Dispersion Of Nanoparticles Research Articles

Humidity-independent gas sensor based on Pt/SnO2/NiO with advanced CO sensing capabilities

Aimed at realizing the sensors capable of functioning effectively in high-humidity environments, the Pt/SnO2/NiO ternary composite materials featuring noble metal and p-n heterojunction structures was synthesized. The dispersion of SnO2 and Pt nanoparticles on NiO nanosheets was found to be excellent, resulting in a nearly twofold increase (99.45 m2g−1 of Pt/SnO2/NiO) in specific surface area compared to pure NiO materials (51.977 m2g−1). The CO sensitivity tests revealed that, in contrast to pure NiO sensors (with an optimal operating temperature of 290°C), Pt/SnO2/NiO ternary composites exhibited an optimal operating temperature (OOT) of 270℃, a decrease of 20℃ for CO detection at a relative humidity of 22 %. At this OOT, Pt/SnO2/NiO sensors consistently displayed high responsiveness (2.5 times higher than that of the pure NiO sensor), good selectivity, and rapid response-recovery times (the recovery time is reduced by nearly half compared to that of the pure NiO sensor). Furthermore, the sensors' responses to CO under different humidity conditions (from 22 % to 91 %) at 270℃ were investigated. The results demonstrated that Pt/SnO2/NiO sensors exhibited minimal variation in their response to CO at a range of relative humidity levels (41.5 % at 91 %, 39.5 % at 22 %, respectively). These results highlight that the enhancement of CO gas sensitivity in the sensors primarily results from the high catalytic activity of noble metal Pt and the p-n heterojunction interaction.

Collagen and chitosan-based biogenic sprayable gel of silver nanoparticle for advanced wound care.

Silver nanoparticles have gained significant attention recently due to their unique antibacterial properties, making them promising candidates for wound care applications. This study proposes a novel approach for advanced wound care using a silver nanoparticle-impregnated biogenic spray hydrogel supplemented with collagen and chitosan. Silver nanoparticles were incorporated into the hydrogel (optimized by a QbD approach) to impart antimicrobial activity, crucial for combating wound infections and promoting faster healing. The study assessed the physical and chemical properties of the biogenic hydrogel, including its viscosity, pH, and nanoparticle dispersion characteristics. In vitro, antimicrobial efficacy against common wound pathogens and in vivo studies using chronic wound models in small animals portrayed the immense potential of the developed biogenic hydrogel in effectively reducing the bacterial load of broad-spectrum pathogens. The hydrogel exhibited excellent biocompatibility, supporting cell proliferation and tissue repair without toxic effects. It accelerated wound healing, improved collagen deposition, and enhanced tissue regeneration in the tested animals by reducing proinflammatory cytokines, ROS, and NF-kb levels. Overall, this innovative silver nanoparticle-impregnated biogenic spray hydrogel of collagen and chitosan presents a uniform spray pattern that proved efficient, showing a promising solution for advanced wound care. Its biocompatibility, safety, anti-inflammatory, antimicrobial efficacy, and wound healing properties hold great potential for improving the management of complex wounds, opening new avenues in wound care and regenerative medicine.

Multi-level pumping water system from bioengineering wood microstructure by self-growing mycelium for boosting photothermal evaporation efficiency

Due to low cost, renewability, high porosity and eco-friendliness, wood has been widely used to design solar steam generation devices, displaying great promise for clean water production in desalination and wastewater treatment. However, cleaner preparation processes and efficient structure design of wood based interfacial evaporators still need further exploration and development. Here, we reported an eco-friendly bio-incising method of wood microstructure modulation to fabricate high-performance wood-based solar steam generator by creating multi-level pumping water system. Self-growing Trametes versicolor (TV) which is a kind of bothersome wood fungus was skillfully used to increase porosity of wood and form interweaved mycelia fibers on wood surface, achieving the resegmentation and transmission of water bodies. These water-absorbing cell fibers and porous wood substrate collectively form a multi-level pumping water system ensuring effective heat management and high water evaporation area. Coupling with densely dispersed polydopamine nanoparticles (PDA NPs) on the surface of TV fiber for light absorption enhancement, the designed wood based solar steam generator with a smallest thickness of 1 mm shows outstanding evaporation rate (1.61 kg·m−2·h−1) and solar energy conversion efficiency (98.4 %) under simulated 1 sun irradiation. Moreover, the obtained clean water using as-prepared steam generator shows high removal rates both in simulated seawater and wastewater. This work presents a novel concept and green method for designing high-performance wood-based solar steam generator with multi-level pumping water system.

