Ultraviolet-visible Diffuse Reflectance Spectra Research Articles

Preparation of CdS/ g-C3N4/ MOF composite with enhanced visible-light photocatalytic activity for dye degradation

CdS nanoparticles was hybridized with graphitic carbon nitride (g-C3N4) sheets and titanium metal-organic framework (MOF) using a facile solvothermal method, for the catalytic photodegradation of Rhodamine B dyes under visible light irradiation. Characterization of as-obtained samples was performed by X-ray diffraction, scanning electron microscopy equipped with an energy dispersive X-ray spectrometer (EDS), Fourier transform infrared spectroscope, thermogravimetric analysis, N2 absorption-desorption and ultraviolet–visible diffuse reflection spectra. The CdS/g-C3N4/MOF composite (238.43 m2/g) exhibited a remarkably high photocatalytic activity under the visible light irradiation, the degradation rate reached almost 90.2% for RhB after 90min reaction, far outperforming other decent photocatalysts like pure CdS, MOF, g-C3N4 under the same conditions. The superior photocatalytic activity of the CdS/g-C3N4/MOF composite is attributed to enhanced separation of the photogenerated electron–hole pairs, as well as increased visible-light absorption. Therefore, CdS/g-C3N4/MOF composites, prepared using a facile method are applicable to the development of the novel high-efficiency photocatalytic samples for future research.

Polyaniline sensitized Pt@TiO2 for visible-light-driven H2 generation

Polyaniline is a typical conducting polymer with high migration electron rate, good stability, eco-friendly properties, and high absorption coefficients for visible light. In the present study, polyaniline decorated Pt@TiO2 for visible light-driven H2 generation is reported for the first time. The above-mentioned nanocomposite is prepared through a simple oxidative-polymerization and characterized by infrared spectroscopy, transmission electron microscopy, X–ray diffraction, thermogravimetric analysis, and ultraviolet–visible diffuse reflectance spectra. Polyaniline modification improves the absorption of the nanocomposite in visible light region via a photosensitization effect similar to dye–sensitization but does not influence the crystal structure and size of Pt@TiO2. The polyaniline modified Pt@TiO2 exhibits a remarkable visible light activity (61.8 μmol h−1 g−1) and good stability for H2 generation (with an average apparent quantum yield of 10.1%) with thioglycolic acid as an electron donor. This work provides new insights into using conducting polymers, including polyaniline, as a sensitizer to modify Pt@TiO2 for visible-light hydrogen generation.

A continuous valence band through N[sbnd]O orbital hybridization in N[sbnd]TiO2 and its induced full visible-light absorption for photocatalytic hydrogen production

Photocatalytic hydrogen production represents an effective approach for solar energy conversion, which can greatly ease the current energy crisis. Herein, we report a successful NO orbital hybridization in N-doped TiO2 nanotube, the absorption wavelength is greatly red-shifted to visible light (from 400 to 800 nm) with large absorbance. The doping N element can partially replace the oxygen sites in TiO2 lattice to form NTiN bonds. The hybridization effect of N 2p and O 2p makes a continuous valence band and the position up-shift from 1.99 to 1.67 eV, the band gap is subsequently narrowed from 3.21 to 2.77 eV for 1.85-NTiO2 nanotube, which has been confirmed by ultraviolet–visible diffuse reflectance spectra and X-ray photoelectron spectroscopy valence band spectra. Benefiting from the enhanced visible light absorption ability and ultrathin shell feature, 1.85-NTiO2 nanotube exhibits exciting photocatalytic hydrogen evolution performance with a rate of 10870 μmol h−1 g−1 under the selected visible light irradiation (λ > 400 nm). This work demonstrates an alternative strategy for tuning visible light absorption ability by doping for wide-band-gap semiconductors in photocatalysts design, and the philosophy can also be extended to other photocatalytic systems.

Synthesis of a high-surface area V2O5/TiO2-SiO2 catalyst and its application in the visible light photocatalytic degradation of methylene blue.

