A novel approach for the synthesis of highly active ZnO/TiO2/Ag2O nanocomposite and its photocatalytic applications

The present work is focused on the preparation of hybrid ZnO/TiO₂/Ag₂O nanocomposite for enhanced photocatalytic activity. The resultant samples are characterized by using XRD, SEM, EDX, HR-TEM, UV-DRS, BET and XPS techniques. X-ray diffraction analysis indicates the co-existence of wurtzite, anatase and cubic phases in ZnO/TiO₂/Ag₂O nanocomposite. The band gap energy value of the photocatalyst is 3.39 eV, which has been evidenced from UV–visible diffuse reflectance spectroscopy measurements. Photocatalytic degradation of methylene blue dye has been investigated by using UV–visible spectrophotometer. From the result, it has been concluded that ZnO/TiO₂/Ag₂O nanocomposite has proven to be an efficient photocatalyst under UV irradiation when compared to that of mono and binary oxide systems. Further, the possible photodegradation mechanism is proposed to support the enhancement of photocatalytic activity towards degradation of dyes.     

Synthesis and characterisation of thin-film TiO2 dye-sensitised solar cell

A TiO₂ dye-sensitised solar cell (DSSC) is fabricated and characterised using: X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), electron diffraction X-ray (EDX) analysis, UV–vis spectrometry and a current?voltage (I?V) test. Thicker anatase TiO₂ gives rise to better crystallinity and subsequently leads to better cell efficiency. Mesoporous TiO₂ with a suitable, average pore size results in higher conversion efficiency. Smaller particle sizes lead to higher dye uptake and increase short circuit current density, J_sc. Addition of scattering layer and/or dual TiCl₄ treatment for DSSCs having optimum thickness enhanced their performance. A DSSC having double TiO₂ layers (20 nm+50 nm) with dual TiCl₄ treatment achieved the highest conversion efficiency of 9.78%.     

Nano Ca–Mg–Zn ferrites as tuneable photocatalyst for UV light-induced degradation of rhodamine B dye and antimicrobial behavior for water purification

We report the synthesis of Ca-doped Mg–Zn ferrite Mg_0.4Zn_(0.6-x)Ca_xFe₂O₄ nanomaterials with x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6 through citrate precursor approach and their structural, morphological, optical, photocatalytic, and antimicrobial properties were systematically studied. The prepared nanoferrites's cubic spinel structure with an average crystallite size of 15–38 nm was evaluated by the XRD examination. The spherical morphology of these ferrite nanoparticles was seen from scanning electron microscopy (SEM). The observed bands at 560 cm⁻¹ and 406 cm⁻¹ in the FTIR spectra confirmed the spinel structure of the synthesized nanoferrite. The optical study confirmed an optical band gap of 1.60 eV–1.86 eV. The photocatalysis was done for the degradation of rhodamine B dye solution under UV light. All the synthesized nano ferrites displayed a promising antimicrobial potential upon Candida albicans fungi. Mg_0.4Zn_0.1Ca_0.5Fe₂O₄ nanoparticles have a better photocatalytic response (99.5%) for the degradation of rhodamine B dye and show superior antimicrobial activity (96.1%) for the inhibition of Candida albicans fungi.     

Characterization and relative photonic efficiencies of a new Fe-ACF/TiO2 composite photocatalysts designed for organic dye decomposition

The effect of Fe treatment on the Fe-activated carbon fiber (ACF)/TiO₂ composite catalysts was studied. Then the characterizations of Fe-ACF/TiO₂ composite catalysts were determined by employing BET, SEM, XRD and EDX instruments to analyze the potential factors. The adsorption data showed that the composites had decreased surface compared with the pristine ACF. From the results, it was shown the blocking of the micropores on the surface of ACF by treatment of Fe compound and Ti source. SEM micrographs for the Fe-ACF/TiO₂ composite catalysts indicated that practically all the ferric compounds and titanium dioxide introduced were located onto the ACF surfaces and consequently, there were dispersed into very small crystallites with growth of titanium dioxide. The XRD results showed patterns for the anatase and rutile typed titanium dioxide structure with a Fe mediated compound from the composites. The EDX results showed that the presence of C and O with Ti peaks on the Fe-ACF/TiO₂ composites decreased with an increase Fe concentration incorporated. Finally, organic dye (MB) decomposition showed the synergetic effects of adsorption, photo-degradation and enhancement of photonic activity of Fe component.     