Colloidal gold dispersions in orogenic gold from the Barberton Greenstone Belt, South Africa

The mechanisms of gold grain growth, as a necessary precursor to gold hyper-accumulation and the formation of high-grade ore deposits, remain equivocal. This is particularly true for orogenic gold deposits where primary growth textures may be poorly preserved due to episodic fault re-activations during successive seismic events. A sample collected from the Fairview Mine in the Barberton Greenstone Belt (South Africa) and subjected to non-destructive SELFRAG sample preparation and subsequent scanning electron microscopy provides rare capture of images of millimeter-scale gold grains associated with dispersed spheroidal gold colloids and nanoparticles (<5 nm to >1 µm diameter). Although the ultimate provenance of these gold spheroids remains equivocal, textural evidence suggests a net addition of mass to the adjacent gold grains. We suggest that Ostwald ripening (a process of particle growth or coarsening by diffusion) and coalescence may contribute to gold grain growth in this sample.

1D, 2D, and 3D Micropatterning of ZnO Nanoparticles and Nanorod by Two‐Photon Polymerization and Surface Functionalization

AbstractIn this paper, a novel method is proposed for selective deposition of ZnO nanoparticles (NPs) and growth of ZnO Nanorods (NRs) on multi‐dimensional patterned polymer surfaces. The method involves microfabrication of functionalized 1D, 2D, and 3D polymer structures by two‐photon polymerization (TPP) followed by selective assembly of ZnO NPs acting as seeds before growing ZnO NRs by chemical bath deposition (CBD) technique at low temperature. The immobilization of the ZnO NPs seed layer is done by electrostatic interaction between the positively charged polymer surface functionalized by amine groups and the negatively charged ZnO NPs functionalized by citrate molecules. The influence of citrate molecules on the stability of the ZnO NPs dispersions and their immobilization on the polymer surface is demonstrated. Spatially controlled and selective growth of ZnO NRs is shown at low temperatures on multi‐dimensional structures up to 9 mm2 and having different shapes, including 1D polymer lines, 2D microplates, and 3D arrays of cones. The diameter of NRs and their orientation can be controlled through the size of ZnO NPs and the shape of the polymer structure respectively.

Investigation of mechanical and electrical properties of photopolymer nanocomposites reinforced with carbon‐based nanoparticles produced by digital light processing 3D printing technique

AbstractDigital Light Processing (DLP) techniques are being increasingly investigated to create advanced composite materials with improved properties by incorporating a variety of nanoparticles. In this study, the mechanical and electrical properties of photopolymer nanocomposite materials reinforced with carbon‐based nanoparticles produced by DLP were investigated. The nanocomposites were produced by incorporating varying proportions of Multi‐Walled Carbon Nanotubes (MWCNT), reduced Graphene Oxide (rGO), and combinations of Carbon Black and Carbon Nanotubes (CB/CNT) into the photopolymer matrix. The mechanical properties of the nanocomposites were assessed by tensile testing, while their electrical conductivity was determined using the four‐point probe technique. This study was the first to investigate the most effective concentrations of three distinct carbon‐based nanoparticles and the impact of their homogeneous distribution on the performance of composites with a holistic approach. The morphological analysis of the composites, conducted using optical microscopy and Scanning Electron Microscopy (SEM), revealed the critical role of nanoparticle distribution in determining composite properties. The findings indicate that the incorporation of nanoparticles at low proportions (up to 0.5 wt%) resulted in a significant improvement, with up to an 82% increase in the ultimate tensile strength of the photopolymer. Nevertheless, as the nanoparticle ratio increased, a rise in material brittleness and a decrease in mechanical strength were observed. On the other hand, electrical conductivity showed a significant increase when the percolation threshold was exceeded in the composites reinforced with MWCNT (0.5%wt) and CB/CNT (0.75%wt).Highlights The properties of DLP composites with carbon nanoparticles are investigated. SEM analysis shows nanoparticle dispersion's key role in composite performance. 0.5% rGO reinforcement boosts tensile strength by up to 82%. Conductivity surges at 0.5% MWCNT, surpassing the percolation threshold. High nanoparticle ratios increase composite brittleness.

