Role Of Surface Functional Groups Research Articles

Pyrite/biochar-activated peroxymonosulfate strengthens tetracycline degradation: Important roles of surface functional groups and Fe(Ⅱ)/Fe(Ⅲ) redox cycling

Nonradical species with high anti-interfering properties have shown significant advantages in complex wastewater treatment. Herein, a pyrite/biochar catalyst (FBC) was prepared using pine sawdust biochar (BC) as a support material loaded with pyrite (FeS2). It exhibited high activity and stability in the FBC/PMS system for effective activation of peroxymonosulfate (PMS) to degrade tetracycline (TC) over a wide pH range (3.0–9.0). According to the characterization and analysis data, a variety of oxygen-containing functional groups (CO, -OH) and Fe and S active sites on the FBC surface assisted in PMS decomposition to produce reactive oxygen species (ROS). The mechanism study showed that the redox cycling of Fe(Ⅱ)/Fe(Ⅲ) and the electron-transfer medium of the BC oxygen functional groups contributed to the formation of SO4•-, •OH, O2•-, 1O2 and FeⅣ=O, but 1O2 was the main active oxidant. The potential pathways for TC degradation were suggested, and the toxicity of by-products was predicted by toxicity evaluation. Furthermore, FBC/PMS system exhibited minimal sensitivity to interference of concomitant materials. Overall, this study provided a reference for the application of green advanced oxidation technology of iron-based mineral composites to treat pharmaceutical contaminants in real water.

Holistic Processing of Sawdust to Enable Sustainable Hybrid Li-Ion Capacitors

AbstractActivated carbon has long been recognized as a promising electrode material for energy storage devices. The extraordinarily high specific area makes it challenging to replace in supercapacitors since electrical double-layer capacitors need such surfaces but also porous networks to enable electrolyte penetration. As a raw material for synthesizing activated carbon, sawdust offers key benefits, such as its renewability, abundance, favorable physical attributes for energy storage, and a more environmentally friendly synthesis process compared to mined alternative sources. In this work, electrochemical characterization is carried out which highlights the critical role of pelletization in enhancing the capacitive performance of sawdust-derived activated carbon, in addition to the implicit handling and logistical benefits. Subsequently, a Li-ion capacitor is assembled with an organic solvent-based electrolyte, sawdust-derived activated carbon serving as the positive electrode, and an Al-based foil negative electrode, potentially combining high energy and power density materials into a hybrid device. Despite commendable electrochemical performance and the use of a sustainable waste-derived positive electrode with a commoditized negative electrode, challenges remain regarding the ability to mitigate the role of surface functional groups that are stabilized by bio-carbon thermal treatments. Nevertheless, this distinctive architecture holds promise as an alternative high-power energy storage technology for a future filled with renewable energy, electric vehicles, and portable electronic devices.

Insights into the Roles of Surface Functional Groups and Micropores in the Sorption of Ofloxacin on Banana Pseudo-Stem Biochars

In the present study, banana pseudo-stem (BS) was pyrolyzed under anaerobic conditions without any physical or chemical modification. Their properties, as well as their sorption affinity to ofloxacin (OFL), were studied. As a result, oxalates and KCl formed at a relatively low temperature of 300 °C, while bicarbonates generally formed at a pyrolysis temperature above 400 °C. Surface functional groups of BS biochars facilitated OFL sorption mainly via specific interactions including electronic attraction (EA), π–π electron donor–acceptor (π–π EDA) interaction, the ordinary hydrogen bond (OHB), and the negative charge-assisted hydrogen bond ((−)CAHB). Except for (−)CAHB, these interactions all decreased with an elevated pH, resulting in overall decreased OFL sorption. Significant OFL sorption by BS biochars produced at 300 °C, observed even at an alkaline condition was attributed to (−)CAHB. Micropores formed in BS biochar prepared at 500 °C, with a specific surface area as high as 390 m2 g−1 after water washing treatment. However, most micropores could not be accessed by OFL molecules due to the size exclusion effect. Additionally, the inherent K-containing salts may hinder OFL sorption by covering the sorption sites or blocking the inner pores of biochars, as well as releasing OH− into the solution. Thus, BS biochar produced at 300 °C is an excellent sorbent for OFL removal due to its high sorption ability and low energy. Our findings indicate that biochar techniques have potential win–win effects in recycling banana waste with low energy and costs, and simultaneously converting them into promising sorbents for the removal of environmental contaminants.

