Carbon quantum dots (CQDs) have potential applications in many fields such as light-emitting devices, photocatalysis, and bioimaging due to their unique photoluminescence (PL) properties and environmental benignness. Here, we report the synthesis of nitrogen-doped carbon quantum dots (NCQDs) from citric acid and m-phenylenediamine using a one-pot hydrothermal approach. The environment-dependent emission changes of NCQDs were extensively investigated in various solvents, in the solid state, and in physically assembled PMMA-PnBA-PMMA copolymer gels in 2-ethyl-hexanol. NCQDs display bright emissions in various solvents as well as in the solid state. These NCQDs exhibit multicolor PL emission across the visible region upon changing the environment (solutions and polymer matrices). NCQDs also exhibit excitation-dependent PL and solvatochromism, which have not been frequently investigated in CQDs. Most CQDs are nonemissive in the aggregated or solid state due to the aggregation-caused quenching (ACQ) effect, limiting their solid-state applications. However, NCQDs synthesized here display a strong solid-state emission centered at 568 nm attributed to the presence of surface functional groups that restrict the π-π interaction between the NCQDs and assist in overcoming the ACQ effect in the solid state. NCQD-containing gels display significant fluorescence enhancement in comparison to the NCQDs in 2-ethyl hexanol, likely because of the interaction between the polar PMMA blocks and NCQDs. The application of NCQDs-Gel as a solid/gel state fluorescent display has been presented. This research facilitates the development of large-scale, low-cost multicolor phosphor for the fabrication of optoelectronic devices, sensing, and bioimaging applications.

This review explores the tribological properties of biosourced lubricants (biolubricants) enhanced by graphene (Gr) and its derivatives and hybrids. Friction and wear at mechanical interfaces are the primary causes of energy loss and machinery degradation, necessitating effective lubrication strategies. Traditional lubricants derived from mineral oils present environmental challenges, leading to an increased interest in biolubricants derived from plant oils and animal fats. Biolubricants offer high biodegradability, renewability, and low toxicity, positioning them as ecofriendly alternatives. This work extensively reviews the role of Gr-based nanoadditives in enhancing the lubrication properties of biolubricants. Gr with its exceptional physicomechanical properties has shown promise in reducing friction and wear. The review covers various Gr derivatives, including Gr oxide (GO) and reduced Gr oxide (r-GO), and their performance as lubrication additives. The discussion extends to Gr hybrids with metals, polymers, and other 2D materials, highlighting their synergistic effects on the tribological performance. The mechanisms through which these additives enhance lubrication, such as the formation of protective films and improved interactions between lubricants and tribopairs, are examined. Emphasis is placed on the environmental benefits and potential performance improvements of Gr-based biolubricants. Finally, by analyzing current research and technological trends, the paper outlines future prospects for optimizing lubricant formulations with Gr-based nanoadditives, aiming for more sustainable and efficient tribological applications.

The development of new conjugated polymers with ‘aggregation-induced emission (AIE)’ characteristics has been of great interest in recent years to avoid the ‘aggregation-caused quenching (ACQ)’ effect and due to their potential applications in PLEDs, chemosensors and bio-imaging. In this work, we have developed a D–π-A-based AIE conjugated oligomer (oTPETP) derived from tetraphenylethylene (TPE) building blocks via a Wittig reaction. The electron-rich bithiophene moiety as a donor and TPE as an acceptor were alternately linked via π conjugation. This alternate D–A structure through π conjugation in the oligomer chain enables intramolecular charge transfer or twisted intramolecular charge transfer (ICT/TICT) interactions between the D and A moieties. Computational studies of a single repeating unit of the oligomer support that the transition is ICT/TICT. The structures of the synthesized compounds and oligomer were characterized by FT-IR, NMR and GPC techniques with good results. The obtained oligomer was readily soluble in common organic solvents such as chloroform, dichloromethane and tetrahydrofuran etc. The oligomer shows weak emission in solution after dissolving it in a solvent and a strong emission is observed in the aggregated state as a result of its ‘Aggregation-Induced Emission Enhancement (AIEE)’ characteristics. This is due to the restricted intramolecular rotation (RIR). The oTPETP oligomer exhibits an abnormal blue-shifted mechanoluminescent effect in contrast to the TPE derivatives, which show red-shifted emission. The causes of this transition in the oligomer have been investigated using PXRD and DSC techniques. In addition, oTPETP has been successfully tested in the sensing of picric acid through photoluminescence (PL) quenching.