【作者】 王志强；

【导师】 周兴平；

【作者基本信息】 东华大学 ， 应用化学， 2008， 硕士

【摘要】 纳米材料的小尺寸效应、量子尺寸效应等特性使其在光、热、电、磁学性质等方面呈现出与常规材料不同的特性,近年来已开始应用于许多高科技领域。随着高科技领域生物芯片技术的崛起,上转换荧光纳米材料应用于制作该技术使用的荧光探针已逐渐成为新的研究热点。迄今为止,六方晶型NaYF₄为基质,Yb,Er共掺杂的NaYF₄;Yb,Er材料是发光效率最高的上转换荧光材料。目前,立方晶型NaYF₄的制备方法主要有水相共沉淀法、固液两相法等,已经可以得到分散良好的NaYF₄纳米级荧光材料。然而,六方晶型NaYF₄的合成条件还非常苛刻,已有报道的最低合成温度为160℃。本课题采用反转胶束法进行NaYF₄纳米晶的合成,以NaYF₄基准样的选择与制备为基础展开,着重研究了反应时间、反应温度、表面活性剂的浓度等影响因素对NaYF₄晶型的影响。本课题还通过ICP-AES元素分析测试,研究了反应开始之后水相中钇元素浓度的变化,并且结合产品的XRD图谱比对研究,取得了一些新的、很有意义的成果;（1）用反转胶束法高产量地制备出了粒径小、大小均一、分散良好的NaYF₄材料,合成出的最小NaYF₄纳米晶直径仅为约7纳米。（2）研究了各种影响因素对NaYF₄产品晶型的影响,并对反转胶束法合成NaYF₄的合成原理做了深入探究;（a）反应时间长短的变化不会造成NaYF₄产品晶型的明显变化;（b）反应温度远大于（高于20℃）油酸熔点（16.3℃）且低于油相有机溶剂的沸点时,反应温度不会对NaYF₄产品的晶型产生质的影响;而当反应温度略高于16.3℃时（低于20℃）,产品NaYF₄可以被控制在立方晶型;但当反应温度明显低于16.3℃时,产品为无定形态;（c）温度大于16.3℃时,且该温度不影响油酸钠/油酸在油相中溶解度的前提下,NaYF₄产品中六方晶型与立方晶型量的比值随着油酸钠浓度的增加而增加;当油酸钠的浓度大于0.4mol/L时,在常温下,可以制备出纯六方晶型的NaYF₄纳米晶;（d）不同的油相有机溶剂具有不同的极性,极性不同使得它们对油酸钠/油酸的溶解能力不同,甲苯、环己烷、正己烷在不同温度下对油酸钠不同的溶解能力使得NaYF₄产品的晶型有所不同;（e）油相中的产品经过高温高压处理用后,NaYF₄颗粒的分散性仍然很好,大小仍然非常均一,且晶型没有改变的趋势;（f）高氯酸钇pH值的改变对NaYF₄产品的晶型没有明显影响;（g）另一种阴离子表面活性剂琥珀酸二异辛酯磺酸钠（AOT）无法起到与油酸钠相同的作用;（h）水相中离子强度的改变会影响表面活性剂的功能;（i）反胶束法制备的荧光材料依然具有很好的荧光特性。（3）对反转胶束法合成NaYF₄的反应原理进行了深入探讨;（a）油酸钠、油相、水相一起构成的反应物周围的微环境,这一微环境使得NaYF₄的生成速度相对水相合成变得缓慢得多;（b）基于ICP测试结果和对应的XRD图谱,对反转胶束法制备NaYF₄的反应原理进行了推测和论证。与常规的反胶束法相比,利用本方法制备出的基质材料除了具有大小均匀、分散良好、颗粒大小可控制等优点外,还具有产量高、产品晶型可控制等优点,这是传统反胶束法所不能达到的。更多还原

【Abstract】 The properties of nanoparticles, such as small size effect, quantum size effect, etc., have equipped the nanomaterials with many unique features that make them quite different from the routine materials in optics, calorifics, electricity and magnetics, etc. Based on their special properties, nanoparticles have been applied in many high-tech fields recently.With the development of biochips, up-conversion fluorescent materials have gradually become a new research focus because of their potential applications as biochips. Until now, ytterbium and erbium co-doped hexagonal sodium yttrium fluoride （NaYF₄: Yb, Er） is among the most efficient up-conversion phosphors. Its potential applications in biological and medical fields have attracted many scientists.Up to now, the main methods to synthesize cubical type NaYF₄ are coprecipitation method, solid-liquid biphase method, etc. Well-dispersed cubical NaYF₄ nanocrystals have been achieved successfully. But the reaction conditions needed to gain hexagonal NaYF₄ nanocrystals are still tough, the lowest temperature needed is about 160℃.A special reverse micelle synthesis method is adopted in this paper to synthesize NaYF₄ nanocrystals. Our research begin with a well-chosen benchmark sample, and then makes extensive studies about the influences of reaction time, reaction temperature, surfactant’s concentration, etc. on the NaYF₄’s crystalline types. ICP-AES elementary analysis is also used to test the Y element’s concentration variance. Together with XRD patterns’ analysis, a lot of novel and meaningful achievements are gained:（1） Well-dispersed, homogeneous NaYF₄ fluorescent matrix nanocrystals have been synthesized by the special reverse micelle method with high yield. The smallest diameter achieved is only around 7 nm.（2） Many influence factors’s effects on NaYF₄’s crystalline type are investigated, and the outcome goes as follows:（a） The variance of reaction time will not affect NaYF₄’s crystalline type obviously.（b） When the reaction temperature is between 20℃and certain organic solvent’s boiling point, it will not affect NaYF₄’s crystalline essentially; when the reaction temperature is a little bit higher then 16.3℃, NaYF₄’s crystalline can be controlled at cubical form; but when the temperature is below 16.3℃, the product is in an amorphous state.（c） When the reaction temperature is above 16.3℃, and when, at this temperature, sodium oleate/oleic acid’s solubility in oil is not affected, the ratio of hexagonal type to cubical type of NaYF₄ increases with the rise of sodium oleate’s concentration. When sodium oleate’s concentration is above 0.4 mol/L, under normal temperature, pure hexagonal nanocrystals are achieved.（d） Different organic solvents have different polarities, the differences cause their different solubilities to sodium oleate/oleic acid, and the differences cause different crystalline types.（e） When the products dispersed in oil phase are collected for high-temperature, high-pressure treatment, NaYF₄ nanoparticles are still well-dispersed and homogeneous, with crystalline type unchanged.（f） Y（ClO₄）₃’s pH value variations won’t affect NaYF₄’s crystalline type.（g） Another anionic surfactant AOT can’t take sodium oleate’s place to achieve similar experimental outcomes.（h） Ionic strength in water phase will affect the surfactant’s function. （i） Fluorescent materials synthesized by this special reverse micelle methed still have good up-conversion luminescence properties. （3） The reaction principles to synthesize NaYF₄ is discussed:（a） The microenvironments formed by oil, water and surfactant have made the formation of NaYF₄ nanoparticles much slower, compared with the ones formed in aqueous solution.（b） The reaction mechanisms are also demonstrated according to the ICP testing results and corresponding XRD patterns.By this special reverse micelle method, not only well-dispersed, homogeneous and size-variable nanocrystals can be processed like the normal reverse micelle method. Controllable crystalline type and high-yield can also be achieved under normal temperature.更多还原