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Crystalline silica (CS) is a well-known toxic particle that may cause severe pathologies including silicosis, lung cancer, and several autoimmune diseases. [1a,b] The hazard associated to crystalline silica is extremely variable and depends on some specific characteristics, including crystal structure and surface chemistry.[1c] In particular, a specific family of surface silanols, called nearly free silanols (NFS), has been recently related to the interaction mechanisms occurring between quartz particles and cell membrane components, which initiate the lung inflammatory reaction. [2] Even though this phenomenon has been studied for decades on quartz, the research on other silica polymorphs was limited, also because of the relative low abundance of some polymorphs. The CS polymorphs, i.e., quartz, cristobalite, tridymite, coesite, and stishovite, share the SiO2 stoichiometry and differentiate for crystal structure. [3] Thus, the different crystal lattices expose differently ordered hydroxyl group patterns at the crystal surface. We proved that the NFS occur and take part in the molecular bio-interactions, not only on quartz, but also on the other CS polymorphs. Five high-purity samples representative of the five CS polymorphs were fully characterized by XRPD, Scanning Electron Microscopy, and IR spectroscopy. When CS polymorphs were contacted with model membranes (red blood cells), all of them were able to disrupt cell membranes, except stishovite, which was the only polymorph without NFS. By thermally modulating the topochemistry of surface silanols, it was possible to show that the membranolytic activity of the CS polymorphs quantitatively paralleled the occurrence of NFS. This observations confirmed the central role of NFS in regulating the interaction of silica with biomembranes. In conclusion, these results put the surface characteristics of CS particles in the foreground with respect to the crystal habit and provide a comprehensive understanding of the molecular mechanisms associated with silica hazard and bio-minero-chemical interfacial phenomena. [4][1] a) KAWASAKI, H. 2015, Inhal Toxicol, 27, 363-77; b) IARC 2012, IARC monographs on the evaluation of carcinogenic risks to humans, Lyon, World Health 543 Organisation c). BORM, P. J. A., et al. 2018, Part. Fibre. Toxicol., 15, 23;[2] PAVAN, C., et al., 2020, Proc Natl Acad Sci U S A, 117, 27836-27846.[3] GUTHRIE, G. D. & HEANEY, P. J. 1995, Scand J Work Environ Health, 21 Suppl 2, 5-8.[4] PAVAN. C., et al., 2023, accepted on Frontiers in Chemistry, DOI: 10.3389/fchem.2022.1092221.

Aryl aldehydes and acids are important industrial intermediates, but their synthesis from the corresponding alcohols often requires the use of high temperatures and harmful solvents and oxidant agents. Heterogeneous photocatalysis represents an interesting option for the partial oxidation of alcohols to aldehydes at room temperature using water as solvent. In this work, the partial photocatalytic oxidation of 2-hydroxybenzyl alcohol (salicyl alcohol) and 4-hydroxybenzyl alcohol to the corresponding aldehydes and acids has been compared, under environmental-friendly conditions, employing TiO2 P25 as photocatalyst in water. The selectivity to the corresponding aldehydes and acids, under the same experimental conditions, was higher for 4-hydroxybenzyl alcohol than for 2-hydroxybenzyl alcohol owing to its greater stability with respect to oxidant attacks and to the lower adsorption of 4-hydroxybelzaldehyde and 4-hydroxybenzoic acid on the photocatalyst surface. The processes occurring at the oxide surface during the reaction were monitored at the molecular level by FT-IR spectroscopy under in situ UV irradiation to get deeper insights into the different behavior of the two alcohols.

Photocatalytic hydrogen (H2) production is a promising route for alternative energetics. Understanding structure–activity relationships is a crucial step towards the rational design of photocatalysts, which requires the application of operando spectroscopy under relevant working conditions. We performed an operando investigation on a catalytic system during the photodeposition of Pt on TiO2 and photostimulated H2 production, using simultaneous laboratory X-ray absorption spectroscopy (XAS), UV–Vis spectroscopy, and mass spectrometry. XAS showed a progressive increase in Pt fluorescence for Pt deposited on TiO2 for over an hour, which is correlated with the signal of the produced H2. The final Pt/TiO2 catalyst contained Pt(0) particles. The electronic features corresponding to the Pt4+ species in the UV–Vis spectrum of the solution disappear as soon as UV radiation is applied in the presence of formic acid, which acts as a hole scavenger, resulting in the presence of Pt(0) particles in solution.

