Drying Acoustically Levitated Droplets as Signal-Amplifying Platforms for Ultrasensitive and Multimode Laser Sensing

摘要

Ultrasensitivesensing to trace atomic and molecular analytes hasgained interest for its intimate relation to industrial sectors andhuman lives. One of the keys to ultrasensitive sensing for many analyticaltechniques lies in enriching trace analytes onto well-designed substrates.However, the coffee ring effect, nonuniform distribution of analytesonto substrates, in the droplet drying process hinders the ultrasensitiveand stable sensing onto the substrates. Here, we propose a substrate-freestrategy to suppress the coffee ring effect, enrich analytes, andself-assemble a signal-amplifying (SA) platform for multimode lasersensing. The strategy involves acoustically levitating and dryinga droplet, mixed with analytes and core-shell Au@SiO2 nanoparticles, to self-assemble an SA platform. The SA platformwith a plasmonic nanostructure can dramatically enrich analytes, enablingenormous spectroscopic signal amplification. Specifically, the SAplatform can promote atomic detection (cadmium and chromium) to the10(-3) mg/L level by nanoparticle-enhanced laser-inducedbreakdown spectroscopy and can promote molecule detection (rhodamine6G) to the 10(-11) mol/L level by surface-enhancedRaman scattering. All in all, the SA platform, self-assembled by acousticlevitation, can intrinsically suppress the coffee ring effect andenrich trace analytes, enabling ultrasensitive multimode laser sensing.

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