Supanit Porntheeraphat

Blue photoluminescent carbon nanodots from limeade.

Carbon-based photoluminescent nanodot has currently been one of the promising materials for various applications. The remaining challenges are the carbon sources and the simple synthetic processes that enhance the quantum yield, photostability and biocompatibility of the nanodots. In this work, the synthesis of blue photoluminescent carbon nanodots from limeade via a single-step hydrothermal carbonization process is presented. Lime carbon nanodot (L-CnD), whose the quantum yield exceeding 50% for the 490nm emission in gram-scale amounts, has the structure of graphene core functionalized with the oxygen functional groups. The micron-sized flake of the as-prepared L-CnD powder exhibits multicolor emission depending on an excitation wavelength. The L-CnDs are demonstrated for rapidly ferric-ion (Fe(3+)) detection in water compared to Fe(2+), Cu(2+), Co(2+), Zn(2+), Mn(2+) and Ni(2+) ions. The photoluminescence quenching of L-CnD solution under UV light is used to distinguish the Fe(3+) ions from others by naked eyes as low concentration as 100μM. Additionally, L-CnDs provide exceptional photostability and biocompatibility for imaging yeast cell morphology. Changes in morphology of living yeast cells, i.e. cell shape variation, and budding, can be observed in a minute-period until more than an hour without the photoluminescent intensity loss.

Fabrication of a micro-direct methanol fuel cell using microfluidics

A direct-methanol fuel cell containing three parts: microchannels, electrodes, and a proton exchange membrane (PEM), was investigated. Nafion resin (NR) and polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (PS) were used as PEMs. Preparation of PEMs, including compositing with other polymers and their solubility, was performed and their proton conductivity was measured by a four point probe. The results showed that the 5 % Nafion resin has lower conductivity than the 5 % PS solution. The micro-fuel cell contained two acrylic channels, PEM, and two platinum catalyst electrodes on a silicon wafer. The assembled micro-fuel cells used 2 M methanol at the flow rate of 1.5 mL min−1 in the anode channel and 5 × 10−3 M KMnO4 at the flow rate of 1.5 mL min−1 in the cathode channel. The micro-fuel cell with the electrode distance of 300 μm provided the power density of 59.16 μW cm−2 and the current density of 125.60 μA cm−2 at 0.47 V.

Poly(methyl methacrylate) and thiophene-coated single-walled carbon nanotubes for volatile organic compound discrimination

Poly(methyl methacrylate) (PMMA) and thiophene-coated single-walled carbon nanotubes (SWNTs) were fabricated for use in volatile organic compound (VOC) detection. Pristine SWNTs were separately coated with PMMA (PMMA/SWNTs) and thiophene (thiophene/SWNTs) by spin-coating. Pristine SWNTs showed the highest response to methanol, while PMMA/SWNTs enabled 5.4-fold improved dichloromethane detection and thiophene/SWNTs enabled 1.4-fold improved acetone detection compared with pristine SWNTs. The sensor response of PMMA/SWNTs to dichloromethane and that of thiophene/SWNTs to acetone can be attributed to the Hildebrand solubility parameter (HSP). The more similar the HSP, the higher the sensor response. The sensor response of pristine SWNTs to methanol is related to the diffusion coefficient and molecular size. The relationships between the vapor concentration and sensor response of PMMA/SWNTs to dichloromethane and thiophene/SWNTs to acetone are based on Henrys adsorption isotherm, while that of pristine SWNTs to methanol is based on the Henry–clustering model. Principal component analysis (PCA) results show that dichloromethane, acetone, and methanol were successfully discriminated.

Fabrication of Low Cost Anodic Aluminum Oxide (AAO) Tubular Membrane and their Application for Hemodialysis

This paper reports the fabrication of AAO tubular membrane using 99.35% and 99.56% pure Al and their potential application for hemodialysis. Here we discussed the effect of impurity on membrane structure. We found that the self organized structure of AAO nanochannels minimizes impurity defects in membrane. If micro size impurity blocks the generation of nanochannels then the neighboring nanochannels bend and make branches to fulfill that gap. We observed that if impurity size is less than the AAO membrane thickness then it does not produce any micro size hole. In low grade Al the periodic hexagonal order was disturbed however there was no big difference in pore diameter. It was observed that such type of membrane do not have any leakage and it can be used for fluid filtration. The fabricated tubular membrane was used for hemodialysis successfully. The hemodialysis results show that AAO tubular membrane can be used for both diffusive and convective filtration

Oxygen Control on Nanocrystal-AlON Films by Reactive Gas-Timing Technique R.F. Magnetron Sputtering and Annealing Effect

