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1.
A light-harvesting complex of photosystem II (LHCII), isolated from spinach, was immobilized onto a gold electrode modified with self-assembled monolayers (SAMs) of alkanethiols, NH2–(CH2) n –SH, n = 2, 6, 8, 11; HOOC–(CH2)7–SH; and CH3–(CH2)7–SH; and a bare electrode. The extent of LHCII complex adsorption according to surface treatment decreased in the order amino groups > carboxylic acid groups > methyl groups and increased with the methylene chain length in NH2–(CH2) n –SH. Interestingly, the photocurrent density depended on the terminal group and the methylene chain length in NH2–(CH2) n –SH and decreased in the order amino groups > methyl groups > carboxylic acid groups. An efficient photocurrent response of the LHCII complex on SAMs of NH2–(CH2) n –SH, n = 8 was observed upon illumination at 680 nm. These results indicated that the LHCII complexes were well organized on the cationic surfaces of the gold electrodes modified with amino alkanethiols. The quantum yield depended on the methylene chain length (n), where the maximum photocurrent response was observed at n = 8, which corresponded to a distance of 1.7 nm between the terminal amino group in NH2–(CH2)8–SH and the gold surface.  相似文献   

2.
Redox reactions of solvated molecular species at gold‐electrode surfaces modified by electrochemically inactive self‐assembled molecular monolayers (SAMs) are found to be activated by introducing Au nanoparticles (NPs) covalently bound to the SAM to form a reactive Au–alkanedithiol–NP–molecule hybrid entity. The NP appears to relay long‐range electron transfer (ET) so that the rate of the redox reaction may be as efficient as directly on a bare Au electrode, even though the ET distance is increased by several nanometers. In this study, we have employed a fast redox reaction of surface‐confined 6‐(ferrocenyl) hexanethiol molecules and NPs of Au, Pt and Pd to address the dependence of the rate of ET through the hybrid on the particular NP metal. Cyclic voltammograms show an increasing difference in the peak‐to‐peak separation for NPs in the order Au<Pt<Pd, especially when the length of the alkanedithiol increases from octanedithiol to decanedithiol. The corresponding apparent rate constants, kapp, for decanedithiol are 1170, 360 and 14 s?1 for NPs of Au, Pt and Pd, respectively, indicating that the efficiency of NP mediation of the ET clearly depends on the nature of the NP. Based on a preliminary analysis rooted in interfacial electrochemical ET theory, combined with a simplified two‐step view of the NP coupling to the electrode and the molecule, this observation is referred to the density of electronic states of the NPs, reflected in a broadening of the molecular electron/NP bridge group levels and energy‐gap differences between the Fermi levels of the different metals.  相似文献   

3.
《Electroanalysis》2003,15(22):1756-1761
Mercaptoundecanoic acid (MUA) and glutathione (GSH) self‐assembled monolayers were prepared on gold‐ wire microelectrode. Cyclic voltammetry was used to investigate the influence of temperature on electrochemical behaviors of Fe(CN)63?/4? and Ru(NH3)63+/2+ at these SAMs modified electrodes in aqueous solution. It is found that temperature shows great influence on electron transfer (ET) and mass transport (MT) for the two SAMs modified electrodes and the influence of temperature depends on the charge properties of the redox couples and terminal groups of SAMs and the structure of the monolayer on gold surface. The temperature can greatly increase MT rate of Fe(CN)63?/4? at both MUA and GSH modified electrodes. However, the increased MT rate doesn't have any effect on the CV's for Fe(CN)63?/4? /MUA system. For Ru(NH3)63+/2+ , temperature can greatly improve the electrochemical reaction in both MUA and GSH modified electrodes, which is ascribed to temperature‐induced diffusion and convection and the electrostatic interaction between Ru(NH3)63+/2+ and negatively charged carboxyl groups on the electrode surface.  相似文献   

4.
Patterning of TiO2 thin films was successfully obtained on different self-assembled monolayers (SAMs) in aqueous solution by micro-contact printing (μCP) method. The substrates were immersed in an aqueous solution containing titanium sulfate (Ti(SO4)2) and hydrogen peroxide for deposition at 80 °C. The growth rates on various surfaces were as follows: sulfonic (–SO3H) > amino (–NH2) > methyl (–CH3) > hydroxyl (–OH). According to the XPS results, SAMs with the terminal groups of –SO3H and –NH2 were favorable for the deposition. The TiO2 film deposited on the SAM with the terminal group of –CH3 could be easily peeled off. Clearly, TiO2 patterns were obtained on the prepatterned surfaces of –SO3H/–CH3 and –NH2/–CH3 SAMs. The deposition mechanism might be relevant to electrostatic interaction, Stern layer, lone pair electrons and Van der Vaals forces. The TiO2 film was anatase after annealing at 500 °C and comprised particles with an average diameter of ca. 10 nm.  相似文献   

