Carbon nanodots
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Carbon nanodots (CNDs) are carbon-based nanoparticles with sizes below 10 nm. Typically CNDs are luminescent, in contrast with most carbon nanomaterials. Their synthesis can be performed from molecular precursors. Depending on the type of precursor and the experimental conditions, CNDs with tuned properties can be obtained. Our research is focused on the study of CNDs synthesis, characterization and modification for applications of interest.
Our main focus is the design of CNDs with specific properties and their exploitation in different applicative areas. This is realized by the tuning of light absorption, fluorescence emission and solubility via specific synthetic processes. We started the research in this field exploring a convenient and easy method to prepare nitrogen-doped carbon nanodots (NCNDs). [1,2] This was achieved by using cheap reagents, L-arginine and ethylenediamine, and by using a microwave-assisted hydrothermal process. The use of a microwave reactor let us to obtain good synthetic performances and reproducibility. Our nanoparticles present multiple surface amino functional groups, strong blue fluorescence, high quantum yields and narrow size distribution. In a direct application, these nanoparticles were successfully employed as photocatalysts for the formation of new C-C bonds in organic synthesis. [3] Under light irradiation, NCNDs can catalyze the fluoroalkylation of organic compounds through a radical mechanism pathway. This leads to the formation of molecules useful in many fields such as medicinal chemistry, agriculture and material science.
Besides the direct application of NCNDs, we strongly devolved our efforts on developing a rational method to tune the NCNDs properties. [4] This is important because it allows to prepare nanoparticles with performances optimized for specific applications. Our methodology is based on the use of specific starting materials that react in a microwave-assisted processes. The advantage of this procedure is that it allows to obtain modified high-quality carbon dots in a simple one-pot processe and short reaction times. For example, we exploited the chemistry of naphthalene dianhydrides to obtain white emissive NCNDs. [5] In addition to the emission tuning, we focused on the introduction of chirality in our NCNDs. Chirality at the nanoscale level is highly relevant in many applications including biological ones, self-assembly, enantioselective reactions, and light or electron spin polarization. Given the importance of this property, the synthesis of chiral nanoparticles would be highly interesting, but the harsh conditions of CNDs synthesis often led to racemization and loss of chiral information. Employing a chiral diamine we successfully produced chiral NCNDs. [6] In line with our rational approach, these NCNDs were conceived by using a chiral precursor able to retain chirality under the synthetic conditions. Moreover, following a full structural characterization, we demonstrated the capability of chiral NCNDs to convey chirality to supramolecular assemblies based on porphyrins.
From the very first stages of this research line, we directed our efforts towards the understanding of the dots core/shell chemical composition. Building on this knowledge, we further investigated NCNDs as building blocks for the synthesis of nano-sized functional hybrids. In particular, this was achieved exploiting the surface functional groups for the coupling with molecules of interest. As a representative example, we coupled the NCNDs electron-accepting features to the electron-donor properties of porphyrins obtaining an interesting photoactive nanosystem for charge separation. [7]
Building on these premises, we intend to tailor new structures that will be used to tackle relevant societal challenges. Hot areas that we are exploring include photocatalysis, optoelectronics and biomedicine.
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Highlighted contributions:
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[1] Synthesis, Separation, and Characterization of Small and Highly Fluorescent Nitrogen-Doped Carbon Nanodots.
F. Arcudi, L. ÐorÄ‘ević, M. Prato. Angew. Chem. Int. Ed. 55 (6), 2107–2112 (2016). Link
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[2] Preparation, functionalization and characterization of engineered carbon nanodots.
L. ÐorÄ‘ević, F. Arcudi, M. Prato. Nat. Protoc. 14, 2931-2953 (2019). Link
[3] Use of Nitrogen-Doped Carbon Nanodots for the Photocatalytic Fluoroalkylation of Organic Compounds.
C. Rosso, G. Filippini, M. Prato. Chem. Eur. J. (2019), in press. Link
[4] Design, Synthesis, and Functionalization Strategies of Tailored Carbon Nanodots.
F. Arcudi, L. ÐorÄ‘ević, M. Prato. Acc. Chem. Res. 52, 2070-2079 (2019). Link
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[5] Rationally Designed Carbon NanoDots En Route to Pure White-Light Emission.
F. Arcudi, L. ÐorÄ‘ević, M. Prato. Angew. Chem. Int. Ed. 56 (15), 4170–4173 (2017). Link
[6] Design Principles of Chiral Carbon Nanodots Help Convey Chirality from Molecular to Nanoscale Level.
L. ÐorÄ‘ević, F. Arcudi, A. D’Urso, M. Cacioppo, N. Micali, T. Bürgi, R. Purrello, M. Prato. Nat. Commun. 9 (1), 3442 (2018). Link
[7] Porphyrin Antennas on Carbon Nanodots: Excited State Energy and Electron Transduction.
F. Arcudi, V. Strauss, L. ÐorÄ‘ević, A. Cadranel, D. M. Guldi, M. Prato. Angew. Chem. Int. Ed. 56 (40), 12097–12101 (2017). Link