Double-layer supercapacitors ( SCs) based on carbon quantum dots (CQDs) are a novel and highly potential electrical energy storage technology. They have a high-power density (Pd) and a long span life, which are desirable for electric automobiles, however, their specific capacitance (Csp) needs to be improved. Here, we introduce an affordable and environmentally sustainable method to enhance the capacitance of Boron-Sulphur doped carbon quantum dots (B,S-CQDs) from Oloptum miliaceum (Grass) via the hydrothermal method. The findings show that heteroatom-doping might greatly enhance the Csp and energy density (Ed) when compared to undoped CQDs. As a consequence, the B,S-CQDs demonstrate a high Csp of 390 F g− 1 at 0.1 A g− 1 and 152 F g− 1 at 1.0 A g− 1, revealing excellent rate performance. Along with the electrode demonstrates superb coulombic efficiency with only 2% efficiency loss after 3000 cycles. Furthermore, the B,S-CQDs with a wide voltage range of 0.8 V yields a remarkable Ed of 48.0 Wh kg− 1 and Pd of 524 W kg− 1. These promising findings demonstrate an economical and environmentally friendly electrode material for high-performance SCs. This study offers ideas for the design and preparation of SCs electrode materials and represents a major endeavour to turn waste biomass (smilograss) into a useful electrode material.

Developing highly durable and active catalysts is essential for improving the performance and longevity of proton exchange membrane fuel cells (PEMFCs). In this study, we propose a novel strategy to enhance catalyst dispersion and stability by incorporating pyrrolic nitrogen-rich carbon (pNC) quantum dots into highly crystalline carbon supports. The introduction of pNC generates strong anchoring sites for Pt nanoparticles, facilitating uniform dispersion and minimizing aggregation, which are key factors in enhancing catalytic performance and durability. The synthesized Pt/CVC150 catalyst exhibited excellent oxygen reduction reaction activity, with a half-wave potential of 0.842 V and a limiting current density of 6.3 mA cm− 2. Under accelerated stress test conditions, the catalyst retained 61.4% of its initial peak power density after prolonged cycling, indicating enhanced durability. Furthermore, single cell testing confirmed its improved electrochemical activity and stability of the Pt/CVC150 catalyst in a practical PEMFC operating environment. These findings suggest that the incorporation of heteroatom-doped carbon moieties onto carbon supports represents a promising strategy for the development of nextgeneration PEMFC catalysts with enhanced performance and longevity.

The avenue to synthesize eco-friendly and high-performing warm-white light emitting diodes (WLEDs) using quantum-dots for color conversion is challenging. Here, the graphene quantum dots (GQDs) are synthesized from Moringa oleifera leaves without the need of any organic solvents or reducing agents by a one-pot hydrothermal method and utilized for the design of efficient warm WLEDs. The photoluminescence of the obtained GQDs is found to be red-shifted as the excitation wavelength increases. This is ascribed to an excitation of multiple transitions due to various surface traps related to surface amino and oxygen functionalized groups as revealed from X-ray-photoelectron–spectroscopy and FTIR results. Three different concentrations of GQDs are embedded in polyvinyl-alcohol matrix acting as color-converters for the design of WLED devices. By increasing the GQDs concentration, the color correlated temperatures are tuned from 3804 to 2593 K and the luminous efficacy from 39.3 to 71.69 lm/W. Moreover, the chromaticity coordinates of the devices are shifted from (0.3825, 0.3665) to (0.4807, 0.4478). The brightness of the fabricated devices based on these green-GQDs are comparable with those of warm LEDs prepared from chemically synthesized graphene and carbon dots and can be suitable for indoor lighting applications.

Designing long-wavelength emissive carbon dots (CDs) with high photoluminescence quantum yield (PL QY) is an inevitable component for lighting applications. However, it is still challenging to develop an efficient CDs with excitation-independent emission in long-wavelength regions. In this work, we developed an excitation-independent yellow emissive CD (y-CDs) with PL emission centered at 568 nm via a facile solvothermal treatment of citric acid and melamine using toluene as solvent. The synthesized, y-CDs contain a high degree of conjugated sp2- carbon domains (fused rings) with different surface groups, which serve as a center for photon absorption. The addition of melamine improves the degree of sp2- conjugated carbon domain and surface groups thereby switching the emission of y-CDs from excitation-dependent to excitation-independent emission with excellent PL QY of 80.2%, UV stability, and large Stoke shift. This work not only developed an efficient yellow emissive CD but also explored the possible mechanism of excitation-independent emission and used it for the development of phosphor-converted LEDs. The LED shows warm yellow light with CIE coordinates of (0.48, 0.49), CCT of 2983 K, excellent color purity of 94%, and high thermal stability. This study promotes the development of cost-effective and ecofriendly optoelectronic devices for smooth lighting applications.

