Materials In Aqueous Solution Research Articles

Solvent Effect on Cation⊗3π Interactions: A First-Principles Study.

Cation⊗3π interactions play a special role in the behaviors of biological molecules and carbon-based materials in aqueous solutions, yet the effects of solvation on these interactions remain poorly understood. This study examines the sequential attachment of water molecules to cation⊗3π systems (cation = Li⁺, Na⁺, K⁺), revealing that solvation influences interaction strengths in opposing ways: solvation of the metal cation decreases the strengths of cation⊗3π interactions, while the solvation of the benzene molecule increases the strengths of cation⊗3π interactions, compared with the strengths of cation⊗3π interactions in the gas phase. The mechanism analyses revealed that in the presence of surrounding water molecules, the stability of cation⊗3π systems is generally enhanced by cation-π, π-π, water-π, and water-ion interactions, while water-water interactions typically have a destabilizing effect. In addition, the primary effect of water molecules at different adsorption sites is to modulate the Coulombic multipole-multipole interactions and the overlap between monomeric charge distributions, thereby influencing the changes in strengths of cation⊗3π interactions. Moreover, AIMD simulations further underscore the practical significance of cation⊗3π interactions. These findings provide valuable insights into the structures and the strengths of cation⊗3π interactions with the effect of solvation.

Fabrication of nitrogen-doped quenched-produced diamond electrodes on titanium substrates by coaxial arc plasma deposition

Nitrogen-doped quenched-produced diamond (N-doped Q-dia) thin films were deposited onto a titanium substrate by coaxial arc plasma deposition (CAPD). The N-doped Q-dia thin film was successfully synthesized at room temperature without peeling. Its performance as an electrode material in aqueous solutions was investigated. The overpotential for the hydrogen evolution reaction was 0.35 V higher than the conventional boron-doped diamond (BDD) electrode. The kinetics of reversible electron transfer for redox species were comparable to the BDD electrode. We have demonstrated the N-doped Q-dia thin films have promising potential as a competitive and alternative electrode material to BDD films for electrochemical applications.

External surface hydrophilic 3D-POSS-COF@GDL for the direct adsorption of bisphenols in milk samples

In case of organic frameworks (COFs) as adsorbents in the pretreatment of complex food matrices, challenges such as poor dispersion and non-specific adsorption of interfering macromolecules like proteins are often encountered. To address this issue, this work prepared a three-dimensional covalent organic framework (3D-COF) with a novel bcu topology based on polyhedral oligomeric silsesquioxane (POSS). Subsequently, gluconolactone (GDL) was modified onto the external surface of the material via the reaction with the exposed reactive residues. The resulting POSS-COF@GDL adsorbent has an enhanced hydrophilicity in the external surface, thereby significantly improves the dispersion of materials in aqueous solution and reduces the adsorption ability toward protein. Whereas, the inner of material retains hydrophobic pores that exhibit high adsorption efficiency to small hydrophobic molecules. Compared with the traditional pretreatment methods, POSS-COF@GDL can directly extract bisphenols (BPs) in milk samples without any additional treatment. The established sample pretreatment method is coupled with high-performance liquid chromatography-ultraviolet detection (HPLC-UV), resulting in recoveries of 71.8 to 93.6%, intra- and inter-day relative standard deviations (RSDs) of <8.3%, and limits of detection (LODs) of 0.042–0.16 ng∙mL−1 for four BPs.

(Invited) Energy Storage in Ti3C2T x MXene in a Wide Temperature Range

Pseudocapacitors have the potential to achieve high energy and high power density simultaneously, a holy grail for electrochemical energy storage. MXene-based pseudocapacitors have made major progress in the last decade, achieving better energy and power density than carbon supercapacitors using the double-layer charge storage mechanism. However, one obstacle facing pseudocapacitors is their shorter lifetime. In MXene-based pseudocapacitors, which showed up to 500,000 cycles lifetime in aqueous electrolyte at room temperature, this concern is pronounced particularly at high temperatures due to the limited stability of the active material in aqueous solutions. This work shows that Ti3C2T x MXene electrodes in 5 M H2SO4 possess excellent rate capabilities from -50 °C to 100 °C but also a sufficient lifetime at 70 °C when using a float test holding at -0.9 V vs. Hg/Hg2SO4. Post-mortem characterization using X-ray photoelectron spectroscopy and Raman spectroscopy showed negligible signs of oxidation in the bulk of the film. This work suggests sufficient stability of Ti3C2T x MXene as a negative electrode in protic aqueous electrolytes across a wide temperature range rooted in thermodynamics, making it promising for pseudocapacitor energy storage.

