Jiye Jin

Novel thiophene -conjugated indoline dyes for zinc oxide solar cells

The application of a series of thiophene-conjugated indoline dyes for zinc oxide solar cells, prepared by the one-step cathode deposition template method, was examined. The introduction of thiophene ring(s) into D131-type indoline dye improved the cell performance due to their appropriate energy levels and bathochromic shift in the UV-vis absorption band on zinc oxide. It is important for the oxidation potential (Eox) of dyes to have a more positive value than ca. 0.25 V vs. Fc/Fc+ in acetonitrile in order to show a high (>70%) incident photon-to-current efficiency.

Enzymatic flow injection method for rapid determination of choline in urine with electrochemiluminescence detection

In order to determine trace choline in human urine, a flow injection analysis (FIA) system has been developed by coupling an enzyme reactor with an electrochemiluminescence (ECL) detector. The enzyme reactor is prepared by covalently immobilizing choline oxidase (ChOx) onto the aminopropyl-controlled pore glass beads, which are then carefully packed into a micro column. The enzyme reactor catalyzes the production of hydrogen peroxide that is in direct proportion to the concentration of choline. In this study, the enzymatically produced hydrogen peroxide was detected by an ECL detector positioned at the down stream of an enzyme reactor based on the luminol/H(2)O(2) ECL system. Under the optimized condition, the enzymatic FIA/ECL provided high sensitivity for the determination of choline with the detection limit as low as 0.05 microM (absolute detection limit was at sub pmol level). The method was successfully applied in the determination of choline in the samples of human urine, and the analytical results were in good agreement with those obtained by using the microbore HPLC with an immobilized enzyme reactor-electrochemical detection system.

Synthesis, Absorption, and Electrochemical Properties of Quinoid-Type Bisboron Complexes with Highly Symmetrical Structures

Novel bisboron complexes of bidentate ligands consisting of 1,4-benzoquinone and two pyrrole rings were synthesized by using a simple two-step reaction. In solution, the bisboron complexes showed absorption maxima at ∼620 and 800 nm, which were attributed to the allowed S0 → S2 and forbidden S0 → S1 transitions, respectively. The bisboron complexes did not show any fluorescence, probably because of their highly symmetrical structure which forbids the S0 → S1 transition. Bisboron complexes underwent a two-electron reduction to yield the corresponding aromatic dianion, which showed absorption maxima at ∼410 nm.

Importance of fluorescence lifetimes for efficient indoline dyes in dye-sensitized solar cells

To make a molecular design of efficient indoline dyes, fluorescence lifetimes should be longer than ca. 0.8 ns in chloroform, in addition to suitable HOMO and LUMO levels and bathochromic UV-vis absorption bands.

Long-term stability of novel double rhodanine indoline dyes having one and two anchor carboxyl group(s) in dye-sensitized solar cells

An indoline dye having both α-cyanoacrylic acid and rhodanine acetic acid anchor groups at the acceptor moiety exhibited improved stability under fluorescence light irradiation.

Application of Electrochemiluminescence for the Evaluation of the Antioxidant Capacity of Some Phenolic Compounds Against Superoxide Anion Radicals.

This paper for the first time reports on novel and non-enzymatic method for studying the free radical-scavenging properties of phenolic compounds against superoxide anion radicals (O2·(-)) by using the cathodic electrochemiluminescence (ECL) of lucigenin (Luc(2+)). The ECL of Luc(2+) at a glassy carbon (GC) electrode is observed in an aeration electrolytic solution (pH 7), which is believed to be due to the reaction of a one-electron reduced form of Luc(2+) (i.e. a radical cation, Luc·(+)) with in situ electrogenerated O2·(-). The ECL intensity is dependent on the concentration of dissolved oxygen, and is suppressed dramatically by superoxide dismutase (SOD), a typical O2·(-) scavenger. Since the coexisting hydrogen peroxide (H2O2) has no influence on the cathodic ECL of Luc(2+), it is thus suggested that the ECL signal specifically reflected the O2·(-) concentration level generated at the electrode surface. When phenolic compounds were added into the solution, this resulted in the inhibition of ECL signals due to the elimination of O2·(-). The ECL inhibition rate measured at each concentration was compared against the SOD equivalent (U mL(-1)), and the relative antioxidant efficiency, Kao (U mmol(-1) equivalent SOD), was used to evaluate the antioxidant activity of some phenolic compounds, including flavonoids, in this study. Structurally different water-soluble phenols were compared, and those compounds containing to catechol skeletal structure are found to present the higher antioxidant capacity.

