Co-doped Carbon Dots Research Articles

Synthesis of Ce, N co–doped carbon dots as green and effective corrosion inhibitor for copper in acid environment

Background: A new high-effectively corrosion inhibitor was used to replace the traditional corrosion inhibitor and reduce the environment pollution.Methods: Through hydrothermal synthesis, Ce and N co-doped carbon dots (Ce@N-CDs) were generated. Before the performance characterization, the microstructure and chemical composition of Ce@N-CDs were firstly investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) techniques. The electrochemical test revealed that the IE of Ce-10% (200 mg/L) on copper was as high as 98%, presenting the best inhibition effect. According to the adsorption isotherm analysis, the Ce@N-CDs mainly adsorbed according to the Langmuir model, and the adsorption process was completed by combining physical and chemical adsorption.Significant findings: Through the morphology, energy dispersive spectrometer (EDS) and XPS analysis of copper surface after corrosion process, it was found that the Ce@N-CDs formed a dense adsorption/passivation film on the copper surface. The adsorption film mainly came from the pairing of unsaturated bonds between N-doped CDs (N-CDs) and copper surface. The passivation film mainly came from the oxide formed by the reaction between Ce and the surrounding environment. Their dense structure could effectively inhibit the infiltration and erosion of corrosive medium.

Preparation of Nitrogen and Sulfur Co-Doped Fluorescent Carbon Dots from Cellulose Nanocrystals as a Sensor for the Detection of Rutin.

The poor water solubility, large particle size, and low accessibility of cellulose, the most abundant bioresource, have restricted its generalization to carbon dots (CDs). Herein, nitrogen and sulfur co-doped fluorescent carbon dots (N, S-CDs) were hydrothermally synthesized using cellulose nanocrystals (CNC) as a carbon precursor, exhibiting a small particle size and excellent aqueous dispersion. Thiourea was selected as a nitrogen and sulfur dopant to introduce abundant fluorescent functional groups into N, S-CDs. The resulting N, S-CDs exhibited nanoscale size (6.2 nm), abundant functional groups, bright blue fluorescence, high quantum yield (QY = 27.4%), and high overall yield (16.2%). The excellent optical properties of N, S-CDs endowed it to potentially display a highly sensitive fluorescence "turn off" response to rutin. The fluorescence response for rutin allowed a wide linear range of 0-40 mg·L-1, with a limit of detection (LOD) of 0.02 μM, which revealed the potential of N, S-CDs as a rapid and simple sensing platform for rutin detection. In addition, the sustainable and large-scale production of the N, S-CDs in this study paves the way for the successful high-value utilization of cellulose.

A facile “off–on” fluorescence sensor for pentachlorophenol detection based on natural N and S co-doped carbon dots from crawfish shells

Natural N and S co-doped carbon dots (NSCDs) were synthesized via hydrothermal synthesis using food-derived crawfish shells as green precursors. The relationship between quantum yield (QY) and protein content of six crawfish shells treated with different alkalis was investigated. The synthesized NSCDs displayed a large QY of 18.57 %, which was higher than most of the chitin-derived CDs. Due to the oxidation of hydroxyl radicals, adding H2O2 and horseradish peroxidase (HRP) quenched the fluorescence of NSCDs, resulting in a detection limit (LOD) of 1.25 μM for H2O2. The addition of pentachlorophenol (PCP) was supposed to consume part of the hydroxyl radicals and protect NSCDs from being oxidized. Accordingly, a facile and rapid “off–on” fluorescence sensor was developed to detect PCP with a LOD of 2.30 μM. Further, the method described was successfully used to detect PCP in three real samples.

