Electrochemical determination of benomyl using MWCNTs interspersed graphdiyne as enhanced electrocatalyst.

Graphdiyne (GDY) has attracted a lot of interest in electrochemical sensing application with the advantages of a large conjugation system, porous structure, and high structure defects. Herein, to further improve the sensing effect of GDY, conductive MWCNTs were chosen as the signal accelerator. To get a stable composite material, polydopamine (PDA) was employed as connecting bridge between GDY and MWCNTs-NH2, where DA was firstly polymerized onto GDY, followed by covalently linking MWCNTs-NH2 with PDA through Michael-type reaction. The formed GDY@PDA/MWCNTs-NH2 composite was then explored as an electrochemical sensor for benomyl (Ben) determination. GDY assists the adsorption and accumulation of Ben molecules to the sensing surface, while MWCNTs-NH2 can enhance the electrical conductivity and electrocatalytic activity, all of which contributing to the significantly improved performance. The proposed sensor displays an obvious oxidation peak at 0.72 V (vs. Hg|Hg2Cl2) and reveals a wide linear range from 0.007 to 10.0 µM and a low limit of detection (LOD) of 1.8 nM (S/N = 3) toward Ben detection. In addition, the sensor shows high stability, repeatability, reproducibility, and selectivity. The feasibility of this sensor was demonstrated by detecting Ben in apple and cucumber samples with a recovery of 94-106% and relative standard deviations (RSDs) less than 2.3% (n = 5). A sensitive electrochemical sensing platform was reported for benomyl (Ben) determination based on a highly stable GDY@PDA/MWCNTs-NH2 composite.

A high-precision, template-assisted, anisotropic wet etching method for fabricating perovskite microstructure arrays.

Cesium lead-halide (CsPbX3; X = Cl, Br, I) perovskite microstructure arrays have become the basis for laser array applications, due to their outstanding spectral coherence, low threshold, and wideband tunability. Furthermore, the common fabrication methods for these arrays have the limitation to achieve both tailored design and high resolution simultaneously. Herein, we report a high-precision, template-assisted, wet etching (TAWE) method for the preparation of perovskite microstructure arrays. This method possesses the advantages of flexible design, controllable size, and ultrahigh accuracy (the resolution can reach 1 µm or higher). A 20 × 20 inverted pyramid array with a diameter of 3 µm and a period of 4 µm was fabricated using this method. CsPbBr3 perovskite quantum dots fabricated by means of hot injection were filled into the inverted pyramid array via spin-coating and pumped using a laser with a wavelength of 400 nm. The lasing characteristics of the array were then measured and analyzed; the threshold was measured to be 37.6 µJ cm-2, and the full width at half maximum of the amplified spontaneous emission spectrum was found to be about 4.7 nm. These results demonstrate that perovskite microstructure arrays prepared via this method have potential applications in laser arrays.

A simple multiple centrifugation method for large-area homogeneous perovskite CsPbBr3 films with optical lasing.

Large scale cesium lead-halide (CsPbX3, X = Cl, Br, and I) perovskite films have become the basis of laser applications. Common fabrication methods such as spin-coating and thermal evaporation have a trade-off between high quality and low cost. Herein, we reported a facile method for preparing a large area homogeneous perovskite CsPbBr3 film via a multiple centrifugal deposition and solvent annealing (MCDSA) method. This method is superior because it can control the thickness (180 nm to 880 nm) of the film, ensure the film is crack and pinhole free, has a large area (2.5 cm × 2.5 cm), and has a low surface roughness (a root mean square of 32 nm). Multiple times of centrifugation and solvent annealing in the MCDSA method are key to improving the quality of the film as well as the laser performance. With increased centrifugation cycles from one to four, the thickness of the film increases from 180 nm to 880 nm, leading to a decrease in the laser threshold from 18.1 µJ cm-2 to 14.2 µJ cm-2 and an increase in the gain coefficient from 78.5 cm-1 to 112.7 cm-1. When solvent annealing is employed, the gain coefficient is further increased to 122.7 cm-1.