In this study, quantum dots with Au/CdSe complex cores composed of Au as a metal base were synthesized, syrup was prepared, and coated on natural simulated LED unit modules, and the optical properties of traffic signs using them were investigated, and the following conclusions were obtained. The nanoparticles synthesized at 260°C and 280°C grew into irregular shapes with PL wavelengths of 624-627㎛, half-widths of 35㎛, PL-QY ratios of 55-61%, and grain diameters of 5-7㎛. The quantum dot syrup was applied to the LED unit module to produce a traffic sign composed of 4CL unit modules, and the luminance of 179 ㏅/㎡, insulation resistance of 10,000㏁, and insulation withstand of 500V were achieved, meeting the performance and specifications of the standard guidelines for luminescent traffic safety signs. The surface temperature of the unit module laminated with 4CL resin is 24~25℃, which shows a stable heat distribution, confirming that it can be applied as a sign using unit modules.

Tannic acid (TA) is one of the active components in the Galla Chinensis and has various effects, including antioxidant and anti-inflammatory properties. However, research on its antiviral properties remains limited. Here, tannic acid carbon dots (TA-CDs) were prepared as potential antiviral drugs from polyphenol TA under different temperature conditions (180, 200, 220 and 240 °C). Compared to TA alone, TA-CDs exhibited lower cytotoxicity and a tenfold enhanced in antiviral activity. Additionally, the antiviral effects of TA-CDs varied with preparation temperatures, with the best effect observed at 200 °C (CDs-2), reaching a titer of 2.8 orders of magnitude in porcine reproductive and respiratory syndrome virus (PRRSV), mainly due to its relatively higher number of functional groups and smaller particle size. Mechanically, CDs-2 was shown to inhibit PRRSV by targeting the stages of inactivation, adsorption, invasion, replication, and down-regulating reactive oxygen species (ROS) levels. Moreover, CDs-2 exhibited a high inhibitory effect on porcine epidemic diarrhea virus (PEDV), reaching a titer of 7 orders of magnitude. This study reveals the importance of temperature in synthesis of traditional Chinese medicine-derived carbon dots (TCM-CDs) and confirms their potential as antiviral drugs, providing valuable information for development of TCM antiviral drugs.

This study details the synthesis and characterization of phosphorus-sulfur co-doped graphitic carbon nitride quantum dots (PSQ) and their integration into g-C3N4 (CN) to form PSQ/CN composites for the enhanced photocatalytic reduction of Cr(VI) and fluorescence detection. Incorporating PSQ into CN was found to significantly improve light absorption, narrow the band gap, and enhance charge separation efficiency. Notably, the composite material exhibits superior photocatalytic performance, especially in acidic environments. Photocatalytic assessments utilizing Cr(VI) demonstrated that the PSQ/ CN composite outperformed both undoped and singly doped materials, indicating its superior photocatalytic activity. Additionally, phosphorus-sulfur co-doping markedly increased the fluorescence quantum yield of PSQ. The fluorescence intensity exhibited a linear decrease with increasing Cr(VI) concentrations, enabling sensitive and selective detection of Cr(VI) with a detection limit as low as 1.69 μmol/L. Collectively, the PSQ/CN composite and PSQ highlight their potential for photocatalysis and fluorescence-based detection of Cr(VI), providing high sensitivity, selectivity, and synergistic interactions within the composite material.

Waste utilization is not only a way to protect the environment and realize green chemistry, but also a means to create novel materials. In this study, based on waste grape seeds as the biowaste-derived carbon dots (G-BCDs), a straightforward one-pot green method was employed for the rapid detection of folic acid (FA). Owing to the internal filter effect and the static mixing quenching mechanism, the sensing principle of G-BCDs was effectively quenched by FA. The results showed fluorescence at an emission wavelength of 415 nm upon excitation at 330 nm with a quantum yield of 1.5%. Particularly, the FA sensing assay obtained a broad linear range of 2–220 μM and the limit of detection was 0.48 μM. In addition, the fluorescence probe was successfully utilized for detecting FA in tablets, blood, and urine samples, yielding desirable results, which indicated promising applications in the fields of biological and pharmaceutical analysis.

