Carbon nanostructures deposition in microwave plasma torch at atmospheric pressure on sensors for heavy metal detection
| Authors | |
|---|---|
| Year of publication | 2007 |
| Type | Article in Proceedings |
| Conference | Book of Contributed Papers of The 3rd Seminar on New Trends on Plasma Physics and Solid State Physics |
| MU Faculty or unit | |
| Citation | |
| Field | Plasma physics |
| Keywords | carbon nanotubes; heavy metals; sensor |
| Description | Carbon nanostructures were directly deposited on a working electrode of a thick film sensor used for heavy metal detection. The sensor structure (Figure 1.) was fabricated by screen-printing techniques on Al2O3 ceramic substrate. The electrodes and conductive layer material was ESL 9912-D paste and for dielectric layer ESL 4913-G paste (both ESL ElectroScience, UK). The base of working electrode is formed from Ag, Au, or Pt to prevent inter-metallic reaction with catalyst during deposition process. Demand for the electrical conductivity of the working electrode was a limiting factor for the choice of the barrier material and a metal-metal interaction during the carbon nanotubes (CNTs) deposition in high temperature (600-700 C) required an optimization of the whole electrode system. The barrier layers were prepared by the screen printing or electroplating and possibly heated up to 500 or 850 C. The catalyst was vacuum evaporated 5-20 nm thick layer of Ni on top of the working electrode surface. Carbon nanotubes (Figure 2.) were deposited on such prepared working electrode surface in microwave plasma torch at atmospheric pressure from the mixture of methane, hydrogen and argon[1]. The plasma torch was generated at the frequency of 2.45 GHz using an iron hollow electrode. Argon (1500 sccm) was flowing through the electrode central channel whereas methane (10-40 sccm) and hydrogen (100-400 sccm) were added to the expanding torch from outside. The sensor substrates were placed at various distances from the torch electrode (35-55 mm). The samples were imaged by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The processes in the discharge were monitored by optical emission spectroscopy (OES). The performance of sensors was evaluated by differential pulse voltammetry. |
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