Effects and mechanisms of proanthocyanidins-derived carbon dots on alleviating salt stress in rice by muti-omics analysis.

Carbon dots (CDs) with different structures were prepared by electrolysis (PE-CDs) and hydrothermal (PH-CDs) methods using proanthocyanidins as precursors. The smaller size and lower zeta potential enabled the PE-CDs treated rice seedlings to exhibit greater resistance to salt stress. The fresh weight of rice seedlings under salt stress was significantly increased by spraying CDs every other day for two weeks. PE-CDs treated group exhibited a faster electron transport rate, and the SOD activity and flavonoid content were 2.5-fold and 0.23-fold higher than those of the salt stress-treated group. Furthermore, the metabolomics and transcriptomics analysis revealed that the PsaC gene of photosystem I was significantly up-regulated under PE-CDs treatment, which accelerated electron transfer in photosystem I. The up-regulation of BX1 and IGL genes encoding indole synthesis allowed rice to enhance stress tolerance through tryptophan and benzoxazine biosynthesis pathways. These findings offer help in purposefully synthesizing CDs and boosting food production.

The afterglow of carbon dots shining in inorganic matrices.

Carbon dots (CDs) are a new type of quasi-spherical and zero-dimension carbon nanomaterial with a diameter less than 10 nm. They exhibit a broad absorption spanning from the ultraviolet (UV) to visible light regions and inspire growing interests due to their excellent performance. In recent years, it was identified that the CDs embedded in various inorganic matrices (IMs) can effectively activate afterglow emission by suppressing the nonradiative transitions of molecules and protecting the triplet excitons of CDs, which hold broad application prospects. Herein, recent advances in CDs@IMs are reviewed in detail, and the interaction and luminescence mechanisms between CDs and IMs are also summarized. We highlight the synthetic strategies of constructing composites and the roles of IMs in facilitating the applications of CDs in diverse areas. Finally, some directions and challenges of future research in this field are proposed.

Multicolor Afterglow from Carbon Dots: Preparation and Mechanism.

Carbon dots (CDs), as emerging long afterglow luminescent material, have attracted the attention of researchers and become one of the hot topics in long afterglow materials. In recent years, researchers have obtained a series of CDs-based long afterglow materials with different properties utilizing matrix-assisted and self-protective methods. To meet diverse application needs, the development of multicolor CDs-based long afterglow materials is a focus and challenge in this field. Most of the previously reported CDs-based long afterglow materials generally emit blue or green afterglow. Recently, some multicolor systems have been discovered, and the emission range can extend from ultraviolet to near-infrared. However, there is a lack of systematic and in-depth analysis regarding the preparation strategy and luminescence mechanism of multicolor afterglow from CDs-based long afterglow materials. Based on this, this review summarizes the preparation strategies of multicolor afterglow from raw materials and reaction parameters. Then, the luminescence mechanisms of multicolor afterglow are analyzed from seven factors, including carbonization degree, surface state, aggregation degree, temperature dependence, excitation dependence, multi-emission center, and energy transfer. Moreover, the applications of multicolor afterglow from CDs-based long afterglow materials are introduced. Finally, the problems and challenges in this field are discussed, and the future development directions are analyzed.

Dynamic Room Temperature Phosphorescence of Silane-Functionalized Carbon Dots Confining within Silica for Anti-Counterfeiting Applications.

Room temperature phosphorescent (RTP) materials with long-lived, excitation-dependent, and time-dependent phosphorescence are highly desirable but very hard to achieve. Herein, this work reports a rational strategy of multiple wavelength excitation and time-dependent dynamic RTP color by confining silane-functionalized carbon dots (CDs) in a silica matrix (Si-CDs@SiO2). The Si-CDs@SiO2 possesses unique green-light-excitation and a change in phosphorescence color from yellow to green. A slow-decaying phosphorescence at 500 nm with a lifetime of 1.28 s and a fast-decaying phosphorescence at 580 nm with a lifetime of 0.90 s are observed under 365 nm of irradiation, which originated from multiple surface triplet states of the Si-CDs@SiO2. Given the unique dynamic RTP properties, the Si-CDs@SiO2 are demonstrated for applications in fingerprint recognition and multidimensional dynamic information encryption. These findings will open an avenue to explore dynamic phosphorescent materials and significantly broaden their applications.

