arXiv subjects

Vinayak Kamble

Publications and source records attributed to Vinayak Kamble.

5 recordsLinked to original sources

arXiv2024

Metal Oxide-based Gas Sensor Array for the VOCs Analysis in Complex Mixtures using Machine Learning

Detection of Volatile Organic Compounds (VOCs) from the breath is becoming a viable route for the early detection of diseases non-invasively. This paper presents a sensor array with three metal oxide electrodes that can use machine learning methods to identify four distinct VOCs in a mixture. The metal oxide sensor array was subjected to various VOC concentrations, including ethanol, acetone, toluene and chloroform. The dataset obtained from individual gases and their mixtures were analyzed using multiple machine learning algorithms, such as Random Forest (RF), K-Nearest Neighbor (KNN), Decision Tree, Linear Regression, Logistic Regression, Naive Bayes, Linear Discriminant Analysis, Artificial Neural Network, and Support Vector Machine. KNN and RF have shown more than 99% accuracy in classifying different varying chemicals in the gas mixtures. In regression analysis, KNN has delivered the best results with R2 value of more than 0.99 and LOD of 0.012, 0.015, 0.014 and 0.025 PPM for predicting the concentrations of varying chemicals Acetone, Toluene, Ethanol, and Chloroform, respectively in complex mixtures. Therefore, it is demonstrated that the array utilizing the provided algorithms can classify and predict the concentrations of the four gases simultaneously for disease diagnosis and treatment monitoring.

physics.app-ph↗

arXiv2023

Suppressed Polaronic Conductivity induced Sensor Response Enhancement in Mo doped V2O5 Nanowires

In this paper, we show the direct correlation between suppression of polaronic oxygen vacancy defect (Vo) density and gas sensor response of 1 at% Mo doped $V_2O_5$ (MVONW) nanowires. Doping 1 at% $Mo^{5+}$ leads to substitution at the $V^{5+}$ site in $V_2O_5$ nanowires (VONW) and thereby reduction in Vo defects. This in turn affects the charge carrier hopping sites and subsequently enhances the sensor response at lower temperatures ($<320^oC$). The $Mo^{5+}$ dopants lead to the lowering of Fermi energy (EF) towards valence band maxima due to reduced $V_o$ donor density. The polaron suppression is confirmed with activation energy of polaron hopping, increasing from 195 meV to 385 meV in VONW and MVONW respectively. As a result, the response to ethanol gas enhanced as the depletion width is widened for the given cross-section of the nanowires. This may lead to large depletion controlled cross-sectional area and thereby better sensitivity. At about $350^oC$ VONW show change in slope of resistance vs temperature (MIT) which is not observed in case of MVONW. This is attributed to presence of enhanced non-stoichiometry of V ion resulting in metallic behaviour and accompanied with sudden rise in sensor response at this temperature. Moreover, the absence of MIT may be attributed to lack of such sudden rise in response in MVONW.

cond-mat.mes-hall↗

arXiv2021

Selective Enhancement in Phonon Scattering leads to High Thermoelectric Figure of Merit in ZnO -- Graphene Oxide Core-shell Nanohybrids

ZnO is a promising candidate as an environment friendly thermoelectric (TE) material. However, the poor TE figure of merit (zT) needs to be addressed to achieve significant TE efficiency for commercial applications. Here we demonstrate that selective enhancement in phonon scattering leads to increase in zT of RGO encapsulated Al-doped ZnO core shell nanohybrids, synthesized via a facile and scalable method. The incorporation of 1 at% Al with 1.5 wt% RGO into ZnO (AGZO) has been found to show significant enhancement in zT (=0.52 at 1100 K) which is an order of magnitude larger compared to that of bare undoped ZnO. Photoluminescence and X-ray photoelectron spectroscopy measurements confirm that RGO encapsulation significantly quenches surface oxygen vacancies in ZnO along with nucleation of new interstitial Zn donor states. Tunneling spectroscopy reveals that the band gap of ~ 3.4 eV for bare ZnO reduces effectively to ~ 0.5 eV upon RGO encapsulation, facilitating charge transport. The electrical conductivity enhancement also benefits from the more than 95% densification achieved, using the spark plasma sintering method, which aids reduction of GO into RGO. The same Al doping and RGO capping synergistically brings about drastic reduction of thermal conductivity, through enhanced phonon-phonon and point defect-phonon scatterings. These opposing effects on electrical and thermal conductivities enhances the power factors as well as the zT value. Overall, a practically viable route for synthesis of oxide - RGO TE material which could find its practical applications for the high-temperature TE power generation.

