Molecularly imprinted polymeric film on semiconductor nanoparticles analyte detection by quantum dot photoluminescence

Incorporation of semiconductor nanoparticles into molecularly imprinted polymer provides a sensor material which can be easily shaped and with better selectivity because the bound template would quench the photoluminescence (PL) emission of quantum dots significantly. In this work, artificial receptors of various templates were synthesized with functional monomers such as methacrylic acid (MAA), semiconductor like CdSe/ZnS core-shell derivatized with 4-vinylpyridine and ethylene glycol dimethacrylic acid as the cross-linker. The quenching of photoluminescence emissions is presumably due to the fluorescence resonance energy transfer between quantum dots and template molecules. The photoluminescence emission is unaffected upon incubation of analyte with the blank control polymer.     

Electrochemistry and electrogenerated chemiluminescence of all-trans conjugated polymer poly[distyrylbenzene-b-(ethylene oxide)]s

The electrochemistry and electrogenerated chemiluminescence (ECL) of two linear, stereoregular, and structurally defined PPV derivatives, poly[distyrylbenzene-b-(ethylene oxide)]s, with respective 12 and 16 of ethylene oxide repeat units in the backbone, abbreviated as DE-1 and DE-2, have been studied on glassy carbon and Pt electrodes in CH2Cl2 and CH3CN containing 0.10 M tetra-n-butylammonium perchlorate (TBAP). In CH2Cl2, a one-electron transfer, reversible oxidation at approximately 0.75 V vs Ag/Ag+ (10 mM AgNO3 in CH3CN) was observed for both polymers. Porous polymer films were electrochemically formed on the electrode with multiple cyclic potential scanning. Cast films of DE-1 and DE-2 on the electrode prepared from 1.0 mM of the corresponding CH2Cl2 solutions were used for studies in CH3CN containing 0.10 M TBAP due to their limited solubility in the solvent. A film-type of oxidation was found at approximately 0.80 V vs Ag/Ag+ in CH3CN when a scan rate of less than 1 V/s was used. The soluble oxidation product can be captured and reduced and then reoxidized in solution-phase at the electrode at a relatively high scan rate of, e.g., 2 V/s. ECL responses with a maximum emission at approximately 1.10 V vs Ag/Ag+ were obtained with the cast films in CH3CN (0.10 M TBAP) in the presence of 43 mM tri-n-propylamine (TPrA) after both TPrA and film were oxidized. The ECL is believed to be resulted from the interaction between the oxidized polymer species and the strong reducing TPrA free radical (TPrA*) generated after the deprotonation of TPrA*+ cation species.     

Synchronous determination of mercury (II) and copper (II) based on quantum dots-multilayer film

A sensitive sensor for mercury (II) and copper (II) synchronous detection was established via the changed photoluminescence of CdTe quantum dots (QDs) multilayer films in this work. QDs were deposited on the quartz slides to form QDs-multilayer films by electrostatic interactions with poly(dimethyldiallyl ammonium chloride) (PDDA). Hg²⁺ or Cu²⁺ could quench the photoluminescence of the QDs-multilayer films, and glutathione (GSH) was used to remove Hg²⁺ or Cu²⁺ from QDs-multilayer films due to strong affinity of GSH-metal ions, which resulted in the recovered photoluminescence of QDs-multilayer films. There are good linear relationships between the metal ions concentration and the photoluminescence intensity of QDs in the quenched and recovered process. It was found that the Stern–Volmer constants for Hg²⁺ are higher than that for Cu²⁺. Based on different quenching and recovery constant between Hg²⁺ and Cu²⁺, the synchronous detection of Hg²⁺ and Cu²⁺ can be achieved. The linear ranges of this assay were obtained from 0.005 to 0.5 μM for Hg²⁺ and from 0.01 to 1 μM for Cu²⁺, respectively. And the artificial water samples were determined by this method with satisfactory results, the recoveries for Hg²⁺ and Cu²⁺ ions were found in the range of 90.4–106.4%. To the best of our knowledge, it is the first report about the synchronous detection of Hg²⁺ and Cu²⁺ by using quenched and recovered photoluminescence of quantum dots multilayer films.     

