[Study on the inclusion behavior of cucurbit [7] uril with methylene blue by spectrofluorometric titrations].

The characteristics of host-guest complexation between cucurbit [7] uril (CB7) and methylene blue (MB) were investigated by fluorescence spectrometry in acetate buffer solution at room temperature. It was found that the fluorescence intensity of methylene blue regularly increased upon the addition of cucurbit [7] uril accompanying with a blue-shift of the position of the emission maximum. The results indicate the formation of complex between CB7 and MB at a 1 : 1 complex stoichiometry and the association constant was calculated by applying a deduced equation. 1H NMR spectra were applied to to complement the fluorescence work to verify the formation of the complex. From the temperature dependence of the equilibrium constants, thermodynamics parametersH andS values were obtained, indicating an enthalpic driving force for complexation. The possible interaction mechanism was also discussed. This work may extend the application range of cucurbit [7] uril in biochemistry and pharmaceutical analysis.

A one-dimensional ladder-like coordination polymer: poly[[hexa-aqua-bis(µ-5-nitro-benzene-1,3-dicarboxyl-ato-κO,O',O'')(µ-oxalato-κO,O':O'',O''')diyttrium(III)] trihydrate].

In the crystal structure of the title one-dimensional coordination polymer, [Y(2)(C(8)H(3)NO(6))(2)(C(2)O(4))(H(2)O)(6)]·3H(2)O, each Y(III) ion is bridged to its neighbours by two 5-nitro-benzene-1,3-dicarboxyl-ate (nbdc) dianions and one oxalate dianion (located on an inversion centre) to form a ladder-like polymeric structure. The two carboxylate groups of nbdc assume different modes of coordination, one is chelating whereas the other is monodentate. Three water mol-ecules coordinate to the Y(III) ion to complete an eight-coordinate distorted dodecahedral geometry. The ladder-like polymers are assembled together by hydrogen bonding and π-π stacking [centrio-centriod distance = 3.819 (9) Å] in the crystal structure.

[Preparation and fluorescence properties of calix[4]arene nanoparticle].

Novel organic nanoparticles of calix[4]arene (CN) were prepared by the reprecipitation method under sonication and vigorous stirring. The nanoparticles showed an average diameter of 40 nm characterized by transmission electron microscopy. It was found that the nanoparticles exhibited better fluorescence compared with that of monomer. In weak acidic medium, the relative fluorescence intensity of these nanoparticles could be quenched remarkably with the addition of appropriate amounts of Fe3+. Based on the obtained results, a novel fluorimetric method has been developed for the rapid determination of Fe3+. Under optimal conditions, the linear range of calibration curves was 1.0 x 10(-6) - 2.4 x 10(-5) mol x L(-1) and the detection limit was 3.0 x 10(-7) mol x L(-1). The proposed method was applied to determine Fe3+ in water samples with satisfactory recovery and relative standard deviation.

[Study on the inclusion behavior of p-sulphonatocalix[4]arene with acridine by spectrofluorometric titrations].

p-sulphonatocalix[4] arene (1) was prepared according to the literature, and spectrofluorometric titrations were performed to investigate the inclusion behavior of (1) and acridine in citrate buffer solution (pH 5.92, 0.1 mol x L(-1)) at different temperatures. It was found that in definite concentration range, the emission peak of acridine exhibited a slight red shift and th fluorescence intensity decreased when (1) was added. They form stable host-guest complex, and the stoichiometry of the inclusion complex is 1 : 1. The stability constants of the inclusion complex at 15.0 degrees C, 20.0, 25.0 and 30.0 degrees C were determined as 3.08 x 10(5), 4.45 x 10(4), 2.58 x 10(4) and 8.90 x 10(3), respectively. The thermodynamic parameters of inclusion process, deltaG, deltaH and deltaS, were determined. The experimental results indicated that the inclusion process was an exothermic and enthalpy-driven process. It was found that the stability constants descended when temperature rose. The most probable pattern of the inclusion complex between (1) and acridine was proposed as: acridine partially goes into the cavity of (1), and the protonated N atom and the negatively charged sulphonyl group bond firmly owing to strong electrostatic interaction. With the main contribution of electrostatic interaction and the assistance of Van de Waals and hydrophobic interaction, the host and the guest molecules form 1 : 1 supramolecular complex.

[Highly sensitive spectrofluorimetric determination of trace amounts of chromium (VI) with mono[6-o-(4-aminobenzoic acid)]-beta-cyclodextrin].

A novel fluorescence probe, mono[6-o-(4-aminobenzoic acid)]-beta-cyclodextrin(ACD), was synthesized, and a new sensitive fluorescence identification reaction was studied based on the reaction of Cr2O7(2-) with compound ACD in NaAc-HAc buffer medium at pH 4.90. Under optimal conditions the determination limit was 1.26 microg x L(-1). The linear range was 5.20-1040 microg x L(-1). This method has been applied to the determination of trace amounts of chromium (VI) in electroplating liquor, electroplating waste water with satisfactory results.

[Highly sensitive spectrofluorimetric determination of trace amounts of nitrite with N-(1-naphthyl) ethylenediamine].

A simple and sensitive fluorescence quenching method for the determination of trace nitrite was developed. The method is based on the reaction of NED with nitrite in acidic medium to form a new compound, which has weak fluorescence. The linear range was 1.07-214.0 microg x L(-1) with a 3sigma detection limit of 0.069 microg x L(-1) under the optimum experimental conditions. This proposed method has been applied to the determination of trace amounts of NO2- in tap water and lake water without extraction.

A novel spectrofluorometric method for the determination of methiocarb using an amphiphilic p-sulfonatocalix[4]arene.

The characteristics of host-guest complexation between tetrabutyl ether derivatives of p-sulfonatocalix[4]arene (SC4Bu) and methiocarb [3,5-dimethyl-4-(methylthio) phenyl methylcarbamate] were investigated by fluorescence spectrometry. Upon addition of methiocarb, the fluorescence intensity of SC4Bu was quenched regularly and a slight red shift was observed for the maximum emission peak. These results indicated that the SC4Bu-methiocarb complex was formed a 1:1 mole ratio. An association constant of 1.67×10(4) L mol(-1) was calculated by applying a deduced equation. The interaction mechanism of the inclusion complex was discussed. Based on the results, a novel spectrofluorimetric method was described for the determination of methiocarb with a detection limit at 0.05 µg mL(-1). This method is very simple and shows high sensitivity and selectivity. Moreover, the proposed method was successfully applied to the determination of methiocarb in water samples.

Application of L-cysteine-capped nano-ZnS as a fluorescence probe for the determination of proteins.

Nanometer-sized L-cysteine-capped ZnS particles have been synthesized and used as a fluorescence probe to investigate the effect of proteins on fluorescent intensity. With Delta lambda=190 nm, maximum and constant synchronous fluorescence enhancement was produced at 267 nm and pH 5.12 in the presence of proteins. A highly sensitive synchronous fluorescence method for the rapid determination of proteins has been developed. Under optimum conditions, calibration graphs are linear over the range 0.03-8.0 microg mL(-1) for bovine serum albumin (BSA), 0.01-6.0 microg mL(-1) for human serum albumin (HSA), 0.05-8.0 microg mL(-1) for gamma-globulin (gamma-G), and 0.04-4.0 microg mL(-1) for ovalbumin, respectively. The relative standard deviations of seven replicate measurements were 1.75% for 1.0 microg mL(-1) BSA, 1.90% for 1.0 microg mL(-1) HSA, 1.65% for 1.0 microg mL(-1) gamma-G, and 2.32% for 1.0 microg mL(-1) ovalbumin.