Surface-modified gold nanoparticles: A novel chemical probe for precise fluorescent detection of aluminium (Al3+) ions; investigating DFT insights and molecular logic gate behaviour

Trivalent metal cation fluorescence chemosensors are one of the most important areas of research because of their rarity. The necessity for easy-to-synthesize molecular chemosensors and to immobilize them on materials platform are enhancing continually. In this paper, we report the rapid sensing of Al3+ ion recognition by naphthalene derivative (N1) and tethered with gold nanoparticles (N1-AuNps). The cysteine-carrying naphthalene derivative is synthesized (Receptor-N1) and it forms a self-assembled monolayer on gold nanoparticles through the thiol moiety (N1-AuNPs). The structure of the synthesized receptor and the chemosensor assembled with AuNPs are characterized using spectroscopic and imaging techniques. On the gold nanoparticles, the surface-assembled compound highly selectively binds with Al3+ ion in the aqueous medium compared with a free receptor (N1). We present an improved colorimetric method that offers both high sensitivity and rapid detection for transition metal ions, specifically Al3+ ions. The determination of the binding stoichiometry and binding ratio between N1 / N1-AuNPs and Al3+ ion was achieved through the utilization of Jobs' plot and B -H plot which confirmed a 1:1 ratio. The binding phenomenon between N1-AuNPs and Al3+ ion has been ascertained to be predominantly according to the limited PET with CHEF impact technique. The N1-AuNPs chemosensor responds to H+ and Al3+ ions by demonstrating XOR molecular logic gate functionality and operating across a wide pH range. The nanoparticle-tethered chemosensor presents an effective system that can be employed in Al3+ ion sensing. The addition of Na2EDTA to the [N1-AuNPs - Al3+] complex solution caused a quenching of the fluorescence emission, which provides evidence of the reversible nature of the chemosensor. To gain further insights into the binding mode of Al3+ with N1-AuNPs, quantum mechanical investigations using density functional theory (TDDFT) have been conducted. We evaluated the effectiveness of our methodology for quantifying Al3+ ions in the water waste produced by significant industrial reactions.