fi=221 Nanotekniikka|sv=221 Nanoteknologi|en=221 Nanoteknology|https://www.doria.fi:443/handle/10024/989322024-03-29T07:13:31Z2024-03-29T07:13:31ZMaterials and Devices for Energy Autonomous Distributed ElectronicsArvani, Maedehhttps://www.doria.fi:443/handle/10024/1817182021-12-03T09:45:04Z2021-09-10T08:24:10ZMaterials and Devices for Energy Autonomous Distributed Electronics
Arvani, Maedeh
The growing energy demand of humankind and the concern about climate change require rethinking how energy is provided, both on a macroscopic scale and a microscopic one, e.g. for distributed electronics. For the latter, a promising approach is to use energy harvesting from ambient sources such as light. Energy harvesting needs intermediate energy storage, such as a supercapacitor or a battery. In contrast to batteries, which store electrical energy chemically, energy is stored in the electric field at the interface between electrode and electrolyte in supercapacitors. Supercapacitors are promising energy storage due to potentially non-toxic materials and longer cycle life compared to batteries. By using printing processes, we can fabricate flexible supercapacitors suitable for Internet of Things purposes.
The goal of the research in this thesis is to develop an environmentally friendly, printable, and flexible energy source for distributed electronics. One focus on the path to this goal is the fabrication and study of flexible printed supercapacitors using novel methods, materials, and architectures with a target of improved performance and manufacturability. Monolithically fabricated supercapacitors were improved by a novel composite made from chitosan and micro-fibrillated cellulose, used as a printable separator in aqueous supercapacitors. The electrical performance of the devices was improved to a level comparable with laminated supercapacitors while maintaining the advantages of monolithic supercapacitors for manufacturing and system integration. We also studied current collectors made from graphite foil and aluminum coated with graphite inks for flexible supercapacitors when low equivalent series resistance (ESR) is required. The ESR decreased by more than 80 % compared to devices using graphite ink alone. The use of a dense graphite protective layer on top of aluminum prevented corrosion, and the supercapacitors' performance was stable for at least 950 days.
The second focus of the research was integrating monolithic printed supercapacitor modules and flexible photovoltaic modules onto a single substrate to provide a monolithic energy module for energy-autonomous, low power Internet of Things devices. The energy module comprised a flexible organic series-connected photovoltaic module and a series-connected supercapacitor module. Indoor light was sufficient for the Photovoltaic (PV) module to charge the supercapacitors to a level that can drive low-power wireless sensor nodes when there is no external energy input, e.g. overnight.
The last part of the thesis aims to improve long-term indoor light harvesting by investigating new materials that can be used in PV modules. This work is related to dye-sensitized solar cells and looks at novel inorganic-organic hybrid systems. To understand and use novel materials in dye solar cells, it is necessary to understand the photo-induced energy and charge transfer processes in the materials. To achieve such an understanding, precise optical spectroscopy tools are needed, such as steady-state and time-resolved spectroscopic methods. The last part of the thesis reports a detailed study of photo-induced processes between an organic material, a novel phthalocyanine, and an inorganic semiconductor quantum dot. The study confirmed hole transfer from the quantum dot valence band to the phthalocyanine highest occupied molecular orbital after photo-excitation of quantum dots. The studied materials can be used potentially for making solar cells.
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Avhandlingens huvudtema handlar om möjliggörande av autonoma energilösningar för distribuerade sensorlösningar i ”alltings internet” (från engelskans Internet of things, IoT). Avhandlingen, som består av fyra publikationer, visar på olika sätt hur vi kan utvinna och lagra energi med hjälp av komponenter som tillverkas med trycktekniker.
De två första publikationen behandlar förbättrade egenskaper i tryckta superkondensatorer. Superkondensatorer är lovande komponenter för korttidslagring av energi tack vare användning av icke-giftiga material och bättre livscykel i förhållande till batterier. I den första artikeln rapporteras ett nytt material – och processkoncept för monolitisk tillverkning av superkondensatorer som ger minimala elektriska förluster. Monolitiska superkondensatorer har fördelar som snabb och enkel tillverkning och förbättrad systemintegration i förhållande till laminerade kondensatorer. Tidiga komponenter uppvisade vissa nackdelar i form av ökad ekvivalent serieresistans (equivalent series resistance, ESR) och läckströmmar. I artikeln visar vi hur man kan tillverka en monolitisk superkondensator med hjälp av ett komposterbart membran som är gjort av ett tryckbart kompositmaterial gjord av en blandning av kitosan och mikrofibrillerad cellulosa och som uppvisar egenskaper likt de laminerade.
