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Nanotechnology is an effective way to stimulate the yield potential of crops.

The activation of immune cells by immunoregulatory active substances can improve the body immunity. Carbon dots (CDs) with immunoregulatory activity are rarely reported. In this study, transmission electron microscopy results demonstrate the existence of CDs in herbal tea, while Fourier transform infrared and X-ray photoelectron spectroscopy results suggest the participation of polyphenol in herbal tea CD (H-CD) formation. The photoluminescence spectrum has shown that H-CDs have fluorescence emission at 565 nm and exhibit an excitation-dependent property. The toxicity and immunostimulatory activity of H-CDs on mouse macrophage RAW264.7 suggested that H-CDs had no toxicity to RAW264.7 cells. Meanwhile, compared with herbal tea, H-CDs have more obvious effect of promoting the expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase. In addition, the secretion of nitric oxide (NO) was promoted by H-CDs. This work suggests that H-CDs have stronger immunoregulatory function than that of original herbal tea, which provides a direction for the application of phenolic hydroxyl-modified CDs in the biomedical field.

A systematic insight into the role of SiO2 as a protective layer in realizing uniform Li-ion deposition is proposed.

As a special type of biomass, herbal medicine often contains a variety of biologically active substances, and taking it as a carbon source, it is expected to produce various types of biologically functional carbon dots (CDs). However, there are few reports in this field, especially in achieving enhanced performance of CDs by improving the utilization efficiency of active substances in medicinal materials. In this work, by adding glycine as an auxiliary agent in the preparation of CDs from herbal medicine (Exocarpium Citri Grandis), the carboxyl and amino groups of the adjuvant provided more reactive sites, which greatly improved the yield of CDs (about 6 times). More importantly, the antioxidant and biological activities of herbal CDs were also improved. By controlling the functional groups of adjuvants, the effects of carboxyl and amino groups in adjuvants on the synthesis of herbal CDs were compared. The results reveal that both carboxyl and amino groups can react with the substances in the carbon source, and the influence of amino groups was greater. After adding glycine, the size of the CDs became larger, resulting from the more abundant functional groups on the carbon skeleton, which was the main reason for the improved performance of the CDs. Finally, the biological activity experiment demonstrated that CDs derived from Exocarpium Citri Grandis and glycine could greatly enhance the vitality of cells and activate immune cells, which are expected to be applied in the field of cell reproduction and biological immunity. The method proposed in this work provides a potential strategy for high-yield preparation of CDs from biomass.

This fluorescent sensing material has the excellent optical properties of g-CDs and the selective detection and adsorption capability of UiO-66 for the target analyte; it determines the norfloxacin concentration via the F432/F530 fluorescence ratio.

Synthesis and purification of three carbon dots and the application of R-CDs in microalgae lipid imaging.

An interfacial engineering strategy is proposed to intimately couple metal chalcogenides with multidimensional carbon nanonetworks, which significantly improves their potassium-ion storage performances and electrochemical kinetic properties.

The desired dynamic spectra of plants can be achieved by placing PSC light convertors with different light qualities on blue LED chips.

With global warming, plants often suffer damage from high temperatures during the growth process, which inhibits their growth. In this work, carbon dots (CDs), synthesized by Salvia miltiorrhiza (S. miltiorrhiza) with a one-step hydrothermal method, were selected as heat-resistant enhancement agents for plants. Inspired by this background, this work studied Italian lettuce grown at 25, 35, and 45 °C and treated with CD and deionized water control (sprayed on leaves). The results showed that the biomass, chlorophyll content, net photosynthetic rate, activities of SOD (superoxide dismutase), POD (peroxidase), CAT (catalase), soluble sugar, and soluble protein contents of lettuce treated by CDs were increased while the contents of malondialdehyde (MDA) and proline (Pro) were decreased at 35 and 45 °C. The application of CDs at 35 and 45 °C could maintain the growth of plants by reducing oxidative damage and lipid peroxidation especially at the temperature of 35 °C, the growth status of lettuce treated by CDs was no different from that of lettuce grown naturally at the optimal temperature of 25 °C, or even better than the latter. This finding verified that the CDs could significantly improve the high-temperature tolerance of lettuce, thus alleviating the heat stress of plants.

