Optimization of TiO<Subscript>2</Subscript>/MWCNT composites for efficient dye sensitized solar cells

This paper deals with the effects of introducing multiwall carbon nanotubes (MWCNTs) into photoanodes of dye sensitized solar cells (DSSCs). Mesoporous titanium dioxide (TiO₂) nanoparticles were synthesized using sol–gel technique. TiO₂/MWCNT composites were prepared by adding functionalized MWCNTs to TiO₂ nanoparticles using two different surfactants (α-terpineol and Triton X-100). Nanoparticles and composites were characterized using Dynamic Light Scattering spectrophotometer, Raman spectrometer, X-ray diffractometer, field emission scanning electron microscope, Brunauer–Emmett–Teller surface area analyzer and UV–Vis spectrophotometer. FESEM depicted that particles were spherical in shape and their size decreased due to addition of MWCNTs. This was attributed to the decrease in the crystallite size which in turn confirmed by XRD. UV–Vis absorption spectra showed the better absorbance for the visible range of light, as the content of MWCNT is increased. From the Tauc plot optical band gap was calculated and noted that it declined gradually with the content of MWCNTs. BET surface area increased drastically which was attributed to the formation of more number of pores in the nanocomposites as visualized from FESEM. UV–Vis spectra of dye desorbed from the photoanode revealed that the dye adsorption increased as a function of MWCNT wt%. I–V studies were carried out under the illumination of 100 mW/cm² simulated sunlight. Photoanodes prepared by both the methods showed better performance compared to pristine TiO₂ photoanode, because of high conducting path and high surface area provided by MWCNTs. Photoanodes with 0.19 wt% MWCNTs in them were able to achieve maximum efficiency of 3.54 and 3.86% for method A and B respectively.     

A novel spray co-precipitation method to prepare nanocrystalline Y<Subscript>2</Subscript>O<Subscript>3</Subscript> powders for transparent ceramics

A novel spray co-precipitation method was adopted to synthesize well dispersed nanocrystalline Y₂O₃ powders for transparent ceramics. Several analytic techniques such as XRD, SEM, BET and UV–Vis–NIR spectrophotometer were used to determine the properties of coprecipitated powders, and the microstructure and optical properties of as-fabricated ceramics. The influences of the aging time on powders and ceramics were systematically investigated. Precursors were completely reached to yield the Y₂O₃ phase after being calcined at 1250 °C in air. The calcined Y₂O₃ powders exhibited an approximately spherical morphology with narrow size distribution and weak agglomeration, with mean particle size of ~140 nm. The co-precipitated nanopowders with an aging time of 12 h exhibited the best sintering activity due to the low agglomeration, and the in-line transmittance of Y₂O₃ ceramic sintered at 1800 °C for 8 h in vacuum reached to 77.2% at 1064 nm (1 mm thickness).     

Novel preparation of ultrafine MnCo<Subscript>1.75</Subscript>Fe<Subscript>0.25</Subscript>O<Subscript>4</Subscript> nanostructures for the photodegradation of Acid Red 88

For the first time, ultrafine MnCo_1.75Fe_0.25O₄ nanostructures were prepared via a novel coprecipitation–calcination route by using tetraethylenepentamine (tepa) and SDBS as precipitating agent and surfactant, respectively. Results of this study show that particle size and morphology of the MnCo_1.75Fe_0.25O₄ samples can be controlled by setting main reaction parameters such as reaction temperature, surfactant type and calcination temperature. The as-prepared MnCo_1.75Fe_0.25O₄ nanostructures were characterized by EDX, TEM, FESEM, VSM, FT-IR, XRD and UV–Vis analysis. The photocatalytic degradation of the acid red 88 dye as water pollutant was performed to examine the photocatalytic performance of as-prepared MnCo_1.75Fe_0.25O₄ nanostructures.     

Luminescence property of Ca<Subscript>3</Subscript>(VO<Subscript>4</Subscript>)<Subscript>2</Subscript>:Eu<Superscript>3+</Superscript> dependence on molar ratio of Ca/V and solution combustion synthesis temperature

Red emitting phosphor Ca₃(VO₄)₂:Eu³⁺ was prepared by citric acid-assisted solution combustion method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and fluorescence spectrophotometer. The influences of Ca to V molar ratio and synthesis temperature on phase composition, morphology, grain size, photofluorescence properties, and ultraviolet–visible diffuse reflectance spectra (UV–Vis DRS) of as-synthesized samples were investigated. The results indicate that Ca to V molar ratio play a key role for the changing of phase composition, excitation spectrum, and luminescence intensity. The sample prepared at 900 °C, keeping Ca/V = 3:2.2, has the highest photoluminescence intensity. The possible causes of the effects on photoluminescence mechanism were also discussed in this work.     

