Molecularly imprinted Ag2S quantum dots with high photocatalytic activity for dye removal: Experimental and DFT insights

Molecular imprinted polymers (MIPs) were developed by carrying out the cocktail solution of Template ((Salata, 2004)-Gingerol), monomer, crosslinker, and Ag2S Quantum Dots (QDs) by ex-situ dissolved in an appropriate solvent, resulting in an efficient crosslinked polymer composite. Degradation of Alizarin red S (ARS) dye and yellowish sunset (SY) azo dye under visible light irradiation was reported first time by the introduction of prepared MIPs composite. In this research, the result shows efficient photocatalyt activity of Ag2S-MIPs composite for the degradation of AR and SY dye with degradation% (80%) and (84%) in the aqueous wastewater. The degradation efficiency of the Ag2S-MIPs composite and the Ag2S QD associated with non-imprinted polymers (NIPs) (i.e.Ag2S-NIPs composite) were calculated by using different parameters such as catalyst dose, pH value, optimum time and concentration variation and the observations are evocative. Moreover, the density functional theory (DFT) approach was also used to analyze the structural, stability/energetics, and electronic features of the organic-inorganic hybrid composites of the Ag2S QD with the MIPs based on (Salata, 2004)-gingerol extract. The proposed QD and MIPs (EGDMA and (Salata, 2004)-Gingerol) composite model has been detected to be the most stable because it shows the largest binding energy (BE) among the three chosen composite models. It was found out that imprinted polymers were superior in enhancing the degradation of dyes when compared to non imprinted polymers. Introducing MIPs into the valence band accelerates the catalysis properties to stabilize newly fashioned excitons that are basically generated as a result of light excitation in presence of Ag2S Quantum Dots (QDs) and molecular imprinted polymer (MIPs). Motivation behind this work is to address the challenges related to environmental pollution causing by organic dyes. These toxins are known to cause diverse symptoms (e.g., skin irritation, eye infection, respiratory disorders, and even cancer) once exposed through ingestion and inhalation. Through incorporation of Ag2S QD into MIP,the purpose of this research is to enhance the selectivity, specificity and photocatalytic activity for dyes and that work holds a potential towards environmental remediation by developing a cost effective and sustainable method for controlling pollution in water.

Recent advances in visible light-activated photocatalysts for degradation of dyes: A comprehensive review

The rapid development in industrialization and urbanization coupled with an ever-increasing world population has caused a tremendous increase in contamination of water resources globally. Synthetic dyes have emerged as a major contributor to environmental pollution due to their release in large quantities into the environment, especially owing to their high demand in textile, cosmetics, clothing, food, paper, rubber, printing, and plastic industries. Photocatalytic treatment technology has gained immense research attention for dye contaminated wastewater treatment due to its environment-friendliness, ability to completely degrade dye molecules using light irradiation, high efficiency, and no generation of secondary waste. Photocatalytic technology is evolving rapidly, and the foremost goal is to synthesize highly efficient photocatalysts with solar energy harvesting abilities. The current review provides a comprehensive overview of the most recent advances in highly efficient visible light-activated photocatalysts for dye degradation, including methods of synthesis, strategies for improving photocatalytic activity, regeneration and their performance in real industrial effluent. The influence of various operational parameters on photocatalytic activity are critically evaluated in this article. Finally, this review briefly discusses the current challenges and prospects of visible-light driven photocatalysts. This review serves as a convenient and comprehensive resource for comparing and studying the fundamentals and recent advancements in visible light photocatalysts and will facilitate further research in this direction.

