Weiyou Yang

Growth of flexible N-doped SiC quasialigned nanoarrays and their field emission properties

In the present work, we report the growth of flexible SiC quasialigned nanoarrays with N dopants on carbon fabric substrate via the catalyst-assisted pyrolysis of a polymeric precursor. The resultant products are systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (EDS). The as-synthesized SiC nanowires are single-crystalline and grow along the [111] direction with a uniform spatial distribution of N dopants. The effect of the distance between the SiC array and the anode on the Field emission (FE) properties was investigated. FE measurements show that these N-doped SiC nanoarrays could be an excellent candidate for field emitters with very low turn-on fields of 1.90–2.65 V μm−1 and threshold fields of 2.53–3.51 V μm−1, respectively, which can be mainly attributed to the decrease of work function induced by the N dopants.

Precise control on the growth of SiC nanowires

We report the precisely controlled growth of SiC nanowires based upon the VLS process by tailoring the cooling rates, which could open a novel and general strategy for well-controlled growth of 1D semiconductor nanostructures.

Triangular prism-shaped p-type 6H-SiC nanowires

We report, for the first time, the growth of p-type 6H-SiC nanowires with a unique triangular prism shape via the pyrolysis of polymeric precursors. The resultant wires were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The triangular prism-shaped SiC nanowires are averagely sized at ∼700 nm in edge widths with lengths of up to tens of microns. The wires are single-crystalline with 1 at% Al dopants and grown along the direction of [102]. A mechanism based on a typical vapor–liquid–solid (VLS) process was discussed for the growth of the 6H-SiC wires. Intense visible photoluminescence was observed with two respective strong emission peaks centered at 2.4 and 3.1 eV, suggesting that the p-type 6H-SiC wires could be useful in the fabrication of optoelectronic nanodevices.

High-performance solar-blind ultraviolet photodetector based on electrospun TiO2-ZnTiO3 heterojunction nanowires

High-performance solar-blind UV (ultraviolet) photodetectors (PDs) based on low-dimension semiconducting nanostructures with high sensitivity, excellent cycle stability, and the ability to operate in harsh environments are critical for solar observations, space communication, UV astronomy, and missile tracking. In this study, TiO2-ZnTiO3 heterojunction nanowire-based PDs are successfully developed and used to detect solar-blind UV light. A photoconductive analysis indicates that the fabricated PDs are sensitive to UV illumination, with high sensitivity, good stability, and high reproducibility. Further analysis indicates that the rich existence of grain boundaries within the TiO2-ZnTiO3 nanowire can greatly decrease the dark current and recombination of the electron-hole pairs and thereby significantly increase the device’s photosensitivity, spectra responsivity (1.1 × 106), and external quantum efficiency (4.3 × 108 %). Moreover, the PDs exhibit good photodetective performance with fast photoresponse and recovery and excellent thermal stability at temperatures as high as 175 °C. According to these results, TiO2-ZnTiO3 heterojunction nanowires exhibit great potential for applications in high-performance optical electronics and PDs, particularly next-generation photodetectors with the ability to operate in harsh environments.

Large-scale synthesis of hydrophobic SiC/C nanocables with enhanced electrical properties

Inhibiting the easy oxidation nature of SiC nanostructure surface is a challenge for its application in nanodevices. Here, we have demonstrated the fabrication of C-sheathed SiC nanocables via a designed chemical vapour deposition method, in which the use of a steel-hoop-like sample support favours the growth of SiC/C nanocables with surface modification of C coatings. The obtained SiC/C nanocables are systematically characterized by scanning electron microscopy, x-ray diffraction, transmission electron microscopy and Raman spectroscopy. The electrical property measurements suggest that the surface modification of SiC nanostructures by C coatings can not only modulate the SiC surface property from hydrophilic to hydrophobic, but also significantly enhance their electrical properties.

Low-aspect ratio graphite hollow nanostructures

The synthesis of hollow nanostructures has attracted great attention in nanotechnology. As compared to the long hollow structures, the short counterparts could serve other compelling applications, and have become a hotspot in the field of nanomedicine. In the present work, a novel brand graphite-based nanostructure with a special cup-shaped feature was synthesized via the pyrolysis of a solid carbon source of polymethylmethacrylate (PMMA). These nanocups are typically characterized with open ends, tapered hollow cavities and slowly convergent roots, which are free standing on the graphene films with very low length/diameter aspect ratios as compared to conventional carbon nanotubes. The growth mechanism of these cups was proposed. It is promising that the present graphite nanocups could have potential applications in drug delivery.

Boosting the photoelectrochemical activities of all-inorganic perovskite SrTiO3 nanofibers by engineering homo/hetero junctions

In the current work, we reported the engineering of homo/hetero junctions for boosting the photoelectrochemical (PEC) behaviors of all-inorganic perovskite SrTiO3 (STO) nanofibers. The engineering of these junctions was accomplished via spin-coating and electrospinning, followed by atomic layer deposition (ALD). The introduced STO film leads to the formation of the STO/STO homojunction, which provided an extended contact area to enhance the electron–hole mobility across the interface. Meanwhile, ALD-deposited ZnO allowed for the construction of the STO/ZnO heterojunction, which could build up internal electric fields at the interface to hinder the recombination of electron–hole pairs, causing a totally enhanced photoelectrochemical (PEC) activity. As a proof of concept, at an applied bias of 1.23 V vs. RHE, the photocurrent density of STO nanofibers with engineered homo/hetero junctions was enhanced more than 600 times that of their pristine STO counterpart. At 0 V vs. Ag/AgCl, their photocurrent density was improved up to ∼61.3 μA cm−2 in comparison to 0.12 μA cm−2 of their pristine STO counterpart. Furthermore, their photocurrent stability was increased from 79.62% of their pristine STO counterpart to 98% at 0.1 V vs. Ag/AgCl.

Efficient Energy Transfer from 1,3,5-Tris( N-phenylbenzimidazol-2,yl) Benzene to Mn:CdS Quantum Dots

In this work, we reported the energy transfer between Mn doped CdS quantum dots (Mn:CdS QDs) with the core–shell structure of MnS/ZnS/CdS and 1,3,5-tris(N-phenylbenz-imidazol-2,yl) benzene (TPBI) in inorganic/organic blend films by steady-state and time-resolved photoluminescence (PL) spectroscopy. The changes in PL excitation intensity of the Mn:CdS QDs and PL lifetime of the TPBI clearly demonstrate an efficient energy transfer process from TPBI to QDs in the blend films. Further, it is found that the efficiency of Forster resonance energy transfer increases with the increasing of the thicknesses of CdS shell. These results highlight the potential of Mn doped QDs for fabricating high-performance QD lightemitting diodes.

Unconventional vapor–liquid–solid growth of SiO2 nanooctopuses

In this study, we demonstrate the unconventional vapor–liquid–solid (VLS) growth of amorphous SiO2 nanooctopuses. The SiO2 nanooctopuses were successfully synthesized by a simple water-assisted reaction on Si wafers. The obtained aggregates have been systematically characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy. A novel VLS model has been proposed for the growth of SiO2 nanooctopuses based on the experimental observations and characterizations. The amorphous SiO2 nanooctopuses emit stable violet-blue light, implying their potential applications in photoelectronic devices.