PVD for Decorative Applications: A Review.

Physical Vapor Deposition (PVD) is a widely utilized process in various industrial applications, serving as a protective and hard coating. However, its presence in fields like fashion has only recently emerged, as electroplating processes had previously dominated this reality. The future looks toward the replacement of the most hazardous and toxic electrochemical processes, especially those involving Cr(VI) and cyanide galvanic baths, which have been restricted by the European Union. Unfortunately, a complete substitution with PVD coatings is not feasible. Currently, the combination of both techniques is employed to achieve new aesthetic features, including a broader color range and diverse textures, rendering de facto PVD of primary interest for the decorative field and the fashion industry. This review aims to outline the guidelines for decorative industries regarding PVD processes and emphasize the recent advancements, quality control procedures, and limitations.

Mixed-Sandwich Titanium(III) Qubits on Au(111): Electron Delocalization Ruled by Molecular Packing.

Organometallic sandwich complexes are versatile molecular systems that have been recently employed for single-molecule manipulation and spin sensing experiments. Among related organometallic compounds, the mixed-sandwich S = 1/2 complex (η8-cyclooctatetraene)(η5-cyclopentadienyl)titanium, here [CpTi(cot)], has attracted interest as a spin qubit because of the long coherence time. Here the structural and chemical properties of [CpTi(cot)] on Au(111) are investigated at the monolayer level by experimental and computational methods. Scanning tunneling microscopy suggests that adsorption occurs in two molecular orientations, lying and standing, with a 3:1 ratio. XPS data evidence that a fraction of the molecules undergo partial electron transfer to gold, while our computational analysis suggests that only the standing molecules experience charge delocalization toward the surface. Such a phenomenon depends on intermolecular interactions that stabilize the molecular packing in the monolayer. This orientation-dependent molecule-surface hybridization opens exciting perspectives for selective control of the molecule-substrate spin delocalization in hybrid interfaces.

Unveiling the Role of PEO-Capped TiO2 Nanofiller in Stabilizing the Anode Interface in Lithium Metal Batteries.

Lithium metal batteries (LMBs) will be a breakthrough in automotive applications, but they require the development of next-generation solid-state electrolytes (SSEs) to stabilize the anode interface. Polymer-in-ceramic PEO/TiO2 nanocomposite SSEs show outstanding properties, allowing unprecedented LMBs durability and self-healing capabilities. However, the mechanism underlying the inhibition/delay of dendrite growth is not well understood. In fact, the inorganic phase could act as both a chemical and a mechanical barrier to dendrite propagation. Combining advanced in situ and ex situ experimental techniques, we demonstrate that oligo(ethylene oxide)-capped TiO2, although chemically inert toward lithium metal, imparts SSE with mechanical and dynamical properties particularly favorable for application. The self-healing characteristics are due to the interplay between mechanical robustness and high local polymer mobility which promotes the disruption of the electric continuity of the lithium dendrites (razor effect).

Magnetic molecules as local sensors of topological hysteresis of superconductors.

Superconductors and magnetic materials, including molecules, are key ingredients for quantum computing and spintronics. However, only a little is known about how these materials interact in multilayer nanostructures like the hybrid architectures nowadays under development for such advanced applications. Here, we show that a single layer of magnetic molecules, Terbium(III) bis-phthalocyaninato (TbPc2) complexes, deposited under controlled UHV conditions on a superconducting Pb(111) surface is sensitive to the topology of the intermediate state of the superconductor, namely to the presence and evolution of superconducting and normal domains due to screening and penetration of an external magnetic field. The topological hysteresis of the superconducting substrate imprints a local evolution of the magnetisation of the TbPc2 molecules in the monolayer. Element and surface selective detection is achieved by recording the X-ray magnetic circular dichroism of the Tb atoms. This study reveals the impressive potential of magnetic molecules for sensing local magnetic field variations in molecular/superconductor hybrid devices, including spin resonators or spin injecting and spin filtering components for spintronics applications.

Probing the Origin of Ferro-/Antiferromagnetic Exchange Interactions in Cu(II)-4f Complexes.

