Strong Photocatalytic Activity Research Articles

Experimental evidences and theoretical calculations on phenanthrene degradation in a solar-light-driven photocatalysis system using silica aerogel supported TiO2 nanoparticles: Insights into reactive sites and energy evolution

Quantitative identification on reactive sites of target organic molecule during photocatalysis can help to get deep insight into the pollutant degradation pathway and energy evolution process. In this study, a new class of silica aerogel supported TiO2 (TiO2/SiO2) photocatalysts were fabricated via a two-step approach, and applied for adsorption and photocatalytic degradation of phenanthrene. Anatase crystalline structure was formed upon calcination at 400 and 600 °C, while mixed crystal interphases of anatase and rutile were generated at 800 °C (anatase:rutile = 0.67:0.33). The higher calcination temperature resulted in better crystallinity of TiO2, higher photocatalytic activity, and reduced adsorption affinity toward phenanthrene. TiO2/SiO2-800 (TiO2/SiO2 calcined at 800 °C) showed minimal phenanthrene uptake (~5.2%) but the strongest photocatalytic activity, and it was able to completely degrade phenanthrene within 3 h. The SiO2 aerogel component in the composite enabled the pre-concentration of phenanthrene on the photoactive sites, while the nanoscale mixed-phases of anatase and rutile of TiO2/SiO2-800 act as an efficient transfer medium for photo-induced charge carriers. Moreover, the formed Ti–O–Si linkage in TiO2/SiO2-800 induced formation of Ti3+ under solar light irradiation, promoting photoexcited electron trap and separation of electron-hole pairs. Based on the degraded phenanthrene intermediates/products, theoretical calculations according to the density functional theory (DFT) reveal that the atoms of phenanthrene with high electrophilic Fukui index (f-) are the most reactive sites towards the radicals. Potential energy surface profile for phenanthrene degradation further reveals the intermediates energy evaluation via radicals attack.

Effect of different doping ratios of Mo doping and Zn vacancy on magneto-optical properties of ZnO

The source of ZnO magnetism in Mo doping and Zn vacancy is not fully understood. Generalized gradient approximate plane wave ultrasoft pseudopotential method was adopted based on the spin density functional theory to solve this problem. The structural stability and magneto-optical properties of Mo doping and Zn vacancy in co-existing ZnO were calculated using the first principle. The band gap of the doping system is narrower than that of the pure ZnO, and the absorption spectrum showed a red shift in the visible light range of 380–600 nm. The Zn34MoO36 had the strongest absorption spectrum intensity, the most significant red shift phenomenon, the easiest electron and hole separation, and the strongest photocatalytic activity. These features are beneficial to the design and preparation of new photocatalysts. When Mo to Zn vacancy ratio of 2:2, the Zn32Mo2O36 has the strongest magnetic properties, and the electron spin polarization was 100%, which is advantageous for designing and preparing the dilute magnetic semiconductors. The Zn32Mo2O36 has shown room temperature ferromagnetism, and the magnetism of the Zn32Mo2O36 came from the hole produced by Zn vacancy. Double exchange interaction occurred between non-pairing itinerant electron in the O–2P orbit near the Zn vacancy and the spin polarization of electrons in Mo-4d orbitals with the hole as a medium. This is consistent with the mean field approximation and the double exchange mechanism theory.

Preparation of hydrogen, fluorine and chlorine doped and co-doped titanium dioxide photocatalysts: a theoretical and experimental approach

Titanium dioxide (TiO2) has a strong photocatalytic activity in the ultra-violet part of the spectrum combined with excellent chemical stability and abundance. However, its photocatalytic efficiency is prohibited by limited absorption within the visible range derived from its wide band gap value and the presence of charge trapping states located at the band edges, which act as electron–hole recombination centers. Herein, we modify the band gap and improve the optical properties of TiO2 via co-doping with hydrogen and halogen. The present density functional theory (DFT) calculations indicate that hydrogen is incorporated in interstitial sites while fluorine and chlorine can be inserted both as interstitial and oxygen substitutional defects. To investigate the synergy of dopants in TiO2 experimental characterization techniques such as Fourier transform infrared (FTIR), X-ray diffraction (XRD), X-ray and ultra-violet photoelectron spectroscopy (XPS/UPS), UV–Vis absorption and scanning electron microscopy (SEM) measurements, have been conducted. The observations suggest that the oxide’s band gap is reduced upon halogen doping, particularly for chlorine, making this material promising for energy harvesting devices. The studies on hydrogen production ability of these materials support the enhanced hydrogen production rates for chlorine doped (Cl:TiO2) and hydrogenated (H:TiO2) oxides compared to the pristine TiO2 reference.

