Ritonavir sulfate is a protease inhibitor widely used in the treatment of acquired immunodeficiency syndrome. In order to elucidate the inherent stability and sensitivity characteristics of ritonavir sulfate, it was i...Ritonavir sulfate is a protease inhibitor widely used in the treatment of acquired immunodeficiency syndrome. In order to elucidate the inherent stability and sensitivity characteristics of ritonavir sulfate, it was investigated under forced thermal and hydration stress conditions as recommended by the Inter- national Conference on Harmonization guidelines. In addition, competency of vibrational （infrared and Raman） spectroscopy was assessed to identify structural changes of the drug symbolizing its stress degradation. High performance liquid chromatography was used as a confirmatory technique for both thermal and hydration stress study, while thermogravimetric analysis]differential thermal analysis and atomic force microscopy substantiated the implementation of vibrational spectroscopy in this frame- work. The results exhibited high thermal stability of the drug as significant variations were observed in the diffuse reflectance infrared Fourier transform spectra only after the drug exposure to thermal radiations at 100 ℃. Hydration behavior of ritonavir sulfate was evaluated using Raman spectroscopy and the value of critical relative humidity was found to be 〉 67%. An important aspect of this study was to utilize vibrational spectroscopic technique to address stability issues of pharmacological molecules, not only for their processing in pharmaceutical industry, but also for predicting their shelf lives and suitable storage conditions.展开更多
Reduced graphene oxide-tin porphyrin(RGO-SnTPP)nanohybrids with good dispersibility have been prepared by two covalent functionalization approaches.The microscopic structure and morphology of the RGO-SnTPP nanohybrids...Reduced graphene oxide-tin porphyrin(RGO-SnTPP)nanohybrids with good dispersibility have been prepared by two covalent functionalization approaches.The microscopic structure and morphology of the RGO-SnTPP nanohybrids were characterized by various spectroscopic techniques including Fourier transform infrared spectroscopy,Raman spectroscopy,transmission electron microscopy,thermogravimetric analysis and X-ray photoelectron spectroscopy.Ground-state absorption and steady-state fluorescence studies indicate considerableπ–πinteractions and effective photo-induced electron and/or energy transfer from the porphyrin moieties to the RGO.Their nonlinear optical properties were investigated using the Z-scan technique at 532 nm with both picosecond and nanosecond laser pulses.The RGO-SnTPP hybrids were found to exhibit large nonlinear optical responses due to a combination of mechanisms,while significant differences in their nonlinear optical responses were observed,highlighting the influence on photophysical properties of the degree of functionalization and the synthetic approach employed.展开更多
Redox activity of copper species immobilized poly(o-aminophenol)/multi-walled carbon nanotube(Cu@MWCNT-POAP)composite is reported for direct electrocatalysis towards detection of H_(2)O_(2).The Cu@MWCNT-POAP composite...Redox activity of copper species immobilized poly(o-aminophenol)/multi-walled carbon nanotube(Cu@MWCNT-POAP)composite is reported for direct electrocatalysis towards detection of H_(2)O_(2).The Cu@MWCNT-POAP composite was prepared by a single step in situ electrochemical method.The as-prepared Cu@MWCNT-POAP composites were characterized by field emission scanning electron microscopy,Fourier transform infrared spectroscopy,Raman spectroscopy,X-ray diffraction,and electrochemical impedance spectroscopy.Cyclic voltammetry(CV)studies highlighted the good redox behavior of the Cu@MWCNT-POAP composite resulting from direct electron transfer behavior of the copper redox couple(Cu^(2+)/Cu^(+)).The Cu@MWCNT-POAP composite displayed superior electrocatalytic activity and high performance towards detection of H_(2)O_(2)because of its large surface area and homogenous immobilization of Cu species on the MWCNT-POAP composite.The analytical sensitivity and detection limit of the sensor were 831μA mM^(-1)cm^(-2)and 30 nM,respectively.In addition,bio-catalytic activity of the sensor was evaluated using the Michaelis-Menten constant.The Cu@MWCNT-POAP composite showed excellent stability and reproducibility,and good recoveries for determination of H_(2)O_(2)in milk,bleach cream,and contact lens solutions.展开更多
文摘Ritonavir sulfate is a protease inhibitor widely used in the treatment of acquired immunodeficiency syndrome. In order to elucidate the inherent stability and sensitivity characteristics of ritonavir sulfate, it was investigated under forced thermal and hydration stress conditions as recommended by the Inter- national Conference on Harmonization guidelines. In addition, competency of vibrational （infrared and Raman） spectroscopy was assessed to identify structural changes of the drug symbolizing its stress degradation. High performance liquid chromatography was used as a confirmatory technique for both thermal and hydration stress study, while thermogravimetric analysis]differential thermal analysis and atomic force microscopy substantiated the implementation of vibrational spectroscopy in this frame- work. The results exhibited high thermal stability of the drug as significant variations were observed in the diffuse reflectance infrared Fourier transform spectra only after the drug exposure to thermal radiations at 100 ℃. Hydration behavior of ritonavir sulfate was evaluated using Raman spectroscopy and the value of critical relative humidity was found to be 〉 67%. An important aspect of this study was to utilize vibrational spectroscopic technique to address stability issues of pharmacological molecules, not only for their processing in pharmaceutical industry, but also for predicting their shelf lives and suitable storage conditions.