I den andra artikeln tillverkades miljövänliga och flexibla superkondensatorer med reducerat ESR med hjälp av en aluminiumbaserad strömkollektor som skyddas av en grafitfolie överstruket med ett kompakt grafitbläck. Dessa förbättrade strömkollektorer minskade ESR med 80% i förhållande till användningen av endast grafitbläck. Vidare kunde vi visa att korrosion i kollektorn förhindrades av det kompakta grafitlagret och ledde till stabila operation i mera än 950 dagar.
Avhandlingens andra tema är integrering av flexibla solcellsmoduler med tryckta, monolitiska superkondensatormoduler för energisnåla autonoma komponenter. Vi kunde visa att solcellsmodulen kunde förse en seriekopplad superkondensator med tillräcklig energi från inomhusbelysning för att potentiellt kunna fungera som en energikälla för trådlösa sensorer i flera dagar.
Avhandlingens sista tema handlar om förbättrad tillvaratagning av solenergi. Vi har studerat fotoinducerad energi- och och elektronöverföring mellan lågdimensionella havledarstrukturer (kvantpunkter) och substituerade phtalocyaniner. Med hjälp av fotoelektrokemiska och noggranna optiska mätningar har vi kunnat påvisa att en exciterad kvantpunkt kan överföra ett elektronhål till den organiska acceptorn. Dessa materialsystem kan bli potentiella fotovoltaiska system i framtiden.
2021-09-10T08:24:10ZNanophotonics on Paper PlatformSaarinen, Jarkko J.https://www.doria.fi:443/handle/10024/1782152020-10-26T08:31:31Z2020-10-12T08:48:19ZNanophotonics on Paper Platform
Saarinen, Jarkko J.
This work concentrated on three nanophotonic applications based on printed and coated functionality on natural fibre based substrates. Hence, the thesis deals with three emerging fields: nanotechnology, nanophotonics, and sustainable materials. Nanotechnology tools have been developed over the past few decades increasing tremendously our abilities to control matter in nanoscale. This has resulted in the growth of nanophotonics, i.e. how light can be controlled by nanoscale structures and particles. This work concentrates on TiO2 and silver nanoparticles, and their applications on paperboard substrate. Demands for sustainability have grown significantly in recent years with growing population and emerging environmental issues. Nanotechnology is an ideal tool for promoting sustainability: with less material and energy consumption one can generate the same or even enhanced properties. Combining such nanoscale structures with renewable materials provides a double advantage compared to the traditional solutions.
First, photocatalytic activity of liquid flame spray (LFS) deposited TiO2 nanoparticles on paperboard was utilized for controlled wettability. It has been shown earlier that it is possible to convert an initially superhydrophobic surface into a highly hydrophilic one by ultraviolet A (UVA) irradiation. However, this process is reversible and the initial superhydrophobicity is returned within 60 days in storage. In this work a protocol was developed for making the wettability conversion permanent by first stage wetting, i.e. by exposing the UVA irradiated TiO2 nanoparticles to water that removed the nanoparticles from the irradiated area permanently.
Additionally, durability of such nanoparticle coated paperboard under compression was studied. Surface-enhanced Raman scattering (SERS) activity was demonstrated by LFS deposited silver nanoparticles on glass substrate, thereafter expanded to paperboard surfaces. A problem with paperboard for SERS analysis is background luminescence, which is typically orders of magnitude larger than the Raman signal, and which thereby easily dominates the measured spectrum. Two different solutions for SERS active paperboard substrates were developed. First, inkjet printing with commercial silver nanoparticle ink was found suitable for SERS activity but only with a full silver coverage on paperboard blocking the luminescence from the base paperboard. A more cost-effective solution was developed by using a simple carbon coating by flexography that allowed even individual LFS deposited silver nanoparticles for SERS measurements on paperboard with significantly reduced silver amount and consequently, cost.
