Kazutoshi Noda

Preparation of a sensor device with specific recognition sites for acetaldehyde by molecular imprinting technique

In order to prepare a quartz crystal microbalance (QCM) sensor device with an acetaldehyde-imprinted polymer layer, methyl methacrylate and ethylene dimethacrylate were polymerized with lauroyl peroxide in chloroform containing acetaldehyde. This resulted in the formation of a polymer layer having a recognition side for the acetaldehyde on the quartz crystal oscillator. When an acetaldehyde aqueous solution was dropped into the solution in which the sensor is immersed, good sensitivity and response were observed. The good selectivity was also proved by testing the sensor in an acetone, chloroform or trichloroethane aqueous solution.

Measurement of methane gas concentration by detecting absorption at 1300 nm using a laser diode wavelength-sweep technique

We develop a simple piece of equipment for measuring methane (CH4) gas concentration based on IR absorption by sweeping the wavelength of light emitted from a laser diode (LD). The principle of IR absorption enables the selective measurement of CH4 gas by detecting an absorption line that appears around 1300 nm in the specific absorption spectrum of CH4. Our method is simpler and more user-friendly than existing measurement methods that involve a measurement system equipped with a cell filled with a known concentration of CH4 gas and a lock-in amplifier. The results of measurements using 220- and 660-mm measurement cells show that CH4 gas concentration is proportional to absorbance within a concentration range of 5 to 90 vol %. It is also found that our measurement system can selectively measure only the concentration of CH4 in city gas, which is composed of a mixture of flammable gases. Moreover, a simple technique for removing humidity using silica gel and calcium chloride reduces the influence of relative humidity. These results represent performance superior to other CH4 measurement methods currently in use.

Measurement of methane gas concentration using an infrared LED

This paper describes a simple method to measure methane (CH4 ) gas concentration using an infrared LED (wavelength=1.6 mum). Recently, CH4 based natural gas is increasingly being used for city gas. However, CH4 gas is hazardous to gas explosion, so that accurate and convenient concentration sensors of CH4 are required. We have developed an infrared absorption system for measurement of CH4 gas concentration. Our method is simpler and more user-friendly than existing measurement methods. The gas concentration is associated with the absorption, the optical path length and the absorption intensity. CH4 molecule has absorption bands in the infrared region (near 1.3 mum, 1.6 mum, 3.3 mum and 7.6 mum) and the infrared LED can access the CH4 absorption band in the wavelength region of 1.6 mum. For the purpose of development of concentration sensor of CH4 gas, examination about the sensing property of absorption of CH4 by the difference of its concentration is performed, and it reports briefly

Investigation of a sterilization system using active oxygen species generated by ultraviolet irradiation.

We have been investigating an advanced sterilization system that employs active oxygen species (AOS). We designed the sterilization equipment, including an evacuation system, which generates AOS from pure oxygen gas using ultraviolet irradiation, in order to study the conditions necessary for sterilization in the systems chamber. Using Geobachillus stearothermophilus spores (10(6) CFU) in a sterile bag as a biological indicator (BI) in the chamber of the AOS sterilization apparatus, we examined the viability of the BI as a function of exposure time, assessing the role of the decompression level in the sterilization performance. We found that the survival curves showed exponential reduction, and that the decompression level did not exert a significant influence on the survival curve. Subsequently, we investigated the sterilization effect as influenced by the spatial and environmental temperature variation throughout the chamber, and found that the sterilization effect varied with position, due to the varying environmental temperature in the respective areas. We confirmed that temperature is one of the most important factors influencing sterilization in the chamber, and estimated the temperature effect on the distribution of atomic oxygen concentration, using the quartz crystal microbalance (QCM) method with fluorocarbon thin film prepared by radio frequency sputtering.

Evaluation of Vacuum Ultraviolet Irradiation Influence under Xenon Excimer Lamp Processing Employing a Quartz Crystal Microbalance with Organic Thin Film

The xenon excimer lamp, which emits vacuum ultraviolet radiation, is frequently used as a dry cleaning device for objects such as flat-panel displays (FPDs). UV dry cleaning processes are generally monitored with UV illuminometers, however these do not detect the direct influence of the cleaning process on the substrate. Therefore, a monitoring method that focuses on the treated substrate is required. In this study, we investigated a method to evaluate VUV influence under xenon excimer lamp processing, using a quartz crystal microbalance technique which can detect very small changes in mass. With an organic (fluorocarbon) thin film as the detecting element of the quartz crystal microbalance, we have investigated mass change through irradiation with a xenon excimer lamp, in nitrogen, oxygen, and air atmosphere, respectively. It was confirmed that mass change increased linearly with time, under all conditions, and that monitoring of VUV influence was possible by means of the quartz crystal microbalance method using fluorocarbon thin film.

Adsorption Properties of Thin Films Prepared by RF Sputtering with a Poly(biphenyltetracarboxylic dianhydride–paraphenylene diamine) Polyimide Target

Thin films were deposited onto a quartz crystal with a poly(biphenyltetracarboxylic dianhydride–paraphenylene diamine) (BPDA–PDA) polyimide target by RF sputtering, and the adsorption properties of these thin films for water, ethanol, acetone, acetaldehyde, toluene, and methyl salicylate were evaluated by the quartz crystal microbalance (QCM) method to characterize the surface properties of these thin films. Chemical structures, especially surface free energies of these thin films would affect the gas adsorption properties. In addition, the number of adsorbed gas molecules increased with decreasing molecular weight on each sputtered thin film. Furthermore, these gas molecules would be adsorbed inside the sputtered thin films as well as on the top surface. The number of adsorbed gas molecules increased with decreasing molecular size on each sputtered thin film.

Gas Adsorption Properties of Fluorocarbon Thin Films Prepared Using Three Different Types of RF Magnetron Sputtering Systems

Fluorocarbon thin films were deposited onto a quartz crystal with a poly(tetrafluoroethylene) target using three different types of RF magnetron sputtering systems with strong, weak, and unbalanced magnetic fields. The adsorption properties of these thin films for water, ethanol, acetone, acetaldehyde, toluene, and methyl salicylate were evaluated using the quartz crystal microbalance (QCM) method in order to characterize the surface properties of these thin films. These thin films have low sensitivities to non-polar solvents that contain methyl and aromatic groups, and high sensitivities to polar solvents that contain carbonyl and hydroxyl groups. Chemical structures, especially, polar moieties in these fluorocarbon thin films would affect the gas adsorption properties.

Rapid detection of fibrinogen and fibrin degradation products by latex piezoelectric immunoassay

It was developed a conventional immunosensor for fibrinogen and fibrin degradation products (FDP) to combine a quartz crystal microbalance (QCM) with the agglutination reaction of immunized latex beads. We successfully measured FDP concentration of in human serum within 10 min by QCM method. The detection range of QCM immunosensor is covered with screening concentration of FDP in serum (less than 10 /spl mu/g/ml of FDP). The time course of latex agglutination obtained from QCM immunosensor is synchronized to that of latex photometric immunoassay. Frequency shift on immunoreaction explains the increased adsorption amount of agglutinated latex on QCM.