The role of polyvinylpyrrolidone (PVP) as a capping and structure-directing agent in the formation of Pt nanocubes

Modulating nanostructures with polyvinylpyrrolidone: Design and development of a porous, biocompatible, and pH-Stable core-shell magnetic microrobot for demonstrating drug absorption from wastewater

Increased antineoplastic drug concentrations in wastewater stem from ineffective treatment plants and increased usage. Although microrobots are promising for pollutant removal, they face hurdles in developing a superstructure with superior adsorption capabilities, biocompatibility, porosity, and pH stability. This study focused on adjusting the PVP concentration from 0.05 to 0.375 mM during synthesis to create a favorable CMOC structure for drug absorption. Lower PVP concentrations (0.05 mM) yielded a three-dimensional nanoflower structure of CaMoO4 and CuS nanostructures, whereas five-fold concentrations (0.25 mM) produced a porous structure with a dense CuS core encased in a transparent CaMoO4 shell. The magnetically movable and pH-stable COF@CMOC microrobot, achieved by attaching CMOC to cobalt ferrite (CoF) NPs, captured doxorubicin efficiently, with up to 57 % efficiency at 200 ng/mL concentration for 30 min, facilitated by electrostatic interaction, hydrogen bonding, and pore filling of DOX. The results demonstrated that DOX removal through magnetic motion showed superior performance, with an estimated improvement of 57% compared to stirring conditions (17 %). A prototype PDMS microchannel system was developed to study drug absorption and microrobot recovery. The CaMoO4 shell of the microrobots exhibited remarkable robustness, ensuring long-lasting functionality in harsh wastewater environments and improving biocompatibility while safeguarding the CuS core from degradation. Therefore, microrobots are a promising eco-friendly solution for drug extraction. These microrobots show promise for the selective removal of doxorubicin from contaminated wastewater.

Role of polyvinylpyrrolidone in the polyol synthesis of platinum nanoparticles

In this work, platinum (Pt) nanoparticles (NPs) were prepared via the reduction of Pt salts in an ethylene glycol induced polyol process with an altered polyvinylpyrrolidone (PVP)/Pt molar ratio. With the systematic elucidation of the hydrodynamic size in a liquid; the solid-state size and morphology, crystal structure, surface chemical state and thermal decomposition behavior of the synthesized Pt NPs; as well as the reducing dynamic of Pt cations, the role of PVP in the polyol synthesis of Pt NPs is clarified for the first time. It was found that the amount of PVP does not affect the reducing dynamic of Pt cations, but the chemical state of PVP capped on Pt NPs and the resultant particle size significantly depend on the initial PVP/Pt molar ratio in the precursor solution. Dense-packed PVP via the chemisorption of carbonyl oxygen on the surface of Pt NPs occurs in the case of a higher PVP/Pt ratio, suppressing particle growth and resulting in smaller Pt NPs. On the contrary, the chemical structure of PVP is tuned by the cleavage of the N-C bond and results in the chemisorption of the N atom on the surface of Pt NPs, which promotes the production of larger Pt NPs when a lower PVP/Pt ratio is applied.

Wet-Chemical Synthesis of Elemental 2D Materials

Wet-chemical synthesis refers to the bottom-up chemical synthesis in solution, which is among the most popular synthetic approaches towards functional two-dimensional (2D) materials. It offers several advantages, including cost-effectiveness, high yields,, precious control over the production process. As an emerging family of 2D materials, elemental 2D materials (Xenes) have shown great potential in various applications such as electronics, catalysts, biochemistry,, sensing technologies due to their exceptional/exotic properties such as large surface area, tunable band gap,, high carrier mobility. In this review, we provide a comprehensive overview of the current state-of-the-art in wet-chemical synthesis of Xenes including tellurene, bismuthene, antimonene, phosphorene,, arsenene. The current solvent compositions, process parameters utilized in wet-chemical synthesis, their effects on the thickness, stability of the resulting Xenes are also presented. Key factors considered involves ligands, precursors, surfactants, reaction time, temperature. Finally, we highlight recent advances, existing challenges in the current application of wet-chemical synthesis for Xenes production, provide perspectives on future improvement.

Development and evaluation of sildenafil/glycyrrhizin-loaded nanofibers as a potential novel buccal delivery system for erectile dysfunction

Erectile dysfunction (ED) is a growing health condition that needs safe and effective therapy. One of the main common treatments is sildenafil which is used in clinics for managing erectile dysfunction by enhancing the blood supply to the penis. In the current study, sildenafil was formulated as nanofibers and mixed with the root extract of Glycyrrhiza glabra (glycyrrhizin) as a natural sweetener to be administrated in the buccal cavity for enhanced drug bioavailability, rapid drug absorption and improved patient compliance. The formulated dual-loaded nanofibers were evaluated by measuring diameter, disintegration, drug loading efficiency, drug release profile, and in vitro cell viability assessment. The results showed that the sildenafil/glycyrrhizin-loaded fibers had a diameter of 0.719 ± 0.177 μm and lacked any beads and pores formation on their surfaces. The drug loading and encapsulation efficiency for sildenafil were measured as 52 ± 7 µg/mg and 67 ± 9 %, respectively, while they were 290 ± 32 μg/mg and 94 ± 10 %, respectively, for glycyrrhizin. The release rate of sildenafil and glycyrrhizin demonstrated a burst release in the first minute, followed by a gradual increment until a complete release after 120 min. The in vitro cell viability evaluation exhibited that the application of sildenafil and glycyrrhizin is safe upon 24-hour treatment on human skin fibroblast cells at all used concentrations (i.e., ≤ 1,000 and 4,000 μg/mL, respectively). However, the application of sildenafil-glycyrrhizin combination (in a ratio of 1:4) demonstrated more than 80 % cell viability at concentrations of ≤ 250 and 1000 μg/mL, respectively, following 24-hour cell exposure. Therefore, sildenafil/glycyrrhizin dual-loaded PVP nanofibers showed a potential buccal therapeutic approach for erectile dysfunction management.