Finally, commercial TiO2 nanoparticles were used together with methylene blue (MB) organic dye. MB has a distinct blue color in the oxidized form that can be converted to the transparent leucomethylene blue form by UVA activation together with TiO2 nanoparticles. Therefore, functional ink combining MB with TiO2 nanoparticles was shown to be suitable for costefficient oxygen indicators. Both reverse gravure coated and flexographic printed indicator labels were demonstrated that are suitable for simple oxygen indicators, for example, in modified atmosphere packages.
The use of metal and metal oxide nanostructures as functional light-activated materials enables creation of both cost-efficient and environmentally sound products, which can be widely used in society enabling a break-through in transformation from the current fossil fuel based economy to a solar driven economy. Therefore, as a summary, it is believed that the results of the thesis can lay ground for the development of new large-scale, nanostructured light-activated materials on natural fibre based substrates providing sustainable solutions for future generations.; Detta arbete koncentrerade sig på tre nanofotoniska applikationer som baserar sig på tryckt och bestruken funktionalitet på naturfiberbaserade substrat. Avhandlingen behandlar tre nya områden: nanoteknologi, nanofotonik och hållbara material. Nanotekniska verktyg har utvecklats under de senaste decennierna och ökat enormt vår förmåga att kontrollera materia i nanoskala. Detta har resulterat i tillväxt av nanofotonik, dvs. hur ljus kan styras av strukturer och partiklar i nanoskala. Detta arbete koncentrerar sig på TiO2- och silvernanopartiklar och deras applikationer på kartongunderlag. Kraven på hållbarhet har vuxit betydligt under de senaste åren samtidigt med ökande befolkning och växande miljöproblem. Nanoteknologi är ett idealt verktyg för främjande av hållbarhet: med mindre material- och energiförbrukning kan man generera samma eller till och med förbättrade egenskaper. Genom att kombinera sådana strukturer i nanoskala med förnybara material fördubblas fördelen jämfört med de traditionella lösningarna.
Fotokatalytisk aktivitet av TiO2-nanopartiklar som utfällts med flytande flamspray (LFS) på kartong användes för kontrollerad vätningsförmåga. Det har tidigare visats att det är möjligt att konvertera en initialt superhydrofob yta till i en hög grad hydrofil yta via ultraviolett A (UVA)-aktivering. Denna process är dock reversibel och den initiala superhydrofobiciteten återkommer inom 60 dagars lagring. I detta arbete utvecklades en metod för att göra vätningsförmågans konvertering permanent genom vätning av första steget, dvs. genom att utsätta de UVA-aktiverade TiO2-nanopartiklarna för vatten som permanent avlägsnade nanopartiklarna från det strålade ytan. Dessutom undersöktes hållbarheten för en nanopartikelbelagd kartong under kompression. Aktiviteten av ytförstärkt Raman-spridning (SERS) demonstrerades med hjälp av LFS-deposition av silverpartiklar på glassubstrat och senare på kartongytor. Ett problem med kartong för SERS-analys är bakgrundsluminescensen som är normalt några storleksordningar större än Raman-signalen och därför enkelt dominerar det mätta spektrumet. Två olika lösningar för SERS-aktiva kartong utvecklades. Den första var bläckstråletryckning med en kommersiell nanopartikulär silvertryckfärg som var lämplig för SERS-aktivitet men endast då kartongytan var totalt täckt så att luminescensen från kartongen blockerades. En mer kostnadseffektiv lösning utvecklades genom att använda en enkel kolbeläggning med hjälp av flexografi som möjliggjorde även SERS-analys av individuella LFS-deponerade silverpartiklar på kartong vilket reducerade silvermängden och kostnaderna. Slutligen användes kommersiella TiO2-nanopartiklar tillsammansmed ett organiskt färgämne, metylenblå (MB). MB har en distinkt blå färg i oxiderad form som kan omvandlas till den genomskinliga leukometylenblå genom UVA-aktivering tillsammans med TiO2-nanopartiklar. Därför visade sig det funktionella bläcket som kombinerar MB med TiO2-nanopartiklar vara lämpligt för kostnadseffektiva syreindikatorer. Både omvänd gravyrbelagda och flexografitryckta indikatoretiketter, som är lämpliga för t.ex. enkla syreindikatorer i förpackningar med modifierad atmosfär, demonstrerades.
