Materials Today Chemistry最新文献

Recently, two-dimensional (2D) new C_2h phase of group III monochalcogenides have exhibited great potentials for applications in the field of photoelectric devices because of their outstanding optoelectronic properties. Here, we theoretically predict the C_2h phase of aluminum monochalcogenide (C_2h-Al₂XY) (X/YS, Se and Te; X≠Y) compounds with Janus structure via first-principles calculations. Janus C_2h-Al₂XY monolayers are found to be thermodynamically, dynamically, energetically, and mechanically stable. The entire Janus C_2h-Al₂XY monolayers exhibit semiconducting properties, with a band gap ranging from 2.25 to 2.57 eV, as calculated using the HSE06 method. The obvious anisotropic mechanical and optical characteristics are observed. All Janus C_2h-Al₂XY monolayers present high optical absorption in the ultraviolet and visible regions, suggesting that these monolayers have a favorable efficiency for absorbing solar light. These significant results imply that Janus C_2h-Al₂XY monolayers can be used in the fields such as nano-electronics and optoelectronics. Specifically, it has been found that the band edge position of Janus C_2h-Al₂SSe is capable of meeting the redox potential requirements for photocatalytic water splitting. Furthermore, biaxial strain can significantly adjust the band gap of the C_2h-Al₂SSe and enhance its visible light absorption. Most importantly, within the biaxial strain range of −6%–6 %, the band edge positions of Janus C_2h-Al₂SSe consistently satisfy the redox potentials required for photocatalytic water splitting. These findings indicate that the Janus C_2h-Al₂SSe monolayer is promising for photocatalytic water splitting due to its moderate band gap and suitable band edge positions as well as good absorption in the visible region.

To address the issues of poor electrical conductivity and volume expansion of SiO₂, the composite SiO₂/Co encapsulated in N-doped Carbon nanofibers is prepared in situ using an electrostatic spinning method followed a high-temperature treatment. Co nanoparticles exist as an elementary substance in the composite and improve the electrical conductivity of the composite, resulting in enhanced electrochemical performance. In addition, the N-doped carbon nanofibers wrap around the outside of SiO₂/Co to form a conductive network, which improves the conductivity of the composite and alleviates the volumetric effects during the charge-discharge process. As expected, the prepared SiO₂/Co@N-doped carbon nanofibers exhibit excellent rate performance, which can provide a very high discharge specific capacity of 1276 mA h g⁻¹ and 493 mA h g⁻¹ at current densities of 0.1 A g⁻¹ and 2 A g⁻¹, respectively. The composite also has a long cycle life, with a reversible discharge capacity of 659 mA h g⁻¹ at 0.5 A g⁻¹ after 400 cycles, and 552 mA h g⁻¹ at 1 A g⁻¹ after 1000 cycles. Furthermore, a full-cell LiFePO₄||SiO₂|Co@N-doped carbon nanofibers can release a reversible capacity of 119 mA h g⁻¹ at 0.1C.

Nanohybrids based on maghemite iron oxide nanoparticles (IONPs) and carbon dots (CDs), with different linkers between the two components, are synthesized, with the idea of combining several properties (magnetic and optical) in one nanomaterial in order to eradicate bacterial biofilm. The photothermal capacities of these materials are expressed by two parameters: the specific absorption rate (SAR) and the photothermal light-to-heat conversion constant (η). They show that the IONP/CD combination is more effective in photothermia (PT) than either of the components, but depends on the linkage (amide > ester > electrostatic). The antibacterial properties of the nanohybrids are first determined for the exponential and stationary growth phases of planktonic S. aureus and B. subtilis with and without PT. In the absence of PT, no nanohybrid has any significant bactericidal effect, but with PT the nanohybrids have different activities, with the IONP-amide-CD pattern the most effective. Combining magnetic actuation and PT on B. subtilis biofilms shows a synergistic effect and reveals the advantages of using such nanohybrid materials for killing bacteria and eradicating biofilm.

