Flexible ultra-sensitive and resistive NO2 gas sensor based on nanostructured Zn(x)Fe(1−x)2O4

Low concentration gas detection, rapid response time and low working temperature are anticipated for a varied range of toxic gas detection applications. Conversely, the existing gas sensors suffer mostly from a high working temperature along with a slow response at low concentrations of analytes. Here, we report an ultrasensitive flexible nanostructured Zn(x)Fe(1−x)2O4 (x = 0.1, 0.5 and 0.9) based chemiresistive sensor for nitrogen dioxide (NO2) detection. We evince that the prepared flexible sensor Zn(0.5)Fe(0.5)2O4 has detection potential as low as 5 ppm at a working temperature of 90 °C in a short phase. Further, the Zn(0.5)Fe(0.5)2O4 sensor exhibits excellent selectivity, stability and repeatability. The optimized sensor sensing characteristics can be helpful in tremendous development of foldable mobile devices for environmental monitoring, protection and control

Angstrofluidics:walking to the limit

Angstrom-scale fluidic channels are ubiquitous in nature, and play an important role in regulating cellular traffic, signaling, and responding to stimuli. Synthetic channels are now a reality with the emergence of several cutting-edge bottom-up and top-down fabrication methods. In particular, the use of atomically thin two dimensional (2D) materials and nanotubes as components to build fluidic conduits has pushed the limits of fabrication to the Angstrom-scale. Here, we provide an overview of the recent developments in the fabrication methods for nano- and angstrofluidic channels while categorizing them on the basis of dimensionality (0D pores, 1D tubes, 2D slits), along with the latest advances in measurement techniques. We discuss the ionic transport governed by various stimuli in these channels and draw comparison of ionic mobility, streaming and osmotic power, with varying pore sizes across all the dimensionalities. Towards the end of the review, we highlight the unique future opportunities in the development of smart ionic devices.Comment: Keywords: Angstrofluidics, nanofluidics, confinement, ion transport, 2D materials, molecular transport 6 figures, review articl

Water friction in nanofluidic channels made from two-dimensional crystals.

From Europe PMC via Jisc Publications RouterHistory: ppub 2021-05-01, epub 2021-05-25Publication status: PublishedFunder: European Research Council; Grant(s): 852674Membrane-based applications such as osmotic power generation, desalination and molecular separation would benefit from decreasing water friction in nanoscale channels. However, mechanisms that allow fast water flows are not fully understood yet. Here we report angstrom-scale capillaries made from atomically flat crystals and study the effect of confining walls' material on water friction. A massive difference is observed between channels made from isostructural graphite and hexagonal boron nitride, which is attributed to different electrostatic and chemical interactions at the solid-liquid interface. Using precision microgravimetry and ion streaming measurements, we evaluate the slip length, a measure of water friction, and investigate its possible links with electrical conductivity, wettability, surface charge and polarity of the confining walls. We also show that water friction can be controlled using hybrid capillaries with different slip lengths at opposing walls. The reported advances extend nanofluidics' toolkit for designing smart membranes and mimicking manifold machinery of biological channels

Fabrication of angstrom-scale two-dimensional channels for mass transport

Fluidic channels at atomic scales regulate cellular trafficking and molecular filtration across membranes and thus play crucial roles in the functioning of living systems. However, constructing synthetic channels experimentally at these scales has been a significant challenge due to the limitations in nanofabrication techniques and the surface roughness of the commonly used materials. Angstrom-scale slit-like channels address this challenge, as these can be made with precise control over their dimensions and can be used to study the fluidic properties of gases, ions and water at unprecedented scales. Here, we provide a detailed fabrication method of the two-dimensional (2D) angstrom-scale channels, which can be assembled as a single channel or up to hundreds of channels made with atomic scale precision using layered crystals. The procedure includes the fabrication of the substrate, flake, spacer layer, flake transfers, van der Waals assembly, and post-processing. We further explain how to perform molecular transport measurements with the angstrom-scale channels, for the development of methods directed at unravelling interesting and anomalous phenomena that help shed light on the physics of nanofluidic transport systems. The procedure requires a total of 1 to 2 weeks for the fabrication of the 2D channel device and is suitable for users with prior experience in clean room working environments and nanofabrication

Minimization of electro-static forces in magnetic force microscopy for detection of single superparamagnetic iron oxide nanoparticles

Hybrid nanomaterial (powdered fungi and ZnFe2O4) was developed and studied for gas sensing application, specifically for NO2 gas detection. In this study, powdered Rhizopus species W3 and ZnFe2O4 nano-powder were mixed at equal proportion to carryout sensing experiments. The conjugated material film was coated on the interdigitated electrodes (IDEs) by drop drying method, to determine the NO2 gas sensing characteristics. It was found that the response of these hybrid materials decrease resistance, thereby resembling the p-type semiconductor. The fungi W3 - ZnFe2O4 hybrid composite sensor showed better response, sensitivity, selectivity, stability and reproducibility at room temperature towards 30 ppm of NO2. N. Miura et al. reported in 2002 ZnFe2O4 showed good sensitivity for NO2 (436 ppm) at 700°C operating temperature. Therefore, in this present work effort was made to prepare novel hybrid material that is feasible, eco-friendly, flexible, cost-effective, low maintenance and light weight new device

