MEAM potential-based MD simulations of melting transition on Ni surfaces.

Based on the modified embedded atom method (MEAM) potential suggested by Jin et al. (Appl. Phys. A120: 189, 2015), the molecular dynamics (MD) simulations were adopted to investigate the melting transition of the FCC transition metal Ni, and in the MD simulations, the forces acting on atoms were calculated by using the newly derived formulas. We first studied the melting points of Ni samples with low-index surfaces including Ni(100), Ni(110), and Ni(111). Then, we investigated the structural properties on the surface layers with increasing temperature up to the melting points. The simulation results exhibit that with the temperature increasing, the (110) surface firstly disorders, followed by the (100) surface, while the stability of the (111) surface is maintained until near the melting point. The disorder of surface layer atoms diffuses from the surface to the inside of the crystal lattice. With the density of atoms decreasing on the surface, the premelting effect also increases, being most pronounced on Ni(110) which corresponds to the lowest surface density. This conclusion is linked with the behavior found for the BCC transition metal Fe in our previous simulation study.

Controlling anisotropic properties by manipulating the orientation of chiral small molecules.

Chiral π-conjugated molecules bring new functionality to technological applications and represent an exciting, rapidly expanding area of research. Their functional properties, such as the absorption and emission of circularly polarized light or the transport of spin-polarized electrons, are highly anisotropic. As a result, the orientation of chiral molecules critically determines the functionality and efficiency of chiral devices. Here we present a strategy to control the orientation of a small chiral molecule (2,2'-dicyano[6]helicene) by the use of organic and inorganic templating layers. Such templating layers can either force 2,2'-dicyano[6]helicene to adopt a face-on orientation and self-assemble into upright supramolecular columns oriented with their helical axis perpendicular to the substrate, or an edge-on orientation with parallel-lying supramolecular columns. Through such control, we show that low- and high-energy chiroptical responses can be independently 'turned on' or 'turned off'. The templating methodologies described here provide a simple way to engineer orientational control and, by association, anisotropic functional properties of chiral molecular systems for a range of emerging technologies.

On-chip integrated graphene aptasensor with portable readout for fast and label-free COVID-19 detection in virus transport medium.

Graphene field-effect transistor (GFET) biosensors exhibit high sensitivity due to a large surface-to-volume ratio and the high sensitivity of the Fermi level to the presence of charged biomolecules near the surface. For most reported GFET biosensors, bulky external reference electrodes are used which prevent their full-scale chip integration and contribute to higher costs per test. In this study, GFET arrays with on-chip integrated liquid electrodes were employed for COVID-19 detection and functionalized with either antibody or aptamer to selectively bind the spike proteins of SARS-CoV-2. In the case of the aptamer-functionalized GFET (aptasensor, Apt-GFET), the limit-of-detection (LOD) achieved was about 103 particles per mL for virus-like particles (VLPs) in clinical transport medium, outperforming the Ab-GFET biosensor counterpart. In addition, the aptasensor achieved a LOD of 160 aM for COVID-19 neutralizing antibodies in serum. The sensors were found to be highly selective, fast (sample-to-result within minutes), and stable (low device-to-device signal variation; relative standard deviations below 0.5%). A home-built portable readout electronic unit was employed for simultaneous real-time measurements of 12 GFETs per chip. Our successful demonstration of a portable GFET biosensing platform has high potential for infectious disease detection and other health-care applications.

Fast estimation method of feedback factor based on the derivative of the self-mixing signal.

The self-mixing (SM) technique has been a promising optical measurement technique for a few decades. The estimation of the optical feedback factor C is the key to SM displacement measurement with a better resolution than half a wavelength. But this estimation is extremely complex and tricky, and thus leads to its time-consuming nature, which is one of the important causes that increases the cost and labor for the development of a self-mixing sensor. There have been many methods reported for the C estimation, but they are very time consuming, very sensitive to noise, or can only work in a certain feedback regime. This paper presents a novel approach to the C estimation, which is straightforward and can work for all feedback regimes including weak, moderate, and strong. The estimation precision of the proposed method is not only comparable to that of the data fitting technique but also much simpler.

Ameliorants to immobilize Cd in rice paddy soils contaminated by abandoned metal mines in Korea.

The cadmium (Cd) content of rice grain grown in metal-contaminated paddy soils near abandoned metal mines in South Korea was found to exceed safety guidelines (0.2 mg Cd kg⁻¹) set by the Korea Food and Drug Administration (KFDA). However, current remediation technologies for heavy metal-contaminated soils have limited application with respect to rice paddy soils. Laboratory and greenhouse experiments were conducted to assess the effects of amending contaminated rice paddy soils with zerovalent iron (ZVI), lime, humus, compost, and combinations of these compounds to immobilize Cd and inhibit Cd translocation to rice grain. Sequential extraction analysis revealed that treatment with the ameliorants induced a 50-90% decrease in the bioavailable Cd fractions when compared to the untreated control soil. When compared to the control, Cd uptake by rice was decreased in response to treatment with ZVI + humus (69%), lime (65%), ZVI + compost (61%), compost (46%), ZVI (42%), and humus (14%). In addition, ameliorants did not influence rice yield when compared to that of the control. Overall, the results of this study indicated that remediation technologies using ameliorants effectively reduce Cd bioavailability and uptake in contaminated rice paddy soils.