Emission enhancement in twisted pyridyl salt using a montmorillonite nanoclay by the intercalation and surface-fixation processes

Abstract

Boosting the fluorescence (FL) intensity for a weak/nonemissive molecule is a challenge. This work describes the improvement of the FL intensity of a nonemissive conformationally twisted π-conjugated pyridyl salt. This pyridyl salt has been treated with montmorillonite nanoclay, where it is confined via both the surface-fixation and intercalation processes. Such entrapment of the probe could restrict its movement, resulting in the enhancement of its FL intensity. This process is unlike the AIE process, and the FL enhancement by both the surface-fixation and intercalation processes is sporadic. The formation of the composite (probe + nanoclay) is supported with the help of powder X-ray diffraction, FT-IR spectroscopy, ¹H-NMR and X-ray photoelectron spectroscopy (XPS). The change in emission intensity was monitored by steady-state FL measurement, followed by determining the lifetime parameters, wherever applicable. The FL enhancement of the probe has been examined by changing the concentration of the probe and using diverse solvent polarities. Although there was no definite trend found by changing the polarity, FL enhancement was noticed for all the solvent systems.