Microwave assisted template synthesis of silver nanoparticles

Easier, less time consuming, green processes, which yield silver nanoparticles of uniform size, shape and morphology are of interest. Various methods for synthesis, such as conventional temperature assisted process, controlled reaction at elevated temperatures, and microwave assisted process have been evaluated for the kind of silver nanoparticles synthesized. Starch has been employed as a template and reducing agent. Electron microscopy, photon correlation spectroscopy and surface plasmon resonance have been employed to characterize the silver nanoparticles synthesized. Compared to conventional methods, microwave assisted synthesis was faster and provided particles with an average particle size of 12 nm. Further, the starch functions as template, preventing the aggregation of silver nanoparticles.     

Performance optimization of dye-sensitized solar cells by gradient-ascent architecture of SiO2@Au@TiO2 microspheres embedded with Au nanoparticles

Highly homogeneous, well dispersed SiO_2@Au@TiO_2(SAT) microspheres decorated with Au nanoparticles(AuNPs) were prepared and incorporated into the photoanode with an optimized concentration gradientascent. The effects of SAT microspheres and the gradient-ascent architecture on the light absorption and the photoelectric conversion efficiency(PCE) of the dye-sensitized solar cells(DSSCs) were investigated.Studies indicate that the introduction of SAT microspheres and the gradient-ascent architecture in the photoanode significantly enhance the light scattering and harvesting capability of the photoanode. The DSSC with the optimized SAT gradient-ascent photoanode has the maximum short circuit current density(J_(sc)) of 17.7 mA cm~(-2) and PCE of 7.75%, remarkably higher than those of the conventional DSSC by 23.7%and 28.0%, respectively. This significantly enhancement of the performance of the DSSC can be attributed to the excellent light reflection/scattering of SAT, the localized surface plasma resonance(LSPR) effect of AuNPs within the microspheres, and the gradient-ascent architecture of SAT microspheres inside the photoanode. This study demonstrates that the tri-synergies of the scattering of SAT microspheres, the LSPR of AuNPs and the gradient-ascent architecture can effectively improve the PCE of DSSC.     

Biosynthesis and stabilization of Au and Au–Ag alloy nanoparticles by fungus,Fusarium semitectum

Crystallized and spherical-shaped Au and Au–Ag alloy nanoparticles have been synthesized and stabilized using a fungus, F. semitectum in an aqueous system. Aqueous solutions of chloroaurate ions for Au and chloroaurate and Ag⁺ ions (1 : 1 ratio) for Au–Ag alloy were treated with an extracellular filtrate of F. semitectum biomass for the formation of Au nanoparticles (AuNP) and Au–Ag alloy nanoparticles (Au–AgNP). Analysis of the feasibility of the biosynthesized nanoparticles and core–shell alloy nanoparticles from fungal strains is particularly significant. The resultant colloidal suspensions are highly stable for many weeks. The obtained Au and Au–Ag alloy nanoparticles were characterized by the surface plasmon resonance (SPR) peaks using a UV-vis spectrophotometer, and the structure, morphology and size were determined by Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), and transmission electron microscopy (TEM). Possible optoelectronics and medical applications of these nanoparticles are envisaged.     

Biosynthesis and stabilization of Au and Au–Ag alloy nanoparticles by fungus,Fusarium semitectum

Abstract

Crystallized and spherical-shaped Au and Au–Ag alloy nanoparticles have been synthesized and stabilized using a fungus, F . semitectum in an aqueous system. Aqueous solutions of chloroaurate ions for Au and chloroaurate and Ag⁺ ions (1 : 1 ratio) for Au–Ag alloy were treated with an extracellular filtrate of F . semitectum biomass for the formation of Au nanoparticles (AuNP) and Au–Ag alloy nanoparticles (Au–AgNP). Analysis of the feasibility of the biosynthesized nanoparticles and core–shell alloy nanoparticles from fungal strains is particularly significant. The resultant colloidal suspensions are highly stable for many weeks. The obtained Au and Au–Ag alloy nanoparticles were characterized by the surface plasmon resonance (SPR) peaks using a UV-vis spectrophotometer, and the structure, morphology and size were determined by Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), and transmission electron microscopy (TEM). Possible optoelectronics and medical applications of these nanoparticles are envisaged.     