The mechanistic investigations between Cu(II) and the anisotropic lanthanides (Ln(III)) are not much explored to date. This is due to the complicated energy spectrum which arises due to the orbital angular momentum of anisotropic lanthanides. Interestingly, the exchange coupling J in Ln(III)-Cu(II) systems was found to be antiferromagnetic for <4f7 metal ions and ferromagnetic for ≥4f7 metal ions, while the net magnitude of JTotal strength gradually decreases moving from f1 to f13. While this is established in several examples, the reason for this intriguing trend is not rationalized. In this article, we have taken up these challenging tasks by synthesizing a family of complexes with the general molecular formula [Cu2Ln(HL)4(NO3)](NO3)2, where Ln = La (1-La), Ce (2-Ce), Pr (3-Pr), Gd (4-Gd), Tb (5-Tb), Dy (6-Dy), and Ho (7-Ho) and HL = C15H15N1O3; (2-methoxy-6-[(E)-2'-hydroxymethyl-phenyliminomethyl]-phenolate) is a monodeprotonated tridentate Schiff base ligand. Detailed dc magnetic susceptibility measurements performed for all the complexes reveal that the Cu(II) ion is coupled ferromagnetically to the respective Ln(III) ion, which has more than seven electrons in the 4f shell, while an antiferromagnetic coupling is witnessed if Ln(III) has less than seven electrons. The strength of the exchange coupling constant was quantitatively determined for representative complexes from the high-field/high-frequency electron paramagnetic resonance spectroscopy which follows the order of 4-Gd (1.50(10) cm-1) > 5-Tb (1.18(10) cm-1) > 6-Dy (0.56(10) cm-1 based on the -2JCu-Ln(SCu1→·JLnz→+SCu2→·JLnz→) spin Hamiltonian. The increased axiality in 5-Tb and 6-Dy due to the presence of 3d ions in the near vicinity of an oblate ion and the increased exchange coupling strength between Cu(II) and Tb(III) or Dy(III) is the ideal combination to stabilize magnetic bistability in these complexes in the absence of an external magnetic field with the effective energy barrier of 15.7 K (τo = 2.49 × 10-6 s) and 12.6 K (τo = 1.70 × 10-5 s), respectively. To rationalize this experimental trend, we have performed ab initio CASSCF and DFT calculations. To compute the J values, we have employed POLY_ANISO routines and utilized the computed data to establish the generic mechanism of magnetic coupling in {Cu-Ln-Cu} motifs. These mechanistic findings reveal the importance of 5d orbitals and their energy with respect to the dx2-y2 orbital of Cu(II) ions in controlling the magnetic coupling of {Cu-4f} complexes.

Smart Magnetic Nanocarriers for Multi-Stimuli On-Demand Drug Delivery.

In this study, we report the realization of drug-loaded smart magnetic nanocarriers constituted by superparamagnetic iron oxide nanoparticles encapsulated in a dual pH- and temperature-responsive poly (N-vinylcaprolactam-co-acrylic acid) copolymer to achieve highly controlled drug release and localized magnetic hyperthermia. The magnetic core was constituted by flower-like magnetite nanoparticles with a size of 16.4 nm prepared by the polyol approach, with good saturation magnetization and a high specific absorption rate. The core was encapsulated in poly (N-vinylcaprolactam-co-acrylic acid) obtaining magnetic nanocarriers that revealed reversible hydration/dehydration transition at the acidic condition and/or at temperatures above physiological body temperature, which can be triggered by magnetic hyperthermia. The efficacy of the system was proved by loading doxorubicin with very high encapsulation efficiency (>96.0%) at neutral pH. The double pH- and temperature-responsive nature of the magnetic nanocarriers facilitated a burst, almost complete release of the drug at acidic pH under hyperthermia conditions, while a negligible amount of doxorubicin was released at physiological body temperature at neutral pH, confirming that in addition to pH variation, drug release can be improved by hyperthermia treatment. These results suggest this multi-stimuli-sensitive nanoplatform is a promising candidate for remote-controlled drug release in combination with magnetic hyperthermia for cancer treatment.

Self Standing Mats of Blended Polyaniline Produced by Electrospinning.

