Plasmonic Elastic Capsules as Colorimetric Reversible pH‐Microsensors. Issue 6 (21st January 2020)

• Record Type: Journal Article
• Authors: Burel, Céline; Teolis, Alexandre; Alsayed, Ahmed; Murray, Christopher B.; Donnio, Bertrand; Dreyfus, Rémi
• Is Part Of: Small. Volume 16:Issue 6(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-01-21
• Subjects: bacteria -- microcapsules -- nanoparticles -- pH‐sensors -- plasmonics; Nanotechnology -- Periodicals; Nanoparticles -- Periodicals; Microtechnology -- Periodicals; 620.5
• DOI: 10.1002/smll.201903897
• Languages: English
• ISSNs: 1613-6810

Abstract

Abstract: There is a crucial need for effective and easily dispersible colloidal microsensors able to detect local pH changes before irreversible damages caused by demineralization, corrosion, or biofilms occur. One class of such microsensors is based on molecular dyes encapsulated or dispersed either in polymer matrices or in liquid systems exhibiting different colors upon pH variations. They are efficient but often rely on sophisticated and costly syntheses, and present significant risks of leakage and photobleaching damages, which is detrimental for mainstream applications. Another approach consists of exploiting the distance‐dependent plasmonic properties of metallic nanoparticles. Still, assembling nanoparticles into dispersible colloidal pH‐sensitive sensors remains a challenge. Here, it is shown how to combine optically active plasmonic gold nanoparticles and pH‐responsive thin shells into "plasmocapsules." Upon pH change, plasmocapsules swell or shrink. Concomitantly, the distance between the gold nanoparticles embedded in the polymeric matrix varies, resulting in an unambiguous color change. Billions of micron‐size sensors can thus be easily fabricated. They are nonintrusive, reusable, and sense local pH changes. Each plasmocapsule is an independent reversible microsensor over a large pH range. Finally, their potential use for the detection of bacterial growth is demonstrated, thus proving that plasmocapsules are a new class of sensing materials. Abstract : Plasmocapsules made of optically active plasmonic gold nanoparticles and pH‐responsive polyacrylate are used as pH microsensors. Upon pH change, the polymer shell of the plasmocapsules swells or shrinks. Concomitantly, the distance between the gold nanoparticles embedded in the polymeric matrix varies, resulting in a color change. Each single plasmocapsule is a reversible independent microsensor over a large range of pH.