氧化物多孔纳米块体及复合发光材料的研究

【作者】 刘秀琳；

【导师】 崔得良；

【作者基本信息】 山东大学 ， 材料学， 2005， 博士

【摘要】 在本文中,我们首次利用溶剂热压方法,以不同种类的纳米颗粒和溶剂为原料制备了ZnO、TiO₂、ZrO₂和AlOOH多孔纳米块体。在此基础上,我们又发展了压差交换方法,成功地将若丹明B和桑色素组装进入多孔纳米块体的孔道中,从而得到了ZrO₂/若丹明B、ZrO₂/桑色素和AlOOH/若丹明B复合发光材料,并对材料的性能进行了较为系统的表征。 考虑到ZnO纳米材料在力、热、光、电、磁以及敏感特性等方面具有一系列特殊的性能,而ZnO多孔纳米块体的研究却一直未见报道,因此,我们用溶剂热压方法成功地制备了ZnO多孔纳米块体,并对其性能进行了分析。结果表明,利用溶剂热压方法可以制备出具有均匀孔径的ZnO多孔纳米块体,而且通过改变溶剂的种类、热压温度和压力,可以在一定范围内调变ZnO多孔纳米块体的孔径分布、孔容、比表面积以及孔隙率。其中,溶剂的种类对ZnO多孔纳米块体的孔径、孔容、比表面积以及孔隙率的影响最大:以水作溶剂制备的多孔块体主孔径较小,而用乙醇、异丙醇和DMF作溶剂时样品的主孔径较大,而且用DMF作溶剂制备的ZnO多孔纳米块体的孔容和孔隙率最大,分别为0.20cm³/g和52%。再有,X-射线衍射和电子显微镜测试结果证实,在溶剂热压过程中,ZnO纳米颗粒既没有发生结构变化也没有经历明显的长大过程,而且溶剂基本上已经全部从样品中逸出。此外,得到的ZnO多孔纳米块体具有较高的热稳定性。 为了进一步改进多孔纳米块体的孔径、孔容、比表面积和孔隙率,同时为研究多孔纳米块体的催化性能做准备,我们义以TiO₂纳米粉为原料制备了具有均匀孔径和大孔容的TiO₂多孔纳米块体。实验中我们发现:与制备ZnO多孔纳米块体的情况类似,通过改变溶剂的种类、热压温度以及恒温时间可以在一定范围内调变TiO₂多孔纳米块体的孔径、孔容、比表面积和孔隙率。同样地,溶剂的种类也是影响TiO₂多孔纳米块体的孔径、孔容、比表面积和孔隙率的关键因素。与水相比,用乙醇、异丙醇和氨水作溶剂时制备的TiO₂多孔纳米块体的孔径、孔容和孔隙率较大,其中,用异丙醇作溶剂制备的样品的孔容和孔隙率最大,分别为0.28cm³/g和49%。再有,利用单一溶剂时,TiO₂多孔纳米块体的孔径分布范围较窄,而多种溶剂混合使用则会使孔径的分布范围明显变宽。与制备ZnO多孔纳米更多还原

