Zhongliang Xiao

Simple and rapid mercury ion selective electrode based on 1-undecanethiol assembled Au substrate and its recognition mechanism

A simple and rapid mercury ion selective electrode based on 1-undecanethiol (1-UDT) assembled Au substrate (Au/1-UDT) has been well constructed. 1-UDT was for the purpose of generating self-assembled monolayer on gold surface to recognize Hg2+ in aqueous solution, which had a working concentration range of 1.0×10-8-1.0×10-4molL-1, with a Nernst response slope of 28.83±0.4mV/-pC, a detection limit of 4.5×10-9molL-1, and a good selectivity over the other tested cations. Also, the Au/1-UDT possessed good reproducibility, stability, and short response time. The recovery obtained for the determination of mercury ion in practical tremella samples was in the range of 99.8-103.4%. Combined electrochemical analysis and X-ray photoelectron spectroscopy (XPS) with quantum chemical computation, the probable recognition mechanism of the electrode for selective recognition of Hg2+ has been investigated. The covalent bond formed between mercury and sulfur is stronger than the one between gold and sulfur and thus prevents the adsorption of 1-UDT molecules on the gold surface. The quantum chemical computation with density functional theory further demonstrates that the strong interaction between the mercury atom and the sulfur atom on the gold surface leads to the gold sulfur bond ruptured and the gold mercury metallophilic interaction.

Molecule counting with alkanethiol and DNA immobilized on gold microplates for extended gate FET

Several molecule counting methods based on electrochemical characterization of alkanethiol and thiolated single-stranded oligonucleotide (HS-ssDNA) immobilized on gold microplates, which were used as extended gates of field effect transistors (FETs), have been investigated in this paper. The surface density of alkanethiol and DNA monolayers on gold microplates were quantitatively evaluated from the reductive desorption charge by using cyclic voltammetry (CV) and fast CV (FCV) methods in strong alkali solution. Typically, the surface density of 6-hydroxy-1-hexanethiol (6-HHT) was evaluated to be 4.639 molecules/nm(2), and the 28 base-pair dsDNA about 1.226-4.849 molecules/100 nm(2) on Au microplates after post-treatment with 6-HHT. The behaviors on surface potential and capacitance of different aminoalkanethiols on Au microplates were measured in 0.1 mol/L Na2SO4 and 10 mmol/L Tris-HCl (pH=7.4) solutions, indicating that the surface potential increases and the double-layer capacitance decreases with the length of carbon chain increased for the thiol monolayers, which obey a physics relationship for a capacitor. Comparably, a simple sensing method based on the electronic signals of biochemical reaction events on DNA immobilization and hybridization at the Au surface of the extended gate FET (EGFET) was developed, with which the surface density of the hybridized dsDNA on the gold surface of the EGFET was evaluated to be 1.36 molecules per 100 nm(2), showing that the EGFET is a promising sensing biochip for DNA molecule counting.

Synthesis, Crystal Structures, and Antimicrobial Activities of Zinc Complexes Derived from Methyl Substituted 2-(Pyridin-2-yliminomethyl)phenols

A new mononuclear zinc(II) complex [ZnL1(MPA)I] (1) (HL1 = 2-[(4-methylpyridin-2-ylimino)methyl]phenol, MPA = 4-methylpyridin-2-ylamine), and a new centrosymmetric dinuclear zinc(II) complex [Zn2L22I2] (2) (HL2 = 2-[(5-methylpyridin-2-ylimino)methyl]phenol), have been synthesized and structurally characterized by elemental analysis and X-ray diffraction. In 1, the Zn atom is four-coordinate in a tetrahedral coordination, while those in 2 are five-coordinate in severely distorted square pyramidal coordinations. The complexes, as well as the two Schiff bases, have been screened and evaluated for their antimicrobial activities.

Synthesis and Crystal Structure of a μ 2-Oxo Bridged Dinuclear Oxovanadium(V) Complex Derived From N′-(2-Hydroxy-4-diethylaminobenzylidene)-3-methylbenzohydrazide

A tridentate hydrazone ligand N′-(2-hydroxy-4-diethylamino benzylidene)-3-methylbenzohydrazide (H2L), reacts with vanadyl sulfate in methanol to give a novel μ 2-oxo bridged dinuclear oxovanadium(V) complex, [V2O2(μ 2-O)L2]. The complex was characterized by physicochemical and spectroscopic methods. The crystal of the complex is triclinic with space group P–1, a = 11.349(2), b = 13.385(3), c = 13.644(2) Å, α = 90.377(2)°, β = 93.772(2)°, γ = 109.239(2)°, V = 1951.8(6) Å3, Z = 2. X-ray crystallography indicates that each V atom is in a distorted square pyramidal coordination. The two V atoms are bridged by one O atom, with a distance of 3.010(1) Å.

Corrosion Behaviors on Polycrystalline Gold Substrates in Self‐Assembled Processes of Alkanethiol Monolayers

Abstract The adsorption response behaviors with n‐alkanethiol self‐assembled monolayers (SAMs) formed on the surface of polycrystalline gold grains have been investigated in nitrogen and oxygen saturated tetrahydrofuran (THF) solutions by using in situ quartz crystal microbalance (QCM) and atomic force microscopy (AFM). Comparing with frequency‐decreased process in the nitrogen saturated solution, the response behavior shows a frequency increased process in the oxygen saturated solution, indicating that the gold corrosion is accompanied to occur in the self‐assembled process of organothiol that is due to the thiol induction and oxygen oxidation. In the presence of thiol and oxygen, the corrosion effect is stronger than the adsorption effect of organothiols, such as n‐dodecanethiol molecules on gold, which causes gold loss from the QCM surface, made evident from the observation of many corrosive defects or holes produced on the surface of gold grains by AFM image. Furthermore, the kinetic behavior on the corrosion rate of gold dissolved in the organothiol solution with time has been examined. The maximum quantity of gold dissolved into the thiol solution can be calculated to be approximately 8.7×1013 Au atoms cm−2 from the QCM data during the strong corrosion process in the oxygen saturated solution. The corresponding gold corrosion rates at fast and slow stages can be estimated to be 9.2×1011 and 5.4×1010 Au atoms cm−2 s−1, respectively. The surface coverage of SAMs increases from 3.2 to 31.2%, while the gold loss decreases from about 6 to 0.6% of an Au monolayer in the self‐assembled process.

Immobilization of DNA molecules on a gold plate for an extended gate FET sensing chip

We have proposed an electrochemical detection method for DNA molecules based on an extended gate field effect transistor (EGFET) sensing chip which consists of one gold plate for molecule recognition and FET part for signal transduction. DNA Probes were immobilized on the gold plate by forming mixed monolayers of thiolated single-stranded oligonucleotide (HS-ssDNA) and alkanethiols, like 6-hydroxy-1-hexanethiol (6-HHT). Electrode reaction corresponding to the reductive desorption of the adsorbed monolayers in strong alkali solution was presented for quantification of surface density of DNA by using fast cyclic voltammetry (FCV). The passivation effects of surface modification with different functional groups on the potential behavior of the gold electrode were also examined. It was feasible to use EGFET chip for detection of DNA hybridization reaction, that the hybridization efficient was estimated to be about 40%.