A phenylboric acid functionalized carbon dot (2-FPBA-CD) for rapid fluorescent sensing of glucose in blood was synthesized by simply mixing N, S-doped carbon dots (CDs) with phenylboric acid at room temperature. At pH 7.4, the response of 2-FPBA-CD to glucose could reach equilibrium in a very short time (10 min), with a wide responsive linear range of 19.70 μM to 2.54 mM, which can be applied to the detection of glucose in serum. The mechanism studies showed that the layered carbon film of 2-FPBA-CD aggregated after adding glucose, thereby leading to the fluorescence quenching of 2-FPBA-CD.

Sulfamonomethoxine (SMM) is widely used to inhibit Gram-positive and Gram-negative bacteria, and improper use of SMM is detrimental to human health and ecological stability. Therefore, a sensitive determination method is of great importance for monitoring SMM residues in water, meat, milk, eggs, etc. Herein, a Pt-functionalized S-doped graphitic carbon nitride (Pt/Sg- C3N4) was constructed for the electrochemical determination of SMM. The as-developed Pt3/ S3-g-C3N4 sensor showed a significant SMM determination performance. The electrochemical oxidation of SMM on Pt3/ S3-g-C3N4/GCE involves two electron transference and was limited by a diffusion process. The as-developed Pt3/ S3-g-C3N4/GCE sensor has good linearity in a wide range of 0.1–120 μmol/L and a remarkably low limit of detection (LOD) of 0.026 μmol/L for SMM determination. In addition, the sensor has high selectivity and anti-interference properties for SMM detection. Furthermore, this Pt3/ S3-g- C3N4/GCE sensor has good reproducibility and stability. Moreover, the recoveries were in the range of 89.6–112.2% for the detection of the SMM in a real sample of egg. The proposed Pt3/ S3-g-C3N4/GCE sensor shows great potential for practical applications in detecting trace amounts of antibiotics.

The presence of tetracycline (TC) has been detected in the human living environment, and its complex structure makes it difficult to degrade. The green and efficient utilization of electroactivated persulfate advanced oxidation technology for the degradation of tetracycline remains a challenge. In this study, N-doped reduced graphene oxide (N-rGO) was prepared using a hydrothermal treatment method with urea as the nitrogen source. Four different mass ratios of graphene oxide (GO) to urea were synthesized, and the optimal mass ratio was determined through degradation experiments of tetracycline. The N-rGO/EC/PMS three-dimensional electrocatalytic system was constructed, and the influence of the experimental data on TC degradation, such as initial pH, PMS dosage and voltage, was determined. Characterization analysis using scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and other methods was conducted. The efficient catalytic ability of N-rGO was demonstrated through the generation of hydrogen peroxide ( H2O2) and consumption of peroxymonosulfate (PMS). The superiority of the three-dimensional (3D) electrochemical advanced oxidation process was proposed by combining different systems. Furthermore, the presence of hydroxyl radicals (.OH), persulfate radicals ( SO4 ·−), and singlet oxygen (1O2) was identified using electron spin resonance (ESR) technology. The utilization of N-rGO as a three-dimensional electrode, coupled with the advantages of PMS activation and electrochemical oxidation processes, is a promising method for treating organic pollutants in wastewater.

4-Nitrophenol (4NP) is a vital intermediate in organic industries, and its exploitation creates serious environmental issues. We propose a fluorescence quenching-based strategy with nitrogen and sulfur co-doped carbon dots (NS-CDs) for highly sensitive 4NP detection with excellent selectivity. The NS-CDs are produced through the hydrothermal process, in which citric acid serves as a carbon source and cysteamine hydrochloride as a source of N and S. The effect of doping was also studied by synthesizing undoped CDs and examining their properties. As-developed NS-CDs exhibit a bright cyan blue color with maximum emission centered at 465 nm. The fluorescence of NS-CDs is significantly quenched in an approximately linear fashion with increasing 4NP concentration (7.5–97.5 μM). The inner filter effect (IFE) and static quenching (SQ) between NS-CDs and 4NP are responsible for such fluorescence reduction. The fluorimetry technique enables the quantification of 4NP with a limit of detection (LOD) of about 0.028 μM. Moreover, the fluorescence quenching is tested for several other chemical compounds but they generate false quenching signals; only 4NP leads to fluorescence quenching of NS-CDs, demonstrating excellent selectivity. The “turn-off” fluorescence properties and visually apparent color change of the fluorescent probe reveal the excellent performance for 4NP sensing. The NS-CDs’ capability of quantifying 4NP in real water samples (tap water and drinking water) produces an excellent recovery rate ranging between 96.24 and 98.36%.

