Effect of Co catalyst on PECVD growth of carbon nanotubes for NEMS applications

In this paper the effect of cobalt (Co) catalyst on the growth of carbon nanotubes (CNTs) was studied. CNTs were vertically grown by plasma enhanced chemical vapor deposition method (PECVD) at 700°C with various sputtered Co catalyst thicknesses. Experimental results shows that for carbon nanotube growth duration of 20 minutes, growth was only achieved with thinner catalyst layers but when the growth duration was doubled, high density of CNTS were also observed with thicker catalyst layers with taller nanotubes formed. The nucleation of the catalyst with various thicknesses was also studied as the absorption of the carbon feedstock is dependent on the initial size of the catalyst island

Amalgamation based optical and colorimetric sensing of mercury (II) ions with silver@graphene oxide nanocomposite materials

The article describes a facile method for the preparation of a conjugate composed of silver nanoparticles and graphene oxide (Ag@GO) via chemical reduction of silver precursors in the presence of graphene oxide (GO) while sonicating the solution. The Ag@GO was characterized by X-ray photoelectron spectroscopy, X-ray powder diffraction, and energy-dispersive X-ray spectroscopy. The nanocomposite undergoes a color change from yellow to colorless in presence of Hg(II), and this effect is based on the disappearance of the localized surface plasmon resonance absorption of the AgNPs due to the formation of silver-mercury amalgam. The presence of GO, on the other hand, prevents the agglomeration of the AgNPs and enhances the stability of the nanocomposite material in solution. Hence, the probe represents a viable optical probe for the determination of mercury(II) ions in that it can be used to visually detect Hg(II) concentrations as low as 100 μM. The instrumental LOD is 338 nM

Gold-silver@TiO2 nanocomposite-modified plasmonic photoanodes for higher efficiency dye-sensitized solar cells

In the present investigation, gold–silver@titania (Au–Ag@TiO2) plasmonic nanocomposite materials with different Au and Ag compositions were prepared using a simple one-step chemical reduction method and used as photoanodes in high-efficiency dye-sensitized solar cells (DSSCs). The Au–Ag incorporated TiO2 photoanode demonstrated an enhanced solar-to-electrical energy conversion efficiency of 7.33%, which is ∼230% higher than the unmodified TiO2 photoanode (2.22%) under full sunlight illumination (100 mW cm−2, AM 1.5G). This superior solar energy conversion efficiency was mainly due to the synergistic effect between the Au and Ag, and their surface plasmon resonance effect, which improved the optical absorption and interfacial charge transfer by minimizing the charge recombination process. The influence of the Au–Ag composition on the overall energy conversion efficiency was also explored, and the optimized composition with TiO2 was found to be Au75–Ag25. This was reflected in the femtosecond transient absorption dynamics in which the electron–phonon interaction in the Au nanoparticles was measured to be 6.14 ps in TiO2/Au75:Ag25, compared to 2.38 ps for free Au and 4.02 ps for TiO2/Au100:Ag0. The slower dynamics indicates a more efficient electron–hole separation in TiO2/Au75:Ag25 that is attributed to the formation of a Schottky barrier at the interface between TiO2 and the noble metal(s) that acts as an electron sink. The significant boost in the solar energy conversion efficiency with the Au–Ag@TiO2 plasmonic nanocomposite showed its potential as a photoanode for high-efficiency DSSCs

A practical carbon dioxide gas sensor using room-temperature hydrogen plasma reduced graphene oxide

10.1016/j.snb.2013.12.017Sensors and Actuators B: Chemical193692-70