基于多尺度变换的动态光散射粒径反演范围的自适应调整

 通过多尺度变换实现了反演范围的自适应调整,使其更接近真实范围。分别采用反演范围固定算法与自适应算法对200～600 nm单峰和200～900 nm双峰分布颗粒的模拟相关函数进行了反演,结果表明：自适应算法的结果更接近理论分布,抗干扰能力更强。相对于固定算法,单峰分布颗粒最多可缩小峰值误差4.73%,缩小峰宽误差185 nm。双峰分布颗粒在0～0.001噪声水平时,峰值误差分别小于11.33%,12.45%,峰宽误差分别小于35,160 nm,而固定算法在噪声水平大于0.000 1时,难以得到合理的反演结果。反演范围自适应调整方法能够有效优化粒径反演结果。     

Improvement of the Performance of an Acousto-Optical Q-Switched Nd:YAG 946 nm Laser Using a Convex–Plane Cavity

We improve the performance of an acousto-optical Q-switched Nd:YAG 946 nm laser using a convex–plane cavity. We obtain the highest output average power of 2.3 W with a pulse width of 15.3 ns in a 10 kHz 946 nm laser with a convex–plane cavity. The maximum peak power 15.0 kW is about three times higher than that in a plane–plane cavity. Also we investigate the output performances of the pulsed 946 nm laser with the convex–plane cavity at 20 and 50 kHz.     

Characterization challenges for a cellulose nanocrystal reference material: dispersion and particle size distributions

Cellulose nanocrystals (CNCs) have high aspect ratios, polydisperse size distributions, and a strong propensity for aggregation, all of which make them a challenging material for detailed size and morphology characterization. A CNC reference material produced by sulfuric acid hydrolysis of softwood pulp was characterized using a combination of dynamic light scattering (DLS), atomic force microscopy (AFM), transmission electron microscopy, and X-ray diffraction. As a starting point, a dispersion protocol using ultrasonication was developed to provide CNC suspensions with reproducible size distributions as assessed by DLS. Tests of various methods for AFM sample preparation demonstrated that spin coating on a positively charged substrate maximizes the number of individual particles for size analysis, while minimizing the presence of agglomerates. The effects of sample-to-sample variability, analyst bias, and sonication on size distributions were assessed by AFM. The latter experiment indicated that dispersion of agglomerates by sonication did not significantly change the size distribution of individual CNCs in suspension. Comparison with TEM data demonstrated that the two microscopy methods provide similar results for CNC length (mean ~?80 nm); however, the particle width as measured by TEM is approximately twice that of the CNC height (mean 3.5 nm) measured by AFM. The individual crystallite size measured by X-ray diffraction is intermediate between the two values, although closer to the AFM height, possibly indicating that laterally agglomerated CNCs contribute to the TEM width. Overall, this study provides detailed information that can be used to assess the factors that must be considered in measuring CNC size distributions, information that will be useful for benchmarking the performance of different industrially sourced materials.     

High-efficiency optical coupling to planar photodiode using metal reflector loaded waveguide grating coupler

For the realization of optoelectronic integrated circuits, it is required to incident light perpendicularly to a planar Si photodiode. We propose a high-efficient vertical optical coupler using an amorphous Si optical waveguide grating coupler with top reflector, which is transparent at 850 nm wavelength range. The optical waveguide (width of 300 nm $\times $ height of 100 nm) coupler is analyzed by using finite element method. The coupling efficiency of 80 % is calculated at the grating period of 380 nm, the duty ratio of 0.75 and the depth of 35–65 nm with top metal reflector.     

Based on Cu as framework constructed nanoporous CuO/Cu composites by a dealloy method for sodium-ion battery anode

Nanoporous CuO/Cu composites with a continuous channel structure were fabricated through a corroding Cu-Al alloy process. The width of the continuous channels was about 20~50 nm. Nanoporous structure could effectively sustain the volume expansion during the Na⁺ insertion/extraction process and shorten the Na⁺ diffusion length as well, which thus helps improve the Na⁺ storage performance. Moreover, the nanoporous structure can improve the contact area between the electrolyte and the electrode, leading to an increment in the number of Na⁺ insertion/extraction sites. When used as the anode for sodium-ion batteries, the CuO/Cu exhibited an initial capacity of ~?580 mAh g^?1, and the capacity is maintained at ~?200 mAh g^?1 after 200 cycles at a current density of 500 mA g^?1.     

