New polymeric materials for vascular surgery

The dramatic impact that vascular diseases have on human life quality and expectancy nowadays is the reason why both medical and scientific communities put great effort in discovering new and effective ways to fight vascular pathologies. Among the many different treatments, endovascular surgery is a minimally-invasive technique that makes use of X-ray fluoroscopy to obtain real-time images of the patient during interventions. In this context radiopaque biomaterials, i.e. materials able to absorb X-ray radiation, play a fundamental role as they are employed both to enhance visibility of devices during interventions and to protect medical staff and patients from X-ray radiations. Organic-inorganic hybrids are materials that combine characteristics of organic polymers with those of inorganic metal oxides. These materials can be synthesized via the sol-gel process and can be easily applied as thin coatings on different kinds of substrates. Good radiopacity of organic-inorganic hybrids has been recently reported suggesting that these materials might find applications in medical fields where X-ray absorption and visibility is required. The present PhD thesis aimed at developing and characterizing new radiopaque organic-inorganic hybrid materials that can find application in the vascular surgery field as coatings for the improvement of medical devices traceability as well as for the production of X-ray shielding objects and garments. Novel organic-inorganic hybrids based on different polyesters (poly-lactic acid and poly-ε-caprolactone) and polycarbonate (poly-trimethylene carbonate) as the polymeric phase and on titanium oxide as the inorganic phase were synthesized. Study of the phase interactions in these materials allowed to demonstrate that Class II hybrids (where covalent bonds exists between the two phases) can be obtained starting from any kind of polyester or polycarbonate, without the need of polymer pre-functionalization, thanks to the occurrence of transesterification reactions operated by inorganic molecules on ester and carbonate moieties. Polyester based hybrids were successfully coated via dip coating on different kinds of textiles. Coated textiles showed improved radiopacity with respect to the plain fabric while remaining soft to the touch. The hybrid was able to coat single fibers of the yarn rather than coating the yarn as a whole. Openings between yarns were maintained and therefore fabric breathability was preserved. Such coatings are promising for the production of light-weight garments for X-ray protection of medical staff during interventional fluoroscopy, which will help preventing pathologies that stem from chronic X-ray exposure. A means to increase the protection capacity of hybrid-coated fabrics was also investigated and implemented in this thesis. By synthesizing the hybrid in the presence of a suspension of radiopaque tantalum nanoparticles, PDMS-titania hybrid materials with tunable radiopacity were developed and were successfully applied as coatings. A solution for enhancing medical device radiopacity was also successfully investigated. High metal radiopacity was associated with good mechanical and protective properties of organic-inorganic hybrids in the form of a double-layer coating. Tantalum was employed as the constituent of the first layer deposited on sample substrates by means of a sputtering technique. The second layer was composed of a hybrid whose constituents are well-known biocompatible organic and inorganic components, such as the two polymers PCL and PDMS, and titanium oxide, respectively. The metallic layer conferred to the substrate good X-ray visibility. A correlation between radiopacity and coating thickness derived during this study allows to tailor radiopacity simply by controlling the metal layer sputtering deposition time. The applied metal deposition technique also permits easy shaping of the radiopaque layer, allowing production of radiopaque markers for medical devices that can be unambiguously identified by surgeons during implantation and in subsequent radiological investigations. Synthesized PCL-titania and PDMS-titania hybrids strongly adhered to substrates and show good biocompatibility as highlighted by cytotoxicity tests. The PDMS-titania hybrid coating was also characterized by high flexibility that allows it to stand large substrate deformations without detaching nor cracking, thus being suitable for application on flexible medical devices.

