Real-time monitoring and scale-up synthesis of concentrated gold nanorods.

The control and monitoring of gold nanorod growth are critical for maintaining the quality of gold nanorods. Through in situ spectroscopic determination of gold nanorod growth in cuvettes, we found that this growth correlates with the evolution of extinction spectra and solution colors. This spectroscopy provides a universal method for in situ observation of the chemical evolution of nano-materials using cuvettes as small reactors at ambient temperature. Synthesis of gold nanorods with high concentrations and high yields is scaled up by simply increasing the solute concentration of the growth solution. Under optimal synthetic conditions, a yield of up to 0.1 g of gold nanorods is obtained, and spectrum monitoring indicates the formation of few spherical gold nanoparticles.