Physical and chemical parameters determining the formation of gold-sp metal (Al, Ga, In, and Pb) nanoalloys.

Alloying is a key step towards the fabrication of advanced and unique nanomaterials demanded by the next generation of nanotechnology solutions. In particular, the alloys of Au with the sp-metals are expected to have several appealing plasmonic and electronic properties for a wide range of applications in optics, catalysis, nanomedicine, sensing and quantum devices. However, little is known about the thermodynamic and synthetic factors leading to the successful alloying of Au and sp-metals at the nanoscale. In this work, Au-M nanoalloys, with M = Al, Ga, In, or Pb, have been synthesized by a green and single step laser ablation in liquid (LAL) approach in two environments (pure ethanol and anhydrous acetone). To delve deeper into the key parameters leading to successful alloying under the typical operating conditions of LAL, a multiparametric analysis was performed considering the mixing enthalpy from DFT calculations and other alloying descriptors such as the Hume-Rothery parameters. The results showed that the dominant factors for alloying change dramatically with the oxidative ability of the synthesis environment. In this way, the tendency of the four sp metals to alloy with gold was accurately predicted (R2 > 0.99) using only two and three parameters in anhydrous and non-anhydrous environments, respectively. These results are important to produce nanoalloys using LAL and other physical methods because they contribute to the understanding of factors leading to element mixing at the nanoscale under real synthetic conditions, which is crucial for guiding the realization of next-generation multifunctional metallic nanostructures.

Metal-Free N-Doped Carbons for Solvent-Less CO2 Fixation Reactions: A Shrimp Shell Valorization Opportunity.

High anthropogenic CO2 emissions are among the main causes of climate change. Herein, we investigate the use of CO2 for the synthesis of organic cyclic carbonates on metal-free nitrogen-doped carbon catalysts obtained from chitosan, chitin, and shrimp shell wastes, both in batch and in continuous flow (CF). The catalysts were characterized by N2 physisorption, CO2-temperature-programmed desorption, X-ray photoelectron spectroscopy, scanning electron microscopy, and CNHS elemental analysis, and all reactivity tests were run in the absence of solvents. Under batch conditions, the catalyst obtained by calcination of chitin exhibited excellent performance in the conversion of epichlorohydrin (selected as a model epoxide), resulting in the corresponding cyclic carbonate with 96% selectivity at complete conversion, at 150 °C and 30 bar CO2, for 4 h. On the other hand, in a CF regime, a quantitative conversion and a carbonate selectivity >99% were achieved at 150 °C, by using the catalyst obtained from shrimp waste. Remarkably, the material displayed an outstanding stability over a reaction run time of 180 min. The robustness of the synthetized catalysts was confirmed by their good operational stability and reusability: ca. (75 ± 3)% of the initial conversion was achieved/retained by all systems, after six recycles. Also, additional batch experiments proved that the catalysts were successful on different terminal and internal epoxides.

Modification of Amorphous Mesoporous Zirconia Nanoparticles with Bisphosphonic Acids: A Straightforward Approach for Tailoring the Surface Properties of the Nanoparticles.

The use of readily prepared bisphosphonic acids obtained in few steps through a thio-Michael addition of commercially available thiols on tetraethyl vinylidenebisphosphonate enables the straightforward surface modification of amorphous mesoporous zirconia nanoparticles. Simple stirring of the zirconia nanoparticles in a buffered aqueous solution of the proper bisphosphonic acid leads to the surface functionalization of the nanoparticles with different kinds of functional groups, charge and hydrophobic properties. Formation of both chemisorbed and physisorbed layers of the bisphosphonic acid take place, observing after extensive washing a grafting density of 1.1 molecules/nm2 with negligible release in neutral or acidic pH conditions, demonstrating stronger loading compared to monophosphonate derivatives. The modified nanoparticles were characterized by IR, XPS, ζ-potential analysis to investigate the loading of the bisphosphonic acid, FE-SEM to investigate the size and morphologies of the nanoparticles and 31 P and 1 H MAS NMR to investigate the coordination motif of the phosphonate units on the surface. All these analytical techniques demonstrated the strong affinity of the bisphosphonic moiety for the Zr(IV) metal centers. The functionalization with bisphosphonic acids represents a straightforward covalent approach for tailoring the superficial properties of zirconia nanoparticles, much straightforward compared the classic use of trisalkoxysilane or trichlorosilane reagents typically employed for the functionalization of silica and metal oxide nanoparticles. Extension of the use of bisphosphonates to other metal oxide nanoparticles is advisable.

