Silver Nanoplates Research Articles

Preparation of triangular silver nanoplates by improved light-driven seed growth method

Triangular silver nanoplates have been synthesized by the improved light-driven seed growth method with only trisodium citrate as both photoreducing reagent and capping reagent under the irradiation of sodium lamp. • Triangular silver nanoplates (TSNPs) can exhibit tunable plasmonic properties across the entire visible spectrum and in the near-infrared region. • TSNPs have been synthesized by the improved light-driven seed growth method with only trisodium citrate as both photoreducing reagent and capping reagent. • The simple rapid preparation process will make it apply in large scale. Triangular silver nanoplates (TSNPs) have attracted much attention for their tunable plasmonic properties. In this letter, TSNPs have been synthesized by the improved light-driven seed growth method with only trisodium citrate (TSC) as both photoreducing reagent and capping reagent. By means of this high efficient method, TSNPs could be produced in high yield. As a kind of promising material, TSNPs will be used for chemical and biological sensing, and they can also be applied in optical limiters against high intensity laser pulse.

Enhanced Antimicrobial Activity of Biocompatible Bacterial Cellulose Films via Dual Synergistic Action of Curcumin and Triangular Silver Nanoplates.

Curcumin and triangular silver nanoplates (TSNP)-incorporated bacterial cellulose (BC) films present an ideal antimicrobial material for biomedical applications as they afford a complete set of requirements, including a broad range of long-lasting potency and superior efficacy antimicrobial activity, combined with low toxicity. Here, BC was produced by Komagataeibacter medellinensis ID13488 strain in the presence of curcumin in the production medium (2 and 10%). TSNP were incorporated in the produced BC/curcumin films using ex situ method (21.34 ppm) and the antimicrobial activity was evaluated against Escherichia coli ATCC95922 and Staphylococcus aureus ATCC25923 bacterial strains. Biological activity of these natural products was assessed in cytotoxicity assay against lung fibroblasts and in vivo using Caenorhabditis elegans and Danio rerio as model organisms. Derived films have shown excellent antimicrobial performance with growth inhibition up to 67% for E. coli and 95% for S. aureus. In a highly positive synergistic interaction, BC films with 10% curcumin and incorporated TSNP have shown reduced toxicity with 80% MRC5 cells survival rate. It was shown that only 100% concentrations of film extracts induce low toxicity effect on model organisms’ development. The combined and synergistic advanced anti-infective functionalities of the curcumin and TSNP incorporated in BC have a high potential for development for application within the clinical setting.

Preparation of Single-layer Triangular Silver Nanoplates on Substrates via a Tape-peeling Method

Silver nanoparticles (NPs) including spherical and triangular plates were prepared. These NP films were constructed on the self-assembled monolayer of 3-aminopropyltrimethoxysilane using a simple dipping method. The tape-peeling method was applied to the films, and only the spherical nanoparticles were removed from the substrate. As a result, a triangular silver nanoplate combined substrate has been obtained.

Use of field-flow fractionation and single particle inductively coupled plasma mass spectrometry for the study of silver nanoparticle shape transformation

Field-flow fractionation-inductively coupled plasma mass spectrometry (FFF-ICP-MS) and single particle ICP-MS (SP-ICP-MS) were used for investigation of silver nanoparticle shape transformation. Commercial and laboratory synthesized silver nanoparticles were employed in this study. For laboratory synthesized silver nanoparticles, silver nanosphere seed was first prepared by reducing silver nitrate with sodium borohydride in starch stabilizing agent. The obtained nanosphere exhibited 27.5 nm hydrodynamic diameter from FFF-ICP-MS analysis with equivalent spherical diameter of 26 nm from SP-ICP-MS analysis. This nanosphere underwent shape transformation induced by varying volumes of hydrogen peroxide. Increasing hydrogen peroxide volume resulted in increased particle diameter, and nanoplate formation. These synthesized nanoparticles and commercial silver nanoplates were subjected to shape transformation induced by bromide etching. General trend was observed that bromide addition caused particles to become smaller. Clear trend was found for commercial silver nanoplates that bromide addition caused both hydrodynamic diameter measured by FFF-ICP-MS and equivalent spherical diameter measured by SP-ICP-MS become smaller. Furthermore, the combined information from FFF-ICP-MS and SP-ICP-MS analysis with the use of TEM data were proposed to provide additional information on the edge length and the thickness of silver nanoplates. With the known edge length of commercial silver nanoplates, the thickness was estimated to be 25.4 nm, 7.64 nm, and 4.95 nm for triangular nanoplates with the edge length of 32 nm, 70 nm, and 153.1 nm, respectively. Both FFF-ICP-MS and SP-ICP-MS provided unique information which are useful for nanoparticle characterization.

