Palladium catalyzed cross coupling reactions are among the most used methods for carbon-carbon bond formation in the agrochemical and pharmaceutical segments. The key step common to all methodologies based on...

In this work, we demonstrate that the reduction of the local internal stress by a low-temperature solvent-mediated thermal treatment is an effective post-treatment tool for magnetic hardening of chemically synthesized nanoparticles. As a case study, we used nonstoichiometric cobalt ferrite particles of an average size of 32(8) nm synthesized by thermal decomposition, which were further subjected to solvent-mediated annealing at variable temperatures between 150 and 320 °C in an inert atmosphere. The postsynthesis treatment produces a 50% increase of the coercive field, without affecting neither the remanence ratio nor the spontaneous magnetization. As a consequence, the energy product and the magnetic energy storage capability, key features for applications as permanent magnets and magnetic hyperthermia, can be increased by ca. 70%. A deep structural, morphological, chemical, and magnetic characterization reveals that the mechanism governing the coercive field improvement is the reduction of the concomitant internal stresses induced by the low-temperature annealing postsynthesis treatment. Furthermore, we show that the medium where the mild annealing process occurs is essential to control the final properties of the nanoparticles because the classical annealing procedure (T > 350 °C) performed on a dried powder does not allow the release of the lattice stress, leading to the reduction of the initial coercive field. The strategy here proposed, therefore, constitutes a method to improve the magnetic properties of nanoparticles, which can be particularly appealing for those materials, as is the case of cobalt ferrite, currently investigated as building blocks for the development of rare-earth free permanent magnets.

Magnetic-plasmonic nanoparticles (NPs) have shown remarkable potential in hyperthermia, magnetic resonance imaging, and surface-enhanced Raman scattering imaging and diagnostics. However, despite their promise, effective clinical translation remains limited due to a lack of fundamental knowledge about the biological response to these materials, and ongoing efforts seek to bridge the gap between nanomaterial design and effective applicability. To overcome these hurdles, the combination of inorganic NPs with lipid membranes has emerged as an attractive strategy for the biocompatibilization of nanomaterials, preserving the inherent properties of each component and exhibiting synergistic functionalities. This study explores the structural and dynamic aspects of magnetic-plasmonic liposomes produced via spontaneous self-assembly of Au-Fe(3)O(4)NPs and synthetic liposomes, as a function of the lipid vesicles' composition and concentration. By combining cryogenic electron microscopy, ultraviolet-visible spectroscopy, and dynamic light scattering, we demonstrated that the bending rigidity and fluidity of the lipid membrane control the aggregation of the NPs on the membrane and the colloidal stability of the hybrids. The experimental results demonstrate that the coexistence of 10 nm Fe3O4 magnetic seeds and 50 nm Au-Fe(3)O(4)NPs plays a crucial role in the assembly of lipid-NP magnetic-plasmonic hybrids. This thermodynamic control allows for fine adjustment of the hybrids' size and composition, thereby allowing for enhancement and tuning of the magnetic response. Overall, these results pave the way for the development of multifunctional nanomaterials with controlled magnetic-plasmonic properties, obtained via spontaneous self-assembly, as combined nanoprobes and nanovectors for potential applications in multimodal imaging and drug delivery.

Although visible light-based stereolithography (SLA) represents an affordable technology for the rapid prototyping of 3D scaffolds for in vitro support of cells, its potential could be limited by the lack of functional photocurable biomaterials that can be SLA-structured at micrometric resolution. Even if innovative photocomposites showing biomimetic, bioactive, or biosensing properties have been engineered by loading inorganic particles into photopolymer matrices, main examples rely on UV-assisted extrusion-based low-resolution processes. Here, SLA-printable composites were obtained by mixing a polyethylene glycol diacrylate (PEGDA) hydrogel with multibranched gold nanoparticles (NPs). NPs were engineered to copolymerize with the PEGDA matrix by implementing a functionalization protocol involving covalent grafting of allylamine molecules that have C═C pendant moieties. The formulations of gold nanocomposites were tailored to achieve high-resolution fast prototyping of composite scaffolds via visible light-based SLA. Furthermore, it was demonstrated that, after mixing with a polymer and after laser structuring, gold NPs still retained their unique plasmonic properties and could be exploited for optical detection of analytes through surface-enhanced Raman spectroscopy (SERS). As a proof of concept, SERS-sensing performances of 3D printed plasmonic scaffolds were successfully demonstrated with a Raman probe molecule (e.g., 4-mercaptobenzoic acid) from the perspective of future extensions to real-time sensing of cell-specific markers released within cultures. Finally, biocompatibility tests preliminarily demonstrated that embedded NPs also played a key role by inducing physiological cell-cytoskeleton rearrangements, further confirming the potentialities of such hybrid nanocomposites as groundbreaking materials in laser-based bioprinting.

