Caixia Wu

Theoretical investigation of armchair silicene nanoribbons with application in stretchable electronics

The electronic and transport properties of a series of 11-ASiNRs (armchair silicene nanoribbons) at different torsion angles were studied by using density functional theory combined with nonequilibrium Greens function method. Several key factors determining the transport properties, such as the electron transmission coefficient and band structure, have been discussed. The interesting results suggest that the transport properties of ASiNRs are insensitive to the torsional silicene nanoribbon configuration in the scattering region. With the increase of the torsion angle, the transmission coefficient is still well maintained within the limits of the torsion angle. Although the torsion angle is increased to 120°, the current dropped by just 22% compared to the initial 11-ASiNRs at a torsion angle of 0°. Furthermore, all the configurations of 11-ASiNRs in this study behave as conventional conductors with nearly linear current–voltage dependence. On the basis of these distinctive transport properties with metabolic structure, ASiNRs present potential promising applications in silicon-based electronic nanodevices.

Theoretical studies on the chiral polyoxoanions [P2Mo18O62]6− and [PMo9O31(OH2)3]3− with histidine: chiral inversion and chiral induction

Herein, the electronic structures and electronic circular dichroism (ECD) spectra of the chiral Wells–Dawson (W–D) polyoxoanion [(L,D-C6H10N3O2)P2Mo18O62]5− (1a/1b) and chiral polyoxoanion [(L,D-C6H10N3O2)PMo9O31(OH2)3]2− (2a/2b) are investigated using density functional theory (DFT) and time-dependent DFT (TDDFT) calculations. Compared to the fully oxidized [P2Mo18O62]6− structure, the Mo–Ob bond lengths in the one-electron reduced state, [P2Mo18O62]7−, tends to be average. It is reasonable that organic ligands can transfer electrons to POMs and affect their chirality. The energy difference between the chiral L-[P2Mo18O62]6− with D3 symmetry and ideal [P2Mo18O62]6− with D3h symmetry is 5.88 kcal mol−1, which suggests that chirality inversion may occur from the L-isomer to the D-isomer through the ideal [P2Mo18O62]6− by crossing a small energy barrier. Meanwhile, the interaction energy between the L-isomer and L-histidine ligand is larger than that of L-isomer and D-histidine, which indicates that L,D-[P2Mo18O62]6− is induced and further separated by the chiral histidine. The origins of the chiral polyoxoanion are mainly ascribed to charge-transfer (CT) transitions from the O atoms to Mo atoms or organic ligands to Mo atoms. These results confirm that organic cations have an induced effect on chiral POMs.

Theoretical studies on lindqvist polyoxometalates [M6O19]n−(M = Mo, W, n=2; M = V, Nb, Ta, n=8) and derivatives: Electronic structures, stability and bonding

The geometrical and electronic structures of [M6O19]n− (M = Mo, W, n=2; M = V, Nb, Ta, n=8) and their derivatives were investigated by using density functional theory methods. The results indicate that the geometrical structure of [V6O19]8− is not different from other Lindqvist-type anions. The energy gap between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) (HOMO−LUMO energy gap) of [V6O19]8− is smaller than those of same charge anions, [Nb6O19]8− and [Ta6O19]8−. In addition, the charge density ρCD of [V6O19]8− is larger when compared with those of other studied clusters. The investigation on the derivatives shows that the valence of V atom (V4+ or V5+) and the methoxy ligand influence the HOMO−LUMO energy gap and the charge density ρCD of the studied clusters.

Simple and efficient polyoxomolybdate-mediated synthesis of novel graphene and metal nanohybrids for versatile applications

The application of nanohybrids based on polyoxomolybdates, reduced graphene oxide (rGO) and/or metal nanoparticles (NPs) high-performance electrode materials in electrocatalysis and energy storage devices is promising but still limited due to the complexity and the cost of the synthesis. Here we introduce a simple polyoxomolybdate, [MoV4O8(OH)2(H2O)2(C4O4)2]2- (MoS), as reducing and stabilizing agent for the facile and one-pot syntheses of large quantity of highly stable MoS/rGO and MoS/Au NPs nanohybrids in aqueous solution without any catalyst or toxic co-solvent. They were characterized by various physical techniques and electrochemistry which confirm strong interaction between MoS and rGO sheets. We also used DFT calculations to investigate the affinity between MoS or its neutral form with graphene. The adsorption energy for the most stable configuration is -1.97 eV, indicating a strong adsorption process of MoS, which can also be confirmed by the distance (3.04 Å) and the charge transfer (0.86 e) between MoS and graphene. These observations are also consistent with the electrochemical results which underscore the excellent redox properties and high stability of MoS/rGO. Importantly, the MoS/rGO nanohybrids are excellent noble metal-free electrocatalysts for hydrogen peroxide reduction with high sensitivity, large detection range and low detection limit. Finally, the preliminary tests reveal that the electrode materials based on MoS/rGO and a low-cost carbon cloth (CC) composite MoS/rGO/CC may have a potential for an application in energy storage as performant and flexible supercapacitor, showing specific capacitance as high as 870 F g-1 at 10 mV s-1 and excellent stability after 5000 cycles.