The optoelectronic and physicochemical properties of nanoscale matter are a strong function of particle size. Nanoparticle shape also contributes significantly to modulating their electronic properties. Several shapes ranging from rods to wires to plates to teardrop structures may be obtained by chemical methods; triangular nanoparticles have been synthesized by using a seeded growth process. Here, we report the discovery that the extract from the lemongrass plant, when reacted with aqueous chloroaurate ions, yields a high percentage of thin, flat, single-crystalline gold nanotriangles. The nanotriangles seem to grow by a process involving rapid reduction, assembly and room-temperature sintering of 'liquid-like' spherical gold nanoparticles. The anisotropy in nanoparticle shape results in large near-infrared absorption by the particles, and highly anisotropic electron transport in films of the nanotriangles.
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We acknowledge the TEM (Renu Pasricha) and ITC (K.N. Ganesh) facilities at the National Chemical Laboratory, Pune; S.P. Joshi for separation of the various lemongrass fractions and Vivek Ganvir, Tata Research and Development and Design Centre, Pune, for assistance with light-scattering measurements.
The authors declare no competing financial interests.
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Shankar, S., Rai, A., Ankamwar, B. et al. Biological synthesis of triangular gold nanoprisms. Nature Mater 3, 482–488 (2004). https://doi.org/10.1038/nmat1152
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