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This work explores the self-assembly and optical properties of a novel chiral, aromatic-rich Boc-Phe-Phe dipeptide derivative functionalized with a benzothiazole bicyclic ring that forms supramolecular structures. Leveraging the well-known self-assembling capabilities of diphenylalanine dipeptides, this modified derivative introduces a heterocyclic benzothiazole unit that significantly enhances the fluorescence of the resulting nanostructures. The derivative’s rich aromatic character drives the formation of supramolecular structures through self-organization mechanisms influenced by quantum confinement. By adjusting the solvent system, the nanostructures exhibit tunable morphologies, ranging from nanospheres to nanobelts. The nonlinear optical properties of these self-assembled structures were studied and an estimated deff of ~0.9 pm/V was obtained, which is comparable to that reported for the highly aromatic triphenylalanine peptide.

In this study, thin films composed of gold nanoparticles embedded in a copper oxide matrix (Au:CuO), manifesting Localized Surface Plasmon Resonance (LSPR) behavior, were produced by reactive DC magnetron sputtering and post-deposition in-air annealing. The effect of low-power Ar plasma etching on the surface properties of the plasmonic thin films was studied, envisaging its optimization as gas sensors. Thus, this work pretends to attain the maximum sensing response of the thin film system and to demonstrate its potential as a gas sensor. The results show that as Ar plasma treatment time increases, the host CuO matrix is etched while Au nanoparticles are uncovered, which leads to an enhancement of the sensitivity until a certain limit. Above such a time limit for plasma treatment, the CuO bonds are broken, and oxygen is removed from the film’s surface, resulting in a decrease in the gas sensing capabilities. Hence, the importance of the host matrix for the design of the LSPR sensor is also demonstrated. CuO not only provides stability and protection to the Au NPs but also promotes interactions between the thin film’s surface and the tested gases, thereby improving the nanocomposite film’s sensitivity. The optimized sensor sensitivity was estimated at 849 nm/RIU, which demonstrates that the Au-CuO thin films have the potential to be used as an LSPR platform for gas sensors.

This study aims to evaluate the lifespan of Ti-Ag dry electrodes prepared using flexible polytetrafluoroethylene (PTFE) substrates. Following previous studies, the electrodes were designed to be integrated into wearables for remote electromyography (EMG) monitoring and electrical stimulation (FES) therapy. Four types of Ti-Ag electrodes were prepared by DC magnetron sputtering, using a pure-Ti target doped with a growing number of Ag pellets. After extensive characterization of their chemical composition and (micro)structural evolution, the Ti-Ag electrodes were immersed in an artificial sweat solution (standard ISO-3160-2) at 37 °C with constant stirring. Results revealed that all the Ti-Ag electrodes maintained their integrity and functionality for 24 h. Although there was a notable increase in electrical resistivity beyond this timeframe, the acquisition and transmission of (bio)signals remained viable for electrodes with Ag/Ti ratios below 0.23. However, electrodes with higher Ag content (Ag/Ti = 0.31) became insulators after 7 days of immersion due to excessive Ag release into the sweat solution. This study concludes that higher Ag/Ti atomic ratios result in heightened corrosion processes on the electrode’s surface, consequently diminishing their lifespan despite the advantages of incorporating Ag into their composition. This research highlights the critical importance of evaluating electrode longevity, especially in remote biomedical applications like smart wearables, where electrode performance over time is crucial for reliable and sustained monitoring and stimulation.

In this study, a material based on polyethylene (PE) and microcrystalline cellulose (MC) was developed as a breathable packaging film. Surface functionalization of MC with 3-aminopropyltriethoxysilane (APTES) has been shown to be an efficient option to tailor their properties and increase opportunities for the application of MC on the reinforcement of polymers such as polyethylene (PE). The functionalization of MC with the mentioned silane derivative was achieved using a green method and later used in the development of composites with PE in three percentages (1, 3, and 5%). All the materials were prepared by melt blending and characterized in terms of structural properties (ATR-FTIR and FTIR in transmittance mode, EDX, and SEM), thermal properties (DSC and TGA), thermomechanical properties (DMA), contact angle measurements and permeability to water vapor. The materials demonstrated the potential to be used as breathable film packaging for fresh products.

Optical biosensors based on localized surface plasmon resonance (LSPR) are the future of label-free detection methods. This work reports the development of plasmonic thin films, containing Au nanoparticles dispersed in a TiO2 matrix, as platforms for LSPR biosensors. Post-deposition treatments were employed, namely annealing at 400 °C, to develop an LSPR band, and Ar plasma, to improve the sensitivity of the Au-TiO2 thin film. Streptavidin and biotin conjugated with horseradish peroxidase (HRP) were chosen as the model receptor–analyte, to prove the efficiency of the immobilization method and to demonstrate the potential of the LSPR-based biosensor. The Au-TiO2 thin films were activated with O2 plasma, to promote the streptavidin immobilization as a biorecognition element, by increasing the surface hydrophilicity (contact angle drop to 7°). The interaction between biotin and the immobilized streptavidin was confirmed by the detection of HRP activity (average absorbance 1.9 ± 0.6), following a protocol based on enzyme-linked immunosorbent assay (ELISA). Furthermore, an LSPR wavelength shift was detectable (0.8 ± 0.1 nm), resulting from a plasmonic thin-film platform with a refractive index sensitivity estimated to be 33 nm/RIU. The detection of the analyte using these two different methods proves that the functionalization protocol was successful and the Au-TiO2 thin films have the potential to be used as an LSPR platform for label-free biosensors.

