Gold Nanorods
During the last 20 years, spherical gold nanoparticles have been used to research photothermal cancer therapies. However, they were not optimized because spherical gold nanoparticles have limited peak absorptions (maximum ~580nm for 100nm diameter particles) which fall below the transmission window of 650 – 900nm for biological entities (skin, tissue and hemoglobin). Gold nanorods behave similarly to the gold nanoparticles, but are elongated to optimize their peak absorption and scattering characteristics (Figure 1). - See more at: http://www.sigmaaldrich.com/materials-science/nanomaterials/gold-nanostructures.html#sthash.K5xjsmQ6.dpuf