An improvised method for the synthesis of ZnAl<Subscript>2</Subscript>O<Subscript>4</Subscript>/ZnO nanocomposite and its use as a photocatalyst

Nanocomposite material ZnAl₂O₄/ZnO was prepared via layered double hydroxides co-precipitation method in the presence of triblock copolymer, Pluronic F127 as the template with different concentrations at pH 7. The material was characterized by XRD, N₂ adsorption/desorption, UV–Vis diffused reflectance, TGA–DTA and SEM. XRD and SEM results reveal that ZnAl₂O₄/ZnO was highly ordered nanocrystalline material. N₂ adsorption/desorption studies indicate that the pore size and pore volume increased significantly with the increase in concentration of F127 copolymer template, while the surface area is slightly decreased with increase of F127 template. TGA–DTA results reveal that the thermal stability of material increased after adding F127 template. The material was tested for its photocatalytic activity for a solution containing methyl orange dye and the 95.6% decolorization was achieved within 1 h. The intensive absorption light observed by UV–Vis reflectance of the catalyst confirmed high activity of the catalyst and suggest the probable photocatalytic degradation mechanism.     

Fabrication of SiO<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> double layer thin films with self-cleaning and photocatalytic properties

Transparent antireflective SiO₂/TiO₂ double layer thin films were prepared using a sol–gel method and deposited on glass substrate by spin coating technique. Thin films were characterized using XRD, FE-SEM, AFM, UV–Vis spectroscopy and water contact angle measurements. XRD analysis reveals that the existence of pure anatase phase TiO₂ crystallites in the thin films. FE-SEM analysis confirms the homogeneous dispersion of TiO₂ on SiO₂ layer. Water contact angle on the thin films was measured by a contact angle analyzer under UV light irradiation. The photocatalytic performance of the TiO₂ and SiO₂/TiO₂ thin films was studied by the degradation of methylene blue under UV irradiation. The effect of an intermediate SiO₂ layer on the photocatalytic performance of TiO₂ thin films was examined. SiO₂/TiO₂ double layer thin films showed enhanced photocatalytic activity towards methylene blue dye.     

Structural,morphological and optical properties of SnS<Subscript>2</Subscript> thin films by nebulized spray pyrolysis technique

The thin films of Nano crystalline tin disulfide (SnS₂) have been prepared by nebulized spray pyrolysis technique (NSP) with different molar concentrations (0.3, 0.4 and 0.5 M). Cleaned glass substrates were used and the substrate temperature was maintained at 300?°C. The films were deposited using tin tetrachloride monohydrate (SnCl₄·H₂O) and thiourea in de-ionized water and Isopropyl alcohol (1:3 ratio). The prepared films structural, morphological and optical properties were studied using X-ray diffraction (XRD), scanning electron microscope (SEM), UV–Vis spectrophotometer. The structure of the films were found to be face centered cubic with preferential orientation along (002) plane. X-ray line profile analysis was used to evaluate the micro structural parameters such as crystallite size, micro strain, dislocation density and texture coefficient. The average crystallite size values are 60 nm. Morphological results of the SnS₂ thin films are small needle shaped particles and the average grain size was 400 nm. The optical studies revealed that the band gap between 2.65 and 2.72 eV and high optical transmittance 98%. EDAX spectrum of tin disulfide result showed some amount of excess tin was present in the sample. This is the method with very low cost of producing tin disulfide (SnS₂) thin films, which is very important for many applications in industry.     

Synthesis and characterization of pure anatase TiO<Subscript>2</Subscript> nanoparticles

Pure anatase TiO₂ nanoparticles were synthesized by microwave assisted sol–gel method and further characterized by powder X-ray diffraction (XRD), energy dispersive x-ray analysis (EDAX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–Visible spectrophotometer, SEM images showed that TiO₂ nanoparticles were porous structure. The XRD patterns indicated that TiO₂ after annealed at 300 °C for 3 h was mainly pure anatase phase. The crystallite size was in the range of 20–25 nm, which is consistent with the results obtained from TEM images. Microwave heating offers several potential advantages over conventional heating for inducing or enhancing chemical reactions.     

