UV Diffuse Reflectance Spectroscopy Research Articles

Preparation and study of ternary polypyrrole-tin oxide-chitin nanocomposites and their potential applications in visible light photocatalysis and sensors

In the present study, nanoparticles of tin oxide were synthesised by co-precipitation method along with polypyrrole-chitin matrix prepared by chemical oxidative polymerisation technique. The synthesized nanocomposites were characterized by Fourier transform–infra red spectroscopy (FT-IR), UV-diffuse reflectance spectroscopy (UV-DRS), X-ray diffraction (XRD) to determine the functional group, optical properties, crystallite size and geometry respectively. Moreover scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDAX) was used to study surface morphology and elemental composition of the sample. The synthesised nanocomposites shows enhanced photocatalytic activity towards RhB dyes under visible light with increasing tin oxide content. The holes and superoxide free radicals were found to be dominant species in photocatalysis confirmed by quenching experiment. The photocatalyst also shows better adsorption capability and recyclability, also the photodegradation favours the acidic medium. Furthermore, the electrocatalytic properties of the nanocomposites were also investigated by cyclic voltammetry for detection of methanol (0.001 M to 0.5 M) by drawing cyclic voltammogram in the range −1.0 to +1.0 V at scan rate of 10 mV/s. The nanocomposites as electrocatalyst showed better sensitivity even at lower concentration of 0.001 M. From the given data, it is evident that the synthesized nanocomposites can be used as effective photocatalyst as well as electrocatalyst in different areas.

In-situ dual applications of ionic liquid coated Co2+ and Fe3+ co-doped TiO2: Superior photocatalytic degradation of ofloxacin at pilot scale level and enhanced peroxidase like activity for calorimetric biosensing

In the present study the synthesis of an inexpensive solar light responsive Co2+ and Fe3+ co-doped TiO2 (CoFeTiO2) for efficient photocatalytic degradation of ofloxacin (OFL) in addition to its excellent activity as peroxidase mimics has been reported. The as-synthesized material was fully investigated morphologically and structurally by X-ray diffraction (XRD) analysis, field emission-scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) and UV diffuse reflectance spectroscopy (UV-DRS). The morphology of the as-synthesized CoFeTiO2 appeared to be more dispersed, porous and uniform. The UV-DRS analysis showed that the band gap of the as-synthesized TiO2, FeTiO2, CoTiO2, CoFeTiO2 was measured as 3.31, 3.22, 3.15 and 3.04 eV, respectively. The pilot scale experiments were conducted in a simple non-concentrating solar photoreactor by using the as-synthesized CoFeTiO2 having total volume of 5 L. To synergize the photocatalytic process the photocatalytic reactor was added with peroxymonosulfate (HSO5−). The effect of various process parameters like [HSO5−]0, flow rate and [CoFeTiO2]0 were optimized. The assessment of degradation products (DPs) of OFL and then their toxicity analysis suggested the as-synthesized CoFeTiO2 provides a safe route for the solar light induced photocatalytic degradation of OFL. The as-synthesized Co-FeTiO2 was also applied as novel peroxidase mimetic that can catalyze 3,3′,5,5′-tetramethylbenzidine (TMB) when H2O2 serves as oxidant. The results showed that the color response and the peroxidase like response of CoFeTiO2 highly rely on the concentration of H2O2 and thus the as-synthesized material can successfully be applied for the calorimetric sensing of H2O2.

