Mahesh Kumar

Bio: Mahesh Kumar is an academic researcher from Indian Institute of Technology, Jodhpur. The author has contributed to research in topics: Molecular beam epitaxy & Heterojunction. The author has an hindex of 29, co-authored 204 publications receiving 4864 citations. Previous affiliations of Mahesh Kumar include Indian Institutes of Technology & Indian Institute of Technology Delhi.

Gas sensing materials roadmap.

Abstract: Gas sensor technology is widely utilized in various areas ranging from home security, environment and air pollution, to industrial production. It also hold great promise in non-invasive exhaled breath detection and an essential device in future internet of things. The past decade has witnessed giant advance in both fundamental research and industrial development of gas sensors, yet current efforts are being explored to achieve better selectivity, higher sensitivity and lower power consumption. The sensing layer in gas sensors have attracted dominant attention in the past research. In addition to the conventional metal oxide semiconductors, emerging nanocomposites and graphene-like two-dimensional materials also have drawn considerable research interest. This inspires us to organize this comprehensive 2020 gas sensing materials roadmap to discuss the current status, state-of-the-art progress, and present and future challenges in various materials that is potentially useful for gas sensors.

Study of inter-relationship of depression, seizure frequency and quality of life of people with epilepsy in India

Abstract: Epilepsy is a chronic neurological disorder that can have profound physical, social and psychological consequences. We aimed to assess the clinical predictors of quality of life of people with epilepsy. We recruited 31 patients suffering from epilepsy in this cross-sectional study. Their clinical profile was recorded. Quality Of Life in Epilepsy (QOLIE-31) was used to assess quality of life of our patients. Depression was screened by Neurological Disorders Depression Inventory in Epilepsy (NDDI-E). Among all the clinical variables, only seizure frequency significantly correlated with seizure worry (P=0.002), emotional well-being (P=0.026) and social functions (P=0.013) subscales of QOLIE-31. NDDIE score showed a significant negative correlation with all the subscales of QOLIE-31 except medication effects (P=0.993). A significant positive correlation was also noted between seizure frequency and NDDI-E score (r=0.417, P=0.020). Seizure frequency and depression are the most important predictors of quality of life in epilepsy patients. The management of patients with epilepsy should not only be aimed at just preventing seizures but the treating clinicians should also be cognizant about depression which itself can significantly affect the quality of life of patients.

MPA-GSH Functionalized AlGaN/GaN High-Electron Mobility Transistor-Based Sensor for Cadmium Ion Detection

Abstract: This paper demonstrates a novel AlGaN/GaN high-electron mobility transistor (HEMT)-based cadmium ion (Cd2+) sensor with mercaptopropionic acid (MPA) and glutathione (GSH) functionalization. The sensing response of the sensor was analyzed by detecting Cd2+ ions at different concentrations. The AlGaN/GaN HEMT sensor exhibits excellent response with the sensitivity of $0.241~\mu \text{A}$ /ppb, a fast response time of ~ 3 s, and a lower detection limit of 0.255 ppb. The observed lower detection limit is significantly lower than the World Health Organization (WHO) standard recommended limit for Cd2+ ions in drinking water. Furthermore, the sensor showed good selectivity of Cd2+ ions toward other heavy metal ions. The results indicate that the binding properties of GSH to Cd and the sensitivity of 2-D electron gas toward the variation of charges at the gate region make the device highly sensitive with rapid detection of Cd2+ ions.

Perspective on the Development of Lead-free Piezoceramics

Abstract: A large body of work has been reported in the last 5 years on the development of lead-free piezoceramics in the quest to replace lead–zirconate–titanate (PZT) as the main material for electromechanical devices such as actuators, sensors, and transducers. In specific but narrow application ranges the new materials appear adequate, but are not yet suited to replace PZT on a broader basis. In this paper, general guidelines for the development of lead-free piezoelectric ceramics are presented. Suitable chemical elements are selected first on the basis of cost and toxicity as well as ionic polarizability. Different crystal structures with these elements are then considered based on simple concepts, and a variety of phase diagrams are described with attractive morphotropic phase boundaries, yielding good piezoelectric properties. Finally, lessons from density functional theory are reviewed and used to adjust our understanding based on the simpler concepts. Equipped with these guidelines ranging from atom to phase diagram, the current development stage in lead-free piezoceramics is then critically assessed.

Room-temperature saturated ferroelectric polarization in BiFeO3 ceramics synthesized by rapid liquid phase sintering

Abstract: Single-phased ferroelectromagnet BiFeO3 ceramics with high resistivity were synthesized by a rapid liquid phase sintering technique. Saturated ferroelectric hysteresis loops were observed at room temperature in the ceramics sintered at 880 °C for 450 s. The spontaneous polarization, remnant polarization, and the coercive field are 8.9 μC/cm2, 4.0 μC/cm2, and 39 kV/cm, respectively, under an applied field of 100 kV/cm. It is proposed that the formation of Fe2+ and an oxygen deficiency leading to the higher leakage can be greatly suppressed by the very high heating rate, short sintering period, and liquid phase sintering technique. The latter was also found effective in increasing the density of the ceramics. The sintering technique developed in this work is expected to be useful in synthesizing other ceramics from multivalent or volatile starting materials.

Room-temperature gas sensing of ZnO-based gas sensor: A review

Abstract: Novel gas sensors with high sensing properties, simultaneously operating at room temperature are considerably more attractive owing to their low power consumption, high security and long-term stability. Till date, zinc oxide (ZnO) as semiconducting metal oxide is considered as the promising resistive-type gas sensing material, but elevated operating temperature becomes the bottleneck of its extensive applications in the field of real-time gas monitoring, especially in flammable and explosive gas atmosphere. In this respect, worldwide efforts have been devoted to reducing the operating temperature by means of multiple methods In this communication, room-temperature gas sensing properties of ZnO based gas sensors are comprehensively reviewed. Much more attention is particularly paid to the effective strategies that create room-temperature gas sensing of ZnO based gas sensors, mainly including surface modification, additive doping and light activation. Finally, some perspectives for future investigation on room-temperature gas-sensing materials are discussed as well.