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As one of the most promising fluorescent nanomaterials, carbon dots (CDs) have been extensively studied for their fluorescent properties in solution. However, research on the synthesis of multicolor solid-state fluorescence (SSF) CDs (from blue to red) is rarely reported. Herein, we used o-phenylenediamine, m-phenylenediamine and p-phenylenediamine with dithiosalicylic acid (DTSA) in the solvothermal reaction using acetic acid as a solvent to obtain aggregation-induced emissive (AIE) CDs of red (620 nm), green (520 nm), and blue (478 nm), respectively. XPS spectra and TEM image show that with the red-shift of luminescence, the particle size and content of C = O of the CDs gradually increases. Finally, based on the non-matrix solid-state multicolor luminescence characteristics of CDs, the application of white light LED devices is realized. Besides, based on the fat-soluble properties of CDs, fingerprint detection applications are realized.

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.

Step-scheme (S-scheme) photocatalysts have been proposed for highly efficient charge separation and strong redox activity in the photocatalysis field. Here, we reported a facile strategy to obtain the S-scheme heterojunction composite TiO2/chlorophyll (Chl). The S-scheme heterojunction enables the significant improvement of electron transfer efficiency at the interfacial heterojunction of TiO2/Chl. Also, the lifted conduction band and valence band of TiO2/Chl resulted in more than 1.61 times generation of reactive oxidizing species, compared to that of bare TiO2. In addition, TiO2/Chl was applied as a photocatalytic bactericidal material to fabricate commercial masks for prolonged life span of the mask. The TiO2/Chl-coated mask filter exhibited excellent bactericidal effect on Escherichia coli under light illumination (2.94 × 107 cfu E. coli were killed by 1 cm-2 coated mask filters within illumination of 3 h), while commercial mask filters showed no bactericidal effect. After three circulation-sterilization tests, the TiO2/Chl-made mask filter maintained the initial bactericidal effect, which greatly extended the life span of the mask that presents a promising strategy to alleviate the supply stress of masks.

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.

Granular friction behaviors are crucial for understanding the ubiquitous packing and flow phenomena in nature and industrial production. In this study, a customized experimental apparatus that can simultaneously measure the time history of normal and tangential forces on the inside-shearing unit is employed to investigate the granular friction behaviors during a linear reciprocating sliding process. It is observed that the evolution behaviors of two normal forces distributed separately on the shearing unit can qualitatively reflect the effects of the force chain network. During the half-loop of the reciprocating sliding, the total normal force, which indicates the load-bearing capacity of the granular system, experiences the following typical stages: decreases abruptly and stabilizes momentarily, further decreases significantly to the minimum, gradually increases to the maximum, and then remains stable. These stages are associated closely with the relaxation, collapse, reconstruction, and stabilization of the force chain, respectively. Interestingly, the coefficient of friction (COF) can reach a stable value rapidly within the initial sliding stage and subsequently remain constant. The average COF within stable ranges decreases significantly with the external load G in the power-function form, G−0.5. Meanwhile, the COF increases slightly with the sliding velocity. Finally, a complete illustration of the dependences of the granular COF on the external load and sliding velocity is provided. Our study contributes to granular friction research by providing an innovative experimental approach for directly measuring the COF and implicitly correlating the evolution of the force chain network.

The discovery of light converter excited by near-ultraviolet (UV) superior broadband blue-emitting lighting source is a main challenge in plant growth LEDs. In this study, SrLu2O4:Ce3+, Li+, F− blue phosphor has been synthesized via a solid-state reaction. Benefitting from doping of F− ions, SrLu2O4:Ce3+, Li+, F− phosphor (λex = 405 nm, λem = 460 nm) shows a strong broadband (FWHM = 90 nm) blue-emitting with lower critical concentration of Ce3+ ions and an increasing 6.9% thermal quenching performance (92.1% @ 423 K of the peak intensity at room temperature). Moreover, a blue light converter composed of SrLu2O4:Ce3+, Li+, F− phosphor and glass matrix is obtained based on phosphor-in-glass (PiG) technology, exhibiting excellent thermal stability and outstanding moisture resistance. A red light converter with commercial red phosphor is obtained by the same method. Furthermore, by combining of two light converters with near-UV chip, a proof-of-concept plant growth high power LED is achieved and applied in indoor Italian lettuce growing in comparison with commercial plant lamps.

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.

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.

Sunlight utilization by plants via the photosynthesis process is limited to the visible spectral range. How to expand the utilization spectral range via construction of a hybrid photosynthetic system is a hot topic in this field. In this work, far-red carbon dots (FR-CDs) with excellent water solubility, good biocompatibility, high quantum yield (QY), and superior stability were prepared by a one-step microwave synthesis in 3 min. The as-prepared FR-CDs is an efficient converter transferring ultraviolet A (UV-A) light to 625-800 nm far-red emission, which can be directly absorbed and utilized by chloroplasts. Due to the broader spectral utilization of solar energy and Emerson effect, increased photosynthetic activity can be achieved both in vivo and in vitro when applied for Roman lettuce. The in vitro hybrid photosynthetic system via coating chloroplasts with FR-CDs presents higher electron transfer efficiency between PS II (photosystem II) to PS I (photosystem I), which consequently increases the ATP production. The in vivo experiment further confirms that FR-CDs-treated lettuce can induce a 28.00% higher electron transfer rate compared with the control group, which results in 51.14 and 24.60% enhancement of fresh and dry weights, respectively. This work is expected to provide a way for improving the conversion efficiency from solar energy to chemical energy. (PS II) to photosystem I (PS I), which consequently increases the ATP production. The in vivo experiment further confirms that FR-CDs-treated lettuce can induce a 28.00% higher electron transfer rate compared with the control group, which results in 51.14 and 24.60% enhancement of fresh and dry weights, respectively. This work is expected to provide a way for improving the conversion efficiency from solar energy to chemical energy.

