Prominent Roles and Conflicted Attitudes of Eumelanin in the Living World.

Eumelanin, a macromolecule widespread in all the living world and long appreciated for its protective action against harmful UV radiation, is considered the beneficial component of the melanin family (ευ means good in ancient Greek). This initially limited picture has been rather recently extended and now includes a variety of key functions performed by eumelanin in order to support life also under extreme conditions. A lot of still unexplained aspects characterize this molecule that, in an evolutionary context, survived natural selection. This paper aims to emphasize the unique characteristics and the consequent unusual behaviors of a molecule that still holds the main chemical/physical features detected in fossils dating to the late Carboniferous. In this context, attention is drawn to the duality of roles played by eumelanin, which occasionally reverses its functional processes, switching from an anti-oxidant to a pro-oxidant behavior and implementing therefore harmful effects.

Shungite Carbon as Unexpected Natural Source of Few-Layer Graphene Platelets in a Low Oxidation State.

The paper reports on the feasibility of obtaining graphene nanomaterials with remarkable structural and chemical features from shungite rocks. The investigation of the composition and structural modifications induced in the pristine, natural C-containing mineraloid by a specifically designed physicochemical purification treatment is performed by a combined use of several techniques (scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, Raman and X-ray photoelectron spectroscopies). The adopted material processing enables efficient extraction of the C phase in the form of thin polycrystalline platelets of a few hundred nanometers sizes, and formed by 6-10 graphene sheets. About 80% of such nanostructures are characterized by a regular sp2 C honeycomb lattice and an ordered stacking of graphene layers with a d-spacing of ∼0.34 nm. The low oxygen content (∼5%), mainly found in the form of hydroxyl functional groups, provides the graphene platelets (GP) with a chemistry strictly close to that of conventional rGO materials. Such a feature is supported by the high conductivity value of 1.041 × 103 S cm-1 found for pelletized GP, which can be considered a valuable active material for a wide spectrum of advanced applications.

Mechanical characterization of polymeric thin films by atomic force microscopy based techniques.

Polymeric thin films have been awakening continuous and growing interest for application in nanotechnology. For such applications, the assessment of their (nano)mechanical properties is a key issue, since they may dramatically vary between the bulk and the thin film state, even for the same polymer. Therefore, techniques are required for the in situ characterization of mechanical properties of thin films that must be nondestructive or only minimally destructive. Also, they must also be able to probe nanometer-thick ultrathin films and layers and capable of imaging the mechanical properties of the sample with nanometer lateral resolution, since, for instance, at these scales blends or copolymers are not uniform, their phases being separated. Atomic force microscopy (AFM) has been proposed as a tool for the development of a number of techniques that match such requirements. In this review, we describe the state of the art of the main AFM-based methods for qualitative and quantitative single-point measurements and imaging of mechanical properties of polymeric thin films, illustrating their specific merits and limitations.

From Protosolar Space to Space Exploration: The Role of Graphene in Space Technology and Economy.

This paper aims to analyse the state-of-the-art of graphene-based materials and devices designed for use in space. The goal is to summarise emerging research studies, contextualise promising findings, and discuss underway strategies to address some specific space-related problems. To complete our overview of graphene-based technology and address the relevance of graphene in the wide scenario of the space economy, we also provide an analysis of worldwide patents and the scientific literature for aerospace applications in the period 2010-2021. We analysed global trends, country distributions, top assignees, and funding sponsors, evidencing a general increase for the period considered. These indicators, integrated with market information, provide a clear evaluation of the related technology trends and readiness levels.

Key Challenges in Diamond Coating of Titanium Implants: Current Status and Future Prospects.

Over past years, the fabrication of Ti-based permanent implants for fracture fixation, joint replacement and bone or tooth substitution, has become a routine task. However, it has been found that some degradation phenomena occurring on the Ti surface limits the life or the efficiency of the artificial constructs. The task of avoiding such adverse effects, to prevent microbial colonization and to accelerate osteointegration, is being faced by a variety of approaches in order to adapt Ti surfaces to the needs of osseous tissues. Among the large set of biocompatible materials proposed as an interface between Ti and the hosting tissue, diamond has been proven to offer bioactive and mechanical properties able to match the specific requirements of osteoblasts. Advances in material science and implant engineering are now enabling us to produce micro- or nano-crystalline diamond coatings on a variety of differently shaped Ti constructs. The aim of this paper is to provide an overview of the research currently ongoing in the field of diamond-coated orthopedic Ti implants and to examine the evolution of the concepts that are accelerating the full transition of such technology from the laboratory to clinical applications.

