Commonly used humidity sensors are based on metal oxides, polymers or carbon. Their sensing accuracy often deteriorates with time, especially when exposed to higher temperatures or very high ...humidity. An alternative solution based on the utilization of Portland cement-based mortars containing in-situ grown carbon nanofibers (CNFs) was evaluated in this study. The relationship between the electrical resistivity, CNF content and humidity were determined. The highest sensitivity was observed for samples containing 10 wt.% of the nanomodified cement which corresponded to 0.27 wt.% of CNFs. The highest calculated sensitivity was approximately 0.01024 per 1% change in relative humidity (RH). The measured electrical resistivity is a linear function of the RH in the humidity range between 11 and 97%. The percolation threshold value was estimated to be at around 7 wt.% of the nanomodified cement, corresponding to ~ 0.19 wt.% of CNFs.
•Simultaneous temperature and relative humidity measurement.•Potential to measure absolute humidity.•Highly linear temperature response in proposed range (3.97 nm/°C, R2>0.99).•Small sensing region ...(one fibre tip) for two parameters.•Low-cost with simple manufacturing process compared with other optical fibre sensors.
Temperature and humidity are essential parameters in monitoring the health of patients in critical care. An optical fibre sensor has been developed for simultaneous measurement of relative humidity (RH) and temperature at a single optical fibre tip based on the reflected intensity. Combining these measurements enables absolute humidity values to be obtained. The fibre tip is first modified with a coating of poly(allylamine hydrochloride) (PAH) / silica nanoparticles (SiO2 NPs) for relative humidity (RH) measurement and then coated with thermochromic liquid crystal (TLC) for temperature measurement. Experimental results demonstrate that the RH and temperature sensitivity are respectively 0.43 %/RH% (intensity at a wavelength of 650 nm) from 55 to 90% RH (R2 = 0.973) and 3.97 nm/°C from 28 to 46 °C (R2>0.99). Moreover, the proposed sensor has low crosstalk between each of the sensing parameters, with a response time of 3.1 s temperature (30–38 °C) and 13.2 s for relative humidity (20–80 %). In comparison to grating based optical fibre sensors the proposed sensor is low-cost with a simple manufacturing process which has the potential to find widespread use in healthcare applications.
Observations of coincident high relative humidity and low surface ozone are common in air quality data sets, but models underpredict the strength of this correlation. We perform a statistical ...analysis of 28 years of ozone and meteorology observations taken as part of the Clean Air Status and Trends Network across the United States and find that vapor pressure deficit (VPD) is the strongest predictor of midday ozone in the spring, summer, and fall, and this correlation is strongest at sites with the largest leaf area index. We argue that stomatal regulation of dry deposition, which is known to have a VPD dependence that is not typically included in model parameterizations, can explain this relationship. Using a box model of ozone production and loss, we show that a negative ozone‐humidity slope is only achieved by the inclusion of VPD‐dependent dry deposition, suggesting that this mechanism may explain the observed ozone‐humidity correlation.
Key Points
Vapor pressure deficit is the strongest predictor of surface ozone over much of the USA from the spring to fall
The ozone‐VPD correlation, and ozone‐humidity correlation, is explained by VPD‐dependent dry deposition
Stomatally controlled dry deposition may play a significant role in controlling day‐to‐day variability in ozone during the growing season
Plain Language Summary
Across the United States in the summer, days with severe ozone pollution frequently occur on days with low relative humidity. Why the strong relationship between ozone pollution and relative humidity exists has been a bit of a mystery, as air quality models underpredict the strength of this relationship. We show that correlation between ozone and humidity can be explained by dry deposition—that is, the uptake of ozone by trees. When relative humidity is high, trees open their stomata (pores for exchanging CO2 and water vapor) and then unintentionally take up ozone. When relative humidity is low, trees close their stomata so they do not dry out, and thus do not remove ozone from the air, allowing it to build up. We show that during the growing season, vapor pressure deficit (a good surrogate for whether stomata are open or closed) is the best predictor on average of ozone levels, suggesting that trees play an important role in regulating day‐to‐day ozone pollution.
