Caratterizzazione di sistemi molecolari e nanoparticelle a trasduzione ottica per lo sviluppo di sensori chimici

With the increasing importance that nanotechnologies have in everyday life, it is not difficult to realize that also a single molecule, if properly designed, can be a device able to perform useful functions: such a chemical species is called chemosensor, that is a molecule of abiotic origin that signals the presence of matter or energy. Signal transduction is the mechanism by which an interaction of a sensor with an analyte yields a measurable form of energy. When dealing with the design of a chemosensor, we need to take into account a “communication requirement” between its three component: the receptor unit, responsible for the selective analyte binding, the spacer, which controls the geometry of the system and modulates the electronic interaction between the receptor and the signalling unit, whose physico-chemical properties change upon complexation. A luminescent chemosensor communicates a variation of the physico-chemical properties of the receptor unit with a luminescence output signal. This thesis work consists in the characterization of new molecular and nanoparticle-based system which can be used as sensitive materials for the construction of new optical transduction devices able to provide information about the concentration of analytes in solution. In particular two direction were taken. The first is to continue in the development of new chemosensors, that is the first step for the construction of reliable and efficient devices, and in particular the work will be focused on chemosensors for metal ions for biomedical and environmental applications. The second is to study more efficient and complex organized systems, such as derivatized silica nanoparticles. These system can potentially have higher sensitivity than molecular systems, and present many advantages, like the possibility to be ratiometric, higher Stokes shifts and lower signal-to-noise ratio

Simple Strategies to Modulate the pH-Responsiveness of Lignosulfonate-Based Delivery Systems

The extensive use of non-degradable microplastics in a wide plethora of daily life products is causing serious pollution problems. More ecofriendly solutions are therefore urgently needed. In this context, the use of lignin, a largely available aromatic polymer, may represent a viable option. Due to the self-assembly ability of its molecules, lignin is in fact an ideal matrix for the fabrication of nanostructures. In this study, lignosulfonate microcapsules containing a limonene core were prepared and characterized in terms of their dimensions and of the physicochemical characteristics of the capsule-forming lignosulfonate molecules. The main purpose is to elucidate the key properties governing the pH-responsive behavior of the capsules to be able to achieve better control over the release kinetics of the entrapped compound(s). The results demonstrate that both the molecular weight and the concentration of sulfonate groups are the most important factors in this respect. Based on these findings, two strategies were followed to further tailor the capsules’ behavior: (i) fractionation of the starting lignosulfonate by solvent extraction and (ii) introduction of a specific additive in the formulation. The first approach permitted to fabricate highly resistant capsules both in acidic, as well as in alkaline conditions, while in the second case the chemical structure of the additive, the diester diveratryl sebacate, allowed for fast kinetics of release, as values above 70% were reached after 24 h of incubation at pH 4 and pH 12

Lignin-based nano-enabled agriculture: A mini-review

Nowadays sustainable nanotechnological strategies to improve the efficiency of conventional agricultural practices are of utmost importance. As a matter of fact, the increasing use of productive factors in response to the growing food demand plays an important role in determining the environmental impact of agriculture. In this respect, low-efficiency conventional practices are becoming obsolete. On the other hand, the exploitation of nanoscaled systems for the controlled delivery of fertilizers, pesticides and herbicides shows great potential towards the development of sustainable, efficient and resilient agricultural processes, while promoting food security. In this context, lignin - especially in the form of its nanostructures - can play an important role as sustainable biomaterial for nano-enabled agricultural applications. In this review, we present and discuss the current advancements in the preparation of lignin nanoparticles for the controlled release of pesticides, herbicides, and fertilizers, as well as the latest findings in terms of plant response to their application. Special attention has been paid to the state-of-the-art literature concerning the release performance of these lignin-based nanomaterials, whose efficiency is compared with the conventional approaches. Finally, the major challenges and the future scenarios of lignin-based nano-enabled agriculture are considered