Modeling and simulations of nanoparticles in liquid crystalline systems

The aim of this work is to investigate, using extensive Monte Carlo computer simulations, composite materials consisting of liquid crystals doped with nanoparticles. These systems are currently of great interest as they offer the possibility of tuning the properties of liquid crystals used in displays and other devices as well as providing a way of obtaining regularly organized systems of nanoparticles exploiting the molecular organization of the liquid crystal medium. Surprisingly enough, there is however a lack of fundamental knowledge on the properties and phase behavior of these hybrid materials, making the route to their application an essentially empirical one. Here we wish to contribute to the much needed rationalization of these systems studying some basic effects induced by different nanoparticles on a liquid crystal host. We investigate in particular the effects of nanoparticle shape, size and polarity as well as of their affinity to the liquid crystal solvent on the stability of the system, monitoring phase transitions, order and molecular organizations. To do this we have proposed a coarse grained approach where nanoparticles are modelled as a suitably shaped (spherical, rod and disk like) collection of spherical Lennard-Jones beads, while the mesogens are represented with Gay-Berne particles. We find that the addition of apolar nanoparticles of different shape typically lowers the nematic–isotropic transition of a non-polar nematic, with the destabilization being greater for spherical nanoparticles. For polar mesogens we have studied the effect of solvent affinity of the nanoparticles showing that aggregation takes places for low solvation values. Interestingly, if the nanoparticles are polar the aggregates contribute to stabilizing the system, compensating the shape effect. We thus find the overall effects on stability to be a delicate balance of often contrasting contributions pointing to the relevance of simulations studies for understanding these complex systems.

Silicon nanocrystals tailored for bioimaging and energy conversion

This thesis focus is the development of hybrid organic-inorganic systems based on Silicon Nanocrystals (SiNCs) with possible applications in the field of bioimaging and solar energy conversion. SiNCs were engineered thanks to the realization of a strong covalent Si-C bond on their surface, which allowed us to disperse them in different solvents with different final purpose. Chapter 1 introduces the basic properties of nanomaterials. Chapter 2 describes all the synthetic procedures to obtain the organic molecules-functionalized SiNCs. Chapter 3 illustrates an organic-inorganic antenna system based on SiNCs conjugated with diphenylanthracene (DPA) photoactive molecules, which was also embedded into Luminescent Solar Concentrators (LSC) made of a polymeric matrix. The optical and photovoltaic performances of this device were compared with the ones of a LSC embedded with a physical mixture made of SiNCs plus DPA at the same concentrations of the two components in the covalent system. Chapter 4 shows many different techniques to functionalize SiNCs with polyethylene glycol (PEG) chains in order to make them dispersible in water, for biomedical imaging applications. Chapter 5 presents the synthesis of dyes and/or SiNCs loaded Polymer Nanoparticles (PNPs) capable of excitation energy transfer (EET) mechanism. Chapter 6 is focused on the realization of photo-switchable systems based on azobenzene derivatives-functionalized SiNCs. These organic-inorganic hybrid materials were studied to possibly obtain a new light-driven response of SiNCs. In the end, chapter 7 reports the activity I followed in America, at The University of Texas at Austin, in the laboratory led by the professor Brian Korgel. Here I studied and compared the properties of high temperature hydrosilylated SiNCs and room temperature, radical promoted, hydrosilylated SiNCs.

Nanocomposites based on poly(caprolactone)-chitosan electrospun nanofibers and metallic oxide nanoparticles. Their potential use to adsorption and photocatalytic degradation of organic contaminants

Pollution of water bodies is one of the most common environmental problems today. Organic pollutants are one of the main drawbacks in this natural resource, among which the following stand out long-lived dyes, pharmaceuticals, and pesticides. This research aims at obtaining nanocomposites based on polycaprolactone-chitosan (PCL-CS) electrospun nanofibers (NFs) containing TiO2 nanoparticles (NPs) for the adsorption and photocatalytic degradation of organic pollutants, using Rhodamine B as a model. The fabricated hybrid materials were characterized by FT-IR, TGA, DSC, SEM, TEM, tensile properties, and the contact angle of water drops. The photoactivity of the NFs was investigated using a batch-type system by following UV-Vis absorbance and fluorescence of rhodamine B (RhB). For this purpose, TiO2NPs were successfully ex-situ incorporated into the polymer matrix promoting good mechanical properties and higher hydrophilicity of the material. The results showed that CS in the NFs increased the absorption and degradation of RhB by the TiO2NPs. CS attracted the pollutant molecules to the active sites vicinity of TiO2NPs, favoring initial adsorption and degradation. In other words, a bait-hook-and-destroy effect was evidenced. It also was demonstrated that the sensitization of TiO2 by organic dyes (e.g., perylene derivative) considerably improves the photocatalytic activity under visible radiation, allowing the use of low amounts of TiO2. (≈0.05 g/1 g of fiber). Hence, the current study is expected to contribute with an environmentally friendly green alternative solution.

