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Research paper thumbnail of Optical gas sensing through nanostructured ZnO films with different morphologies

Sensors and Actuators B: Chemical, 2010

We report on nitrogen dioxide (NO 2 ) sensing measurements by means of zinc oxide films presentin... more We report on nitrogen dioxide (NO 2 ) sensing measurements by means of zinc oxide films presenting different morphologies. The variation in the photoluminescence emission of the films is employed as transduction mechanism to detect the presence of NO 2 gas molecules at room temperature. The significant role of film morphology on the sensing properties is presented and possible limits in the use of ZnO nanostructures for NO 2 detection at high gas concentration (>20 ppm) and low gas flow (50 ml/min), where a worsening of the sensor response is observed, are discussed. These features are ascribed to a likely incomplete reversibility of the NO 2 adsorption process and examined in connection with the mechanisms of interaction between NO 2 molecules and ZnO.

Research paper thumbnail of Temperature dependence of the photoluminescence properties of colloidal CdSe∕ZnS core/shell quantum dots embedded in a polystyrene matrix

Physical Review B, 2005

In this article, we report the growth and characterization of InAsP/InP strained single quantum w... more In this article, we report the growth and characterization of InAsP/InP strained single quantum well (SSQW), strained single quantum well (SSQW) stack, and strained multiple quantum well (SMQW) structures on (1 0 0)-oriented InP substrates grown by metalorganic chemical vapor deposition. Double-crystal X-ray di!raction, photoluminescence (PL) and transmission electron microscope (TEM) are used to characterize the strained quantum wells. The high-quality crystalline InAs W P \W (72A s )/InP SSQW structure with y)0.36 exhibits a 9.9 meV full-width at half-maximum (FWHM) of 10 K PL spectra. The peaks in the PL spectra for SSQW stack structure with a well thickness of 8, 14, and 35 A s vanish above 100, 150, and 296 K, respectively, presumably due to the decrease of photons yielded by electron}hole recombination in thinner quantum well regions on increasing the temperature. The PL peak emission energy dependence of well thickness in the InAsP/InP SSQW stack structure is in good agreement with the calculated results. In addition, the variations of the PL peak energy and FWHM in all the InAsP/InP SSQW, SSQW stack, and SMQW structures are described in detail.

Research paper thumbnail of Substrate-Au catalyst influence on the growth of ZnO nanorods

Materials Science and Engineering: B, 2010

Research paper thumbnail of Zinc oxide nanostructured layers for gas sensing applications

Laser Physics, 2011

Various kinds of zinc oxide (ZnO) nanostructures, such as columns, pencils, hexagonal pyramids, h... more Various kinds of zinc oxide (ZnO) nanostructures, such as columns, pencils, hexagonal pyramids, hexagonal hierarchical structures, as well as smooth and rough films, were grown by pulsed laser deposition using KrF and ArF excimer lasers, without use of any catalyst. ZnO films were deposited at substrate temper atures from 500 to 700°C and oxygen background pressures of 1, 5, 50, and 100 Pa. Quite different morphol ogies of the deposited films were observed using scanning electron microscopy when different laser wave lengths (248 or 193 nm) were used to ablate the bulk ZnO target. Photoluminescence studies were performed at different temperatures (down to 7 K). The gas sensing properties of the different nanostructures were tested against low concentrations of NO 2 . The variation in the photoluminescence emission of the films when exposed to NO 2 was used as transduction mechanism to reveal the presence of the gas. The nanostructured films with higher surface to volume ratio and higher total surface available for gas adsorption presented higher responses, detecting NO 2 concentrations down to 3 ppm at room temperature.

Research paper thumbnail of Optical gas sensing through nanostructured ZnO films with different morphologies

Sensors and Actuators B: Chemical, 2010

We report on nitrogen dioxide (NO 2 ) sensing measurements by means of zinc oxide films presentin... more We report on nitrogen dioxide (NO 2 ) sensing measurements by means of zinc oxide films presenting different morphologies. The variation in the photoluminescence emission of the films is employed as transduction mechanism to detect the presence of NO 2 gas molecules at room temperature. The significant role of film morphology on the sensing properties is presented and possible limits in the use of ZnO nanostructures for NO 2 detection at high gas concentration (>20 ppm) and low gas flow (50 ml/min), where a worsening of the sensor response is observed, are discussed. These features are ascribed to a likely incomplete reversibility of the NO 2 adsorption process and examined in connection with the mechanisms of interaction between NO 2 molecules and ZnO.

Research paper thumbnail of Temperature dependence of the photoluminescence properties of colloidal CdSe∕ZnS core/shell quantum dots embedded in a polystyrene matrix

Physical Review B, 2005

In this article, we report the growth and characterization of InAsP/InP strained single quantum w... more In this article, we report the growth and characterization of InAsP/InP strained single quantum well (SSQW), strained single quantum well (SSQW) stack, and strained multiple quantum well (SMQW) structures on (1 0 0)-oriented InP substrates grown by metalorganic chemical vapor deposition. Double-crystal X-ray di!raction, photoluminescence (PL) and transmission electron microscope (TEM) are used to characterize the strained quantum wells. The high-quality crystalline InAs W P \W (72A s )/InP SSQW structure with y)0.36 exhibits a 9.9 meV full-width at half-maximum (FWHM) of 10 K PL spectra. The peaks in the PL spectra for SSQW stack structure with a well thickness of 8, 14, and 35 A s vanish above 100, 150, and 296 K, respectively, presumably due to the decrease of photons yielded by electron}hole recombination in thinner quantum well regions on increasing the temperature. The PL peak emission energy dependence of well thickness in the InAsP/InP SSQW stack structure is in good agreement with the calculated results. In addition, the variations of the PL peak energy and FWHM in all the InAsP/InP SSQW, SSQW stack, and SMQW structures are described in detail.

Research paper thumbnail of Substrate-Au catalyst influence on the growth of ZnO nanorods

Materials Science and Engineering: B, 2010

Research paper thumbnail of Zinc oxide nanostructured layers for gas sensing applications

Laser Physics, 2011

Various kinds of zinc oxide (ZnO) nanostructures, such as columns, pencils, hexagonal pyramids, h... more Various kinds of zinc oxide (ZnO) nanostructures, such as columns, pencils, hexagonal pyramids, hexagonal hierarchical structures, as well as smooth and rough films, were grown by pulsed laser deposition using KrF and ArF excimer lasers, without use of any catalyst. ZnO films were deposited at substrate temper atures from 500 to 700°C and oxygen background pressures of 1, 5, 50, and 100 Pa. Quite different morphol ogies of the deposited films were observed using scanning electron microscopy when different laser wave lengths (248 or 193 nm) were used to ablate the bulk ZnO target. Photoluminescence studies were performed at different temperatures (down to 7 K). The gas sensing properties of the different nanostructures were tested against low concentrations of NO 2 . The variation in the photoluminescence emission of the films when exposed to NO 2 was used as transduction mechanism to reveal the presence of the gas. The nanostructured films with higher surface to volume ratio and higher total surface available for gas adsorption presented higher responses, detecting NO 2 concentrations down to 3 ppm at room temperature.

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