Influence of halide ions on the structure and properties of copper indium sulphide quantum dots.

In the synthesis of CuInS2 quantum dots (QDs), the halide ions present in the copper salts influence the QD growth and optical properties. X-ray absorption spectroscopy allowed rationalizing the halide incorporation in the lattice and the dependence of electronic properties of the material on the ion's polarizability and interaction with hydrophobic moieties.

Bismuth titanate-based UV filters embedded mesoporous silica nanoparticles: Role of bismuth concentration in the self-sealing process.

The development of new safe inorganic UV filters to effectively protect the skin from ultraviolet (UV) radiation effects is an emerging issue. Bismuth titanate-based UV filters embedded into mesoporous silica nanoparticles (MSN) represent a new class of inorganic sunscreens, with excellent UVA and UVB shielding properties. In addition, the presence of bismuth ions promotes a self-sealing process, allowing (i) the entrapment of the active phases in the deepest core of the system and (ii) the formation of an external glassy silica layer with a consequent suppression of the photocatalytic activity. In this work, aimed at studying in detail the self-sealing mechanism and accessing the role of bismuth ions in the formation of the system, a series of samples impregnated with a different amount of bismuth were investigated. The self-sealing process already occurs at the lowest content of bismuth and the mechanism is demonstrated to be triggered by the ability of Bi to work as a low-melting point agent for silica. Finally, a sunscreen formulation containing the new UV filter was prepared and the Sun Protection Factor (SPF), the pH and the viscosity were measured, demonstrating the potential of the proposed material for large-scale applications.

Engineering efficient upconverting nanothermometers using Eu3+ ions.

Upconversion nanothermometry combines the possibility of optically sensing temperatures in very small areas, such as microfluidic channels or on microelectronic chips, with a simple detection setup in the visible spectral range and reduced heat transfer after near-infrared (NIR) excitation. We propose a ratiometric strategy based on Eu3+ ion luminescence activated through upconversion processes. Yb3+ ions act as a sensitizer in the NIR region (980 nm), and energy is transferred to Tm3+ ions that in turn excite Eu3+ ions whose luminescence is shown to be thermally sensitive. Tridoped SrF2:Yb3+,Tm3+,Eu3+ nanoparticles (average size of 17 nm) show a relative thermal sensitivity of 1.1% K-1 at 25.0 °C, in the range of the best ones reported to date for Ln3+-based nanothermometers based on upconversion emission. The present nanoparticle design allows us to exploit upconversion of lanthanide ions that otherwise cannot be directly excited upon NIR excitation and that may provide operational wavelengths with a highly stable read out to fill the spectral gaps currently existing in upconversion-based nanothermometry.

Bi2SiO5@g-SiO2 upconverting nanoparticles: a bismuth-driven core-shell self-assembly mechanism.

Core-shell systems have attracted increasing interest among the research community in recent years due to their unique properties and structural features, and the development of new synthetic strategies is still a challenge. In this work, we have investigated lanthanide-doped Bi2SiO5 nanocrystal formation inside mesoporous silica nanoparticles (MSNs). The role of both synthesis temperature and concentration of the bismuth precursor impregnated into the MSNs is discussed, showing an unprecedented strategy for the simultaneous stabilization of a crystalline core and a glassy shell. Temperature dependent synchrotron radiation X-ray powder diffraction (SR-XRPD) and high resolution transmission electron microscopy (HR-TEM) analyses allow one to follow the crystalline core growth. A mechanism for the formation of a Bi2SiO5@g-SiO2 core-shell nanosystem is proposed. In addition, the easy tunability of the color output of the upconverting system is demonstrated by means of suitable doping lanthanide ions with potential applications in several fields.

