Special Issue "Carbon Dot Sensors"

A special issue of Nanomaterials (ISSN 2079-4991).

Deadline for manuscript submissions: closed (15 January 2021).

Special Issue Editor

Prof. Dr. Joaquim Esteves da Silva
Website
Guest Editor
Chemistry Research Unit (CIQUP), Faculty of Sciences ofUniversity of Porto (FCUP), Rua do Campo Alegre 687, 4169-007 Porto,Portugal
Interests: Luminescent nanomaterials/materials; Carbon based nanomaterials; Nanosensors; Environmental sustainability; Advanced environmental treatments; Natural bioactive molecules

Special Issue Information

Dear Colleagues,

In 2004, a new family of carbon nanomaterials, named carbon dots or carbon quantum dots, was identified in the purification of carbon nanotubes. Meanwhile, these nanomaterials have been shown to have excellent photophysical and photochemical properties, and low toxicity, and can be produced from renewable materials under sustainable conditions. Currently, on-going research is improving these features far beyond standard values, for example, in terms of their quantum yields, photo and thermal stability, reactivity, and selectivity. Carbon dots are becoming real alternatives to other luminescent nanomaterials in applications involving toxicity and natural resources sustainability issues, such as semiconductors quantum dots. Fluorescent, chemiluminescent, and upconversion fluorescent carbon nanomaterials have been reported. These properties confer an important role in analytical/bioanalytical sensing chemistry and imaging/bioimaging because extended linear concentration ranges, very low detection limits, and high selectivity are foreseen and have already been demonstrated. The present Special Issue is focused on the sensor design, preparation, and analytical applications of carbon dots.

Prof. Dr. Joaquim Esteves da Silva
Guest Editor

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Keywords

  • Carbon dots
  • Carbon quantum dots
  • Chemical sensors
  • Biochemical sensors
  • Environmental sensors
  • Biological sensors
  • Clinical sensors
  • Bioimaging sensors
  • Chemiluminescent sensors
  • Upconversion carbon nanomaterial sensors.

Published Papers (7 papers)

