ZnO Quasi-1D Nanostructures: Synthesis, Modeling, and Properties for Applications in Conductometric Chemical Sensors

One-dimensional metal oxide nanostructures such as nanowires, nanorods, nanotubes, and nanobelts gained great attention for applications in sensing devices. ZnO is one of the most studied oxides for sensing applications due to its unique physical and chemical properties. In this paper, we provide a review of the recent research activities focused on the synthesis and sensing properties of pure, doped, and functionalized ZnO quasi-one dimensional nanostructures. We describe the development prospects in the preparation methods and modifications of the surface structure of ZnO, and discuss its sensing mechanism. Next, we analyze the sensing properties of ZnO quasi-one dimensional nanostructures, and summarize perspectives concerning future research on their synthesis and applications in conductometric sensing devices

Nanostructures of Tungsten Trioxide, Nickel Oxide and Niobium Oxide for Chemical Sensing Applications

AbstractTungsten trioxide nanowires, nickel oxide nanowires and niobium oxide nanostructures weresynthesized by thermal oxidation, vapour-liquid-solid (VLS) technique and hydrothermal method,respectively. Alumina (2 · 2 mm2) substrates were used for growth of the different metal oxidesnanostructures. Thin films of tungsten or niobium are used as source material for WO3 and Nb2O5. Anultrathin film of gold was deposited on alumina as catalyst for NiO. All these materials were depositedby RF magnetron sputtering. The morphology was investigated by scanning electron microscope andthe functional properties of these structures were tested towards several gaseous species at differentworking temperatures. The results obtained show that these sensing materials have similarperformances considering the different n- and p-type semiconductors behaviour. Tungstentrioxide (WO3) nanowires, nickel oxide (NiO) nanowires and niobium oxide (Nb2O5) nanostructures were synthesized by thermal oxidation, vapor-liquid-solid (VLS) technique and hydrothermal method, respectively. The morphology was investigated by scanning electron microscope and the functional properties of these structures as gas sensors were tested for several gaseous species at different working temperatures. In this work a comparison between the sensitivity of these devices towards acetone is shown

Nanostructured metal oxide gas sensors, a survey of applications carried out at SENSOR lab, brescia (Italy) in the security and food quality fields

8partially_openopenPonzoni A. ; Comini E. ; Concina I. ; Ferroni M. ; Falasconi M. ; Gobbi E.; Sberveglieri V. ; Sberveglieri G.Ponzoni, Andrea; Comini, Elisabetta; Concina, Isabella; Ferroni, Matteo; Falasconi, Matteo; Gobbi, Emanuela; Sberveglieri, V.; Sberveglieri, Giorgi

A composite structure based on reduced graphene oxide and metal oxide nanomaterials for chemical sensors

A hybrid nanostructure based on reduced graphene oxide and ZnO has been obtained for the detection of volatile organic compounds. The sensing properties of the hybrid structure have been studied for different concentrations of ethanol and acetone. The response of the hybrid material is significantly higher compared to pristine ZnO nanostructures. The obtained results have shown that the nanohybrid is a promising structure for the monitoring of environmental pollutants and for the application of breath tests in assessment of exposure to volatile organic compounds

Geographic origin differentiation of Philippine civet coffee using an Electronic nose

An increasing interest in geographical indication of origin has emerged to achieve legal protection of specialty coffee in international market. Civet coffee which is considered as the most expensive and best specialty coffee in the world, is one of the important indigenous export products of the Philippines. Thus, geographical origin differentiation of Philippine civet coffee and their control coffee beans (not eaten by civet) using electronic nose (E-nose) was performed. The E-nose instrument was based on six semiconductor metal oxide (SMO) sensor array. Results showed that the sensors exhibited different responses towards civet coffees and non-civet (control) coffees of different provenance. Principal component analysis (PCA) and Heirarchical cluster analysis (HCA) demonstrated a clearly separated civet coffees from their control beans. The cluster separation among civet coffee samples indicated that geographic origins dictate the aroma and flavor variations in coffee. This remarkable performance of E-nose provides proof that it is an excellent tool for authentication of the provenance of civet coffee and non-civet coffee samples

What happens at the aroma of coffee beans after roasting?

The coffee aroma is one of the most important quality evaluation criteria employed for coffee commercialization and consumption. The purpose of this study was following the roasting process VOCs creations with the novel Electronic Nose equipped whit 2 of 6 MOX nanowire sensors. The nanowires exhibit exceptional crystalline quality and a very high length-to-width ratio, resulting in enhanced sensing capability as well as long-term material stability for prolonged operation. Four different methods of roasting, made by ROSTAMATIC (Table 1) machine, were applied to gain a clearer picture of the differences in roasted coffee aromas by means of a volatile compound analysis. Different methods applied on four different origins of green coffee (India, Indonesia, Honduras, Santos and Nicaragua). The commercial coffees products are made from a blending from minimum five different kinds of coffee and the consumers have developed an addiction/expectation to a specific flavor and taste. Different methods of roasting process will provide the coffee different aroma that will add flexibility to those one that already posses the matrix due to different origins. This work tests and illustrates the broad spectrum of potential uses of the EN technique in food quality control

A new approach to evaluate vinegars quality: application of Small Sensor System (S3) device coupled with enfleurage

In this work is illustrated the application of S3 (Small Sensor System) device, equipped with an array of six metal oxide semiconductor (MOX) gas sensors, coupled with enfleurage as new approach to characterize the aromatic profile of Balsamic Vinegars (BVs). Thanks to the enfleurage in fact, the lipophilic volatile compounds are extracted from balsamic vinegar while acetic acid and its derivatives whose high concentration negatively influences MOX sensors sensitivity are not involved in the process. The obtained results show the huge potentiality of this new approach to evaluate BVs quality. All the samples were analyzed in parallel by GC-MS (Gas Chromatography-Mass Spectrometry) with SPME (Solid Phase Micro-Extraction). (C) 2016 The Authors. Published by Elsevier B.V

Detection of microbial contamination in potable water by Nanowire technology

It is well known that the lack of control and sanitation of water in developing countries has cause very significant epidemiological events. In the last decades the situation of water supplies and sanitation has improve all over the world. Despite of it, in the European Union there are a considerable number of confirmed cases of water-borne infections even though the restrictive law. Electronic Noses (ENs) has shown to be a very effective and fast tool for monitoring microbiological spoilage and quality control. The aim of this study was test the ability of a novel EN for the detection of bacterial presence in potable water in cooperation with analytical (pH) and optical (photometer) techniques. The achieved results notably advocate the use of EN in industry laboratories as a very important tool in water quality control

Electronic nose for the early detection of different types of indigenous mold contamination in green coffee

In the last few years Electronic Noses (ENs) have been revealed to be a very effective and fast tool for monitoring the microbiological spoilage and food quality control. European regulations report the maximum concentration of mycotoxins permitted in green coffee beans. The aim of this study was to test the ability of a novel EN, equipped with an array of MOX gas sensors based on thin films as well as nanowires, to early detect mold contaminations from Aspergillus spp., in cooperation with classical microbiological and chemical techniques like Gas Chromatography coupled with Mass Spectroscopy with SPME technique. In general the selection of the green coffee is controlled by visual inspection of shape, color and size. However, this process in often not enough to prevent the entrance in the food chains of contaminated products. We have demonstrated that the novel EN is able to early detect the qualitative and quantitative differences between contaminate and uncontaminated samples. Achieved results vividly recommend the use of our EN as a quality control tool in coffee producer industr