5.
The electrochemical behavior of cytochrome c (cyt‐c) that was electrostatically immobilized onto a self‐assembled monolayer (SAM) of captopril (capt) on a gold electrode has been investigated. Cyclic voltammetry, scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy were employed to evaluate the blocking property of the capt SAM. SECM was used to measure the bimolecular electron transfer (ET) kinetics (kBI) between a solution‐based redox probe and the immobilized protein. In addition, the tunneling ET between the immobilized protein and the underlying gold electrode was calculated. A kBI value of (5.0±0.6)×108 mol?1 cm3 s?1 for the bimolecular ET and a standard tunneling rate constant (k0) of 46.4±0.2 s?1 for the tunneling ET have been obtained.  相似文献   

6.
Rate constants are reported for peroxodisulfate as well as periodate oxidation of[Co(en)2{SCH2CH(COO)NH2}]+, [Co(en)2(SCH2CH2NH2)]2+, and [Co(en)2(SOCH2CH2NH2)]2+ in water–acetonitrile mixtures. The dependence of rate constants on the acetonitrile concentration is established and discussed. Ancillary information relevant to solvation of reactants has been obtained from solvatochromism and from Gibbs transfer functions. The solvent effect is discussed from the viewpoint of change in solvation of initial and transition state on going from water to water–acetonitrile mixtures. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 34–40, 2004  相似文献   

7.
Molecular modeling, electrochemical methods, and quartz crystal microbalance were used to characterize immobilized hexameric tyrosine‐coordinated heme protein (HTHP) on bare carbon or on gold electrodes modified with positively and negatively charged self‐assembled monolayers (SAMs), respectively. HTHP binds to the positively charged surface but no direct electron transfer (DET) is found due to the long distance of the active sites from the electrode surfaces. At carboxyl‐terminated surfaces, the neutrally charged bottom of HTHP can bind to the SAM. For this “disc” orientation all six hemes are close to the electrode and their direct electron transfer should be efficient. HTHP on all negatively charged SAMs showed a quasi‐reversible redox behavior with rate constant ks values between 0.93 and 2.86 s?1 and apparent formal potentials ${E{{0{^{\prime }}\hfill \atop {\rm app}\hfill}}}$ between ‐131.1 and ‐249.1 mV. On the MUA/MU‐modified electrode, the maximum surface concentration corresponds to a complete monolayer of the hexameric HTHP in the disc orientation. HTHP electrostatically immobilized on negatively charged SAMs shows electrocatalysis of peroxide reduction and enzymatic oxidation of NADH.  相似文献   

8.
Anhydrous Lanthanum Acetate, La(CH3COO)3, and its Precursor, ·NH4)3[La(CH3COO)6] · 1/2 H2O: Synthesis, Structures, Thermal Behaviour Single crystals of (NH4)3[La(CH3COO)6] · ½ H2O are obtained by refluxing La2O3in (CH3COO)3 · 1.5 H2O with an excess of NH4CH3COO in methanol. The crystal structure (trigonal, R3 , Z = 6, a = 1 365.0(3) pm, c = 2 360(1) pm, R = 0.088, Rw = 0.061 exhibits the coordination number of nine for La3+, which is surrounded by three chelating-type bidentate and three unidentate acetate groups. Characteristic are monomeric units of [La(CH3COO)6]3? which are connected to a three-dimensional network by hydrogen bonds with the NH ions. Thermal decomposition consists of four steps with La(CH3COO)3, La2(CO3)3 and La2O2CO3 as intermediates and La2O3 as the final Product. Single crystals of La(CH3COO)3 are obtained from La2O3 in a melt of NH4CH3COO (molar ratio 1:12) in a sealed glass ampoule. The crystal structure (trigonal, R3 , Z = 18, a = 2 203.0(5) pm; c = 987.1(3) pm, R = 0.027, Rw = 0.023) shows the coordination number of ten for La3+. These are three-dimensionally connected by oxygen atoms of the acetate groups with two tetradentate double-bridging and one Z,Z-type-bridging bidentate acetate group.  相似文献   

