1,721,198 research outputs found
Graphene-like layers as promising chemiresistive sensing material for detection of alcohols at low concentration
No full textIn the manifold of materials for Volatile Organic Compound (VOC) sensing, graphene related materials (GRMs) gain special attention thanks to their versatility and overall chemico-physical tunability as a function of specific applications. In this work, the sensing performances of graphene-like (GL) layers, a new material belonging to the GRM family, are tested against ethanol and n-butanol. Two typologies of GL samples were produced by employing two different approaches and tested in view of their application as VOC sensors. The experiments were performed under atmospheric pressure, in dry air, and at room temperature and demonstrated that the sensing capabilities are related to the film surface features. The results indicated that GL films are promising candidates for the detection of low concentrations of VOCs at room temperature. The present investigation thus paves the way for VOC sensing optimization using cost-effective and easily scalable materials. © 2018 Author(s)
An innovative approach to overcome saturation and recovery issues of CVD graphene-based gas sensors
No full textIn this work, we present an innovative method which enables to solve fundamental limitations affecting graphene-based chemi-sensors operating under environmental conditions, namely the lack of signal saturation and the scarce recovery after the detection step. The method, which exploits the differential current instead of the current itself, is validated by applying it on different devices having an exposed area equal to 512 pm2. The analysis is performed by adopting nitrogen dioxide (NO2) as target gas in the range from 0.12 ppm to 1.5 ppm. The approach reliability is further confirmed by performing sensing tests towards NO2 with the relative humidity set at two different levels, 30% and 50%. © 2017 IEEE
Concept of MEMS Vibrating Membrane as Particulate Matter (PM) Sensor
No full textThis work shows experimental results obtained in testing a thin film piezo actuated silicon membrane in a controlled environment. The main aim of this work was to select humidity concentration as one of the most influencing factors on vibrating characteristic of the circular clamped membrane. Thanks to fine control of humidity and the parallel feedback due to calibrated sensors we established a precise correlation between humidity and resonant shift
High sensitive gas sensors realized by a transfer-free process of CVD graphene
No full textThe work herein presented investigates the behavior of graphene-based gas sensors realized by using an innovative way to prepare graphene. The sensing layer was directly grown by chemical vapor deposition on pre-patterned CMOS compatible Mo catalyst and then it was eased on the underlying SiO2 through a completely transfer-free process. Devices with different geometries were designed and tested towards NO2 and NH3 in environmental conditions, i.e. room temperature and relative humidity set at 50%. Furthermore, these gas sensors were also calibrated, resulting in the ability to detect concentrations down to 240 ppb and 17 ppm of NO2 and NH3, respectively. These results are in agreement with the best performances reported in literature for graphene-based sensors. They not only confirm the successful devices fabrication through the transfer-free approach, but also pave the route for large-scale production of MEMS/NEMS sensors. © 2016 IEEE
Enhancement in the Selectivity and Sensitivity of Ni and Pd Functionalized MoS2 Toxic Gas Sensors
Full text linkAtmospheric pollution is one of the major aspects of concern which led to the research of sensors for the detection of toxic gases. The supreme surface-To-volume ratio makes two-dimensional MoS2 a promising material to be used as an electronic sensor. Here, we demonstrate the fabrication of a high-performance gas sensor based on atomic-layered MoS2 nanoflakes synthesized by a facile hydrothermal process. Structural and morphological studies confirmed the formation of few-layered phase pure hexagonal MoS2 nanoflakes. The results demonstrate that the Pd-MoS2 layers exhibited a very high relative response to NO gas (700%) at 2 ppm concentration with a minimum NO detection limit of 0.1 ppm and Ni-MoS2 demonstrated a relative response of 80% towards H2S gas with a limit of detection of 0.3 ppm with good repeatability and selectivity, owing to the increased adsorption energy of NO on Pd-MoS2 and H2S on Ni-MoS2 through the formation of PdNOx and NiS2 complexes respectively. The improved sensing performance of this MoS2-based sensor also suggests the great potential and possibility of MoS2 related 2D materials and its combinations for the development of futuristic highly sensitive nanosized gas sensors suitable for anti-pollution automotive system and as volatile biomarkers
Investigation of thermal transport in n-type porous silicon by photo-acoustic technique
No full textNon-destructive thermal and optical characterization of materials can be successfully performed by the photo-acoustic technique. In this work, this technique has been applied to the measure of thermal conductivity in porous silicon by considering the photo-acoustic response at fixed frequency of samples having the same porosity but different thicknesses. Experimental data are interpreted in terms of a model which takes into account both scattering effects and the contribution to the photo-acoustic signal of the interstitial gas expansion. The measured thermal conductivity is found to be lower than the one reported for crystalline silicon by two orders of magnitude. A discussion of the photo-acoustic signal dependence on the morphology of the porous medium is also presented. © 2002 Published by Elsevier Science Ltd
A new chemical sensing material for ethanol detection: Graphene-like film
No full textThe development of volatile organic compounds (VOCs) sensor, operating at room temperature (RT), is a challenge for the research community. In this framework, we present a device based on a graphene-like (GL) material suitably tested as sensing layer for the ethanol detection. GL material was obtained through a two steps oxidation/reduction method starting from a nanostructured carbon black. GL material combines a defect-free basal plane graphenic structure with the presence of oxygen functional groups, mainly carboxylic, located on the layer edges. A GL-based device was realized and investigated for the detection of ethanol. The experiments were performed under atmospheric pressure, in a dry air and at RT. Results showed that GL material is a promising candidate for the detection of low concentration of ethanol at RT. © Springer International Publishing AG 2018
Exfoliation of graphite and dispersion of graphene in solutions of low-boiling-point solvents for use in gas sensors
No full textIn this work we report on the development of an eco-friendly method for the chemical exfoliation of graphite in order to produce high-quality graphene for sensing applications. A mixture of low-boiling-point solvents, such as 1-butanol and 2-propanol, was employed for this purpose. The resulting colloidal suspension was a stable dispersion of few-layer flakes. This material was employed to fabricate chemiresistor devices that showed a remarkable variation of conductance when exposed to 350 ppb of NO2. © 2014 Springer International Publishing Switzerland
- …