Crystalline silica (CS) is a well-known human carcinogen and freshly fractured CS is strongly held to be more toxic than aged dust. Mechanical fracturing indeed generates on CS surface a specific family of Nearly-Free Silanols (NFS), a moiety that was proved to destabilize cell membranes and initiate inflammation in vivo. During milling, silica nanoparticles are also generated, however their contribution to the overall toxicity of quartz is still largely unexplored. Nanoquartz can be synthetized via bottom-up methods, but the surface chemistry of those crystals strongly differs from nanoparticles resulting from fracturing. We report here a top-down milling procedure to obtain a nanometric quartz that shares with fractured quartz the key surface properties relevant to toxicity. Fracturing procedure was optimized by coupling dry and wet milling steps, using water as a dispersing agent, and varying milling times and rotational speeds. We obtained a set of samples that would be classified as nanomaterials under EU CLP regulation (>50% of particles in number are < 100 nm) and exhibited a strong tendency to form submicrometric agglomerates. Deagglomeration with surfactants or simulated body fluids was negligible. Partial lattice amorphization and bimodal crystallite domain size were observed, as confirmed by the presence of two distinct domains of scattering with nanometric (< 50 nm) and submicrometric (0.8-1 µm) crystallite size. A moderate membranolytic activity, which nicely correlated with the amount of surface NFS, signalled that our nanoquartz may induce inflammation in vivo. Overall, a membranolytic nanoquartz for investigating the toxic activity of nanometric silica was obtained.

Occupational exposure to quartz dust is associated with fatal diseases. Quartz dusts generated by mechanical fracturing are characterized by a broad range of micrometric to nanometric particles. The contribution of this nanometric fraction to the overall toxicity of quartz is still largely unexplored, primarily because of the strong electrostatic adhesion forces that prevent isolation of the nano-fraction. Furthermore, fractured silica dust exhibits special surface features, namely Nearly Free Silanols (NFS), which impart membranolytic activity to quartz. Nanoquartz can be synthetized via bottom-up methods, but the surface chemistry of those crystals strongly differs from nanoparticles resulting from fracturing. We report here a top-down milling procedure to obtain a nanometric quartz that shares with fractured quartz the key surface properties relevant to toxicity. Ball milling was optimized by coupling dry and wet milling steps, using water as a dispersing agent, and varying milling times and rotational speeds. Nanoquartz with a strong tendency to form submicrometric agglomerates was obtained. Deagglomeration with surfactants or simulated body fluids was negligible. Partial lattice amorphization and bimodal crystallite domain size were observed. A moderate membranolytic activity, which correlated with the amount of NFS, signaled coherence with previous toxicological data. Membranolytic nanoquartz for toxicological investigations was obtained.

The investigation of secondary effects induced by ionizing radiation represents a new and ever-growing research field in radiobiology. This new paradigm cannot be investigated only using standard instrumentation and methodologies, but rather requires novel technologies to achieve significant progress. In this framework, we developed diamond-based sensors that allow simultaneous real-time measurements with a high spatial resolution of the secretory activity of a network of cells cultured on the device, as well as of the dose at which they are exposed during irradiation experiments. The devices were functionally characterized by testing both the above-mentioned detection schemes, namely: amperometric measurements of neurotransmitter release from excitable cells (such as dopamine or adrenaline) and dosimetric evaluation using different ionizing particles (alpha particle and X-ray photons). Finally, the sensors were employed to investigate the effects induced by X-rays on the exocytotic activity of PC12 neuroendocrine cells by monitoring the modulation of the dopamine release in real-time.

Respirable crystalline silica (RCS) is the leading cause of occupational respiratory diseases worldwide. RCS is associated with inflammatory lung reactions, which can lead to silicosis, cancer, and autoimmune diseases. The extreme variability of silica specimens, including its amorphous forms, the surface heterogeneity, and variable toxicity effects, generated one of the most intriguing enigmas in particle toxicology, i.e., deciphering which physico-chemical features explain and predict the variable hazard of silica. Using a set of ad hoc prepared synthetic and natural quartz particles, we have identified a unique subfamily of surface silanols as a key initiator of the toxicity of silica particles. These moieties, namely the "nearly-free silanols" (NFS), appear on the surface of quartz when crystals are fractured, and their amount can be modulated by physico-chemical processes. The peculiar spatial arrangement of NFS was demonstrated as the most energetically favorable and selective for interacting zwitterionic phospholipids that make up cell membranes. The toxic activity of NFS was also confirmed with amorphous nanosilica synthesized at high temperatures, and our recent findings suggest that NFS could impart toxic properties to other silica polymorphs and hydroxylated surfaces, including aluminosilicates and engineered stones. Overall, NFS occurrence accounts for the origin and variability of the toxicity of silica, opening perspectives for controlling RCS hazard, and may contribute to understand other important interfacial phenomena of hydroxylated materials.

