Nitrogen-doped Multi-walled Carbon Nanotubes Research Articles

Modulating NFO@N‐MWCNTs/CC Interfaces to Construct Multilevel Synergistic Sites (Ni/Fe‐O‐N‐C) for Multi‐Heavy Metal Ions Sensing

AbstractA hierarchical heterogeneous composite electrode of NiFe2O4@nitrogen‐doped multi‐walled carbon nanotubes/carbon cloth (NFO@N‐MWCNTs/CC) is prepared via a dip‐coating method, followed by a hydrothermal process. The flexible carbon cloth (CC) substrate provides robust support and the cross‐linked nitrogen‐doped multi‐walled carbon nanotubes (N‐MWCNTs) on the CC form a highly porous network with a large specific area that facilitates electron‐transfer. The stable support strengthens the framework and prevents pore structure disorder within the porous network, that could lead to the structural instability of the active sites. The decorated NiFe2O4 nanoparticles offer abundant active sites for enhanced electrocatalytic activity. Benefiting from the synergistic effect of the 3D hierarchical heterogeneous microstructure and multilevel bimetallic oxide active site (Ni/Fe‐O‐N‐C) constructs, the NFO@N‐MWCNTs/CC electrode achieves stable detection of multiple heavy metal ions (HMIs) with high reproducibility. The modified electrode allowed stable detection of multiple heavy metal ions with high reproducibility. The sensitivities of the electrode for Cd(II), Pb(II), Bi(III), and Hg(II) are 344.98, 441.02, 176.484, and 371.099 µA µm−1, respectively. The assay recoveries ranged from 95.3% to 106.8%, highlighting its practical applicability. This study provides innovative composites and theoretical insights to facilitate further advances in the simultaneous high‐performance detection of heavy metal ions.

Enhanced oxygen evolution and power density of Co/Zn@NC@MWCNTs for the application of zinc-air batteries

Rechargeable zinc-air batteries (ZABs) are viewed as a promising solution for electric vehicles due to their potential to provide a clean, cost-effective, and sustainable energy storage system for the next generation. Nevertheless, sluggish kinetics of the oxygen evolution reaction (OER), the oxygen reduction reaction (ORR) at the air electrode, and low power density are significant challenges that hinder the practical application of ZABs. The key to resolving the development of ZABs is developing an affordable, efficient, and stable catalyst with bifunctional catalytic. In this study, we present a series of bifunctional catalysts composed of Co/Zn nanoparticles uniformly embedded in nitrogen-doped carbon (NC) and multi-walled carbon nanotubes (MWCNTs) denoted as Co/Zn@NC@MWCNTs. The incorporation of MWCNTs using a facile and non-toxic method significantly decreased the overpotential of the OER from 570 to 430 mV at 10 mA cm−2 and the peak power density from 226 to 263 mW cm−2. Besides, the electrochemical surface area measurements and electrochemical impedance spectroscopy indicate that the three-dimensional (3D) network structure of MWCNTs facilitates mass transport for ORR and reduces electron transfer resistance during OER, leading to a small potential gap of 0.86 V between OER and ORR, high electron transfer number (3.92–3.98) of the ORR, and lowest Tafel slope (47.8 mV dec−1) of the OER in aqueous ZABs. In addition, in-situ Raman spectroscopy revealed a notable decrease in the ID/IG ratio for the optimally configured Co/Zn@NC@MWCNTs (75:25), indicating a reduction in defect density and improved structural ordering during the electrochemical process, which directly contributes to enhanced ORR activity. Hence, this study provides an excellent strategy for constructing a bifunctional catalyst material with a 3D MWCNTs conductive network for the development of advanced ZAB systems for sustainable energy applications.

Construction of Fe/Co-N4 Single-Atom Sites for the Oxygen Reduction Reaction in Zinc-Air Batteries.

