Here, we report the synthesis and characterization of multifunctional Fe3O4-ZrO2:Yb3+/Er3+ hybrid nanoparticles, which simultaneously exhibit magnetic responsiveness, upconversion luminescence, white-light emission, and near-infrared NIR-activated photothermal behavior. The Fe3O4 cores were synthesized by thermal decomposition and subsequently coated with a ZrO2 doped with 2 mol% Yb3+ and 0.8 mol% Er3+ via a modified Stober process, using varied concentrations of zirconium butoxide precursors to modulate the photoactivated response. Structural analyses confirmed the presence of both types of oxides, while spectroscopic and elemental mapping demonstrated successful incorporation of Yb3+/Er3+ ions within the ZrO2 lattice. Magnetic measurements revealed superparamagnetic behavior, characterized by reduced saturation magnetization upon hybrid formation, yet with a preserved magnetothermal response under alternating magnetic fields. Under 975 nm excitation, the nanoparticles initially exhibited green and red upconversion emissions, followed by the emergence of white-light luminescence arising from a multiphoton-driven interconversion mechanism associated with an increase in temperature. Photothermal experiments revealed strong wavelength-dependent heating. Indeed, Fe3O4 cores dominated under 808 nm excitation, whereas Yb3+ dopants enhanced photothermal efficiency at 975 nm, enabling rapid temperature increases up to 212.6 degrees C after 3 min of irradiation. These results underscore the synergistic interface between magnetic and lanthanide-doped upconverting nanomaterials, which allows tuning of optical and thermal outputs by synthesis parameters. Overall, Fe3O4-ZrO2:Yb3+/Er3+ hybrid nanoparticles represent a versatile multifunctional platform with potential for integrated bioimaging, sensing, and therapeutic applications.

Layered transition metal dichalcogenides (TMDs) are widely regarded as chemically inert nanofillers in polymer composites. Here, we demonstrate that this assumption fails under melt-processing conditions. We show that pristine WS2 nanopowders act as heterogeneous catalysts for polyester chain scission during melt extrusion, inducing a catastrophic, 10-fold reduction in molecular weight, severe loss of melt viscosity, printing failure, and brittle mechanical behavior at filler loadings as low as 0.2 wt %. To suppress this unexpected catalytic activity, we develop an edge- and defect-selective functionalization strategy for WS2 based on covalent carboxylation and hydroxylation, followed by surface-initiated ring-opening polymerization of ε-caprolactone. Spectroscopic and microscopic analyses (XPS, XRD, HAADF-STEM, and EELS) demonstrate that polymer grafting is confined to edge and defect sites, while preserving the multilayer 2H-WS2 lattice. When incorporated into a polycaprolactone (PCL) matrix and processed by large-format fused granular fabrication, polymer-grafted WS2 nanostructures exhibit stable melt rheology, excellent printability, and substantial mechanical reinforcement, with Young's modulus and tensile strength increases up to 45% and 65%, respectively, without loss of ductility. Crucially, polymer grafting effectively passivates catalytically active WS2 edge and defect sites, preventing melt-induced polymer degradation. These findings provide direct experimental evidence that exposed edge sites in layered nanomaterials can actively catalyze polymer degradation under melt-processing conditions and establish edge-site passivation as a general design principle to mitigate chemically driven polymer degradation in polyester-based systems during melt processing, with the magnitude of the effect depending on the chemical susceptibility of the host polymer.

In this work, we report the development of novel tungsten disulfide nanocomposites with optical and electrical properties suitable for stereolithography (SL). The dispersion of WS2 nanosheets (WS2-2D) after exfoliation via liquid-phase in DMF could be directly incorporated into commercial photopolymer resins, which allowed the successful printing of WS2-2D nanocomposites with different degrees of complexity. The manufactured nanocomposites, with measured WS2-2D ultra-low concentrations in the range of 0.001 to 0.005 wt%, imparted a green coloration and red fluorescence to the printed parts while maintaining their transparency due to the nanometric size and good exfoliation of the filler. Interestingly, the electrical resistivity of the nanocomposites decreased by eight orders of magnitude compared to the pristine resin, reaching values in the semiconductive range. These findings highlight the potential of WS2-2D nanocomposites for the additive manufacturing of functional components with applications in areas such as plasmonic, photonics, and electronics.