Advanced Functional Organic-Inorganic Hybrid (Nano)Materials: from Theranostics to Organic Electronics and Additive Manufacturing

This work is going to show the activities performed in the frame of my PhD studies at the University of Bologna, under the supervision of Prof. Mauro Comes Franchini, at the Department of Industrial Chemistry “Toso Montanari”. The main topic of this dissertation will be the study of organic-inorganic hybrid nanostructures and materials for advanced applications in different fields of materials technology and development such as theranostics, organic electronics and additive manufacturing, also known as 3D printing. This work is therefore divided into three chapters, that recall the fundamentals of each subject and to recap the state-of-the-art of scientific research around each topic. In each chapter, the published works and preliminary results obtained during my PhD career will be discussed in detail.

Hybrid lead-halide perovskites as novel materials for thin film direct and flexible ionizing radiation detectors

Ionizing radiations are important tools employed every day in the modern society. For example, in medicine they are routinely used for diagnostic and therapy. The large variety of applications leads to the need of novel, more efficient, low-cost ionizing radiation detectors with new functionalities. Personal dosimetry would benefit from wearable detectors able to conform to the body surfaces. Traditional semiconductors used for ionizing radiation direct detectors offer high performance but they are intrinsically stiff, brittle and require high voltages to operate. Hybrid lead-halide perovskites emerged recently as a novel class of materials for ionizing radiation detection. They combine high absorption coefficient, solution processability and high charge transport capability, enabling efficient and low-cost detection. The deposition from solution allows the fabrication of thin-film flexible devices. In this thesis, I studied the detection properties of different types of hybrid perovskites, deposited from solution in thin-film form, and tested under X-rays, gamma-rays and protons beams. I developed the first ultraflexible X-ray detector with exceptional conformability. The effect of coupling organic layers with perovskites was studied at the nanoscale giving a direct demonstration of trap passivation effect at the grain boundaries. Different perovskite formulations were deposited and tested to improve the film stability. I report about the longest aging studies on perovskite X-ray detectors showing that the addition of starch in the precursors’ solution can improve the stability in time with only a 7% decrease in sensitivity after 630 days of storage in ambient conditions. 2D perovskites were also explored as direct detector for X-rays and gamma-rays. Detection of 511 keV photons by a thin-film device is here demonstrated and was validated for monitoring a radiotracer injection. At last, a new approach has been used: a 2D/3Dmixed perovskite thin-film demonstrated to reliably detect 5 MeV protons, envisioning wearable dose monitoring during proton/hadron therapy treatments.

Supramolecular hybrid organic-inorganic multicomponent architectures in solution and on surface

Supramolecular architectures can be built-up from a single molecular component (building block) to obtain a complex of organic or inorganic interactions creating a new emergent condensed phase of matter, such as gels, liquid crystals and solid crystal. Further the generation of multicomponent supramolecular hybrid architecture, a mix of organic and inorganic components, increases the complexity of the condensed aggregate with functional properties useful for important areas of research, like material science, medicine and nanotechnology. One may design a molecule storing a recognition pattern and programming a informed self-organization process enables to grow-up into a hierarchical architecture. From a molecular level to a supramolecular level, in a bottom-up fashion, it is possible to create a new emergent structure-function, where the system, as a whole, is open to its own environment to exchange energy, matter and information. “The emergent property of the whole assembly is superior to the sum of a singles parts”. In this thesis I present new architectures and functional materials built through the selfassembly of guanosine, in the absence or in the presence of a cation, in solution and on the surface. By appropriate manipulation of intermolecular non-covalent interactions the spatial (structural) and temporal (dynamic) features of these supramolecular architectures are controlled. Guanosine G7 (5',3'-di-decanoil-deoxi-guanosine) is able to interconvert reversibly between a supramolecular polymer and a discrete octameric species by dynamic cation binding and release. Guanosine G16 (2',3'-O-Isopropylidene-5'-O-decylguanosine) shows selectivity binding from a mix of different cation's nature. Remarkably, reversibility, selectivity, adaptability and serendipity are mutual features to appreciate the creativity of a molecular self-organization complex system into a multilevelscale hierarchical growth. The creativity - in general sense, the creation of a new thing, a new thinking, a new functionality or a new structure - emerges from a contamination process of different disciplines such as biology, chemistry, physics, architecture, design, philosophy and science of complexity.

