RhB Solution Research Articles

Fabrication of BiVO4@g-C3N4(100) heterojunction with enhanced photocatalytic visible-light-driven activity

The BiVO4@g-C3N4(100) heterojunction composites with increased visible-light response were synthesized by a simple hydrothermal method. The as-prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FT-IR), raman spectra, N2 absorption-desorption isotherm (BET), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). The TEM images show a clear interface between BiVO4(121) and g-C3N4(100), indicating that heterojunction between BiVO4 and g-C3N4 was formed after hydrothermal reaction. The photocatalytic activities of samples were investigated by studying the degradation of RhB under simulated visible-light irradiation (λ ≥ 420 nm). It was found that the 10 wt% BiVO4@g-C3N4 exhibited the highest photocatalytic performance, the photodegradation rate is 2.36 and 30.58 times higher than that of either single-phase g-C3N4 or BiVO4. In addition, radicals trapping experiments demonstrated that h+ and ·O2− are the main active species while ·OH could be negligible in the photocatalytic oxidation of RhB solution.

Shaped Fe2O3 nanoparticles – Synthesis and enhanced photocatalytic degradation towards RhB

Iron oxide nanoparticles of different shape were synthesized via an ion-mediated hydrothermal route. The addition of Zn2+ and Al3+ to the reaction system is no doubt the reason for the formation of hematite with cubic and disc structures, respectively. The growth mechanism of iron oxides is proposed. The morphology of the obtained nanostructures was analyzed by SEM and HR-TEM. The phase identification was performed by XRD and FTIR spectroscopy. Nanopowders were characterized by optical and zeta potential PZ measurements. The overall density of hydroxyl groups depends on the crystal structure and crystal faces. Placing oxides in the Rhodamine B RhB solution reduces the potential value PZ. The observed changes are the most pronounced for discs (ΔPZ = 16.2 mV) and the least pronounced for cubes (ΔPZ = 5.5 mV). A significant degree of adsorption of the dye on the surface of the discs, which confirms the presence of a significant number of hydroxyl groups responsible for surface activity. The photocatalytic activity of the obtained nanostructures investigated by photodecomposing RhB can be improved by applying H2O2 as an electron trap. Cyclic photodegradation experiments show that iron oxides with variously exposed planes can be used multiple times without losing their photocatalytic properties. Discs exhibited the most desirable photocatalytic behavior. Based on the performed addition of hydrogen peroxide, it seems that the shape of the particles affects the diffusion of H2O2 at the surface.

Versatile, metal free and temperature-controlled g-C3N4 as a highly efficient and robust photocatalyst for the degradation of organic pollutants

In the present study, we report novel graphitic carbon nitride (g-C3N4) nanosheets at different calcination temperatures viz 500 °C, 550 °C and 600 °C by the simple hydrothermal synthesis for photocatalytic degradation of organic contaminants. The crystal structure, optical properties, and surface morphology were studied by various tools such as X-ray diffraction, UV–visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy analysis. The as-synthesized g-C3N4 nanosheets exhibited a hexagonal phase and had good crystallinity with a crystallite size of ~ 68 nm. The photodegradation efficiency of g-C3N4 nanosheets showed excellent photocatalytic activity towards RhB and CV dye solution, and the dye degraded within 70 and 60 min, respectively. The g-C3N4 @550 °C nanosheets showed superior photocatalytic activity due to the adsorption capability and delayed electron hole recombination rate. In addition, the photocatalytic mechanism and reusability test were also found by trapping experiments. The proposed photogenerated electron–hole separation mechanism of the g-C3N4 photocatalyst.

Distance dependent fluorescence enhancement of silver nanowires deposited on AAO

Metal nanoparticls deposited on substrate are usually used for the enhancement of fluorescent molecules. In this article, AAO template was introduced into the reaction solution during the preparation of silver nanowires. Then the AAO template with deposited silver nanowires was suspended in RhB solution to study its fluorescence enhancement effect. The results showed that the uneven surface of AAO template caused a series of distances between silver nanowires and RhB molecules which were happen to be below 10 nm that can effectively enhance the fluorescence of RhB solution. Our research is helpful to the study of fluorescence enhancement of metal nanostructures deposited on substrate.