From Soft to Hard Biomimetic Materials: Tuning Micro/Nano-Architecture of Scaffolds for Tissue Regeneration.

Failure of tissues and organs resulting from degenerative diseases or trauma has caused huge economic and health concerns around the world. Tissue engineering represents the only possibility to revert this scenario owing to its potential to regenerate or replace damaged tissues and organs. In a regeneration strategy, biomaterials play a key role promoting new tissue formation by providing adequate space for cell accommodation and appropriate biochemical and biophysical cues to support cell proliferation and differentiation. Among other physical cues, the architectural features of the biomaterial as a kind of instructive stimuli can influence cellular behaviors and guide cells towards a specific tissue organization. Thus, the optimization of biomaterial micro/nano architecture, through different manufacturing techniques, is a crucial strategy for a successful regenerative therapy. Over the last decades, many micro/nanostructured biomaterials have been developed to mimic the defined structure of ECM of various soft and hard tissues. This review intends to provide an overview of the relevant studies on micro/nanostructured scaffolds created for soft and hard tissue regeneration and highlights their biological effects, with a particular focus on striated muscle, cartilage, and bone tissue engineering applications.

Hybrid Au/CNT systems: a novel breakthrough for enhanced Raman sensing of nitrile-based organic solvents.

This work deals with the preparation of carbon nabotube (CNT) deposits decorated with gold nanoparticles, and the use of Surface Enhanced Raman Spectroscopy (SERS) related to the strong plasmon absorption of gold for the detection of cyanide groups. Au nanoparticles with controlled sizes are produced by electrochemical techniques onto ensambles of CNTs deposited from hexane in N2 atmosphere. The synthesis methodologies employed to produce these hybrid materials assure an excellent adhesion to the substrate, avoiding hazardous dispersion of the nanocomponents. The use of Raman spectroscopy in the 2150-2350 cm(-1) frequency range enables to detect the presence of nitrilebased organic solvents and to discriminate between different organic cyanides. The response of the Au/CNT systems contacting nitrile-based solvents is characterized by good sensitivity, selectivity, reversibility and stability. The proposed methodology can detect in real time low levels of organic solvents and of other chemicals able to interact with gold, also in flowing systems and without stringent sample-volume requirements.

Radioactivity to Rethink the Earth's Energy Balance.

This contribution invites to re-examine the whole matter of radioactivity, reconsidering it from the point of view of a realistic source of energy. State-of-the-art and technical aspects are briefly illustrated in this note that aims to open a discussion on this challenging topic.

Carbon nanotubes/polydimethylsiloxanes systems for thermal management of miniaturized electronic components.

The thermal performances of nanocomposite layers formed by Single-walled Carbon Nanotubes (SWCNT) dispersed in 2 different kind of polydimethyl-siloxane (PDMSO) matrices has been investigated by measuring the thermal resistance under conditions similar to the ones used for thermal management in microelectronics. A series of nanocomposite samples with thickness in the range 25 microm(-1) cm have been tested. The nanocomposites were prepared varying the amounts of nanotubes embedded in the matrix (from 0.1 to 5%w). In some cases also microsized graphites were mixed to the nanotube's fillers. For 25 micron thick layers, the thermal resistance of the neat silicone specimen can be reduced of 54% with the addition of 2%w carbon nanotubes. The variation of thermal conductivity as a function of the SWCNT's loading is reported and discussed. Furthermore the dispersion's effects of the nanotubes in the layers and the effects on the realization of a net-like system have been investigated.

Partial alpha-decay half-lives for alpha-emitting Osmium isotopes: Accurate determinations by a semi-empirical model.

Partial alpha-decay half-life-values for twenty-four cases of alpha-decaying Osmium isotopes (161-174, 184, 186-188Os) have been obtained in the framework of a semi-empirical, one-parameter model based on the quantum mechanical tunneling mechanism through a potential barrier. Here the Coulomb, centrifugal and overlapping contributions to the barrier have been considered within the spherical nucleus approximation. The calculation method enabled to reproduce, within a factor 2, the measured half-lives for ground-state to ground-state (gs-gs) α-transitions of twelve artificially produced Osmium isotopes (162-172, 174Os) and of two naturally occurring isotopes (184, 186Os). In addition, a half-life prediction of T½ = (2.0 ± 0.1) × 1016 a has been found for the gs-gs α-transition of naturally occurring 187Os isotope. Two cases of gamma quanta accompanying α-decay possible of being accessed experimentally have been predicted: 184Os decaying to the first level of 180W, with T½ = (0.73 ± 0.04) × 1015 a, and 186Os decaying to the first level of 182W, with T½ = (3.9 ± 0.2) × 1016 a. New α-decay schemes for 184Os, 186Os, 187Os isotopes have been anticipated, and estimated T½-values for rarer cases of α-transitions of Osmium isotopes have been reported.

