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This report demonstrates the synthesis of a trihybrid system (PBI-NP-GO) consisting of perylene bisimide appended peptide (PBI-UW) nanofibers, silver nanoparticles (PBI-AgNP), and graphene oxide (GO) nanosheet. Tryptophan-containing PBI molecules in an aqueous medium can reduce silver ions into silver nanoparticles in the presence of sunlight to form a dihybrid system consisting of nanofibers and nanoparticles; the addition of GO into the dihybrid system ultimately leads to the formation of the trihybrid system. The trihybrid system was thoroughly characterized by various spectroscopic and microscopic techniques, such as ultraviolet-visible (UV-vis), Fourier transform-infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), RAMAN, and field emission transmission electron microscopy (FEG-TEM). The so-formed trihybrid system was successfully utilized as a potential photocatalyst for the reduction of carcinogenic Cr(VI) to non-toxic Cr(III) under irradiation with blue LED light. An almost complete reduction of Cr(VI) was achieved within 30 minutes of irradiation. Moreover, good photo-switching behaviour was observed with the highest photocurrent gain of 5.11 (Ion/Ioff) compared to PBI-AgNP (dihybrid) and PBI-UW, where Ion/Ioff values of 3.92 and 2.31, respectively, were obtained. The photocatalytic activity and photo-switching behaviour of the trihybrid system are due to efficient photo-induced charge separation. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) conjugated with polymers are well-known for their powerful and effective antimicrobial properties. In particular, the incorporation of AgNPs in biocompatible catecholamine-based polymers, such as polydopamine (PDA), has recently shown promising antimicrobial activity, due to the synergistic effects of the AgNPs, silver(I) ions released and PDA. In this study, we generated AgNPs-PDA-patterned surfaces by localised electrochemical depositions, using a double potentiostatic method via scanning electrochemical cell microscopy (SECCM). This technique enabled the assessment of a wide parameter space in a high-throughput manner. The optimised electrodeposition process resulted in stable and homogeneously distributed AgNP-microspots, and their antimicrobial activity against Escherichia coli was assessed using atomic force microscopy (AFM)-based force spectroscopy, in terms of bacterial adhesion and cell elasticity. We observed that the bacterial outer membrane underwent significant structural changes, when in close proximity to the AgNPs, namely increased hydrophilicity and stiffness loss. The spatially varied antimicrobial effect found experimentally was rationalised by numerical simulations of silver(I) concentration profiles. [ABSTRACT FROM AUTHOR]

Efficient and affordable nucleic acid detection methods play a pivotal role in various applications. Herein, we developed an immobilization-free and label-free strategy to construct a photoelectrochemical nucleic acid biosensing platform based on interactions between silver nanoparticles and DNA. First, CRISPR-Cas12a exhibited a trans-cleavage effect on adenine nucleotide sequences upon recognizing the target DNA. The resulting adenine nucleotide sequences of varying lengths then engaged in interactions with silver nanoparticles, leading to a solution characterized by distinct light transmittance. Subsequently, the solution was positioned between the light source and the photoelectrode, strategically impacting the photon absorption step within the photoelectrochemical process. Consequently, the detection of nucleic acid was accomplished through the analysis of the resultant photocurrent signal. The developed platform exhibits a detection limit of 0.06 nM (S/N = 3) with commendable selectivity. The innovative use of adenine nucleotide sequences as cost-effective probes interacting with silver nanoparticles eliminates the need for complex interfacial immobilization processes, significantly simplifying the fabrication of DNA sensors. The outcomes of our research present a promising pathway for advancing the development of economically feasible miniature DNA sensors. [ABSTRACT FROM AUTHOR]

Nanomaterials have demonstrated a wide range of applications and amongst nanomaterials, most of the research has mainly focused on nanoparticles as they can be easily prepared and manipulated. The magnetic properties of certain magnetic nanoparticles have attracted a lot of interest in environmental applications. However, because of their great vulnerability to chemical and physical activity, their magnetic characteristics deteriorate. These nanoparticles are being progressively attempted to be encapsulated by a green organic matrix, which greatly improves usefulness, stability, and affordability, and reduces back toxicity. In this investigation, iron oxide (IO) nanoparticles were prepared by a co-precipitation method and these bear IO particles were stabilized by green synthesized silver nanoparticles to produce IO/Ag nanocomposite particles. The nano size of the prepared particles was confirmed by FE-SEM and TEM analysis. Incorporation of silver nanoparticles (AgNPs) on IO particles was confirmed by UV-Vis, XRD, TGA, and VSM. The improved stability of the magnetic particles was confirmed by DLS and zeta potential. Using the reducing agent NaBH4, the catalytic reduction ability of the IO/Ag nanocomposite particles is investigated in relation to the degradation of Congo Red, a model anionic azo dye. When 40 μg mL−1 of IO/Ag particles were used, complete degradation of 20 mL of CR (0.1 mM) dye solution was accomplished in 2 minutes. The particles also demonstrated moderate antibacterial activity against four pathogens and good DPPH free radical scavenging activity, with 94% scavenging recorded at a concentration of 100 μg mL−1 particles. [ABSTRACT FROM AUTHOR]

Silver and gold nanoparticles have found extensive biomedical applications due to their strong localized surface plasmon resonance (LSPR) and intriguing plasmonic properties. This review article focuses on the correlation among particle geometry, plasmon properties and biomedical applications. It discusses how particle shape and size are tailored via controllable synthetic approaches, and how plasmonic properties are tuned by particle shape and size, which are embodied by nanospheres, nanorods, nanocubes, nanocages, nanostars and core–shell composites. This article summarizes the design strategies for the use of silver and gold nanoparticles in plasmon-enhanced fluorescence, surface-enhanced Raman scattering (SERS), electroluminescence, and photoelectrochemistry. It especially discusses how to use plasmonic nanoparticles to construct optical probes including colorimetric, SERS and plasmonic fluorescence probes (labels/reporters). It also demonstrates the employment of Ag and Au nanoparticles in polymer- and paper-based microfluidic devices for point-of-care testing (POCT). In addition, this article highlights how to utilize plasmonic nanoparticles for in vitro and in vivo bio-imaging based on SERS, fluorescence, photoacoustic and dark-field models. Finally, this article shows perspectives in plasmon-enhanced photothermal and photodynamic therapy. [ABSTRACT FROM AUTHOR]

Silver ions are considered an antibacterial candidate for numerous applications. In this regard, different phases of nanoparticles containing silver were prepared, including silver phosphate and magnesium vanadate, to be incorporated into a polymeric blend based on polyvinyl alcohol (PVA) and hyaluronic acid (HA). These blends were cast in thin films, while different concentrations of the nanoparticles were embedded through the films to promote their adhesion features. In addition, the surface topography of the films was investigated. It was shown that the grain size of silver phosphate was around 84–300 nm, while that of magnesium vanadate was around 43–66 nm. The porosity appeared to be high on the surface. In addition, the surface roughness increased with the addition of nanoparticles. Furthermore, the Mg3(VO4)2@PVA/HA film has the most efficient antibacterial action; the inhibition zone around E. coli species was 19.5 ± 0.5 mm, while that around S. aureus was 16.0 ± 1.0 mm. Additionally, the Ag3PO4@HA film also exhibited germicidal potential; the E. coli inhibition area was 18.0 ± 1.0 mm, while that of S. aureus was 10.5 ± 0.5 mm. Finally, the effect of Ag3PO4/Mg3(VO4)2/CNT@PVA/HA was investigated on the human lung cell line. Cell viability was 81.96% and 125%, respectively, when 5000 and 4.9 g ml−1 were administered. [ABSTRACT FROM AUTHOR]