Polymer blending is an interesting strategy to broaden the combination of properties available for a variety of applications. To understand the behaviour of the new materials obtained as well as the influence of the fabrication parameters used, methods to analyse the distribution of polymers in the blend with resolution below the micrometer are required. In this work, we demonstrate the capability of focused ion beam (FIB) tomography to provide 3D information of the polymer distribution in objects obtained by blending acrylonitrile-styrene-acrylate (ASA) with polycarbonate (PC) (50 wt%), fabricated by Fused Filament Fabrication (FFF) and by Injection Moulding (IM). For this, ion beam induced secondary electron (iSE) images show the capability to distinguish unequivocally the two phases in the blend, providing enough contrasts to perform the 3D experiment. Additionally, Monte Carlo simulations show that the lateral spread for incident electrons in PC is 61.7 nm and for Ga+ ions of 26.2 nm, evidencing a better spatial resolution in iSE imaging. The sputtering rate under the ion beam has been quantified for both neat ASA and neat PC to find optimal parameters for the iSE tomography, resulting in a current of 0.05 nA and a dwell time of 3 µs. Our results reveal significant differences in the morphology of ASA/PC blends depending on the fabrication method. Blends obtained by FFF exhibit strong directionality and a co-continuous morphology, whereas IM objects present a droplet-matrix structure. Also, the interface area between the ASA and PC is quantified to be of 3200 μm² for the FFF sample and 1400 μm² for the IM sample, approximately double in FFF than in IM. The reasons for the different morphologies obtained in the studied blends and possible effects in their mechanical properties are discussed.

This study presents the development of a sustainable composite material by incorporating by-products from the cork industry into acrylonitrile butadiene styrene (ABS), with the aim of reducing the environmental impact of plastic composites while maintaining their performance. ABS, a petroleum-based polymer, was used as the matrix, and maleic anhydride (MAH) with dicumyl peroxide (DCP) served as a compatibilizing system to improve interfacial adhesion with cork microparticles. Composites were prepared with 10% w/w cork in various particle sizes and characterized via FTIR, X-ray computed tomography, SEM, mechanical testing, and thermal analysis. The best performing formulation (CPC-125) showed a reduction of only ~16% in tensile modulus and ~7% in tensile strength compared with ABS-g-MAH, with a more pronounced decrease in strain at break (3.23% vs. 17.47%) due to the cork’s inherent rigidity. Thermogravimetric and calorimetric analysis confirmed that thermal stability and processing temperatures remained largely unaffected. These results demonstrate the feasibility of incorporating cork microparticles as a bio-based reinforcing filler in ABS composites, offering a promising strategy to reduce the use of virgin plastics in applications compatible with conventional injection molding.

Lead halide perovskite nanocrystals are attractive for light emitting devices both as electroluminescent and color-converting materials since they combine intense and narrow emissions with good charge injection and transport properties. However, while most perovskite nanocrystals shine at green and red wavelengths, the observation of intense and stable blue emission still remains a challenging target. In this work, a method is reported to attain intense and enduring blue emission (470-480 nm), with a photoluminescence quantum yield (PLQY) of 40%, originating from very small CsPbBr3 nanocrystals (diameter < 3 nm) formed by controllably exposing Cs4PbBr6 to humidity. This process is mediated by the void network of a mesoporous transparent scaffold in which the zero-dimensional Cs4PbBr6 lattice is embedded, which allows the fine control over water adsorption and condensation that determines the optimization of the synthetic procedure and, eventually, the nanocrystal size. The approach provides a means to attain highly efficient transparent and stable blue light-emitting films that complete the palette offered by perovskite nanocrystals for lighting and display applications.

