Tunable Electronic Properties of Nitrogen and Sulfur Doped Graphene: Density Functional Theory Approach

N-S dual-doped 3D porous laser-induced graphene electrode for curcumin determination in turmeric

The determination of curcumin (CM), the active ingredient of turmeric, can be used to control the quality of turmeric rhizomes and products. A CM sensor was developed based on a nitrogen and sulfur dual-doped laser-induced graphene (N-S@LIG) material fabricated in the form of a three-electrode system on a polyethylene terephthalate (PET) substrate. N-S@LIG was synthesized by the one-step laser ablation of a polyimide (PI) carbon source coated with a methylene blue (MB) N and S source. The surface morphology of the fabricated electrode was studied by scanning electron microscopy, energy dispersive x-ray analysis, Raman spectroscopy, contact angle analysis, and X-ray photoelectron spectroscopy. The electrode showed an excellent electron transfer ability and good electrocatalytic performances for the detection of CM. The N and S dual-doped laser-induced graphene electrode (N-S@LIGE) was employed to determine CM by differential pulse adsorptive stripping voltammetry (DPAdSV). To enable on-site analysis of CM in turmeric samples, the N-S@LIGE was incorporated with a small potentiostat plugged into a smartphone to manage the measurements and to display results. The developed CM sensor displayed a linear determination range from 0.10 to 30 μmol L-1, a detection limit of 0.036 μmol L-1, good repeatability, reproducibility and anti-interference properties. The developed CM sensor was used to measure CM in cultivated rhizomes and commercial turmeric powder. The analysis results correlated well with the results from the standard spectrophotometric analysis and high-performance liquid chromatography.

Smart carbon-based sensors for the detection of non-coding RNAs associated with exposure to micro(nano)plastics: an artificial intelligence perspective

Micro(nano)plastics (MNPs) are pervasive environmental pollutants that individuals eventually consume. Despite this, little is known about MNP's impact on public health. In this article, we assess the evidence for potentially harmful consequences of MNPs in the human body, concentrating on molecular toxicity and exposure routes. Since MNPs are present in various consumer products, foodstuffs, and the air we breathe, exposure can occur through ingestion, inhalation, and skin contact. MNPs exposure can cause mitochondrial oxidative stress, inflammatory lesions, and epigenetic modifications, releasing specific non-coding RNAs in circulation, which can be detected to diagnose non-communicable diseases. This article examines the most fascinating smart carbon-based nanobiosensors for detecting circulating non-coding RNAs (lncRNAs and microRNAs). Carbon-based smart nanomaterials offer many advantages over traditional methods, such as ease of use, sensitivity, specificity, and efficiency, for capturing non-coding RNAs. In particular, the synthetic methods, conjugation chemistries, doping, and in silico approach for the characterization of synthesized carbon nanodots and their adaptability to identify and measure non-coding RNAs associated with MNPs exposure is discussed. Furthermore, the article provides insights into the use of artificial intelligence tools for designing smart carbon nanomaterials.

Investigation of glucose electrooxidation mechanism over N-modified metal-doped graphene electrode by density functional theory approach

In this work, various precious and non-precious metals reported in the literature as the most effective catalysts for glucose electrooxidation reaction were investigated by the density functional theory (DFT) approach in order to reveal the mechanisms taking place over the catalysts in the fuel cell. The use of a single-atom catalyst model was adopted by insertion of one Au, Cu, Ni, Pd, Pt, and Zn metal atom on the pyridinic N atoms doped graphene surface (NG). β form of d-glucose in alkaline solution was used to determine the reaction mechanism and intermediates that formed during the reaction. DFT results showed that the desired glucono-lactone was formed on the Cu-3NG electrode in a single-step reaction pathway whereas it was produced via different two-step pathways on the Au and Pt-3NG electrodes. Although the interaction of glucose with Ni, Pd, and Zn-doped surfaces resulted in the deprotonation of the molecule, lactone product formation did not occur on these electrode surfaces. When the calculation results are evaluated in terms of energy content and product formation, it can be concluded that Cu, Pt, and especially Au doped graphene catalysts are effective for direct glucose oxidation in fuel cells reactor.

