Preparation and characterization of nanostructured thin films of Au and Ag nanoparticles synthesized by ascorbic acid on modified glass surface

Immobilization of Ag and Au nanoparticles (NPs) synthesized by ascorbic acid on chemically modified glass surface has been studied. 3‐[2‐(2‐Aminoethylamino)ethylamino]propyl‐trimethoxysilane (AMPTS), N‐(2‐aminoethyl)‐3‐aminopropyltrimethoxysilan, and 3‐trimethoxysilyl‐1‐propanethiol (MSPT) were used as surface modifying agents. To improve immobilization efficiency, the ammonia solution has been used along with the silane reagents, which assisted to adsorb the metal NPs on glass surface. It was found that AMPTS and MSPT have considerable effect on deposition of Ag and AuNPs on glass substrate. The fabricated thin films were characterized by using UV‐Vis spectroscopy, atomic force microscopy, energy‐dispersive X‐ray spectroscopy and subjected to antimicrobial resistance test. The UV–Vis spectra show a distinctive plasmon resonance absorbance peak for thin films of Au and AgNPs prepared with MSPT and AMPTS, respectively. Atomic force microscopy images indicate that formation of Au and AgNPs with spherical morphology after immobilization on the glass substrate and also the dimensions of NPs on the surface appear larger than those observed in the parent colloidal solution. Energy‐dispersive X‐ray spectroscopy measurements confirmed the presence of silver and gold on the modified glass surface, and elemental composition was measured. The Au and AgNPs thin films show antibacterial activity against gram negative (Escherichia coli) and gram positive (Staphylococcus aureus) bacteria in comparison with a blank sample. Copyright © 2015 John Wiley & Sons, Ltd.     

Preparation and characterization of polyoxometalate/protein ultrathin films grown on electrode surfaces using layer-by-layer assembly

We report a new electrostatic layer-by-layer assembly method for the controlled deposition of electrocatalytically active enzymes onto electrode surfaces using polyoxometalate as the counteranion. Cytochrome c (cyt c), a redox active protein, and P(2)W(18)O(62)(6-), a Dawson-type polyoxometalate, were deposited onto glassy carbon electrodes by two procedures: static dipping and electrochemical cycling. Cyclic voltammetry and UV-vis spectroscopy reveal that approximately 1.5 x 10(-10) mol/cm(2) of P(2)W(18)O(62)(6-) and 2.2 x 10(-11) mol/cm(2) of cytochrome c are deposited per cycle, which correspond to approximately one monolayer of each molecule. The thicknesses of the resulting films measured by atomic force microscopy also indicate that the films are formed in a layer-by-layer fashion. Experimental factors that affect electron-transfer rate in these films, such as scan rate and film thickness, were systematically analyzed. The use of {P(2)W(18)O(62)(6-)/cyt c}n films to catalyze hydrogen peroxide reduction was demonstrated.     

Preparation and characterization of DNA films induced by UV irradiation

Large amounts of DNA-enriched materials, such as salmon milts and shellfish gonads, are discarded as industrial waste. We have been able to convert the discarded DNA to a useful material by preparing novel DNA films by UV irradiation. When DNA films were irradiated with UV light, the molecular weight of DNA was greatly increased. The reaction was inhibited by addition of the radical scavenger galvinoxyl suggesting that the DNA polymerization with UV irradiation proceeded by a radical reaction. Although this UV-irradiated DNA film was water-insoluble and resistant to hydrolysis by nuclease, the structure of the DNA film in water was similar to non-irradiated DNA and maintained B-form structure. In addition, the UV-irradiated DNA film could effectively accumulate and condense harmful DNA-intercalating compounds, such as ethidium bromide and acridine orange, from diluted aqueous solutions. The binding constant and exclusion number of ethidium bromide for UV-irradiated DNA were determined to be 6.8 +/- 0.3 x 10(4) M(-1) and 1.6 +/- 0.2, respectively; these values are consisted with reported results for non-irradiated DNA. The UV-irradiated DNA films have potential uses as a biomaterial filter for the removal of harmful DNA intercalating compounds.     

