Modified Single-Walled Carbon Nanotube Membranes for the Elimination of Antibiotics from Water.

The hydrophilic and hydrophobic single-walled carbon nanotube membranes were prepared and progressively applied in sorption, filtration, and pertraction experiments with the aim of eliminating three antibiotics-tetracycline, sulfamethoxazole, and trimethoprim-as a single pollutant or as a mixture. The addition of SiO2 to the single-walled carbon nanotubes allowed a transparent study of the influence of porosity on the separation processes. The mild oxidation, increasing hydrophilicity, and reactivity of the single-walled carbon nanotube membranes with the pollutants were suitable for the filtration and sorption process, while non-oxidized materials with a hydrophobic layer were more appropriate for pertraction. The total pore volume increased with an increasing amount of SiO2 (from 743 to 1218 mm3/g) in the hydrophilic membranes. The hydrophobic layer completely covered the carbon nanotubes and SiO2 nanoparticles and provided significantly different membrane surface interactions with the antibiotics. Single-walled carbon nanotubes adsorbed the initial amount of antibiotics in less than 5 h. A time of 2.3 s was sufficient for the filtration of 98.8% of sulfamethoxazole, 95.5% of trimethoprim, and 87.0% of tetracycline. The thicker membranes demonstrate a higher adsorption capacity. However, the pertraction was slower than filtration, leading to total elimination of antibiotics (e.g., 3 days for tetracycline). The diffusion coefficient of the antibiotics varies between 0.7-2.7 × 10-10, depending on the addition of SiO2 in perfect agreement with the findings of the textural analysis and scanning electron microscopy observations. Similar to filtration, tetracycline is retained by the membranes more than sulfamethoxazole and trimethoprim.

Self-Powered Broadband Photodetector and Sensor Based on Novel Few-Layered Pd3(PS4)2 Nanosheets.

Optoelectronics and sensing devices are of enormous importance in our modern lives, which has propelled the scientific community to explore new two-dimensional (2D) nanomaterials to meet the requirements of future devices. Herein, we present the exfoliation of palladium thiophosphate (Pd3(PS4)2) by mechanical shear force exfoliation. The Pd3(PS4)2-based photoelectrochemical (PEC) device demonstrated self-powered broadband photodetection in the range of 385-940 nm with an unprecedented responsivity of 2 A W-1 and a specific detectivity of about 8.67 × 1011 cm Hz1/2 W-1 under the illumination of 420 nm LED light. The crucial parameters such as photoresponsivity, response, and recovery time of the device can be controlled by an externally applied voltage and the analyte concentration. Moreover, Pd3(PS4)2-based vapor-sensing devices exhibited frequency-dependent selective acetone sensing in the presence of other organic vapors with an ultrafast response and a recovery time of less than 1 s. Finally, the photocatalytic activity of Pd3(PS4)2 was revealed, which can be attributed to the presence of an appropriate band alignment with the catalytic activity of Pd. This novel material with the aforementioned fascinating phenomenon will pave the way toward practical future applications in optoelectronics and sensing.

Functionalized germanane/SWCNT hybrid films as flexible anodes for lithium-ion batteries.

Germanium, with a high theoretical capacity based on alloyed lithium and germanium (1384 mA h g-1 Li15Ge4), has stimulated tremendous research as a promising candidate anode material for lithium-ion batteries (LIBs). However, due to the alloying reaction of Li/Ge, the problems of inferior cycle life and massive volume expansion of germanium are equally obvious. Among all Ge-based materials, the unique layered 2D germanane (GeH and GeCH3) with a graphene-like structure, obtained by a chemical etching process from the Zintl phase CaGe2, could enable storage of large quantities of lithium between their interlayers. Besides, the layered structure has the merit of buffering the volume expansion due to the tunable interlayer spacing. In this work, the beyond theoretical capacities of 1637 mA h g-1 for GeH and 2048 mA h g-1 for GeCH3 were achieved in the initial lithiation reaction. Unfortunately, the dreadful capacity fading and electrode fracture happened during the subsequent electrochemical process. A solution, i.e. introducing single-wall carbon nanotubes (SWCNTs) into the structure of the electrodes, was found and further confirmed to improve their electrochemical performance. More noteworthy is the GeH/SWCNT flexible electrode, which exhibits a capacity of 1032.0 mA h g-1 at a high current density of 2000 mA g-1 and a remaining capacity of 653.6 mA h g-1 after 100 cycles at 500 mA g-1. After 100 cycles, the hybrid germanane/SWCNT electrodes maintained good integrity without visible fractures. These results indicate that introducing SWCNTs into germanane effectively improves the electrochemical performance and maintains the integrity of the electrodes for LIBs.

