Selective determination of uric acid in the presence of ascorbic acid using a penicillamine self-assembled gold electrode

The electrochemical behaviors of uric acid (UA) at the penicillamine (Pen) self-assembled monolayers modified gold electrode (Pen/Au) have been studied. The Pen/Au electrode is demonstrated to promote the electrochemical response of UA by cyclic voltammetry (CV). The diffusion coefficient D of UA is 6.97 × 10⁻⁶ cm² s⁻¹. In differential pulse voltammetric (DPV) measurements, the Pen/Au electrode can separate the UA and ascorbic acid (AA) oxidation potentials by about 120 mV and can be used for the selective determination of UA in the presence of AA. The detection limit was 1 × 10⁻⁶ mol L⁻¹. The modified electrode shows excellent sensitivity, good selectivity and antifouling properties.     

超分子自组装合成杯[4]芳烃黄原酸镍(Ⅱ)配合物

利用二维和三维的大环及笼状主体分子与金属离子直接进行自组装反应合成新型有机无机杂化分子是当前超分子领域的研究热点之一。这类分子不仅具有新奇的光、电、磁等特性，而且还可作为新型的主体分子在客体识别、催化、吸附与分离等方面有广阔的应用前景。杯芳烃是有机超分子领域广受     

Molecular Dynamics Simulation of the Self-assembled Monolayers of 1-Adamantanethiolate and Its Derivatives on Au（111） Surfaces

The self-assembled monolayers （SAMs） of 1-adamantanethiolate and its derivatives on Au（111） surface were investigated. Density functional theory （DFT） calculation indicates that the most stable configuration for absorption is at the face centered cubic （fcc）-bridge site. Canonical ensemble molecular dynamics （MD） simulations were carried out to study the structures and energies of the SAMs. The ordered structures of the SAMs were analyzed by means of radial distribution function and the relative stability of the SAMs was compared. It was concluded by the comparison of various contributions to the SAM formation energy that the formation of the SAMs was determined by the intermolecular nonbonding interaction and the chemical bonding interaction of sulfur and gold.     

Characterization of self-assembled monolayers of thiols on Au(111)

Self-assembled monolayers (SAMs) of n-butanethiol, n-dodecanethiol and their equimolar mixture on Au(111) were prepared and characterized by ellipsometry, contact angle measurement, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Results revealed that these SAMs are oriented ultrathin films with the thickness of nanometer scale, and the SAMs were influenced by the molecular chain length, the lattice orientation and cleanliness of the substrates. The surface of the longer chain SAM is hydrophobic. The thicknesses of three SAMs of n-butanethiol, n-dodecanethiol and their mixture revealed by ellipsometry and XPS are about 0.59 - 0.67nm, 1.60- 1.69 nm and 1.23 - 1.32nm, respectively. AFM images further demonstrated that the SAM formed by the mixture has some microdomains with two different thicknesses.     

Affinity interactions between phenylboronic acid-carrying self-assembled monolayers and flavin adenine dinucleotide or horseradish peroxidase

A method is provided for the recognition of glycated molecules based on their binding affinities to boronate-carrying monolayers. The affinity interaction of flavin adenine dinucleotide (FAD) and horseradish peroxidase (HRP) with phenylboronic acid monolayers on gold was investigated by using voltammetric and microgravimetric methods. Conjugates of 3-aminophenylboronic acid and 3,3'-dithiodipropionic acid di(N-hydroxysuccinimide ester) or 11-mercaptoundecanoic acid were prepared and self-assembled on gold surfaces to generate monolayers. FAD is bound to this modified surface and recognized by a pair of redox peaks with a formal potential of -0.433 V in a 0.1 M phosphate buffer solution, pH 6.5. Upon addition of a sugar to the buffer, the bound FAD could be replaced, indicating that the binding is reversible. Voltammetric, mass measurements, and photometric activity assays show that the HRP can also be bound to the interface. This binding is reversible, and HRP can be replaced by sorbitol or removed in acidic solution. The effects of pH, incubation time, and concentration of H(2)O(2) were studied by comparing the catalytic reduction of H(2)O(2) in the presence of the electron-donor thionine. The catalytic current of the HRP-loaded electrode was proportional to HRP concentrations in the incubation solution in the range between 5 microg mL(-1) and 0.1 mg mL(-1) with a linear slope of 3.34 microA mL mg(-1) and a correlation coefficient of 0.9945.     

