Under Ultraviolet Light Irradiation Research Articles

Lanthanide-based Single-Chain Nanoparticles as "Visual" Pass/Fail Sensors of Maximum Permissible Concentration of Cu2+ Ions in Drinking Water.

The maximum permissible concentration (m.p.c.) of Cu2+ ions in drinking water, as set by the World Health Organization (WHO) is m.p.c. (Cu2+)WHO = 30 μM, whereas the US Environmental Protection Agency (EPA) establishes a more restrictive value of m.p.c. (Cu2+)EPA = 20 μM. Herein, we develop-for the first time ever-a family of m.p.c. (Cu2+) "visual" pass/fail sensors based on water-soluble lanthanide-containing single-chain nanoparticles (SCNPs) exhibiting an average hydrodynamic diameter less than 10 nm. Both europium (Eu)- and terbium (Tb)-based SCNPs allow excessive Cu2+ to be readily detected in water, as indicated by the red-to-transparent and green-to-transparent changes, respectively, under ultra-violet (UV) light irradiation, occurring at 30 μM Cu2+ in both cases. Complementary, dysprosium (Dy)-based SCNPs show a yellow color-to-transparent transition under UV light irradiation at approximately 15 μM Cu2+. Eu-, Tb- and Dy-containing SCNPs prove to be selective for Cu2+ ions as they do not respond against other metal ions, such as Fe2+, Ag+, Co2+, Ba2+, Ni2+, Hg2+, Pb2+, Zn2+, Fe3+, Ca2+, Mn2+, Mg2+ or Cr3+. These new m.p.c. (Cu2+) "visual" pass/fail sensors are thoroughly characterized by a combination of techniques, including size exclusion chromatography, dynamic light scattering, inductively coupled plasma-mass spectrometry, as well as infrared, UV and fluorescence spectroscopy. This article is protected by copyright. All rights reserved.

Fluorinated TiO2 Hollow Spheres for Detecting Formaldehyde under UV Irradiation.

The fluorinated titanium dioxide (F-TiO2) hollow spheres with varying F to Ti molar ratios were prepared by a simple one-step hydrothermal method followed by thermal processing. The diameter of the F-TiO2-0.3 hollow spheres with a nominal ratio of F:Ti = 0.3:1 was about 200-400 nm. Compared with the sensor based on pristine TiO2 sensing materials, the F-TiO2-0.3 sensor displayed an enhanced sensing performance toward gaseous formaldehyde (HCHO) vapor at room temperature under ultraviolet (UV) light irradiation. The F-TiO2-0.3 sensor demonstrated an approximately 18-fold enhanced response (1.56) compared to the pristine TiO2 sensor (0.085). The response and recovery times of the F-TiO2-0.3 sensor to 10 ppm HCHO were about 56 s and 64 s, respectively, and a limit-of-detection value of 0.5 ppm HCHO was estimated. The F-TiO2-0.3 sensor also demonstrated good repeatability and selectivity to HCHO gas under UV light irradiation. The outstanding HCHO gas-sensing properties of the F-TiO2-0.3 sensor were related to the following factors: the excitation effect caused by the UV light facilitated surface chemical reactions with analyte gas species; the hollow sphere structure provided sufficient active sites; and the surface fluoride (≡Ti-F) created additional chemisorption sites on the surface of the TiO2 material.

Light-Responsive Actuator of Azobenzene-Containing Main-Chain Liquid Crystal Elastomers with Allyl Sulfide Dynamic Exchangeable Linkages.

