Magnetoelastic Humidity Sensors with TiO2 Nanotube Sensing Layers.

In this study, TiO2 nanotubes (TiO2-NTs) are coated with a drop-casting method on Fe40Ni38Mo4B18 amorphous ferromagnetic ribbons and the humidity response of the prepared magnetoelastic sensors (MES) is investigated. The synthesis of TiO2-NTs is performed using a hydrothermal process. Sample characterization is carried out using X-ray diffraction and scanning electron microscopy. The results show that the sensors can measure moisture values in the range of 5% to 95% with very high precision and very low hysteresis. The humidity variation between 5% and 95% shows a change in the sensor resonance frequency of ~3180 Hz, which is a significant change compared to many magnetoelastic humidity sensors developed so far.

Proton enhancement in an extended nanochannel.

Proton enhancement in an extended nanochannel is investigated by a continuum model consisting of three-dimensional Poisson-Nernst-Planck equations for the ionic mass transport of multiple ionic species with the consideration of surface chemistry on the nanochannel wall. The model is validated by the existing experimental data of the proton distribution inside an extended silica nanochannel. The proton enhancement behavior depends substantially on the background salt concentration, pH, and dimensions of the nanochannel. The proton enrichment at the center of the nanochannel is significant when the bulk pH is medium high (ca. 8) and the salt concentration is relatively low. The results gathered are informative for the development of biomimetic nanofluidic apparatuses and the interpretation of relevant experimental data.

Investigation of a weak magnetic field effect on the in vitro catalytic activity of adenosine deaminase and xanthine oxidase.

The effect of a weak magnetic field (MF) on adenosine deaminase (ADA) and xanthine oxidase (XOD) activities have been investigated. A 50 Hz uniform MF was generated, and the magnitude of the field was kept constant at 5.8 mT. The changes in ADA activity over time were significantly different in and out of the MF; MF caused a steeper decline in ADA activity compared to the situation when no MF is present. In addition, MF caused a significant increase in XOD activity. There were no significant time-related changes for either enzyme in the absence of the MF. We suggest that a weak MF affects enzymatic systems.

Multi-scale quantification and modeling of aged nanostructured silicon-based composite anodes.

Advanced anode material designs utilizing dual phase alloy systems like Si/FeSi2 nano-composites show great potential to decrease the capacity degrading and improve the cycling capability for Lithium (Li)-ion batteries. Here, we present a multi-scale characterization approach to understand the (de-)lithiation and irreversible volumetric changes of the amorphous silicon (a-Si)/crystalline iron-silicide (c-FeSi2) nanoscale phase and its evolution due to cycling, as well as their impact on the proximate pore network. Scattering and 2D/3D imaging techniques are applied to probe the anode structural ageing from nm to µm length scales, after up to 300 charge-discharge cycles, and combined with modeling using the collected image data as an input. We obtain a quantified insight into the inhomogeneous lithiation of the active material induced by the morphology changes due to cycling. The electrochemical performance of Li-ion batteries does not only depend on the active material used, but also on the architecture of its proximity.

Rapid synthesis and characterization of maghemite nanoparticles.

Fe2O3-SiO2 nanocomposites were prepared by a sol-gel method using various evaporation surface to volume (S/V) ratios ranging from 0.03 to 0.2. The Fe2O3-SiO2 sols were gelated at various temperatures ranging from 50 degrees C to 70 degrees C, and subsequently they were calcined in air at 400 degrees C for 4 hours. The structure and the magnetic properties of the prepared Fe203-SiO2 nanocomposites were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), differential thermal analysis (DTA), and vibrating sample magnetometer (VSM) measurements. The gelation temperature of the Fe2O3-SiO2 sols influenced strongly the particle size and crystallinity of the maghemite nanoparticles. It was observed that the particle size of maghemite nanoparticles increased with the increasing of the gelation temperature of the sols, which may be due to the agglomeration of the maghemite particles at elevated temperatures inside the microporosity of the silica matrix during the gelation process, and the subsequent calcination of these gels at 400 degrees C resulted in the formation of large size iron oxide particles. Magnetization studies at temperatures of 10, 195, and 300 K showed superparamagnetic behavior for all the nanocomposites prepared using the evaporation surface to volume ratio (S/V) of 0.1, 0.2, 0.09, and 0.08. The saturation magnetization, Ms, values measured at 10 K were 5.5, 8.5, and 9.5 emu/g, for the samples gelated at 50, 60, and 70 degrees C, respectively. At the gelation temperature of 70 degrees C, gamma-Fe2O3 crystalline superparamagnetic nanoparticles with the particle size of 9 +/- 2 nm were formed in 12 hours for the samples prepared at the S/V ratio of 0.2.

Quantifying the Influence of the Crowded Cytoplasm on Small Molecule Diffusion.

Cytosolic crowding can influence the thermodynamics and kinetics of in vivo chemical reactions. Most significantly, proteins and nucleic acid crowders reduce the accessible volume fraction, ϕ, available to a diffusing substrate, thereby reducing its effective diffusion rate, Deff, relative to its rate in bulk solution. However, Deff can be further hindered or even enhanced, when long-range crowder/diffuser interactions are significant. To probe these effects, we numerically estimated Deff values for small, charged molecules in representative, cytosolic protein lattices up to 0.1 × 0.1 × 0.1 µm(3) in volume via the homogenized Smoluchowski electro-diffusion equation. We further validated our predictions against Deff estimates from ϕ-dependent analytical relationships, such as the Maxwell-Garnett (MG) bound, as well as explicit solutions of the time-dependent electro-diffusion equation. We find that in typical, moderately crowded cell cytoplasm (ϕ ≈ 0.8), Deff is primarily determined by ϕ; in other words, diverse protein shapes and heterogeneous distributions only modestly impact Deff. However, electrostatic interactions between diffusers and crowders, particularly at low electrolyte ionic strengths, can substantially modulate Deff. These findings help delineate the extent that cytoplasmic crowders influence small molecule diffusion, which ultimately may shape the efficiency and timing of intracellular signaling pathways. More generally, the quantitative agreement between computationally expensive solutions of the time-dependent electro-diffusion equation and its comparatively cheaper homogenized form suggest that the latter is a broadly effective model for diffusion in wide-ranging, crowded biological media.

Analytical model for charge properties of silica particles.

An analytical model for surface charge density and zeta potential of silica particles is derived and verified. The model takes into account surface chemistry reactions of the silanol groups and multiple ionic species. The predictions are in good agreement with the experimental data available from the literature. Surface charge density and zeta potential of silica particles strongly depend on both pH and background salt concentration of the aqueous solution.