Preparation of functional nanostructured materials by facile and green methods

A challenging goal of Chemistry is its sustainability towards a circular no-waste approach. This statement has been the mainstream of this PhD work, applied to innovative functional materials based on inorganic hosting substrates. The experimental work has used synthetic strategies, optimization tools and characterization methods to identify and pursue materials with facile, rapid and green preparations for functional photoactive materials, improving durability and performances. A part of the work dealt with the study and optimization of the preparation of tailored inorganic hosts, as synthetic layered clay-like materials (saponite), with a study of the synthetic conditions and the thermal treatment features to achieve high yield, morphological and compositional quality with a reduced energetic payload. Aside, in a waste-reduction strategy, a highly innovative approach was carried on using biomasses (i.e. rice husk and straw) as sources of inorganics for materials with controlled composition. The preparation of functional materials via host-guest architectures was targeted on photoactive systems using anionic (i.e. DyeA) and neutral (GAM2-35) photoactive dyes, to be incorporated in hydrotalcite and synthetic saponite clay respectively. A mechanochemical methodology of intercalation of DyeA into hydrotalcite based on the Liquid Assisted Grinding (LAG) was fully optimized using statistical tools as factorial design and Simplex. Intercalating neutral optically active dyes in saponite was then pursued using a quasi-solid state co-intercalation of GAM2-35 and a proper cationic surfactant (CTAB), avoiding the use of harsh conditions of temperature and pH. To fulfill an approach to sustainable hotoactive host-guest materials, a full asset of high throughput characterization techniques, as in situ XRPD and Uv-Vis methods and chemometric methodologies, was applied to an established fully thermal process coming from the past, the Maya Blue formation from palygorskite and indigo

Crystal packing and layered morphology relationships in naphthalene sulfonate compounds

The crystal structure of sodium naphthalene 2-sulfonate (Na2-NS) is reported. This compound raised the attention as a pollutant, being widely used in industry, and its intercalation in inorganic matrices, such as layered double hydroxides (LDH), could be a suitable removal strategy. The crystal structure of the title compound, despite its simplicity, is not known in the literature, so we looked for a strategy to grow crystals suitable for a single crystal study. Although many attempts were made to recrystallize it, Na2-NS grows in bunches of very thin laminae, with a high degree of mosaicity and intergrowth, explaining the absence of a reported crystal structure. The crystal structure shows layers of Na+ cations with the organic part arranged in between. The crystals grow easily in the layer plane, whilst the growth perpendicular to the layers is driven by weak non-bonding interaction and thus unfavored. The crystal packing features were related to the density of charges in the cationic layer with respect to the size of the anion. By comparing the crystal structures of 2-NS salts with different cations, and with or without an amino substituent in different positions, it was possible to find the relationship between the density of the positive charges and the deepness of interdigitation of the 2-NS moieties. We exploited this information to shed light on the structural features of 2-NS and related compounds intercalated into LDH. The X-ray powder diffraction pattern of 2-NS intercalated LDH (V. Toson, E. Conterosito, L. Palin, et al. Facile intercalation of organic molecules into hydrotalcites by liquid-assisted grinding: yield optimization by a chemometric approach. Cryst. Growth Des. 2015, 15, 5368) resulted consistent with a crystal packing characterized by the partial interdigitation of the 2-NS anions

Low‐cost Photoactive Hybrid Materials: From Green Synthesis to Multi‐technique Analytical Characterization

Low-cost photoactive hybrid materials for light management, based on neutral organic molecules intercalated into saponite, were prepared by facile green methods and characterized. TPBI (2-(2'-tosylaminophenyl)benzimidazole) was chosen as an organic host dye, envisioning its application as a downconverter in silicon or dye-sensitized photovoltaic modules. Mixed with a cationic surfactant, the neutral molecule was intercalated with a sort of "trojan horse" approach by an easy, almost solvent-free method, thus limiting its aggregation. The obtained material was characterized by combining spectroscopic, diffractometric, and microscopic techniques. Moreover, the intercalation of the dye, the species present in the interlayer, their stability and mutual interactions were assessed by TGA-GC-MS. We obtained a material containing a fluorescent dye in the solid state and stabilized by intercalation and dispersion into saponite. At last, this material was used to prepare a photoactive polymer by melt blending, obtaining materials with the desired optical properties, with Stokes shifts larger than 100 nm and an emission yield above 50%

