FlatChem最新文献

Flexible conducting polymeric composites (CPC) for applications as electromagnetic interference (EMI) shielding materials were successfully prepared by melt-mixing approach using poly (vinylidene fluoride) (PVDF) as the matrix, loaded with hybrid carbonaceous fillers, carbon nanotube (CNT) and graphene nanoplatelets (GNP). Composites with as low as 3 wt% of filler with conductivity values in between 10⁻³ S/m (PVDF/GNP) and 10⁻¹ S/m (PVDF/CNT) were successfully prepared by using hybrid with different proportions. Multi-layered structure composites displayed significantly higher EMI SE values than the bulk composites, mainly those constituted by CNT and the CNT/GNP (1.5:1.5 wt%) hybrid. By stacking PVDF/CNT, PVDF/CNT/GNP and PVDF/GNP with different arrangements, on can achieve EMI SE around 22 dB (in X-band) and 27 dB (in Ku-band) with absorption contribution of 65–70 % in the X-band and 77–81 % in the Ku-band frequency ranges. The effect of the hybrid composites on the morphological, rheological and thermal properties and on the ability of the β-phase formation on PVDF composites was also investigated. By combining appropriate CNT/GNP ratio, a good compromise between flexibility, conductivity, processability and EM attenuation with absorption characteristics was achieved, thus favoring promising application in stealth technology and also in communication devices.

Recent research has extensively focused on 2D materials such as graphene oxide (GO) and MXene due to their intriguing properties, significantly advancing nanotechnology and materials research. This experimental study explores the use of a vanadium electrolyte-based hybrid nanofluid (HNF) composed of GO and MXene (90:10) to enhance vanadium redox flow batteries (VRFBs). The synthesis and characterization of GO and Mxene nanoparticles (NPs) were conducted using various techniques. The HNF, produced at different weight concentrations, underwent analysis for stability, rheology, thermal conductivity (TC), and electrical conductivity (EC) within a temperature range of 10–45 °C. The results indicate that the HNF exhibits favorable stability and Newtonian behavior in the specified temperature range. At 45 °C, the HNF achieves a maximum enhancement of 20.5 % in EC and 6.81 % in TC for 0.1 wt% compared to the vanadium electrolyte. Subsequently, a prognostic model was developed using an explainable ensemble LSBoost-based machine learning approach, employing a test dataset and applying 5-fold cross-validation to prevent overfitting. Hyperparameter optimization was achieved using the Bayesian technique. The LSBoost-based prognostic models created for TC, EC, and viscosity (VST) demonstrated high effectiveness, with R² values of 0.9981, 0.99, and 0.9954, respectively. The prediction errors were minimal, with RMSE values of 0.00089255, 5.553, and 0.09391 for the TC, EC, and VST models, respectively. Similarly, the MAE values were low, at 0.00068948, 4.0919, and 0.06129.

Motivated by the necessity of efficient detection of COVID-19 through specific biomarkers, such as ethyl butyrate and heptanal, we performed first principles calculations based on density functional theory (DFT) to explore the sensing mechanism of pure, vacancy-induced, and single atom catalyzed CrX₂ (X = Se, Te) monolayers. Both the biomarkers barely bind on pristine CrSe_2. However with Se-vacancy (As-doping) suitable adsorption energies of −1.44 (−0.70), and −0.70 (−0.54) eV were obtained for ethyl butyrate and heptanal, respectively. Te-vacancy (Sn-doping) in CrTe₂ resulted in much stronger binding of ethyl butyrate and heptanal with the adsorption energies of −2.04 (−2.40), and −2.90 (−2.40) eV, respectively. The adsorption of the mentioned biomarkers altered the magnetic and electronic properties of defected CrX₂, which were explored through spin-polarized density of states, electrostatic potential and work function calculations. Measurable changes in electronic and magnetic properties confirmed excellent sensing potential of CrX₂. Statistical thermodynamics analysis based on Langmuir adsorption model was employed to study the sensing of the biomarkers at different temperature and pressure ranges for real-world application.

