Copper indium sulfide quantum dots in photocatalysis

Design of S-Scheme CuInS2/CeO2 Heterojunction for Enhanced Photocatalytic Degradation of Pharmaceuticals in Wastewater

The release of common medications and illegal drugs into the environment could be potentially harmful to the ecosystem and hamper the behavior and growth of plants and animals. These pollutants gain access to water through sewage and factory discharges and have been found to exceed safety limits in water bodies. Therefore, there is an urgent need for improved wastewater purification systems. In this study, semiconductor-based heterojunction photocatalyst CuInS2/CeO2, synthesized through a facile solvothermal process, was explored for the photocatalytic degradation of ciprofloxacin, commonly used antibiotics. Studies on the electronic properties of the heterojunction revealed interfacial characteristics that were suitable for enhanced charge carrier separation and transport and a potential S-scheme charge transfer mechanism. The heterojunction achieved ∼90% efficiency for the degradation of CIP compared to 60% and 12% reported for CeO2 and CuInS2, respectively. This shows an improvement in the activity, which results from the improved charge carrier properties of the heterojunction. Further investigation of the charge transfer mechanism through radical scavenging experiments identified •OH, O2•-, and h+ as active species contributing to the catalyst's efficacy. Based on X-ray photoelectron spectroscopy analysis, a proposed S-scheme charge transfer mechanism was suggested for the CuInS2/CeO2 heterojunction. The findings indicate the potential of the CuInS2/CeO2 heterojunction as a promising photocatalyst for treating waste effluents from the pharmaceutical industry.

Enhanced solar light photocatalytic degradation of tetracycline by aero-GaN and ZnO microtetrapods functionalized with noble metal nanodots

The escalating global problem of antibiotic contamination in wastewater demands innovative and sustainable remediation technologies. This paper presents a highly efficient photocatalytic material for water purification: a three-dimensional ultra-porous structure of interconnected GaN hollow microtetrapods (aero-GaN), its performance being further enhanced by noble metal nanodot functionalization. This novel aero-nanomaterial achieves more than 90 % of tetracycline degradation within 120 min under UV and solar irradiation, demonstrating its effectiveness in both static and dynamic flow conditions, with the potential for reuse and recyclability. The higher surface area and chemical stability of the 3D aero-GaN architecture, compared to analogous ZnO structures, establish its significant potential for advanced water treatment applications and filter technologies.

TiO2-based photocatalysts from type-II to S-scheme heterojunction and their applications

Photocatalysis is a promising sustainable technology to remove organic pollution and convert solar energy into chemical energy. Titanium dioxide has drawn extensive attention in this field owing to its high activity under UV light, good chemical stability, large availability, low price and low toxicity. However, the poor quantum efficiency derived from fast electron/hole recombination, the limited utilization of sunlight, and a weak reducing ability still hinder its practical application. Among the modification strategies of TiO2 to enhance its performance, the construction of heterojunctions with other semiconductors is a powerful and versatile way to maximise the separation of photogenerated charge carriers and steer their transport toward enhanced efficiency and selectivity. Here, the research progress and current status of TiO2 modification are reviewed, focusing on heterojunctions. A rapid evolution of the understanding of the different charge transfer mechanisms is witnessed from traditional type II to the recently conceptualised S-scheme. Particular attention is paid to different synthetic approaches and interface engineering methods designed to improve and control the interfacial charge transfer, and several cases of TiO2 heterostructures with metal oxides, metal sulfides and carbon nitride are discussed. The application hotspots of TiO2-based photocatalysts are summarized, including hydrogen generation by water splitting, solar fuel production by CO2 conversion, and the degradation of organic water pollutants. Hints about less studied and emerging processes are also provided. Finally, the main issues and challenges related to the sustainability and scalability of photocatalytic technologies in view of their commercialization are highlighted, outlining future directions of development.