In the present study, we synthesized several high-surface area V2O5/TiO2–SiO2 catalysts (vanado titanium silicate, VTS). The synthesized materials were characterized by PXRD, FE-SEM/EDAX, TEM, FTIR, UV-Vis, XPS, fluorescence and photocatalytic activity studies. The small-angle powder X-ray diffraction pattern shows that the 110 and 200 planes are merged to become a single broad peak. Field-emission scanning electron microscopy shows that the titanosilicate is spherical in shape and V2O5 has a hexagonal rod-shaped morphology. The presence of various metal ions, such as V, Ti, Si and O, was observed by energy dispersive X-ray analysis and X-ray photoelectron spectroscopy. The transmission electron microscopy image shows clear hexagonal mesoporous fringes with V2O5 distribution. The BET surface area analysis shows that the VTS catalysts have higher surface areas than pure V2O5. Fourier transform infrared spectroscopic analysis shows the presence of Ti4+ ions connected to the silanol groups. The bandwidths of pure titanosilicate, V2O5 and their composites were calculated from their diffuse reflectance ultraviolet-visible spectra. The bandwidth was tuned by heterojunctions in the studied catalysts. The photoluminescence spectra of the VTS catalysts show a distinct behaviour as compared to those of the pure components. The photocatalytic activity of methylene blue degradation was determined with pure constituents and catalysts. VTS-1 (TS and VO weight ratio 2 : 1) shows higher conversion than other catalysts, pure titanosilicate and V2O5. This is probably due to the heterojunctions and higher surface area in VTS-1. Kinetic studies reveal that direct sunlight shows higher activity than pure visible light. A plausible physical and chemical mechanism for the photocatalytic activity is proposed.

Hydrothermal synthesis, characterization and catalytic performance of La3+ and Sm3+ - doped Bi2Mn2O7 nanocatalysts for Biginelli reactions

La3+ and Sm3+ - doped Bi2Mn2O7 nanocatalysts were synthesized in 1 M NaOH aqueous solution, via a stoichiometric 1:1 Bi:Mn molar ratio hydrothermal method at 180 °C for 48 h. Bi(NO3)3, MnO2, La(NO3)3 and Sm2O3 were used as raw materials. The synthesized nanomaterials were characterized by powder X-ray diffraction (PXRD) technique. Both of the La3+ and Sm3+ - doped Bi2Mn2O7 nanomaterials were crystallized in a cubic crystal structure with space group Fd3 m. The morphologies of the synthesized materials were studied by field emission scanning electron microscope (FESEM). The optical properties of the as-synthesized nanomaterials were studied by ultraviolet visible (UV-Vis) diffuse reflectance spectra (DRS). It was found that the optical band gaps were increased with dopoing La3+ and Sm3+ into Bi2Mn2O7. Catalytic performance of the synthesized nanomaterials were investigated in Biginelli reactions which showed excellent efficiency. Correlation between the catalytic performance with the band gap and hard/soft proportion of the metal ions was shown.

Highly efficient and thermally stable of a novel red phosphor Sr3NaSbO6:Mn4+ for indoor plant growth

Far red-emitting Mn4+-activated oxide phosphor based on the substitution of Mn4+ for Sb5+ in the lattice of Sr3NaSbO6 (SNSO) was prepared via solid state reaction process. The crystal structure of the host was carefully discussed and studied. The resultant phosphors were characterized by X-ray powder diffraction, fluorescence spectra, ultraviolet-visible diffuse reflectance spectra, temperature-dependent emission spectra (298–548 K), luminescence decay curves and electroluminescence spectra. Excitation and emission spectra indicated that the sample had a wide excitation band in UV(250–400 nm) and exhibited the strong emission band centered at 695 nm. The band structure for SNSO was calculated based on the density functional theory, and the bandgap value of SNSO host is ∼2.92 eV. In addition, the mechanism of quenching concentration and energy-transfer of SNSO:Mn4+ were explored and analyzed in detail through calculation. The UV–Vis diffusion reflectance spectra demonstrated that samples had strong absorption (200–550 nm) in the ultraviolet(UV) and near-ultraviolet(NUV) region. The thermal stability of SNSO:Mn4+ was excellent (I423K/I273K = 39.84%). The internal quantum efficiency is 56.2%. In brief, the prepared phosphors had potential application in indoor plant growth as a LED lamp.

Ultrathin Visible-Light-Driven Mo Incorporating In2 O3 -ZnIn2 Se4 Z-Scheme Nanosheet Photocatalysts.

