Synthesis and Characterization of Double Metal Hexacyanoferrates

Manganese Hexacyanoferrate (MnHCF) and nickel doped manganese hexacyanoferrate were synthesized by simple co-precipitation method. The water content and chemical formula was obtained by TGA and MP-AES measurements, functional groups by FT-IR analysis, the crystal structure by PXRD and a local geometry by XAS. Elemental species of cycled samples were further investigated by TXM and 2D XRF. Electrochemical tests were performed in the glass cell. With addition of nickel, vacancies and water content increased in the sample. Crystal structure changed from monoclinic to cubic. Ni disturbed the local structure of Mn, site, however, almost no change was observed in Fe site. After charge/discharge cycling of MnHCF intercalation was already found in the peripheries of charged species after 20 cycle in 2D XRF analysis and randomly distributed intercalated regions after 50 cycles in TXM analysis. Cyclic voltammetry showed that peak-to-peak separation is increasing in case of the addition of Ni to MnHCF.

Synthesis and characterization of defective PBAs electrode material

Sodium manganese hexacyanoferrate (NaMnHCF) and its derivatives have been synthesized by simple co-precipitation method with addition of the citric and ascorbic acids respectively. The correspondent crystal structure, water content, chemical formula and a deep structural investigation of prepared samples have been performed by means of the combination of the laboratory and synchrotron techniques (PXRD, FT-IR, TGA, MP-AES and XAS). Electrochemical tests have been done using three-electrode system in sodium nitrate solution at different concentration. From cyclic voltammetry curves, Fe3+/2+ redox peak has been observed, whereas Mn3+/2+ peak was not always evident. Structural stability of the cycled samples has then been tested using 2D XRF imaging and Transmission X-ray microscopy (TXM) techniques. The intercalation of NaMnHCF after 20 cycles has been found by micro-XANES analysis of the highlighted spots which have been found in the XRF images. TXM has also confirmed the appearance of the intercalated particles after 50 cycles comparing the spectra between charged and discharged materials at three different edges (Mn, Fe and N). However, by comparison with lithium samples, it seems obvious that sodium samples are more homogeneous and intercalation is at the very beginning indicating the relative structural stability of sodium manganese hexacyanoferrate electrode material.

I) Improving low photocurrent of pseudorotaxane based solar cell II) Synthesis and characterization of new Fe(0) cyclopentadienone complexes

Next to conventional solar panels that harvest direct sunlight, p-type dye-sensitized solar cells (DSSCs) have been developed, which are able to harvest diffuse sunlight. Due to unwanted charge recombination events p-type DSSCs exhibit low power conversion efficiencies (PCEs). Previous research has shown that dye-redox mediator (RM) interactions can prevent these recombination events, resulting in higher PCEs. It is unknown how the nature of dye-RM interactions affects the PCEs of pseudorotaxane-based solar cells. In this research this correlation is investigated by comparing one macrocycle, the 3-NDI, in combination with the three dyes that contains a recognition sites. 2D-DOSY-NMR experiments have been conducted to evaluate the diffusion constants (LogD) of the three couple. The research project has been stopped due to the coronavirus pandemic. The continuation of this thesis would have been to synthesize a dye on the basis of the data obtained from the diffusion tests and attempt the construction of a solar cell to then evaluate its effectiveness. During my training period I synthetized new Fe(0) cyclopentadienone compounds bearing a N-Heterocyclic Carbene ligand. The aim of the thesis was to achieve water solubility by modifications of the cyclopentadienone ligand. These new complexes have been modified using a sulfonation reaction, replacing an hydroxyl with a sulfate group, on the alkyl backbone of the cyclopentadienone ligand. All the complexes were characterized with IR, ESI-MS and NMR spectroscopy, and a new Fe(0) cyclopentadienone complex, involved as an intermediate, was obtained as a single crystal and was characterized also with X-Ray spectroscopy.

