Abstract Vapor-phase layer-by-layer deposition methods are capable of creating thin films of organic, inorganic, or hybrid organic–inorganic nanostructures. This approach allows the combination of the material properties of inorganic matrices with the molecular properties of organic molecules, such as building structures with optoelectronically active dye molecules. One such attractive class of dyes are the porphyrins. However, being macrocycles, their volatility is generally low, which significantly limits their use in vapor-based processes. We have therefore designed and synthesized variously substituted porphyrin macrocycles with the aim of tuning their sublimation properties, as well as their chemical reactivity, to enable their use in vapor deposition processes. A selection of these compounds has been used in molecular layer deposition (MLD) processes, proving their applicability and verifying that the porphyrin macrocycles retain their functional properties within the film material.

HfxZr1-xO2 (HZO) is a promising ferroelectric material for next-generation neuromorphic devices, where precise compositional control and complementary metal-oxidesemiconductor (CMOS) compatible processing are critical. Atomic layer deposition (ALD) is particularly attractive for HZO integration due to its excellent conformality for future three-dimensional device architectures and possibility to control the composition. However, many widely used Hf and Zr precursors suffer from limited volatility and thermal stability. In this work, we exploit the robustness and favourable growth rates of the β-diketonate precursors Hf(thd)4 and Zr(thd)4 (thd = 2,2,6,6-tetramethyl-3,5heptanedionate) - with ozone co-reactant – to demonstrate the ALD growth of binary HfO2, ZrO2, and ferroelectric HZO thin films with finely controlled Hf/Zr cation ratios enabling the Hf/Zr composition required for ferroelectric thin films. Optimized binary ALD processes yield low growth-per-cycle (GPC) values of 0.085 Å/cycle for HfO2 and 0.12 Å/cycle for ZrO2, these low GPCs enable fine and reproducible control of the Hf:Zr

In this work, we have investigated the semiconducting properties of an unprecedented 1 : 1 pi-stacked donor-acceptor cocrystal of 1,5-dihydroxynaphthalene (DHN) as the pi-donor (D) with 7,7 ',8,8 '-tetracyanoquinodimethane (TCNQ) as the pi-acceptor (A). Molecular semiconductors with electron dominant transport, narrow bandgap, solution processing ability, air-stability are highly sought-after for application in n-channel organic field effect transistors. The DHN : TCNQ cocrystal shows n-type semiconductor nature with a narrow bandgap of around 1 eV, and a low LUMO energy level (-3.8 eV) making it less prone to areal degradation. The electron dominant transport in this cocrystal is described by assuming that electron and hole hop via a super-exchange mechanism along the mixed & ctdot;D-A & ctdot; pi-stack direction. The participation of bridging molecular orbitals other than donor HOMO make a significant contribution to the super-exchange electron transfer, thus resulting in electron hopping from acceptor to acceptor which is four times larger than the value of hole hopping from donor to donor. Detailed analysis of crystal packing and electronic properties demonstrate that the super-exchange charge carrier transport is facilitated by strong pi & ctdot;pi stacking interaction between the donor and acceptor, and prominent charge transfer.

The principle of antimicrobial photodynamic therapy (PDT) is appealing because it can be controlled by an external light source and possibly the use of durable materials. However, to utilise such surfaces requires a process for their production that allows for coating on even complex geometries. We have therefore explored the ability of the emerging molecular layer deposition (MLD) technique to produce and tune PDT active materials. This study demonstrates how the type of aromatic ligand influences the optical and antimicrobial properties of photoactive Zr-organic hybrid thin films made by MLD. The three aromatic dicarboxylic acids: 2,5-dihydroxy-1,4-benzenedicarboxylic acid, 2-amino-1,4-benzenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid have been combined with ZrCl4 to produce hybrid coatings. The first system has not been previously described by MLD and is therefore more thoroughly investigated using in situ quartz crystal microbalance (QCM), Fourier transform infrared (FTIR) and UV-Vis spectroscopy. The antibacterial phototoxic effects of Zr-organic hybrids have been explored in the Staphylococcus aureus bacteria model using a UVA/blue light source. Films based on the 2,6-naphthalenedicarboxylic acid linker significantly reduced the number of viable bacteria by 99.9%, while no apparent activity was observed for the two other photoactive systems. Our work thus provides evidence that the MLD technique is a suitable tool to produce high-quality novel materials for possible applications in antimicrobial PDT, however it requires a careful selection of aromatic ligands used to construct photoactive materials.

