Synthesis Of Photoresponsive Azobenzene Chromophore/Graphene Composites

Since the discovery in2004, graphene has already revealed for a great number ofpotential applications such as solar cells, field effect transistors and capacitors due toits high specifc surface area, superior mechanical strength, the excellent thermal andelectrical conductivity. Azobenzene (AZO) chromophores can undergo a reversibletrans-cis photoisomerization upon UV-vis irradiation, and this unique photoresponsehas been utilized in photo-switches, nonlinear optics, optical storage media. In thisthesis, through diazo-coupling reactions, we synthesized four different AZOmolecules with intra-or inter-molecular hydrogen bonds including2-hydroxy-4-amino-azobenzene (AZO-1),2,2’-dihydroxy-4-amino-azobenzene(AZO-2),4-amino-4’-sulfo-azobenzene (AZO-3) and2-hydroxy-2’-sulfo-4-amino-azobenzene (AZO-4). These AZO derivatives were functionalized with grapheneoxide (GO) or reduced graphene oxide (RGO) through the covalent bond to obtainAZO/graphene composites.1. AZO-1and AZO-2had intramolecular hydrogen bonds and hydrazoneisomers. AZO-4had intramolecular hydrogen bonds, but it can’t form hydrazoneisomers.2. AZO-1and AZO-2were covalently attached on GO through an amide linkageto prepare GO-AZO-1, GO-AZO-2hybrid materials. The azobenzene moieties on GOhad a reversible trans-cis photoisomerization. Theoretical calculation of chemicalenergy storage of AZO-2and GO-AZO-2suggested that the standard free energy ofper azobenzene molecule on GO achieved1.46eV, which was higher than AZO-2by32.7%.3. RGO-AZO-3and RGO-AZO-4nano-composite materials were prepared usingMeerwein reaction. The results showed the grafted ratios of RGO-AZO wereimproved compared with that by the amidation. Azobenzene moieties (AZO-3andAZO-4) on RGO without hydrazone isomers showed a higher isomerization degreethan that of AZO-1and AZO-2on GO. Theoretical calculation showed the standardfree energy of per AZO-3on RGO was1.42eV.