Synergistic Effect of Electron Scattering and Space Charge Transfer Enabled Unprecedented Room Temperature NO2 Sensing Response of SnO2.

Metal oxide gas sensors have long faced the challenge of low response and poor selectivity, especially at room temperature (RT). Herein, a synergistic effect of electron scattering and space charge transfer is proposed to comprehensively improve gas sensing performance of n-type metal oxides toward oxidizing NO2 (electron acceptor) at RT. To this end, the porous SnO2 nanoparticles (NPs) assembled from grains of about 4 nm with rich oxygen vacancies are developed through an acetylacetone-assisted solvent evaporation approach combined with precise N2 and air calcinations. The results show that the as-fabricated porous SnO2 NPs sensor exhibits an unprecedented NO2 -sensing performance, including outstanding response (Rg /Ra  = 772.33 @ 5 ppm), fast recovery (<2 s), an extremely low detection limit (10 ppb), and exceptional selectivity (response ratio >30) at RT. Theoretical calculation and experimental tests confirm that the excellent NO2 sensing performance is mainly attributed to the unique synergistic effect of electron scattering and space charge transfer. This work proposes a useful strategy for developing high-performance RT NO2 sensors using metal oxides, and provides an in-depth understanding for the basic characteristics of the synergistic effect on gas sensing, paving the way for efficient and low power consumption gas detection at RT.

Glutamatergic neurons in the paraventricular hypothalamic nucleus regulate isoflurane anesthesia in mice.

The glutamatergic-mediated excitatory system in the brain is vital for the regulation of sleep-wake and general anesthesia. Specifically, the paraventricular hypothalamic nucleus (PVH), which contains mainly glutamatergic neurons, has been shown to play a critical role in sleep-wake. Here, we sought to explore whether the PVH glutamatergic neurons have an important effect on the process of general anesthesia. We used c-fos staining and in vivo calcium signal recording to observe the activity changes of the PVH glutamatergic neurons during isoflurane anesthesia and found that both c-fos expression in the PVH and the calcium activity of PVH glutamatergic neurons decreased in isoflurane anesthesia and significantly increased during the recovery process. Chemogenetic activation of PVH glutamatergic neurons prolonged induction time and shortened emergence time from anesthesia by decreasing the depth of anesthesia. Using chemogenetic inhibition of PVH glutamatergic neurons under isoflurane anesthesia, we found that inhibition of PVH glutamatergic neurons facilitated the induction process and delayed the emergence accompanied by deepening the depth of anesthesia. Together, these results identify a crucial role for PVH glutamatergic neurons in modulating isoflurane anesthesia.

Designing Cu2+ as a Partial Substitution of Protons in Polyaniline Emeraldine Salt: Room-Temperature-Recoverable H2S Sensing Properties and Mechanism Study.

Hydrogen sulfide (H2S) sensors are in urgent demand in the field of hermetic environment detection and metabolic disease diagnosis. However, most of the reported room-temperature (RT) H2S sensors based on transition metal oxides/salts unavoidably suffer from the poisoning effect, resulting in the unrecoverable behavior to restrain their application. Herein, copper(II) chloride-doped polyaniline emeraldine salt (PANI-CuCl2) was devised for RT-recoverable H2S detection, where the copper ion (Cu2+) was designed as a partial substitution of protons (H+) in PANI. The prepared gas sensor exhibited full recovery capability toward 0.25-10 ppm H2S, good repeatability, and long-term stability under 80% RH. Meanwhile, the changes of the PANI-CuCl2 during the H2S sensing period were analyzed via multiple analytical methods to reveal the reversible sensing behavior. Results showed that doping of Cu2+ not only promoted the PANI's response through the formation of conductive copper sulfide (CuS) and following H+ redoping in the PANI but also facilitated the sensor's recovery behavior because of the Cu2+ regeneration under the H+/oxygen environment. This work not only proves the changes of the interaction between the PANI and Cu2+ during the H2S sensing period but also sheds light on designing recoverable H2S sensors based on transition metal salts.

