Academic literature on the topic 'Shell nanoparticles for hydrogen sensing application'

Developing a simple and convenient approach for glucose sensing is crucially important in disease diagnosis and health monitoring. In this work, a glucose sensor based on plasmonic nanostructures was developed using gold–silver core–shell nanoparticles as the sensing platform. Based on the oxidative etching of the silver shell, the concentration of hydrogen peroxide and glucose could be determined quantitatively via the spectral change. This spectral change could also be observed with the naked eye or with a phone camera, realizing colorimetric sensing. To demonstrate this, glucose solutions at different concentrations were quantitatively detected in a wide concentration range of 0–1.0 mM using this colorimetric sensor. Importantly, shell thickness could significantly affect the sensitivity of our colorimetric sensor. This work provides a deeper understanding of the plasmonic sensing of glucose, which will help to realize its real applications. Based on this strategy, the non-invasive sensing of metabolites may be realized for disease diagnosis and health monitoring.

Solvent-free aerosol jet printing has been investigated for fabricating metallic and semiconductor (gas-sensitive) microstructures based on copper nanoparticles on alumina, borosilicate glass, and silicon substrates. The synthesis of nanoparticles was carried out using a spark discharge directly in the printing process without the stage of preparing nano-ink. Printed lines with a width of 100–150 µm and a height of 5–7 µm were formed from submicron agglomerates consisting of primary nanoparticles 10.8 ± 4.9 nm in size with an amorphous oxide shell. The electrical resistivity, surface morphology, and shrinkage of printed lines were investigated depending on the reduction sintering temperature. Sintering of copper oxides of nanoparticles began at a temperature of 450 °C in a hydrogen atmosphere with shrinkage at the level of 45–60%. Moreover, aerosol heat treatment was used to obtain highly conductive lines by increasing the packing density of deposited nanoparticles, providing in-situ transformation of submicron agglomerates into spherical nanoparticles with a size of 20–50 nm. Copper lines of spherical nanoparticles demonstrated excellent resistivity at 5 μΩ·cm, about three times higher than that of bulk copper. In turn, semiconductor microstructures based on unsintered agglomerates of oxidized copper have a fairly high sensitivity to NH3 and CO. Values of response of the sensor based on non-sintered oxidized copper nanoparticles to ammonia and carbon monoxide concentration of 40 ppm were about 20% and 80%, respectively.

The detection of hydrogen peroxide and the control of its concentration are important tasks in the biological and chemical sciences. In this paper, we developed a simple and quantitative method for the non-enzymatic detection of H2O2 based on the selective etching of Au@Ag nanorods with embedded Raman active molecules. The transfer of electrons between silver atoms and hydrogen peroxide enhances the oxidation reaction, and the Ag shell around the Au nanorod gradually dissolves. This leads to a change in the color of the nanoparticle colloid, a shift in LSPR, and a decrease in the SERS response from molecules embedded between the Au core and Ag shell. In our study, we compared the sensitivity of these readouts for nanoparticles with different Ag shell morphology. We found that triangle core–shell nanoparticles exhibited the highest sensitivity, with a detection limit of 10−4 M, and the SERS detection range of 1 × 10−4 to 2 × 10−2 M. In addition, a colorimetric strategy was applied to fabricate a simple indicator paper sensor for fast detection of hydrogen peroxide in liquids. In this case, the concentration of hydrogen peroxide was qualitatively determined by the change in the color of the nanoparticles deposited on the nitrocellulose membrane.

In recent years, several devices have been developed for the direct measurement of hydrogen peroxide (H2O2), a key compound in biological processes and an important chemical reagent in industrial applications. Classical enzymatic biosensors for H2O2 have been recently outclassed by electrochemical sensors that take advantage of material properties in the nano range. Electrodes with metal nanoparticles (NPs) such as Pt, Au, Pd and Ag have been widely used, often in combination with organic and inorganic molecules to improve the sensing capabilities. In this review, we present an overview of nanomaterials, molecules, polymers, and transduction methods used in the optimization of electrochemical sensors for H2O2 sensing. The different devices are compared on the basis of the sensitivity values, the limit of detection (LOD) and the linear range of application reported in the literature. The review aims to provide an overview of the advantages associated with different nanostructures to assess which one best suits a target application.