Graphitic carbon nitride (g-CN) is a promising material for various applications due to its unique electronic, optical, and photocatalytic properties, tunable by surface modifications. Herein, a novel and straightforward approach to the covalent addition of low molecular weight polyethylene glycol (PEG₅₅₀) to g-CNs surface following non-destructive chemistry benefiting from simultaneous activation of hydroxyl and free-amine surface groups by a weak base, potassium carbonate, is for the first time described. The resulting g-CN-PEG₅₅₀ exhibits almost two-fold enhanced water solubility due to 1 PEG₅₅₀ chain addition for every ∼ 128 g-CN atoms, detected by thermogravimetric analysis. Complementary X-ray photoelectron spectroscopy elemental analysis of the isolated g-CN-PEG₅₅₀ displays an increased C─O chemical environment attributed to the covalent addition of carbon- and oxygen-rich PEG₅₅₀ to the g-CN surface. The g-CN-PEG₅₅₀ photocatalyst performs 2.5-fold better in degrading rhodamine B due to its enhanced light absorption, improved water-dispersibility, and the efficient separation of photogenerated electron-hole pairs compared to the as-prepared g-CN. The study underscores the potential use of covalently PEGylated oxygen-rich g-CNs in photocatalytic applications.

The development of an efficient, bifunctional, and affordable catalyst has emerged as a valuable approach for electrocatalysis, as it enhances the charge transfer capability and the number of active sites of the catalyst. Herein, we synthesized a flower-like structure of nickel and iron co-doped molybdenum disulfide on carbon cloth (Ni/Fe-MoS₂/CC) using a facile hydrothermal method. The Ni/Fe-MoS₂/CC sample exhibited remarkable activity towards the hydrogen evolution reaction, with low overpotentials of −116 mV and a Tafel slope of 43 mV/dec at −10 mA/cm². It also showed excellent performance in the oxygen evolution reaction with an overpotential of 202 mV and a Tafel slope of 65 mV/dec to afford a current density of + 10 mA/cm² along with high stability. This study illustrates the beneficial effect of Ni and Fe co-doping on the synthesized flower-shaped MoS₂ with the formation of 1 T phase on MoS₂/CC, demonstrating significant potential in the field of electrocatalysis.

Two-dimensional (2D) cesium lead halide (CsPbBr₃) nanoflakes have attracted significant attention due to their exceptional optoelectronic properties. Herein, the direct chemical vapor deposition (CVD) method was employed to synthesize high-quality single-crystalline 2D CsPbBr₃ flakes on a sapphire substrate using PbBr₂ and CsBr precursors. The study offers a comprehensive analysis of the reaction mechanisms involved, including precursor vaporization, transport, decomposition, and subsequent reactions. These factors play a crucial role in modifying the growth process and achieving the desired properties of CsPbBr₃ flakes on the sapphire substrate. Additionally, a detailed investigation was conducted into the position-dependent and power-dependent photoluminescence (PL) properties of CsPbBr₃ flakes on sapphire substrates. The results of this study contribute to the expanding knowledge base regarding the growth of 2D perovskite materials. Moreover, they open up avenues for future research and development in the field of advanced optoelectronics.

In this research, we introduce a facile approach utilizing a glucose solution as a precursor to form a protective carbon layer on inherently unstable semiconductor nanostructures, addressing the pervasive issue of photo-corrosion. We focused on CuO photocathode, employing a straightforward technique to envelop them with an ultra-thin, amorphous carbon layer, rendering them suitable for photoelectrochemical (PEC) water-splitting application for hydrogen production. The results demonstrated exceptional photo-stability and significantly improved photocurrent density of CuO arrays equipped with the carbon protective layer. This transformative modification led to a substantial enhancement in PEC performance, yielding a photocurrent density up to 2.19 mA.cm⁻² at 0 V vs. RHE. Furthermore, the maximum photo-to-current conversion efficiency reached 0.12 % at 0.1 V vs. RHE under AM 1.5G illumination condition (100 mW cm⁻²). In-depth investigations revealed that these enhancements results from accelerated electrochemical charge transfer at the electrode/electrolyte interface and concurrent mitigation of photo-corrosion rates. This approach has the potential to address stability concerns among a broad range of non-stable photoelectrodes, offering significant contributions to the field of energy conversion and the advancement of renewable energy technologies.

