The uncatalyzed reaction of p -tolyl isocyanate ( p -TI) with water in N , N -dimethylformamide (DMF) was investigated by high performance liquid chromatography (HPLC). The reactions were carried out at different temperatures from 293 K to 323 K, using various molar ratios of water to p -TI. DMF, as a special amide , was proved to be an efficient catalyst for water–isocyanate reaction. Under the reaction conditions in this study, substituted urea was the only final product observed. An appreciable amount of intermediate p -toluidine was detected. Concentrations of the isocyanate group as well as the amine and urea were determined as a function of time. New kinetic equations were deduced for each of the substance on the basis of a multistep mechanism, instead of a simple second order reaction as usual. Kinetic constants were calculated using the software MATLAB . Furthermore, the effects of temperature and concentrations of reactants on the reaction rate and amine content were discussed. The activation energy of each step was also determined.
Novel three-dimensional Ag nanoflowers (3DAN) were successfully synthesized through a facile Cu2+ mediated solution method using N,N-dimethylformamide (DMF), which serves as both a reducing agent and a solvent at room temperature. It was found that the introduction of a trace amount of Cu2+ could greatly slow the rate of the Ag+ reaction and thus this process effectively reduced the growth speed of Ag nanoparticles allowing 3DAN to be formed. The mechanism underlying the self-assembly process and shape evolution of 3DAN were systematically investigated by varying reaction time. X-Ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) were used to characterize the structure and morphology of the obtained products. X-Ray photoelectron spectroscopy (XPS) was used to assess the chemical state and surface composition of the 3DAN. UV-vis absorption spectra of the products collected from the reaction solution at various stages were taken to study their optical properties. In the measurement of surface-enhanced Raman scattering using rhodamine 6G (R6G) as the probe, the 3DAN exhibited a significant enhancement factor, indicating their potential applications in biosensing and nanodevices.
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