Precisely sensing hydrofluoric acid by photonic crystal hydrogels

Abstract

It is a great challenge to detect hydrofluoric acid (HF) with high precision, good selectivity, and visual readouts characteristics. Herein, a new photonic crystal (PC) hydrogel HF sensor based on the “selective etching-induced swelling” mechanism has been developed. This HF sensor consisting of silica/water/hydroxyethyl acrylate and non-closely packed structures was fabricated through simple non-close-assembling, photopolymerization, and water swelling processes. Silica slightly etched by HF induces the swelling of PC hydrogel, leading to the variation of reflection wavelength and structural colors, thereby realizing visually and spectrally sensing HF (0–10 mM). The unique structure and compositions of PC hydrogel are the keys to the high sensing precision, outstanding selectivity, and low detection limit (0.1 mM). Furthermore, the sensor possesses tailorable, portable, easy-to-operation, and low-cost (<0.01 $/sensor) advantages. This work provides an efficient and convenient tool for sensing and recognizing HF in the aqueous solution for practical applications and upgrades the basic understanding of the photonic sensing mechanism.