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The release of industrial effluents into fresh water is a major contributor of water contamination. Therefore, it is highly desirable to develop a viable solution to this alarming issue to improve the quality of clean water. To enhance the photocatalytic efficiency and hence utilization ratio of CuO, a series of CuO–FeSe2 composites with different varying contents of FeSe2 were prepared through facile synthetic methods. X-ray diffraction (XRD) and energy-dispersive X-rays (EDX) analysis verified that the samples were successfully prepared without any contaminating phases. The average crystallite sizes of CuO and FeSe2 were computed to be 29 and 21 nm respectively. For the CuO–FeSe2 composites, the crystallite sizes varied between 25 and 27 nm. The morphology of CuO was comprised of needle-shaped structures, whereas that of FeSe2 was observed to be flower-shaped structures comprising of irregular crystals. A red shift in the bandgap of CuO–FeSe2 composites was observed with the increase in FeSe2 concentration. The prepared photocatalysts were utilized to evaluate their efficiency under visible light against Rhodamine B (RhB). Among all the prepared composites, CuO–75% FeSe2 revealed a remarkable performance and degraded 96% RhB in 180 min. Rate constants for the degradation of the dye were determined by applying the Langmuir–Hinshelwood model. [ABSTRACT FROM AUTHOR]

In this study, a heterogeneous metal–organic framework catalyst was meticulously prepared and extensively employed for the reduction of nitroarenes, congo red, and methylene blue. The catalyst was synthesized using a straightforward method, resulting in the formation of nanorods with well-defined morphology. These nanorods, composed of nanorod-hydroxyapatite, served as an exceptional and heterogeneous support for the fabrication of a metal–organic framework composite. In the following, surface functionalization was carried out using asparagine and TAZ-IMI, which was prepared by combining imidazole and cyanuric chloride. To enhance the catalytic performance, Pd(OAc)2 was immobilized onto the composite, leading to the formation of a novel n-HA@SiO2–ASP–Pd–TAZ–IMI catalyst. Extensive characterization studies were conducted to confirm the successful formation and structural integrity of the catalyst. The n-HA@SiO2–ASP–Pd–TAZ–IMI catalyst exhibited remarkable catalytic activity in the reduction of nitro compounds, utilizing NaBH4 as the reducing agent, resulting in excellent yields. Notably, the catalyst demonstrated excellent recyclability, as it could be easily reused up to three times with only a slight decrease in reaction yield. [ABSTRACT FROM AUTHOR]

The zeolite-Y/g-C3N4 composites were successfully synthesized by a facile hydrothermal method. The composition, structure and optical properties of the composites were characterized by infrared spectroscopy, X-ray diffraction, UV–Vis diffuse reflectance spectroscopy and other spectral techniques. The as-prepared zeolite-Y/g-C3N4 composite exhibits remarkably enhanced photocatalytic activity for organic dye degradation and nitrogen fixation under visible light irradiation. The optimal hybrid catalyst (YCN-50) shows good photocatalytic activity for methylene blue degradation. The degradation kinetic constant is 26.6 times higher than that of g-C3N4. Photocatalytic degradation of other organic dyes including malachite green, methyl orange and rhodamine B was also studied for comparison. For the photocatalytic nitrogen fixation, the ammonium production rate of zeolite-Y/g-C3N4 composite is 62.7 µmmol g−1 h−1 under the optimal condition, which is 62.7 times higher than that of pure g-C3N4. The high photocatalytic performance of zeolite-Y/g-C3N4 composite is due to the combination of g-C3N4 and zeolite-Y effectively improving the specific surface area and reducing the recombination rate of photogenerated carriers. The zeolite-Y/g-C3N4 composite also shows good photostability and reusability based on recycling experiments. Trapping experiment was also performed to find the responsible radical species for the degradation. The mechanism of dye degradation and nitrogen fixation in the presence of zeolite-Y/g-C3N4 was also discussed. [ABSTRACT FROM AUTHOR]

Novel organic dyes were designed (MAX114-1–MAX114-7) by adding different π-spacer groups to the reference dye (MAX114) for high efficiency of dye-sensitized solar cells (DSSCs). Their geometries, electronic structures and optical properties and photovoltaic performance were theoretically investigated by density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. Photovoltaic parameters influencing power conversion efficiency (PCE) were calculated and discussed for DSSC applications, such as light-harvesting efficiency (LHE), electron injection driving force (∆Ginj), dye regeneration driving force (∆Greg), nonlinear optical properties (NLO) and reorganization energy. The optimized geometries of designed dyes have more coplanarity than the MAX114, which is beneficial for efficient intramolecular charge transfer and the suppression of dye aggregation. The energy gaps of the designed dyes have significantly decreased compared to MAX114, leading to red-shifted absorption spectra and improved light-harvesting ability. It was found that the studied dyes have good electron injection and dye regeneration performance due to a more negative value of ∆Ginj and a lower value of ∆Greg. The results show that the designed dyes have a higher μnormal, higher LHE, higher NLO properties, lower ∆Greg, reasonable ∆Ginj, and a better balance of λh and λe, resulting in a higher VOC and JSC than MAX114. This indicates that the designed dyes (MAX114-1–MAX114-7) could be used as sensitizers to improve the effectiveness of DSSC devices. [ABSTRACT FROM AUTHOR]

