Developing a Low-Cost Wearable Personal Exposure Monitor for Studying Respiratory Diseases Using Metal–Oxide Sensors

As low-cost sensors have become ubiquitous in air quality measurements, there is a need for more efficient calibration and quantification practices. Here, we deploy stationary low-cost monitors in Colorado and Southern California near oil and gas facilities, focusing our analysis on methane and ozone concentration measurement using metal oxide sensors. In comparing different sensor signal normalization techniques, we propose a z-scoring standardization approach to normalize all sensor signals, making our calibration results more easily transferable among sensor packages. We also attempt several different physical co-location schemes, and explore several calibration models in which only one sensor system needs to be co-located with a reference instrument, and can be used to calibrate the rest of the fleet of sensor systems. This approach greatly reduces the time and effort involved in field normalization without compromising goodness of fit of the calibration model to a significant extent. We also explore other factors affecting the performance of the sensor system quantification method, including the use of different reference instruments, duration of co-location, time averaging, transferability between different physical environments, and the age of metal oxide sensors. Our focus on methane and stationary monitors, in addition to the z-scoring standardization approach, has broad applications in low-cost sensor calibration and utility.

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Applications of Nanostructured Materials as Gas Sensors

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.201.131 ◽

2013 ◽

Vol 201 ◽

pp. 131-158 ◽

Cited By ~ 2

Author(s):

Ravi Chand Singh ◽

Manmeet Pal Singh ◽

Hardev Singh Virk

Keyword(s):

Metal Oxide ◽

Gas Sensors ◽

Tin Dioxide ◽

Gas Sensing ◽

Dominant Role ◽

Low Cost ◽

Critical Role ◽

Health And Safety ◽

Chemical Route ◽

Metal Oxide Sensors

Gas detection instruments are increasingly needed for industrial health and safety, environmental monitoring, and process control. To meet this demand, considerable research into new sensors is underway, including efforts to enhance the performance of traditional devices, such as resistive metal oxide sensors, through nanoengineering. The resistance of semiconductors is affected by the gaseous ambient. The semiconducting metal oxides based gas sensors exploit this phenomenon. Physical chemistry of solid metal surfaces plays a dominant role in controlling the gas sensing characteristics. Metal oxide sensors have been utilized for several decades for low-cost detection of combustible and toxic gases. Recent advances in nanomaterials provide the opportunity to dramatically increase the response of these materials, as their performance is directly related to exposed surface volume. Proper control of grain size remains a key challenge for high sensor performance. Nanoparticles of SnO2have been synthesized through chemical route at 5, 25 and 50°C. The synthesized particles were sintered at 400, 600 and 800°C and their structural and morphological analysis was carried out using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The reaction temperature is found to be playing a critical role in controlling nanostructure sizes as well as agglomeration. It has been observed that particle synthesized at 5 and 50°C are smaller and less agglomerated as compared to the particles prepared at 25°C. The studies revealed that particle size and agglomeration increases with increase in sintering temperature. Thick films gas sensors were fabricated using synthesized tin dioxide powder and sensing response of all the sensors to ethanol vapors was investigated at different temperatures and concentrations. The investigations revealed that sensing response of SnO2nanoparticles is size dependent and smaller particles display higher sensitivity. Table of Contents

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Applications and Limitations of Quantifying Speciated and Source-Apportioned VOCs with Metal Oxide Sensors

Atmosphere ◽

10.3390/atmos12111383 ◽

2021 ◽

Vol 12 (11) ◽

pp. 1383

Author(s):

Kristen Okorn ◽

Michael Hannigan

Keyword(s):

