Baseline Recovery Research Articles

Light-Activated Chemoresistive and Plasmonic-Resonant Optical Sensors for NO2 and H2 Sensing Based on ZnO Doped Nanoparticles

Light-Activated Chemoresistive and Plasmonic-Resonant Optical Sensors for NO2 and H2 Sensing Based on ZnO Doped Nanoparticles

Light-Activated Chemoresistive and Plasmonic-Resonant Optical Sensors for NO2 and H2 Sensing Based on ZnO Doped Nanoparticles

Light-Activated Chemoresistive and Plasmonic-Resonant Optical Sensors for NO2 and H2 Sensing Based on ZnO Doped Nanoparticles

Edge-exposed MoS2 nanospheres assembled with SnS2 nanosheet to boost NO2 gas sensing at room temperature

SnS2 nanosheets (NSs) have become an ideal candidate for high performance gas sensors due to their unique sensing properties. However, the restacking and aggregation in the process of sensor manufacturing have great influence on the gas sensing performance. In this study, we synthesized a novel heterojunction of the flower-like porous SnS2 NSs with edge exposed MoS2 nanospheres via a facile hydrothermal method and sensitive response has achieved at room temperature (27℃). After functionalization, the SMS-Ⅱ showed excellent response (Ra/Rg = 25.9–100 ppm NO2), which is 22.3 times higher than that of the pristine SnS2 NSs. The sensor also has the characteristics of short response time of 2 s, excellent base line recovery (28.2 s), long-term stability and reliability within 16 weeks, good selectivity and low detection concentration of only 50 ppb. The p-n heterojunction formed between the edge-exposed spherical MoS2 and the 3D flower-like SnS2 NSs has a synergistic effect, providing a highly active sites for the adsorption of NO2 gas, which greatly enhance the sensitivity of the sensor. Simple fabrication and excellent gas sensing performance of the SnS2/MoS2 heterostructure nanomaterials (NMs) will highly effective for commercial gas sensing application.

The influence of thermal and visible light activation modes on the NO2 response of WO3 nanofibers prepared by electrospinning

The paper reports on the influence of visible light at different wavelengths (red, λ=630nm; green, λ=570nm; purple–blue, λ=430nm), light irradiance conditions (from 30 to 770μW/cm2) and operating temperatures (from 25°C to 100°C) on the electrical response of WO3 electrospun nanofibers (NFs) to 100–400ppb NO2 gas in dry air. WO3 NFs were prepared by mixing a W–O sol–gel transparent solution (WCl6 in ethanol) with a polymeric solution made of polyvinylpyrrolidone (PVP) and dimethylformamide (DMF). Electrospun NFs were annealed between 300°C and 500°C and the their microstructures features investigated by SEM and XRD. Room temperature (25°C) gas responses of the 450°C annealed NFs have shown that, beside a slight reduction of the relative gas response (RRs), a decrease of the light wavelength (toward the purple–blue) and an increase of its irradiance, greatly improve the base line recovery and the response time with respect to dark conditions. At operating temperatures ranging from 25°C to 100°C, sensor relative responses in dark always resulted to be higher as respect to the ones displayed under purple–blue light illumination. The combined action of purple-blue light with an irradiance of 770μW/cm2 and of mild operating temperature of 75°C, relative responses (RRs) of 12.4 and base line recovery percentages (RPs) of 97% were attained at 400ppb NO2. The capability to tune the response of WO3 NFs to NO2 by combining light and mild thermal gas sensors activations is addressed and discussed also considering the involved response mechanisms.

NO2 Gas Response of WO3 Nanofibers by Light and Thermal Activation

Aim of this paper is to compare the electrical responses to sub-ppm NO2 gas concentrations of WO3 electrospun nanofibers both activated by thermal (in the temperature range 25°C - 150°C) and/or light-radiating conditions (Red λ=670nm, Green λ=550nm, and Purple Blue λ=430nm). Blue light resulted the most effective light source with respect to the others. Light illumination at room temperature improves the base line recovery and response time, whereas temperature enhances relative response, with a maximum at 75°C. Light-radiating room temperature gas detection yields a satisfactory response despite the reduction of sensor gas sensitivity. Light induced electrical response mechanisms are presented and discussed.

Fabrication of UV detectors based on ZnO nanowires using silicon microchannel

Aligned ZnO nanowires were grown by metal organic chemical vapor deposition on patterned silicon substrate. The shape of nanostructures was greatly influenced by the micropatterned surface. The aspect ratio, packing fraction and the number density of nanowires on top surface are around 10, 0.8 and 107 per mm2, respectively, whereas the values are 20, 0.3 and 5×107 per mm2, respectively, towards the bottom of the cavity. XRD patterns suggest that the nanostructures have good crystallinity. High-resolution transmission electron microscopy confirmed the single-crystalline growth of the ZnO nanowires along the [0001] direction. Photosensitivity of the nanowires, grown on both top and bottom surface of the microchannel, was observed. However, the nanowires grown on bottom surface have shown better UV response with base line recovery at dark condition.

PRECLINICAL STUDY: Changes in leptin, ghrelin, growth hormone and neuropeptide‐Y after an acute model of MDMA and methamphetamine exposure in rats

Club drug abuse is a growing problem in the United States. Beyond addiction and toxicity are endocrine effects which are not well characterized. Specifically, the changes in appetite following exposure to drugs of abuse are an interesting but poorly understood phenomenon. Serum hormones such as leptin, ghrelin, growth hormone (GH), and neuropeptide-Y (NP-Y) are known to affect appetite, but have not been studied extensively with drugs of abuse. In this work, we examine the effects of club drugs 3,4-methylenedioxymethamphetamine (MDMA) (ecstasy) and methamphetamine (METH) (doses of 5, 20 and 40 mg/kg) on serum concentrations of these hormones in adult male Sprague-Dawley rats 6, 12, 24 and 48 hours after drug administration. In a dose-dependent manner, MDMA was shown to cause transient significant decreases in serum leptin and GH followed by a base line recovery after 24 hours. Conversely, serum ghrelin increased and normalized after 24 hours. Interestingly, serum NP-Y showed a steady decrease in both treatment of MDMA and METH at different time points and dosages. In humans, abuse of these drugs reduces eating. As evident from these data, acute administration of METH and MDMA had significant effects on different serum hormone levels involved in appetite regulation. Future studies should be performed to see how chronic, low dose drug administration would affect hormone levels and try to answer questions about the physiological mechanisms involved in the anorexic paradigm observed in drug use.

NATURE OF THE ACTION CURRENT IN NITELLA

When a stimulus arrives before recovery is complete there may be no response or only a partial response. A typical response appears to involve an immediate loss of potential at the inner protoplasmic surface but not at the outer surface. As long as recovery is incomplete only a part of the total potential is located at the inner protoplasmic surface and the loss of this part of the total potential can cause only a partial response; i.e., one of smaller magnitude than the normal. Even after the action curve has returned to the base line recovery may be incomplete and the response only a partial one. The return of the action curve to the base line means a recovery of total potential but if part of this is located at the outer protoplasmic surface and if this part is not lost when stimulation occurs the response can be only a partial one. During recovery there is a shift of potential from the outer to the inner protoplasmic surface. Not until this shift is completed can recovery be called complete. The response to stimulation then becomes normal because the loss of potential reaches the normal amount. In many cases the partial responses appear to conform to the all-or-none law. In other cases this is doubtful.