Copper-poor Cu2ZnSnS4 (copper zinc tin sulfide, CZTS) inorganic semiconducting nanoparticles were synthesized by an environmentally friendly low-temperature (100 degrees C) synthetic path, which allows precise control of the Sn content without any relevant presence of Zn- and Sn-related secondary phases. The resulting nanoparticles are polycrystalline and quasi-spherical, with an average diameter of 10 nm. The shape and composition were assessed using a multitechnique approach based on X-ray photoelectron spectroscopy (XPS), energy-dispersive fluorescence X-ray spectroscopy (EDXRF), inductively coupled plasma atomic emission spectrometry (ICP-AES), and high-resolution transmission electron microscopy (HR-TEM). The presence of paramagnetic species associated with Cu2+ cations was highlighted by electron paramagnetic resonance (EPR) spectroscopy, pinpointing the presence of significant exchange interactions between Cu2+ ions. The mixed oxidation state of Cu induces the generation of free holes, which are confined in the nanoparticles, giving rise to a plasmonic resonance. The plasmonic properties were investigated as a function of Sn doping through vis-NIR absorption spectroscopy combined with magnetic circular dichroism (MCD). This approach enabled the extraction of charge carriers' density and mass, a key step for further optimization of CZTS-based photovoltaic devices.

By a mild and straightforward synthetic protocol in aqueous solution and without surfactants, hierarchical Cu2O nanospheres were grown on preformed In2O3 nanostructures, varying the ratio In : Cu (2.5, 0.5). Accordingly, two different binary compounds In2O3-Cu2O were prepared and afterwards they were integrated with TiO2 NPs. The ternary composites having a loading of 2.0, 5.0 and 10.0 wt.% respectively of binary In2O3-Cu2O, were tested as photocatalysts in the solar-driven production of hydrogen from water, using as sacrificial agents alcohols derived from the biomass. Satisfyingly, the rate of H2 evolution (20.5 mmol/g h) resulted two orders of magnitude higher respect to bare TiO2 (0.2 mmol/g h). Electrochemical impedance spectroscopy and photoluminescence measurements revealed the formation of a tight heterojunction between In2O3 and Cu2O, which is responsible for the improved charge carrier density and transfer and for the diminished electron-hole recombination.

A family of exchange-coupled core-shell (CS) nanoparticles composed of an antiferromagnetic (AFM) core (Co0.3Fe0.7O) and a ferrimagnetic (FiM) shell (Co0.6Fe2.4O4) was investigated to unravel the role played by the dimension of the two components on the magnetic properties of the system. The series comprises three samples with different core diameters (2, 5, and 16 nm) and fixed shell thickness of ∼2 nm. Although a strong core and shell magnetic coupling occurs in all the samples, the final properties of the hybrid nanosystems are greatly influenced by the size of the two counterparts. Indeed, while the larger sample can be described as a classic T C > T N exchange-bias, where T C and T N denote the ordering temperature of the FiM and AFM phases, respectively, on reducing the size, the blocking transition of the FiM shell decreases to values well below the T N of the AFM. In the first case, the FiM-AFM exchange-bias effect is determined by the magnetic ordering of the AFM core; in the other cases, it is due to the reduction of the thermal-driven magnetic fluctuations of the ordered FiM shell. On the other hand, the AFM properties of the core regions also are extremely sensitive to the particle size reduction, showing, for the smallest sample, the effect of the coupling between the two phases to appear at temperature well below T N displayed by the bulk system, indicating the potential presence of a blocking transition in the AFM core for small particles. These findings highlight the significant influence of the size of the AFM and FiM components on the hybrid system's ultimate properties. This result is potentially relevant for defining the working conditions of nanodevices exploiting exchange-bias phenomena, which have been recently proposed in the literature for application in several technological fields, ranging from rare-earth free magnets, spintronics, optoelectronics, and magnetic-refrigeration.

We performed a sustainable and environmentally benign synthesis of stable Cu nanoclusters in water by UV irradiation of a Cu II complex.