Characterization of Flake Boron Nitride Prepared from the Low Temperature Combustion Synthesized Precursor and Its Application for Dye Adsorption

Flake boron nitride (BN) in large yield was successfully synthesized at low temperature from the combustion synthesized precursor. The precursor was prepared by a low-temperature (350 °C) combustion synthesis (LCS) method using nitric acid (HNO3), urea (CO(NH2)2), boric acid (H3BO3), and glucose (C6H12O6·H2O) as starting materials. The precursor consists of B2O3 and amorphous carbon and the morphology is composed of blocks with average diameters of about 10 μm by statistical methods using SEM at different fields. Then BN was synthesized at 900 °C in NH3 at a heating rate of 5 °C min−1. The as-prepared BN possesses a flake morphology and high specific surface area up to 936 m2 g−1. It also has high density structural defects and abundant –NH2/–OH groups. The surface groups improve its water wettability and electronegativity, which contributes to the rapid and selective adsorption performance, especially towards the cationic dyes. When 4 mg of the sample was added into a 100 mL RhB solution with an initial concentration of 5 mg L−1, 95% of the RhB was removed within 1 min and the adsorption capacity is 125 mg g−1. Importantly, the sample can be regenerated by heating at 400 °C in air.

Facile Synthesis of NaBiS2 Nanoribbons as a Promising Visible Light‐Driven Photocatalyst

NaBiS2 nanoribbons are synthesized by a facile hydrothermal process. They are first tested as visible light‐driven photocatalysts. The dimension of typical nanoribbons is 100–250 nm in width, 10 nm in thickness, and several micrometers in length. The photocatalytic measurement shows that the prepared NaBiS2 nanoribbons are effective in the degradation of the RhB solution under 300–800 nm light. The results indicate that the decomposition efficiency of NaBiS2 for RhB can reach a very high value with the assistance of H2O2, ≈95% after 60 min of irradiation.

Facile ultrasonic-assisted synthesis of micro–nanosheet structure Bi4Ti3O12/g-C3N4 composites with enhanced photocatalytic activity on organic pollutants

Abstract The Bi4Ti3O12/g-C3N4 composites with microsheet and nanosheet structure were prepared through facile ultrasonic-assisted method. The SEM and TEM results suggested that the nanosheets g-C3N4 were stacked on the surface of regular Bi4Ti3O12 sheets. Comparing with pure Bi4Ti3O12 and g-C3N4, the Bi4Ti3O12/g-C3N4 composites showed significant enhancement in photocatalytic efficiency for the degradation of RhB in solution. With the mass ratio of g-C3N4 increasing to 10 wt%, the Bi4Ti3O12/g-C3N4-10% presented the best photocatalytic activity. Its photocatalysis reaction constant was approximately 2 times higher than the single component Bi4Ti3O12 or g-C3N4. Meanwhile, good stability and durability for the Bi4Ti3O12/g-C3N4-10% were confirmed by the recycling experiment and FT-IR analysis. The possible mechanism for the improvements was the matched band positions and the effective separation of photo-excited electrons (e−) and holes (h+). Furthermore, based on the results of active species trapping, photo-generated holes (h+) and superoxide radical ( O2−) could be the main radicals in reaction.

Synthesis and effects on visible light photocatalytic activity of Bi2Ti2O7 photocatalyst

Bi2Ti2O7 photocatalysts were successfully synthesized via the co-precipitation method and the solvothermal method and further characterized by XRD, SEM, BET, XPS and UV-vis DRS. Under visible light irradiation, the photocatalytic performance of Bi2Ti2O7 photocatalysts were evaluated by the degradation of RhB solution. The results indicated that the as-synthesized Bi2Ti2O7 photocatalyst via co-precipitation method has better photocatalytic activity than the photocatalyst prepared by the solvothermal method. The larger surface area and special morphology of the Bi2Ti2O7 synthesized by co-precipitation method were responsible to enhanced photocatalytic performance.