TiO2 nanoparticles (NPs) are intensively studied and widely used due to their huge potential in numerous applications involving their interaction with ultraviolet light (e.g., photocatalysis and sunscreens). Typically, these NPs are in water-containing environments and thus tend to be hydrated. As such, there is a growing need to better understand the physicochemical properties of hydrated TiO2 NPs in order to improve their performance in photochemical applications (e.g., photocatalytic water splitting) and to minimise their environmental impact (e.g., potential biotoxicity). To help address the need for reliable and detailed data on how nano-titania interacts with water, we present a systematic experimental and theoretical study of surface hydroxyl (OH) groups on photoactive anatase TiO2 NPs. Employing well-defined experimentally synthesised NPs and detailed realistic NP models, we obtain the measured and computed infrared spectra of the surface hydroxyls, respectively. By comparing the experimental and theoretical spectra we are able to identify the type and location of different OH groups in these NP systems. Specifically, our study allows us to provide unprecedented and detailed information about the coverage-dependent distribution of hydroxyl groups on the surface of experimental titania NPs, the degree of their H-bonding interactions and their associated assigned vibrational modes. Our work promises to lead to new routes for developing new and safe nanotechnologies based on hydrated TiO2 NPs.

Respirable crystalline silica (RCS) is the leading cause of occupational respiratory disease worldwide. RCS is associated with silicosis, cancer, and autoimmune diseases [1]. Silica (SiO2) is a simple, yet structurally very complex oxide and tens of variable crystalline and amorphous forms exist with different structures and surfaces. Structural heterogeneity is reflected in variable toxic effects, and this in turn generates one of the most intriguing enigmas in particle toxicology, i.e., deciphering the exact molecular nature of the interaction between silica and biological matter.A large set of synthetic and natural, crystalline and amorphous, micrometric and nanometric silica particles were prepared, modified, and characterized. The interaction of these surface-modified silicas with membrane systems of decreasing molecular complexity, e.g., red blood cells, liposomes, and phospholipid supramolecular structures (PLS), was investigated and compared with the results of in vitro and in vivo particle toxicity assessment.A specific silanol (≡Si-OH) sub-group at silica surface, the “nearly free silanols” (NFS), was evidenced as the cause for the membranolytic and inflammatory effect of silica [2]. Silica powders with NFS-rich surfaces caused RBC membrane lysis, and selectively perturbed liposomes and adsorbed PLS. Specific amino groups exposed at the membrane surface are proposed as recognition epitopes for the selective interaction with NFS, which are in turn proposed as the molecular pattern that defines the interaction of silica with biomembranes [3]. Our findings open a new perspective for tailoring less toxic silica particles and for designing improved technological applications of silica. NFS and hydroxylated surface moieties may be also relevant for the toxicity of other respirable mineral dusts, suggesting a new paradigm for particle toxicity mechanism.References[1] Leung et al., Lancet 2012, 379, 2008; [2] Pavan et al., Proc. Natl. Acad. Sci USA 2020, 117, 27836; [3] Pavan et al., sumbitted to ACS Central Science