Biological synergy of greener gold nanoparticles by using Coleus aromaticus leaf extract

Greener nanotechnology plays an important role in developing alternative and effective treatment strategies for various diseases. Biological synthesis of metal nanoparticles (MNPs) has known to possess suitable alternatives than the existing chemical methods. Greener synthesis of MNPs by using plant extracts has become an emerging field due to their safe, eco-friendly and non-toxic nature that are suitable for synergistic biological activities. Hence, the greener method is chosen by the present study. In the present study, the greener synthesis of gold nanoparticles (AuNPs) was successfully done by using Coleus aromaticus leaf extract at three different temperatures (30 °C, 60 °C and 100 °C). The formation of AuNPs was initially monitored by visual observation and then characterized with the help of diverse techniques like UV–Vis spectroscopy (UV–Vis), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Scanning Electron Microscopy (SEM), High Resolution-Transmission Electron Microscopy (HR-TEM) and dynamic light scattering (DLS). Surface plasmon resonance (SPR) peak and crystalline nature of AuNPs were obtained by UV–Vis and XRD spectroscopies respectively. FT-IR analysis shows the different characteristic functional groups in turn responsible for the bio-reduction of gold ions by using leaf extract. The formations of different nano-sized AuNPs with their different morphologies were observed by SEM and HR-TEM analyses. Surface charge and stability of the AuNPs were measured by zeta potential and DLS respectively. The synthesized AuNPs coated with cotton fabric was analyzed by UV-Diffuse Reflectance Spectroscopy (UV-DRS), which revealed excellent UV protection against UV radiation. The AuNPs coated cotton fabric exhibited remarkable antibacterial sensitivity against Staphylococcus epidermidis and Escherichia coli. Further, the synthesized AuNPs showed significant cytotoxicity against human liver cancer (HepG2) cell line. The findings of this study revealed that, AuNPs synthesized using Coleus aromaticus leaf extract could be an alternative, safe, and effective source of UV protection, antibacterial and anticancer agents.

Influence of Surfactant on the Phase Transformation of Bi2O3 and its Photocatalytic Activity

Bismuth oxide with its unique narrow bandgap has gained significant attention in the field of photocatalysis. A new and efficient method to synthesise bismuth oxide with tuneable properties is proposed herein. A surfactant assisted modified sol–gel method is used to synthesise bismuth oxide with excellent photocatalytic activity for the degradation of Rhodamine B dye. Three different surfactants, namely polyethylene glycol-400, sodium lauryl sulfate, and cetyltrimethylammonium bromide (CTAB) have been used. The fabricated bismuth oxide nanoparticles were characterised by X-ray diffraction, IR, scanning electron microscopy, and UV-diffuse reflectance spectroscopy analysis. Evolution of both the α and β crystalline phases of bismuth oxide was observed. The bandgap of the synthesised bismuth oxides ranges from 2.03 to 2.37eV. The CTAB assisted synthesised bismuth oxide with a bandgap of 2.19eV showed the highest photocatalytic activity of 93.6% under visible light for the degradation of Rhodamine B. This bismuth oxide based catalyst opens a new avenue for efficient photocatalysis for environmental remediation.

BiF3 octahedrons: A potential natural solar light active photocatalyst for the degradation of Rhodamine B dye in aqueous phase

Herein, we report the successful synthesis of BiF3 octahedrons via facile hydrothermal process as potential solar light active catalyst for the photocatalytic degradation of Rhodamine B (RhB) dye in aqueous phase. The synthesized BiF3 octahedrons were characterized by several techniques such as X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), Fourier transform infrared (FT-IR) spectroscopy, UV-diffuse reflectance spectroscopy (UV-DRS), photoluminescence (PL) spectroscopy, thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET) techniques in order to observe the structural, morphological, optical and luminescence properties. The synthesized octahedrons possess the high density growth, pure and well-crystalline with cubic phase structure and band gap of 3.98 eV. As a potential solar light active photocatalyst, the synthesized BiF3octahedrons exhibited ˜95.7% degradation of RhB in 50 min. The effect of different process parameters such as pH and catalyst dose on the degradation of RhB was also explored. Interestingly, the synthesized BiF3 octahedrons demonstrated better photocatalytic performance compared to several commercially available photocatalysts such as TiO2 (PC-500), SnO2 and ZnS. Further, it was observed that the degradation of RhB over the prepared BiF3 octahedrons obeyed the pseudo first-order reaction kinetics with rate constant of 0.06393 min−1. The scavenger experiments verified the role of h+, e, O2, OH and OHs in the photocatalytic degradation process and a plausible photocatalytic mechanism has also been proposed.

