A novel magnetic Fe3O4 core-shell nanorods (MCSNs) were synthesized by crosslinking amine functionalized Fe3O4@SiO2 core-shell nanoparticles with 1,2-bromochloroethane. These nanorods were then protonated with dilute HCl. The MCSNs nanorods were characterized using FT-IR, N2 adsorption, VSM, SEM and TEM. The surface area of MCSNs nanorods was found to be 335 m2/g, which is higher than bare iron oxide and amine functionalized Fe3O4@SiO2. These nanorods were used simultaneously as ion-exchanger and adsorbent for the removal of arsenic from aqueous solution. It exhibited high adsorption capacity for arsenic. The kinetic study revealed that adsorption equilibrium attained within five min. The adsorbed arsenic on the nanorods were removed by magnetic separation and regenerated by acid treatment. The percentage removal of arsenic was more than 99%. Such nanorods can be used to remove not only arsenic but also other anions from potable water.

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Sustained release and replenishment of the drug depot are essential for the long-term functionality of implantable drug-delivery devices. This study demonstrates the use nanoporous gold (np-Au) thin films for in-plane transport of fluorescein (a small-molecule drug surrogate) over large (mm-scale) distances from a distal reservoir to the site of delivery, thereby establishing a constant flux of molecular release. In the absence of halides, the fluorescein transport is negligible due to a strong non-specific interaction of fluorescein with the pore walls. However, in the presence of physiologically relevant concentration of ions, halides preferentially adsorb onto the gold surface, minimizing the fluorescein–gold interactions and thus enabling in-plane fluorescein transport. In addition, the nanoporous film serves as an intrinsic size-exclusion matrix and allows for sustained release in biofouling conditions (dilute serum). The molecular release is reproducibly controlled by gating it in response to the presence of halides at the reservoir (source) and the release site (sink) without external triggers (e.g., electrical and mechanical).

A continuous flow sonochemical reactor was developed capable of producing metastable cadmium sulfide (CdS) nanoplatelets with thicknesses at or below 10nm. The continuous flow sonochemical reactor included the passive in-line micromixing of reagents prior to sonochemical reaction. Synthesis results were compared with those from reactors involving batch conventional heating and batch ultrasound-induced heating. The continuous sonochemical synthesis was found to result in high aspect ratio hexagonal platelets of CdS possessing cubic crystal structures with thicknesses well below 10nm. The unique shape and crystal structure of the nanoplatelets are suggestive of high localized temperatures within the sonochemical process. The particle size uniformity and product throughput are much higher for the continuous sonochemical process in comparison to the batch sonochemical process and conventional synthesis processes.

BackgroundBiological systems have complicated environmental conditions that vary both spatially and temporally. It becomes necessary to impose time-varying soluble factor concentrations to study such systems, including cellular responses to pharmaceuticals, inflammation with waxing and waning cytokine concentrations, as well as circadian rhythms and their metabolic manifestations. There is therefore a need for platforms that can achieve time-varying concentrations with arbitrary waveforms.ResultsTo address this need, we developed a microfluidic system that can deliver concentration waveforms in a fast and accurate manner by adopting concepts and tools from electrical engineering and fluid mechanics. Specifically, we employed pulse width modulation (PWM), a commonly used method for generating analog signals from digital sources. We implement this technique using three microfluidic components via laser ablation prototyping: low-pass filter (lower frequency signals permitted, high frequency signals blocked), resistor, and mixer. Each microfluidic component was individually studied and iteratively tuned to generate desired concentration waveforms with high accuracy. Using fluorescein as a small-molecule soluble factor surrogate, we demonstrated a series of concentration waveforms, including square, sawtooth, sinusoidal, and triangle waves with frequencies ranging from 100 mHz to 400 mHz.ConclusionWe reported the fabrication and characterization of microfluidic platform that can generate time-varying concentrations of fluorescein with arbitrary waveforms. We envision that this platform will enable a wide range of biological studies, where time-varying soluble factor concentrations play a critical role. In addition, the technology is expected to assist in the development of biomedical devices that allow precise dosing of pharmaceuticals for enhanced therapeutic efficacy and reduced toxicity.Electronic supplementary materialThe online version of this article (10.1186/s13036-018-0126-3) contains supplementary material, which is available to authorized users.

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Microchannel mixers enable faster mixing times compared with batch stir mixing leading to the promise of higher throughput, better yields and less solvent usage for the solution-phase reactive precipitation of inorganic nanoparticles. However, reliance on diffusive transport for subsecond mixing requires channel dimensions in the tens of micrometers. These channel dimensions make diffusive micromixers vulnerable to clogging. In this paper, an oscillatory flow mixing strategy is explored to increase the contact area between reagents within larger microchannels. Forward and reverse oscillatory signals are designed to pump reactants through a 450 μm high serpentine microchannel to increase advection within the flow. Computational fluid dynamics simulations are performed to provide insight into flow behavior and nanoparticle morphology. Quantification of mixing performance is proposed using mixing quality and particle residence time metrics. Experimental validation is pursued through the reactive precipitation of CdS quantum dots using a reverse oscillatory mixing setup. Transmission electron microscopy provides insights into the particle size distribution and particle crystallinity.

Motheye antireflective coatings (ARCs) are based on periodic or stochastic features with dimensions below the wavelength of visible light which can be used to produce a gradient index of refraction between air and the substrate. In this work, two silica nanoparticle-based motheye ARCs of similar optical performance, but different physical structures, were deposited on glass and characterized for mechanical behavior to provide insights into the mechanisms for abrasion resistance in these films. Optical and mechanical performances were evaluated in light of the mechanical properties and physical structure of the films using models for describing the mechanical behavior of the films. The results show that the three-layer coating was found to have better abrasion resistance than a simple single layer coating largely due to better crack nucleation resistance and scratch resistance. The simple single-layer film showed better crack propagation resistance than the three-layer film due to the existence of nanoparticles (NPs) throughout the cross section of the film. The three-layer film appears to have higher work of adhesion based on exhibiting better delamination and spallation resistance.