Chain Assemblies from Nanoparticles Synthesized by Atmospheric Pressure Plasma Enhanced Chemical Vapor Deposition: The Computational View.

This article refers to the computational study of nanoparticle self-organization on the solid-state substrate surface with consideration of the experimental results, when nanoparticles were synthesised during atmospheric pressure plasma enhanced chemical vapor deposition (AP-PECVD). The experimental study of silicon dioxide nanoparticle synthesis by AP-PECVD demonstrated that all deposit volume consists of tangled chains of nanoparticles. In certain cases, micron-sized fractals are formed from tangled chains due to deposit rearrangement. This work is focused on the study of tangled chain formation only. In order to reveal their formation mechanism, a physico-mathematical model was developed. The suggested model was based on the motion equation solution for charged and neutral nanoparticles in the potential fields with the use of the empirical interaction potentials. In addition, the computational simulation was carried out based on the suggested model. As a result, the influence of such experimental parameters as deposition duration, particle charge, gas flow velocity, and angle of gas flow was found. It was demonstrated that electrical charges carried by nanoparticles from the discharge area are not responsible for the formation of tangled chains from nanoparticles, whereas nanoparticle kinetic energy plays a crucial role in deposit morphology and density. The computational results were consistent with experimental results.

Electrochemical detection of hydrogen peroxide on platinum-containing tetrahedral amorphous carbon sensors and evaluation of their biofouling properties.

Hydrogen peroxide is the product of various enzymatic reactions, and is thus typically utilized as the analyte in biosensors. However, its detection with conventional materials, such as noble metals or glassy carbon, is often hindered by slow kinetics and biofouling of the electrode. In this study electrochemical properties and suitability to peroxide detection as well as ability to resist biofouling of Pt-doped ta-C samples were evaluated. Pure ta-C and pure Pt were used as references. According to the results presented here it is proposed that combining ta-C with Pt results in good electrocatalytic activity towards H2O2 oxidation with better tolerance towards aqueous environment mimicking physiological conditions compared to pure Pt. In biofouling experiments, however, both the hybrid material and Pt were almost completely blocked after immersion in protein-containing solutions and did not produce any peaks for ferrocenemethanol oxidation or reduction. On the contrary, it was still possible to obtain clear peaks for H2O2 oxidation with them after similar treatment. Moreover, quartz crystal microbalance experiment showed less protein adsorption on the hybrid sample compared to Pt which is also supported by the electrochemical biofouling experiments for H2O2 detection.

Integrated Carbon Nanostructures for Detection of Neurotransmitters.

Carbon-based materials, such as diamond-like carbon (DLC), carbon nanofibers (CNFs), and carbon nanotubes (CNTs), are inherently interesting for neurotransmitter detection due to their good biocompatibility, low cost and relatively simple synthesis. In this paper, we report on new carbon-hybrid materials, where either CNTs or CNFs are directly grown on top of tetrahedral amorphous carbon (ta-C). We show that these hybrid materials have electrochemical properties that not only combine the best characteristics of the individual "building blocks" but their synergy makes the electrode performance superior compared to conventional carbon based electrodes. By combining ta-C with CNTs, we were able to realize electrode materials that show wide and stable water window, almost reversible electron transfer properties and high sensitivity and selectivity for detecting dopamine in the presence of ascorbic acid. Furthermore, the sensitivity of ta-C + CNF hybrids towards dopamine as well as glutamate has been found excellent paving the road for actual in vivo measurements. The wide and stable water window of these sensors enables detection of other neurotransmitters besides DA as well as capability of withstanding higher potentials without suffering from oxygen and hydrogen evolution.

Glutamate detection by amino functionalized tetrahedral amorphous carbon surfaces.

In this paper, a novel amperometric glutamate biosensor with glutamate oxidase (GlOx) immobilized directly on NH2 functionalized, platinum doped tetrahedral amorphous carbon (ta-C) film, has been successfully developed. First, we demonstrate that direct GlOx immobilization is more effective on amino-groups than on carboxyl- or hydroxyl-groups. Second, we show that anodizing and plasma treatments increase the amount of nitrogen and the proportion of protonated amino groups relative to amino groups on the aminosilane coating, which subsequently results in an increased amount of active GlOx on the surface. This effect, however, is found to be unstable due to unstable electrostatic interactions between GlOx and NH3(+). We demonstrate the detection of glutamate in the concentration range of 10µM-1mM using the NH2 functionalized Pt doped ta-C surface. The biosensor showed high sensitivity (2.9nA µM(-1)cm(-2)), low detection limit (10µM) and good storage stability. The electrode response to glutamate was linear in the concentrations ranging from 10µM to 500µM. In conclusion, the study shows that GlOx immobilization is most effective on aminosilane treated ta-C surface without any pre-treatments and the fabricated sensor structure is able to detect glutamate in the micromolar range.