A Self-Quenching-Resistant Carbon-Dot Powder with Tunable Solid-State Fluorescence and Construction of Dual-Fluorescence Morphologies for White Light-Emission

Fluorescent Polylactic acid composite incorporating lignin-based carbon quantum dots for sustainable 4D printing applications

Fluorescent 4D printing materials, as innovative materials that combine fluorescent characteristics with 4D printing technology, have attracted widespread interest and research. In this study, green lignin-derived carbon quantum dots (CQDs) were used as the fluorescent module, and renewable poly(propylene carbonate) polyurethane (PPCU) was used for toughening. A new low-cost fluorescent polylactic acid (PLA) composite filament for 4D printing was developed using a simple melt extrusion method. The strength of the prepared composite was maintained at 32 MPa, while the elongation at break increased 8-fold (34 % increase), demonstrating excellent shape fixed ratio (∼99 %), recovery ratio (∼92 %), and rapid shape memory recovery speed. The presence of PPCU prevented fluorescence quenching of the CQDs in the PLA matrix, allowing the composite to emit bright green fluorescence under 365 nm ultraviolet light. The composite exhibited shear thinning behavior and had an ideal melt viscosity for 3D printing. The results obtained demonstrated the versatility of these easy-to-manufacture and low-cost filaments, opening up a novel and convenient method for the preparation of strong, tough, and multifunctional PLA materials, increasing their potential application value.

Generated White Light Having Adaptable Chromaticity and Emission, Using Spectrally Reconfigurable Microcavities

Metal-free, luminescent, carbogenic nanomaterials (LCNMs) constitute a novel class of optical materials with low environmental impact. LCNMs, e.g., carbon dots (CDs), graphitic carbon nitride (g-C3N4), and carbonized polymer microspheres (CPM) show strong blue/cyan emissions, but rather weak yellow/red emission. This has been a serious drawback in applying them to light-emitting and bio-imaging applications. Here, by integrating single-component LCNMs in photonic microcavities, the study spectroscopically engineers the coupling between photonic modes in these microcavities and optical transitions to "reconfigure" the emission spectra of these luminescent materials. Resonant photons are confined in the microcavity, which allows selective re-excitation of phosphors to effectively emit down-converted photons. The down-converted photons re-excite the phosphors and are multiply recycled, leading to enhanced yellow/red emissions and resulting in white-light emission (WLE). Furthermore, by adjusting photonic stop bands of microcavity components, color adaptable (cool, pure, and warm) WLE is flexibly generated, which precisely follows the black-body Planckian locus in the chromaticity diagram. The proposed approach offers practical low-cost chromaticity-adjustable WLE from single-component, luminescent materials without any chemical or surface modification, or elaborate machinery and processing, paving the way for practical WLE devices.

Blood-brain barrier permeable carbon nano-assemblies for amyloid-β clearance and neurotoxic attenuation

Abnormal amyloid β-protein (Aβ42) fibrillation is a key event in Alzheimer's disease (AD), and photodynamic therapy (PDT) possesses great potential in modulating Aβ42 self-assembly. However, the poor blood-brain barrier (BBB) penetration, low biocompatibility, and limited tissue penetration depth of existing photosensitizers limit the progress of photo-oxidation strategies. In this paper, novel indocyanine green-modified graphene quantum dot nano-assemblies (NBGQDs-ICGs) were synthesized based on a molecular assembly strategy of electrostatic interactions for PDT inhibition of Aβ42 self-assembly process and decomposition of preformed fibrils under near-infrared light. Combining the small-size structure of graphene quantum dots and the near-infrared light-responsive properties of ICGs, the NBGQDs-ICGs could achieve BBB penetration under 808 nm irradiation. More importantly, the neuroprotective mechanism of NBGQDs-ICG was studied for the first time by AFM, which effectively weakened the adhesion of Aβ42 aggregates to the cell surface by blocking the interaction between Aβ42 and the cell membrane, and restored the mechanical stability and adhesion of the neuron membrane. Meanwhile, NBGQDs-ICG promoted phagocytosis of Aβ42 by microglia. In addition, the good biocompatibility and stability ensured the biosafety of NBGQDs-ICG in future clinical applications. We anticipate that such multifunctional nanocomponents may provide promising avenues for the development of novel AD inhibitors.

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.

Rare-Earth-Metal-Free Solid-State Fluorescent Carbonized-Polymer Microspheres for Unclonable Anti-Counterfeit Whispering-Gallery Emissions from Red to Near-Infrared Wavelengths

Colloidal carbon dots (CDs) have garnered much attention as metal-free photoluminescent nanomaterials, yet creation of solid-state fluorescent (SSF) materials emitting in the deep red (DR) to near-infrared (NIR) range poses a significant challenge with practical implications. To address this challenge and to engineer photonic functionalities, a micro-resonator architecture is developed using carbonized polymer microspheres (CPMs), evolved from conventional colloidal nanodots. Gram-scale production of CPMs utilizes controlled microscopic phase separation facilitated by natural peptide cross-linking during hydrothermal processing. The resulting microstructure effectively suppresses aggregation-induced quenching (AIQ), enabling strong solid-state light emission. Both experimental and theoretical analysis support a role for extended π-conjugated polycyclic aromatic hydrocarbons (PAHs) trapped within these microstructures, which exhibit a progressive red shift in light absorption/emission toward the NIR range. Moreover, the highly spherical shape of CPMs endows them with innate photonic functionalities in combination with their intrinsic CD-based attributes. Harnessing their excitation wavelength-dependent photoluminescent (PL) property, a single CPM exhibits whispering-gallery modes (WGMs) that are emission-tunable from the DR to the NIR. This type of newly developed microresonator can serve as, for example, unclonable anti-counterfeiting labels. This innovative cross-cutting approach, combining photonics and chemistry, offers robust, bottom-up, built-in photonic functionality with diverse NIR applications.

