Journal
JOURNAL OF PHYSICAL CHEMISTRY C
Volume 123, Issue 46, Pages 28401-28410Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpcc.9b10043
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Funding
- Institute of Nano Science and Technology
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Nonstoichiometric Cu2-xS nanocrystals (NCs) have been synthesized by hot injection method after changing the copper to sulfur ratio. Optical studies confirmed well-defined localized surface plasmon resonance (LSPR) absorbance band from near-infrared to mid-infrared arising due to p-type hole vacancy in the doped semiconductor. Carrier concentrations of the Cu2-xS NCs are calculated to be on the order of similar to 10(21) cm(-3) after following the Drude model, which is one order of magnitude lower as compared to the metallic (Au/Ag) system. To understand ultrafast plasmon dynamics of Cu2-xS NCs, femtosecond broadband (visible-near IR) pump-probe spectroscopy has been employed. Ultrafast plasmon dynamics of the Cu2-xS NCs have been monitored after changing composition (copper to sulfur ratio), pump wavelength, and laser intensity. At moderate pump power hole-phonon relaxation time constant has been observed to be in the range of 240-440 fs for Cu2-xS NCs depending upon pump wavelengths (400, 800 nm). From the ultrafast transient data, hole-phonon coupling constant (G) has been determined in the range (1.6-2.7) x 10(10) J K-1 s(-1) cm(-3) for Cu2-xS NCs at different excitation wavelengths, which is also one order lower as compared to the metallic system. We have proposed a new mechanistic scheme for hot carrier relaxation dynamics, in accordance with the two-temperature model (TTL) as reported in literature for plasmon dynamics.
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