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Article

Nanorods Assembled Hierarchical Bi2S3 for Highly Sensitive Detection of Trace NO2 at Room Temperature

by
Yongchao Yang
1,2,
Chengli Liu
2,
You Wang
1 and
Juanyuan Hao
1,*
1
School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
2
The 49th Research Institute of China Electronics Technology Group Corporation, Harbin 150028, China
*
Author to whom correspondence should be addressed.
Chemosensors 2024, 12(1), 8; https://doi.org/10.3390/chemosensors12010008
Submission received: 4 December 2023 / Revised: 31 December 2023 / Accepted: 3 January 2024 / Published: 4 January 2024
(This article belongs to the Special Issue Functional Nanomaterial-Based Gas Sensors)
Browse Figures
Versions Notes

Abstract

:
The bismuth sulfide nanostructure has become a promising gas sensing material thanks to its exceptional intrinsic properties. However, pristine Bi2S3 as a room-temperature sensing material cannot achieve the highly sensitive detection of ppb-level NO2 gas. Herein, 1D nanorods with self-assembled hierarchical Bi2S3 nanostructures were obtained via a simple hydrothermal process. The as-prepared hierarchical Bi2S3 nanostructures exhibited outstanding NO2 sensing behaviors, such as a high response value (Rg/Ra = 5.8) and a short response/recovery time (τ90 = 28/116 s) upon exposure to 1 ppm NO2. The limit of detection of hierarchical Bi2S3 was down to 50 ppb. Meanwhile, the sensor exhibited excellent selectivity and humidity tolerance. The improved NO2 sensing properties were associated with the self-assembled hierarchical nanostructures, which provided a rich sensing active surface and accelerated the diffusion and adsorption/desorption processes between NO2 molecules and Bi2S3 materials. Additionally, the sensing response of hierarchical Bi2S3 nanostructures is much higher at 100% N2 atmosphere, which is different from the chemisorption oxygen model.

1. Introduction

Nitrogen dioxide (NO2), as a typically hazardous gas released from the burning of fossil fuels, can trigger serious environmental and health problems [1,2]. As reported, continuous exposure to trace NO2 gas may cause respiratory diseases such as chronic bronchitis, asthma, and emphysema [3,4,5,6,7,8,9]. The U.S. Environmental Protection Agency sets 53 ppb NO2 as the ambient exposure concentration standard. Meanwhile, ppb-level NO2 gas detection can contribute to auxiliary diagnoses of humans’ physical health, such as lung disease and gastrointestinal disorder symptoms [10,11,12]. Chemiresistive gas sensors based on metal oxides have shown superb NO2 sensing properties, such as high sensitivity and a short response time [13]. However, such NO2 sensors generally need a high operating temperature to obtain high sensitivity, fast response/recovery speed, and a low limit of detection (LOD). The high working temperature brings about extra power consumption and triggers safety problems, which seriously restrict their potential application in medical treatment and environmental monitoring [14,15,16]. With the rapid development of the emerging 5G network and the Internet of Things, it is very important to research new room-temperature (RT) sensing materials for highly sensitive trace NO2 detection.
The layer metal chalcogenides as sensing nanomaterials were extensively researched in the gas sensor field for recognizing low-concentration NO2 molecules at RT due to their unique physicochemical properties. Among them, Bi2S3 nanostructured materials have a tunable bandgap of 1.3–1.7 eV [17,18,19,20] and high carrier mobility of about 103 cm2 V−1 s−1 [21,22], which can facilitate the electron transfer process between Bi2S3-based sensing materials and target gas molecules at RT. Bi2S3-based gas sensors have been used for various gas detections, such as H2 [23], NH3 [24], H2S [25], etc. In recent years, Bi2S3 nanostructures as RT NO2 sensing materials have gained widespread attention due to their excellent affinity for NO2 molecules [26]. For example, Liu et al. reported that synthesized Bi2S3 nanobelts showed superior RT NO2 sensing performance, such as a short response time and superb selectivity [21]. Yang et al. reported that the Au/Bi2S3 heterojunction nanosheets exhibited rapid sensing response and outstanding selectivity toward NO2 gas at RT, which was associated with the increasing active sites and accelerated electron transfer arising from sulfur vacancies [27]. Zhang et al. constructed a CuS/Bi2S3 nanosheet sensor, which exhibited excellent NO2 sensing response at RT due to a mass of sensing active sites and quantum size effect [28]. Unfortunately, Bi2S3-based gas sensors display some poor RT NO2 sensing properties, such as a long recovery time and a high LOD, which severely impede their spread and applications [21,29].
As we know, the morphology and structure characteristics of gas sensing materials play a key role in improving sensing behaviors because the sensing properties depend on the diffusion and adsorption/desorption processes between the sensing materials and the target gas. Low-dimension nanostructures (nanobelts, nanorods, and nanosheets) easily stack and aggregate together, which would reduce the active surface to adsorb gas molecules and obstruct gas diffusion and adsorption/desorption processes, weakening the sensing materials intrinsic sensing properties. Low-dimensional nanostructures can effectively avoid restacking together and obviously increase active surface via the constructed hierarchical nanostructures method, which can provide rich sensing active sites and promote detection of gas diffusion and adsorption/desorption on the surface of nanomaterials. For example, Liu et al. prepared hierarchical SnS2 nanoflowers, which showed excellent low NO2 LOD due to the mass of the available surface-active sites [30]. Wang et al. synthesized the nanoplate-assembled SnSe2 nanoflowers, which exhibited a highly sensitive response to ppb-level NO2 at RT [31]. Zhang et al. reported that hierarchical MoS2 nanospheres improved the sensing behaviors toward NO2 gas due to the open 3D nanostructure and abundant reaction active sites [32]. The hierarchical nanostructured Bi2S3 (flower-like, urchin-like, sheaf-like, etc.) have been successfully prepared through various means in order to elevate their functional properties [24,33,34,35,36]. For example, Fu prepared a 3D Bi2S3 nanowire network, which showed excellent sensing properties for NH3 at RT due to its large surface area [24]. Therefore, constructed hierarchical Bi2S3 nanomaterials are an effective approach to enhance their NO2-sensitive properties, which may provide a new route for optimizing nanostructures to enhance the sensing behaviors of low-dimensional nanomaterials.
Herein, 1D nanorods with self-assembled Bi2S3 hierarchical nanostructures were prepared using a facile hydrothermal procedure. As-prepared Bi2S3 nanomaterials showed hierarchical morphology, which was conducive to a mass of NO2 molecules rapidly diffused inward and adsorbed on the surface of the hierarchical Bi2S3 nanostructure materials to enhance their gas sensing performance. The NO2 sensors based on 1D nanorods and self-assembled Bi2S3 sensing materials showed high sensitivity, rapid response/recovery speed, and a low LOD for NO2 at RT. These findings demonstrated that the constructed hierarchical Bi2S3 nanostructures serve as promising candidates for hypersensitive NO2 detection devices.

