Nitrogen Co-doped Carbon Research Articles

Nitrogen and sulfur co-doped carbon dots: Facile synthesis and multifunctional applications for pH sensing, temperature sensing and RNA-selective imaging

Heteroatoms doped carbon dots (CDs) have attracted extensive attention for their superior optical properties, facile preparation and multifunctional applications in environmental detection, cell imaging and gene delivery. Herein, Nitrogen and sulfur co-doped carbon dots (N,S-CDs) were synthesized directly from methyl cellulose (MC), l-cysteine (l-cys) and ethylenediamine (EDA), showing excitation-dependent emission properties and relative high quantum yield (QY) of 12.3%. The obtained N,S-CDs are responsive to pH and temperature, suggesting pH- and temperature-dependent fluorescent features. Moreover, N,S-CDs are utilized to image and exhibit selective location inside the nucleus region both in living and fixed cells. Relative mechanisms have been explored by ribonuclease digestion testing and co-staining analysis with commercial nucleic acid dye. N,S-CDs show the specifical distribution in RNA-rich regions and positive response to RNA in cells. In brief, the developed N,S-CDs possess multi-faced application potency in pH sensing, temperature monitoring and RNA-selective imaging in cells.

Cu Catalyst Supported on Nitrogen and Phosphorus Co-Doped Carbon Nanosheets for Homocoupling of Terminal Alkynes Using CO2 as a Soft Oxidant

A bifunctional role of carbon dioxide (CO2) was developed in this research as a medium for catalyst preparation and as a soft oxidant for the subsequent coupling reaction. A highly dispersed and lo...

Iron and Nitrogen Co-doped Carbon Spheres as High Efficiency Oxygen Reduction Catalyst

Iron and Nitrogen Co-doped Carbon Spheres as High Efficiency Oxygen Reduction Catalyst

Influence of sulfur doping on the molecular fluorophore and synergistic effect for citric acid carbon dots* *Project supported by the National Natural Science Foundation of China (Grant No. 51571085) and the Key Scientific Research Projects of Colleges and Universities in Henan Province, China (Grant No. 20A430015).

In citric acid-based carbon dots, molecular fluorophore contributes greatly to the fluorescence emission. In this paper, the nitrogen and sulfur co-doped carbon dots (N,S-CDs) were prepared, and an independent sulfur source is selected to achieve the doping controllability. The influence of sulfur doping on the molecular fluorophore was systematically studied. The introduction of sulfur atoms may promote the formation of molecular fluorophore due to the increased nitrogen content in CDs. The addition surface states containing sulfur were produced, and S element exists as –SO3, and –SO4 groups. Appreciate ratio of nitrogen and sulfur sources can improve the fluorescence emission. The photoluminescence quantum yields (PLQY) is increased from 56.4% of the single N-doping CDs to 63.4% of double-doping CDs, which ascribes to the synergistic effect of molecular fluorophores and surface states. The sensitivity of fluorescence to pH response and various metal ions was also explored.

Excitation-dependent multiple luminescence emission of nitrogen and sulfur co-doped carbon dots for cysteine sensing, bioimaging, and photoluminescent ink applications

The concentration of L-cysteine (Cys), a sulfur-containing amino acid, acts as an indicator and biomarker for various diseases in humans. Therefore, the identification and detection of abnormal concentrations of Cys are critically important for determining human health. In this study, excitation-dependent multiple emission nitrogen and sulfur co-doped carbon dots (NS-CDs) are synthesized using a one-pot hydrothermal method. The prepared NS-CDs exhibit a small particle size, good optical properties with high quantum yield, excellent stability, and excitation-dependent photoluminescence (PL) property. The synthesized NS-CDs display a narrow diameter ranging from 3 to 7 nm with a relatively higher quantum yield (QY) up to 11.4%. Under optimal conditions, these NS-CDs show good selectivity for Cys over other biologically relevant species and even other similar (di)thiols (GSH/DTT). The synthesized NS-CDs show excellent selectivity and sensitivity to Cys, with a low detection limit of 23 nM and a linear detection range from 0 to 10 μM. The NS-CDs and NS-CDs/Cys are used for cell imaging, showing low toxicity to HCT116 cells and exhibits green fluorescence when observed by confocal microscopy. Furthermore, the controllable and strong photoluminescent emission properties of the NS-CDs and NS-CDs/Cys are visualized as green photoluminescent ink under UV light illumination. The present study is an attractive and innovative perception into the biomedical applications of NS-CDs with controllable photoluminescence.

