Chiroselective electron transfer at enantiomer-capped ZnO nanocrystalline surfaces

Chiral recognition of amino acid, D- and L-tryptophan, is achieved using (R )-(-)- or (S)-(+)-1,1'-binaphthyl-2,2'-diylhydrogen phosphate (BHP)-capped quantized ZnO nanocrystallites as a fluorescent sensor. The chiroselective electron transfer is caused by the formation of the BHP capping layer on th e surface of ZnO nanocrystallites. The ability for chiral recognition depen ds on the surface coverage and binding strength of the capping molecules on the nanocrystalline surface. Structural analysis of the capping molecules on the surface using circular dichroic spectra proved that screwness of the chiral molecules depends on the surface coverage. The ability of the BHP-c apped ZnO system was improved when a well-packed surface capping layer of o ne enantiomeric form of chiral molecules was formed on the surface of ZnO n anocrystallites. (C) 1999 Elsevier Science S.A. All rights reserved.