Black carbon particles in the different brain regions were detected via a specific and label-free technique based on the nonincandescence-related white light generation of the particles under femtosecond-pulsed illumination, as previously described by our research group.10 (link),12 (link),13 (link) Images were taken with a confocal microscope (Carl Zeiss) equipped with a 2-photon femtosecond-pulsed laser (810 nm, 150 fs, 80 MHz) (Spectra-Physics) using a Plan-Neofluar 10x/0.3 objective (Carl Zeiss). Two-photon–induced white light emission of carbon particles was acquired in the nondescanned mode after spectral separation and emission filtering using 400-410 nm and 450-650 nm band-pass filters. The resulting tile scans of 13.35 μm × 13.35 μm were recorded with a 1.66 μm pixel size and 4.10 μs pixel dwell time.
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