This document describes the large scale photochemical synthesis of M@TiO2 nanocomposites (M = Ag, Pd, Au, Pt) and investigates their optical properties, catalytic activity for CO oxidation, and antibacterial effects. Well-dispersed M@TiO2 nanocomposites with particle diameters of 200-400 nm were synthesized using a clean photochemical method without additives. The sizes of the noble metal nanoparticles formed on the TiO2 support were approximately 1 nm for Pt, 5 nm for Au and Pd, and 2-20 nm for Ag. The nanocomposites exhibited excellent catalytic activity for CO oxidation at low temperatures. Tests also showed the nanocomposites had antibacterial effects against E
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.
PHOTOCATALYTIC DEGRADATION OF RB21 DYE BY TIO2 AND ZNO UNDER NATURAL SUNLIGHT...IAEME Publication
The present work aims to degrade the RB21 dye from synthetic wastewater using
semiconductors TiO2 and ZnO. The activity of photocatalytic degradation process of dye was
carried out using different light sources of 900 W/m
2
intensity in natural sunlight from 02:00 to
04:00 pm with 48°C temperature in Ahmedabad city in the month of May, 600 Watt microwave
oven and high pressure UV-light photocatalytic reactor of wavelength 200-450 nm. All the
experiments were performed with dye concentration 50 mg/L, catalyst dosage 0.8 g, pH 7, room
temperature, irradiation time 240 min followed by 30 min in dark. All the samples were collected at
different time intervals of 30, 60, 90, 120, 150, 180, 210, 240 min for the analysis of COD
degradation and color removal. The best performances was achieved using high pressure UVphotocatalytic
reactor using TiO2. The successful result obtained using TiO2is 80% COD
degradation and 99% color removal followed by 75% COD and 99% color removal with ZnO.
Chemical kinetics was found to follow first order mechanism. The formation of intermediate
compounds and identification of the final products were carried out using LCMS/MS analysis and
FT-IR techniques.
Visible light solar photocatalytic degradation of pulp and paper wastewater u...eSAT Journals
Abstract
With the growing number of industries there are large volumes of wastewater generated every day. Pulp and paper mills are highly polluting as they release effluents containing organic pollutants, and high levels of Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD). Even though well-established processes exist to treat these effluents, there are only a few processes which are energy efficient. Conventional treatment methods are not effective for the degradation of toxic organic pollutants, hence other treatment techniques are necessary. One of the recent developments in this field is the Advanced Oxidation Process (AOP). Solar photocatalysis is a type of AOP which utilises UV light to activate semiconductor photocatalyst in order to produce highly reactive radical species. TiO2 is a widely used catalyst for this purpose, to oxidise or reduce the organic pollutants in industrial wastewater. However, photocatalysis using visible light has been receiving increased attention hence, modification of TiO2 is necessary for its enhanced response to visible light. There are many methods for modifying TiO2, such as doping and photo-sensitisation. This study focusses on the modification of TiO2 using the method of dye-sensitisation (photo-sensitisation) with the dyes rhodamine B and methylene blue. Solar photocatalytic experiments were carried out for the degradation of pulp and paper wastewater, at different conditions like varying catalyst loading (500mg, 600mg, 750mg and 1000mg of catalyst for 300ml of aqueous wastewater) and effluent concentration (20ml, 25ml, 30ml and 35ml of wastewater). Preliminary tests were done to determine the best conditions for photocatalytic degradation, and these were applied for final tests. Keywords - Solar Photocatalysis, Visible Light, Dye Sensitisation, Pulp and paper, Methylene blue, Rhodamine B, TiO2 catalyst.
Abstract— 2, 4-dinitrophenol and 2, 4, 6- trinitrophenol were successfully photodegraded using visible light active monoclinic BiVO4 as photocatalyst. 10ppm of dinitrophenol is photodegraded using 50mg BiVO4 under irradiation for 3h. 10ppm trinitrophenol is photodegraded using 100mg BiVO4 under irradiation for 3h. Ease of photodegradation of DNP and TNP varied in the order DNP > TNP for the same amount of photocatalyst. Photoluminescence studies confirmed the formation of •OH free radicals due to irradiation. Synergetic effect is noticed between BiVO4 and H2O2.
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.
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.
PHOTOCATALYTIC DEGRADATION OF RB21 DYE BY TIO2 AND ZNO UNDER NATURAL SUNLIGHT...IAEME Publication
The present work aims to degrade the RB21 dye from synthetic wastewater using
semiconductors TiO2 and ZnO. The activity of photocatalytic degradation process of dye was
carried out using different light sources of 900 W/m
2
intensity in natural sunlight from 02:00 to
04:00 pm with 48°C temperature in Ahmedabad city in the month of May, 600 Watt microwave
oven and high pressure UV-light photocatalytic reactor of wavelength 200-450 nm. All the
experiments were performed with dye concentration 50 mg/L, catalyst dosage 0.8 g, pH 7, room
temperature, irradiation time 240 min followed by 30 min in dark. All the samples were collected at
different time intervals of 30, 60, 90, 120, 150, 180, 210, 240 min for the analysis of COD
degradation and color removal. The best performances was achieved using high pressure UVphotocatalytic
reactor using TiO2. The successful result obtained using TiO2is 80% COD
degradation and 99% color removal followed by 75% COD and 99% color removal with ZnO.
Chemical kinetics was found to follow first order mechanism. The formation of intermediate
compounds and identification of the final products were carried out using LCMS/MS analysis and
FT-IR techniques.
Visible light solar photocatalytic degradation of pulp and paper wastewater u...eSAT Journals
Abstract
With the growing number of industries there are large volumes of wastewater generated every day. Pulp and paper mills are highly polluting as they release effluents containing organic pollutants, and high levels of Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD). Even though well-established processes exist to treat these effluents, there are only a few processes which are energy efficient. Conventional treatment methods are not effective for the degradation of toxic organic pollutants, hence other treatment techniques are necessary. One of the recent developments in this field is the Advanced Oxidation Process (AOP). Solar photocatalysis is a type of AOP which utilises UV light to activate semiconductor photocatalyst in order to produce highly reactive radical species. TiO2 is a widely used catalyst for this purpose, to oxidise or reduce the organic pollutants in industrial wastewater. However, photocatalysis using visible light has been receiving increased attention hence, modification of TiO2 is necessary for its enhanced response to visible light. There are many methods for modifying TiO2, such as doping and photo-sensitisation. This study focusses on the modification of TiO2 using the method of dye-sensitisation (photo-sensitisation) with the dyes rhodamine B and methylene blue. Solar photocatalytic experiments were carried out for the degradation of pulp and paper wastewater, at different conditions like varying catalyst loading (500mg, 600mg, 750mg and 1000mg of catalyst for 300ml of aqueous wastewater) and effluent concentration (20ml, 25ml, 30ml and 35ml of wastewater). Preliminary tests were done to determine the best conditions for photocatalytic degradation, and these were applied for final tests. Keywords - Solar Photocatalysis, Visible Light, Dye Sensitisation, Pulp and paper, Methylene blue, Rhodamine B, TiO2 catalyst.
Abstract— 2, 4-dinitrophenol and 2, 4, 6- trinitrophenol were successfully photodegraded using visible light active monoclinic BiVO4 as photocatalyst. 10ppm of dinitrophenol is photodegraded using 50mg BiVO4 under irradiation for 3h. 10ppm trinitrophenol is photodegraded using 100mg BiVO4 under irradiation for 3h. Ease of photodegradation of DNP and TNP varied in the order DNP > TNP for the same amount of photocatalyst. Photoluminescence studies confirmed the formation of •OH free radicals due to irradiation. Synergetic effect is noticed between BiVO4 and H2O2.
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.