Extended Interfacial Charge Transference in CoFe2O4/WO3 Nanocomposites for the Photocatalytic Degradation of Tetracycline Antibiotics

The large-scale utilization of antibiotics has opened a separate chapter of pollution with the generation of reactive drug-resistant bacteria. To deal with this, in this work, different mass ratios of CoFe2O4/WO3 nanocomposites were prepared following an in situ growth method using the precursors of WO3 and CoFe2O4. The structure, morphology, and optical properties of the nanocomposite photocatalysts were scrutinized by X-ray diffraction (XRD), UV-visible diffuse reflectance spectra (UV-Vis DRS), photoluminescence spectrum (PL), etc. The experimental data signified that the loading of CoFe2O4 obviously changed the optical properties of WO3. The photocatalytic performance of CoFe2O4/WO3 composites was investigated by considering tetracycline as a potential pollutant. The outcome of the analyzed data exposed that the CoFe2O4/WO3 composite with a mass ratio of 5% had the best degradation performance for tetracycline eradication under the solar light, and a degradation efficiency of 77% was achieved in 20 min. The monitored degradation efficiency of the optimized photocatalyst was 45% higher compared with the degradation efficiency of 32% for pure WO3. Capturing experiments and tests revealed that hydroxyl radical (·OH) and hole (h+) were the primary eradicators of the target pollutant. This study demonstrates that a proper mass of CoFe2O4 can significantly push WO3 for enhanced eradication of waterborne pollutants.

Hydrogen energy systems: Technologies, trends, and future prospects

This review critically examines hydrogen energy systems, highlighting their capacity to transform the global energy framework and mitigate climate change. Hydrogen showcases a high energy density of 120 MJ/kg, providing a robust alternative to fossil fuels. Adoption at scale could decrease global CO2 emissions by up to 830 million tonnes annually. Despite its potential, the expansion of hydrogen technology is curtailed by the inefficiency of current electrolysis methods and high production costs. Presently, electrolysis efficiencies range between 60 % and 80 %, with hydrogen production costs around $5 per kilogram. Strategic advancements are necessary to reduce these costs below $2 per kilogram and push efficiencies above 80 %. Additionally, hydrogen storage poses its own challenges, requiring conditions of up to 700 bar or temperatures below -253 °C. These storage conditions necessitate the development of advanced materials and infrastructure improvements. The findings of this study emphasize the need for comprehensive strategic planning and interdisciplinary efforts to maximize hydrogen's role as a sustainable energy source. Enhancing the economic viability and market integration of hydrogen will depend critically on overcoming these technological and infrastructural challenges, supported by robust regulatory frameworks. This comprehensive approach will ensure that hydrogen energy can significantly contribute to a sustainable and low-carbon future.

Cu-P@silica-CNT-based catalyst for effective electrolytic water splitting in an alkaline medium with hydrazine assistance

In this study, we prepared a potential catalyst as an electrode modifier for electrolytic water splitting. In the preparation step, the amine was decorated with copper-phosphorus. It was immobilized over the silica surface, and the surface was engineered using N-(3-(trimethoxysilyl) propyl)ethylenediamine for the synthesis of the catalysts (AS). The morphological and structural aspects of the catalyst (AFS-Cu-P) were determined using FE-SEM/EDAX, FTIR, elemental analysis, BET, TGA, and XPS. The catalyst's efficacy for the oxygen evolution reaction (OER) was assessed in an alkaline medium with and without hydrazine. The hydrazine oxidation reaction enhanced the sluggish OER and facilitated water splitting. Detailed electrochemical measurements confirmed an increase in the kinetics of the process and a reduction in the activation energy needed to complete the process. The Tafel slopes, charge transfer coefficients, exchange-specific current densities, apparent rate constants, and diffusion coefficients are provided along with their respective values. The results showed that the presence of Cu and CNT is crucial in the conversion process.

Green and environmentally friendly architecture of starch-based ternary magnetic biocomposite (Starch/MIL100/CoFe2O4): Synthesis and photocatalytic degradation of tetracycline and dye