Boosting the Luminescence of a Europium(III)-β-Diketonate Complex-Nanoclay Aqueous Solution by Acetylcholine.

It is a challenging task to prepare lanthanide complex-based luminescent materials with high quantum efficiency in aqueous solution, since the excited state of Ln3+ can be significantly quenched by water through the excitation of the O-H vibrations. Herein, we present a simple and environmentally friendly strategy to prepare strongly red-light-emitting lanthanide complex-based luminescent materials by loading 2-thenoyltrifluoroacetate (TTA) on the Eu3+-exchanged nanoclay (Eu3+(TTAn)-NC, NC = nanoclay) and coadsorption of choline chloride (ChCl) or acetylcholine chloride (AChCl) in water. The coadsorbed molecules remarkably boosted the luminescence of Eu3+(TTAn)-NC, which is tentatively ascribed to the removal of waters coordinated in the Eu3+ coordination sphere via the complete coordination of TTA mediated by ChCl or AChCl. Highly luminescent films were facilely prepared by mixing a Eu3+(TTAn)-NC aqueous solution with PVA-ChCl (PVA-AChCl) deep eutectic solvents. This work provides a simple and environmentally friendly way for preparing highly luminescent emitting luminescent materials in aqueous solution.

Direct observation and elemental analysis of material nanoparticles in solution using scanning electron-assisted dielectric microscopy and EDS

High-resolution observation and elemental analysis of various particles in solution are important in the fields of materials, analytical chemistry, and industrial applications. Analysis of slurries of raw materials is essential for the development of highly functional materials. Recently, we have developed an SEM-based scanning electron assisted dielectric microscope (SE-ADM), which can directly observe biological samples and organic materials in aqueous solutions. Here, we have developed an SE-ADM system with the addition of energy-dispersive x-ray spectrometry that enables direct observation and elemental analysis of nanoparticles in solution. Using this system, we were able to directly observe and conduct elemental analysis of ceramic slurries and to clarify the dispersion state of alumina particles in solution, the distribution of binder, and the bonding state of silica and magnesium particles. Furthermore, our system can be applied to diverse liquid samples across a broad range of scientific and industrial fields, for example, nanotubes, organic specimens, batteries, and catalytic materials.

Revealing proton-coupled exchange mechanism in aqueous ion-exchange synthesis of nickel-rich layered cathodes for lithium-ion batteries

Ion exchange is a promising synthetic method for alleviating severe cation mixing in traditional layered oxide materials for lithium-ion batteries, leading to enhanced structural stability. However, the underlying mechanisms of ion exchange are still not fully understood. Such a fundamental study of the ion-exchange mechanism is needed for achieving the controllable synthesis of layered oxides with a stable structure. Herein, we thoroughly unearth the underlying mechanism that triggers the ion exchange of Ni-rich materials in aqueous solutions by examining time-resolved structural evolution combined with theoretical calculations. Our results reveal that the reaction pathway of ion exchange can be divided into two steps: protonation and lithiation. The proton is the key to achieving charge balance in the ion exchange process, as revealed by X-ray adsorption spectroscopy and inductive coupled plasma analysis. In addition, the intermediate product shows high lattice distortion during ion exchange, but it ends up with a most stable product with high lattice energy. Such apparent discrepancies in lattice energy between materials before and after ion exchange emphasize the importance of synthetic design in structural stability. This work provides new insights into the ion-exchange synthesis of Ni-rich oxide materials, which advances the development of cathode materials for high-performance lithium-ion batteries.

