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1.
Hong Shen James E. Mark Carl J. Seliskar Harry B. Mark Jr. William R. Heineman 《Journal of Solid State Electrochemistry》1997,1(2):148-154
Self-assembled monolayers (SAMs) with metal electrodes, especially thiols on gold, are the subject of this investigation
because of the unique properties of SAM-modified surfaces. Normal alkanethiols are used to modify the surface of a conventional
gold electrode to block certain ions such as Pb(II) and Cu(II) from the surface of the electrode. Normal alkanethiols are
also used to study the SAM-gold interfacial adsorption-desorption behavior of the self-assembled monolayer. The effects of
varying chain length of SAMs, varying concentration of the alkanethiol solutions, immersion time of the pure gold electrode
in the SAM solution, and the stability of a SAM-modified gold electrode in fresh chloroform are investigated using the oxidation-reduction
peaks of gold. Conditions that optimize the surface coverage and the uniformity of the SAMs have been determined. Normal alkanethiols
proved to be a good insulator on the electrode surface.
Received: 16 January 1997 / Accepted: 4 March 1997 相似文献
2.
Teng-Yuan Dong Chienlin Huang Chiao-Pei Chen Ming-Cheng Lin 《Journal of organometallic chemistry》2007,692(23):5147-5155
We describe the formation of stable dithiol-bifunctionalized Ru(II)-terpyridine monolayer onto gold electrode. The coverage-dependent behavior onto gold electrode has been studied by electrochemical technique. The stability, surface charge coverage, and electron-transfer kinetics were assessed by cyclic voltammetry. Functionalized monolayer-protected Au clusters (MPCs) were also prepared. The spectroscopic characterization data of MPCs using UV-Vis and TEM techniques are discussed. TEM images showed that functionalized spherical nanoclusters of 4.7 ± 0.3 and 4.3 ± 0.2 nm were produced. The particle sizes are uniform with a narrow size distribution. The morphology of Au(1 1 1) metal surface modified with MPCs was imaged using atomic force microscopy (AFM). The nanoparticle layer exhibits a distinct surface morphology, irregularly shaped domains with dimensions from 20 to 60 nm and root mean square heights of 2.401 nm. 相似文献
3.
Self-assembled monolayers(SAMs) of thiol-derivatized porphyrin molecules on Au substrate have attracted extensively interest for use in sensing,optoelectronic devices and molecular electronics.In this paper,tetra-[p-(3-mercaptopropyloxy)-phenyl]porphyrin was synthesized and self-assembled with thiol on Au substrate for porphyrin SAMs(PPS 4).The electrochemical results demonstrated that PPS 4 could form excellent SAMs on gold surface.Self-assembled nanojunctions of PPS 4 were fabricated by using gold nanogap electrodes(gap width:ca.100 nm).With the light on/off,the nanojunctions showed current high/low as nanometer scaled photo switch. 相似文献
4.
A silylated-terpyridine(Si TPy) derivative was newly synthesized and reacted with various transition metal ions in the solutions and self-assembled monolayers(SAMs).Composition and morphology of the SAMs were characterized by using absorption spectra,X-ray photoelectron spectra and atomic force microscope.The silylated-TPy compound gave off a luminescent emission at about 456 nm,which slightly shifted to 452 nm in the Zn2+-Si TPy and Fe2+-Si TPy metalated complexes.The absorbed energy can be further transferred to lanthanide ions(Tb3+and Eu3+) to give off the typical emissions of the lanthanide complexes together with an emission of the silylated-TPy at about 363 nm. 相似文献
5.
Ana Lucero Caro M. Rosario Rodríguez Nio Juan M. Rodríguez Patino 《Colloids and surfaces. A, Physicochemical and engineering aspects》2009,346(1-3):146-157
In this work we have analyzed the topography by atomic force microscopy (AFM) of dipalmitoyl-phosphatidyl-choline (DPPC) monolayers previously spread at the air–water interface and penetrated by β-casein. AFM images of β-casein–DPPC monolayers were taken from Langmuir–Blodgett films deposited onto hydrophilic mica substrates at different initial surface pressures (πi) and after the compression of the mixed films. The monolayer topography depends on the initial structure of the phospholipid:liquid expanded (LE) at 3 mN/m, coexistence between LE and liquid condensed (LC) structures at 7 mN/m, at the end of the LE–LC transition at 10 mN/m, and with a LC structure at 15 mN/m. The area occupied by DPPC domains in the mixed film increases with the πi value, especially for DPPC with a LC structure at 15 mN/m. At this surface pressure the thickness of the film is at a maximum. After the film compression at 25 mN/m, which is above the equilibrium spreading pressure of β-casein (), this protein is displaced from the interface by DPPC and the topography of the mixed monolayer depends on the initial structure of the DPPC monolayer. A notable feature of the topography of these mixed monolayers is the presence of multilayers of β-casein and DPPC of high thickness (50–70 nm) at the lower πi values. Although the film is dominated by DPPC at the highest surface pressures (at 25 mN/m), β-casein is not displaced totally from the interface and coexists as β-casein collapsed domains within the network of the DPPC structure. 相似文献
6.