Generation of web-like structures and nanoparticles by femtosecond laser ablation of silicon target in ambient air

Silicon nanoparticles were produced by femtosecond laser ablation in ambient air. Obtained samples were studied using dark-field optical microscopy, scanning electron microscopy and Raman-scattering spectroscopy. Two groups of structures can be found: (1) branched amorphous structures with a minimum element size of about 10 nm and incorporations of nanocrystals (0.6–6.6 nm from Raman scattering analysis); (2) larger crystal particles with smooth surface and a typical size of 50–200 nm that provide directional visible light scattering (at dark-field optical microscopy observations). An influence of environment on resulting phase composition of silicon nanoparticles was investigated by numerical evaluation of nanoparticle’s cooling rate. The calculation shows that cooling in ambient air ensures cooling rate sufficient for crystallization.     

Automatic dispersion,long-term stability of multi-walled carbon nanotubes in high concentration electrolytes

Nanoparticles have been known as the useful materials in working fluids for petroleum industry. But the stabilization of nano-scaled materials in water-based working fluids at high salinities is still a big challenge. In this study, we successfully prepared the anionic polymer/multi-walled carbon nanotubes (MWNTs) composites by covalently wrapping of MWNTs with poly (sodium 4-styrenesulfonate) (PSS) to improve the stability of MWNTs in high concentration electrolytes. The PSS/MWNTs composites can automatically disperse in salinity up to 15 wt% NaCl and API brines (8 wt% NaCl?+?2 wt% CaCl₂). Hydrodynamic diameters of composites were measured as a function of ionic strength and API brines by dynamic light scattering (DLS). By varying the concentration of brines, hydrodynamic diameter of PSS/MWNTs composites in brines fluctuated between 545?±?110 nm for 14 days and 673?±?171 nm for 30 days. Above results showed that PSS/MWNTs could be well stable in high salts solutions for a long period of time. After wrapped with PSS, the diameters of nanotubes changed from 30?~?40 to ~?430 nm, the thickness of wrapped polymer is about ~?400 nm by analysis of morphologies. The zeta potentials of PSS/MWNTs composites in various salinity of brines kept at approximately ??41?~???52 mV. Therefore, the well dispersion of PSS/MWNTs in high salinity is due to large negative charges of poly (sodium 4-styrenesulfonate), which provide enough electrostatic repulsion and steric repulsion to hinder compression of electric double layer caused by high concentration electrolytes.     

Synthesis,characterization, and effect of concentration variation on metal oxide nanostructures

Zinc oxide (ZnO) has been successfully synthesized by an anodization method, and it has been fabricated through anodization method with different concentration of zinc nitrate. The element composition, surface inspection, structural, and morphological features of the products are depend on the concentration of zinc nitrate. At lower concentration (0.01M), SEM image shows ZnO nanowires with average width of about 30 and 50 nm. With increase in the concentration of zinc nitrate from 0.01 to 0.05 M, the nanowires change into the nanosheets with average width of about 0.5 and 1.5 μm. For samples (0.1 M) exhibits nanodots, morphology was composed of hundreds of nanosheets with thickness is about 90 nm on average. When the concentration increases to 0.2 M, the nanodots trench became bigger with diameter about 1.2–2.0 μm. When the concentration of zinc nitrate is 0.3 M, the average diameter of nanodots is about 2–2.5 μm. The trench of nanosheets becomes thinner and shorter, but the number of nanosheets increases with diameter 20–50 nm. The formation of nanowires, nanodots, and nanosheets nanostructures is also believed to result from actions on concentration of zinc nitrate as an aquas medium. The EDX result shows the atomic percentage (at.%) of the oxygen increased when the concentration of zinc nitrate increased. The pattern of EDX indicates that the ZnO nanostructures are composed of Zn, O, and Al. They represent Al composition in the sample because the anode using the aluminum rod during experiment.     

Temperature dependence of optical properties of InAs quantum dots grown on GaAs(113)A and (115)A substrates

We have investigated the temperature dependence of photoluminescence (PL) peak position of InAs self-assembled quantum dots (QDs) grown on GaAs(11N)A (N = 3, 5) substrates. The interband transition energy is calculated by the resolution of the 3D Schrödinger equation for a parallelepipedic InAs QD, with a width of about 8 nm and a height around 3 nm. Experimentally, it was found that the PL spectra quenches at about 160 K. In addition, the full width at half maximum (FWHM) has an abnormal evolution with varying temperature. The latter effect maybe due to the carrier repopulation between QDs. The disorientation of the GaAs substrate and the low width of terraces which was presented in the high index surfaces have an important contribution in the PL spectra. Despite the non-realist chosen shape of QD and the simplest adopted model, theoretical and experimental results revealed a clear agreement.     