This work has focused on the development of a new analytical alternative based on the laser-induced breakdown spectroscopy (LIBS) technique for the fast, reliable, and economical determination of the gold and silver nanoparticle content in a low linear concentration range between 2.9 and 0.058 μg mL−1 and 2.9–0.116 μg mL−1, respectively, without requiring complicated sample pretreatment procedures or advanced separation techniques. Metallic nanoparticles are currently essential materials for the development of new technologies in different scientific and technical areas. However, numerous studies have pointed out these nanomaterials' toxic and polluting potential and the various health implications for humans, animals, and the ecosystem. The current reality reflects the lack of analytical techniques with low economic, environmental, and health impacts and the capacity to quantify the total metallic nanoparticle content. For this purpose, a novel and simple method for the selective capture of gold and silver nanoparticles, consisting of a chemically functionalized glass surface, has been custom-developed for subsequent analysis with LIBS. The results show that the proposed method, employing a functionalized sample glass support, presents a suitable analytical performance characterized by increased sensitivity, specifically 4.7% and 329.2% for Au-NPs and Ag-NPs, and proportionally decreased error in the slope and intercept of the calibration curves, 68% for Au-NPs and 87% for Ag-NPs, respectively. [ABSTRACT FROM AUTHOR]

Single-cell analysis using inductively coupled plasma mass spectrometry (SC-ICP-MS) is an analytical methodology that allows to obtain qualitative and quantitative information of the element content of bioparticles (cells, bacteria, unicellular algae, yeasts...) on a cell-by-cell basis. In this study, two commercially available nebulisation systems for introduction of intact bioparticles were evaluated, showing similar performance. Bacteria (E. coli) exposed to Ag(I) and 10 nm Ag nanoparticles were detected and their complete silver content distributions successfully recorded. Analysis of the corresponding spheroplasts, obtained after enzymatic digestion of the bacterial outer membrane with lysozyme, allowed information about the intracellular silver to be obtained, providing an insight into the biodistribution of silver in the bacteria. Likewise, validity of the quantitative information obtained by SC-ICP-MS was evaluated by applying methodology based on the estimation of silver mass per bioparticle critical values and successive dilutions. The quantitative information obtained by SC-ICP-MS for the total content of silver in bacteria and spheroplasts was confirmed by acid digestion followed by conventional ICP-MS analysis. Bacteria exposed to silver nanoparticles accumulated lower amounts of silver than those exposed to ionic silver, the latter being totally internalized, showing the higher bioavailability of ionic silver. This study proves for the first time the suitability of SC-ICP-MS for the quantitative determination of silver in bacteria, as well as in spheroplasts when combined with lysozyme digestion. Limits of detection of 7 ag of Ag per bioparticle, 500 bioparticles per mL and 38 ng of total Ag per litre of bacteria/spheroplast suspension were achieved. [ABSTRACT FROM AUTHOR]

Polymers are used in various industries and, particularly in the medical industry, the use of skin-friendly, biocompatible materials is essential. In this field, using natural and biocompatible carbonaceous materials to replace petroleum-derived materials is the most efficient solution. In this study, which was performed in two phases, polyurethane foam made from natural polyol obtained from rapeseed oil (RPO) and containing silver (Ag) nanoparticles for use in wound dressings was prepared and examined. In the first phase, bio-based polyurethane was prepared via a specific method and characterized using Fourier-transform infrared and nuclear magnetic resonance analysis. Polyol foams were prepared using different ratios of natural polyol to a petroleum based polyol. The results of the water absorption test showed that PF-NPO-35 (containing 35% natural polyol) has a 145% absorption rate. The water vapor transfer rate test was also conducted on this sample, giving results in the range of 8–9 mg cm−2 h−1, which is a suitable range for a wound dressing application. After selecting PF-NPO-35 as the optimal sample, different amounts of Ag nanoparticles were added to this sample and the final foams with different percentages of Ag nanoparticles were prepared. The antibacterial properties of the samples showed that PF-NPO-35-Ag-7 (7% Ag nanoparticles) was more sensitive to Escherichia coli than to Staphylococcus aureus. Increasing the amount of Ag nanoparticles improved the antibacterial properties. Cytotoxicity tests also showed that all samples containing Ag nanoparticles survived for 48 h. High levels of cell viability were observed in the presence of the synthetic foams. In the animal tests, the healing process of the wounds treated with a sample containing silver nanoparticles showed improved progress after 14 days. [ABSTRACT FROM AUTHOR]

Carbon dots@noble metal nanoparticle composites are formed by combining carbon dots and metal nanoparticles using various strategies. Carbon dots exhibit a reducing ability and function as stabilisers; consequently, metal-ion solutions can be directly reduced by them to synthesise gold, silver, and gold–silver alloy particles. Carbon dots@gold/silver/gold–silver particle composites have demonstrated the potential for several practical applications owing to their superior properties and simple preparation process. Until now, several review articles have been published to summarise fluorescent carbon dots or noble metal nanomaterials. Compared with metal-free carbon dots, carbon dots@noble metal nanoparticles have a unique morphology and structure, resulting in new physicochemical properties, which allow for sensing, bioimaging, and bacteriostasis applications. Therefore, to promote the effective development of carbon dots@noble metal nanoparticle composites, this paper primarily reviews carbon dots@gold/silver/gold–silver alloy nanoparticle composites for the first time in terms of the following aspects. (1) The synthesis strategies of carbon dots@noble metal nanoparticle composites are outlined. The principle and function of carbon dots in the synthesis strategies are examined. The advantages and disadvantages of these methods and composites are analysed. (2) The characteristics and properties of such composites are described. (3) The applications of these composite materials are summarised. Finally, the potentials and limitations of carbon dots@noble metal nanoparticle composites are discussed, thus laying the foundation for their further development. [ABSTRACT FROM AUTHOR]

Combining the Hg2+-induced oxidization of silver nanoparticles with the cation exchange reaction between Ag+ and CuS nanoparticles for cascade signal amplification, a sensitive, universal and label-free ICP-MS bioassay for nucleic acids and proteins was developed. By replacing the loop sequence of the T–Hg–T hairpin structure with specific sequences or aptamers to different biomarkers, it has great promise for the early detection of biomarkers potentially for diagnosis of cancerous diseases. [ABSTRACT FROM AUTHOR]

This study introduces a thermoplastic microdevice integrated with additive-enhanced allele-specific amplification and hydrazine-induced silver nanoparticle-based detection of single nucleotide polymorphism (SNP) and opportunistic pathogens. For point-of-care testing of SNP, an allele-specific loop-mediated isothermal amplification reaction using nucleotide-mismatched primers and molecular additives was evaluated to discriminate single-nucleotide differences in the samples. The microdevice consists of purification and reaction units that enable DNA purification, amplification, and detection in a sequential manner. The purification unit enables the silica-based preparation of samples using an embedded glass fiber membrane. Hydrazine-induced silver nanoparticle formation was employed for endpoint colorimetric detection of amplicons within three min at room temperature. The versatile applicability of the microdevice was demonstrated by the successful identification of SNPs related to sickle cell anemia, genetically-induced hair loss, and Enterococcus faecium. The microdevice exhibited a detection limit of 103 copies per μL of SNP targets in serum and 102 CFU mL−1 of Enterococcus faecium in tap water within 70 min. The proposed microdevice is a promising and versatile platform for point-of-care nucleic acid testing of different samples in low-resource settings. [ABSTRACT FROM AUTHOR]