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Research

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Open AccessArticle
Carbon Dots Derived from the Maillard Reaction for pH Sensors and Cr (VI) Detection
Nanomaterials 2020, 10(10), 1924; https://doi.org/10.3390/nano10101924 - 26 Sep 2020
Cited by 1 | Viewed by 605
Abstract
The Maillard reaction involves a series of complex reactions; fluorescent compounds have been considered as vital intermediate products of the reaction. In this article, carbon dots (CDs) based on the Maillard reaction (MR-CDs) were prepared with L-tryptophan and D-glucose, and they had excellent [...] Read more.
The Maillard reaction involves a series of complex reactions; fluorescent compounds have been considered as vital intermediate products of the reaction. In this article, carbon dots (CDs) based on the Maillard reaction (MR-CDs) were prepared with L-tryptophan and D-glucose, and they had excellent photoluminescence stability. MR-CDs showed stable pH-dependence behavior and exhibited an excellent linear response to pH in the range of 4.0–7.5 and 7.5–13.0, respectively. Under the masking effect of sodium fluoride for Fe(III), MR-CDs showed excellent selectivity and sensitivity for Cr (VI). The linear range of Cr(VI) was 0.2–50 μM and the limit of detection was 20 nM. (S/N ≥ 3). Furthermore, MR-CDs were used to detect Cr(VI) in tap water samples. The recoveries were between 95.8% and 98.94%, and RSDs were less than 3.17%. Full article
(This article belongs to the Special Issue Carbon Dot Sensors)
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Open AccessArticle
Bioimaging of C2C12 Muscle Myoblasts Using Fluorescent Carbon Quantum Dots Synthesized from Bread
Nanomaterials 2020, 10(8), 1575; https://doi.org/10.3390/nano10081575 - 11 Aug 2020
Viewed by 643
Abstract
Biocompatible carbon quantum dots (CQDs) have recently attracted increased interest in biomedical imaging owing to their advantageous photoluminescence properties. Numerous precursors of fluorescent CQDs and various fabrication procedures are also reported in the literature. However; the use of concentrated mineral acids and other [...] Read more.
Biocompatible carbon quantum dots (CQDs) have recently attracted increased interest in biomedical imaging owing to their advantageous photoluminescence properties. Numerous precursors of fluorescent CQDs and various fabrication procedures are also reported in the literature. However; the use of concentrated mineral acids and other corrosive chemicals during the fabrication process curtails their biocompatibility and severely limits the utilization of the products in cell bio-imaging. In this study; a facile; fast; and cost-effective synthetic route is employed to fabricate CQDs from a natural organic resource; namely bread; where the use of any toxic chemicals is eliminated. Thus; the novel chemical-free technique facilitated the production of luminescent CQDs that were endowed with low cytotoxicity and; therefore; suitable candidates for bioimaging sensors. The above mentioned amorphous CQDs also exhibited fluorescence over 360–420 nm excitation wavelengths; and with a broad emission range of 360–600 nm. We have also shown that the CQDs were well internalized by muscle myoblasts (C2C12) and differentiated myotubes; the cell lines which have not been reported before. Full article
(This article belongs to the Special Issue Carbon Dot Sensors)
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Open AccessArticle
Green Preparation of Fluorescent Nitrogen-Doped Carbon Quantum Dots for Sensitive Detection of Oxytetracycline in Environmental Samples
Nanomaterials 2020, 10(8), 1561; https://doi.org/10.3390/nano10081561 - 08 Aug 2020
Cited by 1 | Viewed by 1008
Abstract
Nitrogen-doped carbon quantum dots (N-CQDs) with strong fluorescence were prepared by a one-step hydrothermal method using natural biomass waste. Two efficient fluorescent probes were constructed for selective and sensitive detection of oxytetracycline (OTC). The synthesized N-CQDs were characterized by UV-visible absorption spectra, fluorescence [...] Read more.
Nitrogen-doped carbon quantum dots (N-CQDs) with strong fluorescence were prepared by a one-step hydrothermal method using natural biomass waste. Two efficient fluorescent probes were constructed for selective and sensitive detection of oxytetracycline (OTC). The synthesized N-CQDs were characterized by UV-visible absorption spectra, fluorescence spectra, Fourier transform infrared spectroscopy (FT-IR), X-ray photon spectroscopy (XPS), atomic force microscopy (AFM), and high-resolution transmission electron microscopy (HRTEM), which proved that the synthesized N-CQDs surface were functionalized and had stable fluorescence performance. The basis of N-CQDs detection of OTC was discussed, and various reaction conditions were studied. Under optimized conditions, orange peel carbon quantum dots (ON-CQDs) and watermelon peel carbon quantum dots (WN-CQDs) have a good linear relationship with OTC concentrations in the range of 2–100 µmol L−1 and 0.25–100 µmol L−1, respectively. ON-CQDs and WN-CQDs were both successfully applied in detecting the OTC in pretreated tap water, lake water, and soil, with the recovery rate at 91.724–103.206%, and the relative standard deviation was less than 5.35%. The results showed that the proposed N-CQDs proved to be green and simple, greatly reducing the detection time for OTC in the determination environment. Full article
(This article belongs to the Special Issue Carbon Dot Sensors)
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Open AccessArticle
Evaluation of Different Bottom-up Routes for the Fabrication of Carbon Dots
Nanomaterials 2020, 10(7), 1316; https://doi.org/10.3390/nano10071316 - 04 Jul 2020
Cited by 3 | Viewed by 711
Abstract
Carbon dots (CDs) are carbon-based nanoparticles with very attractive luminescence features. Furthermore, their synthesis by bottom-up strategies is quite flexible, as tuning the reaction precursors and synthesis procedures can lead to an endless number of CDs with distinct properties and applications. However, this [...] Read more.
Carbon dots (CDs) are carbon-based nanoparticles with very attractive luminescence features. Furthermore, their synthesis by bottom-up strategies is quite flexible, as tuning the reaction precursors and synthesis procedures can lead to an endless number of CDs with distinct properties and applications. However, this complex variability has made the characterization of the structural and optical properties of the nanomaterials difficult. Herein, we performed a systematic evaluation of the effect of three representative bottom-up strategies (hydrothermal, microwave-assisted, and calcination) on the properties of CDs prepared from the same precursors (citric acid and urea). Our results revealed that these synthesis routes led to nanoparticles with similar sizes, identical excitation-dependent blue-to-green emission, and similar surface-functionalization. However, we have also found that microwave and calcination strategies are more efficient towards nitrogen-doping than hydrothermal synthesis, and thus, the former routes are able to generate CDs with significantly higher fluorescence quantum yields than the latter. Furthermore, the different synthesis strategies appear to have a role in the origin of the photoluminescence of the CDs, as hydrothermal-based nanoparticles present an emission more dependent on surface states, while microwave- and calcination-based CDs present an emission with more contributions from core states. Furthermore, calcination and microwave routes are more suitable for high-yield synthesis (~27–29%), while hydrothermal synthesis present almost negligible synthesis yields (~2%). Finally, life cycle assessment (LCA) was performed to investigate the sustainability of these processes and indicated microwave synthesis as the best choice for future studies. Full article
(This article belongs to the Special Issue Carbon Dot Sensors)
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Open AccessArticle
Turning Spent Coffee Grounds into Sustainable Precursors for the Fabrication of Carbon Dots
Nanomaterials 2020, 10(6), 1209; https://doi.org/10.3390/nano10061209 - 21 Jun 2020
Cited by 6 | Viewed by 938
Abstract
Spent coffee grounds (SCGs) are known for containing many organic compounds of interest, including carbohydrates, lipids, phenolic compounds and proteins. Therefore, we investigated them as a potential source to obtain carbon dots (CDs) via a nanotechnology approach. Herein, a comparison was performed between [...] Read more.
Spent coffee grounds (SCGs) are known for containing many organic compounds of interest, including carbohydrates, lipids, phenolic compounds and proteins. Therefore, we investigated them as a potential source to obtain carbon dots (CDs) via a nanotechnology approach. Herein, a comparison was performed between CDs produced by SCGs and classic precursors (e.g., citric acid and urea). The SCG-based CDs were obtained via the one-pot and solvent-free carbonization of solid samples, generating nanosized particles (2.1–3.9 nm). These nanoparticles exhibited a blue fluorescence with moderate quantum yields (2.9–5.8%) and an excitation-dependent emission characteristic of carbon dots. SCG-based CDs showed potential as environmentally relevant fluorescent probes for Fe3+ in water. More importantly, life cycle assessment studies validated the production of CDs from SCG samples as a more environmentally sustainable route, as compared to those using classic reported precursors, when considering either a weight- or a function-based functional unit. Full article
(This article belongs to the Special Issue Carbon Dot Sensors)
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Open AccessArticle
Porphin-Based Carbon Dots for “Turn Off–On” Phosphate Sensing and Cell Imaging
Nanomaterials 2020, 10(2), 326; https://doi.org/10.3390/nano10020326 - 14 Feb 2020
Cited by 2 | Viewed by 767
Abstract
Porphin-based carbon dots (denoted as PCDs) are prepared through a one-step hydrothermal method by using meso-tetra (4-carboxyphenyl) porphin (TCPP), citric acid, and ethanediamine as precursor. PCDs give rise to the optimal photoluminescence at λexem = 375/645 nm, exhibit an excitation-independent [...] Read more.
Porphin-based carbon dots (denoted as PCDs) are prepared through a one-step hydrothermal method by using meso-tetra (4-carboxyphenyl) porphin (TCPP), citric acid, and ethanediamine as precursor. PCDs give rise to the optimal photoluminescence at λexem = 375/645 nm, exhibit an excitation-independent property, excellent water solubility, and good biocompatibility, which provide red emission and avoid the autofluorescence as an efficient fluorescent imaging probe. On the other hand, when Eu3+ is added into PCDs, the carboxylate groups located on the surface of PCDs exhibit high affinity to Eu3+, resulting in the fluorescence of PCDs turning off via static quenching. In the presence of phosphate, owing to the strong coordination with Eu3+, the fluorescence of PCDs turns on. Based on this performance, a novel “turn off–on” phosphate sensing system is developed. The detection limit of this sensing system can attain 3.59 × 10−3 μmol L−1. This system has been utilized for the detection of phosphate in real samples successfully, which further demonstrates potential applications in biological diagnostic and environmental analysis. Full article
(This article belongs to the Special Issue Carbon Dot Sensors)
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Review

