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Diagram of a nanoemulsion bead with a perfluorohexane core and gold nanospheres encapsulated on the oil-water interface, and laser pulse induced bubble formation of the bead. Heat released from the gold nanospheres induces a phase transition in the core, generating stronger photoacoustic signals compared to those by typical laser-sound conversion mechanism (i.e., thermal expansion).
Photoacoustic images of samples in the tube at different laser fluences: ink solution (a)-(c) and dispersion of nanoemulsion beads with gold nanospheres (d)-(f). Note that images are shown with different dynamic ranges and different levels. Ink: −60 dB to −25 dB. Nanoemulsion beads: −45 dB to 0 dB.
Photoacoustic image amplitude of ink (blue circle) and NEB-GNSs (red triangle) versus laser fluence.
Differential photoacoustic images of ink (a) and NEB-GNSs (b) at a laser fluence of 10 mJ/cm2. The reference image is at 5 mJ/cm2. Images are normalized to the maximum of the original images in Fig. 2 (0 dB) and shown with a dynamic range of 25 dB. Note that images are shown at different levels: −70 dB to −45 dB for ink and −40 dB to −15 dB for NEB-GNSs. The contrast between the two differential images is larger than 40 dB.
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