Nanosize Effect Research Articles

Performance Enhancement of Hole Transport Layer-Free Carbon-Based CsPbIBr2 Solar Cells through the Application of Perovskite Quantum Dots.

CsPbIBr2, with its suitable bandgap, shows great potential as the top cell in tandem solar cells. Nonetheless, its further development is hindered by a high defect density, severe carrier recombination, and poor stability. In this study, CsPbI1.5Br1.5 quantum dots were utilized as an additive in the ethyl acetate anti-solvent, while a layer of CsPbBr3 QDs was introduced between the ETL and the CsPbIBr2 light-harvester film. The combined effect of these two QDs enhanced the nucleation, crystallization, and growth of CsPbIBr2 perovskite, yielding high-quality films characterized by an enlarged crystal size, reduced grain boundaries, and smooth surfaces. And a wider absorption range and better energy band alignment were achieved owing to the nano-size effect of QDs. These improvements led to a decreased defect density and the suppression of non-radiative recombination. Additionally, the presence of long-chain organic molecules in the QD solution promoted the formation of a hydrophobic surface, significantly enhancing the long-term stability of CsPbIBr2 PSCs. Consequently, the devices achieved a PCE of 9.20% and maintained an initial efficiency of 85% after 60 days of storage in air. Thus, this strategy proves to be an effective approach for the preparation of efficient and stable CsPbIBr2 PSCs.

Improved Electromagnetic Interference Shielding Efficiency of PVDF/rGO/AgNW Composites via Low-Pressure Compression Molding and AgNW-Backfilling Strategy.

Silver nanowires (AgNWs) have excellent electrical conductivity and nano-sized effects and have been widely used as a high-performance electromagnetic shielding material. However, silver nanowires have poor mechanical properties and are prone to fracture during the preparation of composite materials. In this study, PVDF/rGO/AgNW composites with a segregated structure were prepared using low-pressure compression molding and the AgNW-backfilling process. The low-pressure compression of the composite significantly improves its electromagnetic shielding performance because the low-pressure process can maintain the AgNWs' integrity. The backfilled AgNWs played a vital role in increasing the path of electromagnetic wave propagation and the absorption of electromagnetic waves. The backfilled amount of AgNWs was only 1 wt%, which increased the composite material's conductivity by one order of magnitude. The total electromagnetic interference shielding (SET) of the composite materials increased by 23.3% from 24.88 dB to 30.67 dB. The absorption contribution (SEA/SET) increased from 84.2% to 92.8%, significantly improving the electromagnetic interference shielding and the absorption contribution of the AgNWs in the composites. This was attributed to the backfilling of the porous structure by the AgNWs, which promoted multiple reflections and enhanced the absorption contribution.

Structural Study on the Novel Plasmonic Optical Materials with Copper Selenide Nanoparticles

Background: Semiconductor-doped materials have been treated actively throughout the last decades and continue to be of great interest because of the challenges of the features due to various nanosize effects. Among other semiconductors, copper chalcogenides demonstrate the interesting plasmonic properties in line with quantum confinement effects provided by the size factor. Objective: This study aims to study the structural and optical features of the sol-gel-derived silica glasses with copper selenide nanoparticles, demonstrating the appearance of the plasmonic light absorption in the near IR range. Method: The samples under study were fabricated through an original sol-gel technique, which realized the simultaneous synthesis of copper selenide and sintering of mesoporous silica. The copper selenide glasses were characterized with X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and optical absorption spectroscopy. Results: Formation of nanocrystalline Cu2-xSe particles of the size range from 10 nm through 100-150 nm is established with XRD and TEM techniques. The principal optical properties are presented by the featured absorption in the visible and near-IR ranges. Eg was evaluated for the direct transitions in the range of 2.10-2.36 eV. The plasmonic resonance in the nanoparticles due to increased carrier concentration originated by intrinsic deficiency of Cu2-xSe nanoparticles with variable stoichiometry. Its energy can be controlled by the Cu/Se ratio in the synthesis procedure. Conclusion: The silica sol-gel glasses with copper selenide nanoparticles were fabricated and characterized by XRD and TEM methods, and their optical absorbance spectra were investigated. The principal optical properties are presented by the featured absorption in the visible and near-IR ranges: the steplike proper absorption of the semiconductor particles characterized by Eg and the intense near-IR band is associated with the localized plasmonic resonance in the nanoparticles due to increased carrier concentration.