A grand challenge in the state-of-the-art porous carbons is the lack of reliable synthesis strategy for achieving ultrahigh surface areas while maintaining a high carbonization yield. Generally, the realization of the ultrahigh surface area depends on the inherent properties of the starting precursors. Meanwhile, excessive development of porosity (>3500 m2 g−1) will undoubtedly give rise to low carbonization yield (

The modular High-Temperature Gas-Cooled Reactor nuclear power plant has inherent safety, simple system, high power generation efficiency and wide use. Incoloy800H and 2.25Cr-1Mo heat exchange tubes are used for High-Temperature Gas-Cooled Reactor (HTR-PM) Steam Generator. The steam generator uses the Incoloy800H and 2.25Cr-1Mo heat exchange tubes to transfer the high temperature helium medium to the water medium. The dissimilar steel welds are designed between Incoloy800H and 2.25Cr-1Mo heat exchange tubes. The heat exchange tubes of HTR-PM Steam Generator with small OD, large thickness, and design structure complicated. The dissimilar steel welds between two kinds of heat exchange tubes with limited welding operation space and welding seam quality requirements high. During the HTR-PM Steam Generator operation process, Incoloy800H heat exchange tube, 2.25Cr-1Mo heat exchange tube and the dissimilar steel welds between Incoloy800H and 2.25Cr-1Mo heat exchange tube are service in high temperature environment for a long time, until the steam generator fails. The surface forming quality, conventional properties and high temperature stress-rupture of dissimilar steels weld is required. The quality of dissimilar steel weld of Incoloy800H and 2.25Cr-1Mo heat exchange tubes is directly related to the safe operation of steam generator. Through systematic research including tube-to-tube joint type, the welding material, welding parameters, heat treatment process etc. The results show that using appropriate GTAW process with Nickel base alloy consumable inserts, welded joints can meet all design requirements such as strict inner and outside surface forming quality, conventional performance and the strength of stress-rupture test in HTR-PM Steam Generator service environment. This process has been used in the product manufacturing of demonstration projects, and provides good demonstration experience for similar application scenarios in the industry.

Aqueous zinc ion battery constitutes a safe, stable and promising next-generation energy storage device, but suffers the lack of suitable host compounds for zinc ion storage. Development of a facile way to emerging cathode materials is strongly requested toward superior electrochemical activities and practical applications. Herein, defect engineering, i.e., simultaneous introduction of nitrogen dopant and oxygen vacancy into commercial and low-cost MnO, is proposed as a positive strategy to activate the originally inert phase for kinetically propelling its zinc ion storage capability. Both experimental characterization and theoretical calculations demonstrate that the nitrogen dopant significantly improves the electric conductivity of electrochemical inert MnO. Simultaneously, the oxygen vacancy creates sufficient large inserted channels and available activated adsorption sites for zinc ions storage. These synergistic structural advantages obviously ameliorate the electrochemical performance of inert MnO. Therefore, even without any conductive agent additive, the as-prepared material shows high specific capacity, superb rate capability, prolonged cycling stability and attractive energy density, which are dramatically superior to those of the pristine MnO as well as many other host cathode materials. This work presents fresh insights on the role of defect engineering in the enhancement of the intrinsic electrochemical reactivity of inert cathode, and an effective strategy for scalable fabrication of high-performance cathode for zinc ion battery.

In light of the silicon-reservoir feature of renewable natural resources, the exploitation of the inexpensive biomass towards high value-added silicon-based materials has achieved great attention. However, the biomass-derived silicon is usually extracted by high-temperature metal-reduction, which tends to trigger side reaction and collapse the porous structure. Herein, introducing molten-salt assisted low-temperature aluminothermic reaction, we have fabricated micro/meso-porous carbon network embedded nano Si-SiOx@C (Si-SiOx@C/C) composites directly using sugarcane leaves as silica and carbon sources. This low-temperature synthesis strategy can perfectly preserve the three-dimensional (3D) carbon network embedded by fine Si-SiOx@C nanoparticles, which is beneficial to enhancing the electrochemical conductivity, reducing volume change, and stabilizing solid electrolyte interface membranes. In addition, the content of Si in SiOx can be controlled by the reduction temperature and reaction time. Consequently, the optimized SC-250-16 anode establishes a favorable reversible capacity (1562.8 mAh g−1 after 400 cycles at 200 mA g−1) and superior cyclability at high rates (678.6 mAh g−1 after 3000 cycles at 2 A g−1). Furthermore, the SC-250-16//LiFePO4 full cell delivers a prominent energy density of 412.1 Wh kg−1. This molten-salt assisted low-temperature reaction strategy can boost the advancement of 3D porous Si/C anodes and their relevant functional composites derived from other biomasses.

