Carbon Dots Exhibiting Concentration-Dependent Full-Visible-Spectrum Emission for Light-Emitting Diode Applications

The Emerging Star of Carbon Luminescent Materials: Exploring the Mysteries of the Nanolight of Carbon Dots for Optoelectronic Applications

Carbon dots (CDs), a class of carbon-based nanomaterials with dimensions less than 10 nm, have attracted significant interest since their discovery. They possess numerous excellent properties, such as tunability of photoluminescence, environmental friendliness, low cost, and multifunctional applications. Recently, a large number of reviews have emerged that provide overviews of their synthesis, properties, applications, and their composite functionalization. The application of CDs in the field of optoelectronics has also seen unprecedented development due to their excellent optical properties, but reviews of them in this field are relatively rare. With the idea of deepening and broadening the understanding of the applications of CDs in the field of optoelectronics, this review for the first time provides a detailed summary of their applications in the field of luminescent solar concentrators (LSCs), light-emitting diodes (LEDs), solar cells, and photodetectors. In addition, the definition, categories, and synthesis methods of CDs are briefly introduced. It is hoped that this review can bring scholars more and deeper understanding in the field of optoelectronic applications of CDs to further promote the practical applications of CDs.

Molecularly designed and synthesized of bright blue nitrogen-doped lignin-derived carbon dots applied in printable anti-counterfeiting

With the increased demand for green and sustainable development, the research of advanced biomass-based carbon dots (CDs) has drawn growing attention. Herein, a one-step green solvent integration strategy-assisted solvothermal method to preparing CDs from hydrolyzed lignin and ethylenediamine (EDA) in formamide (FA) was developed. The Schiff reaction between FA and EDA contributes to the formation of -C-N groups, further inducing the high photoluminescence quantum yield (up to 42.69 %)，obviously higher than NCDs prepared in H2O, EtOH and DMF systems (corresponding to H-NCDs, E-NCDs and D-NCDs, respectively). The analysis of structure, composition, photoluminescence (PL) behaviors and DFT calculations showed that F-NCDs have main blue fluorescent emission peak from 410 to 455 nm under 330-390 nm excitation due to the small sp2 structure in carbon core, and the large sp2 conjugated clusters and CO group related surface states leaded to the long wavelength emission. The F-NCDs with excellent optical properties was further used for preparing fluorescent film and invisible anti-counterfeiting ink, which exhibited outstanding fluorescence even at different temperatures and aging times. We provided a facile way for green facile preparation of lignin-based CDs and their sustainable anti-counterfeiting application.

Turning food waste into value-added carbon dots for sustainable food packaging application: A review

Carbon dots (CDs) are a recent addition to the nanocarbon family, encompassing both crystalline and amorphous phases. They have sparked significant research interest due to their unique electrical and optical properties, remarkable biocompatibility, outstanding mechanical characteristics, customizable surface chemistry, and negligible cytotoxicity. Their current applications are mainly limited to flexible photonic and biomedical devices, but they have also garnered attention for their potential use in intelligent packaging. The conversion of food waste into CDs further contributes to the concept of the circular economy. It provides a comprehensive overview of emerging green technologies, energy-saving reactions, and cost-effective starting materials involved in the synthesis of CDs. It also highlights the unique properties of biomass-derived CDs, focusing on their structural performance, cellular toxicity, and functional characteristics. The application of CDs in the food industry, including food packaging, is summarized in a concise manner. This paper sheds light on the current challenges and prospects of utilizing CDs in the packaging industry. It aims to provide researchers with a roadmap to tailor the properties of CDs to suit specific applications in the food industry, particularly in food packaging.

Comprehensive advances in the synthesis, fluorescence mechanism and multifunctional applications of red-emitting carbon nanomaterials

Red emitting fluorescent carbon nanomaterials have drawn significant scientific interest in recent years due to their high quantum yield, water-dispersibility, photostability, biocompatibility, ease of surface functionalization, low cost and eco-friendliness. The red emissive characteristics of fluorescent carbon nanomaterials generally depend on the carbon source, reaction time, synthetic approach/methodology, surface functional groups, average size, and other reaction environments, which directly or indirectly help to achieve red emission. The importance of several factors to achieve red fluorescent carbon nanomaterials is highlighted in this review. Numerous plausible theories have been explained in detail to understand the origin of red fluorescence and tunable emission in these carbon-based nanostructures. The above advantages and fluorescence in the red region make them a potential candidate for multifunctional applications in various current fields. Therefore, this review focused on the recent advances in the synthesis approach, mechanism of fluorescence, and electronic and optical properties of red-emitting fluorescent carbon nanomaterials. This review also explains the several innovative applications of red-emitting fluorescent carbon nanomaterials such as biomedicine, light-emitting devices, sensing, photocatalysis, energy, anticounterfeiting, fluorescent silk, artificial photosynthesis, etc. It is hoped that by choosing appropriate methods, the present review can inspire and guide future research on the design of red emissive fluorescent carbon nanomaterials for potential advancements in multifunctional applications.