Effect of Surface Curvature on Colloidal Stability of Silver Nanoparticles with Monomolecular and Mixed Thiol Ligand Layers in the Presence of Alkali Cations.

Colloidal stability of silver nanoparticles is the critical parameter while designing colloidal colorimetric biosensors. Here, we examined colloidal stability of 11-mercaptoundecanoate-capped quasi-spherical silver nanoparticles and silver nanoplates in 0.02 M phosphate buffers with pH 8.0 containing Li+ , Na+ , K+ , or Cs+ cations. While quasi-spherical nanoparticles demonstrate a good colloidal stability in the presence of all studied cations, nanoplates aggregate in the presence of Na-phosphate buffer. The mechanism of aggregation consists in the ion-specific nanoparticle-cation bridging interaction, which is sensitive to the nanoparticle surface curvature. Increased apparent dissociation constant of carboxyl groups on the zero-curvature nanoplates' surface enhances bridging interactions and makes nanoplates colloidally unstable. Bridging interactions can be eliminated by using mixed bimolecular 11-mercaptoundecanoate-11-mercaptoundecanol surface ligand layer. Silver nanoplates with mixed ligand layer show an enhanced colloidal stability at a standard carbodiimide bioconjugation protocol.

Electrical Switching of Nematic Plasmonic Nanocolloids for Infrared Solar Gain Control

AbstractControlling solar gain is essential to reduce the energy consumption by residential and commercial buildings, which are responsible for ≈40% of all energy generated globally. However, the dynamic control of solar gain in the near‐infrared that corresponds to ≈50% of the overall Sun's energy at the Earth's surface, separately from the visible spectral range has been a challenge, albeit commercial coatings provide passive control while retaining highly visible transmission. To address this problem, in this paper switchable silver colloids (SSCs) are demonstrated, colloidal analogs of the common silver coatings used for solar gain control. When dispersed in a nematic liquid crystal, orientations of such plasmonic silver nanoplates are controlled by ≈1 V low‐voltage electric fields, allowing for sub‐second switching of the near‐infrared‐based solar gain. Installed and retrofit products made from thin films of such nanoplate dispersions confined between glass and plastic substrates, respectively, exhibit electrically controlled infrared‐based solar gain while retaining high visible‐range transparency, low haze, and high color rendering index. This study's findings reveal a great potential of soft‐matter systems in addressing energy‐related problems.

High-throughput synthesis of silver nanoplates and optimization of optical properties by machine learning

High-throughput synthesis of silver nanoplates was performed by two-step reduction via the seed particles to clarify how the absorption spectrum is controlled by the concentrations of AgNO3 and citrate for the seed particle synthesis and that of the seed particles for the nanoplate synthesis. A wide variety of the concentrations, whose combination amounted to 486 conditions, was explored with an automated liquid handler, and the absorption spectrum was measured with a microplate reader. The spectrum was decomposed into two peaks, one around 400 nm from the spherical seed particles and the other at longer wavelength from the nanoplates. The nanoplate peak’s wavelength, width, and height were expressed as functions of the concentrations of AgNO3, citrate, and seed particles by non-linear support vector regression. This enabled us to predict optimum conditions for synthesizing nanoplates with high and narrow absorption peaks at desired wavelengths ranging widely from 450 to 900 nm.

