Graphitic Carbon Dots Research Articles

Fluorometric detection of copper and imidacloprid using nitrogen-doped graphitic carbon dots: A promising method for environmental monitoring.

Pesticides in environmental samples pose significant risks to ecosystems and human health since they require precise and efficient detection methods. Imidacloprid (IMI), a widely used neonicotinoid insecticide, exemplifies these hazards due to its potential toxicity. This study addresses the urgent need for improved monitoring of such contaminants by introducing a novel fluorometric method for detecting IMI using nitrogen-doped graphite carbon dots (N-GCDs). The sensor operates by quenching fluorescence through the interaction of Cu2+ ions with N-GCDs. Subsequently, IMI binds to the imidazole group, chelates with Cu2+, and restores the fluorescence of N-GCDs. This alternating fluorescence behavior allows for the accurate identification of both Cu2+ and IMI. The sensor exhibits linear detection ranges of 20-100 nM for Cu2+ and 10-140 μg/L for IMI, with detection limits of 18 nM and 1.2 μg/L, respectively. The high sensitivity of this sensor enables the detection of real-world samples, which underscores its potential for practical use in environmental monitoring and agricultural safety.

Metallic Mo, Ru coupled with graphitic carbon dots to activate inertness 1D copper-based nanowires as efficient electrocatalyst for pH-universal hydrogen evolution reaction

Designing efficient and robust pH-universal electrocatalysts for hydrogen evolution reaction (HER) is the key to boost the development of eco-friendly hydrogen energy. Herein, metallic Mo, Ru coupled with graphitic carbon dots (GQDs) activate inertness 1D copper-based nanowires (GQDs@ Ru, Mo-Cu2O/CF) by surface chemical oxidation, solvothermal and low temperature calcination. The metals of Mo, Ru favor the water-dissociation and optimize the hydrogen adsorption/desorption. In addition, GQDs owns edge effect and good conductivity, and then benefiting electron transport and active sites exposure. Therefore, the synthesized GQDs@ Ru, Mo-Cu2O/CF requires only 30, 39, 17 and 55 mV in alkaline, acidic, alkaline seawater and neutral to achieve 10 mA cm−2. Moreover, the assembled electrolyzer requires 1.58 V to reach 10 mA cm−2 in alkaline seawater, and maintained well at 200 mA cm−2 for 100 h. This research opens a new avenue for designing efficient catalysts on energy-relation applications through introducing both metal and non-metal.

Facile Synthesis of Graphitic Fungal Carbon Dots for Sensing of Food Adulterants and “Bio‐Imaging” of Human Kidney Cell Line

AbstractIn the current study, a simple and environmentally friendly hydrothermal treatment of fungal biomass for the preparation of carbon nanodots (CND) has been reported. The optical and structural characteristics of the CND have been thoroughly investigated using X‐ray Diffraction (XRD), Transmission Electron Microscopy (TEM), UV‐Visible, and fluorescence spectroscopy methods. Elemental analyses and Fourier Transform Infrared spectroscopy (FTIR) have been used to highlight the surface functionality and composition of the CND.CND have been employed as a fluorescence probe for sensitive and selective detection of rhodamine B (Rh−B) and malachite green (MG) because the presence of food adulterants quenches the fluorescence of the CND. Finally, human embryonic kidney 293 (HEK 293) cell lines have been used to assess the biocompatibility and bio‐imaging features of CND. Fluorescence microscopy has been used for qualitative examination of the cellular uptake of CND, while the MTT test has been used for quantitative analysis of the cell‐type‐dependent uptake of CND. The article further investigates the sensing of food adulterants. Therefore, we have validated the practicality of CND obtained from the new carbon source for versatile applications.

