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Photocatalytic technology exhibits promising prospects in environmental remediation owing to its sustainable and environmentally friendly advantages. Among the bismuth-rich halide oxides, Bi₄O₅I₂ has demonstrated remarkable efficacy in dye degradation due to its favorable valence band and conduction band positions. In this study, we successfully synthesized Bi₄O₅I₂/NaYF₄:Yb,Tm composites through a solvothermal method. When exposed to visible light, the Bi₄O₅I₂/NaYF₄:Yb,Tm composite achieved an impressive degradation rate of 86.7% for RhB solution after 60min of light-induced reaction. Moreover, the incorporation of NaYF₄:Yb,Tm into Bi₄O₅I₂ extended the utilization of near-infrared (NIR) spectroscopy. Under 980nm NIR light irradiation, the degradation rate of Rhodamine B (RhB) solution by the Bi₄O₅I₂/NaYF₄:Yb,Tm composite reached 43.0% after 240min of light reaction. Free radical capture experiments confirmed that h${}^{+}$ and • O${}^{2-}$ played a significant role as the primary active species in the degradation process of RhB by the Bi₄O₅I₂/NaYF₄:Yb,Tm composites. Furthermore, we explored the mechanism behind the photocatalytic degradation of RhB solution using the Bi₄O₅I₂/NaYF₄:Yb,Tm composites. Bi₄O₅I₂/NaYF₄:Yb,Tm holds great potential as a promising candidate for utilization of NIR light for photocatalytic reactions.

As a newly emerging catalysis, tribocatalysis is receiving more and more attention with regard to the criteria to fabricate or choose materials as catalysts for it. In this study, two different commercial silicon (Si) powders, Si30 and Si300, were adopted as catalysts in tribocatalytic degradation of organic dyes. Only round nanoparticles from 30 to 100nm were observed in Si30, while some highly large and irregular particles, as large as 1000nm × 500nm and with a roughly flat major surface, could be observed in Si300. Stimulated through magnetic stirring using Teflon magnetic rotary disks, as much as 95% of 20 mg/L rhodamine B (RhB) solution and 97% of 20 mg/L methyl orange (MO) solution were degraded by Si300 after 3h and 50min, respectively; while only 73% of RhB and 83% of MO were degraded by Si30 after 5h and 4h, respectively. EPR spectra showed that more superoxide and hydroxyl radicals were generated by Si300 under magnetic stirring. It is proposed that in those large particles in Si300, their large flat major surfaces dramatically enhance their absorption of mechanical energy through friction and there are much less lattice defects to hinder electrons and holes from diffusing to the surface, which both results in the contrasting tribocatalytic degradations of organic dyes between Si300 and Si30. These findings reveal a huge difference in tribocatalytic performance among different materials of the same composition.

The Nano-TiO₂/Diatomite compound photocatalyst is used to degrade rhodamine B dye wastewater in photochemical reactor. The test result indicates that the rate of photodegradation of rhodamine B is influenced by reactive conditions. The best technical conditions are concentration of rhodamine B solution 10mg/L, ultraviolet light 300W, the compound photocatalyst amount used 1g/L, the pH 5.8, reaction time 20min. Under these conditions the rate of photodegradation of rhodamine B may reach as high as 97.80%. And the efficiency of photodegradation of catalyst only has a little changed in recycling.

Transition metal oxide photocatalysis is a relatively new method representing advanced oxidation process to be applied in industrial wastewater treatment especially for degradation of organic pollutants. We investigate TiO₂ as a photocatalyst for the photocatalytic degradation of Rhodamine B (RhB) under simulated sunlight. Various parameters and their effectiveness have been studied. The effects of processing parameters including catalyst loading and feed concentration were investigated; and the degradation pathway was proposed based on the UHPLC-MS analysis. The result showed that a higher kinetic rate can be obtained by employing low catalyst loading and feed concentration, i.e., 0.5 g/L of TiO₂ loading and 5 ppm of RhB concentration, respectively. For this particular system, the optimum degradation rate ($k$) can achieve 0.297/min. The effectiveness of solar light-TiO₂ system for RhB degradation shows this method can be used for wastewater treatment.