2. Materials and Methods

2.1. Synthesis of Hierarchical Bi2S3 Nanomaterials

Hierarchical Bi2S3 nanostructures assembled from 1D nanorods were obtained via facile hydrothermal means inspired by the previous studies [37,38]. Typically, 303 mg of Bi(NO3)3·5H2O powder was dispersed in 30 mL of deionized water with vigorous mixing for 30 min, forming a milky suspension. Then, 476 mg of CH4N2S powder was added to the above suspension, followed by continuous mixing for 60 min to form a yellow reaction solution. The above mixture was sealed in a 50 mL hydrothermal reactor. Subsequently, the above solution was heated to 140 °C and kept for 12 h. After naturally cooling down to ambient temperature, the black powder was collected via centrifugation and washed with ethanol and deionized water 3 times. Finally, the obtained product was dried at 60 °C for 12 h.
To study the formation mechanism of the 1D nanorods self-assembled in Bi2S3 hierarchical structures, a series of samples were prepared by adjusting the hydrothermal reaction time from 0 h to 24 h. The corresponding samples were named BS-X, where X stands for the hydrothermal reaction time in an hour.

2.2. Material Characterizations

The crystal structure information of the as-prepared materials was acquired using a Bruker D8 Advance X-ray diffractometer (Bruker Technology Co., LTD, Saarbrucken, Germany). The scanning electron microscopy images of the as-prepared powder were acquired with a Zeiss Sigma 300 (Carl Zeiss AG, Oberkochen, Germany). The high-resolution transmission electron microscopy was carried out on a FEI Talos F200S (FEI Company, Hillsboro, OR, USA). The information on the surface chemical states of the obtained product was studied via X-ray photoelectron spectroscopy (Thermo Scientific K-Alpha spectrometer, Thermo Fisher Scientific, Waltham, MA, USA). The Brunauer–Emmett–Teller (BET)-specific surface area was measured with a Micromeritics ASAP 2460 apparatus (Micromeritics Instruments Corporation, Norcross, GA, USA).

2.3. Gas Sensing Measurements

First, the mixture containing the as-prepared Bi2S3 powder (10 mg) and ethanol (1 mL) was prepared. Then, the 20 μL above mixture was coated on an Al2O3 substrate with Ag-Pd interdigitated electrodes to form a sensing film. Finally, the thin-film gas sensor was dried in a vacuum chamber at 60 °C for 3 h. The detailed parameters of the sensing device are shown in Figure S1.
Gas sensing properties were obtained using a homemade gas sensor test system, as in our previous work [39]. The dynamic gas sensor test system was employed to investigate the sensing mechanism (Figure S2). As-prepared sensors based on different sensing materials were aged for 24 h under a 5 V voltage at RT before the sensing test. The relative humidity (RH) of the testing chamber was controlled with the humidity generator. The real-time resistance information of the sensors was recorded using the electrochemical workstation. The known concentration of detection gas rapidly flowed through the testing chamber. The sensing response value (S) was calculated using the equation: S = Ra/Rg (when Ra > Rg) and Rg/Ra (when Ra < Rg), where Rg and Ra were the RT resistance values recorded in detection gas and clean air, respectively. Herein, the response and recovery times (τ90) were defined as the time to reach 90% of the total resistance variation during gas-in and gas-out, respectively.

3. Results

3.1. Morphology and Structure

The hierarchical Bi2S3 nanostructures are obtained through a one-step hydrothermal process, and their structures are highly dependent on synthesized time (as shown in Figure 1a). The as-prepared hydrolysis product shows 1D rod-like structures, as shown in the SEM image (Figure 1b). According to the calculated method of standard deviation by measuring 20 rod-like structures, the diameter of rod-like structures is about 1.2 μm. Subsequently, many nanowire-assembled microsphere structures appear after a hydrothermal reaction for 1 h (Figure 1c). With increasing hydrothermal reaction for 12 h, the as-prepared sample shows 1D nanorods of self-assembled hierarchical Bi2S3 structures with a diameter of about 4.0 μm (Figure 1d). The length of self-assembled nanorods is approximately 2.0 μm, with a diameter of about 150 nm. The TEM and HRTEM images further show the hierarchical nanostructures of the synthesized Bi2S3 sample (Figure 1e,f). These hierarchical Bi2S3 nanostructures can efficaciously prevent the 1D nanorods from restacking together, which may dramatically add exposure sensing sites and facilitate the diffusion and adsorption/desorption processes of gas molecules. The 1D nanorods assembled into hierarchical nanostructures would show superior sensing behaviors than those of only 1D nanorods [40,41]. The EDS mapping confirms the uniform distribution of Bi and S elementals along the full hierarchical Bi2S3 (Figure S3). The EDS spectrum of the as-prepared Bi2S3 sample further demonstrates the sample consists of Bi and S without other elementals, and the atomic ratio of Bi to S of the sample almost meets the stoichiometry ratio.
In order to obtain the formation mechanism of the hierarchical Bi2S3 nanostructures, serious samples with different reaction times were prepared and analyzed, combined with XRD patterns and SEM images. Firstly, Bi(NO3)3·5H2O powder was dispersed in deionized water and generated hydrolysis, which resulted in the formation of a milky solution. The obtained white hydrolysate shows 1D nanorod structures (Figure 1b). As shown in Figure 2a, the appearing XRD spectrum peaks of the hydrolysis product conform to the bismuth oxide hydroxide nitrate hydrate (JCPDF no. 70-1226). Subsequently, with CH4N2S added to the homogeneous solution, the color of the above solution became yellow due to [Bi(CH4N2S)n]3+ chelates from the strong reaction between Bi3+ and CH4N2S [34,42]. Secondly, the CH4N2S of the reaction mixture could decompose to generate H2S under 140 °C, which would react with the Bi3+ to form Bi2S3 nanocrystals. At the early stage of the hydrothermal reaction for 1 h, the Bi2S3 nanostructures were confirmed with the XRD pattern. With increasing the reaction time from 2 h to 8 h, the microspheres gradually transfer to 1D nanorods assembled into hierarchical nanostructures (Figure S4a–d) [43]. The microsphere structures of the BS-12h sample almost disappear, and the assembled 1D nanorods of hierarchical nanostructures become sturdy and short, with the reaction process lasting 24 h (Figure S4e–f). The diffraction peaks of as-prepared Bi2S3 samples at 2θ = 15.8°, 17.6°, 22.4°, 24.9°, 28.6°, 31.8°, 39.0°, 46.5°, and 52.6° match well with (020), (120), (220), (130), (211), (221), (041), (431), and (351) planes of orthorhombic Bi2S3 (JCPDF no. 17-0320). The intensity of diffraction peaks in the prepared sample shows inconspicuous variation after hydrothermal reaction time over 4 h. The sharp diffraction peaks without any other impurity phase confirm the high purity of the prepared Bi2S3.
The information on the surface chemical states of the as-prepared hierarchical Bi2S3 sample was obtained via XPS. The XPS survey spectrum of the BS-12h sample is shown in Figure 2b. The highly pure Bi2S3 is further confirmed. The high-resolution XPS spectra of the Bi 4f and the S 2p are shown in Figure 2c. The Bi 4f core level spectrum of the hierarchical Bi2S3 shows the Bi 4f7/2 and Bi 4f5/2 strong peaks at 158.6 and 163.9 eV, respectively [44,45]. The peaks located at 161.3 and 162.5 eV can be assigned to S 2p3/2 and S 2p1/2, respectively, confirming the existence of S2− [44,45]. All the above results demonstrate that the hierarchical Bi2S3 was prepared successfully.

