Carbon Dots Research Articles

Enhancing leachate management with antibacterial nanocomposites incorporating plant-based carbon dots and Satureja Khuzestanica essential oils

Landfill leachate, a complex mixture of pollutants, poses a significant environmental hazard. This study reports the synthesis and characterization of superabsorbent nanocomposites (SANs) designed for enhanced performance in waste management applications. SANs were prepared using carboxymethyl cellulose (CMC) and sodium polyacrylate (SPA) as the main components, carbon dots (CDs) to improve absorption, and Satureja Khuzestanica essential oil (SEO) for antibacterial performance. The results demonstrated that the addition of CDs significantly increased the absorption capacity and liquid retention of the samples, with a water absorption capacity reaching up to 8621 %. Furthermore, the samples exhibited high mechanical strength, with tensile strength improving by over 100 % in the presence of CDs. The inclusion of SEO provided strong antibacterial activity against Escherichia coli and Staphylococcus aureus, with inhibition zones measuring up to 26 mm. These SANs, with their high absorption capacity, mechanical robustness, and antibacterial properties, show great potential for improving waste management practices, particularly in leachate absorption strategies.

Synthesis of temperature-sensitive boron, nitrogen and sulphur doped carbon dots and their applications

Boron-Sulfur-Nitrogen doped carbon dots (B, N, S-CDs) were prepared by a simple hydrothermal method using 2-Mercaptopyrimidine (C4H4N2S) and citric acid (C6H8N7•H2O) as raw materials. The B, N, S-CDs showed exceptional fluorescence response to Fe2+, TC. The results of the B, N, S-CDs are very promising for the detection of real water samples. In addition, the B, N, S-CDs had a good temperature response (reversible and recoverable fluorescence in the temperature range of 25–65︒C). The low cytotoxicity and in vitro cellular imaging properties exhibited by this carbon dot also greatly enhance their utility.

Fruit waste-derived carbon dots with rhodamine B for the ratiometric detection of Fe3+ and Cu2.

A green and eco-friendly solvothermal approach is proposed for the synthesis of carbon quantum dots (CQDs) from watermelon rind. The as-prepared CQDs exhibited superior teal fluorescence in aqueous solutions, with a quantum yield of 13.9%. The CQDs and rhodamine B (RhB) were demonstrated to selectively react with Fe3+ and Cu2+, leading to a fluorescence (FL) quenching effect, which was successfully used for constructing "double-response-off" type ratiometric FL probes. A comparative study was conducted to assess the sensitivity and accuracy of ratiometric fluorescent probes, specifically those based on CQDs alone and in combination with RhB, for the selective detection of Fe3+ and Cu2+. By plotting the ratio of the differential fluorescence (ΔF) signals of CQDs to that of RhB against the practical application analyte concentration, the detection limits for Fe3+ (1.75 μM) and Cu2+ (0.43 μM) were markedly improved. The quenching mechanism was further explored, and the detection of Fe3+ and Cu2+ in surface water was demonstrated, showcasing the potential of efficient and effective nanosensors based on a static quenching effect. Futhermore, the addition of ascorbic acid can restore the fluorescence quenched by Fe3+. Therefore, in the presence of copper and iron, the ratiometric probe can demonstrate the ability to identify two different metals.

Unveiling Cellular Secrets: Illuminating Carbon Dot Lighthouses for Improved Mitochondrial Exploration

Unveiling Cellular Secrets: Illuminating Carbon Dot Lighthouses for Improved Mitochondrial Exploration

Nanozyme-mediated ratiometric fluorescence hydrogel for on-site detection of sulfite in food

In this work, a ratiometric fluorescence hydrogel nanosensor was developed by integrating a composite consisting of o-phenylenediamine (OPD), manganese dioxide nanoflakes (MnO2 NFs), and N-doped carbon dots (N-CDs) into an agarose hydrogel for sulfite detection. MnO2 NFs demonstrated intense oxidase-like activity, facilitating the conversion of non-fluorescent OPD into yellow-emissive 2,3-diaminophenazine (DAP). As a result, a significant emission peak belongs to DAP, alongside the fluorescence quenching of N-CDs through FRET. Upon interaction with sulfite, MnO2 NFs lost their oxidase-like function. This process decreased the fluorescence of DAP and restored the blue fluorescence of N-CDs, producing a typical ratiometric response, ranging from 3 nM ∼ 400 μM, with a detection limit (LOD) of 3.79 nM. Employing a smartphone, the fluorescence color change demonstrated by the hydrogel sensor was translated into quantitative data (LOD: 8.44 nM). This hydrogel sensor offers an affordable, portable, and user-friendly solution for sulfite detection and food safety monitoring.