Electrochemical synthesis of gold nanoparticles onto indium tin oxide glass and application in biosensors

A simple one-step method for the electrochemical deposition of gold nanoparticles (GNPs) onto bare indium tin oxide film coated glass substrate without any template or surfactant was investigated. The effect of electrolysis conditions such as potential range, temperature, concentration and deposition cycles were examined. The connectivity of GNPs was analyzed by UV-Vis absorption spectroscopy and scanning electron microscopy. The nanoparticles were found to connect in pairs or to coalesce in larger numbers. The twin GNPs display a transverse and a longitudinal localized surface plasmon resonance (LSPR) band, which is similar to that of gold nanorods. The presence of longitudinal LSPR band correlates with high refractive index sensitivity. Conjugation of the twin-linked GNPs with albumin bovine serum-biotin was employed for the detection of streptavidin as a model based on the specific binding affinity in biotin/streptavidin pairs. The spectrophotometric sensor showed concentration-dependent binding for streptavidin.     

局域表面等离子体共振效应气体传感器的研究进展

贵金属纳米结构的局域表面等离子体共振光学在光催化、光学传感器、表面增强光谱学、太阳能电池等领域具有广阔的应用前景。基于贵金属的局域表面等离子体共振效应传感器的性能主要依赖于贵金属的结构,总结了纳米贵金属粒子性质以及各种结构的制备方法和应用,并展望了未来表面等离子体共振效应传感器的发展趋势。     

Single-layer graphene-based surface plasmon resonance sensor with dynamic evanescent field enhancement for biomarker study

ABSTRACT

In this work, we have developed a kind of single-layer graphene-based surface plasmon resonance (SLG-SPR) biosensor to detect C-reactive protein (CRP) and Prostate-specific antigen (PSA). In the experiment of testing CPR, the results obtained revealed that the changes in resonance wavelength of SLG-SPR biosensors are higher than that of the gold-film based SPR (Au-SPR) biosensors. Moreover, for the experiment of testing PSA, due to the dynamic evanescent field enhancement produced by a strong electric field coupling between the localized SPR (LSPR) of AuNPs and SPR of single-layer graphene-based film (SLG-film) that further amplify the evanescent field signal. We verified the SLG-SPR biosensors exhibited higher sensitivity than the Au-SPR biosensors and the SLG-SPR biosensor exceeded the traditional biosensor detection limit. Accordingly, the SLG-SPR biosensor based on dynamic optical enhancement can realize high sensitivity detection of low concentration biomarkers and can be applied to most of the trace biomarkers in theory.     

Green Synthesis of Silver Nanoparticles Using an Otherwise Worthless Weed Mimosa (Mimosa pudica): Feasibility and Process Development Toward Shape/Size Control

A bioinspired method of silver nanoparticle (AgNP) synthesis using the highly invasive terrestrial weed mimosa (Mimosa pudica) is presented. An aqueous extract of the leaves of the weed that served as a reducing and stabiliaing agent was employed in various proportions with Ag (I) solution for this synthesis. The effect of several key variables that influence the shape/size of the AgNPs—concentrations of the extract relative to Ag (I), temperature, interaction time, stirring, and pH—was studied employing UV-visible spectrophotometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), and x-ray diffraction (XRD). The study provides the basis for selecting processes for synthesizing AgNPs of desired shapes and sizes that can be developed using mimosa as the bioagent. All processes in this synthesis, being simple, nonpolluting, inexpensive, and nonhazardous, raise the possibility of large-scale utilization of mimosa, thereby offering a means to reduce ecological degradation that is caused by mimosa.     

Differential interaction of silver nanoparticles with cysteine

Understanding the characteristics of cysteine on a solid surface is an important issue in protein study and amino acid analysis. Therefore, cysteine was selected as a model biomolecule to study the interaction with plasmonic silver nanoparticles. In this study, we report the differential interaction of cysteine with silver nanoparticles synthesised by Lee and Meisel (using citrate as reductant), and modified Creighton (citrate and borohydride as reductant) methods. In Lee and Meisel's method, the red-shifting of silver plasmon resonance in the UV–vis spectra and the aggregation of the particles occurred owing to a decrease in stability of silver nanoparticles upon interaction with cysteine. In contrast, the other method did not cause any aggregation or significant spectral changes. The differential behaviour may be due to surface chemical changes on cysteine with pH, which plays a major role in the nanoparticle-biomolecule interaction. The synthesis of silver nanoparticles applying two sol gel methods followed by interactions with cysteine induces different functionalities on the nanoparticles, which may find specific applications in bio-sensing and drug delivery.