Refractive Index‐Adaptive Nanoporous Chiral Photonic Crystal Film for Chemical Detection Visualized via Selective Reflection

Abstract

Photonic crystals (PC) are of great importance in technology, especially in optics and photonics. In general, the structural color of PCs responds to external stimuli primarily by changing their periodicity. Herein, the authors report on refractive index (RI) adaptive PCs. Cross‐linked cholesteric films with interconnected nanopores exhibit a very low RI without light scattering. Transparent PC films with maximum reflectance in the ultravoilet (UV) region respond to various chemicals by changing the reflective color of the PC. The authors demonstrate its unique colorimetric chemical detections of hazardous organic liquids. Loading various chemicals into nanopores significantly shifts the structural color into the visible range depending on the chemical's RI. These results are unique in that the structural color of photonic films is mediated by RI changes rather than periodicity changes. In principle, nanoporous photonic crystal films can detect the RI of a chemical substance by its unique color. In contrast to volumetric changes, this sensing mechanism offers several advantages, including durability, excellent sensitivity, fast response time, and wide detection range. These results provide useful insight into stimulus‐responsive PCs. The structural color of PC films can be effectively tuned by adjusting average RIs instead of changing periodicity.

Recyclable soft photonic crystal film with overall improved circularly polarized luminescence

“…1 and 2a ). Compared with the film before washing, the PBG of the SPC film exhibited a blueshift due to the pitch change caused by the absence of liquid crystal molecules 38 . The texture of the SPC S film remained the same after removing the unpolymerized material (Supplementary Fig.…”

Improved N2 photo-fixation performance of nanocrystalline TiO2 films by photon localization effects and Fe doping

“…It can be observed that the absorption peak center of PBG was at 380 nm, which closely coincided with the EBG of 6% FT. Because light with a wavelength of 380 nm corresponded to blue light, the SOPC film appeared bright light blue under natural light. 70 The SOPC was denoted as SOPC-380.…”

Visual Recognition of Volatile Organic Compounds by Photonic Nose Integrated with Multiple Metal‐Organic Frameworks

“…[15] Its unique photonic band gap (PBG) can reflect light at a specific wavelength, so when PBG is in the visible range, the structural color will appear. [16,17] Furthermore, when the refractive index (RI) or thickness of PCs is changed by external stimuli, the PBG position will shift, causing color changes of the PCs, thus converting stimuli into visual detection. [18,19] In view of the sensitivity of human vision to color, this detection method using color transformation to visualize external stimuli has shown great advantages in the field of sensing.…”