Many two-photon absorption (TPA) organic dyes are water insoluble and suffer from strong fluorescence quenching in aqueous media due to the self-aggregation effect. This seriously limits their applications as two-photon fluorescence (TPF) probes in bio-imaging. By employing a reprecipitation method, we prepared ultrabright water-miscible organic nanoparticles (ONPs) of 1,4-dimethoxy-2,5-di[4′-(cyano)styryl]benzene (COPV). The single-crystal structure reveals that the cooperation between π–π stacking and hydrogen-bonding interactions drives COPV molecules into a brickwork arrangement of J-aggregates, in which the coherent excitation delocalization reaches 2–3 molecules. Due to the superradiance of J-aggregates, COPV ONPs are highly emissive in aqueous media with a quantum yield >0.4; meanwhile, their TPA cross-section is greatly enhanced, probably due to exciton–vibration coupling. As TPF probes, COPV J-aggregate ONPs are 3–4 orders of magnitude brighter than conventional fluorescent dyes and an order of magnitude brighter than quantum dots. Moreover, these ONPs exhibit no obvious cytotoxicity at concentrations as high as 100 μg mL−1. Our results demonstrate that ultrabright J-aggregate ONPs of COPV provide a new strategy to construct efficient TPF nano-probes for bio-imaging.
许多双光子吸收(
TPA)有机
染料不溶于
水,在
水介质中会因自聚集效应而产生强烈的荧光淬灭。这严重限制了它们作为双光子荧光(TPF)探针在
生物成像中的应用。我们采用再沉淀法制备了 1,4-二甲氧基-2,5-二[4′-(
氰基)
苯乙烯基]苯(
COPV)的超亮
水溶性有机纳米粒子(ONPs)。单晶结构显示,π-π堆叠和氢键相互作用促使
COPV 分子形成砖砌排列的 J 聚体,其中相干激发脱焦达到 2-3 个分子。由于 J-聚集体的超辐照度,
COPV ONPs 在
水介质中具有很高的发射率,量子产率大于 0.4;同时,可能由于激子-振动耦合,它们的
TPA 截面也大大提高。作为 TPF 探针,
COPV J 聚合 ONP 比传统荧光
染料亮 3-4 个数量级,比量子点亮一个数量级。此外,这些 ONP 在浓度高达 100 μg mL-1 时也没有明显的细胞毒性。我们的研究结果表明,
COPV 的超亮 J 聚合 ONP 为构建用于
生物成像的高效 TPF 纳米探针提供了一种新策略。