Facile one pot microbe-mediatedin situsynthesis and antibacterial activity of reduced graphene oxide-silver nanocomposite.

The present research deals with the development of a novel bioinspiredin situfabrication of reduced graphene oxide (rGO)-silver nanoparticle (AgNPs) nanocomposite (rGO@AgNCs) using microbes namelyPseudomonas aeruginosa(PA) andStaphylococcus aureus(SA). The fabricated rGO@AgNCs were characterized using Ultraviolet-visible (UV-Vis) spectroscopy, Fourier-transform infrared spectroscopy (FTIR), particle size analysis, polydispersity index (PDI), zeta potential analysis, energy dispersive x-ray analysis (EDAX), Raman spectroscopy, powder x-ray diffraction (PXRD), high-resolution transmission electron microscopy (HR-TEM) analysis, etc. Furthermore, the rGO@AgNCs-PA and rGO@AgNCs-SA interaction with serum protein, pH stability study, andin vitrodissolution of AgNPs were also performed. The research findings of the proposed study demonstrated the simultaneous reduction of graphene oxide (GO) and AgNPs and the formation of rGO@AgNCs in the presence of microbes. Thein vitrodissolution studies of rGO@AgNCs composites showed better AgNPs dissolution with controlled release and offered remarkable matrix integrity throughout the dissolution period. The size and stability of rGO@AgNCs-PA and rGO@AgNCs-SA had no significant changes at physiological pH 7.4. A minimal decrease in the zeta potential of rGO@AgNCs was observed, which may be due to the weak interaction of nanocomposites and albumin. The antibacterial application of the synthesized nanocomposite was evaluated against a pathogenic mastitis-forming bacterium. The obtained results suggested an admirable antibacterial activity of synthesized nanocomposites against the tested microbes. This knowledge will assist the scientific fraternity in designing novel antibacterial agents with enhanced antibacterial activity against various veterinary pathogens in near future.

Silver-N-heterocyclic carbene complexes-catalyzed multicomponent reactions: Synthesis, spectroscopic characterization, density functional theory calculations, and antibacterial study.

Nowadays, silver-N-heterocyclic carbene (silver-NHCs) complexes are widely used in medicinal chemistry due to their low toxic nature toward humans. Due to the success of silver-NHCs in medicinal applications, interest in these compounds is rapidly increasing. Therefore, the interaction of N,N-disubstituted benzimidazolium salts with Ag2 O in dichloromethane to prepare novel Ag(I)-NHCs complexes was carried out at room temperature for 120 h in the absence of light. The obtained complexes were identified and characterized by 1 H and 13 C nuclear magnetic resonance, Fourier-transform infrared, UV-Vis, and elemental analysis techniques. Then, the silver complexes were applied for three-component coupling reactions of aldehydes, amines, and alkynes. The effect of changing the alkyl substituent on the NHCs ligand on the catalytic performance was investigated. In addition, it has been found that the complexes are antimicrobially active and show higher activity than the free ligand. The silver-carbene complexes showed antimicrobial activity against specified microorganisms with MIC values between 0.24 and 62.5 µg/ml. These results showed that the silver-NHC complexes exhibit an effective antimicrobial activity against bacterial and fungal strains. A density functional theory calculation study was performed to identify the stability of the obtained complexes. All geometries were optimized employing an effective core potential basis, such as LANL2DZ for the Ag atom and 6-311+G(d,p) for all the other atoms in the gas phase. Electrostatic potential surfaces and LUMO-HOMO energy were computed. Transition energies and excited-state structures were obtained from the time-dependent density functional theory calculations.

Comparative study of antibacterial activity between Schiff base nicotinic hydrazide derivative and its silver architected nanoparticles with atomic force microscopic study of bacterial cell wall.

