Magic sized ZnS quantum dots as a highly sensitive and selective fluorescence sensor probe for Ag+ ions

A green and simple chemical synthesis of magic sized water soluble blue-emitting ZnS quantum dots (QDs) has been accomplished by reacting anhydrous Zn acetate, sodium sulfide and thiolactic acid (TLA) at room temperature in aqueous solution. Refluxing of this mixture in open air yielded ZnS clusters of about 3.5 nm in diameter showing very strong and narrow photoluminescence properties with long stability. Refluxing did not cause any noticeable size increment of the clusters. As a result, the QDs obtained after different refluxing conditions showed similar absorption and photoluminescence (PL) features. Use of TLA as a capping agent effectively yielded such stable and magic sized QDs. The as-synthesized and 0.5 h refluxed ZnS QDs were used as a fluorescence sensor for Ag(+) ions. It has been observed that after addition of Ag(+) ions of concentration 0.5-1 μM the strong fluorescence of ZnS QDs was almost quenched. The quenched fluorescence can be recovered by adding ethylenediamine to form a complex with Ag(+) ions. The other metal ions (K(+), Ca(2+), Au(3+), Cu(2+), Fe(3+), Mn(2+), Mg(2+), Co(2+)) showed little or no effect on the fluorescence of ZnS QDs when tested individually or as a mixture. In the presence of all these ions, Ag(+) responded well and therefore ZnS QDs reported in this work can be used as a Ag(+) ion fluorescence sensor.     

Synthesis, crystal structure, and characterization of new tetranuclear Ag(I) complexes with triazole bridges

The self-assembly of Ag(I) ions with 3,5-dimethyl-4-amino-1,2,4-triazole (L1) and 4-salicylideneamino-1,2,4-triazole (L2) gave two novel complexes, [Ag4(mu2-L1)6][Ag4(mu2-L1)6(CH3CN)2](ClO4)8.2H2O (1) and [Ag4(mu2-L2)6(CH3CN)2](AsF6)4.2H2O (2), both of which contain tetranuclearic clusters constructed via Ag(I) ions and six N1,N2-bridged triazoles with a Ag4N12 core. When 4-(6-amino-2-pyridyl)-1,2,4-triazole (L3) was employed, {[Ag4(mu2-L3)4(mu3-L3)2](CF3SO3)4.H2O}n (3), {[Ag4(mu2-L3)4(mu3-L3)2](ClO4)4}n (4), and {[Ag4(mu2-L3)2(mu3-L3)4](PF6)4.CH3CN.0.75H2O}n (5) were isolated. 3 and 4 are 1D polymers, while 5 is a 2D polymer. 1D and 2D coordination polymers are constructed via the self-assembly of Ag4N12 cores as secondary building units (SBUs). The connection of these SBUs can be represented as a ladderlike structure for 1D polymers and a 4.8(2) net for 2D polymers. Electrospray ionization mass spectrometry measurements and NMR (1H and 13C) studies demonstrate that the tetranuclear SBU retains its integrity and the coordination polymers decompose into the tetranuclear Ag4N12 core in solution. 2 exhibits blue emission in the solid state and green emission in solution at ambient temperature. Strong blue fluorescence for complexes 3-5 in the solid state can be assigned to the intraligand fluorescent emission.     

反应温度诱导的两个类三明治银配合物的异构

通过固定银离子、2,2′-联吡啶-4,4′-二羧酸(H2bina)和1,3-二(4-吡啶基)丙烷(bpp)等原料配比和反应时间,在不同反应温度下分别制备了基于Ag2簇单元的配合物{[Ag2(bpp)2][Ag2(bina)2(H2O)2].6H2O}n(1)和含Ag4簇的配合物{[Ag4(bpp)2(bina)2(H2O)2].4H2O}n(2)。结构研究与性质测试对比表明这两个类三明治型配合物不仅晶体学参数、银离子配位环境、柔性配体构象、客体水分子数目发生了变化,而且荧光及热稳定性各异。     

Novel fluorescent chemosensor for Ag^ ＋ based on coumarin fluorophore

A novel chemosensor 1 （CS1） bearing one coumarin and two carbodithioate groups was synthesized and its fluorescent sensing behavior toward metal ions was investigated. Ag^＋ addition to a CH3COCH3/H2O （3：7, v：v） solution of CS1 gave a significantly quenched fluorescence. Other ions including Pb^2＋, Zn^2＋, Cu^2＋, Ca^2＋, Cd^2＋, Co^2＋, Mg^2＋, Mn^2＋, Hg^2＋, Ag^＋, Ni^2＋ induced no or much smaller spectral changes. This constitutes an ON-OFF Ag^＋-selective fluorescent chemosensor.     

