One-pot synthesis of ferromagnetic Fe2.25W0.75O4 nanoparticles as a magnetically recyclable photocatalyst

ZnO nanostructures, including nanowires, nanorods, and nanoneedles, have been deposited on GaAs substrates by the two-step chemical bath synthesis. It was demonstrated that the O₂-plasma treatment of GaAs substrates prior to the sol?Cgel deposition of seed layers was essential to conformally grow the nanostructures instead of 2D ZnO bunches and grains on the seed layers. Via adjusting the growth time and concentration of precursors, nanostructures with different average diameter (26?C225?nm), length (0.98?C2.29???m), and density (1.9?C15.3?×?10⁹?cm^?2) can be obtained. To the best of our knowledge, this is the first demonstration of ZnO nanostructure arrays grown on GaAs substrates by the two-step chemical bath synthesis. As an anti-reflection layer on GaAs-based solar cells, the array of ZnO nanoneedles with an average diameter of 125?nm, a moderate length of 2.29???m, and the distribution density of 9.8?×?10⁹ cm^?2 has increased the power conversion efficiency from 7.3 to 12.2?%, corresponding to a 67?% improvement.     

Using Saganc loop of optical-injected semiconductor laser scheme for stable and continuous CW wavelength-tuning

We propose and experimentally investigate a stable and continuous wavelength-tuning laser structure by using self-injected Fabry-Perot laser diode (FP-LD) with Saganc loop scheme. In this proposed laser scheme, the lasing wavelength can be tuned in the range of 1526.20 to 1549.75 nm with tuning-step of 1.30 nm in single-longitudinal-mode (SLM) output. Here, the maximum and minimum output powers are −7.4 and −17.0 dBm, and their corresponding side-mode suppression ratios are 52.0 and 52.8 dB/0.05 nm, respectively. Moreover, to achieve the continuous wavelength tuning, we can also adjust the temperature of FP-LD for wavelength shifting.     

Infrared spectroscopy of 17O- and 18O-enriched carbon dioxide in the 1700–8300 cm−1 wavenumber region

The assignment of the high resolution Fourier transform spectra of carbon dioxide enriched in ¹⁷O and ¹⁸O which were recorded in LADIR (Paris, France) with the Bruker IFS 125-HR between 1800 and 9000 cm^?1 and in USTC (Hefei, China) with the Bruker IFS 120-HR between 1700 and 9000 cm^?1 was performed. In total 239 bands of 12 isotopologues: ¹⁶O¹²C¹⁶O, ¹⁶O¹²C¹⁸O, ¹⁶O¹³C¹⁶O, ¹⁶O¹³C¹⁸O, ¹⁸O¹²C¹⁸O, ¹⁸O¹³C¹⁸O, ¹⁶O¹²C¹⁷O, ¹⁷O¹²C¹⁷O, ¹⁷O¹²C¹⁸O, ¹⁶O¹³C¹⁷O, ¹⁷O¹³C¹⁷O and ¹⁷O¹³C¹⁸O were observed. Among them, 99 bands were observed for the first time. The majority of new observed bands belong to ¹⁷OCO isotopologues. The positions of 23,003 lines were determined with the experimental uncertainty on the level of 0.001 cm^?1. The spectroscopic constants were fitted to the observed line positions for all observed bands.     

半导体激光器的自混合散斑干涉测量流体速度

提出了一种简便的激光自混合散斑干涉测量流体速度的方法。根据散斑和法布里-珀罗腔的理论,提出了半导体激光器的自混合散斑干涉模型。研究了流体运动时在半导体激光器内产生的自混合散斑干涉效应(SMPI),给出了激光器输出增益的变化及其概率密度分布。得到了激光自混合散斑干涉平均频率与流体速度之间的关系。模拟计算和实验结果验证了这个关系。利用散斑干涉的平均频率与流体速度的关系测量了高分子材料溶液的速度,并在溶液浓度和背景光变化时,对流体速度进行了测量、比较和分析。实验表明。在溶液浓度不太低时,测量误差小于8％。     

Liquid–Liquid Transition and Detrapping of Trapped Carriers of P(MMA/BA) Copolymers by Thermally Stimulated Depolarization Current