Pumpkin seed oil: a comprehensive review of extraction methods, nutritional constituents, and health benefits.

Pumpkin seed oil (PSO), a rich source of nutrients, is extracted from the seeds of different pumpkin varieties for food and medicines. This article aims to provide an evidence-based review of the literature and to explore the extraction technologies, nutritional properties, and biological activity of PSO. From previous literature, PSO contains a large proportion of unsaturated fatty acids, with linoleic acid as the main component, and an amount of tocopherol, phytosterol, and phenolic acids. Some differences in the yield, composition, and physicochemical properties of PSO can be associated with the pumpkin's cultivars and the extraction methods. Some novel technologies involved in supercritical fluid extraction, enzyme-assisted aqueous extraction, and ultrasound-assisted extraction have been replacing the conventional technologies gradually as promising methods for the safe, non-polluting, and effective recovery of PSO. This healthy vegetable oil was reported by several in vitro and in vivo studies to have potential protective roles in oxidative stress, inflammation, cancer, and cardiovascular diseases. © 2023 Society of Chemical Industry.

"Afterglow" Photodynamic Therapy Based on Carbon Dots Embedded Silica Nanoparticles for Nondestructive Teeth Whitening.

Teeth staining is a common dental health challenge in many parts of the world. Traditional teeth whitening techniques often lead to enamel damage and soft tissue toxicity due to the use of bioincompatible whitening reagents and continuous strong light irradiation. Herein, an "afterglow" photodynamic therapy (aPDT) for teeth whitening is proposed, which is realized by energy transition pathways of intersystem crossing. The covalent and hydrogen bonds formed by carbon dots embedded in silica nanoparticles (CDs@SiO2) facilitate the passage of energy through intersystem crossing (ISC), thereby extending the half-life of reactive oxygen species (ROS). The degradation efficiency of aPDT on dyes was higher than 95% in all cases. It can thoroughly whiten teeth by eliminating stains deep in the enamel without damaging the enamel structure and causing any tissue toxicity. This study illustrates the superiority of aPDT for dental whitening and the approach to exploring carbon-dots-based nanostructures in the treatment of oral diseases.

General Synthesis of Carbon Dot-Based Composites with Triple-Mode Luminescence Properties and High Stability.

Carbon dot (CD)-based luminescent materials have attracted great attention in optical anti-counterfeiting due to their excellent photophysical properties in response to ultraviolet-to-visible excitation. Hence, there is an urgent need for the general synthesis of CD-based materials with multimode luminescence properties and high stability; however, their synthesis remains a formidable challenge. Herein, CDs were incorporated into a Yb,Tm-doped YF3 matrix to prepare CDs@YF3:Yb,Tm composites. The YF3 plays a dual role, not only serving as a host for fixing rare earth luminescent centers but also functioning as a rigid matrix to stabilize the triplet state of the CDs. Under the excitation of 365 nm ultraviolet light and 980 nm near-infrared light, CDs@YF3:Yb,Tm exhibited blue fluorescence and green room-temperature phosphorescence of CDs and upconversion luminescence of Tm3+, respectively. Due to the strong protection of the rigid matrix, the stability of CDs@YF3:Yb,Tm is greatly improved. This work provides a general synthesis strategy for achieving multimode luminescence and high stability of CD-based luminescent materials and offers opportunities for their applications in advanced anti-counterfeiting and information encryption.

Improving Plant Photosynthesis through Light-Harvesting Upconversion Nanoparticles.