Synthesis and post-synthesis strategies for polychromatic carbon dots toward unique and tunable multicolor photoluminescence and associated emission mechanism

Carbon dots (CDs) with unique and tunable multicolor photoluminescence (PL) emission has attracted tremendous attention in the past few years due to their potential multifaceted application, specially in the biomedical and optoelectronic fields. There has been extensive deliberation and efforts to engineer the synthesis or post synthesis approach to obtain multicolor-emissive CDs and tune their optical properties toward longer wavelength. This review mainly focuses on the advancement of strategies for synthesis and post-synthesis techniques of CDs toward tunable multicolor emission. Based on the above discussion to achieve desired goals, several synthesis strategies (selection of proper benzenoid precursor, acid/base treatment of biomass, optimization of reaction conditions, optimization of the reagents, solvent engineering, acid strength regulation, reaction temperature regulation, chemical doping) and various post synthesis strategies (column chromatographic separation or purification, solvatochromism, pH variation, surface functionalization, concentration variation) have been reviewed. Although numerous research articles have been published on the synthesis of multicolor CDs for multifaceted application, there is still a lack of a concise review article focusing on systematic synthesis/post synthesis strategies with PL mechanism elucidation. Thus, we focused on providing a comprehensive overview of the state-of-the-art advances on the strategies for the preparation of polychromatic CDs with tunable emission and elucidating their emission mechanism.

Machine Learning-Mediated Ultrasensitive Detection of Citrinin and Associated Mycotoxins in Real Food Samples Discerned from a Photoluminescent Carbon Dot Barcode Array

Economically viable remote sensing of foodborne contaminants using minimalistic chemical reagents and simultaneous automation calls for a concrete integration of a chemical detection strategy with artificial intelligence. In a first of its kind, we report the ultrasensitive detection of citrinin and associated mycotoxins like aflatoxin B1 and ochratoxin A using an Alizarin Red S (ARS) and cystamine-derived carbon dot (CD) that aptly amalgamate with machine learning algorithms for automation. The photoluminescence response of the CD as a function of various solvents and pH is used to generate array channels that are further modulated in the presence of the mycotoxins whose digital images were acquired to determine pixelation, essentially creating a barcode. The barcode was fed to machine learning algorithms that actualize and intertwine convoluted databases, demonstrating Extreme Gradient Boosting (XGBoost) as the optimized model out of eight algorithms tested. Spiked samples of wheat, rice, gram, maize, coffee, and milk were used to evaluate the testing model where an exemplary accuracy of 100% even at 10 pmol of mycotoxin concentration was achieved. Most importantly, the coexistence of mycotoxins could also be detected through the CD array and XGBoost synergy hinting toward a broader scope of the developed methodology for smart detection of foodborne contaminants.

Transcriptome analysis reveals the molecular mechanisms by which carbon dots regulate the growth of Chlamydomonas reinhardtii

Carbon dots (CDs) have attracted increasing attention for their ability to artificially improve photosynthesis. Microalgal bioproducts have emerged as promising sources of sustainable nutrition and energy. However, the gene regulation mechanism of CDs on microalgae remains unexplored. The study synthesized red-emitting CDs and applied them to Chlamydomonas reinhardtii. Results showed that 0.5 mg/L-CDs acted as light supplements to promote cell division and biomass in C. reinhardtii. CDs improved the energy transfer of PS II, photochemical efficiency of PS II, and photosynthetic electron transfer. The pigment content and carbohydrate production slightly increased, while protein and lipid contents significantly increased (by 28.4% and 27.7%, respectively) in a short cultivation time. Transcriptome analysis identified 1166 differentially expressed genes. CDs resulted in faster cell growth by up-regulating the expression of genes associated with cell growth and death, promoting sister chromatid separation, accelerating the mitotic process and shortening the cell cycle. CDs improved the ability of energy conversion by up-regulating photosynthetic electron transfer-related genes. Carbohydrate metabolism-related genes were regulated and provided more available pyruvate for the citrate cycle. The study provides evidence for the genetic regulation of microalgal bioresources by artificially synthesized CDs.

