P. Limsuwan

Preparation and characterization of alumina nanoparticles in deionized water using laser ablation technique

Al2O3 nanoparticles were synthesized using laser ablation of an aluminum (Al) target in deionized water. Nd:YAG laser, emitted the light at a wavelength of 1064 nm, was used as a light source. The laser ablation was carried out at different energies of 1, 3, and 5 J. The structure of ablated Al particles suspended in deionized water was investigated using X-ray diffraction (XRD). The XRD patterns revealed that the ablated Al particles transformed into γ-Al2O3. The morphology of nanoparticles was investigated by field emission scanning electron microscopy (FE-SEM). The FE-SEM images showed that most of the nanoparticles obtained from all the ablated laser energies have spherical shape with a particle size of less than 100 nm. Furthermore, it was observed that the particle size increased with increasing the laser energy. The absorption spectra of Al2O3 nanoparticles suspended in deionized water were recorded at room temperature using UV-visible spectroscopy. The absorption spectra show a strong peak at 210nm arising from the presence of Al2O3 nanoparticles. The results on absorption spectra are in good agreement with those investigated by XRD which confirmed the formation of Al2O3 nanoparticles during the laser ablation of Al target in deionized water.

Growth of silver nanoparticles by DC magnetron sputtering

Silver (Ag) nanoparticles are of great interest for many applications. However, their fabrications have been limited by the synthesis methods in which size, shape, and aggregation are still difficult to control. Here, we reported on using direct current (DC) magnetron sputtering for growing Ag nanoparticles on unheated substrates. Effects of sputtering condition on grain size of Ag nanoparticle were discussed. At constant sputtering current and deposition time, the average sizes of Ag nanoparticles were 5.9 ± 1.8, 5.4 ± 1.3, and 3.8 ± 0.7 nm for the target-substrate distances of 10, 15, and 20 cm, respectively. The morphology evolution from nanoparticles to wormlike networks was also reported. High-resolution transmission electron microscopy image represented clear lattice fringes of Ag nanoparticles with a d-spacing of 0.203 nm, corresponding to the (200) plane. The technique could be applied for growth of nanoparticles that were previously difficult to control over size and size uniformity.

Synthesis of antibodies-conjugated fluorescent dye-doped silica nanoparticles for a rapid single step detection of campylobacter jejuni in live poultry

The preparation of antibodies-conjugated fluorescent dye-doped silica nanoparticles (FDS-NPs) was developed to detect Campylobacter jejuni cells under a fluorescence microscope. The particles prepared by sol-gel microemulsion techniques have a round shape with an average size of 43±4 nm. They were highly photo stable and could emit strong orange fluorescent for 60min. Both amine- and carboxyl-functionalized properties were evident from FTIR and FT Raman spectra. The FDS-NPs conjugated with antibodies against C. jejuni were well dispersed in PBS solution at 20mM of NaCl. The conjugation with monoclonal antibodies against C. jejuni was successful. The direct observation of the antibodies-conjugated FDS-NPs- that bounds C. jejuni with Petroff Hausser counting chamber at 40x was clear. The different focus lengths clearly separated bound and unbound FDSNPs under the microscope. We successfully synthesis the bio-conjugated dye doped silica nanoparticles for C. jejuni that are easy to use and giving clear detection in due time.

Dynamic in situ spectroscopic ellipsometric study in inhomogeneous TiO2 thin-film growth

We investigate the film-growth process of the inhomogeneous sputtered TiO2 thin films by the in situ real-time spectroscopic ellipsometer. The growth process of the film is analyzed by both the uniform and the island film growth models. Based on the analyses from the Ψ-Δ trajectories, the initial thin-film growth corresponds to the island film growth model for a single-layer film. As the film grows, the microstructural phase changes cause the transition from the single-to the double-layer physical model, because of the development of the inhomogeneity in the TiO2 thin film. The dynamic fits with the double-layer physical model and the Cody–Lorentz optical model indicate three different stages of the film growth: the nucleation stage, the coalescence stage, and the continuous-layer stage. Although our presented model works well for most of the experimental data, the determination of the refractive index at the ultrathin thickness may be problematic.

Structural and Magnetic Properties of Glass Doped with Iron Oxide

Glasses based on borosilicate system were prepared by melt-quenching method in the composition range of (mol%) 20Na2O : 1.0Al2O3 : 13B2O3 : 6.3CaO : 0.2Sb2O3 : 4.5BaO : (55−X)SiO2 : xFe2O3 (where x = 0, 5, 10, 15, 20 and 25) and the structural, optical and magnetic properties were investigated. The result showed that the density and molar volume of glasses increased with increasing of Fe2O3 concentration. This might be due to an increase of Fe2O3 concentration at the expense of SiO2 caused the opened glass network structure. Fe2O3 also affected the change of B2O3 structure detected by FTIR technique. The magnetic measurement revealed that the glass sample exhibited a ferrimagnetic behavior when doping with 25 % mol Fe2O3.