Nanoflower-like CdS and SnS2 loaded TiO2 nanotube arrays for photocatalytic wastewater treatment and hydrogen production

In this work, nanoflower-like CdS/SnS₂/TiO₂ NTs ternary heterojunction photocatalysts were synthesized by a hydrothermal method, the relationship between the morphology, microscopic morphology, crystallinity, elemental presence state and hydrogen production performance of the ternary photocatalysts were investigated by SEM, TEM, XRD and XPS, respectively. The photocatalytic performance, electrochemical property and hydrogen production capacity of CdS/SnS₂/TiO₂ NTs were compared with pure TiO₂ NTs, CdS/TiO₂ NTs and SnS₂/TiO₂ NTs. After 2 h of photocatalytic reaction, the removal efficiency of MB wastewater reached 100%, and the photocatalytic efficiencies toward RhB and Cr(VI) removal reached 86.08% and 80.93% after 3 h, respectively. The electron spin resonance (ESR) technique certified the active radical groups that played a role in the catalytic process and further investigated the possible photocatalytic mechanism. Hydrogen production per unit time achieved 97.14 μmol h^?1 cm^?2, this work provides the new technique to achieve solar energy conversion for hydrogen generation.     

Fullerene modification CdSe/TiO2 and modification of photocatalytic activity under visible light

CdSe, CdSe-TiO₂, and CdSe-C₆₀/TiO₂ composites were prepared using sol–gel method, and their photocatalytic activity was evaluated by measuring the degradation of rhodamine B solutions under visible light. The surface area, surface structure, crystal phase, and elemental identification of these composites were characterized by nitrogen adsorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and UV-visible (vis) absorption spectrophotometry. XRD showed that the CdSe-C₆₀/TiO₂ composite contained a typical single and clear anatase phase. SEM of the CdSe-C₆₀/TiO₂ composites revealed a homogenous composition in the particles. EDX revealed the presence of C and Ti with strong Cd and Se peaks in the CdSe-C₆₀/TiO₂ composite. The degradation of dye was determined by UV–vis spectrophotometry. An increase in photocatalytic activity was observed and attributed to an increase in the photoabsorption effect by fullerene and the cooperative effect of the CdSe. The repeatability of photocatalytic activity was also tested in order to investigate the stability of C₆₀ and CdS-C₆₀/TiO₂ composites.     

Green synthesis of reduced graphene oxide supported TiO2/Co3O4 nanocomposite for photocatalytic degradation of methylene blue and crystal violet

The hybrid rGO-TiO₂/Co₃O₄ nanocomposite was successfully synthesized through co-precipitation method. The structural, morphological, compositional and optical properties of the as synthesized nanocomposite were characterized by X-ray diffraction (XRD), Field Emission scanning electron microscopy (FESEM), energy dispersive X-Ray Spectroscopy (EDS), Fourier transformation infrared spectroscopy (FTIR), UV–visible spectrophotometer (UV–vis) and photoluminescence (PL). XRD, EDS and FTIR confirms the existence of rGO-TiO₂/Co₃O₄ in the prepared nanocomposite. FESEM confirms that the TiO₂/Co₃O₄ nanocomposite are adsorbed on the surface of the rGO. UV–Vis and PL spectra revealed that the absorbance and emission occurred at visible region, which greatly supports the photocatalytic dye degradation through the electron-hole separation. The percentage decolorization of methylene blue dye solution was higher with lesser time compared to crystal violet dye. This result concludes that the commercialization of rGO/TiO₂/Co₃O catalyst may useful for treating various dyes in industries.     

Synthesis and photocatalytic performance of PVA/TiO2/graphene‐MWCNT nanocomposites for dye removal

TiO₂/graphene‐MWCNT nanocomposite was prepared using solvothermal reaction for the effective distribution of TiO₂ nanoparticles on carbonaceous materials. TiO₂/graphene‐MWCNT nanocomposite was immobilized in poly(vinyl alcohol) (PVA) matrix for a convenient recovery after wastewater purification. MWCNT was incorporated in a nanocomposite not only to prevent the restacking of graphene but also to increase the electron transfer from TiO₂. The detailed characterization of the nanocomposite was performed using SEM, EDX, XRD, XPS, and FTIR. The photocatalytic performance of PVA/TiO₂/graphene‐MWCNT nanocomposite was investigated by UV spectroscopy on the basis of degradation of organic pollutants. PVA/TiO₂/graphene‐MWCNT nanocomposite showed improved photocatalytic decomposition of more than 70% of residual dye left in case of using PVA/TiO₂/graphene nanocomposite due to the improved electron transfer and the higher adsorption of organic pollutants. PVA/TiO₂/graphene‐MWCNT nanocomposite was suitable as a promising material for the recyclable photocatalytic wastewater purification system. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40715.     