Formal Insertion of Imines (or Nitrogen Heteroarenes) and Arynes into the C-Cl Bond of Carbon Tetrachloride.

The formal insertion of double and triple bonds into the C-Cl bond of carbon tetrachloride has enabled the full utilization of carbon tetrachloride in chemical synthesis. A range of unactivated imines and electron-deficient nitrogen heteroarenes served as effective sources of C=N bonds to react with arynes and carbon tetrachloride to afford functionalized anilines whose core structures are present in some valuable arthropodicides. Control experiments and DFT calculations suggest the involvement of a trichloromethyl anion intermediate.

Three-component carboarylation of unactivated imines with arynes and carbon nucleophiles.

With 2-(trimethylsilyl)aryl triflates as aryne precursors, an unprecedented three-component carboarylation reaction of unactivated imines with arynes and carbon nucleophiles has been developed to access a variety of functionalized tertiary amines under transition metal-free conditions. Suitable carbon nucleophiles include chloroform, acetonitrile, and methyl propiolate.

Kinetic Resolution of Racemic Allylic Alcohols by Catalytic Asymmetric Substitution of the OH Group with Monosubstituted Hydrazines.

A new strategy has been established for the kinetic resolution of racemic allylic alcohols through a palladium/sulfonyl-hydrazide-catalyzed asymmetric OH-substitution under mild conditions. In the presence of 1 mol % [Pd(allyl)Cl]2 , 4 mol % (S)-SegPhos, and 10 mol % 2,5-dichlorobenzenesulfonyl hydrazide, a range of racemic allylic alcohols were smoothly resolved with selectivity factors of more than 400 through an asymmetric allylic alkylation of monosubstituted hydrazines under air at room temperature. Importantly, this kinetic resolution process provided various allylic alcohols and allylic hydrazine derivatives with high enantiopurity.

Label-free electrochemical immunosensor based on Nile blue A-reduced graphene oxide nanocomposites for carcinoembryonic antigen detection.

In this article, a novel, label-free, and inherent electroactive redox immunosensor for carcinoembryonic antigen (CEA) based on gold nanoparticles (AuNPs) and Nile blue A (NB) hybridized electrochemically reduced graphene oxide (NB-ERGO) is proposed. The composite of NB-graphene oxide (NB-GO) was prepared by π-π stacking interaction. Then, chronoamperometry was adopted to simultaneously reduce HAuCl4 and nanocomposites of NB-GO for synthesizing AuNPs/NB-ERGO. The immunosensor was fabricated by capturing CEA antibody (anti-CEA) at this nanocomposite modified electrode. The immunosensor determination was based on the fact that, due to the formation of antigen-antibody immunocomplex, the decreased response currents of NB were directly proportional to the concentrations of CEA. Under optimal conditions, the linear range of the proposed immunosensor was estimated to be from 0.001 to 40 ng ml(-1) and the detection limit was estimated to be 0.00045 ng ml(-1). The proposed immunosensor was used to determine CEA in clinical serum samples with satisfactory results. The proposed method may provide promising potential application in clinical immunoassays with the properties of facile procedure, stability, high sensitivity, and selectivity.

Overoxidized polypyrrole/graphene nanocomposite with good electrochemical performance as novel electrode material for the detection of adenine and guanine.

Most conducting polymer/graphene composites have excellent electrical conductivity. However, the background currents of these composites modified electrodes are much larger. In order to improve the sensitivities of these methods, it is necessary to decrease the background signal. In this paper, porous structure films of overoxidized polypyrrole/graphene (PPyox/GR) have been electrochemically coated onto glassy carbon electrode (GCE) and successfully utilized as an efficient electrode material for the quantitive detection of adenine and guanine, two of the most important components of DNA and RNA. The permselective polymer coatings with low background current could improve the selectivity and sensitivity of microelectrodes for the electropositive purine bases. The GRs into these polymers would further improve sensitivity by increasing the electroactive surface area. The electrochemical sensor can be applied to the quantification of adenine and guanine with a linear range covering 0.06-100 µM and 0.04-100 µM, and a low detection limit of 0.02 µM and 0.01 µM, respectively. More importantly, the proposed method was applied to quantify adenine and guanine in calf thymus DNA with satisfactory results.

