Synthesis, Characterization and Photocatalytic Activity of MoS2/ZnSe Heterostructures for the Degradation of Levofloxacin

Deciphering the mechanism for encapsulation of MOF (Fe-glutaric acid) onto Se/SnO2 embedded CMC for effective aqueous sequestration of pharmaceutical pollutant via adsorption

Wastewater is commonly contaminated with many pharmaceutical pollutants, so an efficient purification method is required for their removal from wastewater. In this regard, an innovative tertiary Se/SnO2@CMC/Fe-GA nanocomposite was synthesized through encapsulation of metal organic frameworks (Fe-glutaric acid) onto Se/SnO2-embedded-sodium carboxy methyl cellulose matrix to thoroughly evaluate its effectiveness for adsorption of levofloxacin drug from wastewater. The prepared Se/SnO2@CMC/Fe-GA nanocomposite was analyzed via UV-Vis spectroscopy, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermo gravimetric analysis (TGA), energy dispersive X-ray (EDX), and X-ray diffraction (XRD) to valuate optical property, size, morphology, thermal stability, and chemical composition. The results revealed that prepared Se/SnO2@CMC/Fe-GA nanocomposite was crystalline and porous having average particle size of 6.23 nm with energy band gap of 2.60 eV. Specific heat energy of Se/SnO2@CMC/Fe-GA nanocomposite was found to be 0.028 Jg-1 °C-1. Different experimental factors for example, time, temperature, concentration of LEVO, catalyst dose, ionic strength, and pH were optimized for maximum removal of levofloxacin from wastewater. The tertiary Se/SnO2@CMC/Fe-GA nanocomposite showed 99% removal efficiency for levofloxacin at pH = 7, with contact time of 60 min at 50 °C temperature. The adsorption kinetics followed pseudo-second order. Among adsorption isotherm models, Langmuir model was found most appropriate which revealed that the process was chemisorption. Main mechanism of adsorption is pore diffusion that is confirmed from Bangham, Boyd, Crank and PVSDM kinetic models. Spontaneity and endothermic nature of the process were confirmed by the values of thermodynamic parameters. Toxicity of effluent and impact of interfering ions on adsorption were also investigated. Swelling ratio of Se/SnO2@CMC/Fe-GA nanocomposite was calculated, and nanocomposite showed better results and chemical stability even after five cycles.

Sunlight-activated heterostructure MoS2/CdS nanocomposite photocatalyst with enhanced photocatalytic activity: band alignment and mechanism study

A high recombination rate is a major limiting factor in photocatalysis. Mitigating recombination through material engineering and photocatalyst optimization is key to enhancing photocatalytic performance. In this study, a heterostructure MoS2/CdS nanocomposite was synthesized through a hydrothermal method in a Teflon-lined autoclave subjected to a temperature of 200 °C for 16 hours. The resulting photocatalysts were characterized using a variety of techniques to understand their structural, surface, and optical properties. The photocatalytic activity of the as-synthesized photocatalysts was investigated by degrading methyl orange dye under both sunlight and visible light irradiation. Regardless of its MoS2 content, the heterostructure MoS2/CdS NC exhibited enhanced degradation efficiency relative to that of pure CdS, MoS2, and commercial TiO2 P25, with 5 wt% MoS2/CdS NCs exhibiting the highest degradation performance among all the evaluated photocatalysts. This behavior was justified by improved charge separation and reduced charge recombination, which were attributed to the valence band and conduction band offsets at the MoS2/CdS interface, as evidenced by band alignment study. The enhanced charge separation and reduced charge recombination were further validated by photoluminescence (PL), electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) measurements. Furthermore, an active species trapping experiment confirmed that electron transfer to oxygen and the subsequent formation of superoxide anions (O2 -) radical play the most significant roles in photocatalytic degradation under visible light illumination. Finally, the ability to reuse the MoS2/CdS NCs multiple times without substantial loss of activity evidenced their stability, thus paving the way for advancements in large-scale environmental remediation and other industrial applications.

Development of a novel Z-scheme CoxNi1-xTiO3/CdS (x = 0.5) photocatalyst for the efficient degradation of organic pollutants via a visible-light-driven photocatalytic process

Herein, for the first time, we reported the synthesis of a novel Z-scheme CoxNi1-xTiO3/CdS (x = 0.5) heterojunction photocatalyst and the investigation of its visible-light-driven photocatalytic performance toward degradation of methylene blue (MB). The developed photocatalyst was structurally characterized by applying X-Ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), differential reflectance spectroscopy (DRS), and photoluminescence (PL) techniques. The results indicated the formation of a highly porous structure with improved visible light adsorption capacity, favorable for the catalytic activity. At an optimum condition of 10 mg/L of MB and 300 mg/L of catalyst, the ternary photocatalyst demonstrated a MB removal efficiency of 99 % after 75 min of the treatment process. The radical trapping experiments unveiled that hydroxyl and superoxide radicals were two main reactive species formed under visible light, while the valance holes possessed an insignificant role. The synergetic impact of the CoxNi1-xTiO3 (x = 0.5) and CdS on the photodegradation of MB over the as-prepared CoxNi1-xTiO3/CdS (x = 0.5) photocatalyst through Z-scheme photocatalysis was indicated by the results of the mechanism studies. The percentage impact of the treatment time, MB concentration, the ratio of CoxNi1-xTiO3/CdS (x = 0.5), and the dosage of catalyst using analysis of the CCD modeling was obtained as 47.04, 16.67, 7.22 and 0.87 %, respectively. Furthermore, the as-synthesized photocatalyst possessed high recyclability and photostability with only a 3 % decline in activity after four repetitive cycles.

