铕-吡啶二酸配合物的合成、表征和溶液中发光性能

合成了一种新的以TTA(а-噻吩甲酰三氟丙酮)、H₂bpdc(2,2'-联吡啶-3,3'-二羧酸)为配体,单一稀土Eu³⁺的三元配合物。通过元素分析、差热分析、红外光谱、紫外光谱、发光光谱对其进行了表征。发现在中性和弱碱性条件下配合物在醇-水溶液中的发射光谱表现出较强的Eu³⁺离子的特征发射,且Eu³⁺离子的发光强度随pH值改变发生变化,可作为生物医学和食品检测用pH敏感的荧光探针。     

Overcoming matrix interferences in ion-exchange solid phase extraction of As, Cr, Mo, Sb, Se and V species from leachates of cement-based materials using multiple extractions

Solid phase extraction (SPE) methods based on multiple extractions have been developed to overcome matrix interferences in the charge-based fractionation analysis of As, Cr, Mo, Sb, Se and V leached from cement-based materials. Disposable SPE tubes packed with 500 mg strong anion-exchange (SAX) or strong cation-exchange (SCX) sorbents were used to extract the anionic and cationic species of the elements, respectively. The multiple extractions were based on the percolation of a small sample volume (5.0 mL) through a series of identical ion-exchange tubes. For most of the elements, more than 90% of the anionic species were extracted from a sample containing up to 16 g L⁻¹ NO₃⁻ by passing the aliquot through five identical SAX tubes. Percolating a sample aliquot through three identical SCX cartridges gave more than 99% retention for Cr(III) from leachates containing a high concentration of interfering metal cations. The anionic and cationic analytes showed only slight non-specific adsorption on the SCX and SAX sorbents, respectively, except for V(V) on the SCX sorbent. A condition was established for the quantitative elution of the retained analytes from the ion-exchange sorbents with 1.0 mol L⁻¹ HNO₃. The multiple ion-exchange SPE procedures were validated using spike recovery tests. The methods were used to determine the anionic and cationic fractions of the target elements in concrete leachates covering a broad range of pH (3.8-13.4). The elements were found to exist predominantly as anions in the alkaline and neutral leachates. A high fraction (85%) of cationic Cr was detected in the most acidic leachate (pH 3.8).     

Amphiphilic urethane acrylate hydrogels having heterophasic gel structure: swelling behaviors and mechanical properties

 Amphiphilic urethane acrylate hydrogels containing ionic group (dimethylopropionic acid, DMPA) were prepared by varying the molecular weight of the soft segment (polyether type, PTMG) and type of diisocyanate, and their swelling behaviors and mechanical properties were examined. They showed amphiphilic property due to the hydrophilic ionic groups and hydrophobic polyethers comprising the urethane acrylate network. Heterophasic gel structure could be found for the hydrogels prepared in water, but not for the hydrogels in organic solvent (1,4-dioxane), through scanning electron microscopy. Because of this heterophasic gel structure, they were able to take in a large amount of water as well. The hydrophobic interaction generated by the polyether soft segments between urethane acrylate network chains decreased the degree of swelling, however, increased reversibly the tensile strengths at equilibrium swelling state. MDI-based hydrogel showed low swelling ratio and high tensile strength because of its ordered hard domain structure. These amphiphilic urethane acrylate hydrogels showed salt- and pH-dependent swelling behaviors. Received: 26 September 1997 Accepted: 24 December 1997     

pH-dependent cytotoxic effects of extracts of the marine sponge Polymastia janeirensis on cancer cell lines

The purpose of this work was to study the cytotoxic effects of marine sponge Polymastia janeirensis, which has been observed in the field to release an orange substance that is toxic to fish. The result showed that aqueous extract (pH 7.0) was highly cytotoxic to glioma (U87) and neuroblastoma (SHSY5Y) cancer cell lines (IC₅₀ < 1.0 μg/mL). In addition, this extract showed potent antioxidant and procoagulant (decreased the clotting time by 1.7-fold) activities. Interestingly, the cytotoxic effects were pH-dependent since the viability of the cancer cells was not affected with the extract (pH 5.5). The close similarity between the aqueous extract (pH 7.0) and the orange liquid that is released by the sponge indicates that this potential chemical defence of P. janeirensis deserves further investigation.     

