A biomass based photonic crystal made of “konjac tofu”

Hazardous Gases-Responsive Photonic Crystals Cryogenic Sensors Based on Antifreezing and Water Retention Hydrogels

Nowadays, the sensing of hazardous gases is urgent for the consideration of public safety and human health, especially in extreme conditions of low temperatures. In this study, a photonic crystals (PhCs) sensor with water retention and antifreezing properties was developed and applied to visual hazardous gases sensing at low temperature, passively. The sensor was prepared by dip-coating with poly(methyl methacrylate) (PMMA) colloidal microspheres followed by embedding in k-carrageenan/polyacrylamide-ethylene glycol (k-CA/PAM-EG) hydrogel. The sensor responded to hazardous gases, including ammonia, toluene, xylene, acetone, methanol, ethanol, and 1-propanol, with a change in the reflection wavelength and visible structural color. At room temperature, the reflection wavelength of the sensor blue-shifted 49 nm in ammonia, and the structural color changed from red to yellow. For low temperatures, the sensor showed great water retention and antifreezing properties even at -57 °C due to the double network. The sensor still had a great response to hazardous gases after freezing at -20 °C for 12 h and testing at 0 °C, and the obtained results were similar to those at room temperature. Based on this excellent stability and visual sensing at low temperature, the sensor demonstrates the potential for detection of hazardous vapors in extreme environments.

Construction of Wash-Resistant Photonic Crystal-Coated Fabrics based on Hydrogen Bonds and a Dynamically Cross-Linking Double-Network Structure

Structural coloration as the most possible way to realize the ecofriendly dying process for textiles or fabrics has attracted significant attention in the past decades. However, photonic crystals (PCs) are a typical example of materials with structural color usually located on the surface of the fabrics or textiles, which make them not stable when rubbed, bent, or washed due to the weak interaction between the PC coatings and fabrics. Here, double networks were constructed between the PC coatings and the fabrics for the first time via a hydrogen bond by introducing tannic acid (TA) and dynamic cross-linking with 2-formylphenylboronic acid to increase the wash resistance of the structural colored fabrics. On modifying the monodispersed SiO₂ nanoparticles, poly(dimethylsiloxane), and the fabrics, the interaction between the PC coatings and the fabrics increased by the formation of double networks. The structural color, wash, and rub resistance of the PC-coated fabrics were systematically studied. The obtained fabrics with the TA content at 0.030% (SiDT30) showed the best wash and rub resistance. The construction of double networks not only improved the wash and rub resistance of PCs but also retained the bright structural color of the PC coatings, facilitating the practical application of structural coloration in the textile industry.

Specific Alcohol-Responsive Photonic Crystal Sensors Based on Host-Guest Recognition

A photonic crystal material based on β-cyclodextrin (β-CD) with adsorption capacity is reported. The materials ((A-β-CD)-AM PC) consist of 3D poly (methyl methacrylate) (PMMA) colloidal microsphere arrays and hydrogels supplemented with β-cyclodextrin modified by acryloyl chloride. The prepared materials are then utilized for VOCs gas sensing. The 3D O-(A-β-CD)-AM PC was used to detect toluene, xylene, and acetone and the response was seen as the red-shift of the reflection peak. The 3D I-(A-β-CD)-AM PC was used to detect toluene, xylene, and acetone which occurred redshifted, while methanol, ethanol, and propanol and the peaks' red-shifting was observed. However, among these, methanol gave the largest red-shift response The sensor has broad prospects in the detection of alcohol and the detection of alcohol-loaded drug releases in the future.