The photocatalytic activity of three solvothermal prepared steel slag nanocomposites, SSNP-10, SSNP-20, and SSNP-30, was tested in this work for methylene blue (MB) dye degradation. Using SSNP for the first time, the photocatalytic degradation of MB dye was optimized using Box–Behnken design (BBD) in a response surface approach. The influence of essential operating parameters was experimentally examined, modeled, and optimized. The analysis of variance (ANOVA) results revealed that the suggested quadratic models significantly agreed with the experimental investigation, with p-values less than 0.0001 and an R2 value of 0.9914. Accordingly, the optimized conditions were 32.83 mg catalyst dose, 11.42 pH, 41.34 min irradiation times, and 10.63 mg/L MB dye concentration. The optimized degradation efficiency of the MB dye was 89.43% under these conditions. The result was experimentally validated with the optimal operating parameters for SSNP-10, SSNP-20, and SSNP-30, and the photodegradation efficiencies were 90.07%, 88.94%, and 87.28%, respectively. A pseudo-first-order reaction kinetics of 0.0293, 0.0291, and 0.0267 was achieved for SSNP-10, SSNP-20, and SSNP-30 with a regression coefficient of 0.9514, 0.9312, and 0.9042, respectively. According to Pareto analysis, the operational factors that had the greatest effect on dye degradation efficiency were catalyst dosage (F-value 585.32) > MB concentration (F-value 423.89) > irradiation period (F-value 368.01) > pH (F-value 362.34). The results showed that the SSNP catalyst was the key parameter for the generation of hydroxyl radicals responsible for the photodegradation of MB dye and may be useful for other contaminants' degradation. [ABSTRACT FROM AUTHOR]

Organic dyes are used in many industries, e.g., textile, cosmetics and food. Hence, contamination of organic dyes to water sources is a critical issue. To reduce water pollution by organic dyes, we propose a paper-like adsorbent with a practical and economical production procedure. Subsequently, a flexible adsorbent was produced using a one-step approach by vacuum filtration of graphene oxide (GO) and iron oxide nanoparticles (Fe3O4-NPs) containing dispersion through a membrane and quoted as GO/Fe3O4 paper. For comparison, GO paper was also prepared using the same procedure. Both papers were characterized using UV–VIS absorption spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, electron diffraction X-ray analysis, X-ray photoelectron spectroscopy, and powder X-ray diffraction techniques. At the steady-state conditions, GO/Fe3O4 and GO papers were performed as adsorbent for cationic dyes of methylene blue, neutral red, and anionic dyes of methyl orange and fluorescein. In general, the removal efficiency of GO/Fe3O4 paper was higher than that of GO paper for adsorption of all dyes and this adsorbent revealed satisfactory adsorption properties for cationic dyes when compared to anionic dyes. [ABSTRACT FROM AUTHOR]

Photocatalytic degradation is an advanced technique towards remediation of wastewater laden with organic contaminants. In the present study, in order to improve the photocatalytic activity and recycling times of TiO2 under visible light, TiO2 was facilely in situ immobilized on activated carbon fiber (ACF) surface by coating and hydrothermal treatment, called ACF-TiO2. XRD indicated that TiO2 on ACF-TiO2 was nano anatase type with a grain size of 3.72 nm. SEM, XPS and FT-IR analysis showed that TiO2 was uniformly dispersed on the surface of ACF, and the C element of ACF entered the lattice of TiO2, forming Ti–O–C bond. According to the analysis of UV-Vis DRS, the response of ACF-TiO2 to light exhibited a significant red shift, and the bandgap energy value decreased to 3.03 eV; In the process of eliminating MB, the presence of ACF improved the photocatalytic performance of TiO2 and the loaded TiO2 continuously degraded the MB molecules adsorbed by ACF. The whole process of adsorption-photocatalytic degradation was dynamically completed, and the synergistic effect between ACF and nano TiO2 was beneficial to the in situ regeneration and sustainable use of ACF-TiO2. This study may provide a facile reference to prepare ACF supported TiO2 without the sacrifice of the pores and adsorption capacity of substrates of ACF, and the desirable performance can be highly applied in the treatment of wastewater contaminated with organic dyes. [ABSTRACT FROM AUTHOR]

TiO2 mesoporous microspheres were prepared by water heating reflux of TiO2 precursors obtained via hydrolysis of tetrabutyl titanate. TiO2 microspheres were printed on FTO glass substrate and sensitized with CdS nanoparticles for forming CdS/TiO2 thin film via a successive ionic layer adsorption and reaction process. TiO2 microspheres and CdS/TiO2 thin film were characterized using field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis, N2 adsorption desorption measurements, X-ray photoelectron spectroscopy, and UV–Vis absorption spectra. The results indicated that water heating reflux contribute to the crystallization of TiO2 from the amorphous to anatase phase. TiO2 mesoporous microspheres with higher surface area of 268.53 m2/g were formed during the water heating reflux process. A photoresponsive test suggested that the introduction of CdS improves light utilization of TiO2 mesoporous microspheres and reduces recombination of photogenerated electron–hole pairs. Photocurrent density of TiO2 microspheres sensitized with CdS nanoparticles reached 0.2 mA/cm2 while pure TiO2 only obtained 0.036 mA/cm2. The photodegradation performance of the CdS/TiO2 thin film was further investigated. Photodegradation efficiency of CdS/TiO2 thin film reach about 95% within 120 min due to the synergistic effect of CdS and TiO2 heterostructure. The possible catalytic mechanism was also proposed. [ABSTRACT FROM AUTHOR]