Edge-enriched MoS2 nanosheets modified porous nanosheet-assembled hierarchical In2O3 microflowers for room temperature detection of NO2 with ultrahigh sensitivity and selectivity.

Nitrogen dioxide (NO2) is one of the most hazardous toxic pollutants to human health and the environment. However, deficiencies of low sensitivity and poor selectivity at room temperature (RT) restrain the application of NO2 sensors. Herein, the edge-enriched MoS2 nanosheets modified porous nanosheets-assembled three-dimensional (3D) In2O3 microflowers have been synthesized to improve the sensitivity and selectivity of NO2 detection at RT. The results show that the In2O3/MoS2 composite sensor exhibits a response as high as 343.09-5 ppm NO2, which is 309 and 72.5 times higher than the sensors based on the pristine MoS2 and In2O3. The composite sensor also shows short recovery time (37 s), excellent repeatability and long-term stability. Furthermore, the response of the In2O3/MoS2 sensor to NO2 is at least 30 times higher than that of other gases, proving the ultrahigh selectivity of the sensor. The outstanding sensing performance of the In2O3/MoS2 sensor can be attributed to the synergistic effect and abundant active sites originating from the p-n heterojunction, exposed edge structures and the designed 2D/3D hybrid structure. The strategy proposed herein is expected to provide a useful reference for the development of high-performance RT NO2 sensors.

Enhanced Blocking Effect: A New Strategy to Improve the NO2 Sensing Performance of Ti3C2Tx by γ-Poly(l-glutamic acid) Modification.

Titanium carbide (Ti3C2Tx) with a distinctive structure, abundant surface chemical groups, and good electrical conductivity has shown great potential in fabricating superior gas sensors, but several challenges, such as low response kinetics, poor reversibility, and serious baseline drift, still remain. In this work, γ-poly(l-glutamic acid) (γ-PGA) with a blocking effect is exploited to modify Ti3C2Tx, thereby stimulating the positive response behavior of Ti3C2Tx and improving its gas sensing performance. On account of the unique synergetic interaction between Ti3C2Tx and γ-PGA, the response of the flexible Ti3C2Tx/γ-PGA gas sensor to 50 ppm NO2has been improved to a large extent (average 1127.3%), which is 85 times that of Ti3C2Tx (only 13.2%). Moreover, the as-fabricated Ti3C2Tx/γ-PGA sensor not only exhibits a shorter response/recovery time (average 43.4/3 s) compared with the Ti3C2Tx-based sensor (∼18.5/18.3 min) but also shows good reversibility and repeatability (relative standard deviation (RSD) <1%) at room temperature within 50% relative humidity (RH). The improved gas sensing properties of the Ti3C2Tx/γ-PGA sensor can be attributed to the enhancement of effective adsorption and the blocking effect assisted by water molecules. Furthermore, the gas sensing response of the Ti3C2Tx/γ-PGA sensor is studied at different RHs, and humidity compensation of the sensor is carried out using the multiple regression method. This work demonstrates a novel strategy to enhance the gas sensing properties of Ti3C2Tx by γ-PGA modification and provides a new way to realize highly responsive gas detection at room temperature.

Facile and low-cost fabrication of a humidity sensor using naturally available sepiolite nanofibers.

Much effort has focussed on enhancing the humidity-sensing performances of humidity sensors, but their fabrication using facile and low-cost methods is also desirable. In this work, a humidity sensor based on a naturally available nanomaterial, sepiolite nanofibers (SNFs), was facilely fabricated without any expensive raw materials or complex processes. Characterization results show that SNFs have a natural slender nanofiber structure (diameter 20-50 nm) and abundant hydrophilic functional groups (-OH). The results of humidity-sensing tests show that the SNF humidity sensor has outstanding humidity-sensing properties (i.e. large response, good linearity and repeatability) within the relative humidity range from 10.9% to 91.5% at room temperature (25 °C). This work presents a moderate and cost-effective strategy for the fabrication of high-performance humidity sensors using the natural SNF nanomaterial.