Vulnerable users' protection with advanced recycling paving materials. Design and characterisation of rubber-based impact-absorbing pavement materials for bike lanes and sidewalks

Our cities are constantly evolving, and the necessity to improve the condition and safety of the urban infrastructures is fundamental. However, on the roads, the specific needs of cyclists and pedestrians are often neglected. The Vulnerable Road Users (VRUs), among whom cyclists and pedestrians are, rarely benefit from the most innovative safety measures. Inspired by playgrounds and aiming to reduce VRUs injuries, the Impact-Absorbing Pavements (IAP) developed as novel sidewalks, and bike lanes surface layers may help decrease injuries, fatalities, and the related societal costs. To achieve this goal, the End-of-Life Tyres (ELTs) crumb rubber (CR) is used as a primary resource, bringing its elastic properties into the surface layer. The thesis is divided into five main chapters. The first concerns the formulation and the definition of a feasible mix. The second explores the mechanical and environmental properties in detail, and the ageing effect is also assessed. The third describes the modelling of the material to simulate accidents and measure the injury reduction, especially on the head. The fourth chapter is reserved for the field trial. The last gives some perspectives on the research and proposes a way to optimize and improve the data and results collected during the doctoral research. It was observed that the specimens made with cold protocol have noticeable performances and reduce the overall carbon footprint impact of this material. The material modelling and the accident simulation proved the performance of the IAP against head injuries, and the field trial confirmed the good results obtained in the laboratory for the cold-made material. Finally, the outcomes of this thesis opened many prospective to the IAP development, such as the use of a plant-based binder or recycled aggregates and gave a positive prospect of an innovative material to the urban road infrastructures.

Synthesis and characterization of prussian blue analogue materials for post-Li ion batteries

Energy issues have always been a subject of concern to people. During the past 30 years, rechargeable Li-ion batteries (LIBs) have been widely used in portable electronic devices and power tools because of their high energy density and efficiency among practical secondary batteries. While the unevenly distribution of Lithium sources and the increasing cost of lithium-raw material can not satisfy the requirement for further cost reduction, especially for the grid-scale energy storage. Post-lithium ion batteries as promising replacement for LIBs have attracted wide attention, owing to their high abundant resources and adequate insertion potential. Similar with Li-ion batteries, finding a suitable electrode material is the key for the research and application of the post-Li ion batteries. In our project, we focus our study on Prussian blue analogues (PBAs), with formula AxM[M’(CN)6]1-y□y•zH2O (0≤x≤2, 0A is alkali-metal ion, M and M’ are transition metal ions, □ represents the M’(CN)6 vacancy, which are archetype of metal-organic framework, with 3D frameworks which allow for a facile insertion/ extraction of ions with negligible lattice strain. By substituting the metal sites with different transition metals, we can get a series of compounds that can be used as both cathode and anode material for both Li-ion and post-Li batteries. The most commonly studied PBAs are metal haxacyanoferrate, with the carbon-sites of -CN- ligands fix connected with Fe. Here, we synthesized three different PBAs: manganese hexacynoferrate (MnHCF), zinc hexacynoferrate (ZnHCF) and titanium hexacynoferrate (TiHCF), using co-precipitation method, and their electrochemical properties were tested in both aqueous Na+, K+, Mg2+, Zn2+ and organic Li+, Na+ electrolytes. Various X-ray techniques were employed to study their electronic and structural properties of electrodes and electrochemical reaction mechanism during cycling.

Synthesis and characterization of novel selective NKCC1 inhibitors for the treatment of down syndrome and brain disorders characterized by depolarizing GABAergic transmission.

