For developing highly sensitive, selective and stable gas sensing materials for the detection of volatile organic compounds, we report porous micro/nano-level structured Ag-LaFeO3 nanoparticles which have been successfully synthesized using a lotus leaf as a bio-template via a sol–gel process.
detecting ethanol along with response of 53 (50 ppm) at 275 °C. [6] Mesoscale porosity makes a significant contribution to obtaining high response in MOS because of the facile penetration of gas molecules. [7] A number of efforts have been made to synthesize mesoporous materials, [8][9][10][11] one of which involved the nanocast mesostructured metal oxides synthesized by hard template. Compared to soft template and sacrificial colloidal template methods, the hard template can provide a relatively stable matrix during heat treatment over a larger temperature range, as a result, it helps MOS show higher crystallinity. [12] Recently, it has been reported that hetero nanostructures consisting of two or more components with noble metals decorated can improve the sensing performance. [13,14] To improve the gas sensing performance of metal oxides, noble metals, such as Ag, Pd, Pt, and Au are commonly regarded as catalyst, especially, Ag is able to weaken the adsorption and the desorption energy of ethanol molecules on the surface by promoting the electron conduction properties, [15] thus it enables the analyte to access the activated surface. Perovskite type (ABO 3 , where A is rare earth and B is transition metal) MOS have attracted considerable attentions in applications of catalysis, [16] renewable energy storage, [17] and gas sensors [18] due to their numerous favorable physical/chemical properties. Among various perovskite type materials, LaFeO 3 shows considerably sensitive to reducing gases such as ethanol, [19] acetone, [20] and formaldehyde. [21] However, pure LaFeO 3 have some deficiencies such as high resistance, high working temperature, and poor selectivity. Ag/LaFeO 3 has been investigated to detect VOCs at low temperature (<200 °C) according to our previous work. Zhang et al. reported Ag/LaFeO 3 showed excellent gassensing properties to formaldehyde gas. At the optimal working temperature of 90 °C, the response of the sensor to 1 ppm formaldehyde is 25. [22] In addition, it was reported that the substitution of La 3+ in the LaFeO 3 compound by the lower-valent cations, such as Mg 2+ , [23] Ba 2+ , [24] Ca 2+ , [25] Sr 2+ , [26] and Pb 2+ , [27] could significantly improve gas sensing properties of materials, especially gas response and selectivity.In this study, mesoporous Ag/Zn-LaFeO 3 nanocomposites have been synthesized via a simple nanocasting technique shown in Figure 1. This kind of composite not only possesses a highly active and large surface area for ethanol recognition,The rational design of heterojunction between different metal oxides with mesoporous structures has attracted tremendous attention due to their special physicochemical properties and vital importance for practical applications. In this paper, mesoporous Ag/Zn-LaFeO 3 nanocomposite is successfully synthesized through a facile nanocasting technique using KIT-6 as a hard template in sol-gel route and used as sensing materials to achieve an exceptionally sensitive and selective detection of trace ppm-level ethanol. The obtained compos...
An ultrasensitive methanol gas sensing device based on the quasi-molecular imprinting technology (quasi-MIT) is studied in this work. We applied the sol-gel method (ALS denotes Ag-LaFeO3 prepared by the sol-gel method) and combustion synthesis (ALC denotes Ag-LaFeO3 prepared by combustion synthesis) to prepare Ag-LaFeO3 based sensors. The morphologies and structures of the Ag-LaFeO3 materials were examined via various detection techniques. The ALSM and ALCM sensor (ALSM and ALCM denotes the devices prepared by coating the ALS and ALC materials with methanol, respectively) fabricated using the sol-gel method and combustion synthesis combined with quasi-MIT exhibit good gas sensing properties to methanol, in contrast with the two devices (ALSW and ALCW denote the devices prepared for coating the ALS and ALC materials with water, respectively) without the use of quasi-MIT. The results show that quasi-MIT introduced the target gas in the fabrication process of the device, playing an important role in the design of the ultrasensitive methanol gas sensor. The sensing response and the optimum working temperature of ALSM and ALCM gas sensor are 52.29 and 155 °C and 34.89 and 155 °C, respectively, for 5 ppm methanol, and the highest response to other gases is 8. The ALSM and ALCM gas sensors reveal good selectivity and response for methanol.
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