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1.
Artigo em Inglês | MEDLINE | ID: mdl-38621199

RESUMO

Recently, the combination of the piezoelectric effect in the photocatalytic process, referred to as piezo-photocatalysis, has gained considerable attention as a promising approach for enhancing the degradation of organic pollutants. In this investigation, we studied the piezo-photocatalysis by fabricating arrays of barium strontium titanate (Ba0.7Sr0.3TiO3) nanorods (BST NRs) on a glass substrate as recoverable catalysts. We found that the degradation rate constant k of the rhodamine B solution achieved 0.0447 min-1 using poled BST NRs in the piezo-photocatalytic process, indicating a 2-fold increase in efficiency compared to the photocatalytic process (0.00183 min-1) utilizing the same material. This is mainly ascribed to the generation of the piezopotential in the poled BST NRs under ultrasonic vibration. Moreover, the BST NR array demonstrated a hydrogen (H2) production rate of 411.5 µmol g-1 h-1. In the photoelectrochemical process, the photocurrent density of poled BST NRs achieved 1.97 mA cm-2 at an applied potential of 1.23 V (ERHE (reversible hydrogen electrode)) under ultrasonic vibrations, representing a 1.7-fold increase compared with the poled BST NRs without ultrasonic vibrations. The measurement results from the liquid chromatograph mass spectrometer (LC-MS) demonstrated the formulation of a degradation pathway for rhodamine B molecules. Moreover, ab initio molecular dynamics (AIMD) simulation results demonstrate the dominance of hydroxyl radicals (•OH) rather than superoxide radicals (•O2-) in the degradation process. This study not only benefits the understanding of the principle of the piezo-photocatalytic process but also provides a new perspective for improving the catalytic efficiency for organic pollutants degradation.

2.
Sensors (Basel) ; 24(6)2024 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-38544114

RESUMO

Pseudohexagonal Nb2O5 microcolumns spanning a size range of 50 to 610 nm were synthesized utilizing a cost-effective hydrothermal process (maintained at 180 °C for 30 min), followed by a subsequent calcination step at 500 °C for 3 h. Raman spectroscopy analysis unveiled three distinct reflection peaks at 220.04 cm-1, 602.01 cm-1, and 735.3 cm-1, indicative of the pseudohexagonal crystal lattice of Nb2O5. The HRTEM characterization confirmed the inter-lattice distance of 1.8 Å for the 110 plain and 3.17 Å for the 100 plain. The conductometry sensors were fabricated by drop-casting a dispersion of Nb2O5 microcolumns, in ethanol, on Pt electrodes. The fabricated sensors exhibited excellent selectivity in detecting C2H5OH (ΔG/G = 2.51 for 10 ppm C2H5OH) when compared to a variety of tested gases, including CO, CO2, NO2, H2, H2S, and C3H6O. The optimal operating temperature for this selective detection was determined to be 500 °C in a dry air environment. Moreover, the sensors demonstrated exceptional repeatability over the course of three testing cycles and displayed strong humidity resistance, even when exposed to 90% relative humidity. This excellent humidity resistance gas sensing property can be attributed to their nanoporous nature and elevated operating temperature.

3.
Nanomaterials (Basel) ; 14(4)2024 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-38392732

RESUMO

Low-dimensional metal oxides have drawn significant attention across various scientific domains due to their multifaceted applications, particularly in the field of environment monitoring. Their popularity is attributed to a constellation of unique properties, including their high surface area, robust chemical stability, and remarkable electrical conductivity, among others, which allow them to be a good candidate for detecting CO, CO2, H2, NH3, NO2, CH4, H2S, and volatile organic compound gases. In recent years, the Sol-Gel method has emerged as a powerful and versatile technique for the controlled synthesis of low-dimensional metal oxide materials with diverse morphologies tailored for gas sensing applications. This review delves into the manifold facets of the Sol-Gel processing of metal oxides and reports their derived morphologies and remarkable gas-sensing properties. We comprehensively examine the synthesis conditions and critical parameters governing the formation of distinct morphologies, including nanoparticles, nanowires, nanorods, and hierarchical nanostructures. Furthermore, we provide insights into the fundamental principles underpinning the gas-sensing mechanisms of these materials. Notably, we assess the influence of morphology on gas-sensing performance, highlighting the pivotal role it plays in achieving exceptional sensitivity, selectivity, and response kinetics. Additionally, we highlight the impact of doping and composite formation on improving the sensitivity of pure metal oxides and reducing their operation temperature. A discussion of recent advances and emerging trends in the field is also presented, shedding light on the potential of Sol-Gel-derived nanostructures to revolutionize the landscape of gas sensing technologies.

