A colloidal nonaqueous approach to semiconductor-magnetic hybrid nanocrystals (HNCs) withselectable heterodimer topologies and tunable geometric parameters is demonstrated. Brookite TiO2nanorods, distinguished by a curved shape-tapered profile with richly faceted terminations, are exploitedas substrate seeds onto which a single spherical domain of inverse spinel iron oxide can be epitaxiallygrown at either one apex or any location along their longitudinal sidewalls in a hot surfactant environment.The topologically controlled arrangement of the component material lattices, the crystallographic relationshipsholding between them, and strain distribution across individual heterostructures have been studied bycombining X-ray diffraction and absorption techniques with high-resolution transmission electron microscopyinvestigations. Supported by such structural knowledge, the synthetic achievements are interpreted withinthe frame of various mechanistic models offering complementary views of HNC formation. The differentHNC architectures are concluded to be almost equivalent in terms of surface-interface energy balanceassociated with their formation. HNC topology selection is rationalized on the basis of a diffusion-limitedmechanism allowing iron oxide heterogeneous nucleation and growth on the TiO2 nanorods to switch froma thermodynamically controlled to a kinetically overdriven deposition regime, in which the anisotropicreactivity offered by the uniquely structured seeds is accentuated under high spatially inhomogeneousmonomer fluxes. Finally, the multifunctional capabilities of the heterostructures are highlighted throughillustration of their magnetic and photocatalytic properties, which have been found to diverge from thoseotherwise exhibited by their individual material components and physical mixture counterparts.

We performed reproducible atomic resolution Transmission Electron Microscopy and Wide Angle X-ray Scanning Microscopy experiments studying for the first time the nanoscale properties of a pristine fiber taken from the Turin Shroud. We found evidence of biologic nanoparticles of creatinine bounded with small nanoparticles of iron oxide. The kind, size and distribution of the iron oxide nanoparticles cannot be dye for painting but are ferrihydrate cores of ferritin. The consistent bound of ferritin iron to creatinine occurs in human organism in case of a severe polytrauma. Our results point out that at the nanoscale a scenario of violence is recorded in the funeral fabric and suggest an explanation for some contradictory results so far published.

We report on the high resolution transmission electron microscopy (HRTEM) and high angle annular dark field scanning transmissionelectron microscopy (HAADF-STEM) study of TiO2 anatase thin films grown by pulsed laser deposition on LaAlO3 substrates.The analysis provides evidence of a peculiar growth mode of anatase on LaAlO3 that is characterized by the formation ofan epitaxial layer at the film/substrate interface. In particular, the film is split into two adjacent slabs of about 20 nm each, bothdisplaying the same Bravais lattice compatible with the anatase tetragonal cell. The formation of two different families of crystallographicshear (CS) superstructures is observed within the film, namely (103)- and (101)-oriented CS plane structures, occurringin the outer film region and in proximity of the film/substrate interface, respectively. HAADF analysis and Energy DispersiveSpectroscopy highlight the occurrence of Al interdiffusion from the substrate into the film region. By combining HRTEM results,image simulation techniques and DFT calculations we determine the atomic structure of the CS planes, and show that they arecubic-TiO-based structures analogous to the TinO2n-1 Magnéli phases derived from rutile.

The aims of our experiment were to evaluate the uptake and translocation of cerium and titanium oxide nanoparticles and to verify their effects on the growth cycle of barley (Hordeum vulgare L.). Barley plants were grown to physiological maturity in soil enriched with either 0, 500 or 1000 mg center dot kg(-1) cerium oxide nanoparticles (nCeO(2)) or titanium oxide nanoparticles (nTiO(2)) and their combination. The growth cycle of nCeO(2) and nTiO(2) treated plants was about 10 days longer than the controls. In nCeO(2) treated plants the number of tillers, leaf area and the number of spikes per plant were reduced respectively by 35.5%, 28.3% and 30% (p <= 0.05). nTiO(2) stimulated plant growth and compensated for the adverse effects of nCeO(2). Concentrations of Ce and Ti in aboveground plant fractions were minute. The fate of nanomaterials within the plant tissues was different. Crystalline nTiO(2) aggregates were detected within the leaf tissues of barley, whereas nCeO(2) was not present in the form of nanoclusters.

new approach based on hot injection method is proposed to gram-scale Cu2ZnSnS4 nanoparticles production minimizing the use of organic solvents. Nanocrystal synthesis was performed starting from metal chlorides and pure sulphur powder and using Oleylamine as capping agent. As a result, core-shell nanoparticles with a narrow size distribution were obtained. (C) 2015 AIP Publishing LLC.

