Naphat Chathirat

Dielectric Properties of Y2NiMnO6 Ceramics at Various Sintering Times and Temperatures

Dielectric properties of hydrothermally decomposed Y2NiMnO6 ceramics prepared under several sintering conditions were investigated at room temperature. As the results, dielectric constants at 200 Hz were found about 928 and 23x103 for samples sintered at 1000 and 1400 oC, respectively. The dielectric permittivity for samples sintered at 1400 oC for different sintering times from 6 to 24 hours have yielded the best dielectric permittivity value of 104. On the other hand, low sintering temperature had resulted in smaller dielectric loss in comparison to larger dielectric loss generally found in the ceramics with high sintering temperature.

The Dielectric Property of Y2NiMnO6 Ceramics Sintered at High Temperature

The high dielectric permittivity of Y2NiMnO6 ceramics were measured by Agilent E4294A (Impedance Measurement) range of frequency 100 to 10 MHz in this research. In this sample ceramics, passing by a sintering temperature of 1400°C at 6 hours to 24 hours. The phase and microstructure of the deposited materials were investigated as a function of sintering temperature, using X-ray diffraction (XRD) and scanning electron microscopy (SEM). We found that the dielectric properties are very sensitive to the several sintered follow by time, and high temperature can be related to the change ordering of Ni2+ and Mn4+ ions.

Electrical Properties of Y2NiMnO6 Ceramics Sintered at High Temperature

In this work, impedance spectroscopy technique was used in order to investigate the electric properties of double perovskites of the Y2NiMnO6 ceramics, which were prepared by thermal decomposition technique at 800°C for 6 hours and then sintered at a high temperature of 1400°C for 6, 12, 18, and 24 hours. Consequently, the electric characterization of the Y2NiMnO6 ceramics was performed at 30°C °C in the frequency range from 102 Hz to 108 Hz. The results in the Rg with 10,000, 9,990, 6,400, and 1,700 (Ω) at sintering time, respectively. Dispersion was observed in the variation of impedance values with frequency. Possible reason for all the above observation was discussed.

Study Behavior of XPS Spectra of Ni, Mn, Y and O in Y2NiMnO6 Ceramics

Bulk Y2NiMnO6 samples were prepared by thermal decomposition technique at 800 °C for 6 hours. The effects of temperature on the structure of ceramics were investigated for different sintering temperatures in the range of 1000-1300 °C, while kept constant the sintering time of 12 hours. Structural characterization had been investigated via X-ray diffraction (XRD) on samples of different sintering temperatures. Results from the experiment had revealed that high temperature affected oxide in ceramic materials. Further analysis with X-ray photoelectron spectroscopy (XPS) technique had revealed an outstanding point of ceramics by investigating the Ni 2p, 2p3/2, Mn 2p1/2, 2p3/2, and Y 3d3/2, 3d5/2 at the surface of Y2NiMnO6 ceramics. The changes in relative intensity of XPS peaks and the shifts in their binding energy (eV) were observed in the results, while the effect of temperature on oxide in ceramics may be investigated with dielectric property in the future.

A Micrograting Sensor for DNA Hybridization and Antibody Human Serum Albumin–Antigen Human Serum Albumin Interaction Experiments

A biosensor structure comprising silicon nitride (Si3N4) micrograting arrays coated with a spin-on-glass (SOG) material was investigated. This grating structure was located on a silicon groove, which was etched by a deep reactive ion etching (DRIE) process. The biosensor was used as a specific detector of DNA molecules and antibody–antigen interactions. In our DNA sensing experiments, the first step was the activation of the grating surface with amine functional groups, followed by attachment of a 23-base oligonucleotide probe layer for hybridization with a complementary target DNA. The sensing device was tested for detecting specific antigen/antibody interactions for human serum albumin (HSA) and antigen bovine serum albumin (BSA). The readout system consisted of a white light lamp that illuminated a small spot on the grating surface at normal incidence through a fiber optic probe with a spectrometer used to collect the reflected light through a second fiber. We show that these sensing devices have the capability to detect DNA as well as antigen–antibody binding for HSA. The detection sensitivity for HSA was better than that for DNA mainly owing to the larger size and concomitant refractive index changes upon binding to the sensor. We show that it is possible to quantify the amount of biomolecules bound to the grating surface by measuring the wavelength shift of the reflectance spectra upon exposure to the samples.