Influence of tetrabutylammonium hydroxide on the microstructural, optical and photocatalytic properties of sol–gel derived Gd2Ti2O7 for RBR X–3B degradation

Tetrabutylammonium hydroxide (TBAOH) was included in the sol–gel precursor to prepare the porous gadolinium titanates. The influences of the TBAOH template on the characteristics of the gadolinium titanates were investigated. The TBAOH played a key role for the porous structure in the samples. The sample obtained without TBAOH was composed of Gd2Ti2O7 crystals, while the crystallite size slightly decreased from 39.0 to 27.5 nm with rising TBAOH amount. The maximum BET surface area was 8.09 m2/g for the sample obtained using 1.2 mL of TBAOH, and the sample also had the largest external surface area of 7.19 m2/g. The bandgap energy was 3.36 eV for the material obtained without TBAOH, and the bandgap energy of the Gd2Ti2O7(m) was nearly unchanged after using different amount of TBAOH. The largest number of hydroxyl radicals were generated on the Gd2Ti2O7(1.2) sample, which had the strongest photocatalytic activity. After 150 min of reaction, the RBR X–3B degradation efficiencies were 29.3%, 93.4% and 41.4% on the Gd2Ti2O7(0), Gd2Ti2O7(1.2) and Gd2Ti2O7(1.8), respectively. The light absorption intensities of the organic groups in the dye were significantly reduced with extended reaction time.

Preparation of Ga2O3/ZnO/WO3 double S-scheme heterojunction composite nanofibers by electrospinning method for enhancing photocatalytic activity

Ga2O3 is a semiconductor material with ultra-wide band gap (Eg = 4.9 eV), which has photocatalytic activity only under deep ultraviolet light irradiation (λ < 258 nm). In this study, Ga2O3/ZnO/WO3 double S-scheme heterojunction composite nanofibers were prepared by electrospinning method. The results show that the composite nanofibers have strong photocatalytic activity and sensitive response under UV–visible light irradiation. According to the heterojunction energy band matching theory of S-scheme, the photogenerated electrons (e−) of Ga2O3, ZnO, and WO3 are transferred from the valence band (VB) to the conduction band (CB), and photogenerated holes (h+) are generated in VB under the UV–visible light irradiation with sufficient energy. These factors (the internal electric field, band bending, and Coulomb attraction) are the driving forces to promote the useless e− and h+ are eliminated through recombination. Consequently, the powerful e− with strong reducing ability in the CB of Ga2O3 and the h+ with strong oxidizing ability in the VB of WO3 are preserved to engage in photocatalytic reactions. With Rhodamine B (Rh B) dye as the degradation target, the degradation efficiency of WO3, ZnO/WO3, and Ga2O3/ZnO/WO3 nanofibers were measured under UV–visible light irradiation for 120 min. The experimental results show that compared with WO3 and ZnO/WO3 nanofibers, Ga2O3/ZnO/WO3 composite nanofibers have the highest photocatalytic activity and excellent redox ability as photocatalyst. Besides, the response range of Ga2O3/ZnO/WO3 to the ultraviolet–visible spectrum is greatly expanded.