Plasmonic nanoparticles are an emerging tool for developing label-free multicolorimetric sensors for biosensing and chemosensing applications. The color absorbed by nanoparticles from visible light is influenced by their size, shape, orientation, and interparticle distance. Differently sized and shaped gold and silver nanoparticles exhibit a wide range of colors, aiding in the development of label-free sensors. Etching is the process of oxidizing nanoparticles, which alters their aspect ratio, shape, plasmonic peak, and outward appearance. It is typically used to create sensitive sensing platforms. Through etching, analytes could be detected in a simple, sensitive, and selective manner. The multicolor readout of nanoparticle etching-based multicolorimetric sensors can overcome the limitations of conventional colorimetric assays and improve the accuracy of visual inspection. This review discusses different approaches for target sensing using nanoparticle etching strategies like direct etching, enzyme-mediated etching, chemical reaction-driven etching, and anti-etching-based sensors and their mechanisms. In the future, etching strategies could be modified into portable sensing devices to detect a variety of analytes, which will aid in the development of on-time, in situ, and point-of-care sensing systems. [ABSTRACT FROM AUTHOR]

Herein, a 3D SERS substrate based on nickel foam (NF) and silver nanoparticles (AgNPs/NF 3D SERS) was synthesized using vacuum-assisted thermal evaporation deposition. The performance of the AgNPs/NF 3D SERS substrate was investigated using rhodamine 6G (R6G) as a probe molecule at different AgNP deposition levels. The highest sensitivity of the substrate with a limit of detection (LOD) of 10−9 M and an enhancement factor (EF) of 1.56 × 106 was achieved when the optimal amount of AgNPs was reached. Moreover, the use of R6G at 10−6 M concentration as the probe molecule ensured the relative standard deviation (RSD) of 9.2% for the AgNPs/NF 3D SERS substrate, and its SERS performance hardly decreased after 30 days of placement at room temperature, which evidenced that the prepared SERS substrate had favorable stability and repeatability. Finally, the substrate was used to analyze carbendazim in deionized and river water in two different environments. The results revealed that the LOD of CBZ was as low as 10−7 M under both conditions, and there was a good linear relationship between the CBZ concentration and the SERS signal intensity (R2 = 0.955 and 0.927, respectively), which demonstrated the great potential of AgNPs/NF 3D SERS substrates for pesticide residue identification in practical analysis. [ABSTRACT FROM AUTHOR]

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a method with high potential to visualize the distribution of elements in different samples, including a variety of organisms. This study aimed to demonstrate the broad application of LA-ICP-MS in nanomaterial-biota fate studies as a high throughput bioimaging tool and to broaden the choice of standard organism models in material-biota interaction research. In this study, operation parameters of LA-ICP-MS were optimised on one organism, woodlice Porcellio scaber. Subsequently, the scanning conditions were tested on a range of aquatic (Girardia tigrina, Lumbriculus variegatus, and Oncorhynchus mykiss), terrestrial organisms (Lumbricus rubellus, Porcellio scaber) and one plant (Triticum aestivum) upon exposure to Ag2S nanoparticles (NPs) and silver nitrate (AgNO3). Model organisms were exposed in aquatic or terrestrial mesocosm experiments where nominal concentrations of Ag were 10 μg Ag per L of water and 10 mg Ag per kg of soil, respectively. The results showed that both sample preparation and LA-ICP-MS imaging conditions, as optimized on the selected organism (65 μm laser diameter, scan rate 100 μm s−1, measuring duration 35 min), are applicable on different tissues. These LA-ICP-MS imaging conditions enable recognition of the main biological structures and biodistribution of elements of interest. By using fast-screening LA-ICP-MS, we confirmed the presence of Ag2S NPs on the body surface or in the gut lumen (adsorbed and retained), but not in other internal parts of organisms, which is consistent with our previous toxicokinetic studies. The presence of Ag was also confirmed in some parts of wheat roots. The advantage of this technique is the possibility of sequential use of fast- and slow-scanning steps to optimise the duration of analysis and data processing, whilst also improving cost-effectiveness without compromising the quality of results. [ABSTRACT FROM AUTHOR]

By depositing silver nanoparticles (AgNPs) on the surface of aluminum nitride whiskers (AlNw), an AlNw-AgNPs heterogeneous structural filler was rationally designed from the perspective of interface engineering, which was further combined with nanofibrillated cellulose (NFC) to prepare anisotropic composite films by a facile vacuum-assited filtration method. Due to the synergistic effect of cross-linking AlNw and "thermal conducting micro-bridges" of AgNPs, the composite films exhibited an extraordinary in-plane thermal conductivity of 31.329 W m−1 K−1, showing a promising application as thermal management materials. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) exhibit very interesting properties that have been employed in several kinds of applications spanning from antibacterial activity to plasmon–polaritons generation. Nanoparticle size strongly influences these applications. However, the characterization of ultrasmall AgNPs (particle diameter < 10 nm) encompassing different aspects such as average size, polydispersion, shape (anisotropy), concentration, and density remains a challenging task. To address these challenges, we combined TEM measurements with a computational framework based on Mie–Gans theory. This allowed us to describe the aforementioned AgNP features accurately. The synthesis of AgNPs in an aqueous medium involved the use of silver nitrate as a chemical precursor and sodium borohydride as a reducing agent, with polyvinylpyrrolidone acting as a stabilizing agent. Our outcomes showed that increasing the concentration of the precursor and reducing agent with a fixed 1 : 2 molar ratio tends to yield ultrasmall AgNPs with low to moderate polydispersion, a nearly spherical shape (low anisotropy), concentration in the nanomolar range and density close to silver bulk. Also, we established an analytical expression that correlates the extinction molar absorptivity to AgNP size considering the nanoparticle shape. Notably, the computational framework proved to be highly effective in extracting crucial information about the AgNPs from UV-vis spectroscopy data. In conclusion, our study sheds light on the unique properties of ultrasmall AgNPs and presents a comprehensive approach for properly characterizing these nanoparticles, paving the way for further advancements in their applications. [ABSTRACT FROM AUTHOR]

This study reports the anticancer properties of carbazole-containing phthalonitrile/phthalocyanine-modified silver nanoparticles for the first time. In this study, a new mono-substituted phthalonitrile namely 3-[9H-carbazole-9-ethoxy]phthalonitrile and its metal phthalocyanines {M = Zn, Co, and Mn(Cl)} were synthesized by template cyclotetramerization of phthalonitrile derivatives. The newly synthesized compounds were characterized using UV–vis, FT-IR, 1H NMR, 13C NMR, and mass spectroscopy. The resultant compounds were successfully linked to the surface of silver nanoparticles. The characterization of the surficial modification was carried out by applying the TEM technique. The cytotoxic activities of the studied nanoconjugates were tested against A549, DLD-1, and Wi38 cell lines by performing a (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT) assay with/without irradiation. Although the functionalization of silver nanoparticles increased the solubility of phthalocyanines in aqueous media, the presence of phthalonitrile/phthalocyanine derivatives on the silver nanoparticles' surface improved their biological properties. All the studied biological candidates exhibited antiproliferative activities against the cell lines. The IC50 values calculated were between 6.80 and 97.99 μM against the studied cell lines in the dark. However, the IC50 values determined were between 3.11 and 88.90 μM with irradiation. The highest IC50 values obtained were 3.11 and 3.52 μM against the DLD-1 cell line for nanoconjugates 1-AgNP and 3-AgNP, respectively. The findings indicated that the compounds may be utilized as anticancer agents after further studies. [ABSTRACT FROM AUTHOR]