Quantum dot nanocomposite-based luminescent materials have gained attention for solid-state lighting and optical displays. This study presents a one-step, eco-friendly hydrothermal process to synthesize nitrogen, potassium, and calcium-doped carbon quantum dots (N, K, Ca-doped CQDs) from the flower extract of Mesembryanthemum crystallinum L. (ice plant). The CQDs were characterized using HRTEM, EDX, SAED, XPS, XRD, NMR, FTIR, zeta potential, UV–Vis, and photoluminescence spectroscopy. HRTEM revealed an average particle size of 4.6 nm, with a range of 2 to 7 nm. The CQDs exhibited a quantum yield of 20%, excellent water solubility, photostability, and greenish fluorescence under UV (365 nm). The fluorescence spectra were analyzed using CIE (Commission Internationale de l’Eclairage) chromaticity coordinates to determine the emitted color. The fluorescence emission behavior was influenced by solvent polarity, locally excited (LE) states, intramolecular charge transfer (ICT) processes, and hydrogen bonding. The hydrogen bonds between N, K, Ca-doped CQDs and DI water likely enhanced the stability of the ICT state, resulting in a red shift in fluorescence. Additionally, we developed an eco-friendly wheat-starch-based bioplastic nanocomposite by embedding the CQDs. The effects of CQD concentration and pH sensitivity on luminescent properties were explored. Finally, we demonstrated a practical application by designing a conceptual nameplate-like calligraphy using the optimized CQDs@bioplastic nanocomposite film (CQD concentration: 240 mg/mL, pH: 2.7), highlighting its potential for luminescent film applications.

Using durian shell as a carbon source and triethanolamine as a nitrogen dopant, nitrogen-doped carbon dots (N-CDs) were prepared via the hydrothermal method. First, by exploring different reaction times, reaction temperatures, and carbon source/dopant ratios to synthesize nitrogen-doped carbon dots, it is concluded that the best process conditions are 200 ℃, reaction time being 15h, and the dopant addition amount being 2mL. Structure and characteristics of the synthesized CDs were analyzed using X-ray photoelectron spectroscopy, Fourier-transform infrared, fluorescence (FL), ultraviolet–visible absorption, and Raman spectra. The N-CDs showed blue FL with a quantum efficiency of 4.28%. The FL characteristics of the N-CDs were utilized for ion detection, which demonstrated that MnO− 4 and Cr 2 O2− 7 ions caused distinct FL quenching through static quenching, while other ions had no significant quenching effect. The detection limits for MnO− 4 and Cr 2 O2− 7 were 37.5 and 46.2 nM, respectively. The N-CDs were subsequently employed to detect these ions in actual water samples, producing satisfactory results. Therefore, the preparation of N-CDs using durian shell as raw material and its application in practical detection work have good application feedback, which not only provides a new way for the reuse of fruit and vegetable wastes but also provides a new detection means for environmental monitoring pollutants.

This study incorporates the formation of carbon quantum dots (CQDs) via a hydrothermal approach, recording the first-time use of castor leaves as a natural precursor. The used precursor offers various benefits including novelty, abundance, elemental composition, and biocompatibility. CQDs were further characterized with multiple techniques including high-resolution transmission electron microscope (HR-TEM), X-ray photoelectron microscopy (XPS), X-ray diffraction (XRD), Fouriertransform infrared spectroscopy (FTIR), Raman spectroscopy, UV–visible spectroscopy, Zeta analysis, and optical spectroscopy. They are fundamentally composed of carbon (71.37%), nitrogen (3.91%), and oxygen (24.73%) and are nearly spherical, and uniformly distributed with an average diameter of 2.7 nm. They possess numerous interesting characteristics like broad excitation/emission bands, excitation-sensitive emission, marvelous photostability, reactivity, thermo-sensitivity, etc. A temperature sensor (thermal sensitivity of 0.58% C− 1) with repeatability and reversibility of results is also demonstrated. Additionally, they were found selective and sensitive to ions in aqueous solutions. So, they are also utilized as a fluorescent probe for metal ion ( Fe3+) sensing. The lowest limit of detection (LOD) value for the current metal ion sensor is 19.1 μM/L.