Solid-State Red Carbon Dots Based on Biomass Furan Derivatives

In the preparation of carbon dots (CDs), precursors are crucial, and abundant precursors endow CDs with various structures and fluorescence characteristics. Furan (FU) and its derivatives are considered excellent carbonization materials due to their π conjugated structures and active functional groups, such as hydroxyl and aldehyde groups. Herein, we prepare FU-derivative-based CDs by a solvothermal method and investigate the influences of the precursor structure on the fluorescence characteristics. Surprisingly, CDs prepared from 5-hydroxymethylfurfural (HMF) with both aldehyde and hydroxyl groups exhibit red-shifted fluorescence characteristics in the solid state. We postulate that this solid-state fluorescence characteristic is due to the enhancement of supramolecular cross-linking fluorescence between CDs. The unique precursor structure leads to carboxyl groups on the surface of HMF-CDs that are conducive to the hydrogen bond formation. As the concentration of CDs increases, the hydrogen bonding effect increases, leading to a red-shift in the fluorescence wavelength. Therefore, basically full-color CDs/poly(vinyl alcohol) (PVA) phosphor-based light-emitting diodes can be achieved by controlling the degree of supramolecular cross-linking of CDs in PVA. This research provides a new approach for the preparation of solid-state luminescent CDs.

Vacuum-Boosting Precise Synthetic Control of Highly Bright Solid-State Carbon Quantum Dots Enables Efficient Light Emitting Diodes

Carbon quantum dots (C-dots) have emerged as efficient fluorescent materials for solid-state lighting devices. However, it is still a challenge to obtain highly bright solid-state C-dots because of the aggregation caused quenching. Compared to the encapsulation of as-prepared C-dots in matrices, one-step preparation of C-dots/matrix complex is a good method to obtain highly bright solid-state C-dots, which is still quite limited. Here, an efficient and controllable vacuum-boosting gradient heating approach is demonstrated for in situ synthesis of a stable and efficient C-dots/matrix complex. The addition of boric acid strongly bonded with urea, promoting the selectivity of the reaction between citric acid and urea. Benefiting from the high reaction selectivity and spatial-confinement growth of C-dots in porous matrices, in situ synthesize C-dots bonded can synthesized dominantly with a crosslinked octa-cyclic compound, biuret and cyanuric acid (triuret). The obtained C-dots/matrix complex exhibited bright green emission with a quantum yield as high as 90% and excellent thermal and photo stability. As a proof-of-concept, the as-prepared C-dots are used for the fabrication of white light-emitting diodes (LEDs) with a color rendering index of 84 and luminous efficiency of 88.14 lm W-1, showing great potential for applications in LEDs.

Bioinspired Carbonized Polymer Microspheres for Full-Color Whispering Gallery Mode Emission for White Light Emission, Unclonable Anticounterfeiting, and Chemical Sensing Applications

Light-element-based fluorescent materials, colloidal graphene quantum dots, and carbon dots (CDs) have sparked an immense amount of scientific interest in the past decade. However, a significant challenge in practical applications has emerged concerning the development of solid-state fluorescence (SSF) materials. This study addresses this knowledge gap by exploring the unexplored photonic facets of C-based solid-state microphotonic emitters. The proposed synthesis approach focuses on carbonized polymer microspheres (CPMs) instead of conventional nanodots. These microspheres exhibit remarkable SSF spanning the entire visible spectrum from blue to red. The highly spherical shape of CPMs imparts built-in photonic properties in addition to its intrinsic CD-based attributes. Leveraging their excitation-dependent photoluminescence property, these microspheres exhibit amplified spontaneous emission, assisted by the whispering gallery mode resonance across the visible spectral region. Remarkably, unlike conventional semiconductor quantum dots or dye-doped microresonators, this single microstructure showcases adaptable resonant emission without structural/chemical modifications. This distinctive attribute enables a plethora of applications, including microcavity-assisted energy transfer for white light emission, highly sensitive chemical sensing, and secure encrypted anticounterfeiting measures. This interdisciplinary approach, integrating photonics and chemistry, provides a robust solution for light-element-based SSF with inherent photonic functionality and wide-ranging applications.

Crystallization-induced emission from F-doped carbon dots

Herein, F-doped CDs with bright red SSF were synthesized by a solvothermal method using trifluoroethanol as the solvent and m-hydroxybenzaldehyde as the carbon source. Strong F-F interactions are vital for inducing crystallization, and solid luminescence is achieved by blocking the nonradiative energy dissipation pathways of crystalline organizations.

Multi-color polymer carbon dots synthesized from waste polyolefins through phenylenediamine-assisted hydrothermal processing

The large accumulation and low recycling rates of polyolefin waste have posed a threat to the environment and human health. The shortage of chemical recycling methods for polyolefins strongly demands the development of new and sustainable treatment technologies for hydrocarbon plastics to improve their waste management. In this study, polyethylene (PE) and polypropylene (PP) were utilized for the preparation of multi-color polymer carbon dots (PCDs) via a two-step hydrothermal (HT) synthesis involving (i) thermo-oxidative degradation of polyolefins to precursors containing plentiful oxygen-based functional groups, and (ii) modification with phenylenediamine (PDA). The fluorescence of PCDs depends on the structure of isomeric PDA and PCDs modified by ortho-, meta-, and para-PDA emit blue, green, and yellow color fluorescence, respectively. The formation mechanism of PCDs, involving dehydrative condensation and amination of PE or PP-derived precursors by PDA, was proposed. The obtained PCDs were utilized for the detection and quantification of Fe3+ ions at ppm concentrations. The proposed strategy here aims to broaden the scope of the chemical recycling methods for polyolefin plastic waste as well as to develop a conversion route of polyolefin to value-added materials.

Carbon Nanomaterial Fluorescent Probes and Their Biological Applications

Fluorescent carbon nanomaterials have broadly useful chemical and photophysical attributes that are conducive to applications in biology. In this review, we focus on materials whose photophysics allow for the use of these materials in biomedical and environmental applications, with emphasis on imaging, biosensing, and cargo delivery. The review focuses primarily on graphitic carbon nanomaterials including graphene and its derivatives, carbon nanotubes, as well as carbon dots and carbon nanohoops. Recent advances in and future prospects of these fields are discussed at depth, and where appropriate, references to reviews pertaining to older literature are provided.