Low‐temperature bonding of glasses: The role of plasma‐engrafted surface amino groups

AbstractLow‐temperature (<∼200°C) bonding of glasses is a key technology for utilizing them for microfluidics, optical applications, and microelectromechanical systems. In the present study, bonding strength of SiO2 glasses was examined for those after several surface treatment methods. As a result, it was found that two‐step (H2O→ NH3) plasma treatment remarkably strengthened the bonding strength (>1 J/m2) at the annealing temperature of 150°C. The improvement was achieved even when only one side of the bonded surfaces was plasma‐treated. X‐ray photoelectron spectroscopy revealed that the two‐step plasma treatment generated Si–NH2 groups on the topmost surface. Upon the annealing (<200°C), the engrafted Si–NH2 was desorbed from the bonded interface, indicating that the Si–NH2 effectively reacted with Si–OH on the other side to form Si–O–Si covalent bonds. This study contributes to understanding of the role of surface functional groups for bonding reaction. Furthermore, the method proposed here would be promising as a production technology because it enables glass bonding at lower temperatures with a simple plasma system.

Aggregation behavior of polystyrene nanoplastics: Role of surface functional groups and protein and electrolyte variation

Aggregation kinetics of plastics are affected by the surface functional groups and exposure orders (electrolyte and protein) with kinds of mechanisms in aquatic environment. This study investigates the aggregation of polystyrene nanoplastics (PSNPs) with varying surface functional groups in the presence of common electrolytes (NaCl, CaCl2, Na2SO4) and bovine serum albumin (BSA). It also examines the impact of different exposure orders, namely BSA + NaCl (adding them together), BSA → NaCl (adding BSA firstly and then NaCl), and NaCl → BSA (adding NaCl firstly and then BSA), on PSNPs aggregation. The presence of BSA decreased the critical coagulation concentration in NaCl (CCCNa+) of the non-modified PS-Bare from 222.17 to 142.81 mM (35.72%), but increased that of the carboxyl-modified PS-COOH from 157.34 to 160.03 mM (1.71%). This might be ascribed to the thicker absorbed layer of BSA onto the PS-Bare surface, known from Ohshima's soft particle theory. Their aggregation in CaCl2 was both increased because of Ca2+ bridging. Different from the monotonous effects of BSA on PS-Bare and PS-COOH, BSA initially facilitated PS-NH2 aggregation via patch-charge attraction, then inhibited it at higher salt levels through steric repulsion. Furthermore, exposure orders had no significant effect on PS-Bare and PS-COOH, but had a NaCl concentration-dependent impact on PS-NH2. At the low NaCl concentrations (10 and 100 mM), no obvious influence could be observed. While, at 300 mM NaCl, the high concentrations of BSA could not totally stabilize the salt-induced aggregates in NaCl → BSA, but could achieve it in the other two orders. These might be attributed to the electrical double layer compression by NaCl, “patch-charge” force and steric hindrance by BSA. These experimental findings shed light on the potential fate and transport of nanoparticles in aquatic environments.

Carbon Quantum Dots: The Role of Surface Functional Groups and Proposed Mechanisms for Metal Ion Sensing

Carbon dots (CDs) are zero-dimensional nanomaterials composed of carbon and surface groups attached to their surface. CDs have a size smaller than 10 nm and have potential applications in different fields such as metal ion detection, photodegradation of pollutants, and bio-imaging, in this review, the capabilities of CDs in metal ion detection will be described. Quantum confinement is generally viewed as the key factor contributing to the uniqueness of CDs characteristics due to their small size and the lack of attention on the surface functional groups and their roles is given, however, in this review paper, the focus will be on the functional group and the composition of CDs. The surface functional groups depend on two parameters: (i) the oxidation of precursors and (ii) their composition. The mechanism of metal ion detection is still being studied and is not fully understood. This review article emphasizes the current development and progress of CDs, focusing on metal ion detection based on a new perspective.