Prediction of Methyl Orange (MO) Toxicity and Minimizing Its Pollution in Aquatic Environment by Activated Carbon Adsorption

Minimizing environmental pollution is an essential work of the official and scientific communities around the world, especially in water systems. In water, soluble dye works as a blockage in photosynthesis process because of its toxicity. One of these highly applicable dyes in industry is Methyl Orange (MO), documented with more than 10% released to water. Here, a new Iraqi try of converting environmental and health problems to solutions with high quantification was as done by using face tissue (Kleenex) as a carbon source. Primary in Silico testing of this anionic dye (Methyl Orange) was done based on online website confirmed MO dye is unsafe in several toxicological determinations such as foetus health (during pregnancy). Also, it is permeable material to skin, Blood- Brain system (BBB), and Human Colon Carcinoma cell line (CaCO2) compatible with Human Intestinal absorption (74.166%). In experimental section, low quality of face tissue (Kleenex) was subject to a high acidic medium (concentrated sulphuric acid), followed by addition of sodium carbonate to .increase activation of based carbon material with more structural pores yielding high removal efficiency and adsorption capacity ranged (88-98)% and (88-98) mg/g respectively. Qualitative and quantitative evaluations were based upon choosing two wavelengths in ultraviolet (272 nm) and visible (464 nm) regions. In this work, two removal steps were performed with the same adsorbent companied by multiple UV-Vis spectroscopic evaluation of several tested sections. Reviewing of published papers in MO removal presents the extraordinary performance of this prepared material towards using it as an excellent adsorbent of toxic material in aqueous solution.

Conductometric study of hydroelectrochemical parameters for the interaction of cadmium bromide in lump and nano forms with Orange G dye

The hydroelectrochemical behaviour of cadmium bromide was investigated in the presence of the dye Orange G. This information can be used to develop conductometric sensors for detecting these substances, understand how they behave in aqueous solutions, and design effective procedures for removing the extremely toxic heavy cadmium ions from contaminated water sources. The hydroelectrochemical parameters for the interaction between lump and nanoCdBr2 with Orange G dye were investigated conductometrically in aqueous solutions at different temperatures. CdBr2 interacts with Orange G as a ligand, resulting in a decrease in conductivity. However, the interaction was more significant with nanoCdBr2, which showed a higher decrease in conductivity compared to lump CdBr2. Two stiochiometric complexes, 1:1 and 1:2, were produced; Kf and ΔGf are higher for 1:1 than for 1:2 (CdBr2/Orange G). With rising temperatures, the formation constants decreased, and the negative sign of ΔGf indicated the spontaneity of the reaction, which increased with rising temperatures. The negative values of (ΔHf) revealed the complexation's exothermic nature, whereas the positive entropy (ΔS) values confirmed that the complex formation depended on molecular entropy since the complex formation was favored by an increase in molecular disorder. The results of our investigation can be utilised to enhance comprehension of the behaviour of these materials in aqueous solutions and create efficient protocols for the removal of very toxic heavy metal cadmium ions from polluted water sources. We think that our study advances the discipline and offers a distinctive viewpoint on this subject.

Endowing Carbon Dots with Long‐Lived Phosphorescence Emission in Aqueous Solutions

AbstractRoom temperature phosphorescent carbon dots (RTP CDs) have received increasing attention in recent years due to their outstanding optical properties and potential applications. It is worth noting that RTP CDs in aqueous solution have inspired special interests because of their low toxicity, long lifetime, and ability to avoid autofluorescence and background fluorescence, exhibiting wide application prospects in time‐resolved biological imaging and sensing. However, achieving phosphorescent CDs in aqueous solutions remains a considerable challenge because water molecules and oxygen can cause the deactivation of triplet‐state excitons, resulting in phosphorescence quenching. Several strategies have been proposed to counter the problem including encapsulated CDs in a rigid matrix, hydrogen bonding, and covalent bonding fixation. Consequently, a more significant number of RTP CDs materials with excellent optical stability, long lifetime, and multicolor are successfully obtained. Herein, the recent development of RTP CDs materials in aqueous solution as well as the corresponding fabricated strategies and luminescence mechanism is detailly summarized and reviewed. Furthermore, various applications of water‐phase RTP CDs materials in information security, sensing, bioimaging, light‐emitting diodes, and fingerprinting are also discussed. Finally, an outlook on the development of CDs materials and applications is proposed.