Factors influencing the adsorption and photocatalysis of direct red 80 in the presence of a TiO2: Equilibrium and kinetics modeling

Among the different photocatalysts, TiO2 ( Eg = 3.1 eV, zero charge point (pHpzc = 6.3), and surface = 55 m2/g) is currently the most efficient and the most studied semiconductor due to its strong photocatalytic activity, non-toxicity, and chemical stability. The elimination of DR-80 on TiO2 is studied by adsorption in batch mode and by application of heterogeneous photocatalysis onto TiO2 under UV irradiation. The effects of contact time (0–60 min), initial pH (3–11), dose of the adsorbent (0.5–3 g L−1), and DR-80 concentration (40–60 mg L−1) on the adsorption of DR-80 by TiO2 are studied for optimization of these parameters. The kinetic parameters, rate constants, and equilibrium adsorption capacities are calculated and discussed for each applied theoretical model. The adsorption of DR-80 is well described by the pseudo-first-order kinetic model. The fitting of the adsorption isotherms shows that the models of Langmuir and Temkin offering a better fit and an adsorption 64.102 mg/g at 25 °C of DR-80 are eliminated. The results showed that the photocatalytic efficiency strongly depends on the pH while the initial rate of photodegradation is proportional to the catalyst dose, and becomes almost constant above a threshold value. It was found that the photodegradation is favored at low DR-80 concentrations in accordance with the Langmuir–Hinshelwood model with the constants Kad = 6.5274 L/mg and KL–H = 0.17818 mg L−1 min. However, the adsorption is improved for high DR-80 concentrations. It is found that the degradation depends on both the temperature and the pH with a high elimination rate at high temperature. The photocatalyst TiO2 has a better activity for the degradation of DR-80, compared to some commercial catalysts that have been described in the literature.

Hollow Nanorods and Amorphous Co9S8 Quantum Dots Construct S-Scheme Heterojunction for Efficient Hydrogen Evolution

The hollow materials have stronger absorption capacity for visible light than other materials due to their special internal cavity structure. In this paper, NiTiO3 hollow nanorods and Co9S8 QDs were used to prepare composite materials with strong light absorption capacity and photocatalytic hydrogen production activity using an in situ growth method. The results of UV diffuse reflectance spectra prove that the existence of NiTiO3 hollow nanorod effectively improves the visible light absorption capacity of the composite material. Additionally, the existence of hollow nanorods can evenly disperse Co9S8 QDs on the surface and increase the number of active sites. X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and electrochemical measurements further attest that the S-scheme heterojunction constructed between the two semiconductors not only provides a special transmission path for carrier transfer but also retains more useful electrons and holes that participate in the hydrogen evolution reaction. Therefore, the maximum hydrogen production of NiTiO3@Co9S8 QDs can reach 5.38 times that of pure Co9S8 QDs. The consequences show that the S-scheme heterojunction constructed by NiTiO3 has certain development potential in the field of photocatalysis.

Iodine-doped carbon dots with inherent peroxidase catalytic activity for photocatalytic antibacterial and wound disinfection.

A new type of nitrogen-iodine co-doped carbon dot (N/I-CD) was synthesized by a one-step hydrothermal method with a fluorescence quantum yield of 37%. The prepared N/I-CDs exhibit peroxidase-like activity, can catalyze bio-safety levels of H2O2 to generate hydroxyl radicals (•OH) under visible light and enhance the level of reactive oxygen species (ROS) in bacteria cells. All in vitro experiments showed that the designed system has strong photocatalytic antibacterial activity against both E. coli and S. aureus bacteria. The light-induced antibacterial function of N/I-CDs was evaluated under the conditions of changing other experimental parameters. When the visible light irradiation time was extended to 60min, the antibacterial efficiency of N/I-CDs (0.21mg·mL-1) against S. aureus and E. coli reached 100% in the presence of exogenous H2O2 (0.07mM). More importantly, wound disinfection in vivo demonstrates the high antibacterial efficiency, low toxicity and application potential of good biocompatibility due to the nanozyme activity of N/I-CDs.