Toward an accurate determination of half-life of 147Sm isotope.

The task of an accurate determination of alpha-decay rate of 147Sm isotope, a topic of importance in both basic and applied science, has been performed in the present research following two different routes. First, a critical review and data analysis of the whole set of half-life values obtained till date yielded an average of 106.3 ±â€¯0.5 Ga. Second, a one-parameter, semi-empirical model for alpha emission from nuclei, developed in the framework of quantum mechanical tunneling mechanism through a Coulomb-plus-centrifugal-plus-overlapping potential barrier, that yielded a value of 108.2 ±â€¯3.0 Ga. The good agreement found between the half-life values obtained from these procedures represents a net progress toward the assessment of a reliable 147Sm alpha-decay rate to be used in geo- and cosmo-chronological investigations.

Graphene platelets from shungite rock modulate electropolymerization and charge storage mechanisms of soft-template synthetized polypyrrole-based nanocomposites.

We report here on soft-template electropolymerizations of polypyrrole (Ppy)-based nanocomposites triggered by graphene platelets (GP) from shungite (SH) rocks. A properly designed procedure for an efficient extraction of graphene platelets from SH powders is established to produce remarkable graphene materials in a low oxidation state and with a high electrical conductivity (1490 S cm-1). By using positively and negatively charged templating surfactants the role played by the graphene units on the electropolymerization reactions is pointed out by SEM, EDX, TEM, SAED, XPS and Raman spectroscopy. The morphological/structural characterizations highlight that GP from SH have a surface chemistry suitable for selective and mutual interactions with the growing Ppy chains. CV and galvanostatic charge/discharge measurements evidence that GP improve the transport of both electrons and ions within the bulk material by means of a synergistic action with the polymer phase. This cooperative behavior induces an enhancement of the specific capacitance up to 250 F g-1 at 2 A g-1. The Ppy-GP materials produced following the settled protocols result to be appropriate for fabricating multifunctional charge transport and storage electroactive systems.

Nanodiamonds coupled with 5,7-dimethoxycoumarin, a plant bioactive metabolite, interfere with the mitotic process in B16F10 cells altering the actin organization.

For the first time, we coupled reduced detonation nanodiamonds (NDs) with a plant secondary metabolite, citropten (5,7-dimethoxycoumarin), and demonstrated how this complex was able to reduce B16F10 tumor cell growth more effectively than treatment with the pure molecule. These results encouraged us to find out the specific mechanism underlying this phenomenon. Internalization kinetics and quantification of citropten in cells after treatment with its pure or ND-conjugated form were measured, and it was revealed that the coupling between NDs and citropten was essential for the biological properties of the complex. We showed that the adduct was not able to induce apoptosis, senescence, or differentiation, but it determined cell cycle arrest, morphological changes, and alteration of mRNA levels of the cytoskeletal-related genes. The identification of metaphasic nuclei and irregular disposition of ß-actin in the cell cytoplasm supported the hypothesis that citropten conjugated with NDs showed antimitotic properties in B16F10 cells. This work can be considered a pioneering piece of research that could promote and support the biomedical use of plant drug-functionalized NDs in cancer therapy.

Structural and morphological peculiarities of hybrid Au/nanodiamond engineered nanostructures.

Nanostructured Au nano-platelets have been synthesized from an Au(III) complex by growth process triggered by nanodiamond (ND). An electroless synthetic route has been used to obtain 2D Au/ND architectures, where individual nanodiamond particles are intimately embedded into face-centered cubic Au platelets. The combined use of high resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED), was able to reveal the unusual organization of these hybrid nanoparticles, ascertaining the existence of preferential crystallographic orientations for both nanocrystalline species and highlighting their mutual locations. Detailed information on the sample microstructure have been gathered by fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) of HR-TEM images, allowing us to figure out the role of Au defects, able to anchor ND crystallites and to provide specific sites for heteroepitaxial Au growth. Aggregates constituted by coupled ND and Au, represent interesting systems conjugating the best optoelectronics and plasmonics properties of the two different materials. In order to promote realistically the applications of such outstanding Au/ND materials, the cooperative mechanisms at the basis of material synthesis and their influence on the details of the hybrid nanostructures have to be deeply understood.