Ag/AgCl/ZnTiO3 nanohybrids were assembled by the photoreduction–precipitation assisted with ultrasonic method. Rhodamine B (RhB), methylene blue (MB) and methyl orange (MO) were selected to evaluate the photocatalytic performance of Ag/AgCl/ZnTiO3 nanohybrids, and the effects of operating conditions (photocatalyst dosage, dye concentration and pH) were further studied. The photocatalytic debasement of Ag/AgCl/ZnTiO3 for RhB, MB and MO reached 99%, 98% and 95% under UV light (365 nm) for 30 min, respectively, while decreased to 90%, 88% and 73% under visible light (> 420 nm). In comparison with the pure ZnTiO3, the degradation of RhB, MB and MO by Ag/AgCl/ZnTiO3 under UV light increased 14.09-fold, 3.16-fold and 6.18-fold, respectively. Based on UV–visible absorption spectra and photoluminescence spectra, the photocatalytic activity of Ag/AgCl/ZnTiO3 nanoparticles was enhanced by surface plasmon resonance (SPR) and efficient interchange between photogenerated electrons and holes. After five cycling experiments, the degradation ability of Ag/AgCl/ZnTiO3 nanoparticles descended less than 10% and the physicochemical features almost unchanged, which indicated that these hybrid photocatalysts exhibited favorable durability and stability. Moreover, an enhancement photocatalytic mechanism of Ag/AgCl/ZnTiO3 photocatalysts was proposed by band gap analysis and trapping experiments. [ABSTRACT FROM AUTHOR]

In this work, a series of six organic dyes-sensitized solar cells (DSSCs) combining various π-bridges with a fixed donor (triphenylamine) and a fixed electron acceptor (cyanoacrylic acid), namely D1-6, were studied. The geometrical structure, electronic and optical properties of these dyes have been investigated with the density functional theory and TD-BHandHLYP hybrid functional (time-dependent Becke-Half-and-Half-Lee–Yang–Parr's) methods. The effects of π-bridging of the dyes have shown that the rings with a sulfur atom reduce the energy gaps and provide a redshift of the absorption spectra. Similarly, we focus on the description of the ground and excited state properties. On the other hand, the pyrrole group improves the open-circuit voltage (VOC) and the light-harvesting efficiency parameters leading to greater power conversion efficiency. Furthermore, the results revealed lowest total reorganization energy λ (λ+ and λ−) for the dye D3 with pyrrole linkage, which reflects its most favorable charge-transport properties, implying a lower charge recombination rate, faster charge injection and dye regeneration processes. Therefore, this study would provide a new path to design novel conjugated organic molecules as dyes for high-performance DSSCs. [ABSTRACT FROM AUTHOR]

A theoretical study on four organic dyes based on bis(4-hexyloxy)triphenylamine as donor and electron acceptor cyanoacrylic acid with a donor–π–acceptor structure (D–π–(D–A–)–A) using DFT/DFT (TD-DFT)/6-31G(d,p) having a difference of π spacer was designed. The theoretical study of the structural, electronic and optical properties of these dyes (D1, D4) suggests that these materials would be excellent sensitizers as a candidate for the production of dye solar cells, due to the efficient photoinduced electron transfer and strong absorption as well as the electronic properties (HOMO, LUMO, Egap) low band gap, The improved light-harvesting efficiency and free energy change of electron injection (ΔGinject), of new designed sensitizers revealed that these materials would be excellent sensitizers. This theoretical designing paves the way for experimentalists to synthesize more efficient sensitizers for solar cells. [ABSTRACT FROM AUTHOR]

In this research, tin oxide nanoparticles (SnO2-nanoparticles) are synthesized using sol–gel method in polymeric bed and considering the principals of green chemistry. Tin chloride and gelatin were used as tin precursor and stabilizing agent, respectively. The obtained gel was calcined in different temperatures (600, 700, and 800 °C). Different analyses such as TG–DTA, EDX, XRD, FT-IR, TEM, and FESEM were performed to examine the prepared nanoparticles. Results of XRD, TEM, and FESEM showed the spherical SnO2-nanoparticles in a tetragonal rutile morphology with mean particle size ~ 27 nm. The evaluation of optical attributes of SnO2 has been carried out by utilizing the UV–visible spectrophotometry. The photocatalytic activity of SnO2-nanoparticles showed efficiency about 35.9% in degradation of Eriochrome Black T (EBT). [ABSTRACT FROM AUTHOR]

