High-bandwidth photomultiplication-type organic photodetectors with quantum dot interlayer

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Nanoscale Soft Wetting Observed in Co/Sapphire during Pulsed Laser Irradiation

Liquid drops on deformable soft substrates exhibit quite complicated wetting behavior as compared to those on rigid solid substrates. We report on a soft wetting behavior of Co nanoparticles (NPs) on a sapphire substrate during pulsed laser-induced dewetting (PLID). Co NPs produced by PLID wetted the sapphire substrate with a contact angle near 70°, which is in contrast to typical dewetting behavior of metal thin films exhibiting contact angles greater than 90°. In addition, a nanoscale γ-Al2O3 wetting ridge about 15 nm in size and a thin amorphous Al2O3 interlayer were observed around and beneath the Co NP, respectively. The observed soft wetting behavior strongly indicates that the sapphire substrate became soft and deformable during PLID. Moreover, the soft wetting was augmented under PLID in air due to the formation of a CoO shell, resulting in a smaller contact angle near 30°

Nanoscale Soft Wetting Observed in Co/Sapphire during Pulsed Laser Irradiation

Liquid drops on deformable soft substrates exhibit quite complicated wetting behavior as compared to those on rigid solid substrates. We report on a soft wetting behavior of Co nanoparticles (NPs) on a sapphire substrate during pulsed laser-induced dewetting (PLID). Co NPs produced by PLID wetted the sapphire substrate with a contact angle near 70°, which is in contrast to typical dewetting behavior of metal thin films exhibiting contact angles greater than 90°. In addition, a nanoscale γ-Al2O3 wetting ridge about 15 nm in size and a thin amorphous Al2O3 interlayer were observed around and beneath the Co NP, respectively. The observed soft wetting behavior strongly indicates that the sapphire substrate became soft and deformable during PLID. Moreover, the soft wetting was augmented under PLID in air due to the formation of a CoO shell, resulting in a smaller contact angle near 30°

Determination of twisting angle of electrospun nanofiber bundle for continuous electrospinning system

Electrospinning continuously produced twisted nanofibers with a convergence coil and a rotating ring collector. The positively charged nozzle was used in the electrospinning process to deposit electrospun fibers of polyacrylonitrile onto a rotating ring collector. By withdrawing the electrospun fibers from the rotating ring collector, it was possible to spin the electrospun fibers yarn. In this study, theoretical approaches and numerical simulations were used to determine the twisting angle of the yarn. Using the equations developed in this study, we performed numerical simulations and compared the experimental results with the numerical simulation results. Mechanical properties of the fiber bundle were analyzed for twisting angle. It was confirmed the relationship among the winding drum, the ring collector, and flux of the fibers mass per time during electrospinning in the developed system. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 4552

Light–Matter Interactions in Cesium Lead Halide Perovskite Nanowire Lasers

Light–matter interactions in inorganic perovskite nanolasers are investigated using single-crystalline cesium lead halide (CsPbX₃, X = Cl, Br, and I) nanowires synthesized by the chemical vapor transport method. The perovskite nanowires exhibit a uniform growth direction, smooth surfaces, straight end facets, and homogeneous composition distributions. Lasing occurs in the perovskite nanowires at low thresholds (3 μJ/cm²) with high quality factors (<i>Q</i> = 1200–1400) under ambient atmospheric environments. The wavelengths of the nanowire lasers are tunable by controlling the stoichiometry of the halide, allowing the lasing of the inorganic perovskite nanowires from blue to red. The unusual spacing of the Fabry–Pérot modes suggests strong light–matter interactions in the reduced mode volume of the nanowires, while the polarization of the lasing indicates that the Fabry–Pérot modes belong to the same fundamental transverse mode. The dispersion curve of the exciton–polariton model suggests that the group refractive index of the polariton is significantly enhanced

Band-Gap States of AgIn₅S₈ and ZnS–AgIn₅S₈ Nanoparticles

The size-dependent band-gap energies of AgIn₅S₈ nanoparticles were directly measured for the first time using absorption and photoluminescence spectroscopies, which enabled an explanation of the evolution of the band-gap energy with the quantum-confinement effect in AgIn₅S₈ nanoparticles. The band-gap transition in steady-state and time-resolved photoluminescence spectra indicated that the stable structure of the AgIn₅S₈ nanoparticles was the cubic phase. The electronic band structures of the Ag–In–S nanoparticles were mainly related to the crystal structures, although the stoichiometry affected the band energies to some extent. Zn doping led to the formation of a ZnS–AgIn₅S₈ solid solution, as supported by the significant changes in the electronic band structures of the AgIn₅S₈ nanoparticles. Controlling the size and stoichiometry allowed the emission of the Ag–In–S nanoparticles to be tuned in the entire visible regime

Enhancement Mechanism of the Photoluminescence Quantum Yield in Highly Efficient ZnS–AgIn₅S₈ Quantum Dots with Core/Shell Structures

The optical properties of ZnS–AgIn₅S₈ quantum dots (QDs) with core/shell structures are examined to clarify the enhancement mechanism of the photoluminescence (PL) quantum yield (QY). Two types of QDs are synthesized by varying the concentration of zinc precursors, with alloyed-core (ZnS–AgIn₅S₈, ZAIS), inner-shell (ZnIn₂S₄, ZIS), and outer-shell (ZnS) structures, such as ZAIS/ZIS/ZnS and ZAIS/ZnS. Upon alloying/shelling processes from the preformed AgIn₅S₈ QDs, the evolution of the band gap energy indicates the formation of the solid solution of ZAIS. Due to the difference in the degree of alloying between ZAIS/ZIS/ZnS and ZAIS/ZnS QDs, the blue shift of PL, Stokes shift, and QY are different. The alloying/shelling processes improve the QY of the intrinsic defect states more effectively than the QY of the surface defect states, while the time-resolved studies suggest that the enhanced radiative rate of the intrinsic states is responsible for the improvement of the QY, in addition to the reduced nonradiative rate. In ZAIS/ZIS/ZnS QDs, the QY increases to 85%, which is attributed to the existence of the ZIS layer, as well as the reduced nonradiative states and the enhanced radiative states by the alloying/shelling processes. The ZIS layer mitigates the lattice strains and provides the appropriate levels of the electronic structures in the QDs, which further reduces the nonradiative rate and enhances the radiative rate, respectively, leading to the unprecedentedly high PL QY of ZAIS/ZIS/ZnS QDs