Here we describe a new TEM-based coherent diffraction imaging (CDI) method to achieve sub-ångström resolution in lattice images of nanoparticles. The experiments were performed by using a TEM/STEM JEOL 2010F UHR (objective lens spherical aberration coefficient of (0.47±0.01) mm) with resolution at optimum defocus of 0.19nm and equipped by Schottky cathode. The experiments for CDI require the acquisition of HRTEM image and diffraction from the same region of the sample illuminated by a coherent electron probe. The experimental nano-diffraction must be recorded with the beam coherence length larger than the region to be imaged according to the oversampling requirements [1]. A new efficient iterative phase retrieval algorithm [2] based on pioneering work of Gerchberg and Saxton [3] has been developed and successfully applied. Figure 1 is an example of phase retrieval of a TiO2 particle at a resolution of 70 pm that allows to distinguish the O atoms appreciating subtle alterations in the unit cell structure of the nano-crystals, which would not be otherwise detectable by conventional HRTEM. Such structural deviations could be at the origin of peculiar size-dependent physical-chemical properties of the concerned oxide material in the nanoscale regime [2].

The paper focuses on the development of electron coherent diffraction imaging intransmission electron microscopy, made in the, approximately, last ten years in our collaborativeresearch group, to study the properties of materials at atomic resolution, overcoming the limitationsdue to the aberrations of the electron lenses and obtaining atomic resolution images, in whichthe distribution of the maxima is directly related to the specimen atomic potentials projected ontothe microscope image detector. Here, it is shown how augmented coherent diffraction imagingmakes it possible to achieve quantitative atomic resolution maps of the specimen atomic species,even in the presence of low atomic number atoms within a crystal matrix containing heavy atoms.This aim is achieved by: (i) tailoring the experimental set-up, (ii) improving the experimental data byproperly treating parasitic diffused intensities to maximize the measure of the significant information,(iii) developing efficient methods to merge the information acquired in both direct and reciprocalspaces, (iv) treating the dynamical diffused intensities to accurately measure the specimen projectedpotentials, (v) improving the phase retrieval algorithms to better explore the space of solutions.Finally, some of the future perspectives of coherent diffraction imaging in a transmission electronmicroscope are given.

In this study we evaluated an efficient microwave-solvothermal method to synthesize effective visible-light photocatalists based on the use of anatase TiO2 nanorods. The nanocrystals were obtained by hydrolysis of titanium tetraisopropoxide (TTIP) in the presence of benzyl alcohol at 210 C. The method was effective and produced TiO2 nanocrystals in the anatase phase with a rapid kinetics of crystallization. A significant size control was obtained tuning the TTIP to oleic acid molar ratio. High volumetric yield and reduced energy costs were achieved. All synthesized TiO2 nanocrystals showed a high photoactivity in comparison with commercial P25 titania, as they could degrade faster and completely Rhodamine B dye in solution under visible-light irradiation. The nanocrystals were characterized in detail by X-ray diffraction, low- and high-resolution transmission electron microscopy, microRaman and FT-IR spectroscopy. A distorted anatase structure due to oxygen vacancies was identified as being at the origin of the introduction of new energy levels into the anatase band gap, which probably promoted the visible-light photoactivity.

By combining in situ X-ray photoemission spectroscopy, ex situ high resolution transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy, we show that chemical vapor deposition (CVD) on vertically aligned ZnO nanorods can synthesize different carbon nanostructures (CNs), whose morphology is driven by the ZnO nanorods and whose dimensions and structures change as a function of the processtemperature. The CNs range from amorphous carbon cups, completely covering the nanorods, to high density one-dimensional carbon nano-dendrites (CNDs), which start to appear like short hairs on the ZnO nanorods. The nanorods are partially etched when the process is done at 630-800 C, while they are completely etched at temperatures higher than 800 C. In the latter case, CNDs emerge from a porous carbon sponge formed at the substrate interface but they are preferentially aligned along the location of the pristine ZnO nanorods. When used as a chemiresisitor the CND-ZnO structures have a higher sensitivity to ammonia compared to chemiresistors made by bare ZnO nanorods, to other one-dimensional CNs, like carbon nanotubes or other metal/metal-oxides hybrid CNs.

