Materials Research Bulletin最新文献

Here we report low temperature growth of two dimensional freestanding nanoplatelets of manganese oxide (Mn₃O₄) through a simple and cost-effective wet chemical route without the utilization of capping agents. The pristine 2D Mn₃O₄ nanoplatelets have size and thickness between 100 and 200 nm and 3.5–5.1 nm respectively as corroborated by FESEM, TEM and AFM analysis. The electrochemical performance of the 2D Mn₃O₄ based electrode is studied using three electrode configuration and 1 M KOH as electrolyte where the remarkably high specific capacitance of 537 F/g (at 2 A g^-1) is observed. Moreover, the 2D Mn₃O₄ based electrode is also found to exhibit an excellent retention of specific capacitance (∼ 93%) up to 5000 cycles. Thus enriched electrochemical performance of 2D Mn₃O₄ nanoplatelets reveals its potential as electrode material in supercapacitor device applications.

Molybdenum disulfide (MoS₂) has been proven to be an effective and promising electrode material for capacitive deionization (CDI) due to its unique architectures and excellent electrochemical activity. However, MoS₂-based electrodes still suffer from the high contact electrical resistance between MoS₂ and the current collectors because of the necessity of adding binder during their fabrication. In this work, a flexible MoS₂-based electrode with no binders was successfully fabricated. It was found that the frameworks of stainless-steel mesh with surface treatment could serve as an ideal substrate to provide plenty of active nucleation sites for the growth of MoS₂. Consequently, a novel morphology of MoS₂ with Auricularia-like architectures was produced. Based on electrochemical impedance spectroscopy (EIS), the charge transfer resistance was reduced to nearly zero after the treatment, highly increasing the transportation of charges inside the electrodes compared to the common MoS₂-based electrodes. As a result, the binder-free MoS₂-based electrodes demonstrated a superior desalination performance of 28.76 mg g^-1 (1.2 V) for NaCl solution, which was superior to that of common MoS₂-based and many other advanced materials-based electrodes. The novel MoS₂-based electrode not only facilitates the utilization of MoS₂ in CDI but also paves the way for its application in other electrochemical domains.

Commercial Nd-Fe-B magnets without heavy rare earths (HREs) exhibit low coercivity and poor chemical resistance. Here, the coercivity and anti-corrosion performance of sintered Nd-Fe-B magnets have been successfully improved by grain boundary diffusion of Ni alloyed Dy-Co alloy. Starting from Dy-Co binary alloy, the composition of diffusion source was optimized by modifying Dy/Co ratio and Ni substitution for Co. The coercivity of the magnet was enhanced by Dy₆₀Co₁₀Ni₃₀ diffusion with relatively low Dy content from 1362 to 1853 kA/m, which is even 104 and 91 kA/m higher than those of the Dy₈₀Co₂₀ and Dy₇₀Co₁₅Ni₁₅ diffused magnets, respectively. The formation of higher anisotropic field of (Nd,Dy)₂Fe₁₄B and deep diffusion of Dy are the main reasons for the significantly enhanced coercivity. Partial substitution of Co by Ni cannot only promote the infiltration of Dy into the magnet, but also reduce the cost and improve the performance/cost ratio of diffused magnet. Meanwhile, Dy₆₀Co₁₀Ni₃₀ diffusion also improves the corrosion resistance of the magnet by minishing the corrosion electric current density from 9.93 to 3.45 μA·cm⁻². The present results indicate that Ni in diffusion source is conducive to simultaneously improving coercivity and chemical stability.

Herein, the synthesis and application of an entirely novel ZnIn₂S₄/Co(acac)₂ (ZIS-Co-2) nanocomposite for degradation of hazardous pesticide imidacloprid (IMD) under visible-light irradiation has been investigated. The ZIS-Co-2 nanocomposite demonstrated an outstanding 97.43 ± 1.84 % removal effectiveness against IMD within 60 min of 23 W LED. This improved catalytic performance was attributable to synergistic effects from ZnIn₂S₄ doping, which significantly delayed charge recombination and boosted visible-light absorption, promoting efficient photocatalytic degradation. Furthermore, the degradation of IMD was thoroughly verified using chemical oxygen demand (COD), and the total organic carbon (TOC) removal and breakdown mechanism was elucidated using liquid chromatography-mass spectrometry (LC-MS). Notably, the ZIS-Co-2 nanocomposite revealed outstanding recyclability, preserving catalytic activity for up to six cycles and the ability to degrade other emerging contaminants. Furthermore, neither Co(acac)₂ nor the combination of ZnIn₂S₄ with metal complexes has been previously produced or explored for visible light-active photocatalytic applications, highlighting the originality of our study. Overall, the ZIS-Co-2 nanocomposite is a promising and sustainable solution for efficiently removing IMD and other environmental pollutants, with significant practical implications in wastewater treatment and environmental restoration.

This study investigates the electrochemical performance of Ti₃C₂T_x MXene-coated cotton fabric electrodes for supercapacitor applications. The sediment and supernatant parts of synthesized Ti₃C₂T_x MXene were applied onto cotton substrates through a drop-casting technique at various concentrations to explore the influence of MXene dispersion density on the structural, morphological, and electrochemical properties of the fabric electrodes. Findings indicate that the lower-concentration dispersions not only improve the structural integrity of the coatings but also enhance their electrochemical functionality. The fabric electrodes fabricated from MXene supernatant exhibited significantly lower electrical resistance (7.3 Ω sq⁻¹) and higher specific capacitance, reaching 488 F g⁻¹ at a current density of 0.5 A g⁻¹. The study demonstrates the potential of MXene-coated fabrics as adaptable and efficient energy solutions for wearable technologies, highlighting that tuning the concentration and post-synthesis parameters of MXene dispersions can effectively alter their electrochemical properties.

