Intelligent Mixed Trace Gas Recognition Driven by Frequency-Dependent Infrared QDs Laser Phototransistor

The utilization of quantum dots (QDs) in the construction of phototransistors presents a highly promising avenue for the development of responsive sensors, which are compatible with a wide range of gas-sensing systems. However, it is worth noting that the currently prevalent QD-based phototransistors suffer from certain limitations, such as extended recovery time, elevated dark current, and reduced sensing area. These drawbacks significantly impede their effectiveness in the dynamic laser-sensing domain. In this study, we present a novel positive-intrinsic-negative (p-i-n) phototransistor based on infrared (IR) PbSe QDs, which incorporates a laser-sensing enhanced structure. This innovative design yields a phototransistor with an exceptional dynamic detectivity of
$2 \times 10^{{12}}$
Jones and an impressive bandwidth of
$2 \times 10^{{5}}$
Hz. By skillfully modulating the driving frequency within the range of 1–8 kHz, we are able to acquire the frequency-domain
$2{f}$
-harmonic signal associated with various trace gases. This advancement enables the phototransistor to discern the presence of different trace gases, including CH4, CO2, NH3,
$\text{O}_{{2}}$
, and
$\text{H}_{{2}}$
with a remarkable noise equivalent lowest detection limit (LOD) of approximately 10 parts per billion (ppb). The successful demonstration of frequency-dependent multicomponent trace-gas recognition highlights the tremendous potential of the high-detectivity QDs’ phototransistor in the field of multiwavelength laser spectrometry.