Development and study of low-dimensional hybrid and nanocomposite materials based on layered nanostructures

De buitengewone fysisch-chemische eigenschappen en het grote specifieke oppervlak van 2D materialen maken een overvloed aan applicaties mogelijk; ze kunnen gebruikt worden als platform voor de integratie van verschillende eenheden, clusters, moleculen of nanomaterialen in hybriden, wat kan leiden tot composieten met nieuwe en verbeterde eigenschappen. Anderzijds is de mate van controle over de architectuur, dikte en functionaliteit van de gevormde nanostructuren van groot belang voor het bereiden van laag-bij-laag hybride films. Het doel van dit proefschrift concentreert zich op de ontwikkeling en het bestuderen van nieuwe laag-dimensionale films en hybrides gebaseerd op gelaagde nanomaterialen, zoals grafeen en germanaan, geassembleerd met behulp van de Langmuir-Blodgett (LB) techniek.The extraordinary physicochemical properties and the high specific area of 2D materials render them very attractive for a plethora of potential applications; they can be used as platforms for integrating different moieties, clusters, molecules or nanomaterials into hybrids, allowing for the creation of composites with new or enhanced properties. On the other hand, the importance of preparing layer-by-layer hybrid films relies on the ability to control the architecture, the thickness, and the functionality of the formed nanostructures.The aim of this thesis focuses on the development and study of novel low-dimensional films and hybrids based on layered nanomaterials such as graphene and germanane, assembled with the help of the Langmuir-Blodgett (LB) technique

The product formula for regularized Fredholm determinants: two new proofs

For an $m$-summable operator $A$ in a separable Hilbert space the higher regularized Fredholm determinant $\det\nolimits_m(I+A)$ generalizes the classical Fredholm determinant. Recently, Britz et al presented a proof of a product formula $$\det\nolimits_m\bigl( (I+A)\cdot(I+B) \bigr) = \det\nolimits_m (I+A) \cdot \det\nolimits_m (I+B) \cdot \exp\operatorname{Tr}\bigl({X_m(A,B)}\bigr),$$ where $X_m(A,B)$ is an explicit polynomial in $A,B$ with values in the trace class operators. If $m=1$ then $X_1(A,B)=0$, hence the formula generalizes the classical determinant product formula. One of the purposes of this note is to present two very simple alternative proofs of the formula. The first proof is a priori analytic and makes use of the fact that $z\mapsto \det\nolimits_m(I+zA)$ is holomorphic, while the second proof is completely algebraic. The algebraic proof has, in our opinion, some interesting aspects in its own about the trace and commutators. Secondly, we extend the above mentioned formula to several factors $$\det\nolimits_m\Bigl( \prod_{l=1}^r (I+A_l) \Bigr) =\left( \prod_{l=1}^r \det\nolimits_m (I+A_l) \right) \cdot \exp\operatorname{Tr}\bigl({X_{m,r}(A_r,\ldots,A_r)}\bigr).$$ The latter is more than just a straightforward generalization as we will gain more insights into the combinatorics behind it. Also we will present an algebraized version of the analytic proof in the language of formal power series. The upshot is that the two identities are just combinatorial in nature.Comment: 20 pages. This is a major update, almost doubling the paper in size. A second part on the multi-factor case is adde

Life cycle assessment for biodiesel production under Greek climate conditions

The aim of this paper is to understand and to model the environmental performance of biodiesel produced by various Greek raw materials under current conditions. Three energy crops (rapeseed, sunflower and soybean) have been studied, with regard to their levels of biodiesel productivity. Throughout the entire process, current Greek climatic conditions and cultivation parameters have been taken into account. At the stage of assessment, we conclude that the environmental impacts per crop area indicate that soybean has the lowest environmental impacts. However, by assessing the results per quantity of produced biodiesel, the crop with the minimum environmental impacts is sunflower. This paper shows that environmental benefits from biodiesel have better results, compared to conventional diesel, thus leading to the conclusion that it is feasible to succeed improved environmental performance