Facile, Flexible, Cost-Saving, and Environment-Friendly Paper-Based Humidity Sensor for Multifunctional Applications.

Developing a facile, cost-saving, and environment-friendly method for fabricating a multifunctional humidity sensor is of great significance to expand its practical applications. However, most humidity sensors involve a complex fabrication process, resulting in their high cost and narrow application fields. Herein, a multifunctional paper-based humidity sensor with many advantages is proposed. This humidity sensor is fabricated using conventional printing paper and flexible conductive adhesive tape by a facile pasting method, in which the paper is used as both the humidity-sensing material and the substrate of the sensor. Owing to the moderate hydrophilicity of the paper and the rational structure design of the paper-based humidity sensor, the sensor exhibits an excellent humidity-sensing response of more than 103 as well as good linearity ( R2 = 0.9549) within the humidity range from 41.1 to 91.5% relative humidity. Furthermore, the paper-based humidity sensor has good flexibility and compatibility, endowing it with multifunctional applications for breath rate, baby diaper wetting, noncontact switch, skin humidity, and spatial localization monitoring. Although the resistance of the paper-based humidity sensor is relatively large, the humidity-sensing response signals of the sensor can be conveniently processed by the designed signal processing system. The readily available starting materials and facile fabrication technique provide useful strategies for the development of multifunctional humidity sensors.

Plasma microRNAs expression profile in female workers occupationally exposed to mercury.

BACKGROUND: Circulating microRNAs (miRNAs) have attracted interests as non-invasive biomarkers of physiological and pathological conditions. Several studies have examined the potential effects of mercury exposure on miRNAs expression profiles of general population environmentally exposed to mercury. The objective is to identify mercury-related miRNAs of female workers occupationally exposed to mercury. METHODS: In this case-control study, we used a microarray assay to detect the miRNA expression profiles in pooled plasma samples between (I) chronic mercury poisoning group; (II) mercury absorbing group and (III) control group in the discovery stage. Each group has ten individuals. In addition, we conducted a validation of eight candidate miRNAs in the same 30 workers by quantitative real-time PCR. RESULTS: In the discovery stage, eight miRNAs were conformed following our selection criteria. In the validation stage, RT-PCR confirmed up-regulation of miR-92a and miR-486 in the mercury poisoned group (P<0.05) compared to the other two groups. The results were consistent with the microarray analysis. CONCLUSIONS: Plasma miR-92a-3p and miR-486-5p might prove to be potential biomarkers to indicate responses to mercury exposure. However, further studies are necessary to prove the causal association between miRNAs changes and mercury exposure, and to determine whether these two miRNAs are clear biomarkers to mercury exposure.

Prevalence of hypertension and noise-induced hearing loss in Chinese coal miners.

BACKGROUND: Owing to inconsistent epidemiologic evidence and the presence of confounding factors, the relation between occupational noise exposure and hypertension still remained unclear. We aimed to assess whether Chinese coal miners were at risk of developing hypertension and noise induced hearing loss (NIHL), and whether occupational noise exposure was a risk factor of hypertension. METHODS: A questionnaire was designed to collect information from 738 study participants, all of whom were employees from the Datun Xuzhou Coal Company. The participants were divided into a noise-exposed group and a control group based on the noise level to which they were exposed in the workplace. The differences in the mean of systolic blood pressure (SBP) and diastolic blood pressure (DBP) were compared between the noise-exposed and control groups. Also the prevalence and age-adjusted odds ratio (OR) [95% confidence intervals (CIs)] of audiometric deficit and hypertension was compared in the study. Binary logistic regression was used to assess the relation between occupational noise level and hypertension while controlling for potential confounding factors. RESULTS: Hypertension was more prevalent in noise-exposed group than the control group, 29.2% vs. 21.2% (P=0.012). The noise-exposed group faced an increased risk of hypertension (age-adjusted OR =1.52, 95% CI =1.07-2.15) when the control group was used as reference. The mean values of SBP and DBP of the noise-exposed groups were significantly higher than the control group (P=0.006 and P=0.002 respectively). Hearing loss at low frequencies was significantly more prevalent in the noise-exposed group than the control group, 12.8% vs. 7.4% (P=0.015), while the noise-exposed group faced the increased risk of hearing loss at low frequencies (age-adjusted OR =1.81, 95% CI =1.10-2.96). LEX, 8h (OR =1.036, 95% CI =1.012-1.060) was an independent risk of hypertension when controlling for potential confounding factors. CONCLUSIONS: We found that the occupational noise had an effect on the hypertension and hearing loss of Chinese coal miners. And the occupational noise was an independent risk factor for hypertension and could increase the values of SBP and DBP.