Insight into the modulation effect of oxygen reduction reaction (ORR) active centers is of profound significance but remains a great challenge. Here, we designed Co, Fe dual-metal single-atom sites (CoFe-DSAs/NC) uniformly anchored on nitrogen-doped multiwalled carbon nanotubes for boosting ORR performance through regulating the 4d electronic orbitals of the Co-N4 active site. Mechanism studies revealed that for the first time the neighboring Fe-N4 atomic sites were able to regulate the d-band center of Co-N4 single-atom active centers while maintaining the balance of adsorption-desorption affinity for O2 and oxygen-containing species on Co-N4, thereby resulting in a superior ORR performance with a positive half-wave potential (0.90 V vs RHE). The assembled zinc-air battery based on CoFe-DSAs/NC exhibited an increased open-circuit voltage (1.48 V) and an elevated specific capacity (782.33 mAh·g-1). The work provides a new clue for reasonably designing high-performance ORR catalysts through adjusting the d-band center of active sites.

Synthesis and characterization of nitrogen-doped-MWCNT@cobalt oxide for nerve agent simulant detection

Organophosphorus nerve agents are toxic compounds that disrupt neuromuscular transmission by inhibiting the neurotransmitter enzyme, acetylcholinesterase, leading to rapid death. A hybrid composite was synthesized using a hydrothermal process for the early detection of dimethyl methyl phosphonate (DMMP), a simulant of the G-series nerve agent, sarin. Quartz crystal microbalance (QCM) and surface acoustic wave (SAW) sensors were used as detectors. Nitrogen-doped multiwalled carbon nanotubes (N-MWCNTs), cobalt oxide (Co3O4), and N-MWCNT@Co3O4 were compared to detect DMMP concentrations of 25–150 ppm. At 25 ppm, the differential frequencies (Δf) of the N-MWCNT, Co3O4, and N-MWCNT@Co3O4 sensors were 5.8, 2.3, and 99.5 Hz, respectively. The selectivity results revealed a preference for the DMMP rather than potential interference. The coefficients of determination (R2) of the N-MWCNT, Co3O4, and N-MWCNT@Co3O4 sensors for detecting 25–150 ppm DMMP were 0.983, 0.986, and 0.999, respectively. The response times of the N-MWCNT, Co3O4, and N-MWCNT@Co3O4 sensors for detecting 100 ppm DMMP were 25, 27, and 34 s, respectively, while the corresponding recovery times were 85, 105, and 181 s. The repeatability results revealed the reversible adsorption and desorption phenomena for the fixed DMMP concentration of 100 ppm. These unique findings show that synthesized materials can be used to detect organophosphorus nerve agents.

ZnO–ZrO2 coupling nitrogen-doped carbon nanotube bifunctional catalyst for co-production of diesel fuel and low carbon alcohol from syngas

Catalytic syngas conversion to liquid fuel is pivotal for biomass utilization, enhancing energy security, reducing carbon emissions and curbing reliance on petroleum imports. Herein, bifunctional catalysts comprising zinc-zirconium dioxide (ZnZrO2) dispersed on nitrogen-doped multi-walled carbon nanotubes (NCNT) (ZnZrO2/NCNT) were successfully designed, enabling the simultaneous production of both diesel fuels (C9–C16 hydrocarbon) and methanol through direct syngas conversion. Operating at 450 °C, 4.5 MPa, a gas hourly space velocity (GHSV) of 4800 mL h−1·gcat−1, the ZnZrO2/NCNT catalyst, featuring 2.6% nitrogen doping, exhibited exceptional performance, achieving a 50.3% selectivity for C9–C16 hydrocarbons and a 26.4% selectivity for methanol, while maintaining a 52.5% single-pass CO conversion rate. The C9+ selectivity significantly surpasses the bottleneck predicted by the ASF distribution theory (C9+ selectivity <36%). This starkly contrasts that of ZnO/NCNT (1.7% C9–C16 and 6.3% methanol) and ZrO2/NCNT (32.5% C9–C16 and 25.4% methanol) catalysts. Moreover, the ZnZrO2/NCNT catalyst still retained C9+ 51.5% selectivity and 25% methanol selectivity after 100 h of continuous operation. The synergistic effects resulting from the amalgamation of highly active nanostructured units with a well-encapsulation structure efficiently hinder active component migration during catalysis. This significantly enhances both the catalyst's activity and stability. Furthermore, nitrogen introduction serves as a key electron donor to ZnZrO2, thereby catalyzing the activation of CO dissociation. This activation step emerges as a pivotal factor crucial for enhancing selectivity in liquid fuel production.

