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Sustainable active food packaging is essential to reduce the use of plastics, preserve food quality and minimize the environmental impact. Humic substances (HS) are rich in redox-active compounds, such as quinones, phenols, carboxyl, and hydroxyl moieties, making them functional additives for biopolymeric matrices, such as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). Herein, composites made by incorporating different amounts of HS into PHBV were developed using the electrospinning technology and converted into homogeneous and continuous films by a thermal post-treatment to obtain a bioactive and biodegradable layer which could be part of a multilayer food packaging solution. The morphology, thermal, optical, mechanical, antioxidant and barrier properties of the resulting PHBV-based films have been evaluated, as well as the antifungal activity against Aspergillus flavus and Candida albicans and the antimicrobial properties against both Gram (+) and Gram (-) bacterial strains. HS show great potential as natural additives for biopolymer matrices, since they confer antioxidant, antimicrobial, and antifungal properties to the resulting materials. In addition, barrier, optical and mechanical properties highlighted that the obtained films are suitable for sustainable active packaging. Therefore, the electrospinning methodology is a promising and sustainable approach to give biowaste a new life through the development of multifunctional materials suitable in the active bio-packaging.

Photoacoustics (PA) is gaining increasing credit among biomolecular imaging methodologies by virtue of its poor invasiveness, deep penetration, high spatial resolution, and excellent endogenous contrast, without the use of any ionizing radiation. Recently, we disclosed the excellent PA response of a self-structured biocompatible nanoprobe, consisting of ternary hybrid nanoparticles with a silver core and a melanin component embedded into a silica matrix. Although preliminary evidence suggested a crucial role of the Ag sonophore and the melanin-containing nanoenvironment, whether and in what manner the PA response is controlled and affected by the self-structured hybrid nanosystems remained unclear. Because of their potential as multifunctional platforms for biomedical applications, a detailed investigation of the metal-polymer-matrix interplay underlying the PA response was undertaken to understand the physical and chemical factors determining the enhanced response and to optimize the architecture, composition, and performance of the nanoparticles for efficient imaging applications. Herein, we provide the evidence for a strong synergistic interaction between eumelanin and Ag which suggests an important role in the in situ-generated metal-organic interface. In particular, we show that a strict ratio between melanin and silver precursors and an accurate choice of metal nanoparticle dimension and the kind of metal are essential for achieving strong enhancements of the PA response. Systematic variation of the metal/melanin component is thus shown to offer the means of tuning the stability and intensity of the photoacoustic response for various biomedical and theranostic applications.

The existing literature survey reports rare and conflicting studies on the effect of the preparation method of metal-based semiconductor photocatalysts on structural/morphological features, electronic properties, and kinetics regulating the photocatalytic H-2 generation reaction. In this investigation, we compare the different copper/titania-based photocatalysts for H-2 generation synthesized via distinct methods (i.e., photodeposition and impregnation). Our study aims to establish a stringent correlation between physicochemical/electronic properties and photocatalytic performances for H-2 generation based on material characterization and kinetic modeling of the experimental outcomes. Estimating unknown kinetic parameters, such as charge recombination rate and quantum yield, suggests a mechanism regulating charge carrier lifetime depending on copper distribution on the TiO2 surface. We demonstrate that H-2 generation photoefficiency recorded over impregnated CuxOy/TiO2 is related to an even distribution of Cu(0)/Cu(I) on TiO2, and the formation of an Ohmic junction concertedly extended charge carrier lifetime and separation. The outcomes of the kinetic analysis and the related modeling investigation underpin photocatalyst physicochemical and electronic properties. Overall, the present study lays the groundwork for the future design of metal-based semiconductor photocatalysts with high photoefficiencies for H-2 evolution.

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.