Highly Efficient Copper Sulfide-Based Near-Infrared Photothermal Agents: Exploring the Limits of Macroscopic Heat Conversion.

Among the foreseeable therapeutic approaches at the cellular level, nanoplatform-driven photothermal therapy is a thriving tool for the selective eradication of malignant tissues with minimal side effects to healthy ones. Hence, chemically versatile, near-infrared absorbing plasmonic nanoparticles are distinctly appealing and most sought after as efficient photothermal agents. In this work, a straightforward method to synthesize monodisperse PEGylated copper sulfide nanoparticles of pure covellite (CuS) phase, featuring strong localized surface plasmonic resonance absorption in the near-infrared and flexible surface chemistry, imparted by monomethyl ether polyethylene glycol molecules, is developed and optimized. These nanoparticles show a remarkable photothermal heat conversion efficiency (HCE) of 71.4%, which is among the highest for CuS systems and rivals that of plasmonic noble metal nanostructures. Moreover, through critical evaluation and mathematical modeling of the material's properties and measurement methodology, it is assessed that the calculated HCE values drastically depend on experimental conditions such as wavelength-dependent solvent absorption properties, sol concentration, and optical path. These findings are of paramount relevance to the photothermal community, since they call for a standardization of the procedure for the evaluation of the HCE of proposed photothermal agents, in order to make the reported values universally and reliably comparable.

Selective Hydrogenations and Dechlorinations in Water Mediated by Anionic Surfactant-Stabilized Pd Nanoparticles.

We report a facile, inexpensive, and green method for the preparation of Pd nanoparticles in aqueous medium stabilized by anionic sulfonated surfactants sodium 1-dodecanesulfonate 1a, sodium dodecylbenzenesulfonate 1b, dioctyl sulfosuccinate sodium salt 1c, and poly(ethylene glycol) 4-nonylphenyl-3-sulfopropyl ether potassium salt 1d simply obtained by stirring aqueous solutions of Pd(OAc)2 with the commercial anionic surfactants further treated under hydrogen atmosphere for variable amounts of time. The aqueous Pd nanoparticle solutions were tested in the selective hydrogenation reactions of aryl-alcohols, -aldehydes, and -ketones, leading to complete conversion to the deoxygenated products even in the absence of strong Brønsted acids in the reduction of aromatic aldehydes and ketones, in the controlled semihydrogenation of alkynes leading to alkenes, and in the efficient hydrodechlorination of aromatic substrates. In all cases, the micellar media were crucial for stabilizing the metal nanoparticles, dissolving substrates, steering product selectivity, and enabling recycling. What is interesting is also that a benchmark catalyst like Pd/C can often be surpassed in activity and/or selectivity in the reactions tested by simply switching to the appropriate commercially available surfactant, thereby providing an easy to use, flexible, and practical catalytic system capable of efficiently addressing a variety of synthetically significant hydrogenation reactions.

Fluorinated and Charged Hydrogenated Alkanethiolates Grafted on Gold: Expanding the Diversity of Mixed-Monolayer Nanoparticles for Biological Applications.

Low intrinsic toxicity, high solubility, and stability are important and necessary features of gold nanoparticles to be used in the biomedical field. In this context, charged nanoparticles proved to be very versatile, and among them charged mixed-monolayer gold nanoparticles, displaying monolayers with well-defined morphologies, represent a paradigm. By using mixtures of hydrogenated and fluorinated thiols, the formation of monolayer domains may be brought to an extreme because of the immiscibility of fluorinated and hydrogenated chains. Following this rationale, mixed monolayer gold nanoparticles featuring ammonium, sulfonate, or carboxylic groups on their surface were prepared by using amphiphilic hydrogenated thiols and 1H,1H,2H,2H-perfluoro-alkanethiols. The toxicity of these systems was assessed in HeLa cells and was found to be, in general, low even for the cationic nanoparticles which usually show a high cytotoxicity and is comparable to that of homoligand gold nanoparticles displaying amphiphilic-charge neutral-hydrogenated or fluorinated thiolates in their monolayer. These properties make the mixed ligand monolayer gold nanoparticles an interesting new candidate for medical application.

