Synthesis and Applications of Hematite α-Fe2O3 : a Review

This article reviewed the hematite α-Fe2O3, which focuses on its material properties, nanostructures, synthesis techniques, and its numerous applications. Researchers prepared the hematite nanostructure using the synthesis methods, such as hydrothermal, and, further, enhanced it by improving the techniques to accommodate the best performance for specific applications and to explore new applications of hematite in humidity sensing

Design of Polymeric Materials: Novel Functionalized Polymers for Enhanced Oil Recovery & Gas Sorption Applications

As material requirements for particular applications become more specific and strict, using a targeted approach to design polymeric materials becomes a necessity. Following a general design framework prevents researchers from using trial-and-error approaches or shoehorning materials into applications for which they are non-optimal. To obtain polymer products with desirable properties (both fundamental characteristics and for a specific application), one must always begin with an awareness of existing materials and methods. This background knowledge informs preliminary design of experiments, which in turn provides insight for additional experiments to synthesize (and characterize) optimally designed materials. A general framework for the design of polymeric materials has been developed in this thesis, and the specific aspects are grounded in two independent case studies. These two distinct (yet related) case studies have been selected to demonstrate that the framework is not limited to a particular industry or application, nor to a specific type of polymeric material. In Case Study #1, water-soluble terpolymers (and related polymerization kinetics) are investigated for use in polymer flooding during enhanced oil recovery (EOR). In contrast, Case Study #2 examines a variety of polymeric materials that have the potential to be used for acetone gas sensing (for diabetic applications). Both case studies use the same general design framework in a sequential, iterative manner to move towards optimally designed materials for each target application. Polymers are already used in EOR; the most common synthetic material used for polymer flooding is partially hydrolyzed polyacrylamide (HPAM). In many cases, polymers for EOR are exposed to high temperatures, high shear rates, and high concentrations of salt in the reservoir. The shortcomings of HPAM include poor thermal stability, poor shear stability, and poor brine compatibility. As a result, HPAM can degrade during EOR, thus lowering molecular weight averages and reducing oil recovery efficiency. Therefore, the target for Case Study #1 is to build on existing knowledge to improve acrylamide-based polymers for enhanced oil recovery. Important characteristics of polymeric materials for EOR include good viscosity modification (achieved through water solubility, high molecular weight averages and the incorporation of carboxylate ions), reasonable chemical stability (achieved by incorporating high levels of amide groups into the polymer), and a good distribution of ions along the polymer backbone (that is, a targeted sequence length distribution). HPAM (a copolymer of acrylamide (AAm) and acrylic acid (AAc)) meets these requirements, but the thermal and shear stability concerns described above have not been considered. Therefore, a third comonomer, 2-acrylamido-2-methylpropane sulfonic acid (AMPS) can be added to the polymer formulation, as the bulky sulfonic acid groups are expected to improve thermal stability and protect the main chain from shear degradation. When a multi-component polymer like AMPS/AAm/AAc is being considered for any application, understanding and manipulating ternary reactivity ratios (which are related to both the cumulative terpolymer composition and the sequence length distribution) is essential. Therefore, once the AMPS/AAm/AAc terpolymer is selected for enhanced oil recovery, relationships between (experimental) synthesis conditions and polymer properties can be researched, verified and exploited. First, a comprehensive study (involving both an examination of the literature and a series of designed screening experiments) is performed to establish the effect of synthesis conditions (like pH, ionic strength, monomer concentration and feed composition) on the terpolymerization kinetics and product terpolymer properties. Deliberate design of screening experiments (designed considering the ‘rule-of-thumb’ for ternary reactivity ratio estimation) makes it possible to establish that the key factors within the experimental range studied are ionic strength (which affects cumulative terpolymer composition and sequence length distribution), monomer concentration (which affects molecular weight averages) and feed composition (which, of course, impacts the cumulative composition of the terpolymer product). Given the results of the screening experiments, two optimal terpolymers of AMPS/AAm/AAc are designed, synthesized, characterized and tested. The designed terpolymers have polymer properties that agree with model predictions, but (more importantly) show excellent EOR performance. In a series of sand-pack flooding experiments (simulating enhanced oil recovery in a reservoir), the designed terpolymers perform much better than reference materials. The newly synthesized terpolymers achieve an overall oil recovery of (on average) 78.0% for one optimal material and 88.7% for the second optimal material. In contrast, the commercially available reference material allows for an overall oil recovery of 59.8%. Therefore, the design framework has allowed us to converge upon optimal terpolymer formulations with excellent EOR application performance. The same general framework is applied to inform the design, synthesis and characterization of polymeric sensing materials for acetone detection. Highly concentrated breath acetone measurements are correlated with high levels of blood glucose, so detecting acetone gas could be useful in a non-invasive breath sensor for diabetic applications. In this case, key design considerations (to inform potential backbone selection) include operational temperature (and the glass transition temperature of candidate polymeric materials), surface morphology, and the chemical behaviour of the target analyte. Solubility parameters, for example, can be used to provide insight about the compatibility of the target analyte (acetone) and potential sensing materials. For polymeric sensing materials, the most important characteristics are sensitivity and selectivity. Sensitivity studies provide information about how well the target analyte sorbs onto the polymeric material (that is, whether there is a strong affinity towards acetone), and selectivity measures how well the target analyte sorbs in the presence of other interferent gases. After preliminary screening (based on a detailed literature review), three polymer backbones and three metal oxide dopants are selected as promising candidates for acetone sensing. Polyaniline, polypyrrole and poly(methyl methacrylate) are doped with varying quantities of SnO2, WO3 and ZnO nanoparticles. In a series of screening experiments, 30 materials are synthesized and evaluated in terms of acetone sorption (using a uniquely designed gas sensing set-up and a highly specialized gas chromatograph). The most promising materials are evaluated further, both in terms of surface morphology and in terms of selectivity (measurement of acetone sorption in the presence of acetaldehyde, ethanol and benzene). In general, pure polyaniline and pure polypyrrole show the most promise of the materials studied; poly(methyl methacrylate) does not sorb acetone at all, and metal oxide doping (using these dopants and up to 20 wt% doping) does not improve application performance. In the customized experiments, adjustments are made to polymer synthesis steps in an attempt to improve the properties of the polymeric sensing materials (especially in terms of selectivity). One customization option that is investigated is the acid-doping of polyaniline (synthesis in an aqueous oxalic acid solution) to change the backbone charge, thereby taking advantage of the polarity of acetone. Another customization option involves the synthesis of copolymers of polyaniline and polypyrrole (both in water and in oxalic acid solution) by combining the two monomers in a single formulation. Product characterization shows some improvement over the original (screening) materials, but further improvement is still possible. Therefore, this target application can continue to benefit from sequential, iterative steps towards optimality. Ultimately, both case studies overlap when the general design framework is considered. An awareness of existing materials and methods can inform statistically designed preliminary experiments, which eventually lead to optimally designed materials for specific (targeted) applications. The contents of this thesis (especially the two major case studies) and several related publications demonstrate that this framework is useful and relevant for design of polymeric materials. The effectiveness is visible throughout the research process, but it is especially evident in the application performance of the final (optimal) product, along with the flexibility of the design approach with respect to expanding into new areas, at the same time by minimizing time and effort

