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Abstract: In this paper, 2-(2′-hydroxy-phenyl)-4(3H)-quinazolinone (HPQ), a typical compound that exhibits excited state intramolecular proton transfer (ESIPT) reaction and possesses good photophysical properties, is synthesized and used as fluoroionophore for Fe3+ sensitive optochemical sensor. The decrease of fluorescence intensity of HPQ membrane upon the addition of Fe3+ was attributed to the blocking of ESIPT reactions of HPQ and quenching its fluorescence. The effect of the composition of the sensing membrane was studied, and experimental conditions were optimized. The sensor shows a linear response toward Fe3+ in the concentration range of 7.1×10−7 M to 1.4×10−4 M with a limit of detection of 8.0×10−8 M, and a working pH range from 2.5 to 4.5. It shows excellent selectivity for Fe3+ over a large number of cations such as alkali, alkaline earth and transitional metal ions. The proposed sensor is applied to the determination of the content of iron ions in pharmaceutical preparations samples with satisfactory results. [Copyright &y& Elsevier]

Abstract: The design and synthesis of a porphyrin-appended terpyridine, 5-(4-([2,2′:6′,2″]-terpyridin-4-yl-carboxyamidyl)phenyl)-10,15,20-triphenylporphyrin (H2TPPTPy) and its application as potential fluoroionophore for recognition of metal ions are reported. For preparation of the fluoroionophore, a novel simple strategy with improved total yield has been applied for the synthesis of 2,2′:6′,2″-terpyridine-4′-carboxylic acid as a ligand. H2TPPTPy shows chelation-enhanced fluorescence effect with cadmium ion via the interruption of photoinduced electron transfer (PET) process, which has been utilized as the basis of the fabrication of the Cd(II)-sensitive fluorescent chemosensor. The analytical performance characteristics of the proposed Cd(II)-sensitive chemosensor were investigated. It shows a linear response toward Cd(II) in the concentration range of 3.2×10−6 to 3.2×10−4 M with a limit of detection of 1.2×10−6 M. The chemosensor shows good selectivity for Cd(II) over a large number of cations, such as alkali, alkali earth and transitional metal ions except Cu(II) and Zn(II). The sensor has been used for determination of Cd(II) in water samples with satisfactory recoveries. [Copyright &y& Elsevier]

Abstract: An electrochemical immunoassay technique has been developed based on the sensitive detection of the enzyme-generated product with a bi-electrode signal transduction system. The system uses two separate electrodes, an immunoelectrode and a detection electrode to form a galvanic cell to implement the redox reactions on two different electrodes, that is the enzyme-generated reductant in the anode region is electrochemically oxidized by an oxidant (silver ions) in the cathode apartment. Based on a sandwich procedure, after immunoelectrode with antibody immobilized on its surface bound with the corresponding antigen and alkaline phosphatase conjugated antibody successively, the immunoelectrode was placed in enzyme reaction solution and wired to the detection electrode which was immerged into a silver deposition solution. These two solutions are connected with a salt bridge. Thus a bi-electrode signal transduction system device is constructed in which the immunoelectrode acts as anode and the detection electrode serves as cathode. The enzyme bound on the anode surface initiates the hydrolysis of ascorbic acid 2-phosphate to produce ascorbic acid in the anode region. The ascorbic acid produced in the anodic apartment is electrochemically oxidized by silver ions coupled with the deposition of silver metal on the cathode. Via a period of 30min deposition, silver will deposited on the detection electrode in an amount corresponding to the quantity of ascorbic acid produced, leading to a great enhancement in the electrochemical stripping signal due to the accumulation of metallic silver by enzyme-generated product. Compared with the method using chemical deposition of silver, the electrochemical deposition of silver on a separate detection electrode apartment avoids the possible influence of silver deposition on the enzyme activity. [Copyright &y& Elsevier]

Abstract: A fluorescent chemical sensor for Hg(II) using 5,10,15-tris(pentafluorophenyl)corrole (H3(tpfc)) as fluorophore is described in this paper. The response of the sensor is based on the fluorescence quenching of H3(tpfc) by coordination with Hg(II). H3(tpfc) based sensor shows a linear response towards Hg(II) in the concentration range from 1.2×10−7 to 1.0×10−4 M, with a working pH range from 5.0 to 8.0. The response time for Hg(II) concentration ≤1.0×10−5 M is less than 5min. The sensor shows good selectivity for Hg(II) over alkali, and alkaline earth, and most of transition metal cations. The effect of the composition of the sensor membrane has been studied and the experimental conditions optimized. The corrole based sensor membrane can be easily regenerated just by washing with blank buffer solution after each measurement. The sensor has been used for determination of Hg(II) in water samples with satisfactory results. [Copyright &y& Elsevier]

Abstract: Development of fluorescent probes for Hg2+ has become a hot topic in modern chemical research due to its high toxicity. In this paper, we for the first time report the synthesis and application of a thioether spirocyclic rhodamine B derivative (TR) as an efficient fluorescent probe for Hg2+. TR was synthesized using a simple procedure under mild condition. By employing a thioether spirocycle instead of classic spirolactam as recognition unit, our proposed probe TR is acidity-insensitive, and exhibits a pH-independent and ultrasensitive response to Hg2+. The probe works well within a wide pH range from 3.5 to 11.5, and exhibits a 350-fold fluorescence enhancement upon 0.5equiv of Hg2+ triggered, with a detection limit of 2.5nM estimated for Hg2+. In virtue of the strong thiophilic characteristic of Hg2+, the response of the probe to Hg2+ is instantaneous and highly selective, which make it favorable for cellular Hg2+ imaging applications. It has been preliminarily used for highly sensitive monitoring of Hg2+ level in living cells with satisfying resolution, demonstrating its value of the practical applications in biological systems. [Copyright &y& Elsevier]

Abstract: A sensitive immunosensor using colloidal gold as electrochemical label is described. In this method, the capture protein was first immobilized on a carbon paste electrode surface through passive adsorption to bind quantitatively with corresponding antigen and colloidal gold labeled antibody to perform a sandwich assay. To detect the amount of the colloidal gold captured on the electrode surface, the colloid was first oxidized electrochemically to produce AuCl4 − ions which were adsorbed strongly on the electrode surface. Adsorptive voltammetry was then employed for the determination of the adsorbed AuCl4 − ions. A linear relationship between reduction wave peak current and the antigen concentration (human IgG) from 10 to 500ng/ml is obtained with a detection limit of 4.0ng/ml. [Copyright &y& Elsevier]