Nitrogen-Doped Graphitic Carbon Dots Embedded in Carbon Nitride Scaffolds for Water Decontamination

Functionalized carbon dots (CDs) exhibit intriguing photo-exciton dynamics. CDs can donate or accept electrons depending on their functional groups and electrostatic characteristics. We exploited the electron-accepting capability of nitrogen-doped graphitic carbon dots (N-g-CDs) to improve the charge-carrier separation of the polymeric carbon nitride (PCN) photocatalyst. l-Aspartic acid pyrolyzed at 320 °C yielded ∼25 nm size N-g-CDs that were embedded with PCN. The in-plane infiltration of nanosized N-g-CDs increased the surface area of PCN from 11.5 to 104.9 m2 g–1. The N-g-CDs/PCN hybrid catalyst tested for photocatalytic chromium reduction evidenced about a 3-fold higher rate than PCN. Also, the antibiotic tetracycline and rhodamine B dye rapidly degraded with faster degradation kinetics. The carrier dynamic analysis and computational investigations suggest that the electron acceptor feature of N-g-CDs governs the effective separation of photo-excitons and the high surface area of N-g-CDs/PCN contributes to photoactivity enhancement. This study offers insights into designing high-performance metal-free photocatalysts for water treatment applications.

Visible-light photoredox catalysis with organic polymers

The development of photocatalysts to drive organic reactions is a frontier research topic. Organic polymers can be well tuned in terms of structural and photophysical properties and, therefore, constitute a promising class of photocatalysts in photoredox catalysis for organic synthesis. In this review article, we provide an overview of the concept of photoredox catalysis and recent developments in organic polymers as photocatalysts including porous organic polymers, graphitic carbon nitride, carbon dots, and polymer dots with adjustable reactivity that have undergone state-of-the-art advancement in different photoredox catalytic organic reactions.

Photocatalytic Removal of the Greenhouse Gas Nitrous Oxide by Liposomal Microreactors.

Nitrous oxide (N2 O) is a potent greenhouse and ozone-reactive gas for which emissions are growing rapidly due to increasingly intensive agriculture. Synthetic catalysts for N2 O decomposition typically contain precious metals and/or operate at elevated temperatures driving a desire for more sustainable alternatives. Here we demonstrate self-assembly of liposomal microreactors enabling catalytic reduction of N2 O to the climate neutral product N2 . Photoexcitation of graphitic N-doped carbon dots delivers electrons to encapsulated N2 O Reductase enzymes via a lipid-soluble biomolecular wire provided by the MtrCAB protein complex. Within the microreactor, electron transfer from MtrCAB to N2 O Reductase is facilitated by the general redox mediator methyl viologen. The liposomal microreactors use only earth-abundant elements to catalyze N2 O removal in ambient, aqueous conditions.

Photocatalytic Removal of the Greenhouse Gas Nitrous Oxide by Liposomal Microreactors.

Nitrous oxide (N2O) is a potent greenhouse and ozone-reactive gas for which emissions are growing rapidly due to increasingly intensive agriculture. Synthetic catalysts for N2O decomposition typically contain precious metals and/or operate at elevated temperatures driving a desire for more sustainable alternatives. Here we demonstrate self-assembly of liposomal microreactors enabling catalytic reduction of N2O to the climate neutral product N2. Photoexcitation of graphitic N-doped carbon dots delivers electrons to encapsulated N2O Reductase enzymes via a lipid-soluble biomolecular wire provided by the MtrCAB protein complex. Within the microreactor, electron transfer from MtrCAB to N2O Reductase is facilitated by the general redox mediator methyl viologen. The liposomal microreactors use only earth-abundant elements to catalyze N2O removal in ambient, aqueous conditions.

Efficient and Stable Perovskite Solar Cells based on Nitrogen-Doped Carbon Nanodots.

The role of graphitic and amorphous nitrogen‐doped carbon dots (N‐CDs) as additives for perovskite solar cells (PSCs) is investigated. A detailed study of N‐CDs: perovskite (PVSK) blends through X‐ray diffraction, nuclear magnetic resonance, field emission scanning electron microscopy, UV–vis, and photoluminescence spectroscopy reveals the existence of interactions between N‐CDs and PVSK. The amorphous or graphitic nature of these carbon nanoforms, as well as the interactions between CDs and PVSK, clearly determines the photovoltaic outcome of the PSCs. Thus, a small amount of graphitic carbon dots (g‐N‐CDs) leads to more‐stable PSCs, while maintaining and even improving the power conversion efficiency (PCE). In addition, the long‐term evaluation of the g‐N‐CDs‐containing cells shows improvement of the PCE over time, up to 109% of the initial efficiency after 40 days while the reference performance is dropped to 86%.

