| 1. |
- Darmadi, Iwan, 1990, et al.
(author)
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Bulk-Processed Pd Nanocube-Poly(methyl methacrylate) Nanocomposites as Plasmonic Plastics for Hydrogen Sensing
- 2020
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In: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 3:8, s. 8438-8445
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Journal article (peer-reviewed)abstract
- Nanoplasmonic hydrogen sensors are predicted to play a key role in safety systems of the emerging hydrogen economy. Pd nanoparticles are the active material of choice for sensor prototype development due to their ability to form a hydride at ambient conditions, which creates the optical contrast. Here, we introduce plasmonic hydrogen sensors made from a thermoplastic nanocomposite material, that is, a bulk material that can be molded with standard plastic processing techniques, such as extrusion and three-dimensional (3D) printing, while at the same time being functionalized at the nanoscale. Specifically, our plasmonic plastic is composed of hydrogensensitive and plasmonically active Pd nanocubes mixed with a poly(methyl methacrylate) matrix, and we optimize it by characterization from the atomic to the macroscopic level. We demonstrate meltprocessed deactivation-resistant plasmonic hydrogen sensors, which retain full functionality even after SO weeks. From a wider perspective, we advertise plasmonic plastic nanocomposite materials for application in a multitude of active plasmonic technologies since they provide efficient scalable processing and almost endless functional material design opportunities via tailored polymer- colloidal nanocrystal combinations.
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| 2. |
- Darmadi, Iwan, 1990, et al.
(author)
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Plasma Cleaning of Cationic Surfactants from Pd Nanoparticle Surfaces: Implications for Hydrogen Sorption
- 2023
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In: ACS Applied Nano Materials. - 2574-0970. ; 6:10, s. 8168-8177
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Journal article (peer-reviewed)abstract
- Cationic surfactants are widely used in the colloidal synthesis of noble metal nanoparticles in general, and of Pd nanoparticles in particular, to stabilize them toward aggregate formation in solution and to promote shape-specific particle growth. Despite the benefits at the synthesis stage, these surfactants can be problematic once the nanoparticles are to be applied as they may both geometrically block and electronically alter surface sites that are important for surface chemical reactions. This is particularly relevant in applications like bio- and chemosensors where analyte-nanoparticle surface interactions constitute the actual sensing event. Here, H2 sensors based on Pd and its alloys are no exception since the dissociation of H2 on the particle surface is the first step toward hydride formation and thus hydrogen detection, and it has been demonstrated that the presence of surfactant molecules detrimentally affects the hydrogen sorption rate. Here, we therefore develop a scheme to remove cationic surfactants from Pd nanoparticle surfaces by means of subsequent O2 and H2 plasma treatment, whose effectiveness we verify by X-ray photoelectron spectroscopy. Furthermore, we find that the plasma treatment both alters the surface structure of the Pd nanoparticles at the atomic level and leads to surface contamination by so-called H2 plasma swift chemical sputtering of Al, Si and F species present in the plasma chamber, which in combination significantly reduce hydrogen sorption rates and increase apparent activation energies, as revealed by plasmonic hydrogen sorption kinetic measurements. Finally, we show that both these effects can be reversed by mild thermal annealing and that after the complete plasma cleaning-thermal annealing sequence hydrogen sorption rates essentially identical to the ones of neat Pd particles never exposed to cationic surfactants can be achieved. This advertises tailored plasma cleaning and mild heat treatments as an effective recipe for the removal of surfactant molecules from nanoparticle surfaces.
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| 3. |
- Eklöf, Johnas, 1988, et al.
(author)
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Guided selective deposition of nanoparticles by tuning of the surface potential
- 2017
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In: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 119:1
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Journal article (peer-reviewed)abstract
- Guided deposition of nanoparticles onto different substrates is of great importance for a variety of applications such as biosensing, targeted cancer therapy, anti-bacterial coatings and single molecular electronics. It is therefore important to gain an understanding of what parameters are involved in the deposition of nanoparticles. In this work we have deposited 60 nm, negatively charged, citrate stabilized gold nanoparticles onto microstructures consisting of six different materials, (vanadium (V), silicon dioxide (SiO2), gold (Au), aluminum (Al), copper (Cu) and nickel (Ni)). The samples have then been investigated by scanning electron microscopy to extract the particle density. The surface potential was calculated from the measured surface charge density maps measured by atomic force microscopy while the samples were submerged in a KCl water solution. These values were compared with literature values of the isoelectric points (IEP) of different oxides formed on the metals in an ambient environment. According to measurements, Al had the highest surface potential followed by Ni and Cu. The same trend was observed for the nanoparticle densities. No particles were found on V, SiO2 and Au. The literature values of the IEP showed a different trend compared to the surface potential measurements concluding that IEP is not a reliable parameter for the prediction of NP deposition.
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| 4. |
- Gschneidtner, Tina, 1985, et al.