Nanotechnology is considered as an emerging effective means to augment plant photosynthesis. However, there is still a lot of work to be done in this field. Here, we applied the upconversion nanoparticles (UCNPs) on lettuce leaves and found that the UCNPs were able to transport into the lettuce body and colocalize with the chloroplasts. It was proved that UCNPs could harvest the near-infrared light of sunlight and increase the electron transfer rate in the photosynthesis process, thus increasing the photosynthesis rate. The gene expression analysis showed that more than 90% of gene expression in photosynthesis was upregulated. After spraying the UCNP solution on the leaves of lettuce and placing the lettuce under sunlight for 1 week, the wet/dry weight of the leaves increased by 53.33% and 45.71%, respectively. This nanoengineering of light-harvesting UCNPs may have great potential for applications in agriculture.

Carbon Dots in Hydroxy Fluorides: Achieving Multicolor Long-Wavelength Room-Temperature Phosphorescence and Excellent Stability via Crystal Confinement.

Carbon dots (CDs) have aroused widespread interest in the construction of room-temperature phosphorescent (RTP) materials. However, it is a great challenge to obtain simultaneous multicolor long-wavelength RTP emission and excellent stability in CD-based RTP materials. Herein, a novel and universal "CDs-in-YOHF" strategy is proposed to generate multicolor and long-wavelength RTP by confining various CDs in the Y(OH)xF3-x (YOHF) matrix. The mechanism of the triplet emission of CDs is related to the space confinement, the formation of hydrogen bonds and C-F bonds, and the electron-withdrawing fluorine atoms. Remarkably, the RTP lifetime of orange-emissive CDs-o@YOHF is the longest among the reported single-CD-matrix composites for emission above 570 nm. Furthermore, CDs-o@YOHF exhibited higher RTP performance at long wavelength in comparison to CDs-o@matrix (matrix = PVA, PU, urea, silica). The resulting CDs@YOHF shows excellent photostability, thermostability, chemical stability, and temporal stability, which is rather favorable for information security, especially in a complex environment.

In Situ Growth of High-Quality CsPbBr3 Quantum Dots with Unusual Morphology inside a Transparent Glass with a Heterogeneous Crystallization Environment for Wide Gamut Displays.

All-inorganic CsPbBr3 perovskite quantum dots (QDs) are considered to be one of the most promising green candidates for the new-generation backlight displays. The pending barriers to their applications, however, lie in their mismatching of the target window of green light, scalable production, susceptibility to the leaching of lead ions, and instability in harsh environments (such as moisture, light, and heat). Herein, high-quality CsPbBr3 QDs with globoid shapes and cuboid shapes were in situ crystallized/grown inside a well-designed glass to produce nanocomposites with peak emission at 526 nm, which not only exhibited photoluminescence quantum yields of 53 and 86% upon 455 and 365 nm excitation, respectively, but also have been imparted of high stability when they were submerged in water and exposed to heat and light. These characteristics, along with their lead self-sequestration capability and easy-to-scale preparation, can enable breakthrough applications for CsPbBr3 QDs in the field of wide color gamut backlit display. A high-performance backlight white LEDs was fabricated using the CsPbBr3 QDs@glass powder and K2SiF6:Mn4+ red phosphor, which shows a color gamut of ∼126% of the NTSC or 94% of the Rec. 2020 standards.

Carbon Dots with Intrinsic Bioactivities for Photothermal Optical Coherence Tomography, Tumor-Specific Therapy and Postoperative Wound Management.