The threat of multi-drug resistant bacterial pathogens evokes researchers to synthesized safe and effective chemotherapeutic agents for nano-drug delivery system. In current study, Schiff base of nicotinic hydrazide(NHD) and its silver nanoparticles(NHD-AgNPs) were synthesized and characterized. These compounds were investigated for cytotoxicity, antibacterial and AFM activity. The NHD showed LD50 at >1000µg/mL while NHD-AgNPs didn't exhibit toxicity at 1000µg/mL against 3T3 cell line. The NHD showed zone of inhibition against two strains of salmonella enteric (ATCC 14028 and 700408) 45.29±1.66 and 48.01±1.43mm respectively at 160µg/mL (p<0.01) while NHD-AgNPs exhibited 55.87±2.08 and 52.88±1.42 mm respectively at 130µg/mL (p<0.001) in disc diffusion method. NHD showed more than 70% growth inhibition for both strains at 85 and 125µg/ml (p<0.01) respectively, while NHD-AgNPs inhibit 80% and 75% respectively at 75 and 125 µg/ml (p<0.01, p<0.001) against Alamar blue antibacterial assay. For morphological changes in bacterial cell wall NHD and NHD-AgNPs treated bacterial cells were observed under atomic force microscope(AFM) and treated bacterial cells were severely damaged with leaked cytoplasmic contents as compare to untreated bacterial cell. These results validate that NHD-AgNPs were highly active as compared to NHD against both strains at their MIC concentrations. In future, comparative wound healing potential will be emphasized.

Facile synthesis of graphene oxide-silver nanocomposite for decontamination of water from multiple pollutants by adsorption, catalysis and antibacterial activity.

Here in, we presented a facile one-step method for the synthesis of Graphene oxide-silver (GO-Ag) nanocomposite and its applications as a sorbent for the elimination of some toxic pollutants from aqueous medium, as an efficient catalyst in the individual as well as simultaneous reduction reactions of multiple compounds, and as an antibacterial agent for the destruction of some harmful microorganisms existent in wastewater. GO was prepared using a modified Hummers method and Ag nanoparticles were integrated on GO sheets by chemical reduction of Ag+ ions on the surfaces of GO sheets. The composition and morphology of the nanocomposite was extensively characterized with elemental dispersive X-ray analysis (EDX), Fourier transform infra-red (FT-IR) spectroscopy, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and thermal gravimetric analysis (TGA). The GO-Ag nanocomposite demonstrated remarkable adsorption capacities and recyclability for malachite green (MG) and ethyl violet (EV) dyes. Various experimental parameters affecting adsorptive behavior of nanocomposite like temperature, pH, time of contact between dye and adsorbent, and adsorbent dose were evaluated thoroughly. Experimental data was simulated with different adsorption isotherms and kinetic models to evaluate adsorption behavior of both dyes and results confirmed the adsorption of both the dyes to be followed by pseudo 2nd order kinetic model and Langmuir adsorption model. Moreover, adsorbent was regenerated in suitable media for both dyes without any loss in removal efficiency. The catalytic performance for the 2-nitroaniline (2-NA) reduction was investigated in detail. Most importantly, the prepared nanocomposite was found to have potential to adsorb multiple pollutants all together as well as to catalyze the simultaneous reduction of a mixture of dyes (MG, MO, and EV) and 2-NA. An additional advantage of the GO-Ag nanocomposite was its antibacterial activity acquired to the presence of Ag nanoparticles. Two bacterial strains (Gram-negative bacterium, E. coli and the Gram-positive bacterium, S. aureus) were used to test antibacterial activity of composite and the results confirmed the remarkable performance of the nanocomposite in destroying harmful pathogens.

Near-Infrared Fluorescent Ag2S Nanodot-Based Signal Amplification for Efficient Detection of Circulating Tumor Cells.