Preparation, characterization and application of sonochemically doped fe3+ in...eSAT Journals
Abstract In this present study, mechanistic investigation of ultrasound–assisted dye decolorization/degradation was investigated using sonochemically prepared Fe3+ doped ZnO. Fe3+ doped ZnO nanoparticle was prepared under ultrasound (20 kHz) irradiation using a doping concentration of 2 wt% of Fe(III). To investigate the catalytic activity of Fe3+ doped ZnO, Acid Red 14 (azo dye) was chosen for decolorization/degradation using sonolysis, photocatalysis and sono–photocatalysis processes. To study the influence of dopant onto structure, crystallinity, and optical properties, different analytical analyses were performed such as X–ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Zeta potential, Delsa Nano Particle Size Analyzer (PSA), Vibrating Sample Magnetometer analysis (VSM) and Field Emission Scanning Electron Microscopy (FE–SEM) etc. For photocatalytic experiments, a blended high pressure mercury UV lamp with maximum peak emission at 365 nm was used. The decolorization/degradation of dye with modified photocatalyst showed faster reaction kinetics under sono–photocatalytic process. Ultrasound showed an additive effect for degradation/decolorization process. The maximum decolorization of AR14 was achieved (~ 82%) under sono–photocatlytic process with an initial dye concentration of 20 ppm. The sono–photocatalysis process showed 1.4 – 1.6 higher reaction rates with Fe–doped ZnO than pure ZnO. Index Terms: ZnO, Fe–ZnO, Fe-doped ZnO, Sonocatalytic, Photocatalytic, Advanced Oxidation Process, AOP
degradation of pollution and photocatalysisPraveen Vaidya
The presentation deals with the use of conduction of photocatalytic reaction using the transition metal doped transparent semiconducting thinfilms. The precursor to film is prepared by the SILAR method, which is a chemical method.
Photocatalytic application of TiO2/SiO2-based magnetic nanocomposite (Fe3O4@S...Iranian Chemical Society
In this research we have developed a treatment method for textile wastewater by TiO2/SiO2-based magnetic nanocomposite. Textile wastewater includes a large variety of dyes and chemicals and needs treatments. This manuscript presents a facile method for removing dyes from the textile wastewater by using TiO2/SiO2-based nanocomposite (Fe3O4@SiO2/TiO2) under UV irradiation. This magnetic nanocomposite, as photocatalytically active composite, is synthesized via solution method in mild conditions. A large range of cationic, anionic and neutral dyes including: methyl orange, methylene blue, neutral red, bromocresol green and methyl red are used for treatment investigations. Neutral red and bromocresol green have good results in reusing treatment. The high surface area of nanocomposites improve the kinetic of wastewater treatment. In this method, by using the magnetic properties of Fe3O4 nanoparticles, TiO2-based photocatalyst could be separated and reused for 3 times. The efficiency of this method is respectively 100% and 65% for low concentration (10 ppm) and high concentration (50 ppm) of neutral red and bromocrosol green after 3 h treatment. The efficiency of treatment using the second used nanocomposite was 90% for 10 ppm of the same dyes.
Synthesis and Characterization of MOF based Composites for Energy storage app...Danyal Hakeem Jokhio
Despite extensive efforts and research put in the field, conventional energy storage devices (ESDs) such as various supercapacitors and batteries are near their performance limit in terms of power densities, energy densities, capacitance, charge retention, and cyclic stability. This is primarily due to limiting intrinsic properties of the electrode materials such as average surface area and poor porosity, combined with sluggish redox kinetics due to lack of electrode functionality. So, the need of the hour is to explore new materials for efficient storage of the energy. Among these new materials, metal-organic frameworks (MOFs) can serve as potential candidates because they have high specific surface area, high porosity with tuneable morphology and hence tuneable pore size, functionality linking to active metal sites and ligands. However, there remains a gap in fully utilising MOFs in energy storage applications commercially. Due to the highly porous nature of MOFs, their structural stability is compromised especially in aqueous electrolytes. To utilize the maximum potential of MOFs as electrode materials, it is of utmost importance to address poor structural integrity and low intrinsic conductivity of MOFs.
In this work, it has been tried to overcome the above-mentioned drawbacks of MOFs by using additives of conductive nature such as graphene nanoplatelets (GNP). Hydrothermal approach was used to synthesize hybrid MOF by controlling molar ratio of Nickel and Cobalt in combination with different organic ligands. As a battery-type supercapacitor electrode material, the 2:1 Ni/Co hybrid MOF with 40mg GNP, using terephthalic acid as ligand, delivered a high specific capacity of 658.8 C·g−1 at the current density of 1 A·g−1. Similarly, the 1:2 Ni/Co hybrid MOF, using 2-MethylImidazole as ligand, delivered a high specific capacity of 642.4 C·g−1 at the current density of 1 A·g−1. Moreover, breakthrough results were obtained by optimizing synthesis with in-situ deposition on nickel foam of 2:1 Ni/Co (with 40mg GNP) hybrid MOF, which produced an impressive specific capacity of 1264 C·g−1 at 1 A/g, surpassing, to the best of our knowledge, most of the previously reported MOF based electrode materials.
This work not only develops a high-performance electrode material of supercapacitor, but being the first of its kind in Pakistan, also provides the foundation of systematic research for the electrochemical properties of multi-metal MOFs.
Characterization of Clay/Chitosan Nanocomposites and their Use for Adsorption...Editor IJCATR
In this study, composites films were prepared from Chitosan biopolymer and Montmorillonite nanoclay (MMT) by dispersion of MMT into Chitosan solution with different weight percentage (2.5, 5, 7.5, 10, 12.5, 15 and 75% wt. /wt. nanoclay/chitosan), using both sonication and casting technique methods to obtain good dispersion of nanoclay. The structural properties of these nanocomposites samples examined by XRD and FTIR . The XRD patterns indicating that formation of an intercalated nanostructure as exfoliated and flocculated structure . Also the complexion of the dopant with the biopolymer was examined by FTIR studies. The experiments of Mn(ΙΙ) ions adsorption were carried out on MMT/chitosan nanocomposites. The effect of various parameters such as pH, contact time, adsorption mass, initial Mn(ΙΙ) concentration and temperature on the adsorption of Mn(ΙΙ) removal onto MMT/chitosan nanocomposites was investigated. Two adsorption isotherm models were applied Freundlich and Langmuir to fit the experimental data. Langmuir isotherm modeling was suitable for description the data at equilibrium state. The kinetic isotherm was found to follow the pseudo-second-order model. Also, the thermodynamics parameters of the adsorption such as Gibbs free energy∆G^o, entropy ∆S^o and enthalpy ∆H^o were discussed and the results demonstrate that the adsorption process is spontaneous and endothermic.
2014 polymer activation by reducing agent absorption as a flexible tool for t...Alexandra Bautista
Electroless plating is a powerful wet-chemical method for the fabrication
of metal thin films on arbitrarily shaped substrates [1]. Despite its
relative simplicity just involving the immersion of a work piece in a
deposition solution, electroless plating is suitable for the creation of
macroscopic [1] aswell as intricate nanoscale structures [2–5]. Depending
on the type of substrate and depositedmetal, the obtained materials
can be utilized in various fields, including electronics, wear and corrosion
resistance, medical technology and catalysis [1,6]. The special
properties of electrolessly plated metal nanomaterials give rise to
particularly interesting applications such as molecular separation
[4] or microreactors
PHOTOCATALYTIC DEGRADATION AND REMOVAL OF HEAVY METALS IN PHARMACEUTICAL WAST...Journal For Research
In recent years pharmaceutical wastes (PW) deposal of has become a major difficulty for the environment. Therefore, pharmaceutical waste removal is very necessary before its discharge from the pharma industry. The separation of drugs containing organic compounds in wastewater streams is failed by convectional and biological treatments. Thus, the reduction of harmful effects of pharmaceutical compounds is possible by heterogeneous photocatalysis process. Herein we reported the degradation of pharmaceutical concentration in pharmaceutical waste by heterogeneous photocatalyst ZnO doped with Selenium prepared by cost effective hydrothermal method. In addition the heavy metals in pharmaceutical waste were also removed by ZnO/Se nanocomposite. The average band gap of nanocomposite (~2.5 eV) increase the photocatalytic activity and degrade the organic compounds in pharmaceutical waste. The heavy metals get adsorbed on the high surface area of nanocomposite and removed completely by filtration method. The Selenium doped ZnO photocatalyst semiconductor was characterized by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDAX) and also the characteristic crystalline forms of ZnO/Se nanocomposite was confirmed by XRD. The functional groups and particle size distribution of ZnO/Se nanocomposite was characterized by FTIR and DLS respectively. The reduction of organic compounds in the pharmaceutical waste was confirmed by COD analysis and removal of heavy metals was performed by AAS analysis.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Photochemistry Mediated Synthesis and Characterization of Thyroxine Capped Si...priyanka raviraj
Objective:
Silver nanoparticles (AgNPs) are one of the noble metal nanoparticles studied due to their amenability of synthesis, functionalization and ease of detection. Synthesis of silver nanoparticles using thyroxine as a reducing and capping agent through the one step photochemical method
Characterization of synthesized silver nanoparticles (Thy-AgNPs)
1. UV-Spectroscopy Analysis
2. Fourier Transforms-Infra Red Spectroscopy (FT-IR)
3. High Resolution Transmission Electron Microscopy(HR-TEM)
4. Field Emission Scanning Electron Microscopy(FE-SEM)
5. Dynamic Light Scattering (DLS)
6. Zeta potential
Uses:
*AgNPs have unique optical, electrical, and thermal properties
*Exhibit high plasmon efficiency
*More sensitive towards localized surface plasmon resonance
*Less time consuming, economic and more ecofriendly
*It is used in electronics, food industry, cosmetics, photochemical, biomedicine and chemistry.