Carbon dots (CDs) with exciting photoluminescence characteristics, mild toxicity, and good biocompatibility are the research hotspots in biomedical application. Here, a compact antibacterial activity of CDs from levofloxacin hydrochloride is reported. The obtained CDs with an average size of 1.27 nm have fascinating antibacterial properties against both gram-positive and negative bacteria, with minimum inhibitory concentrations (MICs) of 64, 128, 64, and 128 μg/mL for

A single-shot measuring apparatus with optical limiting for temporal pulse contrast of kJ-class petawatt lasers in the nanosecond range is proposed. A temporal linear filter comprising an electro-optical switch, a polarizer, a temporal nonlinear filter composed of cascaded SHG crystals, and a dichromatic mirror are, respectively, used as an optical limiting apparatus for contrast measurement of nanosecond and picosecond pulses to improve dynamic range and temporal resolution. The apparatus has been applied to pulse contrast measurements at the SG-II petawatt facility, achieving a high dynamic range of 1 0 10 and a fast time resolution of 107 ps in the 350 ns range. This technique can also be universally applied to the limiting of the main pulse of varying pulse widths to diagnose pre-pulses during generation and transmission.

By adopting an adhesive polyvinyl alcohol (PVA) to encapsulate fluorescent carbon dots (CDs), a novel approach to prolong foliar fluorescent CD retention for enhancing lettuce photosynthesis was de...

Stimuli-responsive shape-memory materials are a category of fascinating smart materials, which undergo reversible shape transformation with environmental changes. Among a large number of stimuli-responsive shape-memory materials, light-driven materials have sparked tremendous attention because of their stability, remote operability and environmentally friendly. Herein, we report a novel strategy for the synthesis of a light-responsive shape-memory polymer that is made from carbon dots and polyvinyl alcohol. The as-prepared carbon dots are endowed with good visible light absorption and excellent photothermal conversion, which enable the carbon dot/polyvinyl alcohol composite polymer to serve as a light-responsive shape-memory polymer. The carbon dots not only work as photothermal agents but also offer additional hydrogen bond interaction, which accelerates the shape-memory recovery rate. The results show that the composite polymer can realize shape recovery using relatively low laser power. Most importantly, the as-prepared carbon dot/polyvinyl alcohol composite polymer not only possesses great research potential in different types of fields, such as medical and sensing, but also provides a effective and economic strategy for taking the advantage of light.

Carbon dots (CDs), a novel member of the renowned carbon-based nanomaterials family, have gained tremendous attention in various fields. Their extraordinary properties, including facile synthesis procedure, photoluminescence, biocompatibility, tunable surface functionalities, water solubility and low toxicity, have introduced them extensively in biological applications, such as bioimaging, biosensing, photocatalysis and molecule delivery. Recently, CDs have attracted significant interest in agriculture to improve the growth and production of plants and great progress has been achieved in this area. Here, we will review the interactions of CDs with plant systems for the first time, including symptomatic plant growth, internal physiological processes and other external factors involved in plant growth. Furthermore, the current challenges and future perspective of CDs in the field of agriculture are discussed. Looking forward, it indicates that CDs might play an important role in the future of agriculture.

Embedding CsPbBr3 quantum dots (QDs) in inorganic glasses via in situ crystallization has been regarded as a feasible strategy to improve their stability due to the protecting role of the robust glass matrix. However, the influence of the rigidity of the glass network structure on CsPbBr3 crystallization is rarely reported. Herein, we report an approach to control the rigidity of the glass network structure through substituting the [GeO4] tetrahedron with the [SiO4] tetrahedron in mother glass, which allows fine-tuning of the morphology and luminescence properties of CsPbBr3 QDs. The water-resistance of CsPbBr3 QD glass (CsPbBr3 QD@glass) is clearly enhanced by increasing the content of the [SiO4] tetrahedron, while the size of CsPbBr3 nanocrystals decreases gradually and the corresponding quantum efficiency decreases. Moreover, the thermostability and photostability of CsPbBr3 QD@glasses were also studied systematically. The correlation between the rigidity of the glass network structure and the local microenvironment of the crystallization of CsPbBr3 QDs is revealed. Our results provide a reference for the design of mother glass to obtain perovskite QDs with high quantum efficiency and high stability based on the rigidity of the glass network.