In this work, mesoporous CdS (130.7 m2/g) was prepared; then, ZnS was deposited by chemical bath deposition (CBD) and successive ionic layer adsorption and reaction (SILAR) method, to get CdS–ZnS(C) and CdS–ZnS(S), respectively. Subsequently, the highest efficient binary hybrid was sensitized with polyaniline to produce CdS–ZnS–PANI for the first time. XRD and EDX analyses confirmed the coating of CdS with ZnS using CBD and SILAR method. The careful examination for the surface morphology of the binary hybrids illustrated that CdS–ZnS(S) has uniform morphology and the CdS nanoparticles are homogeneously overcoated with ZnS. In contrast, CdS–ZnS(C) exhibits inhomogeneous surface, where there are ZnS particles that aggregate together and there is another region which contains ZnS deposited onto CdS. The estimated band gap of CdS, CdS–ZnS(S), and CdS–ZnS–PANI was 2.36 eV, 2.44 eV, and 1.9 eV, respectively. The removal efficiency for cationic and anionic dyes single and/or in combination using CdS, ZnS, CdS–ZnS(C), CdS–ZnS(S), PANI, and CdS–ZnS–PANI was studied. The effect of the amount of ZnS loaded by SILAR process on the activity of the CdS–ZnS(S) was presented. The results proposed that CdS–ZnS(S) exhibits selective adsorption and high removal efficiency for cationic dye compared to CdS–ZnS(C) due to higher negative zeta potential and large surface area. The CdS–ZnS–PANI ternary nanocomposite showed uptake efficiency of 96.7% for cationic dye (MB) and 94.3% for anionic dye (MO) in a mixed dye solution after 10 min. Finally, the possible adsorption mechanism was proposed. [ABSTRACT FROM AUTHOR]

Existing industrial titania production lines and their intermediate products are economically attractive precursors for synthesis of highly concentrated TiO2 coating sols and soluble nanopowders. Refluxing of aliphatic alcoholic TiOCl2 solutions (with up to 500 g TiO2/L) allows straightforward formation of nonaggregated anatase nanocrystals with size between 5 and 8 nm. Surface modification of these nanoparticles with organosilanes shifts the pH value of point of zero charge from initially 5.3 down to around 2.8. At appropriate Ti/Si ratios, complete suppression of the anatase ultraviolet (UV) photoactivity is possible. Furthermore, we address the optical and photocatalytic data of transparent nanocrystalline layers produced from superconcentrated ZnxTiyOz heterosols. Depending on the Zn/Ti ratio and processing temperature, colorless cubic c-ZnTiO3 and c-Zn2TiO4 spinel nanophases or coupled r-ZnTiO3-ilmenite/r-TiO2-rutile heterojunctions (Zn/Ti = 2/3) can be produced. The cubic spinel films are indirect semiconductors showing band gap transition of around 3.7 eV. In contrast, r-ZnTiO3-ilmenite films have slightly lower band gap of around 3.6 eV. Organic dye photodegradation studies reveal the highest catalytic activity for the coupled r-ZnTiO3-ilmenite/r-TiO2-rutile systems compared with colored (nitridated) or colorless cubic spinel film samples. [ABSTRACT FROM AUTHOR]

Abstract: Photocatalysis using semiconductors has emerged as a promising wastewater treatment process to overcome the major challenges faced by conventional technologies. The advantages of ZnO nanomaterials over other semiconductors, and their structure-dependent properties, make them important building blocks in nanotechnology as multifunctional materials. Moreover, it has been confirmed that ZnO nanomaterials can exhibit high performance in photodegradation of organic dyes for treatment of industrial effluent. The wurtzite structure of ZnO contains polar and nonpolar planes; the low surface energy and thermodynamic stability of the nonpolar planes enable formation of one-dimensional (1D) ZnO structures, which are desirable compared with zero-dimensional (0D) and two-dimensional (2D) nanoarchitectures. Also, relative to other forms, the superiority of 1D ZnO nanostructures in dye photodegradation makes them promising as a future research direction and for commercial use. Therefore, understanding the design and synthesis of 1D ZnO nanomaterials is of critical importance for the development of novel and high-performance photocatalysts. Rational design of 1D ZnO nanophotocatalysts is thus required to enhance their photodegradation activity via efficient separation of charge carriers, increased surface-to-volume ratio, enhanced light absorption capacity, and improved stability/reusability. We briefly describe herein the most widely applied synthesis methods, including vapor-phase and solution-based strategies, to understand different methods for tailoring 1D ZnO nanophotocatalysts. Moreover, to elucidate the effect of their physical/chemical properties on the photodegradation efficiency, all the modification methods are categorized into four different approaches, viz. (1) morphology control, (2) induction of defects, (3) modulation by doping, and (4) formation of hybrids and heterojunctions. An overview of all aspects of charge generation, separation, and transfer during dye photodegradation by engineered 1D ZnO nanomaterials is also provided.Graphical abstract: [ABSTRACT FROM AUTHOR]

In this study, we synthesized novel visible light photocatalyst MIL-88A/BiOI using depositing BiOI particles on the surface of a metal-organic framework (MIL-88A). Photocatalytic application of binary composite MIL-88A/BiOI was obtained by discoloration of Methylene Blue (MB) and Acid Blue 92 (AB92) in aqueous solution under visible light source. The photodegradation experiments for treating organic dyes show that the MIL-88A/BiOI heterojunction structure possess a higher rate for decomposition of dyes due to the decreased aggregation of the BiOI nanoparticles, effective charge carrier separation and the synergistic effect between MIL-88A and BiOI samples as a heterojunction. Also, the MIL-88A/BiOI structure shows better photocatalytic degradation performance for anionic dyes (AB92) than for a cationic dye (MB). It was further found that •OH and •O2− radicals were the most important species responsible for the photodegradation test. [ABSTRACT FROM AUTHOR]

