In Situ Synthesis of Ti3+ Self-Doped TiO2/N-Doped Carbon Nanocomposites and its Visible Light Photocatalytic Performance

This study evaluates Ce and N doped carbon quantum dots (CQDs) integrated into hydrogel matrices for neodymium (Nd) ion removal from aqueous solutions. CQDs were synthesized using Agaricus Bisporus mushrooms and incorporated into hydrogels with 1% mushroom loading, achieving a maximum adsorption capacity of 78.55 mg/g under 180 min, pH 5.0, 298 K, and 1 g/L solid-to-liquid ratio. Adsorption followed the Langmuir isotherm and pseudo-second-order kinetics, with thermodynamic analyses confirming a spontaneous and endothermic process. These findings demonstrate the effectiveness of Ce-N/CQDs@HG composites for environmental remediation.

Blue emissive N-doped carbon quantum dots (N-CQDs) were prepared through a convenient and sustainable microwave synthesis method using citric acid monohydrate (CA) and urea as carbon and nitrogen sources, respectively, with an optimum molar ratio of 1:3 (CA:Urea). The surface functional groups, morphology, and hydrodynamic characteristics of N-CQDs were analysed with Fourier-transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscopy (HRTEM) and dynamic light scattering (DLS). The as-synthesised N-CQDs with a quantum yield of 14.8%, exhibited excitation-independent fluorescence emission at 443 nm due to surface-state-induced fluorescence, with an optimum excitation wavelength at 360 nm. The N-CQDs were spherical, with an average particle size of 7.29 ± 3.91 nm based on HRTEM analysis. However, DLS analysis showed that the hydrodynamic size (293.0 ± 110.8 nm) was larger than the average particle size due to the presence of hydrophilic polymer chains and abundant surface groups on the N-CQDs. The free chorine-induced fluorescence quenching of N-CQDs at pH 9 denotes the sensitivity of N-CQDs towards detection of free chlorine in the form of hypochlorite (ClO-) ion, providing the limit of detection (LOD) of 0.4 mM and limit of quantification (LOQ) of 1.2 mM. The fluorescence quenching effect in the N-CQDs caused by the quencher (ClO-) is attributed to the dynamic quenching mechanism, via an intersystem crossing. The low selectivity of N-CQDs towards various ions justified N-CQDs' selectivity as a free chlorine fluorescent probe that can be used for wastewater testing due to its high range sensitivity.

High temperature hydrothermal etching of g-C3N4 for synthesis of N doped carbon quantum dots-supported CdS photocatalyst to enhance visible light driven hydrogen generation

Insights into the newly synthesized N-doped carbon dots for Q235 steel corrosion retardation in acidizing media: A detailed multidimensional study

Visible-light-activated N-doped CQDs/g-C3N4/Bi2WO6 nanocomposites with different component arrangements for the promoted degradation of hazardous vapors

Efficient photocatalytic-fenton oxidation performance of Fe3+/g-C3N4/NCDs nanorods: Structure-activity relationship of photocatalytic degradation of water pollutants

N-doped carbon quantum dots enhance anaerobic digestion under light condition: The performances and potential mechanisms

Fluorescent carbon quantum dots as a novel solution and paper strip-based dual sensor for the selective detection of Cr(VI) ions

The doping of carbon quantum dots with nitrogen provides a promising direction to improve fluorescence performance and broaden their applications in sensing systems. Herein we report a one-pot solvothermal synthesis of N-doped carbon quantum dots (NCQDs) and the synthesis of a series of NCQDs with different nitrogen contents. The as-prepared NCQDs were compared with carbon quantum dots (CQDs); the introduction of nitrogen atoms largely increased the quantum yield of NCQDs and highest emission efficiency is up to 36.3 %. The fluorescence enhancement may originate from more polyaromatic structures induced by incorporated nitrogen atoms and protonation of nitrogen atoms on dots. It was found that NCQDs can act as a multifunctional fluorescence sensing platform because they can be used to detect pH values, Ag(I), and Fe(III) in aqueous solution. The fluorescence intensity of NCQDs is inversely proportional to pH values across a broad range from 5.0 to 13.5, which indicates that NCQDs can be devised as an effective pH indicator. Selective detection of Ag(I) and Fe(III) was achieved based on their distinctive fluorescence influence because Ag(I) can significantly enhance the fluorescence whereas Fe(III) can greatly quench the fluorescence. The quantitative determination of Ag(I) can be accomplished with NCQDs by using the linear relationship between fluorescence intensity of NCQDs and concentration of Ag(I). The sensitive detection of H2O2 was developed by taking advantage of the distinct quenching ability of Fe(III) and Fe(II) toward the fluorescence of NCQDs. Cellular toxicity test showed NCQDs still retain low toxicity to cells despite the introduction of a great deal of nitrogen atoms. Moreover, bioimaging experiments demonstrated that NCQDs have stronger resistance to photobleaching than CQDs and more excellent fluorescence labeling performance.

Supported N-doped carbon quantum dots as the highly effective peroxydisulfate catalysts for bisphenol F degradation

Nonenzymatic detection of glucose based on Cu2+ catalytic oxidation on N-doped carbon quantum dots

N-doped carbon quantum dots for TiO2-based photocatalysts and dye-sensitized solar cells

N-doped carbon quantum dots from osmanthus fragrans as a novel off-on fluorescent nanosensor for highly sensitive detection of quercetin and aluminium ion, and cell imaging

The establishment of sensing platform for trace analysis of Fe3+ in biological systems is meaningful for health monitoring. Herein, a Fe3+ sensitive fluorescent nanoprobe was constructed based on highly fluorescent N-doped carbon quantum dots (NCQDs) derived from bamboo stems through a hydrothermal method employing ethylenediamine as the nitrogen dopant. The prepared NCQDs had a uniformly distributed size and their mean size was around 2.43 nm. Abundant functional groups (C=N, N-H, C=O, and carboxyl) anchored on NCQDs demonstrated successful doping of N in CQDs. The obtained NCQDs possessed a high fluorescence quantum yield of 20.02% and outstanding fluorescence stability over a wide pH range and at high ionic strengths. Moreover, Fe3+ ions presented a specific fluorescent quenching effect to the as-prepared NCQDs. The calibration curve for fluorescence quenching degree corresponding to Fe3+ concentration showed a linear response in a range of 0.01-10 µM, and detection limit was 0.486 µM, which indicated that the NCQDs had high sensitivity to Fe3+ ions. Ascribed to these unique properties, the NCQDs were selected as luminescent probes for trace amount of Fe3+ ions in human serum. These results demonstrated their promising use in clinical diagnostics and other biologically relevant studies.

N-doped carbon quantum dots as fluorescent probes for highly selective and sensitive detection of Fe3+ ions