We systematically investigated the effects of process conditions and reduced graphene oxide (RGO) loading on the H2S gas-sensing performance of the α-Fe2O3 nanofibers (NFs) fabricated via on-chip ...electrospinning. The annealing temperature and precursor solution contents strongly influenced on the morphology and structure of the α-Fe2O3 NFs that accordingly affected on the gas-sensing performance. The optimum process conditions with the annealing temperature of 600 °C and the precursor solution contents of 11 wt% PVA and 4.0 wt% Fe(NO3)3.9H2O led to the α-Fe2O3 NF sensors having a high response of ∼6.1 at 1 ppm H2S gas. The RGO loading further improved the gas response, increasing the response to 1 ppm H2S gas up to ∼9.2. Also, the RGO-loaded α-Fe2O3 NF sensors enhanced their selectivity and detection limit as compared with pure α-Fe2O3 NF sensors. The enhanced gas-sensing performance was attributed to the presence of nanograins, the increase of surface-to-volume ratio and the formation of potential barriers at nanograin homojunctions and RGO/α-Fe2O3 heterojunctions.
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•The process conditions have been optimized for α-Fe2O3 nanofiber gas sensor.•RGO-loaded α-Fe2O4 nanofiber sensors can detect H2S gas down to ppb level.•The loading RGO-loaded α-Fe2O4 can result in enhanced H2S gas response.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
SnO2 NF sensors were fabricated on-chip using the electrospinning method as illustrate in the inset. Dynamic responses of the SnO2 NF sensors at 350 °C to various gases indicate a high sensitivity of ...the fabricated sensor to H2S gas with a good selectivty.
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•One-step fabrication of SnO2 NFs via electrospinning method was proposed.•Sensing characteristics of fabricated SnO2 NF sensor to 0.1–1 ppm H2S were studied.•Investigating dislocation defect and activation energy of the synthesized SnO2 NFs.•Gas sensing properties were explained by surface depletion/grain boundary mechanisms.
SnO2 porous nanofibers (NFs) were deposited on-chip by using a facile electrospinning method followed by heat treatment at 600 °C and used to detect H2S concentrations at sub-parts per million level. Morphological, compositional, crystal, and atomic structural properties of the as-spun and calcined SnO2 NFs were investigated by field emission electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy, respectively. SnO2 porous NFs with an average diameter of 150 nm and consisting of many nanograins were successfully fabricated by on-chip electrospinning. The NFs were crystallized as the tetragonal structure of SnO2 with an average crystallite size and dislocation density of approximately 13.5 nm and 5.615 × 1015 lines/m2, respectively. The sensing characteristics of the SnO2 NF sensors were tested with 0.1–1 ppm H2S from 150 °C to 450 °C. The sensor achieved the optimal performance at 350 °C and exhibited gas response of 15.2 with fast response/recovery times of 15 s/230 s. The H2S gas sensing mechanisms of the SnO2 porous NF sensors were due to the modulation of the resistance along the surface depletion layer and the grain boundaries. The fabricated sensor also indicated a good selectivity to H2S, short-term stability, and the low detection limit of 1.6 ppb. The influence of humidity on the sensor’s performance in a low temperature range is also discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Facile on-chip electrospinning has been developed for preparing ZnFe2O4 nanofibers.•ZnFe2O4 nanofiber sensors can detect H2S gas down to ppb level.•Nanograin size and crystallinity ...have correlative effect on gas sensing performance.
ZnFe2O4 nanofiber gas sensors are cost-effectively fabricated by direct electrospinning on microelectrode chip with Pt interdigitated electrodes and subsequent calcination under different conditions to maximize their response to H2S gas. The synthesized nanofibers of approximately 30–100 nm in diameter show typical spider-net-like morphology of the electrospun nanofibers. The ZnFe2O4 nanofibers comprise many 10–25 nm nanograins, which results in multi-porous structures. Moreover, the nanofibers exhibit the single phase of cubic-spinel-structure ZnFe2O4. The density, crystallinity and grain size of ZnFe2O4 nanofiber that strongly affect gas-sensing properties can be optimized by controlling electrospun time, annealing temperature, annealing time and heating rate. Under optimal conditions, the ZnFe2O4 nanofiber sensors exhibit high sensitivity and selectivity to H2S at sub-ppm levels. Excellent gas-sensing performances are attributed to effects of multi-porous structure, nanograin size and crystallinity, which is explained by the sensing mechanisms of ZnFe2O4 nanofiber sensors to H2S gas.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Abstract
Background
An endotracheal tube cuff pressure between 20 and 30 cmH2O is recommended to prevent ventilator-associated respiratory infection (VARI). We aimed to evaluate whether continuous ...cuff pressure control (CPC) was associated with reduced VARI incidence compared with intermittent CPC.
