ChemNanoMat最新文献

Cobalt ferrite (CFO) nanoparticles (NPs) are highly promising for data storage, energy conversion, permanent magnets, and biomedical applications owing to their exceptional magnetic properties. However, the presence of phase impurities (particularly FeO and CoO) can severely degrade their magnetic properties, hindering their practical use. Here, we present a simple post-synthesis oxidation approach to address this challenge. Our method involves the thermal decomposition of Fe−Co oleate followed by oxidation using trimethylamine N-oxide. The results reveal the effective elimination of FeO and CoO impurities and the formation of spinel ferrite crystal structures post-oxidation with no change in morphology or size. Magnetic measurements demonstrate a significant enhancement in magnetic properties (e. g., magnetic saturation, coercivity, and blocking temperature) in oxidized CFO NPs compared to the non-oxidized counterparts, indicative of the recovered ferrimagnetic structure upon post-synthesis oxidation. As expected, the restoration of the ferrimagnetic structure, resulting in improved magnetic anisotropy, led to decreased SAR values as the nanoparticles moved away from the optimal anisotropy range. The study underscores the necessity of post-synthesis oxidation for ensuring phase purity and enhancing the magnetic properties of CFO NPs, irrespective of the synthesis method. This approach offers a promising route for producing highly functional magnetic nanoparticles for practical applications.

Copper-doped ceria (CuCeO₂) catalysts with 0–26.5 Cu/(Cu+Ce) at% were synthesized via the reverse microemulsion method. X-ray diffraction analysis of freshly synthesized and spent (post-reaction) catalysts showed no separate phase of copper or copper oxide, indicating that Cu was incorporated into the CeO₂ lattice, replacing Ce. Temperature programmed desorption experiments showed that the activation energy of CO₂ desorption increased for higher Cu loadings, indicating stronger CO₂ adsorption. This phenomenon was attributed to enhanced formation of oxygen vacancies due to Cu doping. X-ray photoelectron spectroscopy further confirmed the enhanced generation of oxygen vacancies due to Cu incorporation. Catalytic performance evaluation with the H₂/CO₂ feed in the 300–600 °C range showed that all catalysts were 100 % selective to CO generation, with higher Cu loadings resulting in CO₂ conversion close to equilibrium values at 500–600 °C. The activation energy of the reaction, determined through reaction tests, exhibited inverse relationship with the activation energy of CO₂ desorption. The relationship between these two energy barriers is explored, providing valuable insights into the mechanism of RWGS activity enhancement.

Ceramide3 (Cer3) is one of the important components of stratum corneum (SC) lipids with good moisturizing and repairing properties. However, it suffers from (a) poor solubility, (b) easy crystallization and precipitation, and (c) strong polarity and difficulty in transdermal application. This study aimed to load Cer3 into nanoemulsions (NEs) to overcome these mentioned defects. The optimized NEs formulation was prepared by high pressure homogenization method and characterized by several methods. The optimized ceramide3 nanoemulsions (Cer3-NEs) exhibited a good physico-chemical stability over 3 months under different conditions, with droplet size of 103.1 nm, PDI of 0.178, zeta potential of −39.09 mV, pH of 6.20 and encapsulation efficiency of 96.39 %. Turbiscan results showed that formulations containing Cer3-NEs have better stability than those containing free Cer3. The dermal delivery ability of Cer3-NEs was assessed by Franz diffusion and confocal Raman spectroscopy (CRM). In vitro and in vivo penetration studies showed that Cer3-NEs serum have almost 2–3 times higher retention in the skin and permeation in the receptor solution compared to serum with free Cer3. The findings show NE is a promising carrier of Cer3 for topical administration in the treatment of dryness and barrier damage due to higher stability and better skin permeability.

Nanozymes-involving colorimetry may represent an effective solution to tetracycline detection due to its affordability and simplicity. To improve the performance in selectivity, molecular imprinting technology has emerged as a promising approach to simulating the interaction between antibodies and receptors. Herein, Mn₂V₂O₇, a form of nanozyme with oxidase-mimicking activity, was synthesized. With tetracycline as the template, the cavities with unique dimensions were constructed through the self-polymerization of dopamine (DA) on Mn₂V₂O₇. In Mn₂V₂O₇@MIP, polydopamine (PDA) acts as molecularly imprinted polymer (MIP) and its cavities are compatible with tetracycline in dimension. It also exhibits oxidase-mimicking activity. With the introduction of tetracycline, the cavity of PDA is blocked, which leads to obvious color fading, which enables precise tetracycline detection with colorimetry. The range of linear detection is from 10 to 100 μM, and the lower limit of detection is 0.82 μM. It is anticipated that the combination between nanozymes-involving colorimetry and molecular imprinting technology would contribute to the accurate detection of organic pollutants in the aquatic environment.

Ag₂Se is categorized as a typical ′phonon-liquid-electron-crystal (PLEC)′material, exhibiting an extremely low $$. In this study, Al substituted Ag₂Se samples were synthesized by mechanical alloying process followed by hot press densification technique. The Al substituted sample shows an exceptionally high mobility of 2360 cm² V⁻¹ S⁻¹ at room temperature and a maximum power factor of 1442 μWm⁻¹ K⁻² at 383 K. The phonon scattering induced by various crystal imperfections due to Al substitution helped to obtain a very low lattice thermal conductivity $$ value of 0.3 W/mK. A high figure of merit (zT) of 0.4 at 383 K was obtained as a result of the simultaneous effect of boosting the electrical transport properties and decreasing the thermal conductivity. This present work summarizes that the Al substitution is highly significant in improving the thermoelectric properties of Ag₂Se.