Two-dimensional transition metal dichalcogenides (2D-TMDs) are essential in energy storage devices. MoS₂/rGO nanostructures have improved energy storage capacity because of their layered shape, proximity effect, inherent broad surface area, and edge locations. Herein, we have synthesized NiCoS@MoS₂@rGO composite electrode material for supercapattery energy storage devices and electrochemical glucose sensors via the hydrothermal method. The electrochemical performance of NiCoS, NiCoS@MoS₂ and NiCoS@MoS₂@rGO were first investigated in three electrode assemblies at different electrolyte temperatures (27 °C to 50 °C). Among all the samples, NiCoS@MoS₂@rGO shows the superior value of Qs (1138C/g or 1896.66 F/g) with 1 M KOH electrolyte solution at 50 °C. The asymmetric NiCoS@MoS₂@rGO//AC device showed a high specific capacity (301C/g, at 1 A/g), energy and power densities of 65.44 (Wh/Kg), and 1267.18 (W/Kg), respectively. A significant value of Coulombic efficiency of 92.79 % and capacity retention of 83.42 % was acquired after 5000 galvanostatic charging/discharging (GCD) cycles. Further, the NiCoS@MoS₂@rGO nanocomposite electrode material is used for oxygen reduction reaction activity. The initial potential for the oxygen reduction was 0.67 V vs. RHE, and the electrode showed high stability. Besides, the hybrid device is used as an electrochemical glucose sensor to detect glucose with a highly precise detection response. This research will open new ideas for developing more efficient TMDs sulfide-based nanocomposite materials for future energy storage systems and biomedical applications.

Recently, solid-state thin film hybrid supercapacitor devices (TFHSCs) have had greater attention due to their miniaturized device assembly, portability, and superior cycling stability. Herein, for the first time, we assembled BiMn_xO_y ǁ PVA-KOH ǁ Bi₂MoO₆ thin-film solid-state supercapacitor devices by pulsed laser deposition (PLD) technique. In the present work, Bi₂MoO₆ and BiMn_xO_y thin film electrodes are fabricated at in-situ annealed conditions and their structural, morphological, and electrochemical performances are examined distinctly. We assembled a thin-film based BiMn_xO_y ǁ PVA-KOH ǁ BiMn_xO_y symmetric supercapacitor device (SSD) and that device delivers a functioning voltage of 1.4 V. Also, the device exhibits an extremely specific areal capacitance of 41 mF cm⁻² at 1 mA cm⁻². Similarly, a thin film-based Bi₂MoO₆ ǁ PVA-KOH ǁ Bi₂MoO₆ SSD attained a maximum specific areal capacitance of 13.33 mF cm⁻². Further, the assembled BiMn_xO_y ǁ PVA-KOH ǁ Bi₂MoO₆ TFHSC device delivers a voltage of 1.6 V and the TFHSC device exhibited a maximum specific areal capacitance of 52 mF cm⁻² at a fixed current density of about 2 mA cm⁻². The BiMn_xO_y ǁ PVA-KOH ǁ Bi₂MoO₆ TFHSC device shows outstanding stability performances such as 99 % of capacitance retention as well as 93 % of coulombic efficiency after 25,000 charge/discharge cycles. Additionally, the TFHSC device delivers a maximum areal energy density and power density of 18.5 μWh.cm⁻², and 978.7 μW cm⁻², respectively.

Layered double hydroxide (LDH) offer great potentialities to design functional coatings with customizable properties by exploiting their anion exchange properties. We investigated the anion exchange properties and expansion capacity of the interlayer space relating to the starting film morphology. ZnAl LDH coatings of different thicknesses and morphologies were first obtained by an in situ method using Al-based substrates. When the anion to intercalate is relatively bigger than the starting nitrates, the intercalation may be constrained by the initial LDH particle size and density composing the film. After optimising the morphology, the intercalation of three functional anions with potential antimicrobial properties was successfully achieved with an expansion of the interlayer space up to 150 % while holding the coating integrity. The release of the guest anion was studied by immersion in physiological saline solution. Finally, the possibility to regenerate the coating was demonstrated supporting the potential of these hybrid coatings for applications.

This study explores the influence of Bi-doping on Co_1-xBi_xCr₂O₄ (x = 0–0.2) nanoparticles synthesized via the solution combustion method, focusing on humidity sensing and magnetocaloric effects. The investigation reveals two magnetic transitions: the Curie temperature (T_C) marks the paramagnetic to ferrimagnetic shift, while the spiral transition temperature (T_S) indicates a spiral spin order transition. Magnetization measurements demonstrate that −ΔS_M and relative cooling power (RCP) values vary with Bi concentration, making these nanoparticles viable for magnetic refrigeration above liquid nitrogen temperatures. Analyzing magnetic entropy variation, the modified Arrott plots and Kouvel-Fisher approach affirm second-order phase transitions. The sensing response exhibits growth alongside relative humidity (RH) and Bi concentration, culminating in an impressive ∼97.56 % sensing response for the 20 % Bi-doped sample. This heightened humidity sensing performance with increased Bi content can be attributed to synergistic effects. These results highlight the potential of 20 % Bi-doped Co_1-xBi_xCr₂O₄ nanoparticles as promising contenders for enduring and practical humidity sensing applications.