Self-nanoemulsifying drug delivery system for adefovir dipivoxil: Design, characterization, in vitro and ex vivo evaluation

Adefovir dipivoxil (ADV) is an anti-viral drug having low bioavailability due to low permeability and pH dependent solubility. In this study, self-nanoemulsifying drug delivery systems (SNEDDS) of ADV were developed with the objective of increasing its bioavailability by enhancing its intestinal permeability and minimizing the effect of pH. Preliminary screening was carried out to select oil, surfactant and co-surfactant. Ternary phase diagrams were constructed to identify the area of nanoemulsification. The nanoemulsion system selected from the phase diagram was transformed into solid-SNEDDS (S-SNEDDS) by lyophilization using D-mannitol as cryoprotectant. The formulations were characterized for transmittance, globule size, polydispersity index, zeta potential, cloud point, robustness to dilution, effect of pH and temperature, microscopic properties, in vitro and ex vivo drug release parameters. The liquid SNEDDS (L-SNEDDS) showed mean globule size of 110 ± 10 nm while mean globule size of 150 ± 16 nm was obtained with S-SNEDDS. The formulations were found to be robust to dilution and showed cloud point at 80-85 °C. TEM and SEM studies of nanoemulsion reconstituted from S-SNEDDS demonstrated the spherical shape and size of the globules. Results of DSC and XRD studies confirmed that the drug was incorporated in the S-SNEDDS. No significant difference was observed in the globule size within physiological variations of pH and temperature. The in vitro and ex vivo drug release from ADV SNEDDS was found to be significantly higher in comparison to that from plain drug suspension, irrespective of pH. Thus, SNEDDS were found to be instrumental in reducing the effect of pH variability of ADV and improving the release performance of ADV, indicating their potential to improve the oral bioavailability and thus the therapeutic efficacy of ADV.     

Multivariate optimization and simultaneous determination of hydride and non-hydride-forming elements in samples of a wide pH range using dual-mode sample introduction with plasma techniques: application on leachates from cement mortar material

Analytical methods have been developed for the simultaneous determination of hydride-forming (As, Sb) and non-hydride-forming (Cr, Mo, V) elements in aqueous samples of a wide pH range (pH 3–13). The methods used dual-mode (DM) sample introduction with ICP-AES and ICP-MS instruments. The effect of selected experimental variables, i.e., sample pH and concentrations of HNO₃, thiourea, and NaBH₄, were studied in a multivariate way using face-centered central composite design (FC-CCD). Compromised optimum values of the experimental parameters were identified using a response optimizer. The statistically found optimum values were verified experimentally. The methods provided improved sensitivities for the hydride-forming elements compared with the respective conventional nebulization (Neb) systems by factors of 67 (As) and 64 (Sb) for ICP-AES and 36 (As) and 54 (Sb) for ICP-MS. Slight sensitivity improvements were also observed for the non-hydride-forming elements. The limits of detection (LOD) of As and Sb were lowered, respectively, to 0.8 and 0.9 μg L⁻¹ with the DM-ICP-AES system and to 0.01 and 0.02 μg L⁻¹ with the DM-ICP-MS system. The short-term stabilities of both methods were between 2.1 and 5.4%. The methods were applied for the analysis of leachates of a cement mortar material prepared in the pH range 3–13. The elemental concentration of the leachates determined by the two DM methods were statistically compared with the values obtained from Neb-ICP-MS analysis; the values showed good agreement at the 95% confidence level. Quantitative spike recoveries were obtained for the analytes from most of the leachates using both DM methods. Figure Schematic of the dual-mode sample introduction system used in combination with ICP-AES and ICP-MS for the simultaneous determination of hydride and non-hydride-forming elements     

pH-Controlled Supramolecular Self-Assembly of Naphthalenediimide Appended l-Alanine and Ethylenediamine Asymmetric Bolaamphiphile