Resistive room temperature LPG sensor based on a graphene/CdO nanocomposite

The authors decribe an ultra-sensitive, room temperature, flexible transparent LPG sensor based on the use of a CdO/graphene nanocomposite. The graphene prevents the accumulation of CdO, enhances the surface area, and acts as a gas sensing material. FESEM images show a uniform decoration of CdO nanoparticles on graphene. The CdO/graphene composite was deposited as a film on interdigitated electrodes (IDEs) which then were used for chemiresistive sensing of liquid petroleum gas (LPG) by using a four probe technique. A Resistivity decreases significantly upon exposure to a LPG. The electrical resistance measurement at a constant bias voltage of 0.5 V. The sensor of type CdO/graphene (1 wt.%) exhibits a sensitivity of 600 ppm of LPG at 27 °C. It is a highly selective, stable and sensitive to low concentration of LPG even at room temperature

Angstrofluidics:Walking to the Limit

Angstrom-scale fluidic channels are ubiquitous in nature, and play an important role in regulating cellular traffic, signaling, and responding to stimuli. Synthetic channels are now a reality with the emergence of several cutting-edge bottom-up and top-down fabrication methods. In particular, the use of atomically thin two dimensional (2D) materials and nanotubes as components to build fluidic conduits has pushed the limits of fabrication to the Angstrom-scale. Here, we provide an overview of the recent developments in the fabrication methods for nano- and angstrofluidic channels while categorizing them on the basis of dimensionality (0D pores, 1D tubes, 2D slits), along with the latest advances in measurement techniques. We discuss the ionic transport governed by various stimuli in these channels and draw comparison of ionic mobility, streaming and osmotic power, with varying pore sizes across all the dimensionalities. Towards the end of the review, we highlight the unique future opportunities in the development of smart ionic devices.Comment: Keywords: Angstrofluidics, nanofluidics, confinement, ion transport, 2D materials, molecular transport 6 figures, review articl

Nanostructure ZnFe2O4 with Bacillus subtilis for Detection of LPG at Low Temperature

The present study deals with the development of a chemical sensor for the detection of liquefied petroleum gas (LPG) at a low operating temperature using Zinc ferrite (ZnFe2O4)/Bacillus subtilis (B. subtilis) hybrid nanostructures. The nanostructure ZnFe2O4 and B. subtilis powder, taken in equal proportion was made into films using the spin coating technique. X-ray diffraction, thermal analysis, scanning electron microscopy, and transmission electron microscopy were used to study morphology, structure and crystallite size. The sensing properties of the hybrid structure were studied and excellent response was observed in the temperature range of 50-55 C for 400 ppm LPG, when compared to the individual components of the hybrid. The signal output of the proposed sensor were extremely stable for more than 30 days. This method proposes the usage of the biomolecule/metal oxide composites in electronics and helps to reduce the metal oxide usage.Scopu

Water friction in nanofluidic channels made from two-dimensional crystals

Membrane-based applications such as osmotic power generation, desalination and molecular separation would benefit from decreasing water friction in nanoscale channels. However, mechanisms that allow fast water flows are not fully understood yet. Here we report angstrom-scale capillaries made from atomically flat crystals and study the effect of confining walls’ material on water friction. A massive difference is observed between channels made from isostructural graphite and hexagonal boron nitride, which is attributed to different electrostatic and chemical interactions at the solid-liquid interface. Using precision microgravimetry and ion streaming measurements, we evaluate the slip length, a measure of water friction, and investigate its possible links with electrical conductivity, wettability, surface charge and polarity of the confining walls. We also show that water friction can be controlled using hybrid capillaries with different slip lengths at opposing walls. The reported advances extend nanofluidics’ toolkit for designing smart membranes and mimicking manifold machinery of biological channels

Room temperature LPG resistive sensor based on the use of a few-layer graphene/SnO2 nanocomposite

A nanocomposite consisting of a few layers of graphene (FLG) and tin dioxide (SnO2) was prepared by ultrasound-assisted synthesis. The uniform SnO2 nanoparticles (NPs) on the FLG were characterized by X-ray diffraction in terms of lattice and phase structure. The functional groups present in the composite were analyzed by FTIR. Electron microscopy (HR-TEM and FE-SEM) was used to study the morphology. The effect of the fraction of FLG present in the nanocomposite was investigated. Sensitivity, selectivity and reproducibility towards resistive sensing of liquid propane gas (LPG) was characterized by the I-V method. The sensor with 1% of FLG on SnO2 operated at a typical voltage of 1 V performs best in giving a rapid and sensitive response even at 27 degrees C. This proves that the operating temperature of such sensors can be drastically decreased which is in contrast to conventional metal oxide LPG sensors