A highly selective and sensitive fluorescence "turn-on" probe for Ag+ in aqueous solution and live cells

A naphthalimide-based fluorescent probe, NPQ, that contains a novel receptor was successfully developed. NPQ exhibited "turn-on" fluorescence and excellent selectivity toward Ag(+) in the presence of various other metal ions in aqueous solution. A series of control compounds were designed and synthesized in order to explore the photoinduced electron transfer (PET) quenching mechanism of NPQ and binding mode of NPQ with Ag(+). Moreover, with the NPQ-Ag(+) complex, I(-) was easily selectively recognized by a marked fluorescence quenching. The live cell imaging experiments demonstrate that NPQ can be used as a fluorescent probe for monitoring Ag(+) in living cells.     

Highly selective thioalcohol modified phthalocyanine sensors for Ag(I) and Pd(II) based on target induced J- and H-type aggregations: synthesis, electrochemistry and peripheral metal ion binding studies

We have described highly selective 1(4),8(11),15(18),22(25)-(1-hydroxyhexan-3-ylthio)-phthalocyanine sensors, M{Pc[α-SCH(C(3)H(7))(C(2)H(5)OH)](4)} (MPc(α-HHT)(4), where M = Zn(II) (2), Cu(II) (3) or Co(II) (4) and HHT: -SCH(C(3)H(7))(C(2)H(5)OH)). The formation of S-M-S {S = sulfur; M = Ag(I) or Pd(II)} bonds on the periphery in the case of Ag(I) and Pd(II) metal ions induces H- or J-aggregation, respectively, which results in significant changes in the absorption of the B- and, in particular, the Q-band. The binding ratios of Ag(I) to the periphery of 2 and 3 were found to be ca. 2:1 and 3:2, respectively. On the other hand, the binding ratios of Pd(II) to the periphery of the same compounds were found to be 3:1 and 4:1. The fluorescence of 2 exhibited distinct changes in response to treatment with Ag(I) and Pd(II) ions in solution. The fluorescence spectra emission intensity of 2 was quenched upon titration with Ag(I) and Pd(II) and a new emission maximum was observed upon titration with Pd(II). FTIR, (1)H-NMR, (13)C-NMR, UV-vis, MALDI-TOF MS and elemental analysis data were used to characterize the novel compounds. Transmission electron microscopy (TEM) and field-emission scanning electron microscopy (FE-SEM) were also used as complementary techniques to investigate the morphology and to image the interfacial aggregates of 2. The redox behaviours of the complexes were examined by voltammetry and in situ spectroelectrochemistry on Pt in a nonaqueous medium.     

Highly sensitive and selective chemosensor for Hg2+ based on the rhodamine fluorophore

A novel tren-based tripodal chemosensor 1 bearing a rhodamine and two tosyl groups was synthesized and its sensing behavior toward metal ions was investigated by UV/vis and fluorescence spectroscopies. Addition of a Hg2+ ion to a CH3CN solution of 1 gave a visual color change as well as significantly enhanced fluorescence, while other ions including Pb2+, Zn2+, Cu2+, Ca2+, Ba2+, Cd2+, Co2+, Mg2+, Ag+, Cs+, Li+, and Na+ induced no or much smaller color/spectral changes, which constituted a Hg2+-selective fluorescent chemosensor (OFF-ON).     

Preparation of pH-sensitive polymer by thermal initiation polymerization and its application in fluorescence immunoassay

A fluorescence immunoassay for human IgG (Ag) was developed using a pH-sensitive polymer prepared by thermal initiation or redox initiation polymerization as a carrier. In the competitive immunoassay, appropriate quantity of Ag was immobilized on the polymer and the standard Ag (or sample) solution, and a constant amount of fluorescein isothiocyanate labeled goat anti-human IgG antibody (Ab-FITC) was added. Immobilized Ag and the standard (or sample) Ag competed for binding to the Ab-FITC in 37 °C in homogeneous format. After changing the pH to separate the polymer-immune complex precipitate, it was re-dissolved and determined by fluorescence method. The results showed that the immobilization efficiency, immunological reaction activities of immobilized Ag and phase transition pH range were improved as Ag was immobilized by thermal initiation instead of redox initiation polymerization. Under optimum conditions, the calibration graphs for the Ag in both methods, thermal initiation and redox initiation, were linear over the concentration range of 0.0-1000 ng mL⁻¹, with detection limits 8 (thermal initiation) and 12 ng mL⁻¹ (redox initiation), respectively. Moreover, some pH-sensitive polymer prepared only in organic solvent or under high temperature could also be used as an immunoreaction carrier by thermal initiation polymerization. Thermal initiation polymerization was a better immobilization mode.     

