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Reshaping of triangular silver nanoplates by a non-halide etchant and its application in melamine sensing.

Journal of colloid and interface science (2019-06-04)
Alexander David Ardianrama, Yosia Nico Wijaya, Seung Hyun Hur, Hee-Chul Woo, Mun Ho Kim
ABSTRACT

Although triangular silver (Ag) nanoplates are intrinsically unstable, this characteristic has been taken advantage of in the development of a novel sensing platform. However, most of these applications have relied on halide ions as etchants. In the current work, we used sodium 4-vinylbenzenesulfonate (Na-VBS) as a new powerful etchant of triangular silver (Ag) nanoplates. When aged with Na-VBS at room temperature, Na-VBS etched Ag nanoplates nearly as powerfully as halides did, and these nanoplates rapidly transformed into oblate nanospheroids. This shape evolution permitted tuning of the corresponding localized surface plasmon resonance (LSPR) features of the Ag nanostructures. Interestingly, passivation of the Ag nanoplate surface with melamine was shown to protect the nanoplates from Na-VBS-induced etching. The rate of change of the color and spectral features of the Ag nanoplate solution exposed to Na-VBS was found to be strongly correlated with the concentration of melamine in the solution. This association allowed us to apply this system to the development of a novel platform for sensing melamine.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Acetonitrile, HPLC Plus, ≥99.9%
Sigma-Aldrich
Hydrogen peroxide solution, contains inhibitor, 30 wt. % in H2O, ACS reagent
Sigma-Aldrich
Sodium sulfate, ACS reagent, ≥99.0%, anhydrous, granular
Sigma-Aldrich
Melamine, 99%
Sigma-Aldrich
Sodium bromide, ACS reagent, ≥99.0%
Sigma-Aldrich
Sodium iodide, 99.999% trace metals basis
Sigma-Aldrich
Cyanuric acid, 98%
Sigma-Aldrich
Sodium 4-vinylbenzenesulfonate, technical, ≥90% (T)
Sigma-Aldrich
Polyvinylpyrrolidone, powder, average Mw ~29,000
Sigma-Aldrich
Sodium fluoride, 99.99% trace metals basis