Herein, we demonstrate an EDI methodology, performed in a Jeol 2010F UHR microscope (spherical aberration coefficient Cs = 0.47±0.01 mm), by which the crystal structure of transition-metal oxide nanocrystals can be determined at 70 pm of resolution while unambiguously revealing the presence and location of light elements atomic columns in the relevant lattice. This approach, applied as a case study to TiO2 in the form of organic-capped nano-rods, also allows appreciating subtle alterations in the unit cell structure of the nano-crystals, relative to that inherent to the bulk material counterpart, which would not be otherwise detectable by conventional HRTEM. Such structural deviations could be at the origin of peculiar size-dependent physical-chemical properties of the concerned oxide material in the nanoscale regime. In addition, it is worthwhile to remark that this result has been achieved exposing the specimen to an electron dose as low as 106 e/nm2. The latter condition usually prevents the specimen against possible structural damages under exposure to 200 keV electrons, the induction of which remains one of the key issues in the ultimate accuracy achievable in the structural determination of materials [4].

We present a novel method to determine the projected atomic potential of a specimen directly from transmission electron microscopy coherent electron nano-diffraction patterns, overcoming common limitations encountered so far due to the dynamical nature of electron-matter interaction. The projected potential is obtained by deconvolution of the inverse Fourier transform of experimental diffraction patterns rescaled in intensity by using theoretical values of the kinematical atomic scattering factors. This novelty enables the compensation of dynamical effects typical of transmission electron microscopy (TEM) experiments on standard specimens with thicknesses up to a few tens of nm. The projected atomic potentials so obtained are averaged on sample regions illuminated by nano-sized electron probes and are in good quantitative agreement with theoretical expectations. Contrary to lens-based microscopy, here the spatial resolution in the retrieved projected atomic potential profiles is related to the finer lattice spacing measured in the electron diffraction pattern. The method has been successfully applied to experimental nano-diffraction data of crystalline centrosymmetric and non-centrosymmetric specimens achieving a resolution of 65 pm.

In the present research a salt of vincamine, a poorly bioavailable indole alkaloid derived from the leaves of Vinca minor L., was synthesized in the solid state by means of a mechanochemical process employing citric acid as a reagent. The mechanochemical process was adopted as a solvent-free alternative to classical citrate synthetic route that involves the use of solvents. Since the mechanochemical salification is little studied to date and presents the disadvantage of offering a low yield, in this work, the influence of three process andformulation variables on the percentage of vincamine citrate was studied. In particular, the time of mechanical treatment (in planetary mill Fritsch P5) and the amount of citric acid were varied in order to evaluate their effect on the yield of the process, and the introduction of a solid solvent, a common pharmaceutical excipient (sodium carboxymethylcellulose, NaCMC), was considered. Due to the complexity of the resulting samples' matrix, an appropriate experimental design was employed to project the experimental trials and the influence of the three variables on the experimental response was estimated with the help of a statistical analysis. The experimental response, that is, the yield of the process corresponding to the percentage of vincamine in the protonated form, was unconventionally calculated by means of X-ray photoelectron spectroscopy analysis (XPS). Out of 16 samples, the one with the highest yield was the coground sample containing vincamine and citric acid in a 1:2 molar ratio, treated for 60 min in the presence of NaCMC. Under the above conditions the salification reaction was completed highlighting the importance of a proper selection of process and formulation variables of the mechanochemical salification, and emphasizing the crucial role of the solid solvent in facilitating the salification. The second step of the research encompassed the characterization of the citrate salt obtained by solid excipient assisted mechanochemical salification (SEAMS) in comparison with the vincamine citrate obtained by classical synthetic route. The samples were characterized by, besides XPS, high resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRPD), in vitro solubilization kinetics and in vivo oral pilot study in rats. Finally, in order to monitor over time possible disproportionation phenomena, stability studies have been performed by repeating XPS analysis after 8 months. As expected, the the SEAMS-vincamine salt consisted of particles both crystalline and amorphous. The solubilization kinetics was superior to the corresponding salt probably thanks to the favorable presence of the hydrophilic excipient although the two salts were bioequivalent in rats after oral administration. Furthermore, no evidence of disporportionation phenomena in the SEAMSvincamine salt was found after storage. In conclusion, in the case of forming salts of poorly soluble drugs, the SEAMS processmay