The presence of tetracycline and dye as organic contaminants has led to the poisoning of wastewater. The aim of this study is to synthesize a novel biocomposite material by decorating natural starch polymer granules with metal-organic framework (MIL100) and cobalt ferrite magnetic (CoFe2O4) nanoparticles. The synthesized ternary magnetic biocomposite (Starch/MIL100/CoFe2O4) was used for the photocatalytic degradation of methylene blue (MB) and tetracycline (TCN) using LED visible light. The synthesis of the biocomposite was confirmed through comprehensive analyses (XRD, SEM, FTIR, BET, EDX, MAP, DRS, pHzpc, TGA, and Raman). The evaluation examined the influence of initial pollutant concentration, catalyst dosage, pH, and the impact of anions on pollutant removal. The results show that the pollutant degradation ability of biocomposite has been significantly improved, so that the base biopolymer, starch, achieved 18% tetracycline degradation, but when decorated with MIL100 and cobalt ferrite, it increased to 91.2%. It was observed that the degradation for methylene blue improved from 12% for starch to 96.6% for the magnetic biocomposite. The tetracycline degradation decreased by more than 20% in the presence of NaCl, NaNO3, and Na2SO4. The finding shows that the biocomposite adheres to first-order kinetics for both pollutants. The scavengers test identified hydroxyl radicals as the most effective active species in the degradation process. High stability, even after passing 5 cycles of recycling was observed for the biocomposite. The results indicated that the facile and green synthesized Starch/MIL100/CoFe2O4 magnetic biocomposite could be used as an effective photocatalyst for the degradation of Tetracycline and dye at room temperature.

Atomically Contacted Cs3Bi2Br9 QDs@UiO-66 Composite for Photocatalytic CO2 Reduction

Metal halide perovskite quantum dots (QDs) are widely studied in the field of photocatalytic CO2 due to their strong light absorption and long carrier migration length. However, it can not exhibit high catalytic performance because of the radiative recombination and the lack of effective catalytic sites. Metal organic frameworks (MOFs) encapsulated QDs can not only solve the aforementioned problems, but also maintain their own unique characteristics with ultra-high specific surfaces area and abundant metal sites. In this work, lead-free bismuth-based halide perovskite QDs are encapsulated into Zr-based MOF (UiO-66), which combines the advantages with high power conversion efficiency of QDs and the high surface area and porosity of UiO-66. In addition, benefiting from the close contact between the Cs3Bi2Br9 QDs and the UiO-66 enables the photogenerated electrons in the QDs to be rapidly transferred to the MOF. As a result, the Cs3Bi2Br9@UiO-66 composite exhibits a higher yield for photocatalytic CO2 reduction than that of the prepared large-sized composite of Cs3Bi2Br9 and UiO-66.

In-situ construct CuInS2/Bi/Bi2MoO6 S-scheme/Schottky dual heterojunctions catalyst for enhanced photocatalytic degradation of diclofenac sodium

In this paper, the S-scheme/Schottky heterojunction photocatalyst (CuInS2/Bi/Bi2MoO6, CIS/Bi/BMO) was successfully constructed via a facile in-situ solvothermal method, aimed at enhancing its photocatalytic performance. The results of the study on the photocatalytic degradation of diclofenac sodium (DCF) under simulated solar light irradiation revealed that the as-prepared composite exhibited remarkable catalytic efficiency in comparison to the pristine Bi2MoO6 and CuInS2. The plasmonic bismuth (Bi) was formed during the solvothermal process. Subsequently, CuInS2 and Bi were grown on the surface of Bi2MoO6 leading to forming CIS/BMO S-scheme heterojunction, along with a Schottky junction between Bi and Bi2MoO6. The use of ethylene glycol as a support was the main reason for the significant improvement in photocatalytic efficiency in the degradation of DCF. Moreover, the probable photocatalytic mechanisms for the degradation of DCF had been proposed based on the active species quenching experiments. The eleven degradation products were detected by HPLC-MS, and the degradation reaction pathway of DCF was deduced. Additionally, the CIS/Bi/BMO photocatalyst exhibited a consistently high removal rate after four cycles. This study proposes a new strategy for designing efficient S-scheme/Schottky heterojunction photocatalysts for solar energy conversion.