Carbon dots (CDs) are considered as promising candidates with superior biocompatibilities for multimodel cancer theranostics. However, incorporation of exogenous components, such as targeting molecules and chemo/photo therapeutic drugs, is often required to improve the therapeutic efficacy. Herein, an "all-in-one" CDs that exhibit intrinsic bioactivities for bioimaging, potent tumor therapy, and postoperative management is proposed. The multifunctional CDs derived from gallic acid and tyrosine (GT-CDs) consist of a graphitized carbon core and N, O-rich functional groups, which endow them with a high near-infrared (NIR) photothermal conversion efficiency of 33.9% and tumor-specific cytotoxicity, respectively. A new imaging modality, photothermal optical coherence tomography, is introduced using GT-CDs as the contrast agent, offering the micrometer-scale resolution 3D tissue morphology of tumor. For cancer therapy, GT-CDs initiate the intracellular generation of reactive oxygen species in tumor cells but not normal cells, further induce the mitochondrial collapse and subsequent tumor cellular apoptosis. Combined with NIR photothermal treatment, synergistic antitumor therapy is achieved in vitro and in vivo. GT-CDs also promote the healing process of bacteria-contaminated skin wound, demonstrating their potential to prevent postoperative infection. The integrated theranostic strategy based on versatile GT-CDs supplies an alternative easy-to-handle pattern for disease management.

Construction of Carbon Dots with Color-Tunable Aggregation-Induced Emission by Nitrogen-Induced Intramolecular Charge Transfer.

As one of the most promising fluorescent nanomaterials, the fluorescence of carbon dots (CDs) in solution is extensively studied. Nevertheless, the synthesis of multicolor solid-state fluorescence (SSF) CDs is rarely reported. Herein, CDs with multicolor aggregation-induced emission are prepared using amine molecules, all of them exhibiting dual fluorescence emission at 480 nm (Em-1) and 580-620 nm (Em-2), which is related to the SS bonds of dithiosalicylic acid and the conjugated structure attached to CO/CN bonds, respectively. As a strong electron-withdrawing group, the increase of CN content makes dual-fluorescent groups on the surface of CDs produce push and pull electrons, which determines intramolecular charge transfer (ICT) between the double emission. With the increase in CN content from 35.6% to 58.4%, the ICT efficiency increases from 8.71% to 45.94%, changing the fluorescence of CDs from green to red. The increase of ICT efficiency causes fluorescence quantum yield enhancement by nearly five times and redshift of the fluorescence peak. Finally, based on the multicolor luminescence properties induced by the aggregation of CDs, pattern encryption and white-LED devices are realized. Based on the fat solubility and strong ultraviolet absorption characteristics of CDs, fingerprint detection and leaf anti-UV hazards are applied.

Near-Infrared-Excited Multicolor Afterglow in Carbon Dots-Based Room-Temperature Afterglow Materials.

Room-temperature afterglow (RTA) materials with long lifetime have shown tremendous application prospects in many fields. However, there is no general design strategy to construct near-infrared (NIR)-excited multicolor RTA materials. Herein, we report a universal approach based on the efficient radiative energy transfer that supports the reabsorption from upconversion materials (UMs) to carbon dots-based RTA materials (CDAMs). Thus, the afterglow emission (blue, cyan, green, and orange) of various CDAMs can be activated by UMs under the NIR continuous-wave laser excitation. The efficient radiative energy transfer ensured the persistent multicolor afterglow up to 7 s, 6 s, 5 s, and 0.5 s by naked eyes, respectively. Given the unusual afterglow properties, we demonstrated preliminary applications in fingerprint recognition and information security. This work provides a new avenue for the activation of NIR-excited afterglow in CDAMs and will greatly expand the applications of RTA materials.

Multiemissive Room-Temperature Phosphorescent Carbon Dots@ZnAl2O4 Composites by Inorganic Defect Triplet-State Energy Transfer.

Room-temperature phosphorescence (RTP) with carbon dots (CDs) can be exploited further if the mechanism of trap-state-mediated triplet-state energy transfer is understood and controlled. Herein, we developed an in situ calcination method for the preparation of a CDs@ZnAl2O4 composite material that exhibits unique UV and visible light-excitable ultra-broad-band RTP. The ZnAl2O4 matrix can protect the triplet emissions of CDs by the confinement effect and spin-orbit coupling. In addition, benefitting from the efficient energy transfer between the inorganic trap state and the triplet state of CDs, the special yellow to red RTP of CDs@ZnAl2O4 composites can be realized. A slow-decaying phosphorescence at 570 nm with a lifetime of 1.05 s and a fast-decaying phosphorescence at 400 nm with a lifetime of 0.41 s were observed with UV irradiation of 290 nm, which originated from the surface and core triplet states of CDs, respectively. Based on the unique RTP performance, anti-counterfeiting and information encryption were successfully realized using the CDs@ZnAl2O4 composites with LED light or UV light.

