| With the development of science and technology,modern material is developing in the direction of intelligence and versatility.Traditional catalysts have failed to meet requirements in the face of complex chemical reaction processes and multi-step reactions involved in actual industrial production.Therefore,it is necessary to add a variety of catalysts to complete the catalytic reaction which may lead to catalysts interaction,affect the efficiency of the catalyst reaction,product separation and catalyst recovery after the reaction ended.Wherefore,it is important to fabricate a reactor with two or more catalysts.Two catalysts form a series system which will be used to catalyze reaction of two-step process.In addition,the general chemical reaction and intermediate products usually can not be controlled and detected effectively.So,it is of great significance to study an intelligent,tandem catalyst.Smart materials can perceive changes of the external environment(such as temperature,pH,light,etc.)and perform as physical and chemical properties.At present,smart materials are mainly divided into temperature-responsive smart materials,pH-responsive smart materials and light-responsive smart materials.Among them,temperature conditions,both in biomedical and chemical reactions,are extremely important and adjustable conditions.So the temperature-responsive smart materials were extensively studied.In this paper,We combined vinylimidazole and Ag nanoparticles as catalysts with temperature-sensitive poly(N-isopropylacrylamide)as the temperature-sensitive phase and carrier for Ag nanoparticles to construct the temperature-sensitive tandem nanoreactor.In the first part,we prepared a temperature-sensitive tandem nanoreactor Ag@air@PNIPAM-VIM.Ag nanoparticles and vinylimidazole acted as two catalysts.Poly(N-isopropylacrylamide)acts as a thermo-sensitive phase with the "on/off" effect.First of all,we analyze the grafting effect by Fourier infrared spectrometry.The morphology of the material and the particle size of Ag nanoparticles werecharacterized by transmission electron microscopy,energy dispersive X-ray spectroscopy,and X-ray diffraction(XRD).Then we use the Comprehensive thermal analysis(TG-DSC)analysis and elemental analysis to calculate the content of each component in it.This proves that the nanoreactor we have prepared meets our expectations.In the second part,we tested the temperature-sensitive performance of nanoreactors,the tandem catalytic ability and the temperature-sensitive controllability in series catalysis.First,we used a laser particle size analyzer to tracing the changes in particle size of the nanoreactor with temperature.At the same time,the contact angle was used to test the change of morphology and contact angle of the nanoreactor at different temperatures.The results all indicated that the nanoreactors we prepared possess temperature-sensitive properties.Electrochemical experiment characterizes the "on/off" effect of the channel of the nanoreactor during the catalytic reaction.Finally,catalyzed by acetic acid p-nitrophenyl ester as the catalytic substrate,the results show that at 25 °C,p-nitrophenyl acetate can be hydrolyzed and reduced in two steps,indicating that two-step tandem reaction can be carried out.At 40°C,p-nitrophenyl acetate can only be hydrolyzed and cannot be reduced.This is because when the temperature is higher than the lowest critical solution temperature(LCST≈32°C)of poly(N-isopropylacrylamide),the polymer chain is in a contracted state leading to the reactants have no contact with the Ag nanoparticles,so the reduction reaction cannot be performed.In this case,the switch is in the closed state.On the contrary,when the temperature is lower than the LCST,the switch is opened.A series of tests can demonstrate that our temperature-sensitive tandem nanoreactors have the capability of series catalysis and temperature controllability.This not only has significance in actual production,but provides new methods and ideas for catalyst research. |
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