Photoelectrochemical aptasensing of lincomycin based on a AgI-carboxylated multiwalled carbon nanotubes-BiOI Z-scheme heterojunction

Lincomycin (LIN) is a common antibiotic that is widely used in animal husbandry and other fields, and the residual problem caused by its abuse has attracted widespread attention. Herein, a novel AgI-carboxylated multiwalled carbon nanotubes (cMWCNT)-BiOI Z-scheme heterojunction material was synthesized via a one-pot hydrothermal method, modified on a fluorine-doped tin oxide (FTO) electrode surface, and used for detecting LIN. The photocurrent on the AgI-cMWCNT-BiOI/FTO photoelectrode is 4.6 times that on the control AgI-BiOI/FTO photoelectrode. An amino-functionalized LIN aptamer was fixed on the AgI-cMWCNT-BiOI/FTO photoelectrode by the cross-linking reaction between chitosan and glutaraldehyde, and then Ru(NH3)63+ was electrostatically attached to the LIN aptamer to increase the photocurrent response to the LIN binding. When LIN binds competitively with Ru(NH3)63+ to the aptamer, the photocurrent signal can be quantitatively decreased. Under optimized conditions, the anodic photocurrent at 0 V vs KCl-saturated calomel electrode in 0.1 M phosphate buffer (pH 7.0) containing 0.100 M ascorbic acid was linear with the common logarithm of LIN concentration from 10.0 pM to 500 nM, with a limit of detection of 2.8 pM (S/N = 3). Satisfactory recovery results were obtained in the analysis of cow milk samples.

Synthesis, characterization and properties of sulfate-modified silver carbonate with enhanced visible light photocatalytic performance

Sulfate-modified Ag₂CO₃ was successfully synthesized via a simple precipitation method. Its visible light photocatalytic performance against the removal of Orange G was found to be significantly enhanced in comparison with the one of pure Ag₂CO₃. While SO₄^2--Ag₂CO₃ ensured a removal efficiency of 100% of OG within 30 min, the unmodified Ag₂CO₃ exhibited a degradation threshold at hardly 60%. Likewise, the degradation rate constant in the presence of SO₄^2--Ag₂CO₃ photocatalyst was assessed to be twice that determined upon the involvement of pristine Ag₂CO₃. Furthermore, Total Organic Carbon (TOC) measurements evidenced the occurrence of a quasi-total mineralization of the dye pollutant upon the use of SO₄^2--Ag₂CO₃ photocatalyst. Scavenger experiments highlighted the dominant role of photo-induced h⁺ along with ˙O₃^- ozonide radicals in the OG photocatalytic oxidation mechanism. Reuse cycles revealed that the modification by SO₄^2- is a promising route to improve the stability of silver carbonate against photocorrosion. All these improvements could be ascribed to electronic transfer from the upper SO₄^2- HOMO to the lower Ag₂CO₃ conduction band.

Multifunctional cotton with PANI-Ag NPs heterojunction for solar-driven water evaporation

Water evaporation using photothermal materials is a cost-effective and sustainable technology for alleviating the world's freshwater crisis, but oil contaminants and organic pollutants exist in the original water sources, which severely degrade the evaporation performance and pose environmental hazards. In this paper, we demonstrate a photothermal material (multifunctional cotton) that simultaneously demonstrates oil-resistance, organic pollutant removal, and a high water evaporation rate. A Schottky heterostructure was formed between polyaniline (PANI) and Ag NPs, which improved the photothermal conversion and achieved a water evaporation rate of 1.37 kg m^-2 h^-1 and photothermal conversion efficiency of 84.7% under one-sun illumination (1 kW m^-2). Notably, various organic pollutants in the water source were thoroughly removed by visible-light catalytic degradation and adsorption, which displayed efficiencies of 99.3% and 97%, respectively. The multifunctional cotton also possessed excellent superoleophobicity, and repelled oil contaminants and organic pollutants in water. Considering these merits, the as-prepared multifunctional cotton is an outstanding candidate for water evaporation from various sources.

Silver nanomaterials: synthesis and (electro/photo) catalytic applications

In view of their unique characteristics and properties, silver nanomaterials (Ag NMs) have been used not only in the field of nanomedicine but also for diverse advanced catalytic technologies. In this comprehensive review, light is shed on general synthetic approaches encompassing chemical reduction, sonochemical, microwave, and thermal treatment among the preparative methods for the syntheses of Ag-based NMs and their catalytic applications. Additionally, some of the latest innovative approaches such as continuous flow integrated with MW and other benign approaches have been emphasized that ultimately pave the way for sustainability. Moreover, the potential applications of emerging Ag NMs, including sub nanomaterials and single atoms, in the field of liquid-phase catalysis, photocatalysis, and electrocatalysis as well as a positive role of Ag NMs in catalytic reactions are meticulously summarized. The scientific interest in the synthesis and applications of Ag NMs lies in the integrated benefits of their catalytic activity, selectivity, stability, and recovery. Therefore, the rise and journey of Ag NM-based catalysts will inspire a new generation of chemists to tailor and design robust catalysts that can effectively tackle major environmental challenges and help to replace noble metals in advanced catalytic applications. This overview concludes by providing future perspectives on the research into Ag NMs in the arena of electrocatalysis and photocatalysis.