التحفيز الضوئي بواسطة أفلام التيتانيوم لتنقية المياه
محاضرة للدكتور حازم فلاح سكيك القاها في المؤتمر الدولي الثاني للعلوم الاساسية والتطبيقة بجامعة الأزهر تتحدث عن تحضير افلام مسامية سميكة من ثاني اكسيد التيتانيوم بطريقة السول جيل لعملية التحفيز الضوئي التي لها تأثير استخدام هام في عملية تنقية الهواء والمياه باستخدام طاقة الضوء ومادة ثاني اكسيد التيتانيوم كمحفز لمزيد من المعلومات
http://www.hazemsakeek.net/magazine/index.php/-1176192324/1494-2011-09-21-10-09-22
Maiyalagan,Electrochemical oxidation of methanol on pt v2 o5–c composite cata...kutty79
Platinum nanoparticles have been supported on V2O5–C composite through the reduction of chloroplatinic
acid with formaldehyde. The catalyst was characterized by X-ray diffraction and transmission electron
microscopy. Catalytic activity and stability for the oxidation of methanol were studied by using
cyclic voltammetry and chronoamperometry. Pt/V2O5–C composite anode catalyst on glassy carbon electrode
show higher electro-catalytic activity for the oxidation of methanol. High electro-catalytic activities
and good stabilities could be attributed to the synergistic effect between Pt and V2O5, avoiding the electrodes
being poisoned.
Maiyalagan,Electro oxidation of methanol on ti o2 nanotube supported platinum...kutty79
TiO2 nanotubes have been synthesized using anodic alumina membrane as template. Highly dispersed
platinum nanoparticles have been supported on the TiO2 nanotube. The supported system
has been characterized by electron microscopy and electrochemical analysis. SEM image shows
that the nanotubes are well aligned and the TEM image shows that the Pt particles are uniformly
distributed over the TiO2 nanotube support. A homogeneous structure in the composite nanomaterials
is indicated by XRD analysis. The electrocatalytic activity ofthe platinum catalyst supported on
TiO2 nanotubes for methanol oxidation is found to be better than that of the standard commercial
E-TEK catalyst.
Preparation, characterization and application of sonochemically doped fe3+ in...eSAT Journals
Abstract In this present study, mechanistic investigation of ultrasound–assisted dye decolorization/degradation was investigated using sonochemically prepared Fe3+ doped ZnO. Fe3+ doped ZnO nanoparticle was prepared under ultrasound (20 kHz) irradiation using a doping concentration of 2 wt% of Fe(III). To investigate the catalytic activity of Fe3+ doped ZnO, Acid Red 14 (azo dye) was chosen for decolorization/degradation using sonolysis, photocatalysis and sono–photocatalysis processes. To study the influence of dopant onto structure, crystallinity, and optical properties, different analytical analyses were performed such as X–ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Zeta potential, Delsa Nano Particle Size Analyzer (PSA), Vibrating Sample Magnetometer analysis (VSM) and Field Emission Scanning Electron Microscopy (FE–SEM) etc. For photocatalytic experiments, a blended high pressure mercury UV lamp with maximum peak emission at 365 nm was used. The decolorization/degradation of dye with modified photocatalyst showed faster reaction kinetics under sono–photocatalytic process. Ultrasound showed an additive effect for degradation/decolorization process. The maximum decolorization of AR14 was achieved (~ 82%) under sono–photocatlytic process with an initial dye concentration of 20 ppm. The sono–photocatalysis process showed 1.4 – 1.6 higher reaction rates with Fe–doped ZnO than pure ZnO. Index Terms: ZnO, Fe–ZnO, Fe-doped ZnO, Sonocatalytic, Photocatalytic, Advanced Oxidation Process, AOP
degradation of pollution and photocatalysisPraveen Vaidya
The presentation deals with the use of conduction of photocatalytic reaction using the transition metal doped transparent semiconducting thinfilms. The precursor to film is prepared by the SILAR method, which is a chemical method.
Photocatalytic application of TiO2/SiO2-based magnetic nanocomposite (Fe3O4@S...Iranian Chemical Society
In this research we have developed a treatment method for textile wastewater by TiO2/SiO2-based magnetic nanocomposite. Textile wastewater includes a large variety of dyes and chemicals and needs treatments. This manuscript presents a facile method for removing dyes from the textile wastewater by using TiO2/SiO2-based nanocomposite (Fe3O4@SiO2/TiO2) under UV irradiation. This magnetic nanocomposite, as photocatalytically active composite, is synthesized via solution method in mild conditions. A large range of cationic, anionic and neutral dyes including: methyl orange, methylene blue, neutral red, bromocresol green and methyl red are used for treatment investigations. Neutral red and bromocresol green have good results in reusing treatment. The high surface area of nanocomposites improve the kinetic of wastewater treatment. In this method, by using the magnetic properties of Fe3O4 nanoparticles, TiO2-based photocatalyst could be separated and reused for 3 times. The efficiency of this method is respectively 100% and 65% for low concentration (10 ppm) and high concentration (50 ppm) of neutral red and bromocrosol green after 3 h treatment. The efficiency of treatment using the second used nanocomposite was 90% for 10 ppm of the same dyes.
Synthesis and Characterization of MOF based Composites for Energy storage app...Danyal Hakeem Jokhio
Despite extensive efforts and research put in the field, conventional energy storage devices (ESDs) such as various supercapacitors and batteries are near their performance limit in terms of power densities, energy densities, capacitance, charge retention, and cyclic stability. This is primarily due to limiting intrinsic properties of the electrode materials such as average surface area and poor porosity, combined with sluggish redox kinetics due to lack of electrode functionality. So, the need of the hour is to explore new materials for efficient storage of the energy. Among these new materials, metal-organic frameworks (MOFs) can serve as potential candidates because they have high specific surface area, high porosity with tuneable morphology and hence tuneable pore size, functionality linking to active metal sites and ligands. However, there remains a gap in fully utilising MOFs in energy storage applications commercially. Due to the highly porous nature of MOFs, their structural stability is compromised especially in aqueous electrolytes. To utilize the maximum potential of MOFs as electrode materials, it is of utmost importance to address poor structural integrity and low intrinsic conductivity of MOFs.
In this work, it has been tried to overcome the above-mentioned drawbacks of MOFs by using additives of conductive nature such as graphene nanoplatelets (GNP). Hydrothermal approach was used to synthesize hybrid MOF by controlling molar ratio of Nickel and Cobalt in combination with different organic ligands. As a battery-type supercapacitor electrode material, the 2:1 Ni/Co hybrid MOF with 40mg GNP, using terephthalic acid as ligand, delivered a high specific capacity of 658.8 C·g−1 at the current density of 1 A·g−1. Similarly, the 1:2 Ni/Co hybrid MOF, using 2-MethylImidazole as ligand, delivered a high specific capacity of 642.4 C·g−1 at the current density of 1 A·g−1. Moreover, breakthrough results were obtained by optimizing synthesis with in-situ deposition on nickel foam of 2:1 Ni/Co (with 40mg GNP) hybrid MOF, which produced an impressive specific capacity of 1264 C·g−1 at 1 A/g, surpassing, to the best of our knowledge, most of the previously reported MOF based electrode materials.