Effect of Fluoride Atoms on the Electrochemical Performance of Tetracyanoquinodimethane(TCNQ) Electrodes in Zinc-ion Batteries.

Tetracyanoquinodimethane (TCNQ) electrode material has achieved excellent performance in aqueous zinc-ion batteries (AZIBs). However, fundamental understanding about effect of substitutes on electrochemical performance of TCNQ remain unknown. In this work, the effects of fluorine (F) as an electron-absorbing group on the structure, morphology and electrochemical performance of TCNQ and storage mechanism of TCNQ in AZIBs are discussed. Theoretical calculation proves that the introduction of fluorine atoms decreases lowest unoccupied molecular orbital (LUMO) energy of TCNQ thus affect the redox potential. Electrochemical performance of TCNQ/Fluoro-7,7,8,8-tetracyanoquinodimethane (FTCNQ)/2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4 TCNQ) is evaluated from 25 °C to -20 °C in AZIBs. Results tend out that with the increasing substituents of F on TCNQ molecular, their stability in AZIBs decrease. Dipole moment calculation further shows that the introduction of fluorine atoms is inconducive to the stability of the electrode material in aqueous solution. Ex-situ characterization demonstrate that electron withdrawing groups do not change the REDOX center of TCNQ electrode materials. Our work provides a new thought for the selection of the electrode material in AZIBs.

ATP-Enhanced Multistimuli-Responsive Förster Resonance Energy Transfer in Organic Coassemblies.

In recent years, ATP has emerged as an anionic biocomponent for the design of dynamic and stimuli-responsive supramolecular assemblies. Herein, we present ATP-enhanced Förster resonance energy transfer (FRET) in the coassemblies of pyrene-imidazolium amphiphiles with pyrene acting as an excellent donor for the coembedded acceptor dyes to generate tunable multiluminescent materials in aqueous solutions and in polymer and solid films. We achieved high energy transfer efficiency up to 95% even at a donor/acceptor (D/A) ratio of 100:1. By a simple variation of the D/A ratio, emission covering almost the whole range of the visible spectrum from blue to red including white light was obtained in solution and in solid and polymer films. Furthermore, the systems exhibited FRET ON/OFF features controlled by various stimuli such as temperature, pH, and metal ions. Most notably, a ratiometric and linear luminescence response to temperature and pH was observed. The stimuli-responsive tunable solid-state emission was further exploited in encryption-decryption applications.

Epitaxial Electrodeposition of Ordered Inorganic Materials.

ConspectusThe quality of technological materials generally improves as the crystallographic order is increased. This is particularly true in semiconductor materials, as evidenced by the huge impact that bulk single crystals of silicon have had on electronics. Another approach to producing highly ordered materials is the epitaxial growth of crystals on a single-crystal surface that determines their orientation. Epitaxy can be used to produce films and nanostructures of materials with a level of perfection that approaches that of single crystals. It may be used to produce materials that cannot be grown as large single crystals due to either economic or technical constraints. Epitaxial growth is typically limited to ultrahigh vacuum (UHV) techniques such as molecular beam epitaxy and other vapor deposition methods. In this Account, we will discuss the use of electrodeposition to produce epitaxial films of inorganic materials in aqueous solution under ambient conditions. In addition to lower capital costs than UHV deposition, electrodeposition offers additional levels of control due to solution additives that may adsorb on the surface, solution pH, and, especially, the applied overpotential. We show, for instance, that chiral morphologies of the achiral materials CuO and calcite can be produced by electrodepositing the materials in the presence of chiral agents such as tartaric acid.Inorganic compound materials are electrodeposited by an electrochemical-chemical mechanism in which solution precursors are electrochemically oxidized or reduced in the presence of molecules or ions that react with the redox product to form an insoluble species that deposits on the electrode surface. We present examples of reaction schemes for the electrodeposition of transparent hole conductors such as CuI and CuSCN, the magnetic material Fe3O4, oxygen evolution catalysts such as Co(OH)2, CoOOH, and Co3O4, and the n-type semiconducting oxide ZnO. These materials can all be electrodeposited as epitaxial films or nanostructures onto single-crystal surfaces. Examples of epitaxial growth are given for the growth of films of CuI(111) on Si(111) and nanowires of CuSCN(001) on Au(111). Both are large mismatch systems, and the epitaxy is explained by invoking coincidence site lattices in which x unit meshes of the film overlap with y unit meshes of the substrate.We also discuss the epitaxial lift-off of single-crystal-like foils of metals such as Au(111) and Cu(100) that can be used as flexible substrates for the epitaxial growth of semiconductors. The metals are grown on a Si wafer with a sacrificial SiOx interlayer that can be removed by chemical etching. The goal is to move beyond the planar structure of conventional Si-based chips to produce flexible electronic devices such as wearable solar cells, sensors, and flexible displays. A scheme is shown for the epitaxial lift-off of wafer-scale foils of the transparent hole conductor CuSCN.Finally, we offer some perspectives on possible future work in this area. One question we have not answered in our previous work is whether these epitaxial films and nanostructures can be grown with the level of perfection that is achieved in UHV. Another area that is ripe for exploration is the epitaxial electrodeposition of metal-organic framework materials from solution precursors.