P(MMA-GMA-AM-St) as transition layer for constructing GO@pPTFE core-shell nanoparticles as hydro-based lubricant additives towards excellent friction reduction and wear resistance

Although polytetrafluoroethylene (PTFE) has attracted significant attention in the lubrication field, it is still challenging for PTFE with low surface energy to achieve uniform dispersion in hydro-based lubricant. Interface regulation is considered as an effective strategy to enhance the dispersibility of PTFE nanoparticles in water. Here, we proposed to improve the interfacial property of PTFE via constructing a poly(methyl methacrylate-co-glycidyl methacrylate-co-acrylamide-co-styrene) transition layer (P(MMA-GMA-AM-St)), which containing rich hydrophilic groups on the surface. Then, graphene oxide@pPTFE (GO@pPTFE) core-shell nanohybrids were prepared by hydrogen bonding-driven self-assembly. Water contact angle (WCA) of GO@pPTFE nanohybrids showed ultra-hydrophilic properties. With the addition of 0.05 wt% GO@pPTFE nanohybrids, friction coefficient (COF) and wear rate (Wr) of the hydro-based lubricant were greatly reduced by 69.4 % and 61.8 %, respectively. Even after a long period of friction (extending up to 120 min), the Wr of GO@pPTFE nanohybrids was an order of magnitude lower than that of pristine PTFE nanoparticles. The improved tribological performance of GO@pPTFE nanohybrids could be benefited from the synergistic effect of the PTFE and GO. Our study advanced the understanding of the intrinsic mechanisms underlying friction and wear by establishing a robust connection between morphological evolution, lubricant film stability, theoretical calculation, and tribological property at the microscopic scale.

Construction of directional electron transfer from Pt to MoO2-x in macroporous structure for efficient hydrogen oxidation

Hydrogen oxidation reaction (HOR) as the anode reaction in proton exchange membrane fuel cell, usually suffers from the high loading of platinum (Pt) and subsequent CO poisoning especially by using industrial crude hydrogen as fuel. In this work, we propose a directional electron transfer route from Pt to MoO2-x in the macroporous structure to significantly enhance the HOR activity as well as the CO tolerance, which is constructed by interface engineering and defect strategy to anchor highly dispersed Pt nanoparticles onto the three-dimensional MoO2-x-C framework. The optimized 2Pt-MoO2-x-C with 1.02 wt% Pt demonstrates higher HOR peak current density (3.57 mA cm−2) and nearly 25 times higher mass activity than 20 wt% Pt/C. The excellent HOR performance is attributed to the synergistic effect between Pt and MoO2-x species, in which the charge transfer from Pt to MoO2-x improves H2 adsorption ability of Pt and accelerates the activation of H2 due to the reduced hydrogen binding energy of MoO2-x caused by Pt-O construction, leading to the release of H* thereby the enhancement of HOR activity. The construction of three-dimensional macroporous structure enhances the HOR dynamics by promoting the conductivity, mass transfer and the exposure of active sites. Moreover, the formed Mo-OH in Pt-MoO2-x-C can effectively react with CO species to remove the CO poisoning of Pt, endowing the excellent CO tolerance.

