Ultrafast Dynamics in Carbon Dots as Photosensitizers: A Review

Abstract

Electron transfer (ET) is an ultimate property of chemical and biological processes and photochemistry, which is the root of the world. Thus, photoinduced electron transfer (PET) is a fundamental focus of modern research applied in biosensing, solar energy conversion, optoelectronics, and photocatalysis, where light-induced charge separation takes place within the reaction system. The reaction system is made by the combination of a photosensitizer, an electron donor or acceptor, and photocatalysis to control the reaction and offers the best path to reach the goal. In this review, we focus on the photosensitizer capability of carbon dots (C-Dots), investigating the fundamental charge-transfer (CT) processes of C-Dots in different confined environments, surface-modified C-Dots, and doped C-Dots utilizing a combined study of steady-state and time-resolved spectroscopic methods, such as time-correlated single photon counting, ultrafast transient absorption, and fluorescence up-conversion techniques. Thus, it is essential to investigate light-induced fundamental phenomena like charge separation, CT, and charge recombination to increase the efficiency of C-Dots-based materials. Both covalent and noncovalent interactions between C-Dots and quenchers (redox-active material) are used here to investigate the CT process in C-Dots. The photosensitizer behavior of C-Dots has been explored in the confined environments of micelle, reverse micelle, and cyclodextrin. Because of the presence of different surface groups, in click chemistry, mainly a coupling reaction is used for the surface modification of C-Dots using different redox-active small organic molecules such as dopamine, porphyrins, etc. Finally, carrier dynamics of doped C-Dots are successfully discussed in the absence and presence of a quencher. Also, it is observed that the fundamental charge-separation process will promote their use in a variety of photocatalysis, photovoltaic, and optoelectronic devices, photodetectors, and photoresponsive electronic transistors.

Development of a carbon dot and methylene blue NIR-emitting FLIM-FRET pair in niosomes for controlled ROS generation

“…[18][19][20] The extremely easy synthetic and purification methods of CDs have made them useful in analytical applications, 21 light harvesting, 22 photocatalysis, 23,24 solar cells, 25,26 designing molecular logic gates, 27 and photosensitization. [28][29][30] The photosensitive CDs are also useful in treating cancer by photodynamic therapy (PDT). 31,32 FRET with CDs were utilized in DNA 33 as fluorescent reporters in the micellar and reverse micellar cavities, and surfactant and lipid bilayers.…”

Fluorescent Carbon Dots from Food Industry By-Products for Cell Imaging

“…The excitation-emission maps, therefore, indicate that both the starting material (chestnut or peanut) and the way in which the material is treated (H2O or NH4OH as dispersing medium) influence the excitation-wavelength-dependent emission of C-dots and can, therefore, be used to tune their properties. It has been widely reported in the literature that the photoluminescent properties of C-dots depend on their surface emissive states [28,43]; therefore, both the starting material and the dispersion solvent must have influ- The normalized excitation-emission maps reveal that the C and P C-dot samples have different photophysical behaviours. While P H 2 O and P NH 4 OH have a markedly red-shifted excitation-dependent emission (λ exc /λ em : 340 nm/450 nm), this feature is less pronounced for the C NH 4 OH and C H 2 O samples, whose excitation and emission maxima are at lower wavelengths (λ exc /λ em : 320 nm/420 nm).…”

Discerning the Ultrafast Charge Dynamics in Photostable Perovskite-Carbon Dot Composite Systems: Role of Doped Carbon Dots

“…Numerous reports are available, where metal chalcogenide semiconductors like ZnS, CdS, CdSe, PbS, and PbSe are used to form heterostructures with PQDs that have an enormous impact in tuning the photoresponsivity and luminescence properties. − Here, we have prepared a zero–zero-dimensional (0D–0D) nanocomposite integrating the PQDs with the 0-D C-Dots. C-Dots are one of the newcomers in carbon family having unique optical and electrical properties which can be modulated by doping with various non-metallic elements such as boron, phosphorus, sulfur, etc. − It is well known that the C-Dots act as an electron donor/acceptor as well as a photosensitizer. − The C-Dots have been used for several applications such as metal-free photocatalysis of polymerization, electronics, bioimaging, magnetic resonance imaging imaging, sensing organic molecules or metal ions, and site-specific drug delivery. − Recently, Ghosh et al have demonstrated different metal chalcogenide semiconductors and PQD hybrid systems, such as CsPbBr 3 –CdSe and CsPbBr 3 –PbS, and explored the carrier dynamics and charge separation pathways. , In the CsPbBr 3 –PbS hybrid system, the charge-transfer process is bidirectional for hot carriers while exciting at high-energy photons due to the proper alignment of hot carrier states . Brumberg et al reported a comparative study to explore the electronic interactions and the rate of electron transfer between 0D–0D, 0D–2D, and 2D–2D systems using CsPbBr 3 and CdSe .…”