Red, orange, yellow and green luminescence by carbon dots: hydrogen-bond-induced solvation effects.

The mechanism of the solvation-dependent multicolor luminescence of carbon dots (CDs) is not clear, despite the fact that multicolor luminescent CDs have important applications in many fields. In this article, we report solvated chromogenic CDs with productivity of up to 57%. The luminescence of the CD particles exhibits a regular redshift in N,N-dimethylformamide (DMF), ethanol, water, and acetic acid. The redshift of the CDs may be ascribed to the linking of the CD surfaces to the solvent through hydrogen bonds (HB). Different surface level states are formed by HB between the surfaces of the CDs and the solvent, and differences in dispersion states lead to different energy resonance transfer (ETR) efficiencies. The CDs/B2O3 composite exhibits excellent fluorescence thermal stability, and it has also been used to manufacture white-light-emitting devices with a high color rendering index of 87. Additionally, the excellent solvation effects of the CDs have application prospects in the detection of the water content in organic solvents. Finally, the CDs are used to realize cell imaging and positioning, which has significant application prospects in biological fields.

Carbon dots as light converter for plant photosynthesis: Augmenting light coverage and quantum yield effect.

Carbon dots (CDs) with gradient-changed quantum yield (QY) were prepared by regulating the graphitic N and hydroxyl group contents. Then, the QY effect of CDs on plant photosynthesis was studied using chloroplasts and rice plants. After incubation for 2 h in the dark, CDs entered into the chloroplasts and converted ultraviolet radiation to photosynthetically active radiation. By this mechanism, CD1:0.2 (300 µg·mL-1) with a moderate QY of 46.42% significantly increased the photosynthetic activity of chloroplast (200 µg·mL-1) to reduce DCPIP and ferricyanide by 43.77% and 25.45%, respectively. After spraying on rice seedlings, CD1:0.2 (300 µg·mL-1) was evenly distributed in the leaves and resulted in maximum increases in the electron transport rate and photosynthetic efficiency of photosystem II by 29.81% and 29.88%, respectively. Furthermore, CD1:0.2 significantly increased the chlorophyll content and RuBisCO carboxylase activity of rice by 64.53% and 23.39%, respectively. Consequently, significant increases were observed in the growth of CD1:0.2-treated rice, including 18.99%, 64.31%, and 61.79% increases in shoot length, dry weights of shoot and root. These findings contribute to the exploitation of solar energy and agricultural production using CDs in the future.

Anchoring Carbon Nanodots onto Nanosilica for Phosphorescence Enhancement and Delayed Fluorescence Nascence in Solid and Liquid States.

Carbon nanodots (CDs) anchored onto inorganic supporter (amorphous nanosilica, SiO2 ) like a core-satellite structure have enhanced the room-temperature phosphorescence (RTP) intensity along with ultralong lifetime of 1.76 s. Special and quite stable structure should account for these superiorities, including hydrogen network, covalent bond, and trap-stabilized triplet-state excitons that are responsible for the generation of phosphorescence. These multiple effects have efficaciously protected CDs from being restrained by the external environment, providing such long-lived emission (LLE) that can subsist not only in powdery CDs-SiO2 but also coexist in aqueous solution, pushing a big step forward in the application prospects of liquid-state phosphorescence. Through construction of CDs-SiO2 compound, electron trap is reasoned between CDs and SiO2 by analyzing thermoluminescent glow curve. Electron trap can capture, store, and gradually release the electrons just like an electron transporter to improve the intersystem crossing (ISC) and reserved ISC, having provided the more stabilized triplet excitons, stronger and longer phosphorescence, and also triggered the formation of thermally activated delayed fluorescence (TADF), offering a new mechanism for exploiting LLE among CD-based field. Moreover, it is more beneficial to the formation of TADF as temperature increases, thus the afterglow color can change with the temperature.

