Room Temperature, Multiphasic Detection of Explosives, and Volatile Organic Compounds Using Thermodiffusion Driven Soret Colloids

Abstract

Achieving a label-free spectroscopic platform for multiphasic analytical detection in real-time, ambient conditions is extremely challenging due to the fundamental dichotomy between ultrahigh sensitivity and reliability of detection. Addressing these challenges, we demonstrate a versatile surface-enhanced Raman scattering (SERS) platform capable of multiphasic, reliable detection with ultrahigh sensitivity. The SERS platform is extremely sensitive and relies on vapor molecules present at the solid–vapor or liquid–vapor interface for reliable detection in ambient conditions (298 K, 1 atm). We observe that metal nanoparticles, subjected to a temperature gradient, migrate and self-assemble into precise nanoparticle assemblies, in a nanoscale analogue of Soret effect. The formation and monodispersity of these nanoparticles assemblies, termed Soret colloids (SCs), is kinetically controllable using the thermal gradient. Soret colloids exhibit excellent size uniformity (monodispersity index, MDI ∼ 0.8) and stron...