TiO₂ hierarchical structure composed of H₂Ti₃O₇ nanoribbons and TiO₂ anatase nanoparticles was synthesized via a two-step hydrothermal process, including the recrystallization of TiO₂ precursor into nanoribbons and the subsequent deposition of TiO₂ nanoparticles on nanoribbon surface. The coated nanoribbons exhibited a good photocatalytic activity to degrade Rhodamine B (RhB) with a kinetics constant of 0.0269/min, 10 times higher than that of the as-produced nanoribbon (0.0026/min). They also possess good sedimentation properties compared to the pristine TiO₂ anatase particles. The excellent photocatalytic performance together with sedimentation property makes these hybrid nanostructures effective and recyclable photocatalysts for wastewater treatment in industrial applications.

Broadband two-photon fluorescence (TPF) imaging system based on femtosecond oscillator is built. Broadband TPF signal generated from Rhodamine B molecule is detected at different detection windows. Both TPF signals detected at short wavelength detection window of 545–615 nm and long wavelength detection window of 642–708 nm are used for TPF imaging. Through switching detection window from short wavelength to long wavelength, deepened imaging depth is achieved. The TPF imaging results, with single $900\times 900$ pixels frame taking time of 4–8 s, demonstrate high performance and the good reliability of the imaging system.

This paper reports the photocatalytic behavior of tin oxide (SnO₂) nanostructures prepared via three different aqueous solution-processed techniques: Precipitation, hydrothermal, and laser ablation. The prepared SnO₂ nanostructures were characterized by X-ray diffraction (XRD) and field electron scanning electron microscopy (SEM). The photocatalytic activity was evaluated by the oxidative degradation of rhodamine blue (RhB) under visible light. The SnO₂ nanostructure prepared by the laser ablation method exhibit significantly improved photocatalytic activity toward RhB due to the size and morphology of the prepared nanostructure.

The performance of a distributed feedback dye laser (DFDL) by employing methyl methacrylate (MMA) co-doped with rhodamine B and methyl violet B base dyes was investigated. The dye mixture was incorporated into a solid polymeric matrix and then in a liquid medium and a laser pulse was pumped into it using a 532 nm Nd:YAG laser. Characteristics of energy transfer DFDL and its output powers on various pump powers and acceptor concentration were evaluated both theoretically and experimentally. Slope efficiency of the dye laser as well as wavelength tunability in both liquid and solid media was studied.

Copper doped Titanium dioxide TiO₂ nanoparticles were synthesized by sol–gel method using titanium tetraisopropoxide and copper sulfate as precursors. The synthesized nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), UV-Visible spectroscopy (UV-Vis), Photoluminesce spectroscopy (PL) and atomic force microscopy (AFM). XRD analysis confirms the formation of anatase titanium dioxide and average particle size was 35nm. Cu– TiO₂ exhibits a shift in the absorption edge toward visible spectrum. The rate of recombination and transfer behavior of the photoexcited electron–hole pairs in the semiconductors was recorded by photoluminescence. From SEM spherical shaped nanoparticles was observed. Comparing with pure TiO₂ nanoparticles, Cu doped TiO₂ photocatalyst exhibited enhanced photocatalytic activity under natural sunlight irradiation in the decomposition of rhodamine B aqueous solution. The maximum 97% of degradation efficiency of Rhodamine B was observed at 0.6% Cu–TiO₂ within 180min. The photocatalytic efficiency of Rhodamine B of Cu doped TiO₂ nanoparticle was higher than the pure TiO₂, which could be attributed to the small crystallinity intense light absorption in Sunlight and narrow bandgap energy of Copper.

This work presents an important analysis and comparative study between two organic waste rhodamine B (RhB) and methyl orange (MO) dyes as pollutant models degeneration under sunlight. Hematite ($\alpha$-Fe₂O₃) nanorods were synthesized and deposited on glass substrates using an efficient and simple one-step hydrothermal method. The nanorods were characterized by XRD, FESEM, EDX, and UV–Vis equipment. The photodegeneration parameters of $\alpha$-Fe₂O₃ films were calculated by modeling the photodegradation of MO and RhB dyes as pollutants under sunlight irradiation for 150min. Results revealed that the degradation efficiency of $\alpha$-Fe₂O₃ films of MO and RhB dyes was 72.7% and 91.9%, respectively. The optimized photocatalyst degraded RhB more efficiently than the MO solution.

