A fluorescent dye, 9-anthraldehyde-thiosemicarbazone (AnthT), used for the determination of Cu(Ⅱ) or Hg(Ⅱ) in aqueous solutions, is described. The fluorescence intensity of the probe decreased with increasing concentration of Cu(Ⅱ) or Hg(Ⅱ), and was proportional to a certain concentration of Cu(Ⅱ) or Hg(Ⅱ). The prepared sensing system presented satisfactory sensitivity and low detection limits. The developed method was successfully employed for preliminary application in natural water and domestic sewage.

A new fluorescent dye, N-allyl-4-morpholinyl-1, 8-naphthalimide (AMN), was synthesized as a fluorescence indicator in the fabrication of a sensor for determining water content in organic solvents. To prevent leakage of the fluorophore, AMN was photo-copolymerized with acrylamide, (2-hydroxyethyl)methacrylate, and triethylene glycol dimethacrylate on a glass surface treated with a silanizing agent. The sensing mechanism is based on the solvatochromic feature of the covalently immobilized AMN. The fluorescence intensity of AMN decreased with increasing water contents when it was excited at 400 nm. In the range of ca. 0.00-4.40% (v/v), the fluorescence intensity of AMN changed as a linear function of water content. The sensor exhibited satisfactory reproducibility, reversibility, and a response time (t99) of the order of 50 s. The detection limit was solvent-dependent, when acetonitrile was used as the solvent, and the detection limit could be as low as 0.006% (v/v) of water. Additionally, the prepared sensor is pH-insensitive and possesses a relatively long lifetime of at least one month

A new fluorescence sensor for determining water content in organic solvents has been successfully demonstrated based on a fluorescent dye. 4′-N, N-dimethylamino-4 methylacryloylamino chalcone (DMC), in which the charge donor and acceptor parts were both contained, was copolymerized with acrylamide, hydroxyethyl methacrylate and triethylene glycol dimethacrylate onto glass surface. The fluorescence intensity of DMC decreased with increasing of water content in organic solvents owing to the formation of solvate complexes. DMC fluorescence intensity changed as a linear function of water content in the range of 0-6% in the samples of acetone, ethanol, and acetonitrile solutions. Satisfactory reproducibility, reversibility and a short response time were realized. With the optimum membrane described, detection limits were of 0.006%, 0.008%, and 0.002% for acetone, ethanol, and acetonitrile, respectively. The sensing membrane was found to have a lifetime at least 2 months.

Two compounds with a terminal double bond, N-allyl-4-piperazinyl-1,8-naphthalimide (APN) and N-(2-methacryloxyethyl)benzo [k,l]thioxanthene-3,4-dicarboximide (MBTD), a benzothioxanthene derivative, have been synthesized as fluorophores for hydrogen ions sensing. To avoid the leakage of the fluorophores, the APN (a pH-sensitive carrier) and MBTD (a pH-insensitive carrier) which served as a referencing fluorophore were co-polymerized with acrylamide, hydroxyethyl methacrylate and triethylene glycol dimethacrylate on the glass surface treated with a silanizing agent. The ratiometric method can offset the influence caused by the external environment and instrument conditions and can improve the measuring precision. The fluorescence enhancement of APN with an increase in hydrogen ions concentration is based on the hindering of photo-induced electron transfer from aliphatic amine group to the napthalimide after its protonation. The proposed pH sensor shows sufficient selectivity, repeatability and short response time. The sensing membrane shows a good stability with a lifetime of at least 1 month. The sensor can be used for the determination of pH between 5.80 and 8.80. Most commonly co-existing inorganic ions and some organic species do not interfere with the determination of pH. The sensor has been applied to the analysis of water and soil samples.

An aminobenzanthrone Schiff base has been synthesized as a new fluorescence carrier for the preparation of an optical chemical sensor for iodine. The response of the sensor is based on fluorescence quenching of the aminobenzanthrone Schiff base by iodine. The sensor shows a linear response toward iodine in the range of 1.0×10-5 to 1.0×10-3 mol l-1, with a detection limit of 6.0×10-6 mol l-1 at pH 8.0. Leaching of the fluorophore from the membrane is effectively hindered by covalent immobilization, resulting in an enhanced sensor lifetime. In addition to satisfactory reproducibility and reversibility, the prepared sensor exhibits sufficient selectivity toward iodine with respect to other coexisting ions. The sensor has been applied to the determination of iodine in common salt samples.