Romanian Journal of Information Science and Technology (ROMJIST)

An open – access publication


ROMJIST is a publication of Romanian Academy,
Section for Information Science and Technology

Editor – in – Chief:
Radu-Emil Precup

Honorary Co-Editors-in-Chief:
Horia-Nicolai Teodorescu
Gheorghe Stefan

Secretariate (office):
Adriana Apostol
Adress for correspondence: (after 1st of January, 2019)

Editing of the printed version: Mihaela Marian (Publishing House of the Romanian Academy, Bucharest)

Technical editor
of the on-line version:
Lucian Milea (University POLITEHNICA of Bucharest)

• National Institute for R & D
in Microtechnologies
(IMT Bucharest),

ROMJIST Volume 23, No. 1, 2020, pp. 93-104

Bogdan Catalin SERBAN, Octavian BUIU, Nicolae DUMBRAVESCU, Cornel COBIANU, Viorel AVRAMESCU, Mihai BREZEANU, Marius BUMBAC, Cristina Mihaela NICOLESCU
Optimization of Sensing Layers Selection Process for Relative Humidity Sensors

ABSTRACT: Electronic devices designed for environmental monitoring have gained an increasing importance in the last years. Parameters such as relative humidity (RH), temperature, pressure, acceleration and speed, measured by devices such as RH, temperature, pressure, and motion sensors, are at the core of the efforts for improving the environmental conditions. The employment of such devices in complex sensing systems enable their use in IoT (Internet of Things) applications, which is of paramount importance for an in-time and appropriate reaction to adverse environmental phenomena. Given all these, the need to design sensors with improved sensing performance, such high sensitivity, reduced cross-sensitivity and low response time, emerges. The aim of this paper is to introduce the Hard-Soft Acid Base (HSAB) concept as a valuable investigative tool to explain, to a certain extent, the increased sensitivity and selectivity experimentally demonstrated by different used metal oxides (MOX) and their nanocomposites to relative humidity. Based on literature data, six different case-studies of RH detection by sensing layers employing metal oxides and related composites, are highlighted and investigated in terms of HSAB theory. To support the thesis that the HSAB principle can be a useful criterion and can be taken in account when either selecting a suitable gas sensing layer (in particular, for RH detection) or optimizing his functional response, we will build our argumentation on three reasons: 1) strong RH detection capabilities of MOX layers classified as hard acids according to the HSAB theory; 2) strong ethanol, ammonia and trimethylamine detection capabilities of MOX layers classified as hard acids; 3) the significant role played by dopants classified as hard acids in the performance of MOX-based RH sensing layers.

KEYWORDS: Humidity Sensor, Metal Oxide, Hard Soft Acid Base

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