Integrating a heterojunction system with the impact of surface plasmon resonance (SPR) is an executable and innovative tactic for photocatalyst amelioration. Ag nanoparticle (Ag NP)-modified WO3/BiOCl/g-C3N4 (WB-CN) was favorably fabricated through in situ photo deposition assembly to form double heterojunctions (A-WBCN). The degradation performance of A-WBCN is better than that of pure g-C3N4 (CN) and WO3/BiOCl (WB), it can degrade more than 90% of OFLX within 20 minutes, due to Ag NPs performing as a bridge for electron mediators, apart from the implications of SPR in A-WBCN. The results of UV diffuse reflectance spectroscopy indicate that loading with Ag NPs can expand the light absorption range of WB-CN to near-infrared. The photoluminescence spectra and transient photocurrent spectra indicate that Ag NP loading significantly improves the separation efficiency of photogenerated carriers. Density functional theory (DFT) simulation results show that the introduction of Ag NPs can change the direction of carrier movement, resulting in bending of the energy bands of WB and CN, improving the redox ability of A-WBCN, and improving its photocatalytic efficiency. In addition, the intermediate products of OFLX was determined by HPLC-MS analysis. The spin electron resonance (ESR) results indicate that ˙O2− and ˙OH are the main active species in photocatalytic degradation. This work furnishes a fresh idea for upgrading photocatalytic performance and advancing electron transfer. [ABSTRACT FROM AUTHOR]

Nanoparticle-based electrochemical immunosensors demonstrate high sensitivity toward biomarker detection due to the large surface area of the nanoparticles and their ability to amplify the signal of the target molecule. Additionally, they have a fast response time, relatively lower cost, and can be easily miniaturized for point-of-care applications. Among noble metals, silver nanoparticles (AgNPs) have been extensively used in electrochemical sensors due to their unique properties, such as catalytic activity and excellent electrical conductivity. This Feature Article describes six approaches for incorporating AgNPs in electrochemical platforms, featuring the most recent developments in the silver–gold galvanic exchange-based detection strategy. With a few exceptions, many of these detection methods use AgNP oxidation into Ag+ ions, followed by electrodeposition of Ag+ ions onto the working electrode as zero-valent Ag metal and a final stripping step using a voltammetric technique. Combining these steps provides desirable low detection limits and good sensitivity for various biomarkers. A few other methods involved the reduction of Ag+ ions and depositing them as Ag metal onto the electrode using a reagent mixture so that the striping analysis could be performed. Typically, this reagent mixture includes Ag+ ions, a reducing agent, or an enzyme substrate. Besides, AgNPs have also been directly used to modify the surface of electrodes to facilitate kinetically favored redox-mediated electrochemical reactions. In addition to Ag detection methods, this report will also provide recent examples to illustrate how the size and shape of AgNPs impact the detection limits and sensitivity of an electrochemical assay. Finally, we discuss recent developments in lab-on-a-chip type immunosensors designed explicitly for Ag-based metalloimmunoassay detection, and we envision that this article will provide a comprehensive summary of the operational principles and new insights into such immunoassay systems. [ABSTRACT FROM AUTHOR]

Different nanostructural composites-capped silver nanoparticles (i.e., Ag-NPs@SHGel-MoX2, where X = S, Se) were explored. Nanocomposites comprising a two-dimensional (2D) metal dichalcogenides (i.e., MoS2, MoSe2, and MoS2–MoSe2) nanosheets-dispersed supramolecular hydrogel (SHGel) structure were used as stabilizing agents of silver nanoparticles synthesized through direct exposure to sunlight without use of external reducing chemicals under atmospheric conditions. The morphological uniqueness of individual nanocomposite-capped Ag-NPs was observed by transmission electron microscopy (TEM). Electron-dispersive X-ray spectroscopy associated with TEM revealed elemental-level confirmation of formation of Ag-NPs@SHGel-MoX2 with distinct nano-stabilizing agents composed of 2D nanosheets of MoS2-, MoSe2-, and combined MoS2–MoSe2-dispersed gel-nanocomposites. X-ray photoelectron spectroscopy of these composite-capped Ag-NPs was undertaken. The bioactivity of three diverse Ag-NPs (i.e., Ag-NPs@SHGel-MoS2, Ag-NPs@SHGel-MoSe2, and Ag-NPs@SHGel-MoS2–MoSe2) was surveyed. The antibacterial properties of three Ag-NPs@SHGel-MoX2 were experimentally tested employing Gram-positive Bacillus subtilis and Gram-negative Klebsiella pneumoniae. The anticancer activity of Ag-NPs@SHGel-MoS2, Ag-NPs@SHGel-MoSe2, and Ag-NPs@SHGel-MoS2–MoSe2 against the human adenocarcinomic alveolar cell line (A549) was also revealed. [ABSTRACT FROM AUTHOR]

Thiol-containing biomolecules, such as cysteine and glutathione, play essential roles in regulating the polarity and reactivity of the systems. Among functional MOFs, thiol MOFs, a subclass with a thiol group-containing ligand, are relatively less explored due to their synthetic challenges and stability and storage issues. Despite these drawbacks, they have many advantages due to the electronically soft thiol groups with strong reactivity and affinity toward soft metal ions. Herein, we have taken advantage of the affinity between thiol groups and a soft metal (Ag) by functionalizing a thiol MOF with Ag ions and finally synthesizing a silver nanoparticle-functionalized heterogeneous catalyst (Ag@Zr-DMBD). The Zr,Ag centre of the thiol MOF catalyst acts as an active centre and synergistically binds with the electron-rich oxygen atom of a terminal epoxide for efficient CO2 fixation to the corresponding cyclic carbonates under atmospheric CO2 pressure in 8 h. Finally, a rationalized reaction mechanism is proposed based on literature reports and current results. This work presents a viable strategy for using thiol MOFs as heterogeneous catalysts for CO2 fixation under mild conditions. [ABSTRACT FROM AUTHOR]

An electrochemical glucose sensor based on flexible materials is significant for wearable devices used for real-time health monitoring and diagnosis. However, applying flexible electrodes involves complex fabrication processes and might reduce detection sensitivity. To overcome these obstacles, we herein report a novel strategy for preparing a highly flexible enzyme electrode based on an electrospun poly(vinyl alcohol) (PVA) mat decorated with in situ grown silver nanoparticles (nano-Ag) for electrochemical glucose sensing. Ferrocene (Fc) was selected as an electron acceptor for glucose oxidase (GOD) in order to minimize the influence of oxygen. Electron transfer between GOD and Fc was facilitated by confining them within a mixed self-assembled monolayer (SAM) formed on a thin layer of gold deposited on top of the PVA/nano-Ag film. Nano-Ag was found to significantly increase the surface area of the electrode and improve the stability of electrode conductivity during tensile deformation. Electrochemical glucose detection was performed by chronoamperometry in the electroactivity domain of ferrocene, and good linearity (R2 = 0.993) was obtained in the range of 0.2–7 mM with a detection limit of 0.038 mM and a relative standard deviation (RSD) of 1.45% (n = 6). After being stuck to a bendable PDMS slice and bent, respectively, at 30° and 60° 50 times, the electrode showed slight changes in detection results (<4.78%), which remained within 8% when the bending angle increased to 90°. With its high flexibility, good detection performance, and convenient fabrication process, the proposed enzyme electrode showed good potential as a flexible platform for wearable glucose sensing systems. [ABSTRACT FROM AUTHOR]