Synthesis and gas sensing properties of inorganic semiconducting, p-n heterojunction nanomaterials

En aquesta tesis utilitzant principalment Aerosol Assited Chemical Vapor Deposition, AACVD, com a metodologia de síntesis d'òxid de tungstè nanoestructurat s'han fabricat diferents sensors de gasos. Per tal d'estudiar la millora en la selectivitat i la sensibilitat dels sensors de gasos basats en òxid de tungstè aquest s'han decorat, via AACVD, amb nanopartícules d'altres òxids metàl·lics per a crear heterojuncions per tal d'obtenir un increment en la sensibilitat electrònica, les propietats químiques del material o bé ambdues. En particular, s'han treballat en diferents sensors de nanofils d'òxid de tungstè decorats amb nanopartícules d'òxid de níquel, òxid de cobalt i òxid d'iridi resultant en sensors amb un gran increment de resposta i selectivitat cap al sulfur d'hidrogen, per a l'amoníac i per a l'òxid de nitrogen respectivament a concentracions traça. A més a més, s'han estudiat els mecanismes de reacció que tenen lloc entre les espècies d'oxigen adsorbides a la superfície del sensor quan interactua amb un gas. I també s'ha treballat en intentar controlar el potencial de superfície de les capes nanoestructurades per tal de controlar la deriva en la senyal al llarg del temps, quan el sensor està operant, a través d'un control de temperatura.En esta tesis utilizando principalmente Aerosol Assited Chemical Vapor Deposition, AACVD, como metodología de síntesis de óxido de tungsteno nanoestructurado se han fabricado diferentes sensores de gases. Para estudiar la mejora en la selectividad y la sensibilidad de los sensores de gases basados en óxido de tungsteno estos se han decorado, vía AACVD, con nanopartículas de otros óxidos metálicos para crear heterouniones para obtener un incremento en la sensibilidad electrónica, las propiedades químicas del material o bien ambas. En particular, se han trabajado en diferentes sensores de nanohilos de óxido de tungsteno decorados con nanopartículas de óxido de níquel, óxido de cobalto y óxido de iridio resultante en sensores con un gran incremento de respuesta y selectividad hacia el sulfuro de hidrógeno, para el amoníaco y para el óxido de nitrógeno respectivamente a concentraciones traza. Además, se han estudiado los mecanismos de reacción que tienen lugar entre las especies de oxígeno adsorbidas en la superficie del sensor cuando interactúa con un gas. Y también se ha trabajado en intentar controlar el potencial de superficie de las capas nanoestructuradas para controlar la deriva en la señal a lo largo del tiempo, cuando el sensor está trabajando, a través de un control de temperatura.In this thesis, using mainly Aerosol Assited Chemical Vapor Deposition, AACVD, as a synthesis methodology for nanostructured tungsten oxide, different gas sensors have been manufactured. To study the improvement in the selectivity and sensitivity of gas sensors based on tungsten oxide, they have been decorated, via AACVD, with nanoparticles of other metal oxides to create heterojunctions to obtain an increase in electronic sensitivity, in the chemical properties of the material or at the same time in both. Particularly, we have worked on different tungsten oxide nanowire sensors decorated with nanoparticles of nickel oxide, cobalt oxide and iridium oxide resulting in sensors with a large increase in response and selectivity towards hydrogen sulfide, for ammonia. and for nitrogen oxide respectively at trace concentrations. In addition, the reaction mechanisms that take place between oxygen species adsorbed on the sensor surface when it interacts with a gas have been also studied. Furthermore, efforts have been put on trying to control the surface potential of the nanostructured layers to control the drift in the signal over time, when operating the sensors, through temperature control