Fabrication of CdS and CuWO4 modified TiO2 nanoparticles and its photocatalytic activity under visible light irradiation

CdS and CuWO₄ modified TiO₂ nanoparticles (CdS–CuWO₄-TiO₂) were prepared by the chemical impregnation method. The as-prepared nanoparticles were characterized using UV–visible-diffuse reflectance spectroscopy (UV–vis-DRS), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and B.E.T. surface area analysis techniques. The photocatalytic activity was evaluated based on the degradation of a dye (eosin-Y) and inactivation of a bacterium (Pseudomonas aeruginosa). The results revealed that CdS–CuWO₄-TiO₂ showed high photocatalytic activity over CdS-TiO₂, CuWO₄-TiO₂ and TiO₂. Moreover the reusability and stability of the photocatalyst for the degradation of eosin-Y was also studied.     

Increasing of Photocatalytic Performance of TiO2 Nanotubes by Doping AgS and CdS

Highly ordered titanium nanotubes (TiO₂ NTs) photocatalyst was prepared by the anodic oxidation method, and AgS, CdS, and AgS/CdS nanoparticles were doped on the surface of TiO₂ NTs by the successive ion adsorption and reaction (SILAR) method. The photocatalysts were characterized by SEM, EDS, XRD, and potentiostat system. The SEM and EDS analyses respectively show that the average outer diameter of prepared photocatalysts is in the range of 50–120?nm, and the presence of Ti, O, Ag, and Cd is successfully proved. The photocatalytic properties of TiO₂ NTs and doped TiO₂ NTs were studied by measuring the degradation of Methylene Blue (MB) solution. The experimental results show that AgS/CdS/TiO₂ photocatalyst exhibited most efficient photocatalytic activity with 340?µA/cm² photocurrent value. AgS/CdS/TiO₂ NTs photocatalyst shows up to 22.20% higher than TiO₂ NTs, 16.42% higher than CdS/TiO₂ NTs, and 4.3% higher than AgS/TiO₂ NTs.     

TiO2 nanofibers doped with rare earth elements and their photocatalytic activity

In the present study rare earth doped (Ln³⁺–TiO₂, Ln = La, Ce and Nd) TiO₂ nanofibers were prepared by the sol–gel electrospinning method and characterized by XRD, SEM, EDX, TEM, and UV-DRS. The photocatalytic activity of the samples was evaluated by Rhodamine 6G (R6G) dye degradation under UV light irradiation. XRD analysis showed that all the synthesized pure and doped titania nanofibers contain pure anatase phase at 500 °C but at 700 °C it shows both anatase and rutile phase. XRD result also shows that Ln³⁺-doped titania probably inhibits the phase transformation. The diameter of nanofibers for all samples ranges from 200 to 700 nm. It was also observed that the presence of rare-earth oxides in the host TiO₂ could decrease the band gap and accelerate the separation of photogenerated electron–hole pairs, which eventually led to higher photocatalytic activity. To sum up, our study demonstrates that Ln³⁺-doped TiO₂ samples exhibit higher photocatalytic activity than pure TiO₂ whereas Nd³⁺-doped TiO₂ catalyst showed the highest photocatalytic activity among the rare earth doped samples.     

High photonic effect of organic dye degradation by CdSe–graphene–TiO2 particles

Photocatalytic activity of CdSe (cadmium selenide) decorated graphene composites coupled with TiO₂ (titanium oxide) was investigated with organic dye solutions. The characterizations of composites were studied by X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscope (SEM), and with transmission electron microscope (TEM). The degradation of methyl orange (MO) and rhodamine B (RhB) was observed by measuring the decrease in the concentration by UV spectrophotometer. The synergistic effect of graphene on CdSe and TiO₂ was demonstrated by comparative study. The composites were tested for recyclability, investigating the stability of CdSe–graphene/TiO₂ composites.     