(Fe, Cr)(OH)3 Coprecipitation in Solution and on Soil: Roles of Surface Functional Groups and Solution pH

The simultaneous precipitation of (Fe, Cr)(OH)3 nanoparticles in solution (homogeneous) and on soil surfaces (heterogeneous), which controls Cr transport in soil and aquatic systems, was quantified for the first time in the presence of model surfaces, i.e., bare and natural organic matter (NOM)-coated SiO2 and Al2O3. Various characterization techniques were combined to explore the surface-ion-precipitate interactions and the controlling mechanisms. (Fe, Cr)(OH)3 accumulation on negatively charged SiO2 was mainly governed by electrostatic interactions between hydrolyzed ion species or homogeneous (Fe, Cr)(OH)3 and surfaces. The elevated pH through protonation of Al2O3 surface hydroxyls resulted in higher Cr/Fe ratios in both homogeneous and heterogeneous coprecipitates. Due to ignorable NOM adsorption onto SiO2, the amounts of (Fe, Cr)(OH)3 precipitates on bare/NOM-SiO2 were similar; contrarily, attributed to favored NOM adsorption onto Al2O3 and consequently carboxyl association with metal ions or (Fe, Cr)(OH)3 nanoparticles, remarkably more heterogeneous precipitates harvested on NOM-Al2O3 than bare-Al2O3. With the same solution supersaturation, the total amounts of homogeneous and heterogeneous precipitates were similar irrespective of the substrate type. With lower pH, decreased electrostatic forces between substrates and precipitates shifted (Fe, Cr)(OH)3 distribution from heterogeneous to homogeneous phases. The quantitative knowledge of (Fe, Cr)(OH)3 distribution and the controlling mechanisms can assist in better Cr sequestration in natural and engineered settings.

The Role of Surface Functional Groups of Iron Oxide, Organic Matter, and Clay Mineral Complexes in Sediments on the Adsorption of Copper Ions

Heavy metal pollution is a global problem affecting the environment and human health. Sediment is the source sink of heavy metals in water. Under certain circumstances, the migration of heavy metals will cause water pollution. Therefore, it is of great significance to study sediment composition and composite complexes in the migration and transformation of heavy metals. To understand the adsorption mechanisms of composite complexes and improve the theoretical understanding of adsorption in multi-component complex systems, this study explored the characteristics and rules of Cu adsorption to organic–inorganic, inorganic minerals, and iron-oxide–clay complexes in the estuary sediments of the Dianchi Lake. The Langmuir and Freundlich isotherm models were used for Cu adsorption experiments on three complexes to study their adsorption kinetics. X-ray diffraction and Fourier transform infrared spectroscopy characterized the samples before and after adsorption. The relationship between adsorption capacity and sediment composition was analyzed through redundant analyses. The results showed that the Freundlich isothermal model was better than the Langmuir model in describing the adsorption behavior of the adsorbents. The contribution of iron and aluminum oxides to Cu adsorption was more than that of organic matter. The organic–inorganic complexes functional groups involved in copper adsorption are the most, which resulting in a higher adsorption capacity. The organic matter removal (organic degradation in sediment) will reduce the polar functional groups and reduce silicide activity, leading to heavy metal desorption and re-entry into the water body.

A study on the role of surface functional groups of metakaolin in the removal of methylene blue: Characterization, kinetics, modeling and RSM optimization