4.
Micromachines (Basel) ; 14(11)2023 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-38004981

RESUMO

Accurate hydrogen leakage detection is a major requirement for the safe and widespread integration of this fuel in modern energy production devices, such as fuel cells. Quasi-1D nanowires of seven different metal oxides (CuO, WO3, Nb-added WO3, SnO2, ZnO, α-Bi2O3, NiO) were integrated into a conductometric sensor array to evaluate the hydrogen-sensing performances in the presence of interfering gaseous compounds, namely carbon monoxide, nitrogen dioxide, methane, acetone, and ethanol, at different operating temperatures (200-400 °C). Principal component analysis (PCA) was applied to data extracted from the array, demonstrating the ability to discriminate hydrogen over other interferent compounds. Moreover, a reduced array formed by only five sensors is proposed. This compact array may be easily implementable into artificial olfaction systems used in real hydrogen detection applications.

5.
Sensors (Basel) ; 23(19)2023 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-37837151

RESUMO

Titanium dioxide nanobelts were prepared via the alkali-hydrothermal method for application in chemical gas sensing. The formation process of TiO2-(B) nanobelts and their sensing properties were investigated in detail. FE-SEM was used to study the surface of the obtained structures. The TEM and XRD analyses show that the prepared TiO2 nanobelts are in the monoclinic phase. Furthermore, TEM shows the formation of porous-like morphology due to crystal defects in the TiO2-(B) nanobelts. The gas-sensing performance of the structure toward various concentrations of hydrogen, ethanol, acetone, nitrogen dioxide, and methane gases was studied at a temperature range between 100 and 500 °C. The fabricated sensor shows a high response toward acetone at a relatively low working temperature (150 °C), which is important for the development of low-power-consumption functional devices. Moreover, the obtained results indicate that monoclinic TiO2-B is a promising material for applications in chemo-resistive gas detectors.

6.
Materials (Basel) ; 16(13)2023 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-37445116

RESUMO

Unlike the conventional one-dimensional (1D) core-shell nanowires (NWs) composed of p-type shells and n-type cores, in this work, an inverse design is proposed by depositing n-type ZnO (shell) layers on the surface of p-type CuO (core) NWs, to have a comprehensive understanding of their conductometric gas-sensing kinetics. The surface morphologies of bare and core-shell NWs were investigated by field emission scanning electron microscope (FE-SEM). The ZnO shell layer was presented by overlay images taken by electron dispersive X-ray spectroscopy (EDX) and high-resolution transmission electron microscopy (HRTEM). The pronounced crystalline plane peaks of ZnO were recorded in the compared glancing incident X-ray diffraction (GI-XRD) spectra of CuO and CuO-ZnO core-shell NWs. The ZnO shell layers broaden the absorption curve of CuO NWs in the UV-vis absorption spectra. As a result of the heterostructure formation, the intrinsic p-type sensing behavior of CuO NWs towards 250 and 500 ppm of hydrogen (H2) switched to n-type due to the deposition of ZnO shell layers, at 400 °C in dry airflow.

7.
Nanomaterials (Basel) ; 13(8)2023 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-37111009

RESUMO

The search for sustainable technology-driven advancements in material synthesis is a new norm, which ensures a low impact on the environment, production cost, and workers' health. In this context, non-toxic, non-hazardous, and low-cost materials and their synthesis methods are integrated to compete with existing physical and chemical methods. From this perspective, titanium oxide (TiO2) is one of the fascinating materials because of its non-toxicity, biocompatibility, and potential of growing by sustainable methods. Accordingly, TiO2 is extensively used in gas-sensing devices. Yet, many TiO2 nanostructures are still synthesized with a lack of mindfulness of environmental impact and sustainable methods, which results in a serious burden on practical commercialization. This review provides a general outline of the advantages and disadvantages of conventional and sustainable methods of TiO2 preparation. Additionally, a detailed discussion on sustainable growth methods for green synthesis is included. Furthermore, gas-sensing applications and approaches to improve the key functionality of sensors, including response time, recovery time, repeatability, and stability, are discussed in detail in the latter parts of the review. At the end, a concluding discussion is included to provide guidelines for the selection of sustainable synthesis methods and techniques to improve the gas-sensing properties of TiO2.

