TY - JOUR
T1 - Nonequilibrium thermodynamics of colloidal gold nanocrystals monitored by ultrafast electron diffraction and optical scattering microscopy
AU - Guzelturk, Burak
AU - Lindenberg, Aaron M.
AU - Utterback, James K.
AU - Coropceanu, Igor
AU - Kamysbayev, Vladislav
AU - Janke, Eric M.
AU - Zajac, Marc
AU - Yazdani, Nuri
AU - Cotts, Benjamin L.
AU - Park, Suji
AU - Sood, Aditya
AU - Lin, Ming Fu
AU - Reid, Alexander H.
AU - Kozina, Michael E.
AU - Shen, Xiaozhe
AU - Weathersby, Stephen P.
AU - Wood, Vanessa
AU - Salleo, Alberto
AU - Wang, Xijie
AU - Talapin, Dmitri V.
AU - Ginsberg, Naomi S.
N1 - Publisher Copyright:
© 2020 American Chemical Society
PY - 2020/4/28
Y1 - 2020/4/28
N2 - Metal nanocrystals exhibit important optoelectronic and photocatalytic functionalities in response to light. These dynamic energy conversion processes have been commonly studied by transient optical probes to date, but an understanding of the atomistic response following photoexcitation has remained elusive. Here, we use femtosecond resolution electron diffraction to investigate transient lattice responses in optically excited colloidal gold nanocrystals, revealing the effects of nanocrystal size and surface ligands on the electron−phonon coupling and thermal relaxation dynamics. First, we uncover a strong size effect on the electron−phonon coupling, which arises from reduced dielectric screening at the nanocrystal surfaces and prevails independent of the optical excitation mechanism (i.e., inter- and intraband). Second, we find that surface ligands act as a tuning parameter for hot carrier cooling. Particularly, gold nanocrystals with thiol-based ligands show significantly slower carrier cooling as compared to amine-based ligands under intraband optical excitation due to electronic coupling at the nanocrystal/ ligand interfaces. Finally, we spatiotemporally resolve thermal transport and heat dissipation in photoexcited nanocrystal films by combining electron diffraction with stroboscopic elastic scattering microscopy. Taken together, we resolve the distinct thermal relaxation time scales ranging from 1 ps to 100 ns associated with the multiple interfaces through which heat flows at the nanoscale. Our findings provide insights into optimization of gold nanocrystals and their thin films for photocatalysis and thermoelectric applications.
AB - Metal nanocrystals exhibit important optoelectronic and photocatalytic functionalities in response to light. These dynamic energy conversion processes have been commonly studied by transient optical probes to date, but an understanding of the atomistic response following photoexcitation has remained elusive. Here, we use femtosecond resolution electron diffraction to investigate transient lattice responses in optically excited colloidal gold nanocrystals, revealing the effects of nanocrystal size and surface ligands on the electron−phonon coupling and thermal relaxation dynamics. First, we uncover a strong size effect on the electron−phonon coupling, which arises from reduced dielectric screening at the nanocrystal surfaces and prevails independent of the optical excitation mechanism (i.e., inter- and intraband). Second, we find that surface ligands act as a tuning parameter for hot carrier cooling. Particularly, gold nanocrystals with thiol-based ligands show significantly slower carrier cooling as compared to amine-based ligands under intraband optical excitation due to electronic coupling at the nanocrystal/ ligand interfaces. Finally, we spatiotemporally resolve thermal transport and heat dissipation in photoexcited nanocrystal films by combining electron diffraction with stroboscopic elastic scattering microscopy. Taken together, we resolve the distinct thermal relaxation time scales ranging from 1 ps to 100 ns associated with the multiple interfaces through which heat flows at the nanoscale. Our findings provide insights into optimization of gold nanocrystals and their thin films for photocatalysis and thermoelectric applications.
KW - Colloidal nanocrystals
KW - Electron−phonon coupling
KW - Hot carriers
KW - Ligands
KW - Thermal transport
KW - Time-resolved microscopy
KW - Ultrafast electron diffraction
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U2 - 10.1021/acsnano.0c00673
DO - 10.1021/acsnano.0c00673
M3 - Article
C2 - 32208676
AN - SCOPUS:85084168080
SN - 1936-0851
VL - 14
SP - 4792
EP - 4804
JO - ACS Nano
JF - ACS Nano
IS - 4
ER -