Combined Liposome-Gold Nanoparticles from Honey: The Catalytic Effect of Cassyopea ® Gold on the Thermal Isomerization of a Resonance-Activated Azobenzene.

Gold nanoparticles (AuNPs) have been synthesized directly inside liposomes using honey as a reducing agent. The obtained aggregates, named Cassyopea ® Gold due to the method used for their preparation, show remarkable properties as reactors and carriers of the investigated AuNPs. A mean size of about 150 nm and negative surface charge of -46 mV were measured for Cassyopea ® Gold through dynamic light scattering and zeta potential measurements, respectively. The formation of the investigated gold nanoparticles into Cassyopea ® liposomes was spectroscopically confirmed by the presence of their typical absorption band at 516 nm. The catalytic activity of the combined liposome-AuNP nanocomposites was tested via the thermal cis-trans isomerization of resonance-activated 4-methoxyazobenzene (MeO-AB). The kinetic rate constants ( k obs ) determined at 25 °C in the AuNP aqueous solution and in the Cassyopea ® Gold samples were one thousand times higher than the values obtained when performing MeO-AB cis-trans conversion in the presence of pure Cassyopea ® . The results reported herein are unprecedented and point to the high versatility of Cassyopea ® as a reactor and carrier of metal nanoparticles in chemical, biological, and technological applications.