Ratiometric fluorescence detection of Cd2+ based on N, S co-doped carbon quantum dots/Au nanoclusters

A new enhanced fluorescent (FL) ratio probe for Cd2+ detection was developed. The gold nanoclusters (AuNCs) with red FL were used as internal reference FL molecules, and the nitrogen and sulfur co-doped carbon quantum dots (N,S-CDs) with blue FL were used as analysis signal molecules. The FRET effect between AuNCs and N,S-CDs result in the FL quenching. The added Cd2+ interacts with AuNCs to form complexes, and interacts with the oxygen atoms in the hydroxyl and carboxyl groups of N,S-CDs to form a stable complex that made N,S-CDs/AuNCs aggregate and resulted in the FL enhancement. The FL intensities of N,S-CDs (F435) and AuNCs (F630) increased to different degrees after Cd2+ added. The ratio of FL intensity F435/F630 exhibited a good linear relationship with Cd2+ concentration in the range of 0–2.1 µM, and the detection limit in tap water was calculated to be 62 nM. The reliability of the prepared FL ratio probe was also demonstrated in actual water samples.

Preparation of magnesium, nitrogen-codoped carbon quantum dots from lignin with bright green fluorescence and sensitive pH response

Eco-friendly, renewable and green biomass materials are considered as the superior carbon precursors for producing carbon quantum dots (CQDs) in large scale. A major challenge is the limited contents of fluorophores in biomass, which then results in low quantum yields (QYs) and inferior fluorescence emission ability of the obtained CQDs. Herein, lignin with amounts of unsaturated aromatic and carbonyl fluorophores was employed as the carbon precursors to prepare CQDs through a green, facile approach. The magnesium and nitrogen elements were successfully introduced into CQDs with the aim of enhancing their QYs and extending their emission wavelengths. The prepared magnesium, nitrogen-doped CQDs (Mg, N-CQDs) could emit green fluorescence with a quantum yield (QYs) up to 46.38 %. The mechanism of their fluorescence ability was discussed extensively. More interestingly, the Mg, N-CQDs displayed a fluorescence transition between green and yellow color at pH value of 5.4, indicating their potential application as a probe to detect pH values of complicated environments. The findings in this paper would provide a viable strategy to converse lignin biomass waste into high-quality fluorescence nanomaterials.

Nitrogen and sulfur co-doped hierarchical porous carbon as functional sulfur host for lithium-sulfur batteries

Nitrogen and sulfur co-doped hierarchical porous carbon (N,S-HPC) is synthesized by using polyaniline and poly(3,4-ethylenedioxythiophene) as doping sources and polytetrafluoroethylene as the silica template removal agent for lithium-sulfur batteries. N,S-HPC shows the interconnected hierarchical porous network, which enables sulfur to be uniformly dispersed in the carbon matrix thus accelerating the transport of electrons and lithium ions. The S@N,S-HPC composite cathode exhibits a high capacity utilization of 1106 mA h/g at 0.2 C, together with excellent rate capacity of 600 mA h/g at 2 C, and also superior cycle life over 500 cycles with a capacity decay of 0.08 % per cycle at 1 C. The outstanding electrochemical performances for S@N,S-HPC cathode are mainly ascribed to the hierarchical porous structure of carbon and N/S co-doping, which offers sufficient interface for the deposition of solid discharge products and impedes the diffusion of polysulfides due to both physical confinement and chemical interaction by porous carbon matrix and N/S atoms.