Retraction Note: Air-stable superparamagnetic metal nanoparticles entrapped in graphene oxide matrix.

This article has been retracted. Please see the Retraction Notice for more detail: https://doi.org/10.1038/s41467-020-19968-3.

Large-Scale Production of Nanocrystalline Black Phosphorus Ceramics.

Black phosphorus is currently among the most explored two-dimensional (2D) materials. Currently, the synthesis methods are dominantly based on vapor-phase growth of black phosphorus. In this manuscript, we demonstrate large-scale synthesis of black phosphorus by rapid high-pressure transition of red phosphorus. The high-pressure conversion of red phosphorus led to high-density nanocrystalline black phosphorus ceramics. The resulting material was explored in detail including structural and morphological characterization in addition to thermal and electrical transport and basic thermophysical properties. The nanocrystalline black phosphorus can be employed for large-scale production of stable few/single-layer black phosphorus colloidal solutions in various solvents.

Flexible freestanding MoS2-based composite paper for energy conversion and storage.

The construction of flexible electrochemical devices for energy storage and generation is of utmost importance in modern society. In this article, we report on the synthesis of flexible MoS2-based composite paper by high-energy shear force milling and simple vacuum filtration. This composite material combines high flexibility, mechanical strength and good chemical stability. Chronopotentiometric charge-discharge measurements were used to determine the capacitance of our paper material. The highest capacitance achieved was 33 mF·cm-2 at a current density of 1 mA·cm-2, demonstrating potential application in supercapacitors. We further used the material as a cathode for the hydrogen evolution reaction (HER) with an onset potential of approximately -0.2 V vs RHE. The onset potential was even lower (approximately -0.1 V vs RHE) after treatment with n-butyllithium, suggesting the introduction of new active sites. Finally, a potential use in lithium ion batteries (LIB) was examined. Our material can be used directly without any binder, additive carbon or copper current collector and delivers specific capacity of 740 mA·h·g-1 at a current density of 0.1 A·g-1. After 40 cycles at this current density the material still reached a capacity retention of 91%. Our findings show that this composite material could find application in electrochemical energy storage and generation devices where high flexibility and mechanical strength are desired.

In Situ Doping of Black Phosphorus by High-Pressure Synthesis.

Black phosphorus is a two-dimensional semiconductor with promising properties for catalysis, energy storage, and conversion as well as electronic device applications, and control of its electronic structure is critical for such applications. Substitutional doping of phosphorus by electron donating (e.g., sulfur) or electron accepting elements (e.g., germanium) can significantly change its properties, especially charge carrier concentration. Here, we report the in situ doping of black phosphorus by its direct synthesis from a mixture of red phosphorus and a dopant by high pressure synthesis. In detail, we study the incorporation of germanium, sulfur, selenium, and tellurium within black phosphorus, showing significant differences in incorporation of individual elements and assess their suitability for potential electrochemical applications.

Author Correction: Air-stable superparamagnetic metal nanoparticles entrapped in graphene oxide matrix.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Black Phosphorus Cytotoxicity Assessments Pitfalls: Advantages and Disadvantages of Metabolic and Morphological Assays.