Glucose-assisted polyol synthesis of silver nanoplates and nanoprisms in the presence of oxyethylated carboxylic acid

This work reports a simple route to synthesizing silver nanoplates and nanoprisms through a polyol approach in the presence of oxyethylated carboxylic acid and glucose. The resulting particles were characterized by electron microscopy and X-ray diffraction (XRD). The introduction of glucose and NaOH into the system substantially increases the yield of nanoplates and reduces their thickness. The optimized reaction conditions can be used to produce, in a one-pot synthesis, silver nanoplates and nanoprisms which may have applications as metallic fillers in ink and paste formulations for 2D and 3D printing to fabricate functional components and devices.

Photo-thermally enhanced antimicrobial efficacy of silver nanoplates against Gram-negative, Gram-positive bacterial and fungal pathogens.

This paper aims to investigate the photo-thermally enhanced antimicrobial efficacy of triangular silver nanoplates for a broad range of harmful pathogens viz., Gram-negative bacteria (Escherichia coli), Gram-positive bacteria (Staphylococcus aureus), and fungus (Candida albicans). Triangular silver nanoplates were synthesized using the chemical method and were characterized for optical absorption, size and morphology, surface charge and concentration via UV-Vis spectroscopy, transmission electron microscopy, zeta potential analysis and inductively coupled plasma mass spectrometry, respectively. Furthermore, the photo-thermally enhanced antimicrobial efficacy of the triangular silver nanoplates (10μg/ml concentration) was evaluated on broadband near-infrared irradiation. The photothermal response shows that for the fixed concentration of silver nanoplates, the smaller-sized nanoplates (~52 nm) lead to higher temperature rise than larger-sized nanoplates (~68 nm). It is demonstrated that within a short exposure duration of 15 min, the photothermal activation of silver nanoplates led to ~5 log10 CFU/ml reduction for E. coli and C. albicans, and ~7 log10 CFU/ml reduction for S. aureus from a considerably high initial load of 5× 108 CFU/ml. The present study demonstrates that photo-thermally enhanced triangular silver nanoplates possess much stronger antimicrobial efficacy over a short exposure duration of few minutes and exhibits the applicability for a broad range of pathogens. The study is highly significant and explains the eradication of broad-spectrum of microbial pathogens by photo-thermally enhanced silver nanoplates in short exposure duration with low nanoparticle concentration, which is useful for diverse antibacterial and antifungal applications.

A SERS Platform for Rapid Detection of Drug Resistance of Non-Candida albicans Using Fe3O4@PEI and Triangular Silver Nanoplates

PurposeCandida infection has a high mortality rate, and the increasing prevalence of non-Candida albicans drug resistance in recent years poses a potential threat to human health. Non-Candida albicans has long culture cycles, and its firm cell walls making it difficult to isolate DNA for sequencing.Materials and MethodsFe3O4@PEI (PEI, polyvinyl imine) was mixed with clinical samples to form Fe3O4@PEI@non-Candida albicans and enriched them with magnets. Triangular silver nanoplates enhanced the surface-enhanced Raman scattering (SERS) signal. SERS was used to detect the fingerprint spectrum of non-Candida albicans. Then, orthogonal partial least squares discriminant analysis (OPLS-DA) was used to analyze the drug resistance of non-Candida albicans.ResultsSERS combined with OPLS-DA could well analyze the drug resistance of non-Candida albicans. Through 10-fold-cross validation, the accuracy of training and test data is greater than 99%, indicating that the model has good classification ability. We used SERS for the first time to detect the drug resistance of non-Candida albicans directly.ConclusionThis approach can be utilized without causing damage to the cell wall and can be accomplished in as little as 90 minutes. It can provide timely guidance for the treatment of patients with good clinical application potential.

