NH2-MIL-125(Ti) and its emeraldine functionalized derivative as a chemical sensor for effective detection of dopamine

Abstract

Abstract This work proposed and demonstrated Emeraldine (a Polyaniline) linking with NH 2 functionalized MIL-125 (Ti) Metal Organic Framework (MOF) to be used as a chemical sensor for detection of Dopamine (DA). The covalent coupling of Emeraldine (E) with NH 2 -MIL-125(Ti) showed marked improvements in electron conductivity as reflected in various intrinsic parameters such as fluorescence intensities, quantum yield and dielectric functions. The fluorescence intensities changed in the following progression: NH 2 -MIL-125(Ti)>1 mM PA-MIL 125(Ti) > 10 mM PA-MIL 125(Ti)>MIL-125(Ti)>E. The quantum yield in water decreased in the following progression: NH 2 -MIL-125(Ti) (84%)>1 mM PA-MIL 125(Ti) (3.17%)> 10 mM PA-MIL 125(Ti) (0.348%). The oscillatory behaviour in dielectric functions, indicating electron delocalization was observed in the following progression: E > 10 mM PA-MIL 125(Ti)> 1 mM PA-MIL 125(Ti) > NH 2 -MIL-125(Ti). DA detection studies were successfully carried out in neutral buffer medium with excellent sensitivity. The corresponding LOD was estimated to be 10 nM and 5 nM in case of NH 2 -MIL-125 and PA-MIL 125 (Ti) respectively. Selectivity studies showed the influence of interferences were in the following progression: in case of NH 2 -MIL-125(Ti); Phenylalanine (13.72%) = Tryptophan (13.72%)>Aspartic acid (10.46%)>Glutamic acid (8.83%)>Urea (8.83%)> Glucose (8.02%) whereas with Emeraldine linking the values were; Urea (50.62%)> Glucose (44.44%)>Glutamic acid (45.62%)>Phenylalanine (45.54%)> Aspartic acid (43.95)>Tryptophan (35.40%). O 2 oxidizes (in the presence of NH 2 -MIL-125 and its Emeraldine linked pair), DA to dopamine-o-quinone (with an absorbance at 420 nm), forming a FRET pair. The present study showed Emeraldine linking to NH 2 -MIL-125(Ti), yielded lower LOD value (5 nM at Signal-to-Noise (S/N) = 3.0).