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.

A new fluorescence chemical sensor for the determination of Cl-, Br-and I-has been successfully demonstrated. The membrane contains two fluorophores that display two largely different response spectra. The first fluorophore, N-(2-methacryloxyethyl) benzo[k,l]thioxanthene-3,4-dicarboximide (MBTD, benzothioxanthene derivative), used as referencewas halide-insensitive. The second fluorophore, quinine sulphate, used as sensitive carrier was halide-quenchable. Both were co-polymerized with acrylamide, hydroxyethyl methacrylate and triethylene glycol dimethacrylate onto glass surface. The fluorescence intensity of quinine decreased with increasing of halide concentration due to dynamic quenching, but the fluorescence intensity of MBTD was almost not affected by halide. Under these conditions, the halide-dependent fluorescence intensity of quinine was converted into a ratio of the two fluorescence intensities, which were expressed as a function of halide concentration. Satisfactory reproducibility, reversibility and a short response time were realized. The sensor also showed good selectivity, common ions and some organic species did not interfere with the measurement of halide. With the optimum membrane described, detection limits were of 2.2×10-4, 7.5×10-5 and 6.2×10-5 mol L-1 for Cl-, Br- and I-, respectively. The proposed method was applied to the determination of halide in earth samples. The sensing membrane was found to have a lifetime at least 2 months.

A fluorescence ratiometric sensor for pH determination is described in this paper. The sensor incorporated the pH-sensitive dye meso-5,10,15,20-tetra-(4-allyloxyphenyl)porphyrin (TAPP) as an indicator and a pH-insensitive dye N-(2-methacryloxyethyl)benzo[k,l] thioxanthene-3,4-dicarboximide (MBTD), a benzothioxanthene derivative, as a reference for fluorescence ratiometric measurement. To prevent leakage of the dyes, both were photocopolymerized with acrylamide, hydroxyethyl methacrylate, and triethylene glycol dimethacrylate on the silanized glass surface. The reproducibility and response time of the prepared sensor were sufficient. Most common coexisting inorganic ions and organic compounds did not interfere with pH sensing. In the acidic pH range from 1.5 to 5.0 the fluorescence intensity ratio of the two dyes varied linearly as a function of pH. The sensing membrane was found to have a lifetime of at least one month. The sensor was applied to the analysis of waste water and artificial samples.

To improve the stability of optochemical sensors (optodes), the fluorescence indicator 1-amino-4-allyloxyanthraquinone (AAA), which was synthesized by reacting allyl bromide with 1-amino-4-hydroxyanthraquinone, was covalently immobilized on surface-modified glass slides. The resulting sensor was used to determine the content of ornidazole based on fluorescence quenching. It showed a linear response toward ornidazole in the concentration range of 9.0×10-6 to 1.0×10-3 mol L-1 with a detection limit of 8×10-6 mol L-1 at pH 7.5. This AAA-immobilized sensor has a rapid response, high stability and good selectivity to ornidazole.

In a search for new type pH sensing fluorophores, the possibility of using the proton "off-on" switch behaviour of naphthalimide derivatives for optical pH sensor preparation has been explored. A new compound, N-allyl-4-(4A-methyl-piperazinyl)-1,8-naphthalimide (AMPN), was synthesized. The enhancement of fluorescence of AMPN with the increase of hydrogen ion concentration is based on arresting photo-induced electron transfer to the naphthalimide fluorophore from aliphatic amine group after its protonation. The Stokes Shift of the proposed type of pH sensing fluorophore is significantly larger than that of the fluorescein counterparts. To avoid the leakage of the fluorophore, AMPN was photo-copolymerized with 2-hydroxyethyl methacrylate and acrylamide on the glass surface. The fluorescence intensity of membrane contacted with a pH 3.50 buffer is 4.7 times of that for pH 12.00 buffer solutions. The proposed pH sensor is not susceptible to ionic strength and shows good selectivity, repeatability and short response time. The membrane shows a good stability with a lifetime over two months. The sensor can be used for the determination of pH in the range of pH 4.5-9.0, without interference of most commonly co-existing inorganic ions and some organic species. The sensor has been applied to the analysis of urine samples.

Carbazole is a promising pharmaceutical species. A novel optical sensor for determining doxycycline based on the fluorescence quenching of N-allylcarbazole immobilized on an quartz glass plate surface by covalent bonding has been described. The sensor shows satisfactory virtues in reversibility, repeatability, selectivity and sufficient lifetime resulting from its excellent optode membrane. Its response time is less than 60 s. The determination range and detection limit of the sensor are 6.0×10-7-2.0×10-3 M and 2.0×10-7 M, respectively. The lifetime of each sensor is at least three to four months. The sensor can be used for direct determination of doxycycline in pharmaceutical preparations and urine samples.