Ethylene sensing by silver(I) salt-impregnated luminescent films

Luminescent oligomers and polymers doped with silver(I) salts were used as optical sensors for ethylene and other gaseous small molecules. Films of poly(vinylphenylketone) (PVPK) or 1,4-bis(methylstyryl)benzene (BMSB) impregnated with AgBF(4), AgSbF(6), or AgB(C(6)F(5))(4) respond to ethylene exposures with a reversible emission quenching that is proportional to the pressure of the gas. Experiments with various analytes revealed that only gases capable of forming coordinate bonds with Ag(I) ions (i.e., ethylene, propylene, and ammonia) produced a sensing response. Comparison of the effects of ethylene and tetradeuterioethylene revealed that the emission quenching was due to enhanced vibrational relaxation. The Ag(I) ions are essential to the observed optical response. The oligomer/polymer support enhances the response characteristics of the impregnated salt by promoting separation of Ag(I) from its anion, a separation that improves accessibility of the Ag(I) ion to the gaseous analytes. Salts with large lattice energies, where the anion is not dissociated from Ag(I) in the matrix, fail to sensitize film responses. Photoluminescence experiments with Ag(I)-impregnated BMSB films established that the Ag(I) ions serve to communicate the analyte-binding signal to the support by altering the support-based emission. These experiments demonstrate a sensing paradigm where simultaneous coordination of Ag(I) ions to the support matrix and to a gaseous analyte enables the optical response.     

Novel blue‐greenish electroluminescent poly(fluorenevinylene‐alt‐dibenzothiophenevinylene)s and their model compounds

Poly(9,9‐dihexylfluorene‐2,7‐vinylene‐alt‐dibenzothiophene‐2,8‐vinylene) (PS) and poly(9,9‐dihexylfluorene‐2,7‐vinylene‐alt‐dibenzothiophene‐5,5‐dioxide‐2,8‐ vinylene) (PSO) as well as corresponding model compounds were synthesized by Heck coupling. Both the polymers and model compounds were readily soluble in common organic solvents such as tetrahydrofuran, dichloromethane, chloroform, and toluene. The polymers showed a decomposition temperature at ～430 °C and a char yield of about 65% at 800 °C in N₂. The glass‐transition temperatures of the polymers were almost identical (75–77 °C) and higher than those of the model compounds (26–45 °C). All samples absorbed around 390 nm, and their optical band gaps were 2.69–2.85 eV. They behaved as blue‐greenish light emitting materials in both solutions and thin films, with photoluminescence emission maxima at 450–483 nm and photoluminescence quantum yields of 0.52–0.72 in solution. Organic light‐emitting diodes with an indium tin oxide/poly(ethylene dioxythiophene):poly(styrene sulfonic acid)/polymer/Mg:Ag/Ag configuration with polymers PS and PSO as emitting layers showed green electroluminescence with maxima at 530 and 540 nm, respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6790–6800, 2006     

Electrochemistry of conductive polymers 39. Contacts between conducting polymers and noble metal nanoparticles studied by current-sensing atomic force microscopy

Electrical properties of contacts formed between conducting polymers and noble metal nanoparticles have been examined using current-sensing atomic force microscopy (CS-AFM). Contacts formed between electrochemically prepared pi-conjugated polymer films such as polypyrrole (PPy), poly(3-methylthiophene) (P3MeT), as well as poly(3,4-ethylenedioxythiophene) (PEDOT) and noble metal nanoparticles including platinum (Pt), gold (Au), and silver (Ag) have been examined. The Pt nanoparticles were electrochemically deposited on a pre-coated PPy film surface by reducing a platinum precursor (PtCl62-) at a constant potential. Both current and scanning electron microscopic images of the film showed the presence of Pt islands. The Au and Ag nanoparticles were dispersed on the P3MeT and PEDOT film surfaces simply by dipping the polymer films into colloid solutions containing Au or Ag particles for specified periods (5 to approximately 10 min). The deposition of Au or Ag particles resulted from either their physical adsorption or chemical bonding between particles and the polymer surface depending on the polymer. When compared with PPy, P3MeT and PEDOT showed a stronger binding to Au or Ag nanoparticles when dipped in their colloidal solutions for the same period. This indicates that Au and Ag particles are predominantly linked with the sulfur atoms via chemical bonding. Of the two, PEDOT was more conductive at the sites where the particles are connected to the polymer. It appears that PEDOT has better aligned sulfur atoms on the surface and is strongly bonded to Au and Ag nanoparticles due to their strong affinity to gold and silver. The current-voltage curves obtained at the metal islands demonstrate that the contacts between these metal islands and polymers are ohmic.     

