Z. Pápa

Interactions at the Peptide/Silicon Surfaces: Evidence of Peptide Multilayer Assembly

Selective deposition of peptides from liquid solutions to n- and p-doped silicon has been demonstrated. The selectivity is governed by peptide/silicon adhesion differences. A noninvasive, fast characterization of the obtained peptide layers is required to promote their application for interfacing silicon-based devices with biological material. In this study we show that spectroscopic ellipsometry-a method increasingly used for the investigation of biointerfaces-can provide essential information about the amount of adsorbed peptide material and the degree of coverage on silicon surfaces. We observed the formation of peptide multilayers for a strongly binding adhesion peptide on p-doped silicon. Application of the patterned layer ellipsometric evaluation method combined with Sellmeier dispersion led to physically consistent results, which describe well the optical properties of peptide layers in the visible spectral range. This evaluation allowed the estimation of surface coverage, which is an important indicator of adsorption quality. The ellipsometric findings were well supported by atomic force microscopy results.

Measurement of nanoplasmonic field enhancement with ultrafast photoemission

Plasmonic enhancement of optical near-fields at nanostructures provides for localization of the energy of light on the nanoscale. This phenomenon allowed pioneering applications in spectroscopy, photovoltaics and sensorics. It remains a challenge to measure the extent of the maximum achievable nanoplasmonic field enhancement for a particular sample. Even though near-field probing methods such as scanning near-field optical microscopy (SNOM) can reach a resolution down to 8–10 nm, probing near-fields on ∼1 nm scale needs a different approach. Here, we demonstrate a method for nanoplasmonic near-field measurement with the help of photoemitted electrons induced by femtosecond laser pulses.

Influence of synthesis parameters on CCVD growth of vertically aligned carbon nanotubes over aluminum substrate

In the past two decades, important results have been achieved in the field of carbon nanotube (CNT) research, which revealed that carbon nanotubes have extremely good electrical and mechanical properties The range of applications widens more, if CNTs form a forest-like, vertically aligned structure (VACNT) Although, VACNT-conductive substrate structure could be very advantageous for various applications, to produce proper system without barrier films i.e. with good electrical contact is still a challenge. The aim of the current work is to develop a cheap and easy method for growing carbon nanotubes forests on conductive substrate with the CCVD (Catalytic Chemical Vapor Deposition) technique at 640 °C. The applied catalyst contained Fe and Co and was deposited via dip coating onto an aluminum substrate. In order to control the height of CNT forest several parameters were varied during the both catalyst layer fabrication (e.g. ink concentration, ink composition, dipping speed) and the CCVD synthesis (e.g. gas feeds, reaction time). As-prepared CNT forests were investigated with various methods such as scanning electron microscopy, Raman spectroscopy, and cyclic voltammetry. With such an easy process it was possible to tune both the height and the quality of carbon nanotube forests.

Ellipsometric Analysis of Aligned Carbon Nanotubes for Designing Catalytic Support Systems

Vertically aligned CNT carpets combined with inorganic semiconductors are expected good prospect in practical applications, especially in photocatalysis. If these devices are in production, a fast and non-invasive characterization method will be required. Ellipsometry is widely used in industry as an in-line monitoring tool, so in this study the applicability of ellipsometry for characterizing CNT carpets is investigated. It is shown that ellipsometric evaluation can provide information about the density and the optical properties of the nanotubes; however, the properties of the individual nanotubes (diameter, wall number) can not be taken into account during ellipsometric modeling. To overcome these limitations, numerical simulations are also presented.