The effect of auxiliary complexing agent on silver crystallization and the application in SERS

Abstract

<p indent="0mm">A crystalized nano-sized silver layer with large area uniformity and smoothness prepared by electrochemical deposition as surface-enhanced Raman scattering (SERS) active substrates was studied. The result shows that an effective binary complementary complex system can be formed to turn the silver’s nucleation mechanism from instantaneous one to progressive one when auxiliary complexing agent of hydroxyethylidene diphosphonic acid (HEDP) and main complexing agent of 5,5-dimethylhydantoin reach sufficient concentration of <sc>4 g/L</sc> and <sc>110 g/L</sc> in electrodeposition solution, respectively. The as-prepared crystalized nano-sized silver layer possesses excellent SERS properties. Its limit of detection (LOD) to Rhodamine 6G is as low as <sc>1.0×10^–13 mol/L,</sc> the relative standard deviation (RSD) of SERS uniformity is below 8%, and the averaged surface enhancement factor to methyl orange can reach 6.3×10⁶. Correspondingly, the particle size of silver-electrodeposited substrate is about <sc>10 nm</sc> and the particle spacing is less than 5 nm, which meets the requirements for generating SERS “hot spots”. Finally, the active substrate was applied to prohibit pigments of Sudan III and Sudan IV, and the LOD is as low as <sc>5.0×10^–12 mol/L</sc> and <sc>1.0×10^–11 mol/L</sc>, respectively, which shows great potential for applications.