High-Performance Photocatalytic Hydrogen Production and Degradation of Levofloxacin by Wide Spectrum-Responsive Ag/Fe3O4 Bridged SrTiO3/g-C3N4 Plasmonic Nanojunctions: Joint Effect of Ag and Fe3O4.

Highly photoresponsive semiconductor photocatalysis for energy and environmental applications require judicious choice and optimization of semiconductor interfaces for wide spectral capabilities. This work aims at rational designing of highly active SrTiO3/g-C3N4 junctions bridged with Ag/Fe3O4 nanoparticles for utilizing Z-scheme transfer and surface plasmon resonance effect of Ag augmented by iron oxide. The SrTiO3/(Ag/Fe3O4)/g-C3N4 (SFC) catalyst was employed for photocatalytic hydrogen production and photodegradation of levofloxacin (LFC; 20 mg/L) under UV, visible, near infra-red, and natural solar light exhibiting high performance. Under visible light (<780 nm), SFC-3 sample (30 wt % g-C3N4 and 3% Ag/Fe3O4) shows a H2 evolution of 2008 μmol g-1 h-1 which is ∼14 times that of bare g-C3N4. In addition, 99.3% removal of LFC was degraded in 90 min under visible light with retention of activity under sun. The inherent topological properties, complete, higher charge separation, and reduced recombination allowed this catalyst for a high photocatalytic response which was proved by UV-diffuse reflectance spectroscopy, photoluminescence, electrochemical impedance spectroscopy, and photocurrent response measurements. Scavenging experiments and electron spin resonance analysis reveal that the mechanism shifts from a dual charge transfer in case of binary junction to essential Z-scheme with incorporation of Ag/Fe3O4. Both •O2- and •OH are main active radicals in visible light, whereas •O2- majorly participate under UV. The synergistic effect of SrTiO3, g-C3N4, and plasmon resonance of Ag/Fe3O4 not only improves light response and reduce recombination but also enhances the redox-ability of charge carriers. A H2 production mechanism and LFC degradation pathway (degradation, defluorination, and hydrolysis) has been predicted. This work paves a way for development of photocatalysts working in practical conditions for pollution and energy issues.

Electronic and magnetic structure investigation of vanadium doped ZnO nanostructure

In the present work, vanadium doped ZnO nanostructure, Zn1-xVxO (x = 0.00, 0.01, 0.02, 0.03) have been synthesized using sol-gel route. Rietveld refined X-ray diffraction confirms the single wurtzite phase for all the prepared samples with crystallite size ranging from 20 to 40 nm. UV-Diffuse reflectance spectroscopy shows the decrease in band gap energy from 3.20 to 3.17 eV on V doping and and Photoluminescence (PL) measurements has a strong visible emission region in the range 500–700 nm. PL broad peak in the visible region is further deconvoluted to study the defect states in the V:ZnO system. V doped ZnO nanostructure shows the room temperature ferromagnetism measured through Vibrating Sample Magnetometer hysteresis curve. The magnetic moment (μB) is found to vary from 0.012 to 0.018 μB per V-atom as x changes from 0.01 to 0.03 in Zn1-xVxO matrix. Magnetic structure properties are correlated with electronic transitions at different atomic levels using near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy. NEXAFS spectral features at OK-, V/Zn L3,2- edge reveals the hybridization of V(3d)-O(2p) orbitals and absence of V-metallic clusters in V:ZnO system. These investigations further envisage the existence of +5 state of vanadium in Zn1-xVxO nanostructure.