(author)
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Constructing a library of metal and metal-oxide nanoparticle heterodimers through colloidal assembly
- 2020
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In: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 12:20, s. 11297-11305
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Journal article (peer-reviewed)abstract
- Nanoparticle dimers composed of different metals or metal oxides, as well as different shapes and sizes, are of wide interest for applications ranging from nanoplasmonic sensing to nanooptics to biomedical engineering. Shaped nanoparticles, like triangles and nanorods, can be particularly useful in applications due to the strong localized plasmonic hot-spot that forms at the tips or corners. By placing catalytic, but traditionally weakly- or non-plasmonic nanoparticles, such as metal oxides and metals like palladium, in these hot-spots, an enhanced function for sensing, photocatalysis or optical use is predicted. Here, we present an electrostatic colloidal assembly strategy for nanoparticles, incorporating different sizes, shapes and metal or metal oxide compositions into heterodimers with smaller gaps than are achievable using nanofabrication techniques. This versatile method is demonstrated on 14 combinations, including a variety of shaped gold nanoparticles as well as palladium, iron oxide, and titanium oxide nanoparticles. These colloidal nanoparticles are stabilized with traditional surfactants, such as citrate, CTAB, PVP and oleic acid/oleylamines, indicating the wide applicability of our approach. Heterodimers of gold and palladium are further analyzed using cathodoluminescence to demonstrate the tunability of these "plasmonic molecules". Since systematically altering the absorption and emission of the plasmonic nanoparticles dimers is crucial to extending their functionality, and small gap sizes produce the strongest hot-spots, this method indicates that the electrostatic approach to heterodimer assembly can be useful in creating new nanoparticle dimers for many applications.
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| 5. |
- Lerch, Sarah, 1990, et al.
(author)
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Robust Colloidal Synthesis of Palladium-Gold Alloy Nanoparticles for Hydrogen Sensing
- 2021
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In: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 13:38, s. 45758-45767
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Journal article (peer-reviewed)abstract
- Metal nanoparticles are currently used in a variety of applications, ranging from life sciences to nanoelectronic devices to gas sensors. In particular, the use of palladium nanoparticles is gaining increasing attention due to their ability to catalyze the rapid dissociation of hydrogen, which leads to an excellent response in hydrogen-sensing applications. However, current palladium-nanoparticle-based sensors are hindered by the presence of hysteresis upon hydride formation and decomposition, as this hysteresis limits sensor accuracy. Here, we present a robust colloidal synthesis for palladium-gold alloy nanoparticles and demonstrate their hysteresis-free response when used for hydrogen detection. The obtained colloidal particles, synthesized in an aqueous, room-temperature environment, can be tailored to a variety of applications through changing the size, ratio of metals, and surface stabilization. In particular, the variation of the viscosity of the mixture during synthesis resulted in a highly tunable size distribution and contributed to a significant improvement in size dispersity compared to the state-of-the-art methods.
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| 6. |
- Stolas, Alicja, 1992, et al.
(author)
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Impact of Surfactants and Stabilizers on Palladium Nanoparticle–Hydrogen Interaction Kinetics: Implications for Hydrogen Sensors
- 2020
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In: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 3:3, s. 2647-2653
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Journal article (peer-reviewed)abstract
- Surfactants and stabilizers are always present on the surfaces of colloidal nanocrystals due to their critical function in promoting selective facet growth and since they are essential to prevent aggregate formation in solution. After synthesis, however, the presence of these molecules on the surface of a nanocrystal is problematic because they potentially significantly alter the nature of the interaction with the environment, which is critical for sensor or catalysis applications. Here, we quantitatively scrutinize this effect experimentally for the four most common stabilizers in Pd nanoparticle synthesis: cetyltrimethylammonium bromide (CTAB), tetraoctylammonium bromide (TOAB), cetyltrimethylammonium chloride (CTAC), and poly(vinylpyrrolidone) (PVP). We use the surface-catalyzed hydrogen sorption and hydride formation reaction in Pd as a model system, due to its high relevance for hydrogen sensors. Specifically, we map in detail the (de)hydrogenation kinetics of arrays of nanofabricated Pd nanodisks in the presence of the surfactants and benchmark it with an uncoated Pd reference. As the key results, we find that the cationic surfactants significantly decelerate the (de)hydrogenation surface reaction, with the amplitude of deceleration mediated by the interplay between the halide-ion–Pd surface interaction strength and surfactant surface density. In contrast, a polymeric PVP coating is found to significantly accelerate hydrogen sorption. For the Pd-based hydrogen sensor application, our findings thus provide important insights for the appropriate choice of a surfactant to minimize the negative impact on hydrogen sorption kinetics and thus hydrogen detection response/recovery times. In a wider perspective, our results dramatically show how nanoparticles can attain different properties depending on what types of surfactants and stabilizers are present on their surface and how critical the quantitative understanding of their impact is for a specific application.