Black phosphorus (BP) belongs to a group of 2D nanomaterials and nowadays attracts constantly increasing attention. Parallel to the growing utilization of BP nanomaterial increase also the requirements for the thorough comprehension of its potential impact on human and animal health. The aim of this study was to compare and discuss five assays commonly used for the cytotoxicity assessments of nanomaterials with a special focus on BP nanoparticles. A comprehensive survey of factors and pitfalls is provided that should be accounted for when assessing their toxicity and pointed to their inconsistency. BP might introduce various levels of interference during toxicity assessments depending on its concentration applied. More importantly, the BP toxicity evaluation was found to be influenced by the nature of assay chosen. These are based on different principles and do not have to assess all the cellular events equally. A commercial assay based on the measurement of protease activity was identified to be the most suitable for the BP toxicity assessment. Further, the benefit of time-lapse quantitative phase imaging for nanomaterial toxicity evaluation was highlighted. Unlike the conventional assessments it provides real-time analysis of the processes accompanying BP administration and enables to understand them deeper and in the context.

WSe2 nanoparticles with enhanced hydrogen evolution reaction prepared by bipolar electrochemistry: application in competitive magneto-immunoassay.

Among groups of layered nanomaterials, transition metal dichalcogenides (TMDs) are the most studied group, especially for their hydrogen evolution reaction (HER) electrocatalytic activity and good stability in a highly corrosive environment. However, TMDs possess only low catalytic activity in the bulk form consisting of 2H phase, therefore, exfoliation must take place to enlarge the surface area and create new catalytically active sites (edges and defects). The most common exfoliation routes use organometallic reagents, such as tert-butyllithium (t-BuLi). Recently, bipolar electrochemistry (BE) was reported as a new efficient exfoliation and down-sizing technique applied on several layered materials. In this work, we used BE for further down-sizing of WSe2 micro-sheets, which were pre-exfoliated using tert-bulyllithium intercalator, down to nanoparticles (NPs). These WSe2 NPs outperformed t-BuLi exfoliated particles in terms of the overpotential needed for HER electrocatalysis. Moreover, WSe2 NPs were used effectively as a label for a competitive magneto-inmunoassay. This competitive magneto-immunoassay offers high selectivity with a wide linearity range, high sensitivity and a low limit of detection. We believe that such labels possess a great potential for bioassays.

Fluorographene and Graphane as an Excellent Platform for Enzyme Biocatalysis.

The application of enzymes is a crucial issue for current biotechnological application in pharmaceutical, as well as food and cosmetic industry. Effective platforms for enzyme immobilization are necessary for their industrial use in various biosynthesis procedures. Such platforms must provide high yield of immobilization and retain high activity at various conditions for their large-scale applications. Graphene derivatives such as hydrogenated graphene (graphane) and fluorographene can be applied for enzyme immobilization with close to 100 % yield that can result to activities of the composites significantly exceeding activity of free enzymes. The hydrophobic properties of graphene stoichiometric derivatives allowed for excellent non-covalent bonding of enzymes and their use in various organic solvents. The immobilized enzymes retain their high activities even at elevated temperatures. These findings show excellent application potential of enzyme biocatalysts immobilized on graphene stoichiometric derivatives.

MoS2 Nanoparticles as Electrocatalytic Labels in Magneto-Immunoassays.

Ability to detect biomolecules with a simple and cost-effective approach has been very demanding in today's medicine. The nanoparticles and two-dimensional materials have been extensively used within this field in devices with high selectivity and sensitivity. Here, we report the use of MoS2 nanoparticles (MoS2 NPs) as a signal-enhancing label in a standard immunoassay test. MoS2 NPs were prepared by a bipolar electrochemistry method. The current response during the hydrogen evolution reaction catalyzed by MoS2 was measured. This current was directly proportional to the amount of the MoS2 NPs and thus also to the concentration of desired protein. The immunoassay containing the MoS2 NPs displays extraordinary low limit of detection (1.94 pg mL-1), good selectivity, and reproducibility. This MoS2 NP detection system could have profound implication for analytical applications.

Hydrogenation of Fluorographite and Fluorographene: An Easy Way to Produce Highly Hydrogenated Graphene.