Design, synthesis and characterization of novel (2S)-2-[7-(2-aminoethyl)-1,3,6,8-tetraoxo-3,6,7,8-tetrahydrobenzo[lmn][3,8]phenanthrolin-2(1H)-yl]propanoic acid ( 1 ) bolaamphiphile, which combine naphthalene diimide (NDI) appended with l -alanine at one end of imide and ethylenediamine at the other end. An l -alanine bearing NDI-based asymmetric bolaamphiphile self-assembled at various pH ranging from 2 to 10 forms a variety of supramolecular nanostructures. The UV-Vis and emission spectroscopic techniques employed for the optical and photophysical properties study of bolaamphiphile 1 at various pH values. It was revealed that the change in pH alters both the optical and photophysical properties of bolaamphiphile 1 . Theoretical calculations used to investigate the electronic properties of the bolaamphiphile 1 . Dynamic light scattering experiments displayed formation of aggregates in solution and scanning electron microscopy (SEM) was used to visualize the nanostructures formed on silicon wafers. Furthermore, the X-ray diffraction was used to determine the nanostructure's packing properties i. e. crystalline/amorphous. Experimental circular dichroism (CD) spectroscopy results inferred and revealed the induction of chirality into the supramolecular systems, which was shown to be pH dependent. This study clearly demonstrates the manipulation of pH can control/tune chiral supramolecular structures and provide future methods for the development of chiral recognition and catalysis study.     

pH- and metal-dependent structural diversity from mononuclear to two-dimensional polymers based on a flexible tricarboxylate ligand

Six complexes based on a flexible tripodal ligand H₃TTTA (2,2′,2″-[1,3,5-triazine-2,4,6-triyltris(thio)]tris-acetic acid) have been hydrothermally synthesized and structurally characterized. X-ray single-crystal diffractions reveal that they have rich structural chemistry: mononuclear, [Zn(HTTTA)(2,2′-bpy)(H₂O)₃]_n (1); dimeric metallamacrocycle, [Zn(HTTTA)(2,2′-bipy)(H₂O)]_n (2) and [Cd(HTTTA)(2,2′-bipy)(H₂O)·H₂O]_n (3); two-dimensional networks with binodal (3,6)-connected CdI₂ topology based on linear trinuclear M₃(μ²-CO²)₄(μ₂-CO₂)₂ SBUs (Secondary Building Units), [M₃(TTTA)₂(2,2′-bipy)₂(H₂O)_m·nH₂O]_n (M=Zn·4, m=0, n=4; Cd·5 and Mn·6, m=2; n=2). The value of pH and the metal ions has large influences on the resulting structures. The flexible tricarboxylic acid exhibits four coordination modes from monodentate to μ⁶-bridge. Fluorescence and magnetic properties of the complexes have also been investigated in details.     

pH-Dependent Assembly of Hybrid Materials Based on Molybdates and Copper/imidazole Complexes

Three novel inorganic-organic hybrid materials, [Cu（imi）2（H2O）（MoO4）]n 1, [Cuz（imi）3（MoO4）E]n.nH2O 2 and [Cu3（imi）2（OH）2（MoO4）2]n 3 （imi = imidazole）, were synthesized and characterized by X-ray single-crystal structure determination. 1 crystallizes in orthorhombic, space group Pca21 with a = 13.382（4）, b = 8.527（2）, c = 9.622（3）A, V = 1098.0（5） A^3 Z = 4, C6H10CuMoN4O5, Mr = 377.66, Dc = 2.285 g/cm^3, F（000） = 740,μ（MoKa） = 3.095 mm^-1, the final R = 0.0256 and wR = 0.0722 for 1896 observed reflections with I 〉 2σ（I）. 2 crystallizes in monoclinic, space group P2t/c with a= 11.170（2）, b = 7.8244（15）, c = 22.631（4）A, β = 115.790（7）°, V = 1780.9（6）A^3 Z = 4, C9H14Cu2Mo2N6O9, Mr = 669.24, Dc= 2.496 g/cm^3, F（000）=1295,μ（MoKa） = 3.792 mm^-1, the final R = 0.0225 and wR = 0.0615 for 3838 observed reflections with I 〉 2σ（I）. 3 crystallizes in monoclinic, space group P21/c with a = 5.5599（19）, b = 23.771（8）, c = 7.3044（18）A , β = 129.356（16）°, V = 746.5（4）A^3, Z = 2, C6H10Cu3Mo2N4O10, Mr = 680.71, Dc = 3.029 g/cm^3, F（000） = 650,μ（MoKa） = 5.900 mm^-1, the final R = 0.0215 and wR = 0.0524 for 1620 observed reflections with I 〉 2σ（I）.