Ultrasmall near-infrared Ag2Se quantum dots with tunable fluorescence for in vivo imaging

A strategy is presented that involes coupling Na(2)SeO(3) reduction with the binding of silver ions and alanine in a quasi-biosystem to obtain ultrasmall, near-infrared Ag(2)Se quantum dots (QDs) with tunable fluorescence at 90 °C in aqueous solution. This strategy avoids high temperatures, high pressures, and organic solvents so that water-dispersible sub-3 nm Ag(2)Se QDs can be directly obtained. The photoluminescence of the Ag(2)Se QDs was size-dependent over a wavelength range from 700 to 820 nm, corresponding to sizes from 1.5 ± 0.4 to 2.4 ± 0.5 nm, with good monodispersity. The Ag(2)Se QDs are less cytotoxic than other nanomaterials used for similar applications. Furthermore, the NIR fluorescence of the Ag(2)Se QDs could penetrate through the abdominal cavity of a living nude mouse and could be detected on its back side, demonstrating the potential applications of these less toxic NIR Ag(2)Se QDs in bioimaging.     

A squaraine-based colorimetric and "turn on" fluorescent sensor for selective detection of Hg2+ in an aqueous medium

A novel squaraine-based chemosensor SQ-1 has been synthesized, and its sensing behavior toward various metal ions was investigated by UV-vis and fluorescence spectroscopies. In AcOH-H(2)O (40:60, v/v) solution, Hg(2+) ions coordinate with SQ-1 causing a deaggregation which induces a visual color and absorption spectral changes as well as strong fluorescence. In contrast, the addition of other metals (e.g., Pb(2+), Cd(2+), Cu(2+), Zn(2+), Al(3+), Ni(2+), Co(2+), Fe(3+), Ca(2+), K(+), Mg(2+), Na(+), and Ag(+)) does not induce these changes at all. Thus SQ-1 is a specific Hg(2+) sensing agent due to the inducing deaggregation of the dye molecule by Hg(2+).     

银掺杂介孔氧化铝抗菌剂的一步合成与表征

以Al(NO_3)_3·9H_2O和AgNO_3为原料,采用水热法制备了介孔氧化铝纳米粒子(Mesoporous Al_2O_3NPs)和银掺杂介孔氧化铝纳米粒子(Mesoporous Ag/Al_2O_3NPs),通过X射线衍射(XRD)、场发射扫描电子显微镜(FE-SEM)、X射线荧光光谱(XRF)、能量分散X射线衍射(EDX)和低温N2吸附-脱附等手段对产物进行了表征,通过最低抑菌浓度和抑菌圈实验研究了材料的抗菌性能.XRD分析表明在介孔Ag/Al_2O_3NPs中Al_2O_3是唯一结晶相,Ag掺杂后,介孔Ag/Al_2O_3NPs晶格常数和半高峰宽增大,晶面间距[(111),(400)和(440)面]减小.FE-SEM形貌分析表明掺杂后的介孔Ag/Al_2O_3NPs颗粒直径减小而孔径增大.EDX和XRF分析表明介孔Ag/Al_2O_3NPs中O/Al摩尔比为1.5,与Al_2O_3NPs中O/Al摩尔比相同.综合XRD和XRF分析结果认为,Ag进入介孔Al_2O_3晶格间隙形成间隙固溶体.低温N2吸附-脱附分析表明掺杂后的介孔Ag/Al_2O_3NPs比表面积、孔体积和孔径增大.曝气抗菌实验结果表明介孔Ag/Al_2O_3NPs的抗菌机理是活性氧和金属银的协同作用.介孔Ag/Al_2O_3NPs对革兰氏阴性菌(大肠杆菌)和革兰氏阳性菌(金黄色葡萄球菌)具有明显的抗菌效果,对大肠杆菌和金黄色葡萄球菌的最低抑菌浓度(MIC)均为80μg/m L,抑菌圈直径分别为26 mm和24 mm.     

Kinetics of the formation of silver dimers: early stages in the formation of silver nanoparticles

Silver clusters too small to support a plasmon band possess interesting fluorescence properties as well as being a convenient route to studying the early stages of nanoparticle formation. Fluorescent silver clusters are synthesized in toluene solution, and the formation is monitored herein by laser flash photolysis (LFP). Kinetic analysis of the formation of the Ag clusters is consistent with the formation of the smallest possible clusters, silver dimers (Ag(2)), whereby a mechanism for the formation of these clusters is provided as well as the first reported extinction coefficient and association constant for Ag(0) to form Ag(2). The formation of Ag(2) clusters is contrasted with the formation of Ag nanoparticles in aqueous media, and the particular stability and selectivity toward Ag(2) in this system is also studied using LFP.     