3.2. Characterization of Gas Sensing Performance

In order to demonstrate the internal linkage between morphologies and structures with sensing characteristics, the RT sensing properties of the as-prepared BS-8h, BS-12h, and BS-24h samples were measured using a dynamic gas sensor analysis system. The RT dynamic sensing response curves of the above sensors (BS-8h, BS-12h, and BS-24h) for low concentration NO2 ranging from 0.1 to 1.0 ppm are shown in Figure 3a. All sensors show typical n-type semiconductor sensing behaviors, and the sensing response resistance gradually increases with increasing exposure to NO2 concentration. Figure 3b displays the linear relationship of all prepared sensors between sensitivity and NO2 concentration. The BS-12h sensor shows high sensitivity and a good linear relationship to trace NO2 gas at RT. The RT response/recovery curves of the BS-8h, BS-12h, and BS-24h sensors upon exposure to 1 ppm NO2 are shown in Figure S5. The sensors based on the hierarchical Bi2S3 display superb response/recovery properties. The response and recovery time of the sensor based on the BS-12h sample toward 1 ppm NO2 were 28 and 116 s, respectively. These results show that the 1D nanorod self-assembled Bi2S3 structures have superior RT NO2 sensing responses, which could be ascribed to the special hierarchical nanostructures. According to the test results, the BS-12h sample was chosen as a promising sensing material for sensors after deeply appraising its NO2 sensing properties.
The RT dynamic response curve of the BS-12h sensor with varied NO2 concentrations is shown in Figure 4a. The recorded real-time response resistance value exhibits an increasing trend when the concentration of NO2 increases from 50 ppb to 10 ppm. The main reason may be associated with more NO2 molecules trapped on the surface of hierarchical nanomaterials and obtaining more electrons from the surface of the Bi2S3 nanostructure. Meanwhile, the BS-12h sensor displays fast response speed and full-recovery sensing properties, which could be ascribed to the hierarchical nanostructures of the Bi2S3 materials. These results confirm the BS-12h sensor can effectively realize low-concentration NO2 detection from 50 ppb to 10 ppm at RT. The sensor based on hierarchical Bi2S3 nanostructures displays two sectional linear relations between sensitivity and NO2 concentration from 0.05 to 2 ppm and 2 to 10 ppm (Figure 4b). These phenomena were associated with decreasing carrier mobility due to the scattering effects of adsorbed gas molecules on the surface of sensing materials [46,47].
The humidity tolerance ability of the BS-12h sensor was investigated considering the practical application of the gas sensor. The response resistance curves of the Bi2S3-based sensors to 1 ppm NO2 under different relative humidity levels from 15% to 85% are shown in Figure 4c. The sensor based on hierarchical Bi2S3 nanostructures displays excellent response/recovery properties under different relative humidity conditions. The RT resistance value of the BS-12h sensor sustainably declines as the relative humidity gradually increases (Figure 4d), which may be attributed to the increased electron density of Bi2S3 sensing materials. As ambient relative humidity increases, abundant H2O molecules adsorbed on the surface of the Bi2S3 nanostructures act as electron donors [48,49,50]. The electrons will transfer from H2O molecules to the surface of Bi2S3 nanostructures, which leads to increased conductivity in the Bi2S3 sensor. The sensitivity of the BS-12h sensor exhibits a downward trend from 5.8 to 4.1 as ambient humidity increases from 15% RH to 85% RH. The calculated sensitivity deviation of the BS-12h sensor is less than 30%, which could be ascribed to the surface-adsorbed H2O molecules occupying NO2 sensing sites, which will decrease the adsorbed amount of NO2 gas molecules [31]. The relatively small attenuation of the sensing response under a high concentration of H2O molecules in the environment proves that the hierarchical Bi2S3 nanostructures have good anti-humidity performance, which could be associated with the improved adsorption of NO2 molecules with the incorporation of H2O molecules in Bi2S3 [26]. Combined RT resistance variation with sensitivity deviation, the hierarchical Bi2S3 sensor could be used to obtain NO2 concentration information under different humidity atmospheres using the humidity compensation method.
The selectivity of the sensor based on the BS-12h sample was investigated to further recognize the specific interaction between hierarchical Bi2S3 nanostructures and NO2 molecules. Figure 5a shows the sensing response of several kinds of interfered gases, including the main hazardous gases (H2S, CO, SO2, and NH3) and green energy gas (H2) existing in the atmosphere. The sensitivity of the BS-12h sensor at RT to 100 ppm H2S, CO, SO2, NH3, and H2 gas is 1.64, 1.07, 1.02, 1.07, and 1.07, respectively. Compared with the sensitivity of 5.8 to 1 ppm NO2, these results confirm the optimal RT NO2 detection performance of Bi2S3 sensing materials. The intrinsic mechanism of the selectivity of pristine Bi2S3 to NO2 has been investigated using first-principle calculations [26]. The calculated adsorption energy between Bi2S3 nanomaterials and NO2 molecules is much larger than that of the other interfered gases, which results in the excellent detection ability of NO2 gas. Meanwhile, the newly formed O-S chemical bonds between NO2 molecules and Bi2S3 further enhance the selectivity.
Repeatability and long-term stability are also key properties of gas sensors. The five consecutive cyclic response/recovery curves of the BS-12h sensor are shown in Figure 5b. Obviously, the fluctuation of the sensing response resistance of the BS-12h sensor is negligible, indicating the optimal NO2 sensing repeatability of the hierarchical Bi2S3 nanomaterials. The long-term stability of the sensor based on the BS-12h sample was also acquired by measuring the sensing behaviors toward 1 ppm NO2 at RT after aging for 60 days (Figure 5c). The sensing response values are in the range of (5.6 ± 0.3) during 60 days of aging, which shows the hierarchical Bi2S3 sensors can acquire stable NO2 concentration data. The insert of Figure 5c shows the dynamic response data of the sensor based on the BS-12h sample to 1 ppm NO2 at RT after aging for 30 and 60 days. The BS-12h sensor, after different aging times, displays fast response speed and full-recovery sensing properties at RT. In comparison to the dynamic resistance curve of the BS-12h sensor after aging for 60 days (Figure S6), the response/recovery time and RT resistance value display a negligible deviation. These results demonstrate its superior stability.
The NO2 sensing properties of typical metal sulfide-based gas sensors in the literature and our prepared 1D nanorods with self-assembled Bi2S3 hierarchical structures are summarized in Table 1. The Bi2S3 nanostructures display obviously competitive NO2 sensing properties, such as high sensitivity, fast response, recovery speed, and low LOD at RT. Combined with the simple prepared means, the synthesized hierarchical Bi2S3 nanostructures as NO2 sensing materials are suitable for practical production.