Methods
We conducted a multicenter open-label randomized controlled trial in intensive care unit (ICU) patients within 24 hours of intubation in Vietnam. Patients were randomly assigned 1:1 to receive either continuous CPC using an automated electronic device or intermittent CPC using a manually hand-held manometer. The primary endpoint was the occurrence of VARI, evaluated by an independent reviewer blinded to the CPC allocation.
Results
We randomized 600 patients; 597 received the intervention or control and were included in the intention to treat analysis. Compared with intermittent CPC, continuous CPC did not reduce the proportion of patients with at least one episode of VARI (74/296 25% vs 69/301 23%; odds ratio OR 1.13; 95% confidence interval CI .77–1.67. There were no significant differences between continuous and intermittent CPC concerning the proportion of microbiologically confirmed VARI (OR 1.40; 95% CI .94–2.10), the proportion of intubated days without antimicrobials (relative proportion RP 0.99; 95% CI .87–1.12), rate of ICU discharge (cause-specific hazard ratio HR 0.95; 95% CI .78–1.16), cost of ICU stay (difference in transformed mean DTM 0.02; 95% CI −.05 to .08, cost of ICU antimicrobials (DTM 0.02; 95% CI −.25 to .28), cost of hospital stay (DTM 0.02; 95% CI −.04 to .08), and ICU mortality risk (OR 0.96; 95% CI .67–1.38).
Conclusions
Maintaining CPC through an automated electronic device did not reduce VARI incidence.
Clinical Trial Registration
NCT02966392.
The results of this randomised controlled trial demonstrate that continuous endotracheal cuff pressure control using an electronic automated device does not reduce the occurrence of ventilator-associated respiratory infection (VARI) in intubated patients compared with intermittent control.
•An effective design has been realized for self-heated sensors using network nanowires.•The density of nanowires was optimized via controlling of the gap size of heat-to-heat electrodes.•The dense of ...network nanowires consumes a high power but is effective for detection of reducing gas.
Developing metal oxide gas sensors for internet-of-things (IoT) and portable applications require low-power consumption because of the limited battery in devices. This requirement is challenging because metal oxide sensors generally need high working temperatures, especially for reducing gases. Herein, we present an effective design and fabrication method of a SnO2 nanowire (NW) sensor for reducing gases by using the Joule heating effect at NW nanojunctions without needing an external or integrated heater. The sensor’s low-power consumption at around 4 mW was controlled by the size and nanojunction density of the device. The sensor has a simple design and is easy to fabricate. A proof-of-concept of a portable gas sensor module can be realised for monitoring highly toxic reducing gases, such as H2S, NH3 and C2H5OH, by using the developed self-heated NWs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Tuberculosis transmission continues to be a major public health challenge. In this cluster-randomized, controlled trial conducted in Vietnam, active community-wide screening for tuberculosis over 4 ...years is shown to decrease the prevalence of tuberculosis.
BACKGROUND: Heavy metal contamination and related risks for the environment and human health are matters of increasing concern. METHODS: The levels of 4 heavy metals (Cr, Cd, Pb, and As) were ...evaluated in 2 water types (surface and well), 4 types of seafood (tiger shrimp, stuffed snail, snake-head fish, and catfish), and 27 types of vegetables (12 leafy vegetables, 4 pea plants, 4 tuber vegetables, and 7 herbs) that are commonly consumed in northern coastal communes located in Vietnam. Atomic absorption spectrometry was employed for quantification. RESULTS: The mean concentrations of heavy metals detected in water, seafood, and vegetable samples exceeded the national permitted standards and World Health Organization (WHO) recommendation values by at least 2-fold, 2.5-fold, and 5-fold for surface water, vegetables, and well water, respectively. The concentrations of all 4 heavy metals detected in seafood samples were higher than the standards. The levels of heavy metals decreased with increasing distance between the sample collection point and the pollution source. CONCLUSIONS: This is the first report of heavy metal contamination of common sources of food and water in the northern coastal area of Vietnam. Significantly, the concentrations of heavy metals detected in study samples exceeded the regulatory limits. These results underscore the importance of continued monitoring and the development of intervention measures to ensure that the quality of food and water meets established standards and protects the health of the local population.