Electrochemical Determination of Chromium(VI) in River Water with Gold Nanoparticles–Graphene Nanocomposites Modified Electrodes

In this study, nanocomposites of ligand-free gold nanoparticles that are anchored onto the graphene surface (Graphene/AuNPs) were synthesized by a sonochemical method in a single reaction step. A highly sensitive amperometric sensor using Graphene/AuNPs is proposed for the determination of trace hexavalent chromium Cr(VI) in environmental water samples. Compared with a gold electrode, a glassy carbon electrode and a AuNPs modified glassy carbon electrode, the Graphene/AuNPs modified glassy carbon electrode exhibits the highest electrocatalytic activity and stability towards the reduction of Cr(VI), based on the results by cyclic voltammetry and electrochemical AC impedance studies. This study shows that the Graphene/AuNPs-based sensor can detect Cr(VI) with a low detection limit of 10 nM (∼0.5 μg/L), a wide dynamic range of 0 to 20 μM (R = 0.999) and very good selectivity and reproducibility. The electrode is applied to the determination of Cr(VI) in river samples with satisfactory recovery values.

Sonochemical preparation of gold nanoparticles for sensitive colorimetric determination of nereistoxin insecticides in environmental samples

A simple colorimetric method using gold nanoparticles (AuNPs) was developed as an efficient strategy for specific and sensitive detection of insecticides that are analogs of nereistoxin (NRT). The AuNPs were synthesized by a surfactant-free sonochemical reaction with ultrasonication at 430 kHz. A color change occurred in the presence of NRT because the AuNPs aggregated if they were coated with a small amount of thioctic acid (TA). At a pH of around 5, the TA adsorbed on the AuNPs was deprotonated, whereas NRT was protonated (NRT-H+). Adsorption of NRT-H+ onto the TA-coated AuNPs surface would decrease the surface charge of the AuNPs, and this resulted in aggregation. Because the aggregation of the TA-coated AuNPs could not be induced by amine compounds without thiol groups, this provided a surface-limited aggregation mechanism for specific sensing of NRT. The absorbance at 700 nm was dependent on the concentration of NRT, and the calibration curve was linear over the concentration range 85 nM (12 ng/mL) to 1000 nM (140 ng/mL). The applicability of the proposed method to detection of trace levels of NRT in environmental water samples was successfully demonstrated using a simple liquid-liquid reverse extraction technique.

Wide-Range Near-Infrared Sensitizing 1H-Benzo[c,d]indol-2-ylidene-Based Squaraine Dyes for Dye-Sensitized Solar Cells

NIR absorbing squaraine dyes SQ1-SQ7 having 1 H-benzo[ c, d]indol-2-ylidene as a donor moiety were designed for application in DSSCs. Annulation of the benzene ring to an 3 H-indolium-based anchor moiety led to a red-shifted and broadened absorption band on TiO2 film, which were reflected in the improved short-circuit current density of SQ2 (6.22 mA cm-2) compared to the nonbenzene fused derivative SQ1 (4.39 mA cm-2). Although the introduction of a butoxy (SQ4: 806 nm) or dialkylamino group (SQ5-SQ7: 815-820 nm) to the 1 H-benzo[ c, d]indol-2-ylidene-based donor moiety resulted in red-shifted absorption maxima in ethanol compared to the nonsubstituted derivative SQ2 (784 nm), the HOMO energy level of SQ4-SQ7 gave rise to an undesirable approximation to the redox potential of I-/I3-. Thus, the butoxy (SQ4: 0.56) and dialkylamino (SQ5-SQ7: 0.25-0.30) derivatives had relatively lower conversion efficiencies. Since the 2-ethylhexyl derivative SQ3 exhibited red-shifted absorption (λmax: 796 nm), suitable HOMO and LUMO energy levels, and relatively efficient restriction of charge recombination, this dye achieved the highest conversion efficiency (1.31%), along with a high IPCE response of over 20% over a wide range from 640 to 860 nm and an onset of IPCE at 1000 nm.

Synthesis and fluorescence properties of novel squarylium–boron complexes

A novel boron complex based on a squarylium dye was synthesized by a simple two-step procedure starting from the pyrrole derivative. The absorption and fluorescence maxima of the squarylium–boron complex were slightly blue-shifted relative to those of the corresponding squarylium dye, and the fluorescence quantum yield of the former increased significantly. Deprotonation of the squarylium–boron complex led to the formation of the corresponding anion, with a further blue-shift of the absorption and fluorescence maxima.