This work not only develops a high-performance electrode material of supercapacitor, but being the first of its kind in Pakistan, also provides the foundation of systematic research for the electrochemical properties of multi-metal MOFs.
Characterization of Clay/Chitosan Nanocomposites and their Use for Adsorption...Editor IJCATR
In this study, composites films were prepared from Chitosan biopolymer and Montmorillonite nanoclay (MMT) by dispersion of MMT into Chitosan solution with different weight percentage (2.5, 5, 7.5, 10, 12.5, 15 and 75% wt. /wt. nanoclay/chitosan), using both sonication and casting technique methods to obtain good dispersion of nanoclay. The structural properties of these nanocomposites samples examined by XRD and FTIR . The XRD patterns indicating that formation of an intercalated nanostructure as exfoliated and flocculated structure . Also the complexion of the dopant with the biopolymer was examined by FTIR studies. The experiments of Mn(ΙΙ) ions adsorption were carried out on MMT/chitosan nanocomposites. The effect of various parameters such as pH, contact time, adsorption mass, initial Mn(ΙΙ) concentration and temperature on the adsorption of Mn(ΙΙ) removal onto MMT/chitosan nanocomposites was investigated. Two adsorption isotherm models were applied Freundlich and Langmuir to fit the experimental data. Langmuir isotherm modeling was suitable for description the data at equilibrium state. The kinetic isotherm was found to follow the pseudo-second-order model. Also, the thermodynamics parameters of the adsorption such as Gibbs free energy∆G^o, entropy ∆S^o and enthalpy ∆H^o were discussed and the results demonstrate that the adsorption process is spontaneous and endothermic.
2014 polymer activation by reducing agent absorption as a flexible tool for t...Alexandra Bautista
Electroless plating is a powerful wet-chemical method for the fabrication
of metal thin films on arbitrarily shaped substrates [1]. Despite its
relative simplicity just involving the immersion of a work piece in a
deposition solution, electroless plating is suitable for the creation of
macroscopic [1] aswell as intricate nanoscale structures [2–5]. Depending
on the type of substrate and depositedmetal, the obtained materials
can be utilized in various fields, including electronics, wear and corrosion
resistance, medical technology and catalysis [1,6]. The special
properties of electrolessly plated metal nanomaterials give rise to
particularly interesting applications such as molecular separation
[4] or microreactors
PHOTOCATALYTIC DEGRADATION AND REMOVAL OF HEAVY METALS IN PHARMACEUTICAL WAST...Journal For Research
In recent years pharmaceutical wastes (PW) deposal of has become a major difficulty for the environment. Therefore, pharmaceutical waste removal is very necessary before its discharge from the pharma industry. The separation of drugs containing organic compounds in wastewater streams is failed by convectional and biological treatments. Thus, the reduction of harmful effects of pharmaceutical compounds is possible by heterogeneous photocatalysis process. Herein we reported the degradation of pharmaceutical concentration in pharmaceutical waste by heterogeneous photocatalyst ZnO doped with Selenium prepared by cost effective hydrothermal method. In addition the heavy metals in pharmaceutical waste were also removed by ZnO/Se nanocomposite. The average band gap of nanocomposite (~2.5 eV) increase the photocatalytic activity and degrade the organic compounds in pharmaceutical waste. The heavy metals get adsorbed on the high surface area of nanocomposite and removed completely by filtration method. The Selenium doped ZnO photocatalyst semiconductor was characterized by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDAX) and also the characteristic crystalline forms of ZnO/Se nanocomposite was confirmed by XRD. The functional groups and particle size distribution of ZnO/Se nanocomposite was characterized by FTIR and DLS respectively. The reduction of organic compounds in the pharmaceutical waste was confirmed by COD analysis and removal of heavy metals was performed by AAS analysis.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Photochemistry Mediated Synthesis and Characterization of Thyroxine Capped Si...priyanka raviraj
Objective:
Silver nanoparticles (AgNPs) are one of the noble metal nanoparticles studied due to their amenability of synthesis, functionalization and ease of detection. Synthesis of silver nanoparticles using thyroxine as a reducing and capping agent through the one step photochemical method
Characterization of synthesized silver nanoparticles (Thy-AgNPs)
1. UV-Spectroscopy Analysis
2. Fourier Transforms-Infra Red Spectroscopy (FT-IR)
3. High Resolution Transmission Electron Microscopy(HR-TEM)
4. Field Emission Scanning Electron Microscopy(FE-SEM)
5. Dynamic Light Scattering (DLS)
6. Zeta potential
Uses:
*AgNPs have unique optical, electrical, and thermal properties
*Exhibit high plasmon efficiency
*More sensitive towards localized surface plasmon resonance
*Less time consuming, economic and more ecofriendly
*It is used in electronics, food industry, cosmetics, photochemical, biomedicine and chemistry.
التحفيز الضوئي بواسطة أفلام التيتانيوم لتنقية المياه
محاضرة للدكتور حازم فلاح سكيك القاها في المؤتمر الدولي الثاني للعلوم الاساسية والتطبيقة بجامعة الأزهر تتحدث عن تحضير افلام مسامية سميكة من ثاني اكسيد التيتانيوم بطريقة السول جيل لعملية التحفيز الضوئي التي لها تأثير استخدام هام في عملية تنقية الهواء والمياه باستخدام طاقة الضوء ومادة ثاني اكسيد التيتانيوم كمحفز لمزيد من المعلومات
http://www.hazemsakeek.net/magazine/index.php/-1176192324/1494-2011-09-21-10-09-22
Maiyalagan,Electrochemical oxidation of methanol on pt v2 o5–c composite cata...kutty79
Platinum nanoparticles have been supported on V2O5–C composite through the reduction of chloroplatinic
acid with formaldehyde. The catalyst was characterized by X-ray diffraction and transmission electron
microscopy. Catalytic activity and stability for the oxidation of methanol were studied by using
cyclic voltammetry and chronoamperometry. Pt/V2O5–C composite anode catalyst on glassy carbon electrode
show higher electro-catalytic activity for the oxidation of methanol. High electro-catalytic activities
and good stabilities could be attributed to the synergistic effect between Pt and V2O5, avoiding the electrodes
being poisoned.
Maiyalagan,Electro oxidation of methanol on ti o2 nanotube supported platinum...kutty79
TiO2 nanotubes have been synthesized using anodic alumina membrane as template. Highly dispersed
platinum nanoparticles have been supported on the TiO2 nanotube. The supported system
has been characterized by electron microscopy and electrochemical analysis. SEM image shows
that the nanotubes are well aligned and the TEM image shows that the Pt particles are uniformly
distributed over the TiO2 nanotube support. A homogeneous structure in the composite nanomaterials
is indicated by XRD analysis. The electrocatalytic activity ofthe platinum catalyst supported on
TiO2 nanotubes for methanol oxidation is found to be better than that of the standard commercial
E-TEK catalyst.
Recent progress in Tungsten disulphide based Photocatalyst for Hydrogen Produ...MaiyalaganT
Semiconductor-based photocatalysis has dramatically increased interest in the field of photocatalysis, because of
its ability to directly utilize solar energy into fuels and for the degradation of various pollutants. However, the
photocatalytic performance of semiconductor-based photocatalys still lower due to the quick recombination
photogenerated electron–hole pairs and low visible light utilization. Therefore, numerous efforts have been made
to solve these complications. Particularly, cocatalysts supported semiconductor have been extensively applied in
designing and developing highly effective composite photocatalysts for hydrogen photocatalytic application.WS2
has attracted enormous attention in photocatalysis due to its unusual properties like enhancing visible lightharvesting,
charge transfer dynamics and surface reactions of a photocatalytic system. In this review, we
begin by describing synthesis route, different morphologies and brief sketch properties of WS2. A brief discussion
of the WS2 supported metal oxide, metal sulphide, carbon based materials, silver based materials and bismuth
based materials photocatalysts is then provided. While various plausible photocatalytic mechanisms of
photogenerated-electrons and holes in WS2 composite should be proposed. The applications of WS2 as cocatalyst
in the Photocatalytic hydrogen production, organic contaminant degradation and Cr(VI) removal. This review
may offer motivation for designing and fabricating novel and efficient WS2 based composite photocatalysts for
highly efficient photocatalytic applications.
