Surface Of AgNPs Research Articles

Tannic Acid-Modified Silver Nanoparticles for Antibacterial and Anticancer Applications

In recent years, antibacterial nanosystems with loading and delivery capacity for anticancer agents have received increasingly widespread attention in the field of cancer treatment involving bacterial infection. Silver nanoparticles (AgNPs) are the most representative and widely used biocompatible metallic nanoparticles, which possess long-lasting and broad-spectrum antibacterial activity. However, conventional AgNPs are difficult to load and deliver anticancer agents directly because of their relatively inert surfaces. Herein, biocompatible silver nanoparticles (TA-AgNPs) were prepared via a simple approach in which tannic acid (TA) served as a “green” reducing and stabilizing agent. The resultant TA-AgNPs have low cytotoxicity against normal cells and exhibit significant antibacterial activity. The minimum inhibitory concentration (MIC) value of TA-AgNPs toward Escherichia coli was about 16 μg/mL, and the elimination rate of TA-AgNPs at a concentration of 0.5 mg/mL was above 99 and 93% at 6 h for E. coli and Staphylococcus aureus, respectively. TA-AgNPs have a good ability to load and deliver anticancer drug epirubicin hydrochloride (EPI). EPI can be adsorbed onto the surface of TA-AgNPs by strong electrostatic interaction between TA and EPI. The TA-AgNPs/EPI nanodrug displays a pH- and glutathione (GSH)-sensitive drug release performance through the protonation of phenolic hydroxyl groups in TA under an acid condition and the disassociation of TA molecules from the surface of AgNPs due to the ligand exchange reaction between GSH thiols and TA molecules. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay results showed an equal cytotoxicity effect against Hep G2 cells between free EPI and EPI-loaded TA-AgNPs. More importantly, the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay results indicated that the cytotoxicity of free EPI was significantly reduced in the presence of bacteria, but the resultant EPI-loaded TA-AgNPs could effectively prevent the influence of bacteria on the cytotoxicity of EPI. The animal tumor suppression and anti-infection model assay results indicated good tumor suppression and antibacterial properties of the TA-AgNPs/EPI nanodrug.

Novel insights into the multistep chlorination of silver nanoparticles in aquatic environments

Due to the increasing applications, silver nanoparticles (AgNPs) are inevitably released into the environments and are subjected to various transformations. Chloride ion (Cl−) is a common and abundant anion with a wide range of concentration in aquatic environments and exhibits a strong affinity for silver. The results indicate that AgNPs experienced multistep chlorination, which was dependent on the concentration of Cl− in a non-linear manner. The dissolution of AgNPs was accelerated at Cl/Ag ratio of 1 and the intensive etching effect of Cl− contributed to the significant morphology changes of AgNPs. The dissolved Ag+ quickly precipitated with Cl− to form an amorphous and passivating AgCl(s) layer on the surface of AgNPs, thus the dissolution rate of AgNPs decreased at higher Cl/Ag ratios (100 and 1000). As the Cl/Ag ratio further increased to 10,000, the overall transformation rate increased remarkably due to the complexation of Cl− with AgCl(s) to form soluble AgClx(x-1)− species, which was verified by the reaction of AgCl nanoparticles with Cl−. Besides, several environmental factors (electrolytes, surfactants and natural organic matter) affected AgNPs dissolution and the following chlorination. These results will expand the understanding of the environmental fate and potential risks of AgNPs in natural chloride-rich waters.

The Mechanisms of Oxygen Accelerated Low‐Temperature Bonding by Ag Nanoparticles

AbstractLow‐temperature bonding (≤300 o C) using Ag nanoparticles (Ag NPs) is considered to be the new generation of bonding technology in power electronics. The oxygen‐accelerated sintering has been observed by many researchers which is attributed to the decomposition of organics covered on Ag NPs. In this work, organic‐free Ag NPs are fabricated to eliminate the influence of organics, and it is found that the accelerated bonding process by oxygen is strongly correlated to the self‐confined amorphous Ag‐O compound shell on the surface of Ag NPs. In experiments, the sintering process is apparently accelerated by the elevating oxygen content, and the amorphous shell is observed after sintering, which do not grow thicker even in pure oxygen ambient for a long time while performing active chemical evolutions. In simulations, the results match well with the experiments and indicate that the amorphous shell performed the dynamic oxidation and decomposition process. This dynamic equilibrium is caused by the instability of silver oxides, which would enable the amorphous shell to activate the mobility of the surface mass flow and promote the surface diffusion. The shear strength of SiC chip increased by 354% when bonding in pure oxygen, targeting a broad variety of applications in electronic packaging.