The level of circulating tumor cells (CTCs) plays a critical role in tumor metastasis and personalized therapy, but it is challenging for highly efficient capture and detection of CTCs because of the extremely low concentration in peripheral blood. Herein, we report near-infrared fluorescent Ag2S nanodot-based signal amplification combing with immune-magnetic spheres (IMNs) for highly efficient magnetic capture and ultrasensitive fluorescence labeling of CTCs. The near-infrared fluorescent Ag2S nanoprobe has been successfully constructed through hybridization chain reactions using aptamer-modified Ag2S nanodots, which can extremely improve the imaging sensitivity and reduce background signal of blood samples. Moreover, the antiepithelial-cell-adhesion-molecule (EpCAM) antibody-labeled magnetic nanospheres have been used for highly capture rare tumor cells in whole blood. The near-infrared nanoprobe with signal amplification and IMNs platform exhibits excellent performance in efficient capture and detection of CTCs, which shows great potential in cancer diagnostics and therapeutics.

Near-Infrared Ag2S Quantum Dots-Based DNA Logic Gate Platform for miRNA Diagnostics.

Dysregulation of miRNA expression is correlated with the development and progression of many diseases. These miRNAs are regarded as promising biomarkers. However, it is challenging to measure these low abundant molecules without employing time-consuming radioactive labeling or complex amplification strategies. Here, we present a DNA logic gate platform for miRNA diagnostics with fluorescence outputs from near-infrared (NIR) Ag2S quantum dots (QDs). Carefully designed toehold exchange-mediated strand displacements with different miRNA inputs occur on a solid-state interface, which control QDs release from solid-state interface to solution, responding to multiplex information on initial miRNAs. Excellent fluorescence emission properties of NIR Ag2S QDs certify the great prospect for amplification-free and sensitive miRNA assay. We demonstrate the potential of this platform by achieving femtomolar level miRNA analysis and the versatility of a series of logic circuits computation.

Photochemical synthesis of biocompatible and antibacterial silver nanoparticles embedded within polyurethane polymers.

In situ light initiated synthesis of silver nanoparticles (AgNP) was employed for AgNP incorporation within the polymeric matrices of medical grade polyurethane. The resulting materials showed improved antibacterial and antibiofilm activity against Pseudomonas aeruginosa with negligible toxicity for human primary skin cells and erythrocytes.

Pressure-induced metathesis reaction to sequester Cs.

We report here a pressure-driven metathesis reaction where Ag-exchanged natrolite (Ag16Al16Si24O80·16H2O, Ag-NAT) is pressurized in an aqueous CsI solution, resulting in the exchange of Ag(+) by Cs(+) in the natrolite framework forming Cs16Al16Si24O80·16H2O (Cs-NAT-I) and, above 0.5 GPa, its high-pressure polymorph (Cs-NAT-II). During the initial cation exchange, the precipitation of AgI occurs. Additional pressure and heat at 2 GPa and 160 °C transforms Cs-NAT-II to a pollucite-related, highly dense, and water-free triclinic phase with nominal composition CsAlSi2O6. At ambient temperature after pressure release, the Cs remains sequestered in a now monoclinic pollucite phase at close to 40 wt % and a favorably low Cs leaching rate under back-exchange conditions. This process thus efficiently combines the pressure-driven separation of Cs and I at ambient temperature with the subsequent sequestration of Cs under moderate pressures and temperatures in its preferred waste form suitable for long-term storage at ambient conditions. The zeolite pollucite CsAlSi2O6·H2O has been identified as a potential host material for nuclear waste remediation of anthropogenic (137)Cs due to its chemical and thermal stability, low leaching rate, and the large amount of Cs it can contain. The new water-free pollucite phase we characterize during our process will not display radiolysis of water during longterm storage while maintaining the Cs content and low leaching rate.

Impact of nanosilver on various DNA lesions and HPRT gene mutations - effects of charge and surface coating.

