Abstract
The γ-phase polymorph of WO3 has been established in the literature as a selective NO sensor. When processed at the nanoscale, this material shows high sensitivity to trace levels of NO gas. Thus, it is intended for use in breath monitors of NO in exhaled breath to diagnose asthma. Focusing on the economic and scalable synthesis of this material, this paper reports on the flame-spray processing of WO3 nanopowders of the monoclinic γ-phase. Structural and chemical characterization of as-sprayed and heat-treated nanopowders were carried out that revealed the conditions for tailored phase and particle size distribution suitable for the intended application of this material in breath-based diagnostics.
Highlights
Nitric oxide belongs to the class of inorganic gaseous chemicals found in exhaled breath and is characterized as a signaling biomarker for disease [1,2,3]
This manuscript describes the scaled up process used to synthesize γ-WO3, by means of flame spray pyrolysis
This paper provides a new recipe and specific process steps for obtaining the required oxide polymorph and to optimize the particle size distribution for NO sensing
Summary
Nitric oxide belongs to the class of inorganic gaseous chemicals found in exhaled breath and is characterized as a signaling biomarker for disease [1,2,3]. The diagnostic value of exhaled NO measurements to differentiate between healthy persons with or without respiratory symptoms and patients with confirmed asthma has been established by Dupont who showed that >16 ppb of NO in lower respiratory tract could be treated as a cutoff for asthma with a 90% specificity and 90% positive predictive value [4] This suggests that a simple and noninvasive measurement of exhaled NO may provide a reliable signal for asthma diagnosis. The challenge has been to produce the NO sensing elements (i.e. nanocrystals of γ-WO3) using a scalable process that will enable the use of the NO breathalyzer and asthma monitor as a home diagnostic tool. This manuscript describes the scaled up process used to synthesize γ-WO3, by means of flame spray pyrolysis. This paper provides a new recipe and specific process steps for obtaining the required oxide polymorph and to optimize the particle size distribution for NO sensing
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