9.
Prussian blue nanoparticles (PBNPs) were prepared by a self‐assembly process on a glassy carbon electrode (GCE) modified with poly(o‐phenylenediamine) (PoPD) film. The stepwise fabrication process of PBNP‐modified PoPD/GCE was characterized using scanning electron microscopy and electrochemical impedance spectroscopy. The prepared PBNPs showed an average size of 70 nm and a homogeneous distribution on the surface of the modified electrode. The PBNPs/PoPD/GCE showed electrocatalytic activity towards the oxidation of pyridoxine (PN) and was used as an amperometric sensor. The modified electrode exhibited a linear response for PN oxidation over the concentration range 3–38.5 μM with a detection limit of ca 6.10 × 10?7 M (S/N = 3) and sensitivity of 2.79936 × 103 mA M?1 cm?2 using an amperometric method. The mechanism and kinetics of the catalytic oxidation reaction of PN were investigated using cyclic voltammetry and chronoamperometry. The values of α, kcat and D were estimated as 0.36, 1.089 × 102 M?1 s?1 and 8.9 × 10?5 cm2 s?1, respectively. This sensor also exhibited good anti‐interference and selectivity. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

10.
Two new three‐dimensional frameworks with zeolite‐like channels were prepared in the presence of 1,6‐diaminohexane. Cu1.5(H3N–(CH2)6–NH3)0.5[C6H2(COO)4] · 5H2O ( 1 ) crystallizes in the triclinic space group P$\bar{1}$ with a = 772.56(7), b = 1110.36(7), c = 1111.98(8) pm, α = 98.720(7)°, β = 108.246(9)°, and γ = 95.559(7)°. Cu2(H3N–(CH2)6–NH3)0.5(OH)[C6H2(COO)4] · 3H2O ( 2 ) crystallizes in the monoclinic space group P2/c with a = 1159.34(11), b = 1059.44(7), c = 1582.2(2) pm, and β = 106.130(11)°. The Cu2+ coordination polyhedra are connected by [C6H2(COO)4]4– anions to yield three‐dimensional frameworks with wide centrosymmetric channel‐like voids. Complex 1 reveals voids extending along [100] with diagonals of 900 pm and 300 pm, whereas in complex 2 the diagonal of the nearly rectangular crossection of the channels extending parallel to [001] is 900 pm. The negative excess charges of the frameworks are compensated by [H3N–(CH2)6–NH3]2+ cations, which occupy the voids along with water molecules. The [H3N–(CH2)6–NH3]2+ cations are not connected to Cu2+ and have served as templates.  相似文献   

11.
Information on the solvation of thiolato complex cations [Co(en)2(SCH2COO)]+ [Co(en)2(SCH2CH(COO)NH2)]+, [Co(en)2(SCH2CH2NH2)]2+, sulfenato complexes [Co(en)2(SOCH2COO)]+ [Co(en)2{SOCH2CH(COO)NH2}]+, [Co(en)2(SOCH2CH2NH2)]2+, the sulfinato [Co(en)2{SO2CH2CH(COO)NH2}]+, [Co(en)2(SO2CH2CH2NH2)]2+ as well as of [Co(en)3]3+ has been obtained from solubility measurements in MeCN–H2O mixtures at 298.2 K. The single-ion Gibbs energies of transfer of the CoIII complexes were derived from the solubilities of picrate and perchlorate salts for the full range of MeCN–H2O mixtures. Single-ion Gibbs energies of transfer for the perchlorate ion are given. The effects of the solvent mixtures were interpreted in the framework of chemical bond formation between the ions and the individual solvent molecules.  相似文献   

12.
From the reduction of heptamolybdate, a polyoxomolybdate was obtained with the formula [Na(H2O)16(NH2CH2­COO)]4+·{Na+[H9MoMoO56(NH2CH2COO)]5?}4?­·20H2O, i.e. hepta­sodium nona­hydrogen tetra­car­bam­ate hexa­deca­aqua­hexa­penta­conta­oxa­octa­deca­molyb­date(V,VI) icosa­hydrate. The 18 Mo atoms are connected by bridging O atoms to form a centrosymmetric girdle‐like structure, in which MoV–MoV units are found. An Na+ cation occupies the central hole of the girdle, while four Na+ cations are bonded to the O atoms on the girdle edge. The girdles are linked into a one‐dimensional chain by the other Na+ cations.  相似文献   

13.
Efficient electron communication between molecular catalyst and support is critical for heterogeneous molecular electrocatalysis and yet it is often overlooked during the catalyst design. Taking CO2 electro-reduction on tetraphenylporphyrin cobalt (PCo) immobilized onto graphene as an example, we demonstrate that adding a relay molecule improves the interfacial electron communication. While the directly immobilized PCo on graphene exhibits relatively poor electron communications, it is found that diphenyl sulfide serves as an axial ligand for PCo and it improves the redox activity of PCo on the graphene surface to facilitate the generation of [PCo].- active sites for CO2 reduction. Thus, the turnover frequencies of the immobilized Co complexes are increased. Systematic structural analysis indicates that the benzene rings of diphenyl sulfide exhibit strong face-to-face stacking with graphene, which is proposed as an efficient medium to facilitate the interfacial electron communication.  相似文献   

