Protein Directed Synthesis Of Gold Nanoparticles And Their Applications

Gold nanoparticles show special optical properties due to the small size effect.Spherical gold nanocrytals show specific surface plasmon resonance absorption (SPR)in the UV-VIS spectrum at the wavelength of about520nm. However, when thediameter is small than2nm, the SPR effect disappeared. These kind of nanoparticlesare called nanoclusters, having discrete energy levels which is similar to the propertiesof molecule. In our work, lysozyme, trypsin and BSA have been utilized as reducingagent and template to direct the synthesis of gold nanoclusters (GNCs), goldnanocomposite and gold nanoparticles (GNPs) with SPR effect. We also studied thegrowth mechanism of GNCs and gold nanocomposite. The nanocomposite wasfurther applied to detect and eliminate heavy metal ions of Pb2+, while GNPs loadedin mesoporous silica was used to catalyze p-nitrophenol.(1) Synthesis of two GNCs with red and blue emission using lysozyme asreducing and stabilizing agent. When the pH of the solution is13, Au25with redemission was acquired while Au8with blue emission was acquired when the pH is3.After a further study of the growth mechanism of gold nanoclusters, we found that thespatial structure of protein is the major factor affecting the size of GNCs: themolecular structure of the lysozyme (vi) is tight under acid conditions, leading to theformation of small GNCs Au8. However, the molecular structure of lysozyme (vi)become loose when the pH is13, leading to the formation of large GNCs Au25.(2) Trypsin directed synthesis of GNP-GNCs nanocomposite. Size exclusionchromatography and transmission electron microscopy reveals that the as-preparedgold nanocomposite (GNP-Trys-GNCs) is composed of GNP with an averagediameter of5.5nm and the GNCs (ca.1nm) embedded trypsins (Trys-GNCs), whichare attached to the surface of GNP. We also studied the interaction behavior of goldnanocomposite with different concentration of lead ions. The unique structure andoptical property of GNP-Trys-GNCs nanocomposite enable it to be used in heavymetal ions sensing and elimination.(3) BSA doped mesoporous silica was used for the synthesis of GNPs. BSAdoped mesoporous silica (MCM-BSA) was synthesized firstly and UV-VIS, FTIR,TEM and BET was utilized to characterize it. Without introducing extra chemical or physical field, GNPs can be synthesized in situ, resulting in the formation of goldnanoparticles loaded in mesoporous silica (GNPs@MCM-BSA). The catalysis abilityof GNPs@MCM-BSA was further studied, and we found that this material can bereused many time for the reduction of nitrophenol.