Inspired by natural photosynthesis, the design of new Z-scheme photocatalytic systems is very promising for boosting the photocatalytic performance of H2 production and CO2 reduction; however, until now, the direct synthesis of efficient Z-scheme photocatalysts remains a grand challenge. Herein, it is demonstrated that an interesting Z-scheme photocatalyst can be constructed by coupling In2 O3 and ZnIn2 Se4 semiconductors based on theoretical calculations. Experimentally, a class of ultrathin In2 O3 -ZnIn2 Se4 (denoted as In2 O3 -ZISe) spontaneous Z-scheme nanosheet photocatalysts for greatly enhancing photocatalytic H2 production is made. Furthermore, Mo atoms are incorporated in the Z-scheme In2 O3 -ZISe nanosheet photocatalyst by forming the MoSe bond, confirmed by X-ray photoelectron spectroscopy, in which the formed MoSe2 works as cocatalyst of the Z-scheme photocatalyst. As a consequence, such a unique structure of In2 O3 -ZISe-Mo makes it exhibit 21.7 and 232.6 times higher photocatalytic H2 evolution activity than those of In2 O3 -ZnIn2 Se4 and In2 O3 nanosheets, respectively. Moreover, In2 O3 -ZISe-Mo is also very stable for photocatalytic H2 production by showing almost no activity decay for 16 h test. Ultraviolet-visible diffuse reflectance spectra, photoluminescence spectroscopy, transient photocurrent spectra, and electrochemical impedance spectroscopy reveal that the enhanced photocatalytic performance of In2 O3 -ZISe-Mo is mainly attributed to its widened photoresponse range and effective carrier separation because of its special structure.

Boosting the photocatalytic oxidative desulfurization of dibenzothiophene by decoration of MWO4 (M=Cu, Zn, Ni) on WO3

The surface of WO3 was partially decorated with transition metal tungstate MWO4 (M = Cu, Zn, Ni) using impregnation method followed by solid-state reaction. It is found that MWO4/WO3 photocatalysts showed a higher activity for photocatalytic oxidative desulfurization (PODS) of dibenzothiophene (DBT) than pure WO3 or MWO4 under visible light irradiation. Moreover, the activity for PODS of DBT on MWO4/WO3 depends on the content of MWO4 decoration on WO3 surfaces. 0.2% CuWO4/WO3, 1% ZnWO4/WO3, and 0.5% NiWO4/WO3 exhibited the highest activity among CuWO4/WO3, ZnWO4/WO3 and NiWO4/WO3 samples. However, as compared with 1% ZnWO4/WO3 and 0.5% NiWO4/WO3, the 0.2% CuWO4/WO3 sample exhibited superior visible light photocatalytic activity for DBT conversion. Brunauer-Emmett-Teller method (BET), SEM, and ultraviolet-visible diffuse reflectance spectra (UV–vis DRS), high resolution transmission electron microscope (HRTEM), photoluminescence spectroscopy (PL), and a series of titration experiments were used to seek the reason for the positive impact of MWO4 on the photocatalytic activity of WO3. As compared with pure WO3, no notable changes of specific surface areas, morphologies, and light absorption are observed after MWO4 (M = Cu, Zn, Ni) decoration. The formation of heterojunction structure between MWO4 and WO3, which promotes charge separation efficiency, was the main reason for the high photocatalytic activity of MWO4/WO3 photocatalyst. Moreover, difference in PODS activity between MWO4/WO3 heterojunctions is proved to be affected by their charge separation and transfer efficiency and amount of active species.

In-situ fabrication of Ag/P-g-C3N4 composites with enhanced photocatalytic activity for sulfamethoxazole degradation.

