CuO nanostructures: Synthesis, characterization, growth mechanisms, fundamental properties, and applications

Functional materials by electrospinning of polymers

Nanotechnology has opened new and exhilarating opportunities for exploring glucose biosensing applications of the newly prepared nanostructured materials. Nanostructured metal-oxides have been extensively explored to develop biosensors with high sensitivity, fast response times, and stability for the determination of glucose by electrochemical oxidation. This article concentrates mainly on the development of different nanostructured metal-oxide [such as ZnO, Cu(I)/(II) oxides, MnO2, TiO2, CeO2, SiO2, ZrO2, and other metal-oxides] based glucose biosensors. Additionally, we devote our attention to the operating principles (i.e., potentiometric, amperometric, impedimetric and conductometric) of these nanostructured metal-oxide based glucose sensors. Finally, this review concludes with a personal prospective and some challenges of these nanoscaled sensors.

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A comprehensive review of glucose biosensors based on nanostructured metal-oxides.

Electrospun Co3O4 nanofibers for sensitive and selective glucose detection

Two-dimensional (2D) nanostructures are highly attractive for fabricating nanodevices due to their high surface-to-volume ratio and good compatibility with device design. In recent years 2D nanostructures of various materials including metal oxides, graphene, metal dichalcogenides, phosphorene, BN and MXenes, have demonstrated significant potential for gas sensors. This review aims to provide the most recent advancements in utilization of various 2D nanomaterials for gas sensing. The common methods for the preparation of 2D nanostructures are briefly summarized first. The focus is then placed on the sensing performances provided by devices integrating 2D nanostructures. Strategies for optimizing the sensing features are also discussed. By combining both the experimental results and the theoretical studies available, structure-properties correlations are discussed. The conclusion gives some perspectives on the open challenges and future prospects for engineering advanced 2D nanostructures for high-performance gas sensors devices.

Two-Dimensional Nanostructured Materials for Gas Sensing

Three-dimensional network films of electrospun copper oxide nanofibers for glucose determination.

In this work, pure and 1–5 mol% Co-doped SnO 2 nanofibers were synthesized via an electrospinning method The morphological and microstructural properties of these nanofibers were obviously changed and the grain size of the SnO 2 nanocrystal were greatly decreased by Co doping Sensors based on these nanofibers were fabricated after a hot pressing process on the ceramic plates The gas-sensing properties of pure and Co-doped SnO 2 nanofibers were tested to several kinds of Volatile Organic Compounds (VOCs) The results indicated that among all the samples (0, 1, 3 and 5 mol% Co-doped SnO 2 nanofibers), 3 mol% Co-doped SnO 2 nanofibers showed the highest response toward 100 ppm ethanol, having a response of 401, which was over 4 times higher than pure SnO 2 nanofibers At the same time, the sensors based on 3 mol% Co-doped SnO 2 nanofibers also exhibited good repeatability and long term stability, which were promising for designing ethanol gas sensor with high performance

Synthesis of Co-doped SnO2 nanofibers and their enhanced gas-sensing properties

Flower-like WO 3 composed of nanosheets were successfully synthesized by calcining the acid-treated hydrothermal precursor. Field emission scanning electron microscopy and transmission electron microscopy results reveal that the flower-like WO 3 are assembled by a number of irregular-shaped nanosheets, which are cross-linked in the interior of the microflower. A possible formation mechanism is proposed on the basis of the results of time-dependent experiments. Moreover, the gas sensing properties of the obtained flower-like nanostructured WO 3 were investigated. It is found that the sensor based on the flower-like WO 3 nanostructure exhibits good selectivity and high response to NO 2 , and the detection limit is about 2 ppb.

Hierarchical flower-like WO3 nanostructures and their gas sensing properties

A three-dimensional hierarchical WO 3 nanostructure with a novel nanosheet-assembled morphology was synthesized through acidification of Na 2 WO 4 ·2H 2 O. Firstly, precipitate got from Na 2 WO 4 ·2H 2 O and HCl was used as precursor. Secondly, the precursor was pretreated by concentrated acid for 24 h. Thirdly, deionized water was poured into the above solution directly to form the final products. The results revealed that the pretreatment by using high-concentration acid is the crucial factor in order to obtain the flower-like nanostructures. The WO 3 samples were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET). The results revealed that the samples were flower-like structure. The subunits of the flower-like nanostructures are ultrathin nanosheets with a thickness of about 20 nm. Sensors based on the synthesized WO 3 exhibited high response to NO 2 . The detection limit can be as low as ∼40 ppb level. Such novel WO 3 nanostructures may be a promising material for sensor application in detecting NO 2 .

Nanosheets assembled hierarchical flower-like WO3 nanostructures: Synthesis, characterization, and their gas sensing properties

Pure and 1–4 mol% W-doped NiO nanotubes were prepared by electrospinning. Sensors based on these nanotubes were fabricated by hot pressing the nanomaterials on the ceramic plates. The responses ( S  =  R g /R a , where R g is the resistance in gas and R a is the resistance in air) to 200 ppm xylene, ethanol, acetone, benzene, toluene, methanol and formaldehyde are significantly enhanced by W doping of NiO nanotubes, while the response of pure NiO nanotubes are very low. In particular, the sensors based on W-doped NiO nanotubes, in which the molar ratio of W 6+ :Ni 2+ is 2:100, exhibit highest response toward 200 ppm xylene, having a response about 8.74, which is almost 3.3 times higher than that of sensor based on pure NiO nanotubes. The results of sensing properties indicate that the xylene sensors based on the W-doped NiO nanotubes exhibit good selectivity, repeatability and long term stability characteristics, which are promising for xylene sensors used to monitor air-quality and environmental.

Xin Li

Papers

Three-dimensional network films of electrospun copper oxide nanofibers for glucose determination.

Synthesis of Co-doped SnO2 nanofibers and their enhanced gas-sensing properties

Hierarchical flower-like WO3 nanostructures and their gas sensing properties

Nanosheets assembled hierarchical flower-like WO3 nanostructures: Synthesis, characterization, and their gas sensing properties

Enhanced sensitive and selective xylene sensors using W-doped NiO nanotubes