Synthesis of N,S co-doped carbon dots for fluorescence detection of Fe3+ ions and intracellular pH imaging

• N,S co-doped dual emission carbon dots (DECDs) were prepared. • The DECDs has high accuracy and selectivity for the determination of Fe 3+ in tap water. • The dual emission of DECDs is contributed by core and surface. • The DECDs have low cytotoxicity and can be used to monitor pH changes in cell. Using citric acid and thiourea as precursors, sulfur-nitrogen co-doped dual emission carbon dots (DECDs) were prepared by a simple solvothermal method. At the excitation wavelength of 360 nm, DECDs have two emission peaks located at 465 nm (blue) and 592 nm (yellow-green) which are attributed by core and surface of DECDs. It is found that Fe 3+ ions can coordinate with oxygen-containing groups on DECDs, and then the electrons transfer from DECDs to Fe 3+ ions, which quench the fluorescence of DECDs. The fluorescence intensity is linear with the concentration of Fe 3+ ions in the range of 0–100 μM and the detection limit is 0.77 μM. Moreover, the designed sensor can be applied to detect Fe 3+ ions in tap water with high selectivity, which provides a basis for the quantitative detection of Fe 3+ ions. At the same time, DECDs can be used as a pH fluorescence probe. In the pH 2.5–11.5 range, the fluorescence increases with pH whilst the solution color changes, providing a visualization platform for pH detection. Moreover, the pH fluorescence probe can be used for intracellular pH fluorescence imaging in living cells, and DECDs have an excellent biocompatibility (e.g., cell viability remains about 80% after treatment for 24 h at 200 μg·mL −1 of DECDs). Therefore, DECDs has a certain application prospect in food detection, biological detection and determination of intracellular pH change.

Fluorescent N, S co-doped carbon dots for tartrazine sensing and mechanistic perception of their radical scavenging activity

Blue fluorescent, biocompatible, nitrogen & sulphur co-doped carbon dots (NSCDs), prepared via microwave-assisted pyrolysis of tartaric acid and thiourea, have been explored as a fluorescent probe for selective and sensitive detection of the yellow-coloured food additive, tartrazine, in the aqueous medium through fluorescence quenching mechanism. The NSCDs (quantum yield ∼ 26%) exhibited static quenching in presence of tartrazine with the limit of detection (LOD) of 48 nM in the linear concentration range from 1 to 50 μM. In addition, NSCDs have also been investigated for their antioxidant activity by probing their ability to scavenge various reactive oxygen species (e.g., superoxide, peroxide, hydroxyl, and KMnO4) along with their total antioxidant capacity and 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) free radicals premised on UV–Vis spectroscopy. From pH-dependent UV–Vis and EPR spectroscopy studies, the scavenging of DPPH free radicals by the NSCDs was affirmed to follow the hydrogen atom transfer (HAT) mechanism in an acidic medium while the proton-coupled electron transfer (PCET) mechanism was predominant in alkaline medium.

Red emissive N, Cl-doped carbon dots for detection of tea polyphenols and lysosomal imaging at the cellular level

Tea polyphenols (TP), which is accounting for 15-30% of the dry weight of green tea and are widely used in the food industry as antioxidants, preservatives, color preservatives, and flavoring agents. To determine the concentration of TP, a fluorescent method based on nitrogen and chlorine co-doped carbon dots (R-CDs) was investigated. The R-CDs we prepared showed red emission with an absolute quantum yield (QY) of approximately 16.67 ± 0.85%. The limit of detection (LOD) was calculated to be approximately 68 ± 0.94 ng/mL, with an R 2 of 0.999 over the TP range of 1-20 μg/mL. Compared to the ferrous tartrate standard curve method, the concentration of TP in green tea, which was purchased from the market, detected using our method showed an error within 5%, indicating good potential applications in the food industry. Cell imaging experiments suggested that the R-CDs exhibit excellent lysosomal targeting as the Pearson’s correlation coefficient (PCC) in colocalization analysis was found to be 0.91. Further experiments showed that owing to their excitation-independent emission and high QY, the R-CDs could be applied to not only for detecting TP content but also for targeting lysosomes as substitute for commercial dyes. • The prepared R-CDs possess red emission with high quantum yield. • The R-CDs could detect TP with high selectivity and sensitivity. • The R-CDs showed wonderful lysosomal targeting compared to commercial dyes.