Proper GABAergic transmission through Cl-permeable GABAA receptors is fundamental for physiological brain development and function. Indeed, defective GABAergic signaling – due to a high NKCC1/KCC2 expression ratio – has been implicated in several neurodevelopmental disorders (e.g., Down syndrome, DS, Autism spectrum disorders, ASD). Interestingly, NKCC1 inhibition by the FDA-approved diuretic drug bumetanide reverts cognitive deficits in the TS65Dn mouse models of DS and core symptoms in other models of brain disorders. However, the required chronic treatment with bumetanide is burdened by its diuretic side effects caused by the antagonization of the kidney Cl importer NKCC2. This may lead to hypokalemia, while jeopardizing drug compliance. Crucially, these issues would be solved by selective NKCC1 inhibitors, thus devoid of the diuretic effect of bumetanide. To this aim, starting from bumetanide’s structure, we applied a ligand-based computational approach to design new molecular entities that we tested in vitro for their capacity to selectively block NKCC1. Extensive synthetic efforts and structure-activity relationships analyses allowed us to improve in vitro potency and overall drug-like properties of the initially identified chemical hits. As a result, we identified a new highly potent NKCC1 inhibitor (ARN23746) that displayed excellent solubility, metabolic stability, and no significant effect on NKCC2 in vitro. Moreover, this novel and selective NKCC1 inhibitor was able to rescue cognitive deficits in DS mice and social/repetitive behaviors in ASD mice, with no diuretic effect and no overt toxicity upon chronic treatment in adult animals. Thus, ARN23746 a selective NKCC1 inhibitor devoid of the diuretic effect – represents a suitable and solid therapeutic strategy for the treatment of Down syndrome and all the brain neurological disorders characterized by depolarizing GABAergic transmission.

Synthesis and coating of silver nanoparticles and their interaction with cells model

La mia tesi si concentra sulla sintesi e funzionalizzazione di nanoparticelle d’argento studiandone l’interazione, tramite esperimenti in vitro, con cellule sane di fibroblasti murini NIH-3T3 e cellule tumorali da nodulo al seno MCF7. L’utilizzo di polielettroliti quali PDADMAC, PAH e PSS ha permesso la modifica delle proprietà superficiali delle nanoparticelle. Le nuove proprietà chimico-fisiche sono state caratterizzate tramite Dynamic Light Scattering, potenziale zeta e spettroscopia UV-vis. L’effetto della ricopertura con polielettroliti è stato valutato tramite test di vitalità cellulare somministrando le nanoparticelle funzionalizzate alle cellule sopracitate. Successivamente, è stata ottimizzata la procedura per un’ulteriore ricopertura sulle nanoparticelle cariche con BSA (Bovine Serum Albumin) valutando diversi fattori chiave. Le nanoparticelle ricoperte di albumina sono state caratterizzate e la composizione qualitativa della loro protein corona è stata ottenuta tramite analisi SDS-PAGE. Infine, le nanoparticelle ricoperte di BSA sono state somministrate alle due linee cellulari valutando l’effetto dell’albumina sulla risposta biologica tramite analisi di vitalità cellulare e immunofluorescenza.

Synthesis and Characterization of Iron carbide carbonyl clusters

This study is focused on the synthesis, characterization and reactivity of new low nuclearity iron carbide carbonyl clusters. In particular, the oxidation of the highly reduced monocarbide tetraanionic cluster [Fe6C(CO)15]4- was studied in details using different oxidants ([Cp2Fe][PF6], HBF4·Et2O, MeI and EtI), different stoichiometries and experimental conditions. Different products were obtained depending on the reaction conditions, among which previously reported [Fe6C(CO)16]2- and [Fe5C(CO)14]2-, and new [Fe6C(CO)14(CO)13]4- and [Fe5C(CO)13(COMe)]3- were isolated and fully characterized. In the second part of this study, the reactions of [Fe6C(CO)15]4- with organic or inorganic molecules containing sulphur (S8, S2Cl2 and PhSH) were investigated aiming at introducing S-atoms within the structure of iron carbide carbonyl clusters. In particular, the reaction of [Fe6C(CO)15]4- with PhSH afforded the new [Fe6C(CO)14(SPh)]3- cluster. Conversely, using S8 and S2Cl2, oxidation of [Fe6C(CO)15]4- occurred following a path similar to that observed with other oxidizing agents. All these species have been analyzed by Single Crystal X-ray diffraction (SC-XRD) and IR spectroscopy.

