Incorporating Photochromic Viologen Derivative to Unprecedentedly Boost UV Sensitivity in Photoelectrochromic Hydrogel

Abstract

Developing ultraviolet (UV) radiation sensors featuring high sensitivity, ease of operation, and rapid readout is highly desired in diverse fields. However, the strategies to enhance sensitivity of UV detection remain limited particularly for photochromic materials, which show colorimetric response toward UV irradiation. Guided by our initial goal of facilitating easier handling, we formulated a viologen derivative ([H 2 L]-SC) incorporating hydrogel-based UV sensor which not only inherits the photochromism of [H 2 L]-SC but also engenders an unprecedented reversible photoelectrochromic response that is absent in either [H 2 L]-SC or hydrogel alone. Judicious synergy between photochromic [H 2 L]-SC and polyacrylamide (PAM) converts the colorimetric response of [H 2 L]-SC into the electrical resistance change of [H 2 L]-SC@PAM, which amplifies the UV sensitivity of [H 2 L]-SC by 2 orders of magnitude. Explicitly, the limit of detection (LOD) for UV decreases from 296.3 mJ/cm 2 based on the UV−vis absorption spectra of [H 2 L]-SC to 2.83 mJ/cm 2 derived from the resistance variation of [H 2 L]-SC@PAM. Moreover, linear correlation between the resistance reduction rate of [H 2 L]-SC@PAM and UV dose rate can be established, rendering it as a dual platform for quantifying both the accumulated UV dose and the instant dose rate. In addition, the proposed strategy based on constructing photoelectrochromic hybrids offers a new pathway to boost the UV sensitivity that could be universal for other photochromic materials.

A Multistimuli-Responsive Cd-MOF Constructed by an Extended Viologen-Based Carboxylate Ligand

“…MOFs constructed by ExV ligands might exhibit interesting photochromic properties, as many viologen derivatives. − Just as we expected, Cd-MOF- 1 also exhibited a color change in vision when exposed to UV–vis light. As shown in Figure a, after about 20 min UV–vis irradiation, Cd-MOF- 1 gradually changes from light yellow to bottle green.…”

Tunable photo/thermochromic properties of Cd(ii)-viologen coordination polymers modulated by coordination modes for flexible imaging films and anti-counterfeiting

“…3e and f). 14 Compounds 1 and 2 showed a weak EPR signal before UV irradiation, which can be attributed to the indoor light during synthesis and storage. 15 When compound 2 was stored for a long time (up to several months) without protection from indoor light, an enhanced EPR signal was observed, indicating that 2 can respond to indoor light (Fig.…”

Photochromism and Photomagnetism in Two Ni(II) Complexes Based on a Photoactive 2,4,6-Tris-2-Pyridyl-1,3,5-Triazine Ligand

“…Photochromic smart molecules, as one of the famous multifunctional materials, have been widely used in optical switch, information storage, sensor, and other fields. − They can show color changes under light irradiation with reversible changes in physicochemical properties (such as luminescence, − magnetism, − , and conductivity − ). So far, the metal–organic hybrid photochromic family has increased the possibilities for integrating the merits of inorganic and organic units at the molecular scale, providing a platform for researchers to design and create novel photochromic materials with diverse photoresponsive functionalities. − Especially, electron-transfer (ET) photochromic complexes containing viologen ligands and their derivatives have attracted extensive attention. − However, works on this photochromic system constructed by new photoactive ligands are still challenging due to the difficulty of synthesis and serendipity of photochromism.…”