Prof. Mostafa El-Sayed, Georgia Tech

Metallic gold is more precious on the nanoscale: Radiative and photo thermal proper ties and some applications of gold nanoparticles in photonics, nanomotors, nanobiology and cancer therapy

Bulk gold is precious because it does nothing but to keep its luster thus been used in decorating ancient artifacts for thousands of years. On the nanoscale, the absorption of resonant light induces in gold nanoparticles the localized surface plasmon oscillations that produce strong surface fields. This gives them new exciting properties1-3 such as being strong light absorbers and scaterers and thus very useful in sensing and in medical diagnostics4,. When assembled, the scaling law5 is used as a ruler to determine inter-site separations in biological systems. The strongly absorbed light energy by the gold nanoparticles is rapidly converted into heat leading to: 1) their melting or ablation causing their propulsion thus making them useful as nanomotors6 ; 2) the coherent oscillation7 of their lattice could be used in light modulation in laser communication, and 3) heating its surroundings could be used to destroy selectively attached cancer or other unhealthy cells in cancer and medical photo-thermal therapy8. Successful animal model experiments of photo-thermal therapy of cancer tumors has been demonstrated.9

REFERENCES
1. Mostafa A. El-Sayed "Some Interesting Properties of Metals Confined in Time and Nanometer Space of Different Shapes", Acc. Chem. Research, 34, (4), 257-264 (2001). Invited
2. Stephan Link, Mostafa A. El-Sayed, "Optical Properties and Ultrafast Dynamics of Metallic Nanocrystals", Annual Review Phys. Chem., 54:331-66, (2003) Invited.
3. Burda, C.; Chen, X.; Narayanan, R.; El-Sayed, M. A. "The Chemistry and Properties of Nanocrystals of Different Shapes", Chem. Rev., 2005, 105(4), 1025-1102. (Invited Review Article)
4. El-Sayed, Ivan; Huang, Xiaohua; El-Sayed, Mostafa A., "Surface Plasmon Resonance Scattering and Absorption of anti-EGFR Antibody Conjugated Gold Nanoparticles in Cancer Diagnostics; Applications in Oral Cancer," Nano Letters 4(5), 829-834, (2005).( ISI hot paper)
5. Prashant K. Jain, Wenyu Huang, and Mostafa A. El-Sayed "On the universal scaling behavior of the distance decay of plasmon coupling in metal nanoparticle pairs, Biological Ruler Equation, Nano Letters, 7(7), 2080-2088, (2007).
6. Huang, W.Y.; Qian, W.; El-Sayed, M.A. Gold Nanoparticles Propulsion from Surface Fueled by Absorption of Femtosecond Laser Pulse at Their Surface Plasmon Resonanceî J. Am. Chem. Soc. :Communication, 128,13330,(2006)
7. X. Huang; Wei Qian; Mostafa A. El-Sayed, "Coherent Vibrational Oscillation in Gold Prismatic Monolayer Periodic Nanoparticle Arrays", Nano Lett, 4, (9), 1741-1747, (2004).
8. Xiaohua Huang; Ivan H. El-Sayed; Wei Qian and Mostafa A. El-Sayed, "Cancer Cell Imaging and Photothermal Therapy in Near-Infrared Region by Using Gold Nanorods," Journal of American Chem. Soc., 128, 2115-2120, (2006) [most cited paper in the field of chemistry, Sept-Oct 2007, most cited paper in JACS in 2007]
9. Erin B. Dickerson , Erik C. Dreaden , Xiaohua Huang , Ivan H. El-Sayed, Hunghao Chu, Sujatha Pushpanketh, John F. McDonald, Mostafa A. El-Sayed," Goldnanorod assisted near-infrared plasmonic photo thermal therapy (PPTT) of Squamous cell carcinoma in mice", Cancer Letters, ASAP