Carbon dots on LAPONITE® hybrid nanocomposites: solid-state emission and inter-aggregate energy transfer

This study delves into the photoluminescent characteristics of solid-state hybrid carbon dots/LAPONITE® (CDLP). These hybrid materials were synthesized using the hydrothermal method with a precise pH control set at 8.5. The LAPONITE® structure remains intact without structural collapse, and we detected the possible deposition of carbon dots (CDs) aggregates on the clay mineral's edges. The use of different concentrations of citric acid (10-, 6-, 2- and 1-times weight/weight of LAPONITE® mass, maintaining the 1 : 1 molar ratio with ethylenediamine) during synthesis results in different CDs concentrations in CDLP-A (low precursors concentration) and CDLP-D (high concentration) with an amorphous structure and average size around 2.8-3.0 nm. The CDLP displayed visible photoluminescence emission in aqueous and powder, which the last underwent quenching according to lifetimes and quantum yield measurements. Low-temperature measurements revealed an enhancement of the non-radiative pathways induced by aggregation. Energy transfer modelling based on Förster-Dexter suggests an approximate mean distance of 9.5 nm between clusters of CDs.

Combination of gold nanoclusters and silicon quantum dots for ratiometric fluorometry: One system, two mechanisms

A ratiometric fluorometry based on silicon quantum dots (SiQDs) and gold nanoclusters (AuNCs) is constructed for detecting activity of butyrylcholinesterase (BChE) in human serum. By using thiobutyrylcholine iodide (BTCh) as the substrate of BChE-catalyzed hydrolysis reaction, variation of fluorescence emission from AuNCs is employed as an indicator of BChE activity since one of the hydrolysis products, thiocholine (TCh), would influence the aggregation state of AuNCs and consequently led to the change of fluorescence quantum efficiency of AuNCs. It is interesting that there are two mechanisms working for the fluorescence emission of aggregated AuNCs: aggregation-induced emission enhancement (AIEE) and aggregation-caused quenching (ACQ) with the presence of TCh at very low and higher concentration levels, respectively. Although both of these mechanisms can be utilized for sensing BChE, their opposite influence on the fluorescence emission of aggregated AuNCs should be worthy of attention, especially in the process of developing fluorescence methods for detecting trace targets by using AuNCs. In order to eliminate the fluctuation of fluorophotometer, SiQDs is chosen as the fluorophore to develop by ratiometric fluorescence methods in this work. Additionally, obvious aggregation of AuNCs induces significant decrease of inner filter effect (IFE) on the fluorescence emitted from SiQDs, while mild aggregation of AuNCs demonstrates little IFE. The linear ranges for detecting activity of BChE are 0.004 - 0.05 U/L and 0.5 - 20 U/L by ratiometric fluorometry based on the AIEE and ACQ, respectively. The very different responses originated from AIEE and ACQ of AuNCs would respectively make their own contributions to the determination of BChE activities at very low or high levels, which facilitate the developments of enhanced or quenched fluorescence methods. However, the detection of BChE activities at medium levels might suffer from the combination of AIEE and ACQ with ambiguous fractions. Therefore, it must be careful during the processes of developing and applying fluorescence methods based on the AIEE and ACQ of AuNCs, as well as the process of evaluating their analytical performance.

Tumor diagnosis using carbon-based quantum dots: Detection based on the hallmarks of cancer

Carbon-based quantum dots (CQDs) have been shown to have promising application value in tumor diagnosis. Their use, however, is severely hindered by the complicated nature of the nanostructures in the CQDs. Furthermore, it seems impossible to formulate the mechanisms involved using the inadequate theoretical frameworks that are currently available for CQDs. In this review, we re-consider the structure-property relationships of CQDs and summarize the current state of development of CQDs-based tumor diagnosis based on biological theories that are fully developed. The advantages and deficiencies of recent research on CQDs-based tumor diagnosis are thus explained in terms of the manifestation of nine essential changes in cell physiology. This review makes significant progress in addressing related problems encountered with other nanomaterials.

Chiral Aggregation-Induced Emission Carbon Dot-Based Multicolor and Near-Infrared Circularly Polarized Delayed Fluorescence via a Light-Harvesting System

Circularly polarized luminescence (CPL) materials are the research frontier of chiral luminescence. As a kind of luminescent carbon material, carbon dots (CDs) are expected to become excellent candidates for the construction of CPL materials. However, the construction of CD-based circularly polarized afterglow emission, especially multicolor and near-infrared emission, remains a great challenge due to aggregation-caused quenching and the instability of triplet excitons. In this work, we synthesized chiral CDs with aggregation-induced emission using dithiosalicylic acid and l/d-arginine as precursors through a one-step solvothermal method. Notably, the CDs exhibit green delayed fluorescence (DF) in poly(vinyl alcohol) films. Furthermore, multicolor and near-infrared circularly polarized delayed fluorescence is successfully realized via engineering a chiral light-harvesting system in which the CDs with green DF emission act as energy donors and fluorescent dyes with emission colors ranging from yellow to the near infrared serve as energy acceptors.

Carbon Quantum Dots for Long-Term Protection against UV Degradation and Acidification in Paper-Based Relics

Paper-based cultural relics constitute a significant and invaluable part of human civilization and cultural heritage. However, they are highly vulnerable to environmental factors such as ultraviolet (UV) photodegradation and acidification degradation, posing substantial threats to their long-term preservation. Carbon quantum dots (CQDs), known for their outstanding optical properties, high water solubility, and good safety, offer a promising solution for slowing down UV damage and acidification of paper-based relics during storage and transportation. Herein, we propose a feasible strategy for the simple preparation of CQDs with high dispersion stability, excellent UV absorption, room-temperature phosphorescence, and photostability for the safety protection of paper. Accelerated aging experiments were conducted using UV and dry-heat aging methods on both CQD-protected paper and unprotected paper, respectively, to evaluate the effectiveness of CQD protection. The results demonstrate a slowdown in both the oxidation and acid degradation processes of the protected paper under both UV-aging and dry-heat aging conditions. Notably, CQDs with complex luminescence patterns of both fluorescence and room-temperature phosphorescence also endue them as enhanced optical anticounterfeiting materials for multifunctional paper protection. This research provides a new direction for the protection of paper-based relics with emerging carbon nanomaterials.