Blue Laser for Production of Carbon Dots.

The synthesis of carbon dots (CDs) is gaining wide-ranging interest due to their broad applicability, owing to their small size and luminescence. CDs were prepared from charcoal via a one-step process using laser ablation in liquid without the use of reagents. The adopted method was based on the use of a commercially available continuous wave (CW) laser diode emitting a 450 nm wavelength and, for the liquid, a phosphate-buffered saline (PBS) solution, routinely used in the biological field. Photoluminescence analysis revealed fluorescence, at 480 nm, increasing with laser irradiation time. The atomic force microscopy (AFM) of the CDs revealed an average sphere shape with a size of about 10 nm. Biodegradable polycaprolactone (PCL), typically adopted in biomedicine applications, was used as a matrix to show the preserved luminescence, ideal for the non-invasive monitoring of implanted scaffolds in tissue engineering.

Concentration-Switchable Assembly of Carbon Dots for Circularly Polarized Luminescent Amplification in Chiral Logic Gates and Deep-Red Light-Emitting Diodes.

Stimuli-responsive circularly polarized luminescent (CPL) materials are expected to find widespread application in advanced information technologies, such as 3D displays, multilevel encryption, and chiral optical devices. Here, using R-/S-α-phenylethylamine and 3,4,9,10-perylenetetracarboxylic dianhydride as precursors, chiral carbon dots (Ch-CDs) exhibiting bright concentration-dependent luminescence are synthesized, demonstrating reversible responses in both their morphologies and emission spectra. By adjusting Ch-CD concentration, the switchable wavelength is extended over 180nm (539-720nm), with the maximum quantum efficiency reaching 100%. Meanwhile, upon increasing Ch-CD concentration, the emission wavelength red-shifts, while the chirality of the assembled nanoribbons is synchronously amplified, ultimately achieving CPL at 709nm and a maximum luminescence asymmetry factor of 2.18 × 10-2. These values represent the longest wavelength and the largest glum reported for CDs. Considering the remarkable optical properties of the synthesized Ch-CDs, multilevel chiral logic gates are designed, and their potential practical applications are demonstrated in multilevel anti-counterfeiting encryption, flexible electronic printing, and solid-state CPL. Furthermore, deep-red chiral electroluminescence light-emitting diodes (EL-LEDs) are prepared using these Ch-CDs, achieving an external quantum efficiency of 1.98%, which is the highest value reported to date for CDs in deep-red EL-LEDs, and the first report of chiral electronic devices based on CDs.

POE-Mediated Tunable Quantum Yield of Carbon Dots-Derived From Agapanthus Africanus (L.) Hoffmann Leaves.

The green synthesis of carbon dots (CDs) from natural sources is a challenging goal. Herein CDs are produced from Agapanthus africanus (L.) Hoffmann leaves by carbonization at 200/300 °C for 2/3h. Samples are named CZ-X-Y, where Z, X, and Y represent carbonization, temperature, and time, respectively. CZ-200-3, CZ-300-2, and CZ-300-3 CDs have average sizes of 3.7 ± 0.7, 5.3 ± 1.2, and 5.1 ± 1.6nm, respectively. Their surface, devoid of chlorophyll, contains ─OH, ─C═O, and ─C(═O)OH groups and sylvite. Isolated CZ-300-3 emits at 400nm (excited at 260nm) and exhibits an emission quantum yield (QY) value of 2 ± 1%. Embedding in the d-U(600)/d-(900) di-ureasil matrices resulted in transparent films with emission intensity maxima at 420/450nm (360nm), and QY values of 7 ± 1/16 ± 2% (400nm). The enhancement of the QY value of the bare CDs agrees withan efficient passivation provided by the hybrid host. The hydrophilic CZ-300-3 CDs also exerted a marked surface modifying role, changing the surface roughness and the wettability of the hybrid films.