Bifunctional Nitrogen and Fluorine Co-doped Carbon Dots as Fluorescence Probe for Silicon and Mercury by pH Switching.

New nitrogen and fluorine co-doped carbon dots were synthesized and used as a dual function fluorescent probe for silicon and mercury ions. The size of CDs was 10 nm. At optimum conditions (pH = 13, λex = 360 nm, and λem = 518 nm), the detection limit (DL) of silicon was 16.6 nM. Linear calibration was observed in the range of 0.8-35 µM. This fluorescence probe for silicon detection is presented for the first time and had the lowest detection limit in comparison with different previously reported techniques. In addition to the above property, these co-doped carbon dots had the second function as a fluorescence probe for mercury detection at pH = 8. The DL for mercury was 38 nM. The performance of this probe was also compared with other co-doped carbon dots. Excellent sensitivity and selectivity, simple method, low-cost materials, and applicability in real sample analysis are advantages of this dual function fluorescence probe.

Well-dispersed pyrite-type RuS2 nanocrystals anchored on porous nitrogen and sulfur co-doped hollow carbon spheres for enhanced alkaline hydrogen evolution

The hydrogen evolution reaction (HER) activity in alkaline condition is generally suppressed due to sluggish water dissociation–related Volmer process. Consequently, developing new highly-active and cost-efficient electrocatalysts for the alkaline hydrogen production is greatly desirable for achieving sustainable water splitting in industrial plants. Pyrite-type RuS2 is a potential excellent electrocatalyst for alkaline HER but the related research is still in its infancy. Herein, well-dispersed crystalline RuS2 nanoparticles (c-RuS2 NPs) with ultrasmall particle size anchored on porous nitrogen and sulfur co-doped hollow carbon spheres (NSC) are synthesized for alkaline HER electrocatalysis. The conductive and porous hollow carbon spheres with nitrogen and sulfur doping is used as the effective support to provide abundant anchoring sites and modify the electronic structure of RuS2, beneficial to increasing the active sites and improving the intrinsic activity. Furthermore, the crystallinity modulation of ruthenium sulfide also has a significant impact on HER activity. In 1.0 M KOH solution, the proposed c-RuS2 NPs/NSC catalyst exhibits admirable activity for HER electrocatalysis with a low overpotential of 11 mV at a current density of 10 mA cm−2 and a small Tafel slope of 35.4 mV dec−1. With low Ru loading, superior hydrogen evolution in alkaline media is achieved for c-RuS2 NPs/NSC compared to the commercial Pt/C and the reported ruthenium-sulfide-based electrocatalysts.

Synthesis of Fluorescent Nitrogen and Phosphorous Co-doped Carbon Quantum Dots for Sensing of Iron, Cell Imaging and Antioxidant Activities.

Carbon quantum dots (CQD) as the result of their exceptional physical and chemical properties show tremendous potential in various field of applications like cell imaging and doping of CQDs with elements like nitrogen and phosphorous increase its fluorescence property. Herein, we have synthesized fluorescent nitrogen and phosphorous codoped carbon quantum dots (NPCQDs) via a one-pot hydrothermal method. Sesame oil, L-Aspartic acid, and phosphoric acid were used as carbon, nitrogen, and phosphorous sources, respectively. UV-Vis spectrophotometer, fluorescence spectrometer, Fourier transform infrared spectrometer (FTIR), X-ray diffraction spectrometer (XRD), field emission scanning microscopy (FESEM), and transmission electron microscopy (TEM) were employed to characterize the synthesized fluorescent NPCQDs. The as-synthesized NPCQDs with a particle size of 4.7nm possess excellent water solubility, high fluorescence with high quantum yield (46%), high ionic stability, and resistance to photobleaching. MTT assay indicated the biocompatibility of NPCQDs and it was used for multicolor live-cell imaging. Besides, the NPCQDs show an effective probe of iron ions (Fe3+) in an aqueous solution with a high degree of sensitivity and selectivity. The DPPH assay showed its good antioxidant activity.

