No abstract

High thermal resistance frequently occurring at both filler−matrix and filler−filler interfaces lays down paramount bottlenecks for thermal management materials (TMMs). Herein, pony-size silver (Ag, 2−8 nm) nanoparticles are first constructed on nanodiamonds (NDs) with the assistance of environmentfriendly polydopamine (PDA), which is rather different from larger Ag nanoparticles (AgNPs, 10−25 nm) simply deposited on NDs. Such ternary heterostructures impart low interfacial thermal resistance in cellulose nanofiber (CNF) composites and thereby allow high thermal conductivity but electric insulation. It is worth noting that the interfacial thermal resistance of CNF/Ag-PDA-ND (4.11 × 10 −7 m 2 K W −1 ) is exceptionally 1−2 orders of magnitude lower than those of CNF/Ag-ND (7.28 × 10 −6 m 2 K W −1 ) and CNF/ND (5.14 × 10 −5 m 2 K W −1 ) mainly due to the improved contact area between NDs assisted by PDA-Ag and even the bridging effect of AgNPs between NDs and CNFs. Of particular interest is our first establishment of an excellent heat interface (94.4% reduction in interfacial heat resistance) by introducing environmentfriendly PDA during the metallization process rather than the reducing agent. With the appearance of such ternary heterostructures, the in-plane thermal conductivity of CNF/Ag-PDA-ND composite papers is high up to 16.36 W m −1 K −1 with about 1202% enhancement, compared to that of pure CNF. Meanwhile, the flexible CNF/Ag-PDA-ND composite papers are also endowed with high strength and toughness. Therefore, interfacial engineering can be extended to diverse materials (e.g., metallic oxides, carbon, and polymers) and can open creative avenues for sustainable high-performance TMMs in advanced high-power electronics.

No abstract

A new CE method based on velocity gap (VG) theory has been developed for high-resolution chiral separations. In VG, two consecutive electric fields are adopted to drive analytes passing through two capillaries, which are linked together through a joint. The joint is immersed inside another buffer vial which has conductivity communication with the buffer inside the capillary. By adjusting the field strengths onto the two capillaries, it is possible to observe different velocities of an analyte when it passes through those two capillaries and there would be a net velocity change (NVC) for the same analyte. Different analytes may have different NVC which may be specifically meaningful for enantioseparations because enantiomers are usually hard to resolve. By taking advantage of this NVC, it is possible to enhance the resolution of a chiral separation if a proper voltage program is applied. The feasibility of using NVC to enhance chiral separation was demonstrated in the separations of three pairs of enantiomers: terbutaline, chlorpheniramine, and promethazine. All separations started with partial separation in a conventional CE and were significantly improved under the same experimental conditions. The results indicated that VG has the potential to be used to improve the resolving power of CE in chiral separations.

No abstract