Doped ZnO Nanostructured Sensor use an Electronic Nose for Detection of ammonia, hydrogen and liquefied petroleum gas

Samir Chandra Dasa, Rajib Bandyopadhyayb, Panchanan Pramanikc

a Secretary, Faculty Councils, University of Kalyani, ,b Dept. of Instrumentation & Electronics Engineering, Jadavpur

University, Kolkata, c Dept.of Chemistry, Indian Institute of Technology, Kharagppur, W.B., India E-mail: samirdasju@yahoo.co.in

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.)2θ (Degree)

Fig. 2: XRD plots of nanostructure (a) ZnO and (b) Pd doped ZnO, calcined at 500°C for 2 h.

Fig. 3: SEM image of ZnO nanostructures.

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Fig.4 : Setup equipment for in-situ resistance measurements: 1) Pellet sample; 2) Two probe sample holder;3) Quartz test chamber; 4) Furnace; 5) Gas inlet; 6) Gas outlet; 7) Gas injection port; 8) Thermocouple; 9) Platinum wires; 10) Flung; 11) Digital multimeter; 12) Personal computer; 13) Temperature controller (PID controller).

CONCLUSIONS

Electrical measurements and gas sensing studies

RESULTS AND DISCUSSION

Average crystallite size and particle size are observed to be between 24 and 33 nm, which were analyzed through XRD and transmission electron microscope, respectively. Electrical as well as gas sensing properties of the synthesized materials have been studied by dc measurement. The response of the material to the test gases have been calculated using the equation:

Where, Ra denotes the resistance in air and Rg the resistance in the presence of a test gas. The response of the material is examined with H2, LPG and NH3 in the temperature range of 200–400◦C and the sensitivity have been observed to be quite reasonable with Pd and Pt doped samples.

Fig. 1: Schematic representation of preparation of nanostructure

ZnO powder

Synthesis of nanosized ZnO powder

EXPERIMENTAL

In this experimental work, a nanostructured ZnO like nano flowers doped with different elements, X=Pd, Pt, Co, Mn, Ni are synthesized. X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) are used for characterization of the materials. The materials were synthesized from pyrolysis of Zn(NO3)2 solution with triethanolamine with adequate dopant. After complete dehydration of the precursor solution, a black, carbonaceous, mesoporous fluffy mass is obtained, which after calcinations produces the desired nanocrystalline materials. Formation of hexagonal single phase ZnO nanoparticle is confirmed by the careful analysis of XRD data. It follows from non oriented growth for undoped nanostructure to strongly (002) oriented, at intermediate (~1at. %) doping level. The materials are also characterized through TEM, and energy dispersive X-ray (EDX) analysis to obtain the shape, size, morphology and elemental compositions.

ABSTRACT