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.

Highlights

  • Increasing the performance of solar energy technologies and developing photocatalytic devices for efficient hydrogen production or for the removal of organic pollutants remain urgent scientific problems, in view of the key environmental issues involved

  • We have explored a route to assemble stable Carbon nanodots (CDs)/carbon nanotubes (CNTs) complexes and addressed their photophysics by the combined use of several different techniques

  • The electrostatic coupling of carbon dots and carbon nanotubes produces a quenching of CD emission which stems from a very efficient electron transfer occurring in less than 100 fs from the photoexcited dot to the coupled nanotube

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Summary

Introduction

Increasing the performance of solar energy technologies and developing photocatalytic devices for efficient hydrogen production or for the removal of organic pollutants remain urgent scientific problems, in view of the key environmental issues involved. Coupling nanomaterials with different electronic characteristics into a single device provides fundamentally new routes in materials science to develop efficient nano-photoelectrodevices for artificial photosynthesis, photocatalysis, and photovoltaics.[1−5]. Coupling carbon-based nanomaterials among them, or with other nanomaterials, holds great promise for the development of optically driven applications.[3,4,7−9] In particular, the interactions between different nanocarbons are an area of intense investigation, pointing toward the perspective of an “all-carbon” nanotechnological paradigm.[7−9] In this respect, one of the key problems is achieving a thorough fundamental understanding of the photophysics of carbon nanohybrids, which can be remarkably complex. Following this idea, two carbonbased nanomaterials, carbon nanodots and carbon nanotubes, are electrostatically coupled and their photophysics is studied in detail

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