Key Takeaways & Executive Findings
- •• Heteroatom atomically doping strategy constructs highly efficient Sn–O–Fe sites on porous Fe2O3 for ultrasensitive NO2 detection. • Atomically dispersed Sn atoms occupy Fe sites in Fe2O3 lattice, creating unique Sn–O–Fe active sites with abundant oxygen vacancies. • Optimized Sn-Fe2O3 sensor exhibits ultra-high sensitivity (Rg/Ra = 2646.6 to 1 ppm NO2), ultra-low detection limit (10 ppb), and high selectivity. • Theoretical calculations reveal strong NO2 adsorption on Sn–O–Fe sites and reduced bandgap, enabling low-temperature operation at 150 °C.
Abstract
Conventional gas sensing materials (e.g., metal oxides) suffer from deficient sensitivity and serve cross-sensitivity issues due to the lack of efficient adsorption sites. Herein, the heteroatom atomically doping strategy is demonstrated to significantly enhance the sensing performance of metal oxides-based gas sensing materials. Specifically, the Sn atoms were incorporated into porous Fe2O3 in the form of atomically dispersed sites. As revealed by X-ray absorption spectroscopy and atomic-resolution scanning transmission electron microscopy, these Sn atoms successfully occupy the Fe sites in the Fe2O3 lattice, forming the unique Sn–O–Fe sites. Compared to Fe–O–Fe sites (from bare Fe2O3) and Sn–O–Sn sites (from SnO2/Fe2O3 with high Sn loading), the Sn–O–Fe sites on porous Fe2O3 exhibit a superior sensitivity (Rg/Ra = 2646.6) to 1 ppm NO2, along with dramatically increased selectivity and ultra-low limits of detection (10 ppb). Further theoretical calculations suggest that the strong adsorption of NO2 on Sn–O–Fe sites (N atom on Sn site, O atom on Fe site) contributes a more efficient gas response, compared to NO2 on Fe–O–Fe sites and other gases on Sn–O–Fe sites. Moreover, the incorporated Sn atoms reduce the bandgap of Fe2O3, not only facilitating the electron release but also increasing the NO2 adsorption at a low working temperature (150 °C). This work introduces an effective strategy to construct effective adsorption sites that show a unique response to specific gas molecules, potentially promoting the rational design of atomically modified gas sensing materials with high sensitivity and high selectivity.
1. Introduction
In contemporary industrial production and residential life, the timely monitoring of particular gases is of paramount importance [1–6]. As one of the most hazardous gases, nitrogen dioxide (NO2) could cause serious respiratory diseases even in a trace amount [7, 8]. The World Health Organization recommends that NO2 concentration in the environment should not exceed 82 ppb, highlighting the importance of monitoring low-concentration NO2 [9]. Generally, metal oxide semiconductors (MOS) have been widely used as gas sensing material owing to their comprehensive features, such as semiconducting character, nontoxicity, abundance, and chemical stability [10, 11]. However, most MOS-based gas sensors for NO2 detection have to operate at a high temperature (>200 °C) and exhibit limited response and selectivity [12]. The unsatisfactory performance is mainly due to the lack of effective adsorption sites on metal oxides, and the cross-sensitivity issues would become more severe for low-concentration gas detection. Therefore, constructing highly efficient adsorption sites on MOS is of great significance to realize the detection of low-concentration NO2.
Recently, single-atom catalysts (SACs) featuring maximum atomic efficiency have attracted extensive attention in (electro)catalysis fields, in which the atomically dispersed sites with specific active structures present unprecedented catalytic performance [13–17]. Compared to nanoparticles or nanoclusters, SAC can maximally expose the active centers to boost the reaction efficiency [18]. Considering that the gas sensing process resembles surface catalysis, the atomically dispersed sites from SACs are expected to offer excellent gas sensing performance. For example, Gu et al. prepared Pt SAC on WO3 using the template method, in which the atomically dispersed Pt with high activity showed exceptional response toward triethylamine [19]. Feng et al. designed the SnO2 nanospheres functionalized by Au SAC, resulting in a Listeria monocytogene sensor with high sensitivity and selectivity [20]. In addition, Wang et al. constructed Cu SAC as catalytic site
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Yihong Zhong, Guotao Yuan, Dequan Bao, Yi Tao, Zhenqiu Gao, Wei Zhao, Shuo Li, Yuting Yang, Pingping Zhang, Hao Zhang, Xuhui Sun (2025). Specific Sn–O–Fe Active Sites from Atomically Sn-Doping Porous Fe2O3 for Ultrasensitive NO2 Detection. Nano-Micro Letters. https://doi.org/10.1007/s40820-025-01770-9
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Frequently Asked Questions
What is the main innovation of this study?
The study introduces a heteroatom atomically doping strategy to construct specific Sn–O–Fe active sites on porous Fe2O3, significantly enhancing the sensitivity and selectivity for NO2 detection at low concentrations.
How does the Sn–O–Fe site improve NO2 sensing performance?
The Sn–O–Fe site provides strong adsorption for NO2 (N atom on Sn, O atom on Fe), leading to a high response (Rg/Ra = 2646.6 to 1 ppm NO2) and ultra-low detection limit (10 ppb), while also reducing the bandgap to facilitate electron transfer at lower operating temperatures.
What is the detection limit of the optimized Sn-Fe2O3 sensor?
The optimized Sn-Fe2O3 sensor achieves an ultra-low detection limit of 10 ppb for NO2, which is well below the WHO recommended exposure limit of 82 ppb.
At what temperature does the sensor operate?
The sensor operates at a relatively low working temperature of 150 °C, which is lower than conventional metal oxide sensors that typically require temperatures above 200 °C.
What are the potential applications of this gas sensor?
This sensor can be used for environmental monitoring, industrial safety, and indoor air quality control, particularly for detecting trace levels of NO2 in real-time.
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