Light Modulation of Charge Transfer Processes in Inorganic-Organic Materials

在外部刺激（光、电场或磁场）的作用下，磁性、光学和导电性能发生变化的功能材料对非易失性存储技术、自旋电子学器件和传感器的发展至关重要。目前的挑战包括开发可在两种功能状态之间切换的材料，用于可扩展存储器和传感器的开发。我们已经开发了一种新的策略，通过光学双稳态光致变色功能化的光驱动功能材料。光致变色在基态和亚稳态的电子结构不同的两种状态之间进行光诱导异构化。我们已经开发了光致变色螺恶嗪配体，可以结合到金属中心或纳入有机多色阵列。一旦结合，光诱导的螺恶嗪结构变化导致功能靶组分（金属中心或发色团）的氧化还原电位、基态能和激发态能的变化。这样的结构变化可以触发两个有机发色团、有机配体和金属中心之间或两个混合价态金属中心之间的能量转移和电荷转移过程。我们实验室之前的工作已经证明了光铬诱导的电荷转移或能量转移过程在电子双稳态钴络合物、荧光共轭聚合物纳米颗粒和荧光有机二元体中的原理证明。在本提案中，我们描述了旨在理解控制这些现象的基本结构和电子因素的实验，光铬门控过程的限制，以及调节信号噪声比的动力学和热力学因素，以优化传感器和存储器应用的光诱导门控。***在本文中，我们将研究(i)控制光致变色螺恶嗪的光化学和热过程的结构参数，以及在开/闭状态下的电子结构；（ii）将光致变色配体整合到一系列电子双稳态金属配合物中，以建立控制这些系统中氧化和自旋状态切换的参数。（iii）将光致变色剂加入纳米结构材料中，如用于生物传感器应用的共轭聚合物纳米颗粒，以及（iv）利用光致变色剂在用于传感器应用的石墨烯ofet中光学触发栅极电压。该研究的短期目标是确定优化光异构化诱导的金属基和显色过程调制的结构参数。长期目标是利用光学门控功能材料用于可扩展的存储设备和基于荧光团的生物传感器，用于医学诊断

* **Functional materials that undergo changes in magnetic, optical, and conducting properties upon application of external stimuli (light, electric field, or magnetic field) are central to the development of non-volatile memory technologies, spintronics devices, and sensors. Current challenges involve developing materials that switch between two functional states with light for scalable memory and sensor development. We have developed a novel strategy for light-driven functional materials through functionalization with optically bistable photochromes. Photochromes undergo light-induced isomerization between two states that differ in the electronic structures of their ground and metastable states. We have developed photochromic spirooxazine ligands that can be bound to metal centers or incorporated into organic multichromophoric arrays. Once bound, light-induced changes in spirooxazine structure lead to changes in the redox potential, ground state energies, and excited state energies at the functional target component (metal center or chromophore). Such structural changes can then trigger energy-transfer, and charge-transfer processes between two organic chromophores, organic ligands, and metal centers, or between two metal centers in a mixed valence state. Previous work in our lab has demonstrated proof-of-principle for photochrome-induced charge transfer or energy transfer processes in an electronically bistable cobalt complex, fluorescent conjugated polymer nanoparticles, and fluorescent organic dyads. In this proposal, we describe experiments designed to understand the fundamental structural and electronic factors that govern these phenomena, the limits of photochrome-gated processes, and the kinetic and thermodynamic factors that regulate signal-to-noise ratios for optimizing light-induced gating for sensors and memory applications. *** In the proposed work, we will investigate (i) the structural parameters that govern photochemical and thermal processes, and electronic structure in open/closed states of photochromic spirooxazines (ii) integrate photochromic ligands into a series of electronically bistable metal complexes to establish the parameters that govern switching of oxidation and spin states in these systems, (iii) incorporate photochromes into nanostructured materials such as conjugated polymer nanoparticles for biosensor applications, and (iv) utilize photochromic dopants for optical triggering of gate voltages in graphene OFETs for sensor applications. The short-range goals of the proposed research are to determine the structural parameters that optimize photoisomerization-induced modulation of metal-based and chromophoric processes. The long-range goals are to utilize optically-gated functional materials for scalable memory devices and fluorophore-based biosensors for medical diagnostics.**