Deep insights to explain the mechanism of carbon dot formation at various reaction times using the hydrothermal technique: FT-IR, 13C-NMR, 1H-NMR, and UV-visible spectroscopic approaches

A well-explained mechanism for synthesizing carbon dots (CDs) is not yet explored and is still a subject of great debate and challenge. This study used a one-step hydrothermal method to prepare highly efficient, gram-scale, excellent water solubility, and blue fluorescent nitrogen-doped carbon dots (NCDs) with the particle size average distribution of around 5 nm from 4-aminoantipyrine. The effects of varying synthesis reaction times on the structure and mechanism formation of NCDs were investigated using spectroscopic methods, namely FT-IR, 13C-NMR, 1H-NMR, and UV-visible spectroscopies. The spectroscopic results indicated that increasing the reaction time affects the structure of the NCDs. As the hydrothermal synthesis reaction time is extended, the intensity of the peaks in the aromatic region decreases, and new peaks in the aliphatic and carbonyl group regions are generated, which display enhanced intensity. In addition, the photoluminescent quantum yield increases as the reaction time increases. The presence of a benzene ring in 4-aminoantipyrine is thought to contribute to the observed structural changes in NCDs. This is due to the increased noncovalent π-π stacking interactions of the aromatic ring during the carbon dot core formation. Moreover, the hydrolysis of the pyrazole ring in 4-aminoantipyrine results in polar functional groups attached to aliphatic carbons. As the reaction time prolongs, these functional groups progressively cover a larger portion of the surface of the NCDs. After 21 h of the synthesis process, the XRD spectrum of the produced NCDs illustrates a broad peak at 21.1°, indicating an amorphous turbostratic carbon phase. The d-spacing measured from the HR-TEM image is about 0.26 nm, which agrees with the (100) plane lattice of graphite carbon and confirms the purity of the NCD product with a surface covered by polar functional groups. This investigation will lead to a greater understanding of the effect of hydrothermal reaction time on the mechanism and structure of carbon dot synthesis. Moreover, it offers a simple, low-cost, and gram-scale method for creating high-quality NCDs crucial for various applications.

Carbon Dots: Opportunities and Challenges in Cancer Therapy

Recently, carbon dots (CDs) have been actively studied and reported for their various properties. In particular, the specific characteristics of carbon dots have been considered as a possible technique for cancer diagnosis and therapy. This is also a cutting-edge technology that offers fresh ideas for treating various disorders. Though carbon dots are still in their infancy and have not yet shown their value to society, their discovery has already resulted in some noteworthy advancements. The application of CDs indicates conversion in natural imaging. Photography using CDs has demonstrated extraordinary appropriateness in bio-imaging, the discovery of novel drugs, the delivery of targeted genes, bio-sensing, photodynamic therapy, and diagnosis. This review seeks to provide a comprehensive understanding of CDs, including their benefits, characteristics, applications, and mode of action. In this overview, many CD design strategies will be highlighted. In addition, we will discuss numerous studies on cytotoxic testing to demonstrate the safety of CDs. The current study will address the production method, mechanism, ongoing research, and application of CDs in cancer diagnosis and therapy.

Multiple Stimuli-Response Polychromatic Carbon Dots for Advanced Information Encryption and Safety

Optical information encryption and safety have aroused great attention since they are closely correlated to data protection and information safety. The development of multiple stimuli-response optical materials for constructing large-capacity information encryption and safety is very important for practical applications. Carbon dots (CDs) have many gratifying merits, such as polychromatic emission, diverse luminous categories, and stable physicochemical properties, and are considered as one of the most ideal candidates for information protection. Herein, carbon core, functional groups, solvents, and other crucial factors are reviewed for outputting polychromatic emission of multiple luminous categories. In particular, substrate engineering strategies have been emphasized for their critical role in yielding excellent optical features of multiple luminous categories. High-capacity information encryption and safety strategies are reviewed by relying on the rich optical properties of CDs, such as polychromatic emission, multiple luminous categories of fluorescence, afterglow, and upconversion, as well as external-stimuli-assisted optical changes. Some perspectives for preparing excellent CDs and further developing information security strategies are proposed. This review provides a good reference for the manipulation of polychromatic CDs and the development of next-generation information encryption and safety.