Ultrafast Electron Transfer from CuInS2 Quantum Dots to a Molecular Catalyst for Hydrogen Production: Challenging Diffusion Limitations

Systems integrating quantum dots with molecular catalysts are attracting ever more attention, primarily owing to their tunability and notable photocatalytic activity in the context of the hydrogen evolution reaction (HER) and CO2 reduction reaction (CO2RR). CuInS2 (CIS) quantum dots (QDs) are effective photoreductants, having relatively high-energy conduction bands, but their electronic structure and defect states often lead to poor performance, prompting many researchers to employ them with a core-shell structure. Molecular cobalt HER catalysts, on the other hand, often suffer from poor stability. Here, we have combined CIS QDs, surface-passivated with l-cysteine and iodide from a water-based synthesis, with two tetraazamacrocyclic cobalt complexes to realize systems which demonstrate high turnover numbers for the HER (up to >8000 per catalyst), using ascorbate as the sacrificial electron donor at pH = 4.5. Photoluminescence intensity and lifetime quenching data indicated a large degree of binding of the catalysts to the QDs, even with only ca. 1 μM each of QDs and catalysts, linked to an entirely static quenching mechanism. The data was fitted with a Poissonian distribution of catalyst molecules over the QDs, from which the concentration of QDs could be evaluated. No important difference in either quenching or photocatalysis was observed between catalysts with and without the carboxylate as a potential anchoring group. Femtosecond transient absorption spectroscopy confirmed ultrafast interfacial electron transfer from the QDs and the formation of the singly reduced catalyst (CoII state) for both complexes, with an average electron transfer rate constant of ≈ (10 ps)-1. These favorable results confirm that the core tetraazamacrocyclic cobalt complex is remarkably stable under photocatalytic conditions and that CIS QDs without inorganic shell structures for passivation can act as effective photosensitizers, while their smaller size makes them suitable for application in the sensitization of, inter alia, mesoporous electrodes.

Construction of S-scheme CuInS2/ZnIn2S4 heterostructures for enhanced photocatalytic activity towards Cr(VI) removal and antibiotics degradation

The efficient and ecofriendly removal of pharmaceutical antibiotics and heavy metal Cr(VI) from water sources is a crucial challenge in current environmental management. Photocatalysis presents a viable environmentally friendly solution for eliminating organic contaminants and heavy-metal ions. In this study, a novel S-scheme CuInS2/ZnIn2S4 (CIS/ZIS) heterojunction was developed using a one-pot solvothermal method. The optimized CIS/ZIS heterojunction exhibited considerably improved photocatalytic activity for the removal of antibiotics and Cr(VI), achieving over 90% removal for both tetracycline hydrochloride (TC) (20 mg/L) and Cr(VI) (20 mg/L) under visible light irradiation. The study also delved into the effect of coexisting inorganic anions and assessed the cyclic stability of the composite photocatalysts. This enhancement mechanism can be delineated into three key elements. First, the incorporation of the narrow-gap semiconductor CuInS2 effectively augmented the photoabsorption capacity. Second, the inclusion of ZnIn2S4 caused an increase in surface active sites. Most importantly, the internal electric field at the interface between CuInS2 and ZnIn2S4 expedited the separation of photogenerated carriers. Furthermore, the results revealed that superoxide radical and photogenerated holes are the primary active substance responsible for TC removal, while photogenerated electrons play a central role in the photoreduction of Cr(VI). To gain insights into the transport pathways of photogenerated carriers, we conducted experiments with nitrotetrazolium blue chloride (NBT) and photodeposited gold. This study offers an innovative approach to enhancing the photocatalytic performance of ternary In-based materials by constructing S-scheme heterojunctions.

The role of surface functionalization in quantum dot-based photocatalytic CO2 reduction: balancing efficiency and stability

Photocatalytic CO2 reduction offers a promising strategy to produce hydrocarbons without reliance on fossil fuels. Visible light-absorbing colloidal nanomaterials composed of earth-abundant metals suspended in aqueous media are particularly attractive owing to their low-cost, ease of separation, and highly modifiable surfaces. The current study explores such a system by employing water-soluble ZnSe quantum dots and a Co-based molecular catalyst. Water solubilization of the quantum dots is achieved with either carboxylate (3-mercaptopropionic acid) or ammonium (2-aminoethanethiol) functionalized ligands to produce nanoparticles with either negatively or positively-charged surfaces. Photocatalysis experiments are performed to compare the effectiveness of these two surface functionalization strategies on CO2 reduction and ultrafast spectroscopy is used to reveal the underlying photoexcited charge dynamics. We find that the positively-charged quantum dots can support sub-picosecond electron transfer to the carboxylate-based molecular catalyst and also produce >30% selectivity for CO and >170 mmolCO gZnSe-1. However, aggregation reduces activity in approximately one day. In contrast, the negatively-charged quantum dots exhibit >10 ps electron transfer and substantially lower CO selectivity, but they are colloidally stable for days. These results highlight the importance of the quantum dot-catalyst interaction for CO2 reduction. Furthermore, multi-dentate catalyst molecules create a trade-off between photocatalytic efficiency from strong interactions and deleterious aggregation of quantum dot-catalyst assemblies.