Caseli L Masui DC Furriel RP Leone FA Zaniquelli ME 《Colloids and surfaces. B, Biointerfaces》2005,46(4):248-254
This work investigates the process of incorporation of a glycosylphosphatidyl inositol (GPI)-anchored alkaline phosphatase into Langmuir monolayers of dimyristoyl phosphatidic acid (DMPA). Three different methods of protein incorporation were assayed. When the protein solution was injected below the air–water interface after formation of the lipid monolayer a micro-heterogeneous distribution of alkaline phosphatase throughout the interface was observed. Adsorption kinetics studied by fluorescence microscopy, associated with surface pressure measurements, led to the proposition of a model in which the protein penetration is modulated by the surface packing of the monolayer and intermolecular interactions occurring between the phospholipid and the protein. At initial surface pressures higher than 20 mN m−1, the protein is quickly adsorbed on the interface and the lateral diffusion drives the alkyl chains to turn towards the air phase while the polypeptide moiety faces the aqueous subphase. 相似文献
7.
Gunwook Park Sung-Wook Choi Jae-Ho Kim Sung-Hoon Kim Sam-Rok Keum Kwangnak Koh 《Microchemical Journal》2005,80(2):207-211
Spiroxazine are of considerable interest as photochromic materials because of their application. On the other hand, surface plasmon resonance (SPR) is a well-known optical method for measuring optical constants of thin film. In this study, photochromic materials were used as self-assembled monolayers (SAMs) of newly synthesized spiroxazine derivatives. We used Fresnel equation (four-layer model) to determine the precise dielectric constant () of the photochromic monolayers. Structure changes of spiroxazine derivatives under UV-light irradiation resulted in the change of optical constants, the dielectric constant and thickness. The obtained results indicated that the ring opening of photochromic spiroxazine can lead to the decrease in the dielectric constant and thickness. 相似文献
8.
Fortier H Westreich P Selig S Zelenietz C Dahn JR 《Journal of colloid and interface science》2008,320(2):423-435
The adsorption capacity of ZnCl(2)-impregnated activated carbon (AC) for NH(3) is reported in terms of stoichiometric ratio of reaction (NH(3) per ZnCl(2)). This ratio depends on the testing conditions used. Compared to the ratio obtained under dry conditions, the ratio is higher under humid conditions or increased NH(3) concentrations. The linear increase of the NH(3) capacity with increasing loading of ZnCl(2) breaks down at about 3.5 mmol ZnCl(2)/g AC. This behavior is explained in terms of preferential adsorption of a monolayer of salt followed by aggregation of the impregnant once a monolayer is completed. The effect of increasing the loading of ZnCl(2) on the capacity for gases for which the impregnants are not intended, namely cyclohexane, nitrogen, and water vapor, is also discussed. A break in the linear relationship between water capacity and impregnant loading at about 3.5 mmol ZnCl(2) seems to correspond to a full monolayer coverage of ZnCl(2) on AC. The monolayer of ZnCl(2) is shown to reduce the uptake of water into AC, while the ZnCl(2) aggregates are shown to be hydrophilic. 相似文献
9.
Gcineka Mbambisa 《Microchemical Journal》2009,93(1):60-66
Self-assembled monolayers (SAMs) based on octapentylthiophthalocyanine complexes of oxovanadium (IV) (OVOPThPc), titanium(IV) (OTiOPThPc), and manganese (III) acetate (AcMnOPThPc), and of tetraphenylthiophthalocyanine complexes of hydroxo manganese(III) (OHMnTPPc) and oxotitanium(IV) (OTiTPPc) are described. The oxidation of l-cysteine was observed at potentials which ranged from 0.52 V to 0.67 V. The detection limits for l-cysteine analysis were of the order of 10− 7 to 10− 6 M. 相似文献
10.
Single crystals of the organic‐inorganic arsenate(III): [(CH3)2NH2]3[As2Cl9] and [(CH3)2NH2][AsOCl2] have been grown from aqueous hydrochloric acid solution. The crystals [(CH3)2NH2]3[As2Cl9] have been investigated by X‐ray diffraction (at 253 K), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dilatometric and dielectric methods. They undergo two structural phase transitions of first order at 228/235 and 298/307 K (on cooling/heating), respectively, which are classified as an "order‐disorder" type. The trigonal [(CH3)2NH2]3[As2Cl9] structure (at 253 K, intermediate phase (II)) refined in the space group R3c, consists of isolated [As2Cl9]3‐ bioctahedral units and dimethylammonium cations hydrogen bonded to the bridging Cl atoms of the anions. The crystals of [(CH3)2NH2][AsOCl2] at 100 K are orthorhombic, space group Cmca. The structure contains one‐dimensional chains formed by strong distorted [AsO2Cl4] octahedra. The dimethylammonium cations reveal distinct disorder. 相似文献
11.