Pharmaceutical products occurring in freshwater bodies create numerous problems for the water bodies owing to their bio-toxic nature. In order to remove such pharmaceutical pollutants, a novel Er-doped Bi4O5Br2/ g-C3N5 nanocomposite was prepared by one-pot synthesis and applied for the photocatalytic removal process. The Er ions doped on the surface of Bi4O5Br2/ g-C3N5 nanocomposite exhibited 97% degradation of tetracycline in 60 min under visible light irradiation, which is higher than pure g-C3N5 and Bi4O5Br2 photocatalysts. The improved photocatalytic properties are attributed to the outstanding visible light harvesting capacity and quick charge carrier separation efficiency which greatly reduced the recombination rate in the heterojunctions. Based on radical trapping experiments, the •O2 −, h+ and •OH radicals played a prominent role in the photodegradation reactions under visible light. Finally, the ternary Er-doped Bi4O5Br2/ g-C3N5 nanocomposite is effectively recyclable with quite a stable photocatalytic removal rate. This work enables a new perspective on the rational design of rare-earth-based nanocomposites for various pharmaceutical pollutants treatment processes.

The development of food packaging materials with mechanical and antimicrobial properties is still a major challenge. N, P-doped carbons (NPCs) were synthesized. Poly(butylene adipate-co-terephthalate) (PBAT), which has an adverse effect on the environment and affects petroleum resources, has been commonly used for applications as food packaging. The development of PBAT composites reinforced with NPCs and studies on their structure and antimicrobial properties are presented in this study. The composite materials in the PBAT/NPCs were processed by solution casting. The plasticizing properties of NPCs enhanced the mechanical strength of composites produced of PBAT and NPCs. The thermal properties of PBAT composites were enhanced with addition of NPCs, according to thermogravimetric analysis (TGA). After reinforcement, PBAT/NPCs composites became more hydrophobic, according to contact angle measurements. In studies against S. aureus and E. coli food-borne pathogenic bacteria, the obtained composites show noticeably improved antimicrobial activity. The composite materials, according to the results of PBAT and NPCs may be a good choice for packing for food that prevents microorganisms.

Sulfur and nitrogen co-doped carbon dots (NSCDs) were quickly synthesized by the microwave-assisted method from triammonium citrate and thiourea. NSCDs showed a quantum yield of 11.5% with excitation and emission bands at 355 and 432 nm, respectively. Also, a fluorescence quenching was observed in the presence of Pb(II) ions, and the as-synthesized CDs were used as a sensitive probe for detecting Pb(II) in water and food samples. The results showed the optimal conditions for Pb(II) determination were CDs concentration of 0.02 mg mL− 1 at pH 6.0–7.0 and an incubation time of 20 min. The relative fluorescence intensity of NSCDs was proportional to Pb(II) concentrations in the range of 0.029–2.40 and 2.40–14.4 μmol L− 1 with a correlation coefficient (R2) of 0.998 and 0.955, respectively, and a detection limit of 9.2 × 10– 3 μmol L− 1. Responses were highly repeatable, with a standard deviation below 3.5%. The suggested method demonstrates the potential of a green, fast, and low-cost approach for Pb(II) determination in water, tea, and rice samples with satisfying results.

The disposal of organic pollutants is one of the important research topics. Some of the studies in this field are based on the degradation of organic pollutants with a catalytic agent. The cobalt tetraoxide/peroxymonosulfate system is an important catalytic system used for the radical degradation of organic pollutants. To increase the catalytic efficiency of such reactions, graphitization of activated carbon used as a support solid and nitrogen doping to the carbon structure are commonly used methods. In this study, cobalt tetraoxide production, N-doping and graphitization were carried out in a single step by heat treatment of activated carbon doped with the phthlocyanine cobalt (II) complex. The catalytic performance of the catalyst/ peroxymonosulfate system was investigated by changing the pH, catalyst, and PMS concentration parameters on rhodamine B and 1,3,5 trichlorophenol, which were used as models. It was seen that the catalysts had 97% activity on rhodamine B in 16 min and 100% on 1,3,5 trichlorophenol in 6 min. It was observed that the catalysts continued to show high catalytic activity for five cycles in reusability studies and had a very low cobalt leaching rate. These results are in good agreement with previously published studies. In line with these results, the synthesized N-doped graphitic carbon/Co3O4 catalyst can be used as an effective catalyst for wastewater treatments.