We present a method to treat spurious intensities in electron diffraction experiments. Coherent electron diffraction imaging requires proper data reduction before the application of phase retrieval algorithms. The presence of spurious intensities in the electron diffraction patterns makes the data reduction complicated and time consuming and jeopardizes the application of mathematical constraints to maximize the information that can be extracted from the experimental data. Here we show how the experimental diffraction patterns can be treated to remove the unwanted artifacts without corrupting the genuine intensities scattered by the specimen. The resulting diffraction patterns are suitable for the application of further processes and constraints aimed at deriving fundamental structural information by applying phase retrieval algorithms or other approaches capable of deriving quantitative atomic resolution information about the specimen structure.

Since its early days electron microscopy has represented a splendid way to study the interactions between charged particles and electromagnetic fields. These efforts produced a flexible and powerful tool to investigate the properties of the matter at the highest spatial resolution. One of the main reason for the high resolution achievable in electron microscopy is related to the small wavelength, l, associated to high-energy electrons, i.e. for 200 keV electrons l = 2.5pm. Unfortunately, the quality of the electron lenses is relatively poor and the diffraction limit is still unreached. The proof of Otto Scherzer in 1936 that skilful lens design could never eliminate the spherical and chromatic aberration of rotationally symmetric lenses [1] promote the efforts of the scientific community to find a gateway. Since that time many attempts were made from one side to find a way to correct spherical and chromatic aberrations via hardware and from the othe r to find different approaches to recovery the information lost in TEM imaging. In the latter approaches it might be mentioned, for example, the invention of Gabor of the holography [2] or the through focal reconstruction of the exit phase wave in high resolution TEM (HRTEM) [3]. Very recently, electron optical devices capable of correcting spherical aberration are available and sub-ångström resolution have been achieved by HRTEM [4] and incoherent imaging in scanning transmission electron microscopy (STEM) by using high angle annular dark field detector [5]. Nevertheless, the diffraction limit in electron microscopy is still not reached. Coherent diffraction imaging (CDI) is an approach combining real and reciprocal space information to achieve images in principle limited only by diffraction limit [6].

High-resolution imaging of low-atomic-number chemical elements using electron microscopy is challenging and may require the use of high doses of electrons. Electron diffractive imaging, which creates real-space images using diffraction intensities and phase retrieval methods, could overcome such issues, although it is also subject to limitations. Here, we show that a combination of electron diffractive imaging and high-resolution transmission electron microscopy can image individual TiO(2) nanocrystals with a resolution of 70 pm while exposing the specimen to a low dose of electrons. Our approach, which does not require spherical and chromatic aberration correction, can reveal the location of light atoms (oxygen) in the crystal lattice. We find that the unit cell in nanoscale TiO(2) is subtly different to that in the corresponding bulk.

Combining reflection high-energy electron diffraction, high-resolution transmission electron microscopy, and high-angle annular dark field scanning transmission electron microscopy we unveil the existence of a peculiar transition from a three-dimensional to a two-dimensional growth mode in anatase TiO2/LaAlO3 heterostructures. Such a growth dynamics is accompanied by Al interdiffusion from substrate to the growing film up to a critical thickness of 20 nm. With the extra support of ab initio calculations, we show that the crossover between the two growth modes corresponds to the formation of two distinct regions characterized by (103)- and (101)-oriented crystallographic shear superstructures, occurring in the upmost film region and in proximity of the film/substrate interface, respectively. © 2013 Springer Science+Business Media Dordrecht.

Coherent Diffractive Imaging is a lensless technique that allows imaging of matter at a spatial resolution not limited by lens aberrations. This technique exploits the measured diffraction pattern of a coherent beam scattered by periodic and non-periodic objects to retrieve spatial information. The diffracted intensity, for weak-scattering objects, is proportional to the modulus of the Fourier Transform of the object scattering function. Any phase information, needed to retrieve its scattering function, has to be retrieved by means of suitable algorithms. Here we present a new approach, based on a memetic algorithm, i.e. a hybrid genetic algorithm, to face the phase problem, which exploits the synergy of deterministic and stochastic optimization methods. The new approach has been tested on simulated data and applied to the phasing of transmission electron microscopy coherent electron diffraction data of a SrTiO3 sample. We have been able to quantitatively retrieve the projected atomic potential, and also image the oxygen columns, which are not directly visible in the relevant high-resolution transmission electron microscopy images. Our approach proves to be a new powerful tool for the study of matter at atomic resolution and opens new perspectives in those applications in which effective phase retrieval is necessary.

