major liquid product with the formation of hydrogen as a byproduct as determined with GC-FID and GC-TCD, respectively. The methanol yield after 24 h irradiationwas found to be 149 mol/0.1 g cat. for Re-cluster@Cu(OH)2/TiO2photocatalyst that is much higher than35 mol/0.1 g cat. for Cu(OH)2/TiO2and 75 mol/0.1 g cat. for equimolar rhenium cluster in the presenceof triethanolamine (TEOA) as a sacrificial donor. The quantum yields (MeOH) of Re-cluster@Cu(OH)2/TiO2and Cu(OH)2/TiO2were found to be 0.018 and 0.004 mol einstein−1, respectively. These values are muchhigher than those reported for other heterogeneous catalysts for six electron transfer reaction
We'd like to understand how you use our websites in order to improve them. Re...Pawan Kumar
The present work demonstrates for the first time the facile fabrication of TiO2 nanotube arrays (TNTAs) by a fluoride-free solid-state anodization process using LiClO4 containing solid polymeric electrolyte. The resulting nanotubes were tested for photoelectrochemical water splitting. The elimination of liquid electrolytes in electrochemical anodization constitutes a paradigm shift for the formation of nanoporous and nanotubular metal oxides. Our results open a new area of research that uses the distinctive properties of solid polymer electrolytes to achieve targeted doping and nano-morphologies. Characterization of the grown TNTAs indicated solid state anodized TNTAs to consist purely of the anatase phase of titania. The solid-state anodization process provides several advantages over conventional liquid electrolytes such as easy handling and processing, better charge transport, environmentally benign …
2. 2
ABSTRACT
In this study, a procedure to synthesize Strontium Titanate (SrTiO3) paste was developed,
in order to use SrTiO3 as an alternative material to Titanium Dioxide (TiO2) for semiconductor
material for dye-sensitized solar cells (DSSCs). This method yielded a viscous paste that was
able to adhere to the substrate well. Moreover, when thin layers of Alumina is deposited onto a
DSSC photoanode, the back reaction, known as recombination, where injected electrons in the
semiconductor transport back to the dye, becomes hindered. Therefore, it is expected that SrTiO3
treated with Alumina will have a higher open circuit voltage. In this study, we investigate the
effects varying levels of deposited Alumina on SrTiO3 have on DSSC performances. SrTiO3
based DSSCs that were deposited with two cycles of Alumina via Atomic Layer Deposition
techniques achieved a high voltage characteristic, comparable to that of TiO2 based DSSCs.
3. 3
INTRO
Every year, the global demand and usage of energy steadily increases. It is common
knowledge that fossil fuels make up a major portion of the energy source relied on today, despite
several severe drawbacks that include limited availability and a harmful contribution to the
climate change phenomenon. For these reasons, great attention has been placed on the
development of an alternative, clean and economically viable source of renewable energy.
With approximately 1017
Joules of energy striking the Earth’s surface every second, the
sun has the capability to easily provide more than one thousand times the worldwide energy
demand.1
However, harnessing from this vast energy source has proved to be a challenge in
terms of cost-efficiency and power conversion efficiency, preventing solar energy from being a
commercially feasible energy source in comparison to fossil fuels today. One form of solar cell
technology, the dye-sensitized solar cell, is gathering interest in the scientific community for
research and is beneficial due to the fact that dye-sensitized solar cells have low production cost,
are relatively easy to make, as well as a multitude of minor aesthetic characteristics.2,3
As of now, the rigid standard model of dye-sensitized solar cells (DSSCs) incorporates
titanium dioxide (TiO2) as the photoanode material, due to its superior electrical and chemical
properties. Since Gratzel’s contribution to the DSSC research field in the late 20th
century with
the nanocrystalline TiO2 based DSSC, the record for highest efficiency obtained has plateaued to
a little over 12%. While researchers have studied rigorously each independent major component
of the photo-related part of the DSSC for over a decade, the standard model for most optimized
DSSC is still essentially unchanged from Gratzel’s model, indicating a model gridlock and a
necessity to investigate new materials that is compatible with other materials to open up new
research opportunities.2
Although undoubtedly proven to be efficient in its respective function to adsorb dye and
transport electrons, TiO2 as a semiconductor has been nearly optimized, shown by the fact that
alterations to TiO2 based DSSCs haven’t significantly improved efficiency over the last two
decade. Strontium titanate (SrTiO3) has been reported as having similar titanium structural
similarities to anatase, the material most DSSCs use for semiconductors, with an even higher
flatband potential. For this reason, it is expected that SrTiO3 based DSSCs will have an open
circuit voltage comparable to, or even greater than that of TiO2 based DSSCs.4-5
4. 4
METHODOLOGY
Materials: Sr-Ti metal alkoxide precursor solutions for the synthesis of SrTiO3
nanocrystals were supplied by Gelest Inc. Ethyl cellulose (Aldrich) and α-Terpineol 96%
(SAFC/USA) were employed to help produce the viscous quality in the SrTiO3 paste. For the
solar cells, cis-Bis(isothiocyanato) bis(2,2'-bipyridyl-4,4'-dicarboxylato ruthenium(II)(N3) dye
(Dyesol) was employed, as well as Lithium Iodide (Alfa Aesar) and Iodine (Aldrich) were used in
the electrolyte solution.
