Functionalization of a Rhodamine-B Based Chemosensor onto Surfaces of Fe3O4, SBA-15 and H2Ti3O7 Support Substrates for Selective Fe3+ Ion Detection

Abstract

The major challenges in the chemosensing approach are the development of analytically uncomplicated and cost-effective method for the selective and sensitive detection of metal ions in the aqueous medium. Rhodamine derivatives have proven as efficient and effective chemosensory probes for selective and sensitive detection of different metal ions in the solution phase, predominantly in aqueous-organic medium, where the interaction of the probe and metal ion translated on signalling module expressed through dual mode photophysical output. A rhodamine-B-based probe 2, incorporated with 3-nitrobenzaldehyde coupled (2-aminoethyl)-piperazinyl receptor, was developed to exhibit selective and sensitive detection of Fe³⁺ ions in aqueous-ethanol medium. Its spiro-cyclic ring-opening on Fe³⁺-complexation resulted in absorption and fluorescence spectral enhancements with concomitant colour change, inferring to the structure-function module of signalling expressions and the extent of their magnitude has contributed the selectivity, sensitivity, interaction affinity, response time, reversibility and other parameters of efficient detection. The probe also exhibited similar photophysical output responses in the selective presence of Fe³⁺ ion on immobilization onto surfaces of silica-coated magnetite, SBA-15 and hydrogen titanate appended through amino-propyl-silyl linker. Apart from retaining the selectivity towards Fe³⁺ ions, these surface-functionalized inorganic support materials (3, 4, and 5) executed the signalling action in aqueous medium, enhancing their scope as efficient chemosensors for practical application. The effect of probe immobilization on the metal ion-induced photophysical signalling behaviour in these hybrid materials was evaluated with their X-ray diffraction pattern, FTIR spectral analysis, thermogravimetric analysis, FESEM images and elemental analysis, surface area determination and particle size analysis for establishing a structure-function correlation in their selective Fe³⁺ ion detection in aqueous suspension.