| SM ISO690:2012|
GERU, Ion; TARABUKIN, Alexandr; IGNAT, Marius; POPOVICI, E.. Controlled synthesis and tunable properties of mesoporous semiconducting carbon nanotubes. In: Materials Science and Condensed Matter Physics. Editia a 6-a, 11-14 septembrie 2012, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2012, p. 201. ISBN 978-9975-66-290-1.
|Materials Science and Condensed Matter Physics
Editia a 6-a, 2012
Conferința "Materials Science and Condensed Matter Physics" |
Chișinău, Moldova, 11-14 septembrie 2012
Mesoporous carbon nanotubes (CNTs) were prepared by a simple nanocasting route, implying SBA-15 as template and glycerol as carbon source. The silica template, SBA-15, was synthesized using a tri-block copolymer (Pluronic P123) by a hydrothermal method during three days. SBA-15 was synthesized using the tri-block copolymer poly(ethylene glycol)-block-poly(propylene glycol)block-poly(ethylene glycol) (Pluronic P123, Molecular weight = 5800, EO20PO70EO20) (Aldrich) as a structure directing agent according to the method reported in the literature . The structure of the synthesized mesoporous carbon was studied using both low and wide angle XRD. The low angle XRD pattern shows three well resolved peaks (100), (110) and (200) which are characteristic to the two-dimensional hexagonal space group p6mm. As the mesoporous carbon material exhibits these kinds of diffractions, it has an ordered structure retained from the silica template. The low angle XRD pattern allowed calculations of the cell parameter (a0 = 9.8 nm) and d-spacing (d100 = 8.5 nm). The wide angle XRD pattern exhibit two peaks: (002) resulting from stacks of parallel layer planes, and (101) peak that is know to be characteristic to the carbon states described as clusters made of small fragments of graphene planes plus some amount of disorganized carbon. The average pore sizes of the mesoporous carbon samples are ranging from 3 nm to 5 nm. The calculated pore size distribution data showed a pore size distribution centered at 3.8 nm. The Raman spectrum shows a strong vibration at 1599 cm-1 (the G-band) that characterizes the E2g mode, which is due to the vibration corresponding to the movement in opposite directions of two neighboring sp2-bonded carbon atoms in a two-dimensional hexagonal lattice. The presence of the G-band suggests that well defined graphitic domains are indeed developed. Another band, centered appreciatively at 1342 cm-1 (the D-band), which results from the defects within the graphite layers, suggests the existence of the disordered graphitized domains. The SEM images show that the mesoporous carbon material is made up of rod/pipe-like particles. These data are consistent with the XRD and nitrogen sorption measurements. EPR spectrum of the semiconducting CNT is characterized by a single slightly asymmetric wide line with ΔHpp= 87.387 mT and g = 2.1914 (T = 300 K) having the shape near to the Gaussian. It was shown that the mesoporous semiconducting CNTs with above noticed properties are characterized by a strong tenzoresistive effect (Fig.1) with great possibilities for applications as tenzoresistive sensors of mechanical values. In Fig.1 ρ and ρ0 are the resistivities at given pressure P and →at P ∞, respectively. In the pressure range of about 0.4 MPa the longitudinal coefficient of tenzoresistivity (tenzosensitivity) is 6⋅10-6 Pa-1 while at pressure P of about 2 MPa the tenzosensitivity is 1.7⋅10-7 Pa-1.figure