The copper-free Heck-Cassar-Sonogashira (HCS) reaction, known since 1975, nowadays represents one of the most powerful methods for C-C bond formation in organic synthesis with several industrial applications. Despite its great success, the mechanism is still under discussion, with several reported possible pathways. To clarify the copper-free HCS reaction mechanism, stoichiometric and catalytic reactions were carried out and monitored by P-31/H-1 NMR spectroscopy, HPLC, and GC chromatography. In particular, the investigation of the role of the base, mimicking the real catalytic conditions, highlighted the fact that secondary amines rapidly induce precatalyst reduction and decrease the energy barrier for the alkyne carbopalladation step. The results supported the mechanism via direct coordination of the terminal alkyne on the oxidative addition complex. Depending on the palladium counterion, and independent of the solvent, aromatic substitutions, temperature, and terminal alkyne substitution, these studies support two different pathways: with halides, a neutral route, and with the triflate, a cationic one.

The crystal site occupancy of different divalent ions and the induction of lattice defects represent an additional tool for modifying the intrinsic magnetic properties of spinel ferrites nanoparticles. Here, the relevance of the lattice defects is demonstrated in the appearance of exchange-bias and in the improvement of the magnetic properties of doped ferrites of 20 nm, obtained from the mild oxidation of core@shell (wustite@ferrite) nanoparticles. Three types of nanoparticles (Fe0.95O@Fe3O4, Co0.3Fe0.7O@Co0.8Fe2.2O4 and Ni0.17Co0.21Fe0.62O@Ni0.4Co0.3Fe2.3O4) are oxidized. As a result, the core@shell morphology is removed and transformed in a spinel-like nanoparticle, through a topotactic transformation. This study shows that most of the induced defects in these nanoparticles and their magnetic properties are driven by the inability of the Co(II) ions at the octahedral sites to migrate to tetrahedral sites, at the chosen mild oxidation temperature. In addition, the appearance of crystal defects and antiphase boundaries improves the magnetic properties of the starting compounds and leads to the appearance of exchange bias at room temperature. These results highlight the validity of the proposed method to impose novel magnetic characteristics in the technologically relevant class of nanomaterials such as spinel ferrites, expanding their potential exploitation in several application fields.

\Efficient remediation of water pollutants requires the continuous development of new technologies. Magnetic biochars offer a sustainable solution by combining the high adsorptive capacity of biochar with easy adsorbent recovery. However, the main existing methods for synthesizing magnetic carbons have some disadvantages, such as obtaining materials with a poor magnetic response or with less surface area available for the adsorption of contaminants. Thus, there is an evident need to develop new methods for the synthesis of magnetic carbons. This study presents an innovative approach to obtaining a magnetic nanocomposite (MNC). Initially, chemically activated biochar (ACP) was produced from the pyrolysis of green coconut husks (GCH). Subsequently, an oleic acid-coated magnetite colloid was employed to incorporate magnetic nanoparticles into the porous structure of ACP. Two additional magnetic carbons were prepared using co-pyrolysis of GCH or GCH biochar, both impregnated with FeCl3 solution, for performance comparison. Characterization of MNC revealed a high BET surface area (1019 m(2).g(-1)) and favorable magnetism (11.2 +/- 1.1 emu.g(-1)). The MNC exhibited similar or superior adsorption capacities for caffeine (153 mg.g(-1)) and salicylic acid (203 mg.g(-1)) when compared to the other materials. These findings highlight the ability of this innovative process to provide a material with good magnetic properties and concomitantly high surface area, resulting in a promising adsorbent for the removal of contaminants from water.

Magnetoplasmonic NPs have shown remarkable potential in hyperthermia, Magnetic Resonance Imaging (MRI), and Surface Enhanced Raman Scattering (SERS) imaging and diagnostics. However, despite their potential, effective clinical translation remains extremely limited due to a lack of fundamental knowledge about the biological response to these materials, and ongoing efforts seek to bridge the gap between nanomaterial production and effective application. To overcome these hurdles, the combination of inorganic NPs with lipid membranes has emerged as a promising strategy for the biocompatibilization of nanomaterials, preserving the inherent properties of each component and exhibiting novel synergistic functionalities. In this study, we synthesize magnetic-plasmonic-liposome adducts via spontaneous self-assembly. The interaction between magnetic-plasmonic NPs and liposomes was addressed from a physicochemical point of view as a function of liposome composition and concentration. By combining Cryogenic Microscopy, UV-visible spectroscopy and Dynamic Light Scattering we demonstrated that the rigidity of the lipid membrane affects the aggregation of the NPs and the colloidal stability of the NPs-vesicle hybrids. The magnetic responsivity of the hybrids is enhanced as a consequence of the colocalization and crowding of NPs on the lipid membranes and can be finely modulated by varying the number of particles per vesicle. Overall, these results pave the way for the development of multifunctional materials with controlled magnetic-plasmonic properties for a variety of technological applications.