We here report on photoactive organic-inorganic hybrid thin films prepared by the molecular layer deposition (MLD) method. The new series of hybrid films deposited using 2,6-naphthalenedicarboxylic acid (2,6-NDC) and either hafnium chloride (HfCl4), yttrium tetramethylheptanedionate (Y(thd)3) or titanium chloride (TiCl4) were compared with the known zirconium chloride (ZrCl4) based system. All metal-naphthalene films are amorphous as-deposited and show self-saturating growth as expected for an ideal MLD process with varied growth rates depending on the choice of metal precursor. The growth was studied in situ using quartz crystal microbalance (QCM) and the films were further characterised using spectroscopic ellipsometry (SE), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and UV-Vis and photoluminescence (PL) spectroscopy to obtain information on their physicochemical properties. The hybrid thin films display intense blue photoluminescence, except for the Ti-organic complex in which titanium clusters were found to be an effective PL quencher for the organic linker. We demonstrate how the optical properties of the films depend on the choice of metal component to make a foundation for further studies on these types of organic-inorganic hybrid materials for applications as photoactive agents.

Depleted oil reservoirs are considered a viable solution to the global challenge of CO2 storage. A key concern is whether the wells can be suitably sealed with cement to hinder the escape of CO2. Under reservoir conditions, CO2 is in its supercritical state, and the high pressures and temperatures involved make real-time microscopic observations of cement degradation experimentally challenging. Here, we present an in situ 3D dynamic X-ray micro computed tomography (μ-CT) study of well cement carbonation at realistic reservoir stress, pore-pressure, and temperature conditions. The high-resolution time-lapse 3D images allow monitoring the progress of reaction fronts in Portland cement, including density changes, sample deformation, and mineral precipitation and dissolution. By switching between flow and nonflow conditions of CO2-saturated water through cement, we were able to delineate regimes dominated by calcium carbonate precipitation and dissolution. For the first time, we demonstrate experimentally the impact of the flow history on CO2 leakage risk for cement plugging. In-situ μ-CT experiments combined with geochemical modeling provide unique insight into the interactions between CO2 and cement, potentially helping in assessing the risks of CO2 storage in geological reservoirs.

Surface area is an important input parameter for reactive transport modelling and it changes with time when rocks dissolve. Here we show direct observations of increased surface area due to chalk (predominantly CaCO3) dissolution, using 3D in situ X-ray microtomography. This transient increase cannot be explained by changes in fluid accessibility or by surface roughening that arises from preferential leaching. We use model simulations to explain how this increase in surface area correlates with the size of the Damkohler space, defined macroscopically using a phenomenological dissolution rate law and the cumulative surface of the microstructure. We attribute this transient increase to the coupling between fluid flow and mineral dissolution and argue that the extent is determined by the advective penetration distance of the reactants. We conclude that using a macroscopic dimensionless number as a qualitative indicator for microstructure evolution has limited applicability.

The dissolution of porous materials in a flow field controls the fluid pathways through rocks and soils and shapes the morphology of landscapes. Identifying the dissolution front, the interface between the reactive and the unreactive volumes in a dissolving medium, is a prerequisite for describing dissolution-induced structure emergence and transformation. Despite its fundamental importance, the report on the dynamics of a dissolution front in an evolving natural microstructure is scarce. Here we show an unexpected, spontaneous migration of the dissolution front against the flow direction. This retraction stems from infiltration instability induced surface generation, which leads to an increase in reactive surface area when a porous medium dissolves in an imposing flow field. There is very good agreement between observations made with in situ, X-ray tomography and model predictions. Both show that the value of reactive surface area reflects a balance between flow-dependent surface generation and destruction, i.e. the "dry" geometric surface area of a porous material, measured without a flow field, is not necessarily the upper limit of its reactive surface area when in contact with reactive flow. This understanding also contributes to reconciling the discrepancies between field and laboratory derived solid-fluid reaction kinetics.

