Abstract
Fast and selective detection of NH3 at parts‐per‐billion (ppb) concentrations with inexpensive and low‐power sensors represents a long‐standing challenge. Here, a room temperature, solid‐state sensor is presented consisting of nanostructured porous (78%) CuBr films. These are prepared by flame‐aerosol deposition of CuO onto sensor substrates followed by dry reduction and bromination. Each step is monitored in situ through the film resistance affording excellent process control. Such porous CuBr films feature an order of magnitude higher NH3 sensitivity and five times faster response times than conventional denser CuBr films. That way, rapid (within 2.2 min) sensing of even the lowest (e.g., 5 ppb) NH3 concentrations at 90% relative humidity is attained with outstanding selectivity (30–260) over typical confounders including ethanol, acetone, H2, CH4, isoprene, acetic acid, formaldehyde, methanol, and CO, superior to state‐of‐the‐art sensors. This sensor is ideal for hand‐held and battery‐driven devices or integration into wearable electronics as it does not require heating. From a broader perspective, the process opens exciting new avenues to also explore other bromides and classes of semiconductors (e.g., sulfides, nitrides, carbides) currently not accessible by flame‐aerosol technology.
Highlights
Ammonia (NH3), a major industrial commodity (142 Mt in 2017[1]), is toxic as well as a tracer for food spoilage detection[2] and putative breath marker for impaired kidney[3] and liver function
They consist of cubic CuO with high crystallinity and average crystal size of 11 nm, as determined by X-ray diffraction (XRD) of filter-collected powder (Figure 2a)
Nanostructured porous and crystalline CuBr films were prepared by flame-aerosol deposition of CuO onto interdigitated electrodes and subsequent dry reduction-bromination
Summary
Ammonia (NH3), a major industrial commodity (142 Mt in 2017[1]), is toxic as well as a tracer for food spoilage detection[2] and putative breath marker for impaired kidney[3] and liver function (e.g., cirrhosis,[4] hepatic encephalopathy,[4] or injury[5]). There is a strong interest in developing reliable sensors over a wide range of NH3 concentrations: from 250 to 2900 ppb[6] in mouth-exhaled breath down to few ppb in indoor air[7] at high relative humidity (RH). We introduce a novel fabrication route yielding highly porous and nanostructured CuBr films for improved NH3 sensitivity and fast response dynamics at room temperature and high RH. Such films are obtained by flame-aerosol deposition[18]. Of CuO nanoparticles onto interdigitated electrodes (Figure 1a) These films are reduced and brominated by a dry process monitored in situ[19] through their resistance (Figure 1b).
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