In this work, rice husk biomass was utilized as an abundant source to controllably prepare high-quality graphene quantum dots (GQDs) with a yield of ca. 15 wt %. The size, morphology, and structure of the rice-husk-derived GQDs were determined by high-resolution transmission electron microscopy, atomic force microscopy, and Raman spectroscopy. The as-fabricated GQDs can be stably dispersed in water, exhibiting bright and tunable photoluminescence. A cell viability test further confirmed that the GQDs possess excellent biocompatibility, and they can be easily adopted for cell imaging via a facile translocation into the cytoplasm. It is worth noting that mesoporous silica nanoparticles were also synthesized as a byproduct during the fabrication of GQDs. As such, our strategy achieves a comprehensive utilization of rice husks, exhibiting tremendous benefits on both the economy and environment.

Crystalline manganese oxides have attracted the most attention in aqueous zinc-ion batteries due to their diverse nanostructures and low cost. However, extensive studies on amorphous manganese oxides are lacking. Herein, we report a mesoporous amorphous manganese oxide (UCT-1-250) as a cathode material with high capacity (222 mAh g–1), good cyclability (57% capacity retention after 200 cycles), and an acceptable discharge plateau (between 1.2 and 1.4 V). An approach to mechanistic studies was performed by comparison of UCT-1-250 and other crystalline manganese oxides through electrochemical, elemental, and structural analyses. An in situ conversion to ZnMn2O4 spinel phase after initial cycling contributes to the high performance. The irreversible capacity fading is due to the formation of the woodruffite phase.

Air pollution issues due to soot/diesel particulate matter (DPM) emitted from incomplete burning of diesel fuel have become a global issue in this century. A series of manganese oxides, namely amorphous manganese oxide (Meso-Mn-A), Mn2O3 (Meso-Mn2O3), MnO2 (epsilon phase) (Meso-ϵ-MnO2) and octahedral molecular sieves MnO2 (Meso-OMS-2) was synthesized via a soft template method. The potential of mesoporous manganese oxides in acceleration of NO2 assisted catalytic oxidation of diesel soot (Printex-U) under lean conditions was investigated. The physiochemical properties of synthesized materials were systematically characterized by X-ray diffraction, N2-sorption, high-resolution transmission electron microscopy, and H2-temperature programmed reduction. A series of temperature programmed oxidation experiments was carried out to investigate the effect of feed gas composition on activity of the catalyst, and TGA-MS experiments were done to calculate the kinetic energy for each system. Mesoporous manganese oxides were found to be effective for complete oxidation of diesel soot under exhaust gas temperatures, and activities of all the manganese oxides were increased in the presence of NO2 in the feed gas. Meso-ϵ-MnO2 possesses the highest performance, exhibiting the lowest Ti and Tm (230 °C and 305 °C), the narrowest temperature range (75 °C), and the lowest Ea (298 kJ/mol).

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