Silver Behenate Research Articles

Crystal Analyzer Based Multispectral Microtomography Using CCD-Sensor.

To solve the problems of spectral tomography, an X-ray optical scheme was proposed, using a crystal analyzer in Laue geometry between the sample and the detector, which allowed for the selection of predetermined pairs of wavelengths from the incident polychromatic radiation to obtain projection images. On a laboratory X-ray microtomography setup, an experiment was carried out for the first time where a mixture of micro-granules of sodium chloride NaCl, silver behenate AgC22H43O2, and lithium niobate LiNbO3 was used as a test sample to identify their spatial arrangement. The elements were chosen based on the presence of absorption edges in two of the elements in the energy range of the polychromatic spectrum of the probing radiation. The method of projection distortion correction was used to preprocess the obtained projections. To interpret the obtained reconstruction results, the segmentation method based on the analysis of joint histograms was used. This allowed us to identify each of the three substances. To compare the results obtained, additional "reference" tomographic measurements were performed: one in polychromatic and two in monochromatic (MoKα-, MoKβ-lines) modes. It took three times less time for the tomographic experiment with the crystal analyzer, while the reconstruction accuracy was comparable to that of the "reference" tomography.

Testing and evaluation of velocity selector control system of small angle neutron scattering spectrometer

Testing and evaluation of velocity selector control system of small angle neutron scattering (SANS) spectrometer has been done. It applied a unit of speed control variable AC, Optidrive Invertek Drives. This system is designed to be manually controlled and computerized. To control the Optidrive in manual mode, it can be done by keypad on the unit. The Optidrives can be controlled using computer by connecting the unit into a computer via USB port and OptiTools Studio software. Optidrive Invertek Drives need alternative current (AC) voltage one phase 220 volt with three phase out 220 volt. This out voltage is used as voltage source for moving the motor of disk in SANS neutron velocity selector. The speed of the disk in SANS neutron velocity selector is changed by adjusting the frequency from the Optidrive Invertek Drives. The numbers of speed of the disk determine the neutron wavelength passed through SANS neutron velocity selector. It is observed that every increasing frequency of 1 Hz, it will increase the disk speed by 59.929 rpm. The calibration that has been done for this system using silver behenate, obtain wavelength of the neutrons dependent to the disk speed. They are 3.10, 3.09, 3.41, 3.76, 4.23, 4.71, and 5.39 Å for disk speed 6500, 6000, 5500, 5000, 4500, 4000, and 3500 rpm respectively.

Calibration of the Suanni small-angle neutron scattering instrument at the China Mianyang Research Reactor

A series of calibration measurements have been performed on Suanni – the first small-angle neutron scattering spectrometer entering into routine user operation in China – aiming to characterize instrument performance and to provide a reference for user experiments. Various calibration standards were used to verify the precise association of the scattering intensity I with the scattering vector magnitude q at short and medium sample–detector distances. The measurements recorded for silver behenate powder revealed a slight shift of the neutron wavelength (λ) at the sample position as compared to the nominal λ calculated by the selector constant. The deviation was more significant with λ > 0.8 nm owing to the shape of the incoming neutron spectrum incident on the selector. The measured dead time for the entire detection system is 2.7 µs, as determined by measurements with varying fluxes. A protonated/deuterated polystyrene blend was employed as the primary standard to calibrate the secondary standard H2O. The instrument covers an effective q range between 0.013 and 5 nm−1, as demonstrated by scattering curves obtained from a monodisperse poly(methyl methacrylate) nanoparticle suspension and a glassy carbon plate.