Narrowing the band gap of TiO2 by co-doping with Mn2+ and Co2+ for efficient photocatalytic degradation of enoxacin and its additional peroxidase like activity: A mechanistic approach

This study presents the synthesis of a novel Mn2+ and Co2+ co-doped TiO2 (Mn-Co-TiO2) for the photocatalytic degradation of enoxacin (ENX) under solar light irradiation. The as-synthesized photocatalysts were fully characterized by X-ray diffraction (XRD) analysis, field emission-scanning electron microscopy (FE-SEM), and UV-diffuse reflectance spectroscopy (UV-DRS). The structural appearance of the Mn-Co-TiO2 suggests porous cylindrical type morphology. Moreover, the co-doping of Mn2+ and Co2+ has successfully reduced the band gap of TiO2 from 2.81 eV to 2.10 eV. Applying Langmuir Hinshelwood kinetic model, the photocatalytic degradation of ENX by Mn-Co-TiO2 followed pseudo-first-order kinetics. A total of twelve (12) DPs of ENX were identified by UPLC/MS-MS. The natural water constituents such as CO32−, HCO3−, Cl− and Fe3+ had great influence on the photocatalytic degradation of ENX by Mn-Co-TiO2 under solar light irradiation. The as-synthesized Mn-Co-TiO2 showed appreciable results for the photocatalytic degradation of ENX in synthetic wastewater (SWW) and real wastewater (RWW) samples. Furthermore, the toxicity assessment of ENX and its DPs towards aquatic organisms (i.e., fish, daphnia and green algae) was measured which are helpful for the practical implementation of this technology for wastewater treatment. The Mn-Co-TiO2 materials also showed good peroxidase-like activity towards the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2 and followed Michaelis-Menten kinetics.

A polyhedral metal-organic framework based on rigid precursor for photocatalytic properties

A 3D polyhedral metal organic framework, [Cu4(L)2(H2O)4∙5DMF]n (1) (H4L = 3,5‑di(3,5‑dicarboxyphenyl)nitrobenzene), has been designed and successfully synthesized. 1 shows a 3D mfj topological framework with 1D triangular channels. The UV diffuse reflectance spectroscopy of the MOF indicates its semiconducting nature which induces photocatalytic property in the MOF. The photocatalytic property of 1 in photo-degradation of organic dyes viz. methyl violet and Rhodamine B have been investigated. The possible mechanism for the photocatalytic activity of 1 against organic dyes has been addressed using density of states (DOS) and partial DOS (pDOS) calculations.

Structural, morphological and dielectric investigations on NiO/CuO/ZnO combined semiconductor metal oxide structures based ternary nanocomposites

NiO/CuO/ZnO combined semiconductor metal oxide structures based ternary nanocomposites were synthesized in 2:1:1, 1:2:1 and 1:1:2 molar ratios using a simple and combined co-precipitation - hydrothermal method without utilizing any fuels, capping agents or surfactants. The structural, bonding, band gaps and morphological behaviour of the synthesized ternary nanocomposites were investigated using x-ray diffraction, Fourier transform infrared spectroscopy, UV-Diffuse reflectance spectroscopy and atomic force microscopic measurements. The dielectric properties recorded for these combined semiconductor metal oxide structures are valid with Maxwell-Wagner (M-W) model which is based on the dielectric nature in conducting grains layered with poorly conducting grain boundaries. The higher values of dielectric constant were observed for the ternary nanocomposite ratio 1:2:1 and the reduction in the values of dielectric constant of other ternary nanocomposite ratios (1:1:2 and 2:1:1) at lower frequencies is due to the fact the grain boundaries are preferably occupied by more Cu2+ ions than Ni2+ and Zn2+ ions. This kind of attempt in investigating the physical insights of combined semiconductor metal oxide structures is needed for the development of novel semiconducting devices.