Ultralong lifetime and efficient room temperature phosphorescent carbon dots through multi-confinement structure design.

Room temperature phosphorescence materials have inspired extensive attention owing to their great potential in optical applications. However, it is hard to achieve a room temperature phosphorescence material with simultaneous long lifetime and high phosphorescence quantum efficiency. Herein, multi-confined carbon dots were designed and fabricated, enabling room temperature phosphorescence material with simultaneous ultralong lifetime, high phosphorescence quantum efficiency, and excellent stability. The multi-confinement by a highly rigid network, stable covalent bonding, and 3D spatial restriction efficiently rigidified the triplet excited states of carbon dots from non-radiative deactivation. The as-designed multi-confined carbon dots exhibit ultralong lifetime of 5.72 s, phosphorescence quantum efficiency of 26.36%, and exceptional stability against strong oxidants, acids and bases, as well as polar solvents. This work provides design principles and a universal strategy to construct metal-free room temperature phosphorescence materials with ultralong lifetime, high phosphorescence quantum efficiency, and high stability for promising applications, especially under harsh conditions.

Room temperature phosphorescence from Si-doped-CD-based composite materials with long lifetimes and high stability.

C-dot-based composites with phosphorescence have been widely reported due to their attractive potential in various applications. But easy quenching of phosphorescence induced by oxygen or instability of matrices remained a tricky problem. Herein, we reported a Si-doped-CD (Si-CD)-based RTP materials with long lifetime by embedding Si-CDs in sulfate crystalline matrices. The resultant Si-CD@sulfate composites exhibited a long lifetime up to 1.07 s, and outstanding stability under various ambient conditions. The intriguing RTP phenomenon was attributed to the C = O bond and the doping of Si element due to the fact that sulfates could effectively stabilize the triplet states of Si-CDs, thus enabling the intersystem crossing (ISC). Meanwhile, we confirmed that the ISC process and phosphorescence emission could be effectively regulated based on the heavy atom effect. This research introduced a new perspective to develop materials with regulated RTP performance and high stability.

Carbon Dots as a Protective Agent Alleviating Abiotic Stress on Rice (Oryza sativa L.) through Promoting Nutrition Assimilation and the Defense System.

Abiotic stress severely threatens agriculture. Herein, we studied the effect of heteroatom-free carbon dots (CDs) on the alleviation of abiotic stresses in rice for the first time. During in vitro coincubation, suspended rice cells were exposed to 2,4-dichlorophenoxyacetate sodium (2,4-D-Na, 30 µg mL-1), 2,4-dichlorophenoxyacetic acid (2,4-D, 5 µg mL-1), NaCl (0.15 mol·L-1), and high light (2000 Lux), both with and without CDs (100 µg mL-1). After a week, CDs significantly reduced the inhibition rate of 2,4-D-Na on the rice cell biomass from 48.16 to 27.44% and increased the biomass of rice cells exposed to 2,4-D, NaCl, and high light, by 4.12, 1.10, and 4.01 times that of the control (pure nutrient medium), respectively. Furthermore, the growth of CD-germinated rice seedlings was not obviously affected by 2,4-D-Na, 2,4-D, and NaCl. Further results showed that the CDs demonstrated an intrinsic free-radical scavenging property and could increase the peroxidase activity and the contents of phenolics and flavonoids in rice by 125.81, 39.60, and 47.63%, respectively. Furthermore, CDs improved the nutrient assimilation of rice cells under 2,4-D stress by 14.69%. With higher antioxidant capacity and sufficient nutrients, the CD-treated rice showed excellent resistance to abiotic stresses. This study suggested the great potential of CDs in protecting crops against abiotic stress.