8.
Chem Commun (Camb) ; 59(10): 1329-1332, 2023 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-36645096

RESUMO

A novel strategy for the improvement in the sensing performance of p-type NiO is developed by employing the unique functional properties of self-assembled monolayers. Specifically, hole concentration near the surface of NiO nanowires (NWs) is modulated by terminal epoxy groups of the organosilane. This modulation leads to the increase in electron transfer from reducing gases to NWs surface. As a result, SAM-functionalized sensors showed 9-times higher response at low-temperature as compared to bare NiO NWs.

9.
Nanomaterials (Basel) ; 12(15)2022 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-35957099

RESUMO

This work presents the results of comparative studies using complementary methods, such as scanning electron microscopy (SEM), X-ray photoemission spectroscopy (XPS), and thermal desorption spectroscopy (TDS) to investigate the local surface morphology and chemistry of flower-like ZnO nanostructures synthesized by the thermal oxidation technique on native Si/SiO2 substrates. SEM studies showed that our flower-like ZnO nanostructures contained mostly isolated and irregular morphological low-dimensional forms, seen as rolled-up floss flowers, together with local, elongated, complex stalks similar to Liatris flowers, which contained joined short flosses in the form of nanodendrites. Beyond this, XPS studies showed that these nanostructures exhibited a slight surface nonstoichiometry, mostly related to the existence of oxygen-deficient regions, combined with strong undesired C surface contamination. In addition, the TDS studies showed that these undesired surface contaminations (including mainly C species and hydroxyl groups) are only slightly removed from the surface of our flower-like ZnO nanostructures, causing an expected modification of their nonstoichiometry. All of these effects are of great importance when using our flower-like ZnO nanostructures in gas sensor devices for detecting oxidizing gases because surface contamination leads to an undesired barrier for toxic gas adsorption, and it can additionally be responsible for the uncontrolled sensor aging effect.

10.
HardwareX ; 11: e00279, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35509923

RESUMO

In this work we have designed and developed a low cost and simple instrument to purify air in an enclosure. The device sucks up the air in the enclosed area, kills the microorganisms and let clean air flow out. A combination of an ultra violet light and an electric field are used to kill the microorganisms in air. Three electric field chambers (radial, parallel, perpendicular) are used to clean air more effectively. Stainless steel meshes were used to increase the density of the electric fields. The outer covers were made with plastic and wood. The instrument was tested against an evaporated bacterial solution (Staphylococcus aureus) by letting it flow through the instrument and measuring the bacterial concentration of the output air. The results showed the instrument is extremely effective even when tested against high bacterial concentrations. The instrument is extremely useful to clean air in closed rooms such as in hospitals, schools, etc. and prevent the spread of airborne diseases.

11.
Sensors (Basel) ; 22(4)2022 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-35214257

RESUMO

This review focuses on the synthesis of p-type metal-oxide (p-type MOX) semiconductor thin films, such as CuO, NiO, Co3O4, and Cr2O3, used for chemical-sensing applications. P-type MOX thin films exhibit several advantages over n-type MOX, including a higher catalytic effect, low humidity dependence, and improved recovery speed. However, the sensing performance of CuO, NiO, Co3O4, and Cr2O3 thin films is strongly related to the intrinsic physicochemical properties of the material and the thickness of these MOX thin films. The latter is heavily dependent on synthesis techniques. Many techniques used for growing p-MOX thin films are reviewed herein. Physical vapor-deposition techniques (PVD), such as magnetron sputtering, thermal evaporation, thermal oxidation, and molecular-beam epitaxial (MBE) growth were investigated, along with chemical vapor deposition (CVD). Liquid-phase routes, including sol-gel-assisted dip-and-spin coating, spray pyrolysis, and electrodeposition, are also discussed. A review of each technique, as well as factors that affect the physicochemical properties of p-type MOX thin films, such as morphology, crystallinity, defects, and grain size, is presented. The sensing mechanism describing the surface reaction of gases with MOX is also discussed. The sensing characteristics of CuO, NiO, Co3O4, and Cr2O3 thin films, including their response, sensor kinetics, stability, selectivity, and repeatability are reviewed. Different chemical compounds, including reducing gases (such as volatile organic compounds (VOCs), H2, and NH3) and oxidizing gases, such as CO2, NO2, and O3, were analyzed. Bulk doping, surface decoration, and heterostructures are some of the strategies for improving the sensing capabilities of the suggested pristine p-type MOX thin films. Future trends to overcome the challenges of p-type MOX thin-film chemical sensors are also presented.