The investigation of highly efficient chlorinated hydrocarbons removal based on metal nanoparticles carbonaceous synthetic particles: The degradation behavior and selective transformation mechanism

Overconsumption in industrial manufacturing has led to critical emissions of chloroalkanes, posing a significant environmental threat. In this study, the innovative biochar (BC) particles containing nanocrystalline: NZVI, Fe/Pd, Fe/Ni were prepared by impregnation-liquid phase reduction using the pyrolysis of coconut husk as precursors to explore the degradation capabilities of chloroform (CF) via orthogonal experiment. The results indicated that when the pH value was 3, the temperature was 20 ℃, and the reaction time was 60 min, the CF removal efficiency of Fe/Ni-BC reached 80.38 ± 2.08 %, outperforming all other tested synthetic particles. Advanced characterization techniques showed that the abundant dispersed metallic nanoparticle sites would refresh the surface crystal morphology, improve the adsorption enrichment ability of biochar, enhance electron transfer capacity of synthetic particles, and further participate in reductive dechlorination by inducing an electrophilic attack of active hydrogen. Theoretical calculations verified that hydrogen activation and CF facile adsorption would be easily achieved after the introduction of metal nanoparticles, profiting from the multiple synergistic effects between special π-delocalized bond of biochar in carbon layer and multiple nanoparticles docking sites, and thus enhancing the specific CF catalytic selectivity of Fe/Ni as the active center. Collectively, the CF degradation on Fe/Ni-BC was a complex chemisorption process along with reductive hydrogenation decomposition, which achieved the parent CF reduction and promoted the conversion of the low-chlorinated benign products. These findings offer new insights into the developed multifunctional BC and their comprehensive assessment of CF sewage remediation.

Ammonia Decomposition via MOF-Derived Photothermal Catalysts.

Three cobalt-based metal-organic framework (MOF)-derived catalysts were developed for photothermal hydrogen production via ammonia decomposition. The selected MOFs were from distinct families, featuring carboxylate and imidazole linkers, and diverse in terms of porosity. The resulting catalysts consisted of uniform and homogeneously dispersed cobalt nanoparticles embedded within a carbon matrix. The carboxylate-based MOF-74 derived catalyst showed the highest initial activity, but gradually deactivated. ZIF-67 derived catalyst, however, demonstrated stable performance. The synergy between photo and thermal effects was confirmed. Additionally, this catalyst was found to be also effective in ammonia synthesis, potentially closing the loop for sustainable ammonia utilization.

Effect of Al2O3 and ZrO2 nanoparticles on microstructure and mechanical properties of Mg-AZ91 hybrid nanocomposites

In the present study, magnesium (Mg) hybrid nanocomposites containing alumina (Al2O3: 1 wt%) and zirconia (ZrO2: 0.5 and 1 wt%) nanoparticles (<50 nm) are fabricated using the stir casting technique under the protection of flux material. Role of two different nanoparticles is analysed on the performance of developed hybrid nanocomposites for implant applications. Compared to the monolithic Mg alloy, microstructural characterization revealed a reasonably uniform dispersion of nanoparticles in the matrix and a reduction in grain size in the hybrid nanocomposites. The addition of nanoparticles enhanced the microhardness and ductility of the composites. SEM, XRD and EDS are used to characterize the prepared composites. The contribution of both nanoparticles to the strengthening mechanisms are analyzed. The microhardness of AZ91 was increased from 61.4 (base alloy) to 68.79 in hybrid nanocomposites. The tensile strength of hybrid nanocomposites was found to increase from 65 MPa to 80 MPa. Adding Al2O3 nanoparticles resulted in improved grain refinement while adding ZrO2 led to an increase in microhardness. Overall, the addition of hybrid reinforcement resulted in better mechanical properties by balancing the strength and ductility of the developed nanocomposites.

Mathematical and Buongiorno nanofluid modelling to predict the thermal and solutal performance of magneto-bioconvective Casson nanofluid flowing in a rotatory disk