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Open AccessReview
Fluorescent Carbon Quantum Dots—Synthesis, Functionalization and Sensing Application in Food Analysis
Nanomaterials 2020, 10(5), 930; https://doi.org/10.3390/nano10050930 - 11 May 2020
Cited by 7 | Viewed by 1039
Abstract
Carbon quantum dots (CQDs) with stable physicochemical properties are one of the emerging carbon nanomaterials that have been studied in recent years. In addition to the excellent optical properties such as photoluminescence, photobleaching resistance and light stability, this material also has favorable advantages [...] Read more.
Carbon quantum dots (CQDs) with stable physicochemical properties are one of the emerging carbon nanomaterials that have been studied in recent years. In addition to the excellent optical properties such as photoluminescence, photobleaching resistance and light stability, this material also has favorable advantages of good biocompatibility and easy functionalization, which make it an ideal raw material for constructing sensing equipment. In addition, CQDs can combined with other kinds of materials to form the nanostructured composites with unique properties, which provides new insights and ideas for the research of many fields. In the field of food analysis, emerging CQDs have been deeply studied in food composition analysis, detection and monitoring trace harmful substances and made remarkable research progress. This article introduces and compares the various methods for CQDs preparation and reviews its related sensing applications as a new material in food components analysis and food safety inspection in recent years. It is expected to provide a significant guidance for the further study of CQDs in the field of food analysis and detection. Full article
(This article belongs to the Special Issue Carbon Dot Sensors)
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