TY - JOUR
T1 - Nonlinear effects in single-particle photothermal imaging
AU - West, Claire A.
AU - Lee, Stephen A.
AU - Shooter, Jesse
AU - Searles, Emily K.
AU - Goldwyn, Harrison J.
AU - Willets, Katherine A.
AU - Link, Stephan
AU - Masiello, David J.
N1 - Publisher Copyright:
© 2023 Author(s).
PY - 2023/1/14
Y1 - 2023/1/14
N2 - Although photothermal imaging was originally designed to detect individual molecules that do not emit or small nanoparticles that do not scatter, the technique is now being applied to image and spectroscopically characterize larger and more sophisticated nanoparticle structures that scatter light strongly. Extending photothermal measurements into this regime, however, requires revisiting fundamental assumptions made in the interpretation of the signal. Herein, we present a theoretical analysis of the wavelength-resolved photothermal image and its extension to the large particle scattering regime, where we find the photothermal signal to inherit a nonlinear dependence upon pump intensity, together with a contraction of the full-width-at-half-maximum of its point spread function. We further analyze theoretically the extent to which photothermal spectra can be interpreted as an absorption spectrum measure, with deviations between the two becoming more prominent with increasing pump intensities. Companion experiments on individual 10, 20, and 100 nm radius gold nanoparticles evidence the predicted nonlinear pump power dependence and image contraction, verifying the theory and demonstrating new aspects of photothermal imaging relevant to a broader class of targets.
AB - Although photothermal imaging was originally designed to detect individual molecules that do not emit or small nanoparticles that do not scatter, the technique is now being applied to image and spectroscopically characterize larger and more sophisticated nanoparticle structures that scatter light strongly. Extending photothermal measurements into this regime, however, requires revisiting fundamental assumptions made in the interpretation of the signal. Herein, we present a theoretical analysis of the wavelength-resolved photothermal image and its extension to the large particle scattering regime, where we find the photothermal signal to inherit a nonlinear dependence upon pump intensity, together with a contraction of the full-width-at-half-maximum of its point spread function. We further analyze theoretically the extent to which photothermal spectra can be interpreted as an absorption spectrum measure, with deviations between the two becoming more prominent with increasing pump intensities. Companion experiments on individual 10, 20, and 100 nm radius gold nanoparticles evidence the predicted nonlinear pump power dependence and image contraction, verifying the theory and demonstrating new aspects of photothermal imaging relevant to a broader class of targets.
UR - http://www.scopus.com/inward/record.url?scp=85146304115&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85146304115&partnerID=8YFLogxK
U2 - 10.1063/5.0132167
DO - 10.1063/5.0132167
M3 - Article
C2 - 36641380
AN - SCOPUS:85146304115
SN - 0021-9606
VL - 158
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
IS - 2
M1 - 024202
ER -