A series of Ag/P-g-C3N4 composites with different Ag content were synthesized for the first time by thermal polymerization combined with photo-deposition method. The composites were characterized by X-ray powder diffraction, field emission scanning electron microscope coupled with energy-dispersive X-ray spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, ultraviolet-visible diffuse reflectance spectra, N2 absorption-desorption and X-ray photoelectron spectroscopy. Ag was successfully dispersed on the surface of P-g-C3N4. The photocatalytic performance of P-g-C3N4 and Ag/P-g-C3N4 was evaluated by degrading sulfamethoxazole (SMX) under visible light irradiation. In the presence of 5% Ag/P-g-C3N4, 100% of SMX was degraded within 20 min. The enhanced photocatalytic activity of Ag/P-g-C3N4 was attributed to the surface plasmon resonance effect of metallic Ag and Schottky barrier formed on the interface between Ag and P-g-C3N4, which could speed up the generation rate of electrons and holes and inhibit the recombination of photogenerated electron-hole pairs. The radical quenching tests indicated that holes and superoxide radicals were the dominant active species involved in SMX degradation. The synthesized materials maintained high catalytic activity after five cycle runs. The concentration and the intermediates during the degradation process were determined by LC-MS/MS, and the tentative degradation pathways of SMX in photocatalytic system were proposed.

Graphitic carbon nitride co-modified by zinc phthalocyanine and graphene quantum dots for the efficient photocatalytic degradation of refractory contaminants

Broad solar light absorption and rapid photogenerated electron-hole pair separation are two critical factors for the efficient enhancement of catalytic performance in a g-C3N4-based photocatalytic system. This study developed a facile method to construct a ternary graphitic carbon nitride/zinc tetracarboxyphthalocyanine/graphene quantum dots (g-C3N4/ZnTcPc/GQDs) composite photocatalyst. Graphene quantum dots (GQDs) were used to modify g-C3N4/ZnTcPc through hydrothermal method, where g-C3N4/ZnTcPc was fabricated by immobilizing zinc tetracarboxyphthalocyanine (ZnTcPc) onto g-C3N4 covalently via amido bonds. The photocatalyst was characterized by transmission electron microscopy, ultraviolet-visible diffuse reflectance spectrum, and X-ray photoelectron spectroscopy. The g-C3N4/ZnTcPc/0.1GQDs composites presented an increased photocatalytic activity by using Rhodamine B, sulfaquinoxaline sodium and carbamazepine as the model pollutants under solar light irradiation. ZnTcPc bonding on the g-C3N4 broadens its visible-light spectral response, and GQDs promotes the photogenerated electron-hole-pair separation efficiency because of its efficient electrons-transfer property. Experiments confirmed that superoxide radicals, photogenerated holes and singlet oxygen are the primary active species. The photocatalytic degradation pathway of Rhodamine B, sulfaquinoxaline sodium and carbamazepine was proposed on the basis of ultra-performance liquid chromatography and high-definition mass spectrometry.

Effective Photocatalytic Activity of Mixed Ni/Fe-Base Metal-Organic Framework under a Compact Fluorescent Daylight Lamp

Mixed Ni/Fe-base metal-organic framework (Ni/Fe-MOF) with different molar ratios of Ni2+/Fe3+ have been successfully produced using an appropriate solvothermal router. Physicochemical properties of all samples were characterized using X-ray diffraction (XRD), Raman, field emission scanning electron microscopes (FE-SEM), fourier-transform infrared spectroscopy (FT-IR), N2 adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectra (UV-Vis DRS), and photoluminescence spectra (PL). The photocatalytic degradation performances of the photocatalysts were evaluated in the decomposition of rhodamine B (RhB) under a compact fluorescent daylight lamp. From XRD, IR, XPS, and Raman results, with the presence of mixed ion Fe3+ and Ni2+, MIL-88B (MIL standing for Materials of Institut Lavoisier) crystals based on the mixed metal Fe2NiO cluster were formed, while MIL-53(Fe) was formed with the presence of single ion Fe3+. From UV-Vis DRS results, Ni/Fe-MOF samples exhibited the absorption spectrum up to the visible region, and then they showed the high photocatalytic activity under visible light irradiation. A Ni/Fe-MOF sample with a Ni2+/Fe3+ molar ratio of 0.3 showed the highest photocatalytic degradation capacity of RhB, superior to that of the MIL-53(Fe) sample. The obtained result could be explained as a consequence of the large surface area with large pore volumes and pore size by the Ni2+ incorporating into the MOF’s structure. In addition, a mixed metal Fe/Ni-based framework consisted of mixed-metal cluster Fe2NiO with an electron transfer effect and may enhance the photocatalytic performance.