Biogenic amines (BAs) from rotten food cause serious harm to sensitive people. Therefore, the development of a smart label that can intuitively monitor the degree of food decay in real-time is of great significance in food safety. Herein, we report the synthesis of pH-responsive carbon dots with red emission (R-CDs) by the solvothermal treatment of citric acid and urea. The fluorescence intensity of R-CDs gradually increased as the pH of the solution increased from 1 to 12. We studied the mechanisms of pH response and found that H-aggregation occurred when R-CDs were in acidic solution and caused quenching; when they were distributed in alkaline solution, the Fermi level shift caused reduced self-absorption and enhanced red fluorescence emission. The intense red emission of R-CDs is beneficial for the visual detection of alkaline organic amines and BAs derived from rotten shrimp to achieve food safety detection. Moreover, the R-CDs can be used as a promising pH-sensitive fluorescent ink, which has broad prospects and significance in anticounterfeiting and information encryption.

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.

C-Dots and composites based on them face the challenges of poor stability, especially under photo-radiation, and low solid-state photoluminescence quantum yields (PLQYs), which hinder their application in optical devices. Herein, a novel 2-dimensional hybrid material of polysiloxane embedded with Si-doped carbon dots (P-E-Si-CDs) was synthesized by a self-assembly approach, and the hybrid composite exhibited broadband blue-green fluorescence emission, outstanding photostability, high thermal stability, and a high PLQY of 82.8%. Moreover, the dual fluorescent emissions were demonstrated the creation of two closed-loop fluorophores. Using the as-prepared hybrid fluorescent material, fabricated light-emitting diodes (LEDs) based on UV and blue-emitting LED chips present safe warm white light emission and adjustable white emission with a high color rendering index of up to 91, respectively. This work provides a novel strategy for the design and realization of Si-CD-based hybrid composites, thus promising their prospective use commercially in LED lighting.

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.

Compared to fluorescence imaging with short-lived emissive probes, the use of phosphorescent probes conveys the advantage of long signal persistance in time and this permits one to discriminate aga...

Embedding CsPbX3 (X = Cl, Br, I) perovskites QDs in inorganic glass matrix via in-situ crystallization has been regarded as a feasible strategy to improve their stability against water, heat, and light irradiation. However, the tunable-emission range of these CsPbX3-nanocrystals-embedded glasses is still narrow, insufficient to cover a wide color gamut. Herein, a simple synthetic method was developed in this study to obtain the tunable-emission CsPb(Cl/Br)3 quantum dots (QDs) in boro-germanate glass (CsPb(Cl/Br)3 QDs@glass) by controlling the molar ratio of PbBr2/PbCl2. With the increase of the PbBr2 concentration from 1.6 to 3.2 mol%, the emission wavelength of CsPb(Cl/Br)3 QDs@glasses can be shifted from 448 to 485 nm, and the corresponding photoluminescence quantum yield (PLQY) increases from 0.61 to 24.43%. In addition, the CsPb(Cl/Br)3 QDs@glass exhibits impressing promotion of thermal stability, photostability, and water resistance due to the excellent protective function of the glass matrix. As a proof-of-concept experiment, a LED device was fabricated by employing the optimal CsPb(Cl/Br)3 QDs@glass with a commercial 375 nm UV chip, yielding an intense cyan light. All the results indicate that the investigated CsPb(Cl/Br)3 QDs@glasses may find promising applications as color convertors in wide-color-gamut liquid crystal displays (LCDs).

Herein, we present a simple strategy to enhance the stability of water-sensitive SrLiAl3N4:Eu2+ phosphor through embedding the phosphor particles into low-melting Sn-P-F-O glass using phosphor-in-glass (PiG) approach. After being immersed in water for 96 h, the emission intensity of the SrLiAl3N4:Eu2+-PiG sample was maintained at 80% of its pristine intensity, indicating the moisture-resistance property of SrLiAl3N4:Eu2+ was significantly enhanced. Employing the narrow-band red-emitting SrLiAl3N4:Eu2+-PiG sample and a blue COB (chip-on-board), a plant growing LED device was fabricated. The emission spectrum of the device matches well with the absorption of Chlorophyl (a and b) in plants, indicating the as-prepared SrLiAl3N4:Eu2+-PiG are suitable to be applied in plant lighting field. We believe that this simple method reported in this communication can be easily expanded to other water-sensitive luminescence materials.

A series green emission phosphors Sr3Lu2(BO3)4:Ce3+,Tb3+ (denoted as SLBO:Ce3+,Tb3+) with broad absorption band matching well with UV LED chip were synthesized by the solid–state reaction method. The phase and structure were analyzed with XRD, EDX, FT-IR measurements. The energy transfer between Ce3+ and Tb3+ in SLBO was proved by spectra and decay curves detailedly. The emission colors vary from blue to green by adjusting the ratio of Ce3+/Tb3+ doped concentration. With temperature increasing, SLBO:Ce3+,Tb3+ phosphor shows well thermal stability that emission intensity retains 70% of its initial at 25 °C even temperature rising to 150 °C. The internal and external quantum efficiency of SLBO:3%Ce3+,8%Tb3+ are 77.5% and 34.8% under 340 nm excitation, respectively. Combining the as-synthesized SLBO:Ce3+,Tb3+ and red emission phosphor CaAlSiN3:Eu2+ coated on a 365 nm UV chip, a warm white LEDs device with CRI of 83 was achieved. All the results indicate that the SLBO:Ce3+,Tb3+ phosphor has potential application in UV pumped white LEDs.