Analytical application of H 2 O 2 -induced chiroptical graphitic carbon dots

Carbon dots (CDs) have emerged as efficient peroxidase mimics in recent years. However, to further increase its efficiency as peroxidase-mimic, it is also desirable to understand the modification of CD’s geometry during the catalytic reaction. Herein, we focused on the change in material property of the CDs upon their reaction with H2O2 during the peroxidase reaction. D-(+)-glucose was transformed into chiroptical CDs bearing peroxidase-like activity and can be used to detect H2O2 with a limit of detection of 630 μM. The addition of H2O2 to the CDs resulted in its increased molecular orderliness leading to the introduction of polycrystallinity without affecting its peroxidase-like activity.

Toxicity of Carbon Nanomaterials-Towards Reliable Viability Assessment via New Approach in Flow Cytometry.

The scope of application of carbon nanomaterials in biomedical, environmental and industrial fields is recently substantially increasing. Since in vitro toxicity testing is the first essential step for any commercial usage, it is crucial to have a reliable method to analyze the potentially harmful effects of carbon nanomaterials. Even though researchers already reported the interference of carbon nanomaterials with common toxicity assays, there is still, unfortunately, a large number of studies that neglect this fact. In this study, we investigated interference of four bio-promising carbon nanomaterials (graphene acid (GA), cyanographene (GCN), graphitic carbon nitride (g-C3N4) and carbon dots (QCDs)) in commonly used LIVE/DEAD assay. When a standard procedure was applied, materials caused various types of interference. While positively charged g-C3N4 and QCDs induced false results through the creation of free agglomerates and intrinsic fluorescence properties, negatively charged GA and GCN led to false signals due to the complex quenching effect of the fluorescent dye of a LIVE/DEAD kit. Thus, we developed a new approach using a specific gating strategy based on additional controls that successfully overcame all types of interference and lead to reliable results in LIVE/DEAD assay. We suggest that the newly developed procedure should be a mandatory tool for all in vitro flow cytometry assays of any class of carbon nanomaterials.

Graphitic Dots Combining Photophysical Characteristics of Organic Molecular Fluorophores and Inorganic Quantum Dots.

Thanks to their photophysical properties, both organic molecular fluorophores (MFs) and inorganic quantum dots (QDs) are extensively used for bioimaging applications. However, limitations such as photobleaching for the former or blinking, size, and toxicity for the latter still constitute a challenge for numerous applications. We report here that embedding MFs in graphitic carbon dots (GDs) results in fluorophores which entirely tackle this challenge. Characterized by ultranarrow, bright, and excitation-independent emission devoid of blinking and photobleaching, these hybrid-featured nanoparticles also demonstrate their unique photophysical performances at the single-nanoparticle scale, making them appealing candidates for bioimaging applications.

A Nanocomposite of Graphitic Carbon Nitride and Carbon Dots as a Platform for Sensitive Voltammetric Determination of 2-chlorophenol in Water

A Nanocomposite of Graphitic Carbon Nitride and Carbon Dots as a Platform for Sensitive Voltammetric Determination of 2-chlorophenol in Water

Influence of Surface States on the Optical and Cellular Property of Thermally Stable Red Emissive Graphitic Carbon Dots.

Red emissive carbon dots from sucrose (SCD) were synthesized using a facile, isolation-free, one-pot method via microwave pyrolysis. Various passivation agents were used along with sucrose, and a relative change in the chemical and optical properties of the carbon dots was investigated. A detailed systematic study of the effect of various passivations, different solvents, pHs, and temperatures on optical properties was carried out. The influence of excitation wavelength and passivation on photoluminescence (PL) is discussed considering the functional groups associated with the passivating agents. The effect of different solvents on dispersibility and PL behavior has been understood in terms of the dielectric properties of the solvents. The decrease in PL intensity of SCD from pH 3 to 11 facilitates pH sensing. The PL of SCD was found to be essentially stable between the temperature range of 20 and 80 °C. Additionally, the effects of physicochemical properties with respect to passivation, such as charge and surface chemistry in determining the cellular uptake and cytotoxicity, are also addressed. Aside from sensors, the potential of SCDs as bioimaging agents has also been studied for mammalian cells. Moreover, SCD exhibits excellent PL stability investigated under different storage conditions for 15 days.

Efficient Combination of G-C3 N4 and CDs for Enhanced Photocatalytic Performance: A Review of Synthesis, Strategies, and Applications.

