The heterostructures of nitrogen doped carbon quantum dots (N-CQDs) with graphitic carbon nitride (g-C3N4)
were fabricated using hydrothermal approach. Physicochemical characterizations, including FTIR, XRD, XPS,
and HR-TEM were used to explore the phase structure, chemical composition and morphological structure of the
heterostructures. The optical characteristics were investigated via using UV–vis spectrophotometry. The results
confirm the strong coupling and compounding between N-CQDs and g-C3N4 to form a 0D/2D heterojunction.
Furthermore, using the Tauc equation, the optical bandgap energy for g-C3N4 was dropped from 2.805 eV after
conjugation with N-CQDs, reaching 2.797 eV, 2.76, and 2.795 as the concentration of N-CQDs in the hetero
structure increased. Meanwhile, the PL of heterostructures is gradually blue shifted. However, upon increasing
the amount of N-CQDs in the heterostructure, the extinction coefficient, refractive index, electronegativity, and
optical conductivity enhanced. It is shown that Skin depth (δ) decreases as photon energy increases up to cut off
wavelength λcutoff ~ 3.8 eV, then increases exponentially with N-CQDs content in surface g-C3N4 sheets. Pho
toacoustic spectroscopy technique (PA) was used to evaluate the thermal diffusivity (α), thermal effusivity (e)
and thermal conductivity (k) of prepared materials. The results show the values of (k) of g-C3N4 reached to 300 %
increase upon conjugation with N-CQDs. Additionally, the thermal conductivity increased from 0.126 w
m1k 1to 0.596 w m1 k 1, and the e values increased from 40 to 63.4 ws1/2m2k 1 as the concentration of N-
CQDs increase in the heterostructures. Finally, these results demonstrate the potential of N-CQDs/g-C₃N₄ het
erostructures for multifunctional optoelectronic and thermal applications.