Herein, a light-responsive and light-induced bond-exchange-reaction (BER)-capable actuator of the monodomain liquid crystal elastomer (xMLCEazo), developed using main-chain mesogenic oligomers containing azobenzene and allyl sulfide linkages, is investigated. Large quantities of the azobenzene and allyl dithiol linkages are incorporated into the main-chain mesogenic oligomer prepared via thiol-acrylate Michael addition polymerization (TAMAP). The xMLCEazo film is generated via visible-light-induced BER of the drawn polydomain xLCEazo (xPLCEazo) film prepared via TAMAP of tetrathiol cross-linkers and diacrylate-terminated mesogenic oligomers. The xMLCEazo film exhibits large length actuation (38%) through the photothermal effect, along with excellent self-healing and reprogramming properties, under ultraviolet (UV) light irradiation. UV light induced BER of the xMLCEazo film is used to develop complex-shaped actuators with a bilayer film, containing the xMLCEazo and xPLCEazo films, which are bonded by the UV light induced BER without glue. The individual arm of the complex eight-arm flower is remotely actuated under UV light irradiation, and a circular band is rolled under blue laser light irradiation, demonstrating the local remote-controlled actuation and fuel-free motion of the motile soft robot using light irradiation, respectively. Thus, the xMLCEazo film can be expanded to other interesting applications requiring reprogrammable, self-healing, reprocessable, patternable, and remote-controlled light-triggered elastic, rubber-like actuators.

Mof-derived MOF(Fe)/FeSx photocatalyst with enhanced photocatalytic activity for tetracycline degradation

Recent years, the quality of human life has substantially improved due to the development of our society. Nonetheless, the rapid pace of societal development has given rise to serious environmental pollution challenges, especially caused by organic contaminants. Herein, a metal–organic framework [MOF(Fe)/FeSx] composite was successfully synthesized using a solvothermal method by employing thioacetamide (TAA) as the sulfur source and MOF(Fe) as the template. The photocatalytic activity of this composite was assessed via the degradation of tetracycline (TC) under ultraviolet (UV) irradiation. The influence of TAA on the photocatalytic activity of the MOF(Fe)/FeSx composite was also investigated. Results revealed that MOF(Fe)/FeSx(2) shown optimal photocatalytic performance. After 35 min of UV light irradiation, MOF(Fe)/FeSx(2) achieved 98.21 % degradation of TC. The exceptional performance of MOF(Fe)/FeSx(2) in photocatalytic degradation positions it as a potential solution for degrading organic pollutants generated in factories and everyday life.

Rhombohedral boron monosulfide as a metal-free photocatalyst

Most of previous photocatalysts contain metal species, thus exploring a metal-free photocatalyst is still challenging. A metal-free photocatalyst has an advantage for the development of economical and non-toxic artificial photosynthesis system and/or environmental purification applications. In this study, rhombohedral boron monosulfide (r-BS) was synthesized by a high-pressure solid-state reaction, and its photocatalytic properties were investigated. r-BS absorbed visible light, and its photocurrent action spectrum also exhibited visible light responsivity. The r-BS evolved hydrogen (H2) from water under ultraviolet (UV) as well as under visible light irradiation, and its internal quantum efficiency reached 1.8% under UV light irradiation. In addition to the H2 evolution reaction, the r-BS photocatalyst drove carbon dioxide (CO2) reduction and dye oxidation reactions under UV irradiation. Although bare r-BS was not so stable under strong light irradiation in water, cocatalyst modification improved its stability. These results indicate that r-BS is a new class of non-metal photocatalyst applicable for H2 production, CO2 reduction, and environmental purification reactions.

Three-Dimensional Cadmium–Organic Framework with Dual Functions of Oxygen Evolution in Water Splitting and Fenton-like Photocatalytic Removal of Organic Pollutants

Metal-organic frameworks (MOFs) have exhibited appreciable potential as catalytic agents in the field of material science. The research of new MOFs with dual functions in electrocatalysis and photocatalysis under ultraviolet (UV) irradiation is extremely pivotal for renewable energy applications. Hence, we synthesized a series of three-dimensional MOFs, namely, [Cd(bimb)2(HITA)2]n (Cd-MOF 1), {[Cd(bimb)6](NO3)2}n (Cd-MOF 2), and [Cd(bimb)4(ONO2)2]n (Cd-MOF 3) (bimb = 1,4-bis(imidazol-1-ylmethyl)benzene; H2ITA = 5-hydroxyisophthalic acid), with applicability in the oxygen evolution reaction process and Fenton-like photocatalysis. The obtained results show that Cd-MOF 1 exhibited the most remarkable catalytic performance, affording a current density of 10 mA cm-2 at a very low overpotential of 279 mV and the smallest Tafel slope of 85.13 mV dec-1. Meanwhile, these MOFs can generate hydroxyl radicals (•OH) under UV light irradiation with the existence of H2O2, enabling the rapid degradation of organic pollutants. This study provides a valuable direction for producing multifunctional and environmentally friendly catalysts.

