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Multidomain-Based Responsive Materials with Dual-Mode Optical Readouts

You, Yil-Hwan, Biswas, Aniket, Nagaraja, Ashvin T., Hwang, Jin-Ha, Coté, Gerard L., McShane, Michael J.
ACS applied materials & interfaces 2019 v.11 no.15 pp. 14286-14295
Raman spectroscopy, alginates, crosslinking, glucose, glucose oxidase, hydrogels, nanogold, oxygen, pH, phosphorescence
Responsive materials designed to generate signals for both surface-enhanced Raman spectroscopy (SERS) and phosphorescence lifetime—“dual-mode”—measurements are described. To demonstrate this concept, we incorporated pH-sensitive and oxygen-sensitive microdomains into a single hydrogel that could be interrogated via SERS and phosphorescence lifetime, respectively. Microdomains consisted two populations of discrete microcapsules containing either (1) gold nanoparticles capped with pH-sensitive Raman molecules or (2) oxygen-sensitive benzoporphyrin phosphors. While the microdomain-embedded hydrogels presented an expected background luminescence, the pH-sensitive SERS signal was distinguishable for all tested conditions. Response characteristics of the dual sensor showed no significant difference when compared to standalone single-mode pH and oxygen sensors. In addition, the feasibility of redundant multimode sensing was proven by observing the reaction produced by glucose oxidase chemically cross-linked within the corresponding alginate matrix. Each optical mode showed a signal change proportional to glucose concentration with an opposite signal directionality. These results support the promise of micro-/nanocomposite materials to improve measurement accuracy using intrinsic multimode responses and built-in redundancy, concepts that have broad appeal in the chemical sensing and biosensing fields.