Electrocatalytic oxidation of phytohormone salicylic acid at copper nanoparticles-modified gold electrode and its detection in oilseed rape infected with fungal pathogen Sclerotinia sclerotiorum

Salicylic acid (SA) is a biological substance that acts as a phytohormone and plays an important role in signal transduction in plants. It is important to accurately and sensitively detect SA levels. A gold electrode modified with copper nanoparticles was used to assay the electrocatalytic oxidation of salicylic acid. It was found that the electrochemical behavior of salicylic acid was greatly improved at copper nanoparticles, indicating that anodic oxidation could be catalyzed at copper nanoparticles. And the pH had remarkable effect on the electrochemical process, a very well-defined oxidation peak appeared at pH 13.3 (0.2 M NaOH). The kinetics parameters of this process were calculated and the heterogeneous electron transfer rate constant (k) was determined to be 1.34 × 10⁻³ cm s⁻¹, and (1 − α)n_α was 1.22. The gold electrode modified with copper nanoparticles could detect SA at a higher sensitivity than common electrodes. The electrode was used to detect the SA levels in oilseed rape infected with the fungal pathogen Sclerotinia sclerotiorum. The results showed that the SA concentration reached a maximum during the 10th-25th hours after infection. This result was very similar to that determined by HPLC, indicating that the gold electrodes modified with copper nanoparticles could be used as salicylic acid sensors.     

Cu Nanoparticles Embedded in N‐Doped Carbon Materials for Oxygen Reduction Reaction

Development of eco‐friendly, cost‐effective, and high‐performance electrocatalysts to replace precious metal platinum for oxygen reduction reaction (ORR) has received increasing attention. Herein, we adopt a facile one‐pot strategy to embed Cu nanoparticles onto N‐doped carbon‐graphene (Cu@NC‐700). The Cu@NC‐700 exhibits robust and efficient ORR catalysis with positive half‐wave potential (~0.86 V vs. RHE) and low Tafel slope (33.9 mV?dec^–1) in 0.1 M KOH solution. Meanwhile, it manifests remarkable electrochemical stability, and strong tolerance to methanol crossover and carbon monoxide poisoning. The synergistic effect between Cu‐N‐C sites, Cu nanoparticles, and N‐doped carbon support speeds up ORR electrocatalysis.     

Cu‐Based Nanoparticles as Emerging Environmental Catalysts

This account provides an overview of current research activities on nanoparticles containing the earth‐abundant and inexpensive element copper (Cu) and Cu‐based nanoparticles, especially in the field of environmental catalysis. The different synthetic strategies with possible modification of the chemical/ physical properties of these nanoparticles using such strategies and/or conditions to improve catalytic activity are presented. The design and development of support and/or bimetallic systems (e. g., alloys, intermetallic, etc.) are also included. Herein, we report synthetic approaches of Cu and Cu‐based nanoparticles (monometallic copper, bimetallic copper and copper (II) oxide nanoparticles/nanostructures) and impregnation of such nanoparticles onto support material (e. g., Co₃O₄ nanostructure), along with their applications as environmental catalyst for various oxidation and reduction reactions. Finally, this account provides necessary advances and perspectives of Cu‐based nanoparticles in the environmental catalysis.     

A novel, environmentally friendly dispersive liquid-liquid microextraction procedure for the determination of copper

A novel, simple and environmentally friendly procedure for copper determination has been developed. The method is based on the formation of an ion associate of Cu(I) with 1,3,3-trimethyl-2-[5-(1,3,3-trimethyl-1,3-dihydroindol-2-ylidene)-penta-1,3-dienyl]-3H-indolium (DIDC) in the presence of chloride ions as ligand, followed by dispersive liquid-liquid microextraction (DLLME) of the formed ion associate into organic phase and UV-Vis spectrophotometric detection. The following experimental conditions were used: pH 3, 0.24 mol L^− 1 chloride ions, 0.06 mmol L^− 1 DIDC. The effect of the nature of the extraction solvent, auxiliary solvent and disperser solvent used was studied. A mixture of amyl acetate, tetrachloromethane, and methanol in a 1:1:3 v/v/v ratio was selected for the DLLME procedure. The absorbance of the coloured extracts at 640 nm wavelength obeys Beer's law in the range 0.020-0.090 mg L^− 1 of Cu. The limit of detection calculated from a blank test (n = 10) based on 3s is 0.005 mg L^− 1 of Cu. The developed procedure was applied to the analysis of water samples. The suggested DLLME is compared with two procedures previously reported from our laboratory based on (1) conventional liquid-liquid extraction, and (2) sequential injection extraction performed in a dual-valve sequential injection system. The advantages and disadvantages of each method are discussed.     