Fig. 1: The apparatus used consists of a three-neck flask to be used as the reaction
chamber, a rotameter, and a bubbler with 200mL of 0.75M HCl. The arrows depict direction of
N2 gas flow in and out of the system.
Apparatus: The apparatus employed for SrTiO3 nanocrystals synthesis via vapor
diffusion is shown in Fig. 1. This consists of a glass bubbler with 200-mL of 0.75 M HCl
solution, and a 100-mL three-neck flask for the reaction. The setup has been described prior in
literature.6
Basically, the input of the bubbler is connected to an N2 gas source and the output is
connected via glass gas adapter to a stopcock. The three-neck flask has two separate
configurations: configuration 1, for during the vapor diffusion sol-gel (VDSG) reaction, where the
flask has an output stopcock B closed, an opened stopcock A connected to an N2 source, and a
rubber suba septum (C), and configuration 2 (shown in Fig 1.), for precursor injection, where the
flask has output stopcock B open, the N2 stopcock A closed, and the rubber suba septum replaced
with the output stopcock C connected to the bubbler’s gas adapter (also open).
Experimental: For our experiment, Strontium Titanate paste was synthesized through the
Vapor Diffusion Sol-Gel (VDSG) route, explained in literature elsewhere.7
First, N2 gas is
5. 5
bubbled through the HCl solution for approximately 30 minutes while configuration 1 is set up to
create an N2 atmosphere inside the flask. 5 mL of SrTi precursor is transported into the three-neck
flash through the suba septum via syringe. After 30 minutes of bubbling, the reaction flask is
changed to configuration 2. The Nitrogen flow from the bubbler provides continuous N2/HCl/H2O
vapor flow over the precursor solution. This flow is maintained at a vigorous rate for 48 hours, to
obtain off-white colored particles.
Within ten minutes, the precursor started to show visible signs of turning into a solid gel
with folds. After being under N2 flow for roughly 48 hours, dry SrTiO3 particles were
synthesized. This is removed from the flask and crushed using a mortar and pestle to obtain a
more powdery form with greater surface area. The powder is then sonicated in ethanol until
completely dispersed, and centrifuged back out to clean the SrTiO3 and remove impurities; a
process that is repeated thrice.
The paste is once again transported to a round-bottom flask and ethanol is added to
dissolve the paste. α-terpineol and ethyl-cellulose is added while stirring vigorously. The solution
is sonicated for thirty minutes, stirred for ten minutes, and then sonicated/stirred two more times.
The majority of the ethanol is then evaporated off in a rotavap until only a viscous paste remains.
This final paste is stirred for an additional hour, and prepared with a mortar and pestle prior to
usage.
Dye-sensitized solar cells were made with this paste using doctor-blade techniques onto
conductive FTO glass. Traditional dye-sensitized solar cell construction methodology follows: the
films were heat treated at 500°C, and soaked in a solution of N3 dye overnight. Counter
electrodes were made out of conductive FTO by drilling two holes (for injecting electrolyte) and
depositing platinum catalyst via H2PtCl6 solution. The two electrodes were sandwiched together
using a 25 um ionomer Surlyn 1702 (Dupont) film. I3
-
/I-
electrolyte was then injected into the
counter electrode hole to cover the active area. SrTiO3 films were also adapted with various
number of Atomic Layer Deposition cycles of Al with Trimethyl Alumina being used as the
precursor.
Photoelectrochemical measurements were performed with an Autolab PGSTAT
potentiostat interfaced with a Xenon Arc Lamp. An AM 1.5 solar filter was employed to simulate
sunlight at 100 mW cm-2
. Additionally, a 400 nm long-pass filter was used in all light
measurements.
6. 6
RESULTS
Characterization of SrTiO3 paste: To ensure the purity of the SrTiO3 made by this new
procedure and to detect exactly what materials were synthesized, an X-ray diffraction
measurement was taken in the 20°-80° 2θ range. As seen in Fig. 2, the nanoparticles produced
from the reaction have the definitive peaks that correspond to SrTiO3.
Fig. 2: X-ray diffraction patterns for SrTiO3.
The physical characteristics of the SrTiO3 nanoparticles were observed under a Scanning
Electron Microscope (SEM). Fig. 3 shows the SEM images of the nanoparticles, which measured
out to be approximately 15-22nm in diameter.
Fig. 3: SEM pictures of synthesized SrTiO3 nanoparticles after 24 hours of N2 flow (left) vs after
48 hours of N2 flow (right).
7. 7
In this project, it was discovered that high quality SrTiO3 nanoparticles could be
synthesized by vapor diffusion under a slow gas flow of N2, HCl vapor and water vapor. It was
found that when placed under flow for a prolonged time of 48 hours and under a not very
vigorous flow rate that the nanoparticles sizes became both smaller and more consistent, to
around 15-22nm, as can be seen in Fig. 3.