Cu2ZnSnS4/N-MWCNTs hybrid systems as counter electrode substitutes for platinum in dye-sensitized solar cells

Copper zinc tin sulfide, Cu2ZnSnS4 (CZTS) is being considered a viable option for a counter electrode due to its abundance, cost-effectiveness, catalytic activity, and other advantageous properties. However, CZTS has low electron transport capabilities, a shortcoming that can be addressed by combining it with high electron mobility carbon nanomaterials. Nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) exhibit higher electron conductivities than their pristine counterparts. This improvement is attributed to the disruption of the sp2-hybridized carbon arrangement, as some of the carbon atoms are replaced by nitrogen atoms. In this study, a counter electrode composed of a 70% CZTS and 30% N-MWCNTs mixture produced a higher electrochemical current density compared to the individual materials. This suggests that it is more electrocatalytic than CZTS and N-MWCNTs alone, ultimately leading to the highest power conversion efficiency of 6.52%.Graphical abstract

Synthesis, magnetoresistance, and thermoelectrical properties of environmentally stable n-type nitrogen-doped multiwalled carbon nanotubes

Nitrogen-doped multiwalled carbon nanotubes (N-MWCNTs) are known as a perspective material for a variety of applications in nanoelectronic devices, sensors, catalysts for carbon dioxide reduction, and flexible thermoelectrics. However, up to date most of the reports on the properties of N-MWCNTs are focused on a narrow niche of research, for example, a study of low-temperature magnetoresistance or room-temperature thermoelectrical properties. In this work, N-MWCNTs were synthesized using benzene:pyridine precursor in different ratios, and both magnetoresistance and thermoelectrical properties of the synthesized N-MWCNTs were systematically investigated in the temperature range 2-300 K and compared with the properties of undoped MWCNTs. Unexpected switching of the magnetoresistance of the N-MWCNTs at low temperatures from negative to positive values was observed, and the processes underlying this effect are discussed. The study of the thermoelectrical properties revealed n-type conductance in the N-MWCNTs, which was attributed to the impact of nitrogen defects incorporated in the MWCNT structure. Performed for the first-time investigations of the thermal stability of the Seebeck coefficient of N-MWCNTs in air revealed that the Seebeck coefficient retains its negative values and even increases after annealing of the N-MWCNTs in air at 500 °C. These findings illustrate the high potential of the presented in this work N-MWCNTs for applications in different devices in a wide range of temperatures.

Precision tuning of highly efficient Pt-based ternary alloys on nitrogen-doped multi-wall carbon nanotubes for methanol oxidation reaction

The electrochemical methanol oxidation is a crucial reaction in the conversion of renewable energy. To enable the widespread adoption of direct methanol fuel cells (DMFCs), it is essential to create and engineer catalysts that are both highly effective and robust for conducting the methanol oxidation reaction (MOR). In this work, trimetallic PtCoRu electrocatalysts on nitrogen-doped carbon and multi-wall carbon nanotubes (PtCoRu@NC/MWCNTs) were prepared through a two-pot synthetic strategy. The acceleration of CO oxidation to CO2 and the blocking of CO reduction on adjacent Pt active sites were attributed to the crucial role played by cobalt atoms in the as-prepared electrocatalysts. The precise control of Co atoms loading was achieved through precursor stoichiometry. Various physicochemical techniques were employed to analyze the morphology, element composition, and electronic state of the catalyst. Electrochemical investigations and theoretical calculations confirmed that the Pt1Co3Ru1@NC/MWCNTs exhibit excellent electrocatalytic performance and durability for the process of MOR. The enhanced MOR activity can be attributed to the synergistic effect between the multiple elements resulting from precisely controlled Co loading content on surface of the electrocatalyst, which facilitates efficient charge transfer. This interaction between the multiple components also modifies the electronic structures of active sites, thereby promoting the conversion of intermediates and accelerating the MOR process. Thus, achieving precise control over Co loading in PtCoRu@NC/MWCNTs would enable the development of high-performance catalysts for DMFCs.