Tailoring the pH-responsiveness of lignin-based microcapsules

Lignosulfonate (LS)-shell limonene-core microcapsules (LMCs) were prepared by ultrasonication. To achieve better control over the pH-responsiveness, (i) fractionation of the starting LS by solvent extraction and (ii) introduction of diveratryl sebacate (DS) into the formulation were performed. High molecular weight fraction enabled the preparation of highly stable LMCs, while the presence of DS caused faster release kinetics

Solvent-based fractionation of lignosulfonates

Lignosulfonates, i.e. technical lignins derived from the sulphite process, suffer from high heterogeneity. With the aim of obtaining materials with more homogeneous and defined characteristics, this contribution focuses on lignosulfonate fractionation, specifically by applying sequential solvent extraction (SSE) to softwood and hardwood lignosulfonate samples. The obtained fractions are fully characterized from the physicochemical point of view

Nanoparticles for Adsorption and Photocatalytic Degradation of Methylene Blue in Water

The full use of biomass plays a central role in transition to a circular bioeconomy. Unlike non-biobased adsorbents, which are criticized for high production costs and the generation of secondary pollutants, lignin nanoparticles (LNPs) are a cost-effective and environmentally benign alternative for water treatment. In this study, LNPs were demonstrated for the first time as multifunctional materials for the adsorption and UV-light driven photocatalytic degradation of methylene blue dye (MB) in water

Lignin Nanoparticles for Adsorption and Photocatalytic Degradation of Methylene Blue in Water

The full use of biomass plays a central role in transition to a circular bioeconomy. Unlike non-biobased adsorbents, which are criticized for high production costs and the generation of secondary pollutants, lignin nanoparticles (LNPs) are a cost-effective and environmentally benign alternative for water treatment. In this study, LNPs were demonstrated for the first time as multifunctional materials for the adsorption and UV-light driven photocatalytic degradation of methylene blue dye (MB) in water

Towards Utilising Photocrosslinking of Polydiacetylenes for the Preparation of { extquotedblleft}Stealth{ extquotedblright} Upconverting Nanoparticles

We demonstrate a novel strategy for preparing hydrophilic upconverting nanoparticles (UCNPs) by harnessing the photocrosslinking ability of diacetylenes. Replacement of the hydrophobic oleate coating on the UCNPs with 10,12- pentacosadiynoic acid, followed by overcoating with diacetylene phospholipid and subsequent photocrosslinking under 254 nm irradiation produces water-dispersible polydiacetylene- coated UCNPs. These UCNPs resist the formation of a biomolecular corona and show great colloidal stability. Furthermore, amine groups on the diacetylene phospholipid allow for functionalisation of the UCNPs with, for example, radiolabels or targeting moieties. These results demonstrate that this new surface-coating method has great potential for use in the preparation of UCNPs with improved biocompatibility

A quest for supramolecular gelators: silver(I) complexes with quinoline-urea derivatives

The quinoline urea derivatives 1,3-di(quinolin-5-yl) urea (DQ5U), 1-phenyl-3-(quinolin-6-yl) urea (PQ6U), 1-(isoquinolin-5-yl)-3-phenylurea (PiQ5U) and 1-phenyl-3-(3,5-bis(pyrid-2-yl)-1,2,4-triazol-4-yl) urea (PPT4U) have been synthesised and structurally characterized by powder and single crystal X-ray diffraction. Their gelator behaviour in the formation of Ag-complexes has been explored. Compound DQ5U proved capable of gelating the mixed solvent EtOH-DMF 1:2 (v/v) when mixed with 1 equivalent of AgNO3. In the case of PQ6U, two polymorphic forms of the complex [Ag(PQ6U)(2)]NO3, plus the solvated form [Ag(PQ6U)(2)]NO3 center dot CH3CN, were crystallized. Photophysical characterization of the ligands has been conducted in solution, while fluorescence microscopy has been used to examine the microstructure and photophysical properties of the gels formed by PQ5U and DQ5U with AgNO3