Tailor-Made Silver Release Properties of Silver-Containing Functional Plasma Polymer Coatings Adjusted Through a Macroscopic Kinetics Approach

Combining a functional plasma polymer matrix with antibacterially active silver (Ag) within a nanocomposite structure allows secure production and applications in various fields, especially in the medical sector. Therefore, nitrogen or oxygen containing hydrocarbon plasma polymers and Ag nanoparticles were simultaneously deposited. Functional groups such as amino or carboxylic groups as well as an adjusted amount of Ag can be incorporated into the growing films by controlling the plasma deposition properties. For this purpose, macroscopic kinetics were used to characterise the deposition behaviour also as a base for possible industrial up-scaling. XPS and ICP-OES were used to analyse the chemical composition of the polymer?CAg nanocomposites and the Ag content which could be incorporated depending on the plasma process conditions. Finally, the Ag release was determined in bi-distilled water for classification and comparison with the antibacterial properties. The antibacterial effect of the polymer?CAg nanocomposites was proofed with the gram? strain Pseudomonas aeruginosa PAO1 and the gram+ strain Staphylococcus aureus (ST12 Group) showing a clear efficacy dependence on the amount of released Ag and the possibility for tailor-made antibacterial active plasma films.     

Electrochemical deposition of mesoporous nickel hydroxide films from dilute surfactant solutions

A series of micelle-templated mesoporous nickel hydroxide films were prepared by electrochemical deposition from dilute surfactant solutions by using different types of template and by varying plating solvent composition. Lamellar mesostructured Ni(OH)2 films are obtained with only anionic surfactant sodium dodecyl sulfate (SDS) as the template. In particular, a unique cooperative assembly fashion, that is, the combination between Ni2+ and a complex composed of the primary template SDS and a cosurfactant, such as triblock poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) copolymers and poly(ethylene glycol), was explored, by which two-dimensional hexagonal mesoporous Ni(OH)2 films were electrodeposited. Meanwhile, the deposition medium also plays a crucial role in determining the mesostructure of Ni(OH)2 films. For the composite nickel hydroxide films deposited from aqueous solution or dilute aqueous solution of ethylene glycol (<20 wt %) in the presence of SDS or the SDS-poly(alkylene oxide) polymer complexes, a mixed lamellar phase with d(001) = 37.4 A and d(001) = 28.5 A was obtained. However, single lamellar phase with d(001) = 37.4 A was electrodeposited from concentrated aqueous solutions of ethylene glycol (> or = 20 wt %). Furthermore, such deposition baths have access to hexagonal mesoporous nickel hydroxide films with d(100) = 37.4 A at 70 degrees C with the SDS-poly(alkylene oxide) polymer complexes as the templates. Within the potential window for Ni(OH)2, the morphology and quality of mesostructured films are significantly dependent on the deposition potential, while the mesostructures of the composite films always remain unchanged.     

Infrared spectroscopic study of solid films of poly(ethylene glycol) doped with cations

The infrared spectra of solid films, prepared on a silicon plate of poly(ethylene glycol) doped with various cations (Li⁺, Na⁺, K⁺, Ca²⁺ and Ba²⁺), have been measured. The spectral analysis indicates that the films are non-crystalline and essentially amorphous. The polymer chain is significantly disordered by assuming diverse conformational states. The interaction between the ether oxygens of the polymer and the cation, as estimated from the C---O stretching wavenumber, is correlated to the size of the cation; the interaction is stronger for the cation with larger size.     

梨形核壳结构氧化锌/银亚微米球的制备、表征及光学性能

利用亚锡离子还原银离子生成的金属银沉积在合成的梨形氧化锌表面作为晶种,进一步生长银纳米粒子,制备了梨形的、核壳结构的、单分散的氧化锌/银亚微米球。利用X射线衍射、透射电镜、能量色散X射线谱、紫外可见吸收谱及光致发光谱对所制备样品的形貌、微观结构、组成和光学性能进行了表征。结果表明:(1)样品是由梨形亚微米氧化锌核和银纳米颗粒壳组成;(2)在氧化锌表面的银纳米粒子作为光激发产生的电子捕获剂提高了光产生的载流子的分离效率,在能量没有改变的情况下减少了紫外发射光的强度,淬灭了可见发射光。     

Polymer-initiated photogeneration of silver nanoparticles in SPEEK/PVA films: direct metal photopatterning

Cross-linking of sulfonated poly(ether-ether)ketone-poly(vinyl alcohol) (SPEEK-PVA) materials yields flexible polymer films, possessing high light-sensitivity and ion-exchange capabilities. Adsorbed Ag+ ions are photoreduced in the film under illumination (lambda = 350 nm), leading to metal nanoparticle formation in places where the film has been exposed to the light. Nanoparticles form via reduction of Ag+ by the polymeric alcohol radicals, generated in the system as a result of photochemical H-abstraction from PVA molecules by the excited carbonyl triplet state of SPEEK. Use of the films for direct metal photopatterning is demonstrated.     

