Synthesis Of Silver Nanoplates Research Articles

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

Synthesis of silver nanoplates with a narrow LSPR band for chemical sensing through a plasmon-mediated process using photochemical seeds

The plasmon-mediated process is one of the most common and well-studied methods to synthesize silver nanoplates (AgNPts). In a typical plasmon-mediated process, silver seeds are generated by chemical reduction using NaBH4 (abbreviated as CR seeds) before the plasmon-mediated process. However, a broad localized surface plasmon resonance (LSPR) band of AgNPts (usually broader than 150 nm) synthesized using the typical plasmon-mediated process would possibly limit their further applications. In this study, silver seeds are generated using a photochemical reduction method (abbreviated as PCR seeds). These PCR seeds then convert to AgNPts with irradiation by green LEDs or by a sodium lamp through the plasmon-mediated process. Furthermore, a very narrow LSPR bandwidth (approximately 67 nm) can be obtained when these AgNPts are further irradiated with red LEDs. Due to high refractive index sensitivity and sharp LSPR bandwidth, the as-prepared AgNPts have a high figure of merit (FOM) and can be used for spectroscopic chemical sensing applications. The silver seeds generated by this photochemical method can provide another choice for the plasmon-mediated process to synthesize AgNPts with high optical quality.

Controlling nanoparticle formation from the onset of nucleation through a multi-step continuous flow approach

HypothesisMetallic nanoparticles of various shapes and sizes can be synthesised through a diversity of bottom-up pathways, such as precipitation induced by chemical reduction. Varying composition, by adjusting concentrations or adding/replacing species, is the predominant strategy to tune nanoparticles structures. However, controlling time down to the onset of precipitation, nucleation, should also provide a powerful means to control nanostructuration. ExperimentsWe perform sequential reagent additions with a time resolution down to the millisecond. We use a millifluidic continuous flow setup consisting of tangential mixers in series, which allows flow rates up to dozens of litres per hour. We systematically vary both addition order and delay for each reagent involved in the synthesis of silver nanoplates. The resulting dispersions are compared using UV–visible spectroscopy, transmission electron microscopy and small-angle X-ray scattering. FindingsWe show that synthesis pathways differing only in the order of sub-second additions lead to drastically different synthetic outcomes. Silver nanoparticles of different shapes and sizes, displaying an array of plasmonic colours, are synthesised at the same final composition by tuning the composition pathways along time. Our results unlock a previously inaccessible portion of the space of parameters, which will lead to an enhanced structural diversity, control and understanding of nanoparticles syntheses.

Synthesis of silver nanoplates using regenerated watermelon rind and their application

In the present study, shape controlled flat square shaped silver nanoplates (SNP’s) were synthesized using aqueous extract of watermelon rind which was regenerated after biosorption of heavy metal ions. The formation of silver nanoparticles was visually confirmed by change in color from yellow to brown and was further confirmed by absorption peak at 465 nm in UV–Visible spectrophotometer. Synthesized SNP’s were characterized using FTIR, XRPD and TEM analysis. TEM analysis revealed the formation of flat and square shaped SNP’s with size less than 50 nm. FTIR analysis further supported the reduction and binding of phytochemicals chemicals present in watermelon rind extract. These SNP’s were tested for the antimicrobial activity against both gram positive bacteria Micrococcus luteus (ATCC 10240) and Staphylococcus aureus (ATCC 29213) , gram negative bacteria Salmonella typhi (ATCC 6539) and Klebsiella pneumonia (ATCC 13883). SNP’s showed good antimicrobial activity against these microbial cultures. The results suggest that regenerated watermelon rind has the capability to synthesize SNP’s with antimicrobial properties.

Synthesis of Silver Nanoplates With a Narrow LSPR Band for Chemical Sensing Through a Plasmon-Mediated Process Using Photochemical Seeds

The plasmon-mediated process is one of the most common and well-studied methods to synthesize silver nanoplates (AgNPts). In a typical plasmon-mediated process, silver seeds are generated by chemical reduction using NaBH4 (abbreviated as CR seeds) before the plasmon-mediated process. However, a broad localized surface plasmon resonance (LSPR) band of AgNPts (usually broader than 150 nm) synthesized using the typical plasmon-mediated process would possibly limit their further applications. In this study, silver seeds are generated using a photochemical reduction method (abbreviated as PCR seeds). These PCR seeds then convert to AgNPts with irradiation by green LEDs or by a sodium lamp through the plasmon-mediated process. Furthermore, a very narrow LSPR bandwidth (approximately 67 nm) can be obtained when these AgNPts are further irradiated with red LEDs. Due to high refractive index sensitivity and sharp LSPR bandwidth, the as-prepared AgNPts have a high figure of merit (FOM) and can be used for spectroscopic chemical sensing applications. The silver seeds generated by this photochemical method can provide another choice for the plasmon-mediated process to synthesize AgNPts with high optical quality.

