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 fro...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.展开更多
Heparin was grafted onto polycarbonate urethane (PCU) surface via a three-step procedure utilizing α, ωdiamino-poly(ethylene glycol) (APEG, M n =2 000) as a spacer. In the first step, isocyanate functional groups we...Heparin was grafted onto polycarbonate urethane (PCU) surface via a three-step procedure utilizing α, ωdiamino-poly(ethylene glycol) (APEG, M n =2 000) as a spacer. In the first step, isocyanate functional groups were introduced onto PCU surface by the treatment of hexamethylene diisocyanate (HDI) in the presence of di-n-butyltin dilaurate (DBTDL) as a catalyst. In the second step, APEG was linked to the PCU surface to obtain the APEG conjugated PCU surface (PCU-APEG). In the third step, heparin was covalently coupled with PCU-APEG in the presence of N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylamidopropyl) carbodiimide (EDAC). The amount of heparin (1.639 μg/cm 2 ) covalently immobilized on the PCU-APEG surface was determined by the toluidine blue method. The modified surface was characterized by water contact angle, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The hemocompatibility was preliminarily studied by platelet adhesion test. The results indicated that heparin was successfully grafted onto the PCU surface, and meanwhile the hydrophilicity and hemocompatibility of the modified PCU surface were improved significantly compared with the blank PCU surface.展开更多
Herein we report a highly sensitive filter-less fluorescence detection method using an APD （avalanche photodiode）. Experimental measurements using the proposed APD-based highly sensitive fluorescence detection metho...Herein we report a highly sensitive filter-less fluorescence detection method using an APD （avalanche photodiode）. Experimental measurements using the proposed APD-based highly sensitive fluorescence detection method exhibits the sensing capability to detect an excitation light and a fluorescence light without band pass filter or grating. The principle of this APD-based highly fluorescence detection method is used the varying multiplication ratio that is decided by wavelength. The wavelength controls running distance of photo-excited carrier by absorption coefficients, and this element decide multiplication ratio on fixed high electrical field. In fluorescence detection, they use two types of light： excitation light and fluorescence light. These lights have different wavelengths and make different multiplication ratio as well. Thus this method can separate two types of light easily by using multiplication ratios of APD without band pass filters/gratings. In this experiment, the excitation light is LED （light emitting diode） and fluorescence light occurs from FITC （fluorescein isothiocyanate） with ethanol. The FITC concentration changes from 0.1 μmol/L to 10 mmol/L. In this measurement circuit, we employ APD （S2385）, power supply voltage, and pico ampere current meter. As a result, these lights are correctly separated by using multiplication ratio with calculation at every concentration FITCs.展开更多
基金Supported by the Key Science and Technology Innovation Team of Zhejiang Province(2011R50007)
文摘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.
基金Supported by International Cooperation from Ministry of Science and Technology of China(No.2008DFA51170)Science and Technology Project of Tianjin Municipal Science and Technology Commission(No.08ZCKFSF03300)
文摘Heparin was grafted onto polycarbonate urethane (PCU) surface via a three-step procedure utilizing α, ωdiamino-poly(ethylene glycol) (APEG, M n =2 000) as a spacer. In the first step, isocyanate functional groups were introduced onto PCU surface by the treatment of hexamethylene diisocyanate (HDI) in the presence of di-n-butyltin dilaurate (DBTDL) as a catalyst. In the second step, APEG was linked to the PCU surface to obtain the APEG conjugated PCU surface (PCU-APEG). In the third step, heparin was covalently coupled with PCU-APEG in the presence of N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylamidopropyl) carbodiimide (EDAC). The amount of heparin (1.639 μg/cm 2 ) covalently immobilized on the PCU-APEG surface was determined by the toluidine blue method. The modified surface was characterized by water contact angle, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The hemocompatibility was preliminarily studied by platelet adhesion test. The results indicated that heparin was successfully grafted onto the PCU surface, and meanwhile the hydrophilicity and hemocompatibility of the modified PCU surface were improved significantly compared with the blank PCU surface.
文摘Herein we report a highly sensitive filter-less fluorescence detection method using an APD （avalanche photodiode）. Experimental measurements using the proposed APD-based highly sensitive fluorescence detection method exhibits the sensing capability to detect an excitation light and a fluorescence light without band pass filter or grating. The principle of this APD-based highly fluorescence detection method is used the varying multiplication ratio that is decided by wavelength. The wavelength controls running distance of photo-excited carrier by absorption coefficients, and this element decide multiplication ratio on fixed high electrical field. In fluorescence detection, they use two types of light： excitation light and fluorescence light. These lights have different wavelengths and make different multiplication ratio as well. Thus this method can separate two types of light easily by using multiplication ratios of APD without band pass filters/gratings. In this experiment, the excitation light is LED （light emitting diode） and fluorescence light occurs from FITC （fluorescein isothiocyanate） with ethanol. The FITC concentration changes from 0.1 μmol/L to 10 mmol/L. In this measurement circuit, we employ APD （S2385）, power supply voltage, and pico ampere current meter. As a result, these lights are correctly separated by using multiplication ratio with calculation at every concentration FITCs.