Modulating carbon dots from aggregation-caused quenching to aggregation-induced emission and applying them in sensing, imaging and anti-counterfeiting

Aggregation Induced Emission Carbon Dots (AIE-CDs) address the problem of conventional CDs being quenched in the solid-state. However, there are still challenges in comprehending the luminescence mechanism. This work proposed a strategy for preparing green, yellow, and near-infrared CDs by modifying the functional groups on the precursor from hydroxyl and amino to p-methylenediamine, in which electronic supply capacity determined the redshift. Additionally, The CDs' properties transformed from Aggregation-Caused Quenching (ACQ) to AIE was realized by substituting non-rotatable hydroxyl or amino groups with the rotatable p-methylenediamine on the precursor. The resulting CDs were then applied in multifield. C-CDs was used for ratiometric detection of Al3+ and F− in pure water through three methods including fluorometer, test strip and smartphone. R-CDs was used for imaging cell nucleus and zebrafish. NIR-CDs (λem = 676 nm) exhibits dual emission, AIE and phosphorescent characteristics was used for triple anti-counterfeiting and binary information encryption. In summary, our finding presented a strategy for preparing multicolor CDs, proposed a mechanism for the transition of CDs from ACQ to AIE, and explore their multiple applications in anti-counterfeiting, information encapsulation, sensing and imaging.

Advances in the study of the biological activity of polysaccharide-based carbon dots: A review.

Carbon dots have attracted worldwide interest due to their customizable nature, luminescent properties, and exceptional biocompatibility. In particular, biomass-derived carbon dots have attracted attention for their environmentally friendly and cost-effective synthesis. Recent research looks into how polysaccharides can be used to make carbon dots. Using them as starting materials for nanomaterials has benefits in terms of structure, morphology, and doping elements. Although research has extensively examined the optical properties of carbon dots, their potential biological applications have not been thoroughly investigated. This review mainly summarises the cytotoxicity and biological functions of polysaccharide-based carbon dots (e.g. agar, alginate, cellulose, carrageenan, chitosan, chitosan, starch, gelatin, etc.), such as antioxidant, antibacterial and anti-tumor functions, highlighting the different scenarios of the methods of preparation of carbon dots. The applications of carbon dots in food, biomedical sciences, soil fertilization, and power generation are highlighted by reviewing the low toxicity of carbon dots with safety and biocompatibility in human contact. Finally, the importance and challenges of polysaccharide-based carbon dots and the prospects and research directions of polysaccharide-based carbon dots are explained by comparing them with other nanomaterials.

Electrochemical synthesis of multicolor carbon dots with room temperature phosphorescence to thermally activated delayed fluorescence via surface state modulation

Solid-state multicolor carbon dots (CDs) have attracted tremendous attention due to their wide applications. However, the fluorescence quenching of solid-state CDs occurs due to the π-π stacking or energy transfer between adjacent carbon dots. In addition, it is difficult to observe the afterglow of solid-state CDs due to their self-quenching and deliquescence. Here, electrochemically prepared multicolor CDs emit the solid-state fluorescence and afterglow emission with lifetimes up to 657 ms by embedding the CDs into urea matrix. More importantly, the surface amino groups and C = O bonds regulate the afterglow emission of CDs from phosphorescence and thermally activated delayed fluorescence at room temperature. Surface amino groups of multicolor CDs can enhance the spin–orbit coupling, increase the intersystem crossing (ISC) and reverse intersystem crossing (RISC). Thus it can promote the generation of triple excited states and regulate the singlet–triplet energy gap value from 0.384 to 0.026 eV. The formation of covalent bonds stabilizes the single and triple excited states and inhibits the non-radiative recombination, which achieves the enhanced fluorescence and visual afterglow of multicolor CDs. The fluorescence and afterglow CDs can be applied to dual signal imaging and anti-counterfeiting, which broadens the practical applications for solid-state CDs via surface state modulation.