In this work, pompon-like structured g-C3N4/ZnO composite photocatalyst was fabricated by a two-step method and characterized through different characterization tools to determine the photophysical properties. It is discovered that the synthesized pompon-like g-C3N4/ZnO photocatalyst is composed of flake g-C3N4 coated on the pompon surface of ZnO to form a heterojunction structure. In the composite photocatalyst, the pompon ZnO has large surface area (41.81 m2/g) which can provide more reactive sites for composite catalysts, the g-C3N4 can absorb the visible light which can effectively expand the absorption range of the composite, and the heterostructure formed between g-C3N4 and pompon ZnO can effectively reduce the coincidence efficiency of photo-generated carriers. The photocatalytic performance of pompon-like g-C3N4/ZnO photocatalyst was evaluated by photocatalytic degradation of rhodamine B (RhB) organic dyes under simulated solar light irradiation and the optimum doping amount of g-C3N4 is 10%. The stability of the composite photocatalyst was tested by five runs of RhB photodegradation under simulated visible light. [ABSTRACT FROM AUTHOR]

Dye effluents play a major role in polluting water bodies, and various treatment technologies are being used for their removal. Among these methods, green photocatalysis involving solar radiation has achieved tremendous momentum because of its economically viable and environmentally friendly nature. Noble metals, especially silver, shows visible light catalytic activity and this makes it a suitable candidate for photodegradation of organic dyes. Here, we report the synthesis of silver nanoparticles supported on graphene oxide sheets by a hydrothermal method. We have grown silver nanoparticles on highly conducting reduced graphene oxide sheets, thereby preventing electron-hole pair recombination. The as-prepared silver-decorated reduced graphene oxide nanocomposite was characterized by UV-Vis spectroscopy, X-ray diffraction, Raman spectroscopy, photoluminescence technique, scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy and BET measurements. The photocatalytic ability of the prepared composite was evaluated against two dyes—indigo carmine and methylene blue—in the presence of sodium borohydride as an inducer. The calculated apparent rate constants and the measured TOC values indicate the enhanced catalytic efficiency of the sample as compared to pure silver nanoparticles. A possible pathway and mechanism for photocatalytic dye degradation under solar radiation is also included in this work. [ABSTRACT FROM AUTHOR]

Bi2O2.7/Bi2Ti2O7 composite photocatalyst films are synthesized by sol-gel dip-coating. The ratio of adding Bi and Ti precursors can be controlled during the preparation process. The phase structure is confirmed by X-ray diffraction. The UV-visible diffuse reflectance spectrum shows that the composite catalysts present light absorption in the visible region. The obtained Bi2O2.7/Bi2Ti2O7 composite films possess superior photocatalytic degradation of rhodamine B, owing to the visible light response of Bi2O2.7 and the separation of photogenerated electrons and holes between the two components. As a result, the Bi2O2.7/Bi2Ti2O7 (Bi/Ti = 1:1) displays the highest photocatalytic activity under visible light or UV light irradiation for the degradation of different organic dyes, including methyl blue, methyl orange and acid orange 7. [ABSTRACT FROM AUTHOR]

A hybrid bismuth titanate Bi4Ti3O12/Bi2Ti2O7 obtained via a one-step annealing procedure was employed as photocatalyst to oxidize rhodamine B dyes (RhB) and reduce hexavalent chromium (Cr(VI)). The prepared Bi4Ti3O12/Bi2Ti2O7 was characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV–vis diffuse reflectance spectra. The photocatalytic experiments revealed that the hybrid bismuth titanate Bi4Ti3O12/Bi2Ti2O7 subjected to heat treatment at 800 °C (BTO-800) exhibited enhanced photocatalytic activity in the oxidation of RhB dyes as well as the reduction of Cr(VI) relative to Bi4Ti3O12. Meanwhile, the removal efficiency of Cr(VI) in the BTO-800/Cr(VI)/RhB system was significantly higher than that in the RhB/Cr(VI) or BTO-800/Cr(VI) mixtures. The enhanced performance of the ternary system (BTO-800/RhB/Cr(VI)) was attributed to the synergistic effect between dyes and Cr(VI). Moreover, the heterostructure constructed by Bi4Ti3O12 and Bi2Ti2O7 was beneficial for the separation of electrons and holes, further improving the photocatalytic ability. A possible photocatalytic mechanism was also explored. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, sheet-like α-MoO3 nanostructures (NS) were prepared by a simple hydrothermal method using ammonium heptamolybdate tetrahydrate as a molybdenum source and nitric acid. The synthesized α-MoO3 NS have been characterized structurally and morphologically using various analytical techniques. The PXRD, FT-IR, Raman and XPS spectroscopic analysis results revealed the formation of phase pure α-MoO3. The SEM–EDX analysis further confirms the purity of the synthesized α-MoO3 NS. FE-SEM and HR-TEM results indicated that the synthesized α-MoO3 has sheet-like morphology. Further, the obtained α-MoO3 NS could be used as the effective photocatalyst for the degradation of methylene blue and rhodamine B dyes. It was found that > 95% dye degradation efficiency was achieved for both the organic dyes within 90 min irradiation times. This enhanced photocatalytic activity of α-MoO3 can be attributed to the presence of a greater number of active sites in the sheet-like morphology that are more vulnerable for adsorption of organic dyes and subsequent elimination by decomposition under visible-light condition.Graphical Abstract: [ABSTRACT FROM AUTHOR]

