arXiv subjects

Puja Ghosh

Publications and source records attributed to Puja Ghosh.

4 recordsLinked to original sources

arXiv2025

Experimental and Computational Demonstration of a Highly Stable, in-situ Pt Decorated Sputtered ZnO Hydrogen Sensor for sub-ppm Level Detection

In this work, we present a Pt decorated ZnO thin film-based gas sensor for hydrogen detection, fabricated using a sputtering technique and an in-situ Pt decoration approach. Specifically, we deposit a ZnO thin film on an interdigitated electrode substrate, with Pt nanoclusters added to the (002) polar plane by brief sputtering (1 to 6 s) to create an active sensing interface. Our sensor demonstrates optimal performance at an operating temperature of 498 K, with rapid response and recovery times (10 and 3 s), high selectivity, and long-term stability. We find the Pt decorated ZnO sensor, with a Pt deposition time of 2 s, to exhibit enhanced response (~52,987%) to 1% hydrogen concentration, indicating its suitability for industrial and environmental monitoring applications. Additionally, our device demonstrates reliable detection of low hydrogen concentrations (~100 ppb), with a response of ~38% and no response drift over one year of testing, underscoring the long-term stability of the sensor. To elucidate the role of Pt deposition and pristine ZnO in hydrogen sensing, we perform density functional theory calculations, analysing adsorption and reaction energetics involving H2, O2, O, OH, and H2O, and lattice oxygen atoms on the ZnO (002) surface with and without Pt decoration. Our computational data is in agreement with our experiments, identifying the oxygen-exposed (002) surface to be most active for hydrogen sensing in both pristine and Pt decorated ZnO. Further, our computations highlight the role of Pt in enhancing hydrogen sensitivity via i) activating an autoreduction pathway of adsorbed OH, ii) spontaneous dissociation of adsorbed molecular H2, and iii) keeping the lattice oxygen pathway of forming H2O active. Our systematic approach of designing sensors combining an experimental setup with theoretical insights, is key in developing and optimizing efficient hydrogen gas sensors.

cond-mat.mtrl-sci↗

arXiv2016

On Symmetry of Birkhoff-James Orthogonality of Linear Operators on Finite-dimensional Real Banach Spaces

We characterize left symmetric linear operators on a finite dimensional strictly convex and smooth real normed linear space $ \mathbb{X},$ which answers a question raised recently by one of the authors in \cite{S} [D. Sain, \textit{Birkhoff-James orthogonality of linear operators on finite dimensional Banach spaces, Journal of Mathematical Analysis and Applications, accepted, $ 2016 $}]. We prove that $ T\in B(\mathbb{X}) $ is left symmetric if and only if $ T $ is the zero operator. If $ \mathbb{X} $ is two-dimensional then the same characterization can be obtained without the smoothness assumption. We also explore the properties of right symmetric linear operators defined on a finite dimensional real Banach space. In particular, we prove that smooth linear operators on a finite-dimensional strictly convex and smooth real Banach space can not be right symmetric.

math.FA↗

arXiv2015

Birkhoff-James orthogonality and smoothness of bounded linear operators

We present a sufficient condition for smoothness of bounded linear operators on Banach spaces for the first time. Let $T, A \in B(\mathbb{X}, \mathbb{Y}),$ where $\mathbb{X}$ is a real Banach space and $\mathbb{Y}$ is a real normed linear space. We find sufficient condition for $ T \bot_{B} A \Leftrightarrow Tx \bot_{B} Ax $ for some $ x \in S_{\mathbb{X}}$ with $ \|Tx\| = \|T\|, $ and use it to show that $T$ is a smooth point in $ B(\mathbb{X}, \mathbb{Y}) $ if $T$ attains its norm at unique (upto muliplication by scalar) vector $ x \in S_{\mathbb{X}},$ $Tx$ is a smooth point of $\mathbb{Y} $ and {\em sup}$_{y \in C} \|Ty\| < \|T\|$ for all closed subsets $C$ of $S_{\mathbb{X}}$ with $d(\pm x,C) > 0.$ For operators on a Hilbert space $ \mathbb{H}$ we show that $ T \bot_{B} A \Leftrightarrow Tx \bot_{B} Ax $ for some $ x \in S_{\mathbb{H}}$ with $ \|Tx\| = \|T\| $ if and only if the norm attaining set $M_T = \{ x \in S_{\mathbb{H}} : \|Tx\| = \|T\| \} = S_{H_0}$ for some finite dimensional subspace $H_0$ and $ \|T\|_{{H_o}^{\bot}} < \|T\|.$ We also characterize smoothness of compact operators on normed spaces and bounded linear operators on Hilbert spaces.

math.FA↗

arXiv2014

On rectangular constant in normed linear spaces

We study the properties of rectangular constant $ \mu(\mathbb{X}) $ in a normed linear space $\mathbb{X}$. We prove that $ \mu(\mathbb{X}) = 3$ iff the unit sphere contains a straight line segment of length 2. In fact, we prove that the rectangular modulus attains its upper bound iff the unit sphere contains a straight line segment of length 2. We prove that if the dimension of the space $\mathbb{X}$ is finite then $\mu(\mathbb{X})$ is attained. We also prove that a normed linear space is an inner product space iff we have sup$\{\frac{1+|t|}{\|y+tx\|}$: $x,y \in S_{\mathbb{X}}$ with $x\bot_By\} \leq \sqrt{2}$ $\forall t$ satisfying $|t|\in (3-2\sqrt{2},\sqrt{2}+1)$.

math.FA↗