Photo-electrocatalytic activity of TiO2 nanotubes prepared with two-step anod...Iranian Chemical Society
To improve the photo-catalytic degradation of salicylic acid, we reported the fabrication of ordered TiO2 nanotube arrays by a simple and effective two-step anodization method and then these TiO2 nanotubes treated in a methanol solution under UV light irradiation. The TiO2 nanotubes prepared in the two-step anodization process showed better photo-catalytic activity than TiO2 nanotubes prepared in one-step anodization process. Also, compared with TiO2 nanotubes without the UV pretreatment, the TiO2 nanotubes pretreated in a methanol solution under UV light irradiation exhibited significant enhancements in both photocurrent and activity. The treated TiO2 nanotubes exhibited a 5-fold enhancement in photocurrent and a 2.5-fold increase in the photo-catalytic degradation of salicylic acid. Also the effect of addition of persulfate and periodate on the photo-catalytic degradation of salicylic acid were investigated. The results showed that the degradation efficiency of salicylic acid increased with increasing persulfate and periodate concentrations. These treated TiO2 nanotubes are promising candidates for practical photochemical reactors.
Synthesis of flower-like magnetite nanoassembly: Application in the efficient...Pawan Kumar
A facile approach for the synthesis of magnetite microspheres with flower-like morphology is reported
that proceeds via the reduction of iron(III) oxide under a hydrogen atmosphere. The ensuing magnetic
catalyst is well characterized by XRD, FE-SEM, TEM, N2 adsorption-desorption isotherm, and
Mössbauer spectroscopy and explored for a simple yet efficient transfer hydrogenation reduction of a
variety of nitroarenes to respective anilines in good to excellent yields (up to 98%) employing hydrazine
hydrate. The catalyst could be easily separated at the end of a reaction using an external magnet and
can be recycled up to 10 times without any loss in catalytic activity.
Synthesis of flower-like magnetite nanoassembly: Application in the efficient...Pawan Kumar
A facile approach for the synthesis of magnetite microspheres with flower-like morphology is reported
that proceeds via the reduction of iron(III) oxide under a hydrogen atmosphere. The ensuing magnetic
catalyst is well characterized by XRD, FE-SEM, TEM, N2 adsorption-desorption isotherm, and
Mössbauer spectroscopy and explored for a simple yet efficient transfer hydrogenation reduction of a
variety of nitroarenes to respective anilines in good to excellent yields (up to 98%) employing hydrazine
hydrate. The catalyst could be easily separated at the end of a reaction using an external magnet and
can be recycled up to 10 times without any loss in catalytic activity.
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
Synthesis MgO nanopowder using Sol-gel technique: A critical reviewPratish Rawat
During the last decade, it has realized that when materials are synthesized to nanoscale dimensions, they will show new and remarkably improved physical and chemical properties. Due to its wide and major applications, in-depth investigations have been carried out on metal oxide nanomaterials. A significant amount of research is going on in synthesis and characterization of MgO/PVA nanocomposites. Some of the literature has been reviewed to get the idea about the synthesis and characterization of MgO/PVA nanocomposites using sol-gel technique.
Optical Control of Selectivity of High Rate CO2 Photoreduction Via Interband-...Pawan Kumar
Photonic crystals consisting of TiO2 nanotube arrays (PMTiNTs) with periodically modulated diameters were fabricated using a precise charge-controlled pulsed anodization technique. The PMTiNTs were decorated with gold nanoparticles (Au NPs) to form plasmonic photonic crystal photocatalysts (Au-PMTiNTs). A systematic study of CO2 photoreduction performance on as-prepared samples was conducted using different wavelengths and illumination sequences. A remarkable selectivity of the mechanism of CO2 photoreduction could be engineered by merely varying the spectral composition of the illumination sequence. Under AM1.5 G simulated sunlight (pathway#1), the Au-PMTiNTs produced methane (302 µmol h-1) from CO2 with high selectivity (89.3%). When also illuminated by a UV-poor white lamp (pathway#2), the Au-PMTiNTs produced formaldehyde (420 µmol h-1) and carbon monoxide (323 µmol h-1) with almost no methane evolved. We confirmed the photoreduction results by 13C isotope labeling experiments using GC-MS. These results point to optical control of the selectivity of high-rate CO2 photoreduction through selection of one of two different mechanistic pathways. Pathway#1 implicates electron-hole pairs generated through interband transitions in TiO2 and Au as the primary active species responsible for reducing CO2 to methane. Pathway#2 involves excitation of both TiO2 and surface plasmons in Au. Hot electrons produced by plasmon damping and photogenerated holes in TiO2 proceed to reduce CO2 to HCHO and CO through a plasmonic Z-scheme.
Reduced graphene oxide–CuO nanocomposites for photocatalyticconversion of CO2...Pawan Kumar
Reduced graphene oxide (rGO)–copper oxide nanocomposites are prepared by covalent grafting of CuOnanorods on the rGO skeleton. Chemical and structural features of rGO–CuO nanocomposites are probedby FTIR, XPS, XRD and HRTEM analyses. Photocatalytic potential of rGO–CuO nanocomposites is exploredfor reduction of CO2into the methanol under the visible light irradiation. The breadth of CuO nanorods andthe oxidation state of Cu in the rGO–CuO/Cu2O nanocomposites are systematically varied to investigatetheir photocatalytic activities. The pristine CuO nanorods exhibited very low photocatalytic activity owingto fast recombination of charge carriers and yielded 175 mol g−1methanol, whereas rGO–Cu2O andrGO–CuO exhibited significantly improved photocatalytic activities and yielded five (862 mol g−1) andseven (1228 mol g−1) folds methanol, respectively. The superior photocatalytic activity of CuO in therGO–CuO nanocomposites was attributed to slow recombination of charge carriers and efficient transferof photo-generated electrons through the rGO skeleton. This study further excludes the use of scavengingdonor.
Reduced graphene oxide–CuO nanocomposites for photocatalyticconversion of CO2...Pawan Kumar
tReduced graphene oxide (rGO)–copper oxide nanocomposites are prepared by covalent grafting of CuOnanorods on the rGO skeleton. Chemical and structural features of rGO–CuO nanocomposites are probedby FTIR, XPS, XRD and HRTEM analyses. Photocatalytic potential of rGO–CuO nanocomposites is exploredfor reduction of CO2into the methanol under the visible light irradiation. The breadth of CuO nanorods andthe oxidation state of Cu in the rGO–CuO/Cu2O nanocomposites are systematically varied to investigatetheir photocatalytic activities. The pristine CuO nanorods exhibited very low photocatalytic activity owingto fast recombination of charge carriers and yielded 175 mol g−1methanol, whereas rGO–Cu2O andrGO–CuO exhibited significantly improved photocatalytic activities and yielded five (862 mol g−1) andseven (1228 mol g−1) folds methanol, respectively. The superior photocatalytic activity of CuO in therGO–CuO nanocomposites was attributed to slow recombination of charge carriers and efficient transferof photo-generated electrons through the rGO skeleton. This study further excludes the use of scavengingdonor.
2. Nano Res (2010) 3: 244–255 245
many bacterial cell membranes, and thus have strong
cytotoxicity to various bacterial cells at lower metal
usage compared to that required for bulk metals [6, 7].
Organic frameworks [6, 7] and metal oxide supports
[8–10] have frequently been used to maintain the
dispersion of such noble metal nanoparticles. Due to
their low price and ability to be prepared on a large
scale, and since they are beneficial or, at worst, inert
in processes catalyzed by noble metals, inorganic Scheme 1 Photochemical route for formation of M@TiO2
nanocomposites. CB: conduction band; VB: valence band; M: Ag,
supports are preferred. TiO2 is an active support for
Pd, Au, Pt; e–: photoexcited electrons; h+: photoexcited holes;
promoting the catalytic performance of Pt or Pd, as NPs: nanoparticles
well as the antibacterial effects of Ag or Au [8, 11, 12].