We have grown an ultrathin epitaxial Fe/MgO bilayer on (Ga, Mn)As by e-beam evaporation in UHV. The system structure has been investigated by high resolution transmission electron microscopy (TEM) experiments which show that the Fe and MgO films, covering completely the (Ga, Mn) As, grow with the epitaxial relationship Fe[100](001) parallel to begin_of_the_skype_highlighting (001) parallel to FREE end_of_the_skype_highlighting MgO[110](001) parallel to (Ga, Mn)As[110](001). The magnetic reversal process, studied by the magneto-optical Kerr effect (MOKE) at room temperature, demonstrates that the iron is ferromagnetic and possesses a cubic anisotropy, confirming the epitaxy relationship found with TEM. Resistivity measurements across the barrier display a non-Ohmic behavior characterized by cubic conductance as a function of the applied voltage suggesting tunneling-dominated transport across the barrier.

A colloidal crystal-splitting growth regime has been accessed, in which TiO2 nanocrystals, selectively trapped in the metastable anatase phase, can evolve to anisotropic shapes with tunable hyperbranched topologies over a broad size interval. The synthetic strategy relies on a nonaqueous sol-gel route involving programmed activation of aminolysis and pyrolysis of titanium carboxylate complexes in hot surfactant media via a simple multi-injection reactant delivery technique. Detailed investigations indicate that the branched objects initially formed upon the aminolysis reaction possess a strained monocrystalline skeleton, while their corresponding larger derivatives grown in the subsequent pyrolysis stage accommodate additional arms crystallographically decoupled from the lattice underneath. The complex evolution of the nanoarchitectures is rationalized within the frame of complementary mechanistic arguments. Thermodynamic pathways, determined by the shape-directing effect of the anatase structure and free-energy changes accompanying branching and anisotropic development, are considered to interplay with kinetic processes, related to diffusion-limited, spatially inhomogeneous monomer fluxes, lattice symmetry breaking at transient Ti5O5 domains, and surfactant-induced stabilization. Finally, as a proof of functionality, the fabrication of dye-sensitized solar cells based on thin-film photoelectrodes that incorporate networked branched nanocrystals with intact crystal structure and geometric features is demonstrated. An energy conversion efficiency of 6.2% has been achieved with standard device configuration, which significantly overcomes the best performance ever approached with previously documented prototypes of split TiO2 nanostructures. Analysis of the relevant photovoltaic parameters reveals that the utilized branched building blocks indeed offer light-harvesting and charge-collecting properties that can overwhelm detrimental electron losses due to recombination and trapping events.

Electron diffractive imaging (EDI) relies on combining information from the high-resolution transmission electron microscopy image of an isolated kinematically diffracting nano-particle with the corresponding nano-electron diffraction pattern. Phase-retrieval algorithms allow one to derive the phase, lost in the acquisition of the diffraction pattern, to visualize the actual atomic projected potential within the specimen at sub-ångström resolution, overcoming limitations due to the electron lens aberrations. Here the approach is generalized to study extended crystalline specimens. The new technique has been called keyhole electron diffractive imaging (KEDI) because it aims to investigate nano-regions of extended specimens at sub-ångström resolution by properly confining the illuminated area. Some basic issues of retrieving phase information from the EDI/KEDI measured diffracted amplitudes are discussed. By using the generalized Shannon sampling theorem it is shown that whenever suitable oversampling conditions are satisfied, EDI/KEDI diffraction patterns can contain enough information to lead to reliable phase retrieval of the unknown specimen electrostatic potential. Hence, the KEDI method has been demonstrated by simulations and experiments performed on an Si crystal cross section in the [112] zone-axis orientation, achieving a resolution of 71 pm.

Using high-resolution transmission electron microscopy and image simulation techniques in combinationwith ab initio calculations, we show the existence of two different superlattices of crystallographic shearplanes, analogous to the Magnéli phases of rutile, in oxygen-deficient films of anatase TiO2 epitaxiallygrown on LaAlO3 substrates. (103)- and (101)-oriented shear plane structures are detected in the outer filmregion and in proximity of the film/substrate interface, respectively. We show that these shear planes arecharacterized by TiO-like cubic local structures, which can deviate from the TinO2n-1 stoichiometry of theclassical rutile-derived Magnéli phases, particularly in the outer part of the film. Computed formation energiesprovide insights into the thermodynamic stability of the observed structures and their relations to the growthdynamics.