Spin-analyzed SANS for soft matter applications

The small angle neutron scattering (SANS) of nearly Q-independent nuclear spin-incoherent scattering from hydrogen present in most soft matter and biology samples may raise an issue in structure determination in certain soft matter applications. This is true at high wave vector transfer Q where coherent scattering is much weaker than the nearly Q-independent spin-incoherent scattering background. Polarization analysis is capable of separating coherent scattering from spin-incoherent scattering, hence potentially removing the nearly Q-independent background. Here we demonstrate SANS polarization analysis in conjunction with the time-of-flight technique for separation of coherent and nuclear spin-incoherent scattering for a sample of silver behenate back-filled with light water. We describe a complete procedure for SANS polarization analysis for separating coherent from incoherent scattering for soft matter samples that show inelastic scattering. Polarization efficiency correction and subsequent separation of the coherent and incoherent scattering have been done with and without a time-of-flight technique for direct comparisons. In addition, we have accounted for the effect of multiple scattering from light water to determine the contribution of nuclear spin-incoherent scattering in both the spin flip channel and non-spin flip channel when performing SANS polarization analysis. We discuss the possible gain in the signal-to-noise ratio for the measured coherent scattering signal using polarization analysis with the time-of-flight technique compared with routine unpolarized SANS measurements.

Characterisation of morphological, antimicrobial and leaching properties of in situ prepared polyurethane nanofibres doped with silver behenate

PU nanofibersin situdoped with silver nanoparticles were prepared using free-surface electrospinning and no post-treatment. Nanofibres with silver behenate exhibited homogenous morphology, strong antimicrobial properties and low silver leaching.

A new small-angle neutron scattering spectrometer at China Mianyang research reactor

A new pinhole small-angle neutron scattering (SANS) spectrometer, installed at the cold neutron source of the 20MW China Mianyang Research Reactor (CMRR) in the Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, has been put into use since 2014. The spectrometer is equipped with a multi-blade mechanical velocity selector, a multi-beam collimation system, and a two-dimensional He-3 position sensitive neutron detector. The q-range of the spectrometer covers from 0.01nm−1 to 5.0nm−1. In this paper, the design and characteristics of the SANS spectrometer are described. The q-resolution calculations, together with calibration measurements of silver behenate and a dispersion of nearly monodisperse poly-methyl-methacrylate nanoparticles indicate that our SANS spectrometer has a good performance and is now in routine service.

In Situ Self-Assembly of Silver Nanoparticles

We have found that the thermal decomposition of [Ag(O2CnH2n–1)]2, where n = 14, 16, 18, and 22, produces the ordered 3D nanostructure (supracrystals) directly during the chemical reaction, which makes it possible to obtain self-assembled structures in large quantities without requiring additional processing steps. The process of self-assembling of silver nanoparticles is characterized by TEM and in situ time-resolved SAXRD and WAXS data. The calculated unit-cell parameters of the fcc nanostructures formed correlate with the aliphatic chain length: these are 9.55 nm for silver myristate (n = 14), 9.8 nm for silver palmitate (n = 16), 10.46 nm for silver stearate (n = 18), and 12.5 nm for silver behenate (n = 22). Structural and morphological characteristics of supracrystals formed in situ during the thermal decomposition of silver carboxylates are found to be dependent on the sample heating rate. The self-assembled ordering of the silver nanoparticles was observed to begin at ∼180, and above ∼280 °C the supracrystalline structures begin to decompose.

Bench-top X-ray microtomography complemented with spatially localized X-ray scattering experiments

This article describes a novel experimental setup that combines X-ray microtomography (XMT) scans within situX-ray scattering experiments in a laboratory setting. Combining these two methods allows the characterization of both the micrometre-scale morphology and the crystallographic properties of the sample without removing it from the setup. Precise control of the position of the sample allows an accurate choice of the scattering beam path through the sample and facilitates the performance of X-ray scattering experiments on submillimetre-sized samples. With the present setup, a voxel size of less than 0.5 µm is achievable in the XMT images, and scattering experiments can be carried out with a beam size of approximately 200 × 200 µm. The potential of this setup is illustrated with the analysis of micrometeorite crystal structure and diffraction tomographic imaging of a silver behenate phantom as example applications.

