Effect of graphene oxide inclusion on the optical reflection of a silica photonic crystal film

The Fabrication of Full Chromatography SiO2@PDA Photonic Crystal Structural Colored Fabric with High Thermal Stability

Traditional textile dyeing and finishing industries are two of the most important sources of high pollution, high energy consumption, and high emissions. Structural color, as a clean ecological staining method that does not require any dye or pigment, has received extreme attention from researchers. In this study, core-shell structures of SiO2@PDA microspheres were prepared by coating polydopamine (PDA) formed by rapid polymerization of dopamine (DA) on the surface of SiO2 microspheres. Moreover, the structural colors of full chromatography were successfully prepared by vertical self-assembly on silk. The morphology and chemical structure of the prepared SiO2@PDA microspheres were studied by SEM and FT-IR, and the morphology and optical properties of the structured colored fabrics were characterized by SEM and material microscope. The different structural colors of the entire visible region were obtained by controlling the particle size of SiO2@PDA microspheres and the viewing angle of the SiO2@PDA photonic crystal, which are consistent with Bragg’s diffraction law. Since the SiO2@PDA photonic crystal has thermal stability, the prepared structural color fabric could remain highly saturated in color at temperatures up to 200 °C. This has a previously unreported high thermal stability on structural colors of silk. Therefore, the research work will demonstrate a structural color fabric that can prepare full chromatography with high thermal stability.

Ternary biogenic silica/magnetite/graphene oxide composite for the hyperactivation of Candida rugosa lipase in the esterification production of ethyl valerate

Oil palm leaves (OPL) silica (SiO₂) can replace the energy-intensive, commercially produced SiO₂. Moreover, the agronomically sourced biogenic SiO₂ is more biocompatible and cost-effective enzyme support, which properties could be improved by the addition of magnetite (Fe₃O₄) and graphene oxide (GO) to yield better ternary support to immobilize enzymes, i.e., Candida rugosa lipase (CRL). This study aimed to optimize the Candida rugosa lipase (CRL immobilization onto the ternary OPL-silica-magnetite (Fe₃O₄)-GO (SiO₂/Fe₃O₄/GO) support, for use as biocatalyst for ethyl valerate (EV) production. Notably, this is the first study detailing the CRL/SiO₂/Fe3O4/GO biocatalyst preparation for rapid and high yield production of ethyl valerate (EV). AFM and FESEM micrographs revealed globules of CRL covalently bound to GL-A-SiO₂/Fe₃O₄/GO; similar to Raman and UV-spectroscopy results. FTIR spectra revealed amide bonds at 3478 cm^-1 and 1640 cm^-1 from covalent interactions between CRL and GL-A-SiO₂/Fe₃O₄/GO. Optimum immobilization conditions were 4% (v/v) glutaraldehyde, 8 mg/mL CRL, at 16 h stirring in 150 mM NaCl at 30 °C, offering 24.78 ± 0.26 mg/g protein (specific activity = 65.24 ± 0.88 U/g). The CRL/SiO₂/Fe₃O₄/GO yielded 77.43 ± 1.04 % of EV compared to free CRL (48.75 ± 0.70 %), verifying the suitability of SiO₂/Fe₃O₄/GO to hyperactivate and stabilize CRL for satisfactory EV production.

Fabrication of UV Laser-Induced Porous Graphene Patterns with Nanospheres and Their Optical and Electrical Characteristics

Many studies have been conducted to fabricate unique structures on flexible substrates and to apply such structures to a variety of fields. However, it is difficult to produce unique structures such as multilayer, nanospheres and porous patterns on a flexible substrate. We present a facile method of nanospheres based on laser-induced porous graphene (LIPG), by using laser-induced plasma (LIP). We fabricated these patterns from commercial polyimide (PI) film, with a 355 nm pulsed laser. For a simple one-step process, we used laser direct writing (LDW), under ambient conditions. We irradiated the PI film at a defocused plane -4 mm away from the focal plane, for high pulse overlap rate. The effect of the laser scanning speed was investigated by FE-SEM, to observe morphological characterization. Moreover, we confirmed the pattern characteristics by optical microscope, Raman spectroscopy and electrical experiments. The results suggested that we could modulate the conductivity and structural color by controlling the laser scanning speed. In this work, when the speed of the laser is 20 mm/s and the fluence is 5.28 mJ/cm2, the structural color is most outstanding. Furthermore, we applied these unique characteristics to various colorful patterns by controlling focal plane.