Formation and Controlled Growth of Bismuth Titanate Phases into Mesoporous Silica Nanoparticles: An Efficient Self-Sealing Nanosystem for UV Filtering in Cosmetic Formulation.

The application of nanosized inorganic UV filters in cosmetic field is limited by their high photocatalytic properties that could induce the degradation or dangerous transformation of the organic molecules in sunscreen formulations. To overcome this problem and simultaneously enlarge the window of filter's absorption, we propose the growth of bismuth titanates BixTiyOz into mesoporous silica nanoparticles (MSN). We investigated the chemical-physical properties by means of XRPD, TEM, UV-vis spectroscopy, N2 physisorption, XPS, and SF-ICP-MS analysis, while the influence on the environment was evaluated through photocatalytic tests. The growing process of this new nanosystem is discussed underlining the key role of the Bi3+ ion that, acting as a low-melting point agent for the silica framework, led to a self-sealing mechanism. The excellent UV shielding properties combined with a radical suppression of the photocatalytic activity make the proposed nanosystem a perfect candidate for the development of the next generation nanomaterials for sunscreen formulations.

Calcium hydroxide nanoparticles from solvothermal reaction for the deacidification of degraded waterlogged wood.

HYPOTHESIS: A combination of acid and iron ions inside the wood has been corroding the cellulose matrix of the Swedish warship Vasa, imposing its deacidification. Past deacidification treatments displayed poor penetration inside the wood matrix with limited efficacy. A vacuum assisted treatment of wood using newly developed calcium hydroxide nanoparticle dispersions represents a possible candidate for the treatment of acidic waterlogged wood objects such as sculptures and decorative artifacts. EXPERIMENTS: A solvothermal process was used for the synthesis of calcium hydroxide nanoparticle dispersions. Before the application on waterlogged wood, the physico-chemical characterization of these systems was carried out using several techniques. The efficacy of the deacidification treatment of wood samples from the Vasa was assessed by determination of pH and Differential Thermal Gravimetric (DTG) measurements. FINDINGS: The proposed solvothermal reactions can be used to produce stable and highly concentrated calcium hydroxide nanoparticle dispersions in alcohols, needing no further purification before the application. This process has also the advantage to be upscalable to industrial level. Both pH and DTG measurements showed that the newly developed dispersions can homogenously penetrate inside the wood up to 20cm, neutralizing acidity and creating an alkaline buffer inside the wooden matrix, to hinder the degradation of residual cellulose.

Polymorphism and magnetic properties of Li2MSiO4 (M = Fe, Mn) cathode materials.

Transition metal-based lithium orthosilicates (Li2MSiO4, M = Fe, Ni, Co, Mn) are gaining a wide interest as cathode materials for lithium-ion batteries. These materials present a very complex polymorphism that could affect their physical properties. In this work, we synthesized the Li2FeSiO4 and Li2MnSiO4 compounds by a sol-gel method at different temperatures. The samples were investigated by XRPD, TEM, (7)Li MAS NMR, and magnetization measurements, in order to characterize the relationships between crystal structure and magnetic properties. High-quality (7)Li MAS NMR spectra were used to determine the silicate structure, which can otherwise be hard to study due to possible mixtures of different polymorphs. The magnetization study revealed that the Néel temperature does not depend on the polymorph structure for both iron and manganese lithium orthosilicates.

Synthesis of nanocomposites from Pd(0) and a hyper-cross-linked functional resin obtained from a conventional gel-type precursor.

