Shamrock 303i spectrometer

Two-photon excited
emission spectra were acquired on a home-built experimental setup,
consisting of a Shamrock 303i spectrometer (Andor) equipped with a
sensitive iDus camera (Andor) and a femtosecond laser system (Ti/sapphire
Chameleon laser, Coherent Inc.) with the repetition rate of 80 MHz
and the pulse duration of ∼120 fs, operating in the range 700–1000
nm. The laser beam power was monitored using a PM100D handheld optical
power and energy meter (Thorlabs). To minimize undesired effects due
to re-absorption and inner filter effects, the fluorescence was measured
for samples at concentrations corresponding to absorbance values below
0.1 in the excitation and emission regions. Resistance to photobleaching
was evaluated by monitoring OPE fluorescence spectra at each OPE wavelength.
All spectroscopic characterizations were performed using 10 ×
10 × 45 mm quartz cuvettes.

TPEF
spectra were recorded on a Shamrock 303i spectrometer (Andor) equipped
with a sensitive iDus camera (Andor). A femtosecond mode-locked Ti:sapphire
chameleon laser (Coherent Inc.) with a repetition rate of 80 MHz and
the pulse duration of 100 fs was used as the multiphoton excitation
source, operating from 690 to 1000 nm. The laser beam power was monitored
with a PM100D Handheld Optical Power and Energy Meter (Thorlabs).
The excitation laser beam was isolated from its reflections with a
high-performance long-pass filter (FELH650, cut-on wavelength 650
nm, Thorlabs). The emitted signals were separated from the excitation
light with a short-pass filter (FESH650, cut-off wavelength 650 nm,
Thorlabs). To minimize inner filter and re-absorption effects, the
fluorescence was measured for diluted samples, whose concentrations
corresponded to absorbance values below 0.1 in the whole absorption
and emission spectra ranges.
All linear and non-linear optical
studies were performed for FA CNDs in aqueous dispersions (with Milli-Q
water as the solvent).