Synthesis of Silver Doped Titanium Dioxide by Wet-Ball Milling Sol–Gel Method for Antibacterial Application

Titanium dioxide (TiO2) has been extensively studied as photo-catalyst for water treatment, air purification and antibacterial applications due to its challenging properties such as chemical stability, environmental friendly and strong photocatalytic activity. However, the limitation of TiO2 on its dependent to ultraviolet radiation for photocatalytic activity is still aroused. In this study, silver doped titanium dioxide (Ag-TiO2) was synthesized by wet-ball milling sol–gel method (WBMS). Ag-TiO2 molar ratio was varied from 0% to 10% to study the effect of silver content on the synthesized Ag-TiO2 characteristics and the ability to apply on antibacterial applications. The objective of this work was to find an optimal concentration of Ag in Ag-TiO2. Characterization of the particle size, morphology, and surface area of synthesized Ag-TiO2 were discussed by techniques of transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET). Photocatalytic activity was investigated from degradation of methylene blue. Antibacterial activity was conducted by finding minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) tests performed on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) under dark condition and under visible light. The results demonstrated that the doping of Ag inhibited crystal growth of Ag-TiO2. The smallest particle size and the highest surface area were obtained from 5% Ag-TiO2. Also, it was found that methylene blue degradation rate increased to the highest number of 1.62x10−3 min−1 when Ag concentration reached 5%, and methylene blue degradation rate reduced when Ag concentration was higher than 5%. The antibacterial activity of Ag-TiO2 was better than TiO2. The optimal concentration of 3-5% Ag-TiO2 was observed from the MIC and MBC tests.

Rapid and Scalable Fabrication of TiO2@g-C3N4 Heterojunction for Highly Efficient Photocatalytic NO Removal under Visible Light

ABSTRACT TiO2@g-C3N4 heterojunction composites were successfully synthesized via one-step pyrolysis using commercial TiO2 and urea. The photocatalytic performance of a composite was investigated by measuring the degradation of nitric oxide (NO) under visible light. The light absorption and bandgap of the selected materials were determined using diffuse reflectance spectroscopy (DRS), which confirmed the strong photocatalytic activity of the materials under visible light. The NO photodegradation efficiency of the composite was almost 90% under visible irradiation. The generation of by-products and nitrogen dioxide (NO2) was calculated to determine the conversion pathway of NO during the photocatalytic reaction. Furthermore, the results for recycling indicated that the TiO2@g-C3N4 composite exhibited excellent stability. Also, the morphology and the chemical compositions of the materials were observed using high-resolution transmission electron microscopy (HR-TEM) images and X-ray photoelectron spectroscopy (XPS). Raman spectroscopy was used to detect the structural vibrations in the materials. Through electron spin resonance (ESR) and trapping tests, the photocatalytic mechanism of the TiO2@g-C3N4 composite was also elucidated, in which superoxide radical anions were found to play a significant role in NO removal.

Facile solvothermal synthesis of a Z-Scheme 0D/3D CeO2/ZnIn2S4 heterojunction with enhanced photocatalytic performance under visible light irradiation

Reasonable designing heterojunction photocatalysts is an effective way to improve the photocatalytic activity of semiconductor. Herein, the efficient binary heterojunction photocatalyst formed between zero-dimensional (0D) CeO2 nanoparticles and three-dimensional (3D) floriated shaped ZnIn2S4 microspheres was synthesized by a simple solvothermal method. A series of analytical methods were used to characterize the optical properties and morphology of CeO2/ZnIn2S4 composite photocatalysts. Photodegradation experimental results showed that CeO2/ZnIn2S4 composites displayed strong photocatalytic activity for the degradation of tetracycline (TC) with heavy concentrations (30 mg/L). The as-obtained optimum 10 wt% CeO2/ZnIn2S4 sample displays high degradation efficiency of 91% within 120 min, which is about 12.9 and 3.03 times higher than that of pure CeO2 and ZnIn2S4, respectively. The enhanced photocatalytic activity is ascribed to the formation of Z-scheme heterojunction between CeO2 and ZnIn2S4, which contributes to the increased surface area, enhanced redox ability and high separation efficiency of photogenerated charge carriers. The degradation pathways and intermediate products of TC over CeO2/ZnIn2S4 composite were analyzed by liquid chromatography-mass spectrometry (LC/MS) measurement. This study provides a new approach to prepare of efficient 0D/3D-based Z-scheme heterojunction photocatalysts.

