Spectroscopic and Electrochemical Characterization of Cytochrome P450st‐DDAB Films on a Plastic‐Formed Carbon Electrode

We have studied the characterization of thermophilic cytochrome P450 (P450st)‐didodecyldimethylammonium bromide (DDAB) films by using UV‐vis absorption, resonance Raman spectroscopy, and electrochemical methods. The observed Raman spectrum indicated near‐native conformation of the heme iron in DDAB film on the surface of a glass slide, while on the surface of a plastic‐formed carbon (PFC) electrode, the conformation of P450st‐DDAB was very similar to that of heme‐DDAB film, suggesting the release of heme from P450st in DDAB films on PFC electrodes. When NaBr was added as salt to the casting solution, the result of Raman spectrum indicated near‐native conformation of P450st in DDAB film even on the PFC electrode, but no redox potential of P450st which has near native structure was observed. This study suggests the essential experimental conditions when working with heme protein‐DDAB films as, in some cases, heme iron from proteins is released on the surface of the electrode.     

Challenges in the structural characterization of thin organic films

This review addresses the special problems associated with the micro-structural characterization of thin and ultrathin organic films, primarily by optical spectroscopies. Films which are deposited by Langmuir-Blodgett techniques, self-assembly chemistry, and bulk film deposition techniques are considered. The use of enhanced optical excitation using surface phasma resonances and integrated optical structures is discussed extensively, as is the use of ellipsometry. Discussion of the spectroscopies used is broken into a section on electronic spectroscopies and an extensive discussion of vibrational spectroscopies. Vibrational information may be obtained with photons (absorption or scattering) or electrons (loss spectra), and the types of experimental systems amenable to each, along with the advantages and disadvantages of each are explored.     

RuO2 electrode surface effects in electrocatalytic oxidation of glucose

We have studied the electrocatalytic activity of RuO₂-PVC film electrodes, fabricated using RuO₂ powders prepared at five different temperatures, viz., 300, 400, 500, 600 and 700°C, for the oxidation of glucose in high alkaline media, 1 to 3 M NaOH. The RuO₂-PVC film electrodes have been first characterized in 1 to 3 M NaOH solution by cyclic voltammetry (CV) and rotating disc electrode (RDE) techniques in a wide potential range −1,100 to 450 mV (SCE), and three redox pairs representing Ru(IV)/Ru(III), Ru(VI)/Ru(IV) and Ru(VII)/Ru(VI) transitions have been identified. The voltammetric peaks at low sweep rates have been analyzed using surface activity theory formulated for interacting electroactive adsorption sites, and interaction terms have been evaluated. The total voltammetric surface charges have been analyzed as per Trassatti’s formalism with respect to their dependence on potential sweep rate, and charges associated with less accessible and more accessible surface sites have been calculated. For glucose oxidation, the results have indicated that RuO₂ (700°C)-PVC electrode shows two oxidation peaks in contrast to RuO₂ (300°C)-PVC electrode. Also, RuO₂ (700°C)-PVC electrode exhibits higher intrinsic electrocatalytic activity than the 300°C electrode, although the former possesses lower electrochemically active surface area. Additionally, kinetic analyses made from RDE results with reference to Michealis–Menten (MM) enzyme catalysis has shown that RuO₂ (700°C) electrode possesses extended glucose-sensing range in terms of MM kinetic constant, K _M , compared to other electrodes. Possible reasons for such differences in the behavior of the electrodes of different temperatures towards glucose oxidation are identified from studies on oxidation of glucose in solutions of different pH, oxidation of different glucose derivatives, and also from physicochemical results from BET, XRD, SEM, DTGA, XPS analysis of RuO₂ powder samples.     

Molecular imprinting in ultrathin titania gel films via surface sol-gel process

Recent progresses of molecular imprinting in metal oxide matrices were summarized. Application of the surface sol-gel process to mixtures of organic carboxylic acids and titanium alkoxide provides ultrathin layers of titania gel (10-20 nm thick), in which molecule-sized cavities are kept intact upon removal of the organic templates. The imprinted cavity reflects the structural and functional features of the template molecule, and the enantioselective imprinting of dipeptide isomers is observed. Robustness and flexibility of the ultrathin titania layer is demonstrated by the formation of interconnected titania hollow structures. Possible practical applications and unsolved problems of this technique are discussed.     