Photocatalysis of cobalt zinc ferrite nanorods under solar light

Co0.7Zn0.3Fe2O4 nanorods were synthesized from hydrazine precursor by co-precipitation technique. Infrared and thermogravimetric–differential thermogravimetric curves of the precursor indicated the bridging bidentate nature of hydrazine and three-step thermal decomposition. The as-synthesized cobalt zinc ferrite nanorods were characterized by powder X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, vibrating sample magnetometry and UV–diffuse reflection spectroscopy which proposed the phase structure, morphology, magnetic and optical properties. Co0.7Zn0.3Fe2O4 nanorods showed a sensible photocatalytic activity on Congo red, Malachite green, Methylene blue, Methyl red, Rhodamine B and Rose bengal under solar light at different time intervals and were magnetically separated.

Highly efficient light responsive BiOCl/AgI composites for photocatalytic degradation of 3-CP under visible and UV light irradiations

Novel visible light sensitive BiOCl/AgI composites were synthesized by a facile precipitation technique. Samples were characterized by SEM (scanning electron microscope), XRD (X-ray diffraction), UV-DRS (UV-diffuse reflectance spectroscopy) and XPS (X-ray photoelectron spectroscopy). Photocatalytic activity of the samples was evaluated using 3-CP under UV–Visible irradiation. Compared to pure BiOCl, AgI and other BiOCl/AgI, the composites exhibited more catalytic activity under both UV and visible lights within 120 min. Optimal content of the BiOCl in the composite system was found as 40%. The excellent degradation of 3-CP under light was attributed to the efficient separation of photo-induced charge carriers, defect levels, iodide and chlorine $$({{\text{I}}^ \cdot },{\text{C}}{{\text{l}}^ \cdot })$$ radicals. The radical scavenging activities also illustrate that holes and superoxide radicals $$({{\text{h}}^+})$$ $$~{\text{and}}\,({\text{O}}_{2}^{{ - \cdot }})$$ are dominant agents in the photocatalytic degradation process. These results demonstrated that BiOCl/AgI systems are very useful to decompose persistent organic pollutants.

Non-Metal Doped Titania Photocatalysts for the Degradation of Neonicotinoid Insecticides Under Visible Light Irradiation.

Recombination of e-/h+ pair, the major issue of any titania based photocatalytic material, is addressed here by doping non-metals such as C, N, B, F into the lattice of nano TiO2. The as-synthesised catalysts were characterized by using various instrumental techniques such as X-ray diffraction (XRD), UV-Diffuse reflectance spectroscopy (UV-DRS), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Nanosize of titania was confirmed by both XRD and TEM studies. Visible light inactivity of TiO2 is overcome by C, N, B, F doped titania catalysts in the degradation of neonicotinoid type insecticides namely imidacloprid (IMI) and thiamethoxam (TMX). The degradation efficiencies of the catalysts under different irradiations namely UV, visible and solar were compared. Among the catalysts, CNBF/TiO2 degraded IMI completely at 150, 240 and 330 min whereas TMX has been degraded completely at 210, 270 and 420 min under UV, solar and visible irradiations respectively. The recyclability test of CNBF/TiO2 confirmed its stability towards photocatalytic reaction.

Structural modulation and band gap optimisation of electrochemically anodised TiO2 nanotubes

This analytical study highlights the effects of dimensional modulations on the characteristic properties of anodically grown Titania nanotubes. Titania nanotubes were grown using electrochemical anodization method employing a two-electrode system. The as-grown nanotubes with different dimensions were characterized in order to study their structural, electrical and optical properties. The investigation reveals that the impact of dimension was pivotal in tuning the band gap of these anodically grown Titania nanotubes which asserts its successful application in various fields. The desired dimensional modulation of the nanotubes was achieved by changing the corresponding anodising voltage. This study also employs a remedial two step anodization technique in addition to the conventional one step method and presents its distinctive edge over the other as established by various characterisation techniques. The comparative variations in the structural and crystallite dimensions of the Titania nanotubes anodised by two different methods were investigated by Field Emission Scanning Electron Microscopy and X-Ray Diffraction spectroscopy respectively, while the band gap tuning ability as well as absorption characteristics were determined by UV-Diffuse Reflectance spectroscopy. Finally, the effective changes in the band gap were corroborated by analysing the field effect dark and photo-conductive nature of the two materials.