This work presents a systematic study to synthesize NiO on nickel foam (NF) using a straightforward and cost-efficient hydrothermal method, followed by calcination. Through comprehensive physicochemical analyses, it was demonstrated that the properties of the NF@NiO could be modulated by adjusting the concentration of the nickel (II) nitrate hexahydrate precursor. Notably, a morphological transition from a 2D sheet-like structure to a 3D rambutan-like formation was observed as the precursor concentration increased. The best-performing NF@NiO 4 mM showed a maximum areal capacity of 723 mC cm⁻² (equivalent to 547.73 F g⁻¹) at a current density of 0.5 mA cm⁻². This electrode also maintained remarkable cycle stability, retaining 78.9% of its capacitance after 10,000 cycles at a current density of 50 mA cm⁻² in 2 M KOH. Furthermore, the assembled asymmetric supercapacitor (ASC) (NiO 4 mM//AC) achieved a specific capacitance of 64.79 F g⁻¹ at a current density of 1 A g⁻¹ with an energy density of 17.63 Wh kg⁻¹ at a power density of 700 W kg⁻¹.

Zinc-air batteries (ZABs) with metal-free cathodes are considered environmentally friendly and cost-effective. However, more active and durable catalysts are required for this purpose. Herein, polyaniline (PANI)-derived carbon materials were obtained to boost the oxygen reduction reaction (ORR) and, consequently, the performance of a primary ZAB. The developed porous N-doped carbon (NDC) materials were engineered by varying the polymerization time and calcination temperature (500–900 °C). SEM micrographs and BET surface areas showed that the polymerization of aniline under cold conditions (5 °C) at 6, 8, or 24 h did not have a significant effect on the morphology or surface area. The fibrous structure of PANI was engineered by temperature, resulting in a progressive increase in the surface area until a three-dimensional porous structure was achieved at 900 °C with the highest area of 601.9 m² g⁻¹. The surface doping of nitrogen species shifted from PANI-rich N species to enriched graphitic N from 12.69 % (500 °C) to 24.26 % at 900 °C. The NDC 900 °C presented a voltage of 1.4 V and power density of 56 mW cm⁻² (only 7 mW cm⁻² lower than that of Pt/C). The results demonstrate that this material is an excellent candidate for high-performance primary ZABs.

New materials for oxygen evolution reaction (OER) electrocatalysts in alkaline conditions have been highly investigated in recent years for the advancement of water splitting. However, questions such as the lack of stability and the use of noble metals as electrocatalysts still need to be addressed. In this study, we report the synthesis and electrocatalytic properties of a series of wolframite tungsten-based materials (MWO₄, M=Fe, Mn, Ni, Co) towards OER in basic conditions. Our results showed that Ni_0.5Mn_0.5WO₄ is a promising electrocatalyst, exhibiting ease of preparation, stability over the course of our experiments, and OER activity comparable to the standard iridium oxide. This study highlights the potential of wolframite tungsten-based materials as a new class of electrocatalysts for OER in alkaline conditions.

Composite materials which combine the advantages of both embedded constituents have been a successful strategy for developing novel multi-functional materials. Here, we demonstrate the synthesis of nanoscale materials of organic-inorganic hybrid lead halide perovskites (OIH-LHP) with enhanced optoelectronic properties and photostability by utilizing biomimetic ligand, chitosan. Notably, nanocrystals fabricated with chitosan mediated ligands exhibit an increase in photoluminescence quantum yield by 300 % and fluorescence lifetime by 1.5 times. Consequently, the lifetime distribution of the photoluminescence emission decreases to a value as low as 6 ns. More interestingly, even though chitosan is a wide band gap insulating material, its incorporation onto the perovskite NCs enhances the bulk hole mobility by at least an order of magnitude in comparison to the pristine material. With detailed spectroscopic and structural studies, we correlate these enhancements in optoelectronic parameters to the improvement in the crystal quality, phase purity, and minimized poly-dispersity of the nanocrystals. Development of such composite materials with unprecedented optoelectronic properties and outstanding stability will contribute immensely towards high performance nanocrystal devices.

Static self-assembly resides in thermodynamically stable global minima of the energy landscape, whereas dynamic self-assembly occupies local minima of the energy profile and remains in the ordered state for a limited time via dissipation of energy to surroundings. This makes the spatiotemporal control over the assembly and disassembly mechanism easily controllable in the case of dynamic self-assembly. However, due to the higher thermal stability of static self-assembly, it is very challenging to perform reverse engineering on these types of systems. Herein we report growth reaction-based reversal of static silver cubes obtained via cucurbit[8]uril (CB[8]) crosslinked self-assembly of silver nanoparticles (AgNP). The AgNP building units with variable CB[8] surface coverage have been used as seeds onto which deposition of gold via growth reaction has been performed. The disassembly of supracube structure has been controlled by the formation of [AuCl₄]⁻–CB[8] complex and successive reduction of [AuCl₄]⁻ to Au⁰ on the surface of the seed. The resulting monodispersed isotropic nanoparticles, formed from the CB[8] based cubic self-assembly after growth, exhibit Au−Ag bimetallic nature. Quenching of the fluorogenic response from the hydrophobic dye coumarin-7, added after growth, suggests direct interaction with the metallic nanoparticle surface after disassembly and thereby confirms successful growth reaction mediated reversal of self-assembly.