A real-time humidity sensor based on a microwave resonator coupled with a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) conducting polymer (CP) film is proposed in this paper. ...The resonator is patterned on a printed circuit board and is excited by electromagnetic field coupling. To enhance the sensitivity of the sensor, the CP film is located in the area with the strongest electric field in the resonator. To investigate the performance, the proposed sensor is placed alongside a reference sensor in a humidity chamber, and humidity is injected at room temperature. The experimental results indicate that the electrical properties of the resonator with the CP film, such as the transmission coefficient (S
) and resonance frequency, change with the relative humidity (RH). Specifically, as the RH changes from 5% to 80%, S
and the resonance frequency change simultaneously. Moreover, the proposed sensor exhibits great repeatability in the middle of the sensing range, which is from 40% to 60% RH. Consequently, our resonator coupled with the CP film can be used as a real-time humidity-sensing device in the microwave range, where various radio-frequency devices are in use.
The coronavirus disease 2019 (COVID-19) pandemic is the defining global health crisis of our time and the greatest challenge facing the world. Meteorological parameters are reportedly crucial factors ...affecting respiratory infectious disease epidemics; however, the effect of meteorological parameters on COVID-19 remains controversial. This study investigated the effects of temperature and relative humidity on daily new cases and daily new deaths of COVID-19, which has useful implications for policymakers and the public. Daily data on meteorological conditions, new cases and new deaths of COVID-19 were collected for 166 countries (excluding China) as of March 27, 2020. Log-linear generalized additive model was used to analyze the effects of temperature and relative humidity on daily new cases and daily new deaths of COVID-19, with potential confounders controlled for, including wind speed, median age of the national population, Global Health Security Index, Human Development Index and population density. Our findings revealed that temperature and relative humidity were both negatively related to daily new cases and deaths. A 1 °C increase in temperature was associated with a 3.08% (95% CI: 1.53%, 4.63%) reduction in daily new cases and a 1.19% (95% CI: 0.44%, 1.95%) reduction in daily new deaths, whereas a 1% increase in relative humidity was associated with a 0.85% (95% CI: 0.51%, 1.19%) reduction in daily new cases and a 0.51% (95% CI: 0.34%, 0.67%) reduction in daily new deaths. The results remained robust when different lag structures and the sensitivity analysis were used. These findings provide preliminary evidence that the COVID-19 pandemic may be partially suppressed with temperature and humidity increases. However, active measures must be taken to control the source of infection, block transmission and prevent further spread of COVID-19.
Display omitted
•First study to explore the effects of temperature and humidity on the daily new cases and deaths of COVID-19 worldwide.•We used log-linear GAM to analyze the effects.•We considered the lag effects and the cumulative effects of weather conditions.•Temperature and relative humidity were both negatively related to the daily new cases and daily new deaths of COVID-19
•Hollow Sn-doped NiO nanofibers are synthesized through a facile electrospinning approach.•The Sn-doped NiO sensor with suitable Sn content (6 at%) shows the highest gas response to triethylamine.•Sn ...doping concentrations can significantly influence the resistance of sensors in air and in target gas under different RH.•The resistances of the sensor change slightly in target gas under different RH with suitable Sn doping content (6 at%).
High stable triethylamine gas sensors under different relative humidity are highly desirable in order to correctly detect the concentrations of target gas. In this study, a series of Sn-doped NiO hollow nanofibers were prepared through a facile electrospinning process followed by heat treatment. Sn doping could inhibit the crystal growth, and the crystal sizes would decrease with the increase of Sn doping concentration. Gas sensing investigation indicates that Sn doping could significantly enhance the gas response towards triethylamine at a relative low temperature. Especially, the gas sensor exhibits the highest response to triethylamine when the doping content of Sn reaches to 6 at%. The response value is about 16.6–100 ppm triethylamine, and it is ∼9.2 times higher than that of pure NiO nanofibers at the same operating temperature. In addition, the resistances of the gas sensors with different doping contents of Sn would change differently in air or in target gas under variable relative humidity. The resistances in target gas are almost unchanged with the increase of relative humidity with the Sn doping content of 6 at%. It is reasonable to speculate that Sn doping can heavily alter the surface state of NiO nanofibers, which is beneficial for the improvement of the gas response and humidity dependence properties.