Conducting nanofibers of polyaniline (PANI) doped with camphor-10-sulfonic acid (HCSA) and blended with different polymers, such as polymethyl methacrylate (PMMA) and polyvinyl acetate (PVAc), have been fabricated using the electrospinning technique. Scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA) were utilized to characterize the morphology and the thermal stability of PANI-blended fibers. An extensive study was performed to understand the copolymer influence on both the structural and surface properties of the realized conductive thin films. Samples main electrical characteristics, as conductivity, specific capacitance and electrochemical performances were tested. The better mats were obtained with the use of PVAc copolymer, which showed a conductivity value two orders of magnitude higher than the PMMA system. Aiming at further improving the electrochemical features of these blended mats, hybrid fibers based on PANI/PVAc/graphene oxide and PANI/PVAc/iron oxide were also produced and characterized. The obtained mats were potentially addressed to numerous practical fields, including sensors, health applications, smart devices and multifunctional textile materials.

Sustainable Materials and their Contribution to the Sustainable Development Goals (SDGs): A Critical Review Based on an Italian Example.

The Sustainable Development Goals (SDGs) have been proposed to give a possible future to humankind. Due to the multidimensional characteristic of sustainability, SDGs need research activities with a multidisciplinary approach. This work aims to provide a critical review of the results concerning sustainable materials obtained by Italian researchers affiliated to the National Interuniversity Consortium of Materials Science and Technology (INSTM) and their contribution to reaching specific indicators of the 17 SDGs. Data were exposed by using the Web of Science (WoS) database. In the investigated period (from 2016 to 2020), 333 works about sustainable materials are found and grouped in one of the following categories: chemicals (33%), composites (11%), novel materials for pollutants sequestration (8%), bio-based and food-based materials (10%), materials for green building (8%), and materials for energy (29%). This review contributes to increasing the awareness of several of the issues concerning sustainable materials but also to encouraging the researchers to focus on SDGs' interconnections. Indeed, the mapping of the achievements can be relevant to the decision-makers to identify the opportunities that materials can offer to achieve the final goals. In this frame, a "Sustainable Materials Partnership for SDGs" is envisaged for more suitable resource management in the future.

Chemisorption of nitronyl-nitroxide radicals on gold surface: an assessment of morphology, exchange interaction and decoherence time.

A combined Tof-SIMS, XPS and STM characterization has been performed to study the deposition of a sulphur-functionalized nitronyl nitroxide radical on Au(111) clearly demonstrating the chemisorption of intact molecules. Continuous -wave EPR characterization showed that the radical molecules maintain their paramagnetic character. Pulsed EPR measurements allowed to determine the decoherence time of the nanostructure at 80 K, which turned out to be comparable to the one measured in frozen solution and longer than previously reported for many radicals and other paramagnetic molecules at much lower temperatures. Furthermore, we conducted a state-of-the-art ab initio molecular dynamics study, suggesting different possible scenarios for chemisorption geometries and predicting the energetically favoured geometry. Calculation of the magnetic properties indicates a partial non-innocent role of the gold surface in determining the magnetic interactions between radicals in packed structures. This suggests that the observed EPR spectrum is to be attributed to low-density domains of disordered radicals interacting via dipolar interactions.

Lanthanide Complexes with a Tripodal Nitroxyl Radical Showing Strong Magnetic Coupling.

A series of isomorphous mononuclear complexes of Ln(III) ions comprising one stable tripodal oxazolidine nitroxyl radical were obtained in acetonitrile media starting from nitrates. The compounds, [LnRad(NO3)3] (Ln = Gd, Tb, Dy, Tm, Y; Rad = 4,4-dimethyl-2,2-bis(pyridin-2-yl)-1,3-oxazolidine-3-oxyl), have a molecular structure. Their coordination polyhedron, LnO7N2, can be described as a tricapped trigonal prism with symmetry not far from D3h. The extracted value of 23 cm-1 for the antiferromagnetic coupling of Gd-Rad established from the DC magnetic and EPR data is a record strength for the complexes of 4f elements with nitroxyl radicals. The terbium derivative displays frequency-dependent out-of-phase signals in zero field, indicating single-molecule magnetic behavior. With an applied field of 0.1 T, an effective barrier of 57 cm-1 is found.

Magnetic Anisotropy Drives Magnetochiral Dichroism in a Chiral Molecular Helix Probed with Visible Light.

