One-Step Combustion Synthesis of Novel Nanocarbons via Magnesiothermic Reduction of Carbon-Containing Oxidants

The aim of this work was to transform carbon-containing ammonium oxalate, (NH₄)₂C₂O₄, and ammonium acetate, NH₄CH₃CO₂, into 3D graphene-like carbon nanomaterials via magnesiothermic reduction. Both raw and purified products were characterized by XRD, SEM, TGA, and Raman spectra. The conversion of the initial amount of carbon (in salts) into solid carbon (in purified product) varied between 8.5% (for oxalate) and 90.0% (for acetate). The XRD results confirmed the absence of starting salts in the raw products (MgO and C). The purified product was found to contain largely the turbostratic carbon forming a petal-like 3D graphene material. The application potential of synthesized materials was demonstrated on the example of the removal of 4-chlorophenol from its aqueous solution.     

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

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.