One-Pot Synthesis of Dual Color-Emitting CDs: Numerical and Experimental Optimization towards White LEDs

Carbon Dots (CDs) are fluorescent carbon-based nanoparticles that have attracted increasing attention in recent years as environment-friendly and cost-effective fluorophores. An application that can benefit from CDs in a relatively short-term perspective is the fabrication of color-converting materials in phosphor-converted white LEDs (WLEDs). In this work we present a one-pot solvothermal synthesis of polymer-passivated CDs that show a dual emission band (in the green and in the red regions) upon blue light excitation. A purposely designed numerical approach enables evaluating how the spectroscopic properties of such CDs can be profitable for application in WLEDs emulating daylight characteristics. Subsequently, we fabricate nanocomposite coatings based on the dual color-emitting CDs via solution-based strategies, and we compare their color-converting properties with those of the simulated ones to finally accomplish white light emission. The combined numerical and experimental approach can find a general use to reduce the number of experimental trial-and-error steps required for optimization of CD optical properties for lighting application.

Color Conversion Light-Emitting Diodes Based on Carbon Dots: A Review

This paper reviews the state-of-the-art technologies, characterizations, materials (precursors and encapsulants), and challenges concerning multicolor and white light-emitting diodes (LEDs) based on carbon dots (CDs) as color converters. Herein, CDs are exploited to achieve emission in LEDs at wavelengths longer than the pump wavelength. White LEDs are typically obtained by pumping broad band visible-emitting CDs by an UV LED, or yellow-green-emitting CDs by a blue LED. The most important methods used to produce CDs, top-down and bottom-up, are described in detail, together with the process that allows one to embed the synthetized CDs on the surface of the pumping LEDs. Experimental results show that CDs are very promising ecofriendly candidates with the potential to replace phosphors in traditional color conversion LEDs. The future for these devices is bright, but several goals must still be achieved to reach full maturity.

Full-Color Long-Lived Room Temperature Phosphorescence in Aqueous Environment

Long-lived room temperature phosphorescence (RTP) materials are widely utilized in the field of biological and chemical sensing, due to their unique characteristics of long-lived luminescence and no background autofluorescence. However, the realization of full-color RTP in aqueous solution still remains a great challenge. Herein, a feasible strategy for achieving high stability and full-color RTP of carbon dots (CDs)-based composite materials in aqueous environment is reported by constructing a rigid hydrogen bonds' network. The obtained m,p-CDs@CA composite materials exhibit deep-blue RTP with phosphorescence quantum yield of 23.2% and lifetime of 1.74 s, and the afterglow can last for over 12 s. More importantly, the m,p-CDs@CA composite materials are desirable in the detection of biomarkers, because of excellent stability, dispersion, and long-lived RTP properties. The m,p-CDs@CA suspension also displays excellent sensitivity, and a limitation of detection as low as 5.61 and 550 nm for biomarkers 5-hydroxyindole-3-acetic acid (HIAA) and serotonin (5-hydroxytryptamine, HT), respectively. Meanwhile, the sensing performance exhibits excellent selectivity even in the presence of other competitive species in blood plasma and urine. With superior selectivity, the long-lived phosphorescence probe based on m,p-CDs@CA suspension can be as an effective biomarker for carcinoid identification, which has potential application in clinical analysis.

Sulfuric-acid-mediated synthesis strategy for multi-colour aggregation-induced emission fluorescent carbon dots: Application in anti-counterfeiting, information encryption, and rapid cytoplasmic imaging

Aggregation-induced emission fluorescent carbon dots (AIE-CDs) have applications in the fields of multi-colour anti-counterfeiting, information encryption, and imaging. In this study, four AIE-CDs (B-AIE-CDs, G-AIE-CDs, Y-AIE-CDs, and O-AIE-CDs) with blue, green, yellow, and orange fluorescence at high concentrations were fabricated using crystal violet as a precursor, solutions with different sulfuric acid concentrations as solvents under different temperatures and reaction times for the first time. The structural properties and fluorescence behaviour of the AIE-CDs were investigated. The results revealed that the sulfuric acid concentration had a significant effect on the fluorescence colour of the AIE-CDs because sulfuric acid can affect the degree of carbonisation, the type and content of nitrogen. Moreover, the reaction temperature and time affected the surface-defect state and the degree of carbonisation of the AIE-CDs, which affected the emission wavelength and quantum yield (QY) of the AIE-CDs. Furthermore, to exploit the unique characteristics (polychromatic aggregation fluorescence and acid-sensitive properties) of the obtained-AIE-CDs, anti-counterfeiting and information encryption methodologies (i.e., acid-stimuli-response producing multi-colour fluorescence) were preliminarily developed. Finally, B-AIE-CDs with a high QY of 43.5% were successfully used for rapid cytoplasmic imaging, demonstrating their applicability in biological fields.

