We report the direct experimental observation of the semiconductor-metal transition in single-wall carbon nanotubes (SWNTs) induced by compression with the tip of an atomic force microscope. This transition is probed via electric force microscopy by monitoring SWNT charge storage. Experimental data show that such charge storage is different for metallic and semiconducting SWNTs, with the latter presenting a strong dependence on the tip-SWNT force during injection. Ab initio calculations corroborate experimental observations and their interpretation.

Ferulic acid (4-hydroxy-3-methoxycinnamic acid) is a phytochemical constituent from the polyphenols group commonly found in whole grains, spinach, parsley, grapes and rhubarb. It has been widely applied in skin care formulations as photoprotective agent and delayer of cutaneous photoaging processes. This work aims to establish a protocol to the development of cosmetic formulations using thermoanalytical techniques (TG/DTG and DSC) and Pearson's correlation by FTIR data, in order to evaluate the compatibility between ferulic acid and excipients used in skin care formulations. The results obtained from the thermoanalytical techniques indicated compatibility between ferulic acid and the following excipients: passion fruit seed oil, Carbopol Ò Ultrez 30, EDTA, Crodabase CR2 Ò , Crodamol TM GTCC and Dow Corning Ò RM 2051. Nevertheless, the analysis also demonstrated the possibility of some interaction between ferulic acid and the following excipients: glyceryl stearate, Rapithix Ò A-60 and Optiphen Ò . To validate these results, it was demonstrated by Pearson's correlation that passion fruit seed oil, Carbopol Ò Ultrez 30, EDTA, Crodabase CR2 Ò , Crodamol TM GTCC, Dow Corning Ò RM 2051, glyceryl stearate and Rapithix Ò A-60 do not have any incompatibility that may compromise ferulic acid properties. Finally, it was also proved a meaningful incompatibility between ferulic acid and Optiphen Ò using Pearson's correlation. Thus, it is not recommended to use Optiphen Ò in the development of cosmetic formulations to carry ferulic acid.

This work presents a resonance Raman study of polyyne molecules ͑linear carbon chains͒ encapsulated inside single-wall carbon nanotubes using many different laser lines. A strong enhancement of the polyyne Raman features is observed around 2.1 eV, and this result is ascribed to dark electronic transitions of the linear carbon chains that can be observed when they are trapped inside a carbon nanotube. The huge observed energy splitting between bright and dark excited states is ascribed to strong Coulomb effects in this strictly onedimensional system.

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