Insights into Plasmon-Induced Dimerization of Rhodanine–A Surface-Enhanced Raman Scattering Study

Plasmon-mediated chemical reactions (PMCRs) have attracted considerable interest in recent times. The PMCR initiated by hot carriers is known to be influenced by the type of metals and the excitation wavelength. Herein, we have carried out the surface-enhanced Raman scattering (SERS) investigation of rhodanine (Rd), an important pharmacologically active heterocyclic compound, adsorbed on silver and gold nanoparticles (AgNP and AuNP) using 514.5 and 632.8 nm lasers. The prominent Raman band at 1566 cm-1 observed in the SERS spectra is attributed to the characteristic ν(C═C) stretching vibration of the Rd dimer and not of Rd tautomers. The chemical transformation of Rd to Rd dimer on metal surfaces is plausibly triggered by the indirect transfer of energetic hot electrons generated during the non-radiative decay of plasmon. The mechanism involved in the dimerization of Rd via the indirect transfer of hot electrons is also presented. The effect of wavelength on the dimerization of Rd is also observed on the AgNP surface, which indicates that the dimerization occurs more efficiently on the AgNP surface with excitation at 514.5 nm wavelength.

Nano-antibiotic based on silver nanoparticles functionalized to the vancomycin-cysteamine complex for treating Staphylococcus aureus and Enterococcus faecalis.

Bacterial resistance is defined as a microorganism's capacity to develop mechanisms for resisting a determined antimicrobial. Gram-positive bacteria, such as Staphylococcus aureus (S. aureus) and Enterococcus faecalis (E. faecalis), are internationally recognized among the isolates with this resistance profile. In this context, the demand for new medicines has risen, and silver nanoparticles (AgNPs) have been highlighted, especially for their anti-bacterial effects. To develop a nano-antibiotic for treating these Gram-positive strains, we herein report synthesizing and characterizing a nano-antibiotic based on AgNPs functionalized with the complex vancomycin-cysteamine. AgNPs were produced using the bottom-up methodology and functionalized with vancomycin modified by the carbodiimide chemistry, forming Ag@vancomycin. Susceptibility tests were performed using S. aureus and E. faecalis strains to assess the bacteriostatic and bactericidal potential of the developed nano-antibiotic. Fourier transform infrared spectroscopy measurements showed the efficacy of vancomycin chemical modification, and the characteristic bands of AgNPs functionalization with the antibiotic. The increase in the nano-antibiotic average hydrodynamic diameter observed by dynamic light scattering proved the presence of vancomycin at the surface of AgNPs. The data from the minimum inhibitory concentration and minimal bactericidal concentration assays tested on standard and clinical planktonic strains of S. aureus and E. faecalis presented excellent performance. The results indicate the promising development of a new nano-antibiotic in which the functionalization potentiates the bacteriostatic action of AgNPs and vancomycin with greater efficacy against Gram-positive strains.

Nanocomposite Films of Silver Nanoparticles and Conjugated Copolymer in Natural and Nano-Form: Structural and Morphological Studies.

The use of conjugated polymers (CPs) and metallic nanoparticles is an interesting way to form nanocomposites with improved optical properties. For instance, a nanocomposite with high sensitivity can be produced. However, the hydrophobicity of CPs may hamper applications due to their low bioavailability and low operability in aqueous media. This problem can be overcome by forming thin solid films from an aqueous dispersion containing small CP nanoparticles. So, in this work we developed the formation of thin films of poly(9,9-dioctylfluorene-co-3,4-ethylenedioxythiophene) (PDOF-co-PEDOT) from its natural and nano form (NCP) from aqueous solution. These copolymers were then blended in films with triangular and spherical silver nanoparticles (AgNP) for future applicability as a SERS sensor of pesticides. TEM characterization showed that the AgNP were adsorbed on the NCP surface, forming a nanostructure with an average diameter of 90 nm (value according to that obtained by DLS) and with a negative potential zeta. These nanostructures were transferred to a solid substrate, forming thin and homogeneous films with different morphology of PDOF-co-PEDOT films, as observed by atomic force microscopy (AFM). XPS data demonstrated the presence of the AgNP in the thin films, as well as evidence that films with NCP are more resistant to the photo-oxidation process. Raman spectra showed characteristic peaks of the copolymer in the films prepared with NCP. It should also be noted the enhancement effect of Raman bands observed on films containing AgNP, a strong indication of the SERS effect induced by the metallic nanoparticles. Furthermore, the different geometry of the AgNP influences the way in which the adsorption between the NCP and the metal surface occurs, with a perpendicular adsorption between the NCP chains and the surface of the triangular AgNP.

