Films of the quasi-2D perovskite based on 1-naphthylmethylamine (NMA) are promising as the gain medium for optically pumped lasing and future electrically pumped lasing because of its low lasing threshold and small electroluminescence efficiency rolloff. However, reasons for the low threshold and small efficiency rolloff are still unclear. Therefore, exciton dynamics are investigated in NMA-based quasi-2D perovskite films. It is found that quenching of bright excitons by other excitons or charge carriers is unlikely in NMA-based quasi-2D perovskite films, which is one reason for the low lasing threshold and small efficiency rolloff. Moreover, thermally stimulated current measurements reveal that the defect levels inside the band gap of the NMA-based quasi-2D perovskite are shallow, with a depth of ≈0.3 eV, causing a decrease in nonradiative exciton recombination through the defects. Therefore, population inversion can be easily achieved, leading to the low lasing threshold as well. For fabrication of NMA-based quasi-2D perovskite laser devices with even lower lasing thresholds, a circular-shaped optical resonator, and small-molecule-based defect passivation are used. Optically pumped lasing can be obtained from these devices, with a threshold of ≈1 µJ cm−2, which is one of the lowest values ever reported in any perovskite lasers. 相似文献
The sorption performance of a modified carbon black was explored with respect to arsenic removal following batch equilibrium technique. Modification was accomplished by refluxing the commercial carbon black with an acid mixture comprising HNO(3) and H(2)SO(4). Modification resulted in the substantial changes to the inherent properties like surface chemistry and morphology of the commercial carbon black to explore its potential as sorbent. The suspension pH as well as the point of zero charge (pH(pzc)) of the material was found to be highly acidic. The material showed excellent sorption performance for the removal of arsenic from a synthetic aqueous solution. It removed approximately 93% arsenic from a 50mg/L solution at equilibration time. The modified carbon black is capable of removing arsenic in a relatively broad pH range of 3-6, invariably in the acidic region. Both pseudo-first-order and second-order kinetics were applied to search for the best fitted kinetic model to the sorption results. The sorption process is best described by the pseudo-second-order kinetic. It has also been found that intra-particle diffusion is the rate-controlling step for the initial phases of the reaction. Modelling of the equilibrium data with Freundlich and Langmuir isotherms revealed that the correlation coefficient is more satisfactory with the Langmuir model although Freundlich model predicted a good sorption process. The sorption performance has been found to be strongly dependent on the solution pH with a maximum display at pH of 5.0. The temperature has a positive effect on sorption increasing the extent of removal with temperature up to the optimum temperature. The sorption process has been found to be spontaneous and endothermic in nature, and proceeds with the increase in randomness at the solid-solution interface. The spent sorbent was desorbed with various acidic and basic extracting solutions with KOH demonstrating the best result ( approximately 85% desorption). 相似文献
Natural mordenite (NM), natural clinoptilolite (NC), HDTMA-modified natural mordenite (SMNM) and HDTMA-modified natural clinoptilolite (SMNC) have been proposed for the removal of As(V) from aqueous solution (HDTMA=hexadecyltrimethylammonium bromide). Influence of time on arsenic sorption efficiency of different sorbents reveals that NM, NC, SMNM and SMNC require about 20, 10, 110 and 20h, respectively to reach at state of equilibrium. Pseudo-first-order model was applied to evaluate the As(V) sorption kinetics on SMNM and SMNC within the reaction time of 0.5h. The pseudo-first-order rate constants, k are 1.06 and 0.52h(-1) for 1 and 0.5g of SMNM, respectively. The observed k values 1.28 and 0.70h(-1) for 1 and 0.5g of SMNC, respectively are slightly high compared to SMNM. Surfactant surface coverage plays an important role and a significant increase in arsenate sorption capacity could be achieved as the HDTMA loading level on zeolite exceeds monolayer coverage. At a surfactant partial bilayer coverage, As(V) sorption capacity of 97.33 and 45.33mmolkg(-1) derived from Langmuir isotherm for SMNM and SMNC, respectively are significantly high compared to 17.33 and 9.33mmolkg(-1) corresponding to NM and NC. The As(V) uptake was also quantitatively evaluated using the Freundlich and Dubinin-Kaganer-Radushkevich (DKR) isotherm models. Both SMNM and SMNC removed arsenic effectively over the initial pH range 6-10. Desorption performance of SMNM and SMNC were 66.41% and 70.04%, respectively on 0.1M NaOH regeneration solution. 相似文献
In the present study, different combinations of multilayer sheets were prepared from 1 and 2 mm Mg AZ31 along with 0.25, 0.5, and 1 mm 304 L stainless steel. The texture and microstructure of the elongated samples (20 and 30 pct strain) were studied. It was found that the transversal stress plays an important role in both texture evolution and twinning in these composites. The obtained pole figures revealed an axial texture tilt with increasing steel layer volume fraction (Vf). It was found that this is a direct effect of transverse stress, which becomes more significant upon reducing Mg Vf. This extra stress component tilts the basal planes away from the original normal direction in monolithic samples. Moreover, our results indicate that with decreasing Mg Vf, twinning activity was increased in the 20 pct deformed samples but reduced in the samples with 30 pct elongation. It is known that at high strains where sufficient transverse stress is generated, the activity of prismatic slip is significantly enhanced, which promotes the motion of dislocations and reduces the necessity of twinning. With decreasing Mg Vf, stronger transversal stress is generated and Mg reaches the critical threshold of prismatic activity at lower strains.
We realize a nonvolatile and rewritable memory effect in an organic field-effect transistor (OFET) structure using polymethylmethacryrate (PMMA) dispersed with 10-methyl-9-phenylacridinium perchlorate (MPA+ClO4−) as a gate dielectric. Applying a voltage between a top source-drain electrode and a bottom gate electrode induces electrophoresis of two ions of MPA+ and ClO4− towards the corresponding electrodes in the memory devices. The drain currents of the memory devices markedly increase from 10− 9 A to 10− 2 A under no gate voltage condition due to the strong space charge polarization effect. Our memory devices have excellent electrical bistability and retention characteristics, i.e. the memory on/off ratio reached 107 and the drain current maintained 40% of the initial value after 104 s. 相似文献
A simple method was developed that uses microbubbles as templates to fabricate hollow microspheres covered with a biodegradable polymer. By stably keeping microbubbles with the diameter of about 2 µm inside a solvent droplet dissolving a biodegradable polymer and then slowly drying the solvent, hollow microspheres that had an average inner diameter of about 2 µm and a shell thickness of about 500 nm were obtained. This simple method was successfully used to easily fabricate uniform hollow microspheres covered with poly-lactic acid (PLA) by using uniform 2-µm-diameter bubbles as templates. 相似文献