Polymer-grafted Gold Nano Capsules as Reversible Colorimetric Sensors

Colloidal colorimetric microsensors have been shown to enable the in-situ detection of mechanical loads within materials [1,2]. Enhancing the sensitivity of these sensors to small scale loads and deformation while enabling reversibility of the sensing capability would expand their utility in various applications including biosensing and chemical sensing [3]. In this presentation, we introduce the synthesis of nano-sized multifunctional colloidal colorimetric sensors using a simple and versatile fabrication method. Multifunctional colloidal nano-sensors (NS) are prepared by emulsion-templated assembly of polystyrene grafted gold nanoparticles. We have explored a potential application of these NSs as mechanical sensors. Gold nanoparticle-based NSs are embedded in an elastomer matrix. The addition of a plasticizer imparts flexibility to the NSs. The plasmonic peak of the NSs shifts towards lower wavelengths upon application of uniaxial tension on the gold NSs/PDMS composite, indicating increased particle-to-particle distance. The composite recovers its original plasmonic peak upon the release of the strain, demonstrating reversibility. This study provides a robust and easily scalable method of producing sensors that can potentially detect the presence of chemicals or small strain present at the nanoscale in biological cells.