Morphological,structural and ellipsometric investigations of Cr doped TiO2 thin films prepared by sol–gel and spin coating

Pure and chromium doped titanium dioxide (TiO₂) thin films at different atomic percentages (0.5%, 1.3% and 2.9%) have been elaborated on ITO/Glass substrates by sol–gel and spin–coating methods using titanium (IV) isopropoxide as a precursor. The surface morphology of films was investigated by scanning electron microscopy (SEM) and Atomic Force Microscopy (AFM), the structure was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and high resolution transmission microscopy (HRTEM). SEM and HRTEM show homogenous and polycrystalline films. XRD patterns indicate a phase transition from anatase to anatase-rutile leading to expand the absorption band of TiO₂ molecules around 520 cm⁻¹ in FTIR spectra. The optical constants such as the refractive index (n), the extinction coefficient (K) and the band gap (E_g) as well as the film thickness are determined using spectroscopic ellipsometry technique and Fourouhi–Blommer dispersion model. Results show three major changes; (i) the thickness of pure TiO₂ layer is 54 nm, which linearly decreases when the layer is doped with chromium and reaches 33 nm for a doping concentration of 2.9%, (ii) the band gap energy (E_g) is also linearly reduced from 3.24 eV to 2.80 eV when the Cr-doping agent increases, and, (iii) a phase transition from anatase to anatase-rutile is observed causing an increase in values of n(λ) for wavelength greater than 350 nm.     

Characterization of microwave processed aluminium powder

Commercial Al powder was exposed to microwave radiation for 45 min. The as received and microwave heated Al powders were characterized by X-ray diffraction analysis (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and transmission electron microscopy (TEM). XRD of the microwave treated Al powder confirmed the formation of Al-Al₂O₃ composite. FTIR studies and EDX analysis indicated the transformation of Al powder into Al-Al₂O₃ core-shell composite powder after microwave processing. SEM showed that the morphology of the microwave processed Al powder was quite different from that of the as-received Al powder. TEM image of the microwave treated Al powder supported the FTIR and EDX data.     

One-pot synthesis of CdS sensitized TiO2 decorated reduced graphene oxide nanosheets for the hydrolysis of ammonia-borane and the effective removal of organic pollutant from water

A hybrid material of reduced graphene oxide (RGO) sheets decorated with CdS-TiO₂ NPs was prepared through a facile one-pot hydrothermal method. The assembly of CdS-TiO₂ nanoparticles (NPs) on RGO sheets was in-situ produced. As-synthesized nanocomposites were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy disperse X-ray spectrum (EDS), fourier transform infrared spectroscopy (FTIR), and photoluminescence spectroscopy (PL). The obtained nanocomposites exhibited a good photocatalytic activity for the visible-light-induced decomposition of methylene blue (MB) dye and hydrolysis of ammonia borane. The results showed that by incorporation of CdS and TiO₂ NPs on graphene oxide sheets the photocatalytic efficiency was enhanced. The significant enhancement in the photocatalytic activity of CdS-TiO₂/RGO nanocomposites under visible light irradiation can be ascribed to the effect of CdS by acting as electron traps in TiO₂ band gap. Reduced graphene oxide worked as the adsorbent, electron acceptor and a photo-sensitizer to efficiently enhance the dye photo decomposition. Such nanocomposite photocatalyst might find potential application in a wide range of fields, including hydrogen energy generation, air purification, and wastewater treatment.     

Synthesis of flake-like bismuth tungstate (Bi2WO6) for photocatalytic degradation of coomassie brilliant blue (CBB)

Bismuth tungstate (Bi₂WO₆) flake-like nanostructures with zigzag periphery and 30–40 nm thickness in high yield were produced by facile and efficient modified hydrothermal technique. The as-synthesized nanostructures were characterized by X-ray diffraction (XRD), energy dispersive x-ray spectroscopy (EDX), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Bi₂WO₆ nanostructures were investigated as visible light photocatalyst to degrade model dye coomassie brilliant blue (CBB). The role of hydrogen peroxide (H₂O₂) used as initiator was also studied by varying concentrations during photocatalysis. It was observed that photocatalytic activity significantly enhanced for lower initiator concentrations. The growth mechanism for nanostructures was also discussed briefly.     

Photo-catalytic degradation of Metanil Yellow dye using TiO2 immobilized into polyvinyl alcohol/acrylic acid microgels prepared by ionizing radiation

Polyvinyl alcohol (PVA) microgels were prepared using electron beam irradiation. To improve the PVA microgel functionality and gel fraction, chains of polyacrylic acid (PAA) were incorporated into PVA microgel by radiation grafting technique. The increase in the acrylic acid (AA) content as well as PVA Mwt is accompanied by a mutual increase in the gel fraction and a decrease in the swelling%. Immobilization of different TiO₂ concentrations on the surface of the prepared PVA–AA microgel was carried out. The structural changes in the prepared PVA–AA microgel immobilized with TiO₂/were investigated using FTIR, EDX and XRD. Photodegradation efficiency of TiO₂/PVA–AA microgel against metnil yellow dyes was studied. TiO₂/PVA–AA microgel activity increases with the increase of the amount of TiO₂ and results in an increase in the rate of the photodegradation reaction. Easily recovery and reusability made TiO₂/PVA/AA of great important in practice use as a photocatalytic degradation composite, for dye removal from wastewater.     