SURFACE MORPHOLOGY OF SUBMICRON CRYSTALS IN ALUMINUM NITRIDE FILMS GROWN BY DC MAGNETRON SPUTTERING

Aluminium nitride (AlN) thin films were fabricated on a glass substrate by reactive magnetron sputtering. Raman microscopy was then employed to follow the characteristics of their optical and acoustic phonon modes. At the optimal sputtering time of 30 minutes, the defect-induced first and second order Raman spectra were observed in 400–800 cm-1 band which were mostly related to the coating compositions. However, at the 30-, 60- and 90-minute sputtering, crystals of submicron size order of AlN were achieved. This could be clearly identified by the presence of Raman peak at 658–662 cm-1. Powder X-ray diffraction (PXRD) patterns revealed the development of (002) and (101) planes of hexagonal wurtzite AlN phase. The optimal average grain size measured by atomic force microscopy (AFM) is at 330 nm. It was found that the hardness was strongly dependent on roughness of the film, the maximum of which was achieved at 20.00 GPa. The presence of F-type defects in AlN films was investigated by X-band (~9.44 GHz) ESR spectrometer at 295 K. The ESR experiments were carried out by applying magnetic field perpendicular to AlN film, which showed the ESR six-peak multiplet signal at ~290 mT arising from superhyperfine interactions between nuclear spin I = 5/2 of 27Al and electron spins trapped in nitrogen vacancies. The ESR signals are simulated and the ESR parameters are calculated. The vacancies are clearly randomly distributed as the ESR signals are independent of rotation angle (φ) about the normal of the film. All these results were analyzed and presented as a function of the deposition parameters and composition, and crystalline phases existed in the films.

Nonproportionality of electron response using CCT: plastic scintillator.

The scintillation response of a plastic scintillator (NE102) has been characterized using compton coincidence technique. The coincidence technique allowed detection of nearly monoenergetic internal electrons resulting from the scattering of incident 662keV gamma-rays within a primary NE102 detector. Scattered gamma-rays were detected using a secondary NaI(Tl) detector in a coincidence mode. The electron response nonproportionality of NE102 plastic scintillator was measured using this technique for electron energies ranging from 28 to 436keV, by varying the scattering angle. The NE102 showed a good proportionality of light yield within 3% at energies between 90 and 436keV. Below 90keV, the light yield decreases by about 20% upon lowering the electron energy to 28keV. The electron energy resolution of NE102 was also measured using this technique in the energy range from 68 to 436keV. It has been found that the energy resolution varies from 25.2% at 68keV to 11.8% at 436keV.

EFFECT OF RARE-EARTH (RE = La, Nd, Ce AND Gd) DOPING ON THE PIEZOELECTRIC of PZT(52:48) CERAMICS

The purpose of this research is to study the effect of doping some rare earth ions into PZT(52:48) ceramics. The ferroelectric Pb(ZrxTi1-x)O3 ceramics are well-known as piezoelectric materials for electro-mechanical transducers such as ultrasonic generator, electronic buzzer, and stress sensor, etc. The highest piezoelectric coupling coefficients as well as maximum permittivity are located near the morphotropic phase boundary (MPB). The region of phase transition between the tetragonal and rhombohedral structures in the Pb(ZrxTi1-x) O3 ceramic shows very adoptable piezoelectric characteristics due to the phase coexistence phenomena, and exhibits a sensitivity of properties to the preparation method, the composition, the firing temperatures and the kinds of additives. The purpose of this research is to study the effect of doping La, Nd, Ce and Gd into Pb(Zr0.52Ti0.48) O3 ceramics prepared by solid state reaction. The properties include microstructure, physical properties, dielectric constant (er) and piezoelectric properties (kp and Qm) of undoped and La, Nd, Ce and Gd doped PZT ceramics. Several effects, such as firing temperature, grain size and dopants, on the properties of PZT were also studied. The undoped PZT ceramics with Zr/Ti at 52/48 indicated the highest er=1969 and kp= 0.381 for La doping. Doping with La, Nd, Ce and Gd led to an improvement in the er but a reduced Qm value. The optimum values of electric properties were found in PZT (52/48) doped La with 10.0 mol% sintered at 1200°C for 2 h.

Design of Salbutamol EOP Tablets from Pharmacokinetics Parameters

Salbutamol elementary osmotic pump (EOP) tablets were developed, and fundamental variables affecting their release characteristics were evaluated. The effects of film thickness and compression force on drug release from the tablets containing fixed amount of sodium chloride used as osmogent were evaluated. The core tablets were directly compressed at four compression forces and coated with 3% wt/vol cellulose acetate in acetone to levels of 2%, 3%, and 4% wt/wt. Coated tablets were drilled with CO2 laser beam to form drug delivery orifice of ∼400 μm in diameter. The drug release was found to follow zero order fashion. The release rate decreased with the increased film thickness and was not affected by the compression force or porosity. The tablets coated to 3% and 4% levels exhibited the release rates within the range calculated from pharmacokinetic data. To illustrate the effect of osmogent content, the tablets were prepared at four osmogent levels and compressed at a constant compression force. The core tablets were coated to a level of 3% wt/wt. The release rate was initially increased with osmogent content and then decreased. At higher osmogent contents, the drug fraction in soluble component was decreased and resulted in the reduction of drug release. In conclusion, film thickness and osmogents played important roles in drug release from EOP tablets.

Antibody-conjugated rubpy dye-doped silica nanoparticles as signal amplification for microscopic detection of vibrio cholerae O1

This study demonstrated the potential application of antibody-conjugated Rubpy dye-doped silica nanoparticles for immunofluorescence microscopic detection of Vibrio cholerae O1. The particle synthesis of 20X of the original ratio was accomplished yielding spherical nanoparticles with an average size of 45 ± 3 nm. The nanoparticles were carboxyl functionalized and then conjugated with either monoclonal antibody or polyclonal antibody against V. cholerae O1. The antibody-conjugated nanoparticles were tested with two target bacteria and three challenge strains. The result showed that monoclonal antibody-conjugated Rubpy dye-doped silica nanoparticles could be effectively used as signal amplification to detect V. cholerae O1 under a fluorescence microscope. Their extremely strong fluorescence signal also enables the detection of a single cell bacterium.