Plasmonic Sensing Studies of a Gas-Phase Cystic Fibrosis Marker in Moisture Laden Air.
ABSTRACT: A plasmonic sensing platform was developed as a noninvasive method to monitor gas-phase biomarkers related to cystic fibrosis (CF). The nanohole array (NHA) sensing platform is based on localized surface plasmon resonance (LSPR) and offers a rapid data acquisition capability. Among the numerous gas-phase biomarkers that can be used to assess the lung health of CF patients, acetaldehyde was selected for this investigation. Previous research with diverse types of sensing platforms, with materials ranging from metal oxides to 2-D materials, detected gas-phase acetaldehyde with the lowest detection limit at the µmol/mol (parts-per-million (ppm)) level. In contrast, this work presents a plasmonic sensing platform that can approach the nmol/mol (parts-per-billion (ppb)) level, which covers the required concentration range needed to monitor the status of lung infection and find pulmonary exacerbations. During the experimental measurements made by a spectrometer and by a smartphone, the sensing examination was initially performed in a dry air background and then with high relative humidity (RH) as an interferent, which is relevant to exhaled breath. At a room temperature of 23.1 °C, the lowest detection limit for the investigated plasmonic sensing platform under dry air and 72% RH conditions are 250 nmol/mol (ppb) and 1000 nmol/mol (ppb), respectively.
Project description:This study reported a novel humidity-insensitive nitrogen dioxide (NO<sub>2</sub>) gas sensor based on tin dioxide (SnO<sub>2</sub>)/reduced graphene oxide (rGO) composites through the sol-gel method. The sensor demonstrated ppb-level NO<sub>2</sub> detection in p-type sensing behaviors (13.6% response to 750 ppb). Because of the synergistic effect on SnO<sub>2</sub>/rGO p-n heterojunction, the sensing performance was greatly enhanced compared to that of bare rGO. The limit of detection of sensors was as low as 6.7 ppb under dry air. Moreover, benefited from the formed superhydrophobic structure of the SnO<sub>2</sub>/rGO composites (contact angle: 149.0°), the humidity showed a negligible influence on the dynamic response (S<sub>g</sub>) of the sensor to different concentration of NO<sub>2</sub> when increasing the relative humidity (RH) from 0 to 70% at 116°C. The relative conductivity of the sensor to 83% relative humidity was 0.11%. In addition, the response ratio (S<sub>g</sub>/S<sub>RH</sub>) between 750 ppb NO<sub>2</sub> and 83% RH was 649.0, indicating the negligible impaction of high-level ambient humidity on the sensor. The as-fabricated humidity-insensitive gas sensor can promise NO<sub>2</sub> detection in real-world applications such as safety alarm, chemical engineering, and so on.
Project description:In this research work, the gas sensing properties of halogenated chloroaluminum phthalocyanine (ClAlPc) thin films were studied at room temperature. We fabricated an air-stable ClAlPc gas sensor based on a vertical organic diode (VOD) with a porous top electrode by the solution process method. The surface morphology of the solution-processed ClAlPc thin film was examined by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The proposed ClAlPc-based VOD sensor can detect ammonia (NH<sub>3</sub>) gas at the ppb level (100~1000 ppb) at room temperature. Additionally, the ClAlPc sensor was highly selective towards NH<sub>3</sub> gas compared to other interfering gases (NO<sub>2</sub>, ACE, NO, H<sub>2</sub>S, and CO). In addition, the device lifetime was tested by storing the device at ambient conditions. The effect of relative humidity (RH) on the ClAlPc NH<sub>3</sub> gas sensor was also explored. The aim of this study is to extend these findings on halogenated phthalocyanine-based materials to practical electronic nose applications in the future.
Project description:Abstract Acetone is a toxic air pollutant and a key breath marker for non?invasively monitoring fat metabolism. Its routine detection in realistic gas mixtures (i.e., human breath and indoor air), however, is challenging, as low?cost acetone sensors suffer from insufficient selectivity. Here, a compact detector for acetone sensing is introduced, having unprecedented selectivity (>250) over the most challenging interferants (e.g., alcohols, aldehydes, aromatics, isoprene, ammonia, H2, and CO). That way, acetone is quantified with fast response (<1 min) down to, at least, 50 parts per billion (ppb) in gas mixtures with such interferants having up to two orders of magnitude higher concentration than acetone at realistic relative humidities (RH = 30–90%). The detector consists of a catalytic packed bed (30 mg) of flame?made Al2O3 nanoparticles (120 m2 g?1) decorated with Pt nanoclusters (average size 9 nm) and a highly sensitive chemo?resistive sensor made by flame aerosol deposition and in situ annealing of nanostructured Si?doped ??WO3 (Si/WO3). Most importantly, the catalytic packed bed converts interferants continuously enabling highly selective acetone sensing even in the exhaled breath of a volunteer. The detector exhibits stable performance over, at least, 145 days at 90% RH, as validated by mass spectrometry. A solid?state detector is presented that quantifies acetone down to 50 parts per billion (ppb) with unmet selectivity in gas mixtures having two orders of magnitude higher interferant concentrations and in exhaled human breath. It is low?cost, combining a nanostructured Pt/Al2O3 catalyst with a Si/WO3 chemoresistive sensor in a compact design, and is promising for hand?held breath analyzers or wearable air quality monitors.
Project description:Two-dimensional (2D) transition metal dichalcogenides (TMDs) and metal chalcogenides (MCs), despite their excellent gas sensing properties, are subjected to spontaneous oxidation in ambient air, negatively affecting the sensor's signal reproducibility in the long run. Taking advantage of spontaneous oxidation, we synthesized fully amorphous <i>a</i>-SnO<sub>2</sub> 2D flakes (≈30 nm thick) by annealing in air 2D SnSe<sub>2</sub> for two weeks at temperatures below the crystallization temperature of SnO<sub>2</sub>