Well-Ordered Bicontinuous Nanohybrids from a Bottom-Up Approach for Enhanced Strength and Toughness.

Biomimicking natural structures to create structural materials with superior mechanical performance is an area of extensive attention, yet achieving both high strength and toughness remains challenging. This study presents a novel bottom-up approach using self-assembled block copolymer templating to synthesize bicontinuous nanohybrids composed of well-ordered nanonetwork hydroxyapatite (HAp) embedded in poly(methyl methacrylate) (PMMA). This structuring transforms intrinsically brittle HAp into a ductile material, while hybridization with PMMA alleviates the strength reduction caused by porosity. The resultant bicontinuous PMMA/HAp nanohybrids, reinforced at the interface, exhibit high strength and toughness due to the combined effects of topology, nanosize, and hybridization. This work suggests a conceptual framework for fabricating flexible thin films with mechanical properties significantly surpassing those of traditional composites and top-down approaches.

Adaptive Size Evolution of an MOFs-in-MOF Nanovehicle for Enhanced Nucleus-Targeted Tumor Chemotherapy.

A metal-organic frameworks (MOFs)-in-MOF nanovehicle (160 nm), which was constructed with newly prepared ultrasmall Cu(I)Cu(II)-BTC MOFs (UCMs, 2.95 nm) loaded with doxorubicin (DOX) and a nuclear localization signal (NLS) peptide as multicores (UCMDNs) and ZIF-8 as the shell MOF, was proposed to cross layers of biological barriers with adaptive size evolution capacity for achieving efficient nucleus-targeted drug delivery. It first enhanced tumor tissue penetration through its larger nanosize effect. Then the acidic tumor environment made the ZIF-8 shell degrade, releasing small-sized UCMDNs to enter into the cell and into the nucleus under the guidance of NLS. Furthermore, due to the distinct surface structural characteristics of UCMs, UCMDNs remained stable in the cytoplasm and collapsed in the nucleus due to the DOX-DNA interaction to deliver DOX precisely. It showed superior performance in the nucleus-directed delivery of DOX (delivery efficiency up to 56.7%) and a high tumor growth inhibition rate (96.4%), offering promising prospects in tumor chemotherapy.

Ion Dynamics in Nanocrystalline Li2S‐LiI – on the Influence of Local Disorder on Short‐Range Hopping and Long‐Range Ion Transport

The enormous interest in developing powerful Li‐based batteries leads to a boost in materials research. Though Li–sulfur batteries offer very high energy densities, the nature of Li‐ion dynamics in the final discharge product has not been fully understood yet. While nanocrystalline shows enhanced ion dynamics compared to its coarse‐grained counterpart, the interaction of with another binary such as LiI seems to be rather unexplored. Herein, an equimolar mixture of and LiI is treated in a high‐energy ball mill, and both the overall and local structural changes are studied by X‐ray powder diffraction and nuclear magnetic resonance (NMR), respectively . Besides the formation of amorphous regions, evidences are found for the generation of anion‐mixed sites that give rise to facile Li exchange on the 2D exchange NMR timescale. Compared to a coarse‐grained reference sample, the overall (bulk) ionic conductivity of nanocrystalline ‐LiI increases by two orders of magnitude. Besides the anion‐mixing effect, this increase benefits from nanosize effects that include the formation of defect‐rich interfacial regions. NMR relaxation measurements fully support this result and reveal heterogeneous dynamics with lower activation energies for both the localized hopping processes and long‐range ion transport in nm‐sized ‐LiI.