12.
ACS Appl Mater Interfaces ; 13(27): 32363-32380, 2021 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-34223766

RESUMO

TiO2/Cu2O/CuO multi-nanolayers highly sensitive toward volatile organic compounds (VOCs) and H2 have been grown in various thicknesses by a cost-effective and reproducible combined spray-sputtering-annealing approach. The ultrathin TiO2 films were deposited by spray pyrolysis on top of sputtered-annealed Cu2O/CuO nanolayers to enhance their gas sensing performance and improve their protection against corrosion at high operating temperatures. The prepared heterostructures were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and ultraviolet visible (UV-vis) and micro-Raman spectroscopy. The gas sensing properties were measured at several operating temperatures, where the nanolayered sensors with oxide thicknesses between 20 and 30 nm (Cu2O/CuO nanolayers) exhibited a high response and an excellent selectivity to ethanol vapor after thermal annealing the samples at 420 °C. The results obtained at an operating temperature of 350 °C demonstrate that the CuO/Cu2O nanolayers with thicknesses between 20 and 30 nm are sensitive mainly to ethanol vapor, with a response of ∼150. The response changes from ethanol vapors to hydrogen gas as the thickness of the CuO/Cu2O nanolayers changes from 50 to 20 nm. Density functional theory-based calculations were carried out for the geometries of the CuO(1̅11)/Cu2O(111) and TiO2(111)/CuO(1̅11)/Cu2O(111) heterostructures and their sensing mechanism toward alcohols of different chain lengths and molecular hydrogen. The reconstructed hexagonal Cu2O(111) surface and the reconstructed monoclinic CuO(1̅11) and TiO2(111) facets, all of which terminate in an O layer, lead to the lowest surface energies for each isolated material. We studied the formation of the binary and ternary heteroepitaxial interfaces for the surface planes with the best-matching lattices. Despite the impact of the Cu2O(111) substrate in lowering the atomic charges of the CuO(1̅11) adlayer in the binary sensor, we found that it is the different surface structures of the CuO(1̅11)/Cu2O(111) and TiO2(111)/CuO(1̅11)/Cu2O(111) devices that are fundamental in driving the change in the sensitivity response observed experimentally. The experimental data, supported by the computational results, are important in understanding the use of the multi-nanolayered films tested in this work as reliable, accurate, and selective sensor structures for the tracking of gases at low concentrations.

13.
ACS Appl Mater Interfaces ; 13(3): 4316-4329, 2021 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-33438989

RESUMO

We report a facile and robust room-temperature NO2 sensor fabricated using bi- and multi-layered 2H variant of tungsten di-selenide (2H-WSe2) nanosheets, exhibiting high sensing characteristics. A simple liquid-assisted exfoliation of 2H-WSe2, prepared using ambient pressure chemical vapor deposition, allows smooth integration of these nanosheets on transducers. Three sensor batches are fabricated by modulating the total number of layers (L) obtained from the total number of droplets from a homogeneous 2H-WSe2 dispersion, such as ∼2L, ∼5-6L, and ∼13-17L, respectively. The gas-sensing attributes of 2H-WSe2 nanosheets are investigated thoroughly. Room temperature (RT) experiments show that these devices are specifically tailored for NO2 detection. 2L WSe2 nanosheets deliver the best rapid response compared to ∼5-6L or ∼13-17L. The response of 2L WSe2 at RT is 250, 328, and 361% to 2, 4, and 6 ppm NO2, respectively. The sensor showed nearly the same response toward low NO2 concentration even after 9 months of testing, confirming its remarkable long-term stability. A selectivity study, performed at three working temperatures (RT, 100, and 150 °C), shows high selectivity at 150 and 100 °C. Full selectivity toward NO2 at RT confirms that 2H-WSe2 nanosheet-based sensors are ideal candidates for NO2 gas detection.

