Purification of carbon nanotubes grown by thermal CVD

We show the results of a set of purifications on carbon nanotubes (CNT) by acid and basic treatments. CNTs were obtained by thermal decomposition of camphor at 850 °C in a CVD growth system, by means of a growth process catalyzed by iron clusters originating from the addition of ferrocene in the precursors mixture. The purification procedures involved HNO₃, H₂SO₄, HSO₃Cl and NaOH for different process temperatures.As-grown CNTs showed a consistent presence of metal catalyst (about 6 wt%), evidenced by TGA. The purification treatments led to a certain amount of opening of the CNT tips, with a consequent loss of metal catalyst encapsulated in tips. This is also confirmed by BET analysis, which showed an increase of the surface area density of CNT after the purification.FT-IR and XPS revealed the presence of carboxylic groups on the CNT surface chemically modified by the harsh environment of the purification process.Among the various treatments that have been tested, the 1:3 solution of nitric and sulphuric acid was the most effective in modifying the CNT surface and inducing the formation of functional groups.     

Experimental evidence of the exciton centre-of-mass quantization in Zn1−x Cd x Se/ZnSe multiple quantum wells

Il Nuovo Cimento D - We report the evidence of exciton-polariton centre-of-mass quantization in II–VI quantum wells consisting of ternary alloy. Absorption and photoluminescence studies on...     

Ueber das Produkt der elektrolytischen Zerstäubung der Kohlenanode und die Existenz von kolloidem Kohlenstoff

Ohne Zusammenfassung     

Über die Konstitution des Olivils aus Olivenharz

Ohne Zusammenfassung     

The impact of the nitridation process on the properties of the Si–SiO2 interface

A newly developed technique for the simultaneous measurement of the oxide–silicon interface properties and of minority carrier lifetime in the silicon volume was used for a systematic study of the nitridation process of oxide films.This technique is based on the surface recombination velocity measurements, and does not require the formation of a capacitor structure, so it is suitable for the measurement of as-grown interface properties. Oxides grown both in dry and in wet environments were prepared, and nitridation processes in N₂O and in NO were compared to N₂ annealing processes. The effect of nitridation temperature and duration were also studied, and processes of rapid thermal oxidation (RTO) and nitridation (RTN) were compared to conventional furnace nitridation processes. Surface recombination velocity was correlated with nitrogen concentration at the oxide–silicon interface obtained by secondary ion mass spectroscopy (SIMS) measurements. Surface recombination velocity (hence surface state density) decreases with increasing nitrogen pile-up at the oxide–silicon interface, indicating that in nitrided interfaces surface state density is limited by nitridation. NO treatments are much more effective than N₂O treatments in the formation of a nitrogen–rich interface layer and, as a consequence, in interface state reduction. X-ray photoelectron spectrometry (XPS) analyses were used to extend our correlation to very thin oxides (3 nm).     

Organo-silane coated substrates for DNA purification

The use of blood as DNA source to be employed in genetic analysis requires a purification process in order to remove proteins, lipids and any other contaminants, such as hemoglobin, which inhibit PCR. On the other hand, the increasing demand of miniaturized and automated biological tests able to reduce time and cost of analysis, requires the development and the characterization of materials aimed to perform the DNA purification processes in micro-devices. In this work we studied the interaction of DNA molecules with modified silicon based substrates, positively charged after deposition of a (3-aminopropyl)triethoxysilane (APTES) or 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane (AEEA) interfacial layer. The evaluation of the DNA adsorption and elution capacity of different substrates (thermally grown silicon oxide, silicon oxide obtained by plasma enhanced chemical vapour deposition, and Pyrex^®) was studied taking into account the nature of the substrate and the effect of DNA length (in the 208-50,000 base pairs range). Main findings are that DNA elution capacity depends both on the utilized substrate and on the choice of the silanizing agent. Higher DNA recovery was obtained from AEEA-modified substrates, but the eluted DNA had different electrophoretic properties from native DNA. DNA with the same electrophoretic behaviour as genomic DNA was instead recovered from APTES-treated surfaces. Furthermore, the length of DNA present in the starting material strongly modulates the elution efficiency, longer DNA being released in a lesser amount, suggesting that opportunely modified surfaces could be used as systems for differential DNA separation.