Activities of BiFeO3/carbon-dots catalysts in piezo-photocatalytic degradation of ciprofloxacin upon light/ultrasonic excitation

Designing catalysts that can effectively make use of renewable energy benefits to solve the current challenges of environmental pollution and increasing energy demands. Piezo-photocatalysis that can utilize solar energy and natural vibration-energy has emerged as a "green" technique. In this work, we fabricated BiFeO3/C nano composites that can harvest solar and vibration energies and degrade organic pollutants. The incorporated carbon quantum dots bring about more efficient visible light absorbance and separation of photoinduced electron-hole pairs. The piezoelectric polarization further suppresses the recombination of photoinduced electron-hole pairs. The catalysts own higher reaction rates in piezo-photocatalysis and the BiFeO3/C-0.12 shows the highest degradation efficiency (k-value of 0.0835 min-1).

A Review of in vivo Toxicity of Quantum Dots in Animal Models

Tremendous research efforts have been devoted to nanoparticles for applications in optoelectronics and biomedicine. Over the past decade, quantum dots (QDs) have become one of the fastest growing areas of research in nanotechnology because of outstanding photophysical properties, including narrow and symmetrical emission spectrum, broad fluorescence excitation spectrum, the tenability of the emission wavelength with the particle size and composition, anti-photobleaching ability and stable fluorescence. These characteristics are suitable for optical imaging, drug delivery and other biomedical applications. Research on QDs toxicology has demonstrated QDs affect or damage the biological system to some extent, and this situation is generally caused by the metal ions and some special properties in QDs, which hinders the further application of QDs in the biomedical field. The toxicological mechanism mainly stems from the release of heavy metal ions and generation of reactive oxygen species (ROS). At the same time, the contact reaction with QDs also cause disorders in organelles and changes in gene expression profiles. In this review, we try to present an overview of the toxicity and related toxicity mechanisms of QDs in different target organs. It is believed that the evaluation of toxicity and the synthesis of environmentally friendly QDs are the primary issues to be addressed for future widespread applications. However, considering the many different types and potential modifications, this review on the potential toxicity of QDs is still not clearly elucidated, and further research is needed on this meaningful topic.

Synthesis and hybridization of CuInS2 nanocrystals for emerging applications

Copper indium sulfide (CuInS2) is a ternary A(I)B(III)X(VI)2-type semiconductor featuring a direct bandgap with a high absorption coefficient. In attempts to explore their practical applications, nanoscale CuInS2 has been synthesized with crystal sizes down to the quantum confinement regime. The merits of CuInS2 nanocrystals (NCs) include wide emission tunability, a large Stokes shift, long decay time, and eco-friendliness, making them promising candidates in photoelectronics and photovoltaics. Over the past two decades, advances in wet-chemistry synthesis have achieved rational control over cation-anion reactivity during the preparation of colloidal CuInS2 NCs and post-synthesis cation exchange. The precise nano-synthesis coupled with a series of hybridization strategies has given birth to a library of CuInS2 NCs with highly customizable photophysical properties. This review article focuses on the recent development of CuInS2 NCs enabled by advanced synthetic and hybridization techniques. We show that the state-of-the-art CuInS2 NCs play significant roles in optoelectronic and biomedical applications.