Synthesis and characterization of Co-doped nano-TiO<Subscript>2</Subscript> through co-precipitation method for photocatalytic activity

The aim of this work was synthesis and investigation of various properties of Co-doped titanium dioxide nanostructures. Synthesis was conducted by the co-precipitation method using cobalt nitrate and titanium isopropoxide as a precursor, followed by thermal treatment at a temperature of 500 °C. The materials were fully characterized using several techniques (X-ray diffraction XRD, SEM, FTIR, TGA/DTA, UV–Vis diffuse reflectance DRS and photoluminescence). However, dopant has no effect on XRD pattern of the host but it can influence on the various characteristics of host such as optical and electrical properties. The scanning electron microscopy was used to detect the morphology of synthesized nanoparticles which sizes changed with the altitude in the doping concentration to 6%. FTIR spectra exhibit broad peaks where anatase phases of TiO₂ demonstrate very sharp UV–Vis band gap results showed the reduction in band gap from from 3.21 eV, for undoped TiO₂, to 2.74 eV, for Co doped 6% TiO₂. The photocatalytic activity of the samples were studied based on the degradation of methyl orange as a model compound, where the results showed that Co doped 6% TiO₂ a good photocatalytic activity.     

A facile one step synthesis of SnO<Subscript>2</Subscript>/CuO and CuO/SnO<Subscript>2</Subscript> nanocomposites: photocatalytic application

Here novel photocatalysts, SnO₂/CuO and CuO/SnO₂ nanocomposites were successfully synthesized by chemical method at room temperature. X-ray Diffraction (XRD), transmission electron microscopy (TEM), Fourier transform Infrared (FT-IR), UV–Visible (UV–Vis) and photoluminescence (PL) spectroscopy were utilized for characterization of the nanocomposites. The photocatalytic activity of the nanocomposites was investigated. The hybrid nanocomposites exhibited high photocatalytic activity as evident from the degradation of methylene blue (MB) dye. The result revealed substantial degradation of the MB dye (92 and 69.5% degradation of SnO₂/CuO and CuO/SnO₂, respectively) under visible light illumination with short period of 30 min. Their large conduction band potential difference and the inner electrostatic field formed in the p–n heterojunction provide a strong driving force for the photogenerated electrons to move from Cu₂O to SnO₂ under visible light illumination. The excellent photodegradation of methylene blue suggested that the heterostructured SnO₂/CuO nanocomposite possessed higher charge separation and photodegradation abilities than CuO/SnO₂ nanocomposite under visible light irradiation.     

Synthesis and characterization of porous platelet-shaped α-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> with enhanced photocatalytic activity for 17α-ethynylestradiol

The porous platelet-shaped α-Bi₂O₃ photocatalyst was successfully synthesized by a novel hydrothermal–calcination method assisted with ethylenediamine and polyvinylpyrrolidone. The physical and chemical properties of α-Bi₂O₃ photocatalyst were characterized based on XRD, XPS, SEM, TEM, EDS, UV–Vis DRS, and PL techniques. The influence of preparation conditions on the formation of α-Bi₂O₃ photocatalyst was investigated, and the effect of catalyst dosage and pH value on the EE2 removal rate was also investigated. The synthesized porous platelet-shaped α-Bi₂O₃ photocatalyst exhibited excellent photocatalytic activity for 17α-ethynylestradiol (EE2), and 97.8% of EE2 was removed after 75 min of visible light irradiation using α-Bi₂O₃ as photocatalyst. The reaction rate constant over the porous platelet-shaped α-Bi₂O₃ photocatalyst was 11.6 and 11.4 times of that of traditional α-Bi₂O₃ and N-TiO₂, respectively. The possible photocatalytic mechanism has been discussed on the basis of the theoretical calculation and the experimental results. The porous platelet-shaped α-Bi₂O₃ was a stable and efficient photocatalyst, proving that it is a promising photocatalyst.     

Optical properties of Eu<Superscript>3+</Superscript> activated SrLa<Subscript>2</Subscript>O<Subscript>4</Subscript> red-emitting phosphors for WLED applications

The SrLa_2?xO₄:xEu³⁺ phosphors are synthesized through high-temperature solid-state reaction method at 1473 K with various doping concentration. Their phase structures, absorption spectra, and luminescence properties are investigated by X-ray diffraction (XRD), UV–Vis spectrophotometer and photoluminescence spectrometry. The intense absorption of SrLa_2?xO₄:xEu³⁺ phosphors have occurred around 400 nm. The prominent luminescence spectra of the prepared phosphors exhibited bright red emission at 626 nm. The doping concentration 0.12 mol% of Eu³⁺ is shown to be optimal for prominent red emission and chromaticity coordinates are x?=?0.692, y?=?0.3072. Considering the high colour purity and appropriate emission intensity of Eu³⁺ doped SrLa₂O₄ can be used as red phosphors for white light emitting diodes (WLEDs).     

