Color tuning of cationic pyrene derivatives on a clay nanosheet: Retardation of gradual redshift on clay

Imidazolium-Modified Bispyrene-Based Fluorescent Aggregates for Discrimination of Multiple Anions in Aqueous Solution

A great number of anions exist in biological systems and natural environment, and are highly relevant to human health and environment quality. It is necessary to develop simple and effective sensors to differentiate and identify those similar or different anions. Here, an imidazolium-modified bispyrene-based fluorescent amphiphilic probe DPyDIM was synthesized and its aggregates were applied to detect and discriminate various anions. The fluorescent aggregates exhibit ratiometric responses to different types of anions. Moreover, the ratiometric responses to different types of anions are featured with multiple-wavelength cross-reactivity. The collection of fluorescence variation at four typical wavelengths can generate distinct recognition patterns to specific anions. The heat map and principal component analysis results verify that this single fluorescent sensor system can effectively and sensitively identify 16 kinds of anions that belong to phosphorus-containing, sulfur-containing anions, and anionic surfactants. The cross-reactive sensing of the amphiphilic fluorescent aggregates was attributed to the different influences on the aggregation behaviors of the probes by different anions. The present work provides a promising strategy for effective detection and discrimination of multiple anions by employing dynamic fluorescent aggregates as a sensing platform.

Light Energy Accumulation from Pyrene Derivative to Tris(bipyridine)ruthenium on Clay Surface

A novel type of energy donor-acceptor system on a clay surface has been prepared. The energy transfer between an energy-donating cationic pyrene derivative (An-Py²⁺) and an energy-accepting tris(bipyridine)ruthenium complex (Ru²⁺) on the clay surface was investigated using absorption, emission, and lifetime measurements. An obvious energy transfer was observed, and one Ru²⁺ molecule quenched the emission from five molecules of An-Py²⁺ with an emission quenching efficiency of 85% on the clay surface. This suggests that the light energies absorbed by five of the An-Py²⁺ molecules were accumulated in the one Ru²⁺ molecule. Near-quantitative emission quenching was observed for stoichiometric amounts of An-Py²⁺ and Ru²⁺. The apparent quenching rate constant is approximately 10¹⁷ L mol^-1 s^-1, and thus the quenching rate constant is 10⁷-10⁸ times higher than the diffusion rate constant in a homogeneous solution.