ZnO/ZnS nanocomposite-based nanostructures exhibit dual light and gas sensing capabilities. To further boost the light/dual sensing properties, gold nanoparticles (Au NPs) were incorporated into the core-shell structures. Multiple material characterizations revealed that Au NPs were successfully well spread and decorated on ZnO/ZnS nanostructures. Furthermore, our findings show that the addition of Au NPs could enhance both 365 nm UV light sensing and hydrogen gas sensing in terms of light/gas sensitivity and light/gas response time. We postulate that the optimization of gas/light dual sensing capability may result from the induced electric field and inhabitation of electron-hole recombination. Owing to their compact size, simple fabrication, and stable response, ZnO/ZnS/Au NPs-based light/gas dual sensors are promising for future extreme environmental monitoring.

The selective enhancement of catalytic activity is a challenging task, as catalyst modification is generally accompanied by both desirable and undesirable properties. For example, in the case of the direct synthesis of hydrogen peroxide, Pt on Pd improves hydrogen conversion, but lowers hydrogen peroxide selectivity, whereas Au on Pd enhances hydrogen peroxide selectivity but decreases hydrogen conversion. Toward an ideal catalytic property, the development of a catalyst that is capable of improving H-H dissociation for increasing H2 conversion, whilst suppressing O-O dissociation for high H2O2 selectivity would be highly beneficial. Pd-core AuPt-bimetallic shell nanoparticles with a nano-sized bimetallic layer composed of Au-rich or Pt-rich content with Pd cubes were readily prepared via the direct seed-mediated growth method. In the Pd-core AuPt-bimetallic shell nanoparticles, Au was predominantly located on the {100} facets of the Pd nanocubes, whereas Pt was deposited on the corners of the Pd nanocubes. The evaluation of Pd-core AuPt-bimetallic shell nanoparticles with varying Au and Pt contents revealed that Pd-core AuPt-bimetallic shell that was composed of 2.5 mol% Au and 5 mol% Pt, in relation to Pd, exhibited the highest H2O2 production rate (914 mmol H2O2 gmetal−1 h−1), due to the improvement of both H2O2 selectivity and H2 conversion.

Philosophiae Doctor - PhD
Transition metal oxides magneli phases present crystallographic shear structure which is of great interest in multiple applications because of their wide range of valence, which is exhibited by the transition metals. The latter affect chemical and physical properties of the oxides. Amongst them we have nanostructures VO2 system of V and O components which are studied including chemical and physical reactions based on non-equilibrium thermodynamics. Due to their structural classes of corundum, rocksalt, wurtzite, spinel, perovskite, rutile, and layer structure, these oxides are generally used as catalytic materials which are prepared by common methods under mild conditions presenting distortion or defects in the case of VO2. Existence of an intermediate phase is proved using an x-ray thermodiffraction experiment providing structural information as the nanoparticles are heated. Potential application as gas sensing device has been the first time obtained due to the high surface to volume ratio, and good crystallinity, purity of the material and presence of suitable nucleating defects sites due to its n-type semiconductor behavior. In addition, annealing effect on nanostructures VO2 nanobelts shows a preferential gas reductant of Ar comparing to the N2 gas. Also, the hysteresis loop shows that there is strong size dependence to annealing treatment on our samples. This is of great interest in the need of obtaining high stable and durable material for Mott insulator transistor and Gas sensor device at room temperature.

