Enantioselective Artificial Receptors Formed by the Spreader-Bar Technique

Abstract

Chiroselective binding sites have been created on thin gold films by application of the spreader-bar approach. Impedometric techniques and surface plasmon resonance were applied to detect binding. (R)-(+)-1,1′-Binaphthyl-2,2′-diol (R-BNOH) and (S)-(−)-1,1′-binaphthyl-2,2′-diol (S-BNOH) were used as model analytes. The artificial receptors were prepared by co-adsorption of 16-mercaptohexadecane (matrix) with a thiol-modified chiral selector (template). The conjugates of D,L-thioctic acid and (R)-(+)- or (S)-(−)-1,1′-binaphthyl-2,2′-diamine were used as templates. Different concentration ratios of the matrix and template were tested. No chiral selectivity of surfaces formed by either the matrix or the template alone was observed. The use of alkylthiols shorter than 16-mercaptohexadecane led to the formation of surfaces with no chiral selectivity. The gold electrodes coated by the spreader-bar technique displayed an enantioselectivity of up to 4.76 or up to 2.55 as measured by the capacitive and SPR methods, respectively.