Carbon Letters最新文献

Photoanode optimization is a fascinating technique for enlightening the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). In this present study, V₂O₅/ZnO and reduced graphene oxide (rGO)-V₂O₅/ZnO nanocomposites (NCs) were prepared by the solid-state technique and used as photoanodes for DSSCs. A wet chemical technique was implemented to generate individual V₂O₅ and ZnO nanoparticles (NPs). The structural characteristics of the as-synthesized NCs were investigated and confirmed using powder X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), and Scanning electron microscope (SEM) with energy dispersive X-ray (EDX) analysis. The average crystallite size (D) of the as-synthesized V₂O₅/ZnO and rGO-V₂O₅/ZnO NCs was determined by Debye-Scherer’s formula. The bandgap (eV) energy was calculated from Tauc’s plots, and the bonding nature and detection of the excitation of electrons were investigated using the Ultra violet (UV) visible spectra, Fourier Transform infrared (FTIR) and photoluminescence (PL) spectral analysis. Electrical studies like Hall effect analysis and the Nyquist plots are also described. The V₂O₅/ZnO and rGO-V₂O₅/ZnO NCs based DSSCs exhibited 0.64% and 1.27% of PCE and the short circuit current densities and open circuit voltages improved from 7.10 to 11.28 mA/cm² and from 0.57 to 0.68 V, respectively.

New tetrazole fused imidazopyridine derivatives (12a–j) were developed to exploit their cytotoxic activity towards cancer cell lines-MCF7, A549, and MDA-MB-231, utilizing MTT reduction assay with doxorubicin as standard drug. The compounds 12 h and 12j demonstrated strong anticancer activity bearing IC₅₀ values 1.44 µM and 1.33 µM against A549 cell line.

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Metals are recognized as electromagnetic interference (EMI) shielding materials owing to their high electrical conductivity. However, the need for light and flexible EMI shielding materials has emerged, owing to the heavyweight and inflexible nature of metals. Carbon nanotube (CNT)/polymer composites have been studied as promising flexible EMI shielding materials because of their lightweight nature due to the low density of CNTs and their high electrical conductivity. CNTs evenly dispersed in the polymer form an electrically conductive network, and the aspect ratio of the CNTs, which are one-dimensional nanofillers, is an important factor affecting electrical conductivity. In this study, we prepared three types of multi-walled carbon nanotubes (MWNTs) with different aspect ratios and fabricated polydimethylsiloxane (PDMS)/MWNT composites. Subsequently, the electrical conductivities and electrical percolation thresholds of the three PDMS/MWNT composites with different MWNT aspect ratios were measured to analyze the behavior of electrically conducting network formation according to the aspect ratio. Furthermore, the total EMI shielding effectiveness of each composite was determined to evaluate the effect of the MWNT aspect ratio on the EMI shielding. Reflection and absorption of electromagnetic wave were measured for the PDMS/MWNT composite with the largest aspect ratio to analyze the EMI shielding mechanism of the composite. Additionally, the effects of the MWNT content on the conductivity and EMI shielding performance were examined. The results provide valuable guidance for designing polymer MWNT composites with good electrical conductivity and EMI shielding performance under different aspect ratios of MWNTs.

The development of biocomposites using renewable resources is a cost-effective and long-term solution to environmental and resource issues. Hydrogels [Poly Sodium Acrylate (PSA)] were created by variable percentages of crosslinker concentration, and banana–cellulose microfibril (CMF) was used as a filler in this study for better reinforcement. When the concentration of crosslinker is increased, the number of covalent crosslinks increases, limiting the movement of water molecules and lowering the diffusion coefficient, equilibrium water content, the initial rate of swelling, and the theoretical equilibrium swelling ratio. The swelling behaviour of reinforced PSA with high concentrations of CMF was unexpected; the hydrophilic OH groups of CMF increase the diffusion of water molecules from the swelling medium to inside the PSA, allowing for better mechanical behaviour of gels without sacrificing the swelling response. The swelling behaviour and swelling exponent of a hydrogel were determined at various temperatures, pH levels, and physiological fluid models. The swelling exponent's maximum value was discovered to be 0.5, which suggests that the hydrogel's water diffusion was non-Fickian in nature. The swelling ratio was found to rise with rising temperature and to have a lower value than that at room temperature. It was also proven that elevating the pH of the medium from 1 to 7 improved the PSA/CMF hydrogels' swelling response. The swelling behaviour of PSA/CMF hydrogels was also investigated as the concentration of CMF rose from 0.2 to 1%. The equilibrium water content, swelling kinetics, and water transport mechanisms were all investigated. The Flory–Rehner equation was applied to determine crosslinking density, polymer mesh size, and molecular weight between crosslinks.