Photoreduction of CO2 into CH4 Using Novel Composite of Triangular Silver Nanoplates on Graphene-BiVO4

Plasmonic photocatalysis, combing noble metal nanoparticles (NMNPs) with semiconductors, has been widely studied and proven to perform better than pure semiconductors. The plasmonic effects are mainly based on the localized surface plasmon resonance (LSPR) of NMNPs. The LSPR wavelength depends on several parameters, such as size, shape, the surrounding media, and the interdistance of the NMNPs. In this study, graphene-modified plate-like BiVO4 composites, combined with silver nanoplates (AgNPts), were successfully prepared and used as a photocatalyst for CO2 photoconversion. Triangular silver nanoplates (TAgNPts), icosahedral silver nanoparticles (I-AgNPs), and decahedra silver nanoparticles (D-AgNPs) were synthesized using photochemical methods and introduced to the nanocomposites to compare the shape-dependent plasmonic effect. Among them, T-AgNPts/graphene/BiVO4 exhibited the highest photoreduction efficiency of CO2 to CH4, at 18.1 μmolg−1h−1, which is 5.03 times higher than that of pure BiVO4 under the irradiation of a Hg lamp. A possible CO2 photoreduction mechanism was proposed to explain the synergetic effect of each component in TAgNPts/graphene/BiVO4. This high efficiency reveals the importance of considering the compositions of photocatalysts for converting CO2 to solar fuels.

Shape-controlled silver nanoplates colored fabric with tunable colors, photothermal antibacterial and colorimetric detection of hydrogen sulfide

Anisotropic silver nanoplates are widely anticipated in multifunctional textiles, but their large-scale promotion is limited by the shortcomings of long reaction time, uncontrollable shape and low yield in the preparation process. In this study, a microwave-assisted strategy is provided to prepare shape-controllable silver nanoplates for coloration of non-woven fabric. Anisotropic Ag nanoplates are efficiently coated on the surface of chitosan-pretreated fabric by a simple solution impregnation method, which generates the fabric with tunable color and multiple functions. The Ag nanoplates loaded fabric exhibits excellent photothermal properties at 808 nm laser irradiation due to its unique plasmonic absorption features. Colored fabric shows a strong synergistic antibacterial effect, including silver ion release and hyperthermia caused by the photothermal effect under near-infrared (NIR) light. Additionally, colored fabrics can be used as colorimetric sensors for selective detection of H2S. The colorimetric values of visible color signal of fabric-based H2S gas sensor can be real-time precisely detected using a smartphone, enlightening its high potential as a wearable toxic gas alarm device for the simple and rapid detection of hazardous gases.

Tubular catalytic polyHIPE reactor with deposited silver nanoplate nanoparticles

Continuously operating heterogeneous catalytic reactors are an important step towards more efficient and controllable processes compared to batch operation. Ideally, reactors should exhibit high permeability with the catalyst having a high surface area to volume ratio to minimize the required amount. An example of such catalyst morphology are nanoparticles with a plate-like morphology. In this work, the catalytic reactor was prepared by depositing plate-like silver nanoparticles on positively charged high internal phase emulsion monoliths by exploiting their negative zeta potential. The silver nanoplates had an edge length of 63 nm and a thickness of 13 nm with a sphericity factor of 0.548. The amount of deposited silver, determined from absorbance measurement and mass difference was 12.5 mg/ml and remained unaffected by the concentration of positively charged groups in the range between 69 and 110 mmol/l, demonstrating the robustness of the proposed approach. The permeability remained unchanged after silver deposition under flow due to the polymer microstructure. The reactor was found to be stable under various elution conditions, even after prolonged catalytic reduction of 4-nitrophenol. The specific catalytic activity of silver nanoplates was 428 min−1 g−1, which is an order of magnitude higher than that of silver nanoparticles with cuboctahedra shape and one of the highest reported. The proposed approach can be applied to various types of catalytic nanoparticles by exploiting a variety of possible interactions.

Grafting of silver nanospheres and nanoplates onto plasma activated PET: Effect of nanoparticle shape on antibacterial activity

