Chemiresistive room temperature H2S sensor based on CunO nanoflowers fabricated by laser ablation

Abstract

Hierarchical Cu_nO nanoflowers were synthesized through the laser ablation of a CuO target in NaOH solutions for room-temperature (27 ℃) H₂S detection. Notably, the pH value of NaOH solutions influenced both the micro-morphologies and compositions of the Cu_nO products, as evidenced by XRD, XPS, SEM and TEM. In high pH solutions, the specific surface area of the Cu_nO products increased, their thickness decreased, and the Cu₂O content diminished, resulting in enhanced sensitivity, selectivity and stability of the Cu_nO products’ response to H₂S. Notably, the pH14^# sample synthesized using an NaOH solution with a pH value of 14 featured pure CuO nanoflowers comprising slightly curled nanosheets with a thickness of approximately 10 nm. This sensor demonstrated excellent H₂S sensing performance at room temperature, exhibiting a response value of 1.17 for 10 ppb H₂S, along with high selectivity and good long-term stability. However, after exposure to H₂S, the resistance of the sensor did not recover to its baseline in air at room temperature. Thermogravimetry results revealed that a temperature of 300 °C was effective for recovery of sensor. Consequently, the operation temperature of the pH14^# sensor was controlled using a micro-hotplate. In the pulse heating mode, the sensor’s response to 100 ppb H₂S was 1.5, with a response time of 135 s and a recovery time of 137 s.