The combination of carbon dots (CDs) and rare-earth ions has attracted increasing attention due to their unique fluorescence properties. Herein, CDs are incorporated with NaYF4:Eu to form stable NaYF4:Eu@CDs nanocomposites by a simple sol-gel route. It has been demonstrated that CDs are successfully embedded in the silica layer outside NaYF4:Eu nanoparticles. These nanocomposites exhibit characteristic emissions of both CDs and NaYF4:Eu under a single excitation wavelength. By using their dual-emissive properties, the nanocomposites can act as ratiometric fluorescent sensor for selective detection of Fe3+ ions in the range of 0–350 μM. The temperature-dependent luminescent property of the nanocomposites makes them also suitable as thermometers in the range from 377 to 467 K. In addition, the luminescent color can be regularly adjusted by tuning the mass ratio of NaYF4:Eu to CDs. This combing strategy enables us to achieve dual emission of CDs and Eu3+ ions in nanocrystals, opening an avenue towards multifunctional applications in widespread fields.

In the present work, static and dynamic tensile tests of unidirectional and plain weave CFRP laminates used for retrofitting building structures were carried out using a universal testing machine and a high-speed servo-hydraulic testing machine (INSTRON VHS 160/100-20), respectively. The strain rate that the CFRP laminate experienced in the tests varies from 4E-5s−1 to 160s−1. Test results show that the tensile behavior of both unidirectional CFRP and plain weave CFRP are strain rate dependent, while the latter is more obvious than the former. Failure processes of the CFRP laminates were also observed with the aid of a high-speed camera. It is found that the failure mode of the CFRP laminate at high strain rate is quite different from that at quasi-static loading and low strain rate, which is believed to contribute to the strain rate sensitivity of both the unidirectional and plain weave CFRP laminate. Empirical formulas of dynamic increase factor (DIF) of tensile strength, Young's modulus and failure strain of the CFRP laminates were derived as a function of strain rate within the strain rate range tested. Available testing data were also collected from other papers and analyzed together with the testing data from the present study.

Carbon dots (CDs) have attracted attention in metal-free afterglow materials, but most CDs were heteroatom-containing and the afterglow emissions are still limited to the short-wavelength region. A universal approach to activate the room-temperature phosphorescence (RTP) of both heteroatom-free and heteroatom-containing CDs was developed by one-step heat treatment of CDs and boric acid (BA). The introduction of an electron-withdrawing boron atom in composites can greatly reduce the energy gap between the singlet and triplet state; the formed glassy state can effectively protect the excited triplet states of CDs from nonradiative deactivation. A universal host for embedding CDs to achieve long-lifetime and multi-color (blue, green, green-yellow and orange) RTP via a low cost, quick and facile process was developed. Based on their distinctive RTP performances, the applications of these CD-based RTP materials in information encryption and decryption are also proposed and demonstrated.

High-velocity compaction (HVC), an innovative approach to obtain green compacts with high and uniform density, is widely used in the powder metallurgy industry. In this study, meso force chains, macro stress transmission, and their relation were investigated using the discrete element method. The simulation details of HVC and the quantitative characterization of force chains and stress transmission were shown. Then, the relation between force chains and stress was investigated. The evolution of force chains showed the same change tendency as the stress distribution. They evolved from top to bottom and then reflected backwards in HVC while they did not show this trend in conventional compaction. The strength of the force chains maintained good consistency with the stress magnitude. Meanwhile, the length of the force chains presented a negative correlation with the stress magnitude, and high stress may cause new force chains to shorten. The average collimation coefficient was affected by the transmission of stress, and the short force chains had better straightness. Furthermore, force chains parallel to the direction of gravity were observed in the region with no stress concentration. The directional coefficient of force chains also had the same fluctuation trend as the variation in the principal stress angle.

Carbon dots (CDs) have been studied for years as one of the most promising fluorescent nanomaterials. However, CDs with red or solid-state fluorescence are rarely reported. Herein, through a one-pot solvothermal treatment, hydrophobic CDs (H-CDs) with blue dispersed emission and red aggregation-induced emission are obtained. When water is introduced, the hydrophobic interaction leads to aggregation of the H-CDs. The formation of H-CD clusters induces the turning off of the blue emission, as the carbonized cores suffer from π-π stacking interactions, and the turning on of the red fluorescence, due to restriction of the surfaces’ intramolecular rotation around disulfide bonds, which conforms to the aggregation-induced-emission phenomenon. This on-off fluorescence of the H-CDs is reversible when the H-CD powder is completely dissolved. Moreover, the H-CD solution dispersed in filter paper is nearly colorless. Finally, we develop a reversible two switch-mode luminescence ink for advanced anti-counterfeiting and dual-encryption., Carbon dots that display long-wavelength and multicolor emission are desirable for biological and anti-counterfeiting applications. Here, the authors design hydrophobic carbon dots with reversible two-mode fluorescence, which exhibit blue emission when dissolved in solution, and red solid-state fluorescence when aggregated.

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.