DFT study of a weakly pi-bonded C2H4 on oxygen-covered Ag(100)

The coadsorption of ethylene, C2H4, and atomic oxygen on Ag(100) was studied using density-functional theory. As for the adsorption of oxygen alone, the on-surface hollow sites are predicted to be the most stable adsorption sites at low coverage (< or =1/2 ML). Above this coverage, mixed on-surface + subsurface oxygen configurations become more stable. The binding of ethylene to the clean Ag(100) is weak and little affected by oxygen when it is adsorbed on-surface. On the other hand, we find that the adsorption energy of C2H4 may increase considerably when oxygen is adsorbed into subsurface sites. Our results indicate that the increased reactivity of surface Ag atoms is because of their decreased coordination due to the push out effect of oxygen underneath, more than to their oxidation.     

金属离子协同效应对血红蛋白分子荧光光谱的影响

本文采用荧光光谱法对血红蛋白(Hb)与Zn^2 、Cu^2 、Ag^ 三种离子的单一离子及混合离子的相互作用进行了研究。结果表明,Zn^2 对Hb有较强的荧光增强作用,Cu^2 具有较强的荧光淬灭作用,而Ag^ 有较弱的荧光淬灭作用;在二元金属离子与Hb的混合体系中,由于金属离子与Hb之间存在竞争配位作用或离子之间相互制约及协同效应,使混合体系中Hb的荧光光谱变化较单一金属离子有明显的差异。     

Formation and photoluminescence of silver nanoparticles stabilized by a two-armed polymer with a crown ether core

Silver nanoparticles were synthesized by the use of a two-armed polymer with a crown ether core [poly(styrene)]-dibenzo-18-crown-6-[poly(styrene)] based on the flexibility of the polymer chains and the complex effect of crown ether with Ag(+) and Ag. The size of silver nanoparticles could be tailored by controlling the initial concentrations of the polymer and Ag(+), and the molecular weight of the polymer. The emission of silver nanoparticles was blue-shifted, and the intensity of the photoluminescence of silver nanoparticles stabilized by the polymer was significantly increased due to the complex effect between the crown ether embedded in the polymer and the silver nanoparticles.     

Lithium ion conduction and ion-polymer interaction in poly（vinyl pyrrolidone） based electrolytes blended with different plasticizers

Poly（ethylene oxide）, poly（vinyl pyrrolidone）（PEO/PVP）, lithium perchlorate salt（Li Cl O4） and different plasticizer based, gel polymer electrolytes were prepared by the solvent casting technique. XRD results show that the crystallinity decreases with the addition of different plasticizers. Consequently, there is an enhancement in the amorphousity of the samples responsible for the process of ion transport. FTIR spectroscopy is used to characterize the structure of the polymer and confirms the complexation of plasticizer with host polymer matrix. The ionic conductivity has been calculated using the bulk impedance obtained through impedance spectroscopy. Among the various plasticizers, the ethylene carbonate（EC） based complex exhibits a maximum ionic conductivity value of the order of2.7279 10 4S cm 1. Thermal stability of the prepared electrolyte films shows that they can be used in batteries at elevated temperatures. PEO（72%）/PVP（8%）/Li Cl O4（8%）/EC（12%） has the maximum ionic conductivity value which is supported by the lowest optical band gap and lowest intensity in photoluminescence spectroscopy near 400–450 nm. Two and three dimensional topographic images of the sample having a maximum ionic conductivity show the presence of micropores.     

Tuning the Redox Chemistry of a Cr/SiO2 Phillips Catalyst for Controlling Activity,Induction Period and Polymer Properties

The Cr/SiO₂ Phillips catalyst has taken a central role in ethylene polymerization ever since its discovery in 1953. This catalyst is unique compared to other ethylene polymerization catalysts, since it is active without the addition of a metal-alkyl co-catalyst. However, metal-alkyls can be added for scavenging poisons, enhancing the catalyst activity, reducing the induction period and altering polymer characteristics. Despite extensive research into the working state of the catalyst, still no consensus has been reached. Here, we show that by varying the type of metal-alkyl co-catalyst and its amount, the Cr redox chemistry can be tailored, resulting in distinct catalyst activities, induction periods, and polymer characteristics. We have used in-situ UV-Vis-NIR diffuse reflectance spectroscopy (DRS) for studying the Cr oxidation state during the reduction by tri-ethyl borane (TEB) or tri-ethyl aluminum (TEAl) and during subsequent ethylene polymerization. The results show that TEB primarily acts as a reductant and reduces Cr⁶⁺ with subsequent ethylene polymerization resulting in rapid polyethylene formation. TEAl generated two types of Cr²⁺ sites, inaccessible Cr³⁺ sites and active Cr⁴⁺ sites. Subsequent addition of ethylene also revealed an increased reducibility of residual Cr⁶⁺ sites and resulted in rapid polyethylene formation. Our results demonstrate the possibility of controlling the reduction chemistry by adding the proper amount and type of metal-alkyl for obtaining desired catalyst activities and tailored polyethylene characteristics.     

