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Gold nanoshell photomodification under a single-nanosecond laser pulse accompanied by color-shifting and bubble formation phenomena

Akchurin, Garif and Khlebtsov, Boris and Akchurin, Georgy and Tuchin, Valery and Zharov, Vladimir and Khlebtsov, Nikolai (2008) Gold nanoshell photomodification under a single-nanosecond laser pulse accompanied by color-shifting and bubble formation phenomena. NANOTECHNOLOGY, 19 (1).

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Laser-nanoparticle interaction is crucial for biomedical applications of lasers and nanotechnology to the treatment of cancer or pathogenic microorganisms. We report on the first observation of laser-induced coloring of gold nanoshell solution after a one nanosecond pulse and an unprecedentedly low bubble formation (as the main mechanism of cancer cell killing) threshold at a laser fluence of about 4 mJ cm(-2), which is safe for normal tissue. Specifically, silica/gold nanoshell (140/15 nm) suspensions were irradiated with a single 4 ns (1064 nm) or 8 ns (900 nm) laser pulse at fluences ranging from 0.1 mJ cm(-2) to 50 J cm(-2). Solution red coloring was observed by the naked eye confirmed by blue-shifting of the absorption spectrum maximum from the initial 900 nm for nanoshells to 530 nm for conventional colloidal gold nanospheres. TEM images revealed significant photomodification of nanoparticles including complete fragmentation of gold shells, changes in silica core structure, formation of small 20-30 nm isolated spherical gold nanoparticles, gold nanoshells with central holes, and large and small spherical gold particles attached to a silica core. The time-resolved monitoring of bubble formation phenomena with the photothermal (PT) thermolens technique demonstrated that after application of a single 8 ns pulse at fluences 5-10 mJ cm(-2) and higher the next pulse did not produce any PT response, indicating a dramatic decrease in absorption because of gold shell modification. We also observed a dependence of the bubble expansion time on the laser energy with unusually very fast PT signal rising (similar to 3.5 ns scale at 0.2 J cm(-2)). Application of the observed phenomena to medical applications is discussed, including a simple visual color test for laser-nanoparticle interaction.

Item Type:Article
Subjects:Biomedical Science > Nanobiotechnology
Analytical Science > Beam methods
ID Code:3540
Deposited By:Farnush Anwar
Deposited On:16 Jan 2009 13:10
Last Modified:16 Jan 2009 13:10

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