3.3. Gas Sensing Mechanism

The sensing mechanism of metal sulfide nanomaterials relies on the electron-migration case between the surface of nanostructures and adsorbed target gas molecules [58,59,60]. The Bi2S3 nanomaterials as n-type semiconductors exhibit increased resistance during the electrophilic NO2 sensing process. In order to confirm the role of O2 molecules during the NO2 sensing process of Bi2S3 nanostructures, a dynamic gas dilution system was adopted to control the O2 concentration during the NO2 sensing test process. The dynamic NO2 sensing curve with different O2 concentrations and N2 as a balance gas is shown in Figure 6. The BS-12h sensor based on hierarchical Bi2S3 nanostructures shows an optimum dynamic response/recovery process to 1 ppm NO2 in different O2 concentrations. The sensitivity of the BS-12h sensor displays a decline trend, which could be associated with more O2 molecules trapped on the surface of Bi2S3 nanostructures with the increasing O2 concentration [30]. The RT resistances of the prepared Bi2S3 nanostructures under different O2 concentrations (N2 as a balance gas) are shown in Figure S7. The resistance value of Bi2S3 nanostructures in a 100% N2 atmosphere is the smallest and exhibits a gradually increasing trend with increasing O2 concentration. The phenomenon confirms that O2 molecules can be trapped on the surface of Bi2S3 nanostructures and capture electrons from their conduction band to form O2−. Upon exposure to NO2, these NO2 molecules competitively adsorb on the sensing active sites and trap the electron to form NO2−. The little fluctuation in the sensing response of the Bi2S3 nanostructures can be associated with the much bigger adsorption energy of NO2 molecules than that of O2 molecules [26]. The result confirms that ambient O2 molecules are not directly involved in NO2 sensitive processes in Bi2S3 nanomaterials. The electron transfer process between the NO2 molecules and Bi2S3 nanostructures could be depicted using the following equation:
NO2 (gas) + e− → NO2− (ads)
The schematic diagram of the NO2 sensing mechanism of hierarchical Bi2S3 nanostructures is shown in Figure 7. The NO2 molecules adsorb on the surface of the Bi2S3 nanostructure and trap electrons, which leads to decreased electron density in Bi2S3 and the formation of an electron depletion layer. The formed electron depletion layer on the surface of the sensing materials will cause the resistance of the Bi2S3 nanomaterials to increase. When the Bi2S3 nanostructure is re-exposed to air, NO2 molecules gradually finish the desorption process and release the electron to the surface of Bi2S3, which results in the resistance value of the sensor recovering up to its baseline resistance.
The enhanced RT NO2 sensing properties of as-prepared hierarchical Bi2S3 nanostructures assembled from 1D nanorods can be illustrated by the following factors. Firstly, the 1D nanorods self-assembled Bi2S3 nanostructure can adequately prevent the 1D nanorods from restacking together, which will markedly increase the exposure-sensing active surface of Bi2S3 materials for NO2 adsorption. The N2 adsorption/desorption cycles of as-prepared hierarchical Bi2S3 nanostructures (BS-8h, BS-12h, and BS-24h samples) were used to calculate the BET surface areas (Figure S8). The specific surface area of the above three samples is 3.6, 4.2, and 4.0 m2 g−1, respectively. The BS-12h sample shows a much larger active surface than that of other samples. According to the process of growth of the hierarchical Bi2S3 nanostructures, the BS-12h sample displays more 1D nanorod-assembled Bi2S3 hierarchical nanostructures than the BS-8h sample (Figure S4), which leads to much larger specific surface areas than that of the BS-8h sample. With increasing the reaction time for 24 h, the nanorods of assembled hierarchical Bi2S3 structures become short and thick due to their continuous growth, which decreases the exposed active surface of the as-prepared BS-24h sample. The BS-12h sensor shows superior RT NO2 sensing properties than that of the other sample, in accordance with the specific surface area test value. The large specific surface areas of the BS-12h sensor will provide a mound of NO2 sensing active sites, which enhance the NO2 sensing response due to massive NO2 molecules adsorbing on the surface of hierarchical Bi2S3 nanostructures and accelerating the electron transfer from the surface of Bi2S3 materials to NO2 molecules. In addition, the 1D nanorod-assembled Bi2S3 as NO2 sensing materials exhibit fast response and recovery speed and full-recovery properties, which could be associated with a special hierarchical nanostructure and intrinsic physicochemical characteristics. As the mechanism diagram shows in Figure 7, these adjacent 1D nanorods form a mass of open voids, which, as inner flow passages, will dramatically accelerate the diffusion and adsorption/desorption processes between NO2 molecules and hierarchical Bi2S3 nanostructures. When NO2 molecules adsorb on the 1D nanorods assembled in Bi2S3 hierarchically, the NO2 molecules rapidly diffuse inward through the inner spread path. On the contrary, upon re-exposure to air, the adsorbed NO2 molecules rapidly and fully desorb from the surface of hierarchical Bi2S3 nanostructures and diffuse into the air. Therefore, the sensor based on the 1D nanorods assembled in Bi2S3 hierarchical structures shows short response/recovery times and full recovery performance. Additionally, the Bi2S3 materials have high carrier mobility and a narrow bandgap [17,18,19,20,21,22]. These superb physical properties endow Bi2S3 with fast electron transfer speed, which will further shorten the response/recovery time. Above all, the special hierarchical nanostructures and unique intrinsic properties of Bi2S3 are advantageous in obtaining high sensitivity and a short response/recovery time at RT.