Recently, heterogeneous photocatalysts have achieved much interest on account of their great potential applications in resolving many tough energy and environmental troubles around the world through an ecologically sustainable way. Heterogeneous nanocomposites composed of graphitic carbon nitride (g-C3 N4 ) and carbon dots (CDs) possess broad spectrum absorption, appropriate electronic band structures, rapid carrier mobility, abundant reserves, excellent chemical stability, and facile synthesis methods, which make them promising composite photocatalysts for suitable applications such as photocatalytic solar fuels production and contaminant decomposition. With the rapid development in photocatalysis by hybridization of g-C3 N4 and CDs, a systematic summary and prospection of performance improvement are urgent and meaningful. This review first focuses on various kinds of effectively synthetic methods of composites. Following, the strategies available for enhanced performance, including morphology optimization, spectral absorption improvement, ternary or quaternary composition hybrid, lateral or vertical heterostructures construction, heteroatom doping, and so forth, are fully discussed. Then, the applications mainly in efficient photocatalytic hydrogen generation, photocatalytic carbon dioxide reduction, and organic pollutants degradation are systematically demonstrated. Finally, the remaining issues and prospect of further development are proposed as some kind of guidance for powerful combination of g-C3 N4 and CDs with high efficiency to photocatalysis.

Tuning the nitrogen content of carbon dots in carbon nitride nanoflakes

Carbon nanodots (CD) can be prepared from simple organic precursors and renewable natural products through user-friendly processes. Functional groups, structure, and morphology of CD determine their fundamental properties. The understanding of the correlation of the latter properties with the nature of precursor materials and synthesis methods is still under debate. In this context, the present work explores a tunable CD synthesis method based on microwave-assisted hydrothermal carbonization of urea/glucose mixtures, allowing variations in CD N-content. Different reaction conditions were tested and products were widely characterized. In the absence of urea, oxidized graphitic carbon dots of ca. 3 nm and low photoluminescence quantum yields (ΦPL∼0.009) were obtained. On increasing the urea molar fraction (χu), N-rich carbon dots were synthesized, characterized by the presence of amide surface groups and enhanced photoluminescence yields (ΦPL∼0.02 for χu∼0.2). In the extreme cases of χu ≥ 0.9, partially oxidized graphitic carbon nitride nanoflakes were obtained with ΦPL∼0.10. Correlations between N:C precursors ratio and synthesis conditions with the structure and photophysical properties of the nanoparticles obtained is thoroughly analyzed and discussed. In summary, a tunable synthesis method for preparing different carbon nanomaterials from the same very abundant and cheap precursors, glucose and urea was developed.

Ultra-thin tubular graphitic carbon Nitride-Carbon Dot lateral heterostructures: One-Step synthesis and highly efficient catalytic hydrogen generation

Lateral heterostructures (LHSs) consisting of two-dimensional (2D) layered materials are generally nanosheets that are unfavourable to various applications, such as photocatalysis, because they are prone to agglomerate and against for multiple absorption and utilization of light. Herein, for the first time, we prepare ultra-thin tubular LHSs of graphitic carbon nitride and carbon dots (CN/C-Dots), with thickness of ~8.0 nm via a facile, one-step thermal polymerization of the supramolecular complexes composed of melamine, cyanuric acid and β-cyclodextrin (β-CyD) as starting monomers. Interestingly, the structural topology of the CN/C-Dots LHSs can be effectively modulated by the amount of β-CyD. The obtained tubular porous LHSs are nearly perfect nanotubes with wall thickness of about 8.0 nm, the smallest one reported so far, which not only greatly increases the accessibility of active sites and light harvesting via high light absorption and scattering, but also shortens the route of carriers migrating towards the surface and improves the mass transport. In comparison with CN, the optimized ultra-thin tubular porous CN/C-Dots100 LHSs exhibit significantly boosted visible light photocatalytic hydrogen evolution activity (up to 113 times) of 24,760 μmol h−1 g−1 (λ > 420 nm), much higher than that over pure or nonmetal modified CN tubes reported to date. Moreover, the tubular porous CN/C-Dots100 LHSs are first demonstrated to be excellent electrocatalysts for hydrogen evolution reaction (HER) and oxgen evolution reaction (OER), achieving a geometrical catalytic current density of 10 mA cm−2 at overpotentials 415 and 340 mV in 0.5 M H2SO4 and 1 M KOH versus the reversible hydrogen electrode (RHE), respectively. These findings may provide insights into constructing highly efficient catalysts by tuning structural topology and heterojunction for different energy-related applications.

