Siriwat Soontaranon

Direct analysis of in-line particle holograms by using wavelet transform and envelope reconstruction method

Summary We propose a new digital method for sizing particles and tracking their positions from an in-line hologram by using a combination of a wavelet transform and a reconstruction of the envelope functions. In the proposed method, the hologram is recorded by a charge-coupled device (CCD) sensor. The wavelet transform of digitized holograms gives information about the position of particles, while the reconstruction of envelope functions provides the size of particles. Preliminary theoretical and experimental verifications are presented. The system limitation of the method is discussed.

Micropower energy harvesting using poly(vinylidene fluoride hexafluoropropylene)

This work explores applications for poly(vinylidene fluoride hexafluoropropylene) or P(VDF-HFP). The P(VDF-HFP) with a 10 wt. % HFP can be prepared to exhibit the piezoelectricity and energy conversion ability. This was achieved by determining the nanostructural parameters by the Small Angle X-Ray Scattering. The unpoled sample gained linear crystallinity with drawing rate. The optimal conditions for poling process were 60 MV/m at 90 °C. The piezoelectric coefficient d31 of 28.7 pC/N and FoM of 8.8 × 10−12 m2/N were obtained from the poled sample drawn at 45 mm/min. The piezoelectric P(VDF-HFP) was proven to deliver a microwatt energy essential for powering small-scale electronics.

Small-Angle X-Ray Scattering Study on PVA/Fe3O4 Magnetic Hydrogels

A synchrotron small-angle X-ray scattering (SAXS) study on PVA/Fe3O4 magnetic hydrogels has been performed to investigate the effect of clustering on their magnetic properties. The hydrogels were prepared through freezing–thawing (F–T) processes. The structure, morphology and magnetic properties of magnetite (Fe3O4) nanoparticles (NPs) were investigated using X-ray diffractometry (XRD), transmission electron microscopy (TEM) and a superconducting quantum interference device (SQUID) magnetometer, respectively. In this study, SAXS data were used to reveal the structural dimensions of the magnetite and its distribution in the polymer-rich PVA and magnetic hydrogels. As calculated using the Beaucage and Teubner–Strey models, the average of the structural dimensions of the PVA hydrogels was 3.9nm (crystallites), while the average distance between crystallites was approximately 18nm. Further analysis by applying a two-lognormal distribution showed that the magnetite NPs comprised secondary particles with a diameter of 9.6nm that were structured by primary particles (∼3.2nm). A two-lognormal distribution function has also been used in describing the size distributions of magnetite NPs in magnetic hydrogels. The clusters of magnetite NPs in the magnetic hydrogels are significantly reduced from 30.4nm to 12.8nm with decreasing concentration of the NPs magnetite from 15wt.% to 1wt.%. The saturation magnetization values of the magnetite NPs, the 15% and 1% magnetic hydrogels were 34.67emu/g, 6.52emu/g and 0.37emu/g, respectively.

Gallic acid conjugated with gold nanoparticles: antibacterial activity and mechanism of action on foodborne pathogens.

Foodborne pathogens, including Plesiomonas shigelloides and Shigella flexneri B, are the major cause of diarrheal endemics worldwide. Antibiotic drug resistance is increasing. Therefore, bioactive compounds with antibacterial activity, such as gallic acid (GA), are needed. Gold nanoparticles (AuNPs) are used as drug delivery agents. This study aimed to conjugate and characterize AuNP–GA and to evaluate the antibacterial activity. AuNP was conjugated with GA, and the core–shell structures were characterized by small-angle X-ray scattering and transmission electron microscopy. Antibacterial activity of AuNP–GA against P. shigelloides and S. flexneri B was evaluated by well diffusion method. AuNP–GA bactericidal mechanism was elucidated by Fourier transform infrared microspectroscopic analysis. The results of small-angle X-ray scattering showed that AuNP–GA conjugation was successful. Antibacterial activity of GA against both bacteria was improved by conjugation with AuNP because the minimum inhibitory concentration value of AuNP–GA was significantly decreased (P<0.0001) compared to that of GA. Fourier transform infrared analysis revealed that AuNP–GA resulted in alterations of lipids, proteins, and nucleic acids at the bacterial cell membrane. Our findings show that AuNP–GA has potential for further application in biomedical sciences.

