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...
Fully printable, hole-conductor-free, carbon-based perovskite solar cells are attractive and promising for industrial production due to their low cost and high stability. However, the efficiency of this type of device is difficult to improve due to the undesirable interfacial contact during the printing process compared to the spin coating process and the higher recombination ratio than the devices with a hole conductor. Herein, a porous anatase nanocrystal (Nano-TiO2) derived by MIL-125, a type of titanium-based metal–organic frameworks (MOFs), was used as the electron transporting material (ETM). The Nano-TiO2 can be conveniently covered on a substrate by screen-printing and still maintain the cakelike morphology, which is beneficial to large-scale production. Moreover, the cakelike morphology composed of nanocrystals is more favorable for the crystallization of perovskites than commercial TiO2 (P25) and can reduce the recombination of photogenerated electron–hole pairs to improve device performance. The device based on Nano-TiO2 shows a V OC of 0.907 V and a fill factor of 68.14% at the forward scan, which is higher than that of the devices based on P25 (0.853 V and 52.95%). It paves a promising way for carbon-based printable perovskite solar cells.
Xylene is a volatile organic compound which is harmful to the human health and requires precise detection. The detection of xylene by an oxide semiconductor gas sensor is an important research direction. In this work, Co 3 O 4 decorated flower-like SnO 2 nanorods (SnO 2 /Co 3 O 4 NRs) were synthesized by a simple and effective two-step method. The SnO 2 /Co 3 O 4 NRs show high xylene response (R g /R a =47.8 for 100 ppm) and selectivity at the operating temperature of 280 °C, and exhibit high stability in continuous testing. The resulting SnO 2 /Co 3 O 4 NRs nanocomposites show superior sensing performance towards xylene in comparison with pure SnO 2 nanorods. The remarkable enhancement in the gas-sensing properties of SnO 2 /Co 3 O 4 NRs are attributed to larger specific surface area and the formation of p-n heterojunction between Co 3 O 4 and SnO 2 . These results demonstrate that particular nanostructures and synergistic effect of SnO 2 and Co 3 O 4 enable gas sensors to selectively detect xylene.
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