Construction of hybrid Ag2CO3/AgVO3 nanowires with enhanced visible light photocatalytic activity

Visible light driven pollutant degradation by photocatalyst was one of most efficient and economical strategies for environmental application. The focus and challenge was to fabricate efficient artificial photocatalysts. In this work, hybrid Ag2CO3/AgVO3 nanowires were first reported to be successfully synthesized by the facile ion-exchange method. The as-prepared Ag2CO3/AgVO3 nanowires showed highly improved visible light photocatalytic activity for RhB degradation, and the optimized Ag2CO3/AgVO3-40% photocatalyst exhibited the best photocatalytic activity, which is 3.6 times of pure Ag2CO3 and 13.3 times of pure AgVO3 catalysts, mainly due to the formation of Ag nanoparticles and Ag2CO3/AgVO3 heterojunction for charge separation. The degradation of RhB solution was mainly attributed to direct hole oxidation, which was also confirmed by the active species trapping experiments. Finally, the possible visible light photocatalytic mechanism of Ag/Ag2CO3/AgVO3 composites for RhB degradation was proposed.

Facile synthesis and photocatalytic activity of Ag3PO4 decorated MoS2 nanoflakes on carbon fiber cloth

A novel CC@MoS2-Ag3PO4 heterostructure, composed of Ag3PO4 nanoparticles decorated MoS2 nanosheets on carbon fiber cloth (CC), is fabricated by a simple hydrothermal method and a successive ionic layer absorption reaction. The CC@MoS2-Ag3PO4 heterostructure displays an excellent photocatalytic activity of ∼96% degradation rate for RhB solution under simulated daylight, which is more than 10 times as much as that of pure Ag3PO4 or MoS2. The CC@MoS2-Ag3PO4 heterostructure with optimized photoactivity is investigated by optical and electrochemical measurements. The CC@MoS2-Ag3PO4 heterostructure can not only broaden the photoresponse range of MoS2, but also alleviate the photodegradation of Ag3PO4, and the easily separated CC provides a proper conductive substrate and rapid charge transfer channels. The probable photocatalytic mechanism of CC@MoS2-Ag3PO4 heterostructure is discussed in detail. Therefore, the CC@MoS2-Ag3PO4 heterostructure with high efficient photocatalytic performance and easy separation is a promising photocatalytic material.

多杂原子掺杂碳材料阴极催化降解罗丹明B

以生物质材料羊毛毡为前驱体，通过热解的方法一步制备了杂原子(N，O、S和P)掺杂碳材料，并用SEM、EDS和FTIR对其进行表征。同时，用该材料作为电Fenton阴极催化降解罗丹明B废水，并对影响电Fenton过程的重要因素如：溶液的初始pH值和Fe2+的浓度进行了优化。实验结果表明，该材料有很高的催化活性，在溶液的初始pH为3，Fe2+的浓度为0.5 mmol∙L−1时，用该催化剂作为电Fenton阴极降解50 mg∙L−1的罗丹明B溶液，降解时间为120分钟，罗丹明B的去除率可达到99.5%。由于该催化剂制备方法简单，成本低，催化活性高，稳定性好，在处理有机废水方面有很好的应用前景。 The heteroatoms (N, O, S and P) doped carbon material were prepared by a facile strategy through pyrolytic treatment of wool felt, and their properties were characterized by SEM, EDS and FTIR. Meanwhile, the material was used as electro-Fenton cathode for rhodamine B degradation. The effect of significant parameters including the initial pH and Fe2+ dosage on the removal efficiency was investigated for electro-Fenton process. It was indicated that initial Fe2+ concentration of 0.5 mmol∙L−1 at pH 3 were the optimum conditions for the removal of 50 mg∙L−1 RhB solution. The degradation time was 120 min, and the removal rate of rhodamine B was 99.5%. Because the catalyst has the advantages of simple preparation method, low cost, high catalytic activity and good stability, the catalyst has a good application prospect in the treatment of organic waste water.

Wet chemical synthesis of ZnO-CdS composites and their photocatalytic activity

The present study is focused on the wet chemical synthesis and the characterization of ZnO-CdS composites. The X-ray diffraction shows that the composites contain ZnO in hexagonal wurtzite structure and CdS in cubic phase. The scanning/transmission electron microscopy images reveal flower-like structures with different sizes depending on the CdS content. The optical investigations on composites reveal that the reflectance spectra disclose two thresholds of ∼370nm and ∼460nm associated with the ZnO and CdS, respectively. The photocatalytic activity measurements evidenced that the degradation efficiency of RhB in the presence of composites is higher comparatively with pristine ZnO, depending on the catalyst morphology, which varies with CdS content and the pH value of RhB solution. The electron paramagnetic resonance revealed the presence of the paramagnetic point defects in the samples. Thus, the wet chemical approaches are suitable for a large scale production of such ZnO-CdS composites having enhanced photocatalytic activity.

