Chemical Sensing on a Single SERS Particle

We report a new chemical sensing platform on a single surface-enhanced Raman scattering (SERS) particle. A cabbage-like Au microparticle (CLMP) with high SERS enhancement was applied as an ultrasensitive SERS substrate. A new Raman reporter bis­[4,4′-[dithiodiphenyl azo-phenol] (DTDPAP) was synthesized to display multiple fingerprints and high reactivity toward sodium dithionite. The reaction of DTDPAP with sodium dithionite was in situ monitored by SERS on a single CLMP. The DTDPAP fingerprint change is dependent on the sodium dithionite concentration, providing a simple and sensitive method for sodium dithionite profiling

CO₂‑Responsive Polymer-Functionalized Au Nanoparticles for CO₂ Sensor

Metallic nanoparticles (NPs) coated with stimuli-responsive polymers (SRPs) exhibit tunable optical properties responding to external stimuli and show promising sensing applications. We present a new CO₂-responsive polymer, poly­(<i>N</i>-(3-amidino)-aniline) (PNAAN), coated gold NPs (AuNPs) synthesized by directly reducing HAuCl₄ with a CO₂-responsive monomer <i>N</i>-(3-amidino)-aniline (NAAN). The amidine group of PNAAN can be protonated into a hydrophilic amidinium group by dissolved CO₂ (dCO₂). This induces the PNAAN to swell and detach from the AuNP surface, resulting in AuNP aggregation and color change. By monitoring the UV absorbance change of AuNPs, a sensitive dCO₂ sensor with a linear range of 0.0132 to 0.1584 hPa and a limit of detection (LOD) of 0.0024 hPa is developed. This method shows dramatic improvement in sensitivity and convenience of sample preparation compared with the previously reported dCO₂ sensor