N and S co-doped graphene enfolded Ni-Co-layered double hydroxides: an excellent electrode material for high-performance energy storage devices

The performance of hybrid supercapacitors (HSCs) can be increased via the selection of higher capacitive electrode materials. Thus, layered double hydroxides (LDHs) have received extensive consideration in HSCs owing to their good ion-exchange properties, structural flexibility, and large specific surface area. Ni–Co-based LDHs show better specific capacitance, good synergy, and high-rate capability in aqueous electrolytes. However, LDHs suffer from low conductivity, which curbs the charge transfer and mass diffusion throughout the electrochemical process. Thus, the high performance of LDH-based supercapacitors is impeded. Hence, composites of LDH and conducting materials are used. Owing to its extraordinary conducting property, huge surface area, and cost-effectiveness, reduced graphene oxide (rGO) is used as conducting material for LDH-based composite electrodes. Moreover, via the incorporation of heteroatoms (N, S, etc.) into rGO, its electrochemical properties are further enhanced. Here, a novel composite electrode is prepared by wrapping Ni–Co-LDH with N and S-co-doped rGO (LDH-rGO-NS) via a hydrothermal process. The XPS C 1s spectra established the existence of N and S doping in the rGO. The electrochemical performance is enhanced due to an excellent ion/charge transfer rate because of N and S co-doping. The LDH-rGO-NS electrode offers a good charge transfer resistance of 0.24 Ω. The obtained anodic and cathodic b-values are 0.73 and 0.72, respectively. An admirable specific capacitance of 1388 F g⁻¹ is accomplished at a sweep rate of 100 mV s⁻¹. Furthermore, the obtained retention capacity is ∼71% after 2000 cycles. Moreover, the achieved specific capacitance is 2193 F g⁻¹ at the discharge current density of 5 A g⁻¹. The excellent electrochemical properties reveal the LDH-rGO-NS composites as encouraging electrode materials for HSCs.

A novel graphene embedded Ni–Co-LDH electrode was developed. The charge transportation rate was enhanced via N and S heteroatom doping, which results in an excellent discharge capacitance of 2193 F g⁻¹ at 5 A g⁻¹.

Carbon defects applied to potassium-ion batteries: a density functional theory investigation

Functionalized carbon nanomaterials are potential candidates for use as anode materials in potassium-ion batteries (PIBs). The inevitable defect sites in the architectures significantly affect the physicochemical properties of the carbon nanomaterials, thus defect engineering has recently become a vital research area for carbon-based electrodes. However, one of the major issues holding back its further development is the lack of a complete understanding of the effects accounting for the potassium (K) storage of different carbon defects, which have remained elusive. Owing to pressing research demands, the construction strategies, adsorption difficulties, and structure-activity relationships of the carbon defect-involved reaction centers for the K adsorption are systematically summarized using first principles calculations. Carbon defects affect the ability to trap K by affecting the geometry, charge distribution, and conductive behavior of the carbon surface. The results show that carbon doping with pyridinic-N, pyrrolic-N, and P defect sites tend to act as trapping K sites because of electron-deficient sites. However, graphite-N and sulfur doping are less capable of trapping K. In addition, it has been proved using calculations that the defects can inhibit the growth of the K dendrite. Finally, using the molten salt method, we prepared the undoped and nitrogen-doped carbon materials for comparison, verifying the results of the calculation.

Improving the electrochemical performance of a natural molybdenite/N-doped graphene composite anode for lithium-ion batteries via short-time microwave irradiation

In the present work, low-cost natural molybdenite was used to make a MoS2/N-doped graphene composite through coulombic attraction with the aid of (3-aminopropyl)-triethoxysilane and the electrochemical performance was greatly improved by solvent-free microwave irradiation for tens of seconds. The characterization results indicated that most (3-aminopropyl)-triethoxysilane can decompose and release N atoms to further improve the N-doping degree in NG during the microwave irradiation. In addition, the surface groups of N-doped graphene were removed and the particle size of MoS2 was greatly decreased after the microwave irradiation. As a result, the composite electrode prepared with microwave irradiation exhibited a better rate performance (1077.3 mA h g-1 at 0.1C and 638 mA h g-1 at 2C) than the sample prepared without microwave irradiation (1013.6 mA h g-1 at 0.1C and 459.1 mA h g-1 at 2C). Therefore, the present results suggest that solvent-free microwave irradiation is an effective way to improve the electrochemical properties of MoS2/N-doped graphene composite electrodes. This work also demonstrates that natural molybdenite is a promising low-cost anode material for lithium-ion batteries.