Synthesis of silver/silver chloride/exfoliated graphite nano-photocatalyst and its enhanced visible light photocatalytic mechanism for degradation of organic pollutants

Silver/silver chloride/exfoliated graphite (Ag/AgCl/EG) nano-photocatalyst was synthesized through precipitation and photoreduction processes. Afterwards, physicochemical properties of Ag/AgCl/EG were systematically studied by series of techniques. Results indicated that spherical-like Ag0 and AgCl with a diameter of 18.6nm were deposited onto the surface of EG, resulting in the large surface area, strong visible absorbance and high charge separation efficiency. In addition, Ag/AgCl/EG exhibited high visible light photocatalytic (PC) activity for degradation of RhB (99.5%) and phenol (89.1%) solution. Also, the enhanced visible light PC mechanism was proposed and confirmed. Furthermore, Ag/AgCl/EG nano-photocatalyst performed good reusability even after six recycles utilization.

Photoluminescence properties of rhodamine B-supported on ZrO2-ZrO2 nanotube array composite films

In this paper, Zr foils were first anodised to prepare zirconia nanotube arrays (ZNA), then ZrO2 nanoparticles were loaded onto the zirconia nanotube arrays by a chemical precipitation method to prepare ZrO2-ZrO2 nanotube array composite films (ZrO2-ZNA), finally RhB was supported on the ZNA and ZrO2-ZNA to prepare RhB/ZNA and RhB/ZrO2-ZNA fluorescent films, respectively. The photoluminescence (PL) properties of RhB/ZNA and RhB/ZrO2-ZNA were tested and the effects of annealing temperature and RhB solution concentration on their PL properties were studied. Results show that the PL intensity of RhB/ZrO2-ZNA was obviously higher than that of RhB/ZNA, and the emission peaks of RhB/ZrO2-ZNA were much stronger when the annealing temperature was 300 °C and the RhB concentrations were between 5 and 40 mg/L. Different from the excitation and emission peaks of RhB/ethanol solutions, those of RhB/ZrO2-ZNA composite films were obviously red shifted, and the luminous efficiency of RhB/ZrO2-ZNA composite films was much higher.

Photocatalytic activity of V-doped TiO2 thin films for the degradation of methylene blue and rhodamine B dye solutions

Highly-transparent V-doped TiO2 thin films were prepared by sol-gel processing, spin coated on fused silica glass substrates, and annealed in air at 450 °C for 2 h. All of the films were comprised of anatase as the sole crystalline phase. The XPS data suggested that V formed an interstitial solid solution with anatase. The formation of an unsaturated solid solution at the lowest doping level of 0.05 mol% resulted in the formation of lattice defect sites, which enhanced anatase recrystallisation, grain growth, and crystallinity. In contrast, the formation of supersaturated/oversaturated solid solutions at the higher doping levels of 0.10–1.00 mol% resulted in lattice deformation, partial amorphisation, precipitation, and liquid formation. The coexistence of multiple valence states, viz., Ti4+/3+, V4+/3+, and possibly V5+ in the doped TiO2 films was attributed to intervalence charge transfer. Dye degradation tests revealed that the 0.05 mol% V-doped films showed the best photocatalyic performance and this was attributed to the combined effects of greater anatase crystallinity and reduced band gap. In contrast, increasing V-doping levels resulted in gradual decreases in the photocatalytic performance, which are attributed principally to the decrease in areal density of the surface-active sites owing to liquid-phase densification. The greater degradation of MB solution relative to that of RhB solution is attributed principally to the cationic nature of MB, which allows greater adsorption on the photocatalyst surface in comparison to the anionic RhB.

