We report, for the first time, that the coherent growth of zinc sulfide (ZnS) on a colloidal indium phosphide (InP) quantum dot (QD) yields a InP/ZnS core/shell structure with a single lattice constant of 0.563 nm.
In this paper, we report on the creation of a virtual surface using a MEMS tactile display and its quantitative analysis. The display consists of 3 ' 3 large-displacement MEMS actuators with hydraulic amplification mechanisms. The MEMS tactile display that we developed can create virtual surfaces that generate various tactile feelings at human fingertips by controlling the displacement, vibration frequency, and period of actuation of the actuators. To quantitatively characterize the virtually created surfaces, we newly proposed a sample comparison method. We compared the tactile feelings with those of 18 samples, such as wood, urethane foam, and sandpaper. These samples were characterized with respect to roughness and hardness using a laser microscope and a compression testing machine. The subjects were requested to select one of these samples that had a tactile texture most similar to the one created by the tactile display. From the experimental results, we could deduce a relationship between the driving conditions of the actuators and the roughness and hardness of the selected samples, and thus, the virtually created surfaces. We experimentally found that the displacement of actuators had a strong correlation with roughness whereas the display created hard surfaces under the tested driving conditions.
The influence of polyethyleneimine (PEI) addition on the crystal size distribution (CSD) of Au was investigated. PEI is a water-soluble cationic polyelectrolyte acting as a reducer of AuCl 4 -and a stabilizer of precipitated Au nanocrystals. The CSD can be controlled by the PEI dosage, and an increase in PEI dosage decreased both the size and the size distribution width of the obtained Au nanocrystals. The idea of PEI-assisted reductive crystallization of Au may be helpful in the production of nanometals by using a simple batch crystallizer.
Despite bulk crystals of silicon (Si) being indirect bandgap semiconductors, their quantum dots (QDs) exhibit the superior photoluminescence (PL) properties including high quantum yield (PLQY > 50%) and spectral tunability in a broad wavelength range. Nevertheless, their low optical absorbance character inhibits the bright emission from the SiQDs for phosphor-type light emitting diodes (LEDs). In contrast, a strong electroluminescence is potentially given by serving SiQDs as an emissive layer of current-driven LEDs with (Si-QLEDs) because the charged carriers are supplied from electrodes unlike absorption of light. Herein, we report that the external quantum efficiency (EQE) of Si-QLED was enhanced up to 12.2% by postproduction effect which induced by continuously applied voltage at 5 V for 9 h. The active layer consisted of SiQDs with a diameter of 2.0 nm. Observation of the cross-section of the multilayer QLEDs device revealed that the interparticle distance between adjacent SiQDs in the emissive layer is reduced to 0.95 nm from 1.54 nm by “post-electric-annealing”. The shortened distance was effective in promoting charge injection into the emission layer, leading improvement of the EQE.
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