Electroactive species-doped poly(3,4-ethylenedioxythiophene) films: enhanced sensitivity for electrochemical simultaneous determination of vitamins B2, B6 and C.

Herein, functionalized PEDOT films were prepared by incorporation of two electroactive species, ferrocenecarboxylic acid (Fc(-)) and ferricyanide (Fe(CN)6(4-)) as doping anions during the electropolymerization of PEDOT at glassy carbon electrodes (GCEs) from aqueous solution. The electrochemically synthesized electroactive species-doped PEDOT films have been carefully characterized by scanning electron microscopy (SEM), FTIR and UV/Vis spectra and various electrochemical techniques. Such nanostructured films combined the advantages of PEDOT (high conductivity and stability) together with electroactive species (good electrochemical activity) and were applied as electrochemical sensors for simultaneous determination of vitamin B2 (VB2), vitamin B6 (VB6) and vitamin C (VC). The results showed that the oxidation peak currents of vitamins obtained at the GCEs modified with electroactive species-doped PEDOT films were much higher than those at the ClO4(-)-doped PEDOT films and bare GCEs. The experiment results also illustrated that the sensors possessed high selectivity with no interference from other potential competing species. Moreover, the proposed sensors were successfully employed for the determination of vitamins in orange juice samples with satisfactory results.

[Spectral analysis of the effect of different polymerization potential on electrosynthesized poly (5-nitroindole) films].

High quality poly (5-nitroindole) (PNI) films can be synthesized electrochemically by direct anodic oxidation of 5-nitroindole (NI) in boron trifluoride diethyl etherate (BFEE) at different polymerization potential in the range of 1.23-2.23 V (vs. SCE). To the best of our knowledge, this is the first time that high quality polymer films of nitro group substituted conducting polymers were electrodeposited. The oxidation onset potential of NI was only 1.04 V vs. SCE in this medium. Chronoamperometric response of NI, FTIR and 1H NMR indicated that the polymerization potential had a great effect on the quality of PNI films. Lower potential is helpful for the electrochemical polymerization of NI and the extension of the conjugation length of PNI. On the other hand, a higher potential led to side reactions and poor polymer film quality. The structural characterization of PNI films by FTIR and 1H NMR indicated that the electrochemical polymerization of NI occurred at C2 and C3 positions.

1,2-Bis[5-(1,3-dioxolan-2-yl)-2-ethyl-3-thienyl]-3,3,4,4,5,5-hexafluorocyclopent-1-ene, a photochromic dithienylethene.

The title compound, C23H22F6O4S2, a photochromic dithienylethene, is a promising material for optical storage and other optoelectrical devices. The molecule adopts a photoactive antiparallel conformation in the crystalline state. The distance between the two reactive C atoms which are involved in potential ring closure is 3.829 (4) A. The dihedral angles between the central cyclopentene ring and the adjacent thiophene rings are 55.38 (7) and 54.81 (9) degrees. The colourless crystals turn magenta when exposed to UV radiation and the process is reversible.

[Size effect of Pt nanoparticles: a study of properties of Pt loaded TiO2 thin film].

TiO2 thin films loaded with Pt nanoparticles of different sizes were prepared. The sizes of the Pt nanoparticles were measured by TEM. The TiO2 thin films were characterized using XRD, UV-Vis and photocurrent measurement. The photocatalytic activities of the films were evaluated by the degradation of methylene blue under UV radiation. With the same molar quantity of loaded platinum, the properties of Pt loaded thin films were affected directly by the sizes of platinum nanoparticles, and showed strong size effect. When the particle size was 5 nm, the photocurrent and photocatalytic activity reached the maximum.