The AlON films grown on Si(100) substrates by using radio frequency (r.f.) magnetron sputtering from high purity aluminum (99.999% Al) target with a novel reactive gas-timing technique. The 100 nm thick of AlON films were deposited with 200 watts r.f. power and the substrate temperature is maintained at room temperature by the technique of gas-timing which varying flow-in sequence of high purity of Ar (99.999%) and N2 (99.9999%) gases fed into the sputtering chamber at 10:90 (sec) ratio. The composition and crystal orientation of AlON films affected by gas-timing of Ar and N2 were analyzed by Auger Electron Spectroscopy (AES) and X-ray diffraction (XRD). The oxygen atoms revealed by AES formed into a corporation in films was studied. This suggests that the oxygen contamination formed as AlOXNY compound may due to the residual oxygen in base pressure of 10-7 mbar and higher reactivity of oxygen in the reactor compared to nitrogen. The gas-timing technique used in the sputtering growth system shows the advantage of the oxygen quantity control, while the general sputtering process (without gas-timing technique) shows an increase of the oxygen composition depended on film thickness. The characterizations results clearly indicate that the gas-timing r.f. magnetron sputtering technique plays an important role to control the incorporation of oxygen and to form the nanocrystal-aluminum oxynitride films which very attractive for various sensors applications.

ITO Thin Films prepared by Gas-Timing RF Magnetron Sputtering for Transparent Flexible Antenna

The transparent flexible plastic antenna was fabricated. Indium tin oxide (ITO) thin film was deposited on flexible plastic substrate at room temperature by radio frequency (RF) magnetron sputtering with a new technique, called gas-timing. By using the X-ray diffraction (XRD) measurement of the ITO thin film grown by this technique, a cubic nanocrystalline structure with predominant (222) orientation was observed. The technique of gas-timing we used, the ITO thin film on flexible substrate was achieved with high transmittance in visible region of 90% and low resistivity. The performance of the new film antenna was studied experimentally with its return loss and radiation patterns.

High Sensitive Nanocrystal Titanium Nitride EG-FET pH Sensor

Solid state pH-sensor device with high efficiency has successfully prepared by using TiN thin film as sensing membrane of extended gate field effect transistor (EG-FET) device. This research has described the physical properties and sensing characteristics of TiN membrane thin film which deposited on SiO2/Si substrate through reactive D.C. magnetron sputtering system. Thenanocrytal-TiNwith anatasestructure depended on substrate heating conditions was revealed from glancing angle x-ray diffraction. The IDS-VGS measurement in the standard buffer solutions showed that the sensitivity of fabricated TiN-EGFET pH deviceis 59.82mV/pH.

Fabrication of Thinner Anodic Aluminum Oxide Based Microchannels

When thickness of a membrane reduces its mechanical properties go down but thinner the membrane better the performance of the membrane in terms of filtration. In this research we fabricated a fluid filtration system with a very thin anodic aluminum oxide (AAO) membrane. The system consists of microchannels at one side of membrane while other side is flat. For both sides inlet and outlet are given. The system can facilitate two types of fluid to flow at two sides of membrane for filtration. The membrane thickness achieved was 4 μm. The average pore diameter was 50 nm. The nanopores inside the membrane are highly straight and perpendicular to the surface. The fabricated channel and wall width was 200 µm and 100 µm successively. The pillars in between microchannels hold the membrane which is termed as partial freestanding alumina (PFA) and thereby retain desired mechanical properties of the membrane. The system was tested for diffusion between DI water and salted water. The DI water was flowed in channels and salted water on other side of membrane. The pH value of DI water changed after flow. Due to channel walls, AAO membrane fabricated in this system can tolerate more pressure which leads it to be used for convective flow by applying higher pressure gradient.

Mobile-platform for automatic fever screening system based on infrared forehead temperature

In this paper, automatic fever screening system is proposed and experimentally implemented using an IR camera and a mobile phone. Our system locates position of patients automatically using face detection algorithm on RGB image and obtains temperature from IR image at detected location. Advantages are fast, portable, non-contacting and simultaneously temperature measurement. Furthermore, face detection algorithm allows the system to track patients face position. Hence, robust and non-contacting temperature measurement can be properly done even patients are not stand still. Our system has been field-tested to measure temperature and screen ill patients at a children medical clinic. In this experiment, the system is calibrated to measure temperature of patients at 1 meter away and gives an alarm sound when the measured temperature is above the desired setting threshold. According to experimental results, the correlation coefficient between temperature obtained from our system and commercial infrared forehead skin thermometer [2] is more than 0.80. In addition, our system achieves a 100% sensitivity and 70% specificity. Although our approach loses specificity, all fever patients are identified correctly. Thus, they are significantly correlated. Therefore, this system can reliably estimate body temperature of patients and can be used for effectively pre-screening fever patients.

Cl app: android-based application program for monitoring the residue chlorine in water

A farmer usually uses a cheap chemical material called chlorine to destroy the cell structure of unwanted organisms and remove some plant effluents in a baby shrimp farm. A color changing of the reaction between chlorine and chemical indicator is used to monitor the residue chlorine in water before releasing a baby shrimp into a pond. To get rid of the error in color reading, our previous works showed how a smartphone can be functioned as a color reader for estimating the chlorine concentration in water. In this paper, we show the improvement of interior configuration of our prototype and the distribution to several baby shrimp farms. In the future, we plan to make it available worldwide through the online market as well as to develop more application programs for monitoring other chemical substances.