Myoglobin/arylhydroxylamine film modified electrode: Direct electrochemistry and electrochemical catalysis

The adsorption processes and electrochemical behavior of 4-nitroaniline (4-NA) adsorbed onto glassy carbon electrodes (GCE) have been investigated in aqueous 0.1 M nitric acid (HNO₃) electrolyte solutions using cyclic voltammetry (CV). 4-NA adsorbs onto GCE surfaces, and upon potential cycling past −0.2 V, is transformed into the arylhydroxylamine (ArHA) derivative which exhibits a well-behaved pH dependent redox couple centered at 0.32 V at pH 1.5. It is noted as arylhydroxylamine modified glassy carbon electrodes (HAGCE). This modified electrode can be readily used as an immobilization matrix to entrap proteins and enzymes. In our studies, myoglobin (Mb) was used as a model protein for investigation. A pair of well-defined reversible redox peaks of Mb (Fe(III)-Fe(II)) was obtained at the Mb/arylhydroxylamine modified glassy carbon electrode (Mb/HAGC) by direct electron transfer between the protein and the GCE. The formal potential (E^0′), the apparent coverage (Γ^*) and the electron-transfer rate constant (k_s) were calculated as −0.317 V, 8.26 × 10⁻¹² mol/cm² and 51 ± 5 s⁻¹, respectively. Dramatically enhanced biocatalytic activity was exemplified at the Mb/HAGC electrode by the reduction of hydrogen peroxide (H₂O₂), trichloroacetic acid (TCA) and oxygen (O₂). The Mb/arylhydroxylamine film was also characterized by UV-visible spectroscopy (UV-vis), scanning electron microscope (SEM) indicating excellent stability and good biocompatibility of the protein in the arylhydroxylamine modified electrode. This new Mb/HAGC electrode exhibited rapid electrochemical response (2 s) for H₂O₂ and had good stability in physiological condition, showing the potential applicability of the films in the preparation of third generation biosensors or bioreactors based on direct electrochemistry of the proteins.     

Conformational studies of substituted nitroanilines: geometry of 2-methyl-5-nitroaniline

The title compound (C₇H₈N₂O₂), is monoclinic, space group P2₁/n, witha=9.552(2),b=5.677(2),c=13.586(3)Å, =92.68(2)⁰, andD _x=1.374 g-cm^–3 forZ=4. The refinement converged toR=0.043,wR=0.038. The molecule is approximately planar, with dihedral angles of 3.7(2.1)⁰ between the amino group and the aromatic ring, and 3.2(2)⁰ between the nitro group and the ring. According to the UV spectrum in solution, the molecular geometry indicates weak intramolecular charge transfer. The three-dimensional structure is stabilized by three intermolecular H bonds. A bifurcated one induces the formation of chains along , while the other two link molecules that belong to adjacent chains and are related by an inversion center.     

Core (Au)-shell (Ag) structure nitrogen dots for the recognition of nitroaniline isomers by surface-enhanced Raman scattering

A facile synthesis method for NDs-Au@AgNPs SERS substrate using Au seeds prepared by nitrogen-rich quantum dots (NDs) as reducing agent and stabilizer was developed for nitroaniline isomers recognition by surface-enhanced Raman scattering.     

Synthesis of functionalized 4-nitroanilines by ring transformation of dinitropyridone with enaminones

2-Functionalized 4-nitroanilines were readily synthesized by ring transformation using 3,5-dinitro-2-pyridone and enaminones prepared from 1,3-dicarbonyl compounds and amines. Modification of the amino group and the ortho-position could be achieved by simply changing the enaminones. Using this strategy, functional groups such as acetyl, benzoyl, and ethoxycarbonyl groups could be introduced into the nitroaniline framework.     