B, N co-doped carbon dots based fluorescent test paper and hydrogel for visual and efficient dual ion detection

It is highly significant to develop water-soluble carbon dots (CDs) for ion detection in the environment via a facile and economical process. Herein, the organic molecules derived boron, nitrogen co-doped CDs (BN-CDs) with water-solubility are solvothermally synthesized towards dual ion detection. The BN-CDs emit bright tangerine fluorescence, and demonstrate a fluorescent quantum yield of 17 %. Besides, the obtained BN-CDs show a good linear relationship with Cu2+/Co2+ in a wide dynamic range of 1–8 μM, along with detection limits of 16 nM (Cu2+) and 24 nM (Co2+). The joint effect of dynamic and static quenching mechanisms is proposed as well for fluorescence quenching by Cu2+/Co2+. Furthermore, two instrument-free BN-CDs-based solid sensors (i.e., test strips and hydrogel beads) are fabricated to sensitively monitor both Cu2+ and Co2+. The paper-based sensors exhibit selective and sensitive response towards Cu2+ and Co2+ in a low-cost manner. The fluorescence hydrogel integrates comprehensive advantages of hydrogel and BN-CDs, which makes it not only conduct as efficient fluorescent sensors to detect Cu2+ and Co2+ but act as the absorbent towards removal of the ions. The simple yet reliable sensing technique developed here favor efficiently detecting and recognizing dual ions in environmental and/or biological samples.

A pH-dependent N, P co-doped carbon dots as fluorescent probe for malachite green assay and its visual application based on fluorescent hydrogel kit

A pH-dependent red fluorescent N, P co-doped carbon dots (N, P-CDs) was firstly developed for rapid, sensitive and visual detection of the toxic dye malachite green (MG). The synthesis of N, P-CDs was carried out by hydrothermal treatment of o-phenylenediamine and phosphoric acid, and the low cytotoxicity of N, P-CDs was verified by Cell Counting Kit-8 (CCK-8) method. The linear decrease of N, P-CDs fluorescence in the pH range of 3.8–5.6 was attributed to the reduction of protonation of nitrogen-containing groups on the surface. And the sensing mechanism for MG was constructed based on the inner filter effect (IFE). The obtained linear ranges were 0.08–1 and 1–50 µmol·L−1 with limit of detections (LODs) of 0.07 and 0.74 µmol·L−1. The proposed method has been successfully applied to the determination of MG in water and fish samples. In addition, a kind of N, P-CDs fluorescent hydrogel kit was prepared for the visual analysis of MG. This method is not only simple, rapid and accurate, but also the prepared fluorescent hydrogel has potential application prospects for on-site qualitative identification and semi-quantitative analysis of MG, which also provides a new idea for monitoring MG in water environment and fish products.

Evaluation of the corrosion inhibition behavior of N, S co-doped memory-type carbon dots for mild steel in HCl solution

Novel N, S co-doped carbon dots (N, S-CDs) with memory effect were prepared by hydrothermal method using citric acid and l-cysteine as precursors. Structural and morphological characterizations confirmed that N, S-CDs are carbon dots with multifunctional groups and excellent water solubility. Electrochemical measurements indicated that N, S-CDs can effectively inhibit the charge transfer in the corrosion process of steel, and the inhibition efficiency is nearly 90%. The obtained N, S-CDs exhibits outstanding inhibition performance for steel corrosion, which offers a new thought for exploring environmentally friendly corrosion inhibitors.