During the synthesis process, the SrTi(OR)6 precursor undergoes a slow reaction to
become SrTi and then form SrTiO3: The slow reaction rate allows the metals to make
homogenous nanostructures by slow diffusion. This reaction and diffusion continues until
homogenous bimetallic oxide nanocrystals are formed.
Optical and electrical properties of SrTiO3 based DSSCs: Transmittance and
reflectance was measured on a UV-VIS spectrometer with an integrated sphere setup and is
shown in Fig. 4. The transmittance of this SrTiO3 paste in the visible range was measured to be
roughly 70%, while the reflectance was under 20% for the 450+ nm wavelengths range. This all
indicates that the film does not inhibit light from reaching the dye.
Fig. 4: Plot of Transmittance and Reflectance for unmodified SrTiO3 films.
When compared to a standard TiO2-based DSSC, SrTiO3 shows photoelectrical
characteristics that are significantly less than TiO2. Key parameters demonstrating this is shown
in Fig. 5. It is notable that although the current density for the SrTiO3 DSSCs was <1% of the
current density of TiO2, the voltage for the former was found to be only about half of that of the
latter.
8. 8
DSSC VOC (V) JSC (A) FF
SrTiO3 -0.300 0.028 45%
TiO2 -0.627 7.320 70%
Fig. 5: Open circuit voltage (VOC), short circuit current (JSC), and fill factor (FF) values for a
SrTiO3 based DSSC and a TiO2 based DSSC are shown. The latter demonstrates superior
characteristics in all regards, especially with current density.
Fig. 6 shows the current density, J, versus applied voltage, V, curves comparing DSSCs
of SrTiO3 film with 2 layers of deposited Alumina versus the DSSCs of SrTiO3 films without
Alumina. In our experiment, the SrTiO3 films were optimized with two atomic layers of
Alumina. As seen in the graph, the short circuit current (JSC) remained relatively unchanged
when adding single atom layers of Alumina, whereas the open circuit (VOC) from the cells
increased because of limited back recombination of electrons from the photoanode to the ground
state dye. But the addition of a third layer of Al led to a significant decrease in JSC, mainly due to
the Alumina blocking electrons from injecting into the photoanode more than it blocked
electrons from recombining back to the dye. The measured JSC values for 0, 1, and 2 layers of Al
gravitate around 0.03A, and the VOC values are consistent, gradually increasing until the VOC
peaks at ~0.54V for 2 layers. Due to the large jump in open circuit voltage from zero to one layer
of Al, as well as the large drop in JSC from two layers to three layers of Al without very
noticeable changes at other major points, it can be deduced that for this particular configuration
of N3 dye, SrTiO3, and I3
-
/I-
electrolyte, 2 ALD cycles of Al deposited on the photoanode yields
optimal electrochemical results in light settings.
9. 9
Fig. 6: Plot of J-V curves measured under AM 1.5 illumination for DSSCs with 0, 1, 2, & 3
atomic layers of Alumina
DSSC
Layers of Al
VOC (V) JSC (A) PMAX
0 -0.300 0.028 0.38
2 -0.546 0.030 0.73
Fig. 7: Table of the Open Circuit Voltages (VOC), Short Circuit Currents (JSC), and Maximum
Output Power (PMAX) values of two solar cells of each varying amount of Al
Fig. 8 shows a plot of multiple dark J-V curves, for the same DSSCs plotted for light J-V
curves in Fig. 6. It is evident from this that the layers of Alumina have an indirect correlation
with the amount of dark current that occurs in the DSSC. For example, when the potential of -0.3
V is applied, the DSSC with 3 layers of Al only has a current density of -0.002, whereas the
DSSC with no Al has a J value of approximately -0.018, signifying more recombination takes
place in this cell. It is reasonable to assume that based on this data, the SrTiO3 solar cells with
deposited Alumina has increased blocking of back electron transfer of injected electrons in
the semiconductor back to the ground state dye. When additional layers of Al were added,
the achieved voltage started to drop again, signifying a possible decrease in initial injection
of electrons into the semiconductor.
10. 10
Fig. 8: Dark J-V curves of the same cells that are plotted in Fig. 7 & 12
As can be seen in Fig. 9, the lifetime of the Alumina added DSSCs demonstrate a longer
lifetime characteristic. When the applied potential is at 0.3V, the DSSC with 0 layers of Al
demonstrated a lifetime characteristic of ~0.1 seconds, less than one tenth the lifetime of the
DSSC with 2 atomic layers of Al at the same applied potential. The increase in lifetime with the
addition of thin layers of Alumina is explained by the reduced rate of injected electrons
transporting back to the ground state dye. It is important to note that excessive additional layers
of Alumina hindered performance with a decreased rate of injection of excited electrons from the
dye to the semiconductor material, cutting current.
11. 11
Fig. 9: Open-circuit voltage decay plot of a DSSC with 0 layers and with 2 layers of Alumina.
CONCLUSION
We have shown the preparation method of SrTiO3 films and the effect of a thin layer of
Aluminum. Although the overall photovoltaic performance of these solar cells was hindered due
to low current, the open circuit voltage is comparable to and very similar to that of TiO2 film
based DSSCs. Furthermore, deposition of Al proved to slow recombination and increase voltage.
12. 12
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