Photo-responsive Azobenzene-dendron Monolayers

Abstract

We prepared azobenzene dendron monolayers on the Au or quartz substrates by DCC(N,N-dicyclohexylcarbodiimide)-catalyzed surface amidation reactions between the carboxyl acid groups at the focal point of the dendrons and the amine groups on the surface of Au or quartz.infrared reflection-absorption spectroscopy(IRRAS),UV-Vis absorption and Raman spectroscopies were performed to characterize these azobenzene dendron monolayers.The thickness of the G-4 monolayers with different isomeric forms was measured using ellipsometry spectra,and a value of(2.38±0.09) nm was obtained for the trans-form,and(1.88±0.08) nm for the cis-form.The interaction between the G-4 monolayers in different isomeric forms and proteins with different isoelectric points(pI) was studied by surface plasma resonance(SPR),which demonstrated that the G-4 monolayers had a negatively charged surface that preferentially adsorbed positive proteins.The surface potential of the dendron monolayers became more negative when the monolayers was changed from the trans-form to cis-form,resulting in adsorbing more positively charged proteins.