Synthesis of N,S co-doped carbon dots for fluorescence turn-on detection of Fe2+ and Al3+ in a wide pH range

N,S co-doped carbon dots (N/S-CDs) was synthesized by using β-cyclodextrin as carbon source and Reactive Black 5 as nitrogen and sulfur source. The structure of the N/S-CDs was characterized and its performance for detection of Fe2+ and Al3+ was evaluated. Experimental results demonstrated that the N/S-CDs had good stability in 10 mmol/L brine and in a wide pH range of 3–12. The N/S-CDs exhibited high selectivity for detection of Fe2+ and Al3+ by dual-modal fluorescence enhancement and visualization with the naked eye over a wide pH range. The N/S-CDs displayed good anti-interference performance and low detection limits of 6.99 nmol/L for Fe2+ and 5.5 nmol/L for Al3+. The N/S-CDs responded to Al3+ rapidly within 3 min. Measurements on particle size, zeta potential, and UV–vis and FT-IR spectra suggested that Fe2+ enhanced fluorescence of the N/S-CDs by chelating while Al3+ promoted aggregation through combination with the N/S-CDs which responded to Al3+ by aggregation-induced enhancement of emission (AIEE) mechanism.

Bifunctional nanoprobe for dual-mode detection based on blue emissive iron and nitrogen co-doped carbon dots as a peroxidase-mimic platform

In this study, iron and nitrogen co-doped carbon dots (Fe/N@C-dots) were fabricated via one pot hydrothermal method. The as-synthesized Fe/N@C-dots exhibited unique properties such as high catalytic activity and fluorescence quantum yield (33.8%). The peroxidase-like activity of Fe/N@C-dots was used to detect H2O2 in the presence of phenol and 4-aminoantipyrine (4-AMAP) to yield a pink colored product (quinoneimine chromogen), which was measured at λmax = 505 nm (colorimetric method). Moreover, the pink colored product quenched the fluorescence of Fe/N@C-dots via inner-filter effect and static quenching (fluorometric method). The enzyme like activity of Fe/N@C-dots was cascaded with the enzymatic activity of glucose oxidase (GOx) to evaluate the practical application of Fe/N@C-dots to develop dual-channel sensor (fluorometric and colorimetric) for high selective and sensitive detection of glucose. It was found that the absorption intensities were increased linearly with glucose concentration in the range of 2.13–130 μM with LOD (S/N = 3) of 0.58 μM, while fluorescence intensities were decreased linearly after addition of glucose in the range of 1.33–140 μM with LOD (S/N = 3) of 0.36 μM. The Fe/N@C-dots/4-AMAP/phenol/GOx system along with the fluorometric method were applied efficiently to determine glucose in many samples including human serum, urine, and saliva with acceptable recoveries % in the range of 93.8–106.1% and RSD % not more than 3.7%, suggesting the reliability of the as-fabricated biosensor.

Green one-step synthesis of boron and nitrogen co-doped carbon dots based on inner filter effect as fluorescent nanosensors for determination of Fe3+

Significant efforts need to be devoted to enhancing the photoluminescence quantum yields (PLQY) of carbon dots (CDs) due to the typically low PLQY (< 10%) of currently synthesized CDs. Moreover, certain special industries such as textiles, paper, and food all have high requirements for water since Fe3+ can affect its color, odor, and taste. The traditional detection methods require expensive equipment, so a facile method to detect Fe3+ is urgently needed. In this work, the self-doping of nitrogen (N-CDs) has been achieved through tea residues as the carbon source to inhibit the oxygen-deficient state, and the doping of boric acid (BN-CDs) can activate the electron transition at the carbon site, which effectively enhanced the PLQY of CDs from 11.4% to 25.79% compared to N-CDs. Furthermore, as hydroxylated polyphenols in tea residues can adsorb metal ions, stable non-fluorescent matrix state complexes have been established between BN-CDs and Fe3+ to quench the FL owing to the inner filter effect. The linear relationship was formed in the concentration range of 0–60 μM, and the detection limit reached 0.07 μM. It demonstrates that along with the effective treatment of waste tea residues, the synthesized high fluorescence property BN-CDs are suitable to detect Fe3+ in water for textiles, paper, food, and other special industries.

