Near‐Room‐Temperature Ethanol Gas Sensor Based on Mesoporous Ag/Zn–LaFeO₃ Nanocomposite

Abstract

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...

Rational Design of Semiconductor‐Based Chemiresistors and their Libraries for Next‐Generation Artificial Olfaction

“…The chemiresistive perovskite oxides reported in the literature are summarized in Table 1 . [ 131–168 ] All the listed perovskite oxides are p‐type oxide semiconductors. Note that the perovskite oxides show distinctive gas sensing behaviors toward many different analyte gases, which can provide a new gas sensing library.…”

Ag Nanoparticles Sensitized In2O3 Nanograin for the Ultrasensitive HCHO Detection at Room Temperature

“…12a, b and Table 1) show that the adsorbed oxygen content (2.46% of O − and 19.54% of O 2 − ) of 5%Ag- In 2 O 3 is higher than that of pure In 2 O 3 (1.83% of O − and 16.05% of O 2 − ), which is mainly due to the Ag Nps spill-over effect on metal oxide semiconductors [44]. Owing to the high conductivity and catalytic properties of Ag NPs [28, 42, 45, 46], Ag NPs on the surface of the metal oxides enhance the chemical activity of the chemisorbed oxygen species and spill the oxygen species over the substrate, which accelerates for gas sensing at low temperature.

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Recent advances in ABO3 perovskites: their gas-sensing performance as resistive-type gas sensors

“…However, despite the fact that Ostwald ripening is a template-free technique, it is difficult to achieve controlled grain/pore size and morphological tuning of ABO 3 perovskite materials. Recently, hard templating approaches for porosity control in perovskite oxides were elucidated [96][97][98][99][100]. Typically, hard templating involves introduction of rigid templates such as solid or mesoporous silica, carbon, and polystyrene (PS) beads, whose elimination by calcination or dissolution in chemicals (acids or alkali etchants) creates various porous and hollow structures, ranging from simple to intricate ones.…”

“…Considering enhanced sensing performance of heterogeneous perovskite oxides compared to their single-phase analogues, further enhancement in performance can be achieved if adsorption/desorption kinetics of oxygen and target gases were enhanced. Chen et al [97] prepared Ag/Zn-LaFeO 3 nanocomposite via nanocasting technique, with KIT-6 (i.e., Korea Institute of Technology-6) as a template. KIT-6 is a three-dimensional (3D) silica material with high surface area and ordered mesostructure.…”