Steric stabilisation of the P_P bond in a bulky tetraorganodiphosphine: synthesis, characterisation and X-ray structure determination of tetrakis(2,4,6-triisopropylphenyl)diphosphine

We report the synthesis and characterisation of tetrakis(2,4,6-triisopropylphenyl)diphosphine. Synthesis is effected by the treatment of PCl3 with an excess of 2,4,6-triisopropylphenyllithium (or the equivalent Grignard reagent) in 70% yield. While under normal circumstances the triarylphosphine would be expected, excessive bulk prevents this, and the resulting diphosphine is, unusually, stable to PP cleavage by further organolithium moieties. The compound is stable, both thermally (m.p. 185°C) and to air and water in the solid state, although conversion to the equivalent diorganophosphinate ester is effected by boiling ethanolic solutions in air. Crystallisation from hexane/ethanol afforded pale yellow crystals of X-ray quality. The molecule is characterised by m.p., IR, NMR, elemental analysis (C, H, P) and MS. The X-ray structure shows an antiperiplanar conformation with a PP separation of 2.2461(16) Å. Comparisons are made with other diphosphines, the title compound being only the fourth simple diphosphine to be structurally characterised.

Synthesis and surface modification of semiconductor nanocrystals

The last decade has witnessed an exponential growth of activities in the field of nanoscience and nanotechnology worldwide, driven both by the excitement of understanding new science and by the potential hope for applications and economic impacts. The largest activity in this field up to date has been in the synthesis and characterization of new materials consisting of particles with dimensions in the order of a few nanometers, so-called nanocrystalline materials. [1-8] Semiconductor nanomaterials such as III/V or II/VI compound semiconductors exhibit strong quantum confinement behavior in the size range from 1 to 10 nm. Therefore, preparation of high quality semiconductor nanocrystals has been a challenge for synthetic chemists, leading to the recent rapid progress in delivering a wide variety of semiconducting nanomaterials. Semiconductor nanocrystals, also called quantum dots, possess physical properties distinctly different from those of the bulk material. Typically, in the size range from 1 to 10 nm, when the particle size is changed, the band gap between the valence and the conduction band will change, too. In a simple approximation a particle in a box model has been used to describe the phenomenon[9]: at nanoscale dimensions the degenerate energy states of a semiconductor separate into discrete states and the system behaves like one big molecule. The size-dependent transformation of the energy levels of the particles is called “quantum size-effect”. Quantum confinement of both the electron and hole in all three dimensions leads to an increase in the effective bandgap of the material with decreasing crystallite size. Consequently, both the optical absorption and emission of semiconductor nanaocrystals shift to the blue (higher energies) as the size of the particles gets smaller. This color tuning is well documented for CdSe nanocrystals whose absorption and emission covers almost the whole visible spectral range. As particle sizes become smaller the ratio of surface atoms to those in the interior increases, which has a strong impact on particle properties, too. Prominent examples are the low melting point [8] and size/shape dependent pressure resistance [10] of semiconductor nanocrystals. Given the size dependence of particle properties, chemists and material scientists now have the unique opportunity to change the electronic and chemical properties of a material by simply controlling the particle size. In particular, CdSe nanocrystals have been widely investigated. Mainly due to their size-dependent optoelectronic properties [11, 12] and flexible chemical processibility [13], they have played a distinguished role for a number of seminal studies [11, 12, 14, 15]. Potential technical applications have been discussed, too. [8, 16-27] Improvement of the optoelectronic properties of semiconductor nanocrystals is still a prominent research topic. One of the most important approaches is fabricating composite type-I core-shell structures which exhibit improved properties, making them attractive from both a fundamental and a practical point of view. Overcoating of nanocrystallites with higher band gap inorganic materials has been shown to increase the photoluminescence quantum yields by eliminating surface nonradiative recombination sites. [28] Particles passivated with inorganic shells are more robust than nanocrystals covered by organic ligands only and have