基金the National Natural Science Foundation of China(51432006,50925207,51172100)the Ministry of Science and Technology of China for the International Science Linkages Program(2011DFG52970)+4 种基金the Ministry of Education of China for the Changjiang Innovation Research Team(IRT13R24)the Ministry of Education and the State Administration of Foreign Experts Affairs for the 111 Project(B13025)100 Talents Program of CASJiangsu Innovation Research Team are gratefully acknowledged.M.G.H.,M.P.C.C.Z.thank the Australian Research Council(ARC)for support.
文摘Reduced graphene oxide-tin porphyrin(RGO-SnTPP)nanohybrids with good dispersibility have been prepared by two covalent functionalization approaches.The microscopic structure and morphology of the RGO-SnTPP nanohybrids were characterized by various spectroscopic techniques including Fourier transform infrared spectroscopy,Raman spectroscopy,transmission electron microscopy,thermogravimetric analysis and X-ray photoelectron spectroscopy.Ground-state absorption and steady-state fluorescence studies indicate considerableπ–πinteractions and effective photo-induced electron and/or energy transfer from the porphyrin moieties to the RGO.Their nonlinear optical properties were investigated using the Z-scan technique at 532 nm with both picosecond and nanosecond laser pulses.The RGO-SnTPP hybrids were found to exhibit large nonlinear optical responses due to a combination of mechanisms,while significant differences in their nonlinear optical responses were observed,highlighting the influence on photophysical properties of the degree of functionalization and the synthetic approach employed.
基金supported by the National Science Council and the Ministry of Education of Taiwan(Republic of China).
文摘Redox activity of copper species immobilized poly(o-aminophenol)/multi-walled carbon nanotube(Cu@MWCNT-POAP)composite is reported for direct electrocatalysis towards detection of H_(2)O_(2).The Cu@MWCNT-POAP composite was prepared by a single step in situ electrochemical method.The as-prepared Cu@MWCNT-POAP composites were characterized by field emission scanning electron microscopy,Fourier transform infrared spectroscopy,Raman spectroscopy,X-ray diffraction,and electrochemical impedance spectroscopy.Cyclic voltammetry(CV)studies highlighted the good redox behavior of the Cu@MWCNT-POAP composite resulting from direct electron transfer behavior of the copper redox couple(Cu^(2+)/Cu^(+)).The Cu@MWCNT-POAP composite displayed superior electrocatalytic activity and high performance towards detection of H_(2)O_(2)because of its large surface area and homogenous immobilization of Cu species on the MWCNT-POAP composite.The analytical sensitivity and detection limit of the sensor were 831μA mM^(-1)cm^(-2)and 30 nM,respectively.In addition,bio-catalytic activity of the sensor was evaluated using the Michaelis-Menten constant.The Cu@MWCNT-POAP composite showed excellent stability and reproducibility,and good recoveries for determination of H_(2)O_(2)in milk,bleach cream,and contact lens solutions.
