Biodegradable iron-silicon implants produced by additive manufacturing.

Due to many negative and undesirable side effects from the use of permanent implants, the development of temporary implants based on biocompatible and biodegradable materials is a promising area of modern medicine. In the presented study, we have investigated complex-shaped iron-silicon (Fe-Si) scaffolds that can be used as potential biodegradable framework structures for solid implants for bone grafting. Since iron and silicon are biocompatible materials, and their alloy should also have biocompatibility. It has been demonstrated that cells, mesenchymal stromal cells derived from the human umbilical cord (UC-MSC) and 3T3, were attached to, spread, and proliferated on the Fe-Si scaffolds' surface. Most of UC-MSC and 3T3 remained viable, only single dead cells were observed. According to the results of biological testing, the scaffolds have shown that deposition of calcium phosphate particles occurs on day one in the scaffold at the defect site that can be used as a primary marker of osteodifferentiation. These results demonstrate that the 3D-printed porous iron-silicon (Fe-Si) alloy scaffolds are promising structures for bone grafting and regeneration.

Role of Nitrogen and Oxygen in Capacitance Formation of Carbon Nanowalls.

Supercapacitors based on carbon nanomaterials are attracting much attention because of their high capacitance enabled by large specific surface area. The introduction of heteroatoms such as N or O enhances the specific capacitance of these materials. However, the mechanisms that lead to the increase in the specific capacitance are not yet well-studied. In this Letter, we demonstrate an effective method for modification of the surface of carbon nanowalls (CNWs) using DC plasma in atmospheres of O2, N2, and their mixture. Processing in the plasma leads to the incorporation of ∼4 atom % nitrogen and ∼10 atom % oxygen atoms. Electrochemical measurements reveal that CNWs functionalized with oxygen groups are characterized by higher capacitance. The specific capacitance for samples with oxygen reaches 8.9 F cm-3 at a scan rate of 20 mV s-1. In contrast, the nitrogen-doped samples demonstrate a specific capacitance of 4.4 F cm-3 at the same scan rate. The mechanism of heteroatom incorporation into the carbon lattice is explained using density functional theory calculations.

Self-assembled nanoparticle patterns on carbon nanowall surfaces.

We observed that thermally treated carbon nanowalls serve efficiently as templates governing the formation of quasiperiodic patterns for nanoparticles deposited. Here we report self-assembled quasi-regular structures of diverse nanoparticles on a freestanding multilayer graphene-like material, i.e. carbon nanowalls. Metallic (Ag, Al, Co, Mo, Ni, and Ta) and semiconductor (Si) nanoparticles form coaxial polygonal closed loop structures or parallel equidistant rows, which evolve upon further deposition into bead-like structures and, finally, into nanowires. Weakly bonded nanoparticles decorate atomic steps, wrinkles and other extended defects on the carbon nanowalls as a result of anisotropic diffusion of atoms or clusters along the hexagonal sp(2)-carbon network followed by their aggregation and agglomeration. The decorated carbon nanowalls are found to be promising materials for surface enhanced Raman scattering (SERS) analysis.

Carbon nanowalls: the next step for physical manifestation of the black body coating.

The optical properties of carbon nanowall (CNW) films in the visible range have been studied and reported for the first time. Depending on the film structure, ultra-low total reflectance up to 0.13% can be reached, which makes the CNW films a promising candidate for the black body-like coating, and thus for a wide range of applications as a light absorber. We have estimated important trends in the optical property variation from sample to sample, and identified the presence of edge states and domain boundaries in carbon nanowalls as well as the film mass density variation as the key factors. Also we demonstrated that at much lower film thickness and density than for a carbon nanotube forest the CNWs yield one order higher specific light absorption.