Study of the capillary blood flow of the mucous membrane of the peri-implant area by laser Doppler flowmetry

Aim: to conduct a clinical analysis of the capillary blood flow of the mucous membrane of the peri-implant zone using laser Doppler flowmetry (LDF), as well as a comparative assessment of the effectiveness of the implanted structure with a surface, modified with silver nanoparticles (AgNP). Materials and methods. The study involved 40 patients undergoing rehabilitation for secondary partial adentia by the method of dental implantation. The examinees were divided into 2 groups: Group 1 (20 patients) – gingival formers with a surface modified by plasma electrooxidation and doped with AgNP were installed; Group 2 (20 patients) – standard gingival formers of the used implant system with a polished surface were installed. A control group (20 patients) was formed to determine the reference values. In total, 60 patients were involved in the study. Blood flow velocity in the studied groups was determined by laser Doppler flowmetry. Results. On the 10th day, when using gingival formers with a surface containing AgNP, a positive trend with increasing the blood flow rate of the mucous membrane of the peri-implant zone (6.97 mm/s) is determined, in contrast of using the gingival formers with a polished surface (5.425 mm/s). In the process of using the gum formers with a surface containing AgNPs, an increase in capillary blood flow rate (by 22.2 %) in a separate location is evidence of a reduction in inflammatory processes and a pronounced anti-inflammatory effect of the AgNP surface. Conclusions. Higher (by 22.2 %) indicators of capillary blood flow rate of the mucous membrane of the peri-implant zone in patients using gingival formers containing AgNP, compared to polished formers, indicates a pronounced anti-inflammatory effect of the proposed AgNP-doped surface. The values obtained in the group with AgNPs are as close as possible to the reference indicators of the blood flow rate in the capillary channel of the marginal gingiva of healthy people, which suggests the presence of a pronounced antimicrobial effect of silver nanoparticles on the surface of the gingival formers. Since blood flow in tissues is directly related to oxygenation of cells, reduction of local acidosis, reduction of inflammatory reactions and determines the state of tissue immunity, as well as directly affects the quality of reparative processes in damaged tissue, the obtained results allow recommending the proposed AgNP – surface for use in clinical practice.

Light-Assisted CO2 Cycloaddition over a Nanochannel Cadmium–Organic Framework Loaded with Silver Nanoparticles

Compared to conventional thermal-driven fixation, the light-assisted CO2 fixation into useful chemicals represents a viable strategy for environmental restoratio n and energy sustainability. Hence, in this work, the type of linker was tuned to control the structure and topology of metal–organic frameworks (MOFs), resulting in a diversity of pore networks ranging from two-dimensional (2D) microporous channels (NWU-Cd1, 2) to three-dimensional (3D) nanochannels (NWU-Cd3). Among them, NWU-Cd3 can be employed as a reducing agent to convert Ag(I) ions to Ag(0) to generate Ag/NWU-Cd3 composite materials in situ due to its large pore size, high CO2 adsorption capacity, and redox activity. Ag/NWU-Cd3 can expand the absorption spectrum to the visible area, and it exhibits excellent photocatalytic activity with the yield of styrene carbonate up to 94.3% at light irradiation and room temperature, which is 5.2 times of that under dark conditions. Notably, each Ag NP of the MOF network functions concurrently as a photosensitizer (harvesting light and producing electrons) and a cocatalyst (serving as the Lewis acid). The plasmonic hot electrons can gather on the Ag NP surface under light irradiation and rapidly transfer to NWU-Cd3 to interact with CO2, resulting in activated CO2*. Simultaneously, the presence of Ag NPs provides an action site for epoxides and accelerates the ring-opening process, and thus, Ag/NWU-Cd3 displays high catalytic reactivity for CO2 cycloaddition under mild circumstances (25 °C, 1 atm). This research clarifies the conjunction of light and Ag NPs in accelerating CO2 conversion and offers a substitutable method to further devise effective heterogeneous catalysts for light-induced CO2 cycloaddition.

Nonreleasing AgNP Colloids Composite Hydrogel with Potent Hemostatic, Photodynamic Bactericidal and Wound Healing-Promoting Properties.