Crystalline silica (CS) is a well-known human toxicant and inhalation of the airborne particles with size lower than 4 µm is associated to severe occupational diseases, such as silicosis and lung cancer.1 The International Agency for the Research on Cancer (IARC) classified CS as carcinogenic to humans and freshly fractured CS is held to be more toxic than aged dust.1,2 Fracturing generates on CS a specific family Nearly-Free Silanols (NFS), which are able to destabilize cell membranes,3 and some nanometric particles. We aim here to create and assess the possible toxicological impact and the chemical characteristics of the nanometric fraction (nano-CS) formed when CS is fractured.A highly pure CS of synthetic origin4 (α-quartz, micrometric in size) was ball-milled to obtain ultrafine particles. We coupled a dry milling step and a wet milling step, using water as dispersing agent, and we generated particles with specific surface area (SSA) ranging from 37 to 60 m2/g. These SSA values signaled the generation of a relevant nanometric fraction. The increase in SSA paralleled the energy delivered to quartz during the milling, that exceeded by far the energies commonly used in industrial processing. Morphology, crystallinity, size, surface silanols, including quantification of NFS, and membranolytic activity toward red blood cells were assessed. The nano-CS samples exhibited: i) a partial lattice amorphization that increased with the increase of the milling energy; ii) the presence of two distinct domains of scattering that indicated the occurrence of crystallite with nanometric (< 50 nm) and submicrometric (0.8-1 µm) size; iii) a strong tendency to form micrometric agglomerates , which could be partially dispersed with ultrasounds and surfactants in water suspensions; and iv) a moderate membranolytic activity that correlated with the presence of NFS. We selected a nano-CS sample that would be classified as a nanomaterial under EU CLP regulation (>50% of particles in number are < 100 nm).5 The nano-CS sample will be used in the next future as a reference material to quantify the nanometric fraction of silica powders and assess the potential exposure to nano-CS in industrial hygiene context.In conclusion, the preparation and characterization of nano-CS was achieved and the physico-chemical characteristics that could be relevant for silica toxicity were assessed. The nano-CS reference material will be used to quantify nano-CS in industrial scenario, and to clarify the toxic activity of nanometric silica obtained by mechanical fracturing. [1] IARC, Monograph Vol. 100C, 2012[2] Turci et al, Part Fibre Toxicol, 2016, 13, 32.[3] Pavan et al, Proc. Natl. Amer. Soc. USA, 2020, 117 (45), 27836[4] Pastero et al., 2016, Cryst. Growth Des. 16, 4, 2394–2403.[5] SCoEaNIHR, E. S., 2010, 'Scientific Basis for the Definition of the Term “nanomaterial”', European Commission.

HCN in the gas form is considered as a primary nitrogen source for the synthesis of prebiotic molecules in extraterrestrial environments. Nevertheless, the research mainly focused on the reactivity of HCN and its derivatives in aqueous systems, often using external high-energy supply in the form of cosmic rays or high energy photons. Very few studies have been devoted to the chemistry of HCN in the gas phase or at the gas/solid interphase, although they represent the more common scenarios in the outer space. In this paper we report about the reactivity of highly pure HCN in the 150-300 K range at the surface of amorphous and crystalline Mg

Inhaled crystalline silica causes inflammatory lung diseases, but the mechanism for its unique activity compared to other oxides remains unclear, preventing the development of potential therapeutics. Here, the molecular recognition mechanism between membrane epitopes and "nearly free silanols" (NFS), a specific subgroup of surface silanols, is identified and proposed as a novel broad explanation for particle toxicity in general. Silica samples having different bulk and surface properties, specifically different amounts of NFS, are tested with a set of membrane systems of decreasing molecular complexity and different charge. The results demonstrate that NFS content is the primary determinant of membrane disruption causing red blood cell lysis and changes in lipid order in zwitterionic, but not in negatively charged liposomes. NFS-rich silica strongly and irreversibly adsorbs zwitterionic self-assembled phospholipid structures. This selective interaction is corroborated by density functional theory and supports the hypothesis that NFS recognize membrane epitopes that exhibit a positive quaternary amino and negative phosphate group. These new findings define a new paradigm for deciphering particle-biomembrane interactions that will support safer design of materials and what types of treatments might interrupt particle-biomembrane interactions.

Three luminescent Eu-containing phosphate materials (Ca-doped europium phosphate monohydrate, Eu-doped carbonated-apatite, and europium phosphate monohydrate) were prepared and analyzed on the level of bulk structure and surface properties and compared to the biomimetic non-luminescent counterpart hydroxyapatite. Europium-containing phosphate materials exhibited nanosized dimensions but different luminescence emissions and luminescence lifetimes depending on their crystalline structures (i.e., lanthanide phosphate or apatites) and chemical composition. The introduction of Eu in the crystal lattice leads to a notable decrease in the overall Lewis acidity of the surface cationic sites detected by CO probing. Further, the mixed Eu/Ca-containing materials surfaces were found to be very similar to the reference hydroxyapatite in terms of water adsorption energy, while the pure europium phosphate resulted to have the notably higher energy values of direct interaction of water molecules with the surface cations with no detected propagation of this effect towards water overlayers., This work was supported by projects PGC2018-102047-B-I00 (MCIN/AEI/FEDER, UE) (Spain) and PCI2020-112108 funded by MCIN/AEI/10.13039 /501100011033 (Spain) and the European Union "NextGenerationEU"/PRTR". PCI2020-112108 is part of the ERA-NET Cofund BlueBio Programme supported by the European Union.