Exploration on the transient evolution of the rheological properties of dense granular inertial flow is essential for revealing how the balance is established between the boundary drive strength and the internal shear strength. In this paper, discrete element method simulations are performed to study the transient flow characteristics of a dense granular system under plane shear in the inertial regime. To this end, we quantitatively analyze the changes in the system’s flow state, interfacial friction coefficient, internal friction coefficient, and microstructure. Simulation results show that the evolution of the horizontal flow experiences three typical stages, namely transmission, adjustment, and stabilization. Meanwhile, the shear dilatancy caused by the vertical movement of particles, gradually loosens the filling state, weakens the spatial geometric constraint and the system’s tangential load-bearing capacity, thereby decreasing the interfacial friction coefficient and reducing the boundary drive strength. On the other hand, the variations in the anisotropies of both contact orientation and contact forces, increase the internal friction coefficient and improve the internal shear strength. Therefore, the evolution of flow state from initially static to finally stable reduces the boundary drive strength while enhances the internal shear strength, and eventually a balance between them is achieved. Distinguished from the micromechanical behaviors, under different shear velocities the internal shear strength always mainly originates from the anisotropies in contact orientation and in normal contact force. Moreover, the contribution of the anisotropy in contact orientation becomes more predominant with the increase of shear velocity.

Aerogels have been widely used in the adsorption of pollutants because of their large specific surface area. As an environmentally friendly natural polysaccharide, cellulose is a good candidate for the preparation of aerogels due to its wide sources and abundant polar groups. In this paper, an approach to construct cellulose nanofibers aerogels with both the good mechanical property and the high pollutants adsorption capability through chemical crosslinking was explored. On this basis, TiO2 nanoparticles were loaded on the aerogel through the sol-gel method followed by the hydrothermal method, thereby the enriched pollutants in the aerogel could be degraded synchronously. The chemical cross-linker not only helps build the three-dimensional network structure of aerogels, but also provides loading sites for TiO2. The degradation efficiency of pollutants by the TiO2@CNF Aerogel can reach more than 90% after 4 h, and the efficiency is still more than 70% after five cycles. The prepared TiO2@CNF Aerogels have high potential in the field of environmental management, because of the high efficiency of treating organic pollutes and the sustainability of the materials. The work also provides a choice for the functional utilization of cellulose, offering a valuable method to utilize the large amount of cellulose in nature.

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.

Vortex retarder is a simple and efficient method to generate vortex beams, and the detection of its modulation characteristics is of great significance for the preparation and application of vortex retarder. A quantitative measurement method for the two-dimensional modulation characteristics of vortex retarder based on PIE is presented. By using circularly polarized incident light, the modulation parameters of the vortex retarder are loaded into the beam phase. We report on the experimental demonstration that the high-precision reconstruction results can be achieved by applying the PIE complex amplitude measurements respectively before and after placing the vortex retarder. Based on the measurement result, the actual modulation effect of the measured vortex retarder to incident vector beam is obtained by the matrix operation and diffraction propagation. This method provides a simple and anti-interference means for quantitative detection of wave plates, liquid crystals and vortex beams.

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.

Recently, bulk nanobubbles have attracted intensive attention due to the unique physicochemical properties and important potential applications in various fields. In this study, periodic pressure change was introduced to generate bulk nanobubbles. N2 nanobubbles with bimodal distribution and excellent stabilization were fabricated in nitrogen-saturated water solution. O2 and CO2 nanobubbles have also been created using this method and both have good stability. The influence of the action time of periodic pressure change on the generated N2 nanobubbles size was studied. It was interestingly found that, the size of the formed nanobubbles decreases with the increase of action time under constant frequency, which could be explained by the difference in the shrinkage and growth rate under different pressure conditions, thereby size-adjustable nanobubbles can be formed by regulating operating time. This study might provide valuable methodology for further investigations about properties and performances of bulk nanobubbles.

UV absorbers are very effective in the fields of antiyellowing, resistance of photocatalytic degradation, and sunscreen cosmetics. However, commercialized UV absorbers have the drawbacks of toxicity, low absorption efficiency, transparency, etc. Here, we report for the first time silicon quantum dots as full-band UV absorbers. The NH-refunctionalized silicon quantum dots with high-performance UV absorption were successfully synthesized under the synergistic effect of sodium citrate and ethanediamine, and the (NH, OH)-functionalized silicon quantum dots (SiQDs) with full-band UV absorption can be achieved by reregulating -NH2 and -OH groups on the surface. The as-prepared (NH, OH)-functionalized SiQDs exhibited good stability and underwent treatment of varying pH and temperature. Furthermore, experimental results demonstrated that compared to commercial water-soluble organic UV absorbers, the (NH, OH)-functionalized SiQDs showed better antiyellowing performance for polyurethane and resistance of photocatalytic degradation for rhodamine B, and presented huge application potential in sunscreen cosmetics. Finally, the UV absorption mechanism of SiQDs was explained to be mainly related to Γ → Γ direct band gap transition, which absorb UV light and release it as thermal radiation.