Nano-Se exhibits limited protective effect against heat stress induced poor breast muscle meat quality of broilers compared with other selenium sources

BackgroundAt present, heat stress (HS) has become a key factor that impairs broiler breeding industry, which causes growth restriction and poor meat quality of broilers. Selenium (Se) is an excellent antioxidant and plays a unique role in meat quality improvement. Recent years, nano-selenium (NanoSe) has received tremendous attention in livestock production, due to its characteristic and good antibacterial performance in vitro. Here, we developed the heat stressed-broiler model to investigate the protective effects of NanoSe on growth performance and meat quality of broilers and compare whether there are differences with that of other Se sources (Sodium selenite, SS; Selenoyeast, SeY; Selenomethionine, SeMet).ResultsHS jeopardized the growth performance and caused poor meat quality of breast muscle in broilers, which were accompanied by lowered antioxidant capacity, increased glycolysis, increased anaerobic metabolism of pyruvate, mitochondrial stress and abnormal mitochondrial tricarboxylic acid (TCA) cycle. All Se sources supplementation exhibited protective effects, which increased the Se concentration and promoted the expression of selenoproteins, improved the mitochondrial homeostasis and the antioxidant capacity, and promoted the TCA cycle and the aerobic metabolism of pyruvate, thus improved the breast muscle meat quality of broilers exposed to HS. However, unlike the other three Se sources, the protective effect of NanoSe on meat quality of heat stressed-broilers was not ideal, which exhibited limited impact on the pH value, drip loss and cooking loss of the breast muscle. Compared with the other Se sources, broilers received NanoSe showed the lowest levels of slow MyHC, the highest levels of fast MyHC and glycogen, the highest mRNA levels of glycolysis-related genes (PFKM and PKM), the highest protein expression of HSP60 and CLPP, and the lowest enzyme activities of GSH-Px, citroyl synthetase (CS) and isocitrate dehydrogenase (ICD) in breast muscle. Consistent with the SS, the Se deposition in breast muscle of broilers received NanoSe was lower than that of broilers received SeY or SeMet. Besides, the regulatory efficiency of NanoSe on the expression of key selenoproteins (such as SELENOS) in breast muscle of heat stressed-broilers was also worse than that of other Se sources.ConclusionThrough comparing the meat quality, Se deposition, muscle fiber type conversion, glycolysis, mitochondrial homeostasis, and mitochondrial TCA cycle-related indicators of breast muscle in heat stressed broilers, we found that the protective effects of organic Se (SeY and SeMet) are better than that of inorganic Se (SS) and NanoSe. As a new Se source, though NanoSe showed some protective effect on breast muscle meat quality of heat stressed broilers, the protective effect of NanoSe is not ideal, compared with other Se sources.

Novel Ti3SiC2-(Ti, Zr)B2 toughened (Ti, Zr)C-based composites with enhanced mechanical properties fabricated by dual in situ reactions hot-pressing at low temperature

The fully dense Ti3SiC2-(Ti, Zr)B2 toughened (Ti, Zr)C-based composites were fabricated at 1400–1600 °C for the first time by dual in situ reactions hot-pressing with TiC, ZrB2, and Si as the initial powders. The influence of ZrB2, Si content and sintering temperature on the microstructure and mechanical properties of the composite was reported. When 10 mol% ZrB2 was added, Si combined with residual TiC to form Ti3SiC2 and SiC. However, with the addition of ZrB2 increase to 20 mol% and 30 mol%, Si participated in the formation of ZrSi and was not enough to react with TiC to form Ti3SiC2. The low-temperature in situ reactions, multiphase coupling effects, and the pinning effect of nano-SiC refine the microstructure of the composites. There are specific crystal orientation relationships between (Zr, Ti)C and (Ti, Zr)B2, as well as between (Ti, Zr)C and SiC. The layered Ti3SiC2 and plate-like (Ti, Zr)B2 by dual in situ reactions effectively improve the fracture toughness of the composites. The 10 ZB-15 possesses a highest fracture toughness of 6.1 MPa⋅m1/2. The 30 ZB-16 has the good comprehensive mechanical properties. The fracture toughness, flexural strength, and hardness of 30 ZB-16 is 5.6 MPa⋅m1/2, 679 MPa, and 26.4 GPa, respectively. The Ti3SiC2 and TiB2 formed during dual in situ reactions enables the composite to exhibit excellent oxidation resistance and wear resistance.

