Exploring Tetrathiafulvalene–Carbon Nanodot Conjugates in Charge Transfer Reactions

Abstract

Carbon nanodots (CNDs) were synthesized using low-cost and biocompatible starting materials such as citric acid/urea, under microwave irradiation, and constant pressure conditions. The obtained pressure-synthesized CNDs (pCNDs) were covalently modified with photo- and electroactive π-extended tetrathiafulvalene (exTTF) by means of a two-step esterification reaction, affording pCND-exTTF. The electronic interactions between the pCNDs and exTTF were investigated in the ground and excited states. Ultrafast pump-probe experiments assisted in corroborating that charge separation governs the deactivation of photoexcited pCND-exTTF. These size-regular structures, as revealed by AFM, are stable electron donor-acceptor conjugates of interest for a better understanding of basic processes such as artificial photosynthesis, catalysis, and photovoltaics, involving readily available fluorescent nanodots.

Use of Nitrogen‐Doped Carbon Nanodots for the Photocatalytic Fluoroalkylation of Organic Compounds

“…Moreover, CNDs may be effectively synthesized from a large variety of substrates by using different preparation approaches . In this regard, it is important to emphasize that the photophysical properties of CNDs, along with their structure and composition, can successfully be designed and tuned through the appropriate choice of starting materials and production procedure . However, despite their unique physical and chemical features, the use of CNDs has found very few applications in synthetic photochemistry at present …”

Charge transfer in graphene quantum dots coupled with tetrathiafulvalenes

“…6 For example, when assembled with perylenediimides (PDI) 7 or single-walled carbon nanotubes (SWCNT), 8 CND seem to donate electrons upon photoexcitation. In stark contrast, when combined with porphyrin 9 or tetrathiafulvalene 10 derivatives, the CND behave as electron-acceptors. Furthermore, the different composition of CND, and the chemical linkage between CND and the aforementioned electroactive units  by means of covalent or non-covalent approaches  has a notable impact on the charge separation and charge recombination dynamics.…”

“…15 Herein, we decided to explore the synthesis of electron-donor acceptor systems based on GQD and the electron donating extended tetrathiafulvalene units (exTTF). 16 Following our previous work on covalently linked CND-exTTF nanoconjugates, 10 we focused in the preparation of GQD-exTTF analogous, to investigate the structural differences between CND and GQD nanomaterials and how their differences might influence the charge-transfer dynamics in excited state events. The production of GQD has been carried out from graphene oxide (GO) obtained by the Kovtyukhova-Hummer's method 17 and subsequent oxidative cutting in a mixture of concentrated H 2 SO 4 /HNO 3 , followed by neutralization of the excess of acid, and dialysis similar to that reported by Haino.…”

“…Analogous results were obtained in CV analyses of an exTTF reference and CND-exTTF conjugates. 10 Following the ground state characterization of GQD-exTTF the excited state features of GQD-exTTF were explored. Fluorescence spectroscopy reveals a nearly quantitative quenching of the GQD emission after their covalent funtionalization with exTTF units (Fig.…”

“…Notable is the lifetime of the GQD •--exTTF •+ charge separated state (SAS2), which is appreciable longer than that determined in the corresponding CND conjugates. 10 The less amorphous character of GQD compared to CND is likely to facilitate a better delocalization of the electrons along the carbon network. In conclusion, we have synthesized GQD-exTTF electron-donor acceptor nanoconjugates through the reaction of edgeoxidized GQD, obtained from graphite, with 2-hydroxymethyl-exTTF.…”