Oxidative dissolution of (U,Ce)O2 materials in aqueous solutions containing H2O2

Homogeneous and heterogeneous U1-xCexO2 (with 0≤ x≤ 0.25) materials were prepared via wet and dry chemistry routes, respectively before being submitted to dynamic leaching experiments. The feeding solution containing 0.20 mmol.L−1 H2O2 was kept under air and renewed to guarantee the stability of H2O2 during the experiment. Normalized alteration rates were determined from U concentration in the leachates. For homogeneous (U,Ce)O2 materials, the dissolution rate was divided by a factor of 3 when increasing the Ce content from 0.08 to 0.25. Surface characterizations revealed that studtite precipitated all over UO2 pellet surface and only on the UO2 grains of heterogeneous U0.92Ce0.08O2 samples. The behaviour of this heterogeneous material was similar to that observed for (U,Pu)O2 in the same conditions, which revealed the reliability of cerium as a plutonium analogue.

Two-Dimensional Transition Metal Dichalcogenide Tunnel Field-Effect Transistors for Biosensing Applications.

Field-effect transistor (FET) biosensors based on two-dimensional (2D) materials have drawn significant attention due to their outstanding sensitivity. However, the Boltzmann distribution of electrons imposes a physical limit on the subthreshold swing (SS), and a 2D-material biosensor with sub-60 mV/dec SS has not been realized, which hinders further increase of the sensitivity of 2D-material FET biosensors. Here, we report tunnel FETs (TFETs) based on a SnSe2/WSe2 heterostructure and observe the tunneling effect of a 2D material in aqueous solution for the first time with an ultralow SS of 29 mV/dec. A bilayer dielectric (Al2O3/HfO2) and graphene contacts, which significantly reduce the leakage current in solution and contact resistance, respectively, are crucial to the realization of the tunneling effect in solution. Then, we propose a novel biosensing method by using tunneling current as the sensing signal. The TFETs show an extremely high pH sensitivity of 895/pH due to ultralow SS, surpassing the sensitivity of FET biosensors based on a single 2D material (WSe2) by 8-fold. Specific detection of glucose is realized, and the biosensors show a superb sensitivity (3158 A/A for 5 mM), wide sensing range (from 10-9 to 10-3 M), low detection limit (10-9 M), and rapid response rate (11 s). The sensors also exhibit the ability of monitoring glucose in complex biofluid (sweat). This work provides a platform for ultrasensitive biosensing. The discovery of the tunneling effect of 2D materials in aqueous solution may stimulate further fundamental research and potential applications.