Ag-decorated octahedral K<Subscript>2</Subscript>Nb<Subscript>2</Subscript>O<Subscript>6</Subscript> nanoparticles with enhanced photocatalytic performance

The Ag-K₂Nb₂O₆ nanocomposites are synthesized by a two-step method where the octahedral K₂Nb₂O₆ is initially prepared by solvothermal reaction and then the Ag particles are anchored onto the surface of K₂Nb₂O₆ through the photoreduction of AgNO₃. The XRD, SEM, TEM, XPS, DRS are applied to characterize the structure, morphology and optical properties, which confirm that the Ag particles are successfully deposited on the surface of K₂Nb₂O₆. Compared with the pure K₂Nb₂O₆, the Ag modified K₂Nb₂O₆ catalysts show an obvious enhancement catalysis under UV–Vis light, because that could efficiently promote the light absorption and the separation of photoelectrons and holes.     

Structural,Conductivity, and Dielectric Properties of Co<Subscript>0.5</Subscript>Mg<Subscript>0.5</Subscript>La<Subscript>0.1</Subscript>Fe<Subscript>1.9</Subscript>O<Subscript>4</Subscript> Ferrite Nanoparticles

The ferrite-based Co_0.5Mg_0.5La_0.1Fe_1.9O₄ nanoparticle system has been synthesized by using the chemical co-precipitation technique. XRD and SEM were used for the structural and morphological characterization of the nanoparticles. The XRD analysis of the synthesized samples confirmed the formation of the single-phase cubic spinel phase without any impurity or secondary phases, and the average crystallite size and lattice parameters were found as 11.89 nm and 8.376 nm, respectively. The cation distribution obtained is found as (Mg_0.19Fe_0.81)_A(Mg_0.31Fe_1.09Co_0.5La_0.1)_BO₄ from Rietveld refinement. The dielectric properties of the sample have been investigated in the frequency range of 20 Hz to 1 MHz. The DC and AC conductivity results obtained from the experiments are explained by the Verwey and correlated barrier hopping (CBH) models, respectively. The optical band gap energy of the sample is found as 0.24 eV. The results denoted the semiconductor nature of the sample, and the sample is a good candidate for applications in high-frequency transformers used for different purposes in the electronics industry.     

Effect of Zn<Superscript>2+</Superscript>, Ti<Superscript>2+</Superscript> dopants on structural,optical and electrochemical properties of V<Subscript>2</Subscript>O<Subscript>5</Subscript> nanoparticles synthesized via non-aqueous sol–gel route

Transition divalent metal cations (Zn²⁺, Ti²⁺) doped V₂O₅ nanoparticles were synthesized via non-aqueous sol–gel route. The influence of dopant materials on the characteristics of V₂O₅ nanoparticles was studied. XRD studies ensure that all the prepared samples possess phase pure orthorhombic structure. From the FESEM images, it was noted that the products possess uniform particle size around 20–30 nm. The presence of functional groups and dopants was confirmed by FTIR, Raman, and elemental analysis respectively. From UV–Vis spectra, the significant blue shift was observed for doped samples compared to pure V₂O₅ nanoparticles, which is attributed to the quantum confinement effect. The high capacity retention of the intercalation compound was measured by using C–V study and implies that the prepared samples are very promising electrode materials for supercapacitor.     

Novel controlled hydrothermal synthesis of three different CeO<Subscript>2</Subscript> nanostructures and their morphology-dependent optical and magnetic properties

In the work, we explored an efficient synthetic platform to purposefully fabricate CeO₂ nanostructures with different morphologies of by controlling the different solution conditions. All the obtained samples were characterized by means of XRD, SEM, TEM, XPS, Raman scattering, UV–Vis, Photoluminescence (PL) spectra and M–H curves. The results show that all the samples have a cubic fluorite structure and the samples synthesized in alkaline, acidic and neutral aqueous solution display nanorod/nanotube, nano-plate and nano-octahedron structure, respectively. It was also found that there is a red-shifting in the band gap of the obtained material compared to bulk one, which is mainly attributed to the influences of Ce³⁺ ions, oxygen vacancies and the change of sample morphology. The existence and increase of Ce³⁺ ions and oxygen defects in the CeO₂ samples can lead to a smaller band gap, stronger PL diffraction and elevated ferromagnetism.     