Zinc oxide nanostructures with carbon nanotube and gold additives for co gas sensing application

Abstract: Zinc oxide (ZnO) nanostructures were synthesised for gas sensing application. In an attempt to improve the surface area and the electrical conductivity of the ZnO, nanomaterials such as the carbon nanotubes (CNTs) and gold nanoparticles (AuNPs) were used separately to produce CNTs/ZnO and Au/ZnO nanocomposites, respectively. The addition of these nanomaterials onto the ZnO nanostructures significantly improved the gas sensing properties such as the sensitivity and response time. Synthesis of gold nanoparticles was successfully achieved via gold salt (HAuCl4.3H2O) reduction using the Turkevich method. Citrate molecules were used as the stabiliser and to systematically control the sizes of the AuNPs. The sizes of AuNPs were found to increase from 14 nm to 40 nm when the concentration of citrate ions was reduced from 1 mM to 0.3 mM. The size distribution of AuNPs was relatively wider as the particle size increased. The synthesized AuNPs were stable for over a period of 4 weeks. Carbon nanotubes synthesis was achieved using chemical vapour deposition (CVD) method using acetylene gas as the carbon source and ferrocene as the catalyst. An increase in the flowrate of the precursor gas (acetylene) yielded an increase in amorphous carbon, which was attached to the walls of the carbon nanotubes. The optimum flowrate of acetylene was found to be 150 m3/min that yielded CNTs with an average diameter of 95 nm and a relatively narrow size distribution. The hydrothermal chemical precipitation method was used to synthesise ZnO nanostructures. Zinc sulphate (ZnSO4) and sodium hydroxide (NaOH) were used as a metal precursor and reducing agent, respectively. The NaOH concentration of 0.3 M yielded ZnO nanosheets with relatively the highest surface area of 102 m2/g. Gas sensing analysis was conducted using carbon monoxide (CO) gas at 250°C. The sensitivity and response time were calculated to be 9.8% and 114 seconds, respectively, at a CO concentration of 200 ppm. The composites CNTs/ZnO and Au/ZnO were prepared, separately. The average surface area of the Au/ZnO composite was 131 m2/g and that of CNTs/ZnO composite was 153 m2/g. The CNTs/ZnO composite showed an optimum sensitivity of 9.9% and the response time of 49 seconds when exposed to 200 ppm of CO gas at 250°C.M.Tech. (Chemical Engineering