RESONANCE RAMAN EVIDENCE FOR 15-cis TO MA,-trans PHOTOISOMERIZATION OF SPIRILLOXANTHIN BOUND TO A REDUCED FORM OF THE REACTION CENTER OF Rhodospirillum rubrum SI

The reaction center (RC) of Rhodospirillum rubrum SI, which was prepared by ultrafiltration, showed one peak in molecular-sieve HPLC, but it showed two peaks in diethylaminoethyl (DEAE) ion-exchange HPLC; they were named as RC-α and RC-β in the order of elution, Nonequilibrated isoelectric electrophoresis, together with DEAE ion-exchange HPLC, showed that RC-β is electronically more negative than RC-α. Oxidation of RC-β by addition of ferricyanide caused its transformation into RC-α, while reduction of RC-α by adding ascorbate and subsequent illumination caused its transformation into RC-β. Resonance Raman spectroscopy of the RC at liquid nitrogen temperature detected the all-trans and the 15-cis isomers in a ratio of 1:1, but HPLC analyses of the carotenoid extracted from the RC before and after the Raman measurements detected the pair of isomers in a ratio of 1:6. Thus, the 15-cis to all-trans isomerization takes place during irradiation at liquid nitrogen temperature, while the reverse isomerization takes place in the dark. The isolated RC-α and RC-β exhibited the bleaching of the 868 nm band, and contained the H, M and L subunits and 1.2-1.4 molecules of ubiquinone-10 per RC. Each RC slowly equilibrated in the dark toward a mixture of RC-α and RC-β. Generation of the all-trans isomer in the light was found not in RC-α but in RC-β.     

Rosamine-based fluorescent chemosensor for selective detection of silver(I) in an aqueous solution

The synthesis and photophysical properties of a rosamine-based fluorescent chemosensor, RosAg, for detecting Ag ion in an aqueous solution are described. This fluorescent sensor has a negligible quantum yield (<0.005) in the absence of Ag(+), whereas a significant increase in fluorescence is observed upon complexation with Ag(+) under physiological conditions. The crystal structure of the silver complex with the chelator moiety of RosAg reveals a trigonal-planar coordination geometry in which three S atoms occupy the metal center. Although a strong coordinative interaction of Ag-N is not observed in the crystal structure, the (1)H NMR experiments suggest that aniline nitrogen is likely to be associated with the Ag(+) center in the solution state. This may inhibit the photoinduced electron transfer process and result in the enhancement of fluorescence.     

Ag Nanowire‐Ag Nanoparticle Hybrids for the Highly Enhanced Fluorescene Detection of Protoporphyrin IX Based on Surface Plasmon‐Enhanced Fluorescence

In this study, we developed an approach to fabricate novel 1D Ag NWs‐Ag NPs hybrid substrate for enhanced fluorescene detection of protoporphyrin IX (PpIX) based on surface plasmon‐enhanced fluorescence. The Ag NWs‐Ag NPs hybrid was synthesized by combining the hydrothermal method and self‐assembly method with the asisstance of polyvinylpyrrolidone (PVP). When the Ag NWs‐Ag NPs hybrid was deposited on the glass substrate and employed as active substrate to detect PpIX, the fluorescence intensity of PpIX was enhanced greatly due to the coupling effect of localized surface plasmon‐localized surface plasmon (LSP‐LSP) and localized surface plasmon‐surface plasmon propagation (LSP‐SPP) which induced great enhancement of the electromagnetic field. Furthermore, the enhancement effect was approximately linear when the concentration of PpIX was ranged from 1×10^?7 mol/L to 2×10^?5 mol/L, and the photobleaching phenomenon of PpIX was reduced greatly, indicating that the fabricated Ag NWs‐Ag NPs hybrid substrate had well performance for PpIX imaging. This work provides an effective approach to prepare highly sensitive and stable fluorescence enhancement substrate, and has great potential application in fluorescence imaging.     