14.
《Mendeleev Communications》2022,32(2):194-197
The amantadinium iodoacetatobismuthate(III) [C10H15NH3·(CH3)2CO]2[BiI3.67(CH3COO)1.33] is a new hybrid halometallate with iodide ions partially replaced by oxygen-containing acetates to form stronger interaction between the anionic and cationic substructures. The title compound as well-shaped orange-red crystals was synthesized by a facile reaction in acetone solution in the presence of glacial acetic acid. The crystal structure of the compound consists of the infinite anionic chains [BiI3.67(CH3COO)1.33]2– and the countercations [C10H15NH3·(CH3)2CO]+; according to the optical absorption data, the test compound is a semiconductor with a band gap of 2.06 eV.  相似文献   

15.
Reported herein is a study of the unusual 3′–3′ 1,4‐GG interstrand cross‐link (IXL) formation in duplex DNA by a series of polynuclear platinum anticancer complexes. To examine the effect of possible preassociation through charge and hydrogen‐bonding effects the closely related compounds [{trans‐PtCl(NH3)2}2(μ‐trans‐Pt(NH3)2{NH2(CH2)6NH2}2)]4+ (BBR3464, 1 ), [{trans‐PtCl(NH3)2}2(μ‐NH2(CH2)6NH2)]2+ (BBR3005, 2 ), [{trans‐PtCl(NH3)2}2(μ‐H2N(CH2)3NH2(CH2)4)]3+ (BBR3571, 3 ) and [{trans‐PtCl(NH3)2}2{μ‐H2N(CH2)3‐N(COCF3)(CH2)4}]2+ (BBR3571‐COCF3, 4 ) were studied. Two different molecular biology approaches were used to investigate the effect of DNA template upon IXL formation in synthetic 20‐base‐pair duplexes. In the “hybridisation directed” method the monofunctionally adducted top strands were hybridised with their complementary 5′‐end labelled strands; after 24 h the efficiency of interstrand cross‐linking in the 5′–5′ direction was slightly higher than in the 3′–3′ direction. The second method involved “postsynthetic modification” of the intact duplex; significantly less cross‐linking was observed, but again a slight preference for the 5′–5′ duplex was present. 2D [1H, 15N] HSQC NMR spectroscopy studies of the reaction of [15N]‐ 1 with the sequence 5′‐d{TATACATGTATA}2 allowed direct comparison of the stepwise formation of the 3′–3′ IXL with the previously studied 5′–5′ IXL on the analogous sequence 5′‐d(ATATGTACATAT)2. Whereas the preassociation and aquation steps were similar, differences were evident at the monofunctional binding step. The reaction did not yield a single distinct 3′–3′ 1,4‐GG IXL, but numerous cross‐linked adducts formed. Similar results were found for the reaction with the dinuclear [15N]‐ 2 . Molecular dynamics simulations for the 3′–3′ IXLs formed by both 1 and 2 showed a highly distorted structure with evident fraying of the end base pairs and considerable widening of the minor groove.  相似文献   

16.
Triclinic single crystals of Cu4(H3N–(CH2)9–NH3)(OH)2[C6H2(COO)4]2 · 5H2O were prepared in aqueous solution at 80 °C in the presence of 1,9‐diaminononane. Space group P$\bar{1}$ (no. 2) with a = 1057.5(2), b = 1166.0(2), c = 1576.7(2) pm, α = 106.080(10)°, β = 90.73(2)° and γ = 94.050(10)°. The four crystallographic independent Cu2+ ions are surrounded by five oxygen atoms each with Cu–O distances between 191.4(3) and 231.7(4) pm. The connection between the Cu2+ coordination polyhedra and the [C6H2(COO)4]4– anions yields three‐dimensional framework with negative excess charge and wide centrosymmetric channel‐like voids. These voids extend parallel to [001] with the diagonal of the nearly rectangular cross‐section of approximately 900 pm. The channels of the framework accommodate [H3N–(CH2)9–NH3]2+ cations and water molecules, which are not connected to Cu2+. The nonane‐1,9‐diammonium cations adopt a partial gauche conformation. Thermoanalytical measurements in air show a loss of water of crystallization starting at 90 °C and finishing at approx. 170 °C. The dehydrated compound is stable up to 260 °C followed by an exothermic decomposition yielding copper oxide.  相似文献   