Användning av metall- och metalloxidnanostrukturer som funktionella ljusaktiverade material möjliggör skapande av både kostnadseffektiva och miljöanpassade produkter som kan i stor utsträckning användas i samhället, och som möjliggör ett genombrott i omvandlingen från en ekonomi baserad på fossilt bränsle till en solstyrd ekonomi. Sammanfattningsvis, resultaten från denna avhandling kan antas ge en bas för utveckling av nya storskaliga, nanostrukturerade ljusaktiverade material på naturfiberbaserade substrat som ger hållbara lösningar för kommande generationer.
2020-10-12T08:48:19ZSolution-Processable Compact and Mesoporous Titanium Dioxide Thin Films as Electron-Selective Layers for Perovskite Solar CellsMasood, Muhammad Talhahttps://www.doria.fi:443/handle/10024/1776842021-02-11T08:22:30Z2020-07-29T07:49:50ZSolution-Processable Compact and Mesoporous Titanium Dioxide Thin Films as Electron-Selective Layers for Perovskite Solar Cells
Masood, Muhammad Talha
Perovskite solar cells (PSCs) is a promising photovoltaic technology for low-cost electricity generation to fulfill future demands. However, the success of any photovoltaic device is highly dependent on the quality of its selective contacts. Having poor selective contacts in a solar cell implies inappropriate extraction of photo-generated charge carriers in the absorbing material upon illumination. The overall aim of this research thesis was to systematically study three different aspects of the TiO2 electronselective layer (ESL) used in PSCs: First, to optimize the thickness of the compact TiO2 layer in order to rule out the possibility of any morphological defects such as pinholes. Second, to activate the surface of the subsequent mesoscopic TiO2 layer using oxygen plasma and UV light, and to investigate its influence on the performance of mesoscopic PSCs. Third, to use block co-polymer-templated ordered mesoporous TiO2 films to model compact TiO2 ESLs containing well-defined pinholes and to study the influence of these “induced” pinholes on the performance of planar heterojunction PSCs.
In the first study of this thesis, the thickness of dip-coated compact TiO2 electron-selective layers (ESLs) was optimized to minimize possible exposure of conductive FTO (fluorine-doped tin oxide) crystals through the ESL (also termed pinholes). The dip coating method was employed as a step towards calable and uniform thin films for PSCs. When the ESL is not thick enough due to insufficient amount of precursor available to cover the entire rough FTO surface, parallel shunt pathways are likely to form between the perovskite and the underlying FTO. This problem was solved by optimizing the TiCl4 precursor concentration in the sol. A 30 nm thick compact TiO2 layer was found to perform optimally in PSCs. With further increase in thickness of the compact TiO2 layer, the device performance remains nearly the same. However, if the layer is too thick, it can potentially reduce the device performance due to increased resistance or increased light absorption by the compact TiO2 layer.
A mesoscopic nanoparticle-based TiO2 scaffold layer is generally coated on the top of the compact TiO2 layer in conventionally structured PSCs. In the second study of this thesis, the surface of such mesoscopic TiO2 layers was activated by oxygen plasma or UV light to enhance the wettability of the nanostructured layer. The different surface activation methods were found to significantly influence the composition of perovskite light absorber and the morphology of its capping layer, which subsequently manifested in changes in the device performance. Oxygen plasma treatment of the nanostructured layer resulted in the activation of both the exterior and interior surfaces of the scaffold, which subsequently resulted in a dense crystallization of the lead iodide (PbI2) precursor within the nanostructure. This significantly reduced its conversion to perovskite upon its reaction with methylammonium iodide. On the other hand, exposure to UV light only activates the top-most surface of the scaffold. Thus, in this case the PbI2 crystallized sparsely within the nanostructure similarly as when no surface activation is performed. Therefore, its conversion to perovskite was still quite efficient. The poor conversion of the plasma-treated sample resulted in a 25% reduction in the device performance in comparison to devices prepared without any surface activation. On the other hand, the performance of devices prepared on top of UV-treated mesostructured TiO2 was found to be improved by 20% in comparison to non-treated samples.