Photoluminescent mesoporous silica with a surface area of 840 m2/g, pore diameter of 4.8 nm, and pore volume of 0.69 cm3/g was synthesized through the calcination of Pluronic 123 (P123) and cetyltrimethylammonium bromide (CTAB) co-templated mesoporous silica at 400 °C for 2 h. The photoluminescence is from the trapped carbon derived from the co-templates.

In this work, a simple and efficient method is introduced to prepare biomass-based porous carbon with excellent performance by changing the content of component (e.g., cellulose, hemicellulose, lignin, and extractives) of the raw materials. When the content of the components change, the corresponding carbon skeleton will be separated, resulting in a structure that is conducive to activation conditions. Using bagasse with fiber tubular structure as carbon precursor, the synthetic hierarchical porous carbon (BHPC-4) possesses a high specific surface area (SSA) of 3135 m2 g−1 more than the control sample (2484 m2 g−1). Benefitting from the improvement of the structure, the BHPC-4 electrode exhibits an appealing capacitance of 410.5F g−1 at 0.5 A g−1 and long-term cycling stability of 100% capacitance retention after 10,000 cycles in the 6.0 M KOH system. Furthermore, a delightful energy density of 25.6 Wh kg−1 at a 226 W kg−1 can be achieved in 1.8 V Na2SO4 aqueous symmetrical supercapacitors. This method has universal significance in preparing high-porosity and high-performance biomass-based carbon materials for various energy storage/conversion.

The effective preparation of high porosity carbonaceous electrode materials is a critical and challenging issue for obtaining superior supercapacitors. In this work, a novel KCl-assisted KOH strategy is developed for the preparation of Moringa oleifera branch-based porous carbon materials (PCMs). Benefiting from the liquid environment of in situ formed molten salts, KCl-assisted KOH activation can effectively decrease the usage of KOH, and thus increase the yield of PCMs from 9.8% to 15.6% whilst maintaining their high porosity. Therefore, the obtained PCMs possess a high specific surface area (i.e., 2314–3470 m2 g−1) and pore volume (i.e., 0.94–1.69 cm3 g−1). When used in supercapacitors, a typical PCM electrode exhibits a high capacitance of 421 F g−1 at 0.5 A g−1 and with an excellent cyclic stability of 4% capacity decay after 20 000 charge/discharge cycles in 6 M KOH electrolyte. Additionally, a maximum energy density of 33.0 W h kg−1 can be achieved at 224.0 W kg−1. This attractive electrochemical performance shows PCMs to be a promising material for use in supercapacitors. Furthermore, this research provides a cost-effective and promising route for the preparation of porous carbon with high porosity.

Spherical carbon materials exhibit great competence as electrode materials for electrochemical energy storage, owing to the high packing density, low surface to volume ratio, and excellent structure stability. How to utilize renewable biomass precursor by green and efficient strategy to fabricate porous carbon microspheres remains a great challenge. Herein, we report a KOH-free and sustainable strategy to fabricate porous carbon microspheres derived from cassava starch with high specific surface area, high yield, and hierarchical structure, in which potassium oxalate monohydrate (K2C2O4·H2O) and calcium chloride (CaCl2) are employed as novel activator. The green CaCl2 activator is crucial to regulate the graphitization degree, specific surface area, and porosity of the carbon microspheres for improving the electrochemical performance. The as-prepared carbon microspheres exhibit high specific surface area (1668 m2 g−1), wide pore size distribution (0.5–60 nm), high carbon content (95%), and exfoliated surface layer. The hierarchical porous carbon microspheres show high specific and areal capacitance (17.1 μF cm−2), superior rate performance, and impressive cycling stability. Moreover, the carbon microspheres based symmetric supercapacitor exhibits high capacitance and excellent cycling performance (100% after 20 000 cycles at a current density of 5 A g−1). This green and novel approach holds great promise to realize low-cost, high-efficient and scalable of renewable cassava starch-derived carbon materials for advanced supercapacitive energy storage applications.

