The properties and applications of molybdenum oxides are reviewed in depth. Molybdenum is found in various oxide stoichiometries, which have been employed for different high-value research and commercial applications. The great chemical and physical characteristics of molybdenum oxides make them versatile and highly tunable for incorporation in optical, electronic, catalytic, bio, and energy systems. Variations in the oxidation states allow manipulation of the crystal structure, morphology, oxygen vacancies, and dopants, to control and engineer electronic states. Despite this overwhelming functionality and potential, a definitive resource on molybdenum oxide is still unavailable. The aim here is to provide such a resource, while presenting an insightful outlook into future prospective applications for molybdenum oxides.

Molybdenum Oxides – From Fundamentals to Functionality

Electrically–transduced sensors, with their simplicity and compatibility with standard electronic technologies, produce signals that can be efficiently acquired, processed, stored, and analyzed. Two dimensional (2D) nanomaterials, including graphene, phosphorene (BP), transition metal dichalcogenides (TMDCs), and others, have proven to be attractive for the fabrication of high–performance electrically-transduced chemical sensors due to their remarkable electronic and physical properties originating from their 2D structure. This review highlights the advances in electrically-transduced chemical sensing that rely on 2D materials. The structural components of such sensors are described, and the underlying operating principles for different types of architectures are discussed. The structural features, electronic properties, and surface chemistry of 2D nanostructures that dictate their sensing performance are reviewed. Key advances in the application of 2D materials, from both a historical and analytical pers...

Electrically-Transduced Chemical Sensors Based on Two-Dimensional Nanomaterials

https://www.econstor.eu/bitstream/10419/244006/1/1693663112.pdf

Enhanced sensing performance of ZnO nanostructures-based gas sensors: A review

Two-dimensional transition metal carbides/nitrides, known as MXenes, have been recently receiving attention for gas sensing. However, studies on hybridization of MXenes and 2D transition metal dichalcogenides as gas-sensing materials are relatively rare at this time. Herein, Ti3C2Tx and WSe2 are selected as model materials for hybridization and implemented toward detection of various volatile organic compounds. The Ti3C2Tx/WSe2 hybrid sensor exhibits low noise level, ultrafast response/recovery times, and good flexibility for various volatile organic compounds. The sensitivity of the hybrid sensor to ethanol is improved by over 12-fold in comparison with pristine Ti3C2Tx. Moreover, the hybridization process provides an effective strategy against MXene oxidation by restricting the interaction of water molecules from the edges of Ti3C2Tx. An enhancement mechanism for Ti3C2Tx/WSe2 heterostructured materials is proposed for highly sensitive and selective detection of oxygen-containing volatile organic compounds. The scientific findings of this work could guide future exploration of next-generation field-deployable sensors.

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Nanohybrids of a MXene and transition metal dichalcogenide for selective detection of volatile organic compounds.

Two-dimensional transition metal dichalcogenides (2D TMDs) have attracted much attention in the field of optoelectronics due to their tunable bandgaps, strong interaction with light and tremendous capability for developing diverse van der Waals heterostructures (vdWHs) with other materials. Molybdenum disulfide (MoS2) atomic layers which exhibit high carrier mobility and optical transparency are very suitable for developing ultra-broadband photodetectors to be used from surveillance and healthcare to optical communication. This review provides a brief introduction to TMD-based photodetectors, exclusively focused on MoS2-based photodetectors. The current research advances show that the photoresponse of atomic layered MoS2 can be significantly improved by boosting its charge carrier mobility and incident light absorption via forming MoS2 based plasmonic nanostructures, halide perovskites–MoS2 heterostructures, 2D–0D MoS2/quantum dots (QDs) and 2D–2D MoS2 hybrid vdWHs, chemical doping, and surface functionalization of MoS2 atomic layers. By utilizing these different integration strategies, MoS2 hybrid heterostructure-based photodetectors exhibited remarkably high photoresponsivity raging from mA W−1 up to 1010 A W−1, detectivity from 107 to 1015 Jones and a photoresponse time from seconds (s) to nanoseconds (10−9 s), varying by several orders of magnitude from deep-ultraviolet (DUV) to the long-wavelength infrared (LWIR) region. The flexible photodetectors developed from MoS2-based hybrid heterostructures with graphene, carbon nanotubes (CNTs), TMDs, and ZnO are also discussed. In addition, strain-induced and self-powered MoS2 based photodetectors have also been summarized. The factors affecting the figure of merit of a very wide range of MoS2-based photodetectors have been analyzed in terms of their photoresponsivity, detectivity, response speed, and quantum efficiency along with their measurement wavelengths and incident laser power densities. Conclusions and the future direction are also outlined on the development of MoS2 and other 2D TMD-based photodetectors.