Synthesis of silver nanoplates on electrospun fibers via tollens reaction for SERS sensing of pesticide residues.

Silver nanoplates were for the first time synthesized on electrospun chitosan/polyethylene oxide (CS/PEO) fibers via tollens reaction. Ag nanoplates/CS/PEO fibers were used as the SERS-active substrates for quantitative evaluation of 2-naphthylthiol, with an enhancement factor (1.41± 0.07)× 106. The SERS-active substrates are flexible, stable, and easy for transportion and preservation, and act as the SERS platform for sensitive detection of the target. Thiram and thiabendazole as the representatives of pesticide residues were identified and detected by the Ag nanoplates/CS/PEO fibers, exhibiting linear response ranges from 10-11 to 10-7M with a detection limit of 10-11 M. The Ag nanoplates/CS/PEO fibers meet the requirement of thiram detection in practical samples, such as apple, pear, tomato, and cucumber juices. The strategy revealed the feasibility of fabrication of Ag nanoplates on electrospun fibers via tollens reaction and SERS sensing of pesticides in real samples. Ag nanoplates/CS/PEO fibers were fabricated by tollens reaction and electrospinning for SERS sensing of pesticide residues with high sensitivity.

Synthesis of Silver Nanoplates with the Assistance of Natural Polymer (Sodium Alginate) Under 0 °C.

Some special conditions are important for chemical syntheses, such as high temperature and the medium used; unfortunately, uncontrollable influences are introduced during the process, resulting in unexpectedly low repeatability. Herein, we report a facile, environmentally friendly, stable, and repeatable methodology for synthesizing silver nanoplates (SNPs) at 0 °C that overcomes these issues and dramatically increases the yield. This method mainly employs sodium dodecyl sulfate (SDS) and sodium alginate (SA) as the surface stabilizer and assistant, respectively. Consequently, we produced hexagonal nanoplates and tailed nanoplates, and the characterization showed that SA dominates the clear and regular profiles of nanoplates at 0 °C. The tailed nanoplates, over time, showed the growth of heads and the dissolving of tails, and inclined to the nanoplates without tails. The synthesis method for SNPs used in this study—0 °C without media—showed high repeatability. We confirmed that these special conditions are not required for the synthesis of silver nanostructures (SNSs). Furthermore, we constructed a new method for preparing noble metal nanostructures and proved the possibility of preparing metal nanostructures at 0 °C.

Roles of zwitterionic charges in polymers on synthesis of Ag seeds with anisotropic growth properties

Polymeric materials have been widely used for the shape-controlled synthesis of metallic nanoparticles. In addition to coordination between the polymers and the particle surfaces during seed growth, a few studies have reported the anisotropic growth as the result of polymer intervention solely during seed formation. However, this mechanism has not been thoroughly elucidated. In this work, we synthesize silver nanoplates (AgNPLs) and investigate the influence of two representative zwitterionic polymers, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) and poly(sulfobetaine methacrylate) (PSBMA), on Ag seed formation. PMPC and PSBMA carry net zero global charges and non-zero local charges, which are ideal for investigating polymer–Ag+ interactions during the early stage of nanoparticle synthesis. The non-zwitterionic polymers carry different global charges, and they are examined in parallel with the zwitterionic polymers. X-ray photoelectron spectroscopy reveals that coordinate bonding between Ag+ and oxygen atoms in polymer functional groups strongly promotes the anisotropic growth of AgNPLs, even without the addition of polymers during growth. In contrast, nitrogen atoms in the polymers inhibit anisotropic growth. Our findings are further generalized in the context of seed-mediated growth by growing the seeds synthesized with the zwitterionic polymers at various concentrations, with various number average molecular weights, and at different temperatures.

