Substituted thiourea incorporated rhodamine-based chemosensors for selective detection of aluminium ions

Abstract

Various metal ions’ contemporary utility, biological essence and environmental impact have stimulated their selective and sensitive detection, particularly when present in traces. In this context, methodological explorations relying on structural and functional modulations of prime components and interactive parameters have been pivotal in developing chemosensors for selective detection of such metal ionic inputs. In this investigation, three thiourea-incorporated rhodamine B derivatives varying in their substituent modified covalent architectures were synthesized, and their photophysical signalling responses were monitored in the presence of different metal ions. The dual mode outputs, colourimetric and fluorescence signals, had displayed significant changes in the selective presence of Al³⁺ ions attributable to the complexation-induced ring-opening of Rhodamine derivatives. In contrast, other metal ions failed to generate such colour and spectral changes in an aqueous-ethanolic medium. Therefore, these probes would be manifested as a colourimetric and fluorescent output-based chemosensor for selective detection of Al³⁺ ions with low detection limits (in nM region), higher association constants (∼10⁷ M⁻¹) inferring to a higher degree of probe-metal ion interactions, efficient response time of Rhodamine spiro-ring opening and counter anion driven reversibility in photophysical signals. Despite the retention of selectivity towards Al³⁺ ion, the parametric signalling variation in these probes was attributed to their stereo-electronic environment of probe-metal ion interaction, which was substantially influenced by the nature of the substituent attached. The paper strip-based investigation endorsed the utility of these probes as potential molecular systems for the selective detection Al³⁺ ions in the presence of various metal ions.