Carbon nanotube-carbon black hybrid counter electrodes for dye-sensitized solar cells and the effect on charge transfer kinetics

In this work, the catalytic activity of carbon nanotubes (CNTs), carbon black (CB), and CNT-CB counter electrodes in the I⁻/I₃⁻ reduction reaction is reported and compared with the Pt counter electrode. The fabricated counter electrodes were evaluated in dye-sensitized solar cells (DSSCs). The results indicate that the best cathodes were made from CNT₁₀ (240 μm) and CB with a charge transfer resistance (R_CT) of 2.70 Ω, and when the complete device shows 19.83 Ω of internal series resistance (R_S), the photovoltaic parameters of these cells were J_SC = 10.47 mA cm⁻²; V_OC = 0.70 V; and FF = 57.90, with an efficiency of 4.29%, indicating a better interaction between the CNT₁₀ in the 3D network of the counter electrode, generating a good charge transfer kinetics, in comparison with only CNT₁₀ or CB.

     

Low-temperature ozone treatment for carbon nanotube template removal: improving the template-based ALD method

This work addresses the production of stand-alone ceramic nanotubes by the template-based ALD method at low temperature. Nitrogen-doped multiwalled carbon nanotubes (CNTs) were coated with ZnO. Afterward, the template removal was evaluated by two different approaches: using oxidation in dry air or in an ozone-rich atmosphere. The samples treated by the two different methods were analyzed by XRD, TEM, SAED, and Raman spectroscopy. The dry air atmosphere requires high temperatures (~?700 °C) for a complete CNT removal; at that temperature, the ZnO tubular shape is completely collapsed due to recrystallization. Under ozone atmosphere, the template can be removed at temperatures as low as 85 °C; this temperature is lower than the ALD preparation temperature (120 °C). The ozone treatment maintains the tubular shape of the ZnO nanostructures. Photocatalytic activity of the ZnO samples was evaluated using the photo-oxidation of Amaranth as probe reaction, showing a higher activity the ZnO nanotubes obtained from the low-temperature ozone treatment than the high-temperature processed materials. The use of ozone for the template removal reinforces the template-based ALD method to produce inorganic nanotubes.     

Influence of organic solvents in the Pt nanoparticle synthesis on MWCNT for the methanol oxidation reaction

Journal of Solid State Electrochemistry - We studied the effect of the organic solvent on the synthesis of platinum nanoparticles anchored on the surface of multi-wall carbon nanotubes (Pt...     

N-methylpyrrolidine-based precursors for chemical vapor deposition of GaNx particles

An attempt to prepare a metalorganic precursor of gallium with reactivity at low temperature in chemical vapor deposition (CVD) systems was done by reacting N-methylpyrrolidine with metal gallium or gallium nitrate under mild conditions. The precursors were bubbled into a CVD assemblage and then reacted with ammonia at temperatures between 400 and 700 °C. The depositions onto silicon substrates were pyramidal particles of 100 nm width at the base and up to 55 nm in height. The rise in growth temperature increased particle density from 0.9 to 27.1 particles per square micron, but reduced the height from 50 to 10 or 2 nm. XPS spectra showed the presence of gallium and nitrogen. The intensity of the gallium spectrum decreased as the process temperature increased indicating that GaN_x particles were deposited rather than the stoichiometric gallium nitride (GaN). An additional N1s band of impurities appeared whose intensity increases with the reaction temperature. The lower impurity content corresponded to the sample prepared with Ga(NO₃)₃ at 400 °C.     

MWCNT-oxazolidinone conjugates with antibacterial activity

Journal of Nanoparticle Research - The electronic and optical properties of the iron-doped bismuth nanoclusters having less than 15 atoms are presented here. This doping is especially interesting...     

Selective interaction of N,N-bis(aminobenzyl)naphthalenediimides with fluoride anion

In this work, the optical properties of N,N-bis(aminobenzyl)naphthalenediimides 2a–2d (BzNDIs) and their interaction with fluoride were studied. The results demonstrated that the amino group position in the benzyl substituent exerts an effect in the absorption and emission properties. Particularly, the N,N-bis(2-aminobenzyl)NDI 2b presented non-typical absorption and emission bands which indicate an intramolecular charge transfer from the amino phenyl group to the NDI core. As the concentration of 2b increases, the solution turns from colourless to a pale orange colour. The interaction of BzNDIs 2a–2d with anions was selective towards fluoride and the affinity was in the order para > ortho > meta with respect to the position of the amino group in the aminophenyl ring. Interestingly, the colour change in the solution of 2b upon addition of fluoride makes it a good candidate for a fluoride colorimetric detection. The voltammetry analysis indicates the ability of these molecules to accept two electrons, in consequence the interaction of two fluoride anions with the BzNDIs was observed.