BACKGROUND: The main goal of this research was to study the interactions of a fully characterized set of silver nanomaterials (Ag ENMs) with cells in vitro, according to the standards of Good Laboratory Practices (GLP), to assure the quality of nanotoxicology research. We were interested in whether Ag ENMs synthesized by the same method, with the same size distribution, shape and specific surface area, but with different charges and surface compositions could give different biological responses. METHODS: A range of methods and toxicity endpoints were applied to study the impacts of interaction of the Ag ENMs with TK6 cells. As tests of viability, relative growth activity and trypan blue exclusion were applied. Genotoxicity was evaluated by the alkaline comet assay for detection of strand breaks and oxidized purines. The mutagenic potential of Ag ENMs was investigated with the in vitro HPRT gene mutation test on V79-4 cells according to the OECD protocol. Ag ENM agglomeration, dissolution as well as uptake and distribution within the cells were investigated as crucial aspects of Ag ENM toxicity. Ag ENM stabilizers were included in addition to positive and negative controls. RESULTS: Different cytotoxic effects were observed including membrane damage, cell cycle arrest and cell death. Ag ENMs also induced various kinds of DNA damage including strand breaks and DNA oxidation, and caused gene mutation. We found that positive Ag ENMs had greater impact on cyto- and genotoxicity than did Ag ENMs with neutral or negative charge, assumed to be related to their greater uptake into cells and to their presence in the nucleus and mitochondria, implying that Ag ENMs might induce toxicity by both direct and indirect mechanisms. CONCLUSION: We showed that Ag ENMs could be cytotoxic, genotoxic and mutagenic. Our experiments with the HPRT gene mutation assay demonstrated that surface chemical composition plays a significant role in Ag ENM toxicity.

Synthesis and characterization of silver(I) pyrazolylmethylpyridine complexes and their implementation as metallic silver thin film precursors.

A series of light- and air-stable silver(I) pyrazolylmethylpyridine complexes [Ag(L(R))]n(BF4)n (L = pyrazolylmethylpyridine; R = H, 1; R = Me, 2; R = i-Pr, 3) and [Ag(L(R))(NO3)]2 (L = pyrazolylmethylpyridine; R = H, 4; R = Me, 5; R = i-Pr, 6) has been synthesized and structurally and spectroscopically characterized. In all of the molecular structures, the pyrazolylmethylpyridine ligands bridge two metal centers, thus giving rise to dinuclear (2, 4, 5, and 6) or polynuclear structures (1 and 3). The role played by the counteranions is also of relevance, because dimeric structures are invariably obtained with NO3(-) (4, 5, and 6), whereas the less-coordinating BF4(-) counteranion affords polymeric structures (1 and 3). Also, through atoms-in-molecules (AIM) analysis of the electron density, an argentophilic Ag···Ag interaction is found in complexes 2 and 4. Thermogravimetric analysis (TGA) shows that the thermolytic properties of the present complexes can be significantly modified by altering the ligand structure and counteranion. These complexes were further investigated as thin silver film precursors by spin-coating solutions, followed by annealing at 310 °C on 52100 steel substrates. The resulting polycrystalline cubic-phase Ag films of ∼55 nm thickness exhibit low levels of extraneous element contamination by X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) and scanning electron microscopy (SEM) indicate that film growth proceeds primarily via an island growth (Volmer-Weber) mechanism. Complex 4 was also evaluated as a lubricant additive in ball-on-disk tribological tests. The results of the friction evaluation and wear measurements indicate a significant reduction in wear (∼ 88%) at optimized Ag complex concentrations with little change in friction. The enhanced wear performance is attributed to facile shearing of Ag metal in the contact region, resulting from thermolysis of the silver complexes, and is confirmed by energy-dispersive X-ray analysis of the resulting wear scars.

Surfactant-assisted synthesis and characterization of stable silver bromide nanoparticles in aqueous media.

Colloidal dispersions of silver bromide (AgBr) in aqueous surfactant medium have been prepared using a surfactant-assisted synthesis approach with hexadecyltrimethylammonium bromide (CTAB). The surfactant acts both as source of bromide ion as well as the stabilizing agent. Upon progressive addition of silver nitrate to aqueous CTAB solution, stable AgBr dispersions were obtained. Formation of surfactant cation (CTA(+)) stabilized AgBr was confirmed by way of XRD, FTIR and NMR studies. Thermal behavior of the isolated nanoparticles was investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), where the occurrence of phase transition in the surfactant-stabilized nanoparticles was observed. Kinetics of the particle growth was investigated by dynamic light scattering measurements, which predicted the formation of surfactant bilayered structures associated with the nanoparticles of AgBr. Band gap of the nanoparticles was determined by suitably analyzing the UV-visible spectral data, which concluded that the particles behaved like insulators. Morphology of the particles, studied by TEM measurements, was found to be spherical. Finally, enthalpy of formation of surfactant-stabilized AgBr, determined calorimetrically, was found to be dependent on the concentration of the precursors.