Electrical properties of hierarchical nitrogen-doped multi-walled carbon nanotubes obtained using cobalt nanoparticles

In this work, for the first time, both initial and secondary branches of hierarchical nitrogen-doped multi-walled carbon nanotubes (h-N-MWCNTs) were obtained using chemical vapor deposition due to the decomposition of ace-tonitrile over Co-based nanoparticles. The results of a study of the electrical conductivity of h-N-MWCNTs for a wide temperature range of 300−4.2 K are presented. It was shown that fluctuation-assisted tunneling between delocalized states is the dominant conduction mechanism at temperatures above 50 K. An analysis of the temperature and electric field dependences of the resistance indicates that the transfer of electric charges below 50 K occurs due to hoppings between localized states located in the vicinity of the Fermi level. It was shown that the Coulomb interaction affects the charge carrier transport. The width of the Coulomb gap estimated from the temperature dependence of the resistance is 0.5 meV. The electrical conductivity of h-N-MWCNTs in the temperature range of 50−4.2 K occurs by the Efros–Shklovskii variable range hopping conduction mechanism. It was found that the charge localization length is ≈150 nm. Electrical property analysis indicates that the dielectric constant of the h-N-MWCNTs is ≈ 100.

Enhanced Four-Electron Selective Oxygen Reduction Reaction at Carbon Nanotubes-Supported Sulfonic Acid-Functionalized Copper Phthalocyanine.

In the present work, oxygen reduction reaction (ORR) is explored in an acidic medium with two different catalytic supports (multi-walled carbon nanotubes (MWCNTs) and nitrogen-doped multi-walled carbon nanotubes (NMWCNTs)) and two different catalysts (copper phthalocyanine (CuPc) and sulfonic acid functionalized CuPc (CuPc-SO3-)). The composite, NMWCNTs-CuPc-SO3- exhibits high ORR activity (assessed based on the onset potential (0.57 V vs. reversible hydrogen electrode) and Tafel slope) in comparison to the other composites. Rotating ring disc electrode (RRDE) studies demonstrate a highly selective four-electron ORR (less than 2.5% H2O2 formation) at the NMWCNTs-CuPc-SO3-. The synergistic effect of the catalyst support (NMWCNTs) and sulfonic acid functionalization of the catalyst (in CuPc-SO3-) increase the efficiency and selectivity of the ORR at the NMWCNTs-CuPc-SO3-. The catalyst activity of NMWCNTs-CuPc-SO3- has been compared with many reported materials and found to be better than several catalysts. NMWCNTs-CuPc-SO3- shows high tolerance for methanol and very small deviation in the onset potential (10 mV) between the linear sweep voltammetry responses recorded before and after 3000 cyclic voltammetry cycles, demonstrating exceptional durability. The high durability is attributed to the stabilization of CuPc-SO3- by the additional coordination with nitrogen (Cu-Nx) present on the surface of NMWCNTs.

Inkjet printing of highly dispersed, shortened, and defect-rich MWCNTs to construct flexible electrochemical sensors for the detection of bisphenol A in milk samples

An inkjet-printed electrochemical bisphenol A (BPA) sensor was developed by exploiting the high dispersibility of shortened and defect-rich nitrogen-doped multi-walled carbon nanotubes (MWCNTs). To enhance the dispersibility of MWCNTs in water-based dispersant, the defect concentration was increased by both creating shortened CNT and heteroatom doping, and modification of their surfaces with sulfonate (SO3H) groups. CNT-based inks were prepared by dispersing modified CNT structures in deionized water and the stability and physical properties of the inks were determined. The results suggested that the shortening of MWCNT and SO3H functionalization strategies improved the stability of CNT-based aqueous inks significantly, which enabled the preparation of highly concentrated inks up to 20 mg/ml with high stability. The CNT-based inks were printed on flexible polyethylene tetraflate (PET) and used as an electrochemical BPA sensor. The electrochemical analytical performance of the printed sensors was evaluated using chronoamperometry and differential pulse voltammetry methods. The sensors showed a wide linear range of 5–100 (CA) and 60–700 (DPV) with a LOD of 0.7 μM. The real sample analysis was conducted in milk and high recoveries were obtained, suggesting the applicability of the sensors in real media.