A critical review on strategies for improving efficiency of BaTiO3-based photocatalysts for wastewater treatment

Barium titanate (BaTiO₃) photocatalysts with perovskite structures are promising candidates for the effective removal of hazardous organic pollutants from water/wastewater owing to several advantages, including low cost, non-toxicity, high stability, environmental friendliness, favorable band positions, high oxygen vacancies, multiple crystal phases, rapid migration of charge carriers at the surface, band bending, spontaneous polarization, and easy tailoring of the sizes and morphologies. However, this high dielectric/ferroelectric material is only active in UV light (band gap: 3.2 eV), which reduces the photocatalytic degradation performance. To make barium titanate more suitable for photocatalysis, the surfaces of the powders can be modified to broaden the absorption band. In this paper, various strategies for improving photocatalysis of barium titanate for removing organic pollutants (mostly dyes and drugs) from water/wastewater are critically reviewed. They include modifying the sizes and morphologies of the particles by varying the reaction times and synthesis temperatures, doping with metals/non-metals, loading with noble metal NPs (Ag and Au), and fabrication of heterojunction photocatalysts (conventional type II and Z-scheme). The current challenges and possible future directions of BaTiO₃-based materials are also discussed. This comprehensive review is expected to advance the design of highly efficient BaTiO₃-based materials for photocatalytic applications in water/wastewater treatment.

Temperature-dependent phonon dynamics of Ag3PO4 microcrystals

In this work, we present the study of the temperature-dependent behavior of silver orthophosphate (Ag₃PO₄) microcrystals using in situ Raman scattering. The Ag₃PO₄ as-synthesized microcrystals were prepared by the precipitation method and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman and infrared spectroscopy, and differential scanning calorimetry (DSC). Temperature-dependent phonon dynamics were performed on Ag₃PO₄ microcrystals and pointed to a first-order phase transition in the temperature range 500-515 °C: Phase I (25-500 °C) → Phase II (515-590 °C). The phase transition is reversible and a temperature hysteresis was observed during the heating - cooling process: Phase II (590-470 °C) → Phase I (455-25 °C). The reversible phase transition is related to the distortion of the tetrahedral symmetry of PO₄ caused by the decrease in the crystalline order. DSC analysis confirmed the results of temperature-dependent Raman spectroscopy.

Strategic Doping Approach of the Fe-BiOI Microstructure: An Improved Photodegradation Efficiency of Tetracycline

The present study describes the strategic doping of Fe metal ions into a BiOI microstructure using ex situ and in situ processes to synthesize a Fe-BiOI microstructure and their effect on photocatalytic degradation of tetracycline (TC). The data suggested that in situ Fe-BiOI (Fe-BiOI-In) has superior performance compared to ex situ Fe-BiOI (Fe-BiOI-Ex) due to the uniform dispersion of Fe within the Fe-BiOI material. Calculated bandgaps ∼1.8, ∼1.5, and 2.4 eV were observed for BiOI (without Fe), Fe-BiOI-In, and Fe-BiOI-Ex, respectively. Interestingly, Fe incorporation within BiOI might decrease the bandgap in Fe-BiOI-In due to the uniform distribution of metal ions, whereas increasing the bandgap in Fe-BiOI-Ex attributed to nonuniform distribution or agglomeration of metal ions. The uniform dispersion of Fe within Fe-BiOI modulates electronic properties as well as increases the exposure of Fe ions with TC, thereby higher degradation efficiency of TC. The in situ Fe-BiOI material shows 67 and 100% degradation of TC at 10 and 1 mg/L, respectively. The TC degradation was also found to be pH-dependent; when increasing the pH value up to 10, 94% degradation was achieved at 10 mg/L within 60 min of solar irradiation. The analysis was also performed over BiOI, which proves that Fe has a profound effect on TC degradation as Fe(II) tends to trigger oxidation-reduction by utilizing the chelate formation tendency of TC. Therefore, the prepared Fe-BiOI-In has the potential ability to degrade pharmaceutical compounds, especially, TC from wastewater.