Dissolution in natural porous media by injected CO2 can undermine the mechanical stability of the formation before carbon mineralization can take place. The geomechanical impact of geologic carbon storage therefore affects the structural integrity of the formation. Here, using in situ X-ray imaging, we show the coupled geochemical and geomechanical processes in natural chalk in the presence of aqueous CO2. We first measured the chalk dissolution rate in a closed, free drift system and obtained a phenomenological correlation between the rate and evolving aqueous calcium concentration. We then used this rate correlation in a segregated flow model to estimate the visual pattern of chalk microstructure dissolution. The model predicted a homogeneous pattern, which resulted from an increase in the reactive subvolume. This prediction was validated using in situ X-ray tomography. The imaging technique further revealed three typical mechanical impacts during microstructure disintegration in an imposed flow field: material compaction, fracturing, and grain relocation. These impacts differ but are strongly coupled with CO2-induced geochemical reactions and provide different types of feedback to the dissolution front migration. These observations led us to conclude that the presence of dissolved CO2 makes the migration of reactive fluid less sensitive to perturbations in the coupled geochemical and geomechanical processes.

To achieve the 2 °C target made in the 2016 Paris Agreement, it is essential to reduce the emission of CO2 into the atmosphere. Carbon Capture and Storage (CCS) has been given increasing importance over the last decade. One of the suggested methods for CCS is to inject CO2 into geologic settings such as the carbonate reservoirs in the North Sea. The final aim of our project is to find out how to control the evolution of petrophysical parameters during CO2 injection using an optimal combination of flow rate, injection pressure and chemical composition of the influent. The first step to achieve this is to find a suitable condition to create a stable 3D space in carbonate rock by injecting liquid to prepare space for the later CO2 injection. Micro-CT imaging is a non-destructive 3D method that can be used to study the property changes of carbonate rocks during and after CO2 injection. The advance in lab source based micro-CT has made it capable of in situ experiments. We used a commercial bench top micro-CT (Zeiss Versa XRM410) to study the microstructure changes of chalk during liquid injection. Flexible temporal CT resolution is essential in this study because that the time scales of coupled physical and chemical processes can be very different. The results validated the feasibility of using a bench top CT system with a pressure cell to monitor the mesoscale multiphase interactions in chalk.

Na-montmorillonite purified either by dialysis or by multiple centrifugation was used for the preparation of two types of clay mineral/TiO2 composites: one obtained by conventional pillaring, the other by mixing of organo-montmorillonite with inverse micelles containing Ti oxo-hydroxy species. The manner of preparation of the parent clay mineral affected strongly the textural properties of pillared montmorillonite materials but had much less effect on the texture of composites prepared with inverse microemulsion. The observed phenomena are discussed in terms of the montmorillonite component structural organization upon formation of composites. Suitability of both purification methods for preparation of Na-montmorillonite designed for synthesis of composite materials is assessed.

A novel design of combustion catalysts is proposed, in which clay/TiO2/MnAl-mixed oxide composites are formed by intermixing exfoliated organo-montmorillonite with oxide precursors (hydrotalcite-like in the case of Mn-Al oxide) obtained by an inverse microemulsion method. In order to assess the catalysts’ thermal stability, two calcination temperatures were employed: 450 and 600 °C. The composites were characterized with XRF (X-ray fluorescence), XRD (X-ray diffraction), HR SEM (high resolution scanning electron microscopy, N2 adsorption/desorption at −196 °C, and H2 TPR (temperature programmed reduction). Profound differences in structural, textural and redox properties of the materials were observed, depending on the presence of the TiO2 component, the type of neutralization agent used in the titania nanoparticles preparation (NaOH or NH3 (aq)), and the temperature of calcination. Catalytic tests of toluene combustion revealed that the clay/TiO2/MnAl-mixed oxide composites prepared with the use of ammonia showed excellent activity, the composites obtained from MnAl hydrotalcite nanoparticles trapped between the organoclay layers were less active, but displayed spectacular thermal stability, while the clay/TiO2/MnAl-mixed oxide materials obtained with the aid of NaOH were least active. The observed patterns of catalytic activity bear a direct relation to the materials’ composition and their structural, textural, and redox properties.