【作者】 陈海波；

【导师】 刘贤伟；

【作者基本信息】 中国科学技术大学 ， 应用化学， 2020， 博士

【摘要】 纳米颗粒因为其独特的物理化学特性而被日益广泛地生产和应用,与此同时纳米颗粒对于环境和人体健康的危害也越来越受到人们的重视。系统地研究纳米颗粒在环境中的迁移转化,尤其是理解单个纳米颗粒之间或者单个纳米颗粒与物理、化学、和生物界面之间的相互作用具有重要的意义。本论文针对纳米颗粒在水环境中的团聚、沉降与转化等关键过程,通过基于表面等离子体共振的单颗粒成像方法开展了一系列工作,实现了该方法在环境分析中的成功应用,在单颗粒尺度上解析了纳米颗粒相互作用的机理。论文的主要研究内容和结果如下:1、利用表面等离子体共振显微镜(SPRM)准确测定了纳米颗粒的沉降效率,并研究了环境因素对颗粒沉降的影响。SPRM的单颗粒实时成像能力和高的时空分辨率,可以原位探测纳米颗粒的沉降动力学;利用修正的沉降效率进一步探究了离子强度、价态、溶液pH和界面表面基团对于沉降的影响。这种方法得到的沉降效率免去了最大沉降速率归一化的步骤,减少了实验过程中因为颗粒浓度、离子强度等外部因素造成的实验偏差,为我们预测纳米颗粒在环境中的迁移命运提供了良好的试验平台。2、通过SPRM的高灵敏度以及颗粒强度与颗粒体积的线性关系,建立了一种在单颗粒尺度上对颗粒团聚体进行定量分析的方法。从团聚体的平均尺寸随时间的变化,得到了颗粒团聚的临界沉降浓度,证明了该方法的有效性;通过对团聚颗粒强度解卷积,定量分析了团聚体中包含的颗粒数目,建立了溶液中单聚体、多聚体的数量与电解质浓度的关系。与目前普遍采用的整体平均法相比,该方法可以提供更多有关颗粒团聚动力学的信息,有助于更好地理解纳米颗粒团聚机理。3、在单颗粒尺度上追踪了纳米颗粒在固液界面的动力学过程。利用SPRM灵敏的z轴分辨率(5 nm)和高的时间分辨率(0.67ms),我们追踪了单个纳米颗粒在界面的运动轨迹,发现其受到明显的水力学阻碍作用,证明了这是造成纳米颗粒在低离子强度溶液中出现多次撞击的原因之一;通过改变固体界面的表面修饰基团,理解了纳米颗粒界面动力学行为与表面化学的相关性。该方法聚焦于单个纳米颗粒瞬时的界面行为,有助于提升对环境中纳米颗粒沉降过程的微观解析。4、利用SPRM对折射率极其敏感的特性,测定了单个纳米颗粒在电极表面氧化溶解的动力学过程。我们不仅可以检测单个银纳米颗粒的瞬时电化学氧化过程,还可以实时观察溶解银离子的扩散行为;通过基准图像识别法对原始图像进行进一步的信号处理和数据分析,实现了颗粒信号与离子信号的成功拆分,更加准确地表征了单个纳米颗粒的氧化溶解过程。该方法可以用于其他类似的单个纳米颗粒的电化学反应和催化过程,提升对电活性纳米颗粒环境行为的理解。更多还原

【Abstract】 Nanoparticles have been widely used for a variety of applications because of their unique physical and chemical properties.The toxicity of nanoparticles to the environment and human health has gained rapidly growing research interest in recent years.It is of great significance to systematically explain the transport and transformation of nanoparticles in the environment,especially to understand the basic principles of the interaction between single nanoparticles and physical,chemical,and biological interface.In this dissertation,aiming at the key processes of aggregation,deposition and transformation of nanoparticles in water environment,a series of research work has been carried out using the single particle imaging method based on surface plasmon resonance(SPR).We have.realized the successful application of this method in environmental analysis,and elucidated the interaction mechanism of nanoparticles.The main research contents and results are as follows:1.The surface plasmon resonance microscopy(SPRM)was used to accurately measure the deposition efficiency of nanoparticles and to study the influence of environmental factors on the deposition of nanoparticles.Benefiting from the real-time imaging ability and high spatial-temporal resolution of SPRM,the deposition dynamics of nanoparticles can be detected in situ.The effects of ion strength,valence,solution pH and surface functional group on the depostion process were further explored by using the modified deposition efficiency.The deposition efficiency obtained by this method avoids the complex procedure of the normalization of the maximum deposition rate,reduces the experimental error caused by external factors such as particle concentration and ionic strength in the experimental process,and provides a promising test platform to predict the fate of nanoparticles in the environment.2.Based on the high sensitivity of SPRM and the linear relationship between image intensity and particle size,a quantitative analysis method for the aggregation of nanoparticles at the level of single nanoparticles was established.By analysing the change of the average size of aggregates with time,the critical coagulation concentration(CCC)of aggregated particles is obtained,proving the validity of this method.By deconvolution of the intensity of aggregated particles,the specific particle number of each aggregates is quantitatively analyzed,and the relationship between the electrolyte concentration and the number of monomers and polymers in solution is established.Compared with the essembled method,this approach can provide more information about the aggregation kinetics of nanoparticles,and help to better understand the aggregation mechanism of nanoparticles.3.The dynamic process of nanoparticles at the solid-liquid interface is tracked at the single nanoparticle level.Taking advantage of the sensitive z-axis resolution(5 nm)and high time resolution(0.67 ms)of SPRM,we track the movement of a single nano particle at the interface,and find that the nanoparticle is obviously hydrodynamicly hindered,which is responsible for the the multicollision process of the nanoparticle at the interface in low ionic strength solution.By chaning the surface functional group of the solid interface,we gain a deeper understanding of the dynamic behavior correlated with surface chemistry.This method focuses on the instantaneously interfacial behaviour of single nanoparticles,which is helpful to elucidate the depositon process of nanoparticles in the environment from microscopic perspective.4.Owing to the refractive index-sensitive features of SPRM,the kinetic process of the oxidation and dissolution of a single silver nanoparticle on the electrode surface was determined.We can not only detect the instantaneous electrochemical oxidation process of single silver nanoparticles,but also monitor the diffusion behavior of dissolved silver ions in real time.Further signal processing and data analysis of the original image through the reference image recognition method ia able to separate the overlapped signal and help us to characterize the oxidation and dissolution process of single nanopartilces more accurately.This method has great potential in the electrochemical reaction and catalytic process of other similar single nanoparticles,which will improve the understanding of the environment behavior of electrically active nanoparticles.更多还原