Recently, hollow carbon spheres (HCS) have aroused great interests in the field of energy storage and conversion owing to their unique morphology, structure and other charming properties. Nevertheless, unsatisfactory electrical conductivity and relatively poor volumetric energy density caused by inevitable gaps between discrete carbon spheres greatly impede the practical application of HCS. In this work, for the first time we propose a novel dual-template strategy and successfully fabricate interconnected 3D hollow N-doped carbon network (HNCN) by a facile and scalable pyrolysis process. By systematical characterization and analysis, it can be found that HNCN is assembled by HCS and lots of mesoporous carbon. Compared to the counterparts, the obtained HNCN exhibits unique 3D interconnected architecture, larger specific surface area, hierarchical meso/macropore structure, higher structure defects, higher N doping amount and more optimized N configurations (especially for pyridinic-N and graphitic-N). As a result, these advantageous features endow HNCN with remarkably promoted electrochemical performance for supercapacitor and oxygen reduction reaction. Clearly, our proposed dual-template strategy provides a good guidance on overcoming the intrinsic shortcomings of HCS, which undoubtedly broadens their application in energy storage and conversion.

Hydrogen energy is a promising source of renewable and clean energy for various industries, such as chemical, automobile, and energy industries. Electrolysis of water is one of the basic methods for the production of hydrogen energy. However, the high overpotential of the oxygen evolution reaction (OER) in water electrolysis has hindered the effective production of hydrogen using this method. Thus, the development of high-efficiency non-precious metal-based electrocatalysts for OER is extremely significant. In this study, we adopted a one-step hydrothermal method to fabricate Ni-based catalysts with N/Sdual doped graphene oxide/carbon nanotube (GO/CNT) supports using thiourea ( CH4N2S) and urea as the S source and the N source. It was observed that the amount of thiourea utilized in the synthesis of the catalyst affected the morphology, composition, and the electrochemical properties of the catalyst. For a GO/CNT-to-thiourea mass ratio of 1:10, the catalyst exhibited the highest activity, where the OER overpotential was 320 mV at a current density of 10 mA/cm2. This was attributed to the high specific surface area, high conductivity, and fast electron transport channels of the N/S-dual doped GO/ CNT composite. Furthermore, sulfurization of the Ni particles to form nickel sulfide played a significant role in enhancing the catalytic performance.

A promising approach to enhance catalytic performance of supported heterogeneous nano-metal catalysts is to uniformly disperse active nanoparticles on the support. In this work, N-doped carbon-modified graphene (G@NC) nanosheet is designed and prepared to anchor Pd–Fe bimetallic nanoparticles (Pd–Fe/G@NC). The N-doped carbon modification on graphene surface could construct a sandwich-like structure (G@NC), which not only prevented the re-stacking of graphene nanosheets but also provided confined space for stable anchoring of bimetallic Pd–Fe nanoparticles. Benefitted from the unique structural property and synergetic effect of metal Pd and Fe species, the as-obtained Pd–Fe/G@NC composite displays excellent catalytic activity toward 4-nitrophenol reduction reaction with a turnover frequency of 613.2 min− 1, which is far superior to that of the mono-metal counterparts (Fe/G@NC and Pd/G@NC). More importantly, Pd–Fe/G@NC catalyst also exhibits favorable catalytic performance in the reduction of other nitroaromatic compounds (nitrobenzene, 4-nitrotoluene, 4-chloronitrobenzene, and so on). In addition, Pd–Fe/G@NC can catalyze the oxidation of furfuraldehyde to furoic acid with a high yield of 88.64%. This work provides a new guide for rationally designing and developing advanced supported heterogeneous bimetallic catalyst.