In this paper, we present the absorption and photoluminescence (PL) spectra of conjugated, metal-free organic dyes, triphenylamine derivatives 3-(4-(bis(4-(5-(4-(hexyloxy)phenyl)thiophenyl)phenyl)amino)phenyl)-2-cyanoacrylic acid ( OD3) and (E)-3-(5′-(4-(bis(4-(5-(4-hexyloxy)phenyl)thiophen-2-yl)phenyl)amino)phenyl)-2,2′-bithiophen-5-yl)-2-cyanoacrylic acid ( OD3DT), with and without a π-conjugated bridge, respectively, in film at a temperature range from 13 to 400 K. We find that the intensities of absorption and PL of OD3 decrease gradually beyond 200 K, as well as the ratios of integral areas of absorption to PL spectra. However, the other compound, OD3DT, shows a very different behavior. An increase is discovered in the ratio of the absorption to PL integral area when the temperature is higher than 200 K. A π-conjugated bridge gives this compound a higher degree of symmetry, and therefore, a better alignment of the molecules in the film, which causes a stacking aggregation such that the temperature effect on this compound is different than OD3. [ABSTRACT FROM AUTHOR]

Photocatalytic decolorization properties of cobalt doped-ZrO-multiwalled carbon nanotubes (Co-ZrO-MWCNTs) and chitosan-sodium alginate encapsulated Co-ZrO-MWCNTs (CS/Alg-Co-ZrO-MWCNTs) with varying weight percentage of Co-ZrO-MWCNTs are presented in this research paper. The Co-ZrO-MWCNTs was first synthesized through homogenous co-precipitation method and introduced into the chitosan-sodium sodium alginate (CS/Alg) biopolymer matrix. The bio-nanocomposites were characterized using X-ray powder diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, (UV-Vis)-spectroscopy and energy dispersive spectroscopy to obtain information on their structure, formation, morphology, size and elemental analysis. The photodecolorization efficiency of the samples was determined through their decolorization of trypan blue dye aqueous solution in 180 min. Recyclability of the catalysts was also assessed. The bio-nanocomposites experienced reduced band gap values with subsequent improvement in visible light activity compared to the uncapped Co-ZrO-MWCNTs. All the CS/Alg-Co-ZrO-MWCNTs exhibited higher photodecolorization activities than the uncapped Co-ZrO-MWCNTs. The most efficient catalyst (CS/Alg-40 % Co-ZrO-MWCNTs) with a band gap of 2.56 eV displayed 94 % decolorization efficiency of the dye. Though reusability of the catalyst is significant, its efficiency diminished consistently after each cycle. [ABSTRACT FROM AUTHOR]

The strong selective adsorption property of monoclinic tungsten trioxide nanowires (WONWs) towards organic dyes was reported in this paper. The effects of pH, initial concentration and types of dyes were systematically investigated. Particularly, methylene blue (MB) was more inclined to be adsorbed in acid solution and a maximum uptake capacity of 148.6 mg g was achieved. 88 % of MB can be rapidly adsorbed within 70 min. The kinetics, isotherms and thermodynamics for the adsorption of MB and methyl orange (MO) were well described. The kinetic adsorption on WONWs followed a pseudo second-order model ( R = 0.998) and the Langmuir isotherm ( R = 0.992) agreed very well with the experimental data. The negative values of Δ G at various temperatures (−5.656, −5.792, and −5.946 kJ mol) and Δ H (−1.343 kJ mol) implied that the adsorption reaction was spontaneous and exothermic. Specific surface area (864.153 m g) and surface acidic groups of WONWs enabled excellent adsorption performance. A highly selective adsorption mechanism involving the electrostatic interaction between hydroxyls on the WONWs' surfaces and different dye molecules was proposed. [ABSTRACT FROM AUTHOR]

Reusable ZnO/Zn-Cr hydrotalcite-like anionic clays (ZnO/Zn-Cr HACs) were synthesized by a co-precipitation method and characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, N adsorption-desorption analysis, elemental mapping patterns, scanning electronic microscope, and UV-Vis diffuse reflectance spectra. Its adsorption and photocatalytic activity towards organic pollutant (congo red as a model pollutant) were evaluated. The Langmuir isotherm was used to fit the equilibrium experiments. Saturated adsorption capacity of ZnO/Zn-Cr HACs was 426.29 mg g at 308 K. The model pollutant exhibited fast and highly efficient removal from aqueous solution by ZnO/Zn-Cr HACs under simulated solar light irradiation. The experiments of cycles demonstrated that there was no evident change in the removal efficiency of Congo red (CR) solution by ZnO/Zn-Cr HACs the fifth time under simulated solar light irradiation, which indicates that ZnO/Zn-Cr HACs can be reused and will be favorable for effective elimination of toxic organic compounds in wastewater. Therefore, it is expected that ZnO/Zn-Cr HACs with layered structures and high surface areas can be potentially used as effective and reusable materials for large-scale environmental purification. [ABSTRACT FROM AUTHOR]