Selective sulfuration at the corner sites of a silver nanocrystal and its use in stabilization of the shape.

This paper describes a new approach to site-selective sulfuration at the corner sites of Ag nanocrystals including triangular nanoplates and nanocubes. The reaction simply involved mixing an aqueous suspension of the Ag nanocrystals with an aqueous solution of polysulfide at room temperature. As a precursor to elemental S, polysulfide is highly soluble in water and can directly react with elemental Ag upon contact to generate Ag(2)S in the absence of oxygen. The reaction was easily initiated at the corner sites and then pushed toward the center. By controlling the reaction time and/or the amount of polysulfide added, the reaction could be confined to the corner sites only, generating Ag-Ag(2)S hybrid nanocrystals with greatly improved stability against aging at 80 and 100 °C in air than their counterparts made of pure Ag.

Biogenic Synthesis, Characterization and Antibacterial Properties of Silver Nanoparticles against Human Pathogens.

Biogenic synthesis of silver nanoparticles (AgNPs) is more eco-friendly and cost-effective approach as compared to the conventional chemical synthesis. Biologically synthesized AgNPs have been proved as therapeutically effective and valuable compounds. In this study, the four bacterial strains Escherichia coli (MT448673), Pseudomonas aeruginosa (MN900691), Bacillus subtilis (MN900684) and Bacillus licheniformis (MN900686) were used for the biogenic synthesis of AgNPs. Agar well diffusion assay revealed to determine the antibacterial activity of all biogenically synthesized AGNPs showed that P. aeruginosa AgNPs possessed significantly high (p < 0.05) antibacterial potential against all tested isolates. The one-way ANOVA test showed that that P. aeruginosa AgNPs showed significantly (p < 0.05) larger zones of inhibition (ZOI: 19 to 22 mm) compared to the positive control (rifampicin: 50 µg/mL) while no ZOI was observed against negative control (Dimethyl sulfoxide: DMSO). Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) concentration against four test strains also showed that among all biogenically synthesized NPs, P. aeruginosa AgNPs showed effective MIC (3.3-3.6 µg/mL) and MBC (4.3-4.6 µg/mL). Hence, P. aeruginosa AGNPs were characterized using visual UV vis-spectroscopy, X-ray diffractometer (XRD), fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The formation of peak around 430 nm indicated the formation of AgNPs while the FTIR confirmed the involvement of biological molecules in the formation of nanoparticles (NPs). SEM revealed that the NPs were of approximately 40 nm. Overall, this study suggested that the biogenically synthesized nanoparticles could be utilized as effective antimicrobial agents for effective disease control.

Synthesis of Ag(2) S-Ag nanoprisms and their use as DNA hybridization probes.

A simple synthetic route to prepare Ag(2) S-Ag nanoprisms consists of the facile addition of Na(2) S to a solution of triangular Ag nanoprisms. The resulting Ag(2) S-Ag nanoparticles are more stable in solution than the original Ag nanoprisms, and two surface plasmon resonance (SPR) bands of the original Ag nanoprisms still remain. In addition, the SPR bands of the Ag(2) S-Ag nanoprisms are tunable over a wide range. The Ag(2) S-Ag nanoprisms can be directly bioconjugated via well-established stable Ag(2) S surface chemistry with readily available sulfur coupling agents. The nanoprisms are used in the hybridization of functionalized oligonucleotides, and show promise as probes for future biosensing applications.

Generation of Ag2O micro-/nanostructures by pulsed excimer laser ablation of Ag in aqueous solutions of polysorbate 80.

