Fig. 2.

a, Single-photon absorbance spectra of nanorods with four aspect ratios measured at a concentration of 4 × 10¹¹ nanoparticles/ml. b, MPL intensity dependence on the excitation laser power (132 µW-4.8 mW) of nanorods at excitation wavelengths of 760, 840 and 1040 nm. c, Quadratic dependence of luminescence intensity of nanorods on excitation laser power at lower power levels (i.e., <1.6 mW) in b. Slopes of 1.7-2.2 (for each aspect ratio of nanorod at different excitation wavelength) confirm the TPL process.