Highly sensitive and selective photoelectrochemical sensor for mercury(II) detection based on efficient Bi2MoO6 photoanode decorated with CuS

Stronger photocatalytic activity and better photoelectrochemical (PEC) performance can Bi2MoO6/CuS photocatalyst accomplish compared to that of pure Bi2MoO6. CuS was also conducive to strengthen the visible light absorption and inhibited the recombination of electron-hole pairs. The addition of glutathione (GSH) in the electrolyte led to a significant enhancement to the reactivity of the PEC sensor in the modified electrode. In contrast, the increase in photocurrent was restrained to a high degree for that the hole scavenging agents were consumed through the addition of mercury (Hg2+). Consequently, the electrode was able to be exploited for Hg2+ detection even though no specific identification component was introduced yet. The wide linear range of 0.5 nM–230 nM and low detection limit of 0.23 nM made the electrode adaptable to the detection of Hg2+ in practical samples. Thanks to a ameliorative PEC performance, thus, the Bi2MoO6/CuS sensor stands a good chance to play a useful part in the detection of Hg2+.

Progress on the nanoscale spherical TiO2 photocatalysts: Mechanisms, synthesis and degradation applications

AbstractTitanium dioxide (TiO2) has the advantages of strong photocatalytic activity, non‐toxicity, and low cost, and so on. It has always occupied a dominant position in many photocatalytic materials, especially nanoscale spherical TiO2 has the characteristics of high specific surface area and pore‐volume, and so on. Therefore, Degussa P25, as a typical representative of the nanoscale spherical structure, is currently the only material produced on a large scale. According to the structure, nanoscale spherical TiO2 can be divided into three types: solid, core‐shell, and hollow spheres. However, there is still a lack of the latest review on the synthetic doping and application of nanoscale spherical TiO2. Therefore, we first describe the degradation mechanism of nanoscale spherical TiO2 and summarize the latest progress of its synthesis strategy in this review, including doping and other modification techniques, and finally introduce the application of nanoscale spherical TiO2 photocatalytic degradation of volatile organic compounds, dye wastewater, antibiotics, pesticides, and oily wastewater. Through this review, it is helpful for researchers to further understand the synthesis and application of nanoscale spherical TiO2, hoping to continuously improve the disadvantages and photocatalytic activity of nanoscale spherical TiO2, and promote the widespread application of nanoscale spherical TiO2 on an industrial scale.

Green synthesis, characterization and photocatalytic activity of silver nanoparticles synthesized with Nigella Sativa seed extract

This study introduces a new method for synthesizes of silver nanoparticles (AgNPs), prepared within Nigella Sativa (NS) extract. NS extract in the process is more advantageous over other processes because NS acts as a highly efficient stabilizing as well as reducing agents due to highly metabolites like flavonoids, terpenoids, proteins etc. These agents are responsible for the formation of AgNPs and contain reducing and stabilizing properties. The as-obtained AgNPs were investigated by various characterization techniques such as Ultra-visible spectroscopy (UV–Vis), X-ray diffraction (XRD), Dynamic light scattering (DLS), Zeta Potential, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and high-resolution TEM (HR-TEM) and Brunauer-Emmett-Teller (BET). Fourier transform infra-red (FTIR) analysis was performed to identify the potential bimolecules responsible for the reduction of silver ions. The elemental composition was accomplished by using energy dispersive spectroscopy (EDS). N2 adsorption-desorption isotherm, pore volume, specific surface area and size of NPs was measured by using BET. The maximum absorbance of UV–Vis was found at 426 nm. TEM, SEM, DLS and BET detected spherical, polydispersed Ag-nano particles with size ranged within 10–12 nm. XRD results demonstrated the formation of well crystallized and smaller nano particles. Furthermore, the synthesized AgNPs exhibited strong photo catalytic activity on degradation of Congo red dye due to high energy and the smaller particles.