Occupational exposure to quartz dust is associated with fatal diseases. Quartz dusts generated by mechanical fracturing are characterized by a broad range of micrometric to nanometric particles. The contribution of this nanometric fraction to the overall toxicity of quartz is still largely unexplored, primarily because of the strong electrostatic adhesion forces that prevent isolation of the nanofraction. Furthermore, fractured silica dust exhibits special surface features, namely nearly free silanols (NFS), which impart a membranolytic activity to quartz. Nanoquartz can be synthetized via bottom-up methods, but the surface chemistry of such crystals strongly differs from that of nanoparticles resulting from fracturing. Here, we report a top-down milling procedure to obtain a nanometric quartz that shares the key surface properties relevant to toxicity with fractured quartz. The ball milling was optimized by coupling the dry and wet milling steps, using water as a dispersing agent, and varying the milling times and rotational speeds. Nanoquartz with a strong tendency to form submicrometric agglomerates was obtained. The deagglomeration with surfactants or simulated body fluids was negligible. Partial lattice amorphization and a bimodal crystallite domain size were observed. A moderate membranolytic activity, which correlated with the number of NFS, signaled coherence with the previous toxicological data. A membranolytic nanoquartz for toxicological investigations was obtained.

In recent decades, nanodiamonds (NDs) have earned increasing interest in a wide variety of research fields, thanks to their excellent mechanical, chemical, and optical properties, together with the possibility of easily tuning their surface chemistry for the desired purpose. According to the application context, it is essential to acquire an extensive understanding of their interaction with water in terms of hydrophilicity, environmental adsorption, stability in solution, and impact on electrical properties. In this paper, we report on a systematic study of the effects of reducing and oxidizing thermal processes on ND surface water adsorption. Both detonation and milled NDs were analyzed by combining different techniques. Temperature-dependent infrared spectroscopy was employed to study ND surface chemistry and water adsorption, while dynamic light scattering allowed the evaluation of their behavior in solution. The influence of water adsorption on their electrical properties was also investigated and correlated with structural and optical information obtained via Raman/photoluminescence spectroscopy. In general, higher oxygen-containing surfaces exhibited higher hydrophilicity, better stability in solution, and higher electrical conduction, although for the latter the surface graphitic contribution was also crucial. Our results provide in-depth information on the hydrophilicity of NDs in relation to their surface chemical and physical properties, by also evaluating the impacts on their aggregation and electrical conductance.

Carboxylic-acid adsorption on anatase TiO2 is a relevant process in many technological applications. Yet, despite several decades of investigations, the acid-proton localization-either on the molecule or on the surface-is still an open issue. By modeling the adsorption of formic acid on top of anatase(101) surfaces, we highlight the formation of a short strong hydrogen bond. In the 0 K limit, the acid-proton behavior is ruled by quantum delocalization effects in a single potential well, while at ambient conditions, the proton undergoes a rapid classical shuttling in a shallow two-well free-energy profile. This picture, supported by agreement with available experiments, shows that the anatase surface acts like a protecting group for the carboxylic acid functionality. Such a new conceptual insight might help rationalize chemical processes involving carboxylic acids on oxide surfaces.

Physica status solidi / Rapid research letters 2100409 (2021). doi:10.1002/pssr.202100409, Published by Wiley-VCH, Weinheim

We investigated the ability of microbial volatile organic compounds (MVOCs) emitted by Bacillus megaterium (a well-known MVOC producer) to modify the dissolution kinetics and surface of hydroxyapatite, a natural soil mineral. Facilitated phosphate release was induced by the airborne MVOCs in a time-dependent manner. Use of each standard chemical of the MVOCs then revealed that acetic and oxalic acids are crucial for the phenomenon. In addition, the ability of such MVOCs to engineer the apatite surfaces was evidenced by FT-IR spectra showing the COO- band variation with incubation time and the prolonged acceleration of phosphate release during the negligible acidification of the hydroxyapatite-containing solutions. The formation of calcium oxalate was revealed through SEM-EDS and XRD analyses, suggesting that MVOC oxalic acid interacts with calcium ions, leading to the precipitation of calcium oxalate, thus preventing the recrystallization of calcium phosphates. Gel- and soil-based plant cultivation tests employing Arabidopsis thaliana and solid calcium phosphates (i.e., nano- and microsized hydroxyapatites and calcium phosphate dibasic) demonstrated that these MVOC mechanisms facilitate plant growth by ensuring the prolonged supply of plant-available phosphate. The relationship between the growth enhancement and the particle size of the calcium phosphates also substantiated the MVOC sorption onto soil minerals related to plant growth. Given that most previous studies have assumed that MVOCs are a molecular lexicon directly detected by the dedicated sensing machinery of plants, our approach provides a new mechanistic view of the presence of abiotic mediators in the interaction between plants and microbes via MVOCs.

