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In this paper, the evaluation of the gas sensing performance of chemoresistive sensor devices based on M-doped CuO (M = Sn, Zn) nanoparticles prepared by a simple wet chemical method is reported. The morphology of samples has been assessed by scanning electron microscope and transmission electron microscope. The sensors were fabricated, depositing by drop coating the nanoparticles on the sensor substrate platform, and the electrical performance upon exposure to different gases in the air was recorded. The CuO-based gas sensors present a p-type semiconductor behavior. The results of electrical tests have shown that Sn and Zn effectively act as promoters improving the gas sensing properties of CuO toward some volatile organic compounds such as acetone and ethanol. Zn–CuO sensor resulted the most sensitive and selective to acetone, revealing that the appropriate choice of dopant plays a key role in the design of CuO-based sensors. [ABSTRACT FROM AUTHOR]

Abstract: Antimony-doped tin oxide (ATO) nanostructures were prepared using chemical precipitation technique starting from SnCl2, SbCl3 as precursor compounds. The antimony composition was varied from 5 to 20wt%. The lower resistance was observed at composition of Sn:95 and Sb:05, when compared with undoped and higher doping concentration of antimony. The average crystalline size of undoped and doped tin oxide was calculated from the X-ray diffraction (XRD) pattern and found to be in the range of 30–11nm and it was further confirmed from the transmission electron microscopy (TEM) studies. The scanning electron microscopy (SEM) analysis showed that the nanoparticles agglomerates forming spherical-shaped particles of few hundreds nanometers. The samples were further analyzed by energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and electrical resistance measurements. [Copyright &y& Elsevier]

A study over Sb-promoted tin oxide nanopowders for sensing applications is reported. SnO2 nanopowders pure and promoted with 5wt% of antimony were prepared by wet chemical methods and widely characterized by TEM, XRD, and XPS techniques. Thick film resistive sensors were fabricated by depositing the synthesized nanopowders by drop-coating on interdigited alumina substrates. The sensing characteristics of the pure SnO2 and Sb-promoted sensors for the monitoring of trace level of NO2 were studied. The response of the sensors to water vapor was also investigated, revealing that Sb acts favorably eliminating the interference of humidity. [ABSTRACT FROM AUTHOR]

Abstract: Tin oxide nanoplatelets (SnO) and nanoparticles (SnO2) were prepared by microwave assisted technique with an operating frequency of 2.45 GHz. This technique permits to produce gram quantity of homogeneous nanoparticles in just 10 min. The crystalline size was evaluated from XRD and found to range from 26 to 34 nm. SEM and TEM analyses showed that the nanoparticles present a platelet-like shaped particle or, a pseudo spherical morphology, after calcination at moderate temperature during which the phase transformation from SnO to SnO2 takes place. Additional FT-IR, density and resistivity measurements were also presented. [Copyright &y& Elsevier]

Abstract: Microwave technique was adopted for preparation of tin dioxide nanoparticles with particles size ranging from 10 to 11 nm within 10 min. The formation of monocrystalline SnO2 nanoparticles was confirmed by the XRD (X-Ray Diffraction) and TEM (Transmission Electron Microscopy) as well as with SAED (Selected Area Electron Diffraction) analysis. The structure of the SnO2 crystal was found to be Cassiterite type tetragonal structure. The FT-IR results further supported the formation of tin dioxide from tin hydroxyl group without any post annealing. The samples were further characterized by thermo gravimetric analysis (TGA), electrical resistance measurements and photoluminescence spectrum. [Copyright &y& Elsevier]

Tungsten oxide (WO x ) nanoparticles were synthesized by a facile and eco-friendly microwave-assisted hydrothermal method without need for using any surfactant. A thorough investigation was performed in order to elucidate the effects of microwave irradiation time (10, 20 and 30 min) on the structural, morphological and optical properties of the as-prepared WO x . Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) of the samples revealed the presence of irregular nanosized particles containing some well-structured rod shape particles. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) indicated that these nanoparticles are crystallines with mean crystalline size of about 16 nm exhibiting both monoclinic and orthorhombic WO x crystal structures. The optical properties were investigated by using ultraviolet visible spectroscopy (UV-VIS) and photoluminescence (PL). A blue-shifted optical absorption spectrum with an enhanced defects emission was observed when it was compared to bulk spectrum of WO 3 . Thermal-aged WO x nanoparticles at mild temperature (350 °C) were also used to fabricate conductometric gas sensors Gas sensing tests showed excellent performance towards ethanol monitoring for each synthesized material. In particular, the highest sensitivity was obtained for the sensor based on WO x synthesized by 10 min irradiation time (S10). At the optimal operating temperature of 300 °C, the S10 sensor showed a response R a /R g  = 8.5 towards 100 ppm ethanol with fast response time of 10 s, in addition to an excellent selectivity against common interfering gases. [ABSTRACT FROM AUTHOR]

Crystalline tin oxide nanoparticles were successfully synthesized by microwave-assisted technique without any post annealing process. The morphology, microstructure and phase composition of the products obtained applying microwave irradiation for different time intervals were examined by XRD, FT-IR, SEM-EDX, TEM and HRTEM. Characterization results indicated that microwave irradiated products are composed of crystalline SnO2 nanoparticles which exhibit the cassiterite-type tetragonal crystal structure. The sensing properties of as-prepared SnO2 nanoparticles towards ethanol at low operating temperature were investigated. Such sensor devices exhibited good response to low concentrations of ethanol at temperature below 100°C. An abnormal sensing behavior was registered, that is the sensor resistance increases in the presence of ethanol maintaining, at the same time, the usual n-type behavior with other reducing gases such as CO. In contrast, after annealing the SnO2 nanoparticles at 400°C, the sensors show the expected regular behavior in all range of operating temperature investigated. A plausible mechanism, linked to a specific interaction between the surface of SnO2 and ethanol molecule through its hydroxyl group, was suggested in order to describe the unusual sensing behavior observed. [ABSTRACT FROM AUTHOR]