L-cysteine modified N-doped carbon quantum dots derived from peach palm (Bactris gasipaes) peels for detection of mercury ions

The process of N-doping is frequently employed to enhance the properties of carbon quantum dots. However, the precise requirements for nitrogen precursors in producing high-quality N-doped carbon quantum dots (NCQDs) remain undefined. This research systematically examines the influence of various nitrogen dopants on the morphology, optical features, and band structure of NCQDs. The dots are synthesized using an efficient, eco- friendly, and rapid continuous hydrothermal flow technique. This method offers unparalleled control over synthesis and doping, while also eliminating convention-related issues. Citric acid is used as the carbon source, and urea, trizma base, beta-alanine, L-arginine, and EDTA are used as nitrogen sources. Notably, urea and trizma produced NCQDs with excitation-independent fluorescence, high quantum yields (up to 40%), and uniform dots with narrow particle size distributions. Density functional theory (DFT) and time-dependent DFT modelling established that defects and substituents within the graphitic structure have a more significant impact on the NCQDs' electronic structure than nitrogen-containing functional groups. Importantly, for the first time, this work demonstrates that the conventional approach of modelling single-layer structures is insufficient, but two layers suffice for replicating experimental data. This study, therefore, provides essential guidance on the selection of nitrogen precursors for NCQD customization for diverse applications.

Voltammetry for quantitative determination of trace mercury ions in water via acetylene black modified carbon paste electrode

Photocatalytic pathways are proved crucial for the sustainable production of chemicals and fuels required for a pollution-free planet. Electron-hole recombination is a critical problem that has, so far, limited the efficiency of the most promising photocatalytic materials. Here, the efficacy of the 0D N doped carbon quantum dots (N-CQDs) is demonstrated in accelerating the charge separation and transfer and thereby boosting the activity of a narrow-bandgap SnS2 photocatalytic system. N-CQDs are in situ loaded onto SnS2 nanosheets in forming N-CQDs/SnS2 composite via an electrostatic interaction under hydrothermal conditions. Cr(VI) photoreduction rate of N-CQDs/SnS2 is highly enhanced by engineering the loading contents of N-CQDs, in which the optimal N-CQDs/SnS2 with 40 mol% N-CQDs exhibits a remarkable Cr(VI) photoreduction rate of 0.148 min-1 , about 5-time and 148-time higher than that of SnS2 and N-CQDs, respectively. Examining the photoexcited charges via zeta potential, X-ray photoelectron spectroscopy (XPS), surface photovoltage, and electrochemical impedance spectra indicate that the improved Cr(VI) photodegradation rate is linked to the strong electrostatic attraction between N-CQDs and SnS2 nanosheets in composite, which favors efficient carrier utilization. To further boost the carrier utilization, 4-nitrophenol is introduced in this photocatalytic system and the efficiency of Cr(VI) photoreduction is further promoted.

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

Multiwall-carbon nanotube modified by N-doped carbon quantum dots as Pt catalyst support for methanol electrooxidation

N-doped carbon quantum dots as corrosion inhibitor for ultra-high voltage etched Al foil

Inspired by the high-water solubility, photoluminescence and low cytotoxicity of N-doped carbon quantum dots (N-CQDs), fluorescent corrosion inhibitors with size of 4–8 nm were synthesized from disodium ethylenediaminetetraacetate, sulfamic acid, and urotropine salt. We expect that these N-CQDs may possess an excellent protective ability to inhibit the corrosion of carbon steel in aggressive solutions owing to its special functional group. The inhibitory mechanism of the inhibitor on N80 steel in saturated CO2 3 wt % NaCl solution was studied by weight loss, adsorption curve fitting, electrochemical measurement, and surface morphology and elemental analysis. The results show that corrosion of N80 carbon steel in saturated CO2 3 wt % NaCl solution is significantly inhibited by the addition of N-CQDs, which is attributed to the formation of its adsorption film, preventing the contact of iron with chloride ions and is an effective corrosion inhibitor.

Selective and sensitive determination of Folic acid amidst interfering metal ions and biomolecules using N- doped carbon quantum dots (N-CQDs)

Carbon quantum dots (CQD) have drawn great interest worldwide for their extensive application as sensors due to their extraordinary physical and chemical characteristics, good biocompatibility, and high fluorescence in nature. Here, we demonstrate a technique for detecting mercury (Hg2+) ion using a fluorescent CQD probe. Ecology is concerned about the accumulation of heavy metal ions in water samples due to their harmful effects on human health. Sensitive identification and removal of metal ions from water samples are required to reduce heavy metals' risk. To find out Mercury in the water sample, carbon quantum dots were used and synthesized by 5-dimethyl amino methyl furfuryl alcohol and o-phenylene diamine through the hydrothermal technique. The synthesized CQD shows yellow emission when exposed to UV irradiation. Mercury ion was used to quench carbon quantum dots, and it was found that the detection limit was 5.2 nM with a linear range of 15-100 µM. The synthesized carbon quantum dots were demonstrated to efficiently detect Mercury ions in real water samples.