Graphene quantum dots have recently gained significant attention for their potential application in the development of optoelectronic materials. The present study focused on the ultrasonic method to synthesize white-light-emitting graphene quantum dots from coal soot in just 2 min at room temperature. The white-light emission was achieved in solution and polymeric film with good Commission Internationale del’Eclairage index (0.28, 0.33) and (0.25, 0.30), respectively. The graphene quantum dots cover a significant fraction of the visible region in the emission spectrum with two prominent bands at 475 and 635 nm at 380 nm photoexcitation, corresponding to monomer and J-aggregate emission. The strong reducing and basic nature of the ethylene diamine facilitated the preparation of self-assembled J-aggregate graphene quantum dots through hydrogen bonding and electrostatic interaction. The mechanism of origin J-aggregate emission in the prepared graphene quantum dots was studied using UV–visible absorption, steady-state, lifetime fluorescence spectroscopy, and zeta potential. The as-synthesized graphene quantum dots are successfully coated on the UV-LEDs' surface and emit white light on the applied voltage. The colours of red, green, blue, and yellow balls appear significantly in the lighting of prepared white LEDs.

Due to the sturdy photoluminescence and absorption, CQDs emerged as a suitable candidate for optical sensing probe. The present study deals with the synthesis of blue-fluorescent Carbon Quantum Dot (TAA-CQD) using tannic acid and glycine as novel precursors. The TAA-CQD were synthesised hydrothermally with the high production yield and QY to be 86.12 and 21%, respectively, and an average particle size of 1.9 nm. The TAA-CQD aqueous solution displays excitation-dependent fluorescence emission in the excited range from 420 to 650 nm. The CIE co-ordinates in a highly blue region at (0.14, 0.19) confirmed the synthesised TAA-CQD were blue in fluorescent. Fluorescence of TAA-CQD was stable under all pH range, resisted the high ionic strengths condition and stable over 8 months. Furthermore, the fluorescent TAA-CQD was capable in detecting a tetracycline-classed antibiotic Doxycycline (DXY) along with remarkable selectivity and sensitivity. The measures limit of detection (LOD) was very low 2.42 mM in comparison to other methods. Moreover, the applicability of the proposed work has been fruitfully employed on the pharmaceutical waste. Thus, our designed TAA-CQD based fluorescence sensing system hold great promise for the advanced sensing materials in the detection of DXY and we believe that our approach will be promising and viable in a clinical applications.

This paper is devoted to synthesizing a new type of CDs (carbon dots) with excellent NIR (near-infrared) emission in a biological water environment synthesized from small molecules. Citric acid was adopted as the precursor and treated by one-pot hydrothermal process in DMF solution with the assistance of a microwave. Urea (MH) and ammonium fluoride (MF) were adopted as nitrogen sources to synthesize two types of CDs, respectively. These conditions contributed to generate nanostructured carbon with a higher content of Pyrrolic-N, enrich the functional groups, and exfoliate the ordered layerstacking structure, which finally contributed to the higher NIR absorption band at 808 nm. The physicochemical properties and photothermal conversion ability were fully evaluated by UV–Vis-NIR (ultraviolet–visible light-NIR) absorption and photothermal experiments. MF possessed stronger absorption property and temperature-rising effect in the NIR region than MH, but both exhibited desirable photothermal stability. Next, the in vitro and in vivo experiments demonstrated that both MF and MH exhibited no significant toxicity for cells. NIR irradiation on CDs solution displayed an excellent killing effect on HeLa (breast cancer) and MCF7 (cervical cancer) cells but strongly depended on the concentration of CDs. MH had a weaker killing effect on MCF7 cells compared with MF in the same concentration. But HeLa cells suffered death from lower concentration of MH under NIR irradiation. Both MH and MF exhibited excellent therapy effects and no obvious tissue damage for these major organs of nude mice and BALB/C mice. Above all, both MF and MH with excellent photothermal effect under NIR irradiation had desirable NIR-triggered therapeutic effect on MCF7 and HeLa cells, while they also exhibited good biocompatibility without NIR irradiation.

