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

Modulation of physicochemical and antioxidant properties of Pickering emulsions using colloidal lignin particles based on kraft softwood and hardwood acetone fractions

Colloidal lignin particles (CLPs) emerge as a sustainable alternative to traditional, fossil-based emulsion stabilizers. However, effectively outperforming the conventional ingredients requires addressing the challenges posed by lignin heterogeneity and structural complexity. In this study, one-step acetone fractionation was applied to softwood and hardwood kraft lignins to tackle the issue. The resulting soluble (AS) and insoluble (AI) fractions, along with the pristine lignins, underwent thorough characterization and were used to create CLPs through the hydrotropic precipitation. The acetone fraction-derived CLPs were tested for the first time as Pickering stabilizers. Notably, a strong correlation emerged between the structural traits of each lignin sample and the properties of the resulting Pickering emulsions. Such correlation allowed for a fine-tuning of their physicochemical and antioxidant features. The AS fractions, characterized by higher phenolic OH content and lower molecular weight, led to CLPs with larger sizes and reduced hydrophilic character compared to those derived from AI- and pristine lignins. The fraction-derived CLPs exhibited superior emulsifying capacity and imparted long-term stability to the formed emulsions. Moreover, the resulting Pickering emulsions showed high potential as antioxidant agents, proving their ability as multifunctional systems. Overall, this work demonstrates how the unique properties of lignin can be selectively enhanced through acetone fractionation method and seamlessly transferred to Pickering emulsions. This advancement promotes the use of lignin in high-value-added sectors such as cosmetics and personal care.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES (PIDDAC) to CIMO UIDB/00690/2020 (DOI: 10.544 99/UIDB/00690/2020) and UIDP/00690/2020 (DOI: 10.544 99/UIDP/00690/2020); SusTEC LA/P/0007/2020 (DOI: 10.54499/ LA/P/0007/2020); LSRE-LCM UIDB/50020/2020 (DOI: 10.544 99/UIDB/50020/2020) and UIDP/50020/2020 (DOI: 10.544 99/UIDP/50020/2020); and ALiCE LA/P/0045/2020 (DOI: 10.54499/ LA/P/0045/2020). FCT for the Ph.D. research grant of G. Colucci (2021.05215.BD). Daniele Massari, Valeria Gagliardi, and Maryam RahimiHaghighi for the technical support and assistance to conduct experiments. Suzano for the kind supply of Ecolig lignin. IngevityTM for the kind supply of Indulin AT lignin. COST Action LignoCOST (CA17128), supported by COST (European Cooperation in Science and Technology), in promoting interaction, exchange of knowledge, and collaborations in the field of lignin valorizationinfo:eu-repo/semantics/publishedVersio

ZnO Low-Dimensional Thin Films Used as a Potential Material for Water Treatment

In this paper the properties of zinc oxide (ZnO) low-dimensional conductive oxide nanostructures in the aspect of their potential applications in microelectronics, in toxic gas sensors as well as checking whether they can be also used in water treatment has been determined. ZnO nanostructured porous thin films deposited by DC reactive sputtering (RS) have been deposited on Si substrates at different temperature conditions. For the surface properties and chemical morphology analysis the X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) have been used. Thanks to those methods, it is possible to obtain information on changes in the structure caused by the adsorption of various gases from the atmosphere, mainly C pollution from air, but also from the water. Investigated ZnO thin films were also tested for their photocatalytic properties performed in UV light. For this purpose the methylene blue as a dye pollutant to evaluate the activity of the nanostructures has been used. Within this work it has been observed that the ZnO thin films, which were used, react in the selected environment and their presence reduces the amount of dye. This shows that in addition to sensor properties, properly selected zinc oxide nanostructures, used so far in toxic gas sensors, can also be used in the process of water purification and treatment, which is crucial in protecting the natural environment primarily from various types of dyes or also medicines

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

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

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

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

A simple and scalable strategy to develop Kraft lignin-based hydrogels for the adsorption of water pollutants

Kraft lignin hydrogels have been synthesized through a simple, green and energy-saving process in the presence of a cross-linking agent, polyethylene glycol diglycidyl ether (PEGDGE), and fully characterized. The hydrogels can be used to entrap active compounds, during the synthesis process, for controlled release purposes, or they can be employed in the removal of water pollutants. Preliminary adsorption tests, carried out with methylene blue, showed excellent results

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