Dispersion-assisted tunable fluorescence from carbon dots

In this study, carbon dots (CDs) synthesized by hydrothermal method with amino-rich surface exhibit tunable fluorescence across entire visible range by simply controlling the concentration. A comprehensive comparison has been performed for the first time between concentration-induced aggregation of the single-type CDs and electrostatic-induced agglomeration of opposite-charged CDs in terms of their fluorescence properties. Experimental results show that both the aggregation of CDs and internal absorption filtration are possible causes of the concentration-dependent fluorescence emission. Subsequently, the inter distance of adjacent CDs in their aggregates was enlarged by forming rigid double-stranded DNA (dsDNA) between adjacent CDs through base pairing. It is clear that the contact of CDs induces the changes of fluorescence emission and light absorption. Through a better understanding of the mechanisms behind concentration-induced multicolor emission, this work can provide a novel strategy to develop the advanced applications of CDs.

Carbon dot/inorganic nanomaterial composites

The preparation methods, formation mechanism, properties and applications of carbon dot/inorganic nanohybrid materials are reported.

Brewery spent grain derived carbon dots for metal sensing

This article presents a proof-of-concept to recycle microbrewery waste as a carbon source for synthesizing carbon dots (CDs). A simple method has been developed to synthesize water-soluble CDs based on microwave irradiation of brewery spent grain. The structures and optical properties of the CDs were characterized by ultraviolet-visible (UV-Vis) spectroscopy, photoluminescence spectroscopy (PL), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy. The effects of reaction time, temperature and pH on the properties of carbon dots were studied. These CDs were found to be spherical with an average diameter of 5.3 nm, N-doped, containing many functional groups (hydroxyl, ethers, esters, carboxyl and amino groups), and to exhibit good photoluminescence with a fluorescent quantum yield of 14%. Finally, the interaction between carbon dots and metal ions was investigated towards developing CDs as a sensing technology for water treatment, food quality and safety detection.

This article presents a proof-of-concept to recycle microbrewery waste as a carbon source for synthesizing carbon dots (CDs).

Structural Engineering toward High Monochromaticity of Carbon Dots-Based Light-Emitting Diodes

Monochromaticity for light-emitting diodes (LEDs) is an important parameter. However, carbon dots-based light-emitting diodes (CDs-LEDs) usually suffer from broad emission, which limits the development of this material. In this work, high-quality carbon dots (CDs) with a quantum yield of 16.2% were synthesized. When they were mixed with poly(N-vinyl carbazole) (PVK) to form a homogeneous film, the solid-state fluorescence of CDs was realized. After fabrication and systematic optimization of the device, the full width at half-maximum (fwhm) of EL spectra could be narrowed to 64 nm in comparison with the fwhm of 77 nm for PL, demonstrating that structural engineering is an effective approach for improving the color purity of CDs-LEDs. Meanwhile, the performance of the devices is improving. The obtained CDs-LEDs display high monochromaticity with a maximum luminance of 681 cd/m². This work provides a new way to optimize the monochromaticity and performance of CDs-LEDs.

Iron ion sensing and in vitro and in vivo imaging based on bright blue-fluorescent carbon dots

Herein, we propose an eco-friendly synthesis of carbon dots (CDs) and ingeniously design a rapid and label-free "turn-off" sensing platform for ultrasensitive recognition of Fe³⁺ in vitro and in vivo. CDs with extraordinary advantages involving exceptional stability, ultra-low toxicity as well as admirable biocompatibility were simply prepared via one-step hydrothermal strategy of Caulis polygoni multiflora. Result indicated that as-acquired CDs not only exhibit excitation dependency, but also have a high quantum yield of (QY) up to 42%. Miraculously, the fluorescence of CDs can be extinguished sharply by Fe³⁺ because of static quenching effect with linear range of 0-400 µM, yielding a detection limit of 0.025 μM. Benefiting from these characteristics, CDs have been extended for multicolourful imaging and tracking Fe³⁺ fluctuations in living cells. Bioimaging of zebrafish larvae exposed to CDs confirmed that it is smoothly circulated to other tissues and organs owing to their small size. Eventually, as-prepared CDs have been implemented for the real-time detection of Fe³⁺ in nude mice.