Preparation and photoelectrochemical characterization of nano-particulate TiO2 and polyaniline composite films on Au

TiO₂ and polyaniline(PANI) composite film was obtained by electrochemical methods^[1] and investigated for solar energy conversion application. A strong rectifying effect was found in the cyclic voltammogram of the film in dark when the scan speed was slow enough (5 mV/s) and a quasi-reversible voltammogram of the film was observed when the scan speed was fast (100 mV/s). The results of both the cyclic voltammograms and the SEM images of the composite film show that the PANI film is almost completely covered with nano-particulate TiO₂. Two anodic photocurrent bands and a cathodic band was observed in the spectra of the photocurrent of the TiO₂/PANI/PATP(p-aminothiophenol)/Au film in 0.05 mol/L Fe(CN)₆^3-/Fe(CN)₆^4- solution. The band at 300~400 nm (3.1~4.1 eV) can be ascribed to the photocurrent band of TiO₂ particles and the bands at 450~730 nm (1.7~2.8 eV) can be ascribed to those of the PANI. The partially-oxidized PANI has internal photoemission function and the insulating matrix of PANI is verified to be reduced PANI with a 3.33 eV bandgap energy. The flat-band potentials of partially-oxidized PANI and TiO₂/PANI composite film in 1.0 mol/LHClO₄ solution are determined as 0.87 V and 0.09(SHE) from Mott-Schottky plots, respectively.     

pH敏感的金纳米颗粒的制备及表征

利用立方硅氧烷(odaaps)作为保护剂合成了金纳米颗粒,利用紫外-可见(UV-vis)吸收光谱、透射电镜(TEM)对纳米颗粒进行了表征。通过改变纳米溶胶的pH值,从而改变立方硅氧烷上羧基的存在形式,控制纳米颗粒表面的电荷,实现金纳米颗粒的可逆聚集与分散;当将其pH值降低至2.5时,颗粒能够完全沉淀,加碱调节其pH与原始值(pH=9)一致时,聚集的颗粒会自动重新分散形成溶胶,其具有与起始一致的高分散性。     

Preparation and characterization of aqueous polyaniline battery using a modified polyaniline electrode

A rechargeable battery of the type Zn/ZnCl₂, NH₄Cl/polyaniline (PAn)-reticulated vitreous carbon was successfully prepared based on a PAn modified electrode. Voltage of the battery was 1.2 V. Charge-discharge behavior at a constant load of 2.5 k, recycle ability and the rate of self-discharge were measured. The results showed that the battery has a capacity of 121 mA h g⁻¹ polymer weight and coulombic efficiency was in the range between 75% and 100%. Self-discharge rate was less than 1% per day and the battery showed a good recycle ability. It was also found that even after 70 cycles, the decrease in the open-circuit voltage was less than 5%.     

Electrochemical properties of niosomes modified Au electrode and DNA recognition

Non-ionic surfactant vesicles (NSVs), also referred to as niosomes, have been studied as an alternative to conventional liposomes. In this paper, electrochemical inspection of the interaction between Herring sperm DNA and niosomes has been investigated after a simple and novel method for the formation of niosomes on Au electrode. Each step of electrode modification has been confirmed with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The assembly of octadecanethiol (ODT) layer on the electrode surface generates a packed film that introduces a barrier to the interfacial electron transfer (R_et), and the subsequent immobilization of niosomes onto the self-assembled monolayer (SAM) layer results in a further increase of R_et, due to the formed bilayer almost blocked the redox probe to the electrode surface. When Herring sperm DNA was added, the R_et value decreased, indicating that the barrier of the redox probe to the surface was disrupted. The addition of DNA caused the formation of some transmembrane channels for the redox probe across the niosomes. A good linear relationship between R_et value and DNA concentration was found over the 0–0.05 mg mL⁻¹ concentration range.     

