Visual determination of trace Cysteine based on promoted corrosion of triangular silver nanoplates by sodium thiosulfate

In this study, triangular silver nanoplates (TAg-NPs) were used to detect trace Cysteine concentration in the presence of sodium thiosulfate (Na2S2O3). Study showed that the TAg-NPs could be gently etched by Cysteine with the concentration of 1.0 x 10(-7) mol L-1 through forming Ag-S covalent bond at the three corners. However, in the presence of Na2S2O3 (only 3.0 x 10(-6) mol L-1), the corrosion of Cysteine on TAg-NPs can be promoted significantly. It was also found that the color, morphology, and the maximum absorption wavelength of TAg-NPs change clearly with the concentrations of Cysteine as low as 2.5 x 10(-8) mol L-1. Furthermore, the wavelength shift values (Delta lambda) of TAg-NPs solution were proportional to the concentrations of Cysteine in the range of 1.0 x 10(-9)-1.0 x 10(-7) mol L-1, and the linear regression equation is Delta lambda = -0.89 + 319.94 c (c, mu M, n = 5) with the correlation coefficient of 0.990. At the same time, the color change of the TAg-NPs solution could be observed clearly by the naked eyes with increasing Cysteine concentrations in the range of 2.5 x 10(-8)-1.0 x 10(-7) mol L-1. Thus, a novel method for the detection of Cysteine by either UV-vis spectrophotometry detection or naked eyes observation is established. It allows determination of Cysteine content in compound amino acid injection sample of 18AA-V. (C) 2014 Elsevier B.V. All rights reserved.