Morphological control of tubular g-C3N4 and their visible-light photocatalytic properties

This paper describes a facile and simple method to prepare g-C3N4 photocalysts by directly heating the protonated melamine precursor. The morphologies of g-C3N4 can be easily adjusted by the heating rate. The g-C3N4 nanotubes were formed when the heating rate is 5°Cmin−1, and g-C3N4 nanofalkes were obtained with the heating rate of 10°Cmin−1. All the samples exhibit high specific surface area and narrow pore size distribution, and they exhibit superior photocatalytic properties. The aqueous RhB solution can be completely degraded after the irradiation time of 180min under visible light irradiation.

Synthesis and Photocatalytic Activities of Bamboo-Like FeVO<sub>4</sub> Nanocrystalline

The bamboo-like FeVO4 nanocrystallines were synthesized by a two-step method of the microwave hydrothermal-calcination, using Fe (NO3)3·9H2O and NH4VO3 as raw materials. The physical and photophysical properties of the as-prepared photocatalysts were fully characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), UV-vis diffuse reflectance spectra and photoluminescence (PL) analysis. The photocatalytic activities were evaluated by the decolorization of RhB solution under UV and visible light irradiation. The results reveal that the precursor solution concentration is 0.15 mol/L, the molar ratio n (Fe)/n (V) is 1, pH=3.0. The microwave hydrothermal reaction is at 180 °C for 120 min and then calcinated under 550 °C for 3 h so as to obtain the triclinic FeVO4 nanocrystalline. Along [120] and [110], the fore and aft phases of the crystal orientation are bonded self-assembly to grow into the bamboo-like nanocrystalline with the energy gap of 2.42 eV. Under the UV-light irradiation for 240 min, the degradation rate of RhB is up to 91.2%. Adding 0.1 mL H2O2 to the solution, the out-phase photo-fenton reaction occurs and the degradation rate to RhB can reach to 98.8% after 8 h visible-light irradiation.

Solvent co-mediated synthesis of ultrathin BiOCl nanosheets with highly efficient visible-light photocatalytic activity

Ultrathin BiOCl nanosheets exhibit outstanding photocatalytic degradation of RhB solution under visible-light irradiation.

Magnetic recoverable Fe3O4-TiO2:Eu composite nanoparticles with enhanced photocatalytic activity

This work refers to the influence of Eu doping on the morphologic, structural and compositional properties of magnetic separable Fe3O4-TiO2 composite nanoparticles with photocatalytic activity. In this respect, Fe3O4-TiO2:Eu nanocomposites were prepared by seed mediated growth of TiO2:Eu through a sol-gel method onto preformed magnetite resulted from co-precipitation method. Different Eu concentration precursors were used for doping. The thermal behavior and the conversion of precursors into corresponding Fe3O4-TiO2:Eu composite nanoparticles were evidenced by FT-IR spectra and thermal analysis. The XRD, XPS and HRTEM investigations results indicate that nanocomposites contain besides Fe3O4-TiO2:Eu some amounts of iron titanate. Formation of FeTiO3 is suppressed by the increase of Eu doping level. Magnetic studies also indicated that nanocomposite exhibit superparamagnetic behavior at room temperature. The large surface area and mesoporous structure of magnetic nanocomposite were confirmed by the surface area (BET) and porosity measurements. It was demonstrated that the composite nanoparticles exhibit good photocatalytic activity toward the degradation of RhB solution and they can be used as efficient and conveniently recoverable photocatalyst.

A facile electrospinning and direct annealing method for the fabrication of multi-porous ZnFe2O4 nanotubes with enhanced photocatalytic activity

The multi-porous ZnFe2O4 (ZFO) nanotubes are fabricated by the direct annealing process of ZFO precursor nanofibers, which is prepared by a facile electrospinning method. The crystal structure, composition, morphology, magnetic property, specific surface area and pore size distribution of multi-porous ZFO nanotubes are systematically characterized. The results indicated the multi-porous ZFO nanotubes with high purity phase possess obvious multi-porous and tubular microstructure, the mean inner diameter, specific surface area and pore volume are about 150nm, 57.42m2g−1 and 0.16cm3g−1, respectively. Moreover, the multi-porous ZFO nanotubes exhibit a better photocatalytic activity than that of ZFO nanoparticles for photocatalytic degradation of RhB solution.