A Review on Carbon Dots: Synthesis, Characterization and Its Application in Optical Sensor for Environmental Monitoring

Omar, Nur Alia Sheh; Fen, Yap Wing; Ramli, Irmawati; Hashim, Hazwani Suhaila; Ramdzan, Nur Syahira Md; Fauzi, Nurul Illya Muhamad

doi:10.3390/nano12142365

Cited by 37 publications

(13 citation statements)

References 248 publications

(411 reference statements)

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“…CQDs made from tris(4-aminophenyl)amine showed red fluorescence with a QY of 84% in ethanol. 22 For a comprehensive summary of recent CD QYs, please refer to Tables 1−9 in ref 23.…”

Section: ■ Synthesis Of Carbon Dotsmentioning

confidence: 99%

Synthesis Processes, Photoluminescence Mechanism, and the Toxicity of Amorphous or Polymeric Carbon Dots

2022

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Conspectus Fluorescence is the emission of light following photon absorption. This optical phenomenon has many applications in daily life, such as in LED lamps, forensics, and bioimaging. Traditionally, small-molecule fluorophores were most common, but the types of molecules and particles with compelling fluorescence properties have expanded. For example, green fluorescent protein (GFP) was isolated from jellyfish and won the Nobel prize in 2008 due to its significant utility as a fluorescent biomarker. Using the intrinsic fluorescence of GFP, many previously invisible biological processes and substances can now be observed and studied. Other fluorescent materials have also been developed, greatly expanding the potential applications. Semiconductor quantum dots (QDs), which have bright fluorescence and a narrow bandwidth, are a popular choice for display technologies. However, QDs are made of heavy metal elements such as Cd and Se, which pose potential safety concerns to the environment and human health. Thus, new fluorescent organic materials are being developed to mitigate the toxicological concerns while maintaining the QD advantages. One type of new material attracting great attention as an environmentally friendly substitute for semiconductor QDs is carbon dots (CDs). CDs have been developed with strong fluorescence, good photostability, and low toxicity using a variety of precursors, and some synthesis processes have good potential for scale-up. However, since they are made of a variety of materials and through different methods, the structure and properties of CDs can differ from preparation to preparation. There are three major types of CDs: graphene quantum dots (GQDs), carbon quantum dots (CQDs), and amorphous or polymeric carbon dots (PCDs). This Account focuses on PCDs and their unique properties by comparing it with other types of CDs. The synthesis processes, fluorescence properties, fluorescence mechanisms, and toxicity are discussed below with an emphasis on the distinct attributes of PCDs. PCDs can be synthesized from small molecules or polymers. They have an amorphous or cross-linked polymer structure with bright fluorescence. This fluorescence is possibly due to cross-link-enhanced emission or clusteroluminescence that arises from the through-space interactions of heteroatomic-rich functional groups. Other fluorescence mechanisms of CDs, including distinct contributions from the carbon core and surface states, may also contribute. The toxicological profiles of CDs are influenced by the chemical composition, surface functionalization, and light illumination. CDs are generally thought to be of low toxicity, and this can be further improved by removing toxic byproducts, functionalizing the surface, and reducing light exposure to minimize the generation of reactive oxygen species.

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“…CQDs made from tris(4-aminophenyl)amine showed red fluorescence with a QY of 84% in ethanol. 22 For a comprehensive summary of recent CD QYs, please refer to Tables 1−9 in ref 23.…”

Section: ■ Synthesis Of Carbon Dotsmentioning

confidence: 99%

Synthesis Processes, Photoluminescence Mechanism, and the Toxicity of Amorphous or Polymeric Carbon Dots

2022

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“…In addition to being one of the most diverse, emerging, carbon‐based nanomaterials, CDs have many marked properties over conventional quantum dots, including exceptional biocompatibility, high stability, superior optical properties, minimal toxicity, inexpensive precursors, and simple and inexpensive synthesis. [ 1 ] In terms of application, since the discovery of CDs in 2004, their application has expanded into different fields such as bio‐sensing, [ 2 ] electrochemical sensors, [ 3 ] fluorescent probes and immunoassay, [ 4 ] bio‐imaging, [ 5 ] drug delivery systems, [ 6 ] and photo‐catalysis. [ 7 ] In addition to these, Shi [ 8 ] stated that CDs have properties of peroxidase mimetics, a new class of CDs nanozyme that has developed.…”