Metal Oxide ◽

Oil And Gas ◽

Low Cost ◽

Positive Matrix ◽

Metal Oxide Sensors ◽

Volatile Organic ◽

Oil And Gas Operations ◽

Sensor Signals ◽

Benzene Toluene ◽

Voc Mixtures

While low-cost air quality sensor quantification has improved tremendously in recent years, speciated hydrocarbons have received little attention beyond total lumped volatile organic compounds (VOCs) or total non-methane hydrocarbons (TNMHCs). In this work, we attempt to use two broad response metal oxide VOC sensors to quantify a host of speciated hydrocarbons as well as smaller groups of hydrocarbons thought to be emanating from the same source or sources. For sensors deployed near oil and gas facilities, we utilize artificial neural networks (ANNs) to calibrate our low-cost sensor signals to regulatory-grade measurements of benzene, toluene, and formaldehyde. We also use positive matrix factorization (PMF) to group these hydrocarbons along with others by source, such as wet and dry components of oil and gas operations. The two locations studied here had different sets of reference hydrocarbon species measurements available, helping us determine which specific hydrocarbons and VOC mixtures are best suited for this approach. Calibration fits on the upper end reach above R2 values of 0.6 despite the parts per billion (ppb) concentration ranges of each, which are magnitudes below the manufacturer’s prescribed detection limits for the sensors. The sensors generally captured the baseline trends in the data, but failed to quantitatively estimate larger spikes that occurred intermittently. While compounds with high variability were not suited for this method, its success with several of the compounds studied represents a crucial first step in low-cost VOC speciation. This work has important implications in improving our understanding of the links between health and environment, as different hydrocarbons will have varied consequences in the human body and atmosphere.

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Therapeutic Aspects of Squill; An Evidence-Based Review

Current Drug Discovery Technologies ◽

10.2174/1570163816666190125154745 ◽

2020 ◽

Vol 17 (3) ◽

pp. 318-324 ◽

Cited By ~ 1

Author(s):

Khadije Saket ◽

Jalil T. Afshari ◽

Ehsan Saburi ◽

Mahdi Yousefi ◽

Roshanak Salari

Keyword(s):

Side Effects ◽

Traditional Medicine ◽

Respiratory Diseases ◽

Low Cost ◽

Current Evidence ◽

Evidence Based ◽

Helminthic Infections ◽

Traditional Persian Medicine ◽

Healing Of Wounds ◽

Bioactive Agents

From ancient times, medicinal plants have been usually utilized to treat many disorders, but today, interest in these herbs is again aroused, because of their fewer side effects and low-cost. In traditional medicine, for many diseases, various medicinal herbs have been suggested so far. Drimia maritime, also named squill, is an important medicinal plant for the treatment of many diseases, especially respiratory diseases. In the current evidence-based study, we conducted a review of the general characteristics, ingredients, administration form, and side effects of squill in traditional medicine. For this purpose, traditional Persian medicine literatures and electronic databases were examined including PubMed, Scopus, and Google Scholar. Many compounds are isolated from D.maritima, including scillaren, scillirubroside, scillarenin, and bufadienolide glycosides. Oxymel is the most commonly used form of squill for various diseases, especially respiratory diseases. Besides, squill has been used in the treatment of cardiovascular, digestive, and dermatological disorders, it is also used against various cancer cells for its antioxidant and cytotoxic properties. Moreover, there is relatively reliable evidence of its benefits for bacterial and helminthic infections, rheumatism, edema, gout, abortion induction, healing of wounds and urine induction. It seems that supplementary studies are required to explore the bioactive agents and their effective mechanisms.

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Sulfur Dioxide Sensors

10.21741/9781644901236 ◽

2021 ◽

Keyword(s):

Ionic Liquids ◽

Sulfur Dioxide ◽

Metal Oxide ◽

Gas Sensors ◽

Optical Sensors ◽

Recent Progress ◽

Amperometric Sensors ◽

Metal Oxide Sensors ◽

Semiconducting Metal Oxide

Recent progress on the sensing and monitoring of sulfur dioxide in the environment is presented. The sensing materials covered include potentiometric gas sensors, amperometric sensors, optical sensors involving colorimetric and fluorescence changes, sensors based on ionic liquids, semiconducting metal-oxide sensors, photoacoustic detectors and biosensors.

