A precise control over individual nanoparticles has huge potential for nano-architectural purposes and for probing nano-scale interactions.

However, the absorption and heating associated with resonant irradiation of an individual gold nanoparticle can be extreme. Moreover, the heating of a nanoparticle cannot be theoretically predicted as the precise focal intensity distribution on the nanoscale is unknown and typically highly aberrated [1]. Utilizing a novel assay based on partitioning of lipophilic dyes between membrane phases we quantify the heating of an individual irradiated gold nanoparticle [2,3]. The heating of the particle is dependent on laser power, and for a nanorod, also on its orientation with respect to the laser polarization [4]. A dramatic and irreversible change in plasmonic behavior of a nanorod occurs at high illumination intensities as the nanorod restructures into a more spherical shape. Nanoparticles can be used inside living cells for precise force measurements [5], and the photo-thermal effect of metallic nanoparticles can be used to create localized heat gradients inside living cells thus investigating cellular responses to heat chocks.

[1] A. Kyrsting, P.M. Bendix, L.B. Oddershede, Mapping 3D focal intensity exposes the stable trapping positions of single nanoparticles, Nano Letters vol.13 p.31-35 (2013).

[2] A. Kyrsting, P.M. Bendix, D.G. Stamou, and L.B. Oddershede. Heat Profiling of Three-Dimensionally Optically Trapped Gold Nanoparticles using Vesicle Cargo Release. Nano Letters, vol 11 p.888-892 (2011).

[3] P.M. Bendix, S.N.S. Reihani and L.B. Oddershede. Direct measurements of heating by electromagnetically trapped gold nanoparticles on supported lipid bilayers. ACS Nano, vol. 4 p.2256-2262 (2010)

[4] H. Ma, P.M. Bendix, L.B. Oddershede. Large-Scale Orientation Dependent Heating from a Single Irradiated Gold Nanorod. Nano Letters vol.12 p.3954-3960 (2012)

[5] L.B. Oddershede. Force probing of individual molecules inside the living cell is now a reality. Nature Chemical Biology vol.8 p.879-886 (2012).

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