Monitoring the gases released during breathing or via the skin has gained significance towards diagnosing diseases. In this study, a sensor chip capable of detecting nonanal gas, which is known to be a marker of lung cancer, was developed. The gas detection agent used was vanillin, which underwent aldol condensation with nonanal in the presence of a basic catalyst, resulting in the formation of an unsaturated aldehyde. Porous glass was used as the reaction field to carry the detection agent. Alkali-resistant porous glass was chosen because conventional porous glasses show low durabilities under basic conditions, as they primarily consist of SiO 2 . Nonanal can be detected through changes in the absorption spectrum of the sensor. An accumulatetype sensor was used in this study, which exhibited a linear relationship between the degree of absorption changes at 470 nm and nonanal concentration in the 60 ppb-1.3 ppm range. Therefore, this biological marker gas sensor is effective for the early diagnosis of diseases. The alkali-resistant porous glass sensor chip exhibited a higher degree of absorption change than the conventional porous glass sensor chip.

In this paper, we evaluated the Ag concentration dependence of the build-up effect of radiophotoluminescence (RPL) in Ag-doped P 2 O 5 -Al 2 O 3 -Na 2 O-SiO 2 (PANS) glasses. After X-ray irradiation, the Ag-doped PANS glasses showed two emission peaks at around 460 and 630 nm, assigned to blue and orange RPL components, respectively. The build-up curves of the orange RPL component had two components corresponding to the formation of the + 2 Ag dimer and Ag 2+ ions. The intensity of the component due to the + 2Ag dimer increased with increasing Ag concentration, whereas that of the component due to Ag 2+ ions decreased. It is assumed that at a high Ag concentration, the Ag + ions have a higher probability of diffusing to Ag 0 sites to form the + 2 Ag dimer because the average distance between neighboring Ag atoms in the glass structure decreases with increasing Ag concentration. Therefore, the intensity of the component due to the + 2 Ag dimer was dominant at a high concentration of Ag in the glass structure.

No abstract

To obtain glass membrane electrodes selective for anions and metal ions, pH electrode glass membranes were modified by a sol-gel method using a quaternary ammonium salt and a bis(crown ether). A chloride ion-sensing glass membrane was designed, in which a pH electrode glass membrane was modified chemically by an alkoxysilyl quaternary ammonium chloride. X-ray photoelectron spectroscopy confirmed the chemical bonding of the quaternary ammonium moiety to the starting glass surface, which afforded the first example of glass-based "anion"-sensing membranes. A neutral carrier-type sodium ion-selective glass membrane was also fabricated which encapsulates a bis(12-crown-4) derivative in its sol-gel-derived surface. Both sol-gel-modified anion and metal ion-selective glass electrodes exhibited high sensitivity to their ion activity changes. The present sol-gel modification paves the way for designing glass-based ion sensors with tailor-made ion selectivities toward anions as well as cations.

No abstract