Electrode Materials for Ionic Liquid Based-Supercapacitors

The development of safe, high energy and power electrochemical energy-conversion systems can be a response to the worldwide demand for a clean and low-fuel-consuming transport. This thesis work, starting from a basic studies on the ionic liquid (IL) electrolytes and carbon electrodes and concluding with tests on large-size IL-based supercapacitor prototypes demonstrated that the IL-based asymmetric configuration (AEDLCs) is a powerful strategy to develop safe, high-energy supercapacitors that might compete with lithium-ion batteries in power assist-hybrid electric vehicles (HEVs). The increase of specific energy in EDLCs was achieved following three routes: i) the use of hydrophobic ionic liquids (ILs) as electrolytes; ii) the design and preparation of carbon electrode materials of tailored morphology and surface chemistry to feature high capacitance response in IL and iii) the asymmetric double-layer carbon supercapacitor configuration (AEDLC) which consists of assembling the supercapacitor with different carbon loadings at the two electrodes in order to exploit the wide electrochemical stability window (ESW) of IL and to reach high maximum cell voltage (Vmax). Among the various ILs investigated the N-methoxyethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR1(2O1)TFSI) was selected because of its hydrophobicity and high thermal stability up to 350 °C together with good conductivity and wide ESW, exploitable in a wide temperature range, below 0°C. For such exceptional properties PYR1(2O1)TFSI was used for the whole study to develop large size IL-based carbon supercapacitor prototype. This work also highlights that the use of ILs determines different chemical-physical properties at the interface electrode/electrolyte with respect to that formed by conventional electrolytes. Indeed, the absence of solvent in ILs makes the properties of the interface not mediated by the solvent and, thus, the dielectric constant and double-layer thickness strictly depend on the chemistry of the IL ions. The study of carbon electrode materials evidences several factors that have to be taken into account for designing performing carbon electrodes in IL. The heat-treatment in inert atmosphere of the activated carbon AC which gave ACT carbon featuring ca. 100 F/g in IL demonstrated the importance of surface chemistry in the capacitive response of the carbons in hydrophobic ILs. The tailored mesoporosity of the xerogel carbons is a key parameter to achieve high capacitance response. The CO2-treated xerogel carbon X3a featured a high specific capacitance of 120 F/g in PYR14TFSI, however, exhibiting high pore volume, an excess of IL is required to fill the pores with respect to that necessary for the charge-discharge process. Further advances were achieved with electrodes based on the disordered template carbon DTC7 with pore size distribution centred at 2.7 nm which featured a notably high specific capacitance of 140 F/g in PYR14TFSI and a moderate pore volume, V>1.5 nm of 0.70 cm3/g. This thesis work demonstrated that by means of the asymmetric configuration (AEDLC) it was possible to reach high cell voltage up to 3.9 V. Indeed, IL-based AEDLCs with the X3a or ACT carbon electrodes exhibited specific energy and power of ca. 30 Wh/kg and 10 kW/kg, respectively. The DTC7 carbon electrodes, featuring a capacitance response higher of 20%-40% than those of X3a and ACT, respectively, enabled the development of a PYR14TFSI-based AEDLC with specific energy and power of 47 Wh/kg and 13 kW/kg at 60°C with Vmax of 3.9 V. Given the availability of the ACT carbon (obtained from a commercial material), the PYR1(2O1)TFSI-based AEDLCs assembled with ACT carbon electrodes were selected within the EU ILHYPOS project for the development of large-size prototypes. This study demonstrated that PYR1(2O1)TFSI-based AEDLC can operate between -30°C and +60°C and its cycling stability was proved at 60°C up to 27,000 cycles with high Vmax up to 3.8 V. Such AEDLC was further investigated following USABC and DOE FreedomCAR reference protocols for HEV to evaluate its dynamic pulse-power and energy features. It was demonstrated that with Vmax of 3.7 V at T> 30 °C the challenging energy and power targets stated by DOE for power-assist HEVs, and at T> 0 °C the standards for the 12V-TSS and 42V-FSS and TPA 2s-pulse applications are satisfied, if the ratio wmodule/wSC = 2 is accomplished, which, however, is a very demanding condition. Finally, suggestions for further advances in IL-based AEDLC performance were found. Particularly, given that the main contribution to the ESR is the electrode charging resistance, which in turn is affected by the ionic resistance in the pores that is also modulated by pore length, the pore geometry is a key parameter in carbon design not only because it defines the carbon surface but also because it can differentially “amplify” the effect of IL conductivity on the electrode charging-discharging process and, thus, supercapacitor time constant.

