Tailoring Structure: Current Design Strategies and Emerging Trends to Hierarchical Catalysts

Nature mimicking implies the design of nanostructured materials, which can be assembled into a hierarchical structure, thus outperforming the features of the neat components because of their multiple length scale organization. This approach can be effectively exploited for the design of advanced photocatalysts with superior catalytic activity for energy and environment applications with considerable development in the recent six years. In this context, we propose a review on the state of the art for hierarchical photocatalyst production. Particularly, different synthesis strategies are presented, including template-free structuring, and organic, inorganic, and hybrid templating. Furthermore, emerging approaches based on hybrid and bio-waste templating are also highlighted. Finally, a critical comparison among available methods is carried out based on the envisaged application

Tailoring Structure: Current Design Strategies and Emerging Trends to Hierarchical Catalysts

Nature mimicking implies the design of nanostructured materials, which can be assembled into a hierarchical structure, thus outperforming the features of the neat components because of their multiple length scale organization. This approach can be effectively exploited for the design of advanced photocatalysts with superior catalytic activity for energy and environment applications with considerable development in the recent six years. In this context, we propose a review on the state of the art for hierarchical photocatalyst production. Particularly, different synthesis strategies are presented, including template-free structuring, and organic, inorganic, and hybrid templating. Furthermore, emerging approaches based on hybrid and bio-waste templating are also highlighted. Finally, a critical comparison among available methods is carried out based on the envisaged application

Electrospun hybrid TiO<inf>2</inf>/humic substance PHBV films for active food packaging applications

Sustainable packaging materials can play a key role in minimizing the environmental footprint of packaged food by preserving its quality and avoiding environmental persistence of plastic waste. Waste to wealth approach can cope with these major challenges by providing for bioavailable active compounds from waste residues. To this regard, humic substances (HS), derived from biowaste oxidative processes, exhibit intrinsic antioxidant and antimicrobial features, which can be significantly boosted by molecular combination with an inorganic nanostructured phase. Herein, this approach has been integrated with the electrospinning technology to design composite films made of electrospun biodegradable and bioderived polymers filled with nanostructured hybrid HS based materials. Therefore, electrospun composites made by including hybrid TiO2_HS nanostructures into PHBV matrix were first produced and then converted into homogeneous and continuous films to obtain an active layer which will be part of a multilayer food packaging solution. These were characterized in terms of morphology, thermal, crystallinity, optical, mechanical and barrier properties as well as antimicrobial performance against Staphylococcus aureus and Escherichia coli, two main strains of food pathogens. The results suggested that the combination of hybrid nanomaterials with electrospinning methodology is a promising and sustainable approach to convert biowaste into multifunctional materials for active packaging.The authors thank the Verde Vita company (s.r.l.) for providing the compost from which the humic substance HS used in this work was extracted. The authors wish to thank the European Union POC Ricerca e Innovazione 2014–2020, Azione I.1 “Dottorati Innovativi con caratterizzazione Industriale”) for funding a XXXV Cycle Ph.D. grant to Dr. Virginia Venezia. The collaboration with this company is foreseen as part of the activity scheduled in the POC doctoral project. The authors would also like to thank the Spanish Ministry of Science and Innovation, project PID2021-128749OB-C31 for financial support.Peer reviewedPID2021-128749OB-C3

Waste to Wealth Approach: Improved Antimicrobial Properties in Bioactive Hydrogels through Humic Substance-Gelatin Chemical Conjugation

: Exploring opportunities for biowaste valorization, herein, humic substances (HS) were combined with gelatin, a hydrophilic biocompatible and bioavailable polymer, to obtain 3D hydrogels. Hybrid gels (Gel HS) were prepared at different HS contents, exploiting physical or chemical cross-linking, through 1-ethyl-(3-3-dimethylaminopropyl)carbodiimide (EDC) chemistry, between HS and gelatin. Physicochemical features were assessed through rheological measurements, X-ray diffraction, attenuated total reflectance (ATR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and scanning electron microscopy (SEM). ATR and NMR spectroscopies suggested the formation of an amide bond between HS and Gel via EDC chemistry. In addition, antioxidant and antimicrobial features toward both Gram(-) and Gram(+) strains were evaluated. HS confers great antioxidant and widespread antibiotic performance to the whole gel. Furthermore, the chemical cross-linking affects the viscoelastic behavior, crystalline structures, water uptake, and functional performance and produces a marked improvement of biocide action

Tuning Functional Behavior of Humic Acids through Interactions with Stöber Silica Nanoparticles

Humic acids (HA) exhibit fascinating multifunctional features, yet degradation phenomena as well as poor stability in aqueous environments strongly limit their use. Inorganic nanoparticles are emerging as a powerful interface for the development of robust HA bio-hybrid materials with enhanced chemical stability and tunable properties. Hybrid organic-inorganic SiO2/HA nanostructures were synthesized via an in-situ sol-gel route, exploiting both physical entrapment and chemical coupling. The latter was achieved through amide bond formation between carboxyl groups of HA and the amino group of 3-aminopropyltriethoxysilane (APTS), as confirmed by Fourier-Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopy. Monodisperse hybrid nanoparticles about 90 nm in diameter were obtained in both cases, yet Electron Paramagnetic Resonance (EPR) spectroscopy highlighted the different supramolecular organization of HA. The altered HA conformation was reflected in different antioxidant properties of the conjugated nanoparticles that, however, resulted in being higher than for pure HA. Our findings proved the key role of both components in defining the morphology of the final system, as well as the efficacy of the ceramic component in templating the HA supramolecular organization and consequently tuning their functional features, thus defining a green strategy for bio-waste valorizatio

Shall We Tune? From Core-Shell to Cloud Type Nanostructures in Heparin/Silica Hybrids

Heparin plays multiple biological roles depending on the availability of active sites strongly influenced by the conformation and the structure of polysaccharide chains. Combining different components at the molecular scale offers an extraordinary chance to easily tune the structural organization of heparin required for exploring new potential applications. In fact, the combination of different material types leads to challenges that cannot be achieved by each single component. In this study, hybrid heparin/silica nanoparticles were synthesized, and the role of silica as a templating agent for heparin supramolecular organization was investigated. The effect of synthesis parameters on particles compositions was deeply investigated by Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). Transmission Electron Microscopy (TEM) reveals a different supramolecular organization of both components, leading to amazing organic-inorganic nanoparticles with different behavior in drug encapsulation and release. Furthermore, favorable biocompatibility for healthy human dermal fibroblasts (HDF) and tumor HS578T cells has been assessed, and a different biological behavior was observed, ascribed to different surface charge and morphology of synthesized nanoparticles