Mechanochromic and Thermochromic Sensors Based on Graphene Infused Polymer Opals

Abstract

High quality opal‐like photonic crystals containing graphene are fabricated using evaporation‐driven self‐assembly of soft polymer colloids. A miniscule amount of pristine graphene within a colloidal crystal lattice results in the formation of colloidal crystals with a strong angle‐dependent structural color and a stop band that can be reversibly shifted across the visible spectrum. The crystals can be mechanically deformed or can reversibly change color as a function of their temperature, hence their sensitive mechanochromic and thermochromic response make them attractive candidates for a wide range of visual sensing applications. In particular, it is shown that the crystals are excellent candidates for visual strain sensors or integrated time‐temperature indicators which act over large temperature windows. Given the versatility of these crystals, this method represents a simple, inexpensive, and scalable approach to produce multifunctional graphene infused synthetic opals and opens up exciting applications for novel solution‐processable nanomaterial based photonics.

Nanophotonic Structural Colors

“…78 Another interesting application is colorimetric sensing. [194][195][196][197][198][199][200][201] Structural color elements can be designed such that they visually respond to different external stimuli such as temperature, chemicals, and humidity through the use of suitable materials in an optically resonant system. [202][203][204][205][206][207][208][209][210][211][212][213] The benefit of colorimetric sensing is in realizing passive devices that are untethered to an energy source.…”

Mechanically responsive luminescent films based on copper iodide clusters

“…Luminescent mechanochromic materials displaying switchable luminescence properties in response to mechanical stimuli 1,2 are attracting wide interest for potential applications in strain detection, optical recording and storage, anti-counterfeiting, to name a few. [3][4][5][6][7][8][9][10] Regarding security issues, mechanically induced damages need to be detected at the early stage of stress formation [11][12][13] and luminescent mechanochromic materials enable the straightforward visible detection of strain with emission changes easily detectable by naked eyes or by simple non-invasive spectroscopic means. [14][15][16] Efficient mechanochromic luminescent materials should exhibit high-contrast luminescent change in emission color or intensity for an easy detection and this effect should be preferentially reversible.…”

Bioinspired structural color nanocomposites with healable capability

“…For example, crosslinking of colloidal crystals via a thermal or chemical process can greatly improve the connection between the individual NPs. [38][39][40][41][42] Structural color nanocomposites which are obtained through the incorporation of the colloidal PCs into polymeric matrices have also been developed to enhance the durability of the PCs since soft polymeric materials with intrinsic flexibility provide the composite PCs with the capability of resisting mechanical deformation, maintaining the integrity of the PCs. 21,[43][44][45][46] Furthermore, the introduction of the polymeric matrix also endows the PCs with unique functionalities.…”

“…For instance, structural color nanocomposites can be used as a visual strain sensor with adhesive capability. 40,47 Our group has also utilized responsive hydrogels to incorporate assembled Fe 3 O 4 colloidal particles and constructed chemical and force structural color sensors. [48][49][50] Although these strategies have been demonstrated to be effective in improving the reliability and functionality of PC materials, challenges, including the large deformation and the abrasion of the surface of the PCs, remain and limit their applications.…”