De Novo Design of Foldamers for Preparation of Nanostructured Materials

This thesis deals with the synthesis and the conformation analysis of hybrid foldamers containing the 4-carboxyoxazolidin-2-one unit or related molecules, in which an imido-type function is obtained by coupling the nitrogen of the heterocycle with the carboxylic acid moiety of the next unit. The imide group is characterized by a nitrogen atom connected to an endocyclic and an exocyclic carbonyl, which tend always to adopt the trans conformation. As a consequence of this locally constrained disposition effect, these imide-type oligomers are forced to fold in ordered conformations. The synthetic approach is highly tuneable with endless variations, so, simply by changing the design and the synthesis, a wide variety of foldamers with the required properties may be prepared “on demand”. Thus a wide variety of unusual secondary structures and interesting supramolecular materials may be obtained with hybrid foldamers. The behaviour in the solid state of some of these compounds has been analyzed in detail, thus showing the formation of different kinds of supramolecular materials that may be used for several applications. A winning example is the production of a bolaamphiphilic gelators that may also be doped with small amounts of dansyl containing compounds, needed to show the cellular uptake into IGROV-1 cells, by confocal laser scanning microscopy. These gels are readily internalized by cells and are biologically inactive, making them very good candidates in the promising field of drug delivery. In the last part of the thesis, a particular attention was directed to the search of new scaffolds that behave as constrained amino acid mimetics, showing that tetramic acids derivatives could be good candidates for the synthesis and applications of molecules having an ordered secondary structure.

Theoretical and experimental study of novel hybrid composite and metal-composites interfaces

The growing demand for lightweight solutions in every field of engineering is driving the industry to seek new technological solutions to exploit the full potential of different materials. The combination of dissimilar materials with distinct property ranges embodies a transparent allocation of component functions while allowing an optimal mix of their characteristics. From both technological and design perspectives, the interaction between dissimilar materials can lead to severe defects that compromise a multi-material hybrid component's performance and its structural integrity. This thesis aims to develop methodologies for designing, manufacturing, and monitoring of hybrid metal-composite joints and hybrid composite components. In Chapter 1, a methodology for designing and manufacturing hybrid aluminum/composite co-cured tubes is assessed. In Chapter 2, a full-field methodology for fiber misalignment detection and stiffness prediction for hybrid, long fiber reinforced composite systems is shown and demonstrated. Chapter 3 reports the development of a novel technology for joining short fiber systems and metals in a one-step co-curing process using lattice structures. Chapter 4 is dedicated to a novel analytical framework for the design optimization of two lattice architectures.