Hyper-cross-linked resins stemming from a gel-type poly-chloromethylated poly(styrene-co-divinylbenzene) resin (GT) have been investigated by a multi-methodological approach based on elemental analysis, scanning electron microscopy, X-ray microanalysis, and solvent absorption. The hyper-cross-linking of the parent resin was accomplished by Friedel-Crafts alkylation of the phenyl rings of the resins with the chloromethyl groups. This produced a permanent pore system comprising both micropores (<2.0 nm in diameter) and mesopores (2.2 nm). The chloromethyl groups that did not react in the hyper-cross-linking step were transformed into methylmercaptan groups and the latter were then converted into sulfonic groups by oxidation with hydrogen peroxide. By this procedure the extensive permanent porosity of the parent unsulfonated hyper-cross-linked polymer (HGT) was retained by the sulfonated polymer (HGTS). The final exchange capacity of HGTS was determined to be 0.36 mmol g(-1). HGTS was easily metalated with Pd(II) and the subsequent reduction of the metal centers with either aqueous sodium borohydride, formaldehyde, or dihydrogen produced three Pd(0)/HGTS nanocomposites. The metal nanoparticles had diameters in the 1-6 nm range for all the nanocomposites, as determined by TEM, but with somewhat different distributions. When formaldehyde was used, more than 90% of the nanoparticles were less than 3 nm and their radial distribution throughout the polymer beads was quite homogeneous. These findings show that with this reducing agent the metal nanoparticles are generated within the pore system of the polymer matrix, hence their size is controlled by the dimensions of the pores of the polymeric support.

Highly hydrophilic copolymers of N,N-dimethylacrylamide, acrylamido-2-methylpropanesulfonic acid, and ethylenedimethacrylate: nanoscale morphology in the swollen state and use as exotemplates for synthesis of nanostructured ferric oxide.

The polymer framework of water-swollen copolymers of N,N-dimethylacrylamide, acrylamido-2-methylpropanesulfonic acid, and ethylenedimethacrylate (nominal cross-linking degrees of 4, 8, and 20 mol %) is composed of highly expanded domains, with "pores" not less than 6 nm in diameter. When the 4% cross-linked copolymer (DAE 26-4) is swollen with a 10(-4) M solution of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL) in water, MeOH, EtOH, or nBuOH, the molecules of the paramagnetic probe rotate rapidly (τ<1000 ps) and as fast as in the bulk liquid in the case of water. The swelling degree of DAE 26-4 is related to the Hansen solubility parameters of a number of liquids, including linear alcohols up to n-octanol. It is also found that the rotational correlation time of TEMPOL in the copolymer swollen by water and the lightest alcohols increases with decreasing specific absorbed volume. Time-domain NMR spectrometry of water-swollen DAE 26-4 shows that sorption of only 14% of the liquid required for its complete swelling is enough for full hydration of the polymer chains. Accordingly, in fully swollen DAE 26-4 the longitudinal relaxation time of water closely approaches the value of pure water. {(13)C} CP-MAS NMR on partially and fully water swollen samples of DAE 26-4 shows that swelling increases the mobility of the polymer chains, as clearly indicated by the narrowing of the best-resolved peaks. DAE 26-4 was used as an exotemplate for the synthesis of nanocomposites composed of the polymer and nanostructured Fe(2)O(3) through a series of ion-exchange/precipitation cycles. After the first cycle the nanoparticles are 3-4 nm in diameter, with practically unchanged size after subsequent cycles (up to five). In fact, the nanoparticle size never exceeded the diameter of the largest available pores. This suggests that the polymer framework controls the growth of the nanoparticles according to the template-controlled synthesis scheme. Selected-area electron diffraction, TEM, and high-resolution electron microscopy show that the nanostructured inorganic phase is composed of hematite.

Gold nanoparticles incarcerated in nanoporous syndiotactic polystyrene matrices as new and efficient catalysts for alcohol oxidations.