In this work, zirconium phosphate (ZrP) supported Ag nanoparticle (NP) catalysts were constructed. The as-obtained catalysts were characterized thoroughly by XRD, HAADF-STEM, py-IR spectroscopy, etc. A coordination interaction was found between Ag NPs and the phosphate group on ZrP, and the acidic sites on ZrP played a very critical role not only in adsorbing nitrobenzene, but also in activating NaBH4 to facilitate hydrogen transfer to Ag sites. It was indicated that the ZrP-supported Ag NP catalysts were highly active for catalytically selective hydrogenation of the substituted nitroarenes into azoxybenzene compounds by using NaBH4 as a hydrogen source. Notably, the catalysts could afford a full conversion of nitrobenzene within 3 min and an exceptional selectivity to azoxybenzene. Moreover, 1%Ag/ZrP-R was recycled eight times without obvious loss of activity. No leaching of Ag species was observed in consecutive catalytic cycles. Methanol was found to be a superior solvent for this reaction and also acted as a hydrogen resource in the reaction. On the basis of the catalytic activity test and density functional theory (DFT) calculations, the reaction pathway was proposed as well. To our knowledge, the ZrP-supported metal catalysts are some of the best catalyst systems for selective hydrogenation of nitrobenzene into azoxybenzene compounds with exceptional activity and selectivity. [ABSTRACT FROM AUTHOR]

The present contribution reports a simple and environmentally friendly method of synthesizing silver nanoparticles (AgNPs) using the aqueous leaf extract of Mentha aquatica. The impacts of different operational parameters such as leaf extract dosage, pH solution, temperature and contact time on the formation of AgNPs were examined in detail. The data revealed that 5% v/v Mentha aquatica leaf extract, pH value 9.0, temperature 18 °C and 60 min reaction incubation time results in the optimum nanoparticle synthesis. The as-formed AgNPs were analyzed by (UV-Vis), FT-IR, X-ray diffraction (XRD), SEM/EDX and TEM. The FT-IR analysis demonstrated the involvement of phytochemicals in the synthesis of AgNPs. The TEM images indicated the mainly spherical forms of the AgNPs with a mean particle size of 25 nm. The XRD spectrum confirmed the face-centered cubic structure for the AgNPs. Additionally, in the DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical antioxidant study, the antimicrobial properties against Gram-positive and Gram-negative pathogens and the catalytic activity of the obtained silver nanoparticles were investigated. The results showed that the nanoparticles presented promising antioxidant and antibacterial activities. Moreover, significant catalytic activity in degrading Methylene blue (MB) with a maximum degradation capacity of up to 98% at a 2 mg catalyst dose was also observed. Hence, an easy and simple green approach for the synthesis of silver nanoparticles, with efficient antioxidant and antimicrobial properties and catalytic degradation of MB dye is reported in this study. [ABSTRACT FROM AUTHOR]

The study of substances with antibacterial properties has expanded greatly in recent years. However, there are few reports about the antibacterial activity of Ag@MOFs and I2@MOFs. In this study, ZIF-7 was used to load iodine (I2@ZIF-7) and silver nanoparticles (Ag@ZIF-7). FT-IR spectroscopy, PXRD, ZP, SEM, TEM, TGA, and BET analysis were used to investigate the successful synthesis of the samples. I2@ZIF-7 and Ag@ZIF-7 showed prolonged release of I2 and Ag+ up to 11 days, in addition to Zn2+ cation release. Finally, S. aureus and E. coli bacteria were used to study the antibacterial activity of the samples. The results showed that the antibacterial activity increased in the samples containing iodine (I2@ZIF-7) and silver nanoparticles (Ag@ZIF-7). ZIF-7 has antibacterial components, zinc metal ions, as an antibacterial agent and a suitable ligand, along with iodine and silver, causing a synergistic effect, which was another reason for choosing ZIF-7. I2@ZIF-7 and Ag@ZIF-7 showed a certain amount of antibacterial substance release such as iodine and silver gradually and for a long time (for about 11 days). I2@ZIF-7 and Ag@ZIF-7 also showed better antibacterial activity than other reported Ag@MOFs and I2@MOFs. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach for the fabrication of low cost Electrochemical-Surface Enhanced Raman Scattering (EC-SERS) sensing platforms. Laser Induced Graphene (LIG) electrodes were readily fabricated by direct laser writing of polyimide tapes and functionalized with silver nanoparticles (Ag NPs) to obtain hybrid Ag NPs – LIG electrodes suitable for EC-SERS analysis. Detection was achieved by coupling a handheld potentiostat with a Raman spectrograph, enabling measurement of SERS spectra of target analytes generated during voltage sweeps in the 0.0 to −1.0 V interval range. The sensing capabilities of the fabricated system were first tested with model molecule 4-aminobenzenethiol (4-ABT). Following sensitive detection of 4-ABT, EC-SERS analysis of food contaminant melamine in milk and antibiotic difloxacin hydrochloride (DIF) in river water was demonstrated, achieving sensitive detection of both analytes without pre-treatment steps. The easiness of fabrication, versatility of design, rapid analysis time and potential miniaturization of the system make Ag NPs – LIG electrodes suitable for a large range of in situ applications in the field of food monitoring and for environmental analysis. [ABSTRACT FROM AUTHOR]

We demonstrate photoisomerization-controlled wavelength-tunable plasmonic lasers by integrating spiropyran derivative-doped PMMA films with two-dimensional Ag nanoparticle arrays. The controllable transformation between spiropyran derivatives and its isomers with different refractive indices by photoexcitation allows for a dynamical and continuous change of the refractive index in the host PMMA film, which is able to tune the lattice plasmon resonance, and hence the lasing wavelength. This result opens up a new avenue for engineering wavelength tunable plasmonic lasers toward practical photonic integration. [ABSTRACT FROM AUTHOR]

A novel enhanced fluorescent sensor system for zearalenone (ZON) determination in flour samples is presented. The ZON-selective molecularly imprinted polymer (MIP) films were developed with a computational modelling method and synthesised with cyclododecyl-2,4-dihydroxybenzoate as a "dummy" template and ethylene glycol methacrylate phosphate as a functional monomer acted as the selective recognition elements for ZON fluorescence detection. Spherical silver nanoparticles (AgNPs) were embedded in the MIP films' structure to enhance the sensor sensitivity. The imprinted films showed a high ZON recognition ability compared to non-imprinted films. Various factors that affected the measurement of the analysed sample were investigated and optimised. Embedding the AgNPs in the MIP films' structure led to an enhanced sensitivity (up to a 200-fold decrease of LOD) compared to unmodified MIP films. This fluorescent sensor system provided ZON analysis with high sensitivity, specificity, and a wider linear dynamic range of 5 ng mL−1 to 25 μg mL−1. An enhanced fluorescent sensor system based on MIP chips with embedded AgNPs could detect trace amounts of ZON in foods and feedstuffs with high sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

In this study, we present a direct colorimetric technique for the sensitive and specific detection of Ba2+ ions in laboratory tap and river water utilizing functionalized 18β-glycyrrhetinic acid peptide silver nanoparticles (GAP-AgNPs). Sodium hydroxide solution was used to carry out chemical reduction during the synthesis of GAP-AgNPs. Several spectroscopic methods, including UV-visible, zetasizer, FTIR, SEM, AFM, and XRD, were used to characterize the GAP-AgNPs. The GAP-AgNPs were found to be extremely stable at high temperatures, and a variety of electrolyte concentrations and pH values. The GAP-AgNPs were selective for Ba2+ compared to other metal ions (Na+, Mg2+, Al3+, Ca2+, Co2+, Hg2+, Mn2+, Ni2+, Fe2+, Cr3+, Cu2+, Fe3+, Zn2+, and Ba2+) leading to a noticeable color change. The addition of barium significantly decreases the absorption intensity and shifts the wavelength toward a red shift of the nanoparticles along with the color change to red from yellow. When competing metal ions were present, it was discovered that they were extremely selective for the Ba2+ ion. The nanoparticles showed sensitivity towards Ba2+ over a wide range of concentrations with a limit of detection of 0.42 μM. The findings of this study reveal the GAP-AgNPs as a selective, sensitive, and easy sensing probe for Ba2+ in human blood plasma, river water, and laboratory tap water. [ABSTRACT FROM AUTHOR]