Analytical Characterization of the Intercalation of Neutral Molecules into Saponite

Organo-modified layered materials characterization poses challenges due to their complexity and how other aspects such as contamination, preparation methods and degree of intercalation influence the properties of these materials. Consequently, a deep understanding of their interlayer organization is of utmost importance to optimize their applications. These materials can in fact improve the stability of photoactive molecules through intercalation, avoiding the quenching of their emission at the solid state, to facilitate their use in sensors or other devices. Two synthetic methods for the preparation of saponites with a cationic surfactant (CTABr) and a neutral chromophore (Fluorene) were tested and the obtained products were initially characterized with several complementary techniques (XRPD, SEM, TGA, IR, UV-Vis, Fluorescence and Raman spectroscopy), but a clear understanding of the organization of the guest molecules in the material could not be obtained by these techniques alone. This information was obtained only by thermogravimetry coupled with gas chromatography and mass spectroscopy (TGA-GC-MS) which allowed identifying the species present in the sample and the kind of interaction with the host by distinguishing between intercalated and adsorbed on the surface

Facile Intercalation of Organic Molecules into Hydrotalcites by Liquid-Assisted Grinding: Yield Optimization by a Chemometric Approach

The liquid-assisted grinding (LAG) method was employed for the preparation of low cost, stable, and efficient functional materials, based on organic molecules intercalated into hydrotalcite (LDH). LAG is here exploited to produce hybrid materials with facile preparation methods, low solvent consumption, short reaction times, and high yields, and to allow an easy scale up of the synthesis to industrial production. Six molecules were tested to assess potentialities and limitations of LAG. The experiments showed a significant sensitivity to the molecular nature of the intercalant, resulting in different final yields and also different physical forms of the products (powdery vs pasty materials). With 2-naphtalenesulfonic acid (2-NSA), where the standard recipe gives a yield of about 50%, experimental procedures were optimized by design of experiment (DoE) and simplex chemometric techniques to find the optimal intercalation conditions, reaching 76% of yield. A chemometric-driven strategy with wide applicability in material chemistry for high throughput screening and preparation of intercalated compounds is thus proposed

Synthesis, identification and quantification of oligomers from polyester coatings for metal packaging

Polyester can coatings protect both food and packaging from mutual contamination. Even though, can coatings may release Non-Intentionally Added Substances (NIAS) in addition to Intentionally Added Substances (IAS). As NIAS are mainly constituted by cyclic or linear side products that are formed during the polymerization process, we focused our attention on these oligomeric species of molecular weight <1000 Da. These oligomers were obtained from two different polyester resins, each synthesized from four monomers (two phthalic acids and two diols), and from the corresponding final enamel can coatings using ethanol at 95% and 50% at 60 degrees C for 4 h and 10 days, respectively, as food simulants. HPLC-ESI-MS analysis on the extracts allowed identifying various cyclic and linear oligomers. For the conclusive identification of the different oligomers and their isomeric structures, ad hoc standards were synthesized by acylation reaction between alkyl diols and phthaloyl chlorides. By comparison of H-1 NMR spectra, linear and cyclic oligomers were characterized by finding the major presence of 2 + 2 cyclic compounds. The 16 synthesized standards, 4 linear and 12 cyclic compounds were used to establish a method for quantification of linear and cyclic oligomers in enamel migration samples by micro HPLC-high-resolution MS (HRMS). The results showed no significant differences between the amounts of cyclic oligomers extracted with both ethanol concentrations (50 and 95%) and time contact. The extracts showed only a small amount of linear compounds and a prevalence of 2 + 2 cyclic oligomers. The work shows the great importance of the synthesis of specific standards to allow exact quantification in food contact material migrate