Handheld detection strategy: Real-time on-site assay of Mn(VII) and GSH integrating ratiometric fluorescent carbon dots paper strip, smartphone, and 3D-printed accessory

Handheld detection platform integrating ratiometric fluorescent N,P co-doped carbon dots (N,P-CDs) paper strip, smartphone, and 3D-printed accessory corroborates its efficacy for visual quantitative detection of Mn(VII) and GSH via a continuous fluorescence color shift. N,P-CDs were synthesized by hydrothermal treatment of 1,8-diaminonaphthalene, phosphoric acid, and formamide. Inspiringly, with increasing Mn(VII) concentrations, blue emission of N,P-CDs decreases gradually at 445 nm and a ratio rising orange band emerges at 600 nm under 340 nm excitation, which concurrently exhibits continuous fluorescence color variation of blue, purplish blue, purplish pink, pink, to orange. Subsequent addition of GSH renders orange fluorescence of N,P-CDs@Mn(VII) gradually quench but blue peak slightly enhance, accompanied by the fluorescence color successively returning from orange to blue. The RGB values of the resulting images were precisely defined by a color recognition application within the smartphone, and the R/B values could be employed for Mn(VII) and GSH quantification with linear ranges of 0 − 40 μM and 0 − 28 μM, respectively, as well as limits of detection of 24.49 nM and 21.41 nM, respectively. It is solicitously anticipated that our research will provide novel insight for the development of effective sensing protocol and the enlargement of practical application prospect.

Reversible detection of Hg(II) in pure water based on thymine modified nitrogen, sulfur co-doped carbon dots combined with antidote

Conventional Hg2+ visual sensors are unsustainable, hindering their practical application for improved water quality and health. In order to address this challenge, herein, N, S co-doped carbon nanodots (NS-CDs) were prepared and well characterized, presented the fluorescent monitoring for Hg2+ over other metal ions with the limit of detection (LOD) of 0.47 µM. Next, the CDs were successfully modified by thymine without any fluorescence labelling (referred to as T-NS-CDs). The sensitivity to Hg2+ cloud be noticeable enhanced due to the formation of T-Hg2+-T specific base pairs. Accordingly, the LOD was calculated with values as low as 1.56 nM. Furthermore, Hg2+ could be released and complexed with antidote (meso-2,3-dimercaptosuccinic acid) (DMSA-Hg2+), being the responsible for the reversible interconversion between T-Hg2+-T and DMSA-Hg2+. Interestingly, the proposed sensing system also applies to the fluorescent sensing for Hg2+ in tap water with satisfactory recoveries (96.97 %–101.38 %, RSD < 2 %). Thus, by simply combination of elemental doping and surface functionalization, the surface state and functionalities of CDs could be tailorable, endowing the fluorometric sensing towards Hg2+ in environmental system.

One-pot green synthesis of N,S co-doped biomass carbon dots from natural grapefruit juice for selective sensing of Cr(VI)

The synthesis of biomass carbon dots (BCDs) using natural products has attracted increasing attention in the past few years owing to its advantages in terms of abundant sources and green environmental protection. However, the low luminescence quantum yield (QY) of BCDs is still a bottleneck for practical applications. Herein, nitrogen and sulfur co-doped biomass carbon dots (N,S-BCDs) with high QY (84.93%) were successfully prepared by one-pot green hydrothermal method using natural grapefruit juice and urea as carbon and nitrogen sources, respectively. The as-obtained N,S-BCDs showed an average size of 3.8 nm with strong blue luminescence and excitation-dependence fluorescence behavior. Furthermore, good selectivity and sensitivity were noticed toward hexavalent chromium (Cr(VI)) due to the dynamic quenching of fluorescence. The limit of detection (LOD) was determined as 0.155 μM, and the linearity was extended from 0 to 400 μM. Furthermore, the paper sensors for the visual semi-quantitative rapid detection of Cr(VI) were constructed by using the as-obtained N,S-BCDs, which reveals the great potential applications as fluorescent probes for the detection of heavy metal ions in the environment.