4. Conclusions

In conclusion, 1D nanorods with a self-assembled Bi2S3 hierarchical nanostructure were successfully prepared via a simple hydrothermal process and showed improved RT NO2 sensing properties. The hierarchical Bi2S3-based gas sensor showed a high sensitivity (Rg/Ra = 5.8 at 1 ppm), a low LOD (50 ppb), optimum selectivity, and anti-humidity. The outstanding RT sensing properties were associated with the special hierarchical nanostructures and unique intrinsic properties of Bi2S3 materials, which accelerate diffusion, adsorption/desorption, and electron transfer processes between NO2 molecules and hierarchical Bi2S3 nanostructures. Additionally, hierarchical Bi2S3 exhibited almost the same sensing response in the absence of O2 gas. The phenomenon confirms that the sensing mechanism of Bi2S3 is different from the chemisorption oxygen model. This study focuses on the fundamental sensing mechanism of the hierarchical Bi2S3 and provides a kind of novel nanostructure material for low-concentration NO2 detection at RT.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/chemosensors12010008/s1, Figure S1: Schematic diagram of the interdigital electrodes, sensors based on different sensing materials, and fixture of sensors; Figure S2: Schematic diagram of the gas sensor dynamic analysis system; Figure S3: The elemental mapping of the BS-12h sample; Figure S4: SEM images of as-prepared samples with different reaction times; Figure S5: RT dynamic response/recovery curves of BS-8h, BS-12h, and BS-24h sensors toward 1 ppm NO2; Figure S6: The dynamic resistance curve of the BS-12h sensor after aging 60 days toward 1.0 ppm NO2; Figure S7: The RT resistance of the BS-12h sensor with different O2 concentration atmosphere; and Figure S8: Nitrogen adsorption/desorption isotherms of as-prepared samples with different reaction times.

Author Contributions

Conceptualization, methodology, validation, formal analysis, investigation, data curation, and writing—original draft, Y.Y.; methodology, investigation, formal analysis, and data curation, C.L.; methodology, writing—review and editing, supervision, and funding acquisition, Y.W.; writing—review and editing, supervision, project administration, and funding acquisition, J.H. All authors have read and agreed to the published version of the manuscript.

