Superior Rate Capability of Small Regenerated Graphite Particles Induced by Homogeneously Distributed Current Density Derived from Cracks and Intrinsic Defects.

As spent batteries can be considered as alternative raw sources of electrode materials; the development of regeneration techniques for spent graphite becomes key to realizing economic and environmental sustainability. Herein, the reutilization of small spent graphite particles is domonstrated due to their special structural characteristics, which may directly contribute to the improvement of lithiation kinetics and high-rate charging during long-term cycling. Such intrinsic defects and external cracked channels may be introduced by the aging of intrinsic bulk structure and exfoliation of surface structure. On account of these potential advantages, a carbonized polypyrrole layer on sieved small graphite particles is developed to obtain superior rate performance. The coated amorphous/graphitic layer could repair the exposed edge and basal plane, and significantly facilitate Li ion diffusion during fast charging. Moreover, the enhanced performance may favor the improved homogeneity of current density distribution during fast charging, which is confirmed by a porous electrode model. The regenerated graphite with a disorder/order coating layer could effectively regulate the Li+ transport channel, exhibiting a high specific capacity at high-rate charging (102.7 mAh g-1 at 4 C after 500 cycles) without severe Li plating. This work provides an opportunity to utilize spent graphite in fast-charging batteries.

A novel dental adhesive containing Ag/polydopamine-modified HA fillers with both antibacterial and mineralization properties.

OBJECTIVES: To evaluate the antibacterial and mineralization properties of a dental adhesive containing Ag/polydopamine-modified HA (HA, hydroxyapatite) fillers. METHODS: First, an HA-polydopamine-Ag-polydopamine (HA-PDA-Ag-PDA) filler was prepared and characterized using SEM, TEM, XPS, XRD and FTIR. Then, the HA-PDA-Ag-PDA filler was mixed into an adhesive at different mass fractions (0 wt%, 0.5 wt%, 1 wt%, 2 wt%) to prepare a functional adhesive. Antibacterial and mineralization tests were carried out, and the cytotoxicity of the functional adhesive against L929 fibroblasts was also examined. RESULTS: The SEM, TEM, XPS, XRD and FTIR characterizations confirmed the successful preparation of the HA-PDA-Ag filler. The 1 wt% and 2 wt% functional adhesives showed the strongest bacterial inhibition effect among all the samples (p < 0.05). Obvious apatite crystals were observed in the SEM micrograph of the surface of the functional adhesive sample after immersion in artificial saliva for predetermined times (1 d, 7 d, 14 d and 28 d). There was no significant difference between the experimental group and the control group in terms of cell proliferation activity (p > 0.05). CONCLUSIONS: The 1 wt% and 2 wt% functional adhesives demonstrated good antibacterial and mineralization properties, as well as good biocompatibility. CLINICAL SIGNIFICANCE: Functional adhesives containing Ag/polydopamine-modified HA fillers with antibacterial and mineralization capabilities might have excellent potential to enhance the stability and durability of hybrid layers and prolong the service life of dental restorations. Our study on bifunctional adhesives has paved the way for future clinical applications to increase restoration longevity.

Synthesis of an urushiol derivative and its use for hydrolysis resistance in dentin adhesive.

Hydrolysis resistance is essential to the durability of the dentin bonding interface. Urushiol is a natural monomer that has been used in different fields over thousands of years but has the disadvantage of a long drying time. In this study, we evaluated a novel photocurable derivative of urushiol as the main monomer for polymerization in dentin adhesive and its effect on hydrolysis resistance. The derivative was characterized by Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy. Compared with the Adper Single Bond 2, the experimentally synthesized adhesives had higher contact angles. In particular, the water sorption/solubility of the experimental samples were significantly lower than that of Adper Single Bond 2. The microtensile bond strengths of the test groups were higher than that of the control group, even after 5000 thermocycles. Cytotoxicity test results showed that adhesives based on the original derivative induced low toxicity to L929 cells. The results of this study may shift the focus of future research to natural monomers and even their derivatives which may perform well in dentistry.

Hydrolysis-resistant and stress-buffering bifunctional polyurethane adhesive for durable dental composite restoration.

A new elastic polyurethane (PU) adhesive was reported in this study to improve the stability and durability of the dental adhesion interface. A polyurethane oligomer was synthesized by the solution polymerization method, and a diluent and solvent were added to prepare PU adhesives. The water sorption, water solubility, contact angle, thermal stability, degree of conversion and mechanical properties of the PU adhesives were evaluated. Experimental applications for tooth restoration (microtensile bond strength and microleakage) were also performed, and cytotoxicity test was carried out. The water sorption and solubility of the PU adhesives were significantly lower than those of three commercial adhesives. The microtensile bond strength of the PU adhesives was improved after thermocycling test, and the extent of microleakage was diminished when compared with that of commercial adhesives. Biocompatibility testing demonstrated that the PU adhesive was non-toxic to L929 fibroblasts. This study shows the ability of PU adhesive to improve the stability and durability of the dental adhesion interface and may refocus the attention of scientists from rigid bonding to flexible bonding for dental adhesion, and it sheds light on a new strategy for the stable and durable bonding interface of dentine adhesives.

Enhancement performance of application mussel-biomimetic adhesive primer for dentin adhesives.

In this study, we evaluated bioinspired adhesive primers for durable adhesion between dentin and composite resins. N-3,4-Dihydroxyphenethyl methacrylamide (DMA) primer monomer (small bifunctional group molecules containing catechol and acrylic groups at opposite ends) was prepared to mimic the interaction between the catechol group and the mineral interface of marine mussels. The shear bonding strength, microleakage, degree of conversion, contact angle, and compatibility were tested. The shear bond strength was significantly improved, and microleakage was diminished after the application of the DMA primer. However, the degree of conversion was decreased. The wettability of the dentin was enhanced, and the DMA primer showed no negative influence on cell proliferation. The results of this study showed the possibility of using DMA primers in clinical practice. This may provide a new strategy for improving adhesion durability.