Search

Here, a WS2-based photodetector is fabricated and its detection range is extended to optical communication waveband by pressure. At ambient pressure, WS2 exhibits a fast photoelectric response speed (rising/decaying time: 35/49 μs) under 635 nm laser illumination. Upon compression, the responsiveness and external quantum efficiency increase by two orders of magnitude under NIR illumination with different wavelengths as the pressure increases up to 17.2 GPa. The pressure-induced band gap reduction is mainly ascribed to the enhanced S-S interlayer interaction, leading to significant enhancement in the WS2 photoresponsiveness. This study paves the way for designing high-performance broadband photodetectors through pressure modification. IMPACT STATEMENT Fast photoelectric response speed and extended detection range were achieved in the WS2-based photodetector via pressure modulation, which paves a new way for designing high-performance broadband photodetectors. [ABSTRACT FROM AUTHOR]

Pressure-induced amorphization (PIA) has drawn great attention since it was first observed in ice. This process depends closely on the crystal structure, the size, the morphology and the correlated pressurization environments, among which the morphology-tuned PIA remains an open question on the widely concerned mesoscale. In this work, we report the synthesis and high-pressure research of VO2(B) nanobelts. XRD and TEM were performed to investigate the amorphization process. The amorphization pressure in VO2(B) nanobelts(~30 GPa) is much higher than that in previous reported 2D VO2(B) nanosheets(~21 GPa), the mechanism is the disruption of connectivity at particular relatively weaker bonds in the (010) plane. These results suggest a morphology-tuned pressure-induced amorphization, which could promote the fundamental understanding of PIA. [ABSTRACT FROM AUTHOR]

Exploring the behavior of nanocrystals with varying shapes and sizes under high pressure is crucial to understanding the relationship between the morphology and properties of nanomaterials. In this study, we investigated the compression behaviors of WS2 nanotubes (NT-WS2) and fullerene-like nanoparticles (IF-WS2) by in situ high-pressure X-ray diffraction (XRD) and Raman spectroscopy. It was found that the bulk modulus of NT-WS2 is 81.7 GPa, which is approximately twice as large as that of IF-WS2 (46.3 GPa). This might be attributed to the fact that IF-WS2 with larger d-spacing along the c-axis and higher defect density are more compressible under isotropic pressure than NT-WS2. Thus, the slender NT-WS2 possess a more stable crystal structure than the IF-WS2. Our findings reveal that the effects of morphology and size play crucial roles in determining the high-pressure properties of WS2 nanoparticles, and provide significant insight into the relationship between structure and properties. [ABSTRACT FROM AUTHOR]

Abstract: We investigate the effects of synthetic parameters on the morphologies during hydrothermal process and the crystal structural transitions from intermediate titanate to final TiO2 products by transmission electron microscopy (TEM) and X-ray diffraction (XRD). It reveals that hydrothermal duration, temperature and reactant amount play important roles in controlling the morphologies and crystal structures of titanate products. Anatase nanotubes, anatase nanorafts, TiO2–B nanoribbons, and anatse/TiO2–B nanoribbons were synthesized by modifying these synthetic parameters. We found that the crystal structures of intermediate titanate products influence on the transitions from titanate to TiO2. Our results show that anatase and TiO2–B derive from the orthorhombic and monoclinic titanate, respectively. We suggest that the crystallographic relationships between the intermediate products (hydrogen titanate) and the final TiO2 products play important roles in heat treatment. [Copyright &y& Elsevier]

TiO2@C core–shell nanostructures with various crystal structures of TiO2-B, anatase, and rutile were successfully synthesized by a simple hydrothermal process and postheat treatments. As-synthesized precursor hydrogen titanate@carbonaceous nanoribbons transformed into TiO2-B@C nanoribbons at 400 °C and further transformed into anatase and rutile TiO2@C nanoribbons at 700 and 800 °C, respectively. The morphology of nanoribbons can be retained up to 800 °C. The transformation temperature (800 °C) from anatase to rutile phase is lower than that of TiO2 nanofibers without carbon layers and anatase TiO2@C nanoparticles. These results show that the carbon shell plays important roles in promoting the phase transition from anatase to rutile phase and protecting the nanoribbon-like morphology. The formation mechanism of the TiO2@C core–shell nanostructures with various crystal structures was discussed. [ABSTRACT FROM AUTHOR]

Abstract: Nanoporous anatase TiO2 rods and rutile TiO2 chrysanthemums were successfully synthesized via a simple ethylene glycol-mediated synthesis route. Their morphologies, phase compositions and components were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman and IR, respectively. The results show that a self-assembly growth takes place in the calcination under vacuum, which makes the titanium glycolate rods transform into rutile TiO2/C chrysanthemums rather than anatase TiO2 rods. It also indicates that the carbon plays an important role in the phase transition process which promotes the phase transition to rutile TiO2 at a lower temperature (400°C). It provides a new approach to prepare nanoporous rutile TiO2 nanomaterials under low temperature. [Copyright &y& Elsevier]

High-pressure Raman studies have been carried out onsingle crystallineC60(Fc)2nanosheets up to 25.4 GPa. Our resultsshow that the charge transfer between Fc (ferrocene) and C60increases in the low-pressure range. Above 5 GPa, C60molecules start to form a chainlike polymer structure, and thispolymerization is reversible upon decompression, in contrast to thatof pristine C60. The special layered structure of C60(Fc)2restricts the polymerization of C60molecules in some directions and explains the formation of the linearchainlike polymeric structure of the C60lattice underpressure. We suggest that the reversible polymerization is relatedto the increased charge transfer and the overridden steric repulsionof counterions. [ABSTRACT FROM AUTHOR]