Surface-Plasma-Induced One-Pot Synthesis of N,S-Carbon Dot Intercalated MoS2/Graphene Nanosheets for Highly Efficient Hydrogen Evolution Reaction

Herein, a facile and rapid surface-plasma-induced method was adopted for the one-pot synthesis of a 2D/0D/2D hybrid nanostructure consisting of N,S co-doped carbon dots (NSCD) intercalated few-layer MoS2/graphene nanosheets (MoS2/G) as an excellent catalyst for the hydrogen evolution reaction (HER). In this process, bulk MoS2 and graphite foil served as the sources of MoS2 and graphene nanosheets, respectively, while glucose and thiourea served as the source of NSCD. The sturdy integration of 0D NSCD and 2D MoS2/G in a well-constructed ternary composite provided a huge number of edge active sites with tunable and extraordinary physicochemical properties for electron transport, facilitating HER performance. The optimal NSCD@MoS2/G exhibited a superior catalytic activity toward HER with a low onset potential (37 mV), an overpotential of 98 mV at 10 mA cm–2, and a Tafel slope as small as 53 mV dec–1, which were better than other 2D electrocatalysts. The increase in double-layer capacitance for NSCD@MoS2/G (12.2 mF cm–2), which was 2-fold of the MoS2/G sample, is strong evidence of the large catalytic edge sites and electrical coupling in the NSCD@MoS2/G ternary system. Moreover, the strong bonding and interaction between NSCD and MoS2/G nanosheets enabled outstanding long-term stability and structural integrity, displaying 95 and 90% activity retention at 10 and 50 mA cm–2 after 48 h i–t test, respectively. This approach paves the way to efficient syntheses of 2D/0D/2D heterostructures with great potential for various energy-related applications.

Nitrogen and sulfur co-doped carbon dots derived from granatums and ammonium persulfate to detect tetracyclines in milk

Highly photoluminescent nitrogen and sulfur co-doped carbon dots (N,S-CDs) derived from the granatum as carbon source and ammonium persulfate as passivator was developed as a probe for the detection of tetracyclines (DOC, TC, OTC, and CTC) in milk products. Transmission electron microscopy (TEM) exhibited that the as-prepared N,S-CDs were quasi-spherical particles with an average diameter of ∼5.5 nm. X-ray diffraction (XRD) showed that the N,S-CDs possessed a graphitic-like structure. Fourier-transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) confirmed the existence of -OH, -COOH, R-SO3H and -NH2 on the surface of N,S-CDs. The amidation reaction between the -COOH of N,S-CDs and -CO-NH2 of TCs combined with the inner-filter effect resulted in the fluorescence (FL) quenching. The FL quenching efficiencies reached 98.5%, 51.6%, 46.5%, and 39.4% after introducing DOC, TC, OTC, and CTC. Highly fluoresce quenched for DOC was ascribed to the existence of H on C6 of DOC induced weak electrostatic repulsion between N,S-CDs and DOC. The nanosensor allowed the detecting TCs in the range of 0.08∼3.05 µmol L-1 for DOC with the detection limit of 2.87 nmol L-1, 0.32∼5.85 µmol L-1 for TC with 14.57 nmol L-1, 0.31∼6.29 µmol L-1 for OTC with 16.99 nmol L-1, and 0.30∼6.06 µmol L-1 for CTC with 17.11 nmol L-1 (S/N=3). Recoveries of 83.93∼126.22% and RSDs of 1.11%∼5.83% were achieved for TCs detection in milk product samples, indicating the optical sensor provided an alternative strategy for real applications in food safety control.