Magnetochiral dichroism (MChD) is a nonreciprocal manifestation of light-matter interaction that can be observed in chiral magnetized systems. It features a differential absorption of unpolarized light depending on the relative orientation of the magnetic field and the light wavevector and on the absolute configuration of the system. The relevance of this effect for optical readout of magnetic data calls for a complete understanding of the microscopic parameters driving MChD with an easy-accessible and nondamaging light source, such as visible light. For this purpose, here we report on MChD detected with visible light on a chiral magnetic helix formulated as [MnIII(cyclam)(SO4)]ClO4·H2O (cyclam = 1,4,8,11-tetraazacyclotetradecane) featuring antiferromagnetically coupled anisotropic MnIII ions. Alternate current susceptibility measurements revealed the existence of a single-chain magnet behavior hidden below the canted antiferromagnetism (TN = 5.8 K) already evidenced by direct current magnetometry. A detailed analysis of the optical absorption gives access to the value of the zero-field splitting parameter D (2.9 cm-1), which quantifies the magnetic anisotropy of the MnIII centers. Below the magnetic ordering temperature of the material, the MChD spectra exhibit intense absolute configuration dependent MChD signals reaching record values of ca. 12% of the absorbed intensity for the two electronic transitions most influenced by the spin-orbit coupling of the MnIII ion. These findings set a clear route toward the design and preparation of highly MChD-responsive molecular materials.

Enhancement of the Magnetic Coupling in Exfoliated CrCl3 Crystals Observed by Low-Temperature Magnetic Force Microscopy and X-ray Magnetic Circular Dichroism.

Magnetic crystals formed by 2D layers interacting by weak van der Waals forces are currently a hot research topic. When these crystals are thinned to nanometric size, they can manifest strikingly different magnetic behavior compared to the bulk form. This can be the result of, for example, quantum electronic confinement effects, the presence of defects, or pinning of the crystallographic structure in metastable phases induced by the exfoliation process. In this work, an investigation of the magnetism of micromechanically cleaved CrCl3 flakes with thickness >10 nm is performed. These flakes are characterized by superconducting quantum interference device magnetometry, surface-sensitive X-ray magnetic circular dichroism, and spatially resolved magnetic force microscopy. The results highlight an enhancement of the CrCl3 antiferromagnetic interlayer interaction that appears to be independent of the flake size when the thickness is tens of nanometers. The estimated exchange field is 9 kOe, representing an increase of ≈900% compared to the one of the bulk crystals. This effect can be attributed to the pinning of the high-temperature monoclinic structure, as recently suggested by polarized Raman spectroscopy investigations in thin (8-35 nm) CrCl3 flakes.

Addressing the Influence of Localized Plasmon Resonance on the Magneto-Optical Properties of Cobalt Ferrite Nanoparticles.

The optical and magneto-optical (MO) properties of magneto-plasmonic nanocomposite films made up of a transparent polymer with a dispersion of cobalt ferrite (CFO) nanoparticles (NPs) and different concentrations of Au NPs are investigated. The volumetric concentrations of CFO and Au NPs, around 3%, and below 7‰ respectively, are below the percolation limit, and hence the nanocom-posite films constitute models for investigating the influence of the electromagnetic field generated at the surface plasmon resonance of Au NPs on the magneto-optical properties of CFO NPs. The plasmon resonance is present in these magneto-plasmonic composites, red-shifted with respect to the bare Au NPs and covering the spectral region where charge-transfer and crystal field MO transitions can be excited. Moreover, the magneto-optical hysteresis loops were measured in the whole spectral region. We observe that the hysteresis loops shape is a fingerprint of the different MO transitions of the CFO NPs. The strength of the MO peak around 750 nm, corresponding to the Crystal Field transition is damped respect to the corresponding peak of the CFO NPs. The strength of this peak evolves non-monotonically with the Au NPs concentration. On the other hand, the MO band around 550 nm, excited by Charge Transfer transitions, changes sign when Au NPs are present. In addition, a second MO contribution is observed. Our results demonstrate that the interactions between plasmon resonance and MO effects are not only determined by the stronger local electromagnetic fields at the resonance but they depend on the type MO transition that is involved in these oxides. This study helps to understand and design the magneto plasmonic nano-structures and applications, for example in biomedicine and sensing, in which random and weak dipolar interparticle interactions between plasmonic and magnetic nanostructures are present.

Multifunctional Nanovectors Based on Polyamidoamine Polymers for Theranostic Application.

