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Onion-like carbon nanoparticles (CNOs) were synthesized via traditional pyrolysis of flaxseed oil. Oxidative treatment of as-synthesized carbon soot introduced numerous carboxyl (−COOH) functionalities, rendering them hydrophilic and stable in aqueous phase. The water-soluble onion-like carbon nanoparticles (wsCNOs) were 4–8 nm in size and exhibited stable green photoluminescence (PL) emission. CNOs were explored as efficient photocatalysts for the degradation of methylene blue (MB) as model organic pollutant dye under visible light irradiation. The wsCNOs exhibited photocatalytic efficiency ∼9 times higher than CNOs for MB degradation. Enhanced photocatalytic efficiency of wsCNOs was attributed to their surface functionalities and nanostructure. The unique morphology (concentric nanographene shells) with considerable surface defects, increased the physisorption of MB on the wsCNOs surface and significantly enhanced the photocatalytic efficiency of wsCNOs. Furthermore, the wsCNOs enabled specific detection of Al­(III), even with interference from high concentrations of other metal ions, with a detection limit of 0.77 μM, which compares favorably to other reported fluorescent probe. Altogether, the wsCNOs showed a significantly enhanced photocatalytic activity and were used as highly selective fluorescent probes for Al­(III) ion detection, suggesting a potential use in environmental wastewater treatment.

Electrically conductive hydrogels (ECHs), an emerging class of biomaterials, have garnered tremendous attention due to their potential for a wide variety of biomedical applications, from tissue-engineered scaffolds to smart bioelectronics. Along with the development of new hydrogel systems, 3D printing of such ECHs is one of the most advanced approaches towards rapid fabrication of future biomedical implants and devices with versatile designs and tuneable functionalities. In this review, an overview of the state-of-the-art 3D printed ECHs comprising conductive polymers (polythiophene, polyaniline and polypyrrole) and/or conductive fillers (graphene, MXenes and liquid metals) is provided, with an insight into mechanisms of electrical conductivity and design considerations for tuneable physiochemical properties and biocompatibility. Recent advances in the formulation of 3D printable bioinks and their practical applications are discussed; current challenges and limitations of 3D printing of ECHs are identified; new 3D printing-based hybrid methods for selective deposition and fabrication of controlled nanostructures are highlighted; and finally, future directions are proposed.

A scalable method to produce high-quality graphene by shear-exfoliation of graphite is presented. High shear mixing of graphite in the Taylor vortex flow regime allows for the bulk production of few-layer graphene with low content of defects.

Carbon nanodots (CNDs) derived from a green precursor, kidney beans, was synthesized with high yield via a facile pyrolysis technique. The CND material was easily modified through simple oxidative treatment with nitric acid, leading to a high density “self-passivated” water soluble form (wsCNDs). The synthesized wsCNDs have been extensively characterized by using various microscopic and spectroscopic techniques and were crystalline in nature. The highly carboxylated wsCNDs possessed tunable-photoluminescence emission behavior throughout the visible region of the spectrum, demonstrating their application for multicolor cellular imaging of HeLa cells. The tunable-photoluminescence properties of “self-passivated” wsCNDs make them a promising candidate as a probe in biological cell-imaging applications.