Structure-controllable Ag aerogel optimized SERS-digital microfluidic platform for ultrasensitive and high-throughput detection of harmful substances

Miniaturized chips or devices based on surface-enhanced Raman (SERS) technology are an important trend for high-throughput and rapid detection of harmful substances such as explosives in the future. The complementary combination of SERS and digital microfluidics (SERS-DMF) achieves a win-win situation and broadens the application fields of both. However, the noble-metal "hot spots" formed by salt screening in SERS-DMF has the problems of uncontrollable structure and low spatial density, which seriously limits the sensitivity and efficiency of practical application. In this work, structure-controllable Ag aerogel was prepared as a SERS substrate, then combined with digital microfluidics (AgA-DMF) to achieve rapid, high-throughput and ultrasensitive detection of harmful substances. SERS performance of Ag aerogels was optimized by adjusting the structural unit size and aspect ratio. The enhancement factor as high as 4.82 x 107. The AgA-DMF SERS platform detected various harmful substances 2,4,6-trinitrotoluene (TNT, 10-8 M), 3-nitro-1,2,4-triazol-5-one (NTO, 10-9 M) and methylene blue (MB, 10-9 M). The platform streamlined all processes with excellent reaction efficiency and completed high-throughput detection of five samples within 10 min. In addition, the platform integrated portable Raman to realize the detection of real samples. The proposed AgA-DMF platform exhibited rapid, high-throughput and ultrasensitive detection of harmful substances in wastewater, also had considerable potential applications for environmental safety monitoring.