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Carbon dots (CDs) emerge as promising luminescent materials for potential applications in optoelectronics on basis of their merits including low cost, eco-friendliness and strong, color-tunable photoluminescence (PL). However, the research on solid-state emissive CDs is still at the primary stage because of the aggregation-caused quenching (ACQ) of PL and their poor film-formation ability. In this work, we produce CDs with branched-polyethylenimine (b-PEI) chemically functionalized on the surfaces. The thus newly synthesized P-CDs successfully overcome the bottleneck of ACQ effect and display efficient red and NIR emission in aggregate state. Under the excitation of 520 nm, a strong red emission (maxima of 640 nm) with a high photoluminescence quantum yield (PLQY) of 21% was observed for the P-CDs in neat film. Moreover, this design strategy endows the P-CDs with good film-formation ability via solution spin-coating, which significantly increases its value for the film-based optoelectronic devices.

The construction of nanoplatforms with combined photothermal property and cascade enzymatic activities has become one of hot spots in anticancer research. However, the overheat of photothermal therapy (PTT) and the specific properties of tumor microenvironment (TME) greatly impaired the therapeutic efficiency. Herein, we rationally fabricated a virus-like SiOx/CeO2/VOx (SCV) nanoplatform for 1064 nm near-infrared (NIR) triggered mild-temperature PTT and nanozyme catalytic therapy. Firstly, the virus-like shape of SiOx/CeO2/VOx made it favorable for cell adhesion and had a better phagocytosis in cells, and the SCV generated effective PTT effect upon 1064 nm laser irradiation. Particularly, the produced VO2+ in TME could be used as a heat shock protein inhibitor to inhibit the expression of heat shock protein 60 (HSP60) to enhance the PTT efficiency. Moreover, SCV nanozyme exhibited obvious peroxidase-mimic (POD) catalytic activity, which could generate highly toxic free radical ion (•OH) under acidic conditions. The mild-temperature heat and •OH produced by enzymatic catalysis effectively blocked the tumor growth, verified firmly by the in vitro and in vivo tests. Our designed virus-like SCV nanozyme with POD mimic enzyme activity and mild photothermal effect may provide a new way of thinking for the combination therapy model.

Some practical strategies are introduced to improve the near-infrared photothermal conversion efficiency of CDs through approaches including size adjustment, self-assembly, surface engineering, element doping, and semiconductor coupling.

It is important to reveal the luminescence mechanisms of carbon dots (CDs). Herein, CDs with two types of optical centers are synthesized from citric acid in formamide by a solvothermal method, and show high photoluminescence quantum yield reaching 42%. Their green/yellow emission exhibits pronounced vibrational structure and high resistance toward photobleaching, while broad red photoluminescence is sensitive to solvents, temperature, and UV-IR. Under UV-IR, the red emission is gradually bleached due to the photoinduced dehydration of the deprotonated surface of CDs in dimethyl sulfoxide, while this process is hindered in water. From the analysis of steady-state and time-resolved photoluminescence and transient absorption data together with density functional theory calculations, the green/ yellow emission is assigned to conjugated sp

Recently, red emissive carbon dots (R-CDs) have drawn widespread attention on account of their desirable fluorescence properties and good biocompatibility. Despite great efforts, facile synthesis of R-CDs for cellular imaging remains challenging and the fluorescence mechanism of R-CDs is still elusive. Herein, p-phenylenediamine-derived R-CDs with excitation-independency were successfully obtained through a facile solvothermal approach together with proportional precipitation. The fluorescent solvatochromism of R-CDs is realized, while high polarity leads to higher degree of dipole interaction between R-CDs and different solvents, favoring for emissive red-shift. Furthermore, density functional theory is adopted to explore the optical and electronic characteristics of some polycyclic aromatic molecules. Among different configurations, pyridine nitrogen and carbonyl bonds could relatively increase the charge density and significantly narrow the band gap, which can provide a crucial theoretical basis for the precise preparation of R-CDs. Moreover, R-CDs possess favorable cellular imaging ability, which indicates their potential for a promising candidate as fluorescence probes in bioimaging.

The regulation of plant growth and developmental processes by carbon dots (CDs) has been frequently reported. However, little is known about how CDs are related to the yield and nutritional quality...