A nano photocatalyst rGO/TiO2 modified by sol–gel‐irradiation and its degradation of deoxynivalenol in liquid products

SummaryThe rGO/TiO2 nanocomposite photocatalyst was synthesised using the sol–gel‐irradiation way to efficiently remove deoxynivalenol (DON) for the grains product's safety and quality. With the nanosize effect of irradiation, the photocatalyst has a smaller average grain size, preventing the recombination of electrons and holes. Moreover, based on UV–Vis DRS study, rGO/TiO2 could utilise visible light and have a broader response range to light. Furthermore, to the application, the photocatalyst rGO/TiO2 with 30 KGy irradiation dosage had an 80.32 ± 4.41% photocatalytic degradation rate of DON. Compared to the photocatalyst without irradiation, there was a 9.98% increase in the degradation rate. This result provided an excellent candidate photocatalyst for the removal of DON and also promoted the development of photocatalysis applications.

Synthesis and high-temperature phase transformation behavior of Dy2O3–Sc2O3 co-stabilized ZrO2 powders prepared by cocurrent chemical coprecipitation

In this study, Dy2O3–Sc2O3 co-stabilized ZrO2 (DyScSZ) powders with various stabilizer ratios were synthesized by cocurrent chemical coprecipitation method. The difference analysis of phase composition and microstructure was conducted on the synthesized powders in detail. The phase evolution and phase transformation behaviors of the synthesized powders were also investigated. Results show that all of the powders were synthesized with nanoscale and exhibit subglobose morphology. The excessive elevation of Sc2O3 fraction in total stabilizers was adverse to the formation of the synthesized powders with pure tetragonal phase, which also exhibit a significant effect both on the phase transformation behaviors and the final volume fractions of transform products. The 2.5Dy1.0ScSZ powders exhibit favorable phase stability resulting from the nano-size effect and the synergies of Dy2O3 and Sc2O3 stabilizers during the phase transformation process. Moreover, a phase transformation mechanism of DyScSZ was proposed based on the new phase nucleation and growth theory.

Low temperature soldering technology based on superhydrophobic copper microlayer

Cu–Cu soldering is realized under certain pressure and low temperature conditions by using a surface silver film to modify the copper microlayer structure, thus solving the problems of high thermal stress and signal delay aggravation caused by high temperature in the traditional reflow soldering process. The copper microlayer modified with silver film is obtained by electrodeposition. The surface substructure of the Cu microlayer is a nano cone-shaped protrusion. The diameter of the bottom of the cone is 500 nm∼1 μm, and the height of the cone is 1∼2 μm. The thickness of the silver film is about 320 nm, and the modification of the copper layer with silver film can effectively prevent the oxidation of the copper layer. Two silver-modified copper microlayers are placed in face-to-face contact as a soldering couple. A certain pressure and low temperature are applied to the contact area to realize the soldering and interconnection.The morphology of the soldered interface and the average shear strength of the soldered joints are analyzed by scanning electron microscopy, transmission electron microscopy and solder joint tester. It is found that under the optimal soldering parameters of soldering temperature 220 °C, soldering pressure 20 MPa and soldering time 20 min, the nano-conical projections of the Cu micrometer layer are inserted into each other to produce a physical blocking effect. The highly surface-meltable silver film effectively connects the surrounding copper layer as an intermediate buffer layer. The average shear strength of soldering joints is significantly increased. Heat treatment experiments have shown that the average shear strength can be effectively increased by heat treatment for an appropriate period of time. Prolonged exposure to heat has little effect on the average shear strength. With the special morphology of the copper microlayer structure and the nano-size effect of the silver layer, soldering can be done at low temperatures. The quality of the soldering interface is good and small soldering dimensions can be obtained.

