Ultrasensitive NO2Gas Sensor Based on Epitaxial Graphene

Highly sensitive NO2 gas sensor based on ozone treated graphene

Abstract

The Berry phase and Landau levels of epitaxial graphene in crossed magnetic and electric fields have been studied in the framework of a simple analytical model. It is established that the Berry phase of electrons in epitaxial graphene near the Dirac point is π. This result is confirmed by published experimental data. The Landau levels in epitaxial graphene can be rearranged with the aid of a longitudinal electric field.

The chemical potential, heat capacity, and magnetic susceptibility of epitaxial graphene formed on a semiconductor substrate have been studied in the framework of the Davydov model. The limiting cases of high and low temperatures are considered.

New Type of Thin-Film Germanium Resistance Thermometer for Use in a Wide Temperature Range

Graphene is a 2D material with remarkable properties. The present study demonstrates the fabrication of a graphene-based sensor for measuring the temperature and humidity of a metal body. The graphene sensor was fabricated by depositing a thin film of graphene nanoparticles between silver electrodes (separated by ∼50 μm) on a glass substrate. The graphene thin film was characterized by XRD, Raman spectroscopy and UV-vis techniques. The capacitance and resistance for both the relative humidity (in the range of 0–100% RH) and temperature (in the range of 230–310 K) were measured using an LCR meter at 1 kHz in a controlled chamber. The graphene-based sensor expressed high sensitivity with fast response and recovery times for both humidity and temperature with long stability and low hysteresis curves. The sensor was also tested on a metal body, which expressed a good response time. Moreover, the measured data of capacitance and resistance was analyzed with classical and neutrosophic analysis as an application of modern material statistics. It was observed that neutrosophic analysis is more flexible for analyzing the capacitance and resistance of the fabricated sensor.

We present the integration of epitaxial graphene with thin film dielectric materials for the purpose of graphene transistor development. The impact on epitaxial graphene structural and electronic properties following deposition of Al(2)O(3), HfO(2), TiO(2), and Ta(2)O(5) varies based on the choice of dielectric and deposition parameters. Each dielectric film requires the use of a nucleation layer to ensure uniform, continuous coverage on the graphene surface. Graphene quality degrades most severely following deposition of Ta(2)O(5), while the deposition if TiO(2) appears to improve the graphene carrier mobility. Finally, we discuss the potential of dielectric stack engineering for improved transistor performance.

The recent success of graphene transistor operation in the giga-hertz range has solidified the potential of this material for high speed electronic applications. Realization of a graphene technology on the production scale; however, requires the ability to synthesize large area graphene, and rapidly characterize the material's structural and electronic quality. We report a direct link between carrier mobility and Raman topography of epitaxial graphene grown on silicon carbide. We have examined epitaxial graphene with mobility values of 25 - 1100 cm2/V-s, and show that the Hall mobility of epitaxial graphene on the Si-face of SiC (SiC(0001)) is not only highly dependent on thickness uniformity, but also on mono-layer strain uniformity. It is not until the thickness and strain uniformity is approaches 50% of the device width that one is able to achieve mobility values higher than 1000 cm2/V-s.

An emerging machine learning (ML) strategy for the fabrication of nanozyme sensor based on multi-walled carbon nanotubes (MWCNTs)/graphene oxide (GO)/dendritic silver nanoparticles (AgNPs) nanohybrid and the voltametric determination of benomyl (BN) residues in tea and cucumber samples is proposed. Nanohybrid is prepared by the electrodeposition of dendritic AgNPs on the surface of MWCNTs/GO obtained by a simple mixed-strategy. The orthogonal experiment design combined with back propagation artificial neural network with genetic algorithm is used to solve multi-factor problems caused by the fabrication of nanohybrid sensor for BN. Both support vector machine (SVM) algorithm and least square support vector machine (LS-SVM) algorithm are used to realize the intelligent sensing of BN compared with the traditional method. The as-fabricated electrochemical sensor displays high electrocatalytic capacity (excellent voltammetric response), unique oxidase-like characteristic (nanozyme), wide working range (0.2–122.2 μM), good practicability (satisfactory recovery). It is feasible and practical that ML guides the fabrication of nanozyme sensor and the intelligent sensing of BN compared with the traditional method. This work will open a new avenue for guiding the synthesis of sensing materials, the fabrication of sensing devices and the intelligent sensing of target analytes in the future.

