TG-DTA, TEM, and IR were used to investigate the thermal decomposition behavior of poly(N-vinyl-2-pyrrolidone) (PVP). The TG-DTA results show that the thermal decomposition behavior of PVP on platinum (Pt) is quite different from that of pure PVP. For pure PVP, 95.25% is decomposed when the temperature is increased up to 500°C; while under the same experimental condition, PVP coated on the Pt nanoparticles is only 66.7% decomposed. This is further supported by IR measurement. TEM results exhibited that the partially decomposed PVP still plays a role in stabilizing Pt nanoparticles: after heating treatment at 500°C for half an hour, the platinum nanoparticles did not aggregate heavily.

Nanocellulose, extracted from the most abundant biomass material cellulose, has proved to be an environmentally friendly material with excellent mechanical performance owing to its unique nano-scaled structure, and has been used in a variety of applications as engineering and functional materials. The great biocompatibility and biodegradability, in particular, render nanocellulose promising in biomedical applications. In this review, the structure, treatment technology and properties of three different nanocellulose categories, i.e., nanofibrillated cellulose (NFC), nanocrystalline cellulose (NCC) and bacterial nanocellulose (BNC), are introduced and compared. The cytotoxicity, biocompatibility and frontier applications in biomedicine of the three nanocellulose categories were the focus and are detailed in each section. Future prospects concerning the cytotoxicity, applications and industrial production of nanocellulose are also discussed in the last section.

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In this work, we carefully designed and synthesized a series of novel polyelectrolyte-functionalized carbon dots (CDs-PEI-X) by a facile and reversible phase transfer method based on the protonation reaction and anion exchange process executed on the surface of polyethylenimine-grafted CDs (CDs-PEI), where X denotes the anionic moieties of polyelectrolyte shells including hexafluorophosphate (PF 6 − ), bis(trifluoromethane)sulfonimide (NTf 2 − ), oleate (OL − ), and bis(salicylato)borate (BScB − ), respectively. Attributed to the favorable compatibility of these anions and polyethylene glycol (PEG) molecules, the hydrophobic CDs-PEI-X displayed excellent dispersibility and long-term stability in PEG200 base oil. Subsequently, the tribological behaviors of CDs-PEI-X as the lubricant additives of PEG200 were systematically investigated. It was proved that the anionic moieties of the polyelectrolyte shells of CDs-PEI-X played a crucial role in regulating their tribological behaviors. Particularly, CDs-PEI-OL was confirmed as an optimal additive, exhibiting the best lubricity, outstanding load-bearing capacity, long service life, and remarkable operational stability under boundary lubrication regime. Based on the tribological evaluations and worn surface analyses, the lubrication mechanism of CDs-PEI-OL was mainly attributed to the formation of the organic−inorganic hybrid adsorption film, the protective tribofilm, and its nanolubrication functions as scrollable "ball-bearing", i.e., the synergistic lubrication effects of surface polyelectrolyte shells and carbon cores. This study provides a feasible and versatile strategy to rapidly and effectively tailor the surface chemistry of CDs and discloses the essential contribution of carbon cores and surface groups on the lubrication process, which facilitates the development of advanced CDs-based nanolubricant additives.

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The development of highly efficient thin-film nanocomposite (TFN) membranes with superior water permeability, maintained rejection performance, and excellent antifouling capacity is critical to meeting the ever-escalating demand for fresh water. Herein, carbon dots (CDs) grafted with hyperbranched zwitterions, denoted as CDs-ZPEI0.6–10k, were first prepared by the hydrothermal treatment of citric acid in the presence of zwitterionic hyperbranched polyethylenimine (ZPEI0.6–10k) with different molecular weights (0.6, 1.8, and 10 kDa). Subsequently, the synthesized nanoparticles were introduced in membrane fabrication to form CDs-ZPEI0.6–10k-embedded TFN (TFN-CDs-ZPEI0.6–10k) membranes. The grafted shells of superhydrophilic ZPEI not only increased the chemical compatibility of CDs in the polyamide layer to suppress the formation of nonselective voids but also created a densely packed network for efficient water transportation and effective divalent salt rejection. The TFN-CDs-ZPEI10k membrane demonstrated a 2.8-fold enhancement in the permeate flux with an increased Na2SO4 rejection rate of 98.1% and improved antifouling properties than the pristine thin-film composite (TFC) membrane. This work provides an insight into the development of functionalized core–shell structured nanoparticles to effectively overcome the permeability-selectivity trade-off limitations and fouling problems in TFC membranes.

Carbon dots (CDs) have lately inspired extensive interest in tribology, especially in the field of friction modifiers. However, it remains an enormous challenge to obtain satisfactory compatibility between CDs and base oils without laborious and tedious chemical modifications. In this work, for the first time, we reported a scalable and sustainable synthesis of CDs from easily and cheaply available biomass via a one-pot solvothermal route, which used ethanol as the renewable reaction medium and H 2 O 2 as the clean oxidant. Typically, ginkgo leaves acting as the precursors were converted into CDs with an ultrahigh yield of 85.3%. As expected, the ginkgo leaf-derived CDs, abbreviated as GCDs, displayed excellent dispersibility, durable stability, and attractive fluorescence-emission behavior in PEG200. The as-prepared GCDs as additives for PEG200 exhibited remarkable lubricity, favorable loadcarrying ability, and long operating life under boundary lubrication. Particularly, the antiwear and friction-reducing performances of PEG200 were promoted by 70.5% and 34.7%, respectively, when only 0.20 wt % of GCDs was blended. Confirmed by the tribological investigations and surface detection of wear tracks, the essential lubrication mechanism of GCDs was chiefly associated with the generation of GCD-inserted tribochemical films with a thickness of about 80 nm and their nanolubrication functions, that is, the synergistic effects of surface organic moieties and carbonaceous cores. This study establishes a technically simple, feasible, versatile, cost-effective, and green methodology to produce CD-based friction modifiers toward PEG synthetic base oils for tribological applications.

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