Multi-peak tunable CW orange laser based on single-pass sum frequency generation in step-chirped MgO: PPLN

We report an all-solid-state tunable CW orange laser based on single-pass sum-frequency generation in step-chirped PPMgO: LN crystal. Two laser sources, a tunable laser (1550 nm) and an ASE laser (1525–1650 nm) are used interchangeably as pumps and mixed with a fixed 975 nm signal laser. Up to 4.3 mW at 597 nm is generated corresponding to 0.87% nonlinear conversion efficiency and the beam quality (M²) value of about 2.5 is measured. The output wavelength can be tuned up to?~?5.66 nm by varying the position of focusing inside the crystal and by temperature, which makes possible the practical application of our device for wavelength selection and diversity in the orange spectral range.     

Small-angle neutron scattering study of the nano-sized features in an oxide dispersion-strengthened Fe12Cr alloy

Small-angle neutron scattering experiments, along with positron lifetime measurements and transmission electron microscopy observations, were performed on samples of an oxide dispersion-strengthened (ODS) Fe12Cr alloy and its non-ODS counterpart in order to characterize their nano-sized features. The nuclear and magnetic scattering data were analysed using the maximum entropy approach for obtaining the size distribution of the scattering centres in these materials. The positron annihilation results and the TEM information have made possible an interpretation of the volume distribution of the scattering centres having sizes below ~16 nm and their proper quantitative analyses. The smaller scattering centres in the ODS alloy exhibit distributions with modal values at ~6–7 and 12–14 nm. The peak at ~6–7 nm appears to be due to the overlapping of more than one type of scattering centres, while the one at ~12–14 nm can be exclusively attributed to the Y-rich centres. The quantitative analysis of the magnetic scattering data yields a volume fraction and number density of the Y-rich particles estimated in 0.70?±?0.03% and 0.77 × 10²² m^?3, respectively.     

Effect of particle size on the photochromic response of PWA/SiO2 nanocomposite

A series of photochromic phosphotungstic acid (PWA)/SiO₂ composites were synthesized using the sol-gel method. Depending on the feeding schedule of PWA during synthesis, the size of the formed PWA/SiO₂ particles varied considerably from as small as 1.2 nm to ca. 10 nm. With decreasing silica particle size, the total contact area/interaction between SiO₂ and PWA increases, as revealed by FT-IR and solid-state ²⁹Si-NMR analyses. Particularly, when the size of PWA/SiO₂ is ~1 nm, crystallization of PWA is inhibited, and PWA presents as amorphous molecular entities distributing uniformly in the SiO₂ host, which is in evidence in the XRD spectroscopy and HR-TEM imaging. In contrast, substantial crystallization of PWA takes place when PWA/SiO₂ particles are as large as 10 nm, in which case less amount of surface free Si-OH is available for PWA to make bonds with. Photochromism occurs activated by ultraviolet light irradiation. The rate of coloration/bleaching is found to depend strongly on the particle size of PWA/SiO₂; specifically, the rate increases twice when the particle size is reduced from 10 nm to 1.2 nm.     

矩形复合抛物面空间双向照明节能多功能反光杯设计

提出了充分利用灯具空间,具有单体双向多功能的光学设计新理念。结合LED与CPC,根据光学扩展量守恒,借助光路可逆原理与边缘光线原理,构造矩形复合抛物面。根据我国最新的《读写作业台灯性能要求》GB/T 9473-2017,以出光口半宽、台灯辐照高度、截短后杯体长度比为3个因素,设计正交实验,确定台灯矩形复合抛物面最适合参数为:出光口半宽50 mm、最大进光半角47.73°、截取杯体长度36 mm。在照明方面,该矩形复合抛物面能够满足关于A、AA级的照度和照度均匀度要求;在弱光聚集方面,其太阳能芯片位置的照度是不经聚光情况的1.25倍;在聚光模式下,太阳能芯片的光伏转化效率是非聚光模式下的1.66倍。这是对当前市面上非聚光模式收集太阳能方式的补充。     

Synthesis of Water Dispersible Fluorescent Carbon Nanocrystals from <Emphasis Type="Italic">Syzygium cumini</Emphasis> Fruits for the Detection of Fe<Superscript>3+</Superscript> Ion in Water and Biological Samples and Imaging of <Emphasis Type="Italic">Fusarium avenaceum</Emphasis> Cells