Electrochemical properties of niosomes modified Au electrode and DNA recognition

Non-ionic surfactant vesicles (NSVs), also referred to as niosomes, have been studied as an alternative to conventional liposomes. In this paper, electrochemical inspection of the interaction between Herring sperm DNA and niosomes has been investigated after a simple and novel method for the formation of niosomes on Au electrode. Each step of electrode modification has been confirmed with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The assembly of octadecanethiol (ODT) layer on the electrode surface generates a packed film that introduces a barrier to the interfacial electron transfer (R(et)), and the subsequent immobilization of niosomes onto the self-assembled monolayer (SAM) layer results in a further increase of R(et), due to the formed bilayer almost blocked the redox probe to the electrode surface. When Herring sperm DNA was added, the R(et) value decreased, indicating that the barrier of the redox probe to the surface was disrupted. The addition of DNA caused the formation of some transmembrane channels for the redox probe across the niosomes. A good linear relationship between R(et) value and DNA concentration was found over the 0-0.05 mg mL(-1) concentration range.     

Pt/Au双金属纳米粒子的制备及表征

Poly (N-vinyl-2-pyrrolidone)-protected Pt/Au bimetallic nanoparticles were obtained by reducing the mixture of HAuCl4 and H2PtCl6 with sodium borohydride. UV-vis spectra, transmission electronic microscopy and X-my diffraction reveal that the prepared bimetallic nanoparticles are of alloy structure.     

Preparation and characterization of polymer-clay nanocomposite films

Polymer/clay nanocomposite films were prepared by means of electrodeposition of aqueous suspension including cathodic electrophoretic acrylic resin (CEAR) and Na⁺-montmorillonite (NMMT). Studies of XRD, SEM and TEM indicated well-dispersed NMMT platelets in the films prepared. The ideal dispersity achieved was thought to be the result of aqueous compatibility between CEAR molecules and NMMT platelets and the result of the water-involved process as well. The modulus and strength of the polymer/clay nanocomposite coatings tested by tensile testing and nano-indentation were effectively improved compared to those of the virgin CEAR film. In addition, the adhesion strength, flexibility and water-resistance represented by Chinese national standard (GB) kept the best grades.     

Preparation and characterization of functional group gradient surfaces

Functional group gradient surfaces where the density of functional groups changes gradually along the sample length were prepared. The functional group (? COOH, ? CONH₂, and ? OH group) gradient surfaces were produced by the treatment of low-density PE sheets using a corona with gradually increasing power, followed by the graft copolymerization of acrylic acid and subsequent substitution reaction of carboxylic acid groups to amide or hydroxyl groups. The prepared gradient surfaces were characterized by the measurement of water contact angle, FTIR-ATR, and ESCA. The gradient surfaces prepared can be used to systematically investigate the interactions of biological or other species in terms of the surface functional groups and their density of polymeric materials. © 1994 John Wiley & Sons, Inc.     

Preparation and characterization of anion-cation surfactants modified montmorillonite

The low-temperature molar heat capacities of CoPc and CoTMPP were measured by temperature modulated differential scanning calorimetry (TMDSC) over the temperature range from 223 to 413 K for the first time. No phase transition or thermal anomaly was observed in the experimental temperature range for CoPc. However, a structural change was found to be nonreversible for CoTMPP in the temperature range of 368–403 K, which was further validated by the results of IR and XRD. The molar enthalpy ΔH _m and entropy ΔS _m of phase transition of the CoTMPP were determined to be 3.301 kJ mol⁻¹ and 8.596 J K⁻¹ mol⁻¹, respectively. The thermodynamic parameters of CoPc and CoTMPP such as entropy and enthalpy relative to reference temperature 298.15 K were derived based on the above molar heat capacity data. Moreover, the thermal stability of these two compounds was further investigated through TG measurements. Three steps of mass loss were observed in the TG curve for CoPc and five steps for CoTMPP.     

