RESUMO
In this work, we present a Fabry-Perot interferometer (FPI) based on a polymer microtip for water content determination in both the gas and liquid phase. The polymer tip of pentaerythritol triacrylate (PETA) is fabricated at the end of an optical fiber by self-guiding photopolymerization, forming at the same time a low-fineness Fabry-Perot interferometer and a sensing layer for water thanks to hydroxyl groups present in PETA. The PETA tip shows a clear interferometric signal, which is highly sensitive to the change of the water content in the environment. The FPI signal shifts with a constant sensitivity of 90 pm/%RH, which corresponds to a relative sensitivity of 104 ppm/% RH, in the range of relative humidity from 30 to 80%. In liquid, the FPI sensor shows a nonlinear sensitivity, up to 158 pm/wt % as the water content is below 40 wt % in water/glycerol mixtures. The cross effect of the temperature on the PETA tip is demonstrated to be negligible as the FPI signal is insensitive to temperature changes from 23 to 70 °C. More importantly, the interaction between the tip and the environment affecting the FPI signal is demonstrated experimentally. The proposed FPI sensor is therefore promising for the direct, sensitive, and reliable determination of the water content of products.
RESUMO
In this paper, silver (Ag) nanoclusters-loaded graphitic carbon nitride (g-C3N4) nanosheets are synthesized and their physical properties as well as photocatalytic activities are systematically investigated by different techniques. The existence of Ag atoms in the form of nanoclusters (NCs) rather than well-crystallized nanoparticles are evidenced by X-ray diffraction patterns, SEM images, and XPS spectra. The deposition of Ag nanoclusters on the surface of g-C3N4 nanosheets affect the crystal structure and slightly reduce the band gap energy of g-C3N4. The sharp decrease of photoluminescence intensity indicates that g-C3N4/Ag heterojunctions successfully prevent the recombination of photo-generated electrons and holes. The photocatalytic activities of as-synthesized photocatalysts are demonstrated through the degradation of rhodamine B (RhB) solutions under Xenon lamp irradiation. It is demonstrated that the photocatalytic activity depends strongly on the molar concentration of Ag⺠in the starting solution. The g-C3N4/Ag heterojunctions prepared from 0.01 M of Ag⺠starting solution exhibit the highest photocatalytic efficiency and allow 100% degradation of RhB after being exposed for 60 min under a Xenon lamp irradiation, which is four times faster than that of pure g-C3N4 nanosheets.