Capping Agents Enable Well-Dispersed and Colloidally Stable Metallic Magnesium Nanoparticles

Mg nanoparticles are an emerging plasmonic material due to Mg's abundance and ability to sustain size- and shape-dependent localized surface plasmon resonances across a broad range of wavelengths from the ultraviolet to the near infrared. However, Mg nanoparticles are colloidally unstable due to their tendency to aggregate and sediment. Nanoparticle aggregation can be inhibited by the addition of capping agents that impart surface charges or steric repulsion. Here, we report that the common capping agents poly(vinyl) pyrrolidone (PVP), polyethylene glycol (PEG), cetyltrimethylammonium bromide (CTAB), and sodium dodecyl sulfate (SDS) interact differently and have varied effects on the aggregation and colloidal stability of Mg nanoparticles. Nanoparticles synthesized in the presence of PVP showed improvements in colloidal stability and reduced aggregation, as observed by electron microscopy and optical spectroscopy. The binding of PVP was confirmed through infrared and X-ray photoelectron spectroscopy. The influence of PVP on the reduction of di-n-butyl magnesium was evaluated through analysis of particle size distribution and Mg yield as a function of reaction time, reducing agent, and temperature. Furthermore, the presence of PVP drastically changes the growth pattern of metallic Mg structures obtained from the reduction of the Grignard reagents butylmagnesium chloride and phenylmagnesium chloride by lithium naphthalenide: large polycrystalline aggregates and well-separated faceted nanoparticles grow without and with PVP, respectively. This study provides new synthetic routes that generate colloidally stable and well-dispersed Mg nanoparticles for plasmonic and other applications.

Effect of PVP Molecular Weights on the Synthesis of Ultrasmall Cus Nanoflakes: Synthesis, Properties, and Potential Application for Phototheranostics

Copper sulfide nanoparticles (CuS) hold tremendous potential for applications in photothermal therapy (PTT) and photoacoustic imaging (PAI). However, the conventional chemical coprecipitation method often leads to particle agglomeration issues. To overcome this challenge, we utilized polyvinylpyrrolidone (PVP) as a stabilizing agent, resulting in the synthesis of small PVP-CuS nanoparticles named PC10, PCK30, and PC40. Our study aimed to investigate how different molecular weights of PVP influence the nanoparticles' crystalline characteristics and essential properties, especially their photoacoustic and photothermal responses. While prior research on PVP-assisted CuS nanoparticles has been conducted, our study delves deeper into this area, providing insights into optical properties. Remarkably, all synthesized nanoparticles exhibited a crystalline structure, were smaller than 10 nm, and featured an absorbance peak at 1020 nm, indicating their robust photoacoustic and photothermal capabilities. Among these nanoparticles, PC10 emerged as the standout performer, displaying superior photoacoustic properties. Our photothermal experiments demonstrated significant temperature increases in all cases, with PC10 achieving an impressive efficiency of 51%. Moreover, cytotoxicity assays revealed the nanoparticles' compatibility with cells, coupled with an enhanced incidence of apoptosis compared to necrosis. These findings underscore the promising potential of PVP-stabilized CuS nanoparticles for advanced cancer theranostics.

PEG-PVP-Assisted Hydrothermal Synthesis and Electrochemical Performance of N-Doped MoS2/C Composites as Anode Material for Lithium-Ion Batteries

Molybdenum disulfide shows promise as an anode material for lithium-ion batteries. However, its commercial potential has been constrained due to the poor conductivity and significant volume expansion during the charge/discharge cycles. To address these issues, in this study, N-doped MoS2/C composites (NMC) were prepared via an enhanced hydrothermal method, using ammonium molybdate and thiourea as molybdenum and sulfur sources, respectively. Polyethylene glycol 400 (PEG400) and polyvinylpyrrolidone (PVP) were added in the hydrothermal procedure as soft template surfactants and nitrogen/carbon sources. The crystal structure, morphology, elemental composition, and surface valence state of the N-doped MoS2/C composites were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS), respectively. The results indicate that the NMC prepared by this method are spherical particles with a nanoflower-like structure composed of MoS2 flakes, having an average particle size of about 500 nm. XPS analysis shows the existence of C and N elements in the samples as C-N, C-C, and pyrrolic N. As anodes for LIBs, the NMC without annealing deliver an initial discharge capacity of 548.2 mAh·g-1 at a current density of 500 mA·g-1. However, this capacity decays in the following cycles with a discharge capacity of 66.4 mAh·g-1 and a capacity retention rate of only 12% after 50 cycles. In contrast, the electrochemical properties of the counterparts are enhanced after annealing, which exhibits an initial discharge capacity of 575.9 mAh·g-1 and an ultimate discharge capacity of 669.2 mAh·g-1 after 70 cycles. The capacity retention rate decreases initially but later increases and elevated afterward to reach 116% at the 70th cycle, indicating an improvement in charge-discharge performance. The specimens after annealing have a smaller impedance, which indicates better charge transport and lithium-ion diffusion performance.

Adsorption characteristics and mechanisms of water-soluble polymers (PVP and PEG) on kaolin and montmorillonite minerals

The excessive use and accumulation of water-soluble polymers (WSPs, known as "liquid plastics") in the environment can pose potential risks to both ecosystems and human health, but the environmental fate of WSPs remains unclear. Here, the adsorption behavior of WSPs with different molecular weight on kaolinite (Kaol) and montmorillonite (Mt) were examined. The results showed that the adsorption of PEG and PVP on minerals were controlled by hydrogen bond and van der Waals force. The Fourier transform infrared (FTIR) spectra and two-dimensional correlation spectroscopy (2D-COS) analysis revealed that there were interactions between the Al-O and Si-O groups of the minerals and the polar O- or N-containing functional groups as well as the alkyl groups of PEG and PVP. The adsorption characteristics of WSPs were closely related to their molecular weight and the pore size of minerals. Due to the relatively large mesopore size of Kaol, both PEG and PVP were absorbed into inner spaces, for which the adsorption capacity increased with molecular weight of the polymers. For Mt, all types of PEG could enter its micropores, while PVP with larger molecular weights appeared to be confined externally, leading to a decrease in the adsorption capacity of PVP with increasing molecular weight. The findings of this study provide a theoretical basis for scientific evaluation of environmental processes of WSPs.

A Fisetin Delivery System for Neuroprotection: A Co-Amorphous Dispersion Prepared in Supercritical Carbon Dioxide

Fisetin (FIS), a senolytic flavonoid, mitigates age-related neuroprotective changes. An amorphous FIS dispersion with a co-carrier was prepared using supercritical fluid extraction with carbon dioxide (scCO2). Characterisation, including powder X-ray diffraction and Fourier-transform infrared spectroscopy, confirmed amorphization and assessed intermolecular interactions. The amorphous FIS dispersion exhibited enhanced solubility, dissolution profiles, and bioavailability compared to the crystalline form. In vitro, the amorphous FIS dispersion demonstrated antioxidant activity (the ABTS, CUPRAC, DDPH, FRAP assays) and neuroprotective effects by inhibiting acetylcholinesterase and butyrylcholinesterase. FIS modulated gut microbiota, reducing potentially pathogenic gram-negative bacteria without affecting probiotic microflora. These improvements in solubility, antioxidant and neuroprotective activities, and gut microbiome modulation suggest the potential for optimising FIS delivery systems to leverage its health-promoting properties while addressing oral functionality limitations.