17.
Summary The solubility isotherms of the systems Cd(HCOO)2-CS(NH2)2-CH3OH and Cd-(CH3COO)2-CS(NH2)2-CH3OH have been investigated at 25°C. Reagents for the equilibrium existence of the salts Cd(HCOO)2, Cd(HCOO)2·2CS(NH2)2, CS(NH2)2, Cd(CH3COO)2, Cd(CH3COO)2·CS(NH2)2, and Cd(CH3COO)2·2CS(NH2)2 are found. The preparation of CdS by thermal decomposition of double salts and from saturated solutions by the dip technique are discussed.
Herstellung von CdS durch thermische Zersetzung von Doppelsalzen und gesättigten Lösungen der Systeme Cd(HCOO)2-CS(NH2)2-CH3OH und Cd(CH3COO)2-CS(NH2)2-CH3OH
Zusammenfassung Untersucht werden die Löslichkeitsisothermen der Systeme Cd(HCOO)2-Cs(NH2)2-CH3OH und Cd(CH3COO)2-CS(NH2)2-CH3OH bei 25 °C. Die Kristallisationsfelder der Salze Cd(HCOO)2, Cd(HCOO)2·2CS(NH2)2, CS(NH2)2, Cd(CH3COO)2, Cd(CH3COO)2·CS(NH2)2 und Cd(CH3COO)2·2CS(NH2)2 werden bestimmt. Die Herstellung von CdS durch thermische Zersetzung von Doppelsalzen und gesättigten Lösungen anhand des Tauchverfahrens wird diskutiert.
  相似文献   

18.
Zhao YD  Pang DW  Hu S  Wang ZL  Cheng JK  Dai HP 《Talanta》1999,49(4):751-756
The covalent immobilization of DNA onto self-assembled monolayer (SAM) modified gold electrodes (SAM/Au) was studied by X-ray photoelectron spectrometry and electrochemical method so as to optimize its covalent immobilization on SAMs. Three types of SAMs with hydroxyl, amino, and carboxyl terminal groups, respectively, were examined. Results obtained by both X-ray photoelectron spectrometry and cyclic voltammetry show that the largest covalent immobilization amount of dsDNA could be gained on hydroxyl-terminated SAM/Au. The ratio of amount of dsDNA immobilized on hydroxyl-terminated SAMs to that on carboxyl-terminated SAMs and to that on amino-terminated SAMs is (3-3.5): (1-1.5): 1. The dsDNA immobilized covalently on hydroxyl-terminated SAMs accounts for 82.8-87.6% of its total surface amount (including small amount of dsDNA adsorbed). So the hydroxyl-terminated SAM is a good substrate for the covalent immobilization of dsDNA on gold surfaces.  相似文献   

19.
Self-assembled monolayers (SAMs) of thiols with carboxylic acid terminal groups were formed on gold substrates. The electron transfer characteristics of redox species on the above SAM-modified electrodes were studied in acid and neutral media with the help of voltammetry under two different conditions: (1) solution phase electron transfer and (2) bridge mediated electron transfer. Two redox systems, viz., [Fe(CN)6]4-/3− and Ru[(NH3)6]2+/3+ were chosen for the solution phase study. Investigations of bridge mediated electron transfer were carried out by functionalising the SAM with redox moieties and then studying their redox behaviour. For this study, ferrocene carboxylic acid and 1,4-diamino anthraquinone were used and they were linked to carboxylic acid terminated thiols by covalent linkage. The voltammetric results with mercaptoundecanoic acid SAM demonstrate the difference in behaviour between solution phase and bridge mediated electron transfer processes.  相似文献   

20.
Silver chalcogenolate cluster assembled materials (SCAMs) are a category of promising light‐emitting materials the luminescence of which can be modulated by variation of their building blocks (cluster nodes and organic linkers). The transformation of a singly emissive [Ag12(SBut)8(CF3COO)4(bpy)4]n (Ag12bpy, bpy=4,4′‐bipyridine) into a dual‐emissive [(Ag12(SBut)6(CF3COO)6(bpy)3)]n (Ag12bpy‐2) via cluster‐node isomerization, the critical importance of which was highlighted in dictating the photoluminescence properties of SCAMs. Moreover, the newly obtained Ag12bpy‐2 served to construct visual thermochromic Ag12bpy‐2/NH2 by a mixed‐linker synthesis, together with dichromatic core–shell Ag12bpy‐2@Ag12bpy‐NH2‐2 via solvent‐assisted linker exchange. This work provides insight into the significance of metal arrangement on physical properties of nanoclusters.  相似文献   

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