14.
Nanomaterials (Basel) ; 10(10)2020 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-33003427

RESUMO

Recently, one-dimensional (1D) nanostructures have attracted the scientific community attention as sensitive materials for conductometric chemical sensors. However, finding facile and low-cost techniques for their production, controlling the morphology and the aspect ratio of these nanostructures is still challenging. In this study, we report the vapor-liquid-solid (VLS) synthesis of one dimensional (1D) zinc oxide (ZnO) nanorods (NRs) and nanowires (NWs) by using different metal catalysts and their impact on the performances of conductometric chemical sensors. In VLS mechanism, catalysts are of great interest due to their role in the nucleation and the crystallization of 1D nanostructures. Here, Au, Pt, Ag and Cu nanoparticles (NPs) were used to grow 1D ZnO. Depending on catalyst nature, different morphology, geometry, size and nanowires/nanorods abundance were established. The mechanism leading to the VLS growth of 1D ZnO nanostructures and the transition from nanorods to nanowires have been interpreted. The formation of ZnO crystals exhibiting a hexagonal crystal structure was confirmed by X-ray diffraction (XRD) and ZnO composition was identified using transmission electron microscopy (TEM) mapping. The chemical sensing characteristics showed that 1D ZnO has good and fast response, good stability and selectivity. ZnO (Au) showed the best performances towards hydrogen (H2). At the optimal working temperature of 350 °C, the measured response towards 500 ppm of H2 was 300 for ZnO NWs and 50 for ZnO NRs. Moreover, a good selectivity to hydrogen was demonstrated over CO, acetone and ethanol.

15.
Materials (Basel) ; 13(13)2020 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-32635229

RESUMO

For the last two decades, titanium dioxide (TiO2) has received wide attention in several areas such as in medicine, sensor technology and solar cell industries. TiO2­based gas sensors have attracted significant attention in past decades due to their excellent physical/chemical properties, low cost and high abundance on Earth. In recent years, more and more efforts have been invested for the further improvement in sensing properties of TiO2 by implementing new strategies such as growth of TiO2 in different morphologies. Indeed, in the last five to seven years, 1D nanostructures and heterostructures of TiO2 have been synthesized using different growth techniques and integrated in chemical/gas sensing. Thus, in this review article, we briefly summarize the most important contributions by different researchers within the last five to seven years in fabrication of 1D nanostructures of TiO2­based chemical/gas sensors and the different strategies applied for the improvements of their performances. Moreover, the crystal structure of TiO2, different fabrication techniques used for the growth of TiO2­based 1D nanostructures, their chemical sensing mechanism and sensing performances towards reducing and oxidizing gases have been discussed in detail.

16.
Nanomaterials (Basel) ; 10(5)2020 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-32413953

RESUMO

Herein, we report the catalyst assisted growth of TiO2 one-dimensional (1D) nanowires (NWs) on alumina substrates by the thermal oxidation technique. RF magnetron sputtering was used to deposit a thin Ti metallic layer on the alumina substrate, followed by an Au catalytic layer on the Ti metallic one. Thermal oxidation was carried out in an oxygen deficient environment. The optimal thermal growth temperature was 700 °C, in a mixture environment composed by Ar and O2. As a comparison, Ti films were also oxidized without the presence of the Au catalyst. However, without the Au catalyst, no growth of nanowires was observed. Furthermore, the effect of the oxidation temperature and the film thickness were also investigated. SEM, TEM, and EDX studies demonstrated the presence of Au nanoparticles on top of the NWs, indicating that the Au catalyst drove the growth process. Raman spectroscopy revealed the Rutile crystalline phase of TiO2 NWs. Gas testing measurements were carried out in the presence of a relative humidity of 40%, showing a reversible response to ethanol and H2 at various concentrations. Thanks to the moderate temperature and the easiness of the process, the presented synthesis technique is suitable to grow TiO2 NWs for many different applications.

17.
Biosensors (Basel) ; 10(5)2020 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-32370241

RESUMO

Parmigiano Reggiano cheese is one of the most appreciated Italian foods on account of its high nutrient content and taste. Due to its high cost, these characteristics make this product subject to counterfeiting in different forms. In this study, an approach based on an array of gas sensors has been employed to assess if it was possible to distinguish different samples based on their aroma. Samples were characterized in terms of rind percentage, seasoning, and rind working process. From the responses of the sensors, five features were extracted and the capability of these parameters to recognize target classes was tested with statistical analysis. Hence, the performance of the sensors' array was quantified using artificial neural networks. To simplify the problem, a hierarchical approach has been used: three steps of classification were performed, and in each step one parameter of the grated cheese was identified (firstly, seasoning; secondly, rind working process; finally, rind percentage). The accuracies ranged from 88.24% to 100%.