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| 7. |
- Stolas, Alicja, 1992
(author)
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Synthesis and characterization of Pd nanoparticles for plastic plasmonic sensing applications
- 2019
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Licentiate thesis (other academic/artistic)abstract
- It is well known that hydrogen mixed with air forms a highly flammable mixture. There is an urgent need for selective and accurate sensors, since hydrogen very often serves as a fuel or energy storage medium. Given the fact that even the smallest leak can lead to an explosion, it is very important for sensors to be reliable and safe, i.e. not ignite the gas themselves. Sensors with an optical read-out are under current interest, hence nanoparticles are examined towards this goal. As a response to the above, this thesis discusses the synthesis of palladium nanoparticles with a standard surfactant as a stabilizer together with their characterization. Nanoforms of palladium are a perfect platform for hydrogen sensing, forming a hydride when exposed to hydrogen, making them very selective. However, there are compounds which strongly influence hydrogen sensing and often obscure the activity of palladium nanoparticles. Four common capping agents utilized in palladium nanoparticles synthesis were investigated to address this issue: hexadecyltrimethylammonium bromide (CTAB), hexadecyltrimethylammonium chloride (CTAC), tetraoctylammonium bromide (TOAB), polyvinylpyrrolidone (PVP). Palladium nanoparticles were applied towards hydrogen sensing giving promising results. In order to achieve the goal to create a hydrogen sensor, nanoparticles were successfully incorporated into a poly(methyl methacrylate) (PMMA) polymer matrix. The created nanocomposite serves as a platform for two hydrogen sensing devices with plasmonic optical read-outs. On top of that it was found that among all four tested capping agents for palladium nanoparticles, PVP enhances hydrogen absorption kinetics whereas CTAB, CTAC and TOAB decrease absorption kinetics.
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| 8. |
- Stolas, Alicja, 1992
(author)
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Synthesis of Nanoparticles and Organometallic Complexes for Gas Sensing
- 2020
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Doctoral thesis (other academic/artistic)abstract
- Currently metal nanoparticles (NPs) are a subject of interest regarding many applications, in particular chemical gas sensing, as the associated environmental issues are of substantial importance. Metal NPs are attractive due to their fascinating optical properties and primarily, localized surface plasmon resonance (LSPR) which strongly depends on size and shape of NPs. Desired size and shape of NPs can be achieved by colloidal synthesis that allows for flexibility in the reaction conditions, although it demands high precision and understanding of how different factors affect NP formation, which can influence the quality of synthesized NPs. Regarding chemical sensing, phthalocyanines possess strong activity towards some gases, and they carry interesting optical properties, therefore their application is also interesting. This thesis focuses extensively on the synthesis and characterization of Pd NPs for hydrogen sensing. The Pd NPs synthesis was optimized with regard to the concentration needed for efficient response from the sensor. The Pd NPs were incorporated into a polymer matrix to be protected from poisoning, which also led the diffusion path between hydrogen and Pd NPs to be extended. Different stabilizing agents for Pd NPs were examined in order to explore how common stabilizing compounds and their interactions with Pd NPs may influence the sensing process. The work was focused on the use of homogeneous surfactant and polymer coatings on Pd nanofabricated surfaces, which were examined and analyzed in hydrogen sensing. Additionally, to address hydrogen sensing problems i.e. hysteresis, PdAu alloys with various Pd:Au ratios were colloidally synthesized and thoroughly characterized. PdAu alloys exhibited excellent results of hysteresis removal at specific Pd:Au ratios. Moreover, phthalocyanine based complexes; Zn, Co, Cu, Fe, were synthesized for application in NOx monitoring.
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| 9. |
- Östergren, Ida, 1991, et al.
(author)
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Highly Permeable Fluorinated Polymer Nanocomposites for Plasmonic Hydrogen Sensing
- 2021
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In: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 13:18, s. 21724-21732
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Journal article (peer-reviewed)abstract
- Hydrogen (H2) sensors that can be produced en masse with cost-effective manufacturing tools are critical for enabling safety in the emerging hydrogen economy. The use of melt-processed nanocomposites in this context would allow the combination of the advantages of plasmonic hydrogen detection with polymer technology; an approach which is held back by the slow diffusion of H2 through the polymer matrix. Here, we show that the use of an amorphous fluorinated polymer, compounded with colloidal Pd nanoparticles prepared by highly scalable continuous flow synthesis, results in nanocomposites that display a high H2 diffusion coefficient in the order of 10-5 cm2 s-1. As a result, plasmonic optical hydrogen detection with melt-pressed fluorinated polymer nanocomposites is no longer limited by the diffusion of the H2 analyte to the Pd nanoparticle transducer elements, despite a thickness of up to 100 μm, thereby enabling response times as short as 2.5 s at 100 mbar (10 vol. %) H2. Evidently, plasmonic sensors with a fast response time can be fabricated with thick, melt-processed nanocomposites, which paves the way for a new generation of robust H2 sensors.
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