Controlled surface functionalization of electrode materials is an important technique in various fields such as analytical chemistry, molecular electronics, and molecular recognition in biological ...systems. In this work, we report the control decoration of boron-doped diamond (BDD) electrodes by electrochemically driven copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition of alkyne and azide (e−CLICK) in which the catalyst is produced by electroreduction of copper(II) species. As the e−CLICK strategy enabled to tune the produced amount of the copper(I) catalyst electrochemically, the alkyne-terminated BDD electrodes were decorated with azide-terminated ferrocene in a controlled manner.
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Nitrate contamination in groundwater requires efficient remediation to prevent adverse environmental impacts. This study illustrates the improvement in nitrate reduction process using copper modified ...BDD (Cu-BDD) with higher stability after annealing treatment. The highest values for nitrate reduction and the selectivity of nitrogen gas were about 71% and 45%, respectively, which were obtained using annealed Cu-BDD electrode. Annealing process promoted the homogeneity of copper oxides that consolidated the electrodeposited copper oxides on the surface of Cu-BDD to enhance the stability of electrode. Meanwhile, annealed Cu-BDD exhibited higher conductivity to facilitate nitrate reduction initiating at a more positive potential. Furthermore, cuprous ions and metallic Cu were formed during the annealing treatment, and had active chemical reaction with nitrate and excellent catalytic capability for the reaction, which efficiently enhanced either the nitrate reduction efficiency or the selectivity of nitrogen gas. The findings advance the current understanding on the enhancement of electrochemical stability and nitrate reduction performance using Cu-BDD after the annealing treatment, and also offer a promising technology for remediation of nitrate-contaminated groundwater.
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•Annealed Cu-BDD exhibited highly stable and efficient performance on electrochemical nitrate reduction.•Annealing treatment consolidated copper oxides on Cu-BDD surface with the improvement of deposited homogeneity•Cuprous ions and metallic copper worked as chemical and catalytic sites to promote nitrate reduction.
We report on the first observation of the production of C2/C3 species from the electrochemical reduction of CO2 at the surfaces of copper-modified boron-doped diamond (Cu-BDD) electrodes in aqueous ...media at room temperature and ambient pressure. The product distribution is dependent on the amount of deposited Cu and the applied potential. At low potential, −1.0 V (vs. Ag/AgCl), ethanol was observed as the main product with acetaldehyde and acetone as side products. The highest faradaic efficiencies obtained for ethanol, acetaldehyde and acetone were 42.4%, 13.7% and 7%, respectively. The Cu particles on the surfaces of the BDD electrodes remained stable, showing insignificant differences after the CO2 electroreduction process under these particular conditions. The efficiency dropped with increasing Cu deposition time and at high reduction potentials. Moreover, we present comparisons with a Cu plate and Cu-modified glassy carbon as working electrodes under the same conditions, which explains the specific behavior of the CO2 reduction process on the Cu-BDD electrode.
The electrochemical detection of oxytocin using boron-doped diamond (BDD) electrodes was studied. Cyclic voltammetry of oxytocin in a phosphate buffer solution exhibits an oxidation peak at +0.7 V ...(vs. Ag/AgCl), which is attributable to oxidation of the phenolic group in the tyrosyl moiety. Furthermore, the linearity of the current peaks obtained in flow injection analysis (FIA) using BDD microelectrodes over the oxytocin concentration range from 0.1 to 10.0 μM with a detection limit of 50 nM (S/N = 3) was high (R(2) = 0.995). Although the voltammograms of oxytocin and vasopressin observed with an as-deposited BDD electrode, as well as with a cathodically-reduced BDD electrode, were similar, a clear distinction was observed with anodically-oxidized BDD electrodes due to the attractive interaction between vasopressin and the oxidized BDD surface. By means of this distinction, selective measurements using chronoamperometry combined with flow injection analysis at an optimized potential were demonstrated, indicating the possibility of making selective in situ or in vivo measurements of oxytocin.
Direct evidence: The existence of methoxy radical species formed during an anodic oxidation in MeOH on a boron‐doped diamond (BDD) electrode was confirmed by ESR spectroscopy. Effective production of ...a neolignan, licarin A, was accomplished by the BDD‐mediated anodic oxidation protocol (see picture).