Assuntos
Queijo/análise , Cobre/química , Nariz Eletrônico , Redes Neurais de Computação , Compostos de Estanho/química , Compostos Orgânicos Voláteis/análise , Semicondutores
18.
Langmuir ; 36(23): 6326-6344, 2020 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-32453573

RESUMO

Day by day, the demand for portable, low cost, and efficient chemical/gas-sensing devices is increasing due to worldwide industrial growth for various purposes such as environmental monitoring and health care. To fulfill this demand, nanostructured metal oxides can be used as active materials for chemical/gas sensors due to their high crystallinity, remarkable physical/chemical properties, ease of synthesis, and low cost. In particular, (1D) one-dimensional metal oxides nanostructures, such as nanowires, exhibit a fast response, selectivity, and stability due to their high surface-to-volume ratio, well-defined crystal orientations, controlled unidirectional electrical properties, and self-heating phenomenon. Moreover, with the availability of large-scale production methods for nanowire growth such as thermal oxidation and evaporation-condensation growth, the development of highly efficient, low cost, portable, and stable chemical sensing devices is possible. In the last two decades, tremendous advances have been achieved in 1D nanostructured gas sensors ever since the pioneering work by Comini on the development of a SnO2 nanobelt for gas sensor applications in 2002, which is one such example from which many researchers began to explore the field of 1D-nanostructure-based chemical/gas sensors. The Sensor Laboratory (University of Brescia) has made major contributions to the field of metal oxide nanowire chemical/gas-sensing devices. Over the years, different metal oxides such as SnO2, ZnO, WO3, NiO, CuO, and their heterostructures have been grown for their nanowire morphology and successfully integrated into chemoresistive gas-sensing devices. Hence in this invited feature article, Sensor Laboratory research on the synthesis of metal oxide nanowires and novel heterostructures and their characterization and gas-sensing performance during exposure to different gas analytes has been presented. Moreover, some new strategies such as branched-like nanowire heterostructures and core-shell nanowire structures adopted to enhance the performance of nanowire-based chemical sensor are presented in detail.

19.
Nanotechnology ; 31(46): 465705, 2020 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-32344389

RESUMO

Novel insight on the local surface properties of ZnO nanowires (NW) deposited by the evaporation-condensation method on Ag-covered Si substrates is proposed, based on the results of comparative studies by using the scanning electron microscopy (SEM), x-ray photoemission spectroscopy (XPS) and thermal desorption spectroscopy (TDS) methods, respectively. SEM studies showed that ZnO nanowires (nanoribbons) are mostly isolated and irregular, having the average length µm and the average at the level of tens nm, respectively. Our XPS studies confirmed their evident surface non-stoichiometry, combined with strong C surface contaminations, which was related to the existence of oxygen-deficient regions. Additionally, TDS studies showed that undesired surface contaminations (including C species and hydroxyl groups) on the surface of ZnO NWs can be removed almost completely, leading to an increase of the final non-stoichiometry. Both effects are of great importance when using ZnO NWs for the detection of oxidizing gases, because the undesired C contaminations (including C-OH species) play the role of undesired barriers for the gas adsorption, especially at the low working temperature, additionally affecting the uncontrolled sensor ageing effect.

20.
Sensors (Basel) ; 20(7)2020 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-32260084

RESUMO

Food poisoning is still the first cause of hospitalization worldwide and the most common microbial agent, Campylobacter jejuni, is the most commonly reported gastrointestinal disease in humans in the EU (European Union) as is reported by the European Union One Health 2018 Zoonoses Report styled by the EFSA (European Food Safety Authority) and ECDC (European Center for Disease Prevention and Control). One of the vehicles of transmission of this disease is milk. Nanostructured MOS (Metal Oxide Semiconductor) sensors have extensively demonstrated their ability to reveal the presence and follow the development of microbial species. The main objective of this work was to find a set up for the detection and development follow up of C. jejuni in milk samples. The work was structured in two different studies, the first one was a feasibility survey and the second one was to follow up the development of the bacteria inside milk samples. The obtained results of the first study demonstrate the ability of the sensor array to differentiate the contaminated samples from the control ones. Thanks to the second study, it has been possible to find the limit of microbial safety of the contaminated milk samples.


Assuntos
Campylobacter jejuni/isolamento & purificação , Microbiologia de Alimentos/métodos , Leite/microbiologia , Nanoestruturas/química , Semicondutores , Animais , Microbiologia de Alimentos/instrumentação , Limite de Detecção , Metais/química , Óxidos/química , Análise de Componente Principal
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