Effect of humidity on the fluorescence properties of a medium- sensitive fluorophore in a hydrophilic polymer film

✍ Scribed by Soichi Otsuki; Kimihiro Adachi

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 464 KB
• Volume: 71
• Category: Article
• ISSN: 1010-6030
• DOI: 10.1016/1010-6030(93)85069-k

✦ Synopsis

The fluorescence characteristics of 5dimethylaminonaphthalene-l-sulphonic acid (DNSA) were examined in a hydroxypropylcellulose (HPC) film as a function of the surrounding relative humidity (RH). When the RH changed from 0% to 87%, a red-wavelength shift in the maximum fluorescence wavelength (A_) from 435 to 465 nm was observed, accompanying a decrease in the maximum fluorescence intensity. A plot of A,, against the water concentration in the film at different RHs was approximately linear, indicating that the A,, of DNSA can be used as a measure of the water vapour uptake in the film. Since the relative intensity at a fixed wavelength of 418 nm showed a monotonic decrease with increasing RH, the DNSA-HPC film can be applied as an optical RH sensor. Kinetic studies clarified that the response of the relative intensity to abrupt RH changes followed a first-order rate law. A small reduction in the fluorescence intensity of DNSA was found after repeated humidification and desiccation of the film, suggesting increasing association of the dye in the film during these processes.