Coordination Polymer-Derived Multishelled Mixed Ni–Co Oxide Microspheres for Robust and Selective Detection of Xylene

Abstract

Multishell, stable, porous metal-oxide microspheres (Ni-Co oxides, CoO and NiO) have been synthesized through the amorphous coordination polymer-based self-templated method. Both oxides of Ni and Co show poor selectivity to xylene, but the composite phase has substantial selectivity (e.g., S/ S = 2.69) and remarkable sensitivity (11.5-5 ppm xylene at 255 °C). The short response and recovery times (6 and 9 s), excellent humidity-resistance performance (with coefficient of variation = 11.4%), good cyclability, and long-term stability (sensitivity attenuation of ∼9.5% after 30 days and stable sensitivity thereafter) all show that this composite is a competitive solution to the problem of xylene sensing. The sensing performances are evidently due to the high specific surface area and the nano-heterostructure in the composite phase.

Recent progress in the syntheses and applications of multishelled hollow nanostructures

“…Significantly, the selectivity and response toward xylene could be maintained with excellent humidity resistance, suggesting the potential of such multishelled Ni-Co oxide microspheres in the detection of ground-level xylene gas in the environment. 222 With the development of industries and widespread utilization of vehicles, the increasing consumption of fossil fuels has generated a large amount of NO x (NO and NO 2 ), which is harmful to the domestic environment as well as the human body. The accurate content of NO 2 in air even at a very low concentration is an important parameter in order to evaluate air quality.…”

Heat Diffusion‐Induced Gradient Energy Level in Multishell Bisulfides for Highly Efficient Photocatalytic Hydrogen Production

“…Synthesis of Photocatalysts—Synthesis of the Multishell ZnCo 2 O 4 Microspheres : The multishell ZnCo 2 O 4 microspheres were prepared by a hydrothermal method according to the previous report. [ 18,44 ] First, 0.033 mmol of hydrated zinc nitrates Zn(NO 3 ) 2 ·6H 2 O, 0.067 mmol of hydrated cobalt nitrates Co(NO 3 ) 2 ·6H 2 O, and 0.100 mmol of isophthalic acid (H 2 IPA) were dissolved in a mixture of acetone (5 mL) and DMF (5 mL), then stirred vigorously for 6 h to form a homogeneous solution. Subsequently the homogeneous solution was transferred into a 50 mL stainless‐steel autoclave lined Teflon and reacted at 160 °C for 4 h. After cooling to room temperature, the obtained product was separated by centrifugation, and washed three times with ethanol and distilled water, then dried in a vacuum oven at 80 °C keep 12 h to form Zn–Co coordination polymer spheres.…”

“…[ 19,28,39–41 ] In general, the preparation and synthesis of multishell structured photocatalysts can be divided into three methods according to the template used: hard templating, soft templating, and self‐templating method. [ 17,21,26,30,34,40,42–44 ] Hard and soft templating methods generally use rigid materials and micelles as templates. However, these methods usually suffer from complex template removing procedures, nonuniform coatings of particles, and difficulty in selecting templates that are compatible with the targeted material.…”

Oxygen-Defective Ultrathin BiVO4 Nanosheets for Enhanced Gas Sensing

“…Metal oxide semiconductor-based gas sensors have been widely applied in Internet of Things (IoT) and Industrial Internet of Things (IIoT) for their advantages such as its simple structure, relatively high response to various gases, low cost, and low power consumption. − However, further improvements in sensing performances regarding the response, selectivity, and sensing mechanism are needed. , The key is to design and prepare high-performance sensing materials with a high response, a well selectivity, and a fast response/recovery speed. − In particular, systematically modulating some parameters of sensing materials to achieve high performance is highly desirable and remains challenging. Great efforts have been devoted to increase the response via material designing, such as doping impurity ions, constructing heterostructures, adjusting morphologies and compositions, and so forth. − However, issues regarding about achieving high sensing characteristics are still unsatisfactorily solved, including the easy tendency of aggregation and the low amount of active sites.…”