SAXS/WAXS Capability and Absolute Intensity Measurement Study at the SAXS Beamline of the Siam Photon Laboratory

A Small Angle X-ray Scattering (SAXS) beamline has been constructed at the Siam Photon Laboratory of the Synchrotron Light Research Institute (SLRI), Thailand. The beamline was commissioned and opened for users in March 2011. In order to maximize the photon flux, a Double Multilayer Monochromator was adopted to monochromatize synchrotron x-rays within the energy range of 6-9 keV. The experimental station is equipped with a CCD detector for SAXS measurements and an Image Plate for wide angle x-ray scattering (WAXS) measurements. Apparatus for in-situ measurements have been developed to enable studies of nano structural changes during temperature and tensile variation. Capability for scattering measurements in absolute unit has been investigated. This work reports the current status of the beamline and results from dispersed Au nanoparticles measurements.

Structural, Optical, and Antifungal Characters of Zinc Oxide Nanoparticles Prepared by Sol-gel Method

The preparation of zinc oxide nanoparticles has been successfully done by employing a sol-gel route. The x-ray diffraction data analysis presented that the zinc oxide particles crystallized as hexagonal wurtzite structure and sized in nanometric scale of 35.8 nm. The scanning electron microscopy image showed that the sample had agglomeration pattern with the particles size of 38.2 nm. Such results were confirmed by a synchrotron small-angle x-ray scattering that the prepared sample agglomerated in 3-dimensional structure with a fractal dimension of about 3. The functional group of the Zn-O as the main component of zinc oxide were observed at the wavelengths of about 454 and 523 cm−1. Moreover, the optical band gap energy of the zinc oxide nanoparticles was of 3.53 eV. Excitingly, the powdered sample in this work had an average inhibition zone diameter of 4.59 mm for Candida albicans fungus. Therefore, the prepared zinc oxide nanoparticles exhibited imperative materials for antifungal agent.

Synchrotron WAXS and XANES studies of silica (SiO2) powders synthesized from Indonesian natural sands

In this study, we have investigated polymorphic silica (SiO2) powders using, Wide Angle X-ray Scattering (WAXS) and X-Ray Absorption Near Edge Spectroscopy (XANES), laboratory X-Ray Diffraction (XRD) instruments. The WAXS and XANES spectra were collected using synchrotron radiation at Synchrotron Light Research Institute (SLRI), Nakhon Ratchasima, Thailand. The silica powders were obtained by processing silica sand from Tanah Laut, South Kalimantan, Indonesia. Purification process of silica sand was done by magnetic separation and immersion with HCl. The purification step was needed to reduce impurity or undesirable non Si elements. Three polymorphs of silica were produced, i.e. amorphous phase (A), quartz (B), and cristobalite (C). WAXS profile for each phase was presented in terms of intensity vs. 2θ prior to analyses. Both XRD (λCuKα=1.54056 A) and WAXS (λ=1.09 A) patttern show that (1) A sample contains no crystallites, (2) B sample is monophasic, contains only quartz, and (3) C sample contains cristobalite and trydimite. XRD quantitative analysis using Rietica gave 98,8 wt% cristobalite, while the associated WAXS data provided 98.7 wt% cristobalite. Si K-edge XANES spectra were measured at energy range 1840 to 1920 eV. Qualitatively, the pre-edge and edge features for all phases are similar, but their main peaks in the post-edge region are different.

Particle tracking from in-line holograms by using single wavelet coefficient

We propose a new digital method for tracking position of particles from in-line holograms by using single wavelet coefficient. By computing a wavelet transform of the 1-D intensity profile of a hologram, resultant wavelet coefficients provide space-varying frequency information of an interference pattern. Our study finds that a dilation which is given by the maximum value of the real wavelet coefficient appeared at the center position of the interference pattern is determined by a recording distance and a wavelength of a coherent illuminating light. Therefore, this dilation can be used for extracting the recording distance of particles from the holograms. A feasibility of this method is experimentally verified by analyzing holograms of a line object.

Holographic particle sizing by using absolute values of the wavelet transform

A new method for sizing particle from in-line Fraunhofer holograms by using absolute values of the wavelet transform is proposed. The method gives zero-crossing points of an envelope function of the hologram which are determined by the particle size. Since the resultant zero-crossing points are functions of the dilation parameter, the frequencies of the fringes at the zero-crossing points are measured. The particle size can be finally calculated from the relationship between the frequencies with the positions of the zero-crossing points. The experimental results agree well with the theory.

Particle tracking and sizing by using wavelet analysis and reconstruction of envelope function

A new digital method for measuring size of particle and its position from in-line particle holograms is proposed. In our proposed method, the position of particle is obtained by using a wavelet transform, while its size is retrieved by a reconstruction of envelope function. Usefulness of our proposed method is experimentally verified. The system limitation of the method is discussed.