Effect of substituents on the UV spectra of supermolecular system: Silver nanoparticles with bi-aryl Schiff bases containing hydroxyl

摘要

Effect of substituents on the ultraviolet (UV) spectra of supermolecular system involving silver nanoparticles (AgNPs) and Schiff bases was investigated. AgNPs and 49 samples of model compounds (MC), bi-aryl Schiff bases containing hydroxyl (XBAY, involving 4-OHArCH(sic)NArY, 2-OHArCH(sic)NArY, XArCH(sic)NAr-4 '-OH, and XArCH(sic)NAr-2 '-OH), were synthesized. The size of AgNPs was characterized by transmission electron microscopy (TEM), and the UV absorption spectra of AgNPs, XBAYs, and MC-AgNPs mixed solutions were measured, respectively. The results show that (1) the size of AgNPs is larger in MC-AgNPs solutions than that in AgNPs solution due to the distribution of MC molecules on the surface of AgNPs; (2) the UV absorption wavelength of XBAYs changes in the action of AgNPs and their wavelength shift exists limitation between XBAY and MC-AgNPs solutions; and (3) the wavelength shift limit of MC-AgNPs (lambda(WSL)) is influenced by the substituents X and Y and the position of hydroxyl OH. The wavenumber Delta nu(WSL) of lambda(WSL) can be quantified by employing the excited-state substituent constant sigma CCex and Hammett constant sigma of substituents X and Y. Comparing with the 4-OH, the 4 '-OH makes the Delta nu(WSL) a red shift, whereas the 2 '-OH, comparing with the 2-OH, makes the Delta nu(WSL) a blue shift.