Graphitic carbon nitride synthesized at different temperatures for enhanced visible-light photodegradation of 2-naphthol

Graphitic carbon nitride (g-C3N4) was synthesized by one-step calcination at different temperatures for enhanced photodegradation of 2-naphthol under visible light (λ ≥ 420 nm). The g-C3N4 photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR) and ultraviolet–visible diffuse reflectance spectra (UV–vis DRS). The morphology, band structure and optical property of g-C3N4 could be controlled by the calcination temperature. The formation of genuine g-C3N4 actually began when the temperature was higher than 500 °C. Moreover, compared to the primary stage (450 °C) and the intermediate stage (500 °C and 550 °C), the g-C3N4 synthesized at the advanced stage (600 °C and 650 °C) had not only the strongest absorption of visible light but also the narrowest band gap, enabling controllable adjustment of the band structure of catalysts. Furthermore, the photodegradation efficiency of 2-naphthol was improved as the calcination temperature of g-C3N4 rising up. Meanwhile, g-C3N4 synthesized at 600 °C performed the best with a rate constant of 1.949 h−1 for the first-order kinetic model, which was 2.67 times that of the catalyst synthesized at 450 °C. Finally, the possible photodegradation pathway of 2-naphthol by g-C3N4 was proposed.

Synthesis of Ti4+-doped ZnWO4 phosphors for enhancing photocatalytic activity

Ti4+-doped ZnWO4 phosphors were synthesized by a facile solid state reaction route. The structural and morphological features of the as-synthesized Ti4+-doped ZnWO4 photocatalysts were intensively characterized by XRD(X-ray diffraction), XPS(X-ray photoelectron spectroscopy), UV–vis DRS(Ultraviolet-visible diffuse reflectance spectrum), PL(photoluminescence spectroscopy). The photocatalytic reaction tests have been decomposed by the solution of rhodamine B(RhB). The results showed that the Ti4+ -doped ZnWO4 phosphors had a high photocatalytic activity, and RhB degradation rate of 97% within 120 min was achieved for the 0.01Ti4+-doped sample. The enhancement of photocatalytic performance for Ti4+-doped ZnWO4 samples can be ascribed to reduce the recombination rate of photogenerated electron-hole pairs with the formation of new defects by Ti4+ doping. This study suggests that Ti4+-doped ZnWO4 photocatalysts are promising for photocatalytic decomposition of organic contaminants.

Synthesis of LaMnO3–Diamond Composites and Their Photocatalytic Activity in the Degradation of Weak Acid Red C-3GN

In this study, a series of LaMnO3–diamond composites with varied LaMnO3 mass contents supported on micro-diamond have been synthesized using a sol–gel method. The as-prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and the Fourier transform infrared spectra (FTIR). Meanwhile, the photocatalytic performances were also tested by photoluminescence (PL) spectroscopy, ultraviolet–visible diffuse reflection spectra (UV-Vis DRS) and the degradation of weak acid red C-3GN (RC-3GN). Results show that the peak position of LaMnO3 is shifted to low angle after the introduction of diamond, and perovskite particles uniformly distributed on the surface of diamond, forming a network structure, which can increase the active sites and the absorption of dye molecules. When the mass ratio of LaMnO3 and diamond is 1:2 (LMO–Dia-2), the composite shows the most excellent photocatalytic activity. This result offers a sample route to enlarge the range of the application of micro-diamond and provide a new carrier for perovskite photocatalysts.

Synthesis of Ag@AgBr/CaTiO3 composite photocatalyst with enhanced visible light photocatalytic activity

A novel efficient visible light driven Ag@AgBr/CaTiO3 composite photocatalyst was successfully fabricated by deposition–precipitation method, followed by photo-reduction route. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, ultraviolet–visible diffuse reflectance spectra and photoluminescence emission spectra were employed to characterize the crystal structure, morphology, chemical composition and optical properties. The photocatalytic activity of the samples was evaluated by the degradation of methyl orange (MO) aqueous solution under visible light irradiation. The results showed that the loading amount of Ag@AgBr had a significant effect on the photocatalytic activity. Among the photocatalysts studied, the as-prepared Ag@AgBr/CaTiO3-3 photocatalyst presented the highest photocatalytic activity under visible light irradiation, degrading more than 98% of MO within 12 min. The enhanced photocatalytic performance could be attributed to the surface plasmon resonance effect induced by Ag nanoparticles, and the formed heterostructure at the interface of Ag@AgBr and CaTiO3, resulting in high separation efficiency of photogenerated electron and hole pairs. In addition, the trapping experiment results demonstrated that h+ and $$^{ \cdot }{{\text{O}}_2}^{ - }$$ played the key roles for MO degradation. The possible degradation mechanism of MO over Ag@AgBr/CaTiO3 composite under visible light was tentatively proposed.

