| 11. |
- Augustsson, Anna, et al.
(författare)
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Failure of generic risk assessment model framework to predict groundwater pollution risk at hundreds of metal contaminated sites : Implications for research needs
- 2020
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Ingår i: Environmental Research. - : Elsevier. - 0013-9351 .- 1096-0953. ; 185, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Soil pollution constitutes one of the major threats to public health, where spreading to groundwater is one of several critical aspects. In most internationally adopted frameworks for routine risk assessments of contaminated land, generic models and soil guideline values are cornerstones. In order to protect the groundwater at contaminated sites, a common practice worldwide today is to depart from health risk-based limit concentrations for groundwater, and use generic soil-to-groundwater spreading models to back-calculate corresponding equilibrium levels (concentration limits) in soil, which must not be exceeded at the site. This study presents an extensive survey of how actual soil and groundwater concentrations, compiled for all high-priority contaminated sites in Sweden, relate to the national model for risk management of contaminated sites, with focus on As, Cu, Pb and Zn. Results show that soil metal concentrations, as well as total amounts, constitute a poor basis for assessing groundwater contamination status. The evaluated model was essentially incapable of predicting groundwater contamination (i.e. concentrations above limit values) based on soil data, and erred on the "unsafe side" in a significant number of cases, with modelled correlations not being conservative enough. Further, the risk of groundwater contamination was almost entirely independent of industry type. In essence, since neither soil contaminant loads nor industry type is conclusive, there is a need for a supportive framework for assessing metal spreading to groundwater accounting for site-specific, geochemical conditions.
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| 12. |
- Auroux, Etienne, 1993-
(författare)
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Solution-processed light-emitting electrochemical cells : challenges and opportunities
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Our world is filling up with electronics. High-tech gadgets are integrated everywhere, from smart fridges able to track expiry dates and food usage, to microchip implants that let us unlock doors and pay with our hands. As innovative as they are, these new products and the many more to come impose new requirements on materials and fabrication methods. For instance, emerging electronic technologies that deliver light emission such as smart labels, authenticity features and light-based medical therapies, are often required to be flexible, see-through and low-cost, and in addition sustainable to fabricate, operate and recycle.In response to these challenges, the light-emitting industry is turning to organic electronics for solutions, a field that promises resource-efficient fabrication using environmentally benign materials. An interesting proposal is that of the light-emitting electrochemical cell (LEC), which, thanks to its simple structure, is well suitedfor high-throughput fabrication. The LEC is in many aspects a smart device, able to reorganize itself during operation via the electrochemical action of mobile ions, which create the injection and transport layers that require additional fabrication steps in other technologies. This elegant behavior makes the LEC tolerant to a large array of materials and fabrication methods, and hence a good fit for many applications.Yet the LEC is still today a scientific curiosity rather than an actual commercial solution and among the very few prototypes available on the market, none are able to meet the combined performance, resource efficiency and sustainability criteria. As a matter of fact, of the three layers that make an LEC, i.e., two electrodes surrounding an active material, only the later meet these requirements thanks to a strong recent research effort. In comparison, the electrodes have received little attention and are almost exclusively comprising metals or metal oxides deposited by time- and energy-expensive fabrication methods, making the LEC as a whole unfit for many applications.In an effort to push the LEC toward the untapped commercial niche of low-cost lighting, we tackle the problem of electrode fabrication with resource-efficiency in mind. We first show that up-scalable spray coating of inks under ambient air is a viable mean of fabrication for both active materials and electrodes alike. However, in doing so, we find that we create electrode interfaces that are open to ion transfer; an up-to-now overlooked issue that needs careful consideration when designing solution-processed LECs. Building on our discovery, we demonstrate that it is possible to fabricate an LEC entirely by using spray coating metal-free and organic inks; thereby demonstrating that an all-organic, metal-free and resource-efficient LEC is possible.I hope that our efforts will encourage others to work on solution-processed LECs, electrodes included, and develop ready-to-use products.
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| 13. |
- Batson, Emma K., et al.
