A highly responsive NH3 sensor based on Pd-loaded ZnO nanoparticles prepared via a chemical precipitation approach

Abstract

The gas-detecting ability of nanostructured ZnO has led to significant attention being paid to the development of a unique and effective approach to its synthesis. However, its poor sensitivity, cross-sensitivity to humidity, long response/recovery times and poor selectivity hinder its practical use in environmental and health monitoring. In this context, the addition of noble metals, as dopants or catalysts to modify the ZnO surface has been examined to enhance its sensing performance. Herein, we report preparation of Pd-loaded ZnO nanoparticles via a chemical precipitation approach. Various Pd loadings were employed to produce surface-modified ZnO nanostructure sensors, and their resulting NH 3 sensing capabilities both in dry and humid environments were investigated. Through a comparative gas sensing study between the pure and Pd-loaded ZnO sensors upon exposure to NH 3 at an optimal operating temperature of 350 °C, the Pd-loaded ZnO sensors were found to exhibit enhanced sensor responses and fast response/recovery times. The influence of Pd loading and its successful incorporation into ZnO nanostructure was examined by X-ray diffraction, high resolution-transmission electron microscopy, and X-ray photoelectron spectroscopy. XPS studies demonstrated that in all samples, Pd existed in two chemical states, namely Pd° and Pd 2+ . The possible sensing mechanism related to NH 3 gas is also discussed in detail.

Catalytic Reduction of Hexavalent Chromium Using Iron/Palladium Bimetallic Nanoparticle-Assembled Filter Paper

“…The mean diameter of the Fe/Pd NPs was measured to be 10.1 ± 1.7 nm (Figure 2c), indicating that the filter paper employed in this study is a good substrate for the growth and assembly of bimetallic Fe/Pd NPs. High-resolution TEM image reveals the lattice structure of the NPs, and the d spacing was calculated to be 0.204 nm and 0.23 nm, corresponding to the [110] plane of α-Fe 0 and the [111] plane of the face-centered cubic crystal structure of Pd, respectively [24,25]. Furthermore, energy-dispersive spectrum (EDS) shows clearly the signals of Pd and Fe elements, confirming the bimetallic nature of the Fe/Pd NP-assembled filter paper.…”

Pd Nanoparticle Adsorption ZnO Nanorods for Enhancing Photodetector UV-Sensing Performance

“…Thus, abundant negative charges can be captured by the oxygen molecules attached to the surface of the nanorods. This process forms a depletion layer on the surface around of ZnO nanorods [17][18][19][20][21][22]. Therefore, the Pd/ZnO sample exhibits a lower current than the ZnO sample in darkness.…”

“…Owing to noble metal nanoparticles (NPs; e.g. Au, Pt and Pd), modified ZnO nanostructures are used often in the field of chemical sensing, such as in CH4, NH3, H2, NO2, CO and organic gas sensors [17][18][19][20][21][22]. Several studies investigate UV photodetector applications with Au and Pt NP-modified ZnO nanostructures.…”

Facile synthesis of Pd@graphene nanocomposites with enhanced catalytic activity towards Suzuki coupling reaction

“…However, the HRG-Py-Pd gave sharp peaks for Pd centered at 337.9 eV, 343.2 eV respectively, indicating the presence of only Pd 0 . The difference of binding energy being 5.3 eV is indicative of existence of Pd 3d 5/2 and Pd 3d 3/2 of Pd(0) in the HRG-Pd and HRG-Py-Pd composite 40 . Upon examination of the reused catalyst using XPS, it was found that there is no change in the intensity and oxidation state of the Pd nanoparticles deposited on the HRG-Py-Pd.…”