Furthermore, ordered mesoporous TiO2 thin films were prepared by di-block copolymer templating in combination with dip coating. These films turned out to be useful for modelling pinholes in compact TiO2 ESLs. Therefore, in the third study, planar heterojunction PSCs were prepared to investigate if these “intentionally-induced” pinholes in the compact TiO2 layers pose any threat to the device performance. The porosity of the TiO2 films was increased to simulate the increase in density of so-called “induced” pinholes. Surprisingly, the increase in porosity had a very small influence on the device performance. The short-circuit currents were found to slightly increase with a decrease in the opencircuit voltage; thus, the overall power conversion efficiencies remained nearly the same. However, the reproducibility of the device performance was found to be strongly reduced when the thickness of TiO2 films (with highest porosity) was lowered down to 20 nm. This study suggests that the presence of narrow pinholes do not adversely affect the device performance provided that the thickness of the TiO2 layer exceeds a certain critical limit.
An important finding from this work was that ultrathin compact TiO2 films possess pinholes, which can be detected by X-ray photoelectron spectroscopy. The pinholes in the compact TiO2 layer not only reduce the device performance but also cause the formation of s-shaped kinks in the negative voltage regime of the current-voltage curves. Another conclusion was that the roughness of the underlying conductive substrate influences the quality of the compact TiO2 layer. Smoother substrates are expected to be completely covered by thin compact TiO2 layers without the formation of pinholes. There is still a possibility of pinholes in thicker compact TiO2 films (due to microbubble formation or improper wettability of the underlying conductive substrate), but they do not significantly reduce the device performance since the perovskite is not able to form interconnected networks throughout the narrow defects down to the underlying conductive substrate. Another important learning outcome was the knowledge that the processing parameters for device fabrication must be carefully controlled to avoid potential reproducibility issues. Such processing parameters include surface activation protocols, treatment times, and storage and handling conditions.
2020-07-29T07:49:50ZDesign and evaluation of nanoparticle-based delivery systems : towards cancer theranosticsvon Haartman, Evahttps://www.doria.fi:443/handle/10024/1339812020-08-27T08:51:52Z2017-03-23T06:37:42ZDesign and evaluation of nanoparticle-based delivery systems : towards cancer theranostics
von Haartman, Eva
The design, characterization and applicability of nanoparticle (NP)-based delivery systems intended for cancer theranostics, are presented in this thesis. Mesoporous silica nanoparticles (MSNs) have been widely established as biocompatible and efficient carriers of hydrophobic molecules, such as drugs for in vitro and in vivo tumor targeting. Although their intracellular delivery and cargo release have been demonstrated, knowledge of the underlying drug release mechanisms still remain unclear. For future control and prediction of these parameters, which from a clinical perspective are imperative to all drug delivery systems (DDSs), the release of hydrophobic cargo from MSNs is studied. In simple aqueous solvents, cargo release is strongly associated with nanocarrier degradation, whereas in media mimicking intracellular conditions, where lipids or hydrophobic structures are present, the physicochemical properties of the cargo molecule itself and its interactions with the surrounding medium are the release-governing parameters. For comparison, the relationship between intracellular cargo release and degradation of poly(alkylcyanoacrylate) (PACA) nanocarriers is also investigated, for which the release is found to be dependent on the biodegradation of the carrier. The influence of NP monomer composition on intracellular delivery and the role of different endocytosis pathways are also assessed.
This thesis moreover presents a novel multifunctional composite NP for combined optical imaging, tracking and drug delivery. The used approaches include creation and optimization of core-shell nanostructures of photoluminescent (PL) nanodiamonds (NDs) encapsulated within mesoporous silica shells that allow tuning of the composite NP size and loading of hydrophobic cargo molecules. Through subsequent surface engineering, efficient passive uptake by endocytosis, followed by intracellular release of cargo, is achieved and displayed by optical fluorescence imaging. The approaches presented in this thesis are highly interdisciplinary, placed at the meeting point between chemistry, physics, engineering, biotechnology and pharmaceutical sciences, and provide a basis for the rational design and evaluation of NP-based DDSs, intended for cancer theranostics, mainly by intravenous (IV) administration.
2017-03-23T06:37:42Z