N-doped Na2Ti6O13@TiO2 (denoted as N-NTO@TiO2) composites are successfully synthesized using a simple two-step process: 1) ball-milling of TiO2 with Na2CO3 followed by heat treatment at 900oC; 2) mixing of the prepared Na2Ti6O13 with titanium isopropoxide and calcining with urea at 500oC. The prepared composites are characterized using XRD, SEM, TEM, FTIR, and BET. The N-NTO@TiO2 composites exhibit well-defined crystalline and anatase TiO2 with exposed {101} facets on the external surface. Moreover, dopant N atoms are uniformly distributed over a relatively large area in the lattice of the composites. Under visible light irradiation, ~51% of the aqueous methylene blue is photodegraded by N-NTO@TiO2 composites, which is higher than the values shown by other samples because of the coupling effects of the hybridization of NTO and TiO2, N-doping, and presence of anatase TiO2 with exposed {101} facets.

Electrochemical water splitting is an important process for next generation of eco-friendly energy systems. The oxygen evolution reaction (OER), which occurs at an anode during the process, requires efficient electrocatalysts to reduce activation energies. Although Ru- or Ir-containing materials show excellent electrocatalytic activities, their high cost is a critical drawback. Consequently, the development of efficient electrocatalysts composed of low-cost metal components is a great challenge. In this study, we develop a new route to produce a hybrid material (Fe–NC) containing Fe3C particles dispersed on the surface of N-doped carbon (NC) materials by heat treatment of a mixture of urea and Fe(II)Cl2(H2O)4. Microscopic analyses prove that the Fe3C particles are placed on the surfaces of thin NC materials. Additionally, various characterizations reveal that the particles contain Fe3C structure. Fe–NC shows good electrocatalytic properties with onset and overpotentials of 1.57 V and 545 mV, respectively, for OER in KOH electrolyte. This study suggests the possibility of the use of Fe3C- based composites as OER electrocatalysts.

In this study, N/S co-doped carbon felt (N/S-CF) was prepared and characterized as an electrode material for electric double-layer capacitors (EDLCs). A commercial carbon felt (CF) was immersed in an aqueous solution of thiourea and then thermally treated at 800 oC under an inert atmosphere. The prepared N/S-CF showed a large specific surface area with hierarchical pore structures. The electrochemical performance of the N/S-CF-based electrode was evaluated using both 3- electrode and 2-electrode systems. In the 3-electrode system, the N/S-CF-based electrode showed a good specific capacitance of 177 F/g at 1 A/g and a good rate capability of 41% at 20 A/g. In the 2-electrode system (symmetric capacitor), the freestanding N/S-CF-based electrode showed a specific capacitance of 275 mF/cm2 at 2 mA/cm2, a rate capability of 62.5 % at 100 mA/cm2, a specific power density of ~ 25,000 mW/cm2 at an energy density of 23.9 mWh/cm2, and a cycling stability of ~ 100 % at 100 mA/cm2 after 20,000 cycles. These results indicate the N/S co-doped carbon felts can be a promising candidate as a new electrode material in a symmetric capacitor.

Nitrogen-doped carbon dots (N-CDs), derived from the biomass (anthocyanin), are the novel additive to the nanocarbon materials, which is expected to bring a wide spectrum of novel applications. Moreover, metallic oxides are emerging for their unique potential for electrocatalysis. Herein, we report the synthesis of N-CDs for the selective detection of Fe3+ with a limit of detection of 2.57 μM in the range of 5–60 μM using ethylenediamine and H2O2 by a hydrothermal method. The obtained N-CDs displayed a spherical morphology with a particle size range of 2–7 nm and emitted blue luminescence at 394 nm under excitation at 319 nm. Meanwhile, we have demonstrated the fabrication of cost-efficient electrocatalysts for oxygen evolution reaction (OER) in an alkaline medium, employing N-CDs. Owing to the successful incorporation of N-CDs into NiO nanospheres, the resulting N-CDs/NiO with large surface areas, fast charge transfer, and increased conductivity vastly improved the catalytic activity. Remarkably, the optimal of N-CDs/NiO composite requires the overpotential of only 380 mV at a current density of 10 mA cm− 2 and a relatively low Tafel slope of 57.96 mV dec− 1 compared with pure NiO. These results open up a facile route for the application of N-CDs and offer prospects for CD-metal hybrids as high OER catalysts in electrochemical energy devices.

