Flexible Composite Inverse Opal Fabrics for Visual Detection of BTEX Vapor

Photonic crystal (PC) is widely used in BTEX vapor colorimetric detection due to its tunable photonic band gap, which has battery-free and signal output instrument-free advantages. Recently, responsive PC fabrics have also attracted a lot of interest. Compared to hard substrates such as glass slide and silicon wafer, these fabrics have better flexibility and portability, which can make them more widely usable. However, at present, the PC fabrics are mainly achieved by deposition of colloidal microspheres or nanosheets, which are easy to be destroyed by stretching, bending, and washing, and the dense stacked structure hinder the diffusion of vapor as well. In this study, the PEGDA inverse opal structure (IOs) with a porous structure and an ultrahigh specific area was constructed on polyester fabrics by sacrificing SiO2 PC template of glass/SiO2 PCs/fabric sandwich structure, and the IOs coating showed a very good bonding force with the fabrics. Benefiting from the porous structure of IOs coating, the diffusion rate of vapor was greatly increased. Besides, functional polymers and flexible MOFs were infiltrated into the IOs to selectively absorb BTEX and enhance the absorption as well, thus effectively reducing the detection limits (2.92, 1.85, 0.52, and 0.13 g/m3 for benzene, toluene, ethylbenzene, xylene, respectively) and response speed (0.3 s for response and 0.8 s for recover), and in addition, the repeatability was good after 10 cycles. More importantly, the method to construct IOs on fabrics was universal; the IOs can be replaced with any polymer, so it is expected to be applied for the detection of other analytes.