Additive Manufacturing (AM) has already attained a reliable level of maturity, specifically Fused Filament Fabrication (FFF), emerging as the most widespread process. Concurrently, the industrial demand for these parts has increased, requiring the analysis of their internal geometry to determine the level of similarity achieved concerning the expected structures. This work aims to provide tools to characterize FFF parts by relating printing properties to geometrical variables. For this purpose, three samples were printed in Polylactic Acid (PLA) with three different layer heights and analyzed by X-ray Computed Tomography (CT). After processing the images, fractal analysis was carried out using the box-counting method on the voids that appear between the filaments in order to obtain the fractal dimension. The porosity of the voids was also calculated. The analysis identifies the parameters characterizing the voids as number, size, shape, and location. In contrast to traditional porosity studies, the novelty of this work is that fractal analysis provides information about shape and distribution of voids in a single value (fractal dimension). It was corroborated that the fractal dimension depends not only on porosity but also on the shape and location of the voids. Additionally, it was found that not all void parameters influence equally the geometrical variables; variables related to porosity (number and size of voids) are more relevant than shape and location. Finally, it was demonstrated that by knowing the parameters of layer height and extrusion flow, the ideal porosity and fractal dimension can be determined, and any deviation from these parameters indicates the geometric printing error incurred.

The structural characterization of polymers and, in particular, of those used in Additive Manufacturing (AM) technologies, is essential to improve the understanding of their structure-property relationship for promising high-performance applications. For this, (scanning) transmission electron microscopy-electron energy loss spectroscopy, (S)TEM-EELS is an outstanding tool for exploring materials chemical and structural characteristics at high spatial resolution. However, the high beam-sensitivity of soft materials, such as polymers, hinders the possibility of probing in-depth analysis provided by (S)TEM-EELS. In this work, we analyse the electron beam irradiation damage of four polymers commonly used in Fused Filament Fabrication (FFF), namely polylactic acid (PLA), polycaprolactone (PCL), acrylonitrile butadiene styrene (ABS) and acrylonitrile styrene acrylate (ASA). For this, sequential low-loss and core-loss EEL spectra have been recorded, and the related signals have been monitored as a function of the accumulated dose. Our results show that the critical electron doses using the specimen thickness variations are larger for polymers containing aromatic groups (ABS and ASA) than for aliphatic polymers (PLA and PCL). Regarding the different elements, a larger sensitivity to the electron beam of oxygen regarding carbon and nitrogen is also evidenced. Our results have shown that polymer degradation occurs to a larger extent in the initial steps of electron irradiation, for very low accumulated electron doses, meaning that care should be taken in the selection of the microscopy settings to avoid artefacts produced by the electron beam. Degradation pathways for the four polymers studied are discussed.

In this study, a series of Acrylate-Styrene-Acrylonitrile (ASA) composites loaded with high amounts of cork agro-waste (10-30 wt.%) are developed to address the increasing demand from industry and society for more sustainable materials, with the aim of reducing the carbon footprint associated with fossil fuel-derived plastics. These materials are suitable for Material Extrusion (ME) technologies, including Large Format Additive Manufacturing (LFAM). We demonstrate that the printing conditions can be optimised to manufacture cork composites with good mechanical properties, even for large particle sizes, around 1 mm. Sustainability analysis of these composites revealed that the carbon footprint can be reduced by up to 25% for composites with 30 wt.% cork, primarily due to the reduction in ASA usage. These composites were used to print a luminaire utilising a biomimetic approach and parametric design, showcasing how new materials and innovative product design can be integrated to produce functional and sustainable prototypes.

