Atomic layer deposition-based functionalization of materials for medical and environmental health applications

Genotoxicity of Aluminum and Aluminum Oxide Nanomaterials in Rats Following Oral Exposure

Due to several gaps remaining in the toxicological evaluation of nanomaterials (NMs), consumers and public health agencies have shown increasing concern for human health protection. In addition to aluminum (Al) microparticles, Al-containing nanomaterials (Al NMs) have been applied by food industry as additives and contact materials. Due to the limited amount of literature on the toxicity of Al NMs, this study aimed to evaluate the in vivo genotoxic potential of Al0 and Al2O3 NMs after acute oral exposure. Male Sprague-Dawley rats were administered three successive gavages at 6, 12.5 and 25 mg/kg bw. A comparison with AlCl3 was done in order to assess the potential effect of dissolution into Al ions. Both DNA strand breaks and oxidative DNA damage were investigated in six organs/tissues (duodenum, liver, kidney, spleen, blood and bone marrow) with the alkaline and the Fpg-modified comet assays. Concomitantly, chromosomal damage was investigated in bone marrow and colon with the micronucleus assay. The comet assay only showed DNA damage with Al2O3 NMs in bone marrow (BM), while AlCl3 induced slight but non-significant oxidative DNA damage in blood. No increase of chromosomal mutations was observed after treatment with the two Al MNs either in the BM or in the colons of rats.

New development of atomic layer deposition: processes, methods and applications

Atomic layer deposition (ALD) is an ultra-thin film deposition technique that has found many applications owing to its distinct abilities. They include uniform deposition of conformal films with controllable thickness, even on complex three-dimensional surfaces, and can improve the efficiency of electronic devices. This technology has attracted significant interest both for fundamental understanding how the new functional materials can be synthesized by ALD and for numerous practical applications, particularly in advanced nanopatterning for microelectronics, energy storage systems, desalinations, catalysis and medical fields. This review introduces the progress made in ALD, both for computational and experimental methodologies, and provides an outlook of this emerging technology in comparison with other film deposition methods. It discusses experimental approaches and factors that affect the deposition and presents simulation methods, such as molecular dynamics and computational fluid dynamics, which help determine and predict effective ways to optimize ALD processes, hence enabling the reduction in cost, energy waste and adverse environmental impacts. Specific examples are chosen to illustrate the progress in ALD processes and applications that showed a considerable impact on other technologies.

Nanoporous solid-state membranes modified with multi-wall carbon nanotubes with anti-biofouling property

PURPOSE

Nanoporous membranes have been employing more than before in applications such as biomedical due to nanometer hexagonal pores array. Biofouling is one of the important problems in these applications that used nanoporous membranes and are in close contact with microorganisms. Surface modification of the membrane is one way to prevent biofilm formation; therefore, the membrane made in this work is modified with carbon nanotubes.

METHODS

In this work, nanoporous solid-state membrane (NSSM) was made by a two-step anodization method, and then modified with carbon nanotubes (NSSM-multi-wall carbon nanotubes [MWCNT]) by a simple chemical reaction. Techniques such as atomic force microscopy (AFM), energy dispersive X-ray (EDAX), field emission scanning electron microscopy (FESEM), Fourier-transform infrared spectroscopy (FTIR), contact angle (CA), surface free energy (SFE), protein adsorption, flow cytometry, and MTT assay were used for membrane characterization.

RESULTS

The BSA protein adsorption capacity reduced from 992.54 to 97.24 (μg mL-1 cm-2) after modification. The findings of flow cytometry and MTT assay confirmed that the number of dead bacteria was higher on the NSSM-MWCNT surface than that of control. Adsorption models of Freundlich and Langmuir and kinetics models were studied to understand the governing mechanism by which bacteria migrate to the membrane surface.

CONCLUSION

The cell viability of absorbed bacteria on the NSSM-MWCNT was disrupted in direct physical contact with carbon nanotubes. Then, the dead bacteria were desorbed from the surface of the hydrophilic membrane. The results of this research showed that NSSM-MWCNT containing carbon nanotubes have significant antimicrobial and self-cleaning property that can be used in many biomedical devices without facing the eminent problem of biofouling.

Porous Alumina as a Promising Biomaterial for Public Health

Porous aluminum is a nanostructured material characterized by unique properties, such as chemical stability, regular uniformity, dense hexagonal porous lattice with high aspect ratio nanopores, excellent mechanical strength, and biocompatibility. This overview examines how the structure and properties of porous alumina can be exploited in the field of public health. Porous alumina can be employed for fabricating membranes and filters for bioremediation, water ultrafiltration, and microfiltration/nanofiltration, being a promising technique for having clean and fresh water, which is essential for human health. Porous alumina-based nanobiosensor coated with specific antibodies or peptides seem to be a useful tool to detect and remove pathogens both in food and in water, as well as for environmental monitoring. Further, these applications, being low-energy demanding and cost-effective, are particularly valuable in resource-limited settings and contexts, and can be employed as point of use devices in developing countries, where there is an urgent need of hygiene and safety assurance.

Sub-nanometer atomic layer deposition for spintronics in magnetic tunnel junctions based on graphene spin-filtering membranes

We report on the successful integration of low-cost, conformal, and versatile atomic layer deposited (ALD) dielectric in Ni–Al2O3–Co magnetic tunnel junctions (MTJs) where the Ni is coated with a spin-filtering graphene membrane. The ALD tunnel barriers, as thin as 0.6 nm, are grown layer-by-layer in a simple, low-vacuum, ozone-based process, which yields high-quality electron-transport barriers as revealed by tunneling characterization. Even under these relaxed conditions, including air exposure of the interfaces, a significant tunnel magnetoresistance is measured highlighting the robustness of the process. The spin-filtering effect of graphene is enhanced, leading to an almost fully inversed spin polarization for the Ni electrode of −42%. This unlocks the potential of ALD for spintronics with conformal, layer-by-layer control of tunnel barriers in magnetic tunnel junctions toward low-cost fabrication and down-scaling of tunnel resistances.

Fabrication of 200 nm period hard X-ray phase gratings

Far field X-ray grating interferometry achieves extraordinary phase sensitivity in imaging weakly absorbing samples, provided that the grating period is within the transverse coherence length of the X-ray source. Here we describe a cost-efficient process to fabricate large area, 100 nm half-pitch hard X-ray phase gratings with an aspect ratio of 32. The nanometric gratings are suitable for ordinary compact X-ray sources having low spatial coherence, as demonstrated by X-ray diffraction experiments.