Enhanced biochemical sensing in the mid-infrared using individual plasmonic particles and quantum cascade laser-based spectral imaging

This work leverages the powerful resonance properties of plasmonic microcubes for surface-enhanced infrared absorption spectroscopy (SEIRAS). A single plasmonic microparticle, synthesized via a high-throughput wet chemical method, is used as a particle-on-a-mirror device, allowing tunable mid-infrared (mid-IR) resonance by adjusting the particle size. Integrated with a quantum cascade laser (QCL)-based mid-IR spectral imaging system, this SEIRAS platform offers superior plasmonic performance, high-throughput data analysis, scalable fabrication, and streamlined biological sample preparation. Experimental and computational approaches, including Finite Difference Time Domain (FDTD) simulations and multipole decomposition analysis, are employed to study the platform's photonic properties. For biosensing applications, the platform is tested to characterize absorption bands of polydimethylsiloxane (PDMS), along with amide I and amide II bands in bovine serum albumin (BSA) and complex human liquid samples. This system provides highly sensitive and efficient molecular detection, with significant potential for medical diagnostics and environmental monitoring.