Proximity effects and exchange coupling across interfaces of hybrid magnetic heterostructures present unique opportunities for functional material design. In this review, we present an overview of recent experiments on magnetic hybrid materials in which magnetism was controlled by proximity to an active material. In particular, we discuss interfacial strain coupling of ferromagnetic materials in contact with a material undergoing a structural deformation. Bilayers containing VO2 and V2O3 as active materials are shown to strongly affect the magnetization and coercivity of ferromagnetic materials due to stress anisotropy caused by a temperature-dependent structural displacement in the oxide. The possibilities of tuning the system by sample morphology and materials choice are discussed in detail. In addition, we highlight a length-scale competition between magnetic and structural domains which leads to a maximum change in the coercivity in a narrow temperature window of the vanadium oxide phase transition.

To fabricate practical light-emitting devices, identification and minimization of nonradiative processes are necessary. In this study, an electrical measurement technique for time-resolved analyses of nonradiative processes was proposed. From the comparison between a commercial light-emitting diode (LED) and rare-earth-doped semiconductors, the technique, called electrical frequency-response analysis (FRA), revealed differences in the charge behaviors in the pn junction of bulk semiconductors and impurities. Although the charge response time constant on the order of a nanosecond realized effective recombination of the electron–hole pairs in a LED, the time constant larger than a microsecond still limited the emission intensity of the rare-earth-doped semiconductors such as Er-doped Si nanocrystals and GaAs with Er and O codopants. The energy-loss processes of the Er-doped semiconductors were investigated, and countermeasures to enhance the emission intensity were proposed.

Density functional theory calculations and molecular dynamics with a recently developed potential for W–He were used to evaluate the thermal stability of helium-vacancy clusters (nHe.mv) as well as pure interstitial helium clusters in tungsten. The stability of such objects results from a competitive process between thermal emission of vacancies, self interstitial atoms (SIAs), and helium, depending on the helium-to-vacancy ratio in mixed clusters or helium number in pure interstitial helium clusters. We investigated in particular the ground state configurations as well as the activation barriers of self trapping and trap mutation, i.e., the emission of one SIA along with the creation of one vacancy from a vacancy-helium or pure helium object.

The reliability of nanomaterials depends on maintaining their specific sizes and structures. However, the stability of many nanomaterials in radiation environments remains uncertain due to the lack of a fully developed fundamental understanding of the radiation response on the nanoscale. To provide an insight into the dynamic aspects of single ion effects in nanomaterials, gold nanoparticles (NPs) with nominal diameters of 5, 20, and 60 nm were subjected to self-ion irradiation at energies of 46 keV, 2.8 MeV, and 10 MeV in situ inside of a transmission electron microscope. Ion interactions created a variety of far-from-equilibrium structures including small (∼1 nm) sputtered nanoclusters from the parent NPs of all sizes. Single ions created surface bumps and elongated nanofilaments in the 60 nm NPs. Similar shape changes were observed in the 20 nm NPs, while the 5 nm NPs were transiently melted or explosively broken apart.

Injectable bone grafts with strength exceeding that of trabecular bone could improve the clinical management of a number of orthopedic conditions. Ceramic/polymer composites have been investigated as weight-bearing bone grafts, but they are typically weaker than trabecular bone due to poor interfacial bonding. We hypothesized that entrapment of surface-initiated poly(ε-caprolactone) (PCL) chains on 45S5 bioactive glass (BG) particles within an in situ-formed polymer network would enhance the mechanical properties of reactive BG/polymer composites. When the surface-initiated PCL molecular weight exceeded the molecular weight between crosslinks of the network, the compressive strength of the composites increased 6- to 10-fold. The torsional strength of the composites exceeded that of human trabecular bone by a factor of two. When injected into femoral condyle defects in rats, the composites supported new bone formation at 8 weeks. The initial bone-like strength of BG/polymer composites and their ability to remodel in vivo highlight their potential for development as injectable grafts for repair of weight-bearing bone defects.

By using microemulsion-mediated solvothermal method in the presence of camphorsulfonic acid as a dopant, self-aggregated polyaniline (PANI) nanowires were synthesized and further organized into three-dimensional cluster-connected networks. So-formed PANI exhibited a hierarchically porous structure, which was significantly different from those obtained by conventional chemical oxidation method, hydrothermal method, and other reported methods. Compared with nanofibers presented in this study, the nanowires in the clusters had a great decrease in diameter from ∼60 to ∼15 nm due to the space-confined polymerization. In addition, the size of the clusters could be easily adjusted by altering the dopant/monomer molar ratio. A probable assembly mechanism for such an interesting morphology was proposed. Used as an electrode material, PANI clusters showed high specific capacitances (510 and 368 F g−1 at 0.5 and 2 A g−1, respectively) and improved cycling stability (66% capacitance retention over 1000 cycles) as compared to PANI fibers and particles obtained by other methods, which may be related to its unique morphology and high doping level.