使用山嵛酸银标定中子小角散射谱仪的关键参数

To calibrate quickly key parameters of a small angle neutron scattering spectrometer,such as selecting neutron wavelengths,wavelength resolution,and the Q resolution under a geometrical layout of the spectrometer,the experiment data of small angle neutron scattering for silver behenate powder were fitted.First,the geometrical layout of spectrometer was chosen including the size of circular source,sample apertures of the collimator,the source-to-sample distance and the sample-to-detector distance.Then,the spectra of small angle neutron scattering on silver behenate were obtained under four different revolving speeds of mechanical velocity selector.Finally,these experiment data were inversed and analyzed.Obtained results show that the velocity selector constant is 2 329.2 r·m-1·nm,correspondingly,four different selecting neutron wavelengths are 0.776、0.582、0.466、0.388 nm,respectively.The wavelength resolution of the velocity selector is 23.75% by fitting these experiment data and the spectrometer Q resolution curves can be obtained by using the chosen layout parameter and different rotating speeds.It concludes that the key parameters of small angle neutron scattering spectrometer can be achieved by using silver behenate,which supports the exact analysis and inversion for experiment data of small angle neutron scattering.

Ultrafast time dynamics studies of periodic lattices with free electron laser radiation

It has been proposed that radiation from free electron laser (FEL) at Hamburg (FLASH) can be used for ultrafast time-resolved x-ray diffraction experiments based on the near-infrared (NIR) pump/FEL probe scheme. Here, investigation probing the ultrafast structural dynamics of periodic nano-crystalline organic matter (silver behenate) with such a scheme is reported. Excitation with a femtosecond NIR laser leads to an ultrafast lattice modification which time evolution has been studied through the scattering of vacuum ultraviolet FEL pulses. The found effect last for 6 ps and underpins the possibility for studying nanoperiodic dynamics down to the FEL source time resolution. Furthermore, the possibility of extending the use of silver behenate (AgBh) as a wavelength and temporal calibration tool for experiments with soft x-ray/FEL sources is suggested.

Silver behenate and silver stearate powders for calibration of SAS instruments

The possibilities of calibrations by silver behenate [CH3(CH2)20COOAg] and silver stearate [CH3 (CH2)16CO2Ag] for the small angle scattering (SAS) technique are considered. It was shown that the long-period spacing of the silver compounds allow us to check the parameters of time-of-flight (TOF) method. Results of the data obtained from small angle neutron scattering (SANS) measurements performed with the silver behenate and the silver stearate powders are presented and compared with small angle X-ray scattering (SAXS) measurements.

Crystal structure determination of the silver carboxylate dimer [Ag(O2C22H43)]2, silver behenate, using powder X-ray diffraction methods

High-resolution powder X-ray diffraction has been used to determine the crystal structure of silver behenate, [Ag(O2C(CH2)20CH3]2. Using CASTEP density functional plane wave pseudopotential techniques to obtain an optimized structural model, Rietveld refinement of the structure givesRwp= 8.66%. The unit cell is triclinic, space groupP1, with cell dimensions ofa= 4.1769(2) Å,b= 4.7218(2) Å,c= 58.3385(1) Å, α = 89.440(3)°,β= 89.634(3)°,γ= 75.854(1)°. The structure is characterized by an 8-membered ring dimer of Ag atoms and carboxyl groups with a fully extended all-trans configuration of the alkyl side chains. The dimers are joined by four-membered Ag-O rings creating a polymeric network, giving rise to one-dimensional chains along theb-axis. This structure is supported by EXAFS measurements of the local structure around the silver atoms and IR measurements.

Ultra-fast dynamics of silver behenate investigated by FEL femtosecond radiation (FLASH)

Ultra-fast dynamics of silver behenate investigated by FEL femtosecond radiation (FLASH)

Applications of 3He neutron spin filters on the small-angle neutron scattering spectrometer SANS-J-II

A polarized 3He neutron spin filter has been applied to polarization analysis on the small-angle neutron scattering spectrometer SANS-J-II at JRR-3. Measurements were taken on silver behenate, which has several coherent peaks in the small-angle region with a background of spin incoherent hydrogen scattering. Here we demonstrate that the coherent and spin incoherent scattering were successfully separated by the polarization analysis using the 3He spin filter on the instrument.

