Over the span of the past decade, carbon dots (CDs) synthesized from renewable organic resources (organic CDs) have gathered a considerable amount of attention for their photoluminescent properties. This review will focus on organic CDs synthesized using clean chemistry and conventional synthetic chemistry from organic sources and their fluorescence mechanisms, such as quantum confinement effect and surface/edge defects, before outlining their performance in electronic applications, including organic photovoltaic devices, organic light-emitting devices, biosensors, supercapacitors, and batteries. The various organic resources and methods of organic CDs synthesis are briefly covered. Many challenges remain before the adoption of CDs can become widespread; their characterization, structure, functionality, and exact photoluminescent mechanism all require additional research. This review aims to summarize the current research outcomes and highlight the area where further research is needed to fully use these materials.

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A lightweight acoustic composite foams with unique sound absorption feature is reported, that is, the foam acoustic composite demonstrates surprisingly stable sound absorption performance in a wide bandwidth of frequency. The unique acoustic properties are attributed to the highly exfoliated nanolayered biocarbon nucleation, derived from the pyrolytic pinus resinosa, with tailoring the foam structure and properties. Polystyrene (PS) composite foams with porous graphitic biocarbon are obtained by sequestering recycled supercritical carbon dioxide assisted with torsion extrusion technology. Unique design concept is validated and implemented in the torsion-induced extrusion process, with good mixing and thermal management, offering a suitable environment for the nucleation, uniform growth, and stability of the cells on the foam structures. The presence of porous graphitic nanolayered characteristics of biocarbon in the composition changes the sound insulation behavior from resonant absorber of pure PS closed cell foam to stable acoustic performance over a wide range in high frequency band (3.5-6.4 kHz), while preserving the closed cell structure. This allows the tailoring of cell structures and properties with varying renewable carbon content, so as to better adapt to a broadband sound absorption applications including absorbing panels, anechoic chamber with high accuracy and aircraft acoustic stealth technology.

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