Comparative investigation on carbon dots and chloride fluxes modified ZnAl2O4:Cr3+ nanophosphors for temperature sensing, cutting-edge forensic, anti-counterfeiting and w-LEDs applications

A novel Cr3+ doped ZnAl2O4 is synthesized by grafting carbon dots (CDs) and chloride fluxes (NaCl, KCl, NH4Cl) through the solid-state reaction method. Upon excitation at 530 nm wavelength, the Cr3+ ions in the ZAO NPs emit red light due to the influence of a strong crystal field. This red emission arises from the electric dipole 2Eg→4A2g of the Cr3+ ions. Among the chloride fluxes examined, NH4Cl had a significant impact on the PL intensity. Notably, when CDs are incorporated into the ZAO:7Cr3+/NH4Cl NPs, a remarkable increase of 17.25-folds in photoluminescence (PL) intensity is observed. This enhancement is substantially higher than that of CDs alone (11.23-folds) and NH4Cl alone (3.82-folds). The increased PL intensity is attributed to the Förster resonance energy transfer (FRET) mechanism. Furthermore, the addition of CDs (5 wt.%) enhanced the colour purity (CP) of ZAO:7Cr3+/NH4Cl NCs to 99.8%, achieving a high Internal quantum efficiency (IQE) of 93.4 %. Notably, the CDs (5 wt.%)@ZAO:7Cr3+/NH4Cl NCs maintained 92.43 % of their emission intensity even at 420 K, demonstrating exceptional thermal stability compared to ZAO:7Cr3+ NPs. Moreover, the NPs holds promise for optical thermometry, boasting a high relative sensitivity (Sr) of 6.74 × 10-2 %K-1 across a temperature range spanning from 300 to 480 K. Moreover, the latent fingerprints (LFPs) developed using CDs(5 wt.%)@ZAO:7Cr3+/NH4Cl NCs demonstrate remarkable selectivity and high contrast. Under UV irradiation, the structural features of LFPs at levels I–III are clearly visible. In addition, the strong red fluorescence emitted by CDs(5 wt.%)@ZAO:7Cr3+/NH4Cl NCs makes them suitable for applications in AC. CDs(5 wt.%)@ZAO:7Cr3+ NCs exhibit significant potential for w-LED fabrication, achieving a correlated colour temperature (CCT) of 5517 K, a CIE coordinate of (0.332, 0.331), and a high colour rendering index (CRI) of Ra = 94, outperforming ZAO:7Cr3+/NH4Cl NPs. Overall results clearly demonstrates that, CDs(5 wt.%)@ZAO:7Cr3+/NH4Cl NCs are effective for applications in optical thermometry, dactyloscopy, w-LEDs, and AC.

Medicinal Plants Derived Green Carbon Dots: Synthesis, Characterization and Their Potential Applications in Cancer Therapy.

This review aims to explore the synthesis, characterization, and potential applications of carbon dots (CDs) derived from medicinal plants for cancer prevention, highlighting their role as a promising alternative in nanotechnological approaches. A comprehensive literature search was conducted to gather information on the synthesis methods, complex matrices, characterization techniques, and potential applications of CDs derived from medicinal plants in cancer therapy. Carbon dots (CDs) have emerged as a subject of significant interest due to their favorable chemical and biological properties. Various precursors, including graphite, carbon black, and organic molecules, are utilized in the synthesis of CDs through chemical or physical methods. Notably, CDs derived from medicinal plants offer environmentally friendly alternatives, leveraging complex matrices such as aqueous, alcoholic, and hydroalcoholic extracts. This review emphasizes the green synthesis approaches, characterization techniques, and diverse applications of CDs, including drug transport, bioimaging, biosensing, and anti-cancer therapies. Furthermore, it highlights the advantages and disadvantages of different synthesis methods, aiding researchers in selecting appropriate techniques for continuous production. Carbon dots (CDs) represent a transformative advancement in nanotheranostics, offering a versatile platform for precise cancer diagnosis and therapy. With inherent anticancer properties, CDs hold promise in photodynamic therapy (PDT) and photothermal therapy (PTT), enabling precise tumor targeting while minimizing systemic toxicity. To address the limitations of standalone PDT and PTT, researchers are exploring multimodal treatment approaches integrating CDs. By leveraging the unique properties of CDs derived from medicinal plants, a new era of precision cancer therapy may be realized, emphasizing enhanced therapeutic outcomes and reduced adverse effects.