Flow injection spectrophotometric determination total antioxidant capacity in human serum samples based on response surface methodology to optimize synthesized peroxidase-like activity carbon dots

Total antioxidant capacity (TAC) is an important indicator for evaluating oxidative stress of the human body. Since TAC is related to the concentration of reducing substances, it can be detected by using peroxidase-like or oxidase-like activity of nanozyme materials. In this work, the cobalt and nitrogen co-doped carbon dots (Co/N-CDs) are fabricated for building stability and high peroxidase-like nanozyme through the Box-Behnken design of response surface methodology. The morphology and luminescence properties of obtained Co/N-CDs were characterized by TEM and fluorophotometer, respectively. Interestingly, the surface charge of Co/N-CDs are innovatively investigated by a simple and widespread gel electrophoresis, which holds the potential to be an alternative to Zeta potential analysis. In addition, a flow injection spectrophotometric assay to detect ascorbic acid is develop with a high sensitivity and automation based on a Co/N-CDs/guaiacol/H2O2 catalytic reaction system. The proposed method is also responsive to other reducing substances such as cysteine and glutathione. Therefore, the presented sensor can realize the determination of TAC, and then, some actual human serum samples are detected accurately and quickly (the recovery rates are 93.46–105.61 %).

Facile preparation of N, S co-doped carbon dots and their application to a novel off-on fluorescent probe for selective determination of Hg2+

In this work, citric acid (CA) and glutathione (GSH) were selected as the raw materials for preparation carbon dote co-doped with N and S (NS-CDs) via microwave heating method. The obtained NS-CDs displayed stable and strong blue luminescence with a maximum emission (λem) wavelength of 442 nm and a maximum excitation (λex) wavelength of 371 nm, and their fluorescence quantum yield (FLQY) was 10.9%. The fluorescence of NS-CDs was quenched by silver nanoparticles (AgNPs) through a combination of static quenching effect and inner filter effect (IFE), and could be recovered by Hg2+ even at nanomolar levels ascribing to redox reaction between Hg2+ and AgNPs. Based upon this phenomenon, a novel off-on fluorescent probe (NS-CDs - AgNPs) for determination trace Hg2+ in aqueous solution was constructed using the obtained NS-CDs and AgNPs. Under optimal conditions, NS-CDs - AgNPs exhibited a wide linearity range of 10–90 nM (R2 = 0.993) for Hg2+and a low LOD of 4.2 nM. NS-CDs - AgNPs was successfully utilized for monitoring Hg2+ in real water samples with the recoveries of 91.4–108.6% (RSD <5.84%), which indicated that the fluorescent probe has enormous application potential to detect trace Hg2+ in real water samples.

Comparative study on corrosion inhibition of N doped and N,S codoped carbon dots for carbon steel in strong acidic solution

Carbon steel is the most widely used engineering material, and its corrosion is one of the main areas of concern in many industries. The most practical approach to control this problem is to use corrosion inhibitors. Currently, because of their good water solubility, excellent chemical stability, low cost and nontoxic features, carbon dots (CDs), especially heteroatom-doped CDs, have been developed as green corrosion inhibitors, but the corrosion inhibition efficiency and underlying mechanisms of single- or dual-element doping have not yet been accurately compared and analyzed. Inspired by this, eco-friendly nitrogen-doped and nitrogen, sulfur codoped CDs (N-CDs and N,S-CDs) are prepared via a one-step hydrothermal process, and a comparative study on their inhibition performance for carbon steel corrosion in strong acidic solution is performed. The results show that both N-CDs and N,S-CDs can restrain the corrosion of carbon steel, and their inhibition efficiency increases with increasing concentration and immersion time, reaching approximately 87.9% (N-CDs) and 96.4% (N,S-CDs) at 200 ppm after 1 h of immersion. Molecular dynamics simulation indicates that the strong interaction ability between N,S-CDs and the Fe substrate leads to higher corrosion inhibition performance than the single N doping case, benefiting from the multi-anchor adsorption of N,S-CDs on carbon steel in a strong acidic solution. Therefore, the facile preparation, eco-friendliness and high corrosion inhibition performance of N,S-CDs will provide a new approach for designing highly efficient carbon dots and broadening the application of carbon dots in the corrosion field.