Reactive oxygen species (ROS) produced by noble metallic nanoparticles under visible light is an effective way to combat drug-resistant bacteria colonized on the wound. However, the photocatalytic efficiency of noble metallic nanoparticles is limited by its self-aggregation in water media. Moreover, the fast release of noble metallic ions from nanoparticles might engender cellular toxicity and hazardous environmental issues. Herein, we chose AgNPs, the most common plasmonic noble metallic nanoparticles, as an example, modifying the surface of AgNPs with oleic acid and n-butylamine and imbedded them into calcium alginate (CA) hydrogel that holds tissue adhesion, rapid hemostatic, sunlight-sensitive antibacterial and anti-inflammatory abilities, and thus effectively promotes the healing of wounds. Unlike conventional AgNP-based materials, the constrain of colloids and hydrogel networks hinders the leach of Ag+. Nonetheless, the CA/Ag hydrogels exhibit on-demand photodynamic antibacterial efficacy due to the generation of ROS under visible light. In addition, the CA/Ag hydrogel can effectively stop the hemorrhage in a mouse liver bleeding model due to their skin-adaptive flexibility and tissue adhesiveness. The potent sunlight-responsive antibacterial activity of the CA/Ag hydrogel can effectively kill multidrug-resistant bacteria both in vitro (>99.999%) and in vivo (>99.9%), while the diminished Ag+ release guarantees its biocompatibility. The CA/Ag hydrogel significantly promotes the wound healing process by the downregulation of proinflammatory cytokines (TNF-α and IL-6) in a rodent full-thickness cutaneous wound model. Overall, the proposed multifunctional CA/Ag nanocomposite hydrogel has excellent prospects as an advanced wound dressing.

Nanoscale Hydrophobicity and Electrochemical Mapping Provides Insights into Facet Dependent Silver Nanoparticle Dissolution.

Metal or metallic nanoparticle dissolution influences particle stability, reactivity, potential fate, and transport. This work investigated the dissolution behavior of silver nanoparticles (Ag NPs) in three different shapes (nanocube, nanorod, and octahedron). The hydrophobicity and electrochemical activity at the local surfaces of Ag NPs were both examined using atomic force microscopy (AFM) coupled with scanning electrochemical microscopy (AFM-SECM). The surface electrochemical activity of Ag NPs more significantly affected the dissolution than the local surface hydrophobicity did. Octahedron Ag NPs with dominant surface exposed facets of {111} dissolved faster than the other two kinds of Ag NPs. Density functional theory (DFT) calculation revealed that the {100} facet elicited greater affinities toward H2O than the {111} facet. Thus, poly(vinylpyrrolidone) or PVP coating on the {100} facet is critical for stabilizing and prevent the {100} facet from dissolution. Finally, COMSOL simulations demonstrated consistent shape dependent dissolution as we observed experimentally.

One-pot green synthesis of silver nanoparticles using brittle star Ophiocoma scolopendrina: Assessing biological potentialities of antibacterial, antioxidant, anti-diabetic and catalytic degradation of organic dyes

In the current study, aqueous extract of O. scolopendrina (OSE) was used to synthesize AgNPs in a simple and environmentally friendly manner. The biosynthesized OSE-AgNPs were also assessed for its catalytic, antibacterial, anti-diabetic, antioxidant and dye degradation properties. The techniques like UV–visible spectroscopic examinations, TEM, SEM, TGA, zeta potential and FT-IR were used in the characterization investigations. The bioproduction of OSE-AgNPs was preliminary confirmed by UV–visible spectroscopic based investigation followed by microscopic visualization. The synthesized OSE-AgNPs exhibited a reddish brown colour and nearly spherical forms with sizes between 5 and 50 nm quantified by TEM and SEM. The attendance of functional groups like –OH and –NH present in OSE caps on the AgNPs surface was confirmed by FTIR analysis. Interestingly, in the presence of OSE-AgNPs, the degradation of dyes (CV, 95% and EY, 96% in 15 min) were noticeably accelerated. Further, OSE-AgNPs demonstrated substantial antibacterial activity; robust antioxidant properties andnotable anti-diabetic activities. This is the first account on the biosynthetic process of AgNPs using the aqueous extract of O. scolopendrina.

Silver nanoparticle interactions with glycated and non-glycated human serum albumin mediate toxicity.