In this study, thermally activated kaolinite clay is explored as a suitable material for dye removal applications, which gave rise to highly reactive silica species in a broad range of aluminosilicate clusters. Multinuclear NMR studies described it as a short-range network in which Al sites in IV, V, and VI are coordinated, and Si is present mainly as Si(Q4(1Al)). Critical parameters for methylene blue (MB) were determined by the Placket Burman Design (PBD) as initial dye concentration, contact time, adsorbent dosage, pH and size. The % of MB removal studied after optimizing the parameters by central composite design (CCD), based on Response Surface Methodology, was found to be 90%. The adsorption kinetics and thermodynamics were systematically studied and reported by fitting them into different models. The maximum removal of the dye reached 97.8 mg/g according to the Freundlich isotherm, accomplished through chemisorption, following a pseudo-second-order reaction and the process is thermodynamically spontaneous and endothermic. The line spectrum of X-ray photoelectron spectroscopy (XPS) shows the participation of Si, Al, O, Ca and Na of Metakaolin (AK) and nitrogen of MB in the adsorption process. The appropriate stabilization of the N atom of the chromophore on the Si and Al atom in AK resulting from the ionic interaction on the surface is established from an increase in the binding energy of Al and Si. A single bridging oxygen signal at 532.32eVcorresponding to AK after dye adsorption tends to form siloanol/aluminol, and their interaction is lowered to 531.58eV. Regeneration of adsorbent after thermal treatment without loss of efficiency proved.

A Perspective on Using Organic Molecules Composing Carbon Dots for Cancer Treatment.

Fluorescent Carbon dots (CDs) derived from biologically active sources have shown enhanced activities compared to their precursors. With their prominent potentiality, these small-sized (<10nm) nanomaterials could be easily synthesized from organic sources either by bottom-up or green approach. Their sources could influence the functional groups present on the CDs surfaces. A crude source of organic molecules has been used to develop fluorescent CDs. In addition, pure organic molecules were also valuable in developing practical CDs. Physiologically responsive interaction of CDs with various cellular receptors is possible due to the robust functionalization on their surface. In this review, we studied various literatures from the past ten years that reported the potential application of carbon dots as alternatives in cancer chemotherapy. The selective cytotoxic nature of some of the CDs towards cancer cell lines suggests the role of surface functional groups towards selective interaction, which results in over-expressed proteins characteristic of cancer cell lines. It could be inferred that cheaply sourced CDs could selectively bind to overexpressed proteins in cancer cells with the ultimate effect of cell death induced by apoptosis. In most cases, CDs-induced apoptosis directly or indirectly follows the mitochondrial pathway. Therefore, these nanosized CDs could serve as alternatives to the current kinds of cancer treatments that are expensive and have numerous side effects.

Significant roles of surface functional groups and Fe/Co redox reactions on peroxymonosulfate activation by hydrochar-supported cobalt ferrite for simultaneous degradation of monochlorobenzene and p-chloroaniline

CoFe2O4/hydrochar composites (FeCo@HC) were synthesized via a facile one-step hydrothermal method and utilized to activate peroxymonosulfate (PMS) for simultaneous degradation of monochlorobenzene (MCB) and p-chloroaniline (PCA). Additionally, the effects of humic acid, Cl-, HCO3-, H2PO4-, HPO42- and water matrices were investigated and degradation pathways of MCB and PCA were proposed. The removal efficiencies of MCB and PCA were higher in FeCo@HC140–10/PMS system obtained under hydrothermal temperature of 140 °C than FeCo@HC180–10/PMS and FeCo@HC220–10/PMS systems obtained under higher temperatures. Radical species (i.e., SO4•-, •OH) and nonradical pathways (i.e., 1O2, Fe (IV)/Co (IV) and electron transfer through surface FeCo@HC140–10/PMS* complex) co-occurred in the FeCo@HC140–10/PMS system, while radical and nonradical pathways were dominant in degrading MCB and PCA respectively. The surface functional groups (i.e., C-OH and CO) and Fe/Co redox cycles played crucial roles in the PMS activation. MCB degradation was significantly inhibited in the mixed MCB/PCA solution over that in the single MCB solution, whereas PCA degradation was slightly promoted in the mixed MCB/PCA solution. These findings are significant for the provision of a low-cost and environmentally-benign synthesis of bimetal-hydrochar composites and more detailed understanding of the related mechanisms on PMS activation for simultaneous removal of the mixed contaminants in groundwater.