Funding

This work was financially supported by the National Natural Science Foundation of China (No. 52272147 and 52272272), the Heilongjiang Touyan Team (HITTY-20190034), and the Fundamental Research Funds for the Central Universities (No. 2022FRFK02015).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data are contained within the article and Supplementary Materials.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Ou, J.Z.; Yao, C.K.; Rotbart, A.; Muir, J.G.; Gibson, P.R.; Kalantar-zadeh, K. Human intestinal gas measurement systems: In vitro fermentation and gas capsules. Trends Biotechnol. 2015, 33, 208–213. [Google Scholar] [CrossRef] [PubMed]
  2. Wong, G.W.K.; Lai, C.K.W. Outdoor air pollution and asthma. Curr. Opin. Pulm. Med. 2004, 10, 62–66. [Google Scholar] [CrossRef] [PubMed]
  3. Vassilyadi, M.; Michel, R. Effect of methylprednisolone on nitrogen dioxide (NO2)-induced pulmonary edema in guinea pigs. Toxicol. Appl. Pharmacol. 1989, 97, 256–266. [Google Scholar] [CrossRef] [PubMed]
  4. Long, H.; Harley-Trochimczyk, A.; Pham, T.; Tang, Z.; Shi, T.; Zettl, A.; Carraro, C.; Worsley, M.A.; Maboudian, R. High surface area MoS2/graphene hybrid aerogel for ultrasensitive NO2 detection. Adv. Funct. Mater. 2016, 26, 5158–5165. [Google Scholar] [CrossRef]
  5. Liu, B.; Chen, L.; Liu, G.; Abbas, A.N.; Fathi, M.; Zhou, C. High-performance chemical sensing using schottky-contacted chemical vapor deposition grown monolayer MoS2 transistors. ACS Nano 2014, 8, 5304–5314. [Google Scholar] [CrossRef] [PubMed]
  6. Kawamoto, T.; Matsuno, K.; Arashidani, K.; Yoshikawa, M.; Kodama, Y. Personal exposure to nitrogen dioxide from indoor heaters and cooking stoves. Arch. Environ. Contam. Toxicol. 1993, 25, 534–538. [Google Scholar] [CrossRef]
  7. Ikram, M.; Liu, L.; Lv, H.; Liu, Y.; Ur Rehman, A.; Kan, K.; Zhang, W.; He, L.; Wang, Y.; Wang, R.; et al. Intercalation of Bi2O3/Bi2S3 nanoparticles into highly expanded MoS2 nanosheets for greatly enhanced gas sensing performance at room temperature. J. Hazard. Mater. 2019, 363, 335–345. [Google Scholar] [CrossRef] [PubMed]
  8. Scott Downen, R.; Dong, Q.; Chorvinsky, E.; Li, B.; Tran, N.; Jackson, J.H.; Pillai, D.K.; Zaghloul, M.; Li, Z. Personal NO2 sensor demonstrates feasibility of in-home exposure measurements for pediatric asthma research and management. J. Expo. Sci. Environ. Epidemiol. 2022, 32, 312–319. [Google Scholar] [CrossRef]
  9. Du, Y.; Yu, D.-G.; Yi, T. Electrospun nanofibers as chemosensors for detecting environmental pollutants: A review. Chemosensors 2023, 11, 208. [Google Scholar] [CrossRef]
  10. Wu, J.; Wu, Z.; Ding, H.; Wei, Y.; Huang, W.; Yang, X.; Li, Z.; Qiu, L.; Wang, X. Flexible, 3D SnS2/reduced graphene oxide heterostructured NO2 sensor. Sens. Actuators B 2020, 305, 127445. [Google Scholar] [CrossRef]
  11. Huang, Y.; Jiao, W.; Chu, Z.; Ding, G.; Yan, M.; Zhong, X.; Wang, R. Ultrasensitive room temperature ppb-level NO2 gas sensors based on SnS2/rGO nanohybrids with p–n transition and optoelectronic visible light enhancement performance. J. Mater. Chem. C 2019, 7, 8616–8625. [Google Scholar] [CrossRef]
  12. Shafiei, M.; Bradford, J.; Khan, H.; Piloto, C.; Wlodarski, W.; Li, Y.; Motta, N. Low-operating temperature NO2 gas sensors based on hybrid two-dimensional SnS2-reduced graphene oxide. Appl. Surf. Sci. 2018, 462, 330–336. [Google Scholar] [CrossRef]
  13. Li, G.; Zhu, X.; Liu, J.; Li, S.; Liu, X. Metal oxide semiconductor gas sensors for lung cancer diagnosis. Chemosensors 2023, 11, 251. [Google Scholar] [CrossRef]
  14. Hu, Z.; Zhou, L.; Li, L.; Ying, B.; Zhao, Y.; Wang, P.; Li, H.; Zhang, Y.; Liu, H. Quantum dots-sensitized high electron mobility transistor (HEMT) for sensitive NO2 detection. Chemosensors 2023, 11, 252. [Google Scholar] [CrossRef]
  15. Tang, T.; Li, Z.; Cheng, Y.; Xu, K.; Xie, H.; Wang, X.; Hu, X.; Yu, H.; Zhang, B.; Tao, X.; et al. Single-step growth of p-type 1D Se/2D GeSexOy heterostructures for optoelectronic NO2 gas sensing at room temperature. J. Mater. Chem. A 2023, 11, 6361–6374. [Google Scholar] [CrossRef]
  16. Tang, T.; Li, Z.; Cheng, Y.; Xie, H.; Wang, X.; Chen, Y.; Cheng, L.; Liang, Y.; Hu, X.; Hung, C.; et al. In-situ mechanochemically tailorable 2D gallium oxyselenide for enhanced optoelectronic NO2 gas sensing at room temperature. J. Hazard. Mater. 2023, 451, 131184. [Google Scholar] [CrossRef]
  17. Ni, J.; Zhao, Y.; Liu, T.; Zheng, H.; Gao, L.; Yan, C.; Li, L. Strongly coupled Bi2S3@CNT hybrids for robust lithium storage. Adv. Energy Mater. 2014, 4, 1400798. [Google Scholar] [CrossRef]
  18. Dong, Y.; Hu, M.; Zhang, Z.; Zapien, J.A.; Wang, X.; Lee, J.-M. Hierarchical self-assembled Bi2S3 hollow nanotubes coated with sulfur-doped amorphous carbon as advanced anode materials for lithium ion batteries. Nanoscale 2018, 10, 13343–13350. [Google Scholar] [CrossRef]
  19. Bernechea, M.; Cao, Y.; Konstantatos, G. Size and bandgap tunability in Bi2S3 colloidal nanocrystals and its effect in solution processed solar cells. J. Mater. Chem. A 2015, 3, 20642–20648. [Google Scholar] [CrossRef]
  20. Guo, Y.; Ao, Y.; Wang, P.; Wang, C. Mediator-free direct dual-z-scheme Bi2S3/BiOV4/MgIn2S4 composite photocatalysts with enhanced visible-light-driven performance towards carbamazepine degradation. Appl. Catal. B 2019, 254, 479–490. [Google Scholar] [CrossRef]
  21. Kan, H.; Li, M.; Song, Z.; Liu, S.; Zhang, B.; Liu, J.; Li, M.-Y.; Zhang, G.; Jiang, S.; Liu, H. Highly sensitive response of solution-processed bismuth sulfide nanobelts for room-temperature nitrogen dioxide detection. J. Colloid Interface Sci. 2017, 506, 102–110. [Google Scholar] [CrossRef] [PubMed]
  22. Rath, A.K.; Bernechea, M.; Martinez, L.; Konstantatos, G. Solution-processed heterojunction solar cells based on p-type PbS quantum dots and n-type Bi2S3 nanocrystals. Adv. Mater. 2011, 23, 3712–3717. [Google Scholar] [CrossRef] [PubMed]
  23. Yao, K.; Gong, W.W.; Hu, Y.F.; Liang, X.L.; Chen, Q.; Peng, L.-M. Individual Bi2S3 nanowire-based room-temperature H2 sensor. J. Phys. Chem. C 2008, 112, 8721–8724. [Google Scholar] [CrossRef]
  24. Fu, T.-X. Gas sensor based on three dimensional Bi2S3 nanowires network for ammonia detection at room temperature. Mater. Res. Bull. 2018, 99, 460–465. [Google Scholar] [CrossRef]
  25. Rosolina, S.M.; Carpenter, T.S.; Xue, Z.L. Bismuth-based, disposable sensor for the detection of hydrogen sulfide gas. Anal. Chem. 2016, 88, 1553–1558. [Google Scholar] [CrossRef] [PubMed]
  26. Feng, Q.; Xie, X.; Zhang, M.; Liao, N. First-principles investigation of Bi2S3 as sensitive and selective NO2 sensor upon humidity exposure. J. Mater. Sci. 2023, 58, 2198–2208. [Google Scholar] [CrossRef]