Facile synthesis of reusable Ag/TiO2 composites for efficient removal of antibiotic oxytetracycline under UV and solar light irradiation

BackgroundsIn this work, Ag-doped TiO2 nanomaterials (TiAgx, where x denotes the weight percentage of Ag) were prepared using a facile one-step sol-gel technique. The combination of Ag with TiO2 promises to enhance the lifetime of photogenerated electron-hole pairs and widen the photocatalytic activity in the visible light region, leading to improved photocatalytic activity. MethodsThe synthesized materials were characterized using different analyses and afterwards applied as photocatalysts to degrade oxytetracycline (OTC) in aqueous solution under ultraviolet (UV) and solar light illumination. Significant findingsThe highest photocatalysis was achieved for TiAg2 with 99.6% OTC removal after 120-min UV irradiation. Moreover, the best OTC removal under solar light irradiation was gotten for TiAg5, of which 94.1% of OTC was removed after 180 min. Reactive species of ∙O2− radicals were presented as the dominant agents in OTC oxidization; meanwhile, ∙OH and h+ contributed to the photodegradation process. The mineralization efficiency of OTC using TiAg2 reached 59.6% after 240-min UV irradiation. Furthermore, the OTC removal of TiAg2 by photocatalysis still maintained over 97% after 5 cycles.

Bio-inspired ZnWO4−x exhibiting vacancy-driven UV-to-NIR photodegradation of antibiotics in wastewater

Complex structures of antibiotics inhibit their breakdown by conventional removal techniques, resulting in persistent environmental pollution and breeding of deadly bacteria, that pose disastrous human health implications. As a remedy, we prepared BW-ZnWO4−x photocatalyst by combining Papilio paris (P. paris) wings as supporting substrates and templating frameworks and oxygen vacant ZnWO4 through modified functionalization and solvothermal processes. The BW-ZnWO4−x photocatalyst exhibited narrowed bandgap, broader photo-absorption, ∼6-fold high surface area and inhibited charge carrier recombination. Consequently, BW-ZnWO4−x photocatalyst degraded 98 %, 94 % and 85 % of levofloxacin (LVFX) antibiotic and 96 %, 93 % and 83 % of tetracycline (TC) antibiotic under ultraviolet (UV), visible and near-infrared (NIR) irradiation, respectively in 60 min. Comparatively, hydrothermally synthesized pristine ZnWO4 photocatalyst (denoted: P-ZnWO4) degraded 83 %, 82 %, 59 % of LVFX antibiotic and 85 %, 79 %, 50 % of TC antibiotic under UV, visible and NIR light irradiation, respectively. Moreover, the BW-ZnWO4−x photocatalyst demonstrated real-world applicability by degrading 95 %, 92 % and 78 % of hexavalent chromium (Cr VI) under UV, visible and NIR light irradiation, respectively. Therefore, these results could be insightful in development of bio-inspired materials for solar harvesting and storage systems, security systems and water treatment applications.

Developing a robust photocatalytic and antifouling performance of PVDF membrane using spinel NiFe2O4/GO photocatalyst for efficient industrial dye wastewater treatment

Photocatalytic nanohybrid polyvinylidene fluoride (PVDF) membrane incorporated by nickel ferrite/ graphene oxide (NiFe2O4/GO) photocatalyst is fabricated in this study. To prevent the fast electron/hole recombination rate in NiFe2O4 photocatalyst, GO nanoparticle was added to synthesize the NiFe2O4/GO photocatalyst. The fabricated membranes were tested for industrial dye wastewater treatment, which mainly contained Remazol red RB-133 as the colorant. The modified membranes were synthesized by adapting the non-solvent induced phase separation (NIPS-blending) technique, and their filtration performance were assessed both in the conventional dark filtration condition and under ultraviolet (UV) light exposure. Scanning electron microscopy – Energy dispersive x-ray (SEM-EDX) results reveal that the PVDF/NiFe2O4/GO membrane features a smooth, defect-free surface with a well-built finger-like structure, as well as a well-distributed NiFe2O4/GO distribution on the membrane's surface. Some new hydrophilic groups are recorded on PVDF/NiFe2O4/GO by the Fourier-transform infrared (FTIR) analysis such as -OH, Fe-O, Ni-O, and CO and some crystallite sites of NiFe2O4 and GO, which is helpful to improve the surface hydrophilicity. The permeability, pollutant removal, membrane stability, photodegradation ability, and antifouling activity of the modified membranes in the filtration process under UV light exposure were significantly improved. This membrane removed 83.22% of COD and 92.38% of dye when it was performed under UV light irradiation. The presence of photocatalytic activity on the membranes’ surface also improves the antifouling activity by converting the irreversible fouling into the reversible fouling, hence, the modified membranes have a better performance stability than the other membranes.