In this work, water dispersible fluorescent carbon nanocrystals (NCs) were synthesized by a simple, green and low cost hydrothermal method using Syzygium cumini (jamun) as a carbon source at 180 °C for 6 h. The average size of carbon NCs was found to be 2.1 ± 0.5 nm and shown bright blue fluorescence when excited at 365 nm under UV lamp. The carbon NCs were characterized by spectroscopic (UV-visible and fluorescence, Fourier transform infrared and dynamic light scattering) and high resolution transmission electron microscopic techniques. The quantum yield of carbon NCs was found to be ~5.9 % at 438 nm emission wavelength when excited at 360 nm. It was noticed that none of the metal ions quenched the fluorescence intensity of carbon NCs at 438 nm except for Fe³⁺, indicating the formation of Fe³⁺ ion-carbon NCs complexes. The linear range was observed in the concentration range of 0.01–100 μM with the corresponding detection limits of 0.001 μM, respectively. Furthermore, the carbon NCs were used as probes for imaging of fungal (Fusarium avenaceum) cells.     

Light absorption in Ge nanoclusters embedded in SiO2: comparison between magnetron sputtering and sol–gel synthesis

SiGeO films have been produced by a sol–gel derived approach and by magnetron sputtering deposition. Post-thermal annealing of SiGeO films in forming gas or nitrogen atmosphere between 600 and 900 °C ensured the phase separation of the SiGeO films and synthesis and growth of Ge nanoclusters (NCs) embedded in SiO₂. Rutherford backscattering spectrometry analysis evidenced a similar Ge concentration (~12 %), but a different Ge out-diffusion after annealing between the two types of techniques with the formation of a pure SiO₂ surface layer (~30 nm thick) in sol–gel samples. The thermal evolution of Ge NCs has been followed by transmission electron microscopy and Raman analysis. In both samples, Ge NCs form with similar size increase (from ~3 up to ~7 nm) and with a concomitant amorphous to crystalline transition in the 600–800 °C temperature range. Despite a similar Ge concentration, a significant lower NCs density is observed in sol–gel samples attributed to an incomplete precipitation of Ge, which probably remains still dispersed in the matrix. The optical absorption of Ge NCs has been measured by spectrophotometry analyses. Ge NCs produced by the sol–gel method evidence an optical band gap of around 2 eV, larger than that of NCs produced by sputtering (~1.5 eV). These data are presented and discussed also considering the promising implications of a low-cost sol–gel based technique towards the fabrication of light harvesting devices based on Ge nanostructures.     

Effect of the particle size on the electrochemical performance of nano-Li2FeSiO4/C composites

Nano-Li₂FeSiO₄/C composites were prepared from three kinds of nano-SiO₂ (their particle sizes are 15?±?5, 30?±?5, and 50?±?5 nm, respectively) by a traditional solid-state reaction method. The as-prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), elementary analyzer, Brunauer–Emmett–Teller (BET) analysis, galvanostatic charge–discharge test, and electrochemical impedance spectroscopy. XRD results reveal that nano-Li₂FeSiO₄ composites fabricated from nano-SiO₂ (smaller than 30 nm) have less impurity. SEM results indicate that the particle size of nano-Li₂FeSiO₄ composites is nearly accord with the particle size of nano-SiO₂. BET analysis indicates that the specific surface areas of LFS15, LFS30, and LFS50 are 35.10, 35.27, and 26.68 m² g, respectively, and the main pore size distribution of LFS15, LFS30, and LFS50 are 1.5, 5.5, and 10 nm, respectively. Electrochemical measurements indicate that nano-Li₂FeSiO₄ composites prepared from nano-SiO₂ of 30?±?5 nm have the best electrochemical performance among the three samples.     

Multipoint contact modeling of nanoparticle manipulation on rough surface

In this paper, the atomic force microscopy (AFM)-based 2-D pushing of nano/microparticles investigated on rough substrate by assuming a multipoint contact model. First, a new contact model was extracted and presented based on the geometrical profiles of Rumpf, Rabinovich and George models and the contact mechanics theories of JKR and Schwartz, to model the adhesion forces and the deformations in the multipoint contact of rough surfaces. The geometry of a rough surface was defined by two main parameters of asperity height (size of roughness) and asperity wavelength (compactness of asperities distribution). Then, the dynamic behaviors of nano/microparticles with radiuses in range of 50–500 nm studied during their pushing on rough substrate with a hexagonal or square arrangement of asperities. Dynamic behavior of particles were simulated and compared by assuming multipoint and single-point contact schemes. The simulation results show that the assumption of multipoint contact has a considerable influence on determining the critical manipulation force. Additionally, the assumption of smooth surfaces or single-point contact leads to large error in the obtained results. According to the results of previous research, it anticipated that a particles with the radius less than about 550 nm start to slide on smooth substrate; but by using multipoint contact model, the predicted behavior changed, and particles with radii of smaller than 400 nm begin to slide on rough substrate for different height of asperities, at first.     

