In the paper published in Chemistry - A European Journal (http://onlinelibrary.wiley.com/), the study team jointly led by Prof. YANG Liangbao from Institute of Intelligent Machines, proposed a novel sodium chloride crystal-induced SERS platform that owns locations and trapping of illicit drugs for highly sensitive detection.
Aggregation of metal colloids is perhaps the simplest method to produce substrates that can exhibit field enhancements large enough for SERS detection. However, the aggregation of colloids is unstable as it gradually become so large that it cannot survive in solution. Moreover, laser focus is easily disturbed by the environment under solution-phase and water or the other liquids between objective lens and SERS substrates would attenuate the collected SERS signal sharply.
Based on it, unlike conventional solution-phase SERS detection methods, the researchers demonstrated a practical approach that sodium chloride crystal induced SERS platform for controlled highly sensitive detection of illicit drugs, which was schematically shown from side and vertical view.
During the process of solvent volatilization, NaCl crystals gradually appeare to assemble the silver aggregates around themselves and analytes can be trapped in the presence of capillary force.
Moreover, the micro-scale crystals state can act as the template to obtain optical position, such that the assembled hot area are conventionally located during SERS measurements to get the reproducible SERS signals and eliminate the need for mapping large areas to get the SERS signals of analytes.
In addition, the chlorine ions can also replace the substances coated on the surface of the silver sol, and further restrain the background signals. Using the novel method, high quality SERS spectra from heroin, methamphetamine (MAMP) and cocaine can be obtained.
This approach not only can easily bring the NPs to form plasmonic hot spots, but also provides effective locations, and this assembled SERS nanostructures can potentially be explored as active substrate for label-free illicit drugs or additives detection.
The authors acknowledge the financial support from the Sci-tech Police Project of Anhui Province (1704d0802186), the National Science Foundation of China (21571180 and 21505138); Special Financial Grant from the China Postdoctoral Science Foundation (2016T90590), and Anhui Natural Science Foundation (1508085MB26).
Figure.Schematic illustration of NaCl crystal-induced SERS platform and the distribution of the effective spots of laser sites