Unveiling the role of surface functional groups for the design of nickel manganese/reduced graphene oxide based composite electrode material for high performance asymmetric supercapacitor

Development of additive-free electrode material on conductive substrates is a cost-effective strategy and is essential for the fabrication of high-performance supercapacitor. Herein, the effect of transition metal ions on the preparation of bimetallic (Ni & Mn)/reduced graphene oxide (RGO) composites through multi-step electrodeposition technique was extensively analysed. Two different composites; nickel manganese oxide/RGO (NiMn-G/NF) and manganese nickel oxyhydroxide/RGO (MnNi-G/NF) were synthesized through step-wise electrodeposition technique. The NiMn-G/NF and MnNi-G/NF were prepared through interchanging the source of host transition metal ions (Ni and Mn). Various physicochemical characterization techniques confirmed that the crystal structure as well as the morphology and electrochemical performance of the composites were largely dependent on the host metal ions. The formation of surface functional groups may play a key role in the electrochemical performance of supercapacitors. The MnNi-G/NF electrode showed high specific capacitance of ~1525 F g−1 at 1.5 A g−1 current density compared to NiMn-G/NF (~1312.5 F g−1) and other synthesized electrode materials. An asymmetric supercapacitor (ASC) device was fabricated using MnNi-G/NF as positive and thermally-RGO as negative electrode materials. The fabricated device exhibited highest specific capacitance of ~173.3 F g−1 at 2 A g−1 current density and maximum energy density of ~54.1 Wh kg−1 and power density of 9 kW kg−1.

Recent Advancement in Rational Design Modulation of MXene: A Voyage from Environmental Remediation to Energy Conversion and Storage.

Use of MXenes (Ti3 C2 Tx ), which belongs to the family of two-dimensional transition metal nitrides and carbides by encompassing unique combination of metallic conductivity and hydrophilicity, is receiving tremendous attention, since its discovery as energy material in 2011. Owing to its precursor selective chemical etching, and unique intrinsic characteristics, the MXene surface properties are further classified into highly chemically active compound, which further produced different surface functional groups i. e., oxygen, fluorine or hydroxyl groups. However, the role of surface functional groups doesn't not only have a significant impact onto its electrochemical and hydrophilic characteristics (i. e., ion adsorption/diffusion), but also imparting a noteworthy effect onto its conductivity, work function, electronic structure and properties. Henceforth, such kind of inherent chemical nature, robust electrochemistry and high hydrophilicity ultimately increasing the MXene application as a most propitious material for overall environment-remediation, electrocatalytic sensors, energy conversion and storage application. Moreover, it is well documented that the role of MXenes in all kinds of research fields is still on a progress stage for their further improvement, which is not sufficiently summarized in literature till now. The present review article is intended to critically discuss the different chemical aptitudes and the diversity of MXenes and its derivates (i. e., hybrid composites) in all aforesaid application with special emphasis onto the improvement of its surface characteristics for the multidimensional application. However, this review article is anticipated to endorse MXenes and its derivates hybrid configuration, which is discussed in detail for emerging environmental decontamination, electrochemical use, and pollutant detection via electrocatalytic sensors, photocatalysis, along with membrane distillation and the adsorption application. Finally, it is expected, that this review article will open up new window for the effective use of MXene in a broad range of environmental remediation, energy conversion and storage application as a novel, robust, multidimensional and more proficient materials.

Sustainable Free‐Standing Electrode from Biomass Waste for Sodium‐Ion Batteries

AbstractBattery sustainability is often neglected in favor of higher performance and economic efficiency in battery technology. The standard electrode containing the use of binder and toxic solvent has a detrimental impact on the environment. For the first time, a sustainable and free‐standing carbonized silk battery anode is prepared from woven silk biomass waste. The unique mechanical structural properties and surface functionality make this material not only avoid the use of binder and organic solvent, but with the possibility of achieving high energy density batteries. An outstanding initial Coulombic efficiency of 75.6 % and a remarkable capacity retention of 100 % after 100 cycles are achieved for the electrode carbonized at 1300 °C (CS_1300 °C) when using a non‐volatile and non‐flammable superconcentrated ionic liquid electrolyte. A uniformly NaF‐distributed solid electrolyte interphase (SEI) layer is produced on the CS_1300 °C surface to facilitate Na+ transfer kinetics, and high capacity utilization. Surface functional groups are elucidated by X‐ray photoelectron spectroscopy (XPS), while density functional theory calculations reveal that these groups accelerate fast Na+ ion adsorption on the surface, but hinder Na+ intercalation kinetics due to the strong binding energy from the sodiophilic sites. This scalable and cost‐efficient strategy opens up a new avenue for mass‐production of battery anode materials, and proposes an argument for the role of surface functional groups in SEI formation and electrochemical performance.

