Nguyen T. B. Thuy

Aqueous synthesis and characterization of Ag and Ag–Au nanoparticles: addressing challenges in size, monodispersity and structure

In this paper, we demonstrate the synthesis of monodispersed silver nanoparticles (NPs) of controlled size (20.5 ± 3.3 nm) in aqueous phase from a silver hydroxide precursor with sodium acrylate as dual reducing–capping agent. We then coat these NPs in a layer of gold with controllable thickness through a reduction–deposition process. The materials are characterized using several techniques including high-resolution transmission electron microscopy, ultraviolet–visible spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The results show that we were able to synthesize not only monodispersed Ag NPs but also core–shell Ag–Au NPs with a discrete structure, which is significant because of the challenges associated with the creation of such materials, namely the propensity of metallic Ag to be oxidized by the presence of ionic Au. The NPs are of interest for use in a wide range of potential applications, including biomedical diagnostics and biomolecular detection as well as many others.

Intensification of surface enhanced Raman scattering of thiol-containing molecules using Ag@Au core@shell nanoparticles

In this paper, we study the relationship between nanoparticles’ structure/composition and the chemical nature of the molecules to be identified in surface enhanced Raman scattering (SERS) spectroscopy. Three types of nanoparticles (NPs) were synthesized, including Ag, Au, and silver coated by gold (Ag@Au), in order to study the resulting enhancement effects. When a rhodamine 6G dye molecule was used to assemble the NPs, it was found that Ag NPs exhibited the highest enhancement activity. However, when a thiol containing 3-amino-1,2,4-triazole-5-thiol molecule was used to assemble the NPs, it was found that the Ag@Au NPs exhibited high Raman activity as well as the Ag NPs. The results give insight into how the chemical properties of the molecules to be analyzed play an important role in the SERS detection. An additional parameter of the analysis reveals the relative stability of the three types of NP probes synthesized with regard to oxidation in the presence of different mediating molecules and varying sa...

A Study on the Plasmonic Properties of Silver Core Gold Shell Nanoparticles: Optical Assessment of the Particle Structure

This paper reports a qualitative comparison between the optical properties of a set of silver core, gold shell nanoparticles with varying composition and structure to those calculated using the Mie solution. To achieve this, silver nanoparticles were synthesized in aqueous phase from a silver hydroxide precursor with sodium acrylate as dual reducing–capping agent. The particles were then coated with a layer of gold with controllable thickness through a reduction–deposition process. The resulting nanoparticles reveal well defined optical properties that make them suitable for comparison to ideal calculated results using the Mie solution. The discussion focuses on the correlation between the synthesized core shell nanoparticles with varying Au shell thickness and the Mie solution results in terms of the optical properties. The results give insight in how to design and synthesize silver core, gold shell nanoparticles with controllable optical properties (e.g., SPR band in terms of intensity and position), and has implications in creating nanoparticle materials to be used as biological probes and sensing elements.

Study on formation mechanism and ligand-directed architectural control of nanoparticles composed of Bi, Sb and Te: towards one-pot synthesis of ternary (Bi,Sb)2Te3 nanobuilding blocks

This paper reports a study on the formation mechanism of nanoparticles (NPs) composed of bismuth, antimony and tellurium for thermoelectric materials using a modified polyol synthetic route. Our one-pot synthesis technique has proven highly versatile in creating a wide range of different anisotropic NPs such as nanowires (NWs), nanodiscs (NDs), nanoribbons and nanospines (NDs studded on NWs) simply by modifying the capping species or elemental precursor feeding ratio used in the synthesis. However, an independent control of morphology and composition is still hugely challenging and the facile synthesis of (Bi,Sb)2Te3 solid solution NPs is not a trivial task, reflecting the complex nature of this multicomponent system. To achieve this goal, it is imperative to understand the formation mechanism based on a systematic investigation of mono- and binary elemental NP systems. Our study clearly shows the different actions of oleylamine (OAM) and decanethiol (DT) capping ligands in our synthesis reaction. In the case of DT capping system, Te NDs are first formed, and then, Bi and Sb are separately incorporated into the Te ND structure viacatalytic decomposition of Bi-DT and Sb-DT complexes on the Te ND surfaces. Therefore, the resulting NPs are phase segregated into Te, Bi2Te3 and Sb2Te3. On the other hand, in the case of the OAM capping system, Te NWs and Bi-Sb solid solution NPs are formed separately, and then, parts of Te NWs are transformed into (Bi,Sb)2Te3 phase via oriented attachment of Bi-Sb NPs and Te NWs. These findings are crucially important towards the one-pot synthesis of uniform (Bi,Sb)2Te3 nanobuilding blocks with controllable characteristics for highly efficient thermoelectric materials.