The quest for efficient and heat-resistant near-infrared (NIR) phosphors to create advanced smart NIR lighting sources continues to pose a significant challenge. This study introduces a new fluoride phosphor, Cr³⁺-doped Cs₂NaScF₆, wherein the Cs₂NaScF₆ host provides a weak crystal field suitable for Cr³⁺ doping. This arrangement allows the production of a broad NIR emission peaking at 797 nm, coupled with a notable internal quantum efficiency of 90.8 % when excited by 446 nm blue light. Meanwhile, due to the relatively mild electron-phonon coupling effect and a high activation energy within this phosphor, the overall NIR emission intensity at 150 °C sustains 81.8 % of its level at room temperature. This highlights exceptional thermal stability in photoluminescence performance. Combining the Cs₂NaScF₆:Cr³⁺ phosphor with a commercially available blue InGaN chip to construct a NIR light-emitting diode (LED) device, which exhibits efficient and stable NIR emission, making it suitable for non-destructive testing applications. These findings affirm that the Cs₂NaScF₆:Cr³⁺ phosphor can function as a promising candidate to fabricate high-performance device for NIR spectroscopy application.

To adjust the balance between the strength and ductility of high-temperature material, we apply the first-principles calculations to explore the structural feature, elastic modulus and brittle or ductile behavior of M₂AlC (M = Mo, Cr and W) layered structure MAX phase. In addition, the thermodynamic properties of M₂AlC carbides are also discussed. The calculated results show that two novel M₂AlC carbides: Mo₂AlC and W₂AlC are predicted. For M₂AlC carbide, the M − C bond in layered structure plays an important role in strength and ductility. In particular, the W₂AlC exhibits better ductility in while has high elastic modulus. Naturally, the strength and ductility of W₂AlC are related to the bond strength and bond orientation of W–C bond in (W–C)–Al-(W–C) layered structure. The weak bond strength of W–C bond in shear direction improves the slip and then improves the ductility of W₂AlC carbide with high strength. In addition, the calculated Debye temperature follows the order of Cr₂AlC > Mo₂AlC ≈ W₂AlC. Therefore, we believe that W₂AlC carbide with (W–C)–Al-(W–C) layered structure can optimize the balance between the strength and ductility of this M₂AlC MAX phase.

Micro/nanomotors exhibit unique self-propulsion capabilities at the micro/nanoscale, offering significant potential as nanocatalysts in the field of catalysis by enhancing the contact probability between catalytic active sites and reactant molecules. Herein, a dual-propelled polydopamine (PDA)@SiO₂@Pt micromotor with asymmetric yolk-mesoporous shell nanostructure is developed to enhance the catalytic reduction performance. The synthesis of PDA@SiO₂@Pt micromotor involves a two-step process. First, the mesoporous silica is grown on the surface of the thermally swelled PDA sphere through heterogeneous interface self-assembly. Subsequently, the Pt nanoparticles (Pt NPs) are selectively loaded onto the PDA yolk. The asymmetric PDA yolk demonstrates outstanding photothermal conversion abilities, generating local thermal gradients under near-infrared (NIR) light irradiation, which propels the micromotor through thermophoresis. Simultaneously, the Pt NPs on PDA yolk catalyze the decomposition of H₂O₂ decomposition, generating O₂ gradient that drives the micromotor through self-diffusiophoresis. The motion behavior of PDA@SiO₂@Pt micromotor can be controlled through adjusting the NIR light illumination power density or varying concentration of H₂O₂. Moreover, the mesostructured architecture of PDA@SiO₂@Pt micromotor can be employed to achieve the efficient catalytic reduction, achieving up to 93 % conversion of methylene blue (MB) within 5 min due to the combined effects of photothermal and particle motion properties induced by NIR light. The PDA@SiO₂@Pt micromotor exhibits immense potential for future applications in complex catalytic systems using multi-driven micro/nanomotors.