Graphitic C3N4 (g-C3N4), as an advanced metal free photocatalyst, is known to be poorly exfoliated and dispersed in water from its powder form which has a layered structure, the intrinsic plane structure is not destroyed, and this has largely limited its application. In this work, we report our progress on successful sonication exfoliation of g-C3N4 nanosheets in graphene oxide (GO) aqueous solution. By making use of the substrate character of GO, g-C3N4 nanosheets of unvaried intrinsic structure were exfoliated and anchored on the GO surface, resulting in a GO/g-C3N4 hybrid. Moreover, the photocurrent of the hybrid was largely reinforced at the optimal weight fraction of GO. As a result, the corresponding photocatalytic performance of the hybrid with optimized photocurrent character was largely improved.
In this paper we report the structural, electrical and optical properties of epitaxial Ba(Sb
x
Sn1−x
)O3 (x = 0–0.30) (BSSO) films grown on SrTiO3(0 0 1) substrates by the pulsed laser deposition method. The investigation reveals that the transport and optical characteristics of BSSO films depend very sensitively on the Sb-doping content. Temperature-dependent resistivity measurements show that at low Sb contents (x = 0.03, 0.07) the metal–semiconductor transition occurs at 150 K and 80 K, respectively, and the semiconductor behaviour appears in high doped (x = 0.15, 0.30) films. The transmittance decreases significantly from about 80% to nearly zero in the visible region and the optical band gap shifts from 3.48 to 4.0 eV with increasing Sb content in the films. The lowest room-temperature resistivity of 2.43 mΩ cm with carrier density and mobility of 1.65 × 1021 cm−3 and 1.75 cm2 V−1 s−1 was obtained in the films with doping at x = 0.07. By employing them as bottom electrodes we have fabricated transparent Pb(Zr0.52Ti0.48)O3 ferroelectric capacitors showing square polarization–electric field hysteresis loops, indicating that these perovskite-type BSSO films at low doping can be potentially used in transparent devices especially based on all-perovskite heterostructures.
Zinc oxide (ZnO) is considered as an ideal candidate for ultraviolet (UV) lasers due to its unique advantages of wide direct bandgap and large exciton binding energy. Recently, whispering-gallery mode (WGM) lasing has attracted considerable attention for its high quality factor and low lasing threshold. The corresponding investigations have very important significance not only for fundamental scientific research but also for the potential applications in short-wavelength optoelectronic devices. In this paper, progress in ZnO microlasers is reviewed systematically. The fabrication methods for ZnO WGM microcavities are introduced first. Then the characteristics of single-photon and multiphoton pumped WGM lasing are presented. The lasing mechanisms on excitonic, electron-hole plasma and exciton-polariton lasing are reviewed in detail. Finally, recent advances in ZnO-based microlaser devices such as heterojunction laser diodes are explored. The further research challenges and some strategies are also indicated for the promising applications.
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