Section: Introductionmentioning

confidence: 99%

Newly synthesized Fe‐doped CDs for colorimetric and fluorometric nanozyme‐based levodopa sensing

Ahmad

Hassan

2023

Luminescence

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A simple single‐pot hydrothermal method was used to fabricate a Fe, N, and S co‐doped carbon dots (Fe‐CDs) nanozyme using ferric chloride and sunset yellow as precursors. The fabricated Fe‐CDs exhibited intense green fluorescence at 460 nm with excitation‐independent properties and a high quantum yield of 40.23%. This nanozyme mimics peroxidase by catalyzing the oxidation of tetramethylbenzidine (TMB) by H2O2 to yield a blue‐coloured TMBox product at 652 nm. Dual detection methods were established for determining levodopa (l‐dopa) by taking advantage of the high nanozyme activity and the distinct fluorescence aspect. Both determination methods are based on the oxidation of l‐dopa by H2O2 in the presence of Fe‐CDs and fading of the blue colour of the TMBox. The colorimetric method monitors the amount of colour fading of TMBox. In the fluorometric method, the formed blue TMBox absorbs the emission light of the Fe‐CDs; when l‐dopa is present, this effect decreases and the intensity of the emission light increases. The nanozyme‐based detection procedures exhibit good linearity in the ranges 2.17 × 10−3 to 34.78 × 10−3 mM [limit of detection (LOD) = 0.84 × 10−3 mM] and 0.85 × 103 to 16.95 × 103 nM (LOD = 0.102 × 103 nM) for colorimetric and fluorometric methods, respectively.

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Section: Introductionmentioning

confidence: 99%

“…Zero-dimensional carbon nanoparticlescarbon dots (CDs)have an attractive combination of properties for many applications: they can be easily synthesized, they are stable, they have low toxicity, and their surfaces can be purposefully modified. − However, CDs primarily attract attention for their optical properties. The quantum yield of photoluminescence (PL) of such nanoparticles can range from fractions of percent to 90+%, − and the radiation itself, depending on the conditions of synthesis of nanoparticles, can be located from the UV to IR region of spectrum . For some types of CDs, PL is observed in the antistokes region. − Due to this unique combination of properties, CDs have broad prospects for use in many fields of science and production: as catalysts in the chemical industry and nanotechnology, , for the production of electronic devices, as photoluminescent nanoagents in biomedicine. ,,,, …”

Section: Introductionmentioning

confidence: 99%

Quenching of Photoluminescence of Carbon Dots by Metal Cations in Water: Estimation of Contributions of Different Mechanisms

Vervald,

Laptinskiy,

Chugreeva

et al. 2023

J. Phys. Chem. C

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All carbon nanoparticles with a developed surface exhibit photoluminescence (PL), the surface origin of which makes it possible to create environmental nanosensors based on it. The active development of sensors for metal ions based on the photoluminescence of carbon dots (CDs) has shown that the quenching of CDs’ photoluminescence can occur due to different mechanisms. However, the magnitude of their contributions to total PL quenching has not been studied. This article presents the results of studies of the mechanisms of photoluminescence quenching in aqueous solutions of carbon dots of hydrothermal synthesis by metal cations: Co2+, Cu2+, Mg2+, Ni2+, Pb2+, Zn2+, Al3+, Cr3+, and Fe3+. It was established that, for different ions, the following mechanisms make significant contributions to the quenching of the photoluminescence of carbon dots in water: the effect of an inner filter; static quenching due to changes in luminophores caused by (de)protonation of the surface groups of carbon dots with a change of pH value; dynamic quenching. Their contributions to the total quenching of photoluminescence of nanoparticles and the limits of detection were quantitatively determined. The conducted research can be used as an algorithm for the analysis of photoluminescence quenching of carbon nanoparticles by any ions in complex media.

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A Review on Carbon Dots: Synthesis, Characterization and Its Application in Optical Sensor for Environmental Monitoring

Cited by 37 publications

References 248 publications

Synthesis Processes, Photoluminescence Mechanism, and the Toxicity of Amorphous or Polymeric Carbon Dots

Synthesis Processes, Photoluminescence Mechanism, and the Toxicity of Amorphous or Polymeric Carbon Dots

Newly synthesized Fe‐doped CDs for colorimetric and fluorometric nanozyme‐based levodopa sensing

Quenching of Photoluminescence of Carbon Dots by Metal Cations in Water: Estimation of Contributions of Different Mechanisms

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