Nitrogen-sulfur Co-doped Carbon Research Articles

Carbon Dots with Spatially-Mediated-N/S-Co-Doping Enabling One-Year Stable Lubricant with Oil Leakage Detection Capability.

The dispersion stability of nano-lubricating additives is crucial for the shelf life of lubricant and its practical applications. Nitrogen-sulfur co-doped carbon dots (N,S@CDs) via a one-step hydrothermal method with nitropyrene and thiourea as raw materials are hereby presented. The N and S elements are selectively distributed throughout the entire carbon skeleton with a doping amount of 22.6 at%. The as-synthesized N,S@CDs exhibit excellent dispersion stability in PEG200 and maintain stability for over one year. The experiment results indicate that N,S@CDs significantly improve the anti-wear and friction reduction properties of PEG200, while the friction coefficientis reduced from 0.25 to 0.09 with 1.5 wt% N,S@CDs addition, and the wear volume, depth, and width are reduced by 68%, 52%, and 57%, respectively. The good lubrication performance is attributed to N,S@CDs excellent dispersion stability, enhanced filling and polishing effects, and complex tribochemical reactions caused by heteroatom doping to form a stable protective film on the worn surface. Furthermore, the as-prepared N,S@CDs exhibit intrinsic fluorescence intensity in PEG200 with the photoluminescence quantum yield (PLQY) of 12.5% and remain fluorescent stable during the long-term friction process, therefore the N,S@CDs have a potential application prospect in non-destructive detection of oil leakage via fluorescence labeling method.

A novel fluorescent aptasensor based on 3D porous nitrogen-sulfur co-doped carbon mesh and hybridization chain reaction for sensitive detection of ochratoxin A.

A novel three-dimensional (3D) porous nitrogen-sulfur co-doped carbon (N-S-C) mesh was synthesized and used for the first timeas the quenching material to construct a fluorescent aptasensor for ochratoxin A (OTA) detection. The fluorescent aptasensor with enzyme-free signal amplification strategy was developed by using cDNA as a promoter to trigger hybridization chain reaction (HCR), which effectively improved the sensitivity of this aptasensor. In the absence of OTA, 3D porous N-S-C mesh can adsorb carboxyfluorescein FAM-labeled hairpin DNA1 (H1-FAM) and hairpin DNA2 (H2) and quench the fluorescence of FAM. In the presence of the OTA, the OTA specifically binds to the aptamer strand and the DNA duplex undergoes dissociation. The released cDNA in turn serves as a promoter for HCR, and the strand assembly of H1-FAM and H2 is triggered by the promoter to generate long-strand DNA polymers via HCR, resulting in an increasing fluorescent signal. Under optimal conditions, there was a good linear relationship between lgCOTA and fluorescence intensity difference in the range 0.01-500ng/mL (R2 = 0.993), and the detection limit was 2.7pg/mL. The designed sensor platform was applied to determine spiked OTA in peanut, wheat flour, corn flour, black tea, and wine with recoveries in the range of 94.4-119.6%.

Concentration-regulated multi-color fluorescent carbon dots for the detection of rifampicin, morin and Al3+

Carbon dots have many new and interesting phenomena, and the concentration dependent luminescence wavelength is an intriguing one. Herein, nitrogen-sulfur co-doped carbon dots (NSCDs) diluted to different concentrations, the high concentration of G-NSCDs (0.2 mg mL−1) with green fluorescence and the low-concentration of B-NSCDs (0.01 mg mL−1) with blue fluorescence were obtained. Further, it was found that the detection behaviors are different for different concentrations. The “turn-off” fluorescent sensor of G-NSCDs can specifically recognize rifampicin in a linear range of 0.2–20 μM with a detection limit of 56.6 nM employing the mutual effect of photo-induced electron transfer and dynamic quenching. Meanwhile, a “turn-off” B-NSCDs fluorescence sensor was constructed to effectively identify morin based on the internal filtration effect and static quenching, achieving a suitable linearity of 0.2–30 μM and a detection limit of 51.2 nM. Due to the strong chelation of morin and Al3+, a “turn-on” fluorescent probe for sequential detection Al3+ was fabricated based on B-NSCDs-morin system, obtaining a good linearity of 0.1–2.0 μM with a satisfactory detection limit of 45.8 nM. These interesting behaviors indicate that NSCDs are expected to become novel sensing materials for the monitoring of rifampicin, morin and Al3+ in organisms, which is beneficial for our health.

Synthesis of multicolor-emitting nitrogen–sulfur co-doped carbon dots and their photochemical studies for sensing applications

Photoluminescent carbon dots (CDs) possess several advantages, which include high stability and a non-toxicity that are essential in different applications such as catalysis, drug delivery, and sensors. The presence of heteroatoms modifies their physicochemical characteristics. In this work, a combination of CDs is manufactured utilizing a solvothermal technique using citric acid and thiourea. After separating each section using column chromatography, green and yellow CDs with average diameters of 8.3 and 7.0 nm, respectively, are generated. Next, optical and structural characterizations indicated that the variation in the emission color was caused by differences in surface functional groups rather than particle size. The photoelectrochemical properties are explored by including quinone derivatives and metal ions, which are quenchers for the CDs. The photoluminescence quenching results showed the presence of anionic functional groups on the surface of the CDs. Furthermore, these functional groups interacted strongly with particular types of metal ions, indicating that they may be employed as metal ion sensors.

