The successful development of quantum computers is dependent on identifying quantum systems to function as qubits. Paramagnetic states of point defects in semiconductors or insulators have been shown to provide an effective implementation, with the nitrogen-vacancy center in diamond being a prominent example. The spin-1 ground state of this center can be initialized, manipulated, and read out at room temperature. Identifying defects with similar properties in other materials would add flexibility in device design and possibly lead to superior performance or greater functionality. A systematic search for defect-based qubits has been initiated, starting from a list of physical criteria that such centers and their hosts should satisfy. First-principles calculations of atomic and electronic structure are essential in supporting this quest: They provide a deeper understanding of defects that are already being exploited and allow efficient exploration of new materials systems and “defects by design.”

A quantum computer will have computational power beyond that of conventional computers, which can be exploited for solving important and complex problems, such as predicting the conformations of large biological molecules. Materials play a major role in this emerging technology, as they can enable sophisticated operations, such as control over single degrees of freedom and their quantum states, as well as preservation and coherent transfer of these states between distant nodes. Here we assess the potential of semiconductor nanowires grown from the bottom-up as a materials platform for a quantum computer. We review recent experiments in which small bandgap nanowires are used to manipulate single spins in quantum dots and experiments on Majorana fermions, which are quasiparticles relevant for topological quantum computing.

Recently, fully reversible dislocation motion was postulated to result in hysteretic nanoindentation load–displacement loops in plastically anisotropic solids. Since microcracking can also result in hysteretic loops, here we define a new parameter, reversible displacement (RD) that can differentiate between the two. For C-plane LiTaO3 surfaces and five other plastically anisotropic solids, the RD values either increase initially or remain constant with cycling. In contradistinction, for glass and A-plane ZnO surfaces, where energy dissipation is presumably due to microcracking or irreversible dislocation pileups, respectively, the RD values decreased continually with cycling.

Potential applications of the molecularly imprinted polymers (MIPs) demand physical configurations in different size ranges. Nowadays, research on MIPs is focused on the development of new or improved morphologies, which involves control and modification of the different parameters during the synthesis. In this study, the effect of different synthesis conditions on the particle size and morphology is investigated. Carbamazepine-imprinted polymers were prepared using precipitation polymerization under various conditions such as: the amounts of cross-linker and functional monomers, initiator, porogen, temperature and time of polymerization. We studied the polymerization conditions to obtain imprinted spherical particles with controllable sizes in the range of 243 nm to 3.4 μm. Scanning electron microscopy and photon correlation spectroscopy were utilized to investigate the morphological characterization. The mole ratio of the functional monomer to the cross-linker was important to obtain smaller uniformly sized particles. In addition, the results showed that the cross-linker in the molecular imprinting synthesis can affect the morphology and composition of the MIPs, which influences the binding affinity.

We report here a successful fabrication of three-dimensional (3D) photoelectrodes fully coated with hydrothermally formed TiO2 nanotubes on multi-layered Ti mesh with significantly increased surface area. A near-vertical array of ~8 nm diameter nanotubes of TiO2 was also produced on the metallic surface of folded Ti mesh electrode. The multi-layered mesh was used as a 3D highly conductive electrode, as this architecture intuitively allows for light passage, reflections, and smooth water flow for possible continuous operation of water splitting reaction. By virtue of substantially increased surface area and more efficient light usage, significantly increased photocurrent densities were obtained.

To improve the electrochemical and kinetic performances of the Mg2Ni-type hydrogen storage alloys, Mg was partially substituted by La, and the rapid solidification technology was used for the preparation of Mg20−xLaxNi10 (x = 0, 2, 4, 6) alloys. The microstructures of the as-cast Mg20−xLaxNi10 (x = 0, 2, 4, 6) and as-spun Mg20−xLaxNi10 (x = 2) alloys were systematically studied through x-ray diffraction and high-resolution transmission electronic microscopy. Electrochemical hydrogen storage properties were measured by the automatic galvanostatic system. Electrochemical impedance spectrum, linear polarization, and step-potential discharge curves were plotted using electrochemical workstation. The results showed that substitution of La for Mg was helpful for forming multiphase structures, increasing the discharge capacity of the as-cast Mg20−xLaxNi10 (x = 0, 2, 4, 6) alloys. The increasing quenching rate facilitated the formation of amorphous and nanocrystalline structures of Mg18La2Ni10 (La2) alloy, effectively improving the electrochemical and kinetic properties of Mg18La2Ni10 (La2) alloys.