Study on light emission diode/carbon modified TiO2 system for tetracycline hydrochloride degradation

In this study, the photocatalytic performance of carbon modified TiO2 (MCT)) synthesized via a facile microwave method was evaluated by degrading tetracycline hydrochloride (TH) under Red-Green-Blue − Light Emission Diode (RGB-LED) light. The materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), N2 sorption isotherm, photoluminescence (PL), Fourier transform infrared (FT-IR), and UV-diffused reflectance spectroscopy (UV-DRS). Parameters employed for optimizing the photocatalytic degradation system were catalyst concentration, pH, light intensity (levels) and RGB-LED colour. The BET surface area, BJH desorption pore volume and diameter of MCT was slightly higher than the pure TiO2. Although both the pure TiO2 and MCT have about the same band gap energy (≈ 3.14 eV), MCT extended into the visible region. Results of the PL experiment showed that MCT had a lower electron-hole recombination rate which invariably improved its photocatalytic performance. Results from the photocatalytic degradation experiments showed that the reactions followed the pseudo first order kinetics. TH had an optimum degradation (74%, Kapp = 1.22 × 10−2 min−1) at pH 7, catalyst concentration of 300 mg/L, and White-LED light intensity of 46 W/m2 after 2 h of irradiation.

Efficient synthesis of perovskite-type oxide photocathode by nonhydrolytic sol-gel method with an enhanced photoelectrochemical activity

The photoelectrochemical activity of PbTiO3 (PTO) for water splitting was studied by linear sweeping voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) techniques. The nanohydrolytic sol-gel method was used to synthesise a crystalline PbTiO3 perovskite nanoparticles. The physical and chemical properties of nanoparticles such as crystal structure, surface area, reducibility, band gap energy, particle morphology and size, surface composition and valence states were investigated by X-Ray diffraction (XRD), BET, temperature-programmed reduction (TPR), UV diffuse reflectance spectroscopy (UV-DRS), high resolution scanning and transmission electron microscopy (HR-SEM and HR-TEM) along with X-Ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). PTO nanoparticles showed pure crystallinity, high surface area (14 m2/g) and high oxygen mobility. PTO has band gap energy of 2.66 eV, which makes it active under visible light irradiation. Moreover, nanoparticles vary in size and create a core-shell structure in a way that small particles surround large particles. The core-shell structure along with a free defected sites on the surface results in high photoelectrochemical activity for water splitting reaction. The IV curve revealed that the PTO nanoparticles are a p-type electrode with the photocurrent efficiency of ≈19%. This suggests that the photoelectrode does not require external bias to initiate the water splitting and the reaction can be initiated simply by making a connection between the anode and the cathode. In addition, a great stability is observed for PTO electrodes during the reaction, as evidenced by no leaching to the reaction medium.

The influence of experimental conditions on photocatalytic degradation of methylene blue using titanium dioxide particle

In this research, the photocatalytic degradation of methylene blue (MB) as a dye pollutant was investigated in the presence of commercial TiO2 particles. The physical and optical characteristics of commercial TiO2 were examined by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), and UV diffuse reflection spectroscopy (UV–DRS) techniques. In addition, the influence of different operating parameters such as catalyst loading, pH value, and temperature on the photodegradation efficiency was evaluated. The results showed that the commercial TiO2 had an anatase phase with a surface area of 9.85 m2/g and a pore size of 85 A; its absorbance spectrum was found to be 388 nm in the UV range involving a band gap of 3.2 eV. Besides, the optimized conditions for the highest photocatalytic activity of commercial TiO2 were 0.7 g/L of TiO2 catalyst and pH 3.0 under 50 °C of temperature, which acheived ~99% of MB removal.