Compared with room temperature, the responsive curve of polymer humidity sensor usually presents a nonlinear shift and distortion at higher temperature conditions, this will sharply decrease the ...accuracy and working stability of polymer humidity sensor. In this paper, an organic–inorganic cross‐linked interpenetrating network (c‐IPN) between silocane compounds and acrylic prepolymer resin has been constructed to prepare a c‐IPN humidity‐sensitive material by in‐situ crosslinking reaction. The results shows that the prepared c‐IPN polymer humidity sensor shows more sensitive in range of 30–90% RH, with higher linearity coefficient of 0.9996 and lower hysteresis coefficient of 1.25% RH. And the c‐IPN polymer humidity sensor exhibits more higher stability at higher temperature than that at room temperature. Meanwhile, the temperature coefficient of the c‐IPN polymer humidity sensor can decrease to 0.53% RH/°C, along with temperature hysteresis curve linear coefficient increase to (R2 = −0.999), when (3‐aminopropyl) triethoxysilane is used at dosage of 10 wt.% druing crosslinking reaction. This study presents a feasible practical technical solution for developing novel high‐performance polymer humidity‐sensitive materials and its humidity sensors at wider temperature range.
Correction for 'Assessing relative humidity dependent photoacoustics to retrieve mass accommodation coefficients of single optically trapped aerosol particles' by Matus E. Diveky
et al.
,
Phys. Chem. ...Chem. Phys.
, 2019,
21
, 4721-4731, DOI:
10.1039/C8CP06980H
.
A high-performance zinc oxide/tin dioxide (ZnO/SnO2) humidity sensor was developed using a simple solvothermal method. The sensing mechanism of the ZnO/SnO2 humidity sensor was evaluated by analyzing ...its complex impedance spectra. The experimental results prove that the ZnO/SnO2 composite material has a larger specific surface area than pure SnO2, which allows the composite material surface to adsorb more water to enhance the response of the ZnO/SnO2 humidity sensor. ZnO can also contribute to the generation of oxygen-rich vacancies on the ZnO/SnO2 composite material surface, allowing it to adsorb a large amount of water and rapidly decompose water molecules into conductive ions to increase the response and recovery speed of the ZnO/SnO2 humidity sensor. These characteristics allowed the Z/S-2 humidity sensor to achieve a higher response (1,225,361%), better linearity, smaller hysteresis (6.6%), faster response and recovery speeds (35 and 8 s, respectively), and long-term stability at 11–95% relative humidity. The successful preparation of the ZnO/SnO2 composite material also provides a new direction for the design of SnO2-based resistance sensors with high humidity-sensing performance.
As an emerging energy‐harvesting technology, the triboelectric nanogenerator (TENG) is considered a powerful driving force toward the new‐era of Internet of Things and artificial intelligence, but ...its output performance is dramatically influenced by environmental humidity. Herein, a direct current TENG (DC‐TENG) based on the triboelectrification effect and electrostatic breakdown is reported to address the problem of output attenuation in high humidity environments for the conventional TENGs. It is found that high humidity not only enhances the sliding triboelectrification effect of hydrophobic triboelectric materials, but also promotes the electrostatic breakdown process for DC‐TENG, thus contributing to the improvement of DC‐TENG output. Furthermore, taking poly(vinyl chloride) film as the friction layer, the effective surface charge density of DC‐TENG with microstructure‐designed electrode achieves a milestone value of ≈2.97 mC m−2 under 90% relative humidity, which is almost 1.42‐fold larger than that under 30% RH. This work not only establishes an effective methodology to boost the output performance of TENG in a high humidity environment, but also establishes a foundation for its practical applications in large‐scale energy harvesting.
A humidity‐resistive direct‐current triboelectric nanogenerator (TENG) based on the triboelectrification effect and electrostatic breakdown is reported to address the output attenuation of conventional TENGs in high humidity environments. This work not only provides a promising guidance on the design of high‐performance TENG in high humidity environments, but also establishes a foundation for its practical applications in large‐scale energy harvesting.
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