Smart and Safe packaging

In line with the latest innovations in the packaging field, this joint project aims at implementing new and innovative micro- and nanoparticles for the development of active and intelligent packaging solutions dedicated to food and medical packaging applications. More specifically, the project combines two major developments which both falls within the scope of active and intelligent packaging. In this work, a specific focus was given to the development of an antibacterial packaging solution and to the development of smart gas sensors. The antibacterial strategy developed was based on the combination of two active materials - silver nanowires and cellulose nanofibrils - to prepare antibacterial surfaces. The formulation as an ink and the deposition processing has been deeply studied for different surface deposition processes that include coatings or screen-printing. Results showed surfaces that display strong antibacterial activity both against Gram-positive and Gram-negative bacteria, but also interesting properties for active packaging applications such as a highly retained transparency or enhanced barrier properties. Regarding the second strategy, gas sensors have been prepared using a combination of Copper benzene-1,3,5-tricarboxylate Metal Organic Framework and carbon-graphene materials, deposited on flexible screen-printed electrodes. The easy-to-produce and optimized sensors exhibit good performances toward ammonia and toward humidity sensing, proving the versatility and the great potential of such solution to be adapted for different target applications. The results of this project lead to innovative solutions that can meet the challenges raised by the packaging industry

Room temperature ammonia gas sensor based on p-type-like V2O5 nanosheets towards food spoilage monitoring

Gas sensors play an important role in many areas of human life, including the monitoring of production processes, occupational safety, food quality assessment, and air pollution monitoring. Therefore, the need for gas sensors to monitor hazardous gases, such as ammonia, at low operating temperatures has become increasingly important in many fields. Sensitivity, selectivity, low cost, Citation: Van Duy, L.; Nguyet, T.T.; Le, D.T.T.; Van Duy, N.; Nguyen, H.; Biasioli, F.; Tonezzer, M.; Di Natale, C.; Hoa, N.D. Room Temperature AmmoniaGasSensor Based on p-Type-like V2O5 Nanosheets towards Food Spoilage Monitoring. Nanomaterials 2023, 13, 146. https:// doi.org/10.3390/nano13010146 Academic Editors: Sergei Kulinich and Li Hai Received: 17 November 2022 Revised: 23 December 2022 Accepted: 24 December 2022 Published: 28 December 2022 Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). and ease of production are crucial characteristics for creating a capillary network of sensors for the protection of the environment and human health. However, developing gas sensors that are not only efficient but also small and inexpensive and therefore integrable into everyday life is a difficult challenge. In this paper, we report on a resistive sensor for ammonia detection based on thin V2O5 nanosheets operating at room temperature. The small thickness and porosity of the V2O5 nanosheets give the sensors good performance for sensing ammonia at room temperature (RT), with a relative change of resistance of 9.4% to 5 ppm ammonia (NH3) and an estimated detection limit of 0.4 ppm. The sensor is selective with respect to the seven interferents tested; it is repeatable and stable over the long term (four months). Although V2O5 is generally an n-type semiconductor, in this case the nanosheets show a p-type semiconductor behavior, and thus a possible sensing mechanism is proposed. The device’s performance, along with its size, low cost, and low power consumption, makes it a good candidate for monitoring freshness and spoilage along the food supply chai

Advanced Materials and Nanotechnology for Sustainable Energy and Environmental Applications

Materials play a very important role in the technological development of a society. As a consequence, the continuous demand for more advanced and sophisticated applications is closely linked to the availability of innovative materials. Although aspects related to the study, the synthesis and the applications of materials are of interdisciplinary interest, in the last few years, great attention has been paid to the development of advanced materials for environmental preservation and sustainable energy technologies, such as gaseous pollutant monitoring, waste water treatment, catalysis, carbon dioxide valorization, green fuel production, energy saving, water adsorption and clean technologies. This Special Issue aims at covering the current design, synthesis and characterization of innovative advanced materials, as well as novel nanotechnologies able to offer promising solutions to the these pressing themes

Innovative ozone sensors for environmental monitoring working at low temperature

L'abstract è presente nell'allegato / the abstract is in the attachmen

Chapter Hydrothermal Synthesis of Zinc Tin Oxide Nanostructures for Photocatalysis, Energy Harvesting and Electronics

The massification of Internet of Things (IoT) and Smart Surfaces has increased the demand for nanomaterials excelling at specific properties required for their target application, but also offering multifunctionality, conformal integration in multiple surfaces and sustainability, in line with the European Green Deal goals. Metal oxides have been key materials for this end, finding applications from flexible electronics to photocatalysis and energy harvesting, with multicomponent materials as zinc tin oxide (ZTO) emerging as some of the most promising possibilities. This chapter is dedicated to the hydrothermal synthesis of ZTO nanostructures, expanding the already wide potential of ZnO. A literature review on the latest progress on the synthesis of a multitude of ZTO nanostructures is provided (e.g., nanowires, nanoparticles, nanosheets), emphasizing the relevance of advanced nanoscale techniques for proper characterization of such materials. The multifunctionality of ZTO will also be covered, with special attention being given to their potential for photocatalysis, electronic devices and energy harvesters