Preparation and characterization of plasma-polymerized styrene thin films

Plasma-polymerized styrene (PPS) thin films (several hundred to several thousand Å thick) have been prepared under a variety of discharge conditions in a tubular reactor inductively coupled to a radio frequency (13.56 MHz) power supply. Studies have focussed on the correlation of deposited polymer structure, evidenced both at the film surface (via XPS analysis) and in the bulk polymer (via transmission FT–IR analysis) with controllable plasma parameters (coupled rf power, monomer flow rate, monomer pressure). It has been determined that the relative number of phenyl rings incorporated into the film intact is an inverse function of the power per styrene molecule ratio. Polymer deposition rate was found to be a strong function of styrene flow rate and substrate temperature. Plausible elements of the styrene plasma polymerization mechanism will be considered.     

Activation of electrode surfaces: semiquantitative characterization of electrode surfaces modified with heteropolyanions

Several Techniques have been used successively or in combination to approach a better understanding of surfaces modified by silicotungstic heteropolyanion. Due to the strikingly high activity of these electrodes for the hydrogen evolution reaction, in particular, there exists a need to identify the chemical composition of the catalyst, to evaluate the amount of catalyst on the surface, and to study the electrochemical behaviour of the “catalyst” itself. Plasma emission spectrometry shows semi-quantitatively that the catalyst resembles the starting material closely, although it is not possible at present to give the exact chemical formula. Electron microprobe analysis (EMA) confirms the presence of tungsten, and especially silicon, on the surface, even though the concentration of this last element is very low. The absence of platinum in the starting HPA, as well as on the electrode surface, is also clearly demonstrated by EMA, which is of prime importance in showing that the “HPA catalyst” is active by itself. Combined coulometry and UV-visible spectroscopy have been used to evaluate the amount of HPA consumed during electrolysis. Cyclic voltammetry shows a surface redox couple corresponding to the catalyst, and well separated from the first redox couple of SiW₁₂O^4-₄ in 0.5 M H₂SO₄ solution. A better understanding of the activation-deactivation processes of the catalytic electrode surface ensues.     

Electrochemical characterization of gold stepped surfaces modified with Pd

Three different single crystals, Au(111), Au(332), and Au(331), were used as the substrate for palladium deposition in the underpotential deposition (UPD) regime. The Au(111) single crystal was used for control experiments to compare the behavior of the vicinal surfaces. Cyclic voltammetry in 0.1 M sulfuric acid solution, as well as electrochemical impedance spectroscopy (EIS) were used to study the hydrogen adsorption on the Pd thin films. Our results suggest that the voltammetric peaks at approximately 0.3 V versus the reversible hydrogen electrode (RHE) are related to the adsorption of hydrogen at large palladium terraces, and that at least two adjacent Pd rows are needed in order for the adsorption to take place. Further cycling to more positive potentials leads to the oxidation and slow dissolution of the Pd film. The behavior of the oxidation cycles is explained in terms of a higher stability of Pd at the steps.     

Preparation and characterization of modified aluminum oxide catalysts

The formation of individual and modified high-purity aluminum oxides (γ-Al₂O₃) prepared from aluminum alcoholates was studied. In the study of the hydrolysis of aluminum alcoholates and modified (Zr, Ti, and Si) aluminum alcoholates, it was found that an increase in the chain length of the alkoxy group and an increase in the aging temperature or aging time in mother liquor resulted in a decrease in the concentration of an amorphous phase, an increase in the concentration of a pseudoboehmite phase, and an improvement in its crystal structure. Hydrolysis in alkaline (a 0.5 wt % solution of ammonia) or neutral solutions made it possible to obtain samples with an almost 100% pseudoboehmite content. At the same time, the samples prepared by hydrolysis in an acidic solution (a 0.1 M solution of HCl) contained a considerable amount of an amorphous phase. It was found that the specific rate of dehydration of n-butanol on the modified aluminum oxide samples linearly decreased with the concentration of donor sites and linearly increased with the concentration of acceptor sites, whose concentration was measured using the spin probe method.     