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Estimation of the Inhaled Dose of Pollutants in Different Micro-Environments: A Systematic Review of the Literature

Toxics ◽

10.3390/toxics9060140 ◽

2021 ◽

Vol 9 (6) ◽

pp. 140

Author(s):

Francesca Borghi ◽

Andrea Spinazzè ◽

Simone Mandaglio ◽

Giacomo Fanti ◽

Davide Campagnolo ◽

...

Keyword(s):

Systematic Review ◽

Residence Time ◽

Low Cost ◽

Pulmonary Ventilation ◽

Personal Exposure ◽

Ventilation Rate ◽

Atmospheric Pollutants ◽

Active Commuting ◽

Review Of The Literature ◽

Future Studies

Recently, the need to assess personal exposure in different micro-environments has been highlighted. Further, estimating the inhaled dose of pollutants is considerably one of the most interesting parameters to be explored to complete the fundamental information obtained through exposure assessment, especially if associated with a dose-response approach. To analyze the main results obtained from the studies related to the estimation of the inhaled dose of pollutants in different micro-environments (environments in which an individual spends a part of his day), and to identify the influence of different parameters on it, a systematic review of the literature was performed. The principal outcomes from the considered studies outlined that (i) exposure concentration and residence time are among the most important parameters to be evaluated in the estimation of the inhaled dose, especially in transport environments. Further, (ii) the pulmonary ventilation rate can be of particular interest during active commuting because of its increase, which increases the inhalation of pollutants. From a methodological point of view, the advent of increasingly miniaturized, portable and low-cost technologies could favor these kinds of studies, both for the measurement of atmospheric pollutants and the real-time evaluation of physiological parameters used for estimation of the inhaled dose. The main results of this review also show some knowledge gaps. In particular, numerous studies have been conducted for the evaluation (in terms of personal exposure and estimation of the inhaled dose) of different PM fractions: other airborne pollutants, although harmful to human health, are less represented in studies of this type: for this reason, future studies should be conducted, also considering other air pollutants, not neglecting the assessment of exposure to PM. Moreover, many studies have been conducted indoors, where the population spends most of their daily time. However, it has been highlighted how particular environments, even if characterized by a shorter residence time, can contribute significantly to the dose of inhaled pollutants. These environments are, therefore, of particular importance and should be better evaluated in future studies, as well as occupational environments, where the work results in a high pulmonary ventilation rate. The attention of future studies should also be focused on these categories of subjects and occupational studies.

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Low-temperature-processed metal oxide electron transport layers for efficient planar perovskite solar cells

Rare Metals ◽

10.1007/s12598-020-01676-y ◽

2021 ◽

Author(s):

Jia-Xing Song ◽

Xin-Xing Yin ◽

Zai-Fang Li ◽

Yao-Wen Li

Keyword(s):

Solar Cells ◽

Electron Transport ◽

Low Temperature ◽

Metal Oxide ◽

Low Cost ◽

Perovskite Solar Cells ◽

Transport Layer ◽

Electron Transport Layer ◽

Future Research ◽

Low Temperature Preparation

Abstract As a promising photovoltaic technology, perovskite solar cells (pero-SCs) have developed rapidly over the past few years and the highest power conversion efficiency is beyond 25%. Nowadays, the planar structure is universally popular in pero-SCs due to the simple processing technology and low-temperature preparation. Electron transport layer (ETL) is verified to play a vital role in the device performance of planar pero-SCs. Particularly, the metal oxide (MO) ETL with low-cost, superb versatility, and excellent optoelectronic properties has been widely studied. This review mainly focuses on recent developments in the use of low-temperature-processed MO ETLs for planar pero-SCs. The optical and electronic properties of widely used MO materials of TiO2, ZnO, and SnO2, as well as the optimizations of these MO ETLs are briefly introduced. The commonly used methods for depositing MO ETLs are also discussed. Then, the applications of different MO ETLs on pero-SCs are reviewed. Finally, the challenge and future research of MO-based ETLs toward practical application of efficient planar pero-SCs are proposed. Graphical abstract

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Sensitive and Low-Power Metal Oxide Gas Sensors with a Low-Cost Microelectromechanical Heater

ACS Omega ◽

10.1021/acsomega.0c04340 ◽

2021 ◽

Author(s):

Yulong Chen ◽

Mingjie Li ◽

Wenjun Yan ◽

Xin Zhuang ◽

Kar Wei Ng ◽

...

