Formaldehyde (HCHO) is widely used in construction, wood processing, furniture, textile, and carpeting industries. However, it is highly toxic. It strongly irritates human eyes and nose, and is a carcinogen. In this paper, the effects of gas concentration and operating temperature on the sensing properties of the nano-SnO2 flat-type coplanar gas sensor arrays to formaldehyde were studied. The results revealed that the nano-SnO2 flat-type coplanar gas sensor arrays exhibited good sensitivity such as a fast response, short recovery time, and low detection limit. In addition, the adsorption and surface reactions of formaldehyde on SnO2 films were also studied by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) at 200–300 °C. Molecularly adsorbed formaldehyde, formate, dioxymethylene, polyoxymethylene, H2O, and CO2 surface species were formed during formaldehyde adsorption at 200–300 °C. Moreover, a possible mechanism of the reaction process was given.

Doping of a heteroatom such as nitrogen in carbon nanomaterials provides a means to tailor their electronic properties and chemical reactivities. In this article, we present simple methods to synthesize carbon quantum dots (CQDs) with high nitrogen doping content (18–22%), involving the reaction of glucose in the presence of urea under hydrothermal conditions or by microwave irradiation. The N-doped carbon quantum dots (N-CQDs) show high aqueous solubility and tunable photoluminescence (PL). Interaction of N-CQDs with exfoliated graphene or dimethylaniline quenches PL. Interaction of N-doped as well as undoped C-dots with electron-donating tetrathiafulvalene and electron-withdrawing tetracyanoethylene has been examined. The intense blue PL of CQDs has been exploited to produce white light by mixing the CQDs with yellow light emitting ZnO nanoparticles or graphene oxide. The N-doped CQDs exhibit superior photocatalytic activity compared to pristine CQDs.

The liquid impingement erosion behavior of a zirconium-based bulk metallic glass (BMG), Zr44Ti11Cu10Ni10Be25, was evaluated in this study. For comparison, commonly used hydroturbine steel was evaluated under the same test conditions. BMG demonstrated more than four times higher resistance against cavitation erosion compared with hydroturbine steel. The unusually high erosion resistance for BMG is attributed to its uniform amorphous structure with no grain boundaries, higher hardness, and ability to accommodate strain through localized shear bands.

New experimental methods have been developed to optimize the accuracy and precision of the measured phase angle in nanoindentation experiments on viscoelastic materials performed with a Berkovich indenter. Measurements conducted in fused silica and sapphire form the basis of a new instrument calibration. Experimental verification of the new calibration and an enhanced test method is demonstrated in polycarbonate (PC) and polymethyl methacrylate (PMMA). In comparison to the standard continuous stiffness measurement (CSM) technique, the new calibration and test method reduces the measurement error in the phase angle of PC from 1900% to 10% and from 135% to 10% in PMMA. Scatter in phase angle measured by the new test method is nearly 10 times less than the level observed using the standard CSM technique. The effect of time dependent deformation on the measured phase angle is also documented. The experimental observations and results are applicable to a variety of dynamic nanoindentation test methods.

In suspensions of magnetic nanoparticles in appropriate carrier liquids—commonly called ferrofluids—an external magnetic field can control the fluid properties such as viscosity. This article provides an overview of the properties and general makeup of ferrofluids, as well as classical fluid dynamics. Some of the applications of ferrofluids are also described.

Access to affordable and reliable energy has been a cornerstone of the world’s increasing prosperity and economic growth since the beginning of the Industrial Revolution. Our use of energy in the 21st century must also be sustainable. This article provides a techno-economic snapshot of the current energy landscape and identifies several research and development opportunities and challenges, especially where they relate to materials science and engineering, to create the foundation for this new industrial revolution.

New strategies for materials fabrication are of fundamental importance in theadvancement of science and technology. Nanocrystals, especially with ananisotropic shape such as cubic, are candidates for building blocks for newbottom-up approaches to materials assembly, yielding a functional architecture.Such materials also receive attention because of their intrinsic size-dependentproperties and resulting applications. Here, we report synthesis andcharacteristics of BaTiO3 and SrTiO3 nanocubes and theordered assemblies as ferroelectric supracrystals. BaTiO3 andSrTiO3 nanocubes with narrow size distributions were obtained inan aqueous process. BaTiO3 films made up of ordered nanocubeassemblies were fabricated on various substrates by evaporation-inducedself-assembly method. Regardless of the substrate, the nanocubes exhibited {100}orientations and a high degree of face-to-face ordering, which remained evenafter heat treatment at 850 °C. Piezoresponse force microscopy wascarried out on the supracrsytal films to obtain plots of thed33 piezoelectric coefficient against the polingfield, and ferroelectric hysteresis curves were shown.

New instrumentation is being developed to better understand the in vivo properties of magnetic particles suspended in solution or lodged in tissue. We describe three novel methods with the necessary sensitivity to measure the microscopic magnetic properties of individual magnetic particles and complexes quantitatively. The first method is based on proton nuclear magnetic resonance of a magnetic particle suspended in water in a microcapillary probe; the second method uses high-resolution magnetic resonance imaging of water surrounding a magnetic particle; and the third method is based on AC susceptometry with a magnetic cantilever that combines magnetic particle imaging concepts with probe microscopy. We present the physical basis for the measurements, estimate sensitivity limits, and discuss future impacts on the development of magnetic particles for bioimaging and bioassays.

This article reviews the principles of magnetic field-directed self-assembly (MFDSA) of magnetic nanoparticles (MNPs), along with recent studies that advance the fundamental understanding and potential capabilities of MNP MFDSA. This technology could eventually find application in manufacturing novel materials and components for biomedicine, energy, optics, functional composites, and microfluidics. In MFDSA, an externally applied field drives the assembly of MNPs. Uniform fields can create complex chains of MNPs, while inhomogeneous fields (such as those created by permanent magnets) apply attractive forces to MNPs that pull them toward the region of strongest field strength. Thus, MNPs can be self-organized as well as directed into user-designed patterns by controlling the external field arrangement. Because of its biocompatibility, nanoscale resolution, and low cost, MFDSA is a highly versatile technique that could enable high volume nanomanufacturing of MNPs into complex, finished materials.

Using computational modeling, we describe and explain the effects resulting from surfaces and interfaces in core–shell nanoparticles. We outline the basis of the atomistic spin model, which is used to simulate the equilibrium and dynamic magnetic properties of magnetic nanoparticles. The physical origin of magnetic surface anisotropy is described, along with its effect on the magnetic spin configuration and energy landscape. Importantly, it is shown that a cubic anisotropic surface can be induced, which leads to a complex energy landscape with a non-trivial size dependence. Additional microstructural effects in realistic nanoparticle microstructures are investigated, and fundamental magnetic properties can be significantly altered as a result. Finally, an important effect known as exchange bias is also described. Exchange bias causes an enhancement of the thermal stability of magnetic nanoparticles, but due to its atomic origin, it also leads to complicated physical behavior.