•Simple liquid-phase exfoliated method to fabricate few-layered MoS2 nanosheets.•Significant NO2 sensing performance of the sensor based on exfoliated MoS2 compared to that based on bulk MoS2.•The ...sensor based on the exfoliated MoS2 nanosheets indicates the highest response of about 8 times to 5 ppm at RT.•The exfoliated MoS2 nanosheet sensor shows good NO2 selectivity, ultra-low detection limit, good short- and long-term stability.
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Gas sensors based on the bulk MoS2 and exfoliated MoS2 nanosheets, were fabricated by the probe ultrasonic vibration followed by the drop-casting method. The sensing performance of the sensor based on the exfoliated MoS2 was much higher than that based on the bulk MoS2. The exfoliated MoS2 sensor showed highest gas response of approximately eight times to 5 ppm NO2 at room temperature. This fabricated sensor showed a good NO2 selectivity, ultra-low detection limit, and good short- and long-term stability.
Features such as surface-to-volume ratio, sensitive surface, and bandgap vary with the number of material layers of semiconductor two-dimensional transition metal dichalcogenides with superior responsivity at room temperature (RT) and their possible application as flexible electronic devices. Herein, a significant enhancement of NO2 gas sensing properties of few-layered MoS2 nanosheets exfoliated from bulk MoS2 through a simple sonication probe was reported. The gas responses of the sensor based on the exfoliated MoS2 nanosheets to 0.5–5 ppm NO2 at RT were as high as 5.3–8 times. At RT, the humidity effect to the performance of the exfoliated MoS2 sensor was insignificant. The exfoliated MoS2 sensor also exhibited an ultra-low detection limit of 27 ppb, excellent selectivity, and reliable long-term stability within 8 weeks, which are crucial for future application of the sensor in practical devices. The NO2 sensing mechanism of the exfoliated MoS2 nanosheets was discussed in detail.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•DWCNTs-Gr hybrid thin film was successfully synthesized by LPCVD method.•A novel structure of DWCNTs-Gr hybrid thin film modified SPE was prepared.•An electrochemical sensor using ...ChOx enzyme for detection of As(V) was developed.•A high sensitive sensor was achieved with low LOD for As(V) detection.
In this work, we demonstrate the preparation of hybrid thin films based on double-walled carbon nanotubes and graphene for electrochemical sensing applications. The hybrid films were synthesized on polycrystalline copper foil by thermal chemical vapor deposition under low pressure. This carbonaceous hybrid film has exhibited high transparency with a transmittance of 94.3 %. The occurrence of this hybrid material on the electrode surface of screen-printed electrodes was found to increase electroactive surface area by 1.4 times, whereas electrochemical current was enhanced by 2.4 times. Such a highly transparent and conductive hybrid film was utilized as a transducing platform of enzymatic electrochemical arsenic(V) sensor. The as-prepared sensor shows the linear detection of arsenic(V) in the range from 1 to 10 ppb, with a limit of detection as low as 0.287 ppb. These findings provide a promising approach to develop new multifunctional electrochemical sensing systems for environmental monitoring and biomedical diagnostics.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The selective detection and classification of NH3 and H2S gases with H2S gas interference based on conventional SnO2 thin film sensors is still the main problem. In this work, three layers of ...SnO2/Pt/WO3 nanofilms with different WO3 thicknesses (50, 80, 140, and 260 nm) were fabricated using the sputtering technique. The WO3 top layer were used as a gas filter to further improve the selectivity of sensors. The effect of WO3 thickness on the (NH3, H2, and H2S) gas-sensing properties of the sensors was investigated. At the optimal WO3 thickness of 140 nm, the gas responses of SnO2/Pt/WO3 sensors toward NH3 and H2 gases were slightly lower than those of Pt/SnO2 sensor film, and the gas response of SnO2/Pt/WO3 sensor films to H2S gas was almost negligible. The calcification of NH3 and H2 gases was effectively conducted by machine learning algorithms. These evidences manifested that SnO2/Pt/WO3 sensor films are suitable for the actual NH3 detection of NH3 and H2S gases.
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•The three layers of the SnO2/Pt/WO3 nanofilms based-gas sensor have been developed.•The SnO2/Pt/WO3 nanofilms can detect NH3 and H2 gases at low concentrations.•The classification of NH3 and H2 gases is made by machine learning algorithms.•The cross-response of sensors to interfering gas such as H2S were almost eliminated.•The gas filter mechanism was explained by the molecular size of the tested gases.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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