Sulfonated poly(ether ether ketone)/poly(vinyl alcohol) sensitizing system for solution photogeneration of small Ag, Au, and Cu crystallites

Illumination of air-free aqueous solutions containing sulfonated poly(ether ether ketone) and poly(vinyl alcohol) with 350 nm light results in benzophenone ketyl radicals of the polyketone. The polymer radicals form with a quantum yield 0.02 and decay with a second-order rate constant 6 orders of magnitude lower than that of typical alpha-hydroxy radicals. Evidence is presented that the polymeric benzophenone ketyl radicals reduce Ag+, Cu2+, and AuCl4- to metal particles of nanometer dimensions. Decreases in the reduction rates with increasing Ag(I), Cu(II), and Au(III) concentrations are explained using a kinetic model in which the metal ions quench the excited state of the polymeric benzophenone groups, which forms the macromolecular radicals. Quenching is fastest for Ag+, whereas Cu2+ and AuCl4- exhibit similar rate constants. Particle formation becomes more complex as the number of equivalents needed to reduce the metal ions increases; the Au(III) system is an extreme case where the radical reactions operate in parallel with secondary light-initiated and thermal reduction channels. For each metal ion, the polymer-initiated photoreactions produce crystallites possessing distinct properties, such as a very strong plasmon in the Ag case or the narrow size distribution exhibited by Au particles.     

电沉积ZnO纳米棒阵列及共形结构杂化太阳能电池

采用电沉积法制备出ZnO致密纳米颗粒膜和不同尺寸的纳米棒阵列。通过在ZnO上旋涂p型聚合物聚3-己基噻酚(P3HT)与n型富勒烯衍生物[6,6]-苯基-C61丁酸甲酯(PCBM)的混合物,并蒸镀金属Ag,制备出不同结构的杂化太阳能电池。通过扫描电镜、X射线衍射、光致发光和模拟太阳光光电性能测试,对ZnO的生长条件、晶体形貌及缺陷与太阳能电池性能之间的关系进行了系统研究。结果表明,ZnO的形貌和晶体缺陷的分布对杂化太阳能电池有重要影响,避免共混聚合物与ZnO缺陷聚集区的直接接触可有效消除电流泄漏。在电池结构方面,与ZnO纳米阵列块状结构杂化太阳能电池相比,共形结构的杂化太阳能电池可有效缩短空穴到金属电极的传输距离,增大聚合物与金属电极的接触面积,光电转换效率可提升64%~101%。     

Experimental and theoretical studies of the interaction of silver cluster cations Ag(n)+ (n = 1-4) with ethylene

Reactions of silver cluster cations Ag(n)+ with ethylene have been studied using a reflectron time-of-flight mass spectrometer. Chemisorbed Ag(n)(C2H4)(m)+ (n = 1-3, m = 1-6) complexes were observed. For a given value of n, the abundances of Ag(n)(C2H4)(m)+ (n = 1-3, m = 1-6) species first increase and then decrease, with the maximum of the intensity distribution usually at m = 4. This maximum does not change with the ethylene concentration in the mixed gas, the stagnation pressure of the mixed gas, or the size of Ag(n) + (n = 1-3). A complementary extensive theoretical study on the structure and binding of Ag(n)(C2H4)(m)+ (n = 1-4, m = 1-4) is also reported. Preferred binding sites, binding energies, geometries, vibrational frequencies, and ionization potentials are determined using density functional theory.     

Nanostructured latex films from poly(butyl methacrylate) latex cross-linked with poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) triblock macro-cross-linker

Biphasic polymer latexes were synthesized by a seeded swelling and polymerization method. The latexes were composed of a poly(butyl methacrylate) core and a poly(ethylene oxide) rich shell cross-linked with poly(ethylene oxide)-poly (propylene oxide)-poly(ethylene oxide) triblock diol diacrylate macro-cross-linker. Nanostructured films were obtained by annealing the biphasic polymer latexes at a temperature between the glass-transition temperatures of the core latex and the cross-linked poly(ethylene oxide) based shell. Atomic force microscope images of the latex film revealed that the poly(butyl methacrylate) core phase is confined in the poly(ethylene oxide)-rich continuous phase with the form of separate nanosized spheres.