Abstract This study aims to improve how heat and mass move in systems that use viscoelastic nanofluids under magnetic fields. These systems are commonly used in industries like biotechnology, energy, and medical devices. The significance of this work lies in exploring the steady flow of magnetohydrodynamic (MHD) Casson nanofluids, incorporating the Buongiorno nanofluid model and swimming microorganisms. This research seeks to deepen the understanding of complex fluid behaviors by examining the effects of thermal radiation and chemical diffusion under thermal and solutal convective boundary conditions. The governing equations, which are inherently nonlinear due to the presence of multiple physical effects, are converted from two-dimensional partial differential equations (PDEs) to ordinary differential equations (ODEs) using a similarity transformation. A semi-analytical solution is derived using the collocation pseudo-spectral method within the MAPLE computational software. The study investigates how factors like Casson and magnetic parameters, Eckert number, Brownian motion, and thermophoresis affect the flow rate, temperature distribution, species concentration, and microorganism motility. These results are validated by comparing them with established benchmarks. The key findings reveal a pronounced oscillatory behavior in the temperature profile at higher Eckert number values, while increased Brownian motion and thermophoresis lead to greater nanoparticle dispersion near the disk surface. Higher Lewis and Peclet numbers lead to increased microorganism concentration, demonstrating stronger convective and advective effects. These insights are vital for optimizing drag force, thermal gradients, and mass transfer in engineering applications that involve rotating disks and magnetic fields.

Turning on Low-Temperature Catalytic Conversion of Biomass Derivatives through Teaming Pd1 and Mo1 Single-Atom Sites.

On-purpose atomic scale design of catalytic sites, specifically active and selective at low temperature for a target reaction, is a key challenge. Here, we report teamed Pd1 and Mo1 single-atom sites that exhibit high activity and selectivity for anisole hydrodeoxygenation to benzene at low temperatures, 100-150 °C, where a Pd metal nanoparticle catalyst or a MoO3 nanoparticle catalyst is individually inactive. The catalysts built from Pd1 or Mo1 single-atom sites alone are much less effective, although the catalyst with Pd1 sites shows some activity but low selectivity. Similarly, less dispersed nanoparticle catalysts are much less effective. Computational studies show that the Pd1 and Mo1 single-atom sites activate H2 and anisole, respectively, and their combination triggers the hydrodeoxygenation of anisole in this low-temperature range. The Co3O4 support is inactive for anisole hydrodeoxygenation by itself but participates in the chemistry by transferring H atoms from Pd1 to the Mo1 site. This finding opens an avenue for designing catalysts active for a target reaction channel such as conversion of biomass derivatives at a low temperature where neither metal nor oxide nanoparticles are.

A green approach to improve antibacterial properties of PVC/PVDF film doped by silver nanoparticles via nanosecond laser ablation for wound healing application

Nanocomposite films of (30% PVC/70% PVDF) blend containing silver nanoparticles were synthesized via pulsed laser ablation route (PLA). Changes in physical characterization of PVC/PVDF blend before and after the incorporation of AgNPs have been studied. FTIR results confirms the interaction between AgNPs and PVC/PVDF. XRD results obtain the existence of peak at 38.42̊ in sample PVC/PVDF/Ag4 which confirm the embedded AgNPs in the high concentration. SEM photos confirm the distribution of silver nanoparticles on the surface of the sample in spherical shape which approved the dispersion of silver nanoparticles in PVC/PVDF blend. The inhibitory zone diameters observed for PVC/PVDF/Ag4 against Escherichia coli, Klebsiella pneumonia, Staphylococcus aureus, and Bacillus cereus were recorded as 11 ± 1, 10 ± 1, 15.7 ± 0.6, and 17.7 ± 0.6, respectively. PVC/PVDF/AgNPs nanocomposite film could be suggested for biomedical applications such as wound healing products.

