Recent Progress on 2D Group II‐VI Binary Chalcogenides ZnX and CdX (X = S, Se, Te): From a Theoretical Perspective

Effects of conjugated structure on electronic and transport properties in organic-inorganic hybrid superlattices Cd2Se2(C2H4N2)1/2

By inducingπ-conjugated organic molecule C₂H₄N₂in group II-VI based CdSe network structure materials, the band structures and carrier transport of organic-inorganic hybrid superlattices Cd₂Se₂(C₂H₄N₂)_1/2were investigated via first-principles calculations based on the density functional theory. With different stacking patterns, it is found that the carrier mobility can be modulated by 5-6 orders of magnitude. The physical mechanism of the high carrier mobility in the hybrid structures has been revealed, which means dipole organic layers realize electron delocalization via electrostatic potential difference and build-in electric field. Our calculations shown that the dipole organic layers originate from asymmetricπ-conjugated organic molecules and the charges movement between molecules, while symmetric organic molecules tend to electrostatic balance. And although the electronic transport properties were highly restrained by the flat bands of organic layers around Fermi energy in most structures, we found that the collective electrostatic effect can lead to very high electron mobility in AA1 and AA2 stacking systems, which might be attributed to the superposition of molecule electrostatic potential along with electrons transfer between molecules. Furthermore, it is also found that the anisotropy of electron mobility can be modulated via the difference directions of dipole layers.

Preparation of ZnS@N-doped-carbon composites via a ZnS-amine precursor vacuum pyrolysis route

ZnS/carbon nanocomposites have potential electrochemical applications due to their improved conductivity and more active sites through modification of the carbon materials. Herein, we report a facile method to synthesize the nanocomposites comprising ZnS nanoparticles and nitrogen-doped carbon (ZnS@NC). The inorganic–organic hybrid ZnS-amine material ZnS(ba) (ba = n-butylamine) is synthesized on a large scale by a reflux method, which effectively shortens the reaction time while maintaining the high yield compared with the solvothermal method. Then ZnS(ba) is used as precursor for obtaining ZnS@NC nanocomposites via a vacuum pyrolysis route, in which the content of carbon and nitrogen can be controlled by adjusting the pyrolysis temperature. Further, a series of ZnS-amine hybrid materials ZnS(ha), ZnS(en)_0.5 and ZnS(pda)_0.5 (ha = n-hexylamine; en = ethylenediamine; pda = 1,3-propanediamine) are synthesized and used as precursors for the preparation of ZnS@NC materials, indicating the universality of this method. Moreover, the as-synthesized ZnS@NC materials exhibit remarkable lithium storage performance with outstanding cycling stability, high-rate capability and remarkable pseudo-capacitance characteristics.

ZnS/N-doped-carbon nanocomposites exhibiting remarkable Li storage performance are facilely prepared through the temperature-controllable vacuum pyrolysis of various ZnS-amine precursors.