Semiconductor photocatalysts that can both photocatalytic evolve hydrogen from water and degrade organic pollutants are very important to solve the problem of energy shortage and environmental pollution. The S-scheme ZnIn_0.2Ga_1.8O_4/CaIn₂S₄ complex was successfully synthesized using sol–gel and oil bath methods. Characterization technique indicates that chrysanthemum-shaped CaIn₂S₄ is anchored on the surface of irregular nanoparticles ZnIn_0.2Ga_1.8O₄, forming a closely packed heterostructure. The bandgap values of CaIn₂S₄ and Zn(In_0.1Ga_0.9)₂O₄ were determined as 2.11 eV and 3.61 eV, respectively. Under visible-light irradiation, the ZnIn_0.2Ga_1.8O_4/CaIn₂S₄-1(ZC-1) photocatalyst exhibited superior performance in degrading an organic pollutant (RhB) and generating hydrogen compared to ZnGa₂O₄, ZnIn_0.2Ga_1.8O₄, and CaIn₂S₄ alone. The photocatalytic degradation of RhB using ZC-1 was 1.7, 1.31, and 1.14 times higher than that of ZnGa₂O₄, ZnIn_0.2Ga_1.8O₄, and CaIn₂S₄, respectively. Moreover, the photocatalytic hydrogen evolution rate of ZC-1 was 5.8, 3.7, and 13 times higher than that of ZnGa₂O₄, ZnIn_0.2Ga_1.8O₄, and CaIn₂S₄, respectively. The formation of S-type heterojunctions in the composite photocatalysts was confirmed through free radical trapping and electron paramagnetic resonance tests, further enhancing hydrogen production and organic pollutant degradation. This study presents a novel approach for developing ZnGa₂O₄-based composite photocatalysts with S-scheme heterojunctions to address energy shortage and environmental pollution in the future.

With the striking release of antibiotic wastewater into the aqueous environments, currently, antibiotic contaminations have become a drastic worldwide issue. To alleviate this issue, diverse studies on the degradation and elimination of these highly stable recalcitrant compounds are carried out. In this respect, heterogeneous photocatalysis has attracted notable consideration of research communities, because of its promising potential to eliminate these pollutants from aquatic environments through an economical, green, and efficacious procedure. As a metal-free photocatalyst, g-C₃N₄ has inspired enormous consideration owing to its extraordinary characteristics. Nonetheless, the finite visible-light harvesting amount, quick recombination of charges, insignificant oxidation power, and poor textural attributes are the crucial disadvantages of g-C₃N₄, limiting its photocatalytic ability. These obstacles can be impressively resolved through the fabrication of g-C₃N₄-based heterojunction systems with semiconductors having proper energy bands. Till now, various semiconductors have been utilized to develop Z- and S-scheme systems by g-C₃N₄. Accordingly, this review summarizes lately developed impressive photocatalysts fabricated by anchoring g-C₃N₄ with various semiconductors through Z- and S-scheme structures for the photocatalytic degradation of various antibiotics. Ultimately, several perspectives on the future progress and challenges in the arena of photocatalytic elimination of antibiotics over promising photocatalysts are represented.

Two-dimensional (2D) materials, including graphene, have emerged as essential building nanoscale blocks for the development of high-performance membranes. At present, the gas separation membrane market is primarily dominated by polymer membranes. Part of the reason for this is the low production cost, high gas flux, and mechanical flexibility associated with polymer membranes. However, polymer membranes often exhibit relatively short lifespans, low thermal and chemical stability, and low selectivity. In contrast, 2D materials are easily modifiable, functionalizable, and amenable to composite with other materials. This makes them possess better mechanical stability, thermal stability, and higher selectivity. The atom-scale thickness of nanosheets can help to minimize transport resistance and permeation flux. Furthermore, these nanomaterials can form sub-nanometer sieving channels for precise molecular separations, particularly in gas separation applications. Notably, 2D gas separation membranes offer significant advantages over traditional membranes in terms of both permeability and selectivity. However, several challenges hinder the widespread utilization of 2D gas separation membranes. These challenges include the mechanical and long-term stability of membranes under harsh working conditions, difficulties in scalability and the high fabrication costs associated with their production. In this article, we review recent developments of composite membranes containing 2D materials to provide perspective on their application as gas separation membranes. We also provide a critical comparison of different materials for gas separation applications. This paper summarizes the current state of the art of 2D gas separation membranes, including porous graphene, GO, 2D MXene, 2D MOFs, and graphitic carbon nitride. Additionally, it describes their specific applications in CO₂ capture and separation, H₂ separation and purification, and helium extraction from natural gas. Furthermore, the current challenges and future development prospects of 2D material gas separation membranes are discussed.