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是非易失性存储技术、自旋电子器件和传感器发展的核心。目前的挑战包括开发可在两种功能状态之间切换的材料，以及用于可扩展存储器和传感器开发的光。我们开发了一种新的策略，通过光学双稳态光致变色的功能化来制备光驱动功能材料。光致变色化合物在基态和亚稳态的电子结构不同的两个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，这些配体可以结合到金属中心或结合到有机多发色分子阵列中。一旦结合，光诱导的螺恶嗪结构的变化会导致功能靶成分(金属中心或生色团)的氧化还原电位、基态能量和激发态能量的变化。这样的结构变化可以触发两个有机生色团、有机配体和金属中心之间的能量转移和电荷转移过程，或者两个处于混合价状态的金属中心之间的能量转移和电荷转移过程。我们实验室以前的工作已经证明了电子双稳钴络合物、荧光共轭聚合物纳米粒子和荧光有机二元体中光致色素诱导的电荷转移或能量转移过程的原理证明。在这项建议中，我们描述了旨在了解支配这些现象的基本结构和电子因素、光致变色门控过程的限制以及调节信噪比以优化传感器和存储器应用的光感应门的动力学和热力学因素的实验。*在拟议的工作中，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，以及开态/闭态的电子结构(Ii)将光致变色配体集成到一系列电子双稳金属络合物中，以建立控制这些体系中氧化和自旋态切换的参数，(Iii)将光致变色引入纳米材料，如用于生物传感器应用的共轭聚合物纳米颗粒，以及(Iv)利用光致变色掺杂剂光学触发用于传感器应用的石墨烯OFET中的栅极电压。这项研究的短期目标是确定结构参数，以优化光异构化诱导的金属和发色过程的调制。长期目标是将光学门控功能材料用于可扩展的存储设备，并将基于荧光团的生物传感器用于医疗诊断。

* **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.**