To meet the increased performance and cost requirements of commercial supercapacitor, a N and O self-doped hierarchical porous carbon is fabricated via a green and simple self-activation route utilizing leaves of wild hollyhock as raw materials. Comparing to commercial activated carbon, the reported material exhibits some marked merits, such as simple and green fabrication process, low cost, and superior capacitance performance. The specific surface area of the obtained N and O codoped hierarchical porous carbon arrives 954 m2 g−1, and the content of the self-doped nitrogen and oxygen reaches 2.64 at.% and 7.38 at.%, respectively. The specific capacitance of the obtained material reaches 226 F g− 1 while the specific capacitance of the symmetric supercapacitor arrives 47.3 F g− 1. Meanwhile, more than 90.3% of initial specific capacitance is kept under a current density of 20 A g− 1, and no arresting degradation is observed for capacitance after 5000 times cycle, perfectly demonstrating the excellent cycle and rate capability of the obtained material. The obtained N and O co-doped hierarchical porous carbon are expected to be an ideal substitution for commercial activated carbon.

Oxygen evolution reaction (OER) is an essential step at an anode in electrochemical water-splitting process and requires efficient electrocatalysts to reduce overpotentials. Although precious metal-based materials, such as RuO2, IrO2 and their hybrids with other components, performed excellently as OER electrocatalysts, their high cost has limited practical applications. Consequently, earth-abundant metal components including Fe, Co, and Ni have been investigated as alternatives. In this work, the hybridization of Ni-containing species with conductive carbon-based materials was used to prevent aggregation of active species and improve electrochemical catalytic performance. A new hybrid material composed of NiO nanoparticles and N-doped carbon materials was prepared. The NiO particles with a narrow size distribution were well dispersed on the surface of carbon-based materials. The hybrid showed improved electrocatalytic performance for OER than single components of NiO and N-doped carbon materials.

Nitrogen-doped carbons have attracted much attention due to their novel application in relation to gas storage. In this study, nitrogen-doped porous carbons were synthesized using SBA-15 as a template, polypyrrole as the carbon and nitrogen precursor, and KOH as an activating agent. The effect of the activation temperature (600–850°C) on the CO2 adsorption capacity of the obtained porous carbons was studied. Characterization of the resulting carbons showed that they were micro-/meso-porous carbon materials with a well-developed pore structure that varied with the activation temperature. The highest surface area of 1488 m2 g–1 was achieved at an activation temperature of 800°C (AC-800). The nitrogen content of the activated carbon decreased from 4.74 to 1.39 wt% with an increase in the activation temperature from 600 to 850°C. This shows that nitrogen is oxidized and more easily removed than carbon during the activation process, which indicates that C-N bonds are more easily ruptured at higher temperatures. Furthermore, CO2 adsorption isotherms showed that AC-800 exhibited the best CO2 adsorption capacity of 110 mg g–1 at 298 K and 1 bar.

Nitrogen-doped titanium dioxide (N-doped TiO2) is attracting continuously increasing attention as a material for environmental photocatalysis. The N-atoms can occupy both interstitial and substitutional positions in the solid, with some evidence of a preference for interstitial sites. In this study, N-doped TiO2 is prepared by the sol–gel method using NH4OH and NH4Cl as N ion doping agents, and the physical and photocatalytic properties with changes in the synthesis temperature and amount of agent are analyzed. The photocatalytic activities of the N-doped TiO2 samples are evaluated based on the decomposition of methylene blue (MB) under visible-light irradiation. The addition of 5 wt% NH4Cl produces the best physical properties. As per the UV-vis analysis results, the N-doped TiO2 exhibits a higher visible-light activity than the undoped TiO2. The wavelength of the N-doped TiO2 shifts to the visible-light region up to 412 nm. In addition, this sample shows MB removal of approximately 81%, with the whiteness increasing to +97 when the synthesis temperature is 600℃. The coloration and phase structure of the N-doped TiO2 are characterized in detail using UV-vis, CIE Lab color parameter measurements, and powder X-ray diffraction (XRD).