Introduction: Biomolecules bind to and transform nanoparticles, mediating their fate in biological systems. Despite over a decade of research into the protein corona, the role of protein modifications in mediating their interaction with nanomaterials remains poorly understood. In this study, we evaluated how glycation of the most abundant blood protein, human serum albumin (HSA), influences the formation of the protein corona on 40nm silver nanoparticles (AgNPs) and the toxicity of AgNPs to the HepG2 human liver cell line. Methods: The effects of glycation on AgNP-HSA interactions were quantified using circular dichroism spectroscopy to monitor protein structural changes, dynamic light scattering to assess AgNP colloidal stability, zeta potential measurements to measure AgNP surface charge, and UV-vis spectroscopy and capillary electrophoresis (CE) to evaluate protein binding affinity and kinetics. The effect of the protein corona and HSA glycation on the toxicity of AgNPs to HepG2 cells was measured using the WST cell viability assay and AgNP dissolution was measured using linear sweep stripping voltammetry. Results and Discussion: Results from UV-vis and CE analyses suggest that glycation of HSA had little impact on the formation of the AgNP protein corona with protein-AgNP association constants of ≈2x107 M-1 for both HSA and glycated HSA (gHSA). The formation of the protein corona itself (regardless of whether it was formed from HSA or glycated HSA) caused an approximate 2-fold decrease in cell viability compared to the no protein AgNP control. While the toxicity of AgNPs to cells is often attributed to dissolved Ag(I), dissolution studies showed that the protein coated AgNPs underwent less dissolution than the no protein control, suggesting that the protein corona facilitated a nanoparticle-specific mechanism of toxicity. Overall, this study highlights the importance of protein coronas in mediating AgNP interactions with HepG2 cells and the need for future work to discern how protein coronas and protein modifications (like glycation) may alter AgNP reactivity to cellular organisms.

TiO2 nanorods based self-supported electrode of 1T/2H MoS2 nanosheets decorated by Ag nano-particles for efficient hydrogen evolution reaction

Molybdenum disulfide (MoS2) has shown significant promise as an economic hydrogen evolution reaction (HER) catalyst for hydrogen generation, but its catalytic performance is still lower than noble metal-based catalysists. Herein, a silver nanoparticles (Ag NPs)-decorated 1T/2H phase layered MoS2 electrocatalyst grown on titanium dioxide nanorod arrays (Ag NPs/1T(2H) MoS2/TNRs) was prepared through acid-tunable ammonium ion intercalation. Taking advantage of MoS2 layered structure and crystal phase controllability, as-prepared Ag NPs/1T(2H) MoS2/TNRs exhibited ultrahigh HER activity. As-proposed strategy combines facile hydrogen desorption (Ag NPs) with efficient hydrogen adsorption (1T/2H MoS2) effectively circumventes the kinetic limitation of hydrogen desorption by 1T/2H MoS2. The as-prepared Ag NPs/1T(2H) MoS2/TNRs electrocatalyst exhibited excellent HER activity in 0.5 mol/L H2SO4 with low overpotential (118 mV vs. reversible hydrogen electrode (RHE)) and small Tafel slope (38.61 mV/dec). The overpotential exhibts no obvious attenuation after 10 h of constant current flow. First-principles calculation demonstrates that as-prepared 1T/2H MoS2 exhibit a large capacity to store protons. These protons can be subsequently transferred to Ag NPs, which significantly increases the hydrogen coverage on the surface of Ag NPs in HER process and thus change the rate-determining step of HER on Ag NPs from water dissociation to hydrogen recombination. This study provides a unique strategy to improve the catalytic activity and stability for MoS2-based electrocatalyst.

Biogenic nanosilver bearing antimicrobial and antibiofilm activities and its potential for application in agriculture and industry.