Effect of nano-SiC on microstructure evolution and enhanced high wear resistance mechanism of laser surface alloyed M42 high-speed steel

M42 high-speed steel is one of the main materials for preparing bimetallic band saw parts. In this paper, nano-SiC particles of different densities (0–1.00 mg/mm2) were precoated on the surface of M42 high-speed steel samples, then, the samples were prepared by laser alloying. The matching relationship between the quantity, size, and type of martensite and MxCy carbides in laser alloyed samples play a decisive role in improving wear resistance. It is found that under the optimized particle density of 0.75 mg/mm2, compared with M42 high-speed steel, the hardness was increased by 50%, the wear rate decreased by 84.7%. The matching relationship between Martensite and MxCy carbides formed by laser alloying of nano-SiC particles on the improvement of wear resistance was elucidated.

Effect of nano-SiC particles on grain orientation and hardness of friction stir processed aluminum matrix composite

The present work concentrates on exploiting electron backscatter diffraction (EBSD) and transmission electron microscope (TEM) to investigate the effect of nano-SiC on the microstructure of Al-SiC composites fabricated by friction stir processing (FSP). With the introduction of nano-SiC, the average grain size and the proportion of low angle grain boundaries (LAGBs) decreased to 3.9 μm and 19.3 %, respectively, while the proportion of ∑3 and ∑9 grain boundaries increased slightly. The intensity of the main texture components in Al-SiC composite is reduced compared to FSPed Al. The Schmid factor of the Al-SiC composite decreased to 0.455, and the microhardness increased from 80.0 HV of FSPed Al to 100 HV. During the FSP process, the introduction of nano-SiC not only generates more randomly oriented grains in the composite, but also facilitates the occurrence of dynamic recrystallization.

Kinetically Controlled Synthesis of Metallic Glass Nanoparticles with Expanded Composition Space.

Nanoscale metallic glasses offer opportunities for investigating fundamental properties of amorphous solids and technological applications in biomedicine, microengineering, and catalysis. However, their top-down fabrication is limited by bulk counterpart availability, and bottom-up synthesis remains underexplored due to strict formation conditions. Here, a kinetically controlled flash carbothermic reaction is developed, featuring ultrafast heating (>105 K s-1) and cooling rates (>104 K s-1), for synthesizing metallic glass nanoparticles within milliseconds. Nine compositional permutations of noble metals, base metals, and metalloid (M1─M2─P, M1 = Pt/Pd, M2 = Cu/Ni/Fe/Co/Sn) are synthesized with widely tunable particle sizes and substrates. Through combinatorial development, a substantially expanded composition space for nanoscale metallic glass is discovered compared to bulk counterpart, revealing that the nanosize effect enhances glass forming ability. Leveraging this, several nanoscale metallic glasses are synthesized with composition that have never, to the knowledge, been synthesized in bulk. The metallic glass nanoparticles exhibit high activity in heterogeneous catalysis, outperforming crystalline metal alloy nanoparticles.

Comparative study between micro- and nano-carbon with epoxy for gamma shielding applications