The mechanisms involved in the formation of titanium (Ti) nanoclusters produced by sputtering and inert gas condensation were investigated experimentally and numerically. Ti nanoclusters were generated inside an ultrahigh vacuum compatible system under different source parameters, i.e., inert gas flow rate (fAr), length of the aggregation region (L), and sputtering discharge power (P). Nanocluster size and yield were measured using a quadrupole mass filter (QMF). The variation of the above source parameters enabled fine-tuning of the nanocluster size and yield. Herein, Ti nanoclusters were produced within the size range 3.0–10.0 nm. The combination between the nanocluster size and yield as a function of source parameters enabled understanding Ti nanocluster formation mechanisms, i.e., three-body and two-body collisions. The results show that two-body collisions dominate nanocluster production at low fAr while the three-body collisions dominate at high fAr. In addition, nanocluster size increases as L increases due to the increase in nanocluster nucleation and growth times. The maximum nanocluster yield was obtained at fAr that maximize the probability of three-body and two-body collisions. Nanoclusters could be produced within an optimum range of the sputtering discharge power wherein the nanocluster size and yield increase with increasing the discharge power as a result of increasing the amount of sputtered material. The experimental results were compared with a theoretical model of nanocluster formation via three-body collision. Detailed understanding of the evolution of size and yield of Ti (and Ti-oxide) nanoclusters is essential for producing nanoclusters that can be utilized for environmental applications such as conversion of carbon dioxide and water vapor into hydrocarbons.

The Ag@SiO2 core–shell structure nanoparticles prepared by chemical method were dispersed into epoxy matrix. By comparing with the epoxy-based composites filled with the mixed Ag and SiO2 nanoparticles (Ag + SiO2), it is found that the Ag@SiO2 core–shell structure fillers had important effects on the improved dielectric properties of the Ag@SiO2/epoxy composites. The core–shell structure fillers introduce a duplex interfacial polarization and a small number of free charge carriers, which enhance the dielectric permittivity of the composites. At the same time, the insulating SiO2 shell layer changes the interfacial interaction between the Ag filler and the epoxy matrix, not only avoiding Ag particles to connect directly and aggregate together but also providing a rough surface to contact with the epoxy host, which enhances the compatibility between the Ag@SiO2 fillers and the epoxy matrix. As the Ag@SiO2 packing ratio increases, the permittivity of the composites straightly increases and the loss tangent decreases, reaching the maximum and minimum respectively with the filler loading up to 60%.

All-oxide ultraviolet (UV) photosensors based on NiO/ZnO nanowire heterostructure were fabricated on corning glass substrates. The p-type NiO layers were directly deposited on the ZnO nanowire arrays grown on the AZO bottom electrode/glass for the formation of a p–n diode, followed by the growth of the ITO top electrode layer for the electrical interconnection of nanostructures. The fabricated device structure showed a transmittance value of about 60% in the visible region, resulting in semitransparent properties. The current–voltage (I–V) characteristics of the fabricated p–n heterostructure showed a typical rectifying behavior with a current rise at about 4 V and an I(forward)/I(reverse) ratio of about 11.3 at 8 V. In addition, the ITO/p-NiO/n-ZnO/AZO structure responded at a wave-length position of 370 nm in reverse bias, together with weak photoresponse in the visible region. An UV sensor based on the all-oxide ZnO nanowire absorber exhibited improved photoresponse compared to the device based on a ZnO thin film.

Nano- and micron-sized metal particles have important applications in catalysis and in the medical and electronic industries. For applications requiring high conductivity, such as thick film conductive pastes or isotropic conductive adhesives, AgCu particles combine high conductivity with advantages of lower costs. Here, we report the generation of AgCu particles by spray pyrolysis, a process that has the advantages of simple experimental setup, large-scale production ability, and controllable particle size. Solutions of copper nitrate and silver nitrate dissolved in deionized water with either 40 vol% ethanol (ET) or 40 vol% ethylene glycol (EG) were used as the precursor. Phase separation was observed during the generation of AgCu particles, and the particles were mainly Ag-rich and Cu-rich solid solutions. The short reactor residence time experiments indicated that both the cosolvent properties and operating conditions affect the particle formation process and change the structure of particles.