On the other hand, TiO2 is a typical semiconductor,
preparing nanoparticles, rather than nanocomposites
widely used as photocatalyst for splitting water,
for practical applications [30, 31]. Current methods of
decomposition of dyes, antibacterial applications under
preparation of noble metal–support nanocomposites,
UV light, and so on [13–17].
as opposed to isolated metals [30], by photochemical
To make the use of noble metals more economic and
routes need careful control of the reaction parameters
to improve their performance, it is crucial to control
and conditions, and amines and organic solvents are
both the size of nanoparticles and their dispersity on
generally required in the synthesis mixture [32–34].
a support [18–20]. Versatile colloidal methods for the
From the viewpoint of applications, any residue of
synthesis of noble metal nanoparticles have emerged
amines or organic solvents on the noble metal loaded
recently, but require the presence of organic molecules
support will obviously affect the performance of the
or solvents [21–23]. Generally, there are two methods
noble metal [35].
to prepare a composite catalyst of such noble metal
In this paper, we report an efficient method for the
nanoparticles loaded on a support. One is a two-step
synthesis of a series of well-dispersed M@TiO 2
method, involving the initial synthesis of noble metal
(M = Ag, Pd, Au, Pt) nanocomposite particles with a
nanoparticles, followed by a subsequent combination
diameter of 200–400 nm on a large scale by a clean
of these particles with a suitable support [24, 25]. The
photochemical route without any additives being
other method involves calcination of a mixed precursor
required and using spherical rutile nanoparticles as
of noble metal and support materials at relatively
support. The catalytic CO oxidation performance
high temperature [26, 27]. However, aggregation of
and antibacterial effects of the products have been
nanoparticles is hard to avoid in the first case, while
investigated.
the size of the noble metal particles is difficult to control
in the second case [25, 28].
The photochemical route is a promising way to 2. Experimental
form noble metal–semiconductor nanocomposites in
2.1 Materials
situ by reducing noble metal ions adsorbed on the
surface of a semiconductor. It is well known that a TiCl3 (Mw = 154.23, solution in 15 wt%–20 wt% dilute
semiconductor can be excited and then generate aqueous hydrochloric acid), chitosan (degree of
electrons (e–) and holes (h+) in the conduction band deacetylation > 90%), AgNO3 (Mw = 169.87), HAuCl4
(CB) and valence band (VB) if the energy of the photons (Mw = 339.79), acetic acid (Mw = 60.06), hydrazine
of the incident light is larger than that of the band gap (Mw = 50.06, 85%v/v), and acetone (Mw = 58.08) were
of the semiconductor (Scheme 1) [13, 29]. However, analytical grade from Shanghai Chemical Reagents
previous work involving photocatalytic reduction of Corporation (SCRC). Ultrapure water was prepared
noble metal precursors was mostly aimed only at using a Millipore Simplicity UV system.
3. 246 Nano Res (2010) 3: 244–255
2.2 Synthesis of rutile TiO2 cultured in Luria-Bertani (LB) liquid medium with a
concentration of 105 cfu/mL of E. coli was plated on
5 grams of chitosan powder was poured into a vessel agar plates with 20 μg/mL of Au@TiO2 or Ag@TiO2
containing 100 mL of deionized water and 5 mL of (cfu: colony-forming units).
acetic acid. The mixture was stirred for 6 h at 90 °C, The detailed antibacterial effects of as-synthesized
and finally cooled naturally to room temperature. 10
materials were assessed by culturing E. coli at 37 °C in
grams of this as-synthesized chitosan solution was
a shaking incubator at 280 rpm (in 50 mL LB broth
added dropwise into a vessel containing 40 mL of
medium supplemented with 107 cfu/mL bacterial
acetone and 4 mL of TiCl3 solution, and then the
solution and different concentrations of as-synthesized
vessel was covered with parafilm and left at room
materials). E. coli inoculum was prepared by culture
temperature for 2 weeks. The resulting white deposit
overnight at 35 °C and 200 rpm in 50 mL LB broth
was immersed in water to dissolve the chitosan, and
medium from a single colony surface on LB agar plates,
then the suspension was centrifuged and washed
and then about 2 mL of the culture was transferred into
several times with deionized water and ethanol.
100 mL of fresh LB medium and further conditioned
Finally, the powder was dried at 60 °C.
at 35 °C and 200 rpm to prepare the inoculum. For
2.3 Synthesis of M@TiO2 nanohybrid materials by each growth inhibtion experiment, 5 mL of E. coli
photoreduction inoculum was added to 50 mL of fresh LB broth
medium containing as-synthesized nanoparticles with
50 mg of as-synthesized TiO2 powder and 1 mL different concentrations, i.e., 0.5–10 μg/mL. For Ag
(5 mol/L AgNO3, or 2.5 mmol/L HAuCl4), or 3 mL nanoparticles or Au@TiO2, the concentrations given
(2.5 mmol/L PdCl2, or 2.5 mmol/L H2PtCl6) of an in Fig. 8 and the main text refer to the concentration
aqueous metal salt solution were dispersed with of the metal. The experiments were performed three
100 mL of deionized water in a Pyrex flask with times. The optical density at 600 nm was measured at
capacity of about 250 mL under stirring. The flask hourly intervals by UV/vis spectrophotometry.
was exposed to light from a high-pressure Xe lamp
(150 W, PerkinElmer Co.). The reaction was carried 2.6 Characterization
for 25 min (AgNO3) or 1.5 h (PdCl2, HAuCl4, H2PtCl6).
Surface charges (zeta potentials) and particle sizes of
Then the powder was collected by centrifugation and
each sample were measured on a Nano-ZS Zetasizer
washed twice by deionizedwater and ethanol. Finally,
dynamic light scattering detector (Malvern Instruments,
the resulting powder was dried at 60 °C.
UK) equipped with a 4.0 mW internal laser. X-ray
2.4 Catalytic oxidation of CO powder diffraction patterns were collected on a
Philips X’Pert Pro Super Diffractometer using Cu Kα
The catalytic activity was evaluated with a fixed-bed radiation (λ = 1.541 874 Å). A Thermo-VG Scientific
flow reactor. The weight of catalyst used was 48.5 mg, ESCALAB 250 instrument was used for X-ray photo-
and the reaction gas consisting of 1%(v/v) CO and electron spectroscopy (XPS) measurements. UV/vis
99%(v/v) dry air was fed at a rate of 20 mL/min. The spectra were recorded with a Shimadzu UV-240
composition of the effluent gas was detected with an spectrophotometer. Fourier transform infrared (FTIR)
online GC-14C gas chromatograph. The conversion and Raman spectra were measured using Magna
of CO was calculated from the difference in CO IR-750 (Nicolet Instrument Co. USA) and Ramanlog
concentrations between the inlet and outlet gases. (Spex, USA) spectrometers, respectively. The photo-
2.5 Antibacterial applications luminescence spectra measurements were conducted
on a Fluorolog3-TAU-P instrument. Transmission
To examine the susceptibility of Gram-negative electron microscope (TEM) images were obtained using
Escherichia coli (E. coli) to different hybrid nanoparticles, a JEOL JEM 2011 microscope with an accelerating
agar plates were employed. Bacterial solution (100 μL) voltage of 200 kV. Scanning electron microscope (SEM)
4. Nano Res (2010) 3: 244–255 247
measurements were carried out using a Zeiss Supra (101), and (111) diffraction peaks using the Scherrer
40 microscope. Two-photon images were recorded formula indicated that the average size of the
using a Zeiss LSM510 instrument. Nitrogen sorption crystallites was about 10 nm. The symmetry of rutile
data were obtained with a Micromeritics TriStar 3000 TiO2 is tetragonal P42/mnm, in which the titanium
automated gas adsorption analyzer. Surface areas atoms (gray) occupy the corners and the body center,
were obtained using the Brunauer–Emmet–Teller and oxygen atoms (red) occupy ± (0.3, 0.3, 0) and
(BET) method. ± (0.8, 0.2, 0.5) sites as shown in Fig. 2(d).
