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Selective growth of Ag nanodewdrops on Au nanostructures: a new type of bimetallic heterostructure.

ABSTRACT: A new type of bimetallic Au-Ag heterostructured material was prepared by a selective growing strategy of a Ag nanodewdrop on the petal tip of a Au flower using an electrochemical method. The whole process was strictly controlled by forming the reactive tip of the flower petal and passivating the facet along the body of the metal petal using poly(vinyl pyrrolidone) (PVP) coating film. The formed Au-Ag heterostructured flowers (HSFs) were observed to be about 2 microm in diameter and have the Ag particles of about 50 nm settled on the tips of Au petals. The Au-Ag HSFs were found to display the superior properties on the surface-enhanced Raman scattering (SERS). The presence of Ag nanodewdrops could also facilitate the oxidation of Ru(bpy)3(2+) complex in electrogenerated chemiluminescence (ECL) measurements and dramatically enhance the emission intensity. The features of Au-Ag HSFs can promise a new type of heterogeneous bimetallic alloy material for the potential applications in chemical and biological sensors.

SUBMITTER: Gao L

PROVIDER: S-EPMC2770871 | biostudies-literature | 2009 Oct

REPOSITORIES: biostudies-literature

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Selective growth of Ag nanodewdrops on Au nanostructures: a new type of bimetallic heterostructure.

Gao Li L Fan Louzhen L Zhang Jian J

Langmuir : the ACS journal of surfaces and colloids 20091001 19

A new type of bimetallic Au-Ag heterostructured material was prepared by a selective growing strategy of a Ag nanodewdrop on the petal tip of a Au flower using an electrochemical method. The whole process was strictly controlled by forming the reactive tip of the flower petal and passivating the facet along the body of the metal petal using poly(vinyl pyrrolidone) (PVP) coating film. The formed Au-Ag heterostructured flowers (HSFs) were observed to be about 2 microm in diameter and have the Ag p ...[more]

PMID: 19788230

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Project description:It is well-known that Ag-Au bimetallic nanoplates have attracted significant research interest due to their unique plasmonic properties and surface-enhanced Raman scattering (SERS). In recent years, there have been many studies on the fabrication of bimetallic nanostructures. However, controlling the shape, size, and structure of bimetallic nanostructures still has many challenges. In this work, we present the results of the synthesis of silver nanoplates (Ag NPls), and Ag-Au bimetallic core/shell and alloy nanostructures, using seed-mediated growth under green LED excitation and a gold salt (HAuCl4) as a precursor of gold. The results show that the optical properties and crystal structure strongly depend on the amount of added gold salt. Interestingly, when the amount of gold(x) in the sample was less than 0.6 μmol (x < 0.6 μmol), the structural nature of Ag-Au was core/shell, in contrast x > 0.6 μmol gave the alloy structure. The morphology of the obtained nanostructures was investigated using the field emission scanning electron microscopy (FESEM) technique. The UV-Vis extinction spectra of Ag-Au nanostructures showed localized surface plasmon resonance (LSPR) bands in the spectral range of 402-627 nm which changed from two peaks to one peak as the amount of gold increased. Ag-Au core/shell and alloy nanostructures were utilized as surface enhanced Raman scattering (SERS) substrates to detect methylene blue (MB) (10-7 M concentration). Our experimental observations indicated that the highest enhancement factor (EF) of about 1.2 × 107 was obtained with Ag-Au alloy. Our detailed investigations revealed that the Ag-Au alloy exhibited significant EF compared to pure metal Ag and Ag-Au core/shell nanostructures. Moreover, the analysis of the data revealed a linear dependence between the logarithm of concentration (log C) and the logarithm of SERS signal intensity (log I) in the range of 10-7-10-4 M with a correlation coefficient (R 2) of 0.994. This research helps us understand better the SERS mechanism and the application of Raman spectroscopy on a bimetallic surface.

Dataset Information

Selective growth of Ag nanodewdrops on Au nanostructures: a new type of bimetallic heterostructure.

Publications

Selective growth of Ag nanodewdrops on Au nanostructures: a new type of bimetallic heterostructure.

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