A critical review on modulation of NiMoO4-based materials for photocatalytic applications

Semiconductor photocatalysis has been widely utilized to solve the problems of energy shortage and environmental pollution. Among the explored photocatalysts, nickel molybdate (NiMoO₄) has revealed many advantages for photocatalytic applications, which include visible light absorption, low cost, environment-friendly, large surface area, good electrical conductivities, and tailorable band structure. However, the recombination of photogenerated carriers, which diminishes photocatalytic efficiency, has been held as a major hurdle to the widespread application of this material. To overcome this limitation, various surface modulations such as morphology control, doping of heteroatom, deposition of noble metal nanoparticles, and fabrication of composite structures have been explored in many published studies. This article comprehensively reviews the recent progress in the modulations of NiMoO₄-based materials to improve the photocatalytic efficiency. The enhanced photocatalytic capabilities of NiMoO₄-based materials are reviewed in terms of such applications as pollutant removal, disinfection of bacteria, and water splitting. The current challenges and possible future direction of research in this field are also highlighted. This comprehensive review is expected to advance the design of highly efficient NiMoO₄-based materials for photocatalytic applications.

Photocatalytic activity of new nanostructures of an Ag(i) metal–organic framework (Ag-MOF) for the efficient degradation of MCPA and 2,4-D herbicides under sunlight irradiation

A new Ag(i) metal–organic framework (Ag-MOF) [Ag(p-OH-C₆H₄COOH)₂(NO₃)]_n [Ag(PHBA)₂(NO₃)]_n, (1) (PHBA: C₈H₆O₄ {p-hydroxybenzoic acid}) was synthesized using two different methods; the laying method (single crystal) and sonochemical irradiation (nanostructures).

Novel Pt-Ag3PO4/CdS/Chitosan Nanocomposite with Enhanced Photocatalytic and Biological Activities

Decorating photocatalysts with noble metal nanoparticles (e.g., Pt) often increases the catalysts' photocatalytic activity and biomedical properties. Here, a simple and inexpensive method has been developed to prepare a Pt-Ag3PO4/CdS/chitosan composite, which was characterized and used for the visible light-induced photocatalytic and antibacterial studies. This synthesized composite showed superior photocatalytic activity for methylene blue degradation as a hazardous pollutant (the maximum dye degradation was observed in 90 min of treatment) and killing of Gram positive bacterial (Staphylococcus aureus and Bacillus cereus) as well as Gram negative bacteria (Klebsiella pneumoniae, Salmonella typhimurium, Escherichia coli, and Pseudomonas aeruginosa) under visible light irradiation. The antibacterial activity of CdS, CdS/Ag3PO4, and Pt-Ag3PO4/CdS/chitosan against E. coli, Pseudomonas aeruginosa, Salmonella typhimurium, Klebsiella pneumoniae, Staphylococcus aureus, and Bacillus cereus showed the zone of inhibition (mm) under visible light and under dark conditions at a concentration of 20 µg mL-1. Furthermore, the cell viability of the CdS/chitosan, Ag3PO4, Ag3PO4/CdS/chitosan, and Pt-Ag3PO4/CdS/chitosan were investigated on the human embryonic kidney 293 cells (HEK-293), Henrietta Lacks (HeLa), human liver cancer cell line (HepG2), and pheochromocytoma (PC12) cell lines. In addition, the results indicated that the photodegradation rate for Pt-Ag3PO4/CdS/chitosan is 3.53 times higher than that of CdS and 1.73 times higher than that of the CdS/Ag3PO4 composite. Moreover, Pt-Ag3PO4/CdS/chitosan with an optimal amount of CdS killed large areas of different bacteria and different cells separately in a shorter time period under visible-light irradiation, which shows significantly higher efficiency than pure CdS and other CdS/Ag3PO4 composites. The superb performances of this composite are attributed to its privileged properties, such as retarded recombination of photoinduced electron/hole pairs and a large specific surface area, making Pt-Ag3PO4/CdS/chitosan a valuable composite that can be deployed for a range of important applications, such as visible light-induced photocatalysis and antibacterial activity.