Ultrasonic assisted synthesis of TiO2–reduced graphene oxide nanocomposites with superior photovoltaic and photocatalytic activities

In this work, TiO₂–reduced graphene oxide (RGO) nanocomposites were successfully produced by an ultrasonication-assisted reduction process. The reduction of graphene oxide (GO) and the formation TiO₂ crystals occurred simultaneously. The synthesized nanocomposite was characterized by SEM, EDX, Raman spectroscopy, FTIR, XRD, XPS, UV–vis spectroscopy, photoluminescence spectrometer and electrochemical impedance spectroscopy. As a result of the introduction of RGO, the light absorption of octahedral TiO₂ was markedly improved. The photocatalytic results revealed that weight percent of RGO has substantial influence on degradation of Rhodamine B under visible light irradiation. The enhancement of the photocatalytic activity can be attributed to the enhancement of the visible-light irradiation harvesting and efficiently separation of the photogenerated charge carriers. Meanwhile, upon the RGO loading, the photoelectric conversion efficiency of TiO₂–RGO nanocomposite modified electrode was also highly improved.     

How different dopants leads to difference in photocatalytic activity in doped TiO2?

This study explores the significance of dopant location in a doped TiO₂ nanostructure in ascertaining its photocatalytic properties. The un-doped TiO₂, boron-doped TiO₂ (B–TiO₂) and nitrogen-doped TiO₂ (N–TiO₂) photocatalysts were synthesized (with variable dopant concentrations) via sol-gel method. The photocatalysts were further characterized for structural, surface, and physico-chemical properties in reference to their influence on photocatalytic properties. The results of X-ray diffraction (XRD), micro Raman, Energy dispersive X-ray technique (EDX), X-ray photoelectron spectroscopy (XPS), and Fourier Transform infrared spectroscopy (FTIR) confirmed the existence of B and N atoms in the TiO₂ crystal lattice. The results also indicated that the B and N doping promoted the formation of rutile phase in doped TiO₂. Further, B doping leads to decrease in the surface area whereas N doping leads to increase in surface area of TiO₂. The UV–Vis DRS analysis revealed that a red shift in absorption band edge occurs upon B and N doping. The band gap values also decreased to 2.96 and 2.27 eV in B–TiO₂ and N–TiO₂, respectively in comparison to 2.98 for un-doped TiO₂. The photocatalytic degradation studies of diclofenac sodium (DCLF) were conducted to examine the effect of dopant role on the efficiency of doped photocatalyst. B–TiO₂ exhibited maximum photocatalytic activity by degrading 98% of DCLF in comparison to N–TiO₂, which showed 95% degradation.     

Optimal engineering of CdS/PbS co-sensitized TiO2 nanotube arrays for enhanced photoelectrochemical performance

TiO₂ nanotube arrays (NTAs) are decorated with CdS/PbS nano-sensitizers by successive ionic layer adsorption and reaction (SILAR) method. The uniform growth of the CdS and PbS nanoparticles on the surface and inner side of TiO₂ Nanotube Arrays (NTAs) has been confirmed by Transmission Electron microscopy measurements. The impact of the CdS and PbS semiconductor quantum dots (SQDs) on the photoelectrochemical performance (PEC) of TiO₂ NTAs was systematically investigated, and the optimal decoration of the CdS and PbS SQDs on the TiO₂ NTAs was obtained. CdS/PbS co-sensitized TiO₂ NTA photoanode films show excellent response to visible light (with absorption extended to 825 nm) and enhanced PEC performance. The best performing device showed an enhanced photocurrent density under the 0.62V vs SCE up to 8.2 mA/cm², and high photoconversion efficiency up to 5.35%, which is 16.7 times higher than the pure TiO₂ NTAs. The enhanced PEC performance of TiO₂ NTAs is attributed to the co-sensitization, heterojunction formation and electron “pool” effect imparted on the NTAs by the coupling of CdS and PbS SQDs.