Semiconductor resistance gas sensors have been widely studied and applied in the detection of harmful gases due to their mature technology, low cost, high response value, and rapid response/recovery, etc. Sensing materials are the core components of semiconductor resistance gas sensors. Although traditional metal oxide sensing materials have been widely used, they generally suffer from problems such as high operating temperature, high power consumption, and limited selectivity. Therefore, conductive polymers have become a research focus for the new generation of gas sensing materials due to their unique π-conjugated electronic structure, tunable molecular design, room temperature operation, and excellent processing flexibility. In this paper, we systematically review the research progress of conductive polymers such as polyaniline (PANI), polypyrrole (PPy), and poly (3,4-ethylenedioxythiophene): poly (styrene sulfonic acid) (PEDOT:PSS) in harmful gas detection in recent years. It focuses on analyzing the intrinsic properties of these materials and explores the mechanism and implementation methods of enhancing their sensitivity, selectivity, and stability towards typical environmental harmful gases through composite construction strategies. Meanwhile, the application progress of conductive polymers-based gas sensors for food safety, medical diagnosis, and environmental monitoring is highlighted. Finally, the development trends and challenges towards intelligent, and integrated gas sensing technology are prospected.

Understanding the effect of additive on the interfacial charge-carrier transfer dynamics is very crucial to obtaining highly efficient perovskite solar cells (PSCs). Herein, we designed a simple additive, dimethyl oxalate (DO), functioning as an effective defect passivator of perovskite grain boundaries via the coordination interaction between the carbonyl (C=O) and the exposed Pb²⁺. The modification with DO produces pinhole-free and compact perovskite films, enhancing the transportation capability of carriers. As a consequence, the DO-treated PSCs exhibited a power conversion efficiency (PCE) of 22.19%, which is significantly higher than that of the control device without additive (19.58%). More importantly, detailed transient absorption characterization reveals that the use of additive can decrease the hot-carrier cooling dynamics, improve the carrier transfer, and eliminate nonradiative recombination in PSCs. This present work provides a profound understanding the additives effect on the carrier dynamics in PSCs toward the Shockley−Queisser limit.

Hazardous gases have been strongly associated with being a detriment to human life within the environment. The development of a reliable gas sensor with high response and selectivity is of great significance for detecting different hazardous gases. TiO₂ nanomaterials are promising candidates with great potential and excellent performance in gas sensor applications, such as hydrogen, acetone, ammonia, and ethanol detection. This review begins with a detailed discussion of the different dimensional morphologies of TiO₂, which affect the gas sensing performance of TiO₂ sensors. The diverse morphologies of TiO₂ can easily be tuned by regulating the manufacturing conditions. Meanwhile, they exhibit unique characteristics for detecting gases, including large specific surface area, superior electron transport rates, extraordinary permeability, and active reaction sites, which offer new opportunities to improve the gas sensing properties. In addition, a variety of efforts have been made to functional TiO₂ nanomaterials to further enhance sensing properties, including TiO₂-based composites and light-assisted gas sensors. The enhanced gas sensing mechanisms of multi-component composite nanomaterials based on TiO₂ include loaded noble metals, doped elements, constructed heterojunctions, and compounded with other functional materials. Finally, several studies have been summarized to demonstrate the comparative sensing properties of TiO₂-based gas sensors.

SnO₂ has been extensively used in the detection of various gases. As a gas sensing material, SnO₂ has excellent physical-chemical properties, high reliability, and short adsorption-desorption time. The application of the traditional SnO₂ gas sensor is limited due to its higher work-temperature, low gas response, and poor selectivity. Nanomaterials can significantly impact gas-sensitive properties due to the quantum size, surface, and small size effects of nanomaterials. By applying nanotechnology to the preparation of SnO₂, the SnO₂ nanomaterial-based sensors could show better performance, which greatly expands the application of SnO₂ gas sensors. In this review, the preparation method of the SnO₂ nanostructure, the types of gas detected, and the improvements of SnO₂ gas-sensing performances via elemental modification are introduced as well as the future development of SnO₂ is discussed.