Design principles of chiral carbon nanodots help convey chirality from molecular to nanoscale level

Abstract

The chirality of (nano)structures is paramount in many phenomena, including biological processes, self-assembly, enantioselective reactions, and light or electron spin polarization. In the quest for new chiral materials, metallo-organic hybrids have been attractive candidates for exploiting the aforementioned scientific fields. Here, we show that chiral carbon nanoparticles, called carbon nanodots, can be readily prepared using hydrothermal microwave-assisted synthesis and easily purified. These particles, with a mean particle size around 3 nm, are highly soluble in water and display mirror-image profile both in the UV–Vis and in the infrared regions, as detected by electronic and vibrational circular dichroism, respectively. Finally, the nanoparticles are used as templates for the formation of chiral supramolecular porphyrin assemblies, showing that it is possible to use and transfer the chiral information. This simple (and effective) methodology opens up exciting opportunities for developing a variety of chiral composite materials and applications.

Preparation, functionalization and characterization of engineered carbon nanodots

“…Tuning these properties includes using the multicomponent approach and hydrothermal microwave-assisted synthesis already described in Step 1. Modifying the electrochemistry is accomplished by adding quinones to the Arg and EDA starting materials in the synthesis 29 , while emission is tuned by adding core-substituted naphthalene dianhydrides as chromophore along Arg and EDA 28 , and finally chirality is conferred by employing chiral cyclohexanediamine instead of EDA 27 .…”

“…In recent years we have worked on the synthesis and purification of nitrogen-doped carbon nanodots (NCNDs) 26 , the modification of their (chiro)optical 27,28 and electrochemical properties 29 and the preparation of (non)covalent hybrids [30][31][32] and nanocomposite materials 33,34 . This work is based on our original procedure, which uses a two-component approach, together with a fast microwave-assisted hydrothermal synthesis 26 .…”

“…Besides filtration and dialysis, NCNDs can be purified by using size-exclusion chromatography, which yields three distinct fractions of NCNDs that feature different size, surface functional groups and fluorescence properties (e.g., the smallest fraction has also the highest PLQY = 46%). We have managed to expand this procedure in order to modulate and tailor the properties of CNDs to exhibit different fluorescence properties 28 , to confer chirality 27 , tuning their band gap 29 , preparing donor-acceptor (supra)molecular assemblies 27,32 , but also have exploited the amino-rich surface to prepare covalent hybrids 30,31 and composites with clay 33 or ionogels 34 .…”

Chiral Carbon Dots Synthesized on Cellulose Nanocrystals

“…No reports exist on the chirality induction and chiroptical properties of hybrid C‐dot/CNC NPs, neither due to C‐dot geometrical arrangement, nor owing to the chirality induction. Notably, the challenge in the bottom‐to‐top synthesis of Ch C‐dots (and graphene quantum dots) stems from the loss of chirality and racemization under harsh reaction conditions, e.g., high temperatures . The mild reaction conditions selected in our work enabled the transfer of the chirality of the CNC moieties to C‐dots.…”

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 …”