Diffraction Properties of Periodic Lattices under Free Electron Laser Radiation

In this Letter, we report the pioneering use of free electron laser radiation for the investigation of periodic crystalline structures. The diffraction properties of silver behenate single nanocrystals (5.8 nm periodicity) with the dimensions of 20 nm x 20 nm x 20 microm and as powder with grain sizes smaller than 200 nm were investigated with 8 nm free electron laser radiation in single-shot modus with 30 fs long free electron laser pulses. This work emphasizes the possibility of using soft x-ray free electron laser radiation for these crystallographic studies on a nanometer scale.

Diffraction gratings as small-angle X-ray scattering calibration standards

It is shown that diffraction gratings can be used as accurate momentum-transfer calibration standards in small-angle X-ray scattering experiments. For demonstration purposes, a silicon diffraction grating with a period of 400 nm is used. The data exhibit 50 diffraction peaks evenly distributed in the momentum-transfer rangeq= 0.0–0.8 nm−1, a regime that is not accessible using the traditional silver behenate standard.

Structure of the N-terminal Regulatory Domain of a Plant NADPH Oxidase and Its Functional Implications

Plant NADPH oxidases (Rboh, for respiratory burst oxidase homolog) produce reactive oxygen species that are key regulators of various cellular events including plant innate immunity. Rbohs possess a highly conserved cytoplasmic N-terminal region containing two EF-hand motifs that regulate Rboh activity. Rice (Oryza sativa) RbohB (OsRbohB) is regulated by the direct binding of a small GTPase (Rac1) to this regulatory region as well as by Ca(2+) binding to the EF-hands. Here, we present the atomic structure of the N-terminal region of OsRbohB. The structure reveals that OsRbohB forms a unique dimer stabilized by swapping the EF-hand motifs. We identified two additional EF-hand-like motifs that were not predicted from sequence data so far. These EF-hand-like motifs together with the swapped EF-hands form a structure similar to that found in calcineurin B. We observed conformational changes mediated by Ca(2+) binding to only one EF-hand. Structure-based in vitro pulldown assays and NMR titration experiments defined the OsRac1 binding interface within the coiled-coil region created by swapping the EF-hands. In addition, we demonstrate a direct intramolecular interaction between the N and C terminus, and that the complete N-terminal cytoplasmic region is required for this interaction. The structural features and intramolecular interactions characterized here might be common elements shared by Rbohs that contribute to the regulation of reactive oxygen species production.

XPS and SEM/STEM Characterization of Silver Nanoparticles Formed from the X-ray-Induced and Thermal Reduction of Silver Behenate

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Silver behenate under high pressure: A powder diffraction study

Silver behenate, a salt of the behenic acid, known mostly for its applications in photothermographic imaging and use as a diffraction reference material, was studied by X-ray diffraction under pressures up to 11.4 GPa. Diffraction patterns were collected using a diamond anvil cell and synchrotron radiation at the I711 beamline (MAXlab, Lund). The variation of the d spacing with pressure is determined and the potential usefulness of this dependence for pressure calibration is discussed.

Improved performances of 36 m small-angle neutron scattering spectrometer BATAN in Serpong Indonesia

SMARTer, a 36 m small-angle neutron scattering (SANS) spectrometer owned by the National Nuclear Energy Agency of Indonesia (BATAN) was installed at the Neutron Scattering Laboratory (NSL) in Serpong, Indonesia. Lots of works on replacing, upgrading and improving the control system, experimental methods, data collection and reduction in the last two years have been carried out to optimize the performance of SMARTer. Some standard samples such as silver behenate, monodisperse polystyrene nanoparticle, porous silica and block copolymer PS-PEP film were measured for the inter-laboratory comparison.