Association between Polymorphism of Exportin-5 and Susceptibility to Lead Poisoning in a Chinese Population.

Lead (Pb) is one of the major contaminants in many industries, and imposes hazardous effects on multiple human organs and systems. Studies have shown that lead is able to induce the alteration of microRNA (miRNA) expression in serum and organs. In this study we investigated whether polymorphisms in miRNA-regulating genes were associated with the risk of lead exposure. We genotyped seven single-nucleotide polymorphisms (SNPs) in 113 lead-sensitive and 113 lead-resistant lead-related Chinese workers by Taqman analysis. The lead-sensitive group showed a significantly higher blood lead level (BLL) than the resistant group based on unconditional logistic regression results. One SNP in XPO5 extron (rs2257082) was significantly associated with lead-poisoning (p = 0.022, odds rate (OR) = 1.63, 95% confidence interval (CI) = 1.07-2.47 in the C allele compared to the T allele). There were no significant associations between the other six SNPs and the blood lead levels. Therefore, polymorphism rs2257082 could be used to distinguish lead-resistant and lead-susceptible populations, and to develop more specific and accurate preventions.

Analysis of plasma microRNA expression profiles in male textile workers with noise-induced hearing loss.

BACKGROUND: Circulating microRNAs (miRNAs) have attracted interests as non-invasive biomarkers of physiological and pathological conditions, which may be applied in noise-induced hearing loss (NIHL). However, no epidemiology studies have yet examined the potential effects of NIHL or noise exposure on miRNA expression profiles. OBJECTIVES: We sought to identify permanent NIHL-related miRNAs and to predict the biological functions of the putative genes encoding the indicated miRNAs. METHODS: In the discovery stage, we used a microarray assay to detect the miRNA expression profiles between pooled plasma samples from 10 noise-exposed individuals with normal hearing and 10 NIHL patients. In addition, we conducted a preliminary validation of six candidate miRNAs in the same 20 workers. Subsequently, three miRNAs were selected for expanded validation in 23 non-exposed individuals with normal hearing and 46 noise-exposed textile workers which including 23 noise-exposed workers with normal hearing and 23 NIHL patients. Moreover, we predicted the biological functions of the putative target genes using a Gene Ontology (GO) function enrichment analysis. RESULTS: In the discovery stage, compared with the noise exposures with normal hearing, 73 miRNAs demonstrated at least a 1.5-fold differential expression in the NIHL patients. In the preliminary validation, compared with the noise exposures, the plasma levels of miR-16-5p, miR-24-3p, miR-185-5p and miR-451a were all upregulated (P < 0.001) in the NIHL patients. In the expanded validation stage, compared with the non-exposures, the plasma levels of miR-24, miR-185-5p and miR-451a were all significantly downregulated (P < 0.001) in the exposures. And compared with the noise exposures, the plasma levels of miR-185-5p and miR-451a were slightly elevated (P < 0.001) in the NIHL patients, which were consistent with the results of preliminary validation and microarray analysis. CONCLUSION: The two indicated plasma miRNAs may be biomarkers of indicating responses to noise exposure. However, further studies are necessary to prove the causal association between miRNAs changes and noise exposure, and to determine whether these two miRNAs are clear biomarkers to noise exposure.