Comparison of Synchrotron and Laboratory X-ray Sources in Photoelectron Spectroscopy Experiments for the Study of Nitrogen-Doped Carbon Nanotubes

The chemical composition and stoichiometry of vertically aligned arrays of nitrogen-doped multi-walled carbon nanotubes (N-CNTs) were studied by photoelectron spectroscopy using laboratory and synchrotron X-ray sources. We performed careful deconvolution of high-resolution core-level spectra to quantify pyridine/pyrrole-like defects in N-CNTs, which are a key factor in the efficiency of the piezoelectric response for this material. It is shown that the XPS method makes it possible to estimate the concentration and type of nitrogen incorporation (qualitatively and quantitatively) in the “N-CNT/Mo electrode” system using both synchrotron and laboratory sources. The obtained results allow us to study the effect of the nickel catalytic layer thickness on the concentration of pyridine/pyrrole-like nitrogen and piezoelectric response in the nanotubes.

Strong metal oxide-support interaction in MoO2/N-doped MCNTs heterostructure for boosting lithium storage performance

The low-rate capability and fast capacity decaying of the molybdenum dioxide anode material have been a bottleneck for lithium-ion batteries (LIBs) due to low carrier transport, drastic volume expansion and inferior reversibility. Furthermore, the lithium-storage mechanism is still controversial at present. Herein, we fabricate a new kind of MoO2 nanoparticles with nitrogen-doped multiwalled carbon nanotubes (MoO2/N-MCNTs) as anode for LIBs. The strong chemical bonding (MoOC) endows MoO2/N-MCNTs a strong metal oxide–support interaction (SMSI), rendering electron/ion transfer and facilitate significant Li+ intercalation pseudocapacitance, which is evidenced by both theoretical computation and detailed experiments. Thus, the MoO2/N-MCNTs exhibits high-rate performance (523.7 mAh/g at 3000 mA g−1) and long durability (507.8 mAh/g at 1000 mA g−1 after 500 cycles). Furthermore, pouch-type full cell composed of MoO2/N-MCNTs anodes and commercial LiNi0.6Co0.2Mn0.2O2 (NCM622) cathodes demonstrate impressive rate performance and cyclic life, which displays an unparalleled energy density of 553.0 Wh kg−1. Ex-situ X-ray absorption spectroscopy (XAS) indicates the enhanced lithium-storage mechanism is originated from a partially irreversible phase transition from Li0.98MoO2 to Li2MoO4 via delithiation. This work not only provides fresh insights into the enhanced lithium-storage mechanism but also proposes new design principles toward efficient LIBs.

Protecting a few-layer MoSe2(1−x)S2x heterostructure with a lower barrier as prolonged high-rate anode for Na+ batteries

Here, S-doped MoSe2(1−x)S2x protected by nitrogen-doped multiwall carbon nanotubes (NMWCNTs) and carbon is prepared by sulfuration/selenization through a high-temperature calcination treatment. The S-doped few-layer MoSe2(1−x)S2x with an expanded layer space and a lower diffusion barrier contributes to Na+ adsorption and diffusion, and nitrogen doping is conducive to improved charge-transfer kinetics. Therefore, as an anode for Na+ batteries, S-doped PEG-200–2-C@MoSe2(1−x)S2x@NMWCNT delivers excellent sodium storage performance (440 mA h g-1 at 0.1 A g-1), and long-term cycle stability (240 mA h g-1 after 500 cycles at 5 A g-1, 198 mA h g-1 after 1000 cycles, 180 mA h g-1 after 1900 cycles). These results provide a novel synthesis strategy for the synthesis of high-performance composites to improve the Na+ storage ability.