In this study, a simple, facile, green, and versatile strategy was developed for the synthesis of water-soluble and well-dispersed fluorescent gold nanoclusters (Au NCs) with wave length-tunable emissions using protein as capping agent and template. The resultant Au NCs exhibited excellent characteristics such as large Stokes shift, good stability, and high resistance to photobleaching. They showed strong emission at 680 nm, with a quantum yield of 4.5%. Heavy metal ion (Hg2+) could quench the fluorescence of Au NCs efficiently and thus the as-prepared Au NCs were successfully developed as “turn-off” fluorescent probes for the detection of Hg2+ sensitively and selectively. The lowest concentration to quantify mercuric ions could be as low as 1 nM and the fluorescence intensity of the Au NCs was proportional to the concentrations of Hg2+ over the range 8 × 10−8 M to 1 × 10−5 M (R = 0.9982). To validate the practicality of this probe, real water samples spiked with Hg2+ were determined with RSD values less than 3%. And the results demonstrated that the developed probes worked well in environmental samples. The action mechanism between the Au NCs and Hg2+ was explored as well.

A facile and reproducible low-temperature (80 °C) solution route has been introduced to synthesize ZnO ellipsoids on silicon substrate without any pretreatment of the substrate or organic/inorganic additives. Scanning electron microscopy, transmission electron microscopy, and x-ray diffraction spectroscopy are performed to analyze the structural evolution, the single crystalline nature, and growth orientation at different stages of the synthetic process. The sequential formation mechanisms of heterogeneous nucleation in primary and secondary crystal growth behaviors have been discussed in detail. The presented results reveal that the morphology of micro/nanostructures with desired features can be optimized. The optical properties of grown structures at different stages were investigated using cathodoluminescence (CL). The monochromatic CL images were recorded to examine the UV and visible band emission contributions from the different positions of the intermediate and final structures of the individual ZnO ellipsoid. Significant enhancement in the defect level emission intensity at the central position of the structure reveals that the quality of the material improves as the reaction time is extended.

The aim of this research study is to produce high-quality TiO2 nanotube arrays using porous alumina templates. The templates are fabricated through anodizing bulk aluminum foils which can be utilized for the production of thick alumina templates. To produce the nanotube arrays, the alumina template pores are filled with the precursor sol by applying a DC electric field. Then, the deposited nanotubes are heat treated at 320 °C for 2 h and, subsequently, sintered for 2 h at 400 and 750 °C to obtain nanotubes with pure anatase and rutile phases, respectively, as confirmed by x-ray diffraction data. Scanning and transmission electron microscopy (SEM and TEM) investigations show that the nanotubes have been deposited in the channels of the nanoporous alumina template. Also, SEM investigations show the existence of a vast area of TiO2 nanotube arrays when we use semiconductor alumina templates.

Nitrogen-doped multiwalled carbon nanotube (CNT) bundles exhibiting pine-tree-like morphologies were synthesized on silicon–silicon oxide (Si/SiO2) substrates using a pressure-controlled chemical vapor deposition process. Electron field emission (FE) measurements showed a notable emission improvement at low turn-on voltages for the CNT pine-like morphologies (e.g., 0.59 V/µm) in comparison with standard aligned N-doped CNTs (>1.5 V/µm). We envisage that these pine-tree-like structures could be potentially useful in the fabrication of efficient FE and photonic devices.

In this study, nickel acetate tetrahydrate (NACTH)/poly(styrene-co-acrylonitrile) (SAN) sol was used for the fabrication of nanocrystalline NiO nanofibers. An indigenous setup was developed to use these nanofibers for the oxidation of carbon monoxide (CO) and unburnt hydrocarbons (HC) from diesel engine exhaust. The morphological, compositional, and crystalline properties of the NiO nanofibers obtained after calcination were studied by scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, and x-ray diffraction (XRD). Clear evidence of defects in the fibers was observed in ultraviolet–visible–near infrared (UV-Vis-NIR) spectra, Raman spectra, and magnetic property measurements. The NiO nanofiber mats supported by glass fiber mats were efficient in oxidizing CO and HC from diesel engine exhaust, and the maximum efficiency was achieved by using NiO nanofibers with the maximum amount of defects.

Nanosized Eu2+-doped AlN phosphor was successfully synthesized by a metal-organic precursor method for the first time. Aluminum and europium chlorides were simultaneously reacted with triethylamine in acetonitrile media to yield solid precipitates, which were transformed into nanosized AlN:Eu2+ phosphor powders upon calcination in an ammonia gas atmosphere. The possible reaction mechanism was proposed, which is in good agreement with the experimental results. The direct formation of Al–N bonds through a coordination reaction in solution is a key factor in the formation of well-crystallized AlN:Eu2+ grains at a moderately low temperature (1200 °C), which significantly suppresses abnormal grain growth and favors the formation of nanocrystalline (∼15 nm) particles with a homogeneous particle size distribution. Due to the homogeneous distribution of a relative high amount of Eu incorporation (2 wt%), the nanophosphors were effectively excited by UV light and featured an intense green emission band with a peak at 506 nm.

The ZrO2 and graphitic carbon nitride (g-C3N4) composite photocatalyst has been prepared by calcination process and hydrothermal treatment. The photocatalyst was characterized by x-ray diffraction, scanning electron microscopy, x-ray photoelectron spectroscopy, UV–vis diffuse reflection spectroscopy, Brunauer–Emmett–Teller and photoluminescence spectra. The photocatalytic activity of the photocatalysts was evaluated by degradation of methylene blue under visible light irradiation. The results showed that the activity of the composite photocatalyst ZrO2/g-C3N4 for photodegradation of MB is much higher than that of either pure g-C3N4 or ZrO2, which is ascribed to the effective electron–hole separation based on the photoluminescence spectra. The •O2− might be the main active species in MB photodegradation, and the •OH and photogenerated electrons are also partly involved in the process of photocatalytic degradation.