Synthesis of Ag nanoparticles for selective dual detection of glutathione and dopamine using N, N-dimethyl-p-phenylenediamine mediated colorimetric probe

We report a simple and easy method to synthesize Ag nanoparticles (Ag NPs) and demonstrate its potential for the detection of glutathione (GSH) and dopamine (DA) via colorimetric assay. The Ag NPs were found to be monodispersed and spherical with a size of 5 ± 2 nm. The X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM) investigations revealed the formation of crystalline Ag NPs. The colour of N, N-dimethyl-p-phenylenediamine assay changed from dark pink to colourless when the concentration of GSH was increased from 1 to 40 μM. Notably, the suspension colour changed from dark pink to blue when a similar set of experiments were performed with DA. The UV/Visible and interference experiments of Ag NPs exhibited excellent sensitivity and selectivity against both GSH and DA even after the addition of 40 μM of different interference biomolecules. The calculated limit of detection (LOD) was 141 and 245 nM for GSH and DA, respectively. The real-time analysis with serum samples showed satisfactory recovery percentages of >95 and 80-90% for GSH and DA, respectively. Hence, the Ag NPs reported here have huge potential to serve as a sensitive and selective colorimetric sensor for the detection of GSH and DA for diverse applications ranging from catalysis to cancer therapy and theranostics.

Heterostructured Ag@MOF-801/MIL-88A(Fe) Nanocomposite as a Biocompatible Photocatalyst for Degradation of Reactive Black 5 under Visible Light

Heterostructured Ag@MOF-801/MIL-88A(Fe) nanocomposite was synthesized through template effects in metal-organic frameworks (MOFs). MIL-88A(Fe) was fabricated on a MOF-801 template using the internal extended growth method (IEGM) via polyvinylpyrrolidone (PVP) as the structure-director agent to create the MIL-88A(Fe)-on-MOF-801 heterostructure. The MOF-801/MIL-88A(Fe) heterostructure was used as a template for the formation of Ag nanoparticles (NPs) inside it via a double solvents method (DSM) combined with a photoreduction route (PR). To characterize synthesized samples to a high level of detail, PXRD, FT-IR, EDX, N2 adsorption-desorption isotherms, TEM, DRS, PL, EIS, and Mott-Sckottky measurements were used. The resulting Ag@MOF-801/MIL-88A(Fe) nanocomposite demonstrated the highest photocatalytic activity of 91.72% for the degradation of Reactive Black 5, after 30 min under visible light irradiation.

Relationship between the Polymer Blend Using Chitosan, Polyethylene Glycol, Polyvinyl Alcohol, Polyvinylpyrrolidone, and Antimicrobial Activities against Staphylococcus aureus

The findings from Pareto charts, main effect plots, and interaction plots demonstrate the importance of polymer concentration. Increasing concentration improves the inhibition percentage and decreases the MIC50. However, the primary factor that influences these changes is chitosan (CS). Additionally, the interaction between CS and PVP, along with other polymers, plays a crucial role in achieving better antimicrobial effects. These results enhance our understanding of the antimicrobial properties of the studied polymers and offer valuable insights for developing effective antimicrobial formulations. The MIC50 value of M1-M16 was at a polymer percentage of 12.5%. At 12.5% polymer percentage, with the limits of [PVA], [PEG], and [PVP] being 0.002-0.004 g/mL and [CS] being 0.001-0.002 g/mL, using the 2-level full factorial method, the inhibition percentage is equal to 174.1 - 27,812 PVA - 18,561 PVP - 25,960 PEG - 38,752 CS + 9,263,047 PVA*PVP + 10,430,763 PVA*PEG + 15,397,157 PVA*CS + 7,088,313 PVP*PEG + 7,841,221 PVP*CS + 14,228,046 PEG*CS - 3,367,292,860 PVA*PVP*PEG - 5,671,998,721 PVA*PVP*CS - 6,619,041,275 PVA*PEG*CS - 3,917,095,529 PVP*PEG*CS + 2,273,661,969,470 PVA*PVP*PEG*CS. Theoretically, the most economical concentrations of PVA, PVP, PEG, and CS are 0.002, 0.002, 0.002, and 0.001 mg/mL at a concentration of 12.5% to reach an inhibition percentage of 99.162%, which coincides with the MBC value.

Guar gum-based stimuli responsive hydrogels for sustained release of diclofenac sodium

In the current study, hydrogels for the controlled release of diclofenac sodium were synthesized from graphene oxide-reinforced guar gum and poly (N-vinyl-2-pyrrolidone) using the Solution Casting Technique. Varying concentrations of 3-Glycidyloxypropyl trimethoxysilane (GLYMO) were employed for the crosslinking of hydrogels. Further, the characterization of hydrogels was carried out using different techniques such as Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction, thermal analysis and scanning electron microscope. The FTIR investigations reveals particular functionalities and development of hydrogel interfaces. While thermal analysis prophesied that, improvement in forces among hydrogel components is directly proportional to the GLYMO concentration. In-vitro biodegradation test and cell viability assay against HEK-293 cell lines confirmed their biodegradable and biocompatible nature. GPG-32 demonstrated maximum antibacterial activity against P.aeruginosa and E.coli strains. The maximum swelling 2001 % and 1814 % in distilled water were recorded for GPG (control) and GPG-8 respectively that obeyed Fick's law. Hydrogels displayed high swelling responses at pH 6 in buffer and non-buffer solutions. In 2.5 h, 88.7 % diclofenac sodium was released which was determined by UV visible spectrophotometer. In conclusion, guar gum-based non-toxic, biocompatible and biodegradable hydrogels would be a model platform for targeting inflammation and pains. Furthermore, improved mechanical and viscoelastic behavior of hydrogels could also be explored for making drug loaded dressings for wound healing applications.

