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[Display omitted] In this study, a high-throughput point-of-care testing (HT-POCT) system for detecting serum iron was developed using a hydrophobic deep eutectic solvent (HDES) fluorescence detection platform. This machine learning-assisted portable platform enables intelligent and rapid detection of trace iron ions. Blue fluorescent hydrophobic carbon quantum dots (CQDs) were synthesized using the solvothermal method. The CQDs exhibit a notable quantum yield (QY) of 36.6%, demonstrating exceptional luminescent characteristics and precise, sensitive detection capabilities for Fe3+ ions. By incorporating CQDs into specially filtered HDESs, this blend serves a dual function of concentrating iron ions from the sample and facilitating their detection. The collaboration between the two enhances the fluorescence detection signal significantly, while reducing interference from hydrophilic substances. The limit of detection can be as low as 33 nM. The principles of synthesizing HDESs and the process of extracting Fe3+ using HDESs fluorescence detection system were modeled using density functional theory (DFT). As the concentration of Fe3+ increases, the fluorescence signal detected from the sample decreases, accompanied by visible color changes when exposed to ultraviolet light. The machine learning-assisted portable platform is designed to capture fluorescence images of samples directly. The application developed using the YOLOv8 algorithm efficiently analyzes multiple samples in single or multiple images, simultaneously extracting color data from each sample and determining the concentration of iron ions. The Relative Standard Deviations (RSDs) for both single-sample and multi-sample tests were less than 10%. The machine learning-assisted portable platform provides a reliable method for detecting trace iron ions. [ABSTRACT FROM AUTHOR]

In this work, a series of carbon quantum dot (CQDs) modified three-dimensional flower-like BiOCl microspheres were synthesized using a simple solvothermal method.A multitude of techniques like XRD, TEM, XPS, BET, XPS UV–vis, PL and EPR were employed to investigate the morphology, structure, optical and electronic properties as well as photocatalytic performance of the samples. The BC-1.5 photocatalyst displays the he best-performing photocatalytic degradation rate of 99% for Rhodamine B (RhB) degradation under visible-light irradiation within 30 min. The photoactivity is 5.3 times of that of the bare BiOCl. This unique three-dimensional flower-like structure can provide a large number of reaction sites and stronger internal light reflection, which can enhance the absorption of photons. Meanwhile, CQDs enable faster charge transfer and more effective separation of photogenerated charge carriers, thereby increasing the degradation rate. The mechanism of photocatalysis was further proposed, and the charge transfer and active substances formed during photocatalysis were unfolded. This study provides a new opportunity for rational design of efficient photocatalysts in environmental remediation. [ABSTRACT FROM AUTHOR]

Ammonia inhibition poses a significant challenge to the efficient and stable operation of anaerobic digestion (AD) systems by leading to the inhibition of volatile fatty acid conversion and reduced methane production. This study explores the utilization of lignin-based hydrochar (LHC) and carbon quantum dots (CQDs) produced via hydrothermal carbonization of alkali lignin to alleviate ammonia inhibition in AD processes. The results showed that both LHC and CQDs help counter the decline in methane yield and production rate typically associated with ammonia inhibition. Notably, the addition of 1 g/L CQDs significantly increased methane production by 24.25% compared to the control group. While LHC showed limited ammonia adsorption, its primary impact was enhancing direct interspecies electron transfer (DIET) through improved redox capacity and promoting humic acid-like organics formation. In contrast, CQDs reduced charge transfer resistance, significantly enhancing system redox capacity. Optimizing the hydrothermal carbonization temperature of LHC to 250 °C further optimized its redox properties, boosting methane production by 30.53% at a concentration of 3 g/L. Microbial community and metabolic pathway analyses indicated that LHC and CQDs enriched hydrolytic and acidifying bacteria, as well as DIET-associated microorganisms, facilitating efficient volatile fatty acid production and conversion. This process enabled the sustained operation of both acetoclastic and hydrogenotrophic methanogenic pathways, effectively mitigating the adverse effects of high ammonia nitrogen concentrations. Highlights: • Two lignin-based carbon materials alleviated ammonia inhibition in different ways. • Both materials enhanced electron transfer, volatile fatty acid conversion, and stabilized methanogenic pathways. • Increasing LHC hydrothermal carbonization temperature enhanced redox properties, boosting methane yield. [ABSTRACT FROM AUTHOR]

Carbon quantum dots (CQDs) have recently drawn enormous attention due to not only their unique chemical, biological, and optical properties but also because a variety of renewable biomasses are readily utilized as carbon sources in their synthesis. This study investigated the synthesis, characterization, and functional evaluation of CQDs from unbleached mechanical pulp as a natural lignocellulosic resource. The CQDs were synthesized using a one-step hydrothermal synthesis with varying temperature, time, and pulp consistency. The resulting CQDs exhibit a spherical shape with a size distribution of 9.73 ± 0.82 nm and lattice parameters of 0.21 and 0.34 nm, indicating a graphite core. The photoluminescence spectra showed evident fluorescence characteristics, with an emission peak at 435 nm at an excitation wavelength of 370 nm. The as-prepared CQDs were also chemically composed of C=C and C=O bonds linked to the hydroxyl and carboxyl functional groups, which are typically found in lignocellulose-based CQDs. The CQDs demonstrated antibacterial activity exceeding 99.9% against E. coli at the lowest concentration of 0.75 mg/mL. Demonstrating its antioxidation property, the DPPH radical scavenging activity surpassed 90% with more than 40 µg/mL of the CQD solution. [ABSTRACT FROM AUTHOR]