Forsterite is a nesosilicate with Mg2SiO4 composition, representing the iron-free endmember of the family of olivines. Interestingly, aside its finding as mineral component of the Earth’s crust and mantle, it has been observed in extraterrestrial environments where have been found as principal inorganic constituents of meteorites, comets and in the core of dust grains found in the interstellar medium and in protoplanetary disks [1]. It has often been indicated that these grains could be possible sites for the occurrence of astrochemical reactions involving simple prebiotic molecules (SPM, e.g. CO, CO2, H2O, HCN, etc.). In order to assess the role of Mg2SiO4 in this prebiotic scenario, the understanding of the surface properties of grain-core phases is of primary importance. We thoroughly characterized two Mg2SiO4 model samples, namely an amorphous magnesium silicate (AMS) and a crystalline forsterite (Forst), and we compared their surface acid-base properties as a function of their structure (amorphous vs crystalline) [2]. The AMS sample was synthesized via thermal plasma route, as proposed by Koike et al. [3], whereas Forst was obtained by thermal annealing of the former at 1073 K. The acid-base properties of the two systems were investigated by monitoring the adsorption of selected probe molecules (CO, CO2 and CD3CN) by IR spectroscopy and then by studying the perturbation of their vibrational fingerprints upon interaction with specific surface functionalities. As an example, the IR spectra of CD3CN adsorbed on AMS and Forst in the υ(CN) frequency range are shown in Figure 1. The spectra for both materials are characterized by three main bands at 2300, 2266 and 2215 cm-1. The 2300 cm-1 component is assigned to CD3CN interacting with Lewis acid sites, i.e. surface Mg2+ cations, whereas the 2266 cm-1 band is assigned to the features of CD3CN interacting with weak Bronsted acid sites (surface silanols) and of not interacting CD3CN forming multilayers. These components are closely similar among both samples. Instead, they remarkably differ with respect to the 2215 cm-1 band, which is much more intense in AMS than in Forst. We assigned this signal to anionic species formed by deprotonation of acetonitrile in presence of strong surface basic sites. These results, confirmed also by the adsorption of other probe molecules, showed as AMS and Forst have a similar population of surface acid sites, whereas only the former shows a significant surface basicity. Finally, we investigated HCN adsorption on both samples. HCN is a molecule of particular interest since its adsorption and reactivity on silicates in interstellar media is supposed to play a role in the synthesis of biomolecules contributing to the development of life [4]. The HCN reaction leads to the formation of a variety of oligomers (at least up to 12 terms) and the surface basicity, already highlighted by the other probe molecules, seems to play a key role in the process. Figure 1. IR spectra of AMS and Forst outgassed for 2 hours at 673 K in vacuum and contacted with 40 mbar of CD3CN at r.t. (curves a) and outgassed for 30 min at r.t. after CD3CN contact (curves b). Spectra collected at decreasing CD3CN pressures are reported as thin lines for both materials. The contribution from the bare activated material has been subtracted. The spectra have been normalized to the specific surface area of the samples. References [1] T. Henning, Cosmic Silicates. Annu. Rev. Astron. Astrophys. 2010, 48, 21–46. [2] M. Signorile, L. Zamirri, A. Tsuchiyama, P. Ugliengo, F. Bonino, G. Martra, ACS Earth Sp. Chem. 2020, 4, 345–354. [3] C. Koike, Y. Imai, H. Chihara, H. Suto, K. Murata, A. Tsuchiyama, S. Tachibana, S. Ohara, Astrophys. J. 2010, 709, 983–992 [4] J. P. Ferris, and W. J. Hagan Jr, Tetrahedron. 1984, 40, 1093-1120.

Understanding the correlation between the morphological and functional properties of particulate materials is crucial across all fields of physical and natural sciences. This manuscript reports on the investigation of the effect of polyethylene glycol (PEG) employed as a capping agent in the synthesis of SrTiO3 crystals. The crucial influence of PEG on both the shape and size of the strontium titanate particles is revealed, highlighting the effect on the photocurrents measured under UV&ndash, Vis irradiation.