Friedel-Crafts alkylation of indoles with nitroalkenes catalyzed by Cu(Ⅱ)-imine complex

A series of new ligands L₁-L₇ were readily prepared in one step.Friedel-Crafts alkylation of indoles with nitroalkenes catalyzed by a novel Cu（Ⅱ）-L complex has been developed.The remarkable advantages of this reaction are mild reaction conditions,simple workup procedure,high yields of products and the use of ethanol as a green solvent.     

Copper(I) complexes of N-(aryl)pyridine-2-aldimines: Spectral, electrochemical and catalytic properties

The reactions of N-(aryl)pyridine-2-aldimines (L-R; R = OCH₃, CH₃, H, Cl and NO₂), derived from pyridine-2-aldehyde and para-substituted anilines, with CuI in methanol under ambient conditions afford a series of brown complexes of the type [{Cu(L-R)I}₂]. The structure of the [{Cu(L-OCH₃)I}₂] complex has been determined by X-ray crystallography. In these dimeric complexes the two copper centers are linked through an iodo-bridge, and the L-R ligands are coordinated to the metal center through the pyridine-nitrogen and imine-nitrogen. All the complexes show characteristic ¹H NMR signals and intense MLCT transitions in the visible region. These complexes also show an emission near 465 nm, whilst they are excited at 340 nm, with relatively poor quantum yields (φ ∼0.002 at 298 K). Cyclic voltammetry on all the complexes shows two successive Cu(I)-Cu(II) oxidations on the positive side of SCE, and a reduction of the coordinated imine ligand on the negative side. These copper(I) complexes are found to efficiently catalyze Suzuki type C-C coupling reactions.     

Ligand free open air copper(II) mediated aryl formamidation and amination of aryl halides

A simple synthetic procedure for direct formamidation and amination of aryl halides mediated by copper(II) salts was developed in open air, without an external ligand in formamide with potassium carbonate as a base. This approach is particularly efficient when electron active aryl halides are used as substrates. In these cases almost quantitative formamidation was observed.     

Cyclisations of alkynoic acids using copper(I) arylspiroborate complexes

In this study we have studied the synthesis, characterization and catalytic activity of phosphinocopper(I) complexes [Cu(PPh₃)₃(NCCH₃)][B(O₂C₆H₄-4-R)₂] (3a: R?=?H; 3b: R?=?Me; 3c: R?=?NO₂) and [Cu(PPh₃)₃(NCCH₃)][B(O₂C₆H₃-3,5-di-^tBu)₂] (3d) containing weakly coordinating arylspiroborate ligands bearing various electronic and sterically defined characteristics. All new compounds have been characterized fully including single crystal X-ray diffraction studies for 3a and 3c and confirm that the arylspiroborate ligands do not coordinate to the copper atoms. Using these new metal complexes as precatalysts in the cyclisation of short chain alkynoic acids gave the corresponding exo-dig cyclic lactones exclusively.     

Complexation Properties and Synthesis of 1,2-Bis(2,2'-bipyridinyl)ethylene and 1,2-Bis(2,2' -bipyridinyl)ethane Ligands with Cu(I)

l,2-Bis(2,2'-bipyridinyl)ethylene(1) ligand was synthesized by Wittig-Horner reaction and 1, 2-Bis(2, 2'-bipyridinyl)ethane(2) ligand(which can be obtained via another route ) was prepared by hydrogenation of (1). The formation of complexes of (1) and (2) with copper (I) has been studied. The influence of the different bridge chains (CH =CH, CH2CH2) on complexation is discussed on the basis of 1H NMR spectra. Keywords Dipyridine aldehyde, Dipyridine derivative, Copper complex     

Nucleation and growth of copper on glassy carbon: Studies in extended overpotential interval

The nucleation and growth of copper crystals on a glassy carbon electrode are investigated at different constant overpotentials. Current transients are recorded and the number of copper nuclei is microscopically registered. The experimental data for the growth current are interpreted according to the theories of progressive and instantaneous nucleation and information is obtained on the stationary nucleation rate, the saturation nucleus number density and the exchange current density at the crystals–solution interface boundary.