Recent Advances in Hybrid Nanocomposites for Aerospace Applications

Hybrid nanocomposites have emerged as a groundbreaking class of materials in the aerospace industry, offering exceptional mechanical, thermal, and functional properties. These materials, composed of a combination of metallic matrices (based on aluminum, magnesium, or titanium) reinforced with a mixture of nanoscale particles, such as carbon nanotubes (CNTs), graphene, and ceramic nanoparticles (SiC, Al2O3), provide a unique balance of high strength, low weight, and enhanced durability. Recent advances in developing these nanocomposites have focused on optimizing the dispersion and integration of nanoparticles within the matrix to achieve superior material performance. Innovative fabrication techniques have ensured uniform distribution and strong bonding between the matrix and the reinforcements, including advanced powder metallurgy, stir casting, in situ chemical vapor deposition (CVD), and additive manufacturing. These methods have enabled the production of hybrid nanocomposites with improved mechanical properties, such as increased tensile strength, fracture toughness, wear resistance, and enhanced thermal stability and electrical conductivity. Despite these advancements, challenges remain in preventing nanoparticle agglomeration due to the high surface energy and van der Walls forces and ensuring consistent quality and repeatability in large-scale production. Addressing these issues is critical for fully leveraging the potential of hybrid nanocomposites in aerospace applications, where materials are subjected to extreme conditions and rigorous performance standards. Ongoing research is focused on developing novel processing techniques and understanding the underlying mechanisms that govern the behavior of these materials under various operational conditions. This review highlights the recent progress in the design, fabrication, and application of hybrid nanocomposites for aerospace applications. It underscores their potential to revolutionize the industry by providing materials that meet the demanding requirements for lightweight, high-strength, and multifunctional components.

A General Approach for Metal Nanoparticle Encapsulation Within Porous Oxides.

Encapsulation of metal nanoparticles within oxide materials has been shown as an effective strategy to improve activity, selectivity, and stability in several catalytic applications. Several approaches have been proposed to encapsulate nanoparticles, such as forming core-shell structures, growing ordered structures (zeolites or metal-organic frameworks) on nanoparticles, or directly depositing support materials on nanoparticles. Here, a general nanocasting method is demonstrated that can produce diverse encapsulated metal@oxide structures with different compositions (Pt, Pd, Rh) and multiple types of oxides (Al2O3, Al2O3-CeO2, ZrO2, ZnZrOx, In2O3, Mn2O3, TiO2) while controlling the size and dispersion of nanoparticles and the porous structure of the oxide. Metal@polymer structures are first prepared, and then the oxide precursor is infiltrated into such structures and the resulting material is calcined to form the metal@oxide structures. Most Pt@oxides catalysts show similar catalytic activity, demonstrating the availability of surface Pt sites in the encapsulated structures. However, the Pt@Mn2O3 sample showed much higher CO oxidation activity, while also being stable under aging conditions. This work demonstrated a robust nanocasting method to synthesize metal@oxide structures, which can be utilized in catalysis to finely tune metal-oxide interfaces.

Effects of nanodiamonds on the mechanical properties, acoustic properties, vibration damping, and flame retardancy of ramie-fiber epoxy composite panels used for indoor applications

This research aims to systematically analyze the impact of nanodiamonds (NDs) in ramie fiber-reinforced epoxy resin acoustic panels used for indoor applications. The panels (four variants) are fabricated using six layers of ramie fiber with various weight percentages of NDs (0.0, 0.2, 0.4, and 0.6) in epoxy resin by the vacuum resin infusion process (VRIP). Mechanical characterization (tensile and flexural strength) was carried out using Instron 8801 universal testing machine. The impedance tube-based sound absorption coefficient (SAC) test was performed at low frequency and higher frequency, respectively. The void content in the panel is evaluated using a micro-x-ray computed tomography (CT) scanner. The dispersion of nanoparticles is studied using scanning electron microscopy (SEM) images. The vertical flame-retardant test and the horizontal flame-retardant test were conducted according to the UL-94 standard. The 0.4 wt.% NDs sample showed good tensile strength (59.178 MPa) and flexural strength (69.134 MPa) compared with other panels. The panels showed differences in SAC values for different weight percentages of NDs, both at lower and higher frequencies. The 0.6 wt.% NDs sample attained the maximum SAC of 0.906 at 6000 Hz in the high-frequency and 0.34 at 1112 Hz in the low-frequency. The SEM reveals an even distribution of NDs in both the 0.2 and 0.4 wt.% NDs panels, while agglomerates form in the 0.6 wt.% panels. The CT scan result shows void content both internally and externally in the panels. There are no voids in the panels where NDs are uniformly distributed. The synergistic effect of NDs in epoxy resin forms a char over the burnt surfaces of samples, enhancing the flame-retardant properties of the panels. According to this study, adding NDs to ramie fiber epoxy composites has improved the panels’ necessary qualities, making them suitable for use as indoor acoustic conditioning materials.