Figure 1(b) shows the Raman-active fundamental
modes of the as-obtained TiO2. The A1g (603 cm–1) and
3. Results and discussion
Eg (432 cm–1) modes as well as a second-order peak
3.1 Synthesis of rutile TiO2 nanostructures at about 240 cm –1 are the dominant peaks and
characteristic of the rutile phase of TiO2. The Raman
Hydrolysis and subsequent oxidation by dissolved peak at about 105 cm–1 and a broad band at about
oxygen of Ti(Ⅲ) species are slow at room temperature 685 cm–1 are due to a size effect and indicate that the
in an acetone/water mixed solvent containing chitosan size of the particles is less than 10 nm [38]. SEM
[36, 37]. After removing the chitosan by extraction images show that uniform spheres with a diameter of
with deionized water, the resulting white powder 200–400 nm can be obtained on a large scale (see
was collected by centrifugation. FTIR spectra indicate Fig. S-3 in the ESM). The small size of the TiO2 particles
that no chitosan residue remains in the powder and a means a high surface-to-volume ratio. The BET surface
relatively strong peak at 1630 cm–1 can be attributed area of the powder is 173 m2/g (Fig. 3).
to hydroxyl groups (see Fig. S-1 in the Electronic The high-magnification TEM images in Figs. 2(a)
Supplementary Material (ESM)). The X-ray photo- and 2(b) show that the spherical aggregates have
electron (XPS) spectra of the powder show the binding good crystallinity and are composed of nanoparticles
energies of Ti 2p1/2 and Ti 2p3/2 are 464.4 and 458.69 eV, with a diameter less than 10 nm, consistent with the
respectively, confirming that no Ti(Ⅲ) species remain Raman spectra and the XRD data discussed above.
in the sample (see Fig. S-2 in the ESM). A high-resolution TEM (HRTEM) image (Fig. 2(c))
The X-ray diffraction (XRD) pattern in Fig. 1(a) shows shows that the lattice fringes on the crystal face have
that the as-synthesized powder is the rutile phase of a spacing of 3.28 Å, corresponding to the (110) face of
TiO2. Calculations based on the half-widths of the (110), rutile TiO2. The (110) surface obtained by cleaving a
Figure 1 (a) XRD pattern of as-synthesized rutile TiO2 and standard reference pattern (JCPDS No. 16-934); (b) Raman spectra of
as-synthesized rutile TiO2, Au@TiO2, and Ag@TiO2
5. 248 Nano Res (2010) 3: 244–255
being localized outside the TiO2
matrix (see Fig. S-4 in the ESM).
Furthermore, the XPS spectra of
the four M@TiO2 samples (M = Ag,
Pd, Au, Pt) all confirm the
presence of the noble metals in
their elemental states (see Fig. S-5
in the ESM). It is believed that
photogenerated electrons from the
conduction band are responsible
for the reduction of metallic ions
adsorbed on the surface of TiO2
nanoparticles (Scheme 1) [30].
Inductively coupled plasma atomic
emission spectrometry (ICP-AES)
of the solution obtained after
Figure 2 (a), (b) TEM, and (c) high-resolution TEM (HRTEM) images of as-synthesized
centrifugation of the reaction sus-
rutile TiO2. (d) Atomic cell model of rutile TiO2, and (e) (110) surface of rutile TiO2 (where
the gray balls and red balls represent Ti and O atoms, respectively) obtained using Accelrys pension indicated an almost total
Materials Studio Modeling 3.1 absence of noble metal ions, which
means that all the noble metal
rutile unit cell is a Ti-rich plane, which indicates that ions were deposited on the TiO2.
it has a positive charge. The exposed titanium atoms
3.3 Catalytic performance of Pt@TiO2 and Pd@TiO2
on the plane are readily coordinated by hydroxyl
in the CO oxidation reaction
groups as shown in the FTIR spectrum (see Fig. S-1 in
the ESM). Moreover, the positively charged plane The loadings (weight ratio of metal to TiO2 support)
leads to the TiO2 colloids having a high zeta potential of Pt and Pd in the catalysts were 2.9 wt% and 1.5 wt%,
(45.8 mV), indicating a good stability in solution. respectively, as given by ICP-AES. The TEM images
of Pt@TiO2 and Pd@TiO2 nanocomposites given in
3.2 Synthesis of M@TiO2 hybrid materials by
Fig. 5 show that metal nanoparticles are decorated
photoreduction
After irradiation by a Xe light source, the white
suspension of TiO2 and an appropriate metallic
precursor became light yellow–green (Ag), dark (Pd),
purple (Au), and yellowish (Pt), as shown in Fig. 4.
Comparison of the bright field images and two-
photon images of the powders showed no obvious
signal intensity increase in the case of pure TiO2. Two-
photon signals only arise from the surface plasmon
resonance (SPR) effect of noble metal nanoparticles
[39] (see Fig. S-4 in the ESM) and the images of noble
metal containing powders after the photoreduction
process showed typical two-photon effects and good
co-localization with the bright field images, which
indicates that the noble metal must be deposited on the Figure 3 BET adsorption-desorption isotherms of the as-
TiO2 nanoparticles with no noble metal nanoparticles synthesized rutile TiO2 powder
6. Nano Res (2010) 3: 244–255 249
1 nm [19, 20, 43]. The Pt and Pd nanoparticles shown
in Fig. 5 are too unstable to give a high-magnification
TEM image, because they melt under the electron
beam of a TEM. For Pd@TiO2, CO conversion reached
100% at 363 K (Fig. 6(b)). Complete conversion at this
low temperature can also be attributed to the small
size of Pd nanoparticles. However, its catalytic activity
was lower in the second pass through the reactor,
which could be due to melting of the nanoparticles or
further growth of unstable Pd nanoparticles [4, 44].
3.4 Antibacterial effect of Ag@TiO2 and Au@TiO2
nanocomposites
Figure 4 Photographs of suspensions of (from left to right) Figure 7 shows TEM and HRTEM images of Ag@TiO2
Ag@TiO2, Pd@TiO2, Au@TiO2, and Pt@TiO2 and Au@TiO2 nanocomposites. The size distribution
of Ag ranges from 2 to 20 nm (Figs. 7(a) and 7(b)). The
homogeneously on TiO2 particles. The sizes of Pt and lattice fringe spacing for Ag@TiO2 is 2.36 Å, which is
Pd nanoparticles are about 1 nm (Figs. 5(a) and 5(b)) consistent with the [111] spacing of Ag (Fig. 7(c)). The
and 5 nm (Figs. 5(c) and 5(d)), respectively. These Au nanoparticles with a diameter of about 5 nm are
should have good catalytic activity for CO oxidation, monodisperse on the surface of TiO2 support as shown
given the well-known activity-size relation [18–20]. in Figs. 7(d) and 7(e). The lattice fringe spacing is
The energy dispersive spectra (EDS)
show the presence of Pt and Pd
elements in the respective samples
(see Figs. S-6 and S-7 in the ESM).
As-prepared Pt@TiO2 particles show
good catalytic activity for CO
oxidation (Fig. 6(a)). On the third
pass through the reactor containing
Pt@TiO 2 , CO conversion reached
100% at 333 K. It is well known that
Pt-loaded metal oxide supported
catalysts are generally not efficient at
low ratios of O2/CO or temperatures
below 443 K, because CO and O2 are
adsorbed at similar sites, and strong
CO adsorption hinders O2 adsorption
on the noble metal catalyst [40–42].