Mechanochemical synthesis and giant dielectric properties of CaCu3Ti4O12

CaCu₃Ti₄O₁₂ powder has been synthesized by mechanochemical milling (C-m) and solid-state reaction (C-ssr) techniques. C-m powder has a grain size of ~24 nm as determined from X-ray diffraction and FE-SEM measurements. The grain size of C-m ceramics has increased to 20 μm compared to a size of 3 μm for C-ssr ceramics after sintering at 1,050 °C for 10 h. Giant dielectric constant was observed in both ceramics with that of C-m larger than that of C-ssr. Impedance results show that the grain conductivity of C-m is more than two orders of magnitude lower than that of C-ssr, whereas its grain boundary conductivity is larger than that of C-ssr. These results are supported by the EDX results that show Cu-enriched grain boundaries in C-m ceramics.     

Synthesis and characterization of microporous hollow core-shell silica nanoparticles (HCSNs) of tunable thickness for controlled release of doxorubicin

Hollow core-shell silica nanoparticles (HCSNs) are being considered as one of the most favorable drug carriers to accomplish targeted drug delivery. In the present study, we developed a simple two-step method, employing polystyrene (PS) nanoparticles (150?±?20 nm) as a sacrificial template for the synthesis of microporous HCSNs of size 230?±?30 nm. PS core and the wall structure directing agent cetyl trimethyl ammonium bromide (CTAB) were removed by calcination. Monodispersed spherical HCSNs were synthesized by optimising the parameters like water/ethanol volume ratio, PS/tetraethyl orthosilicate (TEOS) weight ratio, concentration of ammonia, and CTAB. Transmission electron microscopy (TEM) revealed the formation of hollow core-shell structure of silica with tunable thickness from 15 to 30 nm while tailoring the concentration of silica precursor. The results obtained from the cumulative release studies of doxorubicin loaded microporous HCSNs demonstrated the dependence of shell thickness on the controlled drug release behavior. HCSNs with highest shell thickness of 30 nm and lowest surface area of 600 m²/g showed delay in the doxorubicin release, proving their application as a drug carrier in targeted drug delivery systems. The novel concept of application of microporous HCSNs of pore size ~?1.3 nm with large specific surface area in the field of drug delivery is successful.     

Improved Pt/C electrocatalysts for methanol oxidation prepared by different reducing agents and surfactants and DFT studies on it

In this work, PtCl₄ as precursor; sodium borohydride (Cat I), hydrazinium hydroxide (Cat II), and formaldehyde (Cat III) as reducing agents; and 1-heptanamine (a), N-methyl-1-heptanamine (b), and N,N-dimethyl-1-heptanamine (c) as surfactants were used to prepare platinum nanoparticles which were then dispersed on carbon XC-72 for use as catalysts in the methanol oxidation reaction. XRD and TEM results indicate that the platinum has a face-centered cubic structure and is found as small and agglomerated particles in different shapes, sizes, and densities. Cat I comprises small (~?5 nm) cubic and formless agglomerated (~?20–~?300 nm) particles, Cat II is composed of small (~?5 nm) and a significant number of quite dense spherical agglomerated (~?20–~?150 nm) particles, and Cat III contains large number of small (~?5 nm) and a small number of spherical, less dense, and agglomerated (~?20–~?200 nm) particles. XPS data shows that the platinum exists in two different oxidation states Pt(0) (~?64.5–~?69.6%) and Pt(IV) (~?35.5–~?30.4%), and platinum surface also contains OH, H₂O, C–O, C=O, and carbon. DFT and FTIR show that the surfactants decompose to form partially crystalline carbon. Electrochemical studies reveal that performance order of the catalysts towards the methanol oxidation reaction is Cat II < Cat I < Cat III, and that Cat IIIc has the highest performance, which is 2.23 times larger than E-TEK catalysts. It was found that the performance of the catalysts depends on the kind of surfactant, reducing agent, electrochemical surface area, percent platinum utility, roughness factor, and I_f/I_r ratio.

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