MgFe2O4/CNTs nanocomposite: synthesis, characterization, and photocatalytic activity

Magnesium ferrite is a visible light absorber, and when combined with multiwall carbon nanotubes (MWCNTs), it can lead to low electron–hole recombination rates, thus improving its photocatalytic activity. In this work, a novel MgFe2O4/CNTs nanocomposite catalyst has been synthesized via anchoring MgFe2O4 nanoparticles onto MWCNTs surface by a sol–gel and microwave-assisted route. The prepared catalyst was characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning and transmission electron microscopy, energy-dispersive X-ray analysis and vibrating scanning magnetometry. MgFe2O4 nanoparticles showed a cubic inverse spinel ferrite structure, while MgFe2O4/CNTs nanohybrids showed combinations of both structures. Morphology studies including Brunauer–Emmett–Teller (BET) analysis confirmed a 40 m2 g−1 specific surface area with narrow mesoporous size distribution for the MgFe2O4/CNTs nanocomposite. The photocatalytic performance of the new catalyst was assessed by photodegradation of methylene blue (MB). The experimental results demonstrated that MgFe2O4/CNTs exhibited strong photocatalytic activity, catalysing the photooxidation of about 98% of MB in 25 min under sunlight.

Synthesis of chrysotile based nanocomposites for tuning band gap and photocatalytic property

A novel type of chrysotile@ZnO nanocomposite was prepared by ZnO nanoparticles generated on the surface of chrysotile to improve its utility and tune the band gap and property of ZnO nanoparticles. XRD , SEM, TEM , BET, PL and UV–vis were used to study the phase, morphology, microstructure and properties of the nanocomposite. The study of its photo-degradation performance took methylene blue (MB) as an organic dye model. Compared with chrysotile and ZnO nanoparticles, chrysotile@ZnO nanocomposite has a narrower band gap (1.91 eV) and stronger photo-catalytic activity. The results showed that the synergistic effect of surface passivation and interfacial action of chrysotile reduced the band gap and photon-hole recombination rate of ZnO nanoparticles, to enhance photo-degradability of organic pollutants and meanwhile endowed chrysotile with new performance. This work is novel and can be used as a basic experimental reference for the functionalization of clay minerals and the development of highly active supported catalysts. • Chrysotile@ZnO nanocomposites were prepared through direct precipitation method. • Compared with ZnO, chrysotile@ZnO nanocomposites have a narrow band gap (1.91 eV). • Chrysotile@ZnO nanocomposites showed strong photocatalytic activity. • The combination of chrysotile and ZnO endowed chrysotile to special performance. • The combination of chrysotile and ZnO improved the catalytic activity of ZnO.

Fabrication of highly efficient Bi2WO6/CuS composite for visible-light photocatalytic removal of organic pollutants and Cr(VI) from wastewater

A visible-light-driven Bi2WO6/CuS p-n heterojunction was fabricated using an easy solvothermal method. The Bi2WO6/CuS exhibited high photocatalytic activity in a mixed system containing rhodamine B (RhB), tetracycline hydrochloride (TCH), and Cr (VI) under natural conditions. Approximately 98.8% of the RhB (10 mg/L), 87.6% of the TCH (10 mg/L) and 95.1% of the Cr(VI) (15 mg/L) were simultaneously removed from a mixed solution within 105 min. The removal efficiencies of TCH and Cr(VI) increased by 12.9% and 20.4%, respectively, in the mixed solution, compared with the single solutions. This is mainly ascribed to the simultaneous consumption electrons and holes, which increases the amount of excited electrons/holes and enhances the separation efficiency of photogenerated electrons and holes. Bi2WO6/CuS can be applied over a wide pH range (2–6) with strong photocatalytic activity for RhB, TCH and Cr(VI). Coexisiting dissolved organic matter in the solution significantly promoted the removal of TCH (from 74.7% to 87.2%) and Cr(VI) (from 75.7% to 99.9%) because it accelerated the separation of electrons and holes by consuming holes as an electron acceptor. Removal mechanisms of RhB, TCH, and Cr(VI) were proposed, Bi2WO6/CuS was formed into a p-n heterojunction to efficiently separate and transfer photoelectrons and holes so as to drive photocatalytic reactions. Specifically, when reducing pollutants (e.g., TCH) and oxidizing pollutants (e.g., Cr(VI)) coexist in wastewater, the p-n heterojunction in Bi2WO6/CuS acts as a “bridge” to shorten the electron transport and thus simultaneously increase the removal efficiencies of both types of pollutants.

