Metal–Organic Framework-Derived LaFeO₃@SnO₂/Ag p–n Heterojunction Nanostructures for Formaldehyde Detection

Abstract

Using n-type and p-type semiconductor materials to construct p–n heterostructures has proven effective for improving gas-sensing properties. In this study, we synthesized the nanocomposites of SnO2 derived from a metal–organic framework (MOF) and LaFeO3 by loading atomic silver on its surface. The response value (R a/R g) of the nanocomposites to 10 ppm formaldehyde reached 498 at 140 °C, but they showed almost no response to 50 ppm interference volatile organic compounds (VOCs), and the response–recovery time was 105 and 27 s, respectively. The crystal structure, heterojunction structure, chemical elements, and sensitive mechanism were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), thermogravimetry (TG), Brunauer–Emmett–Teller (BET) analysis, and energy-dispersive spectrometry (EDS) elemental mapping. The characterizations revealed that the improvement of gas sensitivity was mainly due to the MOF-driven strategy, p–n heterojunction, and electron sensitization effect of Ag. This work provides a method and idea for preparing composites and shows the potential application value of LaFeO3@SnO2/Ag nanomaterials in formaldehyde gas detection.

Well-designed g-C 3N 4 nanosheet incorporated Ag loaded Er 0.05La 0.95FeO 3 heterojunctions for isoamyl alcohol detection

“…The XRD patterns of SA, CA, and g-C3N4 samples are shown in Figs. 2(a 112), ( 022), ( 004), ( 204), (040), and (116) crystal planes of orthorhombic LaFeO3 (PDF#74-2203) [22], demonstrating the excellent crystallinity of samples. With the addition of the AgNO3 standard solution, peaks at 38.12 o and 44.30 o emerge obviously, which correspond to the (111) and ( 200) crystal facets of Ag (PDF#04-0783) [23].…”

Nonstoichiometric Doping of La0.9FexSn1–xO3 Hollow Microspheres for an Ultrasensitive Formaldehyde Sensor

“…The reduction of resistance can be attributed to the dissociation of a small amount of H 2 O molecules on the surface of the LFS microspheres, and the dissociated electrons enter the LFS through the carrier channel to combine with holes, resulting in a decrease in the overall resistance of the sensor (eq ). The decrease in the sensor’s response value is attributed to the fact that H 2 O molecules occupy part of the active sites . Because the working temperature of the LFS sensor is much higher than the boiling point of water, the probability of water molecules being adsorbed on the sensor electrode is greatly reduced, and the moisture resistance of the sensor is improved (Figure S4e).…”

“…36 The decrease in the sensor's response value is attributed to the fact that H 2 O molecules occupy part of the active sites. 37 Because the working temperature of the LFS sensor is much higher than the boiling point of water, the probability of water molecules being adsorbed on the sensor electrode is greatly reduced, and the moisture resistance of the sensor is improved (Figure S4e).…”

Study of the Gas Sensing Performance of Ni-Doped Perovskite-Structured LaFeO3 Nanospheres

“…In recent years, LaFeO 3 has been considered as a typical p-type perovskite-type oxide due to its relatively simple preparation, highly stable structure, and excellent thermal stability [16,17]. Previous studies have shown that LaFeO 3 exhibits good gas sensitivity towards gases such as ethanol, acetone, and formaldehyde [18].…”