Fluorographene is an excellent precursor for the synthesis of graphene derivatives. Relative to pure graphene, fluorographene possesses higher reactivity and, in comparison with graphene oxide, is also homogenous in composition, which enables the preparation of well-defined materials. Recently, it has been shown that several graphene derivatives can be synthesized from fluorographene, thus yielding various products such as graphene acid or alkylated graphene. This study focuses on the hydrogenation of fluorographene by using various hydrogenation reactions, including the use complex hydrides and solvated electrons in different media. In addition, a comparison of these reactions shows that fluorinated graphite has significantly lower reactivity than fluorographene. The conversion rates of these reactions are higher when fluorographene is used relative to fluorographite. These reactions can be used to tune the hydrogen/fluorine composition on a graphene backbone.

Synergetic Metals on Carbocatalyst Shungite.

The naturally occurring Palaeoproterozoic carbon mineral shungite is a complex raw carbon microporous matrix, loaded with a wide range of elements. Shungite exhibits a disordered and amorphous structure with highly irregular building blocks. Shungite incorporates metals in its structure; typically catalytic elements such Fe and Ni are present, as well as the toxic elements Pb and As at mg g-1 levels. We show here that incorporation of the metals in the carbon matrix of shungite leads into synergistic catalytic effect. We investigate the application of shungite in energy related electrochemical catalytic reactions, such as the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). All elements have a synergetic effect, thus contributing for shungite's interesting catalytic performance towards a different range of electrochemical reactions, outperforming other tested carbon allotropes, such as carbon black, metal loaded carbon nanotubes, fullerene, and glassy carbon. These findings have profound impact on the application of the natural carbon materials for catalysis.

Pnictogen (As, Sb, Bi) Nanosheets for Electrochemical Applications Are Produced by Shear Exfoliation Using Kitchen Blenders.

Layered materials are of high importance because of their anisotropy and as a source of 2D materials. Whilst there is a plethora of multi-elemental 2D materials, the number mono-elemental 2D materials is rather limited. Herein, we demonstrate that aqueous shear exfoliation can be used to obtain As, Sb, and Bi exfoliated nanosheets. Morphological and chemical characterization of the exfoliated materials shows a decrease in thickness, sheet-to-nanosheet scale, and partial oxidation owing to a higher surface area. The electrochemical performance is tested in terms of inherent electrochemistry, electron transfer, and sensing applications as demonstrated with ascorbic acid. Potential energy-related applications are evaluated in the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR), with shear-exfoliated Sb having the best electrochemical performance overall. These findings will have a profound impact on the preparation and application of 2D mono-elemental materials.

Thin, High-Flux, Self-Standing, Graphene Oxide Membranes for Efficient Hydrogen Separation from Gas Mixtures.

The preparation and gas-separation performance of self-standing, high-flux, graphene oxide (GO) membranes is reported. Defect-free, 15-20 µm thick, mechanically stable, unsupported GO membranes exhibited outstanding gas-separation performance towards H2 /CO2 that far exceeded the corresponding 2008 Robeson upper bound. Remarkable separation efficiency of GO membranes for H2 and bulky C3 or C4 hydrocarbons was achieved with high flux and good selectivity at the same time. On the contrary, N2 and CH4 molecules, with larger kinetic diameter and simultaneously lower molecular weight, relative to that of CO2 , remained far from the corresponding H2 /N2 or H2 /CH4 upper bounds. Pore size distribution analysis revealed that the most abundant pores in GO material were those with an effective pore diameter of 4 nm; therefore, gas transport is not exclusively governed by size sieving and/or Knudsen diffusion, but in the case of CO2 was supplemented by specific interactions through 1) hydrogen bonding with carboxyl or hydroxyl functional groups and 2) the quadrupole moment. The self-standing GO membranes presented herein demonstrate a promising route towards the large-scale fabrication of high-flux, hydrogen-selective gas membranes intended for the separation of H2 /CO2 or H2 /alkanes.

Planar Polyolefin Nanostripes: Perhydrogenated Graphene.

