Synthesis of single-crystalline gold nanoplates in aqueous solutions through biomineralization by serum albumin protein

In this work, single-crystalline gold nanoplates were produced by reacting an aqueous solution of chloroauric acid with one serum albumin protein (BSA) at the physiological temperature, where BSA provided the dual function of Au(III) reduction and directing the anisotropic growth of Au(0) into plate-like structures. Structural characterizations by FESEM, TEM, HRTEM, and SAED showed that the nanoplates were oriented with {111} planes as their basal planes. The effects of environmental factors such as temperature and pH were investigated, which showed low temperature and acidic pH favoring the anisotropic growth of gold nanoparticles. More interestingly, the kinetics of chloroauric acid reduction in BSA solutions could be manipulated through the addition of a trace amount of Ag+ ions, and plates with lateral size ranging from a few micrometers to tens of nanometers could be produced. The growth of gold nanoplates in BSA solution with time was monitored by electron microscopy, allowing the detection of several key intermediate structures in the growth process.