Femtosecond IR Probe of Ultrafast Dynamics of Molecular Adsorbates on Nanoparticles: Solvation and Electron Transfer

埃默里大学的连天全博士是由化学部物理化学项目资助的关于分子在纳米颗粒上吸附的超快动力学的飞秒红外探测器-溶剂化的研究。他将进一步发展和测试溶剂化诱导振动峰移的理论，并使用这种新的方法来研究分子在纳米颗粒/液体界面的溶剂化动力学。对于基态和激发态之间偶极矩变化较大的分子，飞秒激发使激发态分子处于非平衡溶剂构型。随后的溶剂化作用对溶质振动光谱的影响还不清楚，不像对溶质电子光谱的充分研究那样。他正在发展一种溶剂化诱导溶质动态振动峰移的理论，该理论基于溶剂-溶质相互作用的Onsager介电连续模型。测量了Re(Dcbpy)(CO)3Cl及其相关分子在不同溶剂中的动态峰位移。CO伸缩峰位移的大小和动力学将被用来与理论模型进行比较和关键检验。他还将使用振动峰位移作为研究固-液界面溶剂化动力学的一种新方法。红外探头和纳米晶薄膜的结合将使溶剂化动力学研究在广泛的溶剂中得以实现。这种方法是对现有技术的补充，如荧光斯托克斯位移和光学克尔效应，并可能在纳米晶体薄膜等难以用现有技术研究的微散射介质中有独特的应用。这项拟议的研究是连博士在了解分子在纳米颗粒上吸附的超快动力学研究工作的继续。半导体和金属纳米粒子具有许多潜在的应用，从纳米电子学、太阳能转换到生物医学成像。大多数纳米粒子的合成或修饰都是通过连接分子来实现的，比如钝化、结构连接、敏化或分子传感基团。这些分子在这些体系中对电荷和能量的转移、传输和耗散起着至关重要的作用。这项拟议的工作将导致对纳米粒子表面分子动力学的基本理解，如溶剂化和能量松弛。这一知识对于开发更高效的基于纳米颗粒的设备至关重要。拟议的研究还将允许培训纳米科学和纳米技术领域的博士后研究员、研究生和本科生，教育未来的劳动力。

Dr. Tianquan Lian of Emory University is funded for his research on femtosecond IR probe of ultrafast dynamics of molecular adsorbates on nanoparticles - solvation by a grant in the Physical Chemistry program of the Chemistry Division. He will further develop and test the theory of solvation-induced vibrational peak shift and use this novel approach to study solvation dynamics of molecules at nanoparticle/liquid interfaces. For molecules with large dipole moment changes between ground and excited states, femtosecond excitation prepares the excited molecule in a non-equilibrium solvent configuration. The effect of the subsequent solvation on solute vibrational spectra is not yet understood, unlike the well-studied effect on solute electronic spectra. He is developing a theory of solvation-induced solute dynamic vibrational peak shift based on the Onsager dielectric continuum model of solvent-solute interaction. Dynamic peak shifts will be measured in Re(dcbpy)(CO)3Cl and related molecules in different solvents. The magnitude and dynamics of the CO stretching peak shifts will be used to compare with and critically test the theoretical model. He also will use vibrational peak shift as a new method to study solvation dynamics at solid-liquid interfaces. The combination of IR probe and nanocrystalline films will allow the study of solvation dynamics in a wide range of solvents. This approach is complementary to existing techniques such as fluorescence Stokes shift and the optical Kerr effect, and may have unique applications in slightly scattering media such as nanocrystalline thin films, that are difficult to study using these extant techniques. The proposed research is a continuation of Dr. Lian's research effort in understanding ultrafast dynamics of molecular adsorbates on nanoparticles. Semiconductor and metal nanoparticles have many potential applications ranging from nanoelectronics, solar energy conversion, to biomedical-imaging. Most nanoparticles are synthesized or modified with attached molecules as passivating, structural linkage, sensitizing, or molecular sensing groups. These molecules play essential roles in transfer, transport and dissipation of charge and energy in these systems. The proposed work will lead to a fundamental understanding of the dynamics of molecules on the nanoparticle surface, such as solvation and energy relaxation. This knowledge is essential to developing more efficient devices based on nanoparticles. The proposed research will also allow the training of postdoctoral fellows, graduate students and undergraduate students in the area of nanoscience and nanotechnology, educating the workforce of the future.