Xiangnan Chen

Hierarchical ZnO architectures consisting of nanorods and nanosheets prepared via a solution route for photovoltaic enhancement in dye-sensitized solar cells

ZnO nanorod–nanosheet (NR–NS) hierarchical architectures grown on fluorine-doped tin oxide (FTO) coated glass substrates were prepared via a two-step solution route, which involved the growth of the ZnO nanorods on the FTO substrate, followed by a secondary growth of the ZnO nanosheet on the as-grown backbone. The characterization showed that the nanosheets composed of very small nanoparticles underwent oriented attachment by closely covering the nanorods, resulting in an enhancement of the internal surface area. The ZnO nanostructure films were applied to dye-sensitized solar cells (DSSCs). The photovoltaic results demonstrated that the short circuit current density and the energy conversion efficiency of the NR–NS hierarchical architecture DSSCs were 4.806 mA cm−2 and 1.13%, respectively, which was almost two times higher than those of nanorod only arrays. The dye desorption result and diffused reflectance spectra indicated that the dye absorption amount and light scattering within the NR–NS hierarchical architecture photoanode were higher than those for the nanorod photoanode. The significant improvement was a consequence of the enhancement of dye loading and light scattering within the NR–NS hierarchical architecture photoanode.

Growth of Fe3O4 nanosheet arrays on graphene by a mussel-inspired polydopamine adhesive for remarkable enhancement in electromagnetic absorptions

Fe3O4 nanosheet arrays grown on both surfaces of graphene can be achieved by combining a mussel-inspired polydopamine adhesive and ethylene glycol-mediated process. Polydopamine is utilized not only as an efficient linker molecule that binds Fe3O4 nanosheets to the graphene, but also as a carbon source during heat treatment to yield the three dimensional (3D) graphene@carbon@Fe3O4 nanosheet arrays architecture. After the growth of Fe3O4 nanosheet arrays with accompanying reduction of graphene oxide into graphene, the 3D architecture exhibits outstanding microwave absorption properties. The simulated value of maximum reflection loss can reach −52.8 dB at 9.5 GHz with a sample thickness of 2.7 mm. The improved absorption capacity arises from the synergy of dielectric loss and magnetic loss, as well as the enhancement of multiple interfaces among graphene, carbon and Fe3O4 nanosheets. Furthermore, the synthesis strategy presented here can be expended as a facile approach to synthesizing related graphene-based 3D nanostructures for functional design and applications.

Synergistic Enhancement of Microwave Absorption Using Hybridized Polyaniline@helical CNTs with Dual Chirality

In this study, we designed a dual-chirality hierarchical structure to achieve a synergistically enhanced effect in microwave absorption via the hybridization of nanomaterials. Herein, polyaniline (PANi) nanorods with tunable chirality are grown on helical carbon nanotubes (HCNTs), a typical nanoscale chiral structure, through in situ polymerization. The experimental results show that the hierarchical hybrids (PANi@HCNTs) exhibit distinctly dual chirality and a significant enhancement in electromagnetic (EM) losses compared to those of either pure PANi or HCNTs. The maximum reflection loss of the as-prepared hybrids can reach -32.5 dB at 8.9 GHz. Further analysis demonstrates that combinations of chiral acid-doped PANi and coiled HCNTs with molecular and nanoscale chirality lead to synergistic effects resulting from the dual chirality. The so-called cross-polarization may result in additional interactions with induced EM waves in addition to multiscaled relaxations from functional groups and interfacial polarizations, which can benefit EM absorption.

Enhanced performance of core-shell structured polyaniline at helical carbon nanotube hybrids for ammonia gas sensor

A core-shell structured hybrid of polyaniline at helical carbon nanotubes was synthesized using in situ polymerization, which the helical carbon nanotubes were uniformly surrounded by a layer of polyaniline nanorods array. More interestingly, repeatable responses were experimentally observed that the sensitivity to ammonia gas of the as-prepared helical shaped core-shell hybrid displays an enhancement of more than two times compared to those of only polyaniline or helical carbon nanotubes sensors because of the peculiar structures with high surface area. This kind of hybrid comprising nanorod arrays of conductive polymers covering carbon nanotubes and related structures provide a potential in sensors of trace gas detection for environmental monitoring and safety forecasting.

Super-high thermal conductivity of polyamide-6/graphene-graphene oxide composites through in situ polymerization:

Graphene is often used to improve the thermal conductivity of polymers but usually with high amount. The key factor that limits the thermal conductivity is graphene agglomeration as well as the incompatible interface between graphene and polymer. Here, we report super-high thermal conductivity of polyamide-6 (PA6) composites achieved by adding small amounts of graphene oxide (GO)-stabilized graphene dispersions (graphene-GO). The introduction of GO not only acts as an effective dispersant for graphene due to the non-covalent π-stacking interactions but also participates in PA6 polymerization. Therefore, the issues associated with graphene dispersion in PA6 can be resolved and the interface adhesion enhanced by adding small amounts of graphene-GO. Furthermore, this approach reduces the tendency for decreased crystallinity. All these factors enhance the formation of heat conducting pathways among the graphene sheets. Thus, compared with graphene, graphene-GO enhances thermal conductivity at lower filler loading levels by enhancing graphene dispersion and interface adhesion.

Effective improvement in microwave absorption by uniform dispersion of nanodiamond in polyaniline through in-situ polymerization

Uniformly dispersed nanodiamond/polyaniline composite was synthesized by an in situ polymerization, in which the nanodiamond was non-gap combined with polyaniline. The hybrids displayed significant improvement in microwave absorption, which were due to additional and strong polarization originated from the HN-CO groups acting as asymmetric center. Besides, the individually dispersed nanodiamond and the special interface between polyaniline and nanodiamond brought out enhanced interfacial polarization loss. These results could help in understanding the nature of polarization loss, and might open path towards the design of microwave absorbing materials.