We searched for two-dimensional metastable boron sheets by using the particle swarm optimization algorithm combined with first-principles methods. We present several possible boron sheets composed of triangular and hexagonal motifs. The calculated total energy shows that these boron sheets are less stable than α-sheet and two recently predicted 1/8 and 2/15 B-layers. The energy difference between the new proposed struc-1/8 boron sheet and the known α-sheet, 1/8 and 2/15 B-layers, is less than 0.01 eV/atom. The calculated total density states of these boron sheets show that they are metallic. The multicenter chemical bonds of the relatively stable boron sheets are analyzed using the electron localization function. Because two-dimensional sheets are the building blocks of corresponding nanotubes and fullerenes, the proposed metastable boron sheets, not only with the most stable boron sheets, are expected to advance further investigations and understandings on boron nanotubes and fullerenes.

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2D halide semiconductors, a new family of 2D materials in addition to transition metal dichalcogenides, present ultralow dark current and high light conversion yield, which hold great potential in photoconductive detectors. Herein, a facile aqueous solution method is developed for the preparation of large-scale 2D lead dihalide nanosheets (PbF I ). High-performance UV photodetectors are successfully implemented based on 2D PbF I nanosheets. By modulating the components of halogens, the bandgap of PbF I nanosheets can be tuned to meet varied detection spectra. The photoresponse dependence on incident power density, wavelength, detection environment, and temperature are systematically studied to investigate their detection mechanism. For PbI photodetectors, they are dominantly driven by a photoconduction mechanism and show a fast response speed and a low noise current density. A high normalized detectivity of 1.5 × 10 Jones and an I /I ratio up to 10 are reached. On the other hand, PbFI photodetectors demonstrate a photogating mechanism mediated by trap states showing high responsivity. The novel 2D halide materials with wide bandgaps, superior detection performance, and facile synthesis process can enrich the Van der Waals solids family and hold great potential for a wide variety of applications in advanced optoelectronics.

Polyaniline (PANI) nanofibre films were fabricated on an indium–tin oxide (ITO) glass substrate through a controlled electropolymerization process. The PANI nanofibres grow vertically on an ITO substrate and are tapered, with average diameters of 20 and 15 nm for the base and top, respectively. The influence of the electrochemical conditions on the nanostructural formation of the PANI films was investigated and the optimized parameters of the electrodeposition were obtained. The optical and electrical properties of the PANI nanofibre electrodes were studied. Employing these PANI nanofibre films as the electrochromic electrode, we fabricated an electrochromic display (ECD) and a self-powered photoelectrochromic cell. The electrochromic and photoelectric properties of the ECD and photoelectrochromic cell are discussed in this paper. The PANI nanofibre based ECD and photoelectrochromic cells have a rapid response compared to conventional thin films due to the high aspect ratio of the nanostructured PANI film.

A flexible binder-free film composed of Bi2O3 nanoparticles embedded in carbon nanofibers as a sodium ion battery anode shows superior electrochemical properties due to its high active area and conducting framework.

A high-performance self-powered piezo-phototronic effect enhanced broadband photodetector based on a CdS nanorod array/rGO film heterojunction was fabricated facilely by spin-coating.

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