Effectiveness of different CuO morphologies nanomaterials on the permeability, antifouling, and mechanical properties of PVDF/PVP/CuO ultrafiltration membrane for water treatment

The hydrophobic nature of Poly (vinylidene fluoride) (PVDF) is a significant barrier to use in ultrafiltration, resulting in fouling, flux decline, and reduced lifespan in water treatment. This study examines the effectiveness of different morphologies of CuO nanomaterials (NMs) (spherical, rod, plate, and flower), synthesized by the facile hydrothermal method, to modify PVDF membrane with PVP additive for improving the performance of water permeability and antifouling. Such membrane configurations with different morphologies of CuO NMs improved hydrophilicity with a maximum water flux of 222-263 L m-2h-1 compared to 195 L m-2h-1 for the bare membrane and exhibited excellent thermal and mechanical strengths. The characterization results exhibited that plate-like CuO NMs were dispersed uniformly in the membrane matrix, and their incorporation as a composite improved the membrane properties. From the antifouling test with the bovine serum albumin (BSA) solution, the membrane with plate-like CuO NMs had the highest flux recovery ratio (FRR) (∼91%) and the lowest irreversible fouling ratio (∼10%). The antifouling enhancement was due to less interaction between modified membranes and foulant. Further, the nanocomposite membrane showed excellent stability and negligible Cu2+ ion leaching. Overall, our findings provide a new strategy for developing inorganic nanocomposite PVDF membranes for water treatment.

PVP encapsulated MXene coated on PET surface (PMP)-based photocatalytic materials: A novel photo-responsive assembly for the removal of tetracycline

Tetracycline (TC) antibiotic that is effective against wide-range micro-organisms, thereby used to control bacterial infection. The partial metabolism of TC antibiotics in humans and animals leads to the contamination of TC in the environments like water bodies. Thus, requirements to treat/remove/degrade TC antibiotics from the water bodies to control environmental pollution. In this context, this study focuses on fabricating PVP-MXene-PET (PMP) based photo-responsive materials to degrade TC antibiotics from the water. Initially, MXene (Ti2CTx) was synthesized using a simple etching process from the MAX phase (Ti3AlC2). The synthesized MXene was encapsulated using PVP and cast onto the surface of PET to fabricate PMP-based photo-responsive materials. The rough surface and micron/nano-sized pores within the PMP-based photo-responsive materials might be improved the photo-degradation of TC antibiotics. The synthesized PMP-based photo-responsive materials were tested against the photo-degradation of TC antibiotics. The band gap value of the MXene and PMP-based photo-responsive materials was calculated to be ∼1.23 and 1.67 eV. Incorporating PVP within the MXene increased the band gap value, which might be beneficial for the photo-degradation of TC, as the minimum band gap value should be ∼1.23 eV or more for photocatalytic application. The highest photo-degradation of ∼83% was achieved using PMP-based photo-degradation at 0.1 mg/L of TC. Furthermore, ∼99.71% of photo-degradation of TC antibiotics was accomplished at pH ∼10. Therefore, the fabricated PMP-based photo-responsive materials might be next-generation devices/materials that efficiently degrade TC antibiotics from the water.

Elucidating the Role of Capping Agents in Facet-Dependent Adsorption Performance of Hematite Nanostructures

Organic capping agents are a ubiquitous and crucial part of preparing reproducible and homogeneous batches of nanomaterials, particularly nanocrystals with well-defined facets. Despite studies reporting surface ligands (e.g., capping agents) having a non-negligible role in catalytic behavior, their impact is less understood in contaminant adsorption, an important consideration given their potential to obfuscate facet-dependent trends in performance. To ascribe observed behaviors to the facet or the ligand, this report evaluates the impact of poly(N-vinyl-2-pyrrolidone) (PVP), a commonly utilized capping agent, on the adsorption performance of nanohematite particles of varying prevailing facet in the removal of selenite (Se(IV)) as a model system. The PVP capping agent reduces the available surface area for contaminant binding, thus resulting in a reduction in overall Se(IV) adsorbed. However, accounting for the effects of surface area, {012}-faceted nanohematite demonstrates a significantly higher sorption capacity for Se(IV) compared with that of {001}-faceted nanohematite. Notably, chemical treatment is minimally effective in removing strongly bound PVP, indicating that complete removal of surface ligands remains challenging.

Study of Gold Nanoparticles Conjugated with SARS-CoV-2 S1 Spike Protein Fragments

This study reports on the successful conjugation of SARS-CoV-2 S1 spike protein fragments with gold nanoparticles (AuNPs) that were synthesised with Ultrasonic Spray Pyrolysis (USP). This method enables the continuous synthesis of AuNPs with a high degree of purity, round shapes, and the formation of a surface that allows various modifications. The conjugation mechanism of USP synthesized AuNPs with SARS-CoV-2 S1 spike protein fragments was investigated. A gel electrophoresis experiment confirmed the successful conjugation of AuNPs with SARS-CoV-2 S1 fragments indirectly. X-ray Photoelectron Spectroscopy (XPS) analysis confirmed the presence of characteristic O1s and N1s peaks, which indicated that specific binding between AuNPs and SARS-CoV-2 S1 spike protein fragments takes place via a peptide bond formed with the citrate stabiliser. This bond is coordinated to the AuNP's surface and the N-terminals of the protein, with the conjugate displaying the expected response within a prototype LFIA test. This study will help in better understanding the behaviour of AuNPs synthesised with USP and their potential use as sensors in colorimetric or electrochemical sensors and LFIA tests.

Electrospun Fibrous Materials with Propolis Extracts for Edible Food Packagings

In this study, propolis additives provide antibacterial and antifungal effects that prolong the product's shelf life. The aim of the study is to obtain homogeneous fiber membranes of polyvinyl alcohol and propolis by the electrospinning method and to evaluate their suitability for food packaging. Three propolis extracts are used in the study-water, ethyl alcohol, and glycerin-based. The membranes' morphology and fiber diameter distribution, tensile deformation, air permeability, thermogravimetric analysis, differential scanning calorimetry, Fourier-transform infrared spectroscopy, and microbiological tests (Listeria monocytogenes, Salmonella enteritidis, Escherichia coli) were analyzed for electrospun samples. The results of the study show that propolis extracts are incorporated into membranes and the additive provides an antimicrobial effect with the contact surface. The obtained membranes are breathable: gas exchange can be controlled by using a material of appropriate thickness (air permeability coefficient is 0.046 and 0.276 mm/s). The mechanical properties of membranes are affected by moisture, but tensile strength can be improved with thermal post-processing at 100 °C. The propolis-containing fibers' diameters are from 293 ± 8 to 664 ± 11 nm. Depending on membranes' demonstrated properties, it can be concluded that the composites have the potential to increase the shelf life of fresh fruits and berries.