Optical Properties of Carbon Dots in the Deep-Red to Near-Infrared Region Are Attractive for Biomedical Applications

Carbon dots (CDs) represent a recently emerged class of luminescent materials with a great potential for biomedical theranostics, and there are a lot of efforts to shift their absorption and emission toward deep-red (DR) to near-infrared (NIR) region falling in the biological transparency window. This review offers comprehensive insights into the synthesis strategies aimed to achieve this goal, and the current approaches of modulating the optical properties of CDs over the DR to NIR region. The underlying mechanisms of their absorption, photoluminescence, and chemiluminescence, as well as the related photophysical processes of photothermal conversion and formation of reactive oxygen species are considered. The already available biomedical applications of CDs, such as in the photoacoustic imaging and photothermal therapy, photodynamic therapy, and their use as bioimaging agents and drug carriers are then shortly summarized.

One-Step Green Solvothermal Synthesis of Full-Color Carbon Quantum Dots Based on a Doping Strategy

Proposing a simple strategy for developing full-color carbon quantum dots (CQDs) and exploring how the luminescence can be tuned and improved is attractive and encouraging. Herein, blue, green, yellow-green, and orange-red CQDs doped with heteroatoms were synthesized in one pot and separated by column chromatography, with emission peaks of 435 nm, 495 nm [photoluminescence quantum yield (PLQY) of 88.9%], 525 nm, and 595 nm (full width at half-maximum of 31 nm), respectively. The abundant C-O/C-O-C electron donor groups greatly improve the PLQY of green CQDs, and the expended effective conjugated domains (particle size, doped chlorine, and conjugated nitrogen) of CQDs boost the red-shifts of emission spectra. Energy transfer (ET) in a concentrated mixed solution of CQDs was discovered, and possible ET mechanisms are proposed. Furthermore, a high-efficiency white light-emitting diode with Commission Internationale de L'Eclairage coordinates of (0.361, 0.369), a correlated color temperature of 4534 K, and a high color rendering index of 90.8 was fabricated.

Perception on aggregation induced multicolor emission and emission centers in carbon nanodots using successive dilution, anion exchange chromatography, and multi-way statistics

Exploration in the way of understanding the optical behavior and structure of carbon nanodots has been increased due to their vast application. Their emission dependency on excitation wavelengths is the more prevalent and controversial subject. In this report we considered the optical structure of hydrothermally synthesized carbon nanodots using citric acid and 2,3-diaminopyridine as precursors. The presence of different emission centers experimented through anion exchange chromatography which resulted in fractions with more unique optical structures. The quantum confinement effect and energy exchange between different types of carbon nanodots, due to aggregation in higher concentration levels, was studied applying a stepwise dilution experiment. Analysis of the experimental data was done through the parallel factor analysis and the trajectory pattern recognition which resolved more about optical interactions and the presence of different emission centers in different particles. Results from infrared spectroscopy confirmed the dominating density of carboxyl functional groups on the nanodots with negative surface charges and higher influence of amine groups on dots with positive surface charges.

ESIPT fluorophores derived from 2,3-dichloro-5,6-dicyano-p-benzoquinone based carbon dots for dual emission and multiple anti-counterfeiting

Fluorophores and hydrogen bonding interactions play key roles in the fluorescence properties of bottom-up carbon dots. In this work, an excited-state intramolecular proton-transfer (ESIPT) active fluorophore, 5-chloro-6-ethoxy-4,7-dihydroxyisoindoline-1,3-dione (CEDD) and a non-ESIPT 7-cyano-5,8-dihydroxyquinoxaline-6-carboxamide (CDQC) are extracted from 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) based carbon dots. The enol form of CEDD shows a weak blue, small Stokes shift and short lifetime emission under the aprotic or alkali conditions, but the keto form exhibits a strong green, large Stokes shift and long lifetime emission in a protic or an acidic environment. Due to the lack of the ESIPT process, CDQC has no dual emission characteristics, but shows efficient solid-state emission. By virtue of the ESIPT ability of CEDD, multiple anti-counterfeiting methods are achieved by using hydrogen chloride, ammonia, and fluorescence lifetime imaging, as well as dimethyl sulfoxide as the encryption/decryption tools.

The one-step synthesis of B,N co-doped carbon dots as a fracturing crosslinker and fluorescent tracer in flowback fluid and their performance

The carbon dot crosslinker has a unique crosslinking mechanism, that each crosslinking point can crosslink multiple guar gum molecular chains.

Identification of eight pathogenic microorganisms by single concentration-dependent multicolor carbon dots

Single concentration-dependent carbon dots were synthesized and applied to the rapid identification of eight kinds of pathogenic microorganisms.