Novel solution and solid-state emissive long-wavelength carbon dots for water sensing and white LED applications

Carbon dots (CDs) are among the most popular nanomaterials due to their remarkable fluorescent and electronic properties, as well as their good biocompatibility and low cytotoxicity. Currently, CDs with aggregation-induced emission (AIE) are relatively rare and have become a significant research hotspot. This is because most conventional CDs suffer from severe quenching in a solid state. Herein, novel CDs with both solution and solid-state emissions were obtained using a facile one-step hydrothermal synthesis. Specifically, the CDs exhibit yellow solvent-dependent fluorescence in solution state (λem = 580 nm) and red AIE emission in solid state (λem = 640 nm). CDs powder is utilized as a red phosphor for light-emitting diode (LED). The resulting fabricated white LEDs (WLEDs) demonstrate good performance metrics, including a Color Rendering Index (CRI) of 89.5, Correlated Color Temperature (CCT) of 3876 K, and commission Internationale d'Éclairage (CIE) coordinates of (0.350, 0.331). Furthermore, the solvent-dependent phenomenon observed in AIE-CDs can be exploited to apply their solution as a highly sensitive fluorescence sensor for quantitatively detecting amounts of water in various organic solvents. The method offers both high accuracy and sensitivity, with R2 values varying from 0.853 to 0.994 and a low detection limit ranging from 0.296 to 3.23 % across a wide linear range. This inherent versatility makes the CDs suitable for a wide range of applications, including sensing and LED devices.

The emergence and prospects of carbon dots with solid-state photoluminescence for light-emitting diodes

The significant features of carbon dots (CDs), such as bright and tunable photoluminescence, high thermal stability, and low toxicity, endow them with tremendous potential for application in next generation optoelectronics. Despite great progress achieved in the design of high-performance CDs so far, the practical applications in solid-state lighting and displays have been retarded by the aggregation-caused quenching (ACQ) effect ascribed to direct π-π interactions. This review provides a comprehensive overview of the recent progress made in solid-state CD emitters, including their synthesis, optical properties and applications in light-emitting diodes (LEDs). Their triplet-excited-state-involved properties, as well as their recent advances in phosphor-converted LEDs and electroluminescent LEDs, are mainly reviewed here. Finally, the prospects and challenges of solid-state CD-based LEDs are discussed with an eye on future development. We hope that this review will provide critical insights to inspire new exciting discoveries on solid-state CDs from both fundamental and practical standpoints so that the realization of their potential in optoelectronic areas can be facilitated.

Two-Dimensional Porphyrinic Metal-Organic Framework Composites as a Photocatalytic Platform for Chemoselective Hydrogenation

Chemoselective hydrogenation with high efficiency under ambient conditions remains a great challenge. Herein, an efficient photocatalyst, the 2D porphyrin metal-organic framework composite AmPy/Pd-PPF-1(Cu), featuring AmPy (1-aminopyrene) sitting axially on a paddle-wheel unit, has been rationally fabricated. The 2D AmPy/Pd-PPF-1(Cu) composite acts as a photocatalytic platform, promoting the selective hydrogenation of quinolines to tetrahydroquinolines with a yield up to 99%, in which ammonia borane serves as the hydrogen donor. The AmPy molecules coordinated on a 2D MOF not only enhance the light absorption capacity but also adjust the layer spacing without affecting the network structure of 2D Pd-PPF-1(Cu) nanosheets. Through deuterium-labeling experiments, in situ X-ray photoelectron spectroscopy, electron paramagnetic resonance studies, and density functional theory calculations, it is disclosed that Cu paddle-wheel units in 2D AmPy/Pd-PPF-1(Cu) nanosheets behave as the active site for transfer hydrogenation, and metalloporphyrin ligand and axial aminopyrene molecules can enhance the light absorption capacity and excite photogenerated electrons to Cu paddle-wheel units, assisting in photocatalysis.

One-step hydrothermal method synthesized pH-dependent carbon dots for multistage anti-counterfeiting

Work to combat counterfeiting has always been crucial to defending the interests of the public. The usual anti-counterfeiting marks are now fundamental and easy to imitate. Therefore, it is more beneficial to anti-counterfeiting work to develop an anti-counterfeiting mark with more variations to make forgery more difficult. Due to its exceptional stability and fluorescence variability, carbon dots (CDs), a newly developed fluorescent material, offer a wide range of potential applications in anti-counterfeiting. However, there currently needs to be more CD applications in multi-level anti-counterfeiting, and additional issues include high cost and environmental contamination. Therefore, considering the problems of green environmental protection and cost, CDs with excellent green (530 nm) and blue (475 nm, 486 nm) luminescence properties were prepared by a one-step reaction of m-phenylenediamine and glucose. The average fluorescence lifespan is longer than 5 ns, and the optimal quantum yield can reach 37%. Due to the large number of protonated amino groups and surface carboxyl functional groups, the prepared carbon dots exhibit green and blue fluorescence emission modes under acidic and alkaline conditions, respectively. Based on this situation, we produced CD ink and successfully used it for multi-level anti-counterfeiting.

Lemon-derived carbon dots as antioxidant and light emitter in fluorescent films applied to nanothermometry

The design of luminescent nanomaterials for the development of nanothermometers with high sensitivity and free of potentially toxic metals has developed in several fields, such as optoelectronics, sensors, and bioimaging. In addition, luminescent nanothermometers have advantages related to non-invasive measurement, with their wide detection range and high spatial resolution at the nano/microscale. Our study is the first, to our knowledge, to demonstrate a detailed study of a fluorescent film (Film-L) thermal sensor based on carbon dots derived from lemon bagasse extract (CD-L). The CD-L properties were explored as an antioxidant agent; their cytotoxicity was evaluated by using a human non-tumoral skin fibroblast (HFF-1) cell line from an MTT assay. The CD-L were characterized by HRTEM, DLS, FTIR, UV-VIS, and fluorescence spectroscopy. These confirmed their particle size distribution below 10 nm, graphitic structure in the core and surface organic groups, and strong blue emission. The CD-L showed cytocompatibility behavior and scavenging potential reactive species of biological importance: O2•- and HOCl, with IC50 of 276.8 ± 4.0 and 21.6 ± 0.7, respectively. The Film-L emission intensities (I425 nm) are temperature-dependent in the 298 to 333 K range. The Film-L luminescent thermometer shows a maximum relative thermal sensitivity of 2.69 % K-1 at 333 K.