Simultaneous saltwater desalination and power generation using an aluminum-powered cell

In this study, an air-cathode-aluminum-air desalination battery as a new technology for simultaneous desalination and electrical power generation was developed through the optimization of its operating parameters. Nitrogen-sulfur co-doped carbon was synthesized and characterized as a cheap and efficient catalyst for oxygen reduction reaction in the cathode. By optimizing the aluminum anode parameters, utilizing the fabricated air-cathode and modifying the operational conditions, the salt removal and average generated energy reached 2.06 g/L (in 90 min) and 0.55 Wh/L of the processed water, respectively, consuming 0.26 g of aluminum per hour. Moreover, using cost analysis this technology was found competitive with other desalination systems for high salinity water, consuming 2.05 Wh for 1 g salt removal with initial salinity of 12 g/L. Overall, this assembly is a low cost and environmentally friendly process, and with advantages such as continuous desalination and reasonable desalination rate, seems to be a promising candidate for desalination purposes.

Green Synthesis of Fluorescent Nitrogen–Sulfur Co-Doped Carbon Dots from Scallion Leaves for Hemin Sensing

The nitrogen–sulfur co-doped carbon dots (CDs) were synthesized using scallion leaves via an environmentally friendly and facile hydrothermal method, which did not require surface passivating agents. When the hemin concentration was increased from 0.5 to 10.0 μM, the fluorescence emission intensity of the CDs was also linearly quenched. The detection limit was estimated to be 0.1 μM. The fluorescence sensing mechanism was systematically explored by a series of characterization methods. The results revealed that the fluorescence sensing quenching mechanism was ascribed to the inner filter effect and photo-induced electron transfer. The proposed mechanism was further verified by our theoretical calculations. The proposed sensor was successfully applied for the determination of hemin in human serum samples.

Facile Synthesis of N,S-Codoped Hierarchically Porous Carbon with High Volumetric Pseudocapacitance

For the purpose of obtaining high-volumetric-pseudocapacitance carbon materials for supercapacitors, the nitrogen, sulfur-codoped carbon (NSC) with a unique hierarchically porous structure is synth...

Fluorescent Carbon Quantum Dots with Fe(III/II) Irons as Bridge for the Detection of Ascorbic Acid and H2O2

Nitrogen-sulfur co-doped carbon quantum dots (N, S-CQDs) with good photoluminescence properties were prepared by hydrothermal method using citric acid (CA) and methionine (Met) as precursors. Co-doping with N and S facilitates the electron transfer rate and coordination interaction between N,S-CQDs and Fe(III) ions which acts as a quencher of fluorescence. Based on a simple redox principle, a highly sensitive and selective method for the detection of ascorbic acid (AA) and H2O2 was successfully developed. The calibration curves obtained are linear for the current versus AA and H2O2 concentration over the range 50-500μM and 10-140μM, respectively. And the detection limits for AA and H2O2 are 4.2μM and 1.9μM, respectively. The quantitative analysis of AA and H2O2 in various juices and H2O2 disinfectant with Fe3+/CQDs or Fe2+/CQDs gave the recoveries of 87.8%-117.5% and 99.2%-106.4% with relative standard deviations (RSD) of 1.6-5.1% and 1.7-3.1%, respectively, showing satisfactory results for the determination of AA and H2O2 in actual application. The proposed strategy may provide a new pathway to developing inexpensive and sensitive way for the detection of various redox reaction-involved system.

In-situ formation of tin-antimony sulfide in nitrogen-sulfur Co-doped carbon nanofibers as high performance anode materials for sodium-ion batteries

As potential alternatives to lithium-ion batteries in grid energy storage application, sodium-ion batteries (SIBs) have attracted tremendous attention. Absence of high-performance anode material remains a challenge to commercialize SIBs. Herein, a SnSbSx/porous carbon nanofiber (SnSbSx/PCNF) composite with superior performance is successfully prepared via electrospinning, followed by a sulfuration treatment. The as-prepared SnSbSx/PCNF composite exhibits a unique two-dimensional nano-sheet morphology. As a result, the SnSbSx/PCNFs can deliver a high reversible capacity of 566.7 mAh g−1 after 80 cycles and achieve good cycling stability and rate capability when used as anode materials for SIBs. The improved electrochemical performance of SnSbSx/PCNFs can be ascribed to the synergistic effects of SnSbSx nano-sheets and enhanced diffusion coefficient of Na+ in sulfurated PCNFs (SPCNFs), which can not only provide good electronic conductivity but also buffer the volume change of the SnSbSx nano-sheets during sodiation/desodiation process. Additionally, the sulfuration process generates a sulfur doping effect on the PCNFs, further enhancing their sodium storage ability. Therefore, the excellent Na-storage ability demonstrates SnSbSx/PCNFs a great potential as anode material for high-performance SIBs.