# Trace level detection of NH3 at room temperature using Cd-ZnFe2O4 thin films

## TL;DR

Researchers developed a low-cost, efficient ammonia sensor using a Cd-doped ZnFe2O4 thin film that works at room temperature and detects trace ammonia levels.

## Contribution

Cd-doped ZnFe2O4 thin films show enhanced room-temperature ammonia sensing performance compared to undoped films.

## Key findings

- Cd0.5Zn0.5Fe2O4 film achieved a sensor response of ∼8 at 1 ppm NH3 with fast response and recovery times.
- The film exhibited high sensitivity (10.07 ppm-1), repeatability, and stability over 6 weeks.
- Cd doping increased defect density and adsorption-desorption efficiency, improving sensor performance tenfold.

## Abstract

This study focuses on developing economical and efficient ammonia (NH3) gas sensors capable of detecting low concentrations at room temperature. Cd-doped ZnFe2O4 (CdxZn1-xFe2O4, x = 0, 0.1,0.3, and 0.5) thin films were deposited via spray pyrolysis, showing significantly enhanced sensing performance compared to undoped ZnFe2O4. The Cd0.5Zn0.5Fe2O4 (ZFCD5) film demonstrated the best response (∼8) at 1 ppm NH3, with fast response (105 s) and recovery (54 s) times, a sensitivity of 10.07 ppm-1, repeatability, selectivity, and more stability over 6 weeks. The improved sensing is attributed to the angular-rod-like morphology that increases active sites and enhances charge transfer. Cd incorporation effectively boosts defect density and adsorption-desorption efficiency, resulting in a 10-fold higher response than the undoped film (∼0.8). The findings highlight the potential of Cd-doped ZnFe2O4 thin films as promising, room temperature NH3 sensors for industrial, environmental, and safety applications, also supporting safer environments for individuals with disabilities.

•Cd-ZnFe2O4 film prepared via the spray pyrolysis method•ZFCD5 film sensor response of ∼8 at low concentration 1 ppm NH3•Proposed ZFCD5 film moderate response (105 s) and faster recovery (54 s) times•ZFCD5 film exhibits good sensitivity (10.07 ppm-1), repeatability, and stability

Cd-ZnFe2O4 film prepared via the spray pyrolysis method

ZFCD5 film sensor response of ∼8 at low concentration 1 ppm NH3

Proposed ZFCD5 film moderate response (105 s) and faster recovery (54 s) times

ZFCD5 film exhibits good sensitivity (10.07 ppm-1), repeatability, and stability

Materials science; Materials processing; Materials application