Nanomaterials for photo-electrochemical water splitting: a review

Over the last few decades, the global rise in energy demand has prompted researchers to investigate the energy requirements from alternative green fuels apart from the conventional fossil fuels, due to the surge in CO2 emission levels. In this context, the global demand for hydrogen is anticipated to extend by 4-5% in the next 5 years. Different production technologies like gasification of coal, partial oxidation of hydrocarbons, and reforming of natural gas are used to obtain high yields of hydrogen. In present time, 96% of hydrogen is produced by the conventional methods, and the remaining 4% is produced by the electrolysis of water. Photo-electrochemical (PEC) water splitting is a promising and progressive solar-to-hydrogen pathway with high conversion efficiency at low operating temperatures with substrate electrodes such as fluorine-doped tin oxide (FTO), incorporated with photocatalytic nanomaterials. Several semiconducting nanomaterials such as carbon nanotubes, TiO2, ZnO, graphene, alpha-Fe2O3, WO3, metal nitrides, metal phosphides, cadmium-based quantum dots, and rods have been reported for PEC water splitting. The design of photocatalytic electrodes plays a crucial role for efficient PEC water splitting process. By modifying the composition and morphology of photocatalytic nanomaterials, the overall solar-to-hydrogen (STH) energy conversion efficiency can be improved by optimizing their opto-electronic properties. The present article highlights the recent advancements in cleaner and effective photocatalysts for producing high yields of hydrogen via PEC water splitting.

Titanium doped cobalt ferrite fabricated graphene oxide nanocomposite for efficient photocatalytic and antibacterial activities

Dyes and microbes are the main sources of water pollution and their treatment with titanium doped cobalt ferrite nanoparticles (CoTixFe2-xO4 NPs) is highly challenging due to the recombination ability of their electron-hole pairs which could be mitigated by making their composite with graphene oxide (GO). In the present study, titanium doped cobalt ferrite was fabricated on GO (CoTi0.2Fe1.8O4/GO NC) via the facile ultrasonication method and its confirmation was done by various analytical studies. Homogeneous dispersion of spherical CoTi0.2Fe1.8O4 NPs on the GO surface was realized by SEM analysis. Excellent crystallinity was corroborated by XRD while a Zeta Potential value -21.52 mV depicted exceptional stability. The photocatalytic power of CoTi0.2Fe1.8O/GO NC against Congo Red (CR) dye showed 91% degradation efficiency after 120 min visible light irradiation under optimum conditions of pH 9 and dye concentration 1 mg L-1 which was reasonably higher as compared to bare CoTi0.2Fe1.8O NPs (78% degradation efficiency). The improved photocatalytic performance is accredited to its narrow bandgap value (1.07 eV) and enhanced charge separation as indicated by the Tauc plot and Photoluminescence analysis, respectively. Additionally, CoTi0.2Fe1.8O/GO NC could be readily regenerated and reused five times with only ∼2% performance loss. Meanwhile, MICs of CoTi0.2Fe1.8O4/GO NC against P. aeruginosa and S. aureus were 0.046 and 0.093 mg mL-1 while MBCs were 0.093 and 0.187 mg mL-1, respectively. Thereby, optimized NC can open new avenues for the degradation of dyes from polluted water besides acting as a promising antimicrobial agent by rupturing the cell walls of pathogens.

Effects of Tea Polyphenols and Theaflavins on Three Oral Cariogenic Bacteria

In order to investigate the antibacterial mechanism of tea polyphenols and theaflavins against oral cariogenic bacteria, the pH value of the culture medium, the number of bacteria adhering to the smooth glass tube wall, and the electrical conductivity value within 10 h were measured, respectively. The effects of four concentrations of tea polyphenols and theaflavins below the MIC value were studied on acid production, adhesion, and electrical conductivity of oral cariogenic bacteria. The live/dead staining method was used to observe the effects of four concentrations of tea polyphenols and theaflavins below the MIC value on the biofilm formation of oral cariogenic bacteria under a laser scanning confocal microscope. With the increase in concentrations of tea polyphenols and theaflavins, the acid production and adhesion of the cariogenic bacteria gradually decreased, and the conductivity gradually increased. However, the conductivity increase was not significant (p < 0.05). Compared with the control group, the 1/2MIC and 1/4MIC tea polyphenols and theaflavins treatments significantly reduced the biomass of the cariogenic biofilm (p < 0.05). The confocal laser scanning microscope showed that the integrated optical density of green fluorescence of the cariogenic biofilm gradually decreased with the increase in agent concentration after the action of tea polyphenols and theaflavins.