Multiple confinement-limited activation and defect effect co-triggered the ultra-long lifetime of carbon dots

The luminescence process of carbon dots (CDs) is typically influenced by spin-forbidden transition, triplet exciton quenching, and non-radiative transition. Thus, it faces great challenges to achieve efficient and ultra-long lifetime afterglow for CDs. The commonly employed strategy to obtain efficient afterglow performance of CDs is to encapsulate CDs into a rigid matrix to protect the afterglow signal from quenching. Generally, the ultra-long lifetime and excellent luminescent properties of inorganic RTP (room temperature phosphorescence) nanomaterials attribute to the slow release of electrons trapped in defect states of the surfaces. This capture-release mechanism has advanced afterglow lifetime of CDs towards longer levels via the design of defect states. Anchoring CDs onto a rigid matrix can preserve the rigid structure for the restrictive effect, and also can create structural defects. Herein, as-prepared RHCDs@SiO2 composite can exhibit an ultra-long afterglow lifetime of 7.76 s, which is the highest value achieved for CDs in silica matrix to date. This composite is also successfully applied in anti-counterfeiting and cell imaging fields. The synergistic multiple confinement effect and defect effect from the composite provides a universal strategy to design and achieve the ultra-long afterglow lifetime of CDs.

Controlling the emission colour and chemical structure of carbon dots by catalysis-tuned conversion of ortho-aminophenol

The synthesis of carbon dots (CDs) with tailored properties commonly requires time-consuming trial-and-error experimentation, in part because of a poorly understood and controlled chemical conversion of the precursor material. Here, we first report on the solid-state pyrolysis or solvothermal conversion of an ortho-aminophenol (oAP) precursor, comprising ortho-disposed amino and hydroxyl groups on a benzene ring. We find that both conversion reactions resulted in a two emission-colour product, which could be separated into distinct blue-emitting CDs (bCDs, λpeak = 420 nm) and yellow-emitting CDs (yCDs, λpeak = 565 nm) by repetitive column chromatography. Systematic characterization revealed that both CDs comprise a planar graphene-like interior, but that they are distinguished by that the bCDs comprise an intermixed significant amino-rich fluorophore while the yCDs instead comprise a pyridinic-rich fluorophore. This implies that the bCDs are formed via activation of the amino group of the oAP precursor, whereas the synthesis of the yCDs constituted a simultaneous activation of both the amino and hydroxyl groups. With this knowledge at hand, we managed to direct the chemical conversion of the oAP precursor to yield either solely bCDs or yCDs by adding a catalyst (either the Lewis acid AlCl3·6H2O or the Lewis base NaOH) that selectively and efficiently activated only one of the reaction pathways. This demonstration is important in that it shows that the synthesis of CDs with desired properties can be realized with efficient rational instead of trial-and-error means.

One-Pot Synthesis of Sustainable Fluorescent Nanomaterials via Microwave Irradiation as a Probe for the Determination of Metformin in Pure and Pharmaceutical Dosage Forms: Greenness and Whiteness Metrics.

A rapid, green and sensitive technique for the determination of metformin determination was developed based on the direct fluorescence enhancement of carbon dots (CDs) induced by the cited drug. The water-soluble CDs were prepared via a one-pot synthesis from avocado peels using domestic microwave. The prepared CDs exhibited strong fluorescence at 405 nm after excitation at 320 nm with a quantum yield of 51%. The fluorescence of CDs was enhanced linearly by increasing the concentration of metformin within the range 0.5-25 μg/mL with limit of detection 0.087 μg/mL and limit of quantification 0.263 μg/mL. The designed probe was proved to be selective toward metformin in the presence of other drugs such as vildagliptin and alogliptin and also in the presence of excipients in the pharmaceutical dosage form. The suggested and reported methods were compared with the help of the whiteness and greenness tools, specifically the white analytical chemistry and analytical greenness metric tools, for assessing hazardous solvents and reagents used.