Investigation of the luminescence properties and energy transfer mechanisms in Gd3TaO7:Bi3+,Eu3+ phosphors for their potential application in full-spectrum WLEDs.

In recent years, there has been increasing effort devoted to the development of single-phase white phosphors due to drawbacks such as severe reabsorption and color deviation in traditional white light-emitting diodes (WLEDs). A new feasible strategy has emerged for achieving white light emission through the Bi3+-Eu3+ energy transfer in suitable single-phase phosphors. Therefore, a series of Gd3TaO7:xBi3+ and Gd3TaO7:0.01Bi3+,yEu3+ phosphors were synthesized via a high-temperature solid-state method, and their properties were systematically characterized. In Gd3TaO7, Bi3+ occupies two kinds of Gd3+ site, resulting in two broad emission bands peaking at 427 nm and 500 nm respectively under ultraviolet (UV) excitation, which arise from 3P1 → 1S0 transitions. By adjusting the concentration of Eu3+ in Gd3TaO7:0.01Bi3+,yEu3+, effective energy transfer can occur between Bi3+ and Eu3+, thus enabling the regulation of green-white-red luminescence under 332 nm excitation and blue-white-red luminescence under 365 nm UV light irradiation. Upon stimulation with a 365 nm UV chip, Gd3TaO7:0.01Bi3+,0.02Eu3+ emits white light with CIE coordinates of (0.3509, 0.3202), a color temperature of 4629 K, and an impressive color rendering index of 87.96. The above results indicate the potential of Gd3TaO7:0.01Bi3+,yEu3+ phosphor as a viable candidate for WLED applications.

Ultraviolet light-induced decomposition of benzothiophene and dibenzothiophene derivatives for efficient sulfur removal without additives and catalysts

When producing liquid fuels from petroleum, hydrodesulfurization methods reduce the concentration of sulfur to ≤10 mg(S)/L (weight/volume concentration of sulfur), namely, ≤ 0.31 mmol/L. Dibenzothiophene derivatives (DBTs), which are known as particularly difficult desulfurizing substances, have been decomposed reductively in severe conditions of high temperatures (270–372 °C) and high pressure (50–102 atm of H2). In this study, we developed a UV light irradiation-based desulfurization method for aromatic sulfur compounds such as benzothiophene derivatives (BTs) and DBTs under room temperature and atmospheric pressure without the use of catalysts or additives. This method is simple, location-independent, and low-cost, and has low environmental impact. BTs and DBTs completely decomposed in approximately 8 h and 16 h, respectively, under ultraviolet (UV) light irradiation (λ = 254 nm) from a 8 W lamp. The yellow precipitates that were produced upon decomposition were confirmed to be sulfur allotropes (Sn). The residual hydrocarbon portion of DBT after sulfur removal was determined to be benzene. The decomposition reaction was determined to exhibit pseudo-first-order reaction. DFT calculations confirmed the degradation mechanism as follows: UV light irradiation induces a photochemically excited triplet state of DBTs. The excited DBTs reacts with O2 to form a π-complex, which isomerizes to a more stable σ-complex. The DBTs-O2 (σ-complex) then reacts with free DBTs to afford two molecules of dibenzothiophene-5-oxide derivatives (DBTOs), which are excited to singlet states on photoirradiation. The excited DBTOs isomerize through a minimum energy intersection eventually to dibenzofuran episulfides from which sulfur extrusion occurs.