The controlled synthesis of gold nanoparticles (AuNPs), incarcerated in a semicrystalline nanoporous polymer matrix that consisted of a syndiotactic polystyrene-co-cis-1,4-polybutadiene multi-block copolymer is described. This catalyst was successfully tested in the oxidation of primary and secondary alcohols, in which we used dioxygen as the oxidant under mild conditions. Accordingly, (±)-1-phenylethanol was oxidised to acetophenone in high yields (96%) in 1 h, at 35 °C, whereas benzyl alcohol was quantitatively oxidised to benzaldehyde with a selectivity of 96% in 6 h. The specific rate constants calculated from the corresponding kinetic plots were among the highest found for polymer-incarcerated AuNPs. Similar values in terms of reactivity and selectivity were found in the oxidation of primary alcohols, such as cinnamyl alcohol and 2-thiophenemethanol, and secondary alcohols, such as indanol and α-tetralol. The remarkable catalytic properties of this system were attributed to the formation, under these reaction conditions, of the nanoporous ε crystalline form of syndiotactic polystyrene, which ensures facile and selective accessibility for the substrates to the gold catalyst incarcerated in the polymer matrix. Moreover, the polymeric crystalline domains produced reversible physical cross-links that resulted in reduced gold leaching and also allowed the recovery and reuse of the catalyst. A comparison of catalytic performance between AuNPs and annealed AuNPs suggested that multiple twinned defective nanoparticles of about 9 nm in diameter constituted the active catalyst in these oxidation reactions.

Increasing the antibacterial effect of lysozyme by immobilization on multi-walled carbon nanotubes.

We report a facile strategy to obtain multiwalled carbon nanotubes (MWCNTs) functionalized with covalently bonded lysozyme. The functionalization procedure has been investigated by means of several techniques, including thermogravimetry, Raman spectroscopy, transmission electron microscopy, and cyclic voltammetry. A functionalization of about 1 lysozyme molecule every 4000 carbon atoms is obtained. The modified lysozyme-CNTs nanocomposite shows a significant increase of the antibacterial activity towards the Gram-positive S. aureus if compared with lysozyme in solution.

A tri-block copolymer templated synthesis of gold nanostructures.

Stable ultra-small gold nanoparticles have been synthesized in aqueous phase by using a tri-block copolymer (BMB) as a templating agent consisting of two PEG-methylacrylate chains (B blocks) anchored to a poly(methacrylic) moiety containing a trithiocarbonate unit (M block). The effect of the BMB/Au molar ratios on the final particle size, shape and monodispersity has been investigated. The synthesized nanosols have been characterized by means of Visible Absorption, Small Angle X-ray Scattering (SAXS), and Transmission Electron Microscopy (TEM). Results clearly indicate that the polymer plays a key role in determining the size and shape of gold particles, from fractal-like structures to monodisperse spherical particles with a mean diameter of about 3 nm. The aggregation behavior of these nanostructures has been characterized both in solution (SAXS) as well as on mica substrate (AFM) and has been proven to be driven by the polymer to gold concentration ratio.

Gold stabilized aqueous sols immobilized on mesoporous CeO2-Al2O3 as catalysts for the preferential oxidation of carbon monoxide.

Nanostructured Au/Al(2)O(3)-CeO(2) catalysts with a low content of precious metal (0.9% wt.) were prepared immobilizing two different stabilized Au sols on a high surface area Al(2)O(3)-CeO(2) mixed oxide with a uniform pore size distribution, synthesized by a one-pot methodology. The samples were characterized by elemental analysis, N(2) physisorption, XRPD, TEM and (27)Al-MAS NMR techniques. The catalytic activity of the two samples in the preferential oxidation of CO in excess of H(2) (CO-PROX) was comparatively evaluated in the 35-110 degrees C temperature range. The Au-THPS/AlCe20 sample, prepared immobilizing a sol obtained reducing an aqueous solution of gold tetrachloroaurate salt with bis[tetrakis(hydroxymethyl)phosphonium sulfate], resulted very active and selective at low temperatures and its catalytic activity was correlated with the structural characteristics of the metal particles and of the ordered mesoporous support.