Precursor-Dependent Photocatalytic Activity of Carbon Dots.

This work systematically compares both structural features and photocatalytic performance of a series of graphitic and amorphous carbon dots (CDs) prepared in a bottom-up manner from fructose, glucose, and citric acid. We demonstrate that the carbon source and synthetic procedures diversely affect the structural and optical properties of the CDs, which in turn unpredictably influence their photo electron transfer ability. The latter was evaluated by studying the photo-reduction of methyl viologen. Overall, citric acid-CDs were found to provide the best photocatalytic performance followed by fructose- and glucose-CDs. However, while the graphitization of glucose- and citric acid-CDs favored the photo-reaction, a reverse structure–activity dependence was observed for fructose-CDs due to the formation of a large graphitic-like supramolecular assembly. This study highlights the complexity to design in advance photo-active bio-based carbon nanomaterials.

Unusual Thermal Conductivity of Carbon Nanosheets with Self-Emerged Graphitic Carbon Dots.

The thermal conductivity (κ) of two-dimensional conducting and transparent carbon nanosheets (CNSs) prepared by a catalyst- and transfer-free process is calculated for the first time by the optothermal Raman technique. A systematic structural analysis of CNSs reveals that the thickness of polymer films affects the interaction between molecules and a Si wafer significantly, thus helping to determine the ratio of sp2 and sp3 bonding configurations of carbon (C) atoms in the CNS. Notably, the holding time of carbonization can realize a hierarchical structure with graphitic carbon dots emerging from the CNS through the rearrangement of carbon atoms, leading to the excellent κ value of 540 W/(m·K) at 310 K. It is demonstrated that an appropriate increase in carbonization time can be an effective approach for improving the ratio of sp2- to sp3-bonded C atoms in the CNS. The thermal conductivity of the CNS with the highest ratio of sp2- to sp3-bonded C atoms exhibits superior behavior and is comparable to that of reduced graphene oxide and supported graphene, respectively. Finally, when the CNS with the highest κ value of 540 W/(m·K) was applied to a heater as the heat-dissipating material, the heater showed the temperature decrease by 14 °C compared to the case without the CNS. The catalyst- and transfer-free approach for the synthesis of CNSs is highly desirable for use as heat sink materials or substrates with heat dissipation functions for extensively integrated electronic devices.

Exfoliated graphitic carbon dots: Application in heavy metal ion sensing

Highly Exfoliated Graphitic Carbon dot (HEG carbon dot) is reported herein, exploiting commercially available table sugar (sucrose) as a green precursor. An amorphous carbon matrix, made of 7–8 graphenic units constitutes the HEG carbon dot core. This system exhibits excitation energy transfer with the Xanthene dye, Rhodamine-B, which is expressed as a noticeable enhancement in the luminescence of the dye. Metal ion assisted hindrance in FRET is noticed in presence of Hg (II) ion, which paves way to the fabrication of an efficient Hg (II) ion sensing tool. The system exhibits high selectivity and sensitivity with Limit of Detection 98 pM.

Advances in the use of carbonaceous materials for the electrochemical determination of persistent organic pollutants. A review.

Persistent organic pollutants (POPs) are key pollutants due to their persistence, refractory biodegradation, high toxicity and bioaccumulation in the food chain. This review (with 93 refs.) covers the progress made in the past decades in the application of carbonaceous materials for electrochemical detection of POPs as listed in the Stockholm Convention. Following an introduction into the field, typical carbonaceous materials for use in electrodes are discussed, with subsection on carbon nanotubes, graphene, reduced graphene oxide, graphitic carbon nitride and carbon dots. This is followed by a section on application of carbonaceous materials in electrochemical detection, with subsections on the use of carbon nanotubes, of (doped-) graphene, of reduced graphene oxide, of graphitic carbon nitride, and of carbon dots. The review concludes with conclusions and future perspectives. The detection mechanisms of POPs are also discussed. Graphical abstract Advanced carbonaceous materials for the electrochemical determination of persistent organic pollutants.