Evaluation of Colloids and Activation Agents for Determination of Melamine Using UV-SERS

Abstract

UV-SERS measurements offer a great potential for environmental or food (detection of food contaminats) analytics. Here, the UV-SERS enhancement potential of various kinds of metal colloids, such as Pd, Pt, Au, Ag, Au–Ag core–shell, and Ag–Au core–shell with different shapes and sizes, were studied using melamine as a test molecule. The influence of different activation (KF, KCl, KBr, K2SO4) agents onto the SERS activity of the nanomaterials was investigated, showing that the combination of a particular nanoparticle with a special activation agent is extremely crucial for the observed SERS enhancement. In particular, the size dependence of spherical nanoparticles of one particular metal on the activator has been exploited. By doing so, it could be shown that the SERS enhancement increases or decreases for increasing or decreasing size of a nanoparticle, respectively. Overall, the presented results demonstrate the necessity to adjust the nanoparticle size and the activation agent for different experiments in order to achieve the best possible UV-SERS results.

Rainbows at the End of Subwavelength Discontinuities: Plasmonic Light Trapping for Sensing Applications

“…[151,152] Other UV appropriate metals such as platinum and rhodium do not oxidize, but they are rare in abundance and deemed impractical for device design. [153][154][155] Aluminum (Al) on the other hand has received the most attention following the pioneering work by Knight et al in which they demonstrated plasmonic resonance of single Al nanorods, imaged at wavelengths from 248 to 539 nm, showing both UV and visible resonance for transverse and longitudinal modes. [156] Al is a promising candidate for UV plasmonics considering its natural abundance and low cost, UV resonance range down to 210 nm, and a self-limiting native oxide which is typically only 2-3 nm thick.…”

Graphene Oxide-Coated Metal–Insulator–Metal SERS Substrates for Trace Melamine Detection

“…For the case of 532 nm excitation laser, silver nanostructures have a smaller photothermal effect than gold ones, leading to a larger enhancement factor [ 35 , 38 ]. Besides silver, other materials such as aluminum, lead, and platinum are also good choices, but silver could be the best choice with a much easier fabrication process [ 39 , 40 , 41 , 42 ]. A detection limit down to 10 −16 M for Rhodamine 6G has been reported by silver metasurfaces formatted with nanobowties [ 35 ].…”

Rapid colorimetric detection of melamine by H2O2–Au nanoparticles

“…In the presence of melamine, hydrogen peroxide will react with melamine to produce a stable addition compound. 18 With the consumption of hydrogen peroxide, the growth of Au NPs will be slow down, resulting Au NPs aggregations to give a blue solution, which is illustrated by Scheme 1. There is no need to prepare functionalized gold nanoparticles at all.…”