Heating Energy Briquettes from Cashew Nut Shell

We study the heating energy of briquettes from cashew nut shell (CNS), cultivated in south Thailand. CNS briquettes (CNSB) were produced by mixing CNS powder with the cassava starch ratio 5:1w/w. A chemical component analysis of the CNSB was performed, and the heat utilization efficiency was compared with firewood charcoal. CNSB were found to have a fixed carbon content of 49.2%, ash content of 4.2% (750°C°C at 6 hours), and moisture content of 6.6% (105°C for 24 hours). It was observed that CNSB consists of energy consumption at 0.440-0.456 KW/kg and high compressive strength of 60.2 kg/cm2.The value of heat utilization efficiency obtained inside the fuel briquette of 18.01%, attributed to the burn rate average at 11.90 g/min. CNSB could be used to replace firewood and reduce cost for heating manufacturing processes.

DNA Biosensor on Optical Nanograting Structure

We present a nanograting optical biosensor device, fabricated by photolithography, which is sensitive to changes in refractive index at the sensor surface. via changes in the reflectivity spectra. The grating was created by etching of a silicon nitride (Si3N4) film, which has a refractive index of 2.01, resulting in an array of Si3N4 pillars. The grating was coated by the high quality spin on glass material which has a low effective refractive index <1.50. The surface was functionalised with a layer of probe biomolecules for specific binding of the target DNA. Immobilization of the probe molecules was carried out via streptavidin – biotin interaction, the biotin modified ssDNA oligonucleotide probes were 23 bases in length (1010 copies/μl) and the sequence of the complementary ssDNA was 5’-TAC TCA TAC TTG AGG TTG AAA TT-3’(10, 100 and 1000 copies/μl). Results of the experiment showed that when molecules attached to the surface of the device, the position of the reflectance spectrum shifted due to the change of the optical path of light that is coupled into the nanograting structure. The extent of the wavelength shift (Δλ) of the peaks could be used to quantify the amount of materials bound to the sensor surface.

Photolithographic Process for Creating Micro-Grating on Silicon Substrate for Biosensor Application

In this work, we use photolithography in order to fabricate micro-grating structures on silicon. The first step of device was coated by 3.5 μm thick silicon dioxide (SiO2) film on top side, whereas the bottom side was coated with 4.5 μm. Next, we deposited silicon nitride (Si3N4) film of 2 μm by plasma-enhanced chemical vapor deposition, and used photolithography to prepare the gratings. We compared micro-grating period sizes of 1 μm, 0.8 μm and 0.5 μm, and found the 0.5 μm gave the best sensitivity. These devices can be applied with detection in biosensing in the future.

Optical Microarray Grating Biosensors

An optical biosensor based on a grating to be utilized for the detection of DNA target molecules was fabricated by photolithographic techniques. The sensor surface implements a grating to create a low effective refractive index platform via the combination of Si3N4 and SiO2 which allows the detection via changes of the reflectivity spectra. The active surface carried a layer of probe biomolecules for specific binding of the target DNA. Immobilization of the probe molecules was carried out via streptavidin using biotin modified ssDNA complementary to the target ssDNA. When molecules attached to the surface of the device, the position of the reflectance spectrum shifted due to the change of the optical path of light that is coupled into the grating structure. The extent of the wavelength shift of the peaks could be used to quantify the amount of materials bound to the sensor surface thereby allowing detection of the surface modifications as well as the quantification of the DNA analyte. The advantages of this device are that it works with a small sample volumes (few microlitres), are integratable in micro array type of setups and can be used at room temperature.

Predicting the UV Spectrum of Single Stranded DNA

A model was developed to predict the UV absorbance spectra and thus concentration of single stranded DNA (ssDNA) samples. The model was developed from UV absorbance spectra of ssDNA oligodeoxynucleotides determined at different concentrations. The model, which would predict the concentration of ssDNA from the A260 value, is shown to predict absorbance spectra of ssDNA as shown when compared to the experimental result.