Fabrication of silver nanoplates using Nephelium lappaceum (Rambutan) peel: A sustainable approach

In the present report, we developed a sustainable novel method to synthesize silver nanoplates (SNPs) with peel extract of Nephelium lappaceum L. (Rambutan) as reducing and stabilizing agent. The successful formation of SNPs was confirmed by various analytical instruments. The UV–vis spectra showed that two bands of SNPs appear at 370 and 495nm. In TEM images, it was observed that the SNPs formed were a triangle, truncated triangle and the hexagonal shape of average size 132.6±42nm. The prepared SNPs showed good scavenging efficacy (80%, 0.05mM) against 1,1-diphenyl-2-picrylhydrazyl. From the results obtained it is suggested that Rambutan peel extract has the potential to be used in the development of value-added products in the biomedical and nanotechnology-based industries.

Synthesis of Silver Nanoplates with Fibronectin Nanofibril Template and Their SERS Applications

In this work, a novel strategy is provided to prepare silver nanoplates by a fibronectin (Fn) nanofibril template. First, Fn molecules were controlled to assemble into amyloid-like nanofibrils in highly concentrated ethanol aqueous solution. The resultant nanofibrils could serve as a soft template to direct the formation of silver nanoplates. It is worth noting that the silver nanoplates are excellent surface-enhanced Raman scattering (SERS) substrate with 4-aminothiophenol (4-ATP) molecule as a test probe. This high active SERS substrate can also be used to detect drug molecule, 2-thiouracil with high sensitivity.

Synthesis of silver nanoplates with controlled shapes by reducing silver nitrate with poly(vinyl pyrrolidone) in N-methylpyrrolidone

This article describes a simple approach to the synthesis of Ag nanoplates with controlled shapes by reducing silver nitrate (AgNO3) with poly(vinyl pyrrolidone) (PVP) in N-methylpyrrolidone (NMP). The hydroxyl end groups of PVP have been shown to serve as a mild reductant for the kinetically controlled synthesis of Ag nanoplates. Here, we demonstrated that Ag nanoplates with tunable size and aspect ratio could be formed with high yields in a kinetically controlled synthesis using NMP as the reaction medium. NMP plays a critical role in the formation and growth of the nanoplate morphology. The reaction time and weight ratio of PVP to AgNO3 could both be adjusted to permit the shape-controlled synthesis of Ag nanoplates, that is, with control over the nanoplate size and aspect ratio. Shape control permitted tuning of the localized surface plasmon resonance (LSPR) peaks of these Ag nanoplates over the visible and near-IR regions.

LSPR-dependent SERS performance of silver nanoplates with highly stable and broad tunable LSPRs prepared through an improved seed-mediated strategy

The application of the silver plates as a proper substrate for surface enhanced Raman spectroscopy (SERS) was performed to give deep insight on LSPR-dependent SERS performance. Firstly, an improved seed-mediated method is developed to synthesize silver nanoplates (NP) with broad-tuning localized surface plasmon resonance (LSPR) and high stability. The LSPR peaks could be tuned in the range from 485 to ∼1200 nm by controlling the experimental parameters. With the treatment of sodium dodecyl sulfate (SDS), silver NPs exhibit high stability for SERS tests. The LSPR-dependent SERS study was performed by taking four typical silver NPs with LSPR peaks at 485 nm, 614 nm, 906 nm and 1130 nm as substrates. Also, two probe molecules, 4-amino-thiophenol (4-ATP) and rhodamine-6G (R-6G), were used, and both the 458 nm and 633 nm lasers were selected as excitation for the LSPR-dependent SERS study. Our results indicated that the SERS performance is largely dependent on the LSPR of the silver NP substrate at a given excitation wavelength. Specifically, the Raman signals were greatly enhanced when the laser excitation line matched (close to the LSPR band) the peak position of LSPR band. When at the excitation of 633 nm, two orders of magnitude stronger SERS signals would be observed for the Ag-614 substrate than that of the Ag-485 and Ag-1130 substrates with their LSPR peak positions far away from 633 nm. The same result can also be observed when the laser excitation at 458 nm was selected for the Ag-485 substrate. Our study gives a deep insight into LSPR-dependent SERS performance. It also gives a method for giving large SERS enhancement just by selecting a proper excitation wavelength matched to the LSPR of the substrate.

Fabrication of Self-Standing Silver Nanoplate Arrays by Seed-Decorated Electrochemical Route and Their Structure-Induced Properties

We present an electrochemical route to synthesize silver nanoplates on seed-decorated Indium tin oxide (ITO) glass substrate. The nanoplates are several tens of to several hundred nanometers in dimension. The density of nanoplates covered on the substrate can be controlled well by adjusting the amounts of seed. All the nanoplates are standing on the substrate uniformly even at very high density. Silver nanoplate arrays displayed an extraordinary superhydrophobicity after chemical modification and can serve as highly active surface-enhanced Raman scattering (SERS) substrates for microdetection. The arrays can also be used as electrodes for electrochemical capacitor with high power density.