Ti[Formula: see text] self-doped TiO2 (TiO[Formula: see text])/N-doped carbon nanostructure composites were prepared via a facile one-step hydrothermal method to optimize the use of visible light and reduce recombination of photogenerated electrons and holes. The composites were characterized by X-ray diffraction, transmission electron microscopy (TEM), high-resolution TEM, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy. The amounts of carbon and nitrogen sources affect the morphology and photocatalytic performance. At low amounts of the sources, the N-doped carbon nanostructure is an amorphous film and is well-combined with TiO[Formula: see text] nanoparticles through surface carbon–oxygen groups. At high amounts of the sources, N-doped carbon quantum dots (NCQDs) were obtained, and carbon atoms could substitute for oxygen atoms in the TiO2 lattice to form Ti–C structures, which are responsible for the high photocatalytic activity under visible light illumination. Transient photocurrent response and electrochemical impedance spectroscopy results indicate that the amorphous hybrid film becomes a trap for electrons and that NCQDs can accelerate electron transfer. The improved visible light photocatalytic property for the TiO[Formula: see text]/NCQDs composite can be attributed to the enhancement of light absorption and inhibition of the photogenerated electron–hole recombination of anchored NCQDs.

Mercury is a highly toxic environmental contaminant that damages the endocrine and central nervous systems. In view of the contamination of Hong Kong territorial waters with anthropogenic pollutants such as trace heavy metals, we have investigated the application of our recently developed DNA-based luminescence methodology for the rapid and sensitive detection of mercury(II) ions in real water samples. The assay was applied to water samples from Shing Mun River, Nam Sang Wai and Lamma Island sea water, representing natural river, wetland and sea water media, respectively. The results showed that the system could function effectively in real water samples under conditions of low turbidity and low metal ion concentrations. However, high turbidity and high metal ion concentrations increased the background signal and reduced the performance of this assay.

Bedsores (pressure ulcers) exhibit high incidence rates (0.4-38%) and prolonged recovery periods, with bacterial infections posing the most frequent and severe complications, significantly impeding wound healing. Conventional antibiotic therapies face limitations due to antimicrobial resistance, necessitating innovative strategies with enhanced biocompatibility and reduced resistance-inducing potential. This study aimed to develop a photodynamic therapy (PDT)-based antimicrobial approach by converting antimicrobial drugs into N-doped carbon quantum dots (N, CQ-dots) for efficient bacterial inhibition in wound environments. N, CQ-dots were synthesized from protocatechuic acid (a natural antimicrobial metabolite) via solvothermal method, preserving critical functional groups (-COOH, -OH) inherited from the precursor. Structural and optical properties were characterized using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet-to-visible (UV-Vis) spectroscopy. Photodynamic antimicrobial efficacy was evaluated against Staphylococcus aureus and Escherichia coli through colony-count assays, and live/dead staining. The synthesized N, CQ-dots exhibited uniform morphology (~3.5 nm) and abundant oxygen-containing functional groups, as confirmed by XPS and Fourier Transform Infrared (FTIR) spectrometer analysis. Under irradiation, the material demonstrated potent antibacterial activity, achieving >99.9% viability reduction in Gram-positive and Gram-negative strains, with minimal cytotoxicity (MBC >100 μg/mL). This work demonstrates a novel paradigm for transforming antimicrobial drugs into multifunctional N, CQ-dots, leveraging preserved pharmacophores and PDT mechanisms to overcome drug resistance. The system combines intrinsic antibacterial activity with light-triggered responsiveness, offering a promising solution for managing infected bedsores while minimizing systemic toxicity. These findings highlight the translational potential of drug-derived nanomaterials in precision wound care.

Recently, a sponge-like material called carbon nanotube sponges (CNT sponges) has drawn considerable attention because it can remove large-area oil, nanoparticles, and organic dyes from water. In this paper, the feasibility of CNT sponges as a novel solid-phase extraction (SPE) adsorbent for the enrichment and determination of heavy metal ions (Co(2+), Cu(2+), and Hg(2+)) was investigated for the first time. Sodium diethyldithiocarbamate (DDTC) was used as the chelating agent and high performance liquid chromatography (HPLC) for the final analysis. Important factors which may influence extraction efficiency of SPE were optimized, such as the kind and volume of eluent, volume of DDTC, sample pH, flow rate, etc. Under the optimized conditions, wide range of linearity (0.5-400μgL(-1)), low limits of detection (0.089~0.690μgL(-1); 0.018~0.138μg), and good repeatability (1.27~3.60%, n = 5) were obtained. The developed method was applied for the analysis of the three metal ions in real water samples, and satisfactory results were achieved. All of these findings demonstrated that CNT sponges will be a good choice for the enrichment and determination of target ions at trace levels in the future.

Eco-friendly colorimetric detection of mercury(II) ions using label-free anisotropic nanogolds in ascorbic acid solution

An excellent magnetic multi-walled carbon nanotubes (MMWCNT) containing carboxyl material modified with ferroferric oxide (Fe3O4) nanoparticles was synthesized as the adsorbent for magnetic solid-phase extraction (MSPE) of five heavy metal ions (Pb2+, Cu2+, Co2+, Cd2+, Cr4+) in water samples followed by on-line inductively coupled plasma mass spectrometry (ICP-MS) detection. The characteristics of the adsorbent were analyzed using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), and vibrating sample magnetometer (VSM). Some factors affecting extraction efficiency including pH of sample solution, the amount of adsorbent, extraction method and time, concentration and volume of desorption solvent, desorption time and evaluation of coexisting ions were optimized. Under the optimum conditions, good linearity (r ≥ 0.9951) was obtained within the range of 0.1–50.0 ng·mL−1. The limits of detection (LODs) and limits of quantification (LOQs) were 4.0–25.0 ng·L−1 and 15.0–80.0 ng·L−1, respectively. And satisfactory recoveries of five heavy metal ions ranged from 81.11% to 105.53% were acquired, and the relative standard deviations (RSDs) were no more than 6.05%. The MMWCNT synthesized had strong adsorption force for the five investigated heavy metal ions, respectively. Hence, the proposed method was so suitable and sensitive that it can be applied to the determination of trace analysis of heavy metals in water samples.