Several biological membranes have been served as scattering materials of random lasers, but few of them include natural photonic crystals. Here, we propose and demonstrate a facile approach to fabricating high-performance biological photonic crystal random lasers, which is cost-effective and reproducible for mass production. As a benchmark, optical and lasing properties of dye-coated Lepidoptera wings, including Papilio ulysses butterfly and Chrysiridia rhipheus moth, are characterized and show a stable laser emission with a superior threshold of 0.016 mJ/cm², as compared to previous studies. To deploy the proposed devices in practical implementation, we have applied the as-fabricated biological devices to bright speckle-free imaging applications, which is a more sustainable and more accessible imaging strategy.

Climate change, caused by greenhouse gas emissions, is one of the biggest threats to the world. As per the IEA report of 2021, global CO₂ emissions amounted to around 31.5 Gt, which increased the atmospheric concentration of CO₂ up to 412.5 ppm. Thus, there is an imperative demand for the development of new technologies to convert CO₂ into value-added feedstock products such as alcohols, hydrocarbons, carbon monoxide, chemicals, and clean fuels. The intrinsic properties of the catalytic materials are the main factors influencing the efficiency of electrochemical CO₂ reduction (CO₂-RR) reactions. Additionally, the electroreduction of CO₂ is mainly affected by poor selectivity and large overpotential requirements. However, these issues can be overcome by modifying heterogeneous electrocatalysts to control their morphology, size, crystal facets, grain boundaries, and surface defects/vacancies. This article reviews the recent progress in electrochemical CO₂ reduction reactions accomplished by surface-defective electrocatalysts and identifies significant research gaps for designing highly efficient electrocatalytic materials.

In this study, we developed a facile technique to fabricate a surface-enhanced Raman scattering (SERS) substrate. The technique involves self-assembling monodispersive SiO₂ spheres on silicon wafer, then coating with a thin Ag film to form a SERS substrate comprised of a Ag coated monolayer array of SiO₂ spheres. The substrate can detect minute amounts of organic dye. By optimizing the fabrication process, including controlling the size of the SiO₂ spheres, the distribution of the SiO₂ spheres on the silicon wafer, and the thickness of the Ag film, a dramatic increase in the enhancement of Raman scattering signals by surface plasmon resonance can be achieved. The enhancement of Raman scattering is closely correlated to the absorption peak of the organic dye and the excitation wavelength of the Raman system. A 40 000-fold enhancement has been observed for a substrate prepared with 350 nm SiO₂ spheres self-assembled on silicon wafer and coated with a 150 nm Ag layer. Through experimental and theoretical calculations (FDTD), such a strong signal intensity originates from the closeness between the absorption peak of the organic dye and the Raman excitation wavelength occurring at the hot spots of the SERS substrate. The high sensitivity, low cost and quick response provided by this type of SERS substrate are useful for the design and fabrication of functional devices and sensors.

In this work, we synthesized a metal-free sulfonic functionalized graphitic carbon nitride using sulfuric acid through the wet impregnation technique. The functionalization of sulfonic groups (–SO₃H) on g-C₃N₄ will promote a high surface charge density and charge separation owing to its high electronegativity. The g-C₃N₄–SO₃H shows excellent optical/electronic and surface properties towards enhanced photo–redox reactions. The sulfonic groups also facilitate the availability of more separated charge carriers for photocatalytic oxidation and reduction reactions. The as-synthesized material has been characterized by different spectroscopic tools to confirm the presence of functionalized –SO₃H groups and optoelectronic possessions. The photocatalytic responses of g-C₃N₄–SO₃H result in 99.56% photoreduction of Cr (VI) and 99.61% photooxidation of Sunset Yellow FCF within 16 min and 20 min, respectively, of visible light irradiation. The g-C₃N₄–SO₃H catalyst exhibits a high apparent rate constant (K_app) towards the degradation of Cr (VI), and SSY, i.e., 0.783 min⁻¹ and 0.706 min⁻¹, respectively. The intense optical–electrochemical properties and potentially involved active species have been analyzed through transient photocurrent, electrochemical impedance, and scavenging studies. Consequently, the photocatalytic performances are studied under different reaction parameters, and the plausible photocatalytic mechanism is discussed based on the results.