We present multifunctional, biocompatible and biodegradable magnetic nanovectors based on different polyamidoamine (PAA) polymers tailored with different diagnostic and therapeutic properties. Using maghemite nanoparticles with average size 15.5 ± 2.8 nm prepared by thermal decomposition, superparamagnetic nanovectors were obtained by coating the nanoparticles with synthetic polymers of PAA. These have a segmented copolymer structure, and bear PAA segments containing different amount of carboxyl groups per repeating units together with PEG segments. These copolymers are thought to combine the binding properties of the carboxylated PAA segments to inorganic nanoparticles, with the stealth properties of the PEG ones. The magnetic, hyperthermal and relaxometric properties of the synthesized samples were investigated. Magnetic measurements revealed that the samples are superparamagnetic at room temperature and the overall magnetic behavior is not affected by the functionalization process. Calorimetric measurements demonstrated a good heating efficiency at alternating magnetic field parameters below the human tolerability threshold (SAR of ca. 70 W/g at 260 Hz and 10.8 kA/m). 1H-NMR relaxivities were relevant compared to the values of the commercial contrast agents over the whole investigated frequency range.

Electric field modulation of magnetic exchange in molecular helices.

The possibility to operate on magnetic materials through the application of electric rather than magnetic fields-promising faster, more compact and energy efficient circuits-continues to spur the investigation of magnetoelectric effects. Symmetry considerations, in particular the lack of an inversion centre, characterize the magnetoelectric effect. In addition, spin-orbit coupling is generally considered necessary to make a spin system sensitive to a charge distribution. However, a magnetoelectric effect not relying on spin-orbit coupling is appealing for spin-based quantum technologies. Here, we report the detection of a magnetoelectric effect that we attribute to an electric field modulation of the magnetic exchange interaction without atomic displacement. The effect is visible in electron paramagnetic resonance absorption of molecular helices under electric field modulation and confirmed by specific symmetry properties and spectral simulation.

Self-assembly of a terbium(III) 1D coordination polymer on mica.

The terbium(III) ion is a particularly suitable candidate for the creation of surface-based magnetic and luminescent devices. In the present work, we report the epitaxial growth of needle-like objects composed of [Tb(hfac)3·2H2O] n (where hfac = hexafluoroacetylacetonate) polymeric units on muscovite mica, which is observed by atomic force microscopy. The needle-like shape mimics the structure observed in the crystalline bulk material. The growth of this molecular organization is assisted by water adsorption on the freshly air-cleaved muscovite mica. This deposition technique allows for the observation of a significant amount of nanochains grown along three preferential directions 60° apart from another. The magnetic properties and the luminescence of the nanochains can be detected without the need of surface-dedicated instrumentation. The intermediate value of the observed luminescence lifetime of the deposits (132 µs) compared to that of the bulk (375 µs) and the CHCl3 solution (13 µs) further reinforces the idea of water-induced growth.

Type I Collagen and Strontium-Containing Mesoporous Glass Particles as Hybrid Material for 3D Printing of Bone-Like Materials.

Bone tissue engineering offers an alternative promising solution to treat a large number of bone injuries with special focus on pathological conditions, such as osteoporosis. In this scenario, the bone tissue regeneration may be promoted using bioactive and biomimetic materials able to direct cell response, while the desired scaffold architecture can be tailored by means of 3D printing technologies. In this context, our study aimed to develop a hybrid bioactive material suitable for 3D printing of scaffolds mimicking the natural composition and structure of healthy bone. Type I collagen and strontium-containing mesoporous bioactive glasses were combined to obtain suspensions able to perform a sol-gel transition under physiological conditions. Field emission scanning electron microscopy (FESEM) analyses confirmed the formation of fibrous nanostructures homogeneously embedding inorganic particles, whereas bioactivity studies demonstrated the large calcium phosphate deposition. The high-water content promoted the strontium ion release from the embedded glass particles, potentially enhancing the osteogenic behaviour of the composite. Furthermore, the suspension printability was assessed by means of rheological studies and preliminary extrusion tests, showing shear thinning and fast material recovery upon deposition. In conclusion, the reported results suggest that promising hybrid systems suitable for 3D printing of bioactive scaffolds for bone tissue engineering have been developed.

Enhanced hydrogen photogeneration by bulk g-C3N4 through a simple and efficient oxidation route.

