Influence of pH on the synthesis and characterization of CuO powder for thick film room-temperature NH3 gas sensor

• Published in: Journal of materials science Vol. 46; no. 16; pp. 5568 - 5580
• Main Authors: Singh, Iqbal, Bedi, R. K.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-08-2011; Springer Nature B.V
• Subjects: Adsorption; AMMONIA; Characterization and Evaluation of Materials; Citric acid; Classical Mechanics; Coordination compounds; COPPER OXIDE; Crystallites; Crystallography and Scattering Methods; Gas sensors; Materials Science; MATHEMATICAL ANALYSIS; Nanoparticles; Polymer Sciences; Potential barriers; POWDERS; Precursors; Reaction kinetics; Room temperature; Sensors; Sol-gel processes; Solid Mechanics; Structural analysis; Surface chemistry; Synthesis; Thick films; Thickness; Precursor Solution; Cupric Nitrate; Elovich Equation; Post Thermal Treatment; Cu2O
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-011-5507-7

CuO films of 51 μm thickness have been fabricated from nanocrystalline powder, which has been synthesized by a sol–gel auto-combustion method at different pH values of the precursor solution. Studies reveal that the pH value of the precursor solution strongly affects the decomposition rate of the metal–citrate complex formed by precursors (cupric nitrate and citric acid). Structural characterization of the powder samples shows a considerable change in agglomeration behavior, crystallite size and strain with variation in pH value of the precursor solution. Studies show that high pH reaction conditions results in the production of highly porous CuO nanoparticles with lowest crystallite size of 27 nm. Thick films of the synthesized material show an extremely high response of 0.941 to few parts per million level of ammonia at room temperature as well as possesses good stability for a long period of time. The adsorption of ammonia on the sensor surface obeys Elovich equation and the reaction kinetics followed is of first order. The lowest potential barrier of 0.50 MΩ and highest rate constant of 0.0136 s
−1
have been found for ammonia adsorption on the sensor surface in case of film fabricated from CuO powder synthesized at high pH value of precursor.