In situ studies of particle properties during their formation and growth with optical second-harmonic generation

目的是发展光学二次谐波(二次谐波散射，SHS)和双光子荧光(2-PF)作为原位研究纳米颗粒的形成、生长和表面修饰的方法。自蔓延高温合成作为一种非侵入性的非线性散射光谱，对颗粒尺寸、颗粒形状和纳米颗粒表面的变化高度敏感。在纳米颗粒&lt；50 nm表面的配体交换可以用高时间分辨率的SHS进行跟踪，除了获得热力学信息外，还可以区分不同的吸附步骤和表面位置。或者，可以从2-PF获得半导体量子点(尺寸为2-3 nm)的粒子特性。此外，2-PF能够研究颗粒缺陷的形成。金属纳米颗粒和半导体纳米颗粒的颗粒形成将分别在与倍频和2-PF混合的T混合器中进行研究。结合原位紫外可见光谱和透射电子显微镜对颗粒生长动力学进行了研究。通过改变系统参数，考察了稳定剂对颗粒形成动力学的影响。对于氧化锌量子点，将特别关注颗粒生长过程中缺陷的形成。下一步，将利用原位SHS研究不同尺寸的金属纳米颗粒表面的配体交换，以解决不同尺寸颗粒对配体交换动力学和热力学的依赖。除了产生动力学信息外，还将确定配体的表面复盖率，从而确定配体交换的效率。为了实现邻苯二酚在氧化锌上的快速吸附，将采用T混合器。最后，我们将研究SHS和2-PF同时应用于颗粒测量。因此，我们将研究量子点的2-PF和SHS与粒子大小、激发波长和表面修饰的关系。

The objective is the development of optical second harmonic generation (second harmonic scattering, SHS) and two-photon fluorescence (2-PF) as methods for in situ investigations of particle formation, growth and surface modifications of nanoparticles < 50 nm. SHS as a non-invasive nonlinear scattering spectroscopy is highly sensitive to changes of particle size, particle shape and of the surface of nanoparticles. The ligand exchange at the surface of nanoparticles < 50 nm can be followed with SHS with high time resolution and allowed for the discrimination of different adsorption steps and surface sites besides gaining thermodynamic information. Alternatively, particle properties of semiconducting quantum dots (down to sizes of 2 -3 nm) can be obtained from 2-PF. In addition, 2-PF enables the investigation of the formation of defects of the particles.Particle formation of metallic and semiconducting nanoparticles will be studied in a T-mixer with SHG and 2-PF, respectively. In combination with in situ UV-Vis spectroscopy and TEM the kinetics of particle growth will be studied. By variation of system parameters the influence of the stabilizer on the particle formation kinetics will be investigated. For ZnO quantum dots a special focus will be put on the formation of defects during particle growth.In the next step, the ligand exchange at the surface of metallic nanoparticles of different sizes will be studied with in situ SHS in order to resolve the dependence of kinetics and thermodynamics of the ligand exchange on differently sized particles. Besides yielding kinetic information the surface coverage of the ligands and thereby the efficiency of the ligand exchange will be determined. For the fast adsorption of catechol on ZnO the T-mixer will be used.In the last step, the simultaneous application of both SHS and 2-PF for particle measurement will be studied. Therefore, 2-PF and SHS of quantum dots will be investigated in dependence of the particle size, excitation wavelength and surface modification.