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Engineering of activated carbons (ACs) through chemical activation of organic precursors has been extensively studied for a wide variety of biopolymers, biomasses, wastes and other fossil-based precursors. Despite huge efforts to engineer evermore performant and sustainable ACs, “searching-for-the-best-recipe” type of studies are more the rule than the exception in the published literature. Emerging AC applications related to energy and gas storage require strict control of the AC properties and a better understanding of the fundamentals underlying their engineering. In this study, we provide new insights into the K₂CO₃ chemical activation of plant-based polyphenols—lignins and tannins—through careful thermoanalytical and structural analyses. We showed for the the first time that the reactivity of polyphenols during K₂CO₃ chemical activation depends remarkably on their purity and structural properties, such as their content of inorganics, OH functionalities and average molecular weight. We also found that the burn-off level is proportional to the K₂CO₃/lignin impregnation ratio (IR), but only within a certain range—high impregnation ratios are not needed, unlike often reported in the literature. Furthermore, we showed for the first time that the K₂CO₃ chemical activation of different carbon surfaces from lignins and tannins can be modelled using simple global solid-state decomposition kinetics. The identified activation energies lay in the range of values reported for heterogenous gas-carbon surface gasification reactions (O₂-C, H₂O-C, or CO₂-C) in which the decomposition of C(O) surface complexes is the common rate-limiting step.

Activated carbon (AC) is a versatile and extensively employed adsorbent in environmental remediation. It possesses distinct properties that can be enhanced to selectively target specific pollutants through modifications, including chemical impregnation or incorporation into composite materials. In this study, porous calcium alginate beads (PCAB) were synthesized by incorporating AC and natural alginate through ion gelation in a Ca(II) ion-containing solution, with the addition of sodium lauryl sulfate as a surfactant. The prepared PCAB was tested for Cu(II) removal. PCAB exhibited a spherical shape with higher porosity and surface area (160.19 m².g⁻¹) compared to calcium alginate beads (CAB) (0.04 m².g⁻¹). The adsorption kinetics followed the pseudo-first-order model for PCAB and the pseudo-second-order model for CAB. The Langmuir isotherm model provided the best fit for adsorption on PCAB, while the Freundlich model was suitable for CAB. Notably, PCAB demonstrated a maximum adsorption capacity of 75.54 mg.g⁻¹, significantly higher than CAB's capacity of 9.16 mg.g⁻¹. Desorption studies demonstrated that 0.1 M CaCl₂ exhibited the highest efficiency (90%) in desorbing Cu(II) ions from PCAB, followed by 0.1 M HCl and 0.1 M NaCl. PCAB showed efficient reusability for up to four consecutive adsorption–desorption cycles. The fixed-bed column experiment confirmed the match with the Thomas model to the breakthrough curves with q_TH of 120.12 mg.g⁻¹ and 68.03 mg.g⁻¹ at a flow rate of 1 mL.min⁻¹ and 2 mL.min⁻¹, respectively. This study indicated that PCAB could be an effective adsorbent for Cu(II) removal, offering insights for further application and design considerations.

In the current research, a manganese and cobalt oxides-based nanocatalyst was developed which was used to make an efficient cathode electrode for fuel cells. The nano MnO_x/MnCo₂O₄ was synthesized through a hydrothermal procedure followed by sintering at 500–600 °C. X-ray diffraction and scanning electron microscopy besides electrochemical techniques were applied for the characterization of the synthesized nanocatalyst. The carbon black type Vulcan (XC-72R) and PTFE were used to prepare the active reaction material of the cathode electrode named carbon paste (CP). Loading of the synthesized nano MnO_x/MnCo₂O₄ on CP was optimized in a weight ratio of 10–90% for the oxygen reduction process in neutral conditions. The best performance was gained for the 50 W% MnO_x/MnCo₂O₄ loaded CP, whose active surface area was twice the bare CP. The values of the exchange current density of the ORR obtained by electrode containing 50 W% MnO_x/MnCo₂O₄ was calculated as 0.12 mA/cm². The low price, good catalytic efficiency, and cyclic stability of the MnO_x/MnCo₂O₄ nanocatalyst compared to the commercial platinum-based catalysts confirm its ability to develop fuel cell electrodes.

The effects of different plasma agent species (CF₄, N₂) over the conductivity of CF_X cathode material were identified. Both plasma treatments have surface etching effect, while the CF₄ plasma treatment has C–F bond modification effect and the N₂ plasma treatment has defluorination effect. The changes of surface chemical species and porosity along the plasma agent were elucidated. Moreover, the electrochemical properties of plasma-treated CF_X confirmed the effects of plasma treatments. The charge-transfer resistance of plasma-treated CF_X was maximum 60.3% reduced than the pristine CF_X. The effects of surface chemical modification coupled with etching along the plasma gas agents were compared and identified with their reaction mechanisms.

Curing agents are critical components of aqueous epoxy resin systems. Unfortunately, its uses and applications are restricted because of its low emulsifying yields. Epoxy resins are frequently used in electrical devices, castings, packaging, adhesive, corrosion resistance, and dip coating. In the presence of curing agents, epoxy resins become rigid and infusible. Eco-friendliness and mechanical functionality have emerged as vulcanization properties. Curing agents are used for surface modification, thermodynamic properties, functional approaches to therapeutic procedures, and recent advances in a variety of fields such as commercial and industrial levels. The curing agent has superior construction and mechanical properties when compared to the commercial one, which suggests that it has the potential for use as the architectural and industrial coatings. The thermal stability of cured products is good due to the presence of the imide group and the hydrogenated phenanthrene ring structure. Over the course of the projection period, it is anticipated that the global market for curing agents will continue to expand at a steady rate. The growth of the market is mainly driven by its expanding range in future applications such as adhesives, composites, construction, electrical, electronics, and wind energy. This review focused on the most recent advancements in curing techniques, emphasizing their thermal and mechanical properties. The review also presents a critical discussion of key aspects and bottleneck or research gap of the application of curing agents in the industrial areas.