Summary The structures, textures as well as thermodynamic properties of a side chain polymer exhibiting a liquid crystalline phase in addition to a partially crystalline state and the isotropic fluid state were investigated. Furthermore the kinetics of phase transitions between these states were analyzed. It was found that the properties of this polymer are intermediate between that of low molecular weight liquid crystals and common polymers. In particular it was observed that the relation between the liquid crystalline texture and the structure is different from that of low molecular weight liquid crystals and that the properties of the crystalline and liquid crystalline state depend strongly on the tacticity of the polymer.
Zusammenfassung Für ein Seitenkettenpolymeres, das zusätzlich zum teilkristallinen Zustand und zur isotropen Schmelze einen flüssig-kristallinen Zustand aufweist, wurden die Strukturen und Texturen untersucht sowie thermodynamische Eigenschaften. Außerdem wurde die Kinetik der Phasenumwandlungen analysiert. Es zeigt sich, daß die Eigenschaften zwischen denen üblicher Polymerer und denen von niedrigmolekularen flüssigen Kristallen liegen. Insbesondere zeigte sich, daß die Beziehung zwischen molekularer Struktur und Textur von der bei niedrigmolekularen flüssigen Kristallen abweicht, und daß die Taktizität der Kette einen starken Einfluß auf die Eigenschaften nicht nur der kristallinen Phase sondern auch der flüssig-kristallinen Phase ausübt.相似文献
12.
Xueping Ji Baokang Jin Jiye Jin Toshio Nakamura 《Journal of Electroanalytical Chemistry》2006,590(2):46
Horse heart cytochrome c (cyt c) was adsorbed on the binary self-assembled monolayers (SAMs) composed of thioctic acid (T-COOH) and thioctic amide (T-NH2) at gold electrodes via electrostatic interaction. The cyt c adsorbed on the modified gold electrode exhibited well-defined reversible electrochemical behavior in 10 mM phosphate buffer solution (PBS, pH 7.0). The surface concentration (Γ) of electroactive species, cyt c, on the binary SAMs was higher than that in single-component SAMs of T-COOH, and reached a maximum value of 9.2 × 10−12 mol cm−2 when the ratio of T-COOH to T-NH2 in adsorption solution was of 3:2, and the formal potential (E0′=(Epa+Epc)/2) of cyt c was −0.032 V (vs. Ag|AgCl (3 M NaCl)) in a 10 mM PBS. The interaction between cyt c and the binary SAMs made the E0′ shift negatively when compared with that of cyt c in solution (+0.258 V vs. NHE, i.e., +0.058 V vs. Ag|AgCl (3 M NaCl)). The fractional coverage of bound cyt c was a 0.64 theoretical monolayer. The standard electron transfer rate constant of cyt c immobilized on the binary SAMs was also higher than that on single-component SAMs of T-COOH, and the maximum value of 15.8 ± 0.6 s−1 was obtained when the ratio of T-COOH to T-NH2 in adsorption solution was at 3:2. The results suggest that the electrode modified with the binary SAMs functions better than the electrode modified with single-component SAMs of T-COOH. 相似文献
13.
14.
Silicon tetraisocyanate Si(NCO)4 was obtained by reacting SiCl4 and AgNCO in boiling toluene. The colourless liquid was analyzed by Raman and NMR spectroscopy. Structural studies on solid Si(NCO)4 (melting point: +26 °C) have revealed it to exist in two polymorphic modifications. According to the results of single‐crystal X‐ray diffraction, at T = –173 °C, α‐Si(NCO)4 exhibits triclinic symmetry (P$\bar{1}$ ; a = 10.05(5), b = 10.50(2), c = 14.32(1) Å, α = 91.62(1)°, β = 92, 32(1)°, γ = 99.68(1)°; V = 1488.56(3) Å3; Z = 8). Above T = –33 °C, a monoclinic phase evolves, β‐Si(NCO)4 (P21/c; a = 10.78(3), b = 7.11(1), c = 10.27(5) Å, β = 99, 06(9)°; V = 777.39(1) Å3; Z = 4). The charge distribution was studied for both polymorphs. In the solid state, Si(NCO)4 is a tetrahedral molecule with the Si–N=C=O linkages bent at the nitrogen atoms. 相似文献
15.