纳米聚苯胺及聚苯胺/金复合材料的制备与表征

以氯金酸(HAuCl4)为氧化剂,在两种不同无机酸(HCl和H2SO4)的掺杂下,通过调节反应体系中混合溶剂的醇水比例,用一步氧化苯胺聚合法成功制备了不同形貌的纳米聚苯胺及聚苯胺/金复合材料.通过扫描电子显微镜(SEM)、紫外可见吸收光谱(UV-Vis)和红外光谱(FT-IR)对产物的形貌和结构进行了表征.在此基础上,进一步讨论了聚苯胺/金复合材料可能的形成机理.     

Preparation and characterization of poly-N-vinyl carbazole langmuir-blodgett films

Langmuir monolayers of poly-N-vinyl carbazole (PNVK) were obtained by dispensing PNVK dissolved in tetrahydrofuran onto an air-water interface. Surface pressure-area isotherms of mixed monolayer of the PNVK were studied under different subphase conditions such as temperature and pH of the subphase. It was demonstrated that the monolayer of PNVK remained stable over a temperature range of 10–40°C. The area per molecule of the solid phase was found to be 31Ų. These monolayers were transferred onto indium-tin-oxide-coated glass plates and characterized by spectroscopic and electrochemical techniques.     

Preparation of transparent conductive multilayered films using active pentafluorophenyl ester modified multiwalled carbon nanotubes

A mutilayered film was prepared by layer-by-layer (LBL) assembly of active ester modified multiwalled carbon nanotubes (MWCNTs) and poly(allylamine hydrochloride) (PAH). For this purpose, carboxylic groups on the surface of the oxidized MWCNTs were converted to the acyl chlorides by their reaction with thionyl chloride. Subsequent reaction of the acyl chlorides with pentafluorophenol formed the active esters. These active ester modified MWCNTs (MWCNTs-COOC 6F 5) were air-stable and moisture resistant, but showed a high reactivity toward primary or secondary amines resulting in amide bonds. For the preparation of a multilayered film, the surface of a quartz slide was first activated and sacrificial double layers of PAH and poly(sodium 4-styrene sulfonate) (PSS) were deposited. Subsequently, LBL assembly of MWCNTs-COOC 6F 5 and PAH was then conducted on these double layers [(PAH/PSS) 2]. In the process of the assembly, a reaction occurred between the active ester on the surface of MWCNTs and the amine groups of polyallylamine yielding amide bonds, which resulted in a mechanically stable thin film. A free-standing film was obtained after dissolving the sacrificial layer [(PAH/PSS) 2] in a concentrated aqueous NaOH solution. The surface resistance of the multilayered film with 20 bilayers decreased to around 10 kOmega while remaining a reasonable transparency (70% at 500 nm).     

Characterization of self‐assembled phenyl and benzyl isothiocyanate thin films on Au surfaces

Structures of self‐assembled monolayers (SAMs) prepared from benzyl isothiocyanate (BZIT) and phenyl isothiocyanate (PHIT) were comparatively investigated by means of surface enhanced Raman scattering (SERS) on gold nanoparticle surfaces. Both the molecules are assumed to have upright geometries binding via the sulfur atom, from the SERS spectral features. The broad and split bands at ～2100 cm^?1 could be ascribed to the combination band ν_9a + ν₁₂ of the phenyl ring vibrations through a Fermi‐resonance interaction with the ν₃(NCS) band in the neat‐liquid state. Such broad bands became quite symmetric upon adsorption on Au. UV‐vis absorbance spectroscopy and cyclic voltammetry (CV) were used to compare the kinetics of the formation of SAMs on gold. Our results suggest that BZIT should have a relatively faster self‐assembly than PHIT, as indicated from signal decrease in the CV graph, which suggests a more vertical stance for BZIT in line with Raman measurements. Copyright © 2006 John Wiley & Sons, Ltd.