The design of Z-scheme heterojunction to realize the efficient separation of charge carriers still remain challenging. Herein, the defect-assisted Z-scheme heterojunction strategy has been proposed. The binary ZnS/CoS_x nanospheres were successfully prepared via a well-designed hydrothermal approach. The resultant ZnS/CoS_x nanospheres with CoS_x content of 5 wt% exhibit the optimal hydrogen production rate of 2546.6 μmol g⁻¹ h⁻¹, which is 2.6 times higher than that of pure ZnS and superior to the most reported ZnS-based composites. The enhancement of S-vacancy concentration can greatly strengthen photocatalytic hydrogen evolution property, which can be originated from the boosted direct Z-scheme charge-transfer process in ZnS/CoS_x heterostructures. The synergistic effect of direct Z-scheme heterostructures and defects engineering notably enhances the photocatalytic activity of ZnS/CoS_x nanospheres, which could provide a deep insight for the design and synthesis of new types of photocatalysts.

We report Cr doping-induced structural phase transformation (PT) in sputter-deposited polycrystalline-AlN thin film from wurtzite (w) to rocksalt (r) structure. Rietveld analysis shows that the steady substitution of Al ions by Cr ions in the w-AlN lattice distorts and compresses the wurtzite lattice along the c-axis. The chemical pressure exerted in the w-AlN lattice by the compression from the doped Cr ions causes the PT, similar to the high-pressure-induced PT in AlN. Post the PT, the r-Al_1-xCr_xN thin film continues to exhibit compressive residual stress, indicating that such sustained stress may also play a role in stabilizing the metastable r-Al_1-xCr_xN phase. The structural distortion and the PT also affected the optical absorption characteristics of the w-Al_1-xCr_xN thin films. The w-Al_1-xCr_xN exhibit a direct inter-band transition and the band gap (E_g) decreases from ∼ 6.06 eV for pure w-AlN to ∼ 4.15 eV for w-Al_0.73Cr_0.27N. After the PT, the r-Al_0.61Cr_0.39N thin film, on the other hand, exhibits an indirect inter-band transition with an E_g of ∼ 1.84 eV. In addition to the change in E_g, a prominent defect band appears at ∼ 4 eV at low Cr% and another band appears at ∼ 0.98 eV at higher Cr%.

Hybrid systems of two-dimensional (2D) materials (such as graphene-family materials and 2D transition metal dichalcogenides) are attracting much attention due to their distinctive optoelectronic, thermal, mechanical, and chemical properties. The application perspectives of these materials in various fields further expand when enriching those with liquid crystals (LCs) primarily due to their enhanced tunability and functionality. In this study, we report on the hydrothermal synthesis of hybrid nanocomposites composed of MoS₂ and rGO and discuss tuning possibilities of their electro-optical properties by incorporating thermotropic LCs. In particular, we demonstrate that the incorporation of 5CB LC increases the sensitivity and charge storage efficiency of the hybrid nanocomposites. In addition, we also present the responsivity, detectivity, and response time properties of the hybrid nanocomposites of MoS2/rGO, both with and without the inclusion of nematic LCs. Furthermore, we demonstrate that the system exhibits a 5CB-induced photocurrent switching effect. We believe the findings will open new doors for applications of these materials in optoelectronics and photonics.

There is an urgent need for synthesizing red emitting phosphor with high photoluminescence quantum yield (PLQY) and good thermal stability for high performing phosphor converted light emitting diodes (pc-LEDs) which are in demand to mitigate carbon emission. Here we have achieved the same through symmetry alteration and structural modification strategy which leads to high PLQY and improved thermal stability. In this work we have synthesized highly symmetric cubic fluorite Y₂Zr₂O₇:Eu³⁺pyrochlore and replacing the B-site Zr⁴⁺by Ge⁴⁺ to lower the symmetry and induce structural change to tetragonal Y₂Ge₂O₇:Eu³⁺ by organic solvent free solid state reactions. Among the three composition Y₂Ge₂O₇: Eu is exhibiting higher emission intensity, higher asymmetry ratio and enhanced PLQY (32.3 %) by virtue of lower symmetry of tetragonal phase. On the other hand, higher thermal stability was achieved for Y₂Zr₂O₇: Eu (97 % at 450 K) endowed by higher structural integrity and stability of pyrochlore phase.

The plasmonic applications at low temperatures of metallic nanoparticles in glasses doped with rare-earth ions are not yet covered in-depth analysis in the literature. This paper insights into the coupling between gold nanoparticles and Er³⁺ embedded in tellurite glasses via luminescence enhancement of the emission centred at 1.53 µm under controlled temperature. This enhancement is obtained for the sample with 24 h of heat treatment (TErAu24) concerning the Er³⁺ single doped (TEr) at room temperature under 980 nm excitation. The enhancement remains under cooling conditions, consequence of the strong coupling between the plasmon and the Er³⁺, attributed to an increment of the localized plasmon mode volume at low temperatures. Further, the band area increment of the TErAu24 sample comparing the spectra at 98 and 348 K is 414 %, whereas for the TEr is about 348 %. These findings provide advanced understanding of the plasmonics on quantum emitters engineering.