Using cement-based material as a matrix for photocatalytic hybrids is an important development for the large-scale application of photocatalytic technologies. In this work, photocatalytic activity of nanosized hybrids of TiO/SiO (nano-TiO-SiO) for degradation of some organic dyes on cementitious materials was highlighted. For this purpose, an optimal inorganic sol-gel precursor was firstly applied to prepare the composites of nano-TiO-SiO which was characterized by XRD, SEM and UV-Vis. Then, a thin layer was successfully coated on white Portland cement (WPC) blocks using a dipping process in a nano-TiO-SiO solution. The effect of nano-TiO-SiO-coated WPC blocks on photocatalytic decomposition of three dyes, including Malachite green oxalate (MG), Methylene blue (MB) and Methyl orange (MO) were studied under UV irradiation and monitored by chemical oxygen demand tests. The results showed an increase in photocatalytic effects which depends on the structure and pH of the applied cement. [ABSTRACT FROM AUTHOR]

ZnO and Cd-doped ZnO photocatalysts were successfully synthesized by use of a sonochemical method. The as-synthesized ZnO and Cd-doped ZnO photocatalysts were characterized by X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller analysis, inductively couple plasma-optical emission spectrometry, and X-ray photoelectron spectroscopy. The as-synthesized ZnO and Cd-doped ZnO photocatalysts were pure wurtzite hexagonal ZnO phase. The Raman-active E mode of ZnO, located at 437 cm, corresponded to the characteristic band of the hexagonal wurtzite phase. The photocatalytic activity of the pure ZnO and Cd-doped ZnO photocatalysts was investigated by studying the degradation of methylene blue (MB) and methyl orange (MO), in solution, under UV irradiation. Compared with pure ZnO, 3 % Cd-doped ZnO reduced the amounts of MB and MO by 65 % and 45 %, respectively, within 300 min. The results indicated that Cd dopant substantially increased the photocatalytic activity of ZnO. [ABSTRACT FROM AUTHOR]

The ferrous ions (Fe) assistant air-bubble cavitation degradation of some organic dyes (Congo Red, Rhodamine B, Methyl Orange, and Methyl Violet) induced by air bubbles passing small glass balls was systematically investigated. Meanwhile, the influence of five operating factors, including air-bubbling time, FeSO ·7HO amount, dye initial concentration, glass ball diameter, and gas flow rate, on the degradation of Congo Red dye were reviewed. Moreover, the degradation process of Congo Red is inspected by using UV-Vis, TOC, and HPLC techniques. It was found that the highest TOC removal ratio (81.42 %) was achieved under optimal conditions. On the other hand, the production and existence of ·OH radicals was testified through the oxidation of 1,5-diphenylcarbohydrazide (DPCI) forming diphenylcarbazone (DPCO). It can be inferred that the air-bubble cavitation induces ferrous ions to provide additional hydroxyl (·OH) radicals, which results in a rapid oxidation of organic dyes. Furthermore, the possible degradation process and mechanism were also discussed. All results demonstrate that this new degradation method has many advantages, such as high efficiency, energy savings, producing no secondary pollution, and being a simple device. Thus, it is expected to be feasible and promising as an advisable choice for the treatment of organic wastewater in the future. [ABSTRACT FROM AUTHOR]

In this research, photoassisted electrochemical degradation of 13 commercial dyes with various chemical structures and substituent groups was investigated using a cathode containing carbon nanotubes (CNTs) and a titanium/ruthenium oxide (Ti/RuO) anode. The inner and outer diameters of the CNTs and their stabilization on carbon paper support were confirmed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. All experiments were carried out in identical operating conditions using a recirculation system under ultraviolet (UV) light irradiation. The dyes with electron-releasing groups (e.g., amino, hydroxyl, and acetamido) were more degraded than those containing electron-withdrawing groups (e.g., sulfo, sulfonyl, and halo) due to inductive and/or resonance effects. Moreover, the obtained results reveal that the degradation process follows pseudo-first-order kinetics, and the degradation efficiency was evaluated as the electrical energy per order. [ABSTRACT FROM AUTHOR]

The deposition of TiO nanoparticles on SiC was carried out by mechanical milling under different conditions. SiC-TiO samples were used as photocatalysts for the degradation of organic dyes such as methylene blue and rhodamine B. A short time deposition of TiO nanoparticles was observed during mechanical milling (2 min at 200 rpm) to cover the SiC particles. The presence of SiC and TiO (anatase and rutile) was confirmed by means of X-ray diffraction after thermal treatment at 450 °C. The deposition of TiO on SiC was corroborated by scanning electron microscopy analysis; the thickness of the thin layer of TiO deposited on SiC increases as the proportion of TiO increases. The energy band gap values obtained for these compounds were around 3.0 eV. SiC-TiO photocatalysts prepared by mechanical milling exhibited better activity under UV-light irradiation for the degradation of methylene blue and rhodamine B than commercial TiO powder (titania P25). [ABSTRACT FROM AUTHOR]