Antibacterial surfaces are a possible way to prevent bacterial infection. This study aim was to prepare antibacterial surface by grafting silver nanoparticles (Ag NPs) onto plasma activated polyethylene terephthalate (PET) surface via biphenyl-4,4ˈ-dithiol (BPD). To take into account the shape factor, which may significantly influence Ag NPs antibacterial properties, two different shape were used, spherical (Ag0) and triangular (Ag3). Ag NPs were characterized using UV–Vis spectroscopy, transmission electron microscopy (TEM) and further by high resolution transmission electron microscopy (HRTEM). Average dimensions of NPs determined by TEM was 21.0 nm for Ag0 and (20.5 x 5.5) nm for Ag3. By HRTEM analysis was shape of Ag0 resolved as decahedron and Ag3 as triangular nanoplates. Success of BPD and Ag NPs grafting onto PET was proved by X-ray photoelectron and energy dispersive X-ray spectroscopy. Antibacterial tests versus E. coli and S. epidermidis were examined on the prepared substrates. Even though the higher amount of Ag was grafted on PET surface with Ag0, in case of S. epidermidis, sample with Ag3 had slightly better antibacterial activity. E. coli, on the other hand, was not affected significantly by the prepared substrates, probably due to low concentration of grafted Ag onto surface.

Synthesis of Silver Nanoplates by the Polyol Method in the Presence of an Ethoxylated Carboxylic Acid and Glucose

Synthesis of Silver Nanoplates by the Polyol Method in the Presence of an Ethoxylated Carboxylic Acid and Glucose

Designing Triangular Silver Nanoplates with GSH/GSSG Surface Mixed States as Novel Nanoparticle-based Redox Mediators for Electrochemical Biosensing.

Herein, a dual signal-quenched electrochemical (EC) biosensing strategy utilizing surface-engineered trisodium citrate (TSC)-glutathione (GSH)/oxidized glutathione (GSSG)-capped triangular silver nanoplates (Tri-Ag NPsTSC-GSH/GSSG) as a novel nanoparticle-based redox mediator was explored for biomarker determination. In contrast with conventional redox mediators, Tri-Ag NPsTSC-GSH/GSSG provided more admirable EC performance along with a lower oxidation potential (∼0.14 V). Taking advantage of the split-type mode, the immune response in a 96-well microplate was independent from EC detection, which could effectively eliminate the biological interference and thereby greatly enhance the sensitivity. As for the surface engineering process of Tri-Ag NPs, it was composed of partial GSH replacement and the formation of the GSH/GSSG surface mixed state. Primarily, the signal response of Ag NPsTSC-GSH decreased due to the hindrance of GSH on electron transfer. Moreover, varying proportions of GSH/GSSG could further impede the oxidation process of Tri-Ag NPsTSC-GSH/GSSG and eventually realize efficient dual signal quenching of this system. Notably, the ZIF-67@MIL-88B-GOx nanocomposite as the label was applied for a cascade reaction system with GSH peroxidase-like activities to form the optimal GSH/GSSG proportion, causing sensitive changes in signal response with a range of different antigen concentrations. On this basis, the fabricated biosensor provided measurable outputs of aflatoxin B1 concentrations in a linear range of 0.0005-50 ng/mL with a low detection limit of 0.61 pg/mL (S/N = 3). All of the results indicated that the novel biosensor could be a promising analytical tool for future biomarker detection.

Face-to-Face Assembly of Ag Nanoplates on Filter Papers for Pesticide Detection by Surface-Enhanced Raman Spectroscopy

Surface-enhanced Raman spectroscopy (SERS) technology has been regarded as a most efficient and sensitive strategy for the detection of pollutants at ultra-low concentrations. Fabrication of SERS substrates is of key importance in obtaining the homogeneous and sensitive SERS signals. Cellulose filter papers loaded with plasmonic metal NPs are well known as cost-effective and efficient paper-based SERS substrates. In this manuscript, face-to-face assembly of silver nanoplates via solvent-evaporation strategies on the cellulose filter papers has been developed for the SERS substrates. Furthermore, these developed paper-based SERS substrates are utilized for the ultra-sensitive detection of the rhodamine 6G dye and thiram pesticides. Our theoretical studies reveal the creation of high density hotspots, with a huge localized and enhanced electromagnetic field, near the corners of the assembled structures, which justifies the ultrasensitive SERS signal in the fabricated paper-based SERS platform. This work provides an excellent paper-based SERS substrate for practical applications, and one which can also be beneficial to human health and environmental safety.