The absorption wavelengths of the two forms of Rhodamine B, cation and zwitterion, were investigated by Time-Dependent Density Functional Theory (TD-DFT) in combination with polarizable continuum model. The redshift in absorption spectrum of cation relative to zwitterion is attributed to strong inductive effect of carboxyphenyl group and weak electrostatic repulsion between xanthene ring and carboxyphenyl group. The absorption wavelengths of cation and zwitterion decrease linearly with increase of solvent polarity in normal alcohols since in high polar solvents electrostatic repulsion between xanthene ring and carboxyphenyl group increases and affects xanthene π conjugation system. The absorption wavelengths in water and formamide show a deviation from linear relationship because large dielectric constant hinders electrostatic repulsion between carboxyphenyl group and xanthene π system. The hydrogen bonds affect absorption wavelengths because hydrogen bonds could affect conjugation between amino N atoms and xanthene π system or electrostatic repulsion between carboxyphenyl group and xanthene ring. These results indicate electrostatic repulsion between carboxyphenyl group and xanthene ring plays a big role in determining absorption spectrum of Rhodamine B.

The visible-light-driven dechlorination of 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane (DDT) was carried out in the presence of a hydrophobic vitamin B₁₂, heptamethyl cobyrinate perchlorate and Rhodamine B. DDT was successfully dechlorinated to form 1,1-bis(4-chlorophenyl)-2,2-dichloroethane (DDD) as the mono-dechlorinated product upon visible light irradiation with a tungsten lamp (λ > 440 nm). Upon prolonged visible light irradiation to DDT, DDMU (1-chloro-2,2-bis(4-chlorophenyl)ethylene), DDMS (1-chloro-2,2-bis(4-chlorophenyl)ethane) and DCS (trans-4,4′-dichlorostilbene) were obtained as the di- and tri-dechlorinated products. The use of the photostable organic sensitizer enabled prolonged photocatalysis via a noble-metal-free process. The vitamin B₁₂ derivative was replaced by an imine/oxime-type cobalt complex although the cobalt complex system showed a lower catalytic activity than the B₁₂ derivative system. The dechlorination mechanism in the B₁₂-Rhodamin B system was investigated by various methods such as UV-vis absorption and fluorescence quenching.

Herein, two porphyrins with bismuth metal incorporated in the porphyrinic core were synthesized having peripheral carboxyl and hydroxyl functional groups. The successful synthesis of free base porphyrin and their bismuth-integrated metalloporphyrins was identified using ¹H NMR spectroscopy, UV-visible and Fourier transform infrared (FT-IR). Further, these bismuth porphyrins complexes were doped with thermally reduced graphene oxide (TRGO) via simple solvothermal techniques. The intrinsic characteristics of prepared metalloporphyrins-based reduced graphene oxide nanocomposites were examined by using various spectroscopic techniques like, photo-physical properties (UV-Visible spectroscopy and Fluorescence spectroscopy), Fourier transform infrared (FT-IR), powdered X-ray diffraction (P-XRD) patterns, FE-SEM and EDX analysis. At last, the photocatalytic properties of nanocomposites were demonstrated by photocatalytic degradation of industrial pollutant rhodamine B (Rh-b) on irradiation of visible light. The catalytic efficiency of RGO-Bi-P1 and RGO-Bi-P2 came out to be 94.58% and 93.26%, respectively.

GO/Cu₂O nanocomposite had been successfully synthesized by electrostatic interactions method. X-ray powder diffraction (XRD), transmission electron microscope (TEM), selective-area electron diffraction (SAED), Fourier transform infrared spectroscopy (FT-IR) and Raman spectra confirmed the structure of the Cu₂O and GO/Cu₂O nanocomposite. The catalytic degradation of Rhodamine B under the condition of ultrasound was investigated and the result of UV-Vis spectroscopy demonstrated that the nanocomposite can efficiently degraded it.

A facile and effective approach based on magnetic separation was developed for the adsorption of Rhodamine B(RhB) from aqueous solution using magnetic oxidized multi-walled carbon nanotubes (magnetic o-MWCNTs) as adsorbent. The magnetic o-MWCNTs were simply synthesized by assembling magnetic nanoparticles onto the oxidized MWCNTs. Adsorption conditions such as pH values, the dosage of adsorbent added and adsorption time were investigated and optimized to achieve the best removal value. In addition, kinetics, adsorption isotherms and adsorption thermodynamics were studied to understand the mechanism by which the magnetic o-MWCNTs adsorbed RhB. The results indicated that the proposed method based on magnetic o-MWCNTs as magnetic absorbent was rapid and efficient for the removal of RhB. Furthermore, the magnetic o-MWCNTs could be easily removed after adsorption process and regenerated through desorption by ethanol.