Application of nitrogen-doped multi-walled carbon nanotubes decorated with gold nanoparticles in biosensing

Application of nitrogen-doped multi-walled carbon nanotubes decorated with gold nanoparticles in biosensing

156 Nitrogen-Doped Multi-Walled Carbon Nanotubes show Attenuated Pathogenicity in a Mouse Model of Pleural Exposure

Abstract Engineered carbon nanotubes (CNT) are currently used in many industrial products. Multi-walled carbon nanotubes (MWCNT) exhibit unique physicochemical properties and due to their low density and small size are easily aerosolized, making workplace exposure a potential risk to human health. MWCNT are similar to Asbestos in terms of their high aspect-ratio and thus may pose an asbestos-like inhalation hazard, including sporadic pleural Mesothelioma. Mitsui-7 MWCNT (MWCNT-7) have been classified by IARC as a Group 2B carcinogen. Importantly, physicochemically-altered MWCNT synthesized with nitrogen (MWCNT-ND) have been found to elicit attenuated toxicity; however, their pathogenicity in the pleura is unknown. Using a mouse model of direct injection into the pleural cavity, we compared the molecular changes that occur at the mesothelium over 20-months following injection with an occupationally-relevant dose of MWCNT-7, MWCNT-ND, Asbestos or carbon black. When compared to Asbestos or MWCNT-7, mice injected with MWCNT-ND did not develop respiratory symptoms. In contrast, in cell lines established from pleural effusions from MWCNT-7 or Asbestos-exposed mice with pre-neoplastic lesions or tumours, Whole-Exome-Sequencing and RNASeq revealed common molecular changes in both lesions and tumours. This identified genes involved in driving progression of pleural inflammatory lesions to Mesothelioma, whereas pre-neoplastic lesion-derived cell lines allow dissection of the hazard mechanism of pathogenic fibres at the molecular level early in disease development and thus may help predict genotoxic potency in exposed human populations. Our data demonstrate that physicochemical alteration of MWCNT (e.g. synthesis with nitrogen) attenuates pathogenicity and may offer an alternative for use in industrial applications.

Enhancement of the diesel fuel characteristics by using nitrogen-doped multi-walled carbon nanotube additives

Nanoparticles are considered promising additives to diesel fuel and significantly affect engine performance and exhaust emission levels. Nitrogen-doped multiwalled carbon nanotubes (N-doped MWCNTs) are one of the effective catalysts owing to their promising properties, which have recently increased their usability in many applications. These features make them good candidates as a catalyst to enhance diesel engine performance. The effects of adding N-doped MWCNTs into diesel fuel for a single-cylinder CI engine working at a rated speed of 1500 rpm and different loads were studied. Four doses of N-doped MWCNTs were added to diesel fuel using ultrasonic dispersion. Multiwalled carbon nanotubes (MWCNTs) were used as reference additives to compare their results with those obtained by N-doped MWCNTs. The results illustrated that most blends of N-doped MWCNTs were preferred in combustion behavior, engine performance, and exhaust emission analysis with respect to diesel and MWCNTs blends. Thus, there was a significant increase in the in-cylinder pressure and heat release rate compared to pure diesel. Also, the brake thermal efficiency was increased, and the brake specific fuel consumption was reduced compared to diesel. For all N-doped MWCNTs blends, there were remarkable reductions in NOx, soot, and CO formations, and it is mainly preferred over MWCNTs/diesel blends in exhaust emissions reduction.

Enhancement of the waste cooking oil biodiesel usability in the diesel engine by using n-decanol, nitrogen-doped, and amino-functionalized multi-walled carbon nanotube