Carbon Quantum Dots: Synthesis, Structure, Properties, and Catalytic Applications for Organic Synthesis

Carbon quantum dots (CQDs), also known as carbon dots (CDs), are novel zero-dimensional fluorescent carbon-based nanomaterials. CQDs have attracted enormous attention around the world because of their excellent optical properties as well as water solubility, biocompatibility, low toxicity, eco-friendliness, and simple synthesis routes. CQDs have numerous applications in bioimaging, biosensing, chemical sensing, nanomedicine, solar cells, drug delivery, and light-emitting diodes. In this review paper, the structure of CQDs, their physical and chemical properties, their synthesis approach, and their application as a catalyst in the synthesis of multisubstituted 4H pyran, in azide-alkyne cycloadditions, in the degradation of levofloxacin, in the selective oxidation of alcohols to aldehydes, in the removal of Rhodamine B, as H-bond catalysis in Aldol condensations, in cyclohexane oxidation, in intrinsic peroxidase-mimetic enzyme activity, in the selective oxidation of amines and alcohols, and in the ring opening of epoxides are discussed. Finally, we also discuss the future challenges in this research field. We hope this review paper will open a new channel for the application of CQDs as a catalyst in organic synthesis.

Photocatalytic Degradation of Fluoroquinolone Antibiotics in Solution by Au@ZnO-rGO-gC3N4 Composites

The photocatalytic degradation of two quinolone-type antibiotics (ciprofloxacin and levofloxacin) in aqueous solution was studied, using catalysts based on ZnO nanoparticles, which were synthesized by a thermal procedure. The efficiency of ZnO was subsequently optimized by incorporating different co-catalysts of gC3N4, reduced graphene oxide, and nanoparticles of gold. The catalysts were fully characterized by electron microscopy (TEM and SEM), XPS, XRD, Raman, and BET surface area. The most efficient catalyst was 10%Au@ZnONPs-3%rGO-3%gC3N4, obtaining degradations of both pollutants above 96%. This catalyst has the largest specific area, and its activity was related to a synergistic effect, involving factors such as the surface of the material and the ability to absorb radiation in the visible region, mainly produced by the incorporation of rGO and gC3N4 in the semiconductor. The use of different scavengers during the catalytic process, was used to establish the possible photodegradation mechanism of both antibiotics.

Zn-doped SnS with sulfur vacancies for enhanced photocatalytic hydrogen evolution from water

Tin sulfide has attracted considerable attention due to its adjustable optoelectronic properties. However, few present pieces of literature focus on the photocatalytic water splitting performance of stannous sulfide (SnS), despite...

Structural, Optical, and Photocatalytic Properties of ZnSe Nanoparticles Influenced by the Milling Time

ZnSe nanoparticles (NPs) were prepared by combining both hydrothermal and mechanical milling methods. Transmission electron microscopy images show that fabricated ZnSe NPs with a sphere-like shape have an average size (d) in the range of 20–100 nm, affected by changing the milling time from 10 to 60 min. All the samples crystalize in zincblende-type structure without impurities, as confirmed by analyzing X-ray diffraction patterns, Raman spectra, and energy-dispersive X-ray spectroscopy. Carefully checking Raman spectra, we have observed the broadening and redshift of vibration modes as decreasing NP size, which are ascribed to extra appearance of disorder and defects. The photoluminescence study has found a blue emission at 462 nm attributed to the excitonic near-band edge and a broad defect-related emission around 520–555 nm. Increasing milling time leads to the decrease in the exciton-emission intensity, while the defect-related emissions increase gradually. Interestingly, as decreasing d, we have observed an improved photodegradation of Rhodamine B under UV irradiation, proving application potentials of ZnSe NPs in photocatalytic activity.

Cation-exchange synthesis of PbSe/ZnSe hetero-nanobelts with enhanced near-infrared photoelectronic performance

To develop excellent photoelectronic and photovoltaic devices, a semiconductor with high photoelectron production efficiency and broad band absorption is urgently required. In this article, novel II-type PbSe/ZnSe hetero-nanobelts with enhanced near-infrared absorption have been synthesized via a facile strategy of a partial cation-exchange reaction and thermal treatment. Derived from ZnSe·0.5N₂H₄nanobelts as templates, the belt-like morphology was preserved. Due to the mismatch of the crystal type and parameters between PbSe and ZnSe, the formed PbSe in the form of nanoparticles were separated out and decorated on the nanobelts. Furthermore, the composition ratio of Pb/Zn can be tuned through manipulating the adding amount of Pb²⁺cations, the reaction temperature and time. The ultraviolet-visible-infrared diffuse spectra measurements suggest that the as-prepared PbSe/ZnSe hetero-nanobelts exhibited a broad band absorption from 300 to 1000 nm. In addition, they demonstrated excellent photoresponsivity in the same wavelength region and displayed a peak at approximately 840 nm. Finally, the enhanced photoelectronic sensing mechanism was discussed.