Nanometric core@shell wüstite@ferrite (Fe1-x O@Fe3 O4 ) has been extensively studied because of the emergence of exchange bias phenomena. Since their actual implementation in modern technologies is hampered by the low temperature at which bias is operating, the critical issue to be solved is to obtain exchange-coupled antiferromagnetic@ferrimagnetic nanoparticles (NPs) with ordering temperature close to 300 K by replacing the divalent iron with other transition-metal ions. Here, the effect of the combined substitution of Fe(II)  with Co(II)  and Ni(II)  on the crystal structure and magnetic properties is studied. To this aim, a series of 20 nm NPs with a wüstite-based core and a ferrite shell, with tailored composition, (Co0.3 Fe0.7 O@Co0.8 Fe2.2 O4  and Ni0.17 Co0.21 Fe0.62 O@Ni0.4 Co0.3 Fe2.3 O4 ) is synthetized through a thermal-decomposition method. An extensive morphological and crystallographic characterization of the obtained NPs shows how a higher stability against the oxidation process in ambient condition is attained when divalent cation doping of the iron oxide lattice with Co(II)  and Ni(II)  ions is performed. The dual-doping is revealed to be an efficient way for tuning the magnetic properties of the final system, obtaining Ni-Co doped iron oxide core@shell NPs with high coercivity (and therefore, high energy product), and increased antiferromagnetic ordering transition temperature, close to room temperature.

Epsilon cobalt nanoparticles are underexplored in catalysis due to the fact that they are accessible only through wetchemical approaches, which employ ligands as stabilizing agents. Ligands may play a significant role in determining the structure and catalytic performances of nanoparticles, which complicates their comparison in catalysis. Here, we present catalytic performances in cinnamaldehyde hydrogenation of freestanding and few-layer graphene-supported epsilon-Co nanoparticles and hexagonal close-packed (hcp)-Co nanorods, which are stabilized by the same ligands. We show that while hcp-Co nanorods exposing a majority of {11 (2) over bar0}-type facets are the most active, the supported spherical epsilon-Co nanoparticles combine high activity and excellent selectivity for the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol. The concentration-dependent ligand conformation on the surface of the nanostructures influences their catalytic performances, with higher concentrations favoring both activity and selectivity to cinnamyl alcohol. These results should incite the interest in the implementation of epsilon-Co nanoparticles in other catalytic reactions where the cobalt crystal structure may play an important role.

Here, we synthesize a Au@Fe3O4 core@shell system with a highly uniform unprecedented star-like shell morphology with combined plasmonic and magnetic properties. An advanced electron microscopy characterization allows assessing the multifaceted nature of the Au core and its role in the growth of the peculiar epitaxial star-like shell with excellent crystallinity and homogeneity. Magnetometry and magneto-optical spectroscopy revealed a pure magnetite shell, with a superior saturation magnetization compared to similar Au@Fe3O4 heterostructures reported in the literature, which is ascribed to the star-like morphology, as well as to the large thickness of the shell. Of note, Au@Fe3O4 nanostar-loaded cancer cells displayed magneto-mechanical stress under a low frequency external alternating magnetic field (few tens of Hz). On the other hand, such a uniform, homogeneous, and thick magnetite shell enables the shift of the plasmonic resonance of the Au core to 640 nm, which is the largest red shift achievable in Au@Fe3O4 homogeneous core@shell systems, prompting application in photothermal therapy and optical imaging in the first biologically transparent window. Preliminary experiments performing irradiation of a stable water suspension of the nanostar and Au@Fe3O4-loaded cancer cell culture suspension at 658 nm confirmed their optical response and their suitability for photothermal therapy. The outstanding features of the prepared system can be thus potentially exploited as a multifunctional platform for magnetic-plasmonic applications.

