Urea/thiourea based dipodal nanoreceptors: Aqueous medium fluorescent chemosensor for Zn(II) and Hg(II) ions by photoinduced electron transfer.

Organic nanoparticles of 4 ligands i.e. ONPs of JM-1 , JM-2 , JM-3 and JM-4 are prepared. Among them, ONPs of JM-1 and JM-4 have shown chemosensing towards Zn(II) and Hg(II) respectively. [Display omitted] • Four dipodal ligands JM-1 , JM-2 , JM-3 and JM-4 are synthesized and their ONPs are prepared. • ONPs of JM-1 have shown chemosensing towards Zn(II) ions by PET-off mechanism with LOD of 55.7 nM. • ONPs of JM-4 have shown chemosensing towards Hg(II) ions by PET-off mechanism with LOD of 1.35 µM. Zinc (II) plays a pivotal role in sustaining life processes, whereas Mercury (II) stands out as a significant environmental contaminant. It is imperative to accurately identify these elements to gauge potential imbalances, whether in deficiency or excess, within biological and ecological systems. In this manuscript, four dipodal ligands JM-1 i.e. 1,1′-(2,2′-disulfanediylbis(ethane-2,1-diyl))bis(3-(4-nitrophenyl)urea), JM-2 i.e. 1,1′-(2,2′-disulfanediylbis (ethane-2,1-diyl))bis(3-(4-nitrophenyl)thiourea), JM-3 i.e. 1,1′-(2,2′-disulfanediylbis(ethane-2,1-diyl))bis(3-(naphthalen-1-yl)urea) and JM-4 i.e. 1,1′-(2,2′-disulfanediylbis(ethane-2,1-diyl))bis(3-(naphthalen-1-yl)thiourea) are synthesized and characterized by various spectroscopic methods. In order to minimize the organic solvent, organic nanoparticles (ONPs) (0.01 mM) of these ligands (2 mM) have been fabricated by reprecipitation method. ONPs of JM-1 has shown chemosensing towards Zn(II) with limit of detection upto nanomolar level i.e. 55.7 nM and ONPs of JM-4 had shown chemosensing towards Hg(II) with limit of detection as 1.35 µM while ONPs of JM-3 and JM-2 did not show any kind of chemosensing behavior towards any cation or anion. Both of ONPs of JM-1 and ONPs of JM-4 showed recognition behavior via photoinduced electron transfer (PET)-off phenomenon. ONPs of JM-1 showed 18 fold enhancement in its fluorescence emission intensity when bound to Zn(II) with excellent linearity which was quite stable with respect to time. [ABSTRACT FROM AUTHOR]