Nitrogen and phosphorus co-doped mesoporous carbon nanosheets derived from bagasse for lithium-ion batteries

N,P co-doped bagasse-based sheet-like mesoporous carbon (NP-BC) for lithium-ion battery anode material was prepared using bagasse and NH4H2PO4 as raw material. Compared with primary bagasse carbon (BC), the specific surface area and the lattice spacing of the NP-BC increased from 1307.21 to 2118.59 m2/g and from 0.34 to 0.385 nm, respectively. The first discharge specific capacity also increased from 1186.59 to 2347.56 mAh/g at 0.05 A/g, and the reversible capacity increased more than twice.

Sulfur and nitrogen co-doped carbon nanosheets for improved sodium ion storage

Heteroatom doping into specific nanostructure is believed as the leading solution for developing the advanced carbon materials for sodium ion batteries (SIBs), however, the preparation and understanding of heteroatoms co-doped carbon anodes are still challenging. Herein, the sulfur and nitrogen co-doped (weight content of 15.64% for N and 3.1% for S) carbon nanosheets (SNC) are prepared by treating nitrogen-rich carbon nanosheets with sublimation sulfur. The S, N co-doping is responsible for the enlarged interlamellar spacing of 0.38 nm and abundant defect-introduced active sites. These structure features combined with the advantage of nanosheet are significant for activating sodium ion storage properties, endowing SNC with high Na+ storage capacity of 270 mAh g−1 at 0.1 A g−1 and 100 mAh g−1 at 1 A g−1 after 1000 cycles. More importantly, the kinetic analysis is carried out to illustrate that S, N co-doping can improve the Na+ diffusion coefficient in carbon anode and enhance the ion storage. This work deepens the understanding on the boosting effect of heteroatoms dual-doping for the sodium ion storage of carbon materials, which conduces to development of advanced heteroatom doped carbon anodes for SIBs.

Fish bone-derived N, S co-doped interconnected carbon nanofibers network coupled with (Fe, Co, Ni)9S8 nanoparticles as efficient bifunctional electrocatalysts for rechargeable and flexible all-solid-state Zn-air battery

Rational design of efficient, cost-effective and robust bifunctional oxygen electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of vital significance to the large-scale application of rechargeable Zn-air battery (ZAB). Herein, we demonstrate a novel and simple strategy for the synthesis of (Fe, Co, Ni)9S8 nanoparticles embedded in nitrogen and sulfur co-doped interconnected carbon nanofibers network ((Fe, Co, Ni)9S8/NSCFs) derived from fish bone as an efficient bifunctional catalyst. The (Fe, Co, Ni)9S8/NSCFs shows large specific surface area (750 m2g − 1), well-defined interconnected nanofibers network structure with high conductivity, synergistic chemical coupling effects between (Fe, Co, Ni)9S8 and NSCFs with doped heteroatoms of N and S. As expected, in alkaline medium, excellent catalytic activity and outstanding durability toward both ORR and OER are obtained. Moreover, the homemade all-solid-state ZAB based on (Fe, Co, Ni)9S8/NSCFs displays outstanding battery capacity and power density together with excellent durability and flexibility. As an additional advance, a digital display screen powered by (Fe, Co, Ni)9S8/NSCFs-based rechargeable ZAB works steadily at twisted, extruded, combusting, and punctured states, making our bifunctional electrocatalysts attractive for wearable energy storage applications.

