Ultra-Highly Sensitive Ammonia Detection Based on Light-Induced Thermoelastic Spectroscopy.

Yao Mi,Yufei Ma

doi:10.3390/s21134548

Abstract

This invited paper demonstrated an ultra-highly sensitive ammonia (NH3) sensor based on the light-induced thermoelastic spectroscopy (LITES) technique for the first time. A quartz tuning fork (QTF) with a resonance frequency of 32.768 kHz was employed as a detector. A fiber-coupled, continuous wave (CW), distributed feedback (DFB) diode laser emitting at 1530.33 nm was chosen as the excitation source. Wavelength modulation spectroscopy (WMS) and second-harmonic (2f) detection techniques were applied to reduce the background noise. In a one scan period, a 2f signal of the two absorption lines located at 6534.6 cm−1 and 6533.4 cm−1 were acquired simultaneously. The 2f signal amplitude at the two absorption lines was proved to be proportional to the concentration, respectively, by changing the concentration of NH3 in the analyte. The calculated R-square values of the linear fit are equal to ~0.99. The wavelength modulation depth was optimized to be 13.38 mA, and a minimum detection limit (MDL) of ~5.85 ppm was achieved for the reported NH3 sensor.

Highlights

Ammonia (NH3 ), a component gas of the atmosphere, has been widely used in various important fields, such as medicine production, chemical industries, and so on [1]
An ultra-highly sensitive NH3 sensor based on the light-induced thermoelastic spectroscopy (LITES)
A fiber-coupled, near-infrared, continuous wave (CW), distributed feedback (DFB) diode laser emitting at 1530.33 nm was chosen to be the excitation source

Summary

Introduction

Ammonia (NH3 ), a component gas of the atmosphere, has been widely used in various important fields, such as medicine production, chemical industries, and so on [1]. When it comes to a medical diagnostic, NH3 can be used as a biomarker to indicate kidney and liver diseases [2,3]. If people inhale too much, it can cause lung swelling and even death [4]. NH3 is the main cause of air pollution. Carrying out ammonia detection is necessary for both industrial production and the environment. NH3 sensors should be ultra-highly sensitive to satisfy these applications

Methods

Results

Conclusion