Enhanced photocatalytic degradation of methylene blue by nanocomposites prepared by laser ablation of Bi on CNT-α-Fe2O3 nanoparticles

The low conductivity and high combination rate of photogenerated electrons (e-) and photogenerated holes (h+) are the real challenges of photocatalysis. These problems could be mitigated by the synthesis of heterostructured nanocomposites (NCs). In this study, Bi@CNT-Fe2O3 nanocomposite was fabricated via pulsed laser ablation in liquid and characterized by UV–Vis spectroscopy, photoluminescence (PL), X-ray diffraction (PXRD) and field scanning electron microscopy (FESEM). These techniques revealed successfully the formation of CNT-α-Fe2O3 and Bi@CNT-α-Fe2O3 nanocomposites. The photocatalytic activities of the Fe2O3, CNT-α-Fe2O3, and Bi@CNT-Fe2O3 photocatalysts were evaluated by the degradation of methylene blue (MB) dye under ultraviolet (UV) light irradiation in the presence of a very low concentration of hydrogen peroxide (H2O2) as an oxidizing agent. The results show that the Bi@CNT-α-Fe2O3 NC has the highest photocatalytic degradation efficiency of MB which completes in 20 min of UV light irradiation. In addition, the obtained rate constants (min−1) of Bi@CNT-α-Fe2O3 NC were 1.3 and 3.4 times higher than those of CNT-α-Fe2O3 and α-Fe2O3. nanocatalysts, respectively.

Rare metal doping of the hexahydroxy strontium stannate with enhanced photocatalytic performance for organic pollutants

Rare metal (La or Nd) doped hexahydroxy strontium stannate with different dopant contents was synthesized via a facile hydrothermal route. The rare metal doped samples were investigated by X-ray diffraction (XRD), electron microscopy, solid diffuse reflectance spectrum, X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS) and photoluminescence (PL) spectroscopy. The morphology of the doped samples is closely relative to the rare metal dopant content transferring from the nanorods to nanoflakes and nanoscale particles for La and Nd doping, respectively. 2wt.% rare metal doped hexahydroxy strontium stannate possesses the smallest band gap value with 3.26 eV (La doping) and 3.25 eV (Nd doping) which enhances the charge carriers transfer efficiency. The rare metal doped hexahydroxy strontium stannate shows enhanced photocatalytic performance for the crystal violet degradation under ultra-violet (UV) light irradiation. 2wt.% rare metal doped hexahydroxy strontium stannate has the best photocatalytic activity for the removal of crystal violet under UV light irradiation for 120 min. The rare metal doped hexahydroxy strontium stannate possesses high stability, and is reusable for the crystal violet degradation.

Effect of wavelengths on photocatalytic oxidation mechanism of sulfadiazine and sulfamethoxazole in the presence of TiO2

In this paper, the effect of wavelengths on photocatalytic oxidation kinetics and mechanisms of sulfadiazine (SD) and sulfamethoxazole (SMX) in the presence of Degussa P25 TiO2 were discussed, and the influence of humic acids (HA) on the degradation process was further explored. The photocatalytic degradation process of sulfonamides antibiotics (SAs) can be characterized by the pseudo-first-order model, and the removal rates for SAs under ultraviolet (UV) light irradiation were higher than those under visible light irradiation, with the values in the order of 365 nm > 254 nm > 420 nm > 475 nm. The degradation ratios of SAs could reach over 99% within 90 min under UV irradiation, whereas the SAs removal rates were less than 70% after 120 min visible light irradiation. The superoxide radicals (·O2−) were the most important components during the SAs degradation both under UV and visible light irradiation. Due to the existence of special groups, SD mainly performed desulfurization reactions of the S-N bond cleavage and recombination, while SMX underwent ring-opening reactions because of the cleavage of the N-O bond in the isoxazole ring. HA had an inhibitory effect on the photocatalytic oxidation of SAs under UV light irradiation, but had a promotional effect under visible light irradiation. This study and the consequent results would provide a data basis and theoretical reference for the photocatalytic oxidation mechanisms of SAs in real water.