Les contextes mondiaux énergétiques, climatiques et économiques actuels évoluent de manières telles que le dihydrogène H2 prend une place de plus en plus importante en tant que combustible et vecteur énergétique. Le dihydrogène est un gaz incolore, inodore et non-toxique donc indécelable par les sens humains, mais il est extrêmement inflammable et explosif. De plus, H2 est caractérisé par un domaine d'explosivité très large, de 4 % à 75 % de H2 dans l'air. L'objet de ce travail de thèse a donc été de préparer des capteurs de sécurité ou de quantification originaux et ayant des performances accrues pour la détection de H2. Les capteurs préparés sont de types résistifs et les métaux sensibles utilisés sont le palladium et le platine. Afin d'améliorer les performances de détection de ces capteurs à dihydrogène, plusieurs morphologies de couches sensibles ont été conçues : des monocouches organisées à 2 dimensions de nanoparticules cœurs-coquilles Pd@Au et Pt@Au formées par la méthode de Langmuir-Blodgett ou immobilisés sur les substrats par un agent de couplage de type silane (mercaptopropyltrimethoxysilane), des dépôts physiques à 2 dimensions et des films de nanoparticules à 3 dimensions. Selon la morphologie de la couche préparée et le type de métal sensible utilisé, divers mécanismes de détection ont été mis en évidence et diverses performances de détection ont été observées (type et amplitude de réponse, gamme de détection, temps de réponse et de retour,...). Les modèles de Fuchs-Sondheimer et Mayadas-Shatzkes d'une part, et un modèle de percolation par la création de chemins de conduction d'autre part, ont permis d'expliquer les variations de résistivité électrique des couches sensibles à base respectivement de platine et de palladium lors de l'exposition à l'hydrogène
Hydrogen takes is foreseen as a generalized fuel and energy carrier. It is a colorless, odorless and non-toxic gas, and therefore it is undetectable by the human senses. Hydrogen has a severe drawback as it is an extremely flammable and explosive gas. Moreover, H2 has a wide explosive range, from 4 to 75 % H2 in air. Therefore, the aim of this PhD work was to develop safety and concentration sensors with enhanced performances. Resistive sensing layers were designed on several morphologies and sensing materials : 2D Langmuir-Blodgett organized monolayers of core-shell Pd@Au or Pt@Au nanoparticles, immobilized Pd@Au monolayer grafted through a self assembled monolayer, evaporated 2D metal films of Pt or Pd, and 3D platinum nanoparticles arrays. According to the sensing layer morphology and sensing metal, numerous sensing mechanisms and performances were demonstrated (response type and amplitude, sensing range, response and recovery times,…). Fuchs-Sondheimer and Mayadas-Shatzkes models on the one hand, and a percolation model on the other, allowed the origin of electrical resistance changes to be pointed out, respectively for platinum and palladium sensing layers