A novel hybrid thermochemical-biological refinery integrated with power-to-X approach for obtaining biopolymers

In this study, a novel hybrid thermochemical-biological refinery integrated with power-to-x approach was developed for obtaining biopolymers (namely polyhydroxyalkanoates, PHA). Within this concept, a trilogy process schema comprising of, (i) thermochemical conversion via integrated pyrolysis-gasification technologies, (ii) anaerobic fermentation of the bioavailable products obtained through either thermochemistry or water-electrolysis for volatile fatty acids (VFA) production, (iii) and VFA-to-PHA bioconversion via an original microaerophilic-aerobic process was developed. During the first stage of proposed biorefinery where lignocellulosic (wooden) biomass was converted into, theoretically fermentable products (i.e. bioavailables) which were defined as syngas and water-soluble fraction of pyrolytic liquid (WS); biochar as a biocatalyst material; and a dense-oil as a liquid fuel. Within integrated pyrolysis - gasification process, biomass was efficiently converted into fermentable intermediates representing up to 66% of biomass chemical energy content in chemical oxygen demand (COD) basis. In the secondary stage, namely anaerobic fermentation for obtaining VFA rich streams, three different downstream process were investigated. First fermentation test was acidogenic bioconversion of WS materials obtained through pyrolysis of biomass within an original biochar-packed bioreactor, it was sustained up to 0.6 gCOD/L-day volumetric productivity (VP). Second, C1 rich syngas materials as the gaseous fraction of pyrolysis-gasification stage, was fermented within a novel char-based biofilm sparger reactor (CBSR), where up to 9.8 gCOD/L-day VP was detected. Third was homoacetogenic bioconversion within the innovative power-to-x pathway for obtaining commodities via renewable energy sources. More specifically, water-electrolysis derived H2 and CO2 as a primary greenhouse gas was successfully bio-utilized by anaerobic mixed cultures into VFA within CBSR system (VP: 18.2 gCOD/L-day). In the last stage of the developed biorefinery schema, VFA is converted into biopolymers within a new continuous microaerophilic-aerobic microplant, where up to 60% of PHA containing sludges was obtained.

Functional engineering of hybrid heterostructures for application in electronic, optical and optoelectronic nanostructured devices

Interfacing materials with different intrinsic chemical-physical characteristics allows for the generation of a new system with multifunctional features. Here, this original concept is implemented for tailoring the functional properties of bi-dimensional black phosphorus (2D bP or phosphorene) and organic light-emitting transistors (OLETs). Phosphorene is highly reactive under atmospheric conditions and its small-area/lab-scale deposition techniques have hampered the introduction of this material in real-world applications so far. The protection of 2D bP against the oxygen by means of functionalization with alkane molecules and pyrene derivatives, showed long-term stability with respect to the bare 2D bP by avoiding remarkable oxidation up to 6 months, paving the way towards ultra-sensitive oxygen chemo-sensors. A new approach of deposition-precipitation heterogeneous reaction was developed to decorate 2D bP with Au nanoparticles (NP)s, obtaining a “stabilizer-free” that may broaden the possible applications of the 2D bP/Au NPs interface in catalysis and biodiagnostics. Finally, 2D bP was deposited by electrospray technique, obtaining oxidized-phosphorous flakes as wide as hundreds of µm2 and providing for the first time a phosphorous-based bidimensional system responsive to electromechanical stimuli. The second part of the thesis focuses on the study of organic heterostructures in ambipolar OLET devices, intriguing optoelectronic devices that couple the micro-scaled light-emission with electrical switching. Initially, an ambipolar single-layer OLET based on a multifunctional organic semiconductor, is presented. The bias-depending light-emission shifted within the transistor channel, as expected in well-balanced ambipolar OLETs. However, the emitted optical power of the single layer-based device was unsatisfactory. To improve optoelectronic performance of the device, a multilayer organic architecture based on hole-transporting semiconductor, emissive donor-acceptor blend and electron-transporting semiconductor was optimized. We showed that the introduction of a suitable electron-injecting layer at the interface between the electron-transporting and light-emission layers may enable a ≈ 2× improvement of efficiency at reduced applied bias.

