A novel high performance nano chemosensor for copper (II) ion based on an ultrasound-assisted synthesized diphenylamine-based Schiff base: Design, fabrication and density functional theory calculations

A novel high selective colorimetric chemosensor was introduced based on a nano diphenyl-based Schiff base (H2L), 2,2'-((1E,1'E)-(((hexylazanediyl)bis(4,1-phenylene))bis(methanylylidene))bis(azanylylidene))bis(4-methylphenol) that synthesized using sonochemical method. H2L was characterized by FT-IR, MS, TGA, H-1 NMR, C-13 NMR, SEM and elemental analysis techniques, then fabricated as the portable strips for sensing copper (II) ions in aqueous media. The binding interaction between H2L and various metal ions was investigated by UV-Vis spectroscopic that showed favorable coordination toward Cu2+ ion. H2L exhibited binding-induced color changes from yellow to pink and practically no interference in the presence of other metal ions, i.e., Cr2+, Mn2+, Fe2+, Co2+, Ni2+, Zn2+, Cd2+, Hg2+, Pb2+, Mg2+ and Ca2+. The chemsensor showd the color change from yellow to pink in presence of copper (II) ion in aqueous media due to binging of H2L and Cu (II). This sensor can determine the copper (II) at in the rang of 7.5 x 10(-8)-1.8 x 10(-5) mol L-1 with a correlation equation: Absorbance = 0.0450[Cu2+] x 10(-6) + 0.71 and R-2 = 0.975 and low detection limit of 1.89 x 10(-8) mol L-1. Density functional theory (DFT) calculations were carried out at the B3LYP levels of theory with B3LYP/6-311 + G(d,p) and LANL2DZ/6-311 + G(d,p) basis sets for chemosensor and its copper complex respectively. The optimized geometry, harmonic vibrational frequencies, H-1 NMR and C-13 NMR chemical, Molecular orbital (M.O.), Mulliken population analysis (MPA), contour of Electrostatic Potential (ESP) and Molecular Electrostatic Potential (MEP) map of H2L were calculated which show good agreement with behavior of sensor for detection of Cu2+ ion.