Multifunctional photoresponsive organic molecule for electric field sensing and modulation

Abstract

Nonlinear optical organic molecules have advanced a wide range of fields spanning from integrated photonics to biological imaging. With advances in molecular design, an emerging application is multifunctional nonlinear organic materials. Unlike conventional molecules which simply emit light through single or multi photon processes, multifunctional materials can perform multiple tasks, such as modulating the optical signal or reporting an electric field intensity. In this work, we report a multifunctional organic molecular device with electric field ‘sense-and-modulate’ capability. This is achieved by combining two distinct functional modules. The electric field-reporting module relies on a photo-induced electron transfer (PeT) dye, tetraphenylethylene (TPE) as a two-photon (2p) imaging agent; while the electric field-modulating module relies on the organic photoconductor, naphthalimide (NAI). To reduce cross-talk between the two modules, they are separated by a long alkyl chain. The photophysical properties and photoconductivity of the probe molecule are studied in a range of solvents and in the solid state, and the results agree with the density functional theory predictions. Specifically, 2p excitation is demonstrated, and the photoconductivity is rapid and reversible. The entire system is optically controlled, including signal read-out, and the two modules can be operated simultaneously or individually.