Fused granular fabrication (FGF), generally oriented to large format additive manufacturing (LFAM) technologies, are emerging as fast and flexible solutions for manufacturing a variety of large-scale components. These components need to fulfil the mechanical requirements determined by specific applications. Reinforcement of polymeric matrices with different fibres is a common strategy to improve the mechanical properties of 3D printing pieces. Moreover, the manufacturing process of these composites needs to be carefully designed in order to optimize the structural and mechanical characteristics of the material. In this study, carbon fibre (CF) reinforced acrylonitrile styrene acrylate (ASA) composites produced by two different extrusion processes are evaluated, as well as the subsequent fabrication of parts using both FGF and injection moulding (IM). In particular, the porosity proportion and distribution, and the CF length and alignment have been carefully quantified and compared using X-ray computerized tomography (CT). The correlation between these structural features, the different manufacturing conditions used and the mechanical properties of the pieces is discussed.

The development of new nanocomposites with added functionalities for Additive Manufacturing (AM) requires of a deep understanding of the 3D distribution of the selected nano-additives within the polymeric matrix, in order to optimize their performance. For this, electron tomography (ET) is an outstanding analysis technique that requires the material to withstand the electron exposure needed for the acquisition of several tens of images, becoming challenging for beam-sensitive materials. In this work, we analyse the parameters involved in the successful analysis by low dose ET of nanocomposites based in acrylic resins for stereolithography (SLA). Needle-shape electron-transparent specimens have been fabricated by focused ion beam (FIB), minimizing surface damage due to the high energy Ga+ ions. Microscope settings for tuning the electron dose applied during the ET analysis of these nanoneedles are discussed. A phenomenological study of the effect of increasing the electron dose in the scanning transmission electron microscopy (STEM) analysis of the material has been carried out, showing that ET can be effectively performed at low electron doses. Two case studies are presented, to illustrate the relevance of these analyses in the development of nanocomposites with added functionalities. Our results have revealed the crucial role of the dose rate and of inaccuracies in the calculation of critical electron doses for the design of ET experiments.

Herein we show that dispersing inorganic cesium lead bromide (CsPbBr3) perovskite quantum dots (QDs) in optical quality films, possessing an accessible and controlled pore size distribution, gives rise to fluorescent materials with a controlled and highly sensitive response to ambient changes. A scaffold-based synthesis approach is employed to obtain ligand-free QDs, whose pristine surface endows them with high sensitivity to the presence of different vapors in their vicinity. At the same time, the void network of the host offers a means to gradually expose the embedded QDs to such vapors. Under these conditions, the luminescent response of the QDs is mediated by the mesostructure of the matrix, which determines the rate at which vapor molecules will adsorb onto the pore walls and, eventually, condensate, filling the void space. With luminescence quantum yields as high as 60%, scaffold-supported ligand-free perovskite nanocrystals display intense photoemission signals over the whole process, as well as high photo- and chemical stability, which allows illuminating them for long periods of time and recovering the original response upon desorption of the condensed phase. The results herein presented open a new route to explore the application of perovskite QD-based materials in sensing.

Additive Manufacturing (AM) has been one of the technologies that has been booming in recent years. Its main advantages are the versatility in the manufacture of parts, the ability to print limited series and its low acquisition cost, among others. Among these technologies, one of the most widely used by engineering and product design teams is Fused Filament Fabrication (FFF). PLA being one of the materials most employed for FFF. Likewise, for a proper shaping of this material and process, it is necessary to establish several parameters to define the quality and properties of the designed part. In this context, a comparison of two groups of pieces has been carried out. Whereas the first group exhibits a correct process parameters and an adequate calibration of the printing bed; the second, has not any bonding between layers or bonding of beads of the same layer, due to an incorrect establishment of the initial parameters. In order to compare these groups, a study of the internal structure was carried out by X-Ray CT along with a characterization of their tensile mechanical properties. Results show a similar maximum stress for both groups, but a drastic reduction of the plastic area in the parts with defects. The quantification and comparison of the mechanical properties of both tests might provide a rejection criterion for parts that work in tension and present defects similar to those studied for engineering teams in product design.