Electrochemical behavior and determination of epinephrine at a mercaptoacetic acid self-assembled gold electrode

The electrochemical behavior of epinephrine (EP) at a mercaptoacetic acid (MAA) self-assembled monolayer modified gold electrode was studied. The MAA/Au electrode is demonstrated to promote the electrochemical response of epinephrine by cyclic voltammetry. The possible reaction mechanism is also discussed. The diffusion coefficient D of EP is 6.85 × 10⁻⁶ cm² s⁻¹. In 0.1 mol L⁻¹ phosphate buffer (pH 7.20), a sensitive oxidation peak was observed at 0.177 V, and the peak current is proportional to the concentration of EP in the range of 1.0 × 10⁻⁵–2.0 × 10⁻⁴ mol L⁻¹ and 1.0 × 10⁻⁷–1.0 × 10⁻⁶ mol L⁻¹. The detection limit is 5 × 10⁻⁸ mol L⁻¹. The modified electrode is highly stable and can be applied to the determination of EP in practical injection samples. The method is simple, quick, sensitive and accurate.     

1，4二环己基取代六元瓜环与Na(Ⅰ)自组装实体的合成与晶体结构

A novel complex of a new 1,4-dicyclohexyl cucurbituril(DCYQ[6]) with sodium(Ⅰ) ion was synthesized, and the crystal structure was determined by X-ray diffraction technique. In this self-assembled entity both the cavity interaction of DCYQ[6] included a nitrate anion and the portal interaction of the dipole carbonyls of DCYQ[6] with sodium cations lead to form self assembled molecular capsules. The crystal structure of the entity shows a packing of the self assembled molecular capsules connected by hydrogen bonds of water molecules. CCDC: 271400.     

Detection of antisperm antibody in human serum using a piezoelectric immunosensor based on mixed self-assembled monolayers

A novel piezoelectric immunosensor based on mixed self-assembled monolayers (mixed SAMs) formed by short-chain amine- and carboxyl-terminated thiols has been developed to immobilize antigens onto gold electrodes for detecting antisperm antibody (AsAb) in human serum samples. The properties and the enhanced performance of the affinity biosensor interface based on mixed SAMs are investigated. Most importantly, analytical results of several human serum samples using the developed technique are in satisfactory agreement with those given by the enzyme-linked immunosorbent assay (ELISA) method in the concentration ranging from 32.3 to 300.0 mU/ml. It means the procedure proposed in this paper is likely to have a great potential in research and may play an important clinical role in a few years later.     

Stripping voltammetry of copper and lead using gold electrodes modified with self-assembled monolayers

One problem associated with using bare solid metal electrodes, such as gold and platinum, in stripping analysis to determine heavy metal ions such as lead and copper ions in dilute solutions is that underpotential deposition (UPD) gives multiple stripping peaks in the analysis of mixtures. These peaks are often overlapped and cannot be conveniently used for analytical purposes. Bifunctional alkylthiols, such as 3-mercaptopropionic acid, with an ionizable group on the other terminal end of the thiol can form self-assembled monolayers (SAMs) on the surface of the gold electrode. It is shown that such an SAM-modified gold electrode minimizes the UPD effects for the stripping analysis of lead and copper. The anodic peak potential shifts and the peak shape changes, indicating that the SAM changes the deposition and stripping steps of these heavy metal ions. Thus, the sensitivity levels for both single species and mixtures can be significantly improved for the conventional solid electrodes. The mechanism of the deposition reaction at the SAM-modified gold electrodes is discussed. Received: 29 May 1997 / Accepted: 24 June 1997     

末端碳链长度对偶氮苯自组装膜结构的影响

The end-group dominated molecular orientation in the azobenzene self-assembled monolayers (SAMs), CnAzoC2SH (n=1-4), on gold was evaluated for the first time by grazing incidence reflection absorption FTIR spectroscopy (RA-FTIR). All these azobenzene SAMs have highly-organized and closely-parked structures, with the molecule tilting away gradually from surface normal direction with the increase of end group alkyl length.