The depletion of fossil fuels makes it necessary to find alternative fuels to diesel. Waste cooking oil biodiesel (WCO) has interesting properties and could replace diesel fuel. However, WCO biodiesel increased nitrogen oxides (NOx) at high loads compared to diesel. Thus, some fuel additives, such as functionalized MWCNTs and decanol, can be used as they are considered promising diesel fuel additives and significantly affect engine performance and exhaust emission levels. The functionalized MWCNTs, mainly Nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) and amino-functionalized multi-walled carbon nanotubes (NH2-MWCNTs), are excellent catalysts that have been used recently in many applications and have good properties that can be used in diesel engines. Thus, in the current research, an experimental investigation was performed by a CI engine working at a constant speed and different loads to study the effects of a WCO biodiesel-decanol blend on engine performance and exhaust gas emissions. First, n-Decanol was added to WCO biodiesel to enhance the biodiesel combustion properties (80 % biodiesel + 20 % n-decanol by volume). Then, two doses (50 and 75 ppm) for each type of functionalized MWCNTs were inserted into the WCO biodiesel-decanol blend to enhance the engine performance. The results illustrated that WCO biodiesel-decanol blend was close to diesel in engine performance, where the NOx and soot were reduced by about 8 % and 20 % for WCO biodiesel-decanol blends compared to diesel. Also, the addition of functionalized MWCNTs led to a significant reduction in the NOx, CO, and soot levels by around 35 %, 61 %, and 44 % compared to diesel. BTE was diminished by almost 10 %, and BSFC was raised by 15 % for WCO biodiesel-decanol blend compared to diesel. At the same time, these negative impacts have been alleviated with inserting functionalized MWCNTs into the WCO biodiesel-decanol combination. At 75 % load, WCO biodiesel-decanol blends raised the in-cylinder pressure and advanced the start of combustion by a three-crank angle degree. Therefore, it can be implied that WCODNH75 is a recommended combination considering combustion and emission characteristics.

Carboxyl Functionalization of N-MWCNTs with Stone-Wales Defects and Possibility of HIF-1α Wave-Diffusive Delivery.

Nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) are widely used for drug delivery. One of the main challenges is to clarify their interaction with hypoxia-inducible factor 1 alpha (HIF-1α), the lack of which leads to oncological and cardiovascular diseases. In the presented study, N-MWCNTs were synthesized by catalytic chemical vapor deposition and irradiated with argon ions. Their chemical state, local structure, interfaces, Stone-Wales defects, and doping with nitrogen were analyzed by high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Using experimental data, supercells of functionalized N-MWCNTs with an oxygen content of 2.7, 4 and 6 at. % in carboxyl groups were built by quantum chemical methods. Our analysis by the self-consistent charge density functional tight-binding (SCC DFTB) method shows that a key role in the functionalization of CNTs with carboxyl groups belongs to Stone-Wales defects. The results of research in the decoration of CNTs with HIF-1α demonstrate the possibility of wave-diffusion drug delivery. The nature of hybridization and relaxation determines the mechanism of oxygen regulation with HIF-1α molecules, namely, by OH-(OH-C) and OH-(O=C) chemical bonds. The concentration dependence of drug release in the diffusion mode suggests that the best pattern for drug delivery is provided by the tube with a carboxylic oxygen content of 6 at. %.

A Novel Poly(3-hexylthiophene) Engineered Interface for Electrochemical Monitoring of Ascorbic Acid During the Occurrence of Glutamate-Induced Brain Cytotoxic Edemas.

Although neuroelectrochemical sensing technology offers unique benefits for neuroscience research, its application is limited by substantial interference in complex brain environments while ensuring biosafety requirements. In this study, we introduced poly(3-hexylthiophene) (P3HT) and nitrogen-doped multiwalled carbon nanotubes (N-MWCNTs) to construct a composite membrane-modified carbon fiber microelectrode (CFME/P3HT-N-MWCNTs) for ascorbic acid (AA) detection. The microelectrode presented good linearity, selectivity, stability, antifouling, and biocompatibility and exhibited great performance for application in neuroelectrochemical sensing. Subsequently, we applied CFME/P3HT-N-MWCNTs to monitor AA release from in vitro nerve cells, ex vivo brain slices, and in vivo living rat brains and determined that glutamate can induce cell edema and AA release. We also found that glutamate activated the N-methyl-d-aspartic acid receptor, which enhanced Na+ and Cl- inflow to induce osmotic stress, resulting in cytotoxic edema and ultimately AA release. This study is the first to observe the process of glutamate-induced brain cytotoxic edema with AA release and to reveal the mechanism. Our work can benefit the application of P3HT in in vivo implant microelectrode construction to monitor neurochemicals, understand the molecular basis of nervous system diseases, and discover certain biomarkers of brain diseases.