Achieving highly transparent and emissive films based on perovskite quantum dots (PQDs) is a challenging task since their photoluminescence quantum yield (PLQY) typically drops abruptly when they are used as building blocks to make a solid. In this work, we obtain highly transparent films containing FAPbBr3 quantum dots that display a narrow green emission (λ = 530 nm, full width at half-maximum (FWHM) = 23 nm) with a PLQY as high as 86%. The method employed makes use of porous matrices that act as arrays of nanoreactors to synthesize the targeted quantum dots within their void space, providing both a means to keep them dispersed and a protective environment. Further infiltration with poly(methyl methacrylate) (PMMA) increases the mechanical and chemical stability of the ensemble and serves to passivate surface defects, boosting the emission of the embedded PQD and significantly reducing the width of the emission peak, which fulfills the requirements established by the Commission Internationale de l’Éclairage (CIE) to be considered an ultrapure green emitter. The versatility of this approach is demonstrated by fabricating a color-converting layer that can be easily transferred onto a light-emitting device surface to modify the spectral properties of the outgoing radiation.

Lanthanide-activated fluoride-based nanostructures are extremely interesting multifunctional tools for many modern applications in nanomedicine, e.g., bioimaging, sensing, drug delivery, and photodynamic therapy. Importantly, environmental-friendly preparations using a green chemistry approach, as hydrothermal synthesis route, are nowadays highly desirable to obtain colloidal nanoparticles, directly dispersible in hydrophilic media, as physiological solution. The nanomaterials under investigation are new KY3F10-based citrate-capped core@shell nanostructures activated with several lanthanide ions, namely, Er3+, Yb3+, Nd3+, and Gd3+, prepared as colloidal water dispersions. A new facile microwave-assisted synthesis has been exploited for their preparation, with significant reduction of the reaction times and a fine control of the nanoparticle size. These core@shell multifunctional architectures have been investigated for use as biocompatible and efficient contrast agents for optical, magnetic resonance imaging (MRI) and computerized tomography (CT) techniques. These multifunctional nanostructures are also efficient noninvasive optical nanothermometers. In fact, the lanthanide emission intensities have shown a relevant relative variation as a function of the temperature, in the visible and near-infrared optical ranges, efficiently exploiting ratiometric intensity methods for optical thermometry. Importantly, in contrast with other fluoride hosts, chemical dissolution of KY3F10 citrate-capped nanocrystals in aqueous environment is very limited, of paramount importance for applications in biological fluids. Furthermore, due to the strong paramagnetic properties of lanthanides (e.g., Gd3+), and X-ray absorption of both yttrium and lanthanides, the nanostructures under investigation are extremely useful for MRI and CT imaging. Biocompatibility studies of the nanomaterials have revealed very low cytotoxicity in dfferent human cell lines. All these features point to a successful use of these fluoride-based core@shell nanoarchitectures for simultaneous diagnostics and temperature sensing, ensuring an excellent biocompatibility.

A series of nanocomposites containing gold nanoparticles (AuNPs) are prepared by stereolithography (SL) by simply adding a precursor (KAuCl4) to a photoresist. A thermal treatment is performed after manufacturing the nanocomposites, triggering the reduction of KAuCl4 into AuNPs in solid state. In this approach, the photopolymerization of the resin and the formation of the AuNPs occur independently, allowing the optimization of these two processes separately. Advanced electron microscopy analyses reveal the distribution, size and morphology of the AuNPs synthesized within the resin, showing the influence of the gold precursor concentration and different thermal treatments. The localized surface plasmon resonance (LSPR) of the AuNPs modifies the optical properties of the 3D-printed nanocomposites, yielding transparent yet colored materials even for concentrations as low as 0.1 wt% KAuCl4. This behavior can be modelled by the Mie theory, correlating the macroscopic properties of the nanocomposites with the individual AuNPs embedded in the resin. The possibility of tuning the LSPR of the AuNPs together with the ability of manufacturing 3D-structures with sub-millimeter precision by SL, paves the way for the design of advanced platforms for plasmonics, such as sensors for surface enhanced Raman spectroscopy (SERS).

