C2H5OH and LPG sensing properties of -Fe2O3 microflowers prepared by hydrothermal route

Dien Dac Nguyen,Hien Xuan Vu,Phuoc Huu Luong,Tho Duc Do,Vuong Duc Dang

doi:10.32508/stdj.v19i3.522

Abstract

The flower-like micron-structure of α-Fe2O3 was synthesized via hydrothermal treatment at 140 C for 24 h using Fe(NO3)3.9H2O and Na2SO4 as the precursors. A thin film constructed by the as-prepared material was created by spin coating technique. The structure, morphology, and composition of the samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM). The α-Fe2O3 microflowers (MFs) with average diameter of several micrometers are assembled of nanorods which possess average diameter and length of 40 nm and hundred nm, respectively. The gas sensing properties of α-Fe2O3 film were tested with ethanol (C2H5OH) and liquefied petroleum gas (LPG) at the operating temperatures of 225–400 °C. The sensor response of the α-Fe2O3 film reached highest sensitivity to C2H5OH and LPG at 275 C and 350 °C, respectively. The thin film exhibited higher sensitivity and lower working temperature to C2H5OH than those to LPG. The film can detect minimum concentration of 250 ppm C2H5OH. The response time of the film to C2H5OH is approximately 30 s.

Highlights

Hematite (α-Fe2O3) is the most stable iron oxide under ambient conditions which behaves as an n-type semiconducting material with band gap of 2.2 eV [1]
Ferric oxide has been prepared by liquid-phase deposition method (LPD) [16], plasma enhanced chemical vapor deposition (PECVD) [17], ion-sputtering [18], ultrasonic spray pyrolysis [19], sol-gel route [2], hydrothermal method [1, 11, 13, 14], etc
The results indicated that the sensor response of the α-Fe2O3 film reached highest sensitivity to ethanol vapor and LPG at operating temperature of 275 C and 350 C, respectively

Summary

INTRODUCTION

Hematite (α-Fe2O3) is the most stable iron oxide under ambient conditions which behaves as an n-type semiconducting material with band gap of 2.2 eV [1]. Much effort has been focused on the fabrication of nanostructure materials with a desired size, morphology and porosity, owing to their special electrical, optical, magnetic, and physical/chemical properties that are superior to those bulk materials [7,8,9,10] Stimulated by both the promising applications of iron oxide and the novel properties of nanoscale materials, many scientists have synthesized -Fe2O3 nanostructured materials in various geometrical morphologies such as nanotubes [8], nanoparticles [11], nanowires and nanobelts [12], nanorods [1, 10, 13], nanocubes, sea urchin-like [14], nanoplates [15], etc. The results indicated that the sensor response of the α-Fe2O3 film reached highest sensitivity to ethanol vapor and LPG at operating temperature of 275 C and 350 C, respectively

EXPERIMENTAL

RESULTS AND DISCUSSION

CONCLUSION