Dye-Derived Red-Emitting Carbon Dots for Lasing and Solid-State Lighting

Carbon dots are carbon-based nanoparticles renowned for their intense light-emitting capabilities covering the whole visible light range. Achieving carbon dots emitting in the red region with high efficiency is extremely relevant due to their huge potential in biological applications and in optoelectronics. Currently, photoluminescence in such an energy interval is often associated with polyheterocyclic molecular domains forming during the synthesis that, however, present low emission efficiency and issues in controlling the optical features. Here, we overcome these problems by solvothermally synthesizing carbon dots starting from Neutral Red, a common red-emitting dye, as a molecular precursor. As a result of the synthesis, such molecular fluorophore is incorporated into a carbonaceous core while retaining its original optical properties. The obtained nanoparticles are highly luminescent in the red region, with a quantum yield comparable to that of the starting dye. Most importantly, the nanoparticle carbogenic matrix protects the Neutral Red molecules from photobleaching under ultraviolet excitation while preventing aggregation-induced quenching, thus allowing solid-state emission. These advantages have been exploited to develop a fluorescence-based color conversion layer by fabricating polymer-based highly concentrated solid-state carbon dot nanocomposites. Finally, the dye-based carbon dots demonstrate both stable Fabry-Perot lasing and efficient random lasing emission in the red region.

Communicating Supraparticles to Enable Perceptual, Information-Providing Matter

Materials are the fundament of the physical world, whereas information and its exchange are the centerpieces of the digital world. Their fruitful synergy offers countless opportunities for realizing desired digital transformation processes in the physical world of materials. Yet, to date, a perfect connection between these worlds is missing. From the perspective, this can be achieved by overcoming the paradigm of considering materials as passive objects and turning them into perceptual, information-providing matter. This matter is capable of communicating associated digitally stored information, for example, its origin, fate, and material type as well as its intactness on demand. Herein, the concept of realizing perceptual, information-providing matter by integrating customizable (sub-)micrometer-sized communicating supraparticles (CSPs) is presented. They are assembled from individual nanoparticulate and/or (macro)molecular building blocks with spectrally differentiable signals that are either robust or stimuli-susceptible. Their combination yields functional signal characteristics that provide an identification signature and one or multiple stimuli-recorder features. This enables CSPs to communicate associated digital information on the tagged material and its encountered stimuli histories upon signal readout anywhere across its life cycle. Ultimately, CSPs link the materials and digital worlds with numerous use cases thereof, in particular fostering the transition into an age of sustainability.

An all-in-one nanoprinting approach for the synthesis of a nanofilm library for unclonable anti-counterfeiting applications

In addition to causing trillion-dollar economic losses every year, counterfeiting threatens human health, social equity and national security. Current materials for anti-counterfeiting labelling typically contain toxic inorganic quantum dots and the techniques to produce unclonable patterns require tedious fabrication or complex readout methods. Here we present a nanoprinting-assisted flash synthesis approach that generates fluorescent nanofilms with physical unclonable function micropatterns in milliseconds. This all-in-one approach yields quenching-resistant carbon dots in solid films, directly from simple monosaccharides. Moreover, we establish a nanofilm library comprising 1,920 experiments, offering conditions for various optical properties and microstructures. We produce 100 individual physical unclonable function patterns exhibiting near-ideal bit uniformity (0.492 ± 0.018), high uniqueness (0.498 ± 0.021) and excellent reliability (>93%). These unclonable patterns can be quickly and independently read out by fluorescence and topography scanning, greatly improving their security. An open-source deep-learning model guarantees precise authentication, even if patterns are challenged with different resolutions or devices.

Construction of composite films using carbon nanodots for blocking ultraviolet light from the Sun

Carbon nanodots (CNDs) which demonstrate concentration-dependent emission and have a photoluminescence quantum yield of 45% were designed. Transparent CND-containing composite films (CND-films), obtained by combining the CNDs with polyvinyl alcohol in different proportions, were shown to block the UV component of sunlight. Whereas the pure PVA film could not block UV light, the ability of CND-films to block UV light could be adjusted by altering the proportion of CNDs in the film. The larger the proportion of CNDs, the greater the extent of UV blocking. CND-film containing 32 wt% CNDs completely blocked UV light (≤400 nm) from sunlight, without affecting the transmission of visible light (>800 nm). The ability of the CND-films to block the UV component of sunlight was investigated using a commercially available UV-induced color change card, which confirmed that the capacity of the CND-films to block UV light could be adjusted by altering the proportion of CNDs in the film. This study shows that CNDs with concentration-dependent long wavelength emission characteristics can be used as optical barrier units for the preparation of materials to block high-energy short wavelength light.

Ensemble and single-particle level fluorescent fine-tuning of carbon dots via positional changes of amines toward "supervised" oral microbiome sensing

Significance

Carbon dots (CDs) have attracted a host of research interest in recent years mainly due to their unique photoluminescence (PL) properties that make them applicable in various biomedical areas, such as imaging and image-guided therapy. However, the real mechanism underneath the PL is a subject of wide controversy and can be investigated from various angles.

Aim

Our work investigates the effect of the isomeric nitrogen position as the precursor in the synthesis of CDs by shedding light on their photophysical properties on the single particles and ensemble level.

Approach

To this end, we adopted five isomers of diaminopyridine (DAP) and urea as the precursors and obtained CDs during a hydrothermal process. The various photophysical properties were further investigated in depth by mass spectroscopy. CD molecular frontier orbital analyses aided us in justifying the fluorescence emission profile on the bulk level as well as the charge transfer processes. As a result of the varying fluorescent responses, we indicate that these particles can be utilized for machine learning (ML)-driven sensitive detection of oral microbiota. The sensing results were further supported by density functional theoretical calculations and docking studies.