A facile preparation of ZnFe2O4–CuO-N/B/RGO and ZnFe2O4–CuO–C3N4 ternary heterojunction nanophotocatalyst: characterization, biocompatibility, photo-Fenton-like degradation of MO and magnetic properties

To improve the low photocatalytic efficiency, powerful UV light activation, and facile electron transport of ZnFe2O4–CuO the combination of different C3N4 and N/B/RGO nanosheets in ZnFe2O4–CuO–C3N4 and ZnFe2O4–CuO-N/B/RGO ternary nanoheterojunction fabricated that lead to decrease recombination of electron/hole pairs and high photocatalytic efficiency for degradation of MO organic pollutants. The ZnFe2O4, ZnFe2O4-N/B/RGO, CuO-N/B/RGO, ZnFe2O4–CuO, ZnFe2O4–CuO-N/RGO, ZnFe2O4–CuO-B/RGO, ZnFe2O4–CuO-RGO, ZnFe2O4–CuO-N/B/RGO and ZnFe2O4–CuO–C3N4 photocatalysts were fabricated by sol–gel technique using melamine, zinc nitrate, ferric nitrate and copper nitrate hexahydrate as precursors. The prepared ZnFe2O4–CuO–C3N4 photocatalysts have a narrower bandgap than that of ZnFe2O4–CuO-N/B/RGO ternary heterojunction, resulting in higher photocatalytic activity for Fenton-type photodecomposition of methyl orange (MO). The activity of the compounds as a photocatalyst can be attributed to an electron transfer process on the surface of the photocatalyst, where the ZnFe2O4–CuO–C3N4 is a powerful electron donor and electron acceptor for the oxidized MO under ultra-violet (UV) light irradiation. ZnFe2O4–CuO–C3N4 ternary heterojunction photocatalyst show a red shift (lowest bandgap) in absorption and excellent photocatalytic degradation of MO. The particle sizes of ZnFe2O4 and CuO nanoparticles (NPs) were in the ranges of ~ 650–750 and ~ 50–150 nm, respectively. The CuO and ZnFe2O4 samples were displayed spherical and cubic morphology in FESEM images, respectively. Among the as-prepared nanostructures ZnFe2O4–CuO–C3N4 show the highest photocatalytic activity and eliminate 95.84% (80 min) of methyl orange under UV light irradiation.

Synthesis, characterization and photocatalytic activities of Al-doped ZnO for degradation of methyl orange dye under UV light irradiation

Semiconductor photocatalysts with better photocatalytic properties have been widely researched to be an alternative for dye removal application with better photocatalytic properties. In the present work, Al-doped ZnO which act as a photocatalysts was prepared by modified sol-gel technique at different Al concentrations to evaluate the effect of different Al doping concentration towards the photocatalytic degradation performance of methyl orange dye. The crystallinity of Al-doped ZnO was analysed by X-ray diffraction (XRD) at room temperature. The structural properties, surface morphology and elemental composition were studied via scanning electron microscope (SEM) attached with energy dispersive X-ray spectroscopy (EDS). From XRD, all Al-doped ZnO samples show a polycrystalline nature with a hexagonal wurtzite structure. The average crystallite size was determined by Scherrer’s equation in the range of 79.29–86.50 nm. The Al ion was successfully incorporated into the Zn lattice confirmed by (101) peak shifting from the XRD results. The photocatalytic activities have been carried out by irradiating the photocatalysts under ultraviolet (UV) irradiation. The 1 mol% Al-doped ZnO exhibited a significant increase in the percentage degradation and photocatalytic efficiency compared to others with value of 88.87% degradation and rate constant k of 3.45 × 10−2 min−1 under 60 min irradiation. In the present work, Al-doped ZnO could be reused minimum of five cycles in its recyclability reaction.