Co<Subscript>2</Subscript>SiO<Subscript>4</Subscript> nanostructures/nanocomposites: synthesis and investigations of optical,magnetic, photocatalytic,thermal stability and flame retardant properties

Cobalt orthosilicate (Co₂SiO₄) nanostructures and nanocomposites were successfully synthesized via a sol–gel method, by controlling different conditions. The gels were prepared starting from cobalt (II) acetatete tetrahydrate (Co(CH₃COO)₂·4H₂O), tetraethyl orthosilicate, NH₃ and carbohydrate at calcination temperature 500–700 °C for 5 h. We choose 700 °C as optimum calcination temperature base on XRD results. SEM images showed that NH₃ and glucose are optimum catalysis and capping agent, respectively, in our experimental conditions. For the first time, glucose, fructose, sucrose, maltose and lactose were applied as capping agents to green synthesis of cobalt orthosilicates. The optical and magnetic properties of Co₂SiO₄ nanostructures were investigated by UV–Vis and VSM, respectively. Also, for the first time photocatalytic behavior of these nanostructures was evaluated using UV–Vis and degradation of methyl orange, methylene blue, erythrosine and eosine. DSC and TG curves of the nanocomposites showed both thermal stability and flame retardant property for Co₂SiO₄ nanocomposites prepared in the presence of the PS and PSU.     

Synthesis of silver and sulphur codoped TiO<Subscript>2</Subscript> nanoparticles for photocatalytic degradation of methylene blue

In the present work, silver and sulphur codoped TiO₂ (Ag–S/TiO₂) photocatalysts were effectively prepared by sol–gel technique. The prepared samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive x-ray analysis (EDX), Fourier transform infrared (FTIR) spectroscopy, diffuse reflectance UV–Vis spectroscopy (UV-DRS) and photoluminescence (PL). The XRD patterns consisted of anatase crystalline phases and the particle size and shape of the prepared samples were observed by SEM and HR-TEM. The presence of doping ions was confirmed by EDX analysis, the decreased band-gap energy of Ag–S codoped TiO₂ nanoparticles was investigated by UV-DRS. The decreased in the intensity of Ag–S codoped TiO₂ was absorbed due to the lower separation of electron–hole pairs were confirmed by PL spectrum. The Ag–S codoped TiO₂ showed higher photocatalytic activity than pure and single-doped TiO₂ in the photodegradation of methylene blue (MB) aqueous solution under visible light irradiation. The given work was a good model to associate the considering of the synergistic effect of metal and non-metal codoped TiO₂ in the photocatalysis and photo electrochemistry.     

Fabrication and characterization of nanostructured (Sn–Ti)O<Subscript>2</Subscript> pellets and films for liquefied petroleum gas sensing

Present paper reports the synthesis of nanostructured (Sn–Ti)O₂ via physicochemical method, its characterization and performance as liquefied petroleum gas (LPG) sensor. The synthesized material was characterized using XRD that confirmed the formation of (Sn–Ti)O₂ nanocomposite. Minimum crystallite size was found as 7 nm. The material was also investigated through SEM, DSC, FTIR, PL and UV–Vis spectrophotometer. Further, the pellet, thick and thin films were fabricated for the sensing analysis. Pellets (9 mm diameter, 4 mm thickness) of (Sn–Ti)O₂ nanocomposite were made by hydraulic pressing machine by applying uniaxial pressure of 616 MPa, thick films (thickness ~2 µm) were made by screen printing technique and thin films were prepared using a Photo resist spinner unit. Further at room temperature, the pellet and films were exposed to LPG in a gas chamber under controlled conditions at room temperature and variations in resistance with the concentrations of LPG were observed. The maximum value of sensitivity of solid state pellet, thick and thin films based sensors were found 7, 9 and 39 for 5 vol% of LPG, respectively. Sensing characteristics were found to be reproducible, after 6 months of their fabrication, indicating the stability of the sensors.     

An efficient visible light photocatalyst prepared from TiO<Subscript>2</Subscript> and polyvinyl chloride

An efficient visible light photocatalyst has been prepared from TiO₂ nanoparticles and a partly conjugated polymer derived from polyvinyl chloride (PVC). It was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), UV–visible diffuse reflectance spectroscopy (UV–Vis DRS), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The visible light photocatalytic activity of the as-prepared photocatalyst was evaluated by the photocatalytic degradation of Rhodamine B (RhB) under visible light irradiation. The XPS, FT-IR, and Raman spectra show that the partly conjugated polymer derived from PVC exists on the surface of the TiO₂ nanoparticles. The UV–Vis DRS, XRD, and TEM results reveal that the modification of the partly conjugated polymer can obviously improve the absorbance of the TiO₂ nanoparticles in the range of visible light and hardly affect their size and crystallinity. The visible light photocatalytic activity of the as-prepared TiO₂ nanocomposites is higher than that of commercial TiO₂ (Degussa P25) and comparable with those of visible light photocatalysts reported in the literature. Their visible light photocatalytic stability is also good. The reasons for their excellent visible light photocatalytic activity and the major factors affecting their photocatalytic activity are discussed.