Graphene hydrogenation gives an opportunity to introduce a band gap into the graphene electronic structure. Complete hydrogenation may lead to the graphane, a fully hydrogenated counterpart of graphene. However, pure graphane has not been successfully prepared to this day. Here, we show that hydrogenation of single-walled carbon nanotubes by means of Birch reduction leads to graphene-based carbon nanostripes with uniform dimensions. Such a material exhibits interesting electrocatalytic and magnetic properties as well huge potential for hydrogen storage since the weight concentration of hydrogen is 8.78 wt.% corresponding to the composition of C1 H1.22 O0.05 and thus exceeding the theoretical concentration in pure graphane (7.74 wt.%). The obtained concentration of hydrogen is the highest value ever reported for any graphene-based material and significantly exceeds the ultimate goal of the U.S. Department of Energy for a hydrogen storage material of 7.5 wt.%.

The Covalent Functionalization of Layered Black Phosphorus by Nucleophilic Reagents.

Layered black phosphorus has been attracting great attention due to its interesting material properties which lead to a plethora of proposed applications. Several approaches are demonstrated here for covalent chemical modifications of layered black phosphorus in order to form P-C and P-O-C bonds. Nucleophilic reagents are highly effective for chemical modification of black phosphorus. Further derivatization approaches investigated were based on radical reactions. These reagents are not as effective as nucleophilic reagents for the surface covalent modification of black phosphorus. The influence of covalent modification on the electronic structure of black phosphorus was investigated using ab initio calculations. Covalent modification exerts a strong effect on the electronic structure including the change of band-gap width and spin polarization.

Universal Method for Large-Scale Synthesis of Layered Transition Metal Dichalcogenides.

The layered transition metal dichalcogenides are currently amongst the most intensively investigated materials. These compounds constitute a broad family of materials, with characteristic layered structures, covering both semiconductors and metallic materials. The great attention arises from the possibility to exfoliate these materials down to single layers with many unique properties, such as thickness dependent band-gap energy, and the possibility of tuning transport properties by phase transitions. The research in the field of transition metal dichalcogenides is also motivated by their high electrocatalytic activity towards several industrially important reactions, such as the hydrogen evolution reaction, as well as many other applications in nano- and optoelectronics. Although these materials are studied intensively, their availability is extremely limited and only disulfides of molybdenum and tungsten are broadly commercially available. Here an optimized procedure for simple direct synthesis of transition metal dichalcogenides using powder metals and elemental chalcogens is reported. The optimized thermal treatment allowed the synthesis scaling of the sulfides, selenides and tellurides of 4th, 5th, 6th, and 7th group of layered-structure dichalcogenides. The synthesized transition metal dichalcogenides were single phase. The phase purity, structure, and morphology were investigated in detail by electron microscopy and EDS, X-ray diffraction, and Raman spectroscopy.

Graphene oxide layers modified by light energetic ions.

In this paper, the effect of light ion irradiation on graphene oxide foil structure and composition was studied. Due to the excellent properties of graphene based materials suitable for application in electronics, optoelectronics, micro-mechanics and space technologies, the interaction of energetic ions with graphene based structures is worth studying. From the fundamental point of view, it is also interesting to get information about graphene oxide structure modification and the possible functional properties after irradiation by energetic ions. The light ion irradiation of graphene oxide (GO) foil was performed using 2.5 MeV H+ and 5.1 MeV He2+ ions. The change in the elemental composition of the GO foils after ion irradiation was investigated using Rutherford Backscattering Spectrometry and Elastic Recoil Detection Analysis. The influence of ion irradiation was further studied by microscopy methods. The chemical composition and structural changes of the GO foil surface were characterized by spectroscopy techniques including XPS, FTIR and Raman spectroscopy. Although the results of ion beam analysis indicated no significant compositional changes in the bulk of GO foils connected to ion irradiation, XPS, ATR-FTIR and Raman spectroscopy revealed reduction and removal of oxygen functionalities on the surface of graphene oxide. This reduction leads to a surface resistivity decrease after ion irradiation dependent on the ion species, fluence and energy.