General Synthesis of Mixed Semiconducting Metal Oxide Hollow Spheres with Tunable Compositions for Low-Temperature Chemiresistive Sensing

Abstract

Metal oxide hollow spheres (MOHSs) with multicomponent metal elements exhibit intriguing properties due to the synergistic effects of different components. However, it remains a great challenge to develop a general method to synthesize multicomponent MOHSs due to the different hydrolysis and condensation rates of precursors for different metal oxides. Herein, we demonstrate a general strategy for the controllable synthesis of MOHSs with up to five metal elements by decomposition of metal-phenolic coordination polymers (MPCPs), which are prepared by chelation of tannic acid with various metal ions. After calcination to burn out the organic component and induce heterogeneous contraction of MPCPs, a series of MOHSs with multishell structure, high specific surface area (55–171 m2/g), and crystalline mesoporous framework are synthesized, including binary (Fe–Co, Ni–Zn, and Ni–Co oxides), ternary (Ni–Co–Mn and Ni–Co–Zn oxides), and quinary (Ni–Co–Fe–Cu–Zn oxides) MOHSs. The gas sensing nanodevices based on quinary MOHSs show much higher response (10.91) than those based on single component toward 50 ppm of ethanol at 80 °C with the response/recovery time of 85/160 s. The quinary oxides sensor also displays high selectivity toward ethanol against other interfering gases (e.g., methanol, formadehyde, toluene, methane, and hydrogen) and long-term stability (∼94.0% after 4 weeks), which are extremely favorable for practical applications.

Selective Ion Permeation through Stabilized Metal–Phenolic Grafted Graphene Oxide Membranes

“…[ 31 ] It is known that the transition metal cation salts of Co 2+ , Ni 2+ , and Mn 2+ have firmer affinity to form single to multiple metal polyphenolic coordination polymers (MPCPs) owing to the TA molecule being able to concomitantly coordinate with different metal cations in bulk solution. [ 31–34 ] Moreover, the MPCPs can easily disassemble at physiological pH from the mixture solutions with metal cations (e.g., Li + ), which exhibit inferior coordination affinity to form MPCPs. [ 31,33 ] Therefore, it is plausible to hypothesize that the intrinsic molecular disassembly of the metal phenolic coordination molecules at physiological pH provides the impetus for facilitated cation mobility and thus a desirable route for the facilitated transport of the studied divalent metal cations across the membrane.…”

“…[ 31–34 ] Moreover, the MPCPs can easily disassemble at physiological pH from the mixture solutions with metal cations (e.g., Li + ), which exhibit inferior coordination affinity to form MPCPs. [ 31,33 ] Therefore, it is plausible to hypothesize that the intrinsic molecular disassembly of the metal phenolic coordination molecules at physiological pH provides the impetus for facilitated cation mobility and thus a desirable route for the facilitated transport of the studied divalent metal cations across the membrane. The transition metal cations (Ni 2+ , Co 2+ , and Mn 2+ ) with the high affinity to form metal–phenolic coordination, which correspond to the specific interactions between the metal cations and the cation–ligand molecules experience carrier‐assisted transport (facilitated diffusion) when passing through these nanochannels, leading to the faster permeation rates than that of the Li + cations.…”

Small Structures Bring Big Things: Performance Control of Hollow Multishelled Structures

“…Such spatial‐ordered arrangements of shells and voids in HoMSs endow them with temporal–spatial‐ordered mass transfer [ 2 ] which has been formally defined as that mass can only successively go through shells and voids within HoMSs in a defined sequence. Designed with abundant chemical components, HoMSs are widely applied for electromagnetic wave (EW) absorption, [ 8 ] catalysis, [ 9–11 ] lithium ion battery (LIB), [ 12–15 ] medicine therapy, [ 2 ] and sensors, [ 16–23 ] etc. To meet the growing practical requirements in broad applications, great efforts have been devoted to the precise synthesis of HoMSs with complex chemical compositions and structures.…”

Microwave-Assisted Synthesis of Hollow Microspheres with Multicomponent Nanocores for Heavy-Metal Removal and Magnetic Sensing

“…Hollow microspheres, a special class of particles with empty spaces inside distinct shells, have inspired tremendous interest because of their intriguing structures, highly adjustable compositions, and great potential for widespread applications, such as in energy storage and conversion, 1 sensors, 2,3 environmental protection, 4,5 catalysis, 6,7 and biomedicine. 8−10 Various methods have been developed for the synthesis of hollow microspheres, and these can be classified into four types, namely, hard-templating, soft-templating, self-templating, and template-free methods.…”

“…Hollow microspheres, a special class of particles with empty spaces inside distinct shells, have inspired tremendous interest because of their intriguing structures, highly adjustable compositions, and great potential for widespread applications, such as in energy storage and conversion, sensors, , environmental protection, , catalysis, , and biomedicine. − Various methods have been developed for the synthesis of hollow microspheres, and these can be classified into four types, namely, hard-templating, soft-templating, self-templating, and template-free methods . However, the use of hard-templating methods requires a solution for the affinity problem between the coating materials and the templates, and soft-templating methods allow less control over the uniformity of the products due to the variability of the template shape.…”