Electrically nanowired-enzymes for probe modification and sensor fabrication

2D SnSe2 nanoflakes decorated with 1D ZnO nanowires for ppb-level NO2 detection at room temperature

The populations residing near polluted sites are more prone to various types of diseases. The important causes of air pollution are the suspended particulate matter, respirable suspended particulate matter, sulfur dioxide and nitrogen dioxide. As limited information is available enumerating the effect of these pollutants on liver physiology of the population living near the polluted sites; in the present study, we tried to investigate their effect on liver of the population residing near the oil drilling sites since birth. In this study, a randomly selected 105 subjects (46 subjects from oil drilling site and 61 subjects from control site) aged above 30 years were taken under consideration. The particulate matter as well as the gaseous pollutants, sulfur dioxide and nitrogen dioxide, were analyzed through a respirable dust sampler. The level of alkaline phosphatase, alanine transaminase and aspartate transaminase enzymes in serum were measured by spectrophotometer. The generalized regression model studies suggests a higher concentration of respirable suspended particulate matter, suspended particulate matter and nitrogen dioxide lowers the alkaline phosphatase level (p<0.0001) by 3.5 times (95% CI 3.1-3.9), 1.5 times (95% CI 1.4 - 1.6) and 12 times (95% CI 10.74 -13.804), respectively in the exposed group. The higher concentration of respirable suspended particulate matter and nitrogen dioxide in air was associated with increase in alanine transaminase level (p<0.0001) by 0.8 times (95% CI 0.589-1.049) and by 2.8 times (95% CI 2.067-3.681) respectively in the exposed group. The increase in nitrogen dioxide level was also associated with increase in aspartate transaminase level (p<0.0001) by 2.5 times (95% CI 1.862 – 3.313) in the exposed group as compared to control group. Thus, the study reveals that long-term exposure to the environmental pollutants may lead to liver abnormality or injury of populations living in polluted sites.

Measuring solution concentration plays an important role in chemical, biochemical, clinical diagnosis, environmental monitoring, and biological analyses. In this work, we develop a transmission-mode localized surface plasmon resonance sensor chip system and convenient method which is highly efficient, highly sensitive for detection sensing using multimode fiber. The plasmonically active sensor’s surface AuNPs with high-density NPs were decorated onto 1 cm sensing length of various clad-free fiber in the form of homogeneous monolayer utilizing a self-assembly process for immobilization of the target molecule. The carboxyl bond is formed through a functional reaction on the sensor head. Using the significance in the refractive index difference and numerical aperture, which is caused by a variation in the concentration of measuring bovine serum albumin (BSA) protein which can be accurately measured by the output signal. The refractive index variation of the medium analyte layer can be converted to signal output power change at the He–Ne wavelength of 632.8 nm. The sensor detection limit was estimated to be 0.075 ng ml−1 for BSA protein which shows high sensitivity compared to other types of label-free optical biosensors. This also leads to a possibility of finding the improvement in the sensitivity label-free biosensors. The conventional method should allow multimode fiber biosensors to become a possible replacement for conventional biosensing techniques based on fluorescence.

5 - Wireless Sensors Using Semi-passive UWB RFID

Gas sensors have attracted immense attention due to the requirement of controlled processes in the electronic, automobile, agricultural, and pharmaceutical industries. The sensing property of solid-state sensors depends on the surface area and surface chemistry of the sensor materials. In this respect, carbon nanotubes and their composites are ideal candidates for chemical sensing applications due to their large surface to volume ratio. Unlike pristine carbon nanotubes and graphene sensors, composites of CNT and graphene and reduced graphene oxide show greater selectivity toward the target gases. In this chapter a comprehensive discussion on the gas sensing property of carbon nanotubes, graphene/reduced graphene oxide and their composite devices are covered. Apart from this, widely used different types of carbon nanotube and graphene-based sensors are also discussed in detail. Synthesis and fabrication of nanotube sensors are highlighted with stress on resistive sensors. The challenge of fabricating a good gas sensor, i.e., a sensor with high sensitivity, low hysteresis, short response, and recovery time are addressed.