Poly (methyl methacrylate/butyl acrylate) [P(MMA/BA)] copolymers (M _η～2×10⁵) with different mass percentages of PMMA (100/0, 90/10, 81/19, and 75/25), were synthesized by the method of solution polymerization. In addition to the normal α and ρ peak, a third τ peak is observed in thermally stimulated depolarization current (TSDC) spectra of the copolymers in the high temperature region. The α peak‐corresponds to the glass transition, the ρ peak originates from the detrapping of trapped carriers in the bulk amorphous structure related with flexible side groups, and the τ peak can be attributed to the charge detrapping related to the liquid–liquid transition of the copolymers. The three peaks all move to lower temperature with an increase of the BA component, indicating that the flexible side groups of butyl acrylate not only have an effect of plasticization on the glass transition and liquid–liquid transition, but also make the trap depth shallower and the detrapping process easier for the ρ and τ peaks. The experimental results confirm that TSDC analysis is very sensitive for investigating the liquid–liquid transition of polymers. The liquid–liquid transition temperature (T _LL) of the copolymers follows a type of the Fox equation. Fitting the results gives a T _LL of 102°C for polybutyl acrylate.     

Low temperature growth and dimension- dependent photoluminescence efficiency of semiconductor nanowires

Low temperature growth and dimension dependent photoluminescence (PL) efficiency of semiconductor nanowires were investigated with CdS as a model system. The CdS nanowires were prepared with a simple, low temperature metal-organic chemical vapor deposition (MOCVD) process via the vapor–liquid–solid (VLS) mechanism. The low growth temperature of 360 °C was made possible with a newly developed single-source precursor of CdS and by using sputtered Au as the catalyst for the VLS growth. The length and diameter of the nanowires were adjusted by reaction time and sputtering conditions of Au, respectively. Nanowires of up to several μm in length and 20 to 200 nm in diameter were obtained. The PL quantum yield of the nanowires was found to decrease with increasing wire length, but to increase with decreasing wire diameter. This dimension-dependent PL efficiency of one-dimensional nanostructure, unlikely resulting from the quantum size confinement effect, appears to be a new observation that carries application significance. PACS 74.25.Gz; 78.55.Et; 78.67.Lt     

Femtosecond laser ablation of Au film around single pulse threshold

Ablation process of 1-kHz femtosecond lasers (pulse duration of 148 fs, wavelength of 775 nm) of Au film on silica substrates is studied. The thresholds for single and multi pulses can be obtained directly from the relation between the squared diameter D2 of the ablated craters and the laser fluence φo. From the plot of the accumulated laser fluence Nφth(N) and the number of laser pulses N, incubation coefficient of Au film is obtained to be 0.765. Some experimental data obtained around the single pulse threshold are in good agreement with the theoretical calculation.     

Study of three rotating radio transients with FAST

Rotating radio transients(RRATs) are peculiar astronomical objects whose emission mechanism remains under investigation.In this paper, we present observations of three RRATs, J1538+2345, J1854+0306 and J1913+1330, carried out with the Fivehundred-meter Aperture Spherical radio Telescope(FAST). Specifically, we analyze the mean pulse profiles and temporal flux density evolutions of the RRATs. Owing to the high sensitivity of FAST, the derived burst rates of the three RRATs are higher than those in previous reports. RRAT J1854+0306 exhibited a time-dynamic mean pulse profile, whereas RRAT J1913+1330 showed distinct radiation and nulling segments on its pulse intensity trains. The mean pulse profile variation with frequency is also studied for RRAT J1538+2345 and RRAT J1913+1330, and the profiles at different frequencies could be well fitted with a cone-core model and a conal-beam model, respectively.     

Field Patterns of the TE Modes in Ridge-Trough Waveguide

A single-ridge waveguide with a symmetrical longitudinal trough, designated as a ridge-trough waveguide has been used as a transition in a V-band (50-75 GHz) wafer probe recently. In this paper, the field patterns for the dominant TE mode and the first higher TE mode in ridge-trough waveguide with different configurations are presented by finite element method. The field patterns in this paper have important values for us to understand the transmission characteristics of ridge-trough waveguide, and will be of practical significance in designing ridge-trough waveguide components in microwave and millimeter wave engineering.