Photo-synthesized copper phenylacetylide nanobelts with preferential photocatalytic active facet exposure

We recently reported that PhC2Cu nanobelt exhibits excellent photocatalytic degradation of organic pollutants and activation of molecular O2. However, there has been no further research about the relationship between its crystal structure and photocatalytic activity. Herein, a new safe and energy-save method, photo-synthesis, to prepare PhC2Cu nanobelts with preferential active exposure facet was developed. It was used to study the relationship between its crystal structure and photocatalytic activity, compared to the PhC2Cu nanobelts prepared by thermal-synthesis method. The prepared samples were characterized by X-ray powder diffractometer (XRD), field-emission scanning electron microscopy (FE-SEM), ultraviolet-visible (UV-vis) absorbance spectra and diffuse reflectance spectra (UV-vis Abs and DRS), N2 adsorption-desorption isotherms, FT-IR and Raman spectra. The degradation of MB experiments under visible light irradiation shows that the photocatalytic activity of PhC2Cu prepared by photo-synthesis method is much higher than that by traditional thermal-synthesis method. Moreover, the photocatalytic mechanism of PhC2Cu nanobelts was further studied by the photocatalytic generation of O 2 -• and •OH.

Enhanced Photocatalytic Activity and Biosensing of Gadolinium Substituted BiFeO3 Nanoparticles

AbstractGadolinium (Gd3+) substituted bismuth ferrite (BF) photocatalysts were synthesized using sol‐gel method and the effect of Gd3+ substitution was investigated on the structural, optical and surface properties of Gd3+ substituted BF nanoparticles. Different techniques such as X‐ray diffraction (XRD), high‐resolution transmission electron microscopy (HRTEM) with Selected area electron diffraction pattern (SAED), Fourier transform infrared spectra (FTIR), ultraviolet‐visible diffuse reflection spectra (UV‐DRS), field emission scanning electron microscopy (FESEM), Brunauer‐Emmett‐Teller (BET), and photoluminescence spectra (PL) were employed to characterize the nanoparticles. Compared to nascent BF, the Gd3+ substituted BF nanoparticles showed improved long‐range ordering, smaller pore diameter, higher porosity and redshift of the band gap. These properties were responsible for their improved photocatalytic activity, when tested for the photodegradation of organic dyes. It was found that 3 % Gd3+ substituted BF nanoparticles exhibited enhanced the photocatalytic activity of indigo carmine dye with a degradation ranging from 34 % to 69 %, while for Congo red dye the degradation varied from 37 % to 73 % under the visible light. Furthermore, bio‐sensing properties of BF materials were improved as detected by the uric acid using cyclic voltammogram technique.

Photocatalytic hydrogen production with reduced graphene oxide (RGO)-CdZnS nano-composites synthesized by solvothermal decomposition of dimethyl sulfoxide as the sulfur source