Ultrasound-assisted synthesis of mixed calcium magnesium oxide (CaMgO2) nanoflakes for photocatalytic degradation of methylene blue

In the present study, mixed calcium magnesium oxide (CaMgO2) nanoflakes were synthesized using an ultrasound-assisted co-precipitation method. The physicochemical, structural and functional properties and elemental composition of the nanoflakes had been characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), High-resolution transmission electron microscopy (HR-TEM), Fourier Transform Infrared spectroscopy (FTIR), UV–VIS spectroscopy, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Moreover, the photocatalytic actions of the nanoflakes were evaluated by the removal rates of methylene blue (MB) and p-nitrophenol (4-NP) under UV irradiation at room temperature. SEM-EDS studies revealed that the nanoflakes consisted of mixed oxide such as magnesium oxide (MgO) and calcium oxide (CaO) particles. The size of the nanoflakes was found to be in the range of 10–30 nm and the average size was 25 nm as confirmed by HR-TEM analysis. XRD revealed that the standard crystal size was calculated to be 25 nm. The synthesized nanoflakes had a strong photocatalytic activity for methylene blue (MB) and p-nitrophenol (4-NP) degradation in the presence of H2O2 under UV light irradiation within 60 min and 30 min, respectively. Hence, the present study proposes that the CaMgO2 nanoflakes can be employed for the removal of dyes from wastewater.

Robust Photodegradation of Methylene Blue with the Biphenyl-Porphyrin/TiO₂ Photocatalyst Under Visible Light Condition.

Herewith, we approached a synthesis of new biphenyl porphyrin derivative and confirmed its structure with 1H-NMR and 13C-NMR studies, FT-IR and mass analytical methods. The porphyrin derivative grafted with TiO₂ and the composite (PORBP-TiO₂) was further confirmed with different analytical techniques like diffuse reflectance spectra, XRD, FT-IR, XPS, SEM analysis. PORBP-TiO₂ was checked for photodegradation of methylene blue in visible light condition and degradation results were compared with bare TiO₂. Our newly synthesized photocatalyst showed a very fast and efficient photocatalytical activity in comparison with bare TiO₂. Fluoresence life time results also supported the strong photocatalytic activity of PORBP-TiO₂. The reusability studies also showed that PORBP-TiO₂ is having very good stability upto 10 cycles also. Finally we proposed a suitable catalytic diagram for PORBP-TiO₂ photocatalysis.

Photoluminescence and photocatalytic activity of spin coated Ag+ doped anatase TiO2 thin films

Abstract Ag + doped TiO2 (Ag-TiO2) thin films were coated on glass substrates with different dopant concentrations (1%, 3%, 5% 7% and 10%) and were subsequently annealed at 550 °C. The crystalline structure and phase formation of Ag–TiO2 was examined using XRD. The HRTEM analysis of pure and 5% Ag doped TiO2 thin films was revealed that the particles are spherical in shape with sizes around 23.8 and 11.6 nm respectively. Raman spectrometer was also used to identify the phase formation and vibrational modes present in the prepared silver doped TiO2 coatings. EPR spectra confirm the presence of oxygen vacancies (Vo) and Ti3+ sites in the Ag–TiO2 thin films. With excitation at 325 nm, Ag doped TiO2 nanoparticles show characteristic photoluminescence (PL) corresponding to the visible spectral range. Ag doped TiO2 thin films showed enhanced photocatalytic behaviour due to their narrow band gap energy (3.17–2.75 eV), high surface area (85–231 m2/g), and a reduced luminescence. Among all the films 5% Ag–TiO2 film exhibited strong photocatalytic activity (PCA) and was estimated by visible light decolorization of methylene blue (MB) and methyl orange (MO).