Silver-based semiconductor Z-scheme photocatalytic systems for environmental purification

Silver-based semiconductor photocatalysts are promising materials for solving environmental and energy issues due to their strong optical absorption, excellent quantum efficiency and photoelectrochemical properties. However, the uncontrollable photocorrosion and high use cost of single silver-based semiconductor photocatalysts limit its practical application. The construction of Z-scheme photocatalytic systems that mimic natural photosynthesis can not only enhance the photocatalytic activity of silver-based semiconductor photocatalysts, but also improve their stability and reduce the use costs. This critical review concisely highlights the basic principles of Z-scheme photocatalytic systems, and discusses the construction of silver-based semiconductor Z-scheme photocatalytic systems and the roles of metallic Ag in there and summarizes the synthesis methods of silver-based semiconductor Z-scheme photocatalytic systems. Then, a series of the solar-driven applications are elaborated, including organic pollutants degradation, hydrogen production, and carbon dioxide reduction. Meanwhile, the mechanism and difficult level of these photocatalytic reactions are also described. Besides, metal organic frameworks (MOFs) as a novel type of photocatalysts have attracted growing attention. The novel combination of silver-based semiconductors with typical photoactive MOFs is highlighted based on the Z-scheme photocatalytic systems. Eventually, the future challenges and prospects in the development of silver-based semiconductor Z-scheme photocatalytic systems are presented.

Activation of atom-precise clusters for catalysis

The use of atom-precise, ligand-protected metal clusters has exceptional promise towards the fabrication of model supported-nanoparticle heterogeneous catalysts which have controlled sizes and compositions. One major challenge in the field involves the ease at which metallic clusters sinter upon removal of protected ligands, thus destroying the structural integrity of the model system. This review focuses on methods used to activate atom-precise thiolate-stabilized clusters for heterogeneous catalysis, and strategies that can be used to mitigate sintering. Thermal activation is the most commonly employed approach to activate atom-precise metal clusters, though a variety of chemical and photochemical activation strategies have also been reported. Material chemistry methods that can mitigate sintering are also explored, which include overcoating of clusters with metal oxide supports fabricated by sol-gel chemistry or atomic layer deposition of thin oxide films or encapsulating clusters within porous supports. In addition to focusing on the preservation of the size and morphology of deprotected metal clusters, the fate of the removed ligands is also explored, because detached and/or oxidized ligands can also greatly influence the overall properties of the catalyst systems. We also show that modern characterization techniques such as X-ray absorption spectroscopy and high-resolution electron microscopy have the capacity to enable careful monitoring of particle sintering upon activation of metal clusters.

Graphene-based plasmonic nanocomposites for highly enhanced solar-driven photocatalytic activities

High-efficiency photocatalysts are crucial for the removal of organic pollutants and environmental sustainability. In the present work, we report on a new low-temperature hydrothermal chemical method, assisted by ultrasonication, to synthesize disruptive plasmonic ZnO/graphene/Ag/AgI nanocomposites for solar-driven photocatalysis. The plasmonic nanocomposites were investigated by a wide range of characterization techniques, confirming successful formation of photocatalysts with excellent degradation efficiency. Using Congo red as a model dye molecule, our experimental results demonstrated a photocatalytic reactivity exceeding 90% efficiency after one hour simulated solar irradiation. The significantly enhanced degradation efficiency is attributed to improved electronic properties of the nanocomposites by hybridization of the graphene and to the addition of Ag/AgI which generates a strong surface plasmon resonance effect in the metallic silver further improving the photocatalytic activity and stability under solar irradiation. Scavenger experiments suggest that superoxide and hydroxyl radicals are responsible for the photodegradation of Congo red. Our findings are important for the fundamental understanding of the photocatalytic mechanism of ZnO/graphene/Ag/AgI nanocomposites and can lead to further development of novel efficient photocatalyst materials.