A new route to synthesis of Ag(2)O micro-/nanostructures, including a mixture of cubes, pyramids, triangular plates, pentagonal rods, and bars, has been developed by pulsed excimer laser ablation of bulk silver in water using polysorbate 80 as surfactant. The polysorbate 80 played an important role in the formation of the Ag(2)O structures, and similar structures could be obtained in polysorbates 20 and 40 aqueous solutions. We have proposed a mechanism to explain the formation of Ag(2)O structures. This laser ablation method provides a unique approach to discover and fabricate new Ag(2)O morphologies.

Synthesis of Ag-TiO2 composite nano thin film for antimicrobial application.

TiO2 photocatalysts have been found to kill cancer cells, bacteria and viruses under mild UV illumination, which offers numerous potential applications. On the other hand, Ag has long been proved as a good antibacterial material as well. The advantage of Ag-TiO2 nanocomposite is to expand the nanomaterial's antibacterial function to a broader range of working conditions. In this study neat TiO2 and Ag-TiO2 composite nanofilms were successfully prepared on silicon wafer via the sol-gel method by the spin-coating technique. The as-prepared composite Ag-TiO2 and TiO2 films with different silver content were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) to determine the topologies, microstructures and chemical compositions, respectively. It was found that the silver nanoparticles were uniformly distributed and strongly attached to the mesoporous TiO2 matrix. The morphology of the composite film could be controlled by simply tuning the molar ratio of the silver nitrate aqueous solution. XPS results confirmed that the Ag was in the Ag(0) state. The antimicrobial effect of the synthesized nanofilms was carried out against gram-negative bacteria (Escherichia coli ATCC 29425) by using an 8 W UV lamp with a constant relative intensity of 0.6 mW cm(-2) and in the dark respectively. The synthesized Ag-TiO2 thin films showed enhanced bactericidal activities compared to the neat TiO2 nanofilm both in the dark and under UV illumination.

Kinetics and mechanisms of nanosilver oxysulfidation.

Among the many new engineered nanomaterials, nanosilver is one of the highest priority cases for environmental risk assessment. Recent analysis of field samples from water treatment facilities suggests that silver is converted to silver sulfide, whose very low solubility may limit the bioavailability and adverse impact of silver in the environment. The present study demonstrates that silver nanoparticles react with dissolved sulfide species (H(2)S, HS(-)) under relevant but controlled laboratory conditions to produce silver sulfide nanostructures similar to those observed in the field. The reaction is tracked by time-resolved sulfide depletion measurements to yield quantitative reaction rates and stoichiometries. The reaction requires dissolved oxygen, and it is sensitive to pH and natural organic matter. Focused-ion-beam analysis of surface films reveals an irregular coarse-grained sulfide phase that allows deep (>1 µm) conversion of silver surfaces without passivation. At high sulfide concentrations, nanosilver oxysulfidation occurs by a direct particle-fluid reaction. At low sulfide concentration, quantitative kinetic analysis suggests a mechanistic switch to an oxidative dissolution/precipitation mechanism, in which the biologically active Ag(+) ion is generated as an intermediate. The environmental transformation pathways for nanosilver will vary depending on the media-specific competing rates of oxidative dissolution and direct oxysulfidation.

Antileishmanial effect of silver nanoparticles: Green synthesis, characterization, in vivo and in vitro assessment.