White-light-emitting carbon dots (CDs) with fluorescence/phosphorescence dual-emission features are of great importance for single-phase white-light-emitting diodes (WLEDs), but so far rather limited due to weak phosphorescence. Herein, a highly efficient white-light emissive CD-based material is developed by one-step heat treatment of lycorine hydrochloride and boric acid (BA). The prepared CD@BA powders show prominent fluorescence/phosphorescence dual-emission with extraordinarily high overall quantum yield (QY) of 46%, phosphorescence QY of 30% and a broad full width at half maximum over 180 nm. Doping of N and B atoms as well as the strong interaction between CDs and the BA matrix not only effectively prevents aggregation-induced quenching in the solid state, but also greatly promotes phosphorescence emission, leading to the emergence of an ultrabroad-band emission spectrum. Based on the unique dual-emissive performance of CD@BA powders, they are successfully applied to single-component WLEDs. This work provides a new strategy for mass production of efficient white-light emissive CD-based materials, which have promising applications for single-phase WLEDs.

Carbon dot (CD)-based room temperature phosphorescence (RTP) nanomaterials have constituted a research hotspot in multidisciplinary fields. Among the promising RTP CDs, fluorescence–phosphorescence dual emissive CDs (FP-CDs) are currently drawing enormous attention. Herein, highly efficient blue-green FP-CDs were easily prepared by a solvent-free pyrolysis treatment of hydroxyurea. The obtained FP-CDs showed high photoluminescence and phosphorescence quantum yields of 21% and 13%, respectively. Detailed experimental characterization revealed that the efficient dual-emission property is derived from the aromatic carbonyl groups at the edge of FP-CDs. Benefiting from the unique optical performance, FP-CDs exhibited good potential in anticounterfeiting and information encryption. This study offers a new strategy for developing dual-emission fluorescence–phosphorescence nanomaterials.

Drought stress is widespread worldwide, which severely restricts world food production. The antioxidant property of carbon dots (CDs) is promising for inflammation and disease treatment. However, little is known about the functions of CDs in the abiotic stress of plants, especially in drought-resistant fields. In this study, CDs were synthesized using cysteine and glucose by the hydrothermal method. The in vitro antioxidant capacity of CDs and the reactive oxygen species (ROS) scavenging capacity were evaluated. We speculate on the antioxidant mechanism of CDs by comparing size distribution, fluorescence spectra, elements, and surface functional groups of CDs before and after oxidation. Besides, we evaluated the effects of CDs on seed germination and seedling physiology under drought stress. Also, the responses of antioxidant CDs to long-term drought stress and subsequent recovery metabolism in tomato plants were evaluated. The results show that CDs accelerated the germination rate and the germination drought resistance index by promoting the water absorption of seeds. CDs enhanced the drought resistance of seedlings by improving the activity of peroxidase (POD) and superoxide dismutase (SOD). Moreover, CDs can activate the antioxidant metabolism activity and upregulate the expression of aquaporin (AQP) genes

Carbonized polymer dots (CPDs) have received tremendous attention during the last decade due to their excellent fluorescent properties and catalytic performance. Doping CPDs with transition metal atoms accelerates the local electron flow in CPDs and improves the fluorescent properties and catalytic performance of the CPDs. However, the binding sites and the formation mechanisms of the transition-metal-atom-doped CPDs remain inconclusive. In this work, Mn

The construction of nanoplatforms with combined photothermal properties and cascading enzymatic activities has become an active area of anticancer research. However, the overheating of photothermal therapy (PTT) and the specific properties of tumor microenvironment (TME) greatly impaired the therapeutic efficiency. Herein, we rationally fabricated a virus-like SiO

Lead halide perovskites have attracted tremendous attention because of their impressive optoelectronic properties. However, the toxicity of lead remains a bottleneck for further commercial development. Two-dimensional Ruddlesden-Popper tin-based perovskites are lead-free and more stable compared to their three-dimensional counterparts, which have great potential in the optoelectronic device field. Herein, we demonstrate high-quality two-dimensional phenylethylammonium tin-iodide perovskite (PEA2SnI4) thin films by using toluene as the antisolvent. Furthermore, the PeLED performance is greatly improved by replacing the PEAI spacer cation with 2-thiopheneethyllamine iodide (TEAI). As a result, a TEA-based PeLED device is achieved with a low turn-on voltage of 2.3 V, a maximum luminance of 322 cd m-2, and maximum external quantum efficiency of 0.62%, which are the highest efficiency and brightness for pure red (emission peak = 638 nm) tin-based PeLEDs to date.