Core-shell structured metal organic framework materials derived cobalt/iron–nitrogen Co-doped carbon electrocatalysts for efficient oxygen reduction

Homogeneous dispersion of active sites and abundant pore structure for non-precious metal electrocatalysts are favorable for the oxygen reduction reaction (ORR) activity. Herein, a nitrogen-doped carbon core supported CoFe alloy-nitrogen co-doped carbon shell nanopolyhedron (NC@CoFe,N–CNP) electrocatalyst, which has rich pore structure and uniformly distributed active sites, is prepared through a facile thermal conversion of a ZIF-8 core and Fe,Co-ZIF shell composite precursor (ZIF-8@Fe,Co-ZIF) without any post-treatments. The existence of ZIF-8 core can maintain the structure of the ZIF-8@Fe,Co-ZIF composite controllable, avoiding the damage to the pore structure for fast mass transfer during pyrolysis. Meanwhile, the bi-metal iron and cobalt co-doping shell is more conducive for uniform dispersion of CoFe alloy particles than single one due to the interval effects, which can create various active sites and efficiently promote the ORR activity. As expected, the optimal NC@CoFe,N–CNP electrocatalyst exhibits an excellent catalytic activity with a high onset potential and half-wave potential (0.970 V and 0.865 V) compared to commercial Pt/C (0.934 V and 0.846 V). The kinetic current density of NC@CoFe,N–CNP reached to 7.99 mA cm−2, which is higher than Pt/C (5.14 mA cm−2) at 0.85 V. Furthermore, the NC@CoFe,N–CNP electrocatalyst demonstrates better electrochemical stability and anti-poisoning ability.

Nitrogen and oxygen co-doped mesoporous carbon spheres as capacitive anode for high performance sodium-ion capacitors

The poor rate capability of battery-type anode is usually the bottleneck of the power-energy outputs of a hybrid alkaline metal ion capacitor. In this work, nitrogen and oxygen co-doped mesoporous carbon spheres with excellent rate performance and cycle stability are used as anode materials of sodium ion capacitors (SICs). The high N and O element doping levels as well as the amorphous and mesoporous structure have enabled prominent capacitive Na ion storage behavior, which in turn match well with the capacitive cathode in the hybrid device. Under optimum conditions, the SIC delivers a high energy density of 103.1 Wh kg−1 at a power density of 205.6 W kg−1. Even at a high power density of 7520 W kg−1, an energy density of 23.5 Wh kg−1 is still maintained. Moreover, a robust cycle stability with capacity retention of 84.6 % after 2500 cycles at 1 A g-1 is maintained. Such excellent electrochemical performances convincingly demonstrate that the all-carbon based SICs with the highly capacitive N and O co-doped mesoporous carbon anode can be promising Na ion-based energy storage devices alternative to their Li ion-based counterparts.

Azithromycin detection in cells and tablets by N,S co-doped carbon quantum dots

Azithromycin (AZM)11AZM: azithromycin. is one of the most widely used antibiotics. AZM abuse is easy to cause great harm to human body, so developing a rapid and sensitive method to detect AZM is of great importance. Herein, 3-aminothiophenol as only reaction precursor, nitrogen and sulfur co-doped carbon quantum dots (N,S-CQDs)22N,S-CQDs: nitrogen and sulfur co-doped carbon quantum dots. were fabricated by one-step hydrothermal carbonization method. All characteristics demonstrate that N,S-CQDs possess good water solubility, high fluorescence stability and low cytotoxicity. Without being disturbed by amino acids and drugs, the most interesting finding is that AZM can efficiently quench the fluorescence of N,S-CQDs by a synergistic effect of electrostatic interaction and static quenching. A fluorescent probe for the detection of AZM was constructed with high selectivity and good sensitivity, achieving two linear ranges of 2.5–32.3 μM and 37.2–110 μM and a limit of detection of 0.76 µM. The proposed fluorescent method was used for the detection of AZM in cells with fulfilling results. More importantly, the fluorescent probe was successfully used to the detection of AZM in tablets and human urine with recovery rate and relative standard deviations of 98.2–104.8% and 0.04–3.46%, respectively, which was confirmed by the standard method of HPLC-UV. This finding illustrates the usefulness and feasibility of N,S-CQDs as an effective fluorescent probe for the detection of AZM in tablets and human urine, which is helpful for supervising and guiding pharmacy.

