On the Emission Properties of Carbon Dots: Reviewing Data and Discussing Models

Abstract

The emission properties of carbon dots (CDs) have already found many potential applications, from bio-imaging and cell labelling, to optical imaging and drug delivery, and are largely investigated in technological fields, such as lighting and photonics. Besides their high efficiency emission, CDs are also virtually nontoxic and can be prepared through many green chemistry routes. Despite these important features, the very origin of their luminescence is still debated. In this paper, we present an overview of sounding data and the main models proposed to explain the emission properties of CDs and their tunability.

Carbon-based antiviral nanomaterials: graphene, C-dots, and fullerenes. A perspective

“…It is worth considering another family of carbon-based nanomaterials that has attracted great attention in recent years due to their excellent optical properties and ease of synthesis, the carbon dots (Cdots). [41][42][43] Studies on the antiviral properties of carbon dots are very recent and in small numbers. Nevertheless, they show promising opportunities for such nanomaterials.…”

Evaluation of Different Bottom-up Routes for the Fabrication of Carbon Dots

“…While top-down strategies are restricted to using carbon "bulk" samples as precursors (such as graphite powders, graphene, and black carbon) [5], bottom-up procedures can use a myriad of molecular organic precursors, which range from smaller chemicals (as carbohydrates and acids) [1,3] to more heterogenous sources (as rice, coffee beans, and waste) [32][33][34][35]. Due to the structure, surface-functionalization and photoluminescence of the CDs are heavily dependent on the choice of precursors and synthesis procedures.…”

“…Among the several existent possibilities for organic precursors, citric acid (CA) is arguably the most popular one [1,3,5]. CA is readily available (being present even in several citrus fruits), cheap, nontoxic, and has a low carbonization temperature, thereby being the choice for several researchers.…”

“…Moreover, significant efforts to determine the role of precursors in the structure, surface-functionalization, and photoluminescence of CDs have recently been made [1,5]. The effect exerted by the employed bottom-up route is still poorly understood due to the lack of systematic studies.…”

“…The core of these nanomaterials is expected to be composed mainly of graphitic sp 2 carbon connected by amorphous sp 3 carbon atoms in between. The surface can present different functionalization degrees, depending on the chosen precursors and synthesis routes, and thus, different functional groups can be found (such as carboxylic acids, alcohols, and amines) [ 1 , 5 ].…”