In the current study, the epoxy material was mixed with 10%, and 30% weight percent carbon material as filler in different thicknesses (1 cm, 1.5 cm, and 2 cm). Transmission electron microscope (TEM) measurements showed the average size of the nano-carbon was 20 nm with a standard deviation of 5 nm. The morphology of samples was examined using scanning electron microscopy (SEM), which showed the flatness of the epoxy surface, and when the content of carbon increases, the connection between the epoxy array and carbon increases. The compression test indicates the effect of nano-size on enhancing the mechanical properties of the studied samples. To survey the shielding properties of the epoxy/carbon composites using gamma-rays emitted from Am-241, Ba-133, Cs-137, Co-60, and Eu-152 sources, which covered a wide range of energies from 0.059 up to 1.408 MeV, the gamma intensity was measured using the NaI (Tl) detector. The linear and mass attenuation coefficients were calculated by obtaining the area under each peak of the energy spectrum observed from Genie 2000 software in the presence and absence of the sample. The experimental results obtained were compared theoretically with XCOM software. The comparison examined the validity of experimental results where the relative division rate ranged between 0.02 and 2%. Also, the measurement of the relative division rate between linear attenuation coefficients of micro- and nano-composites was found to range from 0.9 to 21% The other shielding parameters are calculated at the same range of energy, such as a half-value layer (HVL), mean free path (MFP), tenth-value layer (TVL), effective atomic number (Zeff), and the buildup factors (EBF and EABF). The data revealed a consistent reduction in the particle size of the shielding material across various weight percentages, resulting in enhanced radiation shielding capabilities. The sample that contains 30% nano-carbon has the lowest values of TVL (29.4 cm) and HVL (8.85 cm); moreover, it has the highest value of the linear attenuation coefficient (LAC), which makes it the best in its ability to attenuate radiation.

Nano‑selenium alleviates the pyroptosis of cardiovascular endothelial cells in chicken induced by decabromodiphenyl ether through ERS-TXNIP-NLRP3 pathway

Decabromodiphenyl ether (BDE-209) is one of the most widely used flame retardants that can infect domestic and wildlife through contaminated feed. Nano‑selenium (Nano-Se) has the advantage of enhancing the anti-oxidation of cells. Nonetheless, it remains uncertain whether Nano-Se can alleviate vascular Endothelial cells damage caused by BDE-209 exposure in chickens. Therefore, we established a model with 60 1-day-old chickens, and administered BDE-209 intragastric at a ratio of 400 mg/kg bw/d, and mixed Nano-Se intervention at a ratio of 1 mg/kg in the feed. The results showed that BDE-209 could induce histopathological and ultrastructural changes. Additionally, exposure to BDE-209 led to cardiovascular endoplasmic reticulum stress (ERS), oxidative stress and thioredoxin-interacting protein (TXNIP)-pyrin domain-containing protein 3 (NLRP3) pathway activation, ultimately resulting in pyroptosis. Using the ERS inhibitor 4-PBA in Chicken arterial endothelial cells (PAECs) can significantly reverse these changes. The addition of Nano-Se can enhance the body's antioxidant capacity, inhibit the activation of NLRP3 inflammasome, and reduce cellular pyroptosis. These results suggest that Nano-Se can alleviate the pyroptosis of cardiovascular endothelial cells induced by BDE-209 through ERS-TXNIP-NLRP3 pathway. This study provides new insights into the toxicity of BDE-209 in the cardiovascular system and the therapeutic effects of Nano-Se.

Regulating the Nanosize Effect of LiCoO2 for High-Performance Battery-Supercapacitor Hybrid Devices

Regulating the Nanosize Effect of LiCoO₂ for High-Performance Battery-Supercapacitor Hybrid Devices

Nanoscale engineering of solid-state materials for boosting hydrogen storage.