Results

The generating isomers have a significant effect on the overall photophysical properties at the bulk/ensembled level. On the single-particle level, although some of the photophysical properties such as average intensity remained the same, the overall differences in brightness, photo-blinking frequency, and bleaching time between the five samples were conceived. The various photophysical properties could be explained based on the different chromophores formed during the synthesis. Overall, an array of CDs was demonstrated herein to achieve ∼ 100 % separation efficacy in segregating a mixed oral microbiome culture in a rapid (< 0.5    h ), high-throughput manner with superior accuracy.

Conclusions

We have indicated that the PL properties of CDs can be regulated by the precursors' isomeric position of nitrogen. We emancipated this difference in a rapid method relying on ML algorithms to segregate the dental bacterial species as biosensors.

Magnetic Polaron States in Photoluminescent Carbon Dots Enable Hydrogen Peroxide Photoproduction

Photoactivation of aspartic acid-based carbon dots (Asp-CDs) induces the generation of spin-separated species, including electron/hole (e- /h+ ) polarons and spin-coupled triplet states, as uniquely confirmed by the light-induced electron paramagnetic resonance spectroscopy. The relative population of the e- /h+ pairs and triplet species depends on the solvent polarity, featuring a substantial stabilization of the triplet state in a non-polar environment (benzene). The electronic properties of the photoexcited Asp-CDs emerge from their spatial organization being interpreted as multi-layer assemblies containing a hydrophobic carbonaceous core and a hydrophilic oxygen and nitrogen functionalized surface. The system properties are dissected theoretically by density functional theory in combination with molecular dynamics simulations on quasi-spherical assemblies of size-variant flakelike model systems, revealing the importance of size dependence and interlayer effects. The formation of the spin-separated states in Asp-CDs enables the photoproduction of hydrogen peroxide (H2 O2 ) from water and water/2-propanol mixture via a water oxidation reaction.

Single-particle dispersion of carbon dots in the nano-hydroxyapatite lattice achieving solid-state green fluorescence

Carbon dots (CDs), as new carbon nanomaterials, have potential applications in multiple fields due to their superior optical properties, good biocompatibility, and easy preparation. However, CDs are typically an aggregation-caused quenching (ACQ) material, which has a huge limitation on the practical application of CDs. To solve this problem, in this paper, CDs were prepared by the solvothermal method using citric acid and o-phenylenediamine as precursors and dimethylformamide as solvent. Then using CDs as nucleating agents, solid-state green fluorescent CDs were synthesized by in situ growth of nano-hydroxyapatite (HA) crystals on the surface of CDs. The results show that CDs are stably dispersed single-particlely in the form of bulk defects in the nano-HA lattice matrices with a dispersion concentration of 3.10%, and solid-state green fluorescence of CDs is achieved with a stable emission wavelength peak position near 503 nm, which provides a new solution to the ACQ problem. CDs-HA nanopowders were further used as LED phosphors to obtain bright green LEDs. In addition, CDs-HA nanopowders showed excellent performance in cell imaging (mBMSCs and 143B) applications, which provides a new scheme for further applications of CDs in the field of cell imaging and even in vivo imaging.

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.

One-pot synthesis of nitrogen-doped carbonized polymer dots with tunable emission for multicolor light-emitting diodes

Carbonized polymer dots (CPDs) have highly potential application value in the field of optoelectronic devices due to their preferable stability, excellent optical properties and low cost. Here, the nitrogen-doped carbonized polymer dots (HNCDs) with self-quenching-resistant fluorescence were prepared via a simple solvothermal method with citric acid, urea and 2-hydroxyethyl methacrylate (HEMA) as raw materials. The structure and optical properties of the HNCDs have been explored in detail by various contrast experiments. The results show that HEMA form the poly(HEMA) to modify on the surface of carbonized core, which can overcome the quenching effect of carbonized core. The nitrogen doping is crucial for the red shift emission of solid-state HNCDs. Furthermore, the HNCDs exhibit concentration-dependent emission and excellent compatibility with silicone sol, which lead to their emission red shifted from blue to red with increasing concentration. The HNCDs were further applied to construct the light-emitting diodes (LEDs), and the multicolor LEDs ranging from blue to red can be prepared by simply varying the type of chips and adjusting the concentration of HNCDs in encapsulating material.

Understanding the aggregation of excitation wavelength independent emission of amphiphilic carbon dots for bioimaging and organic acid sensing

Herein, excitation wavelength-independent, tunable emissive and amphiphilic CDs with high quantum yield were synthesized by a low-temperature oxidation method employing banana peel waste as a carbon source. These CDs showed longer wavelength emissions (green to yellow) independent of the excitation wavelength when dispersed in different polar to non-polar solvents. The quantum yields of the same CDs were 9-32% in different solvent polarities for different emissions. On the other hand, a large stokes-shifted emission (∼9606 cm^-1) was observed for CDs in the non-polar and weak polar solvents. The particle size of CDs increases from a hydrophobic to a hydrophilic environment with the change in emission colour from yellow to green. A polar and a non-polar host matrix were used to overcome the limitation of aggregation-caused quenching of CDs in the solid state to obtain bright emissions. These CDs were potentially used for naked-eye detection of trifluoroacetic acid (TFA) by changing the emission colour from yellow to orange under UV 365 nm. Sensing of TFA was also shown reversibly switch emission colour and average lifetime for multiple cycles. Additionally, the highly emissive CDs show negligible cytotoxicity in 3T3 fibroblast cells, indicating possible bioimaging applications in 3T3 cells.