The drugs used to treat cutaneous leishmaniasis (CL) cannot effectively penetrate lesions. Nanogold and nanosilver have been used for treating or enhancing drug delivery in CL. The present study used Commiphora molmol (myrrh) to synthesize silver nanoparticles (MSNPs). The MSNPs were characterized using transmission electron microscopy and energy-dispersive spectroscopy. In addition, antiparasitic effect of myrrh silver nanoparticles (MSNPs) was assessed on Leishmania major both in vitro and in vivo. Five concentrations of MSNPs (10, 50, 80, 100, and 150 µl/100 µL) were used to study their effect on L. major cultures in vitro, and MSNPs were also applied topically to subcutaneous lesions in mice in vivo. The results showed that the MSNPs were 49.09 nm in size. MSNPs, showed a marked and significant (p ≤ 0.05) growth inhibition of L. major promastigotes which was concentration dependent. Overall, the higher concentrations (100, 150 µl/100 µL had a significantly greater inhibitory effect for the MSNPs in comparison to the chemical nanoparticles (CNPs) and pentostam at the same concentrations. Lesions healed completely in 21 d after MSNP treatment in vivo, while pentostam, a commercial drug, and CNPs showed a moderate healing effect on the lesions. Thus, MSNPs were more effective than pentostam and CNPs both in the in vivo and in vitro studies. MSNPs can therefore be promising candidates for various nanomedicine applications.

One-pot fabrication of Ag @Ag2O core-shell nanostructures for biosafe antimicrobial and antibiofilm applications.

Microbial contamination is one of the major dreadful problems that raises hospitalization, morbidity and mortality rates globally, which subsequently obstructs socio-economic progress. The continuous misuse and overutilization of antibiotics participate mainly in the emergence of microbial resistance. To circumvent such a multidrug-resistance phenomenon, well-defined nanocomposite structures have recently been employed. In the current study, a facile, novel and cost-effective approach was applied to synthesize Ag@Ag2O core-shell nanocomposites (NCs) via chemical method. Several techniques were used to determine the structural, morphological, and optical characteristics of the as-prepared NCs. XRD, Raman, FTIR, XPS and SAED analysis revealed a crystalline hybrid structure of Ag core and Ag2O shell. Besides, SEM and HRTEM micrographs depicted spherical nanoparticles with size range of 19-60 nm. Additionally, zeta potential and fluorescence spectra illustrated aggregated nature of Ag@Ag2O NCs by - 5.34 mV with fluorescence emission peak at 498 nm. Ag@Ag2O NCs exhibited higher antimicrobial, antibiofilm, and algicidal activity in dose-dependent behavior. Interestingly, a remarkable mycocidal potency by 50 µg of Ag@Ag2O NCs against Candida albican; implying promising activity against COVID-19 white fungal post-infections. Through assessing cytotoxicity, Ag@Ag2O NCs exhibited higher safety against Vero cells than bulk silver nitrate by more than 100-fold.

Synthesis, morphological control, and antibacterial properties of hollow/solid Ag2S/Ag heterodimers.

Ag(2)S and Ag are important functional materials that have received considerable research interest in recent years. In this work, we develop a solution-based synthetic method to combine these two materials into hollow/solid Ag(2)S/Ag heterodimers at room temperature. Starting from monodisperse Cu(2)O solid spheres, CuS hollow spheres can be converted from Cu(2)O through a modified Kirkendall process, and the obtained CuS can then be used as a solid precursor for preparation of the Ag(2)S/Ag heterodimers through ion exchange and photo-assisted reduction. We have found that formation of the Ag(2)S/Ag heterodimers is instantaneous, and the size of Ag nanocrystals on the hollow spheres of Ag(2)S can be controlled by changing the concentration and power of reducing agents in the synthesis. The growth of Ag nanoparticles on hollow spheres of Ag(2)S in the dimers is along the [111] direction of the silver crystal; the light absorption properties have also been investigated. Furthermore, coupling or tripling of Ag(2)S/Ag heterodimers into dumbbell-like trimers ((Ag(2)S)(2)/Ag, linear) and triangular tetramers ((Ag(2)S)(3)/Ag, coplanar) can also be attained at 60 degrees C by adding the bidentate ligand ethylenediamine as a cross-linking agent. To test the applicability of this highly asymmetric dipolar composite, photocatalytic inactivation of Escherichia coli K-12 in the presence of the as-prepared Ag(2)S/Ag heterodimers has been carried out under UV irradiation. The added Ag(2)S/Ag heterodimers show good chemical stability under prolonged UV irradiation, and no appreciable solid dissolution is found. Possible mechanisms regarding the enhanced antibacterial activity have also been addressed.