Porous Cr₂O₃ Architecture Assembled by Nano-Sized Cylinders/Ellipsoids for Enhanced Sensing to Trace H₂S Gas

Abstract

How to achieve high sensing of Cr2O3-based sensors for harmful inorganic gases is still a challenge. To this end, Cr2O3 nanomaterials assembled from different building blocks were simply prepared by chromium salt immersion and air calcination with waste scallion roots as the biomass template. The hierarchical architecture calcined at 600 °C is constructed from nanocylinders and nanoellipsoids (named as Cr2O3-600), and also possesses multistage pore distribution for target gas accessibility. Interestingly, the synergism of two shapes of nanocrystals enables the Cr2O3-based sensor to realize highly sensitive detection of trace H2S gas. At 170 °C, Cr2O3-600 exhibits a high response of 42.8 to 100 ppm H2S gas, which is 3.45 times larger than that of Cr2O3-500 assembled from nanocylinders. Meanwhile, this sensor has a low detection limit of 1.0 ppb (S = 1.4), good selectivity, stability, and moisture resistance. These results show that the combination of nanosized cylinders/ellipsoids together with exposed (104) facet can effectively improve the sensing performance of the p-type Cr2O3 material. In addition, the Cr2O3-600 sensor shows satisfactory results for actual monitoring of the corruption process of fresh chicken.

Design Synthesis of ZnO Tube Bundles Rich in Oxygen Vacancies Assembled by Nanorods/Quasi-Nanospheres for Enhanced Sensing to NO/NO2

“…As shown in Figure c and d, high-resolution O 1s XPS spectra display three peaks at 531.9/532.1, 530.9/531.1, and 529.8/530.1 eV, which are separately identified as hydroxyl oxygen (O H ), O A (O 2 – and V O ), and lattice oxygen (O L ) . Notably, the O A content of ZnO-6 (36.43%) is higher than that (32.03%) of ZnO-5, implying the high V O concentration in the former and further helping to increase the content of O A . , Meanwhile, their EPR spectra (Figure e) display unpaired electronic signals ( g = 2.003), which mainly stem from surface V O defects. , As reported, a large peak area (or strong signal) in an EPR spectrum means more contents of unpaired electrons . Accordingly, ZnO-6 has more V O defects than ZnO-5.…”

“…For instance, Zhen et al 18 utilized a poplar branch as a biotemplate to synthesize V O -enriched SnO 2 hierarchical tubes constructed from smallsized nanoparticles and "cookie-like" nanoaggregates, which presented ultrahigh response and rapid recovery to NO 2 at low temperatures. Song et al 19 prepared a Cr 2 O 3 hierarchical structure assembled from nanocylinders and nanoellipsoids using a waste scallion root template. The related sensor first presented a large response value toward trace H 2 S, which is 3.45 times higher than that of nanocylinders.…”

Black Phosphorus Nanosheet/Tin Oxide Quantum Dot Heterostructures for Highly Sensitive and Selective Trace Hydrogen Sulfide Sensing

“…Upon H 2 S adsorption, electrons were released from reducing H 2 S molecules to the conduction band of SnO 2 , as indicated by eq 6, which resulted in a shrunken depletion layer and then decreased resistance (Figure 8c). 49,56…”

Highly Selective and Humidity-Resistant Triethylamine Sensors Based on Pt and Cr2O3 Nanoparticles

“…Especially, Cr 2 O 3 has the unique properties of thermodynamic stability that it is hardly oxidized to toxic Cr 6+ in most instances. 24 These properties make Cr 2 O 3 widely used in coatings, pigments, catalytic fields, lithium ion batteries, magnetic materials, 25−27 gas sensors, 28 and so on. At present, in the field of sensing, chromium oxide is mainly used for modification but is rarely used as a subject sensitive material.…”

“…As an environmentally friendly p-type semiconductor, Cr 2 O 3 has a wide band gap ( E g = 3.4 eV), excellent corrosion resistance, conductivity, and catalytic activity. Especially, Cr 2 O 3 has the unique properties of thermodynamic stability that it is hardly oxidized to toxic Cr 6+ in most instances . These properties make Cr 2 O 3 widely used in coatings, pigments, catalytic fields, lithium ion batteries, magnetic materials, − gas sensors, and so on.…”