Detection of enrofloxacin residues in dairy products based on their fluorescence quenching effect on AgInS2 QDs

Water-soluble AgInS₂ (AIS) quantum dots (QDs) were successfully prepared through the one-pot water phase method with thioglycolic acid (TGA) as the stabilizing agent. Because enrofloxacin (ENR) effectively quenches the fluorescence of AIS QDs, a highly-sensitive fluorescence detection method is proposed to detect ENR residues in milk. Under optimal detection conditions, there was a good linear relationship between the relative fluorescence quenching amount (ΔF/F₀) of AgInS₂ with ENR and ENR concentration (C). The detection range was 0.3125-20.00 μg/mL, r = 0.9964, and the detection limit (LOD) was 0.024 μg/mL (n = 11). The average recovery of ENR in milk ranged from 95.43 to 114.28%. The method established in this study has advantages including a high sensitivity, a low detection limit, simple operation and a low cost. The fluorescence quenching mechanism of AIS QDs with ENR was discussed and the dynamic quenching mechanism of light-induced electron transfer was proposed.

CdS nanocrystallites sensitized ZnO nanosheets for visible light induced sonophotocatalytic/photocatalytic degradation of tetracycline: From experimental results to a generalized model based on machine learning methods

CdS/ZnO nanosheets heterostructures ((x)CdS/ZNs) with different mole ratios of Cd/Zn ((x) = 0.2, 0.4, and 0.6) were synthesized by the impregnation-calcination method. PXRD patterns showed that the (100) diffraction of ZNs was the most significant in the (x)CdS/ZNs heterostructures, and it confirmed that CdS nanoparticles (in cubic phase) occupied the (101) and (002) crystal facets of ZNs with hexagonal wurtzite crystal phase. UV-Vis DRS results indicated that CdS nanoparticles decreased the band gap energy of ZNs (2.80-2.11 eV) and extended the photoactivity of ZNs to the visible light region. The vibrations of ZNs were not observed clearly in the Raman spectra of (x)CdS/ZNs due to the extensive coverage of CdS nanoparticles shielding the deeper-laying ZNs from Raman response. The photocurrent of (0.4) CdS/ZNs photoelectrode reached 33 μA, about 82 times higher than that for ZNs (0.4 μA, 0.1 V vs Ag/AgCl). The formation of an n-n junction at the (0.4) CdS/ZNs reduced the recombination of electron-hole pairs and increased the degradation performance of the as-prepared (0.4) CdS/ZNs heterostructure. The highest percentage removal of tetracycline (TC) in the sonophotocatalytic/photocatalytic processes was obtained by (0.4) CdS/ZNs under visible light. The quenching tests showed that O₂^•-, h⁺, and OH^• were the main active species in the degradation process. The degradation percentage decreased negligibly in the sonophotocatalytic (84%-79%) compared to the photocatalytic (90%-72%) process after four re-using runs due to the presence of ultrasonic waves. For the estimation of degradation behavior, two machine learning methods were applied. The comparison between the ANN and GBRT models evidenced that both models had high prediction accuracy and could be used for predicting and fitting the experimental data of the %removal of TC. The excellent sonophotocatalytic/photocatalytic performance and stability of the fabricated (x)CdS/ZNs catalysts made them promising candidates for wastewater purification.

Fe3O4@MIL-100(Fe) modified ZnS nanoparticles with enhanced sonocatalytic degradation of tetracycline antibiotic in water

Sonocatalysis has attracted excellent research attention to eradicate hazardous pollutants from the environment effectively. This work synthesised an organic/inorganic hybrid composite catalyst by coupling Fe3O4@MIL-100(Fe) (FM) with ZnS nanoparticles using the solvothermal evaporation method. Remarkably, the composite material delivered significantly enhanced sonocatalytic efficiency for removing tetracycline (TC) antibiotics in the presence of H2O2 compared to bare ZnS nanoparticles. By adjusting different parameters such as TC concentration, catalyst dosage and H2O2 amount, the optimized composite (20 %Fe3O4@MIL-100(Fe)/ZnS) removed 78.25% antibiotic in 20 min at the cost of 1 mL of H2O2. These much superior activities are attributed to the efficient interface contact, effective charge transfer, accelerated transport capabilities and strong redox potential for the superior acoustic catalytic performance of FM/ZnS composite systems. Based on various characterization, free radical capture experiments and energy band structures, we proposed a mechanism for the sonocatalytic degradation of tetracycline based on S-scheme heterojunctions and Fenton like reactions. This work will provide an important reference for developing ZnS-based nanomaterials to study sonodegradation of pollutants.