Encapsulation of Fe2O3/NiO and Fe2O3/Co3O4 nanosheets into conductive polypyrrole for superior lithium ion storage

Hollow-Out Fe2O3-Loaded NiO Heterojunction Nanorods Enable Real-Time Exhaled Ethanol Monitoring under High Humidity

The analysis of exhaled breath has opened up new exciting avenues in medical diagnostics, sleep monitoring, and drunk driving detection. Nevertheless, the detection accuracy is greatly affected due to high humidity in the exhaled breath. Here, we propose a regulation method to solve the problem of humidity adaptability in the ethanol-monitoring process by building a heterojunction and hollow-out nanostructure. Therefore, large specific surface area hollow-out Fe₂O₃-loaded NiO heterojunction nanorods assembled by porous ultrathin nanosheets were prepared by a well-tailored interface reaction. The excellent response (51.2 toward 10 ppm ethanol at 80% relative humidity) and selectivity to ethanol under high relative humidity with a lower operating temperature (150 °C) were obtained, and the detection limit was as low as 0.5 ppb with excellent long-term stability. The superior gas-sensing performance was attributed to the high surface activity of the heterojunction and hollow-out nanostructure. More importantly, GC-MS, diffuse reflectance Fourier transform infrared spectroscopy, and DFT were utilized to analyze the mechanisms of heterojunction sensitization, ethanol-sensing reaction, and high-humidity adaptability. Our integrated low-power MEMS Internet of Things (IoT) system based on Fe₂O₃@NiO successfully demonstrates the functional verification of ethanol detection in human exhalation, and the integrated voice alarm and IoT positioning functions are expected to solve the problem of real-time monitoring and rapid initial screening of drunk driving. Overall, this novel method plays a vital role in areas such as control of material morphology and composition, breath analysis, gas-sensing mechanism research, and artificial olfaction.

Design of highly sensitive and selective ethanol sensor based on α-Fe2O3/Nb2O5 heterostructure

The introduction of heterostructures is a new approach in gas sensing due to their easy and quick transport of charges. Herein, facile hydrothermal and solid-state techniques are employed to synthesize an α-Fe₂O₃/Nb₂O₅ heterostructure. The morphology, microstructure, crystallinity and surface composition of the synthesized heterostructures are investigated by scanning electron microscope, transmission electron microscope, x-ray diffraction, x-ray photoelectron spectroscopy and Brunauer-Emmett-Teller analyses. The successful fabrication of the heterostructures was achieved via the mutual incorporation of α-Fe₂O₃ nanorods with Nb₂O₅ interconnected nanoparticles (INPs). A sensor based on the α-Fe₂O₃(0.09)/Nb₂O₅ heterostructure with a high surface area exhibited enhanced gas-sensing features, maintaining high selectivity and sensitivity, and a considerable recovery percentage towards ethanol gas. The sensing response of the α-Fe₂O₃(0.09)/Nb₂O₅ heterostructure at lower operating temperature (160 °C) is around nine times higher than a pure Nb₂O₅ (INP) sensor at 180 °C with the flow of 100 ppm ethanol gas. The sensors also show excellent selectivity, good long-term stability and a rapid response/recovery time (8s/2s, respectively) to ethanol. The superior electronic conductivity and upgraded sensitivity performance of gas sensors based on the α-Fe₂O₃(0.09)/Nb₂O₅ heterostructure are attributed due to its unique structural features, high specific surface area and the synergic effect of the n-n heterojunction. The promising results demonstrate the potential application of the α-Fe₂O₃(0.09)/Nb₂O₅ heterostructure as a good sensing material for the fabrication of ethanol sensors.

A structurally aligned nickel oxide encapsulated polypyrrole nanocomposite for hydrogen peroxide sensing

Chemically responsive and structurally aligned nickel oxide encapsulated polypyrrole nano-composite has been prepared for H₂O₂ sensing in liquid and vapor phase.

Three-dimensional porous Co3O4-CoO@GO composite combined with N-doped carbon for superior lithium storage

Transition metal oxides (TMOs) as anode materials have potential for lithium-ion batteries (LIBs). However, the poor rate capacity and cycle stability restrict its application. Herein, we demonstrate a facile one-step hydrothermal method to construct a three-dimensional porous conductive network structure, which consists of thin-layered graphene, ultrafine Co₃O₄-CoO nanoparticles and nitrogen-doped carbon. This unique structure can effectively prevent particle agglomeration and cracking caused by volume expansion, provide fast passage for lithium ion/electron transport during cycling and improve the electrical conductivity of the electrode. Moreover, the electrochemical kinetic analysis proves that this is a process dominated by pseudocapacitive behavior. Consequently, the N-C@Co₃O₄-CoO@GO hybrid electrode delivers an ultrahigh capacity of 1 273.1 mA h g^-1 at 0.1 A g^-1 and superior rate performance (725.1 mA h g^-1 at 5 A g^-1). Additionally, it exhibits a high reversible cycling capacity of 787.4 mA h g^-1 at 1 A g^-1 over 600 cycles and even maintains excellent cycling stability for a ultra-long cycles at 5 A g^-1. This work provides a feasible strategy for fabricating the N-C@Co₃O₄-CoO@GO composite as a promising high-performance TMOs anode for LIBs.