A facile one-step method was developed for the first time to fabricate BiOCl film on Cu substrate by simply dipping the Cu substrate in the mixed solution containing HCl, glycol, H₂O₂ and BiCl₃. This method shows the advantages of a simple technique, uniform and controllable morphology, as well as easy mass production. The absorption capacity of BiOCl film was investigated by adsorption of Rhodamine B and Congo red (CR) and their maximum adsorption capacities were 1667mgg${}^{-1}$ and 1429mgg${}^{-1}$, respectively. The negative values of free energy and the positive values of enthalpy suggested that the adsorption were spontaneous and endothermic, respectively. Moreover, both adsorptions were matched with the pseudo-second-order equation. This film could be reused and the recycle rates for Rhodamine B and CR were still about 95% and 75% after five cycles, respectively. The adsorption mechanism revealed that hydrogen bond mainly accounted for the adsorption of dyes.

A time- and energy- saving solution-based chemical precipitation method was developed to synthesize leaf-like CuO nanostructures. The morphology and size of the leaf-like CuO nanostructures could be simply manipulated by controlling the type and concentration of precursors, and the oriented attachment mechanism is responsible for the formation of leaf-like shape. With the concurrent reduction reaction and at appropriate concentration, CuO/Ag microspheres could be prepared and the growth mechanism is proposed. These two structures could serve as effective photocatalyst for the degradation of rhodamine B under visible light irradiation in the presence of hydrogen peroxide. Moreover, compared to pure CuO nanostructures, the photodecomposition activity of CuO/Ag microspheres increases by 42.9% due to plasmon-enhanced light absorption.

The Bi₂S₃-TiO₂-RGO composites were synthesized by a facile one-step hydrothermal method and applied for the photocatalytic degradation of Rhodamine B (Rh B) under the visible light. The Bi₂S₃-TiO₂-RGO composites were characterized by transmission electron microscopy, X-ray diffraction, Raman and Fourier transform infrared spectrometer. The results indicated that the Bi₂S₃-TiO₂-RGO composites were successfully prepared, and Ti-O-C and S-C bonds were existing among Bi₂S₃, TiO₂ as well as RGO. Furthermore, the photocatalytic ability of Bi₂S₃-TiO₂-RGO composites was excellent under visible light due to its responding to the whole visible light region, low recombination rate of photogenerated electron–hole pairs and relatively negative conduction band. Rh B photocatalytic degradation rate was 99.5% after 50min and still could reach 98.4% after five cycles. Finally, a formation mechanism as well as a photocatalytic mechanism of Bi₂S₃-TiO₂-RGO composites were proposed based on the experimental results.

Water pollution caused by intensive use of organic dyes has become an increasingly serious problem recently. Green and efficient processes are desperately needed to remove persistent organic pollutants from waste waters. Herein, Ag nanoparticles loaded ZnO hollow microspheres were synthesized through a simple solvothermal method and used as a photocatalyst for dye degradation. The calculated band gap of Ag/ZnO — 5% (2.97eV) is much narrower than that of pure ZnO (3.37eV). The obtained Ag/ZnO samples show a remarkable photocatalytic activity in photodegradation of Rhodamine B (RhB) under simulated sunlight irradiation. The degradation efficiency of RhB for Ag/ZnO — 5% is 98.8% after 100min irradiation while only 52.8% degradation rate is obtained over pure ZnO. The enhancement is attributed to the exposed active ZnO (001) plane and the surface plasmon resonance (SPR) effect of Ag nanoparticles that promote the separation of photogeneated electrons and holes.

Au@MoS₂-CdS, as ternary composite structure, was successfully synthesized by a facile process combining hydrothermal and seed-growth methods. The introduction of Au nanoparticles (NPs) into MoS₂ spheres, forming a core–shell structure, demonstrates strong plasmonic absorption enhancement. The incorporation of CdS NPs into the Au@MoS₂ core–shell structure further extends the absorption range of visible light and enhances exciton dissociation. The resultant composite structure exhibits the highest photocatalytic activity in photocatalytic degradation of rhodamine B (RhB) solution, compared with Au NPs, MoS₂ spheres, Au@MoS₂ core–shell and MoS₂-CdS heterostructures. The above phenomena are supported by a series of characterization results such as SEM, TEM, XRD, EDS and UV-Vis, etc. Based on structural and morphological analyses, we propose the synthesis method of ternary composite structure photocatalysts, which is helpful for the synthesis of future multicomponent photocatalytic materials.