Enhanced photocatalytic performance of auto-combusted nanoparticles for photocatalytic degradation of azo dye under sunlight illumination and hydrogen fuel production

In this study, an innovative nanomaterial was synthesized for hydrogen production from methanolysis on sodium borohydride (NaBH₄) in order to be a solution for future energy problems. The nanocomposite containing FeCo, which does not contain noble metals, and whose support material is Polyvinylpyrrolidone (PVP), was synthesized by means of a thermal method. TEM, XRD and FTIR characterization methods were used for the analysis of the morphological and chemical structure of the nanocomposite. Nanocomposite particle size was 2.59 nm according to XRD and 5.45 nm according to TEM analysis for scale of 50 nm. For catalytic properties of nanomaterial in the methanolysis reaction of NaBH₄, temperature, catalyst, substrate, and reusability experiments were carried out and kinetic calculations were obtained. Among the activation parameters of FeCo@PVP nanoparticles, turnover frequency, enthalpy, entropy and activation energy were calculated as 3858.9 min^-1, 29.39 kJ/mol, -139.7 J/mol.K, and 31.93 kJ/mol, respectively. As a result of the reusability test of the obtained FeCo@PVP nanoparticles catalysts, which was carried out for 4 cycles, the catalytic activity was 77%. Catalytic activity results are given in comparison with the literature. In addition, the photocatalytic activity of FeCo@PVP NPs was evaluated against MB azo dye under solar light irradiation for 75 min and was found to be as 94%.

Ligand Chemistry in Antitumor Theranostic Nanoparticles

ConspectusTheranostic nanoparticles' potential in tumor treatment has been widely acknowledged thanks to their capability of integrating multifaceted functionalities into a single nanosystem. Theranostic nanoparticles are typically equipped with an inorganic core with exploitable physical properties for imaging and therapeutic functions, bioinert coatings for improved biocompatibility and immunological stealth, controlled drug-loading-release modules, and the ability to recognize specific cell type for uptake. Integrating multiple functionalities in a single nanosized construct require sophisticated molecular design and precise execution of assembly procedures. Underlying the multifunctionality of theranostic nanoparticles, ligand chemistry plays a decisive role in translating theoretical designs into fully functionalized theranostic nanoparticles. The ligand hierarchy in theranostic nanoparticles is usually threefold. As they serve to passivate the nanoparticle's surface, capping ligands form the first layer directly interfacing with the crystalline lattice of the inorganic core. The size and shape of nanoparticles are largely determined by the molecular property of capping ligands so that they have profound influences on the nanoparticles' surface chemistry and physical properties. Capping ligands are mostly chemically inert, which necessitates the presence of additional ligands for drug loading and tumor targeting. The second layer is commonly utilized for drug loading. Therapeutic drugs can either be covalently conjugated onto the capping layer or noncovalently loaded onto nanoparticles via drug-loading ligands. Drug-loading ligands need to be equally versatile in properties to accommodate the diversity of drugs. Biodegradable moieties are often incorporated into drug-loading ligands to enable smart drug release. With the aid of targeting ligands which usually stand the tallest on the nanoparticle surface to seek and bind to their corresponding receptors on the target, theranostic nanoparticles can preferentially accumulate at the tumor site to attain a higher precision and quantity for drug delivery. In this Account, the properties and utilities of representative capping ligands, drug-loading ligands, and targeting ligands are reviewed. Since these types of ligands are often assembled in close vicinity to each other, it is essential for them to be chemically compatible and able to function in tandem with each other. Relevant conjugation strategies and critical factors with a significant impact on ligands' performance on nanoparticles are discussed. Representative theranostic nanoparticles are presented to showcase how different types of ligands function synergistically from a single nanosystem. Finally, the technological outlook of evolving ligand chemistry on theranostic nanoparticles is provided.

Graphene oxide reinforced biopolymeric (chitosan) hydrogels for controlled cephradine release

In the current study, chitosan, poly (N-vinyl-2-pyrolidone) and polyamidoamine based hydrogels were prepared by Solution Casting Method using different quantity of graphene oxide (GO) for controlled cephradine (CPD) release. The hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, thermal analysis, scanning electron microscope and atomic force microscopy. FTIR results endorsed the presence of particular functionalities and developed interfaces in hydrogels. The thermal stability was directly proportional to the amount of GO. Antibacterial activity was investigated against gram-negative bacteria resultantly; CAD-2 exhibited maximum bactericidal activity against Escherichia coli and Psuedomonas aeruginosa. In addition, in-vitro biodegradation was examined in phosphate buffer saline solution and proteinase K for 21 and 07 days respectively. The maximum swelling was exhibited by CAD-133777 % in distilled water that was governed by quasi-Fickian diffusion. The swelling volumes were inversely proportional to the amount of GO. In the same way, pH sensitive CPD release was detected by UV visible spectrophotometer that followed zero order and Higuchi models. However, in 4 h, 89.4 % and 83.7 % of CPD was released in PBS and SIF solution correspondingly. Therefore, the chitosan-based biocompatible and biodegradable hydrogel platforms offered substantial potential for the controlled CPD release in medico-biological applications.

Polyvinylpyrrolidone Nanofibers Incorporating Mesoporous Bioactive Glass for Bone Tissue Engineering

Composite biomaterials that combine osteoconductive and osteoinductive properties are a promising approach for bone tissue engineering (BTE) since they stimulate osteogenesis while mimicking extracellular matrix (ECM) morphology. In this context, the aim of the present research was to produce polyvinylpyrrolidone (PVP) nanofibers containing mesoporous bioactive glass (MBG) 80S15 nanoparticles. These composite materials were produced by the electrospinning technique. Design of experiments (DOE) was used to estimate the optimal electrospinning parameters to reduce average fiber diameter. The polymeric matrices were thermally crosslinked under different conditions, and the fibers' morphology was studied using scanning electron microscopy (SEM). Evaluation of the mechanical properties of nanofibrous mats revealed a dependence on thermal crosslinking parameters and on the presence of MBG 80S15 particles inside the polymeric fibers. Degradation tests indicated that the presence of MBG led to a faster degradation of nanofibrous mats and to a higher swelling capacity. The assessment of in vitro bioactivity in simulated body fluid (SBF) was performed using MBG pellets and PVP/MBG (1:1) composites to assess if the bioactive properties of MBG 80S15 were kept when it was incorporated into PVP nanofibers. FTIR and XRD analysis along with SEM-EDS results indicated that a hydroxy-carbonate apatite (HCA) layer formed on the surface of MBG pellets and nanofibrous webs after soaking in SBF over different time periods. In general, the materials revealed no cytotoxic effects on the Saos-2 cell line. The overall results for the materials produced show the potential of the composites to be used in BTE.