Due to the increasing resistance of bacteria and fungi to antimicrobials, it is necessary to search for effective alternatives to prevent and treat pathogens causing diseases in humans, animals, and plants. In this context, the mycosynthesized silver nanoparticles (AgNPs) are considered as a potential tool to combat such pathogenic microorganisms. AgNPs were synthesized from Fusarium culmorum strain JTW1 and characterized by Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Nanoparticle Tracking Analysis (NTA), Dynamic Light Scattering (DLS) and Zeta potential measurement. The minimum inhibitory (MIC) and biocidal concentrations (MBC) were determined against 13 bacterial strains. Moreover, the combined effect of AgNPs with antibiotics (streptomycin, kanamycin, ampicillin, tetracycline) was also studied by determining the Fractional Inhibitory Concentration (FIC) index. The anti-biofilm activity was examined by crystal violet and fluorescein diacetate (FDA) assays. Furthermore, antifungal activity of AgNPs was evaluated against a panel of phytopathogenic fungi viz., Botrytis, Colletotrichum, Fusarium, Phoma, Sclerotinia, and an oomycete pathogen Phytophthora by agar well-diffusion and micro-broth dilution method to evaluate the minimal AgNPs concentrations that inhibit fungal spore germination. Fungi-mediated synthesis resulted in the formation of small (15.56 ± 9.22 nm), spherical and stable (zeta potential of - 38.43 mV) AgNPs with good crystallinity. The results of FTIR spectroscopy indicated the presence of various functional groups, namely hydroxyl, amino, and carboxyl ones, from the biomolecules on the surface of AgNPs. The AgNPs showed antimicrobial and antibiofilm formation activities against Gram-positive and Gram-negative bacteria. The values of MIC and MBC ranged between 16-64 and 32-512 μg mL-1, respectively. The enhanced effect of AgNPs in combination with antibiotics was confirmed against human pathogens. The highest synergistic effect (FIC = 0.0625) was demonstrated by the combination of AgNPs with streptomycin against two strains of Escherichia coli (ATCC 25922 and ATCC 8739), followed by Klebsiella pneumoniae and Pseudomonas aeruginosa (FIC = 0.125). Enhanced effects of AgNPs with ampicillin were also shown against Staphylococcus aureus ATCC 25923 (FIC = 0.125) and P. aeruginosa (FIC = 0.25), as well as kanamycin against S. aureus ATCC 6538 (FIC = 0.25). The crystal violet assay revealed that the lowest concentration of AgNPs (0.125 μg mL-1) reduced the development of biofilms of Listeria monocytogenes and Salmonella enterica, while the maximum resistance was shown by Salmonella infantis, its biofilm was reduced after exposure to a concentration of 512 μg mL-1. A high inhibitory effect on the activity of bacterial hydrolases was observed by the FDA assay. AgNPs at a concentration of 0.125 μg mL-1 reduced the hydrolytic activity of all biofilms formed by the tested pathogens, except E. coli ATCC 25922, P. aeruginosa, and Pectobacterium carotovorum (efficient concentration was 2-fold higher, at 0.25 μg mL-1), while the hydrolytic activity of E. coli ATCC 8739, Salmonella infantis and S. aureus ATCC 6538 was suppressed after treatment with AgNPs at concentrations of 0.5, 2 and 8 μg mL-1, respectively. Moreover, AgNPs inhibited fungal growth and spore germination of Botrytis cinerea, Phoma lingam, and Sclerotinia sclerotiorum. MIC and MFC values of AgNPs against spores of these fungal strains were determined at 64, 256, and 32 μg mL-1, and zones of growth inhibition were 4.93, 9.54, and 3.41 mm, respectively. Fusarium culmorum strain JTW1 was found to be an eco-friendly biological system for an easy, efficient and inexpensive synthesis of AgNPs. In our study, the mycosynthesised AgNPs demonstrated remarkable antimicrobial (antibacterial and antifungal) and antibiofilm activities against a wide range of human and plant pathogenic bacteria and fungi singly and in combination with antibiotics. These AgNPs could be applied in medicine, agriculture, and food industry to control such pathogens that cause numerous human diseases and crop losses. However, before using them extensive animal studies are required to evaluate the toxicity, if any.

Investigation of silver nanoparticles interaction with human proteins (IgG & Fib)

Silver nanoparticles (AgNPs) have been extensively investigated and used in various areas due to their excellent antimicrobial and unique optical properties. When NPs and their derivatives encounter a physiological environment (e.g., blood, plasma, or interstitial fluid), they will be rapidly encapsulated by proteins existing in the biological fluids, which will form a type of nanoparticle called protein corona (PC). During this process, the protein type, concentration, and ratio of two proteins (IgG and Fib) were altered. The goal of this study was to understand the physicochemical reactions in the system. Dynamic light scattering (DLS) and multi-barreled light scattering (Turbiscan) were two major techniques used in this study. Our results showed that at low ionic strength, separated segments of IgG preferentially adsorbed on the surface of AgNPs and played a bridging role in increasing AgNPs aggregation. However, highly self-association Fib preferentially adsorbed and played a net capture role in decreasing the aggregation. When both proteins were present, the reverse inhibitory effect of Fib was more advantageous than the forward promoting effect of IgG. At high ionic strength, IgG and Fib could cooperate to inhibit AgNPs aggregation while Fib had a greater effect than IgG. Moreover, with a small amount of protein existing in the system, a stable PC did not form in a short time. In contrast, with a high amount of protein, a stable PC formed within 10 min. The movement of protein molecules around AgNPs corona was more vigorous when there was a higher amount of protein in the system.