In this work, alpha-tocopherol (α-TOC) was encapsulated in poly(lactic acid) nanoparticles (PLA NPs) and added to low-density polyethylene (LDPE) films with the aim of producing an active film for food packaging applications. PLA NPs loaded with α-TOC were produced through nanoprecipitation and dried using two methods (freeze-dryer and oven). LDPE-based films with final polymeric matrix concentrations of 10 and 20 g/kg were then produced through blow extrusion. The results showed that LDPE-based films loaded with α-TOC can be produced using blow extrusion, and a good distribution of PLA NPs can be obtained within the LDPE matrix as observed using scanning electron microscopy (SEM). The mechanical properties were affected by the incorporation of α-TOC and PLA NPs loaded with α-TOC, with the observation of a decrease in tensile strength and Young’s Modulus values and an increase in elongation at break. Regarding water vapor permeability, the films showed a reduction in the values with the addition of α-TOC and PLA NPs loaded with α-TOC compared to the LDPE film (control). Films with α-TOC in the free state and loaded in PLA NPs showed antioxidant activity, but their behavior was affected by the encapsulation process.

Microbial development, enzymatic action, and chemical reactions influence the quality of untreated natural orange juice, compromising its organoleptic characteristics and causing nutritional value loss. Active low-density polyethylene (LDPE) films containing green tea extract (GTE) were previously prepared by a blown film extrusion process. Small bags were prepared from the produced films, which were then filled with fresh orange juice and stored at 4 °C. Ascorbic acid (AA) content, sugar content, browning index, color parameters, pH, total acidity (TA) and microbial stability were evaluated after 3, 7, and 14 days of storage. The packaging containing GTE maintained the microbial load of fresh juice beneath the limit of microbial shelf-life (6 log CFU/mL) for the bacterial growth, with a more prominent effect for LDPE with 3%GTE. Regarding yeasts and molds, only the CO_LDPE_3GTE package maintained the microbial load of fresh juice below the limit for up to 14 days. At 14 days, the lowest levels of AA degradation (32.60 mg/100 mL of juice) and development of brown pigments (browning index = 0.139) were observed for the packages containing 3% of GTE, which had a pH of 3.87 and sugar content of 11.4 g/100 mL of juice at this time. Therefore, active LDPE films containing 3% of GTE increase the shelf-life of fresh juice and can be a promising option for storage of this food product while increasing sustainability.

Bio-based polyurethane materials are broadly applied in medicine as drug delivery systems. Nevertheless, their synthesis comprises the use of petroleum-based toxic amines, isocyanates and polyols, and their biocompatibility or functionalization is limited. Therefore, the use of lysine residues as amine sources to create non-isocyanate urethane (NIU) linkages was investigated. Therefore, a five-membered biscyclic carbonate (BCC) was firstly synthetized and reacted with a protected lysine, a tripeptide and a heptapeptide to confirm the urethane linkage formation with lysine moiety and to optimize reaction conditions. Afterwards, the reactions between BCC and a model protein, elastin-like protein (ELP), and β-Lactoglobulin (BLG) obtained from whey protein, respectively, were performed. The synthesized protein materials were structural, thermally and morphologically characterized to confirm the urethane linkage formation. The results demonstrate that using both simple and more complex source of amines (lysine), urethane linkages were effectively achieved. This pioneering approach opens the possibility of using proteins to develop non-isocyanate polyurethanes (NIPUs) with tailored properties.

The entrapment of quantum dots (QDs) in the inner part of micelles formed by surfactant polymers is a powerful methodology to prepare stable and photoluminescent core nanoparticles with enhanced optical properties. These features are crucial for the application of QDs in the design of hybrid assemblies for light harvesting applications, where energy transfer processes are required. The present work was focused on the synthesis of a surfactant homopolymer, poly (acrylic acid) (PAA) macroRAFT, to be used as a stabilizer of hydrophobic cadmium telluride (CdTe) QDs in aqueous solution. PAA macroRAFT was synthesized by reversible addition-fragmentation chain-transfer (RAFT) polymerization in a single chemical reaction. Its micelles were used to entangle and entrap hydrophobic CdTe QDs, with different molar ratio of polymer and QDs. The morphology and optical properties of the entrapped QDs were determined. The results showed that PAA macroRAFT is able to form micelles with a critical micelle concentration of 2.08 mg/mL. It was also noticed that the molar ratio of polymer and QDs have high influence on the QDs’ morphology and their optical properties. The QDs’ photoluminescence quantum yield was enhanced approximately 23% upon their entrapment in PAA macroRAFT micelles, using 60 equivalents of polymer. Moreover, while in solution, QDs are well-dispersed, having a 3.5 nm diameter, upon being entrapped in the micelles, tend to form clusters with a size around 100 nm. Graphical Abstract ᅟ

The negative impact of the used tires residues can be reduced by reusing their rubber as a constituent of asphalt rubber (AR) mixtures, thus contributing for a sustainable development of road infrastructures. However, the increasing demands on the durability of pavements require a deeper knowledge about the physicochemical changes of the AR binders. The main objective of this research is to characterize the influence of bitumen in the rubber morphology and the changes in the density of bitumen, rubber and AR during its production. Four base bitumens interacted with crumb rubber in order to produce AR binders, which were then separated by using a modified \"basket drainage method\". The changes in rubber were studied through microscopy, swelling and depolymerization tests. It was concluded that i) the rubber particles swelled 250% their weight, but only increased 2.5% their equivalent diameter; ii) rubber particles can swell till saturation after interacting with softer bitumens; iii) re-vulcanization and re-polymerization among the rubber particles can eventually occur.