The development of novel materials capable of securely storing hydrogen at high volumetric and gravimetric densities is a requirement for the wide-scale usage of hydrogen as an energy carrier. In recent years, great efforts via nanoscale tuning and designing strategies on both physisorbents and chemisorbents have been devoted to improvements in their thermodynamic and kinetic aspects. Increasing the hydrogen storage capacity/density for physisorbents and chemisorbents and improving the dehydrogenation kinetics of hydrides are still considered a challenge. The extensive and fast development of advanced nanotechnologies has fueled a surge in research that presents huge potential in designing solid-state materials to meet the ultimate U.S. Department of Energy capacity targets for onboard light-duty vehicles, material-handling equipments, and portable power applications. Different from the existing literature, in this review, particular attention is paid to the recent advances in nanoscale engineering of solid-state materials for boosting hydrogen storage, especially the nanoscale tuning and designing strategies. We first present a short overview of hydrogen storage mechanisms of nanoscale engineering for boosted hydrogen storage performance on solid-state materials, for example, hydrogen spillover, nanopump effect, nanosize effect, nanocatalysis, and other non-classical hydrogen storage mechanisms. Then, the focus is on recent advancements in nanoscale engineering strategies aimed at enhancing the gravimetric hydrogen storage capacity of porous materials, reducing dehydrogenation temperature and improving reaction kinetics and reversibility of hydrogen desorption/absorption for metal hydrides. Effective nanoscale tuning strategies for enhancing the hydrogen storage performance of porous materials include optimizing surface area and pore volume, fine-tuning nanopore sizes, introducing nanostructure doping, and crafting nanoarchitecture and nanohybrid materials. For metal hydrides, successful strategies involve nanoconfinement, nanosizing, and the incorporation of nanocatalysts. This review further addresses the points to future research directions in the hope of ushering in the practical applications of hydrogen storage materials.

Spectroscopic analysis of nanosized Zn(Ag, Ni)O systems and observation of superparamagnetism at low temperature.

To understand the impact of binary doping in ZnO, nanosized Zn(Ag, Ni)O systems were synthesized by the sol-gel method. The amount of Ag was fixed at 2 at%, and that of Ni was varied from 1 to 15 at%. Ni incorporation equal to or beyond 3 at% gave rise to the development of the NiO phase. The presence of Ag and Ni did not have much influence on the lattice constants of ZnO. However, a larger addition of Ni impacted the unit cell of NiO, as indicated by the reduction of the lattice constant of NiO. The increase in NiO and Ag contents in ZnO reduced the second and third harmonic intensities under non-linear investigations. X-ray photoelectron spectroscopy analysis indicated that initial Ni addition varied randomly along with Ag, and it stabilized itself at higher concentration. Field emission scanning electron microscopy revealed that interlinked particles and chains with tamarind shapes were formed, closely matching the rod-like structures under high resolution. Ag and Ni addition altered the structures slightly and randomly till 5 at% Ni; thereafter they deviated from the particle shape to flat disc-shapes. Interestingly, the magnetic response of the sample was determined by the NiO phase, and the effect of Ni and Ag substitution in the ZnO host matrix was almost irrelevant at low temperatures toward magnetic contribution. Weak ferromagnetism at low temperatures (≤50 K) with superparamagnetic-like behavior (cusp in ZFC magnetization) was observed in all the samples. This could be attributed to the finite nano-size effect and uncompensated spins at the surface of the particle.

Highly air-stable magnesium hydrides encapsulated by nitrogen-doped graphene nanospheres with favorable hydrogen storage kinetics

Severe surface oxidation and sluggish kinetic rates of Mg hydrides (MGHs) are the main bottlenecks for their industrial applications. Herein, we present a strategy to simultaneously tackle these problems. The nano-size MGHs were encapsulated in nitrogen-doped graphene nanospheres (NGNSs) via a facile wet-chemical method. This configuration not only prevented the MGHs from oxidation when exposed to air even after a long duration, but also stimulated faster kinetic rates of hydrogen absorption and desorption owing to the nano-size effect of MGHs and the unique electronic structure of NGNSs. As a result, MGHs of ca. 20 nm were coated by a few layered NGNSs to form MGH@NGNSs nanocomposite. A high hydrogen absorption capacity of 6.5 wt% was achieved at 200 °C within 0.4 h, with a releasing hydrogen capacity of 5.5 wt% at 300 °C within 0.5 h, indicating that this composite has obtained remarkably hydrogen storage performance. Density Functional Theory (DFT) based calculations suggested that the hydrogen adsorption/desorption kinetics were significantly fast at the interface of Mg surface and NGNSs with pyridinic configuration. This strategy paves a way for the development of high-performance Mg-based hydrogen storage materials for industrial applications.