Facile Green Synthesis of ZnO NPs and Plasmonic Ag-Supported ZnO Nanocomposite for Photocatalytic Degradation of Methylene Blue

Removing organic pollutants, textile dyes, and pharmaceutical wastes from the water bodies has become an essential requirement for a safe environment. Therefore, the present study aimed to prepare semiconductor zinc oxide nanoparticles (ZnO NPs) and plasmonic Ag-supported ZnO nanocomposite (ZnO–Ag) using an environmentally friendly bio-approach as an alternative to hazardous synthesis approaches. ZnO NPs and ZnO–Ag nanocomposite were characterized by using UV–Vis diffuse reflectance spectroscopy (UV–DRS) (the Ag-supported ZnO nanocomposite exhibited an absorption band between 450–550 nm, attributed to the Ag NPs surface plasmon resonance (SPR)), Photoluminescence (PL) spectral investigation, which revealed the PL emission intensity of ZnO–Ag NPs was lower than pure ZnO NPs, describing an extended electron-hole pair (e--h+) lifespan of photogenerated charge carriers, Fourier transform infrared spectroscopy (FTIR), FT-Raman, and X-ray diffraction (XRD) analyses were deduced. In addition, energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) were performed and further ascertained the successful biosynthesis and thermally stable ZnO Nps and ZnO–Ag nanocomposite. The as-prepared ZnO–Ag nanocomposite displayed increased photocatalytic characteristics due to the decline in the bandgap energy from 3.02 eV (ZnO NPs) to 2.90 eV (ZnO–Ag nanocomposite). The photocatalytic activity of the developed nanocomposite for the degradation of methylene blue (MB) dye, a primary textile industry released water-pollutant, was conducted under UV light irradiation. Meanwhile, the maximum % degradation of MB dye molecules was attained by 98.0 % after 60 min exposure of UV-light irradiation. Increased photocatalytic activity of ZnO–Ag nanocomposites and a faster rate of MB degradation were achieved by the deposition of plasmonic Ag NPs and the surface plasmon resonance (SPR) effect possessed by Ag NPs. The primary oxidative route that resulted in MB degradation was the production of hydroxyl radicals (OH•). The SPR effect of the photocatalyst induced the synergistic enhancement of the optical response and separation of the photo-induced charge carriers. The combined study gives comprehensive information and directions for future research on noble metal-modified nanocatalysts for direct applications in the photocatalytic degradation of textile and organic wastes in water.

Facile ligand-exchange strategy to promote low-temperature nano-sintering of oleylamine-capped Ag nanoparticles

PurposeThis study aims to develop a facile ligand-exchange strategy to promote nano-sintering of oleylamine (OAM)-capped silver nanoparticles (AgNPs). By using ligand exchange process with NH4OH to remove OAM from the surface of AgNP, this study reports effectively reducing the sintering temperature of AgNPs to achieve low-temperature nano-sintering. Compared with untreated AgNPs of OAM-capped, NH4OH-treated AgNPs possess superior sintering performance that could be applied to a fractional generator device as conductor and in favour of the fabrication of flexible circuit modules.Design/methodology/approachFirst, oleylamine is used as reductant to synthesize monodisperse AgNPs by a simple one-step method. Then ligand exchange is used with NH4OH at different treating times to remove OAM, and micro-Fourier transform infrared spectroscopy and contact angle test are applied to clear the mechanism and structure characteristics of these processes. Finally, NH4OH-treated AgNPs sediment sintering is used at different temperatures to test electrical resistivity and use ex situ scanning electron microscopy combined with in situ X-ray diffraction to study changes in microstructure in the whole nano-sintering process.FindingsThe AgNPs are always capped by organic ligands to prevent nanoparticles agglomeration. And oleylamine used as reductant could synthesize desirable size distributions of 8–32 nm with monodisperse globular shapes, but the low-temperature nano-sintering seemed not to be achieved by the oleylamine-capped AgNPs because OAM is an organic with long C-chain. The ligand exchange approach was enabled to replace the original organic ligands capped on AgNPs with organic ligands of low thermal stability which could promote nano-sintering. After ligand exchange treated AgNPs could be sintered on photo paper, polydimethylsiloxane (PDMS) and polyethylene terephthalate flexible substrates at low temperature.Originality/valueIn this research, the method ligand exchange is used to change the ligand of AgNPs. During ligand exchange, NH4OH was used to treat AgNPs. Through the treatment of NH4OH, the change of hydrophilic and hydrophobic properties of AgNPs was successfully realized. The sintering temperature of AgNPs can also be reduced and the properties can be improved. Finally, the applicability of the AgNPs sediment with this nano-sintering process at low temperature for obtaining conductive patterns was evaluated using PDMS as substrates.

A highly selective Hg2+ colorimetric sensor and antimicrobial agent based on green synthesized silver nanoparticles using Equisetum diffusum extract.