Dielectric capacitors offer immense application potential in advanced electrical and electronic systems with their unique ultrahigh power density. Polymer-based dielectric composites with high energy density are urgently needed to meet the ever-growing demand for the integration and miniaturization of electronic devices. However, the universal contradictory relationship between permittivity and breakdown strength in traditional ceramic/polymer nanocomposite still poses a huge challenge for a breakthrough in energy density. In this work, all-organic carbon quantum dot CDs were synthesized and introduced into a poly(vinylidene fluoride) PVDF polymer matrix to achieve significantly boosted energy storage performance. The ultrasmall and surface functionalized CDs facilitate the polar β-phase transition and crystallinity of PVDF polymer and modulate the energy level and traps of the nanocomposite. Surprisingly, a synergistic dielectric enhancement and loss reduction were achieved in CD/PVDF nanocomposite. For one thing, the improvement in εr and high-field Dm originates from the CD-induced polar transition and interface polarization. For another thing, the suppressed dielectric loss and high-field Dr are attributed to the conductive loss depression via the introduction of deep trap levels to capture charges. More importantly, Eb was largely strengthened from 521.9 kV mm−1 to 627.2 kV mm−1 by utilizing the coulomb-blockade effect of CDs to construct energy barriers and impede carrier migration. As a result, compared to the 9.9 J cm−3 for pristine PVDF, the highest discharge energy density of 18.3 J cm−3 was obtained in a 0.5 wt% CD/PVDF nanocomposite, which is competitive with most analogous PVDF-based nanocomposites. This study demonstrates a new paradigm of organic quantum dot-enhanced ferroelectric polymer-based dielectric energy storage performance and will promote its application for electrostatic film capacitors. [ABSTRACT FROM AUTHOR]

In this study, carbon quantum dots (CQDs) were effectively synthesized from Carissa carandas using a cost-effective and energy-efficient one-step hydrothermal process. The CQDs were thoroughly characterized using various analytical techniques, including FTIR, XRD, SEM, TEM, and XPS. The resulting CQDs exhibited impressive optical properties with a bandgap of 2.7 eV, along with stable fluorescence, excellent biocompatibility, and a quantum yield (QY) of 24.44%. These CQDs demonstrated exceptional photocatalytic performance, achieving 98.13% degradation of Crystal Violet (CV) dye within 30 min under visible light. The high photocatalytic efficiency was consistent across different dye concentrations (5, 10, 15, 20, and 25 mg/L), highlighting the CQDs' ability to enhance the separation and migration of photoexcited electron–hole pairs. The study identified hydroxyl radicals (·OH) as the primary agents driving CV degradation, while superoxide anions (O2·⁻) and holes (h⁺) played secondary roles. Key operational parameters such as catalyst dosage, pH, and contact time were optimized to maximize dye degradation. Adsorption studies revealed that CV adsorption onto CQDs followed the Freundlich isotherm model (R2 = 0.98) and conformed to pseudo-first-order kinetics, demonstrating the CQDs' efficiency in the adsorption process. The total material cost was calculated at 52 INR per 100 g, with an energy consumption of 10 kW during synthesis. Additionally, the interaction between CQDs and lysozyme protein was explored through fluorescence quenching, indicating potential applications in biosensing. This work underscores the versatility and efficiency of CQDs as a multifunctional material for environmental and biological applications. [ABSTRACT FROM AUTHOR]

Photocatalysis purifies industrial paper wastewater by selectively breaking bonding bonds in lignin. To address the shortcomings of single photocatalysts such as narrow photoresponsive region, high photogenerated carrier complexation rate, and low photocatalytic activity. In this paper, Mg and N doped carbon quantum dots (Mg/N doped CQDs) were prepared by hydrothermal method. Then Zn4In2S7 series catalysts with different loadings (0, 0.3, 0.6, 1.2 wt %) of Mg/N doped CQDs (denoted as ZIS 350 °C, ZIS-3 350 °C, ZIS-6 350 °C, ZIS-12 350 °C) were constructed based on condensation reflux and inert gas calcination method. The catalyst possesses highly efficient visible light-catalyzed depolymerization of sodium lignosulfonate (SLS), an industrial waste material. From the BET curve, the specific surface area of ZIS-6 350 °C was the largest. The composite of Mg/N doped CQDs reduced the band gap of Zn4In2S7 while promoting the separation and transfer of photogenerated electrons/holes, as confirmed by DRS, Mott-Schottky, transient photocurrent and EIS analyses. From the photocatalytic activity test, the photocatalytic depolymerization of lignin by ZIS-6 350 °C was increased by 21.2% compared with that of ZIS 350 °C, and the reactions all follow the pseudo first order kinetic model. A possible photocatalytic mechanism was proposed based on the active species capture experiments. [ABSTRACT FROM AUTHOR]