Boyu Wang,Yani Huo,Cheng Chen,Xiao-Ye Wang,Chuancheng Jia,Jinying Wang,Xuefeng Guo
Achieving dynamic control over stereostructures and electronic properties of rigid molecules remains a significant challenge due to the delicate balance between stability and flexibility. Here, the construction of butterfly-shaped molecular junctions stabilized by moderate-strength boron-nitrogen (B←N) coordination between boraacenes and pyridines is reported. By leveraging the pivot-like flexibility of B←N bonds, molecular conductance switching with on/off ratios exceeding 100 is achieved through force-driven dynamic transitions between distinct stacking conformations. Single-molecule electrical measurements combined with first-principle calculations identify distinct charge transport mechanisms—through-space and through-bond—associated with the butterfly-wing open and closed configurations. Furthermore, external factors like electric fields and substituent effects modulate π – π interactions and charge transport properties. The introduction of destructive quantum interference effects can be achieved by replacing molecular units. The findings demonstrate that B←N coordination serves as a dynamically tunable linkage, offering a pathway to design molecular platforms with multifunctional units, customized stereo-conformations, and quantum effects.
Graphene is a two-dimensional (2D) material with excellent physical properties, and its special charge transport characteristics promote extensive exploration based on graphene electronic devices. In order to determine the effect of the mesostructure on the electromagnetic transport properties of graphene, the temperature dependencies of the resistance and the magnetoresistance (MR) of reduced graphene oxide paper (rGOP) and reduced graphene oxide aerogel fiber (rGAF) were systematically measured. The conduction mechanism was systematically studied, and the graphene paper and aerogel fiber were in accordance with Mott’s 2D and 3D variable-range hopping (VRH) models, respectively. With the decrease of temperature, the transition from small-negative MR to large-positive MR was observed, the influences of wave function shrinkage and quantum interference effects on positive and negative MR were discussed in the framework of hopping conduction.
Layered cathode materials for lithium-ion batteries have been extensively investigated; however, comparatively scant attention has been paid to Mn-rich layered cathode materials. Herein, LiNi 0.5 Mn 0.5 O 2 cathode materials are doped to investigate the effect of doping elements on the electrochemical properties of Mn-rich layered cathodes. XRD (X-ray diffraction), XPS (X-ray photoelectron spectroscopy), and SQUID (superconducting quantum interference device) results reveal that Mo doping affects the electrochemical properties of the cathode materials by changing the valence state of transition metal ions. Due to the Mo 6+ ions doping, a large proportion of Mn 3+ ions present in LiNi 0.5 Mn 0.5 O 2 were converted to Mn 4+ ions, which alleviated the Jahn-Teller effect and reduced the elongated Mn-O octahedra, thus increasing the Li layer spacing and facilitating Li + diffusion. Therefore, 1 % Mo-doped cathode exhibits a significantly improved Li-ion diffusion coefficient and superior rate performance with a specific discharge capacity of 103 mAh·g −1 at 5C. Meanwhile, the cathode materials significantly improve cycling performance due to the reduction in the amount of Mn 3+ . The current study provides guidelines for the modification of Mn-rich layered cathodes in the future.
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