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产生（二次谐波散射，SHS）和双光子荧光（2-PF）作为原位研究< 50 nm纳米颗粒形成、生长和表面修饰的方法。SHS作为一种非侵入式非线性散射光谱技术，对纳米颗粒的粒径、形状和表面变化具有高度的敏感性。在< 50 nm的纳米颗粒表面的配体交换可以用高时间分辨率的SHS来跟踪，除了可以获得热力学信息外，还可以区分不同的吸附步骤和表面位置。另外，半导体量子点的粒子特性（小到2- 3nm的尺寸）可以从2- pf中获得。此外，2-PF能够研究颗粒缺陷的形成。金属纳米粒子和半导体纳米粒子的形成将分别在与SHG和2-PF的t型混合器中进行研究。结合原位紫外可见光谱和透射电镜研究颗粒生长动力学。通过改变体系参数，研究稳定剂对颗粒形成动力学的影响。对于ZnO量子点，将特别关注粒子生长过程中缺陷的形成。下一步，我们将利用原位SHS研究不同尺寸金属纳米颗粒表面的配体交换，以解决配体交换动力学和热力学对不同尺寸金属纳米颗粒的依赖。除了得到动力学信息外，还可以确定配体的表面覆盖率，从而确定配体交换的效率。为了使邻苯二酚在ZnO上的快速吸附，将采用t型混合器。最后，我们将研究SHS和2-PF在粒子测量中的同时应用。因此，将研究量子点的2-PF和SHS与粒子尺寸、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.