Titanium‐implanted CaTiO3 films and their changes in Hanks' solution

Titanium‐implanted CaTiO₃ film was prepared and then characterized by x‐ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS) before and after immersion in Hanks' solution for 7 days. An as‐prepared specimen contained a small amount of Ar implanted during sputtering, although the pressure was as low as 10^?4 Torr. Even though Ar convolution increased with an increase in the relative Ti ion dose, most of the convoluted Ar was not from the Ar gas used for Ti ion production but rather was from the Ar gas used for sputtering the CaTiO₃. During Ti implantation, the CaTiO₃ films were ion‐etched by Ti ions. The composition of the CaTiO₃ film was not changed to any great degree by the Ti implantation, however its properties changed considerably. After immersion in Hanks' solution, the thickness of the specimen not implanted with Ti decreased the most whereas the [Ca]/[P] ratio, which was nearly unity before exposure, decreased significantly, becoming 0.23 on the Ti‐implanted specimen prepared at 200 W and 0.13 on the Ti‐implanted specimen prepared at 50 W. It was also observed by XPS that the ratio [Ca]/[P] was ～1.9 for all Ti‐implanted specimens after immersion in Hanks' solution for 7 days. Judging from the binding energies of Ca 2p_3/2 and P 2p electrons and the [Ca]/[P] ratio, it was suggested that a hydroxyapatite‐like substance had formed on the surfaces of the Ti‐implanted specimens after immersion in Hanks' solution. Copyright © 2003 John Wiley & Sons, Ltd.     

溶液成膜的温度对聚对苯二甲酸乙二酯结晶度的影响

<正> 用溶液成膜是制备聚合物薄膜的常用方法之一。但是溶液成膜的条件,如成膜温度,溶液浓度等对半结晶聚合物结晶度的影响研究报道较少。制备聚对苯二甲酸乙二酯(PET)非晶态薄膜通常使用熔融热压其后淬火的方法。由于PET在熔点附近易于降解,在薄膜中产生气泡,因而很难制备较大面积的均一厚度的薄膜,如在拉伸试验中所需     

铜膜差分脉冲阳极溶出伏安法测定药物中铋的含量

研究了铜膜电极代替汞膜电极测定重金属铋的差分脉冲溶出伏安法。实验了同位镀膜法测定铋的条件。在最佳实验条件下,Bi3+浓度在5×10-8~2×10-5mol/L范围内,其溶出峰峰高与浓度呈线性关系,检出限达到1×10-8mol/L。测定了一些药物中铋的含量,结果准确。     

金属基上以YSZ为过渡层的YBCO薄膜的微观结构

采用透射电子显微术（ＴＥＭ），研究了用磁控溅射技术在柔性金属基体上制备的、钇稳定的ＺｒＯ２（ＹＳＺ）为过镀层的ＹＢａ２Ｃｕ３Ｏ７－ｙ（ＹＢＣＯ）薄膜的横断面结构。所得ＹＢＣＯ膜的超导临界转变温度Ｔｃ为９１Ｋ，临界电流密度Ｊｃ＝２×１０３Ａ／ｃｍ２（７７Ｋ，０Ｔ）。基体为Ｎｉ基合金（ＨａｓｔｅｌｏｙＣ）。ＹＳＺ层为致密、均匀的细晶组织，约１２μｍ厚，具有织构取向，并与基体紧密连接。ＹＢＣＯ层的厚度不均匀，约５００ｎｍ；ＹＢＣＯ／ＹＳＺ界面有时连接较差，在该界面上有杂质出现，杂质有可能引发裂纹。     

Sol-Gel Preparation and Photoelectrochemical Properties of Fe2TiO5 Thin Films

Polycrystalline Fe₂TiO₅ films were prepared on nesa silica glass substrates by the sol-gel method, and their photoanodic properties were measured in a three-electrode wet cell with an aqueous buffer solution of pH = 7. Gel films were crystallized into Fe₂TiO₅ when fired at 500°C. The photoanodic current significantly increased when the films were fired at 700°C, and then decreased with increasing firing temperature. Thicker films obtained by repeating the gel film deposition and firing showed smaller photocurrent, and the 50 nm thick film prepared via non-repetitive deposition exhibited the maximum photocurrent. Although the photoresponse was extended to wavelengths near 500 nm, the maximum quantum yield was as low as 0.12 at a wavelength of 340 nm.     

Perfluorinated polymer surfaces comprising SF5-terminated long-chain perfluoroacrylate

A new perfluorinated acrylate monomer containing the SF₅(CF₂)₆-perfluorinated side chain was synthesized and polymerized into films. Bulk monomer characterization is consistent with the molecular structure based on FTIR, mass spectrometry and NMR analyses. The surface properties of polymer coatings were studied with aqueous wetting (contact angle) and X-ray photoelectron spectroscopy (XPS) methods. The surface composition is shown to be highly enriched in the terminal side chain SF₅-chemistry and exhibits properties consistent with a highly apolar, non-wetting perfluorinated polymer surface. Depth-dependent XPS studies using angular-resolved methods (ADXPS) confirmed a non-stoichiometric enrichment of sulfur and fluorine at the film ambient interface, consistent with a surface presence of the terminal SF₅-group and possibly film structural anisotropy in the surface zone. Time-of-flight (TOF) secondary ion mass spectrometry (SIMS) analysis supplements the XPS data by showing the presence of all expected SF₅-acrylate chemistry components in the outer 15 Å of the film surface.