Ultrafast Interface Charge Separation in Carbon Nanodot–Nanotube Hybrids

Abstract

Carbon dots are an emerging family of zero-dimensional nanocarbons behaving as tunable light harvesters and photoactivated charge donors. Coupling them to carbon nanotubes, which are well-known electron acceptors with excellent charge transport capabilities, is very promising for several applications. Here, we first devised a route to achieve the stable electrostatic binding of carbon dots to multi- or single-walled carbon nanotubes, as confirmed by several experimental observations. The photoluminescence of carbon dots is strongly quenched when they contact either semiconductive or conductive nanotubes, indicating a strong electronic coupling to both. Theoretical simulations predict a favorable energy level alignment within these complexes, suggesting a photoinduced electron transfer from dots to nanotubes, which is a process of high functional interest. Femtosecond transient absorption confirms indeed an ultrafast (<100 fs) electron transfer independent of nanotubes being conductive or semiconductive in nature, followed by a much slower back electron transfer (≈60 ps) from the nanotube to the carbon dots. The high degree of charge separation and delocalization achieved in these nanohybrids entails significant photocatalytic properties, as we demonstrate by the reduction of silver ions in solution. The results are very promising in view of using these “all-carbon” nanohybrids as efficient light harvesters for applications in artificial photocatalysis and photosynthesis.

Right or Left moving ? Investigating Asymmetric Energy Dispersion Effects on Charge-Transfer between a Quantum Dot and Single-Walled Carbon Nanotube

“…Since the electron in the excited state generally is in a higher orbital compared to the electron in the ground state, and since the electron in the higher orbital has the dipole being stronger than the lower orbital electron, the electron transfer in the excited state has coupling interaction stronger than the electron transfer in the ground state (g f >> g b ). Therefore, the transfer from QD to SWCNT is much faster than the opposite transfer as the research 26 shows that the lifetime in the former case is around 100 f s while the latter case is 10 ps approximately.…”

“…The pink line is backward electron transfer from SWCNT to QD. and back, with the related characteristic timescales as obtained by a fitting procedure 26 . Femtosecond transient absorption confirms indeed an ultrafast (< 100 f s) electron transfer independent of nanotubes being conductive or semiconductive in nature, followed by a much slower back electron transfer (≈ 60ps) from the nanotube to QD.…”

Investigating valley-dependent current generation due to asymmetric energy dispersion for charge-transfer from a quantum dot to single-walled carbon nanotube

“…Since the electron in the excited state is generally in a higher orbital compared to the electron in the ground state, and since the electron in the higher orbital has the dipole being stronger than the lower orbital electron, the electron transfer in the excited state has coupling interaction stronger than the electron transfer in the ground state . Therefore, the transfer from QD to SWCNT is much faster than the opposite transfer as the research 36 shows that the lifetime in the former case is around 10 fs while the latter case is approximately.…”

“… 28 , 29 , the composite system is considered as the transition process of electron to SWCNT interaction, having defined the system Hamiltonian as With an understanding of quantum confinement 38 , the exciton is described by the Hamiltonian with the excited state and the ground state, where is the lifetime of exciton state and the electron creation and annihilation operators in the excited state ( the ground state) for the QD system. Schematized models of forward- and backward-electron transfer from CDs to SWCNTs with the related characteristic timescales as obtained by a fitting procedure 36 . Femtosecond transient absorption confirms indeed an ultrafast electron transfer independent of nanotubes being conductive or semiconductive in nature, followed by a much slower back electron transfer from the nanotube to QD.…”

Optimized photoelectric conversion properties of PbS x Se1−x -QD/MoS2-NT 0D–1D mixed-dimensional van der Waals heterostructures

“…Unlike Auger-assisted mechanism, in which the excessive charge transfer driving force can be used to excite another Coulomb-coupled charge, the Marcus inverted region exhibits the energy-wasting carrier recombination process. As displayed in the inset of figure 3(c), there are two steps in Marcus inverted region, i.e., charge transfer process (step I) and charge recombination process (step II) [47,48]. Clearly, the charge recombination process is followed immediately after the charge transfer in the case of large driving force (i.e., inverted region), resulting in a decreasing charge transfer rate with driving force.…”