In order to increase photocatalytic activity, to control particle size and to diminish photo-corrosion of CdZnS based photocatalysts, different compositions of Cd(1-x)ZnxSphotocatalysts were decorated on the reduced graphene oxide (RGO). The target photocatalytic composite structures (RGO-Cd(1-x)ZnxS) were firstly prepared by a solvothermal method using dimethyl sulfoxide (DMSO) as the solvent and sulfur source. RGO-Cd(1-x)ZnxSnanocomposites were characterized by the x-ray diffraction (XRD), the transmission electron microscopy (TEM), the scanning electron microscopy (SEM), ultraviolet-visible (UV–vis) diffuse reflectance spectra (DRS), photoluminescence (PL) spectra, The transient photocurrent responses, and the energy-dispersive X-ray spectrometry (EDS).Purity, the particle size of 40 nm, the crystallite sizes between 20.8 and 19.1 Å and cubic structure of the photocatalysts could be easily achieved by controlled thermal decomposition of DMSO. Decorating the photocatalysts on RGO structure prevented aggregation of Cd(1-x)ZnxS particles, enhanced transfer of photogenerated charge carriers, and increased the electron transfer rate of the photocatalysts, which provided a better photocatalytic activity. Moreover, loading photo-reduced platinum (Pt) nanoparticles on the RGO-Cd(1-x)ZnxSnanocomposite showed a significant increase in hydrogen evolution rate. Among the photocatalysts employed herein, RGO-Cd0.6Zn0.4S-Pt (5%) structure showed the highest activity with 184 μmol h−1 hydrogen evolution rate and 24.1% apparent quantum efficiency. Presences of RGO in the nanocomposite structure and synthesizing it with solvothermal method by using DMSO apparently increased the stability and activity of the nanocomposites.

Molybdenum substitution induced luminescence enhancement in Gd2W1-xMoxO6:Eu3+ phosphors for near ultraviolet based solid-state lighting

A series of the Eu3+-activated Gd2W1-xMoxO6 phosphors were synthesized by a high-temperature solid-state reaction method. The phase composition, ultraviolet-visible diffuse reflectance spectra, photoluminescence and decay properties of the phosphors were investigated. Through adjusting the Mo6+ ion concentration, the excitation band of the studied sample was gradually shifted to longer wavelength. Under 376 nm excitation, the strong red emission at 610 nm and weak yellow emission centered at 591 nm were detected, indicating that Eu3+ occupies non-inversion symmetry sites in the host lattices. With elevating the dopant concentration, the emission intensity of synthesized products was greatly enhanced and achieved its optimum value when x = 0.95 which was 2.33 times higher than that of the Gd2WO6:Eu3+ compounds. The quantum efficiency of resultant samples was as high as 76.1%. Moreover, the Judd-Oflet theory was used to study the local structure environment behaviors of the Eu3+ ions in the host lattices. Finally, a red LED device, which consisted of a near-ultraviolet chip and prepared Gd2W0.05Mo0.95O6:Eu3+ phosphors, was successfully fabricated. These results confirmed that the Eu3+-doped Gd2W1-xMoxO6 phosphors have potential value as the red component for WLEDs.

Construction of a Pt-modified chestnut-shell-like ZnO photocatalyst for high-efficiency photochemical water splitting

Super-slenderness-ratio, chestnut-shell-like ZnO, ZnO flowers, ZnO nanorods (NRs), and ZnO nanoparticles (NPs) were synthesized as photocatalysts using a facile hydrothermal method. To enhance its photocatalytic H2 production rates, Pt serving as a co-catalyst was loaded onto the surface of ZnO to form a Schottky heterostructure. A series of different Pt-modified chestnut-shell-like ZnO, ZnO flowers, ZnO NRs and ZnO NPs were prepared, and their photochemical water-splitting ability was investigated in detail. X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy results confirmed that approximately 5–10-nm-diameter Pt NPs were well dispersed on three-dimensional (3D) chestnut-shell-like ZnO, ZnO flowers, ZnO NRs, and ZnO NPs matrixes to form a Pt/ZnO heterojunction. Low-band-gap energies (minimum value 2.83 eV) and low electron-hole recombination rates were confirmed by ultraviolet–visible diffuse reflectance spectra and photoluminescence spectra, respectively, which demonstrated that the Pt-modified 3D chestnut-shell-like ZnO composites have excellent photochemical properties. The time-course I-t cycles and photocatalytic H2 production rate cycle measurements for the photocatalyst confirmed that the photochemical performance of Pt-modified ZnO nanocomposite have superstability and altitudinal reusability. The photochemical water-splitting results confirmed that the optimal sample was 4-wt.%-Pt-modified ZnO composites, the H2 production rate of which was approximately1.97 mmol h−1 g−1, which was approximately 4, 2.7, 3.2, and 5.8 times that of pristine chestnut-shell-like ZnO, 4-wt.%-Pt modified ZnO flowers, ZnO NRs, and ZnO NPs, respectively. This indicated that 4-wt.%-Pt-modified chestnut-shell-like ZnO exhibits excellent photocatalytic performance.