The nanocomposite of graphene oxide and silver nanoparticles has attracted great interest from scientists. In this work, silver@graphene oxide (Ag@GO) nanocomposite was synthesized via a biological reduction route using Andrographis paniculata extract as the reducing agent. The factors affecting the material preparation, comprising AgNO3 volume, temperature, reaction time, and the amount of GO used, were investigated to select the appropriate conditions. As a result, silver nanoparticles were indicated to successfully form spherical-shaped particles with an average size of 31.93 ± 3.42 nm at 0.8 mL of the AgNO3, pH 10, and 90 °C for 30 min of the reaction time with a ratio of AgNO3 : GO = 1 : 1, corresponding to the Ag@GO-1.6 sample. Moreover, Ag@GO-1.6 showed high antibacterial activity against both Gram-negative and Gram-positive bacteria. The composite also induced notable cytotoxicity against the cancerous KB cells while barely affecting the normal HEK-293 ones. Besides, Ag@GO-1.6 showed great sensing ability for H2O2 with a relatively low limit of detection (2.65 μL) along with a wide detection range of 0–15 μM. Therefore, those results confirmed the potential applications of bio-synthesized Ag@GO in the medical and environmental fields. [ABSTRACT FROM AUTHOR]

Designing efficient catalysts for the chemical fixation of CO2 on reactive organics under mild conditions is very challenging from the perspectives of green and sustainable chemistry. Here we report a triazinetriamine-based porous organic polymer (TzTa-POP) and immobilized silver nanoparticles at its surface to fabricate a metal nanoparticle embedded catalyst AgNPs@TzTa-POP. The characterizations of AgNPs@TzTa-POP have been carried out by using FTIR, PXRD, TGA, SEM, EDAX, TEM, N2 sorption and XPS analyses. The catalytic activity of Ag-NPs@TzTa-POP was evaluated in the carboxylative cyclization (intramolecular nucleophilic) of propargyl alcohols by using CO2 as a reactant to obtain α-alkylidene cyclic carbonates. The desired α-alkylidene cyclic carbonates with high selectivity (>99%) and significantly high yield (87–98%) were achieved via atmospheric fixation of CO2 at room temperature under easily operative reaction conditions. Furthermore, Ag-NPs@TzTa-POP showed excellent catalytic activity in the three component coupling reaction involving CO2, aromatic/aliphatic amine and aliphatic/aromatic halide for the synthesis of value added organic carbamates. High isolated yield (∼87–95%) of the desired carabamate product was obtained using 1 atm CO2 pressure under mild reaction conditions at room temperature. The catalyst sustains its activity for five consecutive reaction cycles for both the reactions. Post catalytic characterizations of AgNPs@TzTa-POP after five reaction cycles were carried out to figure out any materialistic changes in the metal nanoparticle embedded porous organic polymer. [ABSTRACT FROM AUTHOR]

Arsenic is one of the most harmful heavy metals, and needs constant monitoring and control. A susceptible and selective sensor for arsenic (III) detection in polluted water samples has been developed by using chitosan-stabilized silver nanoparticles (AgNPs). A glassy carbon electrode (GCE) is modified with chitosan-stabilized silver nanoparticles, which provides sufficient sites for interaction with the analyte. The synthesized silver nanoparticles are characterized using different characterization techniques, such as UV-Visible spectroscopy, transmission electron spectroscopy (TEM) and particle size distribution. The particle size and polydispersity index (PDI) value of the chitosan stabilized silver nanoparticles are found to be 6 nm and 0.3, respectively, which enhances the electroactive surface area and hence the sensor sensitivity. The ion imprinting technique is used to improve the selectivity of the sensor. The arsenic sensor is found to be very selective in the presence of other possible interferents like Pb2+, Zn2+, Cu2+, Ag+ and Fe2+. The detection of As(III) was performed using differential pulse anodic stripping voltammetry (DPASV) and the detection limit was found to be 11.39 pM. The developed sensor is successfully tested for the picomolar level detection of arsenic (III) in different water samples. [ABSTRACT FROM AUTHOR]

In this work, spherical silver nanoparticles (AgNPs) with a mean diameter of 50.4 nm were prepared by sodium citrate reduction. The interaction mechanism of AgNPs with γ-globulin fibrinogen and hyaluronidase (HAase) was studied using multispectral methods. The results presented clearly indicate that the intrinsic fluorescence of γ-globulin, fibrinogen and HAase is effectively quenched by AgNPs through a static quenching mechanism, which is further confirmed by UV-vis analysis. The order of the binding constant and Hill coefficient is the same, fibrinogen–AgNPs > γ-globulin–AgNPs > HAase–AgNPs. The interaction between γ-globulin/fibrinogen and AgNPs is an endothermic and entropy-driven process, and the main non-covalent force is hydrophobic interaction. The interaction between HAase and AgNPs is an exothermic, enthalpy-driven process, and van der Waals force and hydrogen bonding are the main non-covalent forces. The interaction of γ-globulin/fibrinogen with AgNPs reduces the hydrophobicity of the tryptophan (Trp) microenvironment, but has no effect on the tyrosine (Tyr) microenvironment. The interaction between HAase and AgNPs has no obvious effect on the microenvironment of Trp and Tyr. CD spectra indicate that the secondary structure of γ-globulin/fibrinogen/HAase changes with the increase of AgNP concentration, and the content of α-helix (fibrinogen and HAase) or β-sheet (γ-globulin) decreases, inducing partial unfolding of the three proteins. [ABSTRACT FROM AUTHOR]

Bacterial infections pose a large threat to human health, and it is necessary to look for various strategies for inhibiting the growth of pathogenic bacteria. Silver-based nanomaterials have become good candidates for designing antibacterial agents. Different from the synthesis of silver nanoparticles (AgNPs) using an additional ligand and reducing agent, our simpler strategy involves constructing carbon–silver nanocomposites (C–Ag NCs) using polysaccharide-derived CDs as a reductant and stabilizer. The facile C–Ag NCs possessed superior antibacterial activity with a minimum bactericidal concentration (MBC) of 1.3 μg mL−1 Ag after incubation for 6 h, and could kill a wide range of bacteria, including Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, Salmonella typhimurium, Vibrio parahemolyticus, and Shigella castellani. We believe that the simple hybrid C–Ag NCs provide an alternative strategy for the design of antimicrobial agents in biomedicine and food industry. [ABSTRACT FROM AUTHOR]

This work reports the direct synthesis of organochalcogen-modified silver nanoparticles (A1-7), their cytotoxic potentials against glioma cells (C6) and their interaction with DNA. The influence of the presence of electron-withdrawing and donating groups on the structures of the diselenide were evaluated. MTT data suggest that A3 and A6 reduced C6 cell viability via an addictive effect of the organochalcogen and silver and that the A7 activity had been only attributed to the silver component of the nanoparticle. A3, A6 and A7 showed interaction with DNA by intercalation and, at higher concentrations, a groove binding prevalence was observed. [ABSTRACT FROM AUTHOR]