Synthesis of Silver Nanoplates by Two-Dimensional Oriented Attachment

Synthesis of silver nanoplates was studied in the modified polyol method, where the nucleation and seed stage occurred in a poly(ethylene glycol) (PEG)-water mixture solution, and the growth stage happened in the PEG environment. The morphological evolution of nanoplates was characterized using UV, SEM, and TEM. Interestingly, plane nanostructures with unusual jagged edges were finally formed in our modified polyol method. Using TEM, we observed the medium state of fusion between two nanoplates, resulting in generating unusual jagged edges. Therefore, a novel two-dimensional oriented attachment occurred in our modified polyol method, which involves smaller nanoplates as the building blocks. Further control experiments showed that the presence of water could break this kinetic preferred reactivity, leading to the formation of nanoparticles.

Synthesis of Silver Nanoplates without Agitation and Surfactant

Abstract Dispersed silver nanoplates were prepared using silver nitrate and vitamin C in absence of agitation and surfactants in aqueous solution. In contrast, aggregated silver nanoparticles were obtained under mechanical agitation. The morphology and phases of products were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffractometer (XRD). The results show that the dispersed silver nanoplates can be obtained under the conditions of no mechanical agitation and no surfactants. The shear will induce the formation of aggregation.

Facile fabrication of silver nanoplates via a solvothermal method

This paper describes a simple solvothermal route to synthesize silver nanoplates by reduction of silver nitrate (AgNO3) with N,N-dimethylformamide. In this approach, ferric chloride (FeCl3) servers as the controlling agent, enabling the control over the concentration of free Ag+ ions in the solution. As the concentration of FeCl3 added to the reaction was increased, the morphologies of silver nanostructures evolved from triangular silver nanoplates to hexagonal silver nanoplates. The structures of these nanoplates were characterized by X-ray diffraction, electron microscopy and electron diffraction. A possible mechanism is proposed to interpret the shape-controlled synthesis of silver nanostructures. Finally, our results suggest that this method provides a convenient way to prepare silver nanostructures with different morphologies.

Polyol synthesis of silver nanoplates: The crystal growth mechanism based on a rivalrous adsorption

A polyol reducing approach has been applied to synthesize silver nanoplates with an average thickness of 50 nm and edge length of 3 μm in the presence of poly (vinylpyrrolidone) (PVP) and HNO 3. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscropy (TEM), and electron diffraction are used to characterize these silver nanoplates. Findings indicate that the nanoplates are single crystals and with their basal plane as (1 1 1) lattice plane. On the basis of the results from thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy, a crystal growth mechanism based on the rivalrous adsorption between PVP and CN − ions on the surface of silver nanoplates is supposed to explain the crystal anisotropic growth.

Efficient preparation of silver nanoplates assisted by non-polar solvents

In the paper, we report an efficient method to prepare high yield (up to 97%) of silver nanoplates. Synthesis of silver nanoplates was carried out in a binary solvent system of N , N -dimethylformamide (DMF) and toluene, in which DMF served as the reductant and polyvinylpyrrolidone (PVP) as the capping agent. By increasing the ratio of toluene to DMF to 7:6, silver nanoplates can be successfully synthesized; otherwise other shaped nanoparticles would be the major products. The nanoplate sample was characterized by TEM, HRTEM, SAED, XRD, AFM and UV–visible spectroscopy, proving the high nanoplate purity of this sample. The influence of toluene content, other solvents, AgNO 3 concentration, preparation temperature and chloride ions was also examined, which suggests that the function of non-polar solvents in this system is to enhance the PVP coverage on silver surface and, furthermore, to facilitate the preferential adsorption of PVP on two (111) facets of silver nanoplates.

Cover Picture: Surfactantless Synthesis of Silver Nanoplates and Their Application in SERS (Small 11/2007)

Cover Picture: Surfactantless Synthesis of Silver Nanoplates and Their Application in SERS (Small 11/2007)

Synthesis of silver nanoplates at high yields by slowing down the polyol reduction of silver nitrate with polyacrylamide

This communication describes a simple route to Ag nanoplates by slowing the polyol reduction of silver nitrate with polyacrylamide (PAM). In addition to its role as a stabilizer for Ag colloids, the amino groups of PAM can form complexes with Ag+ ions in the solution to substantially reducing the reduction rate, leading to the formation of thin nanoplates.