Tuning the Nature of N-Based Groups From N-Containing Reduced Graphene Oxide: Enhanced Thermal Stability Using Post-Synthesis Treatments

The synthesis of N-containing graphene derivatives by functionalization and doping of graphene oxide (GO) has been widely reported as an alternative to tune both their chemical and physical properties. These materials are of interest for a wide range of applications, including biomedicine, sensors, energy, and catalysis, to name some. Understanding the role of the nature, reactivity, concentration, and distribution of the N-based species, would pave the way towards the design of synthetic routes to obtain improved materials for specific applications. The N-groups can be present either as aliphatic fractions (amides and amines) or becoming part of the planar conjugated lattice (N-doping). Here, we have modified the distribution of N-based moieties present in N-containing RGO samples (prepared by ammonolysis of GO) and evaluated the role of the concentration and nature of the species in the thermal stability of the materials once thermally annealed (500–1050 °C) under inert environments. After these post-synthesis treatments, samples underwent marked structural modifications that include the elimination and/or transformation of N-containing fractions, which might account for the observed enhanced thermal stability. It is remarkable the formation of pyridinic N-oxide species, which role in the properties of N-containing graphene derivatives has been barely reported. The presence of this fraction is found to confer an enhanced thermal stability to the material.

One-step synthesis of sulfur-incorporated graphene quantum dots using pulsed laser ablation for enhancing optical properties

To tune the electronic and optoelectronic properties of graphene quantum dots (GQDs), heteroatom doping (e.g., nitrogen (N), boron (B), and sulfur (S)) is an effective method. However, it is difficult to incorporate S into the carbon framework of GQDs because the atomic size of S is much larger than that of C atoms, compared to N and B. In this study, we report a simple and one-step method for the synthesis of sulfur-doped GQDs (S-GQDs) via the pulsed laser ablation in liquid (PLAL) process. The as-prepared S-GQDs exhibited enhanced fluorescence quantum yields (0.8% → 3.89%) with a huge improved absorption band in ultraviolet (UV) region (200 ∼ 400 nm) and excellent photo stability under the UV radiation at 360 nm. In addition, XPS results revealed that the PLAL process can effectively facilitate the incorporation of S into the carbon framework compared to those produced by the chemical exfoliation method (e.g., hydrothermal method). And also, the mechanisms related with the optical properties of S-GQDs was investigated by time-resolved photoluminescence (TRPL) spectroscopy. We believe that the PLAL process proposed in this study will serve as a simple and one-step route for designing S-GQDs and opens up to opportunities for their potential applications.

Modeling of Complex Interfaces: From Surface Chemistry to Nano Chemistry

For a few years now, quantum chemical modeling of materials has experienced a tremendousboost due to the increasing computational power [...].

Graphene Foam Cantilever Produced via Simultaneous Foaming and Doping Effect of an Organic Coagulant

Inspired by the role of cellular structures, which give three-dimensional robustness to graphene structures, a new type of graphene cantilever with mechanical resilience is introduced. Here, NH₄SCN is incorporated into graphene oxide (GO) gel using it as a coagulant for GO fiber self-assembly, a foaming agent, and a dopant. Subsequent thermal treatment of the GO fiber at 600 °C results in the evolution of gaseous species from NH₄SCN, yielding internally porous graphene cantilevers (NS-GF cantilevers). The results reveal that NS-GF cantilevers are doped with N and S and thus exhibit higher electrical conductivity (150 S cm^-1) than that of their nonporous counterparts (38.4 S cm^-1). Unlike conventional fibers, the NS-GF cantilevers exhibit mechanical resilience by bending under applied mechanical force but reverting to the original position upon release. The tip of the NS-GF cantilevers is coated with magnetic Fe₃O₄ particles, and fast mechanical movement is achieved by applying the magnetic field. Since the NS-GF cantilevers are highly conductive and elastic, they are employed as bendable, magnetodriven electrical switches that could precisely read on/off signals for >10 000 cycles. Our approach suggests a robust fabrication strategy to prepare highly electroconductive and mechanically elastic foam structures by introducing unique organic foaming agents.

First-principles study of the effect of compressive strain on oxygen adsorption in Pd/Ni/Cu-alloy-core@Pd/Ir-alloy-shell catalysts

Through synergism between the ligand effect, the d-band center shift, and the surface alloying effect, the Pd₃CuNi@PdIr catalyst exhibits the poorest dioxygen adsorption and, consequently, the best catalytic ORR performance.