Blue, Yellow, and Red Carbon Dots from Aromatic Precursors for Light-Emitting Diodes

In this work, multicolor fluorescent carbon dots with red (R-CDs), yellow (Y-CDs), and blue (B-CDs) emissions were prepared by choosing proper aromatic precursors with different amounts of benzene rings through a simple solvothermal method. The characterization showed that the prepared carbon dots were spherical with a size under 10 nm, rich surface functional groups, and good stability. The emission wavelengths were located at 440, 530, and 580 nm under the excitation of 370 nm. The relative fluorescence quantum yield (QY) of R-CDs, Y-CDs, and B-CDs was 11%, 59%, and 33%, respectively. The related characterization demonstrated that the redshift in the photoluminescence was caused by the synergistic effect of the increasing graphitic nitrogen content, quantum size effect and surface oxidation state. By mixing the three prepared CDs into a PVA matrix, the transparent and flexible films produced relucent blue, yellow, and red emissions under 365 nm UV light, and solid-state quenching was effectively avoided. LEDs were fabricated by using B-CDs, Y-CDs, and R-CDs/PVA with a semiconductor chip. These CDs-based LEDs produced bright blue, yellow, and red light with CIE color coordinates of (0.16, 0.02), (0.38, 0.58), and (0.50, 0.49) were successfully manufactured utilizing the prepared blue, yellow and red multicolor carbon dots as the solid luminescent materials. The results showed that the synthesized CDs can be potentially applied in multi-color monitors as a promising candidate for light-emitting diodes (LEDs). This work blazes a novel trail for the controllable preparation of multicolor fluorescent carbon dots.

A Molecular Engineering Strategy for Achieving Blue Phosphorescent Carbon Dots with Outstanding Efficiency above 50

Highly efficient emission has been a long-lasting pursuit for carbon dots (CDs) owing to their enormous potential in optoelectronic applications. Nevertheless, their room-temperature phosphorescence (RTP) performance still largely lags behind their outstanding fluorescence emission, especially in the blue spectral region. Herein, high-efficiency blue RTP CDs have been designed and constructed via a simple molecular engineering strategy, enabling CDs with an unprecedented phosphorescence quantum efficiency of to 50.17% and a long lifetime of 2.03 s. This treating route facilitates the formation of high-density (n, π*) configurations in the CD π-π conjugate system through the introduction of abundant functional groups, which can evoke a strong spin-orbit coupling and further promote the intersystem crossing from singlet to triplet excited states and radiative recombination from triplet excited states to ground state. With blue phosphorescent CDs as triplet donors, green, red, and white afterglow composites are successfully fabricated via effective phosphorescence Förster resonance energy transfer. Importantly, the color temperature of the white afterglow emission can be widely and facilely tuned from cool white to pure white and warm white. Moreover, advanced information encryption, light illumination, and afterglow/dynamic visual display have been demonstrated when using these multicolor-emitting CD-based afterglow systems.

Solid-State Fluorescent Carbon Dots with Unprecedented Efficiency from Visible to Near-Infrared Region

Developing solid-state luminescent materials with bright long-wavelength emissions is of considerable practical importance in light-emitting diodes (LEDs) but remains a formidable challenge. Here, a novel structure engineering strategy is reported to realize solid-state fluorescence (FL)-emitted carbon dots (CDs) from visible to near-infrared region. This is the first report of such an extended wavelength emission of self-quenching-resistant solid-state CDs. Notably, the quantum yields of these CDs are remarkably improved up to 67.7%, which is the highest value for solid-state CDs. The surface polymer chains of CDs can efficiently suppress the conjugated sp² carbon cores from π-π stacking inducing aggregation caused FL quenching, and the redshift of FL emissions is attributed to narrowing bandgap caused by an enlarged sp² carbon core. Using these CDs as conversion phosphors, the fabrication of white LEDs with adjustable correlated color temperatures of 1882-5019 K is achieved. Moreover, a plant growth LED device is assembled with a blue-LED chip and deep-red/near-infrared-emitted CDs. Compared with sunlight and white LEDs, the peanuts irradiated by plant growth LED lamp show higher growth efficiency in terms of branches and leaves. This work provides high-quality solid-state CD-based phosphors for LED lighting sources that are required for diverse optoelectronic applications.

Growth of carbon dots in nanoporous silica glasses for highly enhanced dual-wavelength emission

Solid-state carbon dots (CDots) have great potential applications in photonics and optoelectronic devices due to their excellent optical properties, such as broad absorption bands, and tunable photoluminescence wavelengths. However, owing to the aggregation-induced quenching and thermal quenching effect, it is a challenge to achieve strong luminescent solid-state CDots with excellent thermal stability. Herein, solid-state CDots were designed and fabricated using a triple confinement nanoporous glass. The triple confinement in nanoporous glass by a highly rigid network, stable covalent bonding, and 3D spatial restriction efficiently inhibited the Föster resonance energy transfer of the CDots in the solid-state and highly confined the CDots in the nanopores and nanochannels of the nanoporous glass. The as-designed triple confined solid-state CDots exhibit dual emission wavelengths at 448 nm and 638 nm, 51 times enhanced photoluminescence intensity, and exceptional thermal stability up to 400 °C. This work provides design principles and a universal strategy to construct dual emission fluorescence materials with high photoluminescence intensity, and high thermal stability for promising applications.

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.

The Advance and Critical Functions of Energetic Carbon Dots in Carbon Dioxide Photo/Electroreduction Reactions

As a unique carbon-based nano material, carbon dots (CDs) have attracted great attention because of their special structures and properties, and have been widely used in various fields, such as bio-imaging technology, catalyst design, pollutant degradation, chemical analysis, clean energy development and so on. CDs are used as catalysts or cocatalysts for multiple energy conversion reactions due to their advantages of valid visible light utilization, fast transmission of charge carriers, excellent catalytic activity, and good electrical conductivity. This review first summarizes the basic structure and properties of CDs. The advance and critical functions of energetic CDs in carbon dioxide photo/electroreduction reactions are discussed in detail. Due to the excellent optical absorption, electron transfer properties and good conductivity of CDs, they can enhance catalytic activity and stability effectively. In the end, the existing problems and future development opportunities of CDs-based catalysts in CO₂ reduction reaction are proposed and outlined.