Fabrication of poly(maleic acid)-grafted cross-linked chitosan/montmorillonite nanospheres for ultra-high adsorption of anionic acid yellow-17 and cationic brilliant green dyes in single and binary systems

In this contribution, poly(maleic acid)-grafted cross-linked chitosan/montmorillonite composite nanospheres (PMAL-CTS/MMT) were synthesized via a facile approach for adsorption of organic dyes. The adsorption capacity of PMAL-CTS/MMT towards anionic acid yellow-17 (AY17) and cationic brilliant green (BG) was compared to PMAL-CTS, CTS/MMT, and MMT to emphasize the role of surface functional groups introduced by poly(maleic acid) and montmorillonite. Interestingly, the adsorption efficiency of PMAL-CTS/MMT nanocomposite towards both dyes in the single and binary systems was extremely high due to plenty of functional groups. The affinity of PMAL-CTS/MMT towards cationic and anionic dyes resulted from the feasible modulation of the surface charges as a function of the solution pH. The PMAL-CTS/MMT nanocomposite exhibited a maximum adsorption capacity of 518 and 1910 mg g–1 for AY17 and BG, respectively, which is higher than most of the adsorbents reported in recent literature studies. The proposed mechanism based on the characterization of PMAL-CTS/MMT after the adsorption highlighted that the adsorption is mainly controlled by electrostatic interaction, π − π interactions, and hydrogen bonding. More importantly, the PMAL-CTS/MMT nanocomposite was successfully applied to separate the AY17 and BG dyes from real-life aquatic environments. Collectively, the simple fabrication and superior adsorption performance reveal that PMAL-CTS/MMT has the potential to treat concomitant organic dyes effectively.

The high catalytic activity and strong stability of 3%Fe/AC catalysts for catalytic wet peroxide oxidation of m-cresol: The role of surface functional groups and FeO particles

FeO x supported on activated carbon (AC) has been shown to be an ideal catalyst for catalytic wet peroxide oxidation (CWPO) due to its high CWPO reaction activity and stability. Although there have been some studies on the mechanism of Fe/AC catalysis in CWPO, the specific contribution of each component (surface oxygen groups and FeO x on AC) inside an Fe/AC catalyst and their corresponding reaction mechanism remain unclear, and the reaction stability of CWPO catalysts has rarely been discussed. Then the optimal CWPO catalyst in our laboratory, 3%Fe/AC, was selected. (1) By removing certain components on the AC through heat treatment, its contribution to the reaction and the corresponding reaction mechanism were investigated. With the aid of temperature-programmed desorption-mass spectrometry (TPD-MS) and the CWPO reaction, the normalized catalytic contributions of components were shown to be: 37.3% (carboxylic groups), 5.3% (anhydride), 19.3% (ether/hydroxyl), −71.4% (carbonyl groups) and 100% (FeO x ), respectively. DFT calculation and EPR analysis confirmed that carboxylic groups and Fe 2 O 3 are able to activate the H 2 O 2 to generate ·OH. (2) The catalysts at were characterized at different reaction times (0 h, 450 h, 900 h, 1350 h, and 1800 h) by TPD-MS and Mössbauer spectroscopy. Results suggested that the number of carboxylic goups gradually increased and the size of paramagnetic Fe 2 O 3 particle crystallites gradually increased as the reactions progressed. The occurrence of strong interactions between metal oxides and AC was also confirmed. Due to these effects, the strong stability of 3%Fe/AC was further improved. Therefore, the reasons for the high activity and strong stability of 3%Fe/AC in CWPO were clearly shown. We believe that this work provides an idea of the removal of cresols from wastewater into the introduction to show the potential applications of CWPO.