White lighting sources based on laser diodes (LDs) are strongly regarded as the next generation of high luminance lighting sources because the luminous efficiency of LDs increases linearly with operating current, which can resolve the “efficiency droop” of LEDs. To facilitate the advent of high brightness solid state lighting, searching for a light convertor with high thermal stability, high conversion efficiency, and irradiation stability is essential. Herein, we developed a robust light convertor, YAG:Ce3+ based on phosphor-in-glass (denoted as YAG-PiG), exhibiting a quantum efficiency of 70.1% and a high thermal conductivity of 0.89 W m−1 K−1. The microstructure and luminescent properties of YAG-PiG were also investigated in detail. Compared to YAG-PiS (phosphor-in-silicone), this YAG-PiG shows an overall increase in irradiation and thermal stability performances. A high power white LDs was constructed by coupling the YAG-PiG with a 445 nm blue laser and a sapphire plate modified by an antireflection layer and a blue-pass filter serving as the heat sink. The constructed PiG converted LDs@sapphire exhibits a luminous efficacy of 217 lm W−1 and a CRI (color rendering index) of 57 at 3646 K under a driven power of 3 W. Compared to the conventional white LDs, the luminous efficacy and the resistance to laser irradiation of the white LDs@sapphire are obviously enhanced. Therefore, we predict that this white emitting PiG converted LDs@sapphire will become a promising candidate for future lighting sources and promote the use of sapphire plate as the heat sink.

All-inorganic perovskite CsPbBr3 quantum dots (QDs) are becoming the most popular narrow-band green emitter for use as a critical material in next generation wide-color-gamut backlight displays. However, their intrinsic poor stability greatly hinders their development for practical applications. Herein, CsPbBr3 QDs were successfully precipitated in boro-germanate glass (CsPbBr3 QDs@glass) with well-designed compositions, not only retaining a high photoluminescence quantum yield (PLQY of 43% upon 450 nm excitation) and narrow bandwidth (FWHM of 22 nm), but also showing significantly enhanced stability in relation to water, heat, and UV/blue irradiation. The relative PL intensity of CsPbBr3 QDs@glass was maintained at 60% or 85% after being immersed in water for 22 days or exposed to UV light for 100 hours, respectively. Moreover, CsPbBr3 QDs@glass samples present impressive recovery abilities in thermal cycling experiments or upon intermittent blue light irradiation. Finally, an all-inorganic white light-emitting diode (white LED) achieving 125% of National Television Standards Committee (NTSC) performance was fabricated through employing green-emitting CsPbBr3 QDs@glass and red-emitting Cs2SiF6:Mn4+ phosphor-in-glass (PiG) plates as color convertors. The design rules established here could initiate the further exploration of other glass systems with moderate halide solubilities and low melting temperatures to precipitate highly efficient and stable CsPbX3 (X = Cl, Br, I) QDs.

In this paper, a facile hydrothermal route was proposed to synthesize a bright blue-emitting solution of silicon nanoparticles (s-Si NPs) with a high photoluminescence quantum yield (PLQY) of 66%. And a self-quenching-resistant solid-state fluorescent powder of Si NPs (p-Si NPs) was obtained by freeze drying, which exhibited dual wavelengths with blue and yellow emission peaks. In addition, the blue-band emission of p-Si NPs was ascribed to the graphitizing cores, while the yellow-band emission of p-Si NPs originated from the trapping surface state. Based on this finding, a high temperature calcining strategy was proposed to obtain multicolor Si NP powders by adjusting the surface defects of p-Si NPs for the first time. A series of multicolor Si NP powders with wavelengths from blue to red was obtained by adjusting the calcination time/temperature. Structural and spectroscopic characterizations also proved that the mechanism of their PL red shift was attributed to the oxygen-related surface state, rather than the size effect. Because of their unique multicolor emission, their related multicolor light-emitting diode (LED) devices were obtained to explore their possible application in the field of solid-state lighting. Moreover, SSF-2-based films were fabricated by combining carboxymethyl cellulose (CMC) and SSF-2 powder to explore their potential application as light conversion films (LCFs) in the field of agricultural planting.

A simple sol–gel method was used to integrate carbon dots (CDs) with upconversion (UC) luminescent materials NaYF4:Yb,Er(Tm) to form composites. We found for the first time that the CDs acted as a sub-energy level to mediate energy transfer between different levels of the rare earth ions. Impressively, enhanced red and NIR upconversion emissions were achieved in the NaYF4:Yb,Er(Tm)@CDs composites.

At present, blue-red composite LED light sources used for plant lighting are mainly composed of blue light and red light; the blue light is provided by gallium nitride LED chips, but the full-width at half-maximum (FWHW) is only approximately 25 nm, while the blue light required by plants for photosynthesis is wider. Focusing on this problem, this work reported that a dual emitting phosphor-in-glass plate (Dual-PiGP) was prepared towards a high power and dual broadband emitter, in which BaMgAl10O17:Eu2+ (BAM) and CaAlSiN3:Eu2+ (CASN) provide blue and red emission, respectively. Dual-PiGP exhibited several merits, including a high quantum efficiency of 93.90%, a superior thermal stability (80.1%@150 °C of the peak intensity at 25 °C), and a dual broad spectrum with a full-width at half-maximum (FWHM) of 50 and 106 nm at 446 and 645 nm, respectively. Moreover, a proof-of-concept Dual-PiGP plant lamp for application in indoor plant factories was successfully fabricated with Dual-PiGP and a 385 nm emitting LED chip, yielding blue- (400–500 nm) and red-light (580–780 nm) emission that matches well with the absorption spectrum of chlorophyll. The Dual-PiGP plant lamps were applied indoors to cultivate Italian lettuce, and commercial plant lamps assembled by LED chips were chosen as reference. The cultivation results indicated that the biomass of Italian lettuce was 12.12% greater than those cultivated using commercial plant lamps. Further analysis also certificated that the content of soluble protein and total chlorophyll were also improved. The Dual-PiGP light converter strategy provides an option for next-generation plant growth LEDs.

