Pis’ma v ZhETF, vol. 118, iss. 9, pp. 637 - 638
© 2023 November 10
Size-dependent one- and two-photon fluorescence of acetonitrile-derived
carbon dots
+∗
A. A. Astafiev
+1), A. M. Shakhov
+, V.A.Nadtochenko
+N. N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, 119991 Moscow, Russia
∗Chemistry Department, Moscow State University, 119991 Moscow, Russia
Submitted 7 September 2023
Resubmitted 27 September 2023
Accepted 28
September 2023
DOI: 10.31857/S1234567823210024, EDN: prpaol
Carbon dots (CD)
- carbonaceous luminescent
10 kDa dialysis containers to separate the sample into
nanoparticles - are increasingly employed in bioimag-
three fractions: “small” or CD-1, “medium” or CD-2 and
ing, fluorescent sensing, photocatalysis, and light emit-
“large” or CD-3 (Fig. 1a). Then chemical composition
ting devices [1-3]. Photoluminescence mechanisms of
and optical properties of the fractions were analyzed in
CD are versatile and include contributions from the
comparison with the original sample.
quantum confinement effects, surface groups and de-
Elemental analysis and infrared microscopy revealed
fects, heteroatoms and organic molecular fluorophores
that the three fractions had elemental content and
in their structure [4, 5]. In addition to linear excitation
chemical groups similar to the original CD sample. All
luminescence of CD can be excited by nonlinear absorp-
the fractions exhibited broad and featureless absorp-
tion of ultrashort laser pulses. Nonlinearly excited lumi-
tion spectrum spanning the ultraviolet (UV) and visible
nescence of CD is important for fluorescent imaging and
range and bright visible fluorescence. Their fluorescence
photocatalysis. Previous works demonstrated that char-
was multicomponent and its emission maxima shifted
acteristics and mechanism of nonlinear luminescence of
from deep blue to yellow spectral region with increase
CD can be different from luminescence excited by linear
of the excitation wavelength. The strongest fluorescence
absorption [6].
intensity was emitted under excitation at 340-350 nm
There is a demand for tailoring optical properties
with peak emission intensity at 420-430 nm. The fluo-
of CD for various applications. The nanoparticle size
rescence lifetime was within nanoseconds range.
is the key morphological parameter, affecting optical
Carbon dot size influenced optical properties of
properties of carbon dots and this size can be controlled
CD: larger size led to stronger broadband visible and
with synthetic procedures or size separation techniques.
near-UV absorption, red shift of excitation and emis-
Given diverse absorption and luminescence mechanism
sion spectra, stronger green fluorescence, shorter fluo-
of CD the effect of the size is not straightforward and
rescence lifetimes and exerted effect of opposing direc-
can vary for different types of carbon dots. This ef-
tions on quantum yields of different components of het-
fect can also elucidate the mechanism of CD lumines-
erogeneous photoluminescence emission. Size-dependent
cence [7].
shifts of excitation and emission peaks were too small
Previously we demonstrated that femtosecond
(< 0.12 eV) to support quantum confinement effects
pulsed laser synthesis in liquid medium is a viable
in CD. We explain the influence of the nanoparti-
method for production of CD from simple organic
cle diameter with a number of effects, including size-
precursors [8, 9]. It is instructive to analyze the re-
dependent shits of CD’s energy levels, accumulation of
lation between the size and optical properties of
nanographene domain and resonance energy transfer in
laser-synthesized CD. For this purpose we chose carbon
large carbon dots.
dots obtained by laser synthesis from acetonitrile [9].
Carbon dots emitted visible fluorescence excited by
Acetonitrile carbon dots were polydisperse colloidal
two-photon absorption of femtosecond laser pulses of
nanoparticles with diameters in the nanometers range.
the near-infrared range. Two-photon fluorescence (TPF)
We used dialysis of CD’s aqueous solution in 2 and
spectra were excitation-dependent and shifted to longer
wavelength with increase of the excitation laser wave-
1)e-mail: astafiev.artyom@gmail.com
length. TPF spectra were always broader and redshifted
Письма в ЖЭТФ том 118 вып. 9 - 10
2023
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