Sustainable, environment-friendly phosphors produced from cheap and readily available precursor materials using green preparation processes are in high demand for lighting applications. Herein, a composite phosphor comprising carbon dots (CDs) and graphitic carbon nitride (g-C3N4) is prepared on a large scale from citric acid and urea in water, through a green microwave assisted in situ heating method. An optimized CDs@g-C3N4 composite with a 1 wt% loading of CDs shows a strong green emission under 410 nm excitation, with a photoluminescence quantum yield of 62% in the solid state. Using this composite as a phosphor in the color conversion layer, a white light emitting diode with a power efficiency of up to 42 lm W−1 is fabricated.

Cyan emissive sulfur dots with a record high photoluminescence (PL) quantum yield of 49.25% have been successfully prepared via a microwave-assisted top-down route. The PL enhancement induced by electrostatic repulsion of sulfite groups and steric hindrance of polyethylene glycol 400 (PEG-400) were investigated for the first time.

Along the line of offering surface modification strategies to tune emission properties of carbon dots (CDs), a co-crystallization strategy with cyanuric acid (CA) was developed to modulate the bandgap emissions of CDs and produce highly emissive solid composite CD-based materials. The original blue emission of the CDs changed to a green emission of the CDs@CA crystals, which showed a high photoluminescence quantum yield of 62% and room temperature phosphorescence. The CA molecules firmly bonded to the surface of the CDs and cannot be disrupted by polar solvents or temperature stimuli under ambient conditions, which influenced electron transitions of CDs leading to improved luminescence with excellent thermal stability both in solution and solid states.

Multifunctional solid-state luminescent materials are strongly desired in a wide variety of applications. In this work, green emissive carbon dots@montmorillonite (g-CDs@MMT) composites were synthesized based on green emissive carbon dots and MMT clays in a convenient method by embedding g-CDs into the MMT clays. Due to the confinement of g-CDs in the layered structure of the MMT clay matrix, g-CDs are uniformly dispersed in the resulting g-CDs@MMT solid-state composites. This efficiently prevents the aggregation-induced solid-state luminescence quenching of g-CDs, and a photoluminescence quantum yield of 11% could be achieved by the g-CDs@MMT composites under a 405 nm light. Additionally, the g-CDs@MMT composites exhibit low-toxicity, excellent thermal stability, photostability, resistance to organic solvents, and a small particle size. All of these advantages enable applications in fabricating white light-emitting diodes with different color temperatures, where the g-CDs@MMT composites are applied as the color conversion layer. Furthermore, by using the g-CDs@MMT composites as a fluorescence labeling marker, the latent fingerprint detection on a variety of object surfaces could be realized.

It is of a primary importance to realize the intrinsic emission from the inner carbogenic cores of carbon dots (CDs). In this work, CDs with three emission centers were synthesized by a microwave-assisted method using phloroglucinol as a precursor. The emission of these three centers has been identified as originating from molecular fluorophores, surface states of CDs, and the intrinsic CD core state. The emission from molecular fluorophores and from the surface state of CDs exhibited a weak photostability and could be photobleached as a result of UV laser irradiation. The emission from the intrinsic state of the inner carbogenic core has been found to be stable against photobleaching. On the basis of this difference in photostability, we demonstrate how the surface of CDs can be deoxidized under prolonged UV irradiation, resulting in a narrow intrinsic emission with a photoluminescence quantum yield of 17%.

Nitrogen-doped porous carbon has attracted great attention in lithium ion batteries (LIBs). Herein, new three-dimensional nitrogen-doped porous carbon frameworks (N-PCFs) doped with a nitrogen cont...

As a new type of luminescent material, carbon dots (CDs) have attracted increased attention for their superior optical properties in recent years. However, CDs generally suffer from aggregation-ind...

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.

