Abstract
A simple technique of seed-mediated growth has been successfully performed to grow anisotropy gold nanoparticles on solid substrates. The growth of the gold nanoparticles has been carried out in the presence of a binary surfactant mixture of hexadecyltrimethylammonium bromide with two different molecular weights of a capping agent, namely polyvinylpyrrolidone: 40,000 and 55,000. In this study, the effect of process parameters, growth time and molecular weight of capping agent was investigated. The growth time shows a significant impact on the shape and size of nanoparticles. The shorter growth time produced small spherical to square-like shape particles, whereas bigger particles including nanorods, nanosquares and nanotriangles were formed with longer growth time. The shape controlling agent, polyvinylpyrrolidone, was used to synthesis gold nanoparticles. It was found that monodisperse gold nanoparticles with uniform shape and size are hardly obtained when polyvinylpyrrolidone 40,000 was used as capping agent. Polyvinylpyrrolidone 55,000 produced more uniform shape and size of gold nanoparticles. Thus, these process parameters were found affected to the size, shape, surface density and uniformity of gold nanoparticles. This sample was further applied as a sensing material in the detection of toxic fungicide, namely chlorothalonil. The sensitivity of the sensor system was determined by the changes in peak positions and intensities of the transverse and longitudinal surface plasmon resonance peaks on different medium, that is, air, deionized water and chlorothalonil solution. The sensor response of gold nanoparticles thin film in 30 mM chlorothalonil showed two resonance peaks in comparison to the control experiment without gold nanoparticle thin film. The gold nanoparticles thin film sensor was successfully synthesized and potentially useful as a sensing material for fungicide detection.
Highlights
Throughout the last decade, size and shape-dependent metal nanoparticles (NPs) have exhibited properties that are beneficial for applications ranging from drug delivery,[1] diagnosis and therapy,[2] sensor,[3] disease detection[4] and biomedical imaging.[5]
gold nanoparticles (GNPs) was successfully synthesized on the substrate using seed-mediated growth method (SMGM)
All samples exhibit two distinct surface plasmon resonance bands, transverse surface plasmon resonance (t-SPR) and longitudinal surface plasmon resonance (l-SPR), which correspond to the oscillation of electrons in the shorter (t-SPR) and longer axis (l-SPR), respectively, except for 2 h growth time
Summary
Throughout the last decade, size and shape-dependent metal nanoparticles (NPs) have exhibited properties that are beneficial for applications ranging from drug delivery,[1] diagnosis and therapy,[2] sensor,[3] disease detection[4] and biomedical imaging.[5]. Intrinsic properties of the nanostructure cause homogeneous broadening,[24] whereas inhomogeneous broadening is the result of an averaging of the individual spectrum from a group of differing NPs.[25] Alternatively, an anisotropic NPs exhibit distinctive optical and electronic properties, improved mechanical properties and specific surfaceenhanced spectroscopy compared to isotropy NPs. Anisotropic gold nanoparticles (GNPs) have dual-band surface plasmon resonance peaks corresponding to the transverse and the longitudinal plasmon mode.[26] The absorption and scattering of light along the short axis of the NPs results in transverse surface plasmon resonance (t-SPR), which occurs at the shorter wavelength, while the longitudinal surface plasmon resonance (l-SPR) lays along the long axis. In this research, anisotropic GNP was fabricated as a thin film to manipulate their benefits for plasmonic sensing application
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