Catalytic performance of PVP-coated CuO nanosheets under environmentally friendly conditions

Aromatic nitro compounds are an increasing concern worldwide due to their potential toxicity, prompting a quest for efficient removal approaches. This study established a simple and environmentally friendly method to synthesize a highly efficient, recoverable and stable CuO nanosheets catalyst to overcome public health and environmental problems caused by nitro aromatic compounds. In the current research, the effect of different concentrations of copper nitrate on the size and shape of CuO nanostructures in the chemical synthesis was studied. The CuO nanosheets were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectrophotometry. It was found that at concentrations of 0.07 M and 0.1 M of copper nitrate, pure CuO was formed. The FTIR results showed that carbonyl group in PVP coordinated with CuO and formed a protective layer. The as-synthesized CuO nanosheets with an average width of 60 ± 23 nm and length of 579 ± 154 were used as a catalyst for highly selective and efficient reduction of aromatic nitro and aromatic carboxylic acid to the corresponding amine and alcohol compounds. The reduction reaction was monitored by either UV-Vis absorption spectroscopy or high performance liquid chromatography (HPLC). 4-Nitrophenol and 4-nitroaniline were reduced to corresponding amine compounds within 12 min and 6 min, respectively in the presence of a reasonable amount of catalyst and reducing agent. The CuO nanosheets also exhibited excellent stability. The catalyst can be reused without loss of its activity after ten runs.

Colloidal metal nanocatalysts to advance orange II hydrogenolysis tracked by a microplate reader

The thermal reduction method was applied to synthesize metal nanoparticles using poly(1-vinyl-2-pyrrolidone) as an organic stabilizer to control metal nanoparticle agglomeration. Colloidal metal nanoparticles, gold, palladium, and gold–palladium nanoparticles were synthesized, and UV–visible spectrophotometry and high-resolution transmission electron microscopy analyses were conducted to characterize them. The metal nanoparticle micrographs showed well-dispersed particles with an average size of 9.6 nm (Au), 15.4 nm (Pd), and 10.6 nm (AuPd). All the colloidal metal nanoparticles served as nanocatalysts to advance a reductive degradation of orange II in presence of borohydride ions. For a prompt screening of catalytic activity, the microplate reader system was considered at a fixed maximum absorbance wavelength of λ 489 nm respected by orange II. Excess borohydride ions were used to construct pseudo-first kinetic conditions. The Langmuir–Hinshelwood model allowed the finding of kinetic activity on the surface of metal nanoparticles. AuPd nanocatalyst interface exhibited low activation energy (5.38 kJ mol−1) compared to the one on Au (8.19 kJ mol−1) and Pd (7.23 kJ mol−1).

Graphical Abstract

Polyvinylpyrrolidone-passivated fluorescent iron oxide quantum dots for turn-off detection of tetracycline in biological fluids

Tetracycline is an antibiotic that has been prescribed for COVID-19 treatment, raising concerns about antibiotic resistance after long-term use. This study reported fluorescent polyvinylpyrrolidone-passivated iron oxide quantum dots (IO QDs) for detecting tetracycline in biological fluids for the first time. The as-prepared IO QDs have an average size of 2.84 nm and exist a good stability under different conditions. The IO QDs' tetracycline detection performance could be attributed to a combination of static quenching and inner filter effect. The IO QDs displayed high sensitivity and selectivity toward tetracycline and achieved a good linear relationship with the corresponding detection limit being 91.6 nM.

PVC containing silver nanoparticles with antimicrobial properties effective against SARS-CoV-2

Poly (vinyl chloride) (PVC) is commonly used to manufacture biomedical devices and hospital components, but it does not present antimicrobial activity enough to prevent biofouling. With the emergence of new microorganisms and viruses, such as Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) that was responsible for the global pandemic caused by Coronavirus Disease 2019 (COVID-19), it is evident the importance of the development of self-disinfectant PVC for hospital environments and medical clinics where infected people remain for a long time. In this contribution, PVC nanocomposites with silver nanoparticles (AgNPs) were prepared in the molten state. AgNPs are well-known as antimicrobial agents suitable for designing antimicrobial polymer nanocomposites. Adding 0.1 to 0.5 wt% AgNPs significantly reduced Young’s modulus and ultimate tensile strength of PVC due to the emergence of microstructural defects in the PVC/AgNP nanocomposites, but the impact strength did not change significantly. Furthermore, nanocomposites have a higher yellowness index (YI) and lower optical bandgap values than PVC. The PVC/AgNP nanocomposites present virucidal activity against SARS-CoV-2 (B.1.1.28 strain) within 48 h when the AgNP content is at least 0.3 wt%, suitable for manufacturing furniture and hospital equipment with self-disinfectant capacity to avoid secondary routes of COVID-19 contagion.

Two-Dimensional Metal Nanostructures: From Theoretical Understanding to Experiment

This paper reviews recent studies on the preparation of two-dimensional (2D) metal nanostructures, particularly nanosheets. As metal often exists in the high-symmetry crystal phase, such as face centered cubic structures, reducing the symmetry is often needed for the formation of low-dimensional nanostructures. Recent advances in characterization and theory allow for a deeper understanding of the formation of 2D nanostructures. This Review firstly describes the relevant theoretical framework to help the experimentalists understand chemical driving forces for the synthesis of 2D metal nanostructures, followed by examples on the shape control of different metals. Recent applications of 2D metal nanostructures, including catalysis, bioimaging, plasmonics, and sensing, are discussed. We end the Review with a summary and outlook of the challenges and opportunities in the design, synthesis, and application of 2D metal nanostructures.

Experimental and DFT studies on the structural and optical properties of chitosan/polyvinyl pyrrolidone/ZnS nanocomposites

Chitosan/Polyvinyl pyrrolidone (CS/PVP) semi-natural polymeric blend involving gradient concentrations of ZnS nanoparticles (ZnS-NPS) was prepared via a simple casting method. In conjunction with computational density functional theory approaches (DFT), prepared samples were characterized by UV/Vis spectrophotometric studies and Fourier transform infrared measurements (FTIR) to take into account a detailed description of the different reaction mechanisms within the polymeric matrices. To conduct all calculations, the Becke three-parameter hybrid functional (B3LYP) correlation function used with the electron core potential basis set LANL2DZ was used. A detailed study of different reaction regimes was studied and reaction via Oxygen was observed to be preferred and compatible with that of the experimental data. UV/vis. Absorption experimental data were used to calculate the optical energy gap using the Mott-Davis equation and observed data was found to follow an indirect transition route.