Microporous carbons with large oxygen content have been successful synthesized from biomass by the sodium alginate assisted strategy. During the activation process, the Na2O formed by the decomposition of sodium alginate combines with the activator KOH to undergo a redox reaction in situ with precursor, thereby forming a rich porosity in the samples. The obtained samples possess not only high SSA (2310~3001 m2 g−1) and large pore volume (0.89~1.19 cm3 g−1) arising almost completely (>90%) from micropores, but also retains a high content of oxygen (21.86~32.47 wt %). As supercapacitor electrodes, the oxygen-doped microporous carbons display a high specific capacitance of 385 F g−1 at 0.5 A g−1 with capacity stability of 91.5% after 20 000 cycles at 5 A g−1. As hydrogen storage materials, the oxygen-doped microporous carbons exhibit enhanced hydrogen storage capacity of 2.84 wt% (77 K, 1 bar) and 0.91 wt% (303 K, 50 bar). Experimental data indicate that this work provides a simple-efficient and universal strategy for preparing oxygen-doped microporous carbon for high-performance energy and hydrogen storage.

Porous carbon has been constructed in various strategies for hydrogen storage. In this work, a simple-effective strategy was proposed to transform sustainable biomass into porous carbon by degrade partial lignin and hemicellulose with Na2SO3 and NaOH aqueous mixture. This method collapses the biomass structure to provide more active sites, and also avoid the generation and accumulation of non-porous carbon nanosheets. As a result, the as-prepared sample possesses high specific surface area (2849 m2 g−1) and large pore volume (1.08 cm3 g−1) concentrating almost completely on micropore. Benefit to these characteristics, the as-prepared sample exhibits appealing hydrogen storage capacity of 3.01 wt% at 77 K, 1 bar and 0.85 wt% at 298 K, 50 bar. The isosteric heat of hydrogen adsorption is as high as 8.0 kJ mol−1, which is superior to the most biochars. This strategy is of great significance to the conversion of biomass and the preparation of high-performance hydrogen storage materials.

The ever-increasing electric vehicles and portable electronics make lithium-ion barreries (LIBs) toward high energy density, resulting in long driving range and standby times. Generally, excellent electrochemical performance can be obtained in thin electrode materials with low mass loadings ( 10 mg cm−2). In this work, we report a facile method for fabricating nitrogen doped carbon microtubes (N-CMTs) consisted of crumped carbon nanosheets for high-performance LIBs with ultrahigh mass loading, where non-tubular biomass waste (i.e., peanut dregs) is employed as the precursor. Benefiting from the hollow tubular conductive network, high graphitization, and hierarchical structure, the as-synthesized N-CMTs exhibit ultrahigh area capacity of 6.27 mAh cm−2 at a current density of 1.5 mA cm−2 with a high mass loading of 15 mg cm−2 and superior cycling stability for LIBs. Our approach provides an effective strategy for the preparation of nitrogen-doped carbon microtubes to develope high energy LIBs with high mass loading electrodes.

Recently, researchers are no longer satisfied with the investigation of the fluorescence properties of carbon dots (CDs), but instead focus on the more attractive afterglow luminescence, especially room temperature phosphorescence (RTP) and thermal activation delayed fluorescence (TADF). Numerous attempts have been made to construct CD-based afterglow materials, including embed CDs in various rigid matrices or construct self-protective structures. Because of the diversity of construction methodologies, different mechanisms and effects would be produced, thus resulting in distinguishing afterglow characteristics. Afterglow of CDs in organic matrices is mainly due to the formation of hydrogen bonds, which can suppress intramolecular vibration and stabilize triplet states, thus generating afterglow emission. Afterglow of CDs in diverse inorganic matrices are completely different because the multifarious interactions between CDs and different matrices are generated (e.g., rigid structure covalent bonds, structural confinement, energy transform, etc). The self-protective CDs always possess polymer-like structure or polymer-chains on their surface, which can act as rigid matrix to activating afterglow emission. This review aims to sum up the relationships between structure construction and afterglow characteristics, and the mechanism of afterglow generation, which are of great significance for stimulating more exciting progress in the purposeful design of afterglow materials.