Sustainable energy planning for remote islands and the waste legacy from renewable energy infrastructure deployment

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record The transition towards a sustainable energy mix is required to achieve Sustainable Development Goal 7 for affordable and clean energy. Remote islands not connected to grid which depend on diesel generators may appear ideal because they can benefit from a variety of renewable energy sources. However, renewable energy deployment requires a lifetime perspective to not inherit waste and other problems to future generations. The aim of this paper is to present a life cycle sustainability framework developed and applied for the case of the island of Ushant off North West France. Seven renewable energy generation scenarios were examined and assessed using technoeconomic, social and environmental indicators utilising life cycle costing and life cycle assessment modelling. The results show that only three out of the seven examined renewable energy scenarios manage to cover the 6807 MWh per annum demand. These scenarios can improve all the indicators against the business-as-usual diesel generation scenario except the ones related to toxicity and reduce greenhouse gas emissions by more than 92%. The easy-to-use framework allows the users to adjust their scenarios and receive useful insight about the nature of the trade-offs between the various indicators. It can also be adapted and updated to include more technologies and support the investigation of more sustainable energy scenarios of other remote island cases in the future.France (Channel) England INTERREG VA programm

Performance and life cycle assessment of a small scale vertical axis wind turbine

This is the author accepted manuscriptWind energy is one of the most popular renewable energy technologies that is considered indispensable in any low carbon energy mix. Small scale wind technologies that occupy less space and can supply electricity directly to their owners are thought to be more environmental friendly than the large turbines and therefore attract less criticism. Based on these, smaller scale renewables especially micro wind turbines should be the ideal solution but this might be just a leap of logic. The aim of this paper is to investigate whether it is worth developing smaller scale vertical axis wind turbines (VAWT) as a solution towards mitigating climate change. A real case of a H-Rotor 5 kW Darrieus vertical axis wind turbine in Poland is investigated for its performance using actual generation data. More importantly, a life cycle assessment (LCA) is undertaken, by compiling a very detailed life cycle inventory based on primary data and two scenarios were examined for the end-of-life treatment, including recycling and incineration. The performance assessment results show that the actual performance is very poor mainly due to the low wind speed. For this reason a series of hypothetical capacity factors were used to facilitate comparison with other studies. Using the CML impact assessment methodology, eleven environmental impact categories are assessed. The results show that the majority of the impacts are accredited to the supporting infrastructure - especially the mast and the foundations - rather than the turbine itself, which in the case of the Global Warming Potential (GWP) accounts for only 30%. Although the specific VAWT cannot achieve a generation that could reduce the environmental impacts to the level of the existing wind energy in Poland, a feasible capacity factor of 1.4% could make the GWP lower than the average low voltage electricity mix in Poland. The environmental performance is very sensitive to the fluctuations of the capacity factor and recommendations are given for appropriate siting, recycling of the metals and integration of the turbine on existing building structure.France (Channel) England INTERREG IV

Twitter Sentiment Analysis: The Good the Bad and the OMG!

In this paper, we investigate the utility of linguistic features for detecting the sentiment of Twitter messages. We evaluate the usefulness of existing lexical resources as well as features that capture information about the informal and creative lan-guage used in microblogging. We take a supervised approach to the problem, but leverage existing hashtags in the Twitter data for building training data

Germanane Monolayer Films as Antibacterial Coatings

Germanane (GeH), a graphane analogue, has attracted significant interest because of its optoelectronic properties; however, the environmental and biological effects of GeH have scarcely been investigated so far. Here we report a facile approach based on the Langmuir-Schaefer deposition to produce homogeneous and dense GeH monolayer films on various substrates. In view of possible applications and to extend the use of GeH to unexplored fields, we investigated its antibacterial activity for the first time and found that this promising 2D structure exhibits remarkable antibacterial activity against both Gram-negative and Gram-positive bacterial strains