Heteroatom nitrogen and oxygen co-doped three-dimensional honeycomb porous carbons for methylene blue efficient removal

High carbon content and low-priced coal tar pitch (CTP) was a suitable precursor to prepare porous carbon. However, the porous carbon directly prepared by CTP showed an amorphous two-dimensional structure, which limited its subsequent applications in certain respects. In this paper, under the oxidation of H2O during KOH activation, nitrogen and oxygen co-doped three-dimensional honeycomb porous carbons (HPCs) were prepared with carbon disulfide extract of CTP as raw material and melamine sponge as structural framework and nitrogen precursor. HPCs exhibited a unique three-dimensional honeycomb structure, which was able to prevent the stacking of nano materials and provide larger effective specific surface area (2246 m2 g−1) to supply more adsorption space for pollutants in wastewater. In addition, HPC-3, prepared by an impregnation ratio (char:KOH) of 3, displayed excellent adsorption performance of methylene blue, the maximum adsorption capacity was 631.0 mg g−1, which was 2–5 times higher than most of biomass porous carbons previously reported. The adsorption process conformed to Langmuir and pseudo-second order kinetic model. As can be clearly seen from the adsorption results, HPC-3, as a kind of adsorbent, effectively contributed to removing synthetic dyes from wastewater.

Experimental and DFT insights into nitrogen and sulfur co-doped carbon nanotubes for effective desulfurization of liquid phases: Equilibrium & kinetic study

Herein, nitrogen and sulfur co-doped carbon nanotubes (NS-CNT) adsorbents were synthesized via the chemical vapor deposition technique at 1000°C by employing the camphor, urea and sulfur trioxide pyridine. In this study, desulfurization of two types of mercaptans (dibenzothiophene (DBT) and tertiary butyl mercaptan (TBM) as nonlinear and linear forms of mercaptan) was studied. In this regard, a maximum capacity of NS-CNT was obtained as 106.9 and 79.4 mg/g and also the removal efficiencies of 98.6% and 88.3% were achieved after 4 h at 298K and 0.9 g of NS-CNT for DBT and TBM, respectively. Characterization of the NS-CNTs was carried out through exploiting scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and elemental analysis (CHN). The isotherm equilibrium data could be ascribed to the Freundlich nonlinear regression form and the kinetic data was fitted by nonlinear form of the pseudo second order model. The negative values of ΔS0, ΔH0 and ΔG0 specify that the adsorption of both types of mercaptans was a natural exothermic process with a reduced entropy. Maintenance of more than 96% of the adsorption capacity even after nine cycles suggest the NS-CNT as a superior adsorbent for mercaptans removal in the industry. Density functional theory (DFT) calculations were also performed to peruse the effects of S/N co-doping and carbon monovacancy defects in CNTs toward the adsorption of DBT and TBM.

Effect of KOH on the Energy Storage Performance of Molasses-Based Phosphorus and Nitrogen Co-Doped Carbon

In this study, we have evaluated the effect of potassium hydroxide (KOH) on the energy storage performance of metal-free carbon-based materials prepared from molasses. Molasses are a renewable-resource biomass and economical by-product of sugar refinement, used here as a carbon precursor. Two co-doped carbon materials using molasses were synthesized via a time and cost-efficient microwave carbonization process, with ammonium polyphosphate as a phosphorus and nitrogen doping agent. The phosphorus and nitrogen co-doped carbon (PNDC) samples were prepared in the presence and absence of a chemical activating agent (KOH), to study the role of chemical activation on PNDCs. Physical characterizations were performed to gain insight into the composition, pore size and topographical data of each material. Electrochemical characterization via cyclic voltammetry in 1 M sulfuric acid (H2SO4) as well as in 6 M KOH as electrolytes, revealed high current density and specific capacitance for the chemically activated material (PNDC2) compared to one without chemical activation (PNDC1). The capacitance value of 244 F/g in KOH electrolyte was obtained with PNDC2. It is concluded that addition of KOH prior to carbonization increases the surface functionality, which significantly enhances the electrochemical properties of the PNDC material such as current density, stability, and specific capacitance.