咔唑基四苯乙烯多功能发光材料的合成与性能

设计合成了一个以四苯乙烯为核心,四端连接长烷基链的咔唑基四苯乙烯衍生物(TPECz),该化合物具有典型的聚集诱导发光(AIE)特性.紫外光谱(UV-Vis)、荧光光谱(PL)、热重(TG)和示差扫描量热(DSC)研究表明,该化合物属于深蓝光材料、具有较好的热稳定性,并且对金属Fe3+具有很好的识别作用,有望用于金属离子检测;同时,该化合物外围的咔唑基团具有电化学活性,采用电化学聚合方法可制备其聚合物交联荧光薄膜,扫描电镜(SEM)和原子力显微镜(AFM)研究表明,该荧光薄膜表面平整,有望用于制备有机电致发光器件(OLED),可见该化合物是一种多功能材料.     

罗丹明类荧光探针的合成及对铜离子的检测

合成了罗丹明类Cu2+荧光增强型分子探针3',6'-双(二乙氨基)-2-(N-乙叉基氨基)螺[异吲哚-1,9'-占吨]-3-酮（RA）,并研究了它的光谱性能及对铜离子的识别作用.在乙腈/水（体积比1/1）的介质中,当加入Cu2+后探针RA显玫瑰红色,最大吸收波长为548 nm,最大发射波长为571 nm,且荧光强度显著增强,但是,其它常见离子如Na+, K+, Mg2+, Ca2+, Mn2+, Cd2+, Cr3+, Co2+, Ni2+, Ag+, Pb2+, Zn2+, Fe3+, Hg2+不引起或引起很小的紫外/可见或荧光光谱变化.RA的选择性荧光增强主要是由于Cu2+诱导分子中的酰胺闭环结构发生开环,导致分子结构的共轭程度增大.在6.5×10-8～2.9×10-6 mol?L-1范围内RA可以有效检测Cu2+,检测限为5.0×10-8 mol?L-1.RA对Cu2+的识别不可逆,而且探针RA对pH值不敏感,可以在比较宽的范围内（pH=4.1～10.5）高灵敏、高选择性检测Cu2+.     

Benzimidazole conjugate of 1,1'-thiobis(2-naphthol) as switch-on fluorescence receptor for Ag+ and the complex as secondary recognition ensemble toward Cys, Asp, and Glu in aqueous methanolic solution: synthesis, characterization, ion and amino acid recognition, computational studies, and microscopy features

A new 1,1'-thiobis(2-naphthoxy)-based receptor molecule (L) containing a benzimidazole moiety has been synthesized and characterized by (1)H NMR, ESI-MS, and elemental analysis. The selectivity of L has been explored in aqueous methanol, resulting in selective (7.5 ± 0.5)-fold switch-on fluorescence response toward Ag(+) among 14 different transition, alkali, and alkaline earth metal ions studied. The complexation of Ag(+) by L has been addressed by ESI-MS, (1)H NMR, and UV-vis spectra. Microstructural features of L and its Ag(+) complex have been measured by AFM and TEM. The morphological features of L alone and L in the presence of Ag(+) differ dramatically both in shape and size, and the ion induces the formation of chains owing to its coordinating ability toward benzimidazole. Further, the in situ [Ag(+)-L] complex was titrated against 20 naturally occurring amino acids and found that this complex acts as a secondary recognition ensemble toward Cys, Asp, and Glu by switch-off fluorescence.     

Fluorescence signaling of Zr4+ by hydrogen peroxide assisted selective desulfurization of thioamide

Thioamide derivative with a pyrene fluorophore was smoothly transformed to its corresponding amide by Zr(4+) ions in the presence of hydrogen peroxide. The transformation was evidenced by (1)H NMR spectroscopy and the signaling was completed within 10 min after sample preparation. Interference from Ag(+) and Hg(2+) ions in Zr(4+)-selective fluorescence signaling was readily suppressed with the use of Sn(2+) as a reducing additive. Discrimination of Zr(4+) from closely related hafnium, which is a frequent contaminant in commercial zirconium, was not possible. Prominent Zr(4+)-selective turn-on type fluorescence signaling was possible with a detection limit of 4.6 × 10(-6) M in an aqueous 99% ethanol solution.     

Poly(amine ester) dendrimer with naphthyl units as a fluorescent chemosensor for Al(III), Cu(II), and Zn(II).

A poly(amine ester) dendrimer with naphthyl units (G1N6) has been synthesized as a fluorescent chemosensor for metal ions. We investigated the metal-ion recognition of G1N6 by adding each of Ag(+), Al(3+), Ba(2+), Ca(2+), Cd(2+), Co(2+), Cu(2+), Fe(3+), Mg(2+), Ni(2+), and Zn(2+) in acetonitrile solution. Large changes were observed in the fluorescence spectra of G1N6 upon the addition of Al(3+), Cu(2+), and Zn(2+).