High-resolution neutron powder diffraction is particularly suited for structure solution and refinement of low-melting point organic crystals of moderate complexity. Here we present the ab initio structure solution and refinement of stable-phase and metastable-phase perdeuterated acetaldehyde (m.p.: 151 K). In the stable phase, the molecule crystallises in the space group P21/c (no. 14) with a=3.9069(1) Å, b=5.4224(1) Å, c=12.1868(1) Å, β=94.2970(2)° at 5 K, Z=4. In the metastable phase, the molecule crystallises in the space group Pna21 (no. 33) with a=5.1973(1) Å, b=6.9791(1) Å, c=6.9712(1) Å at 5 K, Z=4. The metastable to stable phase transition is characterised by heat capacity measurements. 相似文献
16.
We present all-atom molecular dynamics simulations ofn-hexane on the basal plane of graphite at monolayer and multilayer coverages. In keeping with experimental data, we find the
presence of ordered adsorbed layers both at single monolayer coverage and when the adsorbed layer coexists with excess liquid
adsorbate. Using a simulation method that does not impose any particular periodicity on the adsorbed layer, we quantitatively
compare our results to the results of neutron diffraction experiments and find a structural transition from a uniaxially incommensurate
lattice to a fully commensurate structure on increasing the coverage from a monolayer to a multilayer. The zig-zag backbone
planes of all the alkane molecules lie parallel to the graphite surface at the multilayer coverage, while a few molecules
are observed to attain the perpendicular orientation at monolayer coverage.
Dedicated to Professor C N R Rao on his 70th birthday 相似文献
17.
The synthesis, structural, and thermal characterization of lithium cyanate are reported in this work. LiOCN forms crystals in the trigonal crystal system. The structure was solved in the space group R$\bar{3}$ m. It is isomorphous to the structure of sodium cyanate. In the temperature range from –90 °C up to the melting point no phase transition was observed. Furthermore the vibrational Raman spectrum was measured. The system KOCN‐LiOCN shows a dystecticum and the new phase was confirmed by powder X‐ray diffraction. 相似文献
18.
The structures of 28 compounds in the two series Ba2LnSbO6 and Ba2LnNbO6 have been examined using synchrotron X-ray and in selected cases neutron powder diffraction at, below and above ambient temperature. The antimonate series is found to undergo a sequence of phase transitions from monoclinic to rhombohedral to cubic symmetry with both decreasing ionic radii of the lanthanides and increasing temperature. Compounds in the series Ba2LnNbO6, on the other hand, feature an intermediate tetragonal structure instead of the rhombohedral structure exhibited by the antimonates. This difference in symmetry is thought to be caused by π-bonding in the niobates that is absent in the antimonates. The bonding environments of the cations in these compounds have also been examined with overbonding of the lanthanide and niobium cations being caused by the unusually large B-site cations. 相似文献
19.
Five molecular dynamics computer simulations were performed to study the structural and dynamical properties of water next to uncharged and charged Pt surfaces. The results show that the structure of a water layer adsorbed on the metal surface is very sensitive to the details of the water–metal potential. While patches of short-living hexagonal ice-like structure are observed in the adsorbed water layer next to the uncharged Pt(111) surface, a square lattice solid-like structure is seen for the layer on top of the uncharged Pt(100) surface. The orientational ordering for the following two layers of water next to uncharged Pt is displaying a preference towards the orientations that are characteristic of hexagonal ice-I, while water is liquid-like in these layers. In the presence of a high value external electric field water reorients and undergoes a layering transition. 相似文献
20.
A new (β‐)modification of the mercury molybdate Hg2Mo2O7, thermodynamically stable at temperatures above 390 ± 10 °C, was prepared by solid state reaction of HgO with MoO2 in sealed silica tubes. Its crystal structure, determined from single‐crystal X‐ray data, has a very pronounced subcell: space group P2/c, a = 600.9(1) pm, b = 388.7(1) pm, c = 1428.4(2) pm, β = 105.88(1)°, Z = 2, R = 0.052 for 797 structure factors and 52 variable parameters. In the superstructure of this high‐temperature β‐modification the a and the b axes of the subcell are doubled: C2/c, a = 1201.9(2) pm, b = 777.3(1) pm, c = 1428.4(2) pm, β = 105.88(1)°, Z = 8, R = 0.040 for 1490 F values and 110 variables. Like the previously reported low‐temperature α‐modification, the β‐modification consists of two‐dimensionally infinite sheets of edge‐ and corner‐sharing MoO6 octahedra. These sheets are linked by Hg2 pairs. Thus, the structures of the two modifications (α and β) differ essentially only in the orientation of the Hg2 pairs, which are located between the sheets of the MoO6 octahedra. The superstructure of the β‐modification differs from the subcell‐structure by the puckering of the sheets of MoO6 octahedra. A hypothetical displacive phase transition between the subcell‐structure (corresponding to the potential high‐temperature structure) and the superstructure of β‐Hg2Mo2O7 is discussed. 相似文献