PbMoO molybdate with scheelite structure was synthesized by a simple co-precipitation method. The material was characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), and adsorption-desorption N isotherms (BET). The photocatalytic activity of PbMoO molybdate was evaluated with the degradation reactions of rhodamine B (rhB), indigo carmine (IC), orange G (OG), and methyl orange (MO) under UV irradiation. In order to elucidate aspects of the degradation mechanism of the organic dyes, some experimental variables were modified such as pH and O level in solution. The total organic carbon (TOC) analysis of samples irradiated revealed that mineralization of organic dyes by the action of PbMoO was feasible in rhB (60%), IC (80%), and OG (65%) after 96 h of irradiation. For the same time of irradiation, a recalcitrant behavior to the mineralization was observed in MO reaching only a 10% of mineralization degree. [ABSTRACT FROM AUTHOR]

The photodegradation of an aqueous solution of methyl orange by the TiO/SnS powders was studied in different ratios of SnS against TiO. The effects of the initial pH value and light resource were investigated. The SnS extends the light absorption edge of the TiO to ~940 nm of the SnS (1.32 eV). The results indicated that the optimal SnS proportion for the maximum degradation efficiency increased in relation to a decrease in the initial pH in both sunlight and visible light, and decreased when changing from visible light to sunlight. The pure TiO powder had maximum efficiency in conditions of pH 9 and visible light irradiation or in conditions of pH 7 and sunlight irradiation. In visible light, the degradation efficiency on the powders containing the SnS was larger than that on the pure TiO powder in a range of pH 3-7. The maximum efficiency in visible light was found to be in conditions of pH 5 and TiO:SnS = 3:2 and 2:3, beyond which the efficiency decreased. The efficiency was, overall, larger in sunlight than in visible light. The mechanism of the effects of pH and light resource was discussed in view of the surface charge of the catalysts. [ABSTRACT FROM AUTHOR]

The Er:YAlO as an upconversion luminescence agent, which can transform visible light into ultraviolet light, was synthesized by nitrate-citrate acid and calcined method. Then, a novel photocatalyst, Er:YAlO/TiO-ZrO, was prepared using ultrasonic dispersion and liquid boiling method. The samples were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). In succession, the degradation process of organic dye was monitored by UV-Vis spectrum and ion chromatography for verifying the photocatalytic activity of Er:YAlO/TiO-ZrO. The influences on its photocatalytic activity such as Ti/Zr molar ratio, heat-treated temperature, and time were studied. In addition, the influences of initial concentration, Er:YAlO/TiO-ZrO amount, solar light irradiation time, and organic dye category on the photocatalytic degradation efficiency were also investigated. It was found the photocatalytic activity of Er:YAlO/TiO-ZrO was superior to Er:YAlO/TiO and Er:YAlO/ZrO. Therefore, the Er:YAlO/TiO-ZrO is a useful photocatalytic material for the wastewater treatment duo to efficient utilization of solar light. [ABSTRACT FROM AUTHOR]

Nanoparticles of α-BiMoO were prepared by the Pechini method. The process of formation of the bismuth molybdate was followed by simultaneous thermogravimetric and differential thermal analysis (TGA/DTA). Different samples of α-BiMoO were obtained at 400, 450, and 500 °C, and characterized by X-ray powder diffraction (XRD), nitrogen physisorption (BET), and scanning electron microscopy (SEM). When observed by SEM, the morphology of the sample obtained at the lowest temperature consisted of semi-spherical particles with an average diameter of 150 nm. On the other hand, the highest calcination temperature led to the formation of sintered particles of 500-600 nm. The photocatalytic activity of α-BiMoO was tested by photodegradation of the organic dyes rhodamine B (rhB) and indigo carmine (IC) under visible-light irradiation. The bismuth molybdate nanoparticles were able to bleach aqueous solutions of both organic dyes. The sample obtained at 400 °C was the best photocatalyst with half-lives, t, of 108 and 154 min for rhB and IC, respectively. [ABSTRACT FROM AUTHOR]

In this work we present the synthesis and characterization of four compositions of the solid solution with the general formula Na2ZrxTi6–xO13 (0 ≤ x ≤ 1) which was prepared by a sol–gel method. The main goal of this work is to evaluate the influence of the incorporation of different amounts of zirconium into the binary phase Na2Ti6O13 on two properties: the textural surface and Eg values. This titanate phase crystallizes in a monoclinic unit cell and is built into an octahedral TiO6 framework forming a rectangular tunnel structure. Additionally, we have compared their photocatalytic performances in degradation of organic dyes under visible light. The heat-treated sol–gel samples were characterized by X-ray powder diffraction, N2 physisorption, thermal analysis, UV and FT-IR spectroscopy. According to the X-ray powder diffraction results, the new ternary tunnel compound Na2ZrTi5O13 was obtained as a single phase at 800°C. The cell parameters for the two end-member phases of that solid solution were refined to confirm that Zr ion was incorporated into the structural framework. This ternary compound had an Eg value of about 2.9 eV. The activity of all heat-treated Na2ZrTi5O13 samples was tested in the photocatalytic degradation of methylene blue and Rhodamine B under visible light. The Na2ZrTi5O13 calcined at 400°C showed the best performance with 95% of photodegradation of methylene blue and a half time t1/2 of 15 min. [ABSTRACT FROM AUTHOR]