The search for new environment-friendly visible-light absorbing catalysts is an urgent task. g-C3N4 has excellent photocatalytic properties and the possibility of developing cost-effective routes to make this material a viable alternative to the currently used catalysts is required. In this work, we show that a simple chemical oxidation process of g-C3N4 with nitric acid allowed significantly enhancing the hydrogen photogeneration from aqueous triethanolamine, under simulated solar light. An 8-fold improvement of the H2 production, with respect to the pristine sample, was achieved by properly controlling the physical-chemical parameters of the oxidation process, reaching a value of about 4000 µmol g-1 h-1, which is one of the highest hydrogen production rates for bulk g-C3N4. Such high levels of photocatalytic activity result from the combination of improved surface area and changes in the electronic structure induced by the oxidation process.

Cobalt(II) Ions Connecting [CoII4] Helicates into a 2-D Coordination Polymer Showing Slow Relaxation of the Magnetization.

The reactions of cobalt(II) perchlorate with a diazine tetratopic helicand, H4L, in the presence of sodium carbonate afford two coordination polymers constructed from tetranuclear anionic helicates as building blocks: ∞3[Co4L3Na4(H2O)4]·4H2O (1) and ∞2[Co5L3Na2(H2O)9]·2.7H2O·DMF (2). The tetranuclear triple-stranded helicates, {CoII4L3}4-, are connected in 1 by sodium(I) ions and in 2 by sodium(I) and cobalt(II) ions (H4L results from the condensation reaction between 3-formylsalicylic acid and hydrazine). The crystal structures of the two compounds have been solved. In both compounds the anionic helicates interact with the assembling cations through the carboxylato oxygen atoms. Compound 2 features chains resulting from connecting the tetranuclear helicates through cobalt(II) ions. The analysis of the magnetic properties of compounds 1 and 2 evidenced a dominant antiferromagnetic coupling for 1, resulting in a diamagnetic ground state. In contrast, the magnetic behavior of 2 is dominated at low temperature by the CoII ion which connects the antiferromagnetically coupled {CoII4} helical moieties. The ac magnetic measurements for 2 reveal the occurrence of slow relaxation of the magnetization that is due to the single, uncorrelated cobalt(II) ions, which are diluted in an essentially diamagnetic matrix of {CoII4} moieties (ΔEeff = 26.7 ± 0.3 cm-1 with τ0 = (2.3 ± 0.2) × 10-6 s).

Synthesis, Crystal Structure, and Magnetic Properties of a New Mixed Metal (Co(II), Ni(II)) Cubane.

The mixed Co(II)/Ni(II) complex, [Co2.67Ni1.33L4(CH3COO)2][BPh4]2·0.75H2O where HL = 4-(salicylaldimine)antipyrine, was isolated as an orange solid from the reaction of 4-(salicylaldimine)antipyrine, with mixed cobalt(II) acetate and nickel(II) acetate in ethanol. The complex was characterized by Frustrated Total Internal Reflection (FTIR), UltraViolet Visible spectroscopy (UV-Vis), X-ray single crystal diffraction, and by elemental analysis. The complex is composed of two symmetry independent cationic units, A and B. The two units are essentially isostructural; nevertheless, small differences exist between them. The units contain four metal atoms, arranged at the corners of a distorted cubane-like core alternately with phenoxy oxygen of the Schiff base. The overall eight corners occupied by metal ions in the asymmetric unit are shared between cobalt and nickel in a 5.33:2.67 ratio. Each metal divalent cation binds three coordinated sites from the corresponding tridentate Schiff base ligand, the fourth one is bound by the acetate oxygen, the fifth and the sixth donor sites come from the phenolate oxygens of other Schiff base ligands. Intermolecular hydrogen bonds join the complexes to the water molecules present in the crystal packing. The magnetic characterization was carried out for this new complex and for its isostructural counterpart containing only cobalt ions. The magnetic measurements for the cobalt(II)/nickel(II) mixed compound indicate either antiferromagnetic interactions among the two cubanes or an anisotropic contribution, whereas a ferromagnetic interaction is observed within the cubane, for both the complexes, as expected by geometrical considerations. A comparison between the magnetic properties of the pure cobalt(II) derivative and similar systems discussed in literature, is presented.