Bottom-Up Assembled Photonic Crystals for Structure-Enabled Label-Free Sensing

Abstract

Photonic crystals (PhCs) display photonic stop bands (PSBs) and at the edges of these PSBs transport light with reduced velocity, enabling the PhCs to confine and manipulate incident light with enhanced light–matter interaction. Intense research has been devoted to leveraging the optical properties of PhCs for the development of optical sensors for bioassays, diagnosis, and environmental monitoring. These applications have furthermore benefited from the inherently large surface area of PhCs, giving rise to high analyte adsorption and the wide range of options for structural variations of the PhCs leading to enhanced light–matter interaction. Here, we focus on bottom-up assembled PhCs and review the significant advances that have been made in their use as label-free sensors. We describe their potential for point-of-care devices and in the review include their structural design, constituent materials, fabrication strategy, and sensing working principles. We thereby classify them according to five sensing principles: sensing of refractive index variations, sensing by lattice spacing variations, enhanced fluorescence spectroscopy, surface-enhanced Raman spectroscopy, and configuration transitions.

Artificial Chameleon Skin with Super-Sensitive Thermal and Mechanochromic Response

“…According to Bragg’s law (eqs and , details are explained in Supporting Information), the main parameters affecting the frequency and intensity of PSB are the RIs and the lattice constant. − Thanks to both the suitable RI contrast between guanine nanocrystals and cytosols and the flexibility in tuning the lattice constant of the NCP structure, chameleons can easily and sensitively change their brilliant skin color. Inspired by this kind of biological photonic structure, numerous stimuli-responsive devices were created to offer exclusive prospects as various sensors, including pH, electric field, magnetic field, stress, temperature, humidity, and so on. − …”

Trends in Nanophotonics‐Enabled Optofluidic Biosensors

“…To overcome these constraints, surface-enhanced vibrational spectroscopic techniques have been introduced, in particular SERS and SEIRAS, which rely on the amplification of molecular vibrations through contact with nanostructured surfaces (Figure 3a,e). [32,146] In this section, we discuss the use of these surface-enhanced techniques for molecular identification, [147][148][149] with a particular focus on recently introduced strategies toward the ultimate goal of performing diagnostically relevant bioassays in bodily fluids.…”

Progress on Rapidly and Self-Assembly Magnetically Responsive Photonic Crystals With High Tunability and Stability

“…Photonic Crystals (PCs) are one of the most popular nanomaterials in recent years (John, 1987;Yablonovitch, 1987) which are regular multi-dimensional periodic structures that are composed of two or more materials with different refractive indexes. As a unique photonic metamaterial, it has found many important applications in dynamic color displays (Liao, et al, 2019;Lai, et al, 2022), optical sensing (Wang, et al, 2021), and anticounterfeiting (Wang, et al, 2020). At present, they are mainly prepared by self-assembly methods, among which vertical self-assembly (Hong et al, 2014), centrifugal self-assembly (Hu et al, 2013), electrophoretic deposition self-assembly (Katagiri et al, 2017), electrostatic and capillary action self-assembly (Lee et al, 2014) and microfluidic synthesis (Yin et al, 2016)are commonly used.…”