Hybrid materials composed of superparamagnetic iron oxide nanoparticles (SPIONs) and lipid self-assemblies possess considerable applicative potential in the biomedical field, specifically, for drug/nutrient delivery. Recently, we showed that SPIONs-doped lipid cubic liquid crystals undergo a cubic-to-hexagonal phase transition under the action of temperature or of an alternating magnetic field (AMF). This transition triggers the release of drugs embedded in the lipid scaffold or in the water channels. In this contribution, we address this phenomenon in depth, to fully elucidate the structural details and optimize the design of hybrid multifunctional carriers for drug delivery. Combining small-angle X-ray scattering (SAXS) with a magnetic characterization, we find that, in bulk lipid cubic phases, the cubic-to-hexagonal transition determines the magnetic response of SPIONs. We then extend the investigation from bulk liquid-crystalline phases to colloidal dispersions, i.e., to lipid/SPIONs nanoparticles with cubic internal structure ("magnetocubosomes"). Through Synchrotron SAXS, we monitor the structural response of magnetocubosomes while exposed to an AMF: the magnetic energy, converted into heat by SPIONs, activates the cubic-to-hexagonal transition, and can thus be used as a remote stimulus to spike drug release "on-demand". In addition, we show that the AMF-induced phase transition in magnetocubosomes steers the realignment of SPIONs into linear string assemblies and connect this effect with the change in their magnetic properties, observed at the bulk level. Finally, we assess the internalization ability and cytotoxicity of magnetocubosomes in vitro on HT29 adenocarcinoma cancer cells, in order to test the applicability of these smart carriers in drug delivery applications.

The development of reproducible protocols to synthesize hard/soft nano-heterostructures (NHSs) with tailored magnetic properties is a crucial step to define their potential application in a variety of technological areas. Thermal decomposition has proved to be an effective tool to prepare such systems, but it has been scarcely used so far for the synthesis of Co-based metal/ferrite NHSs, despite their intriguing physical properties. We found a new approach to prepare this kind of nanomaterial based on a simple one-pot thermal decomposition reaction of metal-oleate precursors in the high boiling solvent docosane. The obtained NHSs are characterized by the coexistence of Co metal and Co doped magnetite and are highly stable in an air atmosphere, thanks to the passivation of the metal with a very thin oxide layer. The investigation of the influence of the metal precursor composition (a mixed iron-cobalt oleate), of the ligands (oleic acid and sodium oleate) and of the reaction time on the chemical and structural characteristics of the final product, allowed us to rationalize the reaction pathway and to determine the role of each parameter. In particular, the use of sodium oleate is crucial to obtain a metal phase in the NHSs. In such a way, the one-pot approach proposed here allows the fine control of the synthesis, leading to the formation of stable, high performant, metal/ferrite NHSs with tailored magnetic properties. For instance, the room temperature maximum energy product was increased up to 19 kJ m-3 by tuning the Co content in the metal precursor.

The exploitation of the exchange coupling between hard and soft magnetic materials has been proposed for enhancing the magnetic performances of rare-earth free permanent magnets, with the aim of extending their use to all applications where moderate energy product (35–100 kJ m−3) is required. Strontium hexaferrite (SFO)/spinel ferrite composites seem particularly promising to achieve this target, although the conditions to maximize the effect while using techniques easily scalable to industrial production have not yet been identified. Within this framework, the optimization of the structural, chemical, and magnetic properties of the two moieties before the coupling procedure is crucial to enhance the energy product of the final composite. Here we report the syntheses of both nanometric SFO with high coercivity (ca. 525 kA m−1) and quasi-bulk saturation magnetization (68 Am2 kg−1) and a series of nanosized zinc-doped ferrite (Zn x Fe3−x O4, 0.0 ⩽ x ⩽ 0.4) through cheap, easily scalable and eco-friendly approaches. The structural and chemical stability of the two magnetic phases as a function of temperature were investigated up to 1100 °C, with the aim of finding the best compromise between preservation of the nanometric scale and magnetic properties. A very high-magnetization (106 Am2 kg−1) ferrite was obtained by annealing Zn0.3Fe2.7O4 nanopowder at the highest investigated temperature. A preliminary attempt at coupling the two phases, starting from a mixture of the nanopowders, was performed through a classic annealing process in the temperature range 500 °C–1100 °C. The adopted procedure allowed for obtaining an exchange coupled composite at 1100 °C where the two phases are intimately and homogeneously mixed, with micrometric (0.3–5 μm) and nanometric (up to 50 nm) spinel ferrite particles. Despite these promising results, no enhancement of the energy product was found, highlighting the need for further experimental efforts to improve the coupling procedure.