Ibuprofen (IBU), a common pharmaceutical and personal care product (PPCP), is a pervasive water pollutant with adverse ecological and human health effects after transformation and accumulation. In this study, we synthesized Fe, N-doped carbon quantum dots (Fe, N-CQDs) using pig blood and FeCl3 as a precursor via a one-step hydrothermal method. TEM, XRD, XPS, and UV–Vis were used to characterize the physical and chemical properties of Fe, N-CQDs. We investigated the feasibility of Fe, N-CQDs in activating peroxymonosulfate (PMS) for IBU degradation under visible light. The experimental results revealed that Fe in Fe, N-CQDs predominantly formed a stable complex through Fe–N and Fe-OH, with a high degree of graphitization and a sp2- hybridized graphitic phase conjugate structure. The Fe, N-CQDs/Light/PMS system exhibited strong activity, degrading over 87% of IBU, maintaining a wide pH range (3–10) adaptability. Notably, Fe, N-CQDs acted as visible-light catalysts, promoting Fe3+/ Fe2+ cycling and PMS activation, generating both free radicals ( SO4 •–, ·OH) and non-radicals (1O2, h+) to effectively degrade IBU. This study presents an innovative approach for the sustainable utilization of pig blood as a biomass precursor to synthesize Fe- and N-doped carbon materials. This study provides a new approach for the sustainable and value-added utilization of natural wastes and biomass precursors of Fe- and N-doped carbon materials, which can be used to treat pollutants in water while treating discarded pig blood.

In this study, high-efficiency InZnP/ZnSe/ZnS quantum dots (QDs) were synthesized and applied to the development of self-luminous traffic signs. The synthesized QDs exhibited a photoluminescence (PL) peak wavelength of 613 nm and a uniform nanoparticle size of 6 nm in diameter. Quantum dot films were coated using a roll-to-roll process with varying thicknesses (110 μm, 85 μm, and 75 μm), and color coordinate analysis confirmed that all films fell within the red region. A 4CL resin and PCB with high thermal dissipation properties were employed to fabricate the self-luminous traffic signs. Performance evaluations showed a white luminance of 625.4 cd/㎡, a red luminance of 220.2 cd/㎡, an insulation resistance of 10,000 MΩ, and an insulation breakdown voltage of 500V, indicating excellent performance. This study confirms the potential of InZnP-based QDs as an environmentally friendly alternative to conventional Cd-based QDs. Furthermore, the integration of high-efficiency QD films with advanced heat-dissipating PCB technology is expected to improve traffic safety, particularly in low-visibility and nighttime environments

We report the simple one-step hydrothermal green synthesis of carbon dots (CDs) without any chemical reagents using mangosteen pulp (CDs1), peel (CDs2), and leaf (CDs3) extract as a green carbon source. In the aqueous medium, these CDs had a size of 8–15 nm with an energy gap of about 4 eV. The CDs emitted a bright green color under ultraviolet (UV) irritation with an average fluorescence quantum yield of the CDs of 1.6%. Moreover, the CDs contained various functional groups, such as C = C, C–C, C–O–C, C–O, C = O, C–H, and O–H, which were beneficial for enhancing their fluorescence property. Furthermore, the CDs were applied in the stain fluorescent imaging of myosatellite chicken stem cells and Vero cells. The CDs2 and CDs3 induced a strong fluorescence emission intensity of the strain cells, whereas CDs1 acted as the highest potential enhancer in cell proliferation as confirmed by its cellular viability which was the around four times that of the control. Therefore, the CDs were highly biocompatible and acted as enhancers in cell proliferation in myosatellite chicken stem cells and Vero cells. Thus, simple, cost-effective, scalable, and green synthetic approach-based CDs show promise for the development of selective organelle labeling and optical sensing probes.

Lithium-ion batteries (LIBs) are widely used as essential power sources for electric vehicles and energy storage systems. Among various cathode materials, Li[Ni0.9Mn0.1]O2 (NM90) has gained significant attention for enhancing the performance of LIBs due to its high energy density and nontoxicity. However, increasing the nickel content introduces challenges, including structural instability and cation mixing. To address these issues, we propose a surface coating strategy using nitrogendoped carbon quantum dots (NCQDs). NCQDs provide high electrical conductivity and electrochemically active sites, so the NCQDs coating effectively enhanced both structural stability and electrical/ionic conductivity. The NCQDs were synthesized via a hydrothermal method, and NM90 were synthesized by co-precipitation. The fabricated NCQD/NM_5 electrode exhibited superior electrochemical properties, including a high initial capacity of 189.6 mAh/g, excellent rate performance, and an outstanding capacity retention of 81.5 % after 200 cycles in 1C. These superior results demonstrate that surface modification using the NCQDs strategy for Li[Ni0.9Mn0.1]O2 cathode materials will contribute to the further development of cycle stability and ultrafast performance in energy storage systems.