Optoelectronic investigation of defects in hybrid metal halide perovskites

The growing demand for flexible and low-cost electronics has driven research towards the study of novel semiconducting materials to replace traditional semiconductors like silicon and germanium, which are limited by mechanical rigidity and high production cost. Some of the most promising semiconductors in this sense are metal halide perovskites (MHPs), which combine low-cost fabrication and solution processability with exceptional optoelectronic properties like high absorption coefficient, long charge carrier lifetime, and high mobility. These properties, combined with an impressive effort by many research groups around the world, have enabled the fabrication of solar cells with record-breaking efficiencies, and photodetectors with better performance than commercial ones. However, MHP devices are still affected by issues that are hindering their commercialization, such as degradation under humidity and illumination, ion migration, electronic defects, and limited resistance to mechanical stress. The aim of this thesis work is the experimental characterization of these phenomena. We investigated the effects of several factors, such as X-ray irradiation, exposure to environmental gases, and atmosphere during synthesis, on the optoelectronic properties of MHP single crystals. We achieved this by means of optical spectroscopy, electrical measurements, and chemical analyses. We identified the cause of mechanical delamination in MHP/silicon tandem solar cells by atomic force microscopy measurements. We characterized electronic defects and ion migration in MHP single crystals by applying for the first time the photo-induced current transient spectroscopy technique to this class of materials. This research allowed to gain insight into both intrinsic defects, like ion migration and electron trapping, and extrinsic defects, induced by X-ray irradiation, mechanical stress, and exposure to humidity. This research paves the way to the development of methods that heal and passivate these defects, enabling improved performance and stability of MHP optoelectronic devices.

Molecular and hybrid systems for solar-to-chemical energy conversion

My Ph.D. thesis was dedicated to the exploration of different paths to convert sunlight into the shape of chemical bonds, by the formation of solar fuels. During the past three years, I have focused my research on two of these, namely molecular hydrogen H2 and the reduced nicotinamide adenine dinucleotide enzyme cofactor NAD(P)H. The first could become the ideal energy carrier for a truly clean energy system; it currently represents the best chance to liberate humanity from its dependence on fossil fuels. To address this, I studied different systems which can achieve proton reduction upon light absorption. More specifically, part of my work was aimed to the development of a cost-effective and stable catalyst in combination with a well-known photochemical cycle. To this extent, I worked on transition metal oxides which, as demonstrated in this work, have been identified as promising H2 evolution catalysts, showing excellent activity, stability, and previously unreported versatility. Another branch of my work on hydrogen production dealt with the use of a new class of polymeric semiconductor materials to absorb light and convert it into H2. The second solar fuel mentioned above is a key component of the most powerful methods for chemical synthesis: enzyme catalysis. The high cost of the reduced forms prohibits large-scale utilization, so artificial photosynthetic approaches for regenerating it are being intensively studied. The first system I developed exploits the tremendous reducing properties of a scarcely known ruthenium complex which is able to reduce NAD+. Lastly, I sought to revert the classical role of the sacrificial electron donor to an active component of the system and, to boost the process, I build up an autonomous microfluidic system able to generate highly reproducible NAD(P)H amount, demonstrating the superior performance of microfluidic reactors over batch and representing another successful photochemical NAD(P)H regeneration system.

Investigation on the role of polymeric ligands in heterogeneous nanocatalysis towards the development of hybrid metal-polymer catalysts

The relationship between catalytic properties and the nature of the active phase is well-established, with increased presence typically leading to enhanced catalysis. However, the costs associated with acquiring and processing these metals can become economically and environmentally unsustainable for global industries. Thus, there is potential for a paradigm shift towards utilizing polymeric ligands or other polymeric systems to modulate and enhance catalytic performance. This alternative approach has the potential to reduce the requisite amount of active phase while preserving effective catalytic activity. Such a strategy could yield substantial benefits from both economic and environmental perspectives. The primary objective of this research is to examine the influence of polymeric hydro-soluble ligands on the final properties, such as size and dispersion of the active phase, as well as the catalytic activity, encompassing conversion, selectivity towards desired products, and stability, of colloidal gold nanoparticles supported on active carbon. The goal is to elucidate the impact of polymers systematically, offering a toolbox for fine-tuning catalytic performances from the initial stages of catalyst design. Moreover, investigating the potential to augment conversion and selectivity in specific reactions through tailored polymeric ligands holds promise for reshaping catalyst preparation methodologies, thereby fostering the development of more economically sustainable materials.