Synthesis of Nitroanilines Catalyzed by Horseradish Peroxidase in the Presence of NaNO2 and H2O2

The synthesis of nitroanilines catalyzed by horseradish peroxidase（HRP） in the presence of sodium nitrite and hydrogen peroxide was investigated, o-Nitroaniline and p-nitroaniline were found in the nitrated products. 2-Aminotoluene and 4-aminotoluene could also be nitrated to give corresponding nitrated products. This protocol has great potentials to open new avenues useful for the synthesis of nitroaniline and its derivatives.     

Sensitive determination of carbohydrates labelled with p-nitroaniline by capillary electrophoresis with photometric detection using a 406 nm light-emitting diode

p-Nitroaniline was explored as a derivatising reagent for UV absorbance detection of carbohydrates after separation by CE. This derivatising agent has three advantages: first, it has excellent water solubility; second, it has high molar absorptivity; and third, it is possible to obtain sensitive detection using a UV or blue light-emitting diode (LED) as the light source. The labelling reaction took less than 30 min to complete with high reaction yield. The separation process was modelled and optimised using an artificial neural network. Nine carbohydrates were separated by a CE system within 16 min using a 0.17 M boric acid buffer at pH 9.7. On-column LED detection at 406 nm allowed the detection of carbohydrates with good detection limits (<1.1 microM or 8.8 fmol) and reproducible quantification in the concentration range of 2.6-200 microM. This method was applied successfully to the determination of component carbohydrates in some food samples.     

Solutal convection during growth of organic NLO crystals

Effect of solutal and thermal convection plays very important role when a large thermal gradient is applied during crystal growth. To address this problem, we have purified m.nitroaniline (m.NA) and m. dinitrobenzene (m.DNB) and studied crystal growth and effect of growth parameters on the optical quality. Crystals of pure and binary alloy of m.dinitrobenzene and m.nitroaniline were grown by vertical directional solidification method in a two zone transparent furnace. Effect of doping and temperature gradient on the solid-liquid interface morphology and quality of crystal was determined by studying the bulk transparency and nonlinearity.     

硒催化的邻硝基苯胺类化合物的羰基化反应

用硒作催化剂，三乙胺为助催化剂，CO为羰基化试剂，通过氧化还原羰基化的方法，将邻硝基苯胺类化合物在分子内羰基化成环，反应生成相应的一系列环脲类物质，此催化合成方法的反应选择性近秋100％，收率较高，操作简单，并提出了可能的反应机理。     

Spectrophotometric simultaneous determination of nitroaniline isomers by orthogonal signal correction-partial least squares

The simultaneous determination of nitroaniline isomer mixtures by using spectrophotometric methods is a difficult problem in analytical chemistry, due to spectral interferences. By multivariate calibration methods, such as partial least squares (PLS), it is possible to obtain a model adjusted to the concentration values of the mixtures used in the calibration range. Orthogonal signal correction (OSC) is a preprocessing technique used for removes the information unrelated to the target variables based on constrained principal component analysis. OSC is a suitable preprocessing method for partial least squares calibration of mixtures without loss of prediction capacity using spectrophotometric method. In this study, the calibration model is based on absorption spectra in the 200–500 nm range for 21 different mixtures of nitroaniline isomers. Calibration matrices were containing 1–21, 1–15 and 1–18 μg ml⁻¹ of m-nitroaniline, o-nitroaniline and p-nitroaniline, respectively. The RMSEP for m-nitroaniline, o-nitroaniline and p-nitroaniline with OSC and without OSC were 0.6567, 0.2692, and 0.3134, and 1.3818, 1.2181, and 0.3953, respectively. This procedure allows the simultaneous determination of nitroaniline isomers in real matrix samples and good reliability of the determination was proved.     

锌粉还原法合成对苯二胺的研究

在酸性介质中，用锌粉还原对硝基苯胺制备对苯二胺，通过影响反应因素的研究，如反应物配比、温度、反应时间等，寻找出了较佳反应条件：对硝基苯胺与锌粉的摩尔比为1:4，反应温度为80-85℃，反应时间为6h，对苯二胺的产率可达90%。克服了铁粉还原法的弊端，为对苯二胺的工业化生产提供了可靠的依据。