Uranyl-organic hybrid material with semi-rigid polycarboxylate: Synthesis, structure, luminescence and photocatalytic properties

One novel uranyl carboxylate complex [(UO2) (L)·2H2O] (1) (H2L=4-carboxymethoxy-benzoic acid) was synthesized under hydrothermal conditions by the reaction of UO2(NO3)2·6H2O and H2L in aqueous system. X-ray analysis of single crystal structure determined that complex 1 exhibits one-dimensional ribbon structure, in which, the UO22+ ions are bridged by L2−. The one-dimensional chains are further connected into 3D supramolecular network by OH…O hydrogen bond interactions between the coordinated water molecule and the coordinated carboxylic oxygen. The π…π interactions between adjacent benzene rings also contribute the structure formation. Complex 1 exhibits emblematic charge-transfer green emission of uranyl-bearing complexes. The UV–vis absorption spectra reveal distinct light absorption both on the ultraviolet and visible regions for 1. Photocatalytic degradation of rhodamine B (RhB) in aqueous solutions using Complex 1 was studied, 78.3% of the RhB was degraded in only 80 min. Our obtained uranyl coordination polymer represents effective RhB photocatalytic degradation materials in aqueous solution. Infrared spectroscopy, TGA and PXRD were also discussed.

Synthesis of amino talc-like clay-supported Au nanoparticles with outstanding catalytic activity for 4-nitrophenol reduction

Studies on synthesizing gold nanoparticle-based catalysts to reduce the amount of gold and improve the catalytic activity at the same time are still crucial. The reduction reaction of 4-nitrophenol (a toxic compound) to 4-aminophenol (a non-toxic compound and essential material for the pharmaceutical industries) is a standard reaction for analyzing the catalytic activity of AuNPs. A capping agent is indispensable for producing stable and size-controlled gold nanoparticles (AuNPs) and in maintaining the catalytic activity of the AuNPs. However, some previous studies reported that capping agents reduced the catalytic activity of AuNPs through a surface-blocking phenomenon. Moreover, introducing a framework for capped AuNPs could be another consideration to increase the dispersion of AuNPs in an aqueous medium, eventually improving the catalytic activity of the AuNPs. Amino talc-like clay, a relatively non-toxic and well-dispersed layered material in aqueous solution, has been used as a framework for AuNPs. The present study reports the AuNP synthesis using delaminated amino talc-like clay (DAC) as a framework that brings about gold nanoparticles with superior catalytic activity to other supports. Moreover, the effect of the reducing agent concentration, Mn addition and pH conditions are discussed in determining this excellent property. DAC shows a promising role as a AuNP framework which increases the catalytic activity by improving the dispersion and stability of the material in the colloidal system. The pH-dependent stacking structure arrangement of the DAC support was a determining factor of Kapp for the 4-nitrophenol reduction reaction by DAC stabilized AuNPs. Under acidic conditions, the stacking structure of DAC was destroyed, providing more open space for the AuNPs attached to the clay surface, which increased the Kapp value. On the contrary, under basic conditions, the stacking structure of DAC was re-arranged, closing the surface space of the AuNPs attached to the interlayer clay, which decreased the Kapp value. Moreover, the DAC stabilizer provided a partially capped AuNP structure in neutral and acidic aqueous solutions, which prevented the catalytically active surface blocking phenomenon occurring in the ordinary capping type. Mn addition during the synthesis process controlled the production of small-size gold nanoparticles and increased the catalytic activity of the material.

Nanostructured ZnxMn3‒xO4 thin films by pulsed laser deposition: A spectroscopic and electrochemical study towards the application in aqueous Zn-ion batteries