Plasmonic nanoparticles such as Ag have gained great interest in the biomedical domain and chemical analysis due to their unique optical properties. Herein, we report a simple, cost-effective, and highly selective colorimetric sensor of mercury(ii) based on E. diffusum (horsetail) extract-functionalized Ag nanoparticles (ED-AgNPs). The ED-AgNPs were synthesized by exploiting the coordination of Ag+ with the various functional groups of ED extract under sunlight exposure for only tens of seconds. ED-AgNPs (63 nm) were characterized using various techniques such as UV-vis, FTIR, DLS, SEM and EDX. FTIR spectra suggested the successful encapsulation of the AgNPs surface with ED extract and XRD confirmed its crystalline nature. This ED-AgNPs colorimetric sensor revealed remarkable selectivity towards Hg2+ in aqueous solution among other transition metal ions through a redox reaction mechanism. Besides, the sensor exhibited high sensitivity with rapid response and a detection limit of 70 nM. The sensor demonstrated feasibility for Hg(ii) detection in spiked tap and river water samples. In addition, the synthesized ED-AgNPs revealed enhanced antimicrobial activity with higher efficacy against the Gram-positive bacterium (L. monocytogenes with an inhibition zone of 18 mm) than the Gram-negative bacterium (E. coli with an inhibition zone of 10 mm). The simplicity and adaptability of this colorimetric sensor render it a promising candidate for on-site and point-of-care detection of heavy metal ions in diverse conditions.

Eco-friendly synthesis, characterization, catalytic, antibacterial, antidiabetic, and antioxidant activities of Embelia robusta seeds extract stabilized AgNPs

The current research study is to develop and easy and eco-friendly method for the synthesis of AgNPs using aqueous seed extract of Embelia robusta (Er-AgNPs) and evaluated the extract to know the effects of catalytic, anti-bacterial, anti-diabetic, and anti-oxidant activity. Er-AgNPs were characterized via several techniques including UV-vis absorption, PL, XRD, FTIR, and TEM UV-vis study confirmed the formation of Er-AgNPs. Face centered cubic (FCC) crystal structure of biosynthesized Er-AgNPs was governed by the XRD analysis. FTIR study confirmed the presence of OH and NH functional groups of secondary molecules of seed extract capped on the AgNPs surface. The produced Er-AgNPs were dark brown in color with almost spherical shape in the size ranging from 5 to 15 nm. The presence of Er-AgNPs (1 mL) exhibited considerably enhanced dyes degradation (CY, 95.12% and EY, 97.82% in 18 min), antibiotics degradation (TC, 96.45% and CIP, 98.01% in 21 min), and nitroaromatics reduction (4-NP, 88.12% and 4-NA, 92.45% in 15 min). The Er-AgNPs have showed significant antibacterial activity on multi drug resistance bacteria. The synthesized Er-AgNPs exhibited strong antioxidant activities for the DPPH assay. Remarkable anti-diabetic (α-glucosidase, α-amylase, and HbA1C) activities were noticed for biosynthesized Er-AgNPs. This is the first report on the biosynthesis of AgNPs using seeds extract of Embelia robusta. • Eco-friendly synthesis of AgNPs were carried out using Embelia robusta seeds extract. • The synthesized Er-AgNPs were found to be fcc structure and average diameter is 8±2 nm. • Biosynthesized Er-AgNPs exhibited excellent catalytic activity for the degradation of dyes, antibiotics, and nitrocompounds reduction at low NaBH 4 content. • Biogenic Er-AgNPs showed good antibacterial, antidiabetic and antioxidant activities. • Er-AgNPs were developed as a four-in-one platform for the environmental remediation of waste water treatment and biological applications.

Boric acid-functionalized silver nanoparticles as SERS substrate for sensitive and rapid detection of fructose in artificial urine

The accurate detection of fructose in human urine can help prevent and screen for diseases such as fructokinase deficiency and hereditary fructose intolerance. Surface-enhanced Raman spectroscopy (SERS) is an analytical technique with selectivity and high sensitivity, which has been widely applied to the detection of targets with complex backgrounds. In this work, 4-mercaptophenylboronic acid (4-MPBA) was modified on the surface of silver nanoparticles (AgNPs) under mild conditions to obtain a boronic acid-functionalized SERS substrate for the detection of fructose in artificial urine. The detection mechanism was based on the deboronization reaction of 4-MPBA on the surface of AgNPs, which was induced by fructose, and the Raman signal of the generated thiophenol (TP) molecules was significantly enhanced by the silver nanoparticles, with a linear increase in SERS peak intensity at 1570 cm−1. We achieved the detection limits of 0.084 µmol/L in water and 0.535 µmol/L in urine by this method. The relative standard deviation (RSD) in the recovery experiments of urine ranged from 1.01 % to 2.22 %, and the whole detection time was less than 10 min, which indicated that this method is highly reliable for fructose detection and has a good prospect in bioassay and clinical medicine.