Electrochemical control of emission enhancement in solid-state nitrogen-doped carbon quantum dots

Because of their excellent optical and electrical properties, doped carbon quantum dots (CQDs) are expected to be used in novel film optoelectronic devices such as light-emitting diodes and solar cells. However, these device advancements are currently hindered by the elusive photophysical process of doped CQDs in solid-state films. Here, the optical properties of nitrogen-doped CQD (N-CQD) films are studied using spectro-electrochemical (SEC) methods. A distinctive photoluminescence (PL) enhancement phenomenon is observed, in which the PL intensity of the N-CQD film can be increased in both positive and negative electrochemical potential sweeps. The effect of positive potential on PL enhancement is greater (∼340% at +1.4 V), while that of negative potential is slightly weaker (∼10% at -1.4 V). To the best of our knowledge, no similar brightening process has been reported in all previous SEC studies on a variety of QDs, wherein the emission intensity can only exhibit enhancement under positive or negative potential at most. We propose that the above PL brightening is related to the weakened π-π stacking effect after electrochemical charge injection and nitrogen doping plays a crucial role in it. Finally, a low hysteresis reversible electrochemistry regulation of the PL spectrum can be achieved by increasing electrolyte fluidity with argon gas bubbling to reduce local charge aggregation.

Carbon Nanodots with Nearly Unity Fluorescent Efficiency Realized via Localized Excitons

Carbon nanodots (CDs) have emerged as an alternative option for traditional nanocrystals due to their excellent optical properties and low toxicity. Nevertheless, high emission efficiency is a long-lasting pursuit for CDs. Herein, CDs with near-unity emission efficiency are prepared via atomic condensation of doped pyrrolic nitrogen, which can highly localize the excited states thus lead to the formation of bound excitons and the symmetry break of the π-electron conjugation. The short radiative lifetimes (<8 ns) and diffusion lengths (<50 nm) of the CDs imply that excitons can be efficiently localized by radiative recombination centers for a defect-insensitive emission of CDs. By incorporating the CDs into polystyrene, flexible light-converting films with a high solid-state quantum efficiency of 84% and good resistance to water, heating, and UV light are obtained. With the CD-polymer films as light conversion layers, CD-based white light-emitting diodes (WLEDs) with a luminous efficiency of 140 lm W-1 and a flat-panel illumination system with lighting sizes of more than 100 cm2 are achieved, matching state-of-the-art nanocrystal-based LEDs. These results pave the way toward carbon-based luminescent materials for solid-state lighting technology.

Cation-π aggregation-induced white emission of moisture-resistant carbon quantum dots: a comprehensive spectroscopic study

Controlling mechanisms involved in the aggregation of carbon quantum dots (CQDs) can lead to new application developments for these quantum dot materials. In this study, an unusual aggregation-induced white emission of CQDs with strong intrinsic green emission is reported. Due to the deprotonation/protonation of the surface functional groups during the aggregation of CQDs induced by pH variations of the solution through the addition of sodium hydroxide, and hydrophobic interactions between CQDs, it results in the formation of aggregated CQDs through an avalanche-like process. Our results suggest that sodium hydroxide not only plays a critical role in the formation of strong cation-π interactions, but also polishes the surface of CQDs, leading to the formation of the aggregated CQDs. The aggregated CQDs present excellent dispersibility characteristics in water. Moreover, optical studies suggest a combined aggregation mechanism in the presence of both J-type and H-type aggregation monoliths involved in forming the aggregated CQDs. The findings obtained from the deconvolution of the as-synthesized CQDs can perceptively elucidate the cation-π aggregation process.

Preparation of Multicolour Solid Fluorescent Carbon Dots for Light-Emitting Diodes Using Phenylethylamine as a Co-Carbonization Agent

Carbon dots (CDs), as a new type of photoluminescent nanomaterial, have attracted extensive attention in various fields because of their unique luminescence properties. However, CDs will exhibit fluorescence quenching in the solid state or aggregate state, which limits their application. In this paper, a unique strategy is proposed to regulate solutions to achieve multicolour fluorescence of CDs in the solid state. We report the successful preparation of orange, green and blue solid fluorescent CDs using citric acid, urea and phenylethylamine as precursors and methanol, ethanol and water as solvents, respectively. The solid-state fluorescence of CDs may be caused by the linkage of the phenylethyl structure to the surface of CDs during formation, which effectively disperses the CDs and prevents π-π interactions between graphitized nuclei. Meanwhile, multicolour solid fluorescent CDs are realized by adjusting the solvent in the preparation process. Based on the excellent fluorescence properties of CDs, orange, green and blue light-emitting diodes (LEDs) are prepared. A white LED (WLED) can be obtained by mixing the three colours of solid fluorescent CDs, which shows the application potential of CDs in display lighting equipment.

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.

Polymer-Induced Emission-Active Fluorine-Embedded Carbon Dots for the Preparation of Warm WLEDs with a High Color Rendering Index

Exploration of many strategies has continuously contributed to producing aggregation-induced red-emissive carbon dots (CDs). In this work, we designed fluorine-embedded (F-embedded) CDs from 1,2,4-triaminobenzene, thiourea, and ammonium fluoride (NH₄F) exhibiting polymer-induced emission (PIE). The PIE phenomenon of fluorescent CDs is obtained in poly(vinyl alcohol) (PVA), showing emissions at 611 and 617 nm in the dispersed and solid states, respectively. The CDs exhibited a red shift of 28 nm in the PVA solution because PVA hydroxyl groups formed a robust bridge-like H-bonding network between CDs. The fluorine embedded in CDs enhanced the H-bond affinity toward PVA. It showed that this H-bond restricted the coupling of CDs' surface states and inhibited the nonirradiation transfer. For the solid state, surface PVA chains eliminated the π-π interaction of the conjugated core and constructed a self-quenching resistance polymeric system around CDs. As a result, CDs showed an unexpected red shift of fluorescence emission in PVA. Furthermore, white light-emitting diodes (WLEDs) have a correlated color temperature (CCT) of 5232 K, and a high color rendering index of 95 has been fabricated by integrating the red- and green-emissive films over the UV LEDs. Interestingly, the as-synthesized CDs showed room temperature phosphorescence (RTP), which enabled us to employ the CDs in double-security protection. Simultaneously, CDs have been used in fingerprint detection.