【Abstract】 In this thesis, ZnO, TiO₂, ZrO₂ and AlOOH bulk porous nanosolids have been prepared by a unique solvothermal hot-press method, using several kinds of nanoparticles and solvents as the starting materials. Furthermore, some novel composite fluorescent materials ZrO₂/RhB, ZrO₂/morin and AlOOH/RhB composites have also been synthesized by assembling RhB and morin molecules into the channels of the above porous nanosolids through a pressure-driving assembling process, and the properties of these composites are systematically investigated.ZnO nanomaterials have excellent mechanical, thermal, optical, electrical and sensing properties, so many papers on the preparation of ZnO nanomaterials have been published. However, to our best knowledge, there has been no report on bulk ZnO porous nanosolids up to now. Here we have prepared ZnO porous nanosolids by a unique solvothermal hot-press method, and their properties are preliminarily characterized. The results show that, ZnO porous nanosolids with uniform pore diameters can be obtained by this method, and the pore diameter, pore volume, specific surface area and porosity of the porous nanosolids can be adjusted by changing either the hot-press temperature, pressure or the kinds of solvents. Among these factors, the kind of solvents is an important one that dominating the above properties. For example, the primary pore diameter is larger when anhydrous ethanol, isopropyl alcohol or N, N-Dimethyl formamide is used as the solvent, compared with that of the sample prepared by using deionized water as the solvent. Besides, the pore volume and porosity of the porous nanosolids reach the maximum values when N, N-Dimethyl formamide is used as the solvent, namely, 0.20 cm³/g and 52%, respectively. In addition, during the process of solvothermal hot-press treatment, ZnO nanoparticles have not undergone any phase transformation or changing in particle size, and nearly all the solvents have escaped from the samples. Besides, the results of thermal analysis of the samples also show that their thermal stability is very high.In order to further increase the pore diameter, porosity and specific surface area, and investigate the catalytic properties of the porous nanosolids, TiO₂ porous nanosolids with uniform pore diameter and large pore volume are prepared using TiO₂nanoparticles as the starting materials. It is found that the pore diameter, pore volume, specific surface area and porosity of the porous nanosolids can be adjusted by changing either the kind of solvent, hot-press temperature or the hot-pressing time. Similar to the above, the kind of solvents is also a key factor that dominating the above properties of the porous nanosolids. Compared with that of the sample prepared by using deionized water as the solvent, the pore diameter, pore volume and porosity of TiO2 porous nanosolids prepared by using anhydrous ethanol, isopropyl alcohol or ammonia as the solvent are comparatively larger. Among these samples, the TiO2 porous nanosolids prepared by using isopropyl alcohol as the solvent has the largest specific surface area and porosity, i.e. 0.28 cm3/g and 49%, respectively. On the other hand, the uniformity of the pore diameters of TiCh porous nanosolids prepared by using single solvent is much better than that of samples obtained by using multiple solvents. Similar to that of ZnO porous nanosolids, no phase transformation and changing in particle size have been observed during the process of solvothermal hot-press treatment. This phenomenon is beneficial to preserving the catalytic activity of TiC>2 nanoparticles. The thermal analysis results also show that the TiC>2 porous nanosolids is rather stable under high temperature conditions.On the basis of successfully preparing TiO2 porous nanosolids, TiO2/RhB composites have been synthesized by assembling RhB into the channels, and the catalytic effect of T1O2 porous nanosolids on the degradation of RhB is also investigated. From the experiments we find that RhB can be degraded under the catalytic effect of TiO2 porous nanosolids, and the catalytic efficiency is affected by both the temperature and time of assembling process. When the temperature is increased, the catalytic efficiency of TiO2 porous nanosolids on the degradation of RhB is improved, and it becomes degenerated if the time of assembling process is extended.On the other hand, the results indicate that, the photoluminescence of TiO2/RhB composites is very poor, even though it has been prepared under optimized conditions. In order to further improve the photoluminescence efficiency of composites, ZrO2 porous nanosolids with the highest porosity of 45% are prepared by the same solvothermal hot-press method. The key factors that affecting the pore diameter, porosity and specific surface area of ZrO2 porous nanosolids have been studied. Similarto the situation of TiC>2 porous nanosolids, TxOj nanoparticles have undergone neither phase transformation nor changing in particle size during the process of solvothermal hot-press treatment. The results also show that the thermal stability of ZrO2 porous nanosolids is very high.On the basis of above experimental results, ZrC>2 porous nanosolids/RhB fluorescent composites are synthesized by assembling RhB into the channels of Z1O2 porous nanosolids. It is found that the photoluminescence efficiency of this composite is rather high. Besides, the results also indicate that the light absorption of the composites mainly come from the RhB molecules assembled into the channels, and the corresponding photoluminescence of the composites also comes from these RhB molecules. In the assembling experiments, we find that the concentrations of RhB and the time of assembling process have much effect on the photoluminescence of the composites. When the concerntration of RhB is increased, the photoluminescence intensity of composites increases at first and followed by a decrease. At the same time, the peak position shows a red shift （from 600nm to 614nm）. On the other hand, the photoluminescence intensity of the composites shows a similar trend with the extending of assembling time, but the peak position remains unchanged.From the above analysis we know that, the photoluminescence of both TiO2/RhB and Z1O2 porous nanosolids/RhB composites mainly come from RhB molecules, and the role of the porous nanosolids is restricted to preventing the aggregation of RhB molecules. In order to synthesize real composite fluorescent materials, Z1O2 porous nanosolids/morin composites have been synthesized by assembling morin molecules into the channels of ZrO2 porous nanosolids. The results reveal that the photoluminescence efficiency of Z1O2 porous nanosolids/morin composites is very high, contrasting to the poor photoluminescence efficiency of both morin and ZrO2 porous nanosolids. The FTIR spectra of the composites reveal that chemical bonds have formed between morin molecules and the atoms on the surface of pores in Z1O2 porous nanosolids, which is beneficial to improving the photoluminescence efficiency of the composites. In addition, the photoluminescence intensity of the composites increases dramatically at first and then decreases gradually with the increasing of morin concentrations and the extending of assembling time, and the peak position shows a redshift. This phenomenon shows that porous nanosolids may find many applications in the fabrication of novel and high fluorescent efficiency composites.For investigating the effects of porous nanosolids, A100H porous nanosolids and the corresponding composite materials have been prepared. It is found that the largest specific surface area of this porous nanosolid was 119m2/g, and the pore volume and porosity reach to 0.36cm3/g and 51%, respectively. On the other hand, the pore diameter, pore volume, specific surface area and porosity of A100H porous nanosolids can be adjusted by changing either the hot-press temperature or the kinds of solvents. At the same time, both the hot-press temperature and kinds of solvents have great effects on the phase of A100H porous nanosolids. Thermal stability testing of the sample indicates that A100H porous nanosolids could be transformed into AI2O3 by heating at 520°C for4h.By using A100H porous nanosolids prepared above, A100H porous nanosolids /RhB composites are synthesized by assembling RhB into the channels of A100H porous nanosolids. The results reveal that, similar to the situation of Z1O2 porous nanosolids/RhB composites, the light absorption of the A100H porous nanosolids/RhB composites also mainly come from RhB molecules assembled into the channels. Correspondingly, the photoluminescence of these composites also come from these RhB molecules. Similarly, the photoluminescence intensity of composites also increases at first and then decreases with the increasing of RhB concentrations and extending of assembling time. Correspondingly, the peak position shows a red shift （from 588nm to 592nm） with the increasing of RhB concentrations, but it remains unchanged with the extending of assembling time.更多还原