Ultrasensitive and Stable Au Dimer‐Based Colorimetric Sensors Using the Dynamically Tunable Gap‐Dependent Plasmonic Coupling Optical Properties

Abstract

A novel Au dimer-based colorimetric sensor is reported that consists of Au dimers to a chitosan hydrogel film. It utilizes the ultrasensitively gapdependent properties of plasmonic coupling (PC) peak shift, which is associated with the dynamical tuning of the interparticle gap of the Au dimer driven by the volume swelling of the chitosan hydrogel film. The interparticle gap and PC peak shift of the Au dimer can be precisely and extensively controlled through the pH-driven volume change of chitosan hydrogel film. This colorimetric sensor exhibits a high optical sensitivity and stability, and it works in a completely reversible manner at high pH values. Importantly, the sensitivity of the composite film can be tuned by controlling the crosslinking time of the composite film, and thus leading to a wide dynamic tuning sensitive range for different applications. This presented strategy paves a way to achieve the construction of high-quality colorimetric sensors with ultrahigh sensitivity, stability and wide dynamic tuning sensitive range.

pH-Driven Reversible Assembly and Disassembly of Colloidal Gold Nanoparticles

“…Noble metal nanoparticles have been intensively studied for a wide range of applications because of the localized surface plasmon resonance (LSPR), which is strongly dependent on nanoparticle size, shape, and composition (Gao et al, 2014 ; Chen et al, 2016 ). Low-dimensional plasmonic nanoparticle assemblies with new optical properties have recently attracted considerable attention because of the near-field coupling between adjacent particles (Liu D. et al, 2018 ; Li and Yin, 2019 ; Li et al, 2020a ). The ideal way is the reversible assembly of such plasmonic nanostructures, which could enable dynamic tuning of the surface plasmon coupling by responding the external stimuli, and therefore by taking advantage of the ultrasensitive gap-dependent properties of plasmonic coupling, they have great promises for applications such as colorimetric sensors, bio- and chemical detection, and therapeutics (Bonacchi et al, 2016 ; Pillai et al, 2016 ; Liu L. et al, 2018 ; Zhou et al, 2021 ).…”

Plasmonic biosensors fabricated by galvanic displacement reactions for monitoring biomolecular interactions in real time

“…Here, top-down methods rely on the fabrication of masks by rather sophisticated methods, for example, e-beam lithography, which facilitate the formation of highly defined nanostructures upon subsequent deposition of gold using physical vapor deposition or other appropriate techniques for creating thin metallic films [3]. Bottom-up strategies are mainly based on wet-chemically synthesized building blocks which are often arranged on appropriate substrates [4] or in hydrogel using self-assembly [5]. However, plasmonic nanoparticles have also been investigated as optical sensors directly in solution by e.g.…”

Dynamic Color‐Switching of Plasmonic Nanoparticle Films

“…One approach to creating solid-state plasmonic colorswitching is by embedding the NMNPs into stimuli-responsive polymer gels [15] or chemically grafting the plasmonic particles by stimuli-responsive polymer brushes. [16] Thereversible switching of plasmonic color can then occur by the structural changes of the polymer upon introducing external stimuli, such as pH, [17] temperature, [7] humidity [18] and light. [9] However,r apid and reversible tuning of plasmonic color in solid-state films still remains agreat challenge as such systems suffer from problems such as slow plasmonic switching rate, small modulation range of LSPR peak shift, poor reversibility and duration, complicated and time-consuming fabrication process,and difficulty in scaling up.Inaddition, the reversible color-switching is mainly limited to the plasmonic properties of AuNPs,a lthough AgNPs offer advantages of higher plasmonic activity,o ptical responses in the blue-UV region, and lower cost.…”