Thermal-Responsive Photonic Crystal with Function of Color Switch Based on Thermochromic System

Responsive photonic crystals have attracted considerable attention. The responsiveness is usually achieved through the variation of reflection wavelengths based on Bragg diffraction. However, distinguishing external stimuli from intrinsic angle dependence is a challenge. Herein, a novel thermal-responsive photonic crystal was constructed based on the synergistic effect of the low-angle dependence of SnO₂ inverse opals and a thermochromic phase change system. The organic thermochromic phase change system was obtained by mixing the fluoran dye (heat-sensitive red TF-R₂), bisphenol A, and aliphatic alcohols in a certain proportion. By filling the thermochromic phase change system into SnO₂ inverse opals, the thermal-responsive photonic crystal was fabricated. Through simple external thermal stimulation, the mutual transformation of low-angle-dependent structural color and pigmentary color is realized and inverse opal patterns can be displayed and hidden. The proposed system, while preventing the interference of the observation angle to the thermal stimulation, shows potential application prospect in the fields of anti-counterfeiting and information encryption fields.

Graphene hybrid colloidal crystal arrays with photo-controllable structural colors

An intelligent structural color hydrogel with photo-controllable capability was developed by adding graphene oxide (GO) into colloidal particle solutions. The high charge characteristic of GO could significantly enhance the electrostatic repulsion effect between adjacent particles and promote the ordered assembly of the colloidal particles. The resultant colloidal crystal arrays (CCAs) with a small amount of GO additive were imparted with vivid angle-dependent structural colors due to the enhanced photon absorption of the hybrid materials, whereas their structural colors became dull and angle-independent with a high GO concentration, which contributes to the isotropic short-range ordered CAA nanostructures. It was demonstrated that the GO hybrid structural color hydrogels with temperature-sensitive polymer components featured photo-responsive properties, which provided remotely controllable dynamic structural colors for different patterns. These features of the GO hybrid structural color hydrogels make them promising for the applications of anti-counterfeiting barcode and other related fields.

Graphene Oxide as an Optical Biosensing Platform: A Progress Report

A few years ago, crucial graphene oxide (GO) features such as the carbon/oxygen ratio, number of layers, and lateral size were scarcely investigated and, thus, their impact on the overall optical biosensing performance was almost unknown. Nowadays valuable insights about these features are well documented in the literature, whereas others remain controversial. Moreover, most of the biosensing systems based on GO were amenable to operating as colloidal suspensions. Currently, the literature reports conceptually new approaches obviating the need of GO colloidal suspensions, enabling the integration of GO onto a solid phase and leading to their application in new biosensing devices. Furthermore, most GO-based biosensing devices exploit photoluminescent signals. However, further progress is also achieved in powerful label-free optical techniques exploiting GO in biosensing, particularly using optical fibers, surface plasmon resonance, and surface enhanced Raman scattering. Herein, a critical overview on these topics is offered, highlighting the key role of the physicochemical properties of GO. New challenges and opportunities in this exciting field are also highlighted.

Review on Fabrication of Structurally Colored Fibers by Electrospinning

Structural color derived from the physical interactions of photons, with the specific chromatic mechanism differing from that of dyes and pigments, has brought considerable attention by the conducive virtue of being dye-free and fadeless. This has recently become a research hot-spot. Assemblies of colloidal nanoparticles enable the manufacture of periodic photonic nanostructures. In our review, the mechanism of nanoparticle assemblies into structurally colored structures by the electrospinning method was briefly introduced, followed by a comparatively comprehensive review summarizing the research related to photonic crystals with periodically aligned nanostructures constructed by the assembly of colloidal nanoparticles, and the concrete studies concerning the fabrication of well-aligned electrospun nanofibers incorporating with colloidal nanoparticles based on the investigation of relevant factors such as the sizes of colloidal nanoparticles, the weight ratio between colloidal nanoparticles, and the polymer matrix. Electrospinning is expected to be a deserving technique for the fabrication of structurally colored nanofibers while the colloidal nanoparticles can be well confined into aligned arrangement inside nanofibres during the electrospinning process after the achievement of resolving remaining challenges.

B, Lal C. Praseodymium-decorated graphene oxide as a corrosion inhibitor in acidic media for the magnesium AZ31 alloy

In the present work, Pr-decorated graphene oxide was synthesized and tested as a corrosion barrier layer in acidic media for the magnesium AZ31 alloy. The morphology, composition and structure of Pr-decorated graphene oxide sheets were characterized via HRTEM, FESEM, Raman, XRD, DLS, UV and FTIR studies. The corrosion inhibition efficiency on the alloy surface was monitored via microstructural and electrochemical methods. The results indicate that Pr-decorated graphene oxide provides improved protection for the Mg AZ31 alloy compared to conventional epoxy coatings. The proposed mechanism arises from a combination of the barrier activities of the composite, GO + Pr, and the epoxy coating on the Mg alloy in acidic media.

The Mg alloys 111 surface is covered by the praseodymium decorated graphene oxide sheet, and (A) & (B) indicates ions diffusion control (C) indicates epoxy coating failure.