Aggregation-induced luminescence quenching of carbon nanodots (CDs) is the main obstacle for their applications in solid-state light emitting devices. Herein, we developed a one-step synthesis of solid-state emissive CDs with surface aluminum-based polymerization by adding AlCl3 in citric acid and urea via a microwave-heating dehydration process. Due to the strong coordination ability of Al ions with N and O atoms, considerable steric hindrance of Al-based cross-linked polymerization was introduced on the surface of the CDs, which not only avoided aggregation of the green emissive carbon cores but also facilitated efficient energy transfer from the blue emissive polymerized surface to the green emissive carbon cores in aggregates, leading to enhanced green emissions with a photoluminescence quantum yield (PLQY) of 72.7% in the solid state.

Cancer immunotherapy based on carbon-quantum-dots (CQDs) has proven effective. The CQDs composited cancer cell (CM-cancer) exhibit robust customized immunogenicity, which can recruit macrophages and dendritic cells to effectively deliver the cancer antigens into lymph nodes to activate CD8+ T cells, and eventually leads to an anti-cancer immune response all over the body. The CM-cancer is not only able to inhibit primary tumors, but also clearly eliminate metastatic tumors. Our research demonstrates a promising personalized cancer immunotheraputic technology for potential clinical applications.

Cancer immunotherapy based on carbon-quantum-dot (CQD) modified cancer cells (CM-cancer) has proven effective. The CQDs non-distinctively modify the conformational structure of proteins by hydrogen bonding between the protein chains and the permeated CQDs via a thermal treatment. CM-cancer vaccines exhibit robust immunogenicity, which can recruit macrophages and dendritic cells to effectively deliver the cancer antigens into lymph nodes to activate CD8+ T cells, and eventually leads to an anti-cancer immune response all over the body. The CM-cancer vaccinations are not only able to inhibit primary tumors, but also clearly eliminate metastatic tumors. Our research demonstrates a promising personalized cancer immunotheraputic technology for potential clinical applications.

In this work, we report a successful extension of the family of light-emitting colloidal carbon nanostructures to a number of different shapes and morphologies, namely, carbon nanorolls (CNRs) and carbon nanobelts (CNBs). Near infrared (NIR)-emissive CNRs were synthesized via a solvothermal fusion of carbon dots (CDs) triggered by a dehydration process of their surface functional groups. They appear in a form of short cylinders, with diameters ranging from 20 to 40 nm and cylinder lengths ranging from 7 to 20 nm. In ethanol solution, CNRs have a maximum absorption peak at 665 nm and a NIR emission band extending from 650 to 800 nm, with a photoluminescence quantum yield of 9.2%. Intriguingly, the rolled structure of CNRs can be uncoiled under 655 nm laser irradiation (power density 1 W·cm-2) of their solution in ethanol, forming CNBs with a width of 7-20 nm and lengths reaching several hundreds of nanometers, which is accompanied by a considerably decreased absorption band at 665 nm and a decreased NIR emission. This unfolding is ascribed to the decrease of the strength of interlayer hydrogen bonding, owing to the photothermally induced dehydration and further carbonization of the CNRs. Alongside the decreased NIR emission, CNBs exhibit enhanced green and red emissions under UV and green light excitation, respectively, which allows us to demonstrate multiple-level luminescence encryptions on a paper stamped with CNR- and CNB-inks.

There has been a long standing debate on the luminescence origination from carbon nanodots (CDs). Herein, we report the solvent dependent piezochromism of CDs by diamond anvil cells experiment. Red- and blue-shift piezochromism were observed in CDs with N,N-dimethylformamide and water as pressure transmitting medium (PTM) with increasing pressure from atmospheric pressure to 25 GPa, which were related to increased π-π stacking and protic-solvent-induced surface chemical structural changes, respectively. Based on theoretical modeling and structural analysis of hydrothermally treated CDs (h-CDs), the reversible and irreversible piezochromism from green emission to blue emission with water as PTM was attributed to pressure induced enhanced intermolecular hydrogen bonding and addition reaction between water molecules and surface electron withdrawing groups on the CDs, respectively. The decreased electron withdrawing ability of the surface chemical structures of CDs further affects their intrinsic luminescence. This work provides a new understanding of the piezochromic luminescence origination from CDs, which is related to the surface related intrinsic luminescence.