High-efficiency of plasmonic ZnO/graphene/Ag/AgI nanocomposites for solar-driven photocatalysis activities.

Cobalt oxide as a selective co-catalyst for water oxidation in the presence of an organic dye

In photobiocatalytical processes involving the simultaneous oxidation of water and reduction of specific organic molecules (e.g., cofactors), the lack of physical separation of the redox half-reactions adversely affects the product stability. This is largely because organic molecules are generally less stable within harsh oxidative environments. In general, surface co-catalysts are able to improve the selectivity of photocatalysts towards water oxidation. However, harsh oxidative environments reduce the chemical stability of the organic molecules. Herein, we show that the use of Co₃O₄ as a surface co-catalyst on silver orthophosphate improve water photo-oxidation in the presence of organic dye molecules, such as methylene blue, that typically exhibits susceptibility toward photodegradation. The presence of Co₃O₄ on the photocatalyst surface prevents the adsorption of the organic dye, thus reducing its degradation rate. These findings provide a promising scenario for the visible light-driven reduction of organic molecules using water as an electron donor.

Multifunctionality of silver closo-boranes

Silver compounds share a rich history in technical applications including photography, catalysis, photocatalysis, cloud seeding and as antimicrobial agents. Here we present a class of silver compounds (Ag₂B₁₀H₁₀ and Ag₂B₁₂H₁₂) that are semiconductors with a bandgap at 2.3 eV in the green visible light spectrum. The silver boranes have extremely high ion conductivity and dynamic-anion facilitated Ag⁺ migration is suggested based on the structural model. The ion conductivity is enhanced more than two orders of magnitude at room temperature (up to 3.2 mS cm⁻¹) by substitution with AgI to form new compounds. Furthermore, the closo-boranes show extremely fast silver nano-filament growth when excited by electrons during transmission electron microscope investigations. Ag nano-filaments can also be reabsorbed back into Ag₂B₁₂H₁₂. These interesting properties demonstrate the multifunctionality of silver closo-boranes and open up avenues in a wide range of fields including photocatalysis, solid state ionics and nano-wire production.

Silver compounds have long been known to possess exceptional solid-state conductivity. Here the authors present silver closo-boranes in which facile Ag⁺ migration occurs, leading to exceptionally high ion conductivities and potential utility in silver nanowire production and photocatalysis due to their semiconductivity.

An Au/AgBr–Ag heterostructure plasmonic photocatalyst with enhanced catalytic activity under visible light

An efficient bimetallic–semiconductor (Au/AgBr–Ag) plasmonic heterostructure with plasmon enhanced absorption and plasmonic sensitization for visible light induced photocatalysis.

Synthesis and characterization of Z-scheme In2S3/Ag2CrO4 composites with an enhanced visible-light photocatalytic performance

Efficient charge transfer at the interfaces of an In₂S₃/Ag₂CrO₄ composite, due to the formation of a Z-scheme system between In₂S₃ and Ag₂CrO₄, effectively facilitates photogenerated electron–hole pair separation.

Metal-based quantum dots: synthesis, surface modification, transport and fate in aquatic environments and toxicity to microorganisms

The intense interest in metal-based QDs is diluted by the fact that they cause risks to aquatic environments.

Facile fabrication and enhanced visible-light photocatalytic activity of In2O3/Ag2CrO4 composites

The efficient charge transfer at the interfaces of In₂O₃/Ag₂CrO₄ composite due to the formation of Z-scheme system composed of In₂O₃, Ag and Ag₂CrO₄, which effectively improved the separation and transfer of photogenerated charge carriers.

Minuscule weight percent of graphene oxide and reduced graphene oxide modified Ag3PO4: new insight into improved photocatalytic activity

Improved photocatalytic activity of controllably reduced and minuscule weight percent graphene oxide modified Ag₃PO₄ composite.

New insights into Ag-doped BiVO4 microspheres as visible light photocatalysts

This study describes the synthesis of Ag–bismuth vanadate (Ag–BiVO₄) microspheres, a highly efficient visible light photocatalyst for the degradation of methylene blue, via a one-step hydrothermal method.