greater tolerance to processing conditions necessary for incorporation into solid state structures or for other applications. Some examples of core-shell nanocrystals reported earlier include CdS on CdSe [29], CdSe on CdS, [30], ZnS on CdS, [31] ZnS on CdSe[28, 32], ZnSe on CdSe [33] and CdS/HgS/CdS [34]. The characterization and preparation of a new core-shell structure, CdSe nanocrystals overcoated by different shells (CdS, ZnS), is presented in chapter 4. Type-I core-shell structures as mentioned above greatly improve the photoluminescence quantum yield and chemical and photochemical stability of nanocrystals. The emission wavelengths of type-I core/shell nanocrystals typically only shows a small red-shift when compared to the plain core nanocrystals. [30, 31, 35] In contrast to type-I core-shell nanocrystals, only few studies have been conducted on colloidal type-II core/shell structures [36-38] which are characterized by a staggered alignment of conduction and valence bands giving rise to a broad tunability of absorption and emission wavelengths, as was shown for CdTe/CdSe core-shell nanocrystals. [36] The emission of type-II core/shell nanocrystals mainly originates from the radiative recombination of electron-hole pairs across the core-shell interface leading to a long photoluminescence lifetime. Type-II core/shell nanocrystals are promising with respect to photoconduction or photovoltaic applications as has been discussed in the literature.[39] Novel type-II core-shell structures with ZnTe cores are reported in chapter 5. The recent progress in the shape control of semiconductor nanocrystals opens new fields of applications. For instance, rod shaped CdSe nanocrystals can enhance the photo-electro conversion efficiency of photovoltaic cells, [40, 41] and also allow for polarized emission in light emitting diodes. [42, 43] Shape control of anisotropic nanocrystals can be achieved by the use of surfactants, [44, 45] regular or inverse micelles as regulating agents, [46, 47] electrochemical processes, [48] template-assisted [49, 50] and solution-liquid-solution (SLS) growth mechnism. [51-53] Recently, formation of various CdSe nanocrystal shapes has been reported by the groups of Alivisatos [54] and Peng, [55] respectively. Furthermore, it has been reported by the group of Prasad [56] that noble metal nanoparticles can induce anisotropic growth of CdSe nanocrystals at lower temperatures than typically used in other methods for preparing anisotropic CdSe structures. Although several approaches for anisotropic crystal growth have been reported by now, developing new synthetic methods for the shape control of colloidal semiconductor nanocrystals remains an important goal. Accordingly, we have attempted to utilize a crystal phase control approach for the controllable synthesis of colloidal ZnE/CdSe (E = S, Se, Te) heterostructures in a variety of morphologies. The complex heterostructures obtained are presented in chapter 6. The unique optical properties of nanocrystals make them appealing as in vivo and in vitro fluorophores in a variety of biological and chemical investigations, in which traditional fluorescence labels based on organic molecules fall short of providing long-term stability and simultaneous detection of multiple emission colours [References]. The ability to prepare water soluble nanocrystals with high stability and quantum yield has led to promising applications in cellular labeling, [57, 58] deep-tissue imaging, [59, 60] and assay labeling [61, 62]. Furthermore, appropriately solubilized nanocrystals have been used as donors in fluorescence resonance energy transfer (FRET) couples. [63-65] Despite recent progress, much work still needs to be done to achieve reproducible and robust surface functionalization and develop flexible (bio-) conjugation techniques. Based on multi-shell CdSe nanocrystals, several new solubilization and ligand exchange protocols have been developed which are presented in chapter 7. The organization of this thesis is as follows: A short overview describing synthesis and properties of CdSe nanocrystals is given in chapter 2. Chapter 3 is the experimental part providing some background information about the optical and analytical methods used in this thesis. The following chapters report the results of this work: synthesis and characterization of type-I multi-shell and type-II core/shell nanocrystals are described in chapter 4 and chapter 5, respectively. In chapter 6, a high–yield synthesis of various CdSe architectures by crystal phase control is reported. Experiments about surface modification of nanocrystals are described in chapter 7. At last, a short summary of the results is given in chapter 8.