Algae derived carbon dots and its polymeric composites for white light emission

Nanomaterials with multicolor emission have been of great interest due to their versatility. Recently, environmentally friendly carbon dots (CDs) with excitation wavelength/solvent/dopant dependent emission have been used for designing different types of white light emitting diodes (W-LED). In this work, single-green precursor (Arthrospira platensis) derived CDs from a one-step hydro/solvothermal synthesis, have been implemented in the elaboration of W-LEDs. The white emission of CDs was modulated by the solvent engineering and doping strategies. A CDs/PVA composite based W-LED with a color render index (CRI) upper to ∼90 %, Commission Internationale Eclairage (CIE) coordinates of (0.31, 0.33) and correlated color temperature (CCT) of 6500 K is demonstrated. These findings suggest that white CDs derived from A. platensis possess promising potential in the field of optoelectronic devices, especially in the production of efficient and high-quality white illumination.

3D printing of aligned silk fibroin microfibers covered with nitrogen-doped carbon dots for anti-counterfeiting

Counterfeiting has serious economic and social consequences, prompting researchers worldwide to develop innovative and highly secure anti-counterfeiting methods, including the use of various polymer printing techniques and the integration of functional materials to create patterns with customized designs that are easy to detect and cannot be falsified. Composite inks made of silk fibroin microfibers and polyvinyl alcohol or polyethylene glycol were developed to produce patterns with the microstructures aligned in the direction of extrusion during the 3D printing process. Fibroin microfibers were obtained via high temperature treatment and used as a precursor for carbon dot synthesis. This approach allowed the microfiber structure to be maintained and be amenable to the synthesis of carbon dots doped with N-heteroatom on its surface, resulting in a material that fluoresces bright blue when irradiated at 365 nm but remains invisible in normal lighting conditions

Multichannel sensor array based on carbon dots and metal ions system for physiological phosphates sensing

The detection of physiological phosphates is crucial for elucidating metabolic processes and related diagnoses of diseases. Herein, a carbon dots (CDs) modulated multichannel fluorescent sensor array was proposed for detecting and distinguishing physiological phosphates. In this sensor, three metal ions (Nd3+, Ag+, and Fe3+) with significantly different binding forces with phosphate ions were selected to trigger fluorescence quenching of three CDs (BCDs, GCDs, and RCDs). Upon adding physiological phosphates, the fluorescence intensity of CDs changed. Depending on the discrepancy in the content of phosphate units in different physiological phosphates, the sensor array realized the detection and differentiation of five physiological phosphates related to adenosine triphosphate (ATP) hydrolysis, and has good anti-interference ability, which can realize the differentiation of physiological phosphates in complex serum samples.

Switching Photoluminescence “On‐Off‐On” for Detection of Chromium (VI) Ion and Ascorbic Acid with N,S‐Codoped Carbon Dots

AbstractA photoluminescent‐based “Turn On → Off → On” technique was adopted for a toxic, heavy metal ion detection, that is, specifically chromium (VI) and a pharmaceutically relevant ascorbic acid molecule. Metal‐free, environmentally benign, and fluorescent carbon dots, a potential vehicle for spectrofluorometric detection, were successfully deployed as sensors. Carbon dots synthesized from citric acid and sulfanilamide conserve the fragments of the precursor molecule on the surface. Zeta potential measurement evidenced the positively charged carbon nanoparticles physically interact with the Cr(VI)/Cr2O72− in acidic pH, resulting in a remarkable quenching in net fluorescence. Thorough studies revealed that the static quenching and inner filter effect were responsible for the reduction in fluorescence intensity. We have demonstrated a new rapid (in seconds) detection platform for Cr(VI) and ascorbic acid.