Carbon quantum dots and their applications

Even though, owing to the complexity of nanoporous carbons' structure and chemistry, the origin of their photoactivity is not yet fully understood, the recent works addressed here clearly show the ability of these materials to absorb light and convert the photogenerated charge carriers into chemical reactions. In many aspects, nanoporous carbons are similar to graphene; their pores are built of distorted graphene layers and defects that arise from their amorphicity and reactivity. As in graphene, the photoactivity of nanoporous carbons is linked to their semiconducting, optical, and electronic properties, defined by the composition and structural defects in the distorted graphene layers that facilitate the exciton splitting and charge separation, minimizing surface recombination. The tight confinement in the nanopores is critical to avoid surface charge recombination and to obtain high photochemical quantum yields. The results obtained so far, although the field is still in its infancy, leave no doubts on the possibilities of applying photochemistry in the confined space of carbon pores in various strategic disciplines such as degradation of pollutants, solar water splitting, or CO2 mitigation. Perhaps the future of photovoltaics and smart‐self‐cleaning or photocorrosion coatings is in exploring the use of nanoporous carbons.

Section: Applications Of the Photochemical Activity Of Nanoporous Carmentioning

confidence: 99%

Origin and Perspectives of the Photochemical Activity of Nanoporous Carbons

Bandosz

Ania

2018

“…Generally, CDs exhibit quantum yield values ranging from 0.01 to 0.65, depending on the carbon source used, reaction condition, etc. The CDs prepared in this study have a moderate quantum yield among all CDs, but a relatively high value among green CDs 14. On the other hand, as shown in Figure 1E, under two‐photon excitation at 800 nm, the system exhibits a redshifted emission band at 500 nm.…”

Section: Resultsmentioning

confidence: 74%

“…Preparation of CDs : The preparation of C‐dots was performed following a literature‐reported procedure 14. Briefly, citric acid (3 g) and urea (6 g) were added to distilled water (10 mL) to form a transparent solution.…”

Section: Methodsmentioning

confidence: 99%

“…This nanoparticle‐based ALA‐releasing strategy for enhancing the efficacy of PDT is shown in Scheme 1 . For this strategy, CD, which features low cytotoxicity, high fluorescent emission, and good water dispersibility,14 serves as the fluorescent carrier for the nanosystem; and the PPIX precursor 5‐ALA is linked onto CD via a photo‐cleavable coumarin structure. Moreover, a biocompatible and hydrophobic cation triphenylphosphonium (TPP) is covalently incorporated onto the carrier to facilitate the cell penetration capability and allow for the delivery of 5‐ATA to the close vicinity of mitochondria.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A Nanosystem Capable of Releasing a Photosensitizer Bioprecursor under Two‐Photon Irradiation for Photodynamic Therapy

Zeng

Zhang

et al. 2015

The applications of photodynamic therapy (PDT) are usually limited by photosensitizers' side effects and singlet oxygen's short half‐life. Herein, a mitochondria‐targeted nanosystem is demonstrated to enhance the PDT efficacy by releasing a bio‐precursor of photosensitizer under two‐photon irradiation. A phototriggerable coumarin derivative is first synthesized by linking 5‐aminolevulinic acid (5‐ALA, the bio‐precursor) to coumarin; and the nanosystem (CD‐ALA‐TPP) is then fabricated by covalently incorporating this coumarin derivative and a mitochondria‐targeting compound triphenylphosphonium (TPP) onto carbon dots (CDs). Upon cellular internalization, the nanosystem preferentially accumulates in mitochondria; and under one‐ or two‐photon irradiation, it releases 5‐ALA molecules that are then metabolized into protoporphyrin IX in mitochondria through a series of biosynthesis processes. The subsequent red light irradiation induces this endogenously synthesized photosensitizer to generate singlet oxygen, thereby causing oxidant damage to mitochondria and then the apoptosis of the cells. Analysis via 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyltetrazolium bromide (MTT) assays indicate that the novel PDT system exhibits enhanced cytotoxicity toward cancer cells. This study may offer a new strategy for designing PDT systems with high efficacy and low side effects.

“…In this context, for instance, the photoluminescence (PL) wavelength could be controlled via the energy‐level engineering,6, 7 the ion selectivity could be endowed for detecting metal ions,8 and the biocompatibility could be improved for biomedical applications 9, 10, 11. On the basis of these unique characteristics,12, 13 CNDs have been exploited for a variety of biomedical applications, such as diagnostic applications,14 photoacoustic imaging, and the photothermal therapy 15, 16, 17…”

mentioning

confidence: 99%

Dual‐Color‐Emitting Carbon Nanodots for Multicolor Bioimaging and Optogenetic Control of Ion Channels

Kim¹,

Park

Beack

et al. 2017

The development of intrinsically multicolor‐emitting carbon nanodots (CNDs) has been one of the great challenges for their various fields of applications. Here, the controlled electronic structure engineering of CNDs is performed to emit two distinct colors via the facile surface modification with 4‐octyloxyaniline. The so‐called dual‐color‐emitting CNDs (DC‐CNDs) can be stably encapsulated within poly(styrene‐co‐maleic anhydride) (PSMA). The prepared water‐soluble DC‐CNDs@PSMA can be successfully applied to in vitro and in vivo dual‐color bioimaging and optogenetics. In vivo optical imaging can visualize the biodistribution of intravenously injected DC‐CNDs@PSMA. In addition, the light‐triggered activation of ion channel, channelrhodopsin‐2, for optogenetic applications is demonstrated. As a new type of fluorophore, DC‐CNDs offer a big insight into the design of charge‐transfer complexes for various optical and biomedical applications.