Evolution of fast-charging alkali-metal ion battery (AIB) is of great importance, but severely limited by the high ion/electron transport resistance in the electrode structure. Carbon-based composites have demonstrated competitive results for accelerating the related technology development. However, their efficient design, versatile synthesis and diverse structural variability remain the major challenges. Herein, we propose a general and versatile protocol for synthesizing a hierarchical network structure composed of metal compound (e.g., metal oxide, metal selenide and metal sulfide) encapsulated in carbon nanoparticle unit, and demonstrate its superiority for fast-charging anode of AIB. Key to this strategy is utilization of a rational hybrid assembly comprising of chelating resin and metal ions as building blocks. The strong coordinate-covalent bond between chelating resin and metal ions not only realizes a highly homogeneous organic/inorganic interface at the molecular level, but also confines metal ions to in-situ generate metal compound nanoparticles uniformly distributed into the carbon framework after a carbonization treatment, endowing a strong binding at the carbon/non-carbon interface structure. Benefitting from the well-organized structure, the resultant network-structured metal compound@carbon composites exhibit extraordinary fast-charging alkali-metal ion storage performance. For example, the typical network-structured Fe2O3@carbon composite anode can be fully charged within 2.2 ​min and discharge continuously for more than 120 ​min with a large charge/discharge capacity of 730 ​mAh g−1 in lithium ion batteries, and is able to be fully charged within 5.6 ​min accompanying with a long discharge time of about 110 ​min and a high charge/discharge capacity of 92 ​mAh g−1 in potassium ion batteries.

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.

Potassium-ion batteries (KIBs) have been developed as an emerging electrochemical energy storage device due to the low cost and abundant resource of potassium. However, they suffer insufficient cyclability and poor rate capability caused by the large K+, severely limits their further applications. Herein, a nanonetwork-structured carbon (NNSC) is reported to address the issue. Cycling stability with very low decay rate of 0.004% per cycle over 2000 cycles and excellent rate capability (i.e., 261 mAh g−1 at 100 mA g−1 and 108 mAh g−1 at 5000 mA g−1) are achieved. The superior performance is attributed to the unique structure of NNSC, in which the three-dimensional interconnected hierarchical porous structure with hollow nanosphere as network units not only can effectively alleviate the volume expansion induced by the insertion of large K+, but also can offer fast pathways for K+ diffusion. In addition, the local graphitized carbon shell of NNSC can promote conductivity of material and reduce the resistance to K+ transportation. Thus, the NNSC has great potential in developing stable-structure and high-rate electrodes for next generation KIBs.

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

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.

Two-dimensional carbon-based composite nanosheets (2D-CCNSs) are expected to be promising electrodes for fast charging lithium-ion batteries. Even though synthesis procedures exist for these materials, current approaches often require rigid reaction conditions and complicated synthetic steps. Herein, we develop a facile and general approach to fabricate a new type of 2D-CCNSs and demonstrate its superiority as a high-rate anode for lithium-ion batteries. It is found that the introduction of a nanocellulose as building unit can guide itself to self-assemble with polydopamine and metal ions to form a 2D inorganic–organic hybrid, which can be directly transformed into 2D-CCNSs after a carbonization treatment without structural deterioration. Unlike common 2D-CCNSs with a pure graphitic or amorphous carbon framework, the as-constructed materials possess a distinctively heterogeneous carbonaceous skeleton comprising graphitic nanorods with a crystalline framework and amorphous carbon with a microporous structure. The synthetic strategy is also demonstrated to be general for embedding numerous metal oxides, such as Fe2O3, CoO, NiO nanoparticles, into the carbon framework just by adjusting the types of metal ions. Profiting from the well-orchestrated structure, the as-prepared 2D-CCNSs exhibit impressive high-rate lithium ion storage performance. For instance, after being fully charged within 40.8 s, a long discharge time as high as 342 min can be achieved accompanied with a high and stable reversible capacity of 560 mA h g−1.