Electrochemical surface oxidation in acidic solutions was investigated on a boron-doped diamond film electrode, fabricated on a silicon prism, using attenuated total reflection infrared spectroscopy. ...At positive potentials above +1.3 V (reversible hydrogen electrode, RHE), the bands of surface oxygen species appear at 1745 and 1250 cm–1. Since these bands exhibit no isotope shift in deuterium solution, they are assigned to the CO and C–O stretching modes, respectively. These bands have the maximum intensity at +3.3 V (RHE) and reversibly disappear around +0.9 V (RHE) in the potential step to the negative direction. The potentials at which the bands appear and disappear are identical to those of the anodic and cathodic peaks of the cyclic voltammogram, respectively.
A straightforward electro-conversion of cumene into acetophenone has been reported using boron-doped diamond (BDD) electrodes. This particular conversion is driven by the addition reaction of a ...cathodically generated hydroperoxide anion to an anodically generated cumyl cation, where the BDD’s wide potential window enables the direct anodic oxidation of cumene into the cumyl cation. Since electricity is directly employed as the oxidizing and reducing reagents, the present protocol is easy to use, suitable for scale-up, and inherently safe.
To introduce halogen‐bond interactions between a cation and an anion, a novel FeIII complex from iodine‐substituted ligands involving a paramagnetic nickel dithiolene anion was prepared and ...characterized. The compound exhibited the synergy between a spin‐crossover transition and a spin‐Peierls‐like singlet formation. The halogen‐bond interactions between the iodine and the sulfur atoms stabilized the paramagnetic state of π‐spins and played a crucial role in the synergistic magnetic transition between d‐ and π‐spins. In addition, the compound showed the light‐induced excited spin state trapping effect.
Something to get crossover: An FeIII complex with iodine‐substituted ligands involving a paramagnetic nickel dithiolene anion shows a synergy between a spin‐crossover transition and a spin‐Peierls‐like singlet formation. The halogen‐bond interactions between the iodine and the sulfur atoms stabilized the paramagnetic state of π‐spins and played a significant role in the synergistic magnetic transition between d‐ and π‐spins.
An important technique to realize novel electron- and/or proton-based functionalities is to use a proton–electron coupling mechanism. When either a proton or electron is excited, the other one is ...modulated, producing synergistic functions. However, although compounds with proton-coupled electron transfer have been synthesized, crystalline molecular compounds that exhibit proton-transfer-coupled spin-transition (PCST) behavior have not been reported. Here, we report the first example of a PCST Fe(II) complex, wherein the proton lies on the N of hydrazone and pyridine moieties in the ligand at high-spin and low-spin Fe(II), respectively. When the Fe(II) complex is irradiated with light, intramolecular proton transfer occurs from pyridine to hydrazone in conjunction with the photoinduced spin transition via the PCST mechanism. Because the light-induced excited high-spin state is trapped at low temperatures in the Fe(II) complexa phenomenon known as the light-induced excited-spin-state trapping effectthe light-induced proton-transfer state, wherein the proton lies on the N of hydrazone, is also trapped as a metastable state. The proton transfer was accomplished within 50 ps at 190 K. The bistable nature of the proton position, where the position can be switched by light irradiation, is useful for modulating proton-based functionalities in molecular devices.
A previous dose-escalation study of sulfasalazine (SSZ), an inhibitor of cystine-glutamate exchange transporter xc (–), in the variant form of CD44 (CD44v)-positive cancer stem cells (CSCs) suggested ...that administration of SSZ induces the reduction of CD44v-positive cells and intracellular reduced glutathione (GSH) levels in patients with advanced gastric cancer (AGC). Here we report a study to evaluate SSZ in combination with cisplatin in patients with CD44v-expressing AGC refractory to cisplatin. SSZ was given by oral administration four times daily with 2 weeks on and 1 week off. Cisplatin at 60 mg/m
2
was administered every 3 weeks. Of the 15 patients who underwent prescreening of CD44v expression, 8 patients were positive, and 7 patients were treated with the dose level of SSZ at 6 g/day. One patient experienced dose-limiting toxicity (DLT) as grade 3 anorexia. Although no other patients experienced DLT, 4 patients required dose interruption or reduction of SSZ; thus, we terminated further dose escalation. No patient achieved objective response, but 1 patient completed six cycles with stable disease for more than 4 months as well as reduction of intratumoral GSH level. The combination of SSZ plus cisplatin was manageable, although dose modification was frequently required during a short observational period.
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