One of the key challenges in nanoparticle synthesis is the quality control on scaling up the operation from bench to plant scale, which is constrained by conventionally adopted batch operation. Translation from batch operation to continuous green synthesis (metal, bi-metallic core-shell, and alloy nanoparticles (NPs)) with low polydispersity index (PDI) could unlock potential applications of metallic nanostructures with a projected market of $40.6 Billion and more by 20271. However, the continuous large-scale production suffers from high polydispersity due to lack of process optimization. We attempt to address such scale-up challenges while using the green synthesis of metallic nanoparticles in this work. The objective of this thesis is to optimize continuous processing of metal nanoparticle synthesis and demonstrate application of metallic nanostructure printed of flexible substrate using inkjet printing technology. The first part of the thesis is motivated by the desire to translate the batch protocol for NPs synthesis (developed in our group earlier)2,3 to a continuous process, and hence increase the affordability of NPs for end users. In this work, nanoparticle colloids are synthesized using different designs of CFRs and steady-state synthesis of nanoparticles is achieved with insignificant variation in particle size. Our results further showed that a balance between engineering and chemical parameters are required to obtain desired particle size distribution (PSD) and morphology during green synthesis of NPs. We improved our reactor design from channel to pool-based to address poor reagent mixing and our results show that the pool reactors could produce uniform particles of sizeii 7.2±1.0 nm with the production rate of 7.1 mg/h. We later moved to a CSTR-based reactor to address variations in the particles’ morphology while changing the flow rate of precursor salt. We found that the CSTR-based reactor can synthesise colloids (Gold, Silver, bimetallic gold-silver core-shell, and gold-silver alloy) at higher (10 times) flow rates and offers a better and affordable route for continuous nanoparticles synthesis within numerous applications in the healthcare and energy sectors. For the first time, to the best of my knowledge, the steady-state synthesis of metal nanoparticles is demonstrated here. After attaining steady state, the particle size distribution does not vary significantly. Investigations are performed to find out the effect of engineering parameters as well as chemical parameters. Particle size distribution is more sensitive to chemical parameters in comparison to engineering parameters. Although, engineering parameters like reactor design, mixing, temperature are important parameters to tailor nanoparticle size in a controlled fashion. Hence, there must be a balance between both to get desired particle size and morphology. In the second part of the thesis, we demonstrated the application of in-situ fabricated silver nanowires on copier paper for non-enzymatic glucose, using a form of inkjet printing technology. The inkjet printing technique is another avenue of fabrication of nanostructure-based flexible substrates that can be scaled using roll to roll printing techniques. Using this technique, we could fabricate, and customize electroadhesive pads based on interdigitated electrode designs with an interelectrode distance of 1 mm on paper. It was observed that, if left as a residue, lateral silver ion migration on applying high voltage leads to lowering of the gaps between electrodes, which resultsiii in increased load capacity. Further electromigration can be controlled by chemical fixing of the sample, i.e., by immersing printed samples in 0.5 M Sodium thiosulphate. The advantage of this process is that different designs of electrodes can be easily fabricated depending upon the required application. The in-situ fabricated silver nanowires incorporated with CuO/Cu2O nanoparticles are used for non-enzymatic glucose detection. Non-enzymatic sensors (4th generation) can replace the enzymatic detectors (3rd generation)4, but major challenge associated with 4th generation detectors is that it requires alkaline pH for reaction to be initiated. Paper based standard electrode (Ag/AgCl); silver nanowire incorporated with CuO/Cu2O nanoparticles (synthesised by wet chemical method) are used as working electrode. Ag nanowires modified with CuO nanoparticles show a linear increment in current with increase in glucose concentration. Glucose detection is performed in the concentration range of normal sugar level in human body in the range from 2.2 – 6.6 mM.iv References: 1 Metal Nanoparticles - Global Market Trajectory & Analytics 2021, (19/09/2021). 2 Sivaraman, S. K., Kumar, S. Santhanam, V. Room-temperature synthesis of gold nanoparticles; Size-control by slow addition. Gold Bulletin 43, 275-286 (2010). 3 Sivaraman, S. K., Kumar, S. Santhanam, V. Monodisperse sub-10nm gold nanoparticles by reversing the order of addition in Turkevich method – The role of chloroauric acid. Journal of Colloid and Interface Science 361, 543-547 (2011). 4 Toghill, K. E. & Compton, R. G. Electrochemical non-enzymatic glucose sensors: a perspective and an evaluation. Int. J. Electrochem. Sci 5, 1246-1301 (2010).

Metal/SnO2 is one of the most popular composite systems because of its application in gas sensors, where the metal in contact with the SnO2 (semiconductor) enhances sensor performance in terms of sensitivity, response, and recovery time. This is because the metal acts as an electron reservoir, improving the depletion layer formation by interfacial charge-transfer process and delaying the electrons-holes recombination process in SnO2. Conventionally, the metal nanoparticles are anchored on the surface of SnO2 to produce hetero-interfaces. Despite effective catalytic activity, this structural drawback exposes metals to other chemical species. Therefore, it is necessary to design new strategies to improve the chemical and thermal stability of metal/SnO2. Recently, nanocomposites with metal core and SnO2 shell became potential candidates due to their chemical and thermal stability and superior material property. In this chapter, fabrication of metal@SnO2 core-shell nanocomposites are discussed as a potential gas sensing material.