  27. Chen, X.; Shi, J.; Wang, T.; Zheng, S.; Lv, W.; Chen, X.; Yang, J.; Zeng, M.; Hu, N.; Su, Y.; et al. High-performance wearable sensor inspired by the neuron conduction mechanism through gold-induced sulfur vacancies. ACS Sens. 2022, 7, 816–826. [Google Scholar] [CrossRef]
  28. Chen, X.; Wang, T.; Shi, J.; Lv, W.; Han, Y.; Zeng, M.; Yang, J.; Hu, N.; Su, Y.; Wei, H.; et al. A novel artificial neuron-like gas sensor constructed from CuS quantum dots/Bi2S3 nanosheets. Nano-Micro Lett. 2021, 14, 8. [Google Scholar] [CrossRef]
  29. Luo, J.; Feng, X.; Kan, H.; Li, H.; Fu, C. One-dimensional Bi2S3 nanobelts-based surface acoustic wave sensor for NO2 detection at room temperature. IEEE Sens. J. 2021, 21, 1404–1408. [Google Scholar] [CrossRef]
  30. Liu, D.; Tang, Z.; Zhang, Z. Nanoplates-assembled SnS2 nanoflowers for ultrasensitive ppb-level NO2 detection. Sens. Actuators B 2018, 273, 473–479. [Google Scholar] [CrossRef]
  31. Wang, T.; Wang, Y.; Zheng, S.; Sun, Q.; Wu, R.; Hao, J. Design of hierarchical SnSe2 for efficient detection of trace NO2 at room temperature. CrystEngComm 2021, 23, 6045–6052. [Google Scholar] [CrossRef]
  32. Zhang, Y.; Zeng, W.; Li, Y. Hydrothermal synthesis and controlled growth of hierarchical 3D flower-like MoS2 nanospheres assisted with CTAB and their NO2 gas sensing properties. Appl. Surf. Sci. 2018, 455, 276–282. [Google Scholar] [CrossRef]
  33. Fang, L.; Qiu, Y.; Zhai, T.; Wang, F.; Lan, M.; Huang, K.; Jing, Q. Flower-like nanoarchitecture assembled from Bi2S3 nanorod/MoS2 nanosheet heterostructures for high-performance supercapacitor electrodes. Colloids Surf. A 2017, 535, 41–48. [Google Scholar] [CrossRef]
  34. Lu, J.; Han, Q.; Yang, X.; Lu, L.; Wang, X. Microwave-assisted synthesis and characterization of 3D flower-like Bi2S3 superstructures. Mater. Lett. 2007, 61, 2883–2886. [Google Scholar] [CrossRef]
  35. Tang, J.; Alivisatos, A.P. Crystal splitting in the growth of Bi2S3. Nano Lett. 2006, 6, 2701–2706. [Google Scholar] [CrossRef] [PubMed]
  36. Shen, G.; Chen, D.; Tang, K.; Li, F.; Qian, Y. Large-scale synthesis of uniform urchin-like patterns of Bi2S3 nanorods through a rapid polyol process. Chem. Phys. Lett. 2003, 370, 334–337. [Google Scholar] [CrossRef]
  37. Kumari, P.; Awasthi, K.; Agarwal, S.; Ichikawa, T.; Kumar, M.; Jain, A. Flower-like Bi2S3 nanostructures as highly efficient anodes for all-solid-state lithium-ion batteries. RSC Adv. 2019, 9, 29549–29555. [Google Scholar] [CrossRef]
  38. Li, H.; Yang, J.; Zhang, J.; Zhou, M. Facile synthesis of hierarchical Bi2S3 nanostructures for photodetector and gas sensor. RSC Adv. 2012, 2, 6258. [Google Scholar] [CrossRef]
  39. Zheng, S.; Yin, D.; Zhang, S.; Wang, Y.; Li, J.; Wang, Z.; Yuan, Y.; Tsai, H.-S.; Hao, J. Tailoring selenium vacancies in MoSe2 through oxygen passivation for room-temperature NO2 sensing enhancement. J. Mater. Chem. A 2023, 11, 18755. [Google Scholar] [CrossRef]
  40. Miller, D.R.; Akbar, S.A.; Morris, P.A. Nanoscale metal oxide-based heterojunctions for gas sensing: A review. Sens. Actuators B 2014, 204, 250–272. [Google Scholar] [CrossRef]
  41. Hao, J.; Zhang, D.; Sun, Q.; Zheng, S.; Sun, J.; Wang, Y. Hierarchical SnS2/SnO2 nanoheterojunctions with increased active-sites and charge transfer for ultrasensitive NO2 detection. Nanoscale 2018, 10, 7210–7217. [Google Scholar] [CrossRef] [PubMed]
  42. Yang, X.; Tian, S.; Li, R.; Wang, W.; Zhou, S. Use of single-crystalline Bi2S3 nanowires as room temperature ethanol sensor synthesized by hydrothermal approach. Sens. Actuators B 2017, 241, 210–216. [Google Scholar] [CrossRef]
  43. Yu, Y.; Jin, C.H.; Wang, R.H.; Chen, Q.; Peng, L.M. High-quality ultralong Bi2S3 nanowires:  structure, growth, and properties. J. Phys. Chem. B 2005, 109, 18772–18776. [Google Scholar] [CrossRef] [PubMed]
  44. Cheng, Y.; Chang, Y.; Feng, Y.; Jian, H.; Tang, Z.; Zhang, H. Deep-level defect enhanced photothermal performance of bismuth sulfide–gold heterojunction nanorods for photothermal therapy of cancer guided by computed tomography imaging. Angew. Chem. Int. Ed. 2018, 57, 246–251. [Google Scholar] [CrossRef] [PubMed]
  45. Grigas, J.; Talik, E.; Lazauskas, V. X-ray photoelectron spectra and electronic structure of Bi2S3 crystals. Phys. Status Solidi 2002, 232, 220–230. [Google Scholar] [CrossRef]
  46. Sun, Q.; Wang, J.; Hao, J.; Zheng, S.; Wan, P.; Wang, T.; Fang, H.; Wang, Y. SnS2/SnS p-n heterojunctions with an accumulation layer for ultrasensitive room-temperature NO2 detection. Nanoscale 2019, 11, 13741–13749. [Google Scholar] [CrossRef] [PubMed]
  47. Cui, S.; Pu, H.; Wells, S.A.; Wen, Z.; Mao, S.; Chang, J.; Hersam, M.C.; Chen, J. Ultrahigh sensitivity and layer-dependent sensing performance of phosphorene-based gas sensors. Nat. Commun. 2015, 6, 8632. [Google Scholar] [CrossRef] [PubMed]
  48. Li, Y.; Song, Z.; Li, Y.; Chen, S.; Li, S.; Li, Y.; Wang, H.; Wang, Z. Hierarchical hollow MoS2 microspheres as materials for conductometric NO2 gas sensors. Sens. Actuators B 2019, 282, 259–267. [Google Scholar] [CrossRef]
  49. Han, Y.; Liu, Y.; Su, C.; Wang, S.; Li, H.; Zeng, M.; Hu, N.; Su, Y.; Zhou, Z.; Wei, H.; et al. Interface engineered WS2/ZnS heterostructures for sensitive and reversible NO2 room temperature sensing. Sens. Actuators B 2019, 296, 126666. [Google Scholar] [CrossRef]
  50. Guo, R.; Han, Y.; Su, C.; Chen, X.; Zeng, M.; Hu, N.; Su, Y.; Zhou, Z.; Wei, H.; Yang, Z. Ultrasensitive room temperature NO2 sensors based on liquid phase exfoliated WSe2 nanosheets. Sens. Actuators B 2019, 300, 127013. [Google Scholar] [CrossRef]
  51. Simon Patrick, D.; Bharathi, P.; Krishna Mohan, M.; Muthamizchelvan, C.; Harish, S.; Navaneethan, M. Liquid phase exfoliated WS2 nanosheet-based gas sensor for room temperature NO2 detection. J. Mater. Sci. Mater. Electron. 2022, 33, 9235–9245. [Google Scholar] [CrossRef]
  52. Duan, Y.; Feng, S.; Zhang, K.; Qiu, J.; Zhang, S. Vertical few-layer WSe2 nanosheets for NO2 sensing. ACS Appl. Nano Mater. 2021, 4, 12043–12050. [Google Scholar] [CrossRef]
  53. Kwon, K.C.; Suh, J.M.; Lee, T.H.; Choi, K.S.; Hong, K.; Song, Y.G.; Shim, Y.-S.; Shokouhimehr, M.; Kang, C.-Y.; Kim, S.Y.; et al. SnS2 nanograins on porous SiO2 nanorods template for highly sensitive NO2 sensor at room temperature with excellent recovery. ACS Sens. 2019, 4, 678–686. [Google Scholar] [CrossRef] [PubMed]
  54. Camargo Moreira, Ó.L.; Cheng, W.-Y.; Fuh, H.-R.; Chien, W.-C.; Yan, W.; Fei, H.; Xu, H.; Zhang, D.; Chen, Y.; Zhao, Y.; et al. High selectivity gas sensing and charge transfer of SnSe2. ACS Sens. 2019, 4, 2546–2552. [Google Scholar] [CrossRef] [PubMed]