A stable hydrazine click fluorescent probe based on photo switch

One novel aggregation induced emission (AIE) fluorescent probe for hydrazine (N2H4) (T) was synthesized. This is an optically controlled process. The probe is very stable before light, which is different from many probes with ester bonds that are easily hydrolyzed during storage. Only under ultraviolet (UV) light irradiation, T responded to N2H4 rapidly in aqueous solution along with the fluorescence change from yellow to blue. The detection limit is as low as 0.25 μM, and it works well at a wide pH range (3–10) in aqueous solutions. Bio-imaging of N2H4 in living cell demonstrated a favorable biocompatibility. Moreover, the optically controlled mechanism was exploited. The result indicated that the Schiff base structure of T would be twisted under UV light irradiation, which loosened the original aggregation state. Consequently, T became more accessible to N2H4. That is, aggregation state of T is inactive, only in the presence of UV light the reactivity could be activated. Interestingly, the torsion of this compound can be restored by visible light irradiation or heating. This is the first report about optically controlled AIE fluorescent probe.

Formation and decomposition of gold oxides prepared by an oxygen-dc glow discharge from gold films and studied by X-ray photoelectron spectroscopy

Formation and decomposition of thin (<1 nm) gold oxides prepared by an oxygen-dc glow discharge from gold films were studied by X-ray photoelectron spectroscopy (XPS). Four oxygen species comprising O 1s components Ⅰ, Ⅱ, Ⅲ, and Ⅳ are present in the XPS spectra. Component Ⅳ appears in the early formation periods and then changes into the oxide component Ⅲ. Components Ⅰ and Ⅱ are both stable at high temperatures and assigned to hydroxyl groups. The angular dependence of the XPS spectra of the gold oxides indicates that the oxygen species of components Ⅰ and Ⅱ are present in this order from the top surface of the gold oxide (component Ⅲ). The gold oxides decompose after 36 h at room temperature and decompose immediately at temperatures exceeding 121 °C in a dark atmosphere. The oxides also decompose under ultraviolet (UV) light irradiation at 254, 302, and 365 nm and decompose more rapidly at the shorter wavelengths. The decomposition of the gold oxides under UV light irradiation is slower in a high vacuum but is faster in a water vapor atmosphere. The decomposition caused by UV light irradiation and its wavelength dependence indicate reaction of the gold oxides with excited water molecules produced by UV light absorption.

Enhanced Photocatalytic Properties of N and Fe Co-Doped TiO2 Nanocomposites with Reduced Graphene Oxide for Volatile Organic Compounds

Photocatalytic nanocomposites of titanium dioxide (TiO2) were prepared by hydrothermal method. Reduced graphene oxide (RGO) was applied to prepare various TiO2 composites of doped nanoparticles by using NH4Cl and FeCl3 as sources. The structure and morphology of these composites showed that TiO2 was loaded on surface of RGO. Meanwhile, the agglomeration of TiO2 decreased and the dispersion became uniform for doped materials. Under ultraviolet (UV) light irradiation, the photocatalytic degradation of volatile organic compounds (VOC) by RGO/TiO2 composites with codoping of N and Fe reached to 90.5%. The photocatalytic degradation was higher than RGO/TiO2 composites and pure TiO2 by 1.8 and 5.9 times, respectively. The role of co-doping composites may have a possible mechanism for toluene under UV light irradiation. The enhanced photocatalytic properties were attributed to N and Fe doping which generated intermediate energy level, extended absorption and decreased band gap of UV light.

Enhanced Photocatalytic Properties of N and Fe Co-Doped TiO2 Nanocomposites with Reduced Graphene Oxide for Volatile Organic Compounds

Photocatalytic nanocomposites of titanium dioxide (TiO2) were prepared by hydrothermal method. Reduced graphene oxide (RGO) was applied to prepare various TiO2 composites of doped nanoparticles by using NH4Cl and FeCl3 as sources. The structure and morphology of these composites showed that TiO2 was loaded on surface of RGO. Meanwhile, the agglomeration of TiO2 decreased and the dispersion became uniform for doped materials. Under ultraviolet (UV) light irradiation, the photocatalytic degradation of volatile organic compounds (VOC) by RGO/TiO2 composites with codoping of N and Fe reached to 90.5%. The photocatalytic degradation was higher than RGO/TiO2 composites and pure TiO2 by 1.8 and 5.9 times, respectively. The role of co-doping composites may have a possible mechanism for toluene under UV light irradiation. The enhanced photocatalytic properties were attributed to N and Fe doping which generated intermediate energy level, extended absorption and decreased band gap of UV light.