(författare)
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Effects of Helium Ion Exposure on the Single-Photon Sensitivity of MgB $_{2}$ and NbN Detectors
- 2024
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Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 34:7
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Tidskriftsartikel (refereegranskat)abstract
- Improving the scalability, reproducibility, and operating temperature of superconducting nanowire single photon detectors (SNSPDs) has been a major research goal since the devices were first proposed. The recent innovation of helium-ion irradiation as a post-processing technique for SNSPDs could enable high detection efficiencies to be more easily reproducible, but is still poorly understood. Additionally, fabricating detectors at micron-wide scales from high-T$_{\mathrm{C}}$ materials could improve scalability and operating temperature, respectively. At the same time, fabrication of successful devices in wide wires and from higher-T$_{\mathrm{C}}$ materials like magnesium diboride has proven challenging. In this work, we compare helium ion irradiation in niobium nitride and magnesium diboride detectors with different material stacks in order to better understand the mechanics of irradiation and practical implications of encapsulating layers on effective dose. We examine the effects of experimental effective dose tests and compare these results to the damage per ion predicted by simulations in corresponding material stacks. In both materials, irradiation results in an increase in count rate, though for niobium nitride this increase has not fully saturated even at the highest tested dose of $2.6\times 10^{17}$ ions/cm$^{2}$, while for resist-encapsulated magnesium diboride even the lowest tested dose of $1\times 10^{15}$ ions/cm$^{2}$ appears higher than optimal. Our results demonstrate the general applicability of helium ion irradiation to vastly different devices and material stacks, albeit with differing optimal doses, and show the reproducibility and effectiveness of this post-processing technique in significantly improving SNSPD efficiency.
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| 14. |
- Belotcerkovtceva, Daria, et al.
(författare)
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Insights and Implications of Intricate Surface Charge Transfer and sp3-Defects in Graphene/Metal Oxide Interfaces
- 2022
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 14:31, s. 36209-36216
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Tidskriftsartikel (refereegranskat)abstract
- Adherence of metal oxides to graphene is of fundamental significance to graphene nanoelectronic and spintronic interfaces. Titanium oxide and aluminum oxide are two widely used tunnel barriers in such devices, which offer optimum interface resistance and distinct interface conditions that govern transport parameters and device performance. Here, we reveal a fundamental difference in how these metal oxides interface with graphene through electrical transport measurements and Raman and photoelectron spectroscopies, combined with ab initio electronic structure calculations of such interfaces. While both oxide layers cause surface charge transfer induced p-type doping in graphene, in sharp contrast to TiOx, the AlOx/graphene interface shows the presence of appreciable sp3 defects. Electronic structure calculations disclose that significant p-type doping occurs due to a combination of sp3 bonds formed between C and O atoms at the interface and possible slightly off-stoichiometric defects of the aluminum oxide layer. Furthermore, the sp3 hybridization at the AlOx/graphene interface leads to distinct magnetic moments of unsaturated bonds, which not only explicates the widely observed low spin-lifetimes in AlOx barrier graphene spintronic devices but also suggests possibilities for new hybrid resistive switching and spin valves.
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| 15. |
- Berggren, Andreas, 1979
(författare)
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Colloidal suspensions of mesostructured silica
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mesoporous silica is a porous material with walls made of silica and pores in the size range of 2-50 nm. Since the silica most often is amorphous, the material lacks short range order but the pores may be arranged in different structures generating a long-range order. The main objective of this project has been to study and develop syntheses of mesoporous silica suitable for large scale applications. Therefore this licentiate thesis focuses on the development of a new synthesis of mesoporous silica based on a sodium silicate solution and a commercially available non-ionic surfactant. The synthesis results in a stable colloidal suspension of hexagonally mesostructured silica and the particle size of the material can be controlled within the range of 50-300 nm by the electrolyte concentration. Since the synthesis is based on near neutral conditions and cheap starting materials, it is also a suitable synthesis route for development towards industrial production and applications.Another important objective of the project is to obtain a better understanding of the formation of mesostructured materials and of the interaction between silica and non-ionic surfactants. This has been studied by changing several variables in the synthesis procedure and a mechanism for the particle formation is proposed. The mechanism is based on a burst nucleation process followed by growth through aggregation. The mesoorder of the particles is then achieved by reorganization within the particles.
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| 16. |
- Berggren, Andreas, 1979, et al.
(författare)
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Particle Size Control in Colloidal Suspensions of Mesostructured Silica
- 2008
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Ingår i: Journal of Physical Chemistry C. ; 112:3, s. 732-737
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Tidskriftsartikel (refereegranskat)abstract
- Stable colloidal suspensions of ordered mesostructured silica have been prepared in a concentrated reaction solution under mild acidic conditions using an inorganic silica source and Pluronic P123. This synthesis method results in a high yield, and it is also suitable for studies of formation and growth mechanisms of colloidal mesostructured silica particles. The size of the obtained particles can be controlled within the range of 50−300 nm by varying the amount of water used in the synthesis or addition of salt to the synthesis solution. The pH of the solution is important since it affects the mesoorder of the material, colloidal stability, and product yield. Ordered material was obtained at pH 1.7−5, whereas stable colloidal suspensions were obtained in the range 3−8. A mechanism for formation of the colloidal particles based on a burst nucleation process followed by growth through aggregation is also proposed.
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