cond-mat.mtrl-sci↗

arXiv2020

Proof-of-concept thermoelectric oxygen sensor exploiting oxygen mobility of GdBaCo2O5+δ

In this paper, we demonstrate a proof-of-concept oxygen sensor based on the thermoelectric principle using polycrystalline $GdBaCo_2O_{5+δ}$ where 0.45<$δ$<0.55 (GDCO). The lattice oxygen in layered double perovskite oxides is highly susceptible to the ambient oxygen partial pressure. The as-synthesized GDCO sample processed in ambient conditions shows pure orthorhombic ($P_{mmm}$ space group) phase and a $δ$-value close to 0.5 as confirmed from X-ray diffraction reitveld refinement. The X-ray photoelectron spectroscopy shows significant $Co^{3+}$ oxidation state in non-octahedral sites in addition to $Co^{3+}$ and $Co^{4+}$ in octahedral sites. The insulator-to-metal transition (MIT) is observed at nearly 340 K as seen in electrical resistivity and seebeck coefficient measurements. The seebeck coefficient shows a large change of about 10-13 $μ$V/K with time constant of ~20 sec, at room temperature (300 K) when the gas ambience changes from 100% oxygen to 100% nitrogen and vice versa, under a constant temperature gradient of 1 K. The response in seebeck is found to be particularly large below MIT. The diffusion of oxygen into the lattice leading to hole doping shows a large change in carrier concentration resulting in a large change in the seebeck coefficient in insulating state. On the other hand, due to insignificant increase in already large carrier concentration in metallic state the change in seebeck is minimal. Nevertheless, below MIT the response is fairly reproducible within stoichiometry $δ$ = 0.5 $\pm$ 0.05. This principle shall be of significant utility to design the oxygen sensors which work at room temperature or even cryogenic temperatures.

cond-mat.mtrl-sci↗

arXiv2020

High Entropy Alloy Nanoparticles Decorated, p-type 2D-Molybdenum Disulphide (MoS2) and Gold Schottky Junction Enhanced Hydrogen Sensing

Molybdenum Disulphide (MoS2) is an interesting material which exists in atomically thin multilayers and can be exfoliated into monolayer or a few layers for multiple applications. It has emerged as a promising material for development of such efficient sensors. Here, we have exfoliated and decorated MoS2 flakes with novel, single phase High Entropy Alloy (HEA) nanoparticles using facile and scalable cryomilling technique, followed by sonochemical method. It is found that the decoration of HEA nanoparticles impart surface enhanced Raman scattering effect and reduction in the work function of the material from 4.9 to 4.75 eV as measured by UV photoelectron spectroscopy. This change in the work function results in a schottky barrier between the gold contact and HEA decorated MoS2 flakes as a result of drastic changes in the surface chemical non-stoichiometry. The response to hydrogen gas is studied at temperatures 30 to 100 oC and it shows unusual p-type nature due to surface adsorbed oxygen species. The nanoscale junction formed between HEA and MoS2 shows 10 times increase in the response towards hydrogen gas at 80 oC. The experimental observations are further explained with DFT simulation showing more favourable hydrogen adsorption on HEA decorated MoS2 resulting for enhanced response.

cond-mat.mtrl-sci↗