The Photochemistry of carbon dots


Ubach Mases, Pol  


Carbon dots are fluorescent nanoparticles with a diameter less than 20 nm. They are made up of a carbon nucleus and several functional groups or polymers connected to its surface. There are three main types of carbon dots in relation to their size, shape, crystallinity, surface polymers, and surface functionalization: graphene quantum dots (GQDs), carbon nano dots (CNDS), and polymer dots (PD). They have several differences between them, but all three are characterized by excitation-dependent fluorescence emission, high biocompatibility, and being highly inert. Despite their differences, there are four general confirmed photoluminescence mechanisms: the quantum confinement effect, the surface state, the molecular state, and the emission effect favored by crosslinking. By controlling all the parameters that influence these four emission mechanisms, it is possible to adjust the optical properties of the carbon points at will. Carbon spots are used for various applications, such as cationic and molecular sensors, drug and gene delivery, Bioimaging techniques, and photocatalysis. The intensity and color of the fluorescence emission are specifically chosen for your application. They can be modified by changing the size of these nanoparticles, the synthetic method used and the functional groups attached to their surface. Another important aspect of carbon spots is their phosphorescence emission. Although this is a fairly new field and requires much more study, triplet states and phosphorescence decays have been measured by these carbon nanoparticles. Some similarities have been established between the phosphorescence of the carbon points and that of benzophenone, which can be associated with the presence of long domains conjugated with ketones at the carbon points. Consequently, experimental data of photochemical reactions of benzophenone have been studied for comparison with carbon points. With the KinTekExplorer software, these data have been analyzed and a model fitted in order to find the kinetic constants of two reactions: the energy transfer reaction of the triplet from benzophenone to naphthalene and the energy transfer reaction of the triplet. from naphthalene to oxygen, which leads to the formation of singlet oxygen. This study aims to open a door in the field of phosphorescence of carbon points for future possible applications, such as photodynamic therapy.



Nonell i Marrugat, Santiago 


IQS SE - Undergraduate Program in Chemistry