Urinary potassium is an important parameter in clinical health diagnosis. Rapid and convenient detection of potassium ions (K+) in urine is essential for personal healthcare and health management. Here, crown ether (4-aminodibenzo-18-crown-6, ADC) modified silver nanoparticles (ADC-Ag NPs) were successfully prepared for one-step rapid colorimetric detection of urinary potassium. The detection mechanism is as follows: due to the matching sizes of the diameter of K+ and the cavity in crown ether 6, K+ is encapsulated between the cavities of two crown ethers, resulting in the clumping of ADC-Ag NPs and the color of the solution being altered. The colorimetric detection method has a fast response and is completed within 20 minutes. It also shows good selectivity and interference immunity. The lowest detectable concentration is 20 μM with the naked eye and 2.16 μM for UV-vis absorption spectroscopy. A good linear relationship (R2 = 0.9931) between the absorption intensity ratio and K+ concentration (0–100 μM) indicates that this colorimetric probe can be used to detect K+. The method was also applied for quantitative analysis of K+ in real urine samples with recovery between 116 and 120%. [ABSTRACT FROM AUTHOR]

Prussian Blue (PB) is an inexpensive, biocompatible, photothermally active material. In this paper, self-assembled monolayers of PB nanoparticles were grafted on a glass surface, protected with a thin layer of silica and decorated with spherical silver nanoparticles. This combination of a photothermally active nanomaterial, PB, and an intrinsically antibacterial one, silver, leads to a versatile coating that can be used for medical devices and implants. The intrinsic antibacterial action of nanosilver, always active over time, can be enhanced on demand by switching on the photothermal effect of PB using near infrared (NIR) radiation, which has a good penetration depth through tissues and low side effects. Glass surfaces functionalized by this layer-by-layer approach have been characterized for their morphology and composition, and their intrinsic and photothermal antibacterial effect was studied against Gram+ and Gram− planktonic bacteria. [ABSTRACT FROM AUTHOR]

Surface enhanced Raman spectroscopy (SERS) is a powerful tool for the investigation of low concentration analytes. To improve this method, magnetic nanoparticles were introduced to the system. Magnetic nanoparticles together with plasmonic silver or gold nanoparticles or shells not only enhance the SERS signal but also facilitate to focus the sample and direct it to the place of need. In this work, different chemicals were used for the modification of magnetite in order to improve the attachment of plasmonic nanoparticles on the surface of magnetic nanoparticles. In addition to this, the modification using PEI was chosen for a further decoration procedure with different ratios of AgNPs and AuNPs in various sequences. Composites having silver, gold, and magnetite nanoparticles were obtained and the best modification conditions for optimal SERS signal were evaluated by employing multiwavelength excitation. It was noticed that the order of the decoration makes a difference in the obtained signal enhancement. These composites can improve the adsorption and sensing of different analytes as both silver and gold surfaces are accessible to the solution. [ABSTRACT FROM AUTHOR]

Near-infrared-emitting quantum dots (QDs) are very interesting for (bio)medical uses because they penetrate biological tissues more deeply and emit light in the biological diagnostic window, that is, the region from 650 to 1450 nm. Among the semiconductors with appropriate band gaps to provide photoluminescence at wavelengths longer than 650 nm, silver chalcogenides are distinguished mainly by being environmentally friendly. This work proposes the use of experimental design techniques to optimize a one-pot aqueous procedure to synthesize photoluminescent silver selenide (Ag2Se) QDs capped with mercaptosuccinic acid (MSA). The best conditions found were Ag/Se and MSA/Ag molar ratios of 8 : 1 and 6 : 1, respectively, pH 5.0, and stirring for 20 minutes at 60 °C. The Ag2Se nanocrystals synthesized under those experimental parameters showed a photoluminescence quantum yield of 16.3%, absorption edge at 583 nm, and emission within the biological diagnostic window, at 789 nm, with orthorhombic crystal structure and an average diameter of 5.7 nm. [ABSTRACT FROM AUTHOR]

Manganese oxides have wide application in the ambient decomposition of ozone, although their activities are affected by many parameters. Morphology engineering and metal doping are, together, one of the most effective methods to enhance catalytic activity for O3 decomposition. Herein, a topochemical transformation route to Mn3O4 nanospheres composed of 2D nanosheets is first provided by using layered β-MnOOH as the precursor. Then, silver nanoparticles are deposited over the Mn3O4 nanosheets via a redox reaction without any extra reducing agents. In comparison with Mn3O4 with a conventional octahedral morphology, the prepared Mn3O4 nanosphere (Mn3O4-NF), and its Ag-doped composite, Mn3O4@Ag (Mn3O4@Ag-NF), both retain the morphology of β-MnOOH, and display better reducibility and higher oxygen vacancies. The best catalytic performance for O3 decomposition is found over Mn3O4@Ag-NF, which exhibits ∼88.5% removal efficiency within 24 h at a space velocity of 600 L g−1 h−1 and a relative humidity of 50% at room temperature. This work emphasizes the advantages of nanosheet morphology and metal doping in optimizing the catalytic activity for O3 elimination of manganese oxide. [ABSTRACT FROM AUTHOR]

Silver oxide nanoparticles (Ag2ONPs) were synthesized by a one-step, green, and novel method. Ag2ONPs were characterized independently as well as in mixtures with common antibiotics. The antibacterial activity of Ag2ONPs and antibiotics was evaluated by the minimum inhibitory concentration method and the effect of the combination by the checkerboard assay against representative reference strains and five multidrug-resistant (MDR) bacteria, which were isolated from patients with skin wound infections. The viability and cytotoxic effects were evaluated on human dermal fibroblasts (HDF) by the calcein/EthD-1 method and the MTT assay. TEM analysis showed that the Ag2ONPs are spherical with an average size of 8.72 nm and zeta potential of −63.68 mV. The XRD diffractogram revealed that Ag2ONPs have a cubic crystal structure, and the Raman spectrum confirmed the characteristic vibrational modes of the structure. FT-IR spectra suggest that Ag2ONPs interact with amino and carboxyl groups present in antibiotics. It was found that Ag2ONPs have a broad-spectrum antibacterial effect, and a concentration of less than 8 μg mL−1 was required to inhibit the development of MDR bacteria. Both basic antibiotics were able to enhance the antimicrobial effect of Ag2ONPs; however, combination with ciprofloxacin showed that concentrations <1 μg Ag2ONPs per mL inhibit the growth of all the tested bacteria. The calcein/EthD-1 method revealed that concentrations ≤1 μg Ag2ONPs per mL are tolerated by HDF, showing their characteristic phenotype, while the MTT assay showed that concentrations ≤0.5 μg Ag2ONPs per mL do not affect cell proliferation during four days in culture. Ag2ONPs used in this study were biocompatible with HDF and inhibit the growth of MDR bacteria, properties that were improved in combination with commercial antibiotics, suggesting that these combinations could be used to prevent infections of skin wounds by MDR bacteria and their dissemination. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs), as a novel platform for the synthesis of metal nanoparticles, display abundant properties of adjustable porosity, high crystallinity and large surface area. In particular, three-dimensional (3D)-COFs are unique skeletons with greater surface areas, numerous easily accessible active sites and interpenetrating channels compared to 2D-COFs. These eminent properties of 3D-COFs are very beneficial for anchoring metal nanoparticles, and effectively restrict the size and growth of nanoparticles, enhancing the catalytic performance. In this study, we prepare hybrid nano-materials (denoted as AgNPs-3D-COF) based on Ag nanoparticles and a hydroxy functional 3D-COF. The strong coordination between OH groups and metal Ag and finite aperture generate uniform and small size Ag nanoparticles. When applied to the catalytic reduction of 4-nitrophenol and the degradation of organic dyes, namely methylene blue and Congo red, AgNPs-3D-COF delivers high activity and enduring cycling stability. We expect that this study can offer a strategy for constructing advanced heterogeneous metal nanoparticle catalysts and accelerate the advancements of 3D-COFs. [ABSTRACT FROM AUTHOR]