In our case, the high conversion
obtained at low temperature indicates
the high activity of the small
nanoparticles with a large number of
Pt atoms with low coordination
number present on the surface of Figure 5 TEM images of the M@TiO2 nanocomposites: (a) and (b) Pt@TiO2; (c) and
nanoparticles with a diameter of (d) Pd@TiO2
7. 250 Nano Res (2010) 3: 244–255
Figure 6 Catalytic performance of the nanocomposites (a) Pt@TiO2 and (b) Pd@TiO2. The weight of catalyst was 48.5 mg. The reaction
gas consisted of 1% CO and 99% dry air, and was fed at a rate of 20 mL/min
Figure 7 TEM and HRTEM images: (a)–(c) Ag@TiO2, and (d)–(f) Au@TiO2. The lattice fringe spacing in (c) is 2.36 Å, corresponding
to the [111] direction of Ag (JCPDS Card No. 89-3722); the lattice fringe spacing in (f) is 2.04 Å, corresponding to the [200] direction
of Au (JCPDS Card No. 4-784)
2.04 Å, which corresponds to the (200) plane of Au ICP-AES indicates that the loadings of Ag and Au
(Fig. 7(f)). The EDS show the presence of Au and Ag in Ag@TiO2 and Au@TiO2 are about 1.08 wt% and
elements in the samples, respectively (see Figs. S-8 0.99 wt%, respectively. The small size of the metal
and S-9 in the ESM). The XPS spectra of the Ag@TiO2 nanoparticles should lead to high antibacterial
composites show peaks at 367.4 and 373.5 eV which activity.
can be attributed to Ag 3d5/2 and Ag 3d3/2 of elemental A visual antibacterial test against E. coli was used
Ag, respectively [45] (see Fig. S-5 in the ESM). to compare colonies on agar plates in the presence or
8. Nano Res (2010) 3: 244–255 251
absence of the hybrid nanomaterials. Approximately bacterial growth was carried out by measuring the
104 colony-forming units (cfu) of E. coli were cultured optical density (O.D.) of the LB broth medium by
on LB agar plates as control, and LB agar plates UV/vis spectrophotometry [6]. Plots of normalized
supplemented with 20 μg/mL Ag@TiO2 and Au@TiO2 O.D. [(cfu/mL)/(cfu/mL)] as a function of time are
particles. After incubation at 37 °C for 24 h, bacterial shown in Fig. 8. Addition of TiO2 with different
colony crowding was observed on the control plates concentrations of 0.5, 1, and 5 μg/mL results in no
in the absence of any additives (see Fig. S-10 in the significant inhibition of bacterial growth (Fig. 8(a))
ESM). The presence of the Au@TiO2 nanocomposite compared with that in the control experiment without
inhibited bacterial growth by approximately 80%, any added TiO2. In contrast, adding the Au@TiO2
indicating that it has a good antibacterial effect (the nanocomposite with concentrations of 1, 2, 5, and
purple plate in the insert in Fig. 8(b)). The smooth 10 μg/mL has a notable antibacterial effect (Fig. 8(b)),
yellow plate containing Ag@TiO2 nanoparticles (the and increasing the concentration of Au@TiO2 leads to
insert in Fig. 8(c)) displays nearly complete inhibition increasing inhibition of bacterial growth.
of bacterial growth, which shows the excellent An excellent antibacterial effect can be achieved in
antibacterial effect of Ag nanoparticles when loaded the case of the Ag@TiO2 nanocomposite (Fig. 8(c)).
on TiO2 particles. When the concentration of the nanocomposite was
A detailed investigation of the dynamics of 10 μg/mL, the growth of E. coli was completely
Figure 8 Curves showing the antibacterial effects as a function of time of (a) pure TiO2, (b) Au@TiO2, (c) Ag@TiO2, and (d) pure
silver nanoparticles with a diameter of 30–50 nm. Photographs inserted in (b) and (c) show petri dishes supplemented with Au@TiO2
(b) and Ag@TiO2 (c) at a loading of 20 μg/mL dispersed in medium with 100 μL of 105 cfu/mL E. coli
9. 252 Nano Res (2010) 3: 244–255
inhibited, which is similar to what was observed in nanoparticles are loaded on monodisperse rutile
the LB agar plate (the insert in Fig. 8(c)). It has nanospheres, preventing their aggregation and
previously been found [8, 9, 46, 47] that silver-doped protecting their high surface activity. Furthermore,
titania has better antibacterial effect than pure silver the zeta potentials of Au@TiO2 and Ag@TiO2 are
particles, only when the loading is very high, about positive, +29.8 and +33.2 mV, respectively. It is well
5–70 times more than we used here. In fact, lowering known that the charge on the membrane of E. coli is
the concentration of the nanocomposite to 5 μg/mL, negative. Hence, electrical attraction between the
also has a significant effect on bacterial growth. bacteria and as-synthesized hybrid materials increases
Although the detailed mechanism of the antibacterial their collision possibility and results in the metal
effect of silver nanoparticles is still unclear, there are nanoparticles being highly efficient inhibitors of
some clues in the literature. Silver nanoparticles can bacterial growth.
interact with sulfur-containing proteins from cell
3.5 Photoluminescence of TiO2, Ag@TiO2, and
membrane and phosphorus-containing compounds
Au@TiO2
in cells, attacking the respiratory chain, with cell
division leading to cell death [48, 49]. For a given The photoreduction process and deposition of metal
dosage of silver, smaller particle sizes mean a larger nanoparticles have no obvious effect on the Raman
number of particles, which increases the contact spectrum of the TiO2 matrix (Fig. 1(b)). In their UV/vis
between the bacterial cell membrane and the silver spectra, the as-synthesized TiO2 and metal@TiO2
nanoparticles. A control experiment (Fig. 8(d)) shows materials all have strong absorbance around 300 nm
the antibacterial effect of pure silver nanoparticles and broad photoabsorption region in the visible region
synthesized by a previous microwave method [50]. (400–800 nm) [16, 51] (see Fig. S-11 in the ESM). No
The silver nanoparticles, with diameters of 30–50 nm, typical absorbance peaks of nanosized silver and gold
cannot completely depress the bacterial growth even are observed, which is similar to a previous report
when the silver concentration reached 20 μg/mL. It is for materials with such a low metal concentration
observed that the nanoparticles aggregated together [51]. Photoluminescence (PL) bands of TiO 2 and
and sedimented during the shaking process, decreasing metal@TiO2 hybrid materials are located in the violet
the possibility of interaction of the bacterial cells with region (Fig. 9). The observed narrow emission band
the silver nanoparticles. is in contrast to the broad emission band reported
Small silver nanoparticles, with a diameter less than previously when the size of TiO2 particles was very
10 nm, give rise to electronic effects which enhance small [52]. When as-synthesized TiO2 nanoparticles
their surface reactivity. In our case, the tiny Ag or Au were excited at 366 nm (Fig. 9(b)), the maximum
Figure 9 Photoluminescence spectra of as-synthesized TiO2, Ag@TiO2, and Au@TiO2: (a) excitation spectra; (b) emission spectra
10. Nano Res (2010) 3: 244–255 253
emission occured at 417 nm (2.97 eV), which arises antibacterial agents and in other fields.
from free excitons and is near to the bandgap of bulk
rutile (3.0 eV) [53]. A large shoulder band around
Acknowledgements
450 nm (2.76 eV) shown in Fig. 9(b) can be ascribed to
oxygen vacancies or a defect state in the nanostructure S. -H. Yu acknowledges the funding support from
[53]. During the irradiation process, the in situ the National Basic Research Program of China (No.
absorbance and reduction of the metallic precursor 2010CB934700), the Program of International S & T
on the surface change the defect state of TiO2. Hence, Cooperation (No. 2010GR0314), the National Science
the maximum excitation and emission bands of the Foundation of China (NSFC) (Nos. 50732006,
Ag@TiO2 or Au@TiO2 show a small blue-shift compared 20671085), and the Partner-Group of the Chinese
with TiO2, with emission peaks observed at 400 nm Academy of Sciences & the Max Planck Society. S. F.
(3.10 eV) for Au@TiO 2 and 399 nm (3.11 eV) for Chen thanks the Innovation Fund for Graduate
Ag@TiO2 when excited at 352 nm. The introduction Students of USTC (2006) for support.
of nanosized metal nanoparticles on TiO2 leads to
quenching of the PL intensity, but the emission bands Electronic Supplementary Material: Two-photon
remain narrow [51]. The narrow emission bands of images, FTIR spectra, EDS, UV/vis spectra, and SEM
the nanocomposites may enable them to act as selective images are available in the online version of this
optical windows for some special applications. article at http://dx.doi.org/10.1007/s12274-010-1027-z
and are accessible free of charge.
4. Conclusions Open Access: This article is distributed under the terms
of the Creative Commons Attribution Noncommercial
A general photochemical route to synthesize Ag@TiO2, License which permits any noncommercial use,
Pd@TiO2, Au@TiO2, and Pt@TiO2 nanocomposites on distribution, and reproduction in any medium,
a large scale has been devised. Four kinds of metal provided the original author(s) and source are credited.
(Ag, Pd, Au, Pt) precursors can be reduced to uniform
nanoparticles in a clean way when the solution is
irradiated by a Xe light source, and are deposited on References
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