The employment of ionizing radiation is a powerful tool in cancer therapy, but beyond targeted effects, many studies have highlighted the relevance of its off-target consequences. An exhaustive understanding of the mechanisms underlying these effects is still missing, and no real-time data about signals released by cells during irradiation are presently available. We employed a synchrotron X-ray nanobeam to perform the first real-time simultaneous measurement of both X-ray irradiation and in vitro neurotransmitter release from individual adrenal phaeochromocytoma (PC12) cells plated over a diamond-based multielectrode array. We have demonstrated that, in specific conditions, X-rays can alter cell activity by promoting dopamine exocytosis, and such an effect is potentially very attractive for a more effective treatment of tumors.

X-ray synchrotron sources, possessing high power density, nanometric spot size and short pulse duration, are extending their application frontiers up to the exploration of direct matter modification. In this field, the use of atomistic and continuum models is now becoming fundamental in the simulation of the photoinduced excitation states and eventually in the phase transition triggered by intense X-rays. In this work, the X-ray heating phenomenon is studied by coupling the Monte Carlo method (MC) with the Fourier heat equation, to first calculate the distribution of the energy absorbed by the systems and finally to predict the heating distribution and evolution. The results of the proposed model are also compared with those obtained removing the explicit definition of the energy distribution, as calculated by the MC. A good approximation of experimental thermal measurements produced irradiating a millimetric glass bead is found for both of the proposed models. A further step towards more complex systems is carried out, including in the models the different time patterns of the source, as determined by the filling modes of the synchrotron storage ring. The two models are applied in three prediction cases, in which the heating produced in Bi2Sr2CaCu2O8+δ microcrystals by means of nanopatterning experiments with intense hard X-ray nanobeams is calculated. It is demonstrated that the temperature evolution is strictly connected to the filling mode of the storage ring. By coupling the MC with the heat equation, X-ray pulses that are 48 ps long, possessing an instantaneous photon flux of ∼44 × 1013 photons s−1, were found to be able to induce a maximum temperature increase of 42 K, after a time of 350 ps. Inversely, by ignoring the energy redistribution calculated with the MC, peaks temperatures up to hundreds of degrees higher were found. These results highlight the importance of the energy redistribution operated by primary and secondary electrons in the theoretical simulation of the X-ray heating effects.

Everybody dreams to have X-ray eyes and discover the most invisible secrets of the world around us. X-rays can probe matter (depth resolved) down to atomic resolution, if relying on diffraction-based techniques. An X-ray diffraction pattern may contain information over many length scales (atomic structure, microstructure, mesostructure). This peculiarity justifies the well-recognized impact of several X-ray diffraction-based techniques to diverse fields of research. On the other hand, X-ray spectroscopies (both in absorption and in emission) provide insights on the electronic structure and, exploiting element selectivity and local environment, can complement or even replace scattering techniques for diluted systems and amorphous materials. Herein, we provide a theoretical foundation which spans from very basic concepts, through well-known techniques, with applications to nanomaterials research. An increasing level of material complexity is explored: size and shape analysis of nanoparticles dispersed in solution or single nanostructures localized onto surfaces; local morphology/strain analysis of nanostructured surfaces; average defects analysis of stacking faulted nanocrystals; regular 2D and 3D lattices of self-assembled nanocrystals; clusters of nanocrystals without any nanoscale lattice order, standing alone as isolated objects or embedded in tenths-of-µm-thick polymers (here coherent and focused X-rays are mandatory to explore the spatial inhomogeneity and lattice (in)coherence of the materials).

The anatase to rutile phase transformation via thermal and chemical (HF etching) routes of TiO2 P25 has been investigated. The treatment parameters and properties of the resulting anatase and rutile nanoparticles are analyzed and discussed. Since the nature of TiO2 surfaces plays a significant role in determining the physical and chemical properties of the TiO2 nanoparticles, it is important to investigate the surface properties, including the morphology, the main exposed faces, the defectiveness, to be correlated with their peculiar properties, and then reactivity. Herein, we report an infrared spectroscopy investigation, employing the adsorption of CO probe molecule at low temperature, including 12CO and 12CO-13CO isotopic mixtures, at the surface sites of TiO2 P25, previously heated from room temperature to 1,023 K under vacuum conditions. The same FTIR experiments were adopted on HF-etched TiO2. X-ray diffraction and transmission electron microscopy analyses were adopted to elucidate the role played by the thermal and the HF-etching treatments in modifying not only the distribution of exposed surfaces, but even the phase composition of the pristine TiO2 P25 samples, which are initially dominated by the most thermodynamically stable (101) facets of the anatase phase. The present study helps in the crystal and exposed facet engineering for the development of highly efficient photocatalysts.

