Stability and control of radial deployment of electric solar wind sail

Nonlinear Dynamics - The paper studies the stability and control of radial deployment of an electric solar wind sail with the consideration of high-order modes of elastic tethers. The electric...     

Synthesis of thiazolidin-4-ones via [3+2] cycloaddition of in situ generated aza-oxyallylic cations with isothiocyanates

A highly efficient one-pot synthesis of thiazolidin-4-ones via [3+2] cycloaddition of aza-oxyallylic cations with isothiocyanates is developed. The aza-oxyallyic cations were generated in situ in the present of a base. This cycloaddition reaction allows the rapid access to a variety of thiazolidin-4-one derivatives in mild conditions, good yield, and excellent functional group compatibility.     

SnS Nanosheets for 105th Harmonic Soliton Molecule Generation

As a member of the 2D group IV monochalcogenides (MX; M = Sn, Ge; X = S, Se), SnS has attracted great interest due to its outstanding optical, electrical, and optoelectronic properties. Especially, SnS nanosheets material have a large absorption coefficient and high photoelectric conversion efficiency, it can be potentially used in optical modulators, saturable absorbers, solar cells, supercapacitors, and other optical devices. However, the nonlinear optical properties of SnS nanosheets and their applications in ultrafast photonics are seldom studied. In this paper, the nonlinear optical properties of SnS nanosheets have been characterized through a dual‐balance detection system, whose modulation depth is 5.8%. More importantly, 105th harmonic soliton molecule based on SnS saturable absorbers has been realized for the first time to the authors’ knowledge. A compact mode‐locked fiber laser with a pulse duration of 1.02 ps and a repetition rate of 459 MHz is realized near 1.5 µm. It is demonstrated that SnS nanosheets have outstanding nonlinear properties and play an extremely important role in the field of ultrafast photonics.     

The photocatalytic mechanism of BiOI with oxygen vacancy and iodine self-doping

The photocatalytic mechanism of BiOI with an oxygen vacancy and iodine self-doping is investigated by studying their structural, electronic and optical properties. The results of the first-principle calculations indicate that the utilization of the visible light region is broadened, and thus the photocatalytic performance is improved, via introducing an oxygen vacancy or I dopant. Among them, I-Bi doped BiOI shows the best photocatalytic performance, and it is also the preferred one of the three structures due to its better stability. The occurrence of I-Bi or I-I interactions in the original double iodine layer along with the introduction of I dopant leads to a planar localization of the photocatalytic mechanism. Then it is expected that the photo-generated carriers will transfer to the catalyst surface more easily; the photocatalytic activity of BiOI relies on the planar localization to a great degree.     

Continuum background reduction in orthogonal-acceleration time-of-flight mass spectrometry with continuous ion sources

The continuum ion background in an inductively coupled plasma time-of-flight mass spectrometer (TOFMS) has been reduced by 2 orders of magnitude by using energy discrimination (ED). A potential barrier placed in front of the ion detector effectively discriminates between higher-energy signal ions and the lower-energy background ions. The signal-to-noise ratio was increased tenfold and detection limits of 0.4–4.2 ppt were achieved for 11 elements ranging from Li to U. The resolving power was observed to degrade from 1520 to 1230 with the addition of the potential barrier. The residual background count rate was found to be limited by neutrals formed after exiting the ion reflectron via charge exchange with the background gas. This ED method can be employed to effectively reduce the continuum ion background in any TOFMS that uses orthogonal acceleration with a continuous ion source.     

Controllable synthesis of PbI2 nanocrystals via a surfactant-assisted hydrothermal route

PbI₂ nanostructures were successfully prepared via a surfactant-assisted hydrothermal method at a low temperature of 100°C for 8 h. Polyvinyl pyrrolidone (PVP) and cetyltrimethylammonium bromide (CTAB) were used as surfactants. The resulting products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–vis spectroscopy. It was found that the formation of PbI₂ nanostructures with various morphologies could be well controlled by the adjustment of the pH of the synthesis solution, selection of suitable surfactant, and the amount of the desired surfactant. UV–vis absorption results showed an apparent shift of the band gap energy of the PbI₂ nanoparticles relative to that of the bulk.     

XPS and SRUPS study of oxygen adsorption on Cd0.9Zn0.1Te (1 1 1)A surface

Synchrotron radiation ultraviolet photoemission spectroscopy (SRUPS) and X-ray photoelectron spectroscopy (XPS) have been applied to investigate oxygen adsorption on a cadmium zinc telluride (CZT) (1 1 1)A surface. The surface chemical composition and the surface oxidation process were monitored by recording the Te 3d, O 1s, Zn 2p, Cd 4d core level peaks, and the Cd MNN Auger peak. The CZT (1 1 1)A surface was effectively oxidized by dosing oxygen directly. The typical surface state of the clean CZT (1 1 1)A surface was identified. After oxygen exposure, this surface state disappeared and a signal due to the formation of O–CZT appeared. In addition, the work function of CZT decreased with the increasing oxygen exposure.     

CdZnTe伽马射线探测器的能谱特性分析

CdZnTe(CZT)探测器目前在国内外天体物理研究中占有重要的地位。本文采用蒙特卡洛软件GEANT4模拟了CZT伽马射线探测器对伽马射线的能谱响应,研究了电子和空穴的输运特性、外加偏压、探测器厚度等因素对平面型探测器的能谱特性的影响规律。结果表明,在电子收集效率较高时,能量分辨率明显受迁移率寿命积比值((μτ)_e/(μτ)_h)的影响,比值越小,能量分辨率越好。增加工作电压可以提高载流子的收集效率和探测器的能量分辨率。在电子收集效率较高时,增大厚度可以弱化空穴信号贡献,提高能量分辨率。漂移程与晶体厚度之比(μτ)_eE/d可以用来估算平面型CZT探测器对低能射线的收集效率,并计算出其对应关系。