Amorphous titanium dioxide $\left({\mathrm{TiO}}_2\right)$ thin films doped with rhodamine 6G (R6G) were deposited on glass substrates by the sol-gel process. The optical properties of the films were characterized by photoacoustic, excitation, and fluorescence spectroscopies. The absorption spectra of the R6G-doped ${\mathrm{TiO}}_2$ films exhibited two well-defined absorption regions: an absorption band over 2.0 eV attributed to rhodamine 6G and a band above 3.0 eV corresponding to ${\mathrm{TiO}}_2$ absorption. While the onset of the R6G absorption band was shifted by 0.06 eV towards lower energies as the R6G doping concentration increased within the interval of 0.01–0.10 mol %, the onset to high absorption (${\mathrm{TiO}}_2$ band) for the doped films decreased only by 0.01 eV within the same interval. In addition, the optical absorption of undoped rutile-phase bulk ${\mathrm{TiO}}_2$ was calculated and compared to the experimental results. The estimated theoretical value of rutile ${\mathrm{TiO}}_2$ sample was 3.0 eV. This theoretical result shows good agreement when compared with the experimental data of undoped ${\mathrm{TiO}}_2$ sol-gel films, as well as the undoped ${\mathrm{TiO}}_2$ film prepared by sputtering.

An ultraviolet (UV) light induced fluorescence study to discriminate fake tequila from genuine ones is presented. A portable homemade system based on four light emitting diodes (LEDs) from 255 to 405 nm and a miniature spectrometer was used. It has been shown that unlike fake and silver tequila, which produce weak fluorescence signal, genuine mixed, rested, and aged tequilas show high fluorescence emission in the range from 400 to 750 nm. The fluorescence intensity grows with aging in 100% agave tequila. Such fluorescence differences can even be observed with naked eyes. The presented results demonstrate that the fluorescence measurement could be a good method to detect counterfeit tequila.

Journal de Physique IV, Journal de Physique Archives représente une mine d informations facile à consulter sur la manière dont la physique a été publiée depuis 1872.