As an environmentally unfriendly and low-cost by-product produced during the manufacturing of pulp and paper, ca.170 million tons of black liquor is generated per year in the world. Efforts to effectively convert black liquor into high-value products are very critical but remain challenging. Herein, we successfully prepare porous carbons using black liquor powders as precursors through a simple carbonization technique without any extra activators or templates. The black liquor-derived porous carbons (BL-PCs) exhibit a remarkable three-dimensional (3D) honeycomb-like morphology and a hierarchical porous structure. Additionally, the disordered degree of BL-PCs can be controlled by simply regulating carbonization temperature. A combination of 3D honeycomb-like morphology, hierarchical porous structure and decreased disordered degree not only contributes to the fast electrolyte ion transport, but also improves the rate performance and cycling stability when BL-PCs are used as anode materials for sodium-ion batteries. A typical BL-PC anode exhibits attractive electrochemical performances, including high rate capability and long-term cycling stability.

As emerging carbon materials, carbon dots (CDs) have received extensive attention in recent years. Since CDs have excellent optical properties, most reports on carbon dots focus on research of their optical applications. However, their diverse surface functional groups also afford broad application prospects in chemical engineering. This review article focuses on the research progress in the chemical applications of CDs in the following three aspects: CDs used as structural regulators of the morphology and size of materials; CDs used as chemical additives, such as consolidant, antirust, antifreeze, lubricant, and scale inhibitors; CDs used as reinforcing reagents to improve water dispersibility and enhance mechanical properties of materials. Finally, we focus on existing problems in this field and look forward in the direction of future development.

Afterglow including thermally activated delayed fluorescence (TADF) and room-temperature phosphorescence (RTP) has stimulated considerable attention owing to bright potential applications in optoelectronic devices, sensing, and security systems. However, previously reported afterglow materials are mostly single-mode (one of RTP or TADF only), a tunable multi-mode afterglow emission is still rarely achieved. Herein, we report the temperature-responsive conversion characteristics of TADF and RTP of carbon dots in silica (CDs@SiO2) for the first time. The unique temperature-responsive afterglow characteristics, that is, phosphorescence and TADF can be mutually transformed as the temperature changes, resulting in the free conversion of the RTP/TADF ratio as well as the afterglow color change through simple temperature control. The Si–O network plays multiple roles to strengthen and confine the embedded CDs, thus resulting in ultralong RTP emission and unique afterglow characteristics. Furthermore, CDs@SiO2 exhibited excellent stability against water, acid, alkali, salt and oxidants as well as polar solvents. CDs@SiO2 with unique afterglow characteristics and high stability can have multiple potential applications in rapid fingerprint detection and temperature sensing, especially in advanced temperature-responsive multicolor anti-counterfeiting and encryption.

Exploration of effective ways to highly porous carbon is a critical but remains challenging issue for high-performance supercapacitors. Here, we propose a new and facile strategy to synthesize polyacrylonitrile-based porous carbon (PPC) material. The as-prepared PPC not only possesses a well-defined hierarchical pore structure, but also exhibits the highest BET surface area of 3751 m2 g−1 and the largest pore volume of 2.48 cm3 g−1 among all the materials derived from polyacrylonitrile. The key to this preparation strategy is utilization of KNO3 as a mediator for pre-oxidation of polyacrylonitrile, which leads to construction of a fluffy and rigid semi-carbonized framework for the easy accessibility of activator KOH. Benefiting from the well-developed porosity, the PPC electrode exhibits an unusually high capacitance of 448 F g−1 at 0.5 A g−1 and an outstanding long-term stability of 96.5% capacitance retention after 10000 cycles in 1.0 V aqueous supercapacitors. Additionally, a remarkable energy density of 23.6 Wh kg−1 can be delivered at a high out-put power density of 220 W kg−1 in 1.8 V aqueous supercapacitors. These attractive electrochemical properties enable PPC to go far beyond many reported carbonaceous electrodes, which is expected to be as competitive candidate for high-performance supercapacitor electrode.