New supported transition metal complexes: synthesis, characterization and application as catalysts for oxidation/hydrodesulphurization reactions

This thesis deals with the synthesis and charcterisation of some supported transition metal complexes and their catalytic properties. Two industrially important reactions were carried out: i) cyclohexanol oxidation and ii) hydrodesulphurization of diesel. Thesis is divided into nine chapters. An overview of the heterogenised homogeneous systems is given in Chapter 1. Chapter 2 deals with the materials and methods used for the preparation and characterisation. Details regarding the synthesis and characterisation of zeolite encapsulated transition metal complexes are given in Chapter 3 to Chapter 7. In Chapter 8, the results of catalytic activity studies of the cyclohexanol oxidation using the zeolite encapsulated complexes are presented. Details of preparation of hydrodesulphurization catalysts through the molecular designed dispersion method, their characterization and catalytic activity studies are presented in Chapter 9. References are given at the end of the thesis.

On the Synthesis and Multifunctional Properties of some Nanocrystalline Spinel Ferrites and Magnetic Nanocomposites

This thesis lays importance in the preparation and characterization of a few selected representatives of the ferrite family in the nanoregime. The candidates being manganese zinc ferrite and cobalt ferrite prepared by coprecipitation and sol-gel combustion techniques respectively. The thesis not only stresses importance on the preparation techniques and optimization of the reaction conditions, but emphasizes in investigating the various properties namely structural, magnetic and electrical. Passivated nickel nanocomposites are synthesized using polystyrene beads and adopting a novel route of ion exchange reduction. The structural and magnetic properties of these magnetic nanocomposites are correlated. The magnetocaloric effect (MCE) exhibited by these materials are also investigated with a view to finding out the potential of these materials as magnetic refrigerants. Calculations using numerical methods are employed to evaluate the entropy change on selected samples.

Synthesis and some properties of hybrid gels of titanium oxide containing europium (III)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Metabolism and action of 9-$\beta$-D-arabinofuranosyl-2-fluoroadenine

9-$\beta$-D-arabinofuranosyl-2-fluoroadenine (F-ara-A) is an analogue of adenosine and 2$\sp\prime$-deoxyadenosine with potent antitumor activity both in vitro and in vivo. The mechanism of action of F-ara-A was evaluated both in whole cells and in experimental systems with purified enzymes. F-ara-A was converted to its 5$\sp\prime$-triphosphate F-ara-ATP in cells and then incorporated into DNA in a self-limiting manner. About 98% of the incorporated F-ara-AMP residues were located at the 3$\sp\prime$-termini of DNA strands, suggesting a chain termination property of this compound. DNA synthesis in CEM cells was inhibited by F-ara-A treatment with an IC$\sb{50}$ value of 1 $\mu$M. Cells were not able to restore the normal level of DNA synthesis even after being cultured in drug-free medium for 40 h. A DNA primer extension assay with M13mp18(+) single-stranded DNA template using purified human DNA polymerases $\alpha$ and further revealed that F-ara-ATP competed with dATP for incorporation into the A sites of the elongating DNA strands. The incorporation of F-ara-AMP into DNA resulted in a termination of DNA synthesis at the incorporated A sites. Pol $\alpha$ and $\delta$ were not able to efficiently extend the DNA primer with F-ara-AMP at its 3$\sp\prime$-end. Furthermore, the presence of F-ara-AMP at the 3$\sp\prime$-end of an oligodeoxyribonucleotide impaired its ligation with an adjacent DNA fragment by human and T4 ligases. Human DNA polymerase $\alpha$ incorporated more F-ara-AMP into DNA than polymerase $\delta$ and was more sensitive to the inhibition by F-ara-ATP, suggesting that polymerase $\alpha$ may be a preferred target for this analogue. On the other hand, DNA-dependent nucleotide turnover experiments and sequencing gel analysis demonstrated that DNA polymerase $\delta$ was able to remove the incorporated F-ara-AMP residue from the 3$\sp\prime$-end of the DNA strand with its 3$\sp\prime$-5$\sp\prime$ exonuclease activity in vitro, subsequently permitting further elongation of the DNA strand.^ The incorporation of F-ara-AMP into DNA was linearly correlated both with the inhibition of DNA synthesis and with the loss of clonogenicity. Termination of DNA synthesis and deletion of genetic material resulted from F-ara-AMP incorporation may be the mechanism responsible for cytotoxicity of F-ara-A. (Abstract shortened with permission of author.) ^