Simultaneous Analysis of Dopamine and Ascorbic Acid Using Polymelamine/Gold Nanoparticle-Modified Carbon Paste Electrode

Modification of electrode using polymelamine (PM) and gold nanoparticles (AuNPs) has been successfully developed via electropolymerization and electrodeposition onto carbon paste electrode (CPE) using cyclic voltammetry (CV) technique. The modified electrode (AuNPs/PM/CPE) was applied as voltammetry sensors in a simultaneous of dopamine (DA) and ascorbic acid (AA). AuNPs/PM/CPE presented an effective surface area 5 times wider than CPE and demonstrated good electrocatalytic performance in the oxidation of DA and AA in 0.1 M phosphate buffer solution (pH 3) with a scan rate of 100 mV s−1. The differential pulse voltammetry (DPV) technique was chosen as the best method for separating potential peaks of DA and AA. The linear response for determining DA and AA using the DPV technique produced a concentration range of 0.1–13 and 0.4–12 µM with coefficient linearity of 0.9999 and 0.9997, the limit of detection of 0.1405 and 0.2187 µM, the accuracy of 89.62–109.16%, and 83.63–105.08%, and the precision of 0.017–0.701% and 0.066–0.626%, respectively. In addition, this electrode was applied in a real sample of infant urine with a concentration of 1 µM by spike method and found 98.86 and 98.28% as percent recovery of DA and AA, respectively

Flexible bis(pyridyl-tetrazole) ligand-induced ring-containing metal–organic coordination polymers: synthesis, structures, and properties

<p>Three coordination polymers (CPs), [Co(3-bptzp)(BDC)] (<b>1</b>), [Zn(3-bptzp)(BDC)] (<b>2</b>), and [Cd(3-bptzp)(BDC)] (<b>3</b>) (3-bptzp = 1,4-bis(5-(3-pyridyl)tetrazolyl)propane, H₂BDC = 1,3-benzenedicarboxylic acid), were synthesized under hydrothermal conditions. The CPs were structurally characterized by single-crystal X-ray diffraction, infrared spectroscopy (IR), elemental analyses, and powder X-ray diffraction (PXRD). Complexes <b>1–3</b> represent the first examples of CPs based on the flexible bis(pyridyl-tetrazole) 3-bptzp. Structure analyses reveal that <b>1–3</b> are 1-D ring-containing polymeric chains. For <b>2</b> and <b>3</b>, adjacent 1-D chains are extended to 2-D supramolecular networks by hydrogen bonding. Dye adsorption properties of <b>1–3</b>, electrochemical properties of <b>1</b>, and fluorescent-sensing behaviors of <b>2</b> and <b>3</b> have also been investigated.</p

Unprecedented Application of Flexible Bis(pyridyl-tetrazole) Ligands To Construct Helix/Loop Subunits To Modify Polyoxometalate Anions

By introducing the unprecedented and flexible isomeric bis­(pyridyl-tetrazole) ligands into a polyoxometalates (POMs) system, three POM-based compounds, {Ag₂(4-bptzb)₂(H₂O)₂[H₂PMo₁₂O₄₀]₂}·4-bptzb·5H₂O (<b>1</b>), [Ag₄(3-bptzb)₂(PMo^VMo^VI₁₁O₄₀)]·2H₂O (<b>2</b>), and Ag₃(3-bptzb)_2.5(H₂O)₂[H₃P₂W₁₈O₆₂] (<b>3</b>) [4-bptzb = 1,4-bis­(5-(4-pyridyl)­tetrazolyl)­butane and 3-bptzb =1,4-bis­(5-(3-pyridyl)­tetrazolyl)­butane], were synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction analyses. Compound <b>1</b> exhibits a dimeric structure constructed from two Keggin [PMo₁₂O₄₀]^3– anions and a binuclear [Ag₂(<i>trans</i>-4-bptzb)₂]²⁺ subunit in which the <i>trans</i>-4-bptzb acts as a bidentate bridging ligand with one tetrazolyl group. In <b>2</b>, the 3-bptzb acts as a tetradentate bridging ligand with the tetrazolyl and pyridyl groups linking Ag^I ions to generate a 3D metal–organic framework (MOF), which contains charming <i>meso</i>-helix chains. The Keggin anions acting as bidentate inorganic ligands reside in the distorted tetragonal channels of the MOF. In compound <b>3</b>, the 3-bptzb adopts versatile coordination modes linking Ag^I ions to first construct loop connecting loop 1D chains, which are linked by {Ag­[P₂W₁₈O₆₂]}_<i>n</i> zigzag chains to form a scarce hamburger-style 2D sheet. These adjacent sheets are further fused by 3-bptzb ligands to construct a 3D framework. The influences of isomeric bptzb ligands and POMs on the construction of Ag-bptzb subunits and the whole structures of the title compounds are discussed. The electrochemical behaviors and electrocatalytic activities of compounds <b>2</b> and <b>3</b> and their corresponding parent POMs as well as the fluorescent properties of the title compounds have been studied in detail. In addition, the photocatalytic activities of compounds <b>2</b> and <b>3</b> and their corresponding parent POMs for decomposition of methylene blue, rhodamine B, and methyl orange under UV irradiation have also been investigated