Aqueous Zn-ion batteries (AZIBs) represent a safe and sustainable technology amongst the post-lithium systems, though the poor understanding of the material behaviour at the cathode prevents the full development of efficient AZIBs. ZnMn2O4 (ZMO) has been considered one of the cathode candidates owing to its analogy to the well-established LiMn2O4 cathode for lithium-ion batteries, however its electrochemical mechanism in the presence of Zn ions in aqueous environment is unclear and still debated. In this work, we synthesised nanostructured ZMO thin films by Pulsed Laser Deposition (PLD) and we evaluated, through extensive characterization by microscopic, spectroscopic, and diffraction techniques, how the deposition and annealing conditions affect the film properties. The self-supported nature and the high degree of control down to the nanoscale make a thin film an ideal model system to study the electrochemistry of the material in aqueous solution and to emphasize the impact of the film properties on its electrochemical response. We highlighted the crucial role of the oxygen pressure in the modulation of the film porosity and the combined effect of deposition pressure and annealing temperature to produce a film with tailored properties in terms of morphology, crystallinity, and Zn stoichiometry. A complex redox mechanism involving multiple concurrent reactions and the formation of zinc hydroxide sulphate hydrate (ZHS) was reported, as well as the influence of the film porosity on the voltammetric behaviour of the film at higher scan rate. Our results confirm the intricate electrochemical mechanism of the ZMO material, which does not merely involve the Zn2+ insertion/extraction but also the crucial participation of Mn2+ from the electrolyte, and pave the way for the nanoscale design of engineered ZMO-based electrodes.

Electrochemical Pourbaix diagrams of monolayer MoSSe with different atomic ratios of chalcogens

MoSSe material is a very promising photoelectric material, and its application environment is aqueous solution. However, there is no research of the electrochemical stability of MoSSe materials in aqueous solution. In this work, the Pourbaix diagrams of monolayer MoSSe with different atomic ratios of molybdenum, sulfur and selenium are constructed based on density functional theory, and the thermodynamic stabilities and electrochemical corrosion behaviors under different pH values and electrode potentials are studied. The study of the pourbaix diagram of MoSSe shows that part of the corrosion-free region of MoSSe exists within the stable region of water in the Pourbaix diagram, indicating that the MoSSe can exist stably in the water environment. Compared with alkaline solutions, MoSSe has good corrosion resistance in acidic solution and neutral solution. The Pourbaix diagram of Mo&lt;sub&gt;4&lt;/sub&gt;S&lt;sub&gt;2&lt;/sub&gt;Se&lt;sub&gt;6&lt;/sub&gt;, Mo&lt;sub&gt;4&lt;/sub&gt;S&lt;sub&gt;6&lt;/sub&gt;Se&lt;sub&gt;2&lt;/sub&gt;, Mo&lt;sub&gt;4&lt;/sub&gt;S&lt;sub&gt;7&lt;/sub&gt;Se and Mo&lt;sub&gt;4&lt;/sub&gt;SSe&lt;sub&gt;7&lt;/sub&gt; show that in the case of high molar fraction of sulfur in monolayer MoSSe with different atomic ratios of molybdenum, sulfur and selenium, the conditions for the stable existence of materials in aqueous solution can have a larger range, and the corrosion resistance becomes better. In the case of high molar fractions of selenium in monolayer MoSSe with different atomic ratios of molybdenum, sulfur and selenium, the range of conditions for the stable existence of materials in aqueous solution becomes smaller, and the corrosion resistance becomes worse. In this work, the stabilities and corrosion behaviors of monolayer MoSSe with different atomic ratios of molybdenum, sulfur and selenium in aqueous solution are predicted, and the degradation behaviors of MoSSe materials are further explored, which can provide theoretical guidance for the application of MoSSe materials in the field of optoelectronics.

Laser-induced graphene and its modification with polypyrrole for increasing microsupercapacitor capacitance

Laser-induced graphene (LIG) films were synthesized by line-by-line scanning of cw CO2 laser focused radiation on the surface of industrial polyimide film as a result of pyrolysis of its near-surface layer. The structure of the synthesized film material is shown to be heterogeneous in thickness by Raman spectroscopy. The results of the study of the effect of the laser power and the distance between the lines on the specific electrical capacitance c of the synthesized material in aqueous solution of sulfuric acid are presented. It is shown that modification of LIG with polypyrrole (PPy) allows to increase c up to 60 mF/cm2. PPy-modified LIG films were used to make a prototype of a flexible film microsupercapacitor with an area of 8 cm2, using a gel electrolyte based on sulfuric acid and polyvinyl alcohol, with a 230 mF capacitance. Keywords: laser-induced graphene, electric capacitance, polypyrrole, microsupercapacitor.