Boosting hydroisomerization of n-hexadecane by designing core-shell bifunctional catalysts with partially blocked micropores

Hydroisomerization of long-chain n-alkanes is an indispensable route for upgrading fossil fuels and lubricant oils to meet the state of art regulations. Precisely regulate the distribution of acidic and metal active sites to suppress unwanted cracking reaction is hitherto a difficult task. In this work, we develop a simple coating-carbonation strategy for constructing novel core-shell bifunctional catalysts, comprising ZSM-22 zeolite core with the partially blocked channels and Pt nanoparticles loaded on the mesoporous SiO2 shell. The unique treatment not only adjusted the distribution of acid sites located within the micropore channels and external surface, but also alter the locations and dispersion of Pt nanoparticles. Owing to the short diffusion lengths, nanoscale distance between acid sites and Pt species, and high metal dispersions, the core-shell bifunctional catalyst exhibits outperformed performance in n-hexadecane hydroisomerization, i.e., the yield of isomerized hexadecane can reach 87.9 %, which is among the relatively high level compared with the previous reported Pt/zeolite counterparts. Moreover, the catalyst also displays excellent stability (no deactivation within 100 h). The disclosed structure-catalysis relationship provides rational reference for designing the synergistic meta-acid active sites in the hydroisomerization of long-chain n-alkanes.

Poly(lactic acid) and copper‐modified montmorillonite nanocomposite films for antimicrobial food packaging

AbstractPolymer‐based nanocomposites loaded with metal nanoparticles are an interesting alternative for the development of antimicrobial food packaging. However, affinity and dispersion of metal nanoparticles could be improved using nanoclays. Therefore, nanocomposite films based on poly(lactic acid) (PLA) and copper modified‐montmorillonite were developed by melt‐extrusion technique. Copper‐modified montmorillonite at different valence states (MtCu2+ and MtCu0) were prepared. The nanocomposites were evaluated by means of their structural, optical, thermal and antimicrobial properties. Results showed that both nanoclays were intercalated in PLA but MtCu2+ was better dispersed. Therefore, color change ΔE &lt; 2, higher thermal stability and higher elongation at break was evidenced for MtCu2+/PLA in comparison to pure PLA. Contrary, MtCu0 showed the displacement of Cu0 nanoparticles to the polymer matrix. These free nanoparticles were agglomerated and they leaded on a ΔE &gt; 9 for MtCu0/PLA nanocomposites compared with PLA. Moreover, Cu0 nanoparticles in the matrix accelerated the thermal degradation and decreased the ductility of nanocomposites. On the other hand, both nanocomposites were able to reduce over 2 log10 of Escherichia coli growth and MtCu2+/PLA showed a higher antimicrobial activity against Listeria innocua. These results showed the potential of nanocomposite films based on PLA and copper‐modified montmorillonite for antimicrobial food packaging applications.

The fabrication of graphene supported Ni nanoparticles and its doping influence on the microstructure and superconductivity of MgB2

A highly dispersed Ni nanoparticle supported on a graphene matrix (nano-Ni/G) has been successfully synthesized using a novel chemical reduction process to overcome agglomeration in traditional MgB2 preparation methods. The influence of the reduction technique on nanoparticle size and structure was thoroughly investigated using a model system. The resulting nanoparticles were small enough (10 nm) to decorate the 2D graphene layers as sandwich structures. This unique morphology contributes to providing more effective flux pinning centers by forming tiny MgNi2.5B2 and efficiently substituting C for B in MgB2 bulks through the principle of double action. Moreover, the low-melting eutectic liquid formed by Mg-Ni at 506 °C is beneficial for the fast fabrication of well-connected MgB2 at low temperatures. Furthermore, a small enhancement of critical current density (Jc) was observed in the doped sample with respect to the undoped ones. However, the advantages of the as-prepared nanoparticles were greatly suppressed by the large presence of MgO during the deposition process, leading to lower superconducting performance than undoped MgB2 bulks. Based on the analysis, further investigation should focus on inducing more flux pinning centers by controlling impurities during the deposition process for achieving optimal performance.