In present work, a series of luminescent glass ceramic plates were prepared via phosphor-in-glass (PiG) technology, in which included the phosphor of ZnGa2O4:Cr3+ (ZGO:Cr3+) and glass host with composition of 30SiO2-30ZnO-22B2O3-12BaO-6Al2O3 as matrix. The structure of ZnGa2O4:Cr3+-based PiG (ZGO:Cr3+-PiG) samples are characterized by powder X-ray diffraction, scanning electron microscope, and energy dispersive spectrometer mapping. These phosphors are found to be embedded in glass matrix without interfacial reaction. In addition, the ZGO:Cr3+-PiG sample shows a quantum efficiency of ∼52.8% and its fluorescence intensity maintains 68.2% when temperature reaching 150 °C. Finally, high-power and color-stable far-red emission plant growth LEDs was fabricated by ZGO:Cr3+-PiG and 400 nm near-UV LED chip, which spectra matches well the absorption of plant's photosynthetic pigments. More importantly, it responds to all of phytochrome, triggering providing broad spectral range for plant growth LEDs.

Flax fibre reinforced polymer (FFRP) has been heavily studied in terms of static properties. To study its dynamic behaviour, experimental work also needs to be carried out. This study presents the tensile properties of flax fibre reinforced polymer (FFRP) composite under static and dynamic loadings. Experiments and Weibull distribution analysis were performed to investigate the strain rate effect on the dynamic properties of FFRP composites. In total, 45 specimens were considered. Dynamic tensile tests were performed by using a high-speed servo-hydraulic testing machine with a strain rate ranging from 0.764 s−1 to 135.68 s−1. Empirical formulas of dynamic increase factor (DIF) were derived at various strain rates. Weibull distribution analysis was applied to quantify the variability of tensile strength at different strain rates. Failure process and failure modes of FFRP were discussed via analysing high-speed camera recording. The results show that the tensile strength, failure strain, DIF and energy absorption of FFRP increased with the strain rate when it was higher than 79.12 s−1.

Fluorescence of carbon dots (CDs) has grown well for substantial applications, but the long-lived photoluminescence, such as room temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF), still catch less attention due to the serious deactivation of triplets under ambient conditions, leading to extremely low radiative efficiency. Herein, we simultaneously achieved both of them by incorporating CDs into poly(vinyl alcohol) (PVA) with the assistance of electrospinning technology. Through systematic investigation, ordered mesoporous structure from the electrospun CDs/PVA nanofibers can effectively stabilize the triplet states of CDs, thus enabling the reverse intersystem crossing (RISC) process for TADF and realizing the first example in CDs/polymer system. RTP is closely related to the triplet excited states of the carbonyls located at the surface of CDs and PVA molecule can rigidify these groups with hydrogen bonds, which can prevent quenching from atmospheric oxygen to promote the RTP and TADF behaviors in the air atmosphere. The afterglow spectrum of these nanofibers exhibits dual emission centered at 456 nm and 569 nm, originated from TADF and RTP, respectively. By changing the excitation wavelength or by adjusting the temperature of measurement, the color of the photoluminescence (PL) can be systematically tailored, the white-light emitting is promising. Moreover, these nanofibers show a long average afterglow lifetime of 1.61 s with visually recognizable period of 9 s. Moreover, CDs/PVA composites (nanofibers, solution, film, and aerogel) demonstrate potentialities in optical imaging, writing, anti-counterfeiting, temperature sensing.

Carbon dots (CDs) have gained intensive interests owing to their unique structure and excellent optoelectronic performances. However, to acquire CDs with a broadband emission spectrum still remains an issue. In this work, nitrogen-doped CDs (N-CDs) with near-ultraviolet (NUV), visible, and near-infrared (NIR) emission were synthesized via one-pot solvothermal strategy, and the excitation-independent NUV and NIR emission and excitation-dependent visible emission were observed in the photoluminescence (PL) spectra of N-CDs. Moreover, the as-synthesized N-CDs displayed two-photon fluorescence emission. It is important to note that N-CDs also exhibited piezochromic luminescence with reversibility, in which the red- and blue-shifted PL with increasing applied pressure (0.07-5.18 GPa) and the red- and blue-shifted PL with releasing applied pressure (5.18 GPa to 1 atm) were developed for the first time. Combined with good hydrophilicity, high photobleaching resistance, and low toxicity, the piezochromic luminescence would greatly boost the valuable applications of N-CDs.