A photoelectrochemical immunosensor based on magnetic all-solid-state Z-scheme heterojunction for SARS-CoV-2 nucleocapsid protein detection

Rapid, convenient and accurate detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is urgently needed to timely diagnosis of coronavirus pandemic (COVID-19) and control of the epidemic. In this study, a signal-off photoelectrochemical (PEC) immunosensor was constructed for SARS-CoV-2 nucleocapsid (N) protein detection based on a magnetic all-solid-state Z-scheme heterojunction (Fe₃O₄@SiO₂@TiO₂@CdS/Au, FSTCA). Integrating the advantages of magnetic materials and all-solid-state Z-scheme heterostructures, FSTCA was implemented to ligate the capture antibody to form magnetic capture probe (FSTCA/Ab₁). It can simplify the separation and washing process to improve reproducibility and stability, while allowing immune recognition to be performed in the liquid phase instead of the traditional solid-liquid interface to improve anti-interference. Besides, the heterojunction inhibited the recombination of photogenerated electron/hole (e^-/h⁺) and promoted the light absorption to provide superior photoelectric substrate signal. The mechanism of photogenerated e^-/h⁺ transfer of FSTCA were investigated by the electron spin resonance (ESR) spectroscopy. SiO₂ spheres loaded with Au NPs utilized as an efficient signal quencher. The steric hindrance effect of SiO₂@Au labeled detection antibodies (SiO₂@Au-Ab₂) conjugates significantly diminished light absorption and hindered the transfer of photogenerated electrons, further amplifying the signal change value. Based on the above merits, the elaborated immunosensor had a wide linear range of 10 pg mL^-1-100 ng mL^-1 and a low detection limit down to 2.9 pg mL^-1 (S/N = 3). The fabricated PEC immunosensor demonstrated strong anti-interference, easy operation, and high sensitivity, showing enormous potential in clinical diagnosis of SARS-CoV-2.

Biofunctional peptide-click PEG-based hydrogels as 3D cell scaffolds for corneal epithelial regeneration

Poly(ethylene glycol) (PEG)-based hydrogels as highly promising 3D cell scaffolds have been widely implemented in the field of tissue regrowth and regeneration, yet the functionalized PEG hydrogel providing dynamic, cell-instructive microenvironments is inherently difficult to obtain. Here, we have exploited the specificity of click reaction to develop a set of hydrogels based on 4-arm PEG tetraazide (4-arm-PEG-N₃) and di-propargylated peptides (GRGDG and GRDGG) with tunable physicochemical properties applicable for 3D cell scaffolds. The azide groups of PEG were reacted with the alkynyl groups of peptides, catalyzed by copper to form triazole rings, thus generating a cross-linked hydrogel. The gelation time and mechanical strength of the hydrogels varied according to the PEG/peptide feed ratio. The resulting hydrogel exhibited a typical porous microstructure and suitable swelling behavior. The in vitro cytotoxicity test indicated that the resulting hydrogels did not cause apparent cytotoxicity against human corneal epithelial cells (HCECs). After co-incubation with HCECs, the density of RGD as well as peptide sequence in the hydrogels remarkably affected the cell attachment, spreadability, and proliferation. Additionally, the proposed hydrogel showed high ocular biocompatibility after being embedded subconjunctivally into rabbit eyes. Overall, these findings highlighted that the biofunctional hydrogels formed by PEG and RGD motifs via a controllable click reaction might be promising 3D cell scaffolds for corneal epithelial regeneration.

Flory-Huggins VOC Photonics Sensor Made of Cellulose Derivatives

As a widespread air pollutant, volatile organic compounds (VOCs) are harmful to the human body's skin, nervous system, and respiratory system. Low-cost, extensive, and continuous detection of VOCs is of great significance to human health. We infiltrated and coated cellulose acetate on the inverse opal photonic crystal skeleton of methylcellulose-polyvinyl alcohol-graphene oxide to construct a degradable, high-toughness cellulose VOC sensor. Cellulose acetate enhances the response to VOCs and achieves a highly selective response to acetone vapor due to the smaller Flory-Huggins parameter with acetone. This work proposes a general, simple, easy-to-use, and highly selective photonic crystal VOC sensor development strategy. Calculated from the Flory-Huggins solution theory, a suitable polymer was selected to modify the inverse opal photonic crystal framework and achieve high selectivity detection.