Hydrogen Adsorption Properties of Carbon Nanotubes and Platinum Nanoparticles from a New Ammonium-Ethylimidazolium Chloroplatinate Salt.

Self-supporting membranes built entirely of carbon nanotubes have been prepared by wet methods and characterized by Raman spectroscopy. The membranes are used as supports for the electrodeposition of Pt nanoparticles without the use of additional additives and/or stabilizers. The Pt precursor is an ad hoc synthesized ammonium-ethylimidazolium chloroplatinate(IV) salt, [NH3 (CH2 )2 MIM)][PtCl6 ]. The Pt complex was characterized using NMR spectroscopy, XRD, ESI-MS, and FTIR spectroscopy. The interaction between the Pt-carbon nanotubes nanocomposites and hydrogen is analyzed using electrochemical and quartz microbalance measurements under near-ambient conditions. The contribution of the Pt phase to the hydrogen adsorption on nanotube is found and explained by a kinetic model that takes into account a spillover event. Such a phenomenon may be exploited conveniently for catalysis and electrocatalysis applications in which the hybrid systems could act as a hydrogen transfer agent in specific hydrogenation reactions.

Polyaniline-nanodiamond fibers resulting from the self-assembly of nano-fibrils: a nanomechanical study.

Based on atomic force microscopy (AFM), torsional harmonics atomic force microscopy (TH-AFM, also referred to with the commercial name HarmoniX™) allows one to perform a quantitative characterization of the mechanical properties of soft samples on the nanometer scale. In this work, such a technique has been employed to study the mechanical properties of self-assembled micrometric fibers of polyaniline (PANI) doped with nanodiamond (ND) particles and to investigate the role of ND in the assembly. In particular, besides PANI-ND fibers, other features, i.e., nano-fibrils and blobs, have also been observed on the sample, the mechanical properties of which have been determined and compared after correcting for the effect of the substrate and of the cylindrical geometry of nano-fibrils. Their similar mechanical properties suggest that PANI-ND micro-fibers are constituted by self-assembly of nano-fibrils. Finally, the combination of nanomechanical characterization with energy dispersive X-ray (EDX) and Raman analyses allowed us to determine that softer blobs are residuals of amorphous PANI not polymerized in nano-fibrils.

Nanodiamonds for field emission: state of the art.

The aim of this review is to highlight the recent advances and the main remaining challenges related to the issue of electron field emission (FE) from nanodiamonds. The roadmap for FE vacuum microelectronic devices envisages that nanodiamonds could become very important in a short time. The intrinsic properties of the nanodiamond materials indeed meet many of the requirements of cutting-edge technologies and further benefits can be obtained by tailored improvements of processing methodologies. The current strategies used to modulate the morphological and structural features of diamond to produce highly performing emitting systems are reported and discussed. The focus is on the current understanding of the FE process from nanodiamond-based materials and on the major concepts used to improve their performance. A short survey of non-conventional microsized cold cathodes based on nanodiamonds is also reported.

Nanocarbon surfaces for biomedicine.

The distinctive physicochemical, mechanical and electrical properties of carbon nanostructures are currently gaining the interest of researchers working in bioengineering and biomedical fields. Carbon nanotubes, carbon dendrimers, graphenic platelets and nanodiamonds are deeply studied aiming at their application in several areas of biology and medicine.   Here we provide a summary of the carbon nanomaterials prepared in our labs and of the fabrication techniques used to produce several biomedical utilities, from scaffolds for tissue growth to cargos for drug delivery and to biosensors.

Quantitative evaluation of bacteria adherent and in biofilm on single-wall carbon nanotube-coated surfaces.

Biofilm is a common bacterial lifestyle, and it plays a crucial role in human health, causing biofilm-mediated infections. Recently, to counteract biofilm development, new nano-structured biomaterials have been proposed. However, data about the antibacterial properties of nano-structured surfaces are fragmentary and controversial, and, in particular, the susceptibility of nano-structured materials to colonization and biofilm formation by bacterial pathogens has not been yet thoroughly considered. Here, the ability of the pathogenic Streptococcus mutans and Pseudomonas aeruginosa to adhere and form biofilm on surfaces coated with single-wall carbon nanotubes (SWCNTs) was analyzed. Our results showed that the surfaces of SWCNTs-coated glass beads (SWCNTs-GBs) were colonized at the same extent of uncoated GBs both by S. mutans and P. aeruginosa. In conclusion, our results demonstrate that single wall SWCNTs-coated surfaces are not suitable to counteract bacterial adhesion and biofilm development.