Far-red/phytochrome (PFR) plays a key role in photomorphogenesis of plants. However, how to obtain a near-infrared (NIR) emitting phosphor with high external quantum efficiency (EQE), suitable spectral profile, and low thermal quenching remains a huge challenge. Herein, a NIR phosphor, Gd2.4Lu0.6Ga4AlO12:Cr3+,H3BO3 (GLGA:Cr3+) was developed via regulating the crystal field environment and adding fluxes, which exhibits a peak maximum at 728 nm with a relatively narrow full-width at half maximum (FWHM) of 107 nm, matching well with the absorption band of PFR. Upon 450 nm excitation, the internal quantum efficiency (IQE) and EQE of the optimal phosphor are 90.3% and 32.0%, respectively. At 423 K, the integrated emission intensity of the investigated phosphor is about 75% of that at room temperature. Benefiting from the excellent optical performance, a NIR phosphor-converted light-emitting diode (pc-LED) was fabricated, which shows a NIR output power of 505.99 mW and photoelectric conversion efficiency of 11.24% at 300 mA. Moreover, plant growth experiments demonstrate that the biomass of pea seedlings is increased by 67.72% under supplementary NIR light irradiation. The findings of this research will motivate further research on new Cr3+-doped NIR phosphors for regulating photomorphogenesis of plants.

Developing high-performance carbon dots (CDs) with high photoluminescence quantum yield, excellent stability, and good biocompatibility as well as explore the related luminescence mechanism is still an urgent problem to be solved at present. Herein, we develop a new class of green-emitting silanized carbon dots (Si-CDs) featuring average size of ~ 2.8 nm, ultrahigh photoluminescence quantum yield of ~ 93%, robust photostability, and low cytotoxicity by high-temperature dehalogenation/polymerization process. Our experiments verify the dehalogenation process can alleviate the spin–orbit coupling (SOC) effect of heavy-atom-rich organic fluorophores with severe intersystem crossing through high-temperature hydrothermal reaction, meanwhile, the possibility of transition from the excited state (S1) to triplet state (T1) in the Si-CDs is significantly reduced, thus enhancing the fluorescence intensity and prolong fluorescent lifetime of Si-CDs. Besides, multiple fluorescent emitters can be integrated into one nanodot to effectively enhance the emission intensity by cross-linking polymerization. Owing to good optical properties of the obtained Si-CDs, when used as fluorescent nanoprobes, Si-CDs can rapidly and universally label dead bacteria, fungi, and mammalian cells, which can meet the needs of green fluorescent nanoprobes for specific imaging of dead cells, so as to fast discriminate live/dead cells. We believe that Si-CDs with excellent optical performance, ultrasmall particle size, and low cytotoxicity can be applied to the fields of biological imaging, optical devices, and anti-counterfeiting.

The investigation of efficient red phosphors is highly desired for the development of novel warm white light emitting diodes (WLEDs). In this paper, we report on an efficient red phosphor of Mn4+-activated BaTiF6 by a facile co-precipitation method as a promising candidate for warm white LEDs. BaTi1−xF6:xMn4+ phosphors show efficient pure red emission with a high quantum yield (QY) of 44.5% under 460 nm excitation. The BaTi1−xF6:xMn4+ phosphor exhibits a number of advantages. Firstly, the corresponding excitation/absorption profile matches the commercial blue LED chip well. Secondly, it also exhibits appropriate CIE coordinates (x = 0.694, y = 0.306) with an activation energy of 0.603 eV. The demonstration of a blue chip combined with a blend of yellow-emitting YAG:Ce3+ and newly developed BaTi0.97F6:0.03Mn4+ red phosphor greatly improved the colour rendering index (CRI) from 69.9 to 83.5, while significantly decreasing the correlated colour temperature (CCT) from 5088 to 4213 K, thus validating their application in warm white LEDs.

To obtain white light-emitted diodes (wLEDs) with a low correlated color temperature (CCT) and a high color rendering index (CRI), red-emission is indispensable in their emission spectra. Herein, CaO:Ce3+,Li+,F− yellow phosphors with more red spectral component have been prepared via a high temperature solid-state reaction. As compared to the F− undoped samples, CaO:Ce3+,Li+,F− phosphor have lower critical doping concentration of Ce3+ and show stronger luminescence. At the critical concentration, a quantum efficiency of 66.4% and enhanced thermal and chemical stability were obtained in CaO:Ce3+,Li+,F−. Furthermore, a CaO:Ce3+,Li+,F−-based phosphor-in-glass (PiG) using the red-emitting glass system with the composition of SiO2–Na2CO3–Al2O3–CaO:Eu3+ as the host material was constructed and used for high-power white LED applications. Such PiG samples with different phosphor doping concentrations can satisfy various light color demands and display higher reliability than the CaO:Ce3+,Li+,F− phosphor. An optimal PiG-based wLED exhibits color coordinates of (0.3769, 0.3386), a CCT of 3774 K, a CRI of 82.5 and a LE of 73.1 when the mass ratio of phosphor to glass matrix was 7 : 50 in PiG. Moreover, such PiG-based wLED also showed acceptable color stability under different drive currents. All the above results demonstrate that CaO:Ce3+,Li+,F− can be expected to be a potential alternative yellow phosphor for blue light excited PiG based warm wLEDs, particularly for high-power devices.