Preliminary investigation on the impact of engineered PVP-capped and uncapped silver nanoparticles on Eudrilus eugeniae, a terrestrial ecosystem model

Recently, the production of silver nanoparticles and their commercial products has generated increased concern and caused a hazardous impact on the ecosystem. Therefore, the present study examines the toxic effect of chemically engineered silver nanoparticles (SNPs) and polyvinylpyrrolidone-capped silver nanoparticles (PVP-SNPs) on the earthworm Eudrilus eugeniae (E. eugeniae). The SNPs and PVP-SNPs were synthesized, and their characterization was determined by UV-vis spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy. The toxicity of SNPs and PVP-SNPs was evaluated using E. eugeniae. The present result indicates that the lethal concentration (LC₅₀) of SNPs and PVP-SNPs were achieved at 22.66 and 43.27 μg/mL, respectively. The activity of antioxidant enzymes including superoxide dismutase (SOD) and catalase (CAT) was increased in SNPs compared to PVP-SNPs. Importantly, we have noticed that the E. eugeniae can amputate its body segments after exposure to SNPs and PVP-SNPs. This exciting phenomenon is named "autotomy," which describes a specific feature of E. eugeniae to escape from the toxic contaminants and predators. Accordingly, we have suggested this unique behavior may facilitate to assess the toxic effect of SNPs and PVP-SNPs in E. eugeniae.

Chick chorioallantoic membrane (CAM) assay for the evaluation of the antitumor and antimetastatic activity of platinum-based drugs in association with the impact on the amino acid metabolism

The combination of in ovo and ex ovo chorioallantoic membrane (CAM) assay provides an excellent platform which extends its relevance in studying carcinogenesis to the field of screening of anticancer activity of platinum nanoparticles (PtNPs) and further study of the amino acids' fluctuations in liver and brain. PtNPs are promising candidates for replacing cisplatin (CDDP); however, insufficient data of their antitumor efficiency and activity on the cancer-related amino acid metabolism are available, and the assessment of the in vivo performance has barely scratched the surface. Herein, we used CAM assay as in vivo model for screening of novel therapeutic modalities, and we conducted a comparative study of the effects of CDDP and polyvinylpyrrolidone coated PtNPs on MDA-MB-231 breast cancer xenograft. PtNPs showed a higher efficiency to inhibit the tumor growth and metastasis compared to CDDP. The amino acids profiling in the MDA-MB-231 ​cells revealed that the PtNPs had an overall depleting effect on the amino acids content. Noteworthy, more side effects to amino acid metabolism were deduced from the depletion of the amino acids in tumor, brain, and liver upon CDDP treatment. Different sets of enzymes of the tricarboxylic acid (TCA) cycle were targeted by PtNPs and CDDP, and while mRNA encoding multiple enzymes was downregulated by PtNPs, the treatment with CDDP affected only two TCA enzymes, indicating a different mechanism of action. Taken together, CAM assay represents and invaluable model, demonstrating the PtNPs capability of repressing angiogenesis, decrease amino acid contents and disrupt the TCA cycle.

Novel insight on chemo-specific detection of toxic environmental chromium residues existing as recalcitrant Cr(III)-carboxyl complexes using plasmonic silver nanoplatform bi-functionalized with citrate and PVP

Chromium (Cr) is a toxic environmental pollutant that majorly exists in trivalent and hexavalent forms. Though Cr(VI) is more dangerous than Cr(III), the trivalent Cr forms complexes with environmentally-available organic molecules. This makes them potentially harmful and difficult to detect. In this study, we have designed an ultrasensitive plasmonic nanosensor using citrate and PVP functionalized Ag nanoparticles (Ag-citrate-PVPNPs) for the detection of trivalent chromium organic complexes such as Cr(III)-EDTA (Cr-E), Cr(III)-acetate (Cr-A), Cr(III)-citrate (Cr-C) and Cr(III)-tartrate (Cr-T). The nanoparticles (NPs) were structurally characterized by XRD, SEM, HRTEM, SAED, EDX and elemental mapping. The citrate and PVP molecules played a vital role in the detection mechanism and stability of the sensor. Upon detection, the yellow-colored Ag-citrate-PVP NPs turned into different shades of brown depending on the type of the Cr complex and concentration. It was accompanied by diminishing and/or shifting UV-Visible absorbance peaks due to the aggregation of Ag-citrate-PVP NPs. Further, a linear relationship was observed between absorbance reduction and analyte concentration. The selectivity tests showed that the sensor was non-functional to other metal ions and inorganic anions. The sensor was optimized using pH and temperature studies. The mechanism of detection was elucidated with the help of characterization techniques such as Raman spectroscopy, FTIR, XPS and UV-visible spectrophotometer. The limit of detection (LOD) was found to be 3.29, 4.87, 1.76 and 1.79 nM for Cr-E, Cr-A, Cr-C and Cr-T complexes respectively. This study provides a rapid and sensitive approach for the detection of multiple Cr(III)-organic complexes present in an aqueous solution.

A Conductive Hydrogel Microneedle-Based Assay Integrating PEDOT:PSS and Ag-Pt Nanoparticles for Real-Time, Enzyme-Less, and Electrochemical Sensing of Glucose

Continuous glucose meters (CGMs) have tremendously boosted diabetes care by emancipating millions of diabetic patients' need for repeated self-testing by pricking their fingers every few hours. However, CGMs still suffer from major deficiencies regarding accuracy, precision, and stability. This is mainly due to their dependency on an enzymatic detection mechanism. Here a low-cost hydrogel microneedle (HMN)-CGM assay fabricated using swellable dopamine (DA)-hyaluronic acid (HA) hydrogel for glucose interrogation in dermal interstitial fluid (ISF) is introduced. Platinum and silver nanoparticles are synthesized within the 3D porous hydrogel scaffolds for nonenzymatic electrochemical sensing of the glucose. Incorporation of a highly water dispersible conductive polymer, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) enhances the electrical properties of HMN array, making the patch suitable as the working electrode of the sensor. The in vitro and ex vivo characterization of this newly developed HMN patch is fully studied. The performance of the HMN-CGM for real-time measurement of glucose is also shown using a rat model of type 1 diabetes. The device introduces the first HMN-based assay for tracking important disease biomarkers and expect to pave the way for next generation of polymeric-based sensors.

