Growth And Properties Of ZnO Nanowires Confined In3D Macropores

ZnO nanowires were prepared through crystal seed pre-treatment and in situ hydrothermalsynthetic process in large-sized macroporous SiO2, and further ZnO NWs/SiO2complexes wereobtained. On the one hand, these complexes were employed as carriers to immobilize lipase, andtheir properties of adsorption were also studied. On the other hand, they were used to load fourcarboxylic phthalocyanine iron (Fe (Ш)-taPc) to prepare ternary composite photocatalyst (Fe(Ш)-taPc/ZnO NWs/SiO2) and investigate the degradation property of the catalyst. The specificresearch methods and achievements are given as follows:ZnO nanowires were prepared through crystal seed pre-treatment and in situ hydrothermalsynthetic process at the3D channel of large-sized SiO2macroporous materials. The effectsfocusing on the growth of ZnO nanowires with the introduction of ZnO seeds and the temperatureof hydrothermal reaction were specially investigated. The ZnO seeds was prepared in-situ on thewall of macroporous SiO2by using a ternary mixture of Zn(Ac)2/PEG600/H2O as precursor viatwo-step heating process at the respective temperature of100and200℃, and then calcinating athigh temperature. Zinc-ammonia complex solution was filled into the ZnO seed-formedmacroporous SiO2and converted into insoluble Zn(OH)2at90℃, then the growth of ZnOnanowires occurred during hydrothermal process at100℃. The composition of ternary precursorstrongly influenced the size and distribution of ZnO seeds which could further-step control theZnO nanowires randomly coiled but evenly dispersed in the3D macropores of SiO2with diameterin the range of15～20nm. The characterizations by XRD and Raman spectroscopy confirmed thatthe ZnO nanowires had hexagonal wurtzite crystal structure rature on the growth of the nanowires,debugging for ZnO NWs optimization of growth conditions.ZnO NWs/SiO2complexes were employed as carriers to immobilize porcine pancreatic lipase.The experimental results showed that the adsorption capacity of the composites is5～6fold incomparison with the adsorption of macroporous SiO2alone. The maximum adsorption capacitywas up to286.8mg.g-1and the highest enzyme activity was425.5U.g-1，Both adsorption capacityand the immobilizing ability against lipase remained almost unchanged when the samples were soaked in buffer solution for as long as48h.It is cleared that ZnO NWs/SiO2composites hasstrong adsorption ability, is likely to be a better immobilized enzyme carrier.The ternary complexes photocatalyst (Fe(Ш)-taPc/ZnO NWs/SiO2) was synthesized byloading Fe (Ш)-taPc on ZnO NWs/SiO2composites with maximum load up to11.5wt%. Thestructure of ternary composite photo-catalyst Fe(Ш)-taPc/ZnO NWs/SiO2was characterized bymeans of SEM, XRD, UV-Vis diffuse reflectance spectrometry and Raman spectrometry and thevisible light photo-catalytic degradation was determined by using Rhodamine B as the objectivesubstance. The catalyst exhibited good activity for the degradation of Rhodamine B and thereaction followed first-order kinetic equation. The catalyst containing3.5wt%of Fe(Ш)-taPcshowed highest activity,and98.6%of Rhodamine B could be degraded within60min. The resultsalso showed that the presence of ZnO NWs promoted the photocatalytic activity by an average of77%. The stability of the catalyst was examined through6recycles of utilization and the activitydecreased very slightly.