  55. Zhao, Y.; Song, J.-G.; Ryu, G.H.; Ko, K.Y.; Woo, W.J.; Kim, Y.; Kim, D.; Lim, J.H.; Lee, S.; Lee, Z.; et al. Low-temperature synthesis of 2D MoS2 on a plastic substrate for a flexible gas sensor. Nanoscale 2018, 10, 9338–9345. [Google Scholar] [CrossRef] [PubMed]
  56. Zhang, S.; Nguyen, T.H.; Zhang, W.; Park, Y.; Yang, W. Correlation between lateral size and gas sensing performance of MoSe2 nanosheets. Appl. Phys. Lett. 2017, 111, 161603. [Google Scholar] [CrossRef]
  57. Kim, Y.; Kwon, K.C.; Kang, S.; Kim, C.; Kim, T.H.; Hong, S.-P.; Park, S.Y.; Suh, J.M.; Choi, M.-J.; Han, S.; et al. Two-dimensional NbS2 gas sensors for selective and reversible NO2 detection at room temperature. ACS Sens. 2019, 4, 2395–2402. [Google Scholar] [CrossRef]
  58. Bag, A.; Lee, N.-E. Gas sensing with heterostructures based on two-dimensional nanostructured materials: A review. J. Mater. Chem. C 2019, 7, 13367–13383. [Google Scholar] [CrossRef]
  59. Zappa, D.; Galstyan, V.; Kaur, N.; Munasinghe Arachchige, H.M.M.; Sisman, O.; Comini, E. “Metal oxide-based heterostructures for gas sensors”—A review. Anal. Chim. Acta 2018, 1039, 1–23. [Google Scholar] [CrossRef]
  60. Lee, E.; Yoon, Y.S.; Kim, D.J. Two-dimensional transition metal dichalcogenides and metal oxide hybrids for gas sensing. ACS Sens. 2018, 3, 2045–2060. [Google Scholar] [CrossRef]
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Figure 1. (a) Schematic illustration of the formation process of hierarchical Bi2S3 nanomaterials. SEM images of the hydrolysis product (b), the as-prepared sample with a 1 h hydrothermal reaction time (c), and the sample with a 12 h reaction (d); TEM (e) and (f) HRTEM images; and the EDS spectrum of the BS-12h sample (g).
Figure 1. (a) Schematic illustration of the formation process of hierarchical Bi2S3 nanomaterials. SEM images of the hydrolysis product (b), the as-prepared sample with a 1 h hydrothermal reaction time (c), and the sample with a 12 h reaction (d); TEM (e) and (f) HRTEM images; and the EDS spectrum of the BS-12h sample (g).
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Figure 2. (a) XRD patterns of prepared samples with different reaction times. (b) XPS survey; (c) Bi4f and S2p core level spectrum of the BS-12h sample.
Figure 2. (a) XRD patterns of prepared samples with different reaction times. (b) XPS survey; (c) Bi4f and S2p core level spectrum of the BS-12h sample.
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Figure 3. RT NO2 sensing performance of BS-8h, BS-12h, and BS-24h samples: (a) dynamic sensing response curves and (b) the corresponding linear relationship between sensitivity and NO2 concentration ranging from 0.1 to 1.0 ppm.
Figure 3. RT NO2 sensing performance of BS-8h, BS-12h, and BS-24h samples: (a) dynamic sensing response curves and (b) the corresponding linear relationship between sensitivity and NO2 concentration ranging from 0.1 to 1.0 ppm.
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Figure 4. The RT NO2 sensing properties test of the BS-12h sensor: (a) Dynamic NO2 sensing response curves with different concentrations. (b) Linear relationship fitting curve. (c) Repeatability toward 1 ppm NO2. (d) Selective response toward interfering gases.
Figure 4. The RT NO2 sensing properties test of the BS-12h sensor: (a) Dynamic NO2 sensing response curves with different concentrations. (b) Linear relationship fitting curve. (c) Repeatability toward 1 ppm NO2. (d) Selective response toward interfering gases.
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Figure 5. The RT NO2 sensing properties test of the BS-12h sensor: (a) Anti-humidity ability to 1 ppm NO2 under different relative humidity. (b) Baseline resistance and sensitivity to 1 ppm NO2 under varied humidity environments. (c) Long-term stability.
Figure 5. The RT NO2 sensing properties test of the BS-12h sensor: (a) Anti-humidity ability to 1 ppm NO2 under different relative humidity. (b) Baseline resistance and sensitivity to 1 ppm NO2 under varied humidity environments. (c) Long-term stability.
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Figure 6. Dynamic RT response/recovery curve of the hierarchical Bi2S3 sensor based on the BS-12h sample to 1 ppm NO2 in 100% N2, 100% O2, and different O2 concentration with N2 as a balance gas.
Figure 6. Dynamic RT response/recovery curve of the hierarchical Bi2S3 sensor based on the BS-12h sample to 1 ppm NO2 in 100% N2, 100% O2, and different O2 concentration with N2 as a balance gas.
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Figure 7. Schematic illustration of the NO2 sensing mechanism of the 1D nanorod-assembled Bi2S3 nanostructures.
Figure 7. Schematic illustration of the NO2 sensing mechanism of the 1D nanorod-assembled Bi2S3 nanostructures.
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Table 1. Comparison of NO2 sensing behaviors of reported metal sulfide nanomaterials and our prepared hierarchical Bi2S3 nanostructures.
Table 1. Comparison of NO2 sensing behaviors of reported metal sulfide nanomaterials and our prepared hierarchical Bi2S3 nanostructures.
MaterialsNO2 Conc.
(ppm)		Responseτres/τrec
(s/s)		LOD
(ppb)		Reference
WS2 nanosheets101.445/602000[51]
WSe2 nanosheets11.366/1020100[52]
SnS2 nanograins107.0272/38001000[53]
SnSe2 nanosheets11.6142/935100[54]
MoS2 nanograins5003.5~180/~48025,000[55]
MoSe2 nanosheets 51.4450/6005000[56]
NbS2 nanosheets51.2~3000/~9000241[57]
Bi2S3 nanobelts16.972/400500[21]
CuS/Bi2S3 nanosheets103.418/388500[27]
Au/Bi2S3 nanosheets55.618/338250[28]
Bi2S3 hierarchical nanostructures15.828/11650This study
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Yang, Y.; Liu, C.; Wang, Y.; Hao, J. Nanorods Assembled Hierarchical Bi2S3 for Highly Sensitive Detection of Trace NO2 at Room Temperature. Chemosensors 2024, 12, 8. https://doi.org/10.3390/chemosensors12010008

AMA Style

Yang Y, Liu C, Wang Y, Hao J. Nanorods Assembled Hierarchical Bi2S3 for Highly Sensitive Detection of Trace NO2 at Room Temperature. Chemosensors. 2024; 12(1):8. https://doi.org/10.3390/chemosensors12010008

Chicago/Turabian Style

Yang, Yongchao, Chengli Liu, You Wang, and Juanyuan Hao. 2024. "Nanorods Assembled Hierarchical Bi2S3 for Highly Sensitive Detection of Trace NO2 at Room Temperature" Chemosensors 12, no. 1: 8. https://doi.org/10.3390/chemosensors12010008

APA Style

Yang, Y., Liu, C., Wang, Y., & Hao, J. (2024). Nanorods Assembled Hierarchical Bi2S3 for Highly Sensitive Detection of Trace NO2 at Room Temperature. Chemosensors, 12(1), 8. https://doi.org/10.3390/chemosensors12010008

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