Fabrication of Functionalized UiO-66 Anchored on Disorderly Layered Clinoptilolite via Surfactant-Assisted Induction for Selective Adsorption of CO2 and CH4

The amine (NH₂)-functionalized UiO-66 was successfully anchored on disorderly layered clinoptilolite (CP) via surfactant (poly(ethylene glycol) (PEG) and poly(vinylpyrrolidone) (PVP))-assisted induction. The structural features and physicochemical parameters of the resultant UiO-66-on-CPs were characterized by powder X-ray diffraction (XRD) patterns, scanning/transmission electron microscopy (SEM/TEM) images, Fourier transform infrared (FT-IR) spectra, N₂ sorption isotherms, and small-angle X-ray scattering (SAXS) patterns. The results demonstrated that the growth of UiO-66-NH₂ nanoparticles facilitated the disorder degree of the crystal plane of CP along the a-axis, while the addition of PEG in the hydrothermal synthesis system of CP was conducive to the formation of a flower-like microstructure and the introduction of PVP was beneficial to the nucleation and growth of UiO-66-NH₂ nanoparticles with a small size (40 nm) on the surfaces of the obtained CP-PEG lamellas. Finally, the gas-selective adsorption and separation performances of CO₂ and CH₄ were evaluated using the synthesized disorderly layered UiO-66-on-CP heterostructures as adsorbents, indicating that the NH₂-functionalized UiO-66-on-CP exhibited a superior selective factor (3.66) of CO₂/CH₄. These results elucidated that the proposed approach is a promising strategy for constructing MOF-on-zeolite heterostructures, which may open an avenue to expand CP application and improve their performance.

Controlled Synthesis of Carbon-Supported Pt-Based Electrocatalysts for Proton Exchange Membrane Fuel Cells

Proton exchange membrane fuel cells are playing an increasing role in postpandemic economic recovery and climate action plans. However, their performance, cost, and durability are significantly related to Pt-based electrocatalysts, hampering their large-scale commercial application. Hence, considerable efforts have been devoted to improving the activity and durability of Pt-based electrocatalysts by controlled synthesis in recent years as an effective method for decreasing Pt use, and consequently, the cost. Therefore, this review article focuses on the synthesis processes of carbon-supported Pt-based electrocatalysts, which significantly affect the nanoparticle size, shape, and dispersion on supports and thus the activity and durability of the prepared electrocatalysts. The reviewed processes include (i) the functionalization of a commercial carbon support for enhanced catalyst–support interaction and additional catalytic effects, (ii) the methods for loading Pt-based electrocatalysts onto a carbon support that impact the manufacturing costs of electrocatalysts, (iii) the preparation of spherical and nonspherical Pt-based electrocatalysts (polyhedrons, nanocages, nanoframes, one- and two-dimensional nanostructures), and (iv) the postsynthesis treatments of supported electrocatalysts. The influences of the supports, key experimental parameters, and postsynthesis treatments on Pt-based electrocatalysts are scrutinized in detail. Future research directions are outlined, including (i) the full exploitation of the potential functionalization of commercial carbon supports, (ii) scaled-up one-pot synthesis of carbon-supported Pt-based electrocatalysts, and (iii) simplification of postsynthesis treatments. One-pot synthesis in aqueous instead of organic reaction systems and the minimal use of organic ligands are preferred to simplify the synthesis and postsynthesis treatment processes and to promote the mass production of commercial carbon-supported Pt-based electrocatalysts.

Graphical Abstract

This review focuses on the synthesis process of Pt-based electrocatalysts/C to develop aqueous one-pot synthesis at large-scale production for PEMFC stack application.

Effects of Silica Shell Encapsulated Nanocrystals on Active χ-Fe5C2 Phase and Fischer-Tropsch Synthesis

Among various iron carbide phases, χ-Fe₅C₂, a highly active phase in Fischer-Tropsch synthesis, was directly synthesized using a wet-chemical route, which makes a pre-activation step unnecessary. In addition, χ-Fe₅C₂ nanoparticles were encapsulated with mesoporous silica for protection from deactivation. Further structural analysis showed that the protective silica shell had a partially ordered mesoporous structure with a short range. According to the XRD result, the sintering of χ-Fe₅C₂ crystals did not seem to be significant, which was believed to be the beneficial effect of the protective shell providing restrictive geometrical space for nanoparticles. More interestingly, the protective silica shell was also found to be effective in maintaining the phase of χ-Fe₅C₂ against re-oxidation and transformation to other iron carbide phases. Fischer-Tropsch activity of χ-Fe₅C₂ in this study was comparable to or higher than those from previous reports. In addition, CO₂ selectivity was found to be very low after stabilization.

Surface modification of ZnIn2S4 layers to realize energy-transfer-mediated photocatalysis

Photocatalytic selective aerobic oxidation reactions are crucial in designing advanced organic intermediates, but suffer from low conversion efficiency. Hence, activating O2 to create suitable reactive oxygen species, such as singlet oxygen (1O2), can significantly increase the yield of desired products. Herein, using ZnIn2S4 nanosheets as a model system, we build a surface-modified theoretical structure, where a surface-covered non-conductive macromolecular chain, polyvinyl pyrrolidone (PVP), is bound to ZnIn2S4 and influences the O2 adsorption process. PVP on the surface significantly changes the electronic structure and suppresses electron conduction of ZnIn2S4 nanosheets. Therefore, abundantly photogenerated and long-lived species transfer their energy to physically absorbed O2 to efficiently generate 1O2, which can oxidize sulphides into their corresponding sulphoxides. For sulphoxidation of different sulphides, surface modification brings a 3-9-fold increase in conversion efficiency and high selectivities ≥98%. This study provides a feasible way of boosting 1O2-generation-related photocatalytic reactions.

Efficient all-in-one removal of total chromium over nonconjugated polymer-inorganic ZnIn2S4 semiconductor hybrid

Chromium (Cr)-containing wastewater has caused a serious threat to the environment due to its high toxicity and mobility. The traditional Cr removal methods are generally based on an inconvenient two-step process with the first transformation of Cr(VI) to Cr(III) and the consecutive removal of Cr(III) by precipitation. Herein, we demonstrate the efficient all-in-one removal of total Cr through the simultaneous photocatalytic reduction of Cr(VI) to Cr(III) and in-situ fixation of Cr(III) over the nonconjugated polymer engineered ZnIn₂S₄ (P-ZIS) photocatalyst. By in-situ polyvinylpyrrolidone (PVP) modification of ZIS during the preparation process, the resulted P-ZIS can completely reduce Cr(VI) within 60 min under visible light irradiation. The kinetics of Cr(VI) reduction over P-ZIS is 2.8 times as that of pure ZIS, which is proved to be benefited from the enhanced light absorption, uplifted conduction band for strengthening reducibility, and accelerated charge carrier transfer. Moreover, as compared to ZIS, P-ZIS also exhibits significantly improved in-situ adsorption ability for Cr(III), thus resulting in efficient all-in-one elimination of total Cr within a single system. We show that this polymer engineered strategy could be a facile and versatile protocol for modulating the electronic structure and surface chemistry of the semiconductor photocatalysts towards complete, safe, and cost-efficient removal of Cr.