/pdf/a-review-of-molybdenum-disulfide-mos2-based-photodetectors-5dugidies6.pdf

A review of molybdenum disulfide (MoS2) based photodetectors: from ultra-broadband, self-powered to flexible devices

This paper presents the development of an extremely sensitive and selective acetone sensor prototype which can be used as a platform for non-invasive diabetes detection through exhaled human breath. The miniaturized sensors were produced in high yield with the use of standard microfabrication processes. The sensors were based on a heterostructure composed of MoO3 and nano-porous silicon (NPS). Features like acetone selective, enhanced sensor response and 0.5 ppm detection limit were observed upon introduction of MoO3 on the NPS. The sensors were found to be repeatable and stable for almost 1 year, as tested under humid conditions at room temperature. It was inferred that the interface resistance of MoO3 and NPS played a key role in the sensing mechanism. With the use of breath analysis and lab-on-chip, medical diagnosis procedures can be simplified and provide solutions for point-of-care testing.

https://iopscience.iop.org/article/10.1088/1361-6528/aabcef/pdf

MoO3/nano-Si heterostructure based highly sensitive and acetone selective sensor prototype: a key to non-invasive detection of diabetes.

Growing Perovskite Quantum Dots on Carbon Nanotubes for Neuromorphic Optoelectronic Computing

Pandemic like Coronavirus disease (COVID-19) shows that there is an urgent need for changing our traditional healthcare monitoring system which produces a lot of waste and pollutes the environment. At present patients need to visit a doctor/clinic to check-up their health. Due to COVID-19, there are risks for doctors and patients to be infected by COVID-19. There are many cases reported worldwide where doctors/nurses and low immunity power people are easily affected by Coronavirus. Many clinics, hospitals are not able to treat regular patients. Therefore, there is a need to change the system for healthcare monitoring. Different types of micro/nano, wearable sensors and devices are developed for diagnosing diseases. The advantages of these micro and wearable sensors are higher sensitivity, fast response and low power consumption. Other hand, Instead of bulky instruments these wearable microsensors can be embedded/attached with the patient and it can monitor the patient’s health remotely. Using modern computer and electronics technology like the Internet of Things (IoT) platform (which includes computer vision, Very Large Scale Integration (VLSI), big data analysis, deep learning, machine learning and artificial intelligence), it will become a real time health monitoring system. In this chapter we will initially discuss the present day’s healthcare system, followed by micro and wearable sensors used for diagnostic purposes. Further focus of the chapter will be on the electronics used for driving the sensors, devices and the collected data will be transmitted. Finally the frameworks for IoT based wearable sensors will be discussed. These IoT based wearable sensors will be a solution for sustainable healthcare systems.

IoT Based Wearable Healthcare System: Post COVID-19

This paper presents the selective and highly sensitive performance of porous TiO2/nano-Si heterostructure for ethanol sensing. The fabrication steps involved were scalable and reproducible making the device eligible for batch fabrication suitable for industry production. The sensor response was recorded as a change in resistance upon exposure to a variety of organic vapors in the concentration range of 5–500 ppm and in simulated real breath conditions. Although the response was obtained at room temperature, however, the operating temperature of the sensor was found to be around 100 °C. The sensing mechanism has been explained on the basis of adsorption–desorption theory of gases, physical, and chemical properties of the materials. A prototype was built for complete realization of the sensor. The sensor data from the sensor array comprising of hetersostructure and its single-layer counterparts were collated and signal conditioning like Regression model and PCA was done. These were used for assessing the alcohol concentration and separation of analytes for the development of E-nose system.

Interfacial Engineering in TiO 2 /Nano-Si Heterostructure-Based Device Prototype for E-Nose Application

Coronavirus disease (COVID-19) pandemic has intensively damaged human socio-economic lives and the growth of countries around the world. Many efforts have been made in the direction of artificial i...

Priyanka Dwivedi

Papers

MoO3/nano-Si heterostructure based highly sensitive and acetone selective sensor prototype: a key to non-invasive detection of diabetes.

Growing Perovskite Quantum Dots on Carbon Nanotubes for Neuromorphic Optoelectronic Computing

IoT Based Wearable Healthcare System: Post COVID-19

Interfacial Engineering in TiO 2 /Nano-Si Heterostructure-Based Device Prototype for E-Nose Application

Application of Artificial Intelligence on Post Pandemic Situation and Lesson Learn for Future Prospects