On the role of surface functional groups in enhancing methylene blue adsorption by low-temperature biochar derived from Platanus orientalis bark

On the role of surface functional groups in enhancing methylene blue adsorption by low-temperature biochar derived from Platanus orientalis bark

Role of surface functional groups to superconductivity in Nb2C-MXene: Experiments and density functional theory calculations

The recently discovered surface-group-dependent superconductivity in Nb2C-MXene fabricated by the molten salts method is attracting wide attention. However, regarding the superconductivity of Nb2C-MXene with functional F groups (Nb2CFx), there were some conflicting results in experimental and theoretical studies. Herein, we systematically carried out experimental and theoretical investigations on the superconductivity in Nb2C-MXene with the Cl functional group (Nb2CClx) and Nb2CFx. The experimental results of the Meissner effect and zero resistivity have proved that Nb2CClx is superconducting with the transition temperature (Tc) ∼ 5.2 K. We extract its superconducting parameters from the temperature dependence of resistivity and the field dependence of the magnetization. The Ginzburg-Landau parameter κGL is estimated to be 2.41, indicating that Nb2CClx is a typical type-Ⅱ superconductor. Conversely, both magnetic and electrical transport measurements demonstrate that Nb2CFx is not superconducting. The first-principles density functional theory (DFT) calculations show that the Tc of Nb2CClx is ∼ 5.2 K, while Nb2CFx is dynamically unstable with imaginary frequency in phonon spectrum, which is in good agreement with the experimental results. Our studies not only are useful for clarifying the present inconsistency but also offer referential significance for future investigations on the superconductivity of MXenes.

Plasma treatment for enhancement of the sorption capacity of carbon fabric

In this work we carried out an experimental investigation into enhancement of the sorption capacity of carbon fabric using plasma treatment methods. Carbon fabric is based on viscose fiber and is hydrophobic by nature. Enhancement of the fabric sorption capacity is required for its application in medicine. For this purpose, two plasma treatment methods were considered, i.e. atmospheric nonequilibrium radiofrequency (RF) discharge and a vacuum RF plasma source with an external magnetic field. Samples treated by atmospheric discharge demonstrated aging effects during the first week after treatment. The sorption capacity of samples treated by the RF plasma source was stable over the same period and reached values as high as 0.95. Parameters of the beam created by the vacuum RF plasma source were analyzed and dependences of the fabric sorption capacity and specific surface area on plasma treatment time were investigated. We found that sorption capacity reached its maximum value after 30 min of treatment and did not change significantly if processing was continued, while the specific surface area reached its maximum after 3 min of treatment and quickly decreased after that. It was found that the micropore structure of the fabric remained almost the same during plasma treatment. The volume of mesopores in a unit of the fabric mass (specific volume) doubled during the first 5 min of treatment and returned to initial values after 30 min of treatment. The sorption capacity continued to increase even when the specific surface area decreased after reaching its peak value. This indicates the important role of surface functional groups formed on carbon fibers during plasma treatment. This is consistent with the results of x-ray photoelectron spectroscopy analysis showing changes in surface oxidation during plasma treatment.

Controlling the emissive pathways of carbon nanoparticles by selective surface functionalization

Environmental friendly and biocompatible fluorescent carbon nanoparticles (CNPs) show great potential for various applications. The functional groups on the surface of the NPs dramatically influence the absorption and emission characteristics of the particles. However, a conclusive emission mechanism of CNPs and the exact role of functional groups are still lacking. Herein, a systematic investigation has been carried out by quantifying the oxygen-based function groups (–OH, –CHO, –COOH, –CO, –COO) present on the surface of activated carbon (AC) nanoparticles to identify their role in the emission characteristics. AC samples, prepared by the activation process of green waste of mandarin peels, were subjected to further treatments to achieve different levels of surface functionality with oxygen containing functional groups such as carbonyl, carboxyl, phenol and lactone. Various characterization techniques were employed to identify and quantify the functional groups. A detailed emission study revealed the role of specific functional groups in the emission process. Our results suggests that various emissive pathways in CNPs can be controlled by selective surface functionalization. This study shows significant results, which could shed more light on the emission mechanism of CNPs and the pivotal role of surface functional groups.