PHOTOCATALYTIC DEGRADATION OF PARAQUAT USING N-TiO2/SiO2 UNDER VISIBLE LIGHT

In the present paper, photocatalytic degradation of paraquat using N-TiO2/SiO2 with different molar ratio of titanium: nitrogen (Ti:N) under visible light was investigated. The catalyst was prepared via immersed SiO2 in N-TiO2. N-TiO2 was synthesized by sol-gel method. The N-TiO2/SiO2 catalyst was characterized using X-ray diffraction, UV diffuse reflectance spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy. The results from characterizations indicated that N-doped anatase TiO2 had a 20-25 nm size. Degradation of paraquat, at an initial concentration of 10 mg/L was determined by UV-Vis. Chemical oxygen demand (COD) was used for process performance. Based on the COD tests, the COD values in residual paraquat was lower than that in initial paraquat concentration after 8 hours illumination of visible light. Moreover, the experiment’s results indicated that 80% of paraquat was degraded within 8 h of illumination time. These results showed that N-TiO2/SiO2 with molar Ti:N=2:1 gives the highest degradation efficiency of paraquat under visible light. This catalyst was stable and reusable suggesting it can be applied to treat organic pollutant in water.

Molybdenum doped graphene/TiO2 hybrid photocatalyst for UV/visible photocatalytic applications

Graphene/TiO2 photocatalysts are gaining increasing attention for its application in the decomposition of aqueous organic compounds. In this perspective, we have synthesized molybdenum doped graphene/TiO2 (Mox-GT) hybrids via simple sol-gel method. The physico-chemical properties of the samples were characterized by various analytical and spectroscopic techniques. X-ray diffraction studies indicate that pure TiO2 and graphene/TiO2 were composed of anatase with minor brookite phase while Mo doped graphene/TiO2 powders were composed of only anatase phase. Scanning and transmission electron microscopy results showed particles spherical morphology and uniform distribution of particles on graphene nanoflakes. X-ray photoelectron microscopy revealed the presence of surface defects (Ti3+ centers and oxygen vacancies), dopants electronic states (Mo6+/Mo5+), surface hydroxyl groups and the chemical linkage of graphene with TiO2. UV-diffuse reflectance spectroscopy analysis showed that addition of Mo dopant to graphene/TiO2 greatly extends the absorption band edge to the visible region. In UV and visible light photocatalytic tests Mox-GT composites showed enhanced activities, specifically the Mo0.8-GT powder outperformed the rest of the prepared photocatalysts in the decomposition of synthetic textile dye, methylene blue. This highest photocatalytic performance is ascribed to the enhanced photo absorption and electron-hole separation, high surface area and pore size and surface defects. Moreover, the obtained encouraging results portrays that the performed work could provide new insights into the fabrication of metal doped graphene/TiO2 nano-hybrid materials as high performance photocatalyst and facilitates their applications in areas such as; environmental remediation’s, hydrogen productions, solar and fuel cells.

Visible light sensitive activated carbon-metal oxide (TiO2, WO3, NiO, and SnO) nano-catalysts for photo-degradation of methylene blue: a comparative study

Four composites of metal oxide doped with activated carbon with a metal oxide weight of 20% were prepared using mechano-mixing method. The nano-catalysts were characterized by N2-adsorption–desorption, X-ray diffraction analysis, transmission electron microscopy, Fourier-transform infrared spectroscopy, UV-diffuse reflectance, and photoluminescence spectroscopy. Photo-catalytic degradation of methylene blue dye under UV 254 nm and visible light was examined. In general, prepared catalysts are more active for degradation of dye under visible light than UV, reaching 96% within 180 min irradiation using the SnO catalyst. Photo-degradation of methylene blue followed pseudo first order reaction mechanism with a rate constant of 14.8 × 10−3 min−1, and the time required for removal of 50% of dye was 47 min.