Remarkable improvement of gas-sensing abilities in p-type oxide nanowires by local modification of the hole-accumulation layer (original) (raw)

Growth and sensing properties of networked p-CuO nanowires

Sensors and Actuators B: Chemical, 2015

Networked p-CuO nanowires were grown on patterned-electrode pads by the thermal oxidation of Cu layers. Vertically aligned CuO nanowires grown on adjacent round-shape electrode pads were entangled, eventually forming nanowire-nanowire junctions. The sensing properties of the networked CuO nanowires were examined for a range of oxidizing gases, such as NO 2 , SO 2 and O 2 , and reducing gases, such as CO, C 6 H 6 , C 7 H 8 , and H 2 , and compared with those of networked n-SnO 2 nanowires. The gas responses of the networked CuO nanowires to the tested oxidizing gases were inferior to those of networked n-SnO 2 nanowires. In contrast, for reducing gases, the networked CuO nanowires showed comparable gas responses to the networked n-SnO 2 nanowires. The results suggest that the networked CuO nanowires are more promising for the detection of reducing gases rather than oxidizing gases.

Facile synthesis of p-type semiconducting cupric oxide nanowires and their gas-sensing properties

2009

Cupric oxide nanowires were successfully synthesized by thermal oxidation of copper wire in air and their gas-sensing properties were investigated. High-resolution transmission electron microscopy (HRTEM) analysis indicated that single crystal CuO nanowires with an average diameter of about 60 nm and length up to several micrometers were grown. The sensor resistance increased upon exposure to reducing gases and decreased with oxidizing gas, indicating p-type semiconducting properties of CuO. The nanowires-based gas sensor could detect a wide range of gases including 1% H 2 , 60 ppm CO, 60 ppm NH 3 , and 60 ppm NO x and found a potential application in environmental monitoring.

Nanowires of metal oxides for gas sensing applications

Surface and Interface Analysis, 2008

Nanowires of different metal oxides (SnO2, ZnO) have been grown by evaporation–condensation process. Their chemical composition has been investigated by using XPS. The standard XPS quantification through main photoelectron peaks, modified Auger parameter and valence band spectra were examined for the accurate determination of oxidation state of metals in the nanowires.Morphological investigation has been conducted by acquiring and analyzing the SEM images. For the simulation of working conditions of sensor, the samples were annealed in ultra high vacuum (UHV) up to 500 °C and XPS analysis repeated after this treatment. Finally, the nanowires of SnO2 have were used to produce a novel gas sensor based on Pt/oxide/SiC structure and operating as Schottky diode. Copyright © 2008 John Wiley & Sons, Ltd.

Metal oxides nanowires chemical/gas sensors: recent advances

Materials Today Advances

Chemical/gas sensors are playing and will play a crucial role in smart building, smart houses, environmental monitoring, food quality monitoring and in the customization of personalized medicine, as they allow a constant data collection to monitor all the parameters needed for a preventive intervention related to health and wealth of human beings together with the environment. Nanowires (NWs) and NW-based heterostructures thanks to their peculiar properties such as high crystallinity, flexibility, conductivity, and optical activity are key components of future sensing devices. Notwithstanding a rapid growth in smart, portable, and wearable chemical sensing devices, the development of reliable devices for the detection of chemicals, gases, and vapors is still needed together with the possibility to correlate the sensing data with health and wealth of the analyzed system: food, environment, and human beings. In this short review, I am going to report few recent studies and achievements devoted to increase the functional performances of chemical sensing devices, keeping the focus on materials, sensing transduction, and data extraction/evaluation.

Highly sensitive and selective gas sensors using p-type oxide semiconductors: Overview

2014

Ag-and Pd-loaded SnO 2 nanowire network sensors were prepared by the growth of SnO 2 nanowires via thermal evaporation, the coating of slurry containing SnO 2 nanowires, and dropping of a droplet containing Ag or Pd nanoparticles, and subsequent heat treatment. All the pristine, Pd-loaded and Ag-loaded SnO 2 nanowire networks showed the selective detection of C 2 H 5 OH with low cross-responses to CO, H 2 , C 3 H 8 , and NH 3 . However, the relative gas responses and gas selectivity depended closely on the catalyst loading. The loading of Pd enhanced the responses(R a /R g : R a : resistance in air, R g : resistance in gas) to CO and H 2 significantly, while it slightly deteriorated the response to C 2 H 5 OH. In contrast, a 3.1-fold enhancement was observed in the response to 100 ppm C 2 H 5 OH by loading of Ag onto SnO 2 nanowire networks. The role of Ag catalysts in the highly sensitive and selective detection of C 2 H 5 OH is discussed.

Copper oxide nanowires prepared by thermal oxidation for chemical sensing

Procedia Engineering, 2011

Copper oxide nanowires (NWs) were prepared grown by thermal oxidation of metallic Cu thin layer deposited by RF sputtering on various substrates. A strong relation between oxidation parameters and morphology has been detected, and thus optimal growth parameters were found. The preliminary response of this alternative p-type sensing material, using nanowire's mat-based device, to various oxidizing and reducing target gases has been evaluated, in order to corroborate the functional properties of the CuO NWs as potential sensing material under certain conditions.

Metal oxide nanowires as chemical sensors

Materials Today, 2010

health and for safety stress the need of real-time monitoring of the environment, therefore there is a remarkable effort in terms of research for the development of sensors devoted to several applications 1-9 .

Attachment of Co3O4 layer to SnO2 nanowires for enhanced gas sensing properties

Sensors and Actuators B: Chemical, 2017

We prepared nanocomposites of n-SnO 2 /p-Co 3 O 4 for application in chemical sensors. In order to fabricate p-Co 3 O 4-decorated n-SnO 2 nanowires, we sputtered a Co layer and subsequently annealed the material in air ambient. Characterization revealed that crystalline cubic Co 3 O 4 with a tubular-like structure was attached to the surface of SnO 2 core nanowires. We carried out sensing tests at 573 K in at NO 2 gas concentrations ranging between 2 and 10 ppm. The sensor response was increased both by adding the Co 3 O 4 layer and also by decreasing the thickness of the Co 3 O 4 layer from 19.2 to 6.4 nm. We proposed possible mechanisms to explain the enhanced sensor properties obtained by Co 3 O 4-functionalization. Co 3 O 4-functionalized SnO 2 nanowires exhibited a higher sensor response than pristine nanowires, not only due to the heterostructure-induced depletion of n-SnO 2 region but also due to the surface effects of Co 3 O 4. The generation of hole-accumulated Co 3 O 4 layer in case of thicker-layered nanowires will decrease the sensor response. We demonstrated that Co 3 O 4-functionalized SnO 2 nanowire sensors can be used as gas sensors at very low concentrations.