Nanomaterials - 06

Abstract

Functional molecular liquids (FMLs) combine π-cores with bulky alkyl chains to prevent aggregation, yielding room-temperature liquids with optoelectronic properties, deformability, low volatility, and easy processability[1]. Here, we explore a supramolecular strategy to obtain near-infrared (NIR) luminescent liquids by combining alkyl-pyrene liquids[2] as donor molecules with alkylated naphthalenediimide (NDI) as acceptor dopants. The alkyl-pyrene liquids readily form charge-transfer (CT) complexes with the alkylated NDI (Fig.1). These CT complexes exhibit pronounced color changes under UV irradiation, with emissions shifting from dark red to blue depending on the degree of CT formation. For instance, the PN1 composite shows a CT band that overlaps with the fluorescence of Py1. This spectral overlap enables cascaded energy transfer, resulting in a NIR emission beyond 700 nm. In contrast, the PN4 composite lacks a CT band and therefore has no NIR emission. This is because the pyrene core is isolated by being covered with bulky, branched alkyl chains; therefore, no D-A interaction occurs with the NDI molecule. Thus, alkyl chain engineering precisely controls CT interactions, optical response, and fluidic properties.