Keyword(s):

Metal Oxide ◽

Low Power ◽

Gas Sensors ◽

Low Cost ◽

Metal Oxide Gas Sensors

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Reducing the Influence of Environmental Factors on Performance of a Diffusion-Based Personal Exposure Kit

Sensors ◽

10.3390/s21144637 ◽

2021 ◽

Vol 21 (14) ◽

pp. 4637

Author(s):

Huixin Zong ◽

Peter Brimblecombe ◽

Li Sun ◽

Peng Wei ◽

Kin-Fai Ho ◽

...

Keyword(s):

Exposure Assessment ◽

Real Time ◽

Low Cost ◽

Personal Exposure ◽

Sensor Technology ◽

Heterogeneous Environments ◽

Mathematical Algorithms ◽

Personal Exposure Assessment ◽

Address System ◽

The Impact

Sensor technology has enabled the development of portable low-cost monitoring kits that might supplement many applications in conventional monitoring stations. Despite the sensitivity of electrochemical gas sensors to environmental change, they are increasingly important in monitoring polluted microenvironments. The performance of a compact diffusion-based Personal Exposure Kit (PEK) was assessed for real-time gaseous pollutant measurement (CO, O3, and NO2) under typical environmental conditions encountered in the subtropical city of Hong Kong. A dynamic baseline tracking method and a range of calibration protocols to address system performance were explored under practical scenarios to assess the performance of the PEK in reducing the impact of rapid changes in the ambient environment in personal exposure assessment applications. The results show that the accuracy and stability of the ppb level gas measurement is enhanced even in heterogeneous environments, thus avoiding the need for data post-processing with mathematical algorithms, such as multi-linear regression. This establishes the potential for use in personal exposure monitoring, which has been difficult in the past, and for reporting more accurate and reliable data in real-time to support personal exposure assessment and portable air quality monitoring applications.

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Nanostructure-directed chemical sensing: The IHSAB principle and the dynamics of acid/base-interface interaction

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.4.3 ◽

2013 ◽

Vol 4 ◽

pp. 20-31 ◽

Cited By ~ 6

Author(s):

James L Gole ◽

William Laminack

Keyword(s):

Metal Oxide ◽

Self Assembly ◽

Chemical Sensing ◽

Optical Pumping ◽

Relative Strength ◽

Acid Base ◽

Semiconductor Interfaces ◽

Surface Basicity ◽

Metal Oxide Sensors ◽

Type Semiconductor

Nanostructure-decorated n-type semiconductor interfaces are studied in order to develop chemical sensing with nanostructured materials. We couple the tenets of acid/base chemistry with the majority charge carriers of an extrinsic semiconductor. Nanostructured islands are deposited in a process that does not require self-assembly in order to direct a dominant electron-transduction process that forms the basis for reversible chemical sensing in the absence of chemical-bond formation. Gaseous analyte interactions on a metal-oxide-decorated n-type porous silicon interface show a dynamic electron transduction to and from the interface depending upon the relative strength of the gas and metal oxides. The dynamic interaction of NO with TiO2, SnO2, NiO, Cu x O, and Au x O (x >> 1), in order of decreasing acidity, demonstrates this effect. Interactions with the metal-oxide-decorated interface can be modified by the in situ nitridation of the oxide nanoparticles, enhancing the basicity of the decorated interface. This process changes the interaction of the interface with the analyte. The observed change to the more basic oxinitrides does not represent a simple increase in surface basicity but appears to involve a change in molecular electronic structure, which is well explained by using the recently developed IHSAB model. The optical pumping of a TiO2 and TiO2− x N x decorated interface demonstrates a significant enhancement in the ability to sense NH3 and NO2. Comparisons to traditional metal-oxide sensors are also discussed.

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