A multicolor-SERS dual-mode pH sensor based on smart nano-in-micro particles

A multicolor and surface-enhanced Raman scattering (SERS) dual-mode pH sensing method based on microparticles was proposed, which combined the advantages of high sensitivity of SERS and convenience of colorimetric visualization. Polyethylene glycol diacrylate microgels were fabricated using a T-channel microfluidic chip, and the polyaniline-coated gold nanorods were encapsulated in the microgels. Based on the nano-in-micro particles, pH monitoring within the range of 1.0–12.0 was achieved through multicolor and SERS dual-mode sensing. The protonation and deprotonation of polyaniline led to changes in Raman signal intensity and color of microparticles. The pH changes during cell culture were successfully monitored by SERS quantification and microscopic images of the microparticles. And the microparticles exhibit excellent stability, reversibility, biocompatibility, anti-interference ability and signal enhancement ability. The pH sensing method has a wide pH detection range and is especially suitable for pH monitoring in microsystems and micro-environments.