Drug resistance has become a serious global concern, and therefore developing a new antibacterial agent that can fight drug-resistant bacteria without generation of resistance is urgent. Herein, we synthesize indole functionalized silver nanoparticles (Ag NPs) through a simple one-pot method to fight drug-resistant bacteria. When silver nanoparticles are modified with 5-nitroindole and tryptophan, these two silver nanoparticles (5NI-Ag NPs and Try-Ag NPs) exhibit excellent antibacterial activities against both Gram-positive and Gram-negative bacteria (S. aureus and E. coli). In particular, Try-Ag NPs exhibit better antibacterial activity against both normal bacteria and drug-resistant bacteria with a low MIC of 6 μg mL−1 for E. coli and 8 μg mL−1 for S. aureus, respectively. Moreover, it is not easy for bacteria to generate resistance toward Try-Ag NPs. In conclusion, our research provides a possibility for developing new antibacterial materials to fight DR bacteria by modifying silver nanoparticles with small molecule ligands. [ABSTRACT FROM AUTHOR]

Nanosilver is a versatile biomedical agent that can potentially battle against bacterial infection. Herein, we introduce an energy-efficient green approach to synthesize phytonutrient modified silver nanoparticles (AgNPs) using the cogon grass extract (CGE) in 15 minutes. The biogenic AgNPs were characterized using UV-Vis, FT-IR, TEM, XRD, XPS, and zeta-potential measurements. The results from in vitro biological assays indicated that CGE-mediated AgNPs possess good antioxidant activity, broad-spectrum antibacterial activity, satisfactory dispersion stability, and trivial hemolytic activity. Among the reported biogenic AgNP studies, AgNPs synthesized using the CGE displayed a superior antibacterial performance against two drug-resistant Acinetobacter baumannii strains and showed stronger bactericidal capability toward E. coli and S. aureus. Investigation of the antibacterial mechanism of CGE-mediated AgNPs toward bacteria indicated the accumulation of AgNPs in the bacterial cells, steady release of silver ions, and production of reactive oxygen species to damage the bacterial surface structure. Additionally, our mass spectrometric screening revealed that several putative phytochemicals in the CGE act as the reducing agent capping on the AgNP surfaces, which intensifies the antibacterial activity. These data indicate that the CGE-mediated AgNPs can act as a broad-spectrum antibacterial agent in public health. [ABSTRACT FROM AUTHOR]

The flexible surface-enhanced Raman scattering (SERS) platform has ceaselessly propelled the development of point-of-care testing (POCT) in diverse fields. Herein, we report a facile strategy for the SERS-chemometric analysis of four β-blockers (bisoprolol, metoprolol, acebutolol and esmolol) based on a super-sticky mussel-inspired hydrogel SERS tape. The surface morphology and mechanical properties of the hydrogel tape can be easily controlled by adjusting the compositional ratio. The optimized tape with excellent toughness and adhesiveness allows efficient collection of analytes through a simple "paste and peel off" approach, further by spraying with silver nanoparticles using a household sprayer to instantly assemble a flexible SERS substrate, the analytes can then detected by a portable Raman spectrometer. This POCT strategy enables the identification and discrimination of four similar β-blockers with high sensitivity and accuracy in combination with the statistical algorithms. The developed SERS tape is finally utilized for the recognition of β-blockers in simulated urine solution, which realizes a limit of detection of 1.0 ng mL−1, revealing a promising potential of this SERS-based POCT for the clinical detection of doping abuse. [ABSTRACT FROM AUTHOR]

This study presents simultaneous colorimetric detection of two very similar amino thiols viz. cysteine and homocysteine at their micro and sub-micromolar levels, respectively, through the aggregation of citrate capped silver nanoparticles. A rare kind of categorical naked-eye detection of homocysteine over cysteine was accomplished through the conjugation of these AgNPs with thiosulphate. The UV-Vis and SERS characteristics of these AgNPs were also more prominent with homocysteine compared to cysteine. The quantification of cysteine was performed in a pharmaceutic sample with an accuracy of 89 ± 5%. [ABSTRACT FROM AUTHOR]

As the usage of antibiotics and vitamin tablets becomes more widespread, detrimental impacts on living beings are increasing by consuming polluted water contaminated with drug residues. Because of the emergence of drug-resistant bacteria, there is an increasing requirement for determining frequently accessible medicines in water sources. We have developed a rapid colorimetric sensor for the selective recognition of neomycin and thiamine. A simple reduction method was followed to synthesize citrate capped silver nanoparticles (AgNPs) as a sensor. The presence of functional groups and the surface charge of AgNPs were characterized by FT-IR and zeta potential measurements. The colloidal solution of AgNPs displayed an instantaneous chromatic change from yellow to purple and brown-red after the respective treatment with neomycin and thiamine, although the other drugs showed infectivity. The plasmonic characteristic peak at a 405 nm wavelength of AgNPs underwent a gradual decrease with an increase in the concentration of the drug. In addition, it showed a bathochromic shift and broadening to longer wavelengths of 520 nm and 565 nm after the incubation with neomycin and thiamine, respectively. The simultaneous quenching and shift of the plasmonic peak were ascribed to the aggregation of AgNPs in the presence of the analytes via hydrogen bonding and proved by spectroscopic and microscopic techniques. The colloidal AgNPs displayed an excellent performance for the determination of these drugs at concentrations ranging between 7.5 nM and 0.05 mM with low detection limits of 70.8 pM and 0.42 nM for neomycin and thiamine, respectively. The selectivity towards neomycin and thiamine was prolonged even in the presence of interfering drug mixtures and in real sample analysis. [ABSTRACT FROM AUTHOR]

Radical polymerization reactions were employed to synthesize thermo-responsive poly(N-isopropylacrylamide-co-2-acrylamido-2-methyl-1-propanesulfonic acid) hydrogels at room temperature. The results of Fourier Transform Infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) confirmed the chemical composition of the synthesized thermo-sensitive hydrogels. The following steps were used to construct P(NIPAM-co-AMPS)-Ag-L/H (1) loading Ag into thermo-sensitive hydrogels at 25 °C and 60 °C, (2) removing loosely-bound Ag ions, and (3) reducing Ag ions with sodium borohydride (NaBH4). Transmission electron microscopy (TEM) and high resolution X-ray photoelectron spectroscopy (HRXPS) were used to depict metal nanoparticle embedded p(NIPAM-co-AMPS)-Ag. To identify the hydrodynamic radius of the combinations and the thermo-sensitivity of the synthesized hydrogels, dynamic light scattering (DLS) was utilized. Atomic absorption spectroscopy (AAS) was also employed to measure the concentrations of metals in all compounds. In the process of alcohol and olefin oxidation, p(NIPAM-co-AMPS)-Ag composites with different parameters functioned as catalysts. The results confirmed the easy separation of the prepared catalysts from the reaction media. Moreover, the catalysts could efficiently be recycled eight times without losing their quality. FT-IR spectroscopy and atomic absorption spectroscopy also proved that the catalysts were recyclable, durable, and leaching-resistant. [ABSTRACT FROM AUTHOR]