This study focuses on developing hydroxyapatite synthesized from a CaCO3-rich byproduct of sugar beet processing called Carbocal® using a hydrothermal reactor. The purpose of this biomaterial is to enhance the osteoinductivity of implantable surfaces and serve as a bone filler, providing a sustainable and economically more affordable alternative. This research involved compositional analysis and micro- and macrostructural physicochemical characterization, complemented with bioactivity and live/dead assays. The biphasic nature of the Carbocal®-derived sample was significant within the context of the bioactivity concept previously proposed in the literature. The bioactivity of the biomaterial was demonstrated through a viability test, where the cell growth was nearly equivalent to that of the positive control. For comparison purposes, the same tests were conducted with two additional samples: hydroxyapatite obtained from CaCO3 and commercial hydroxyapatite. The resulting product of this process is biocompatible and possesses properties similar to natural hydroxyapatite. Consequently, this biomaterial shows potential as a scaffold in tissue engineering and as an adhesive filler to promote bone regeneration within the context of the circular bioeconomy in the geographical area proposed.

The ADICORK project is associated with an agreement between the Ministry of Agriculture, Livestock, Fisheries and Sustainable Development of the Junta de Andalucía and the INNANOMAT research group of the University of Cádiz. It is oriented to the development of industrial applications with polymer-based composite materials based on cork, which allow the manufacture of innovative value-added products, using the technology of Large Format Additive Manufacturing. This technology makes it possible to manufacture high-volume industrial products, compared to the usual additive manufacturing technologies. Some of the polymer bases studied to develop the composite materials presented in this communication, within the framework of the indicated project, are ABS, PET-G, PLA and ASA. The incorporation of cork in the form of a microparticulate powder, properly processed, has made it possible to achieve improvements in certain properties of the composite materials and, in some cases, after carrying out a screening, in the particle size. Among the properties that have been improved, the mechanical and thermal ones stand out. With the methodology developed, it has been possible to obtain recyclable and more sustainable composite materials than the starting polymeric material. This type of technology has made it possible to obtain attractive and differentiated products of complex geometries, based on and inspired by the territorial and natural origin of cork and its collection, which by other types of manufacturing processes could be impossible or very expensive to create. The sectors in which these developments make sense are varied and in this communication we will focus on the presentation of prototypes developed with the composite materials developed for the furniture, lighting and habitat sectors.

Additive Manufacturing (AM) offers remarkable advantages in relation to traditional methods used to obtain solid structures, such as the capability to obtain customized complex geometries adapted to individual requirements. The design of novel nanocomposites suitable for AM is an excellent strategy to widen the application field of these techniques. In this work, we report on the fabrication of metal/polymer nanocomposites with enhanced optical/electrical behaviour for stereolithography (SLA). In particular, we analyse the in situ generation of Ag nanoparticles (NPs) from Ag precursors (AgNO3 and AgClO4) within acrylic resins via SLA. Transmission electron microscopy (TEM) analysis confirmed the formation of Ag NPs smaller than 5 nm in all nanocomposites, providing optical activity to the materials. A high density of Ag NPs with a good distribution through the material for the larger concentration of AgClO4 precursor tested was observed, in contrast to the isolated agglomerations found when the precursor amount was reduced to 0.1%. A significant reduction in the electrical resistivity up to four orders of magnitude was found for this material compared to the unfilled resin. However, consumption of part of the photoinitiator in the formation process of the Ag NPs contributed to a reduction in the polymerization degree of the resin and, consequently, degraded the mechanical properties of the nanocomposites. Experiments with longer curing times showed that, for the higher AgClO4 concentrations tested, post-curing times of 300 min allowed an 80% degree of polymerization to be achieved. These conditions turned these materials into promising candidates to obtain solid structures with multifunctional properties.