Folic Acid and Chitosan-Functionalized Gold Nanorods and Triangular Silver Nanoplates for the Delivery of Anticancer Agents.

BackgroundAdvances in the field of nanotechnology have shed light on the applications of nanoparticles for cancer treatment.MethodsFolic acid and chitosan-functionalized gold nanorods (FACS-R) and triangular silver nanoplates (FACS-T) were synthesized and their properties were elucidated by UV-visible spectrophotometry, Fourier-transform infrared spectroscopy, field emission transmission electron microscopy and high-resolution X-ray diffraction.ResultsThe average size of the FACS-R was determined to be a transverse length of 13.1 ± 1.8 nm and a longitudinal length of 47.2 ± 8.9 nm with an aspect ratio of 3.6. The average size of FACS-T was measured to be 31.8 ± 7.7 nm. Colloidal solutions of FACS-R and FACS-T were stable on the shelf at ambient temperature for 14 days in the dark. Anticancer agents were encapsulated in FACS-R and FACS-T. FACS-T showed a higher encapsulation efficiency with docetaxel, paclitaxel and diallyl disulfide than FACS-R. The cell viability on human gastric adenocarcinoma cells (AGS), human epithelial cervix adenocarcinoma cells (HeLa) and human colorectal adenocarcinoma cells (HT-29) after treatment with anticancer agent-encapsulated FACS-R and FACS-T was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Interestingly, paclitaxel-encapsulated FACS-R and FACS-T showed the highest percentages of early and late apoptosis on HeLa cells. A cell cycle analysis demonstrated increased G2/M arrest on HeLa cells with docetaxel and paclitaxel-encapsulated FACS-R and FACS-T. The FACS-T induced more G2/M arrest on HeLa cells than the FACS-R. To assess applications in near-infrared photothermal therapy (PTT), the cell viability on HeLa cells with the anticancer agent-encapsulated FACS-R and FACS-T was assessed in the presence or absence of 808 nm laser irradiation. The results showed that 808 nm laser irradiation significantly decreased cell viability.ConclusionCollectively, the triangular silver nanoplates were more effective than the gold nanorods for PTT. We believe that as-prepared nanoparticles have remarkable features and will become promising future nanomedicine.

Aggregative stability of colloidal 3D and 2D silver nanoparticles, stabilised by 11-mercaptoundecanoic acid, in the presence of singly charged cations

We studied the aggregative stability of colloidal silver quasi-spherical nanoparticles and two-dimensional nanoplates, stabilised by 11-mercaptoundecanoic acid, in the presence of phosphate buffers containing different singly charged cations (Li+ , Na+ , K+ , Cs+) and tris-HCl at pH 8.0 and concentration 0.02 mol/L which mimics the carbodiimide conjugation conditions of nanoparticles with biomolecules. Aggregation of silver nanoplates occurs in the presence of Na-phosphate buffer whereas at the same conditions the quasi-spherical nanoparticles retain colloidal stability. The difference in colloidal stability between 3D and 2D silver nanoparticles is due to the increase of the apparent acid dissociation constant on the nanoplates’ basal faces and the subsequent increase in specific bridging interactions nanoparticle – cation – nanoparticle which can be eliminated by introducing of non-ionic spacer (11-mercapto-1-undecanol) in the ligand layer. Silver nanoplates with mixed ligand layer have increased colloidal stability across the pH.

Tailored Structure and Antibacterial Properties of Silica-Coated Silver Nanoplates by Pulsed Laser Irradiation.

We coated triangular-shaped silver nanoparticles, a type of anisotropic nanoplate (NPL), with silica (i.e., prepared Ag@SiO2 NPLs). When we irradiated Ag@SiO2 NPLs with nanosecond-pulsed laser light for 10 s, the triangular shape changed to spherical because of the photothermal effect. A high laser power exposed the silver core, and the particles exhibited strong antimicrobial activity. In contrast, at a moderate laser power, the silica layer crystallized, and the particles’ antimicrobial activity decreased. Thus, a combination of Ag@SiO2 NPLs and an appropriately tuned power of pulsed laser irradiation facilitated a decreased or an increased antimicrobial activity.