The effect of the reactivity and kinetics of photogenerated e––h+ pairs induced by postsynthesis treatments on shape-controlled TiO2 anatase nanosheets with dominant {001} facets is reported. Anata...

Herein we report on two photoinduced reactions occurring at the surface of the CrVI/SiO2 Phillips catalyst. The first is the photoreduction of CrVI/SiO2 in CO at room temperature, that leads to the reduction of a fraction of the CrVI sites to CrIV(═O) intermediates and then to CrII. With respect to the thermal reduction of CrVI/SiO2 in CO, the relative amount of highly uncoordinated CrII sites is larger, suggesting that the relaxation of the CrII sites at the silica surface strongly depends on the temperature at which they are formed. The second is the photoinduced ethylene polymerization on CrVI/SiO2 at room temperature that is reported here for the first time. We demonstrate that UV–vis light has the potential to trigger the reduction of chromates by ethylene and the successive ethylene polymerization. Diffuse reflectance (DR) UV–vis and FT-IR spectroscopies allowed us to identify the nature of the Cr sites involved in the polymerization (i.e., 6-fold coordinated CrII) and of the oxidized byproducts rem...

X-ray nanofabrication has so far been usually limited to mask methods involving photoresist impression and subsequent etching. Herein we show that an innovative maskless X-ray nanopatterning approach allows writing electrical devices with nanometer feature size. In particular we fabricated a Josephson device on a Bi2Sr2CaCu2O8+δ (Bi-2212) superconducting oxide micro-crystal by drawing two single lines of only 50 nm in width using a 17.4 keV synchrotron nano-beam. A precise control of the fabrication process was achieved by monitoring in situ the variations of the device electrical resistance during X-ray irradiation, thus finely tuning the irradiation time to drive the material into a non-superconducting state only in the irradiated regions, without significantly perturbing the crystal structure. Time-dependent finite element model simulations show that a possible microscopic origin of this effect can be related to the instantaneous temperature increase induced by the intense synchrotron picosecond X-ray pulses. These results prove that a conceptually new patterning method for oxide electrical devices, based on the local change of electrical properties, is actually possible with potential advantages in terms of heat dissipation, chemical contamination, miniaturization and high aspect ratio of the devices.

Carboxylic acids adsorption on anatase TiO2 is a key process in circular economy and sustainability. Yet, in spite of several decades of investigations, its intimate working mechanisms still remain elusive. In particular, the behavior of the acid proton and its localization – either on the molecule or on the surface – are still open issues. By modeling the adsorption of formic acid on top of regular (101) anatase TiO2 surfaces, we found that, in the 0 K limit, the acid proton is shared between a carboxylic oxygen and a surface oxygen. In this regime, the proton behavior is mainly governed by quantum delocalization effects in a single potential well. Nonetheless, as temperature is raised to room conditions, simulations evidenced a rapid “classical” shuttling of the proton due to the onset of a two-wells free energy profile separated by a free energy barrier of the order of kT. This picture, supported by the agreement between simulated and experimental IR spectra, shows that the titania surface acts like a protecting group for the carboxylic acid functionality. Such a conceptual insight might help rationalize the chemical processes of carboxylic species on TiO2 surfaces.

International audience; We investigated the electrical modifications induced by hard X-ray synchrotron radiation on the YBa2Cu3O7-delta high temperature superconductor. We explored two different irradiation regimes. At low X-ray doses a progressive shift of the critical temperature of the superconductor has been obtained. Conversely, increasing the X-ray dose, a transition to a non-superconducting high resistance state is observed. These results pave the way to the realization of electrical devices by X-ray nanopatterning on this kind of oxide, extending the previous studies on Bi2Sr2CaCu2O8+delta

TiO2-based (nano)materials are widely exploited in systems and devices of actual technological interest, because of their outstanding physical and chemical properties, including chemical stability, long durability, non-toxicity abundance and low cost. For this, they are considered ideal for many practical applications including energy-related devices, photocatalysis, but are known to have some limitations. To improve their performance and then to find more efficient materials in the energy and environmental remediation fields, at first the investigation of the surface/interface properties at the molecular scale is required. In this contribution, a critical review of advances in the field of the TiO2 surface chemistry, highlighting the role of interactions at the molecular level, grafting and assembling/fabrication of suitable heterostructures, is reported. A few case studies, from the H2O, CO2 and acetylene interactions until to the grafting of organic/inorganic systems (graphene, MoS2) at the TiO2 surface, are highlighted. The discussed case studies are argued from their principles to the technological relevance.