The interaction of gold nanoparticles (AuNPs) withcysteine and its derivatives is the basis of a number of bionanotechnologies,and for these, the most important process is aggregation (orantiaggregation), which enables an array of colorimetric detection methods.When AuNPs were functionalized with cysteine, its dimer cystine, or thecysteine-derived tripeptide, glutathione, three different mechanisms ofaggregation were observed. Both cysteine and glutathione inducedaggregation of AuNPs without further pH modification: the first byinterparticle zwitterionic interaction and the second by interparticlehydrogen bonding. Cystine, however, did not induce aggregation, althoughit dissociated into two cysteinate moieties upon adsorption on the AuNPs,which appear to be chemically identical to cysteinate produced from cysteine adsorption. We show that the difference is due tothe lower coverage of cysteinate from cystine and differences in charge states of the adsorbates. On modifying the pH to 1.5, thesurface species become cationic (neutral COOH and protonated NH3+), and aggregation of cystine/AuNPs occurs immediatelyby interparticle hydrogen bonding. Thus, cysteine may induce aggregation by neutral hydrogen bonding or zwitterionicinteraction between nanoparticles, but the mechanism depends sensitively on a number of parameters.

The action of dopamine on the aggregation of the unstructured alpha-synuclein (alpha-syn) protein may be linked to the pathogenesis of Parkinson's disease. Dopamine and its oxidation derivatives may inhibit alpha-syn aggregation by non-covalent binding. Exploiting this fact, we applied an integrated computational and experimental approach to find alternative ligands that might modulate the fibrillization of alpha-syn. Ligands structurally and electrostatically similar to dopamine were screened from an established library. Five analogs were selected for in vitro experimentation from the similarity ranked list of analogs. Molecular dynamics simulations showed they were, like dopamine, binding non-covalently to alpha-syn and, although much weaker than dopamine, they shared some of its binding properties. In vitro fibrillization assays were performed on these five dopamine analogs. Consistent with our predictions, analyses by atomic force and transmission electron microscopy revealed that all of the selected ligands affected the aggregation process, albeit to a varying and lesser extent than dopamine, used as the control ligand. The in silico/in vitro approach presented here emerges as a possible strategy for identifying ligands interfering with such a complex process as the fibrillization of an unstructured protein.

Nanohybrids formed by the multiwalled carbon nanotubes (MWCNTs) and metallic nanoparticles (NPs) have gained immense interest recently for their potential biological applications. In this paper, we present a comprehensive study of the nanohybrid formed with varied concentrations of Au-NPs with MWCNTs. It is demonstrated that the concentration of Au-NPs in the nanohybrid is crucial in defining ultimate characteristics of the nanohybrid. The MWCNTs were functionalized with varied concentrations of Au-NPs (40-100 nano Molar (nM)) and characterized extensively by the X-ray diffraction, electron microscopy, Raman spectroscopy and UV-Vis absorption spectroscopy. The process of purification and acid treatment led to the activation of -COOH bond at the surface of MWCNTs and functionalization with Au-NPs also induced stresses as observed in the X-ray diffraction patterns. The fusion of Au-NPs in the MWCNTs was clearly observed in the high resolution TEM images, which affected the D and G - Raman bands of the MWCNTs significantly as studied by the line shape analysis. The Au-NPs-MWCNTs nanohybrids were then used to study the effect of various concentrations of E-coli using Raman spectroscopy and absorption spectroscopy. Due to intrinsic negative charge present on the E-coli, the local charge densities varied at the surface of MWCNTs as soon as it was covered with E-coli, and resulted in the shift of both G and D bands and increased intensity ratio of the two bands. The variation in the charge density in Au-NPs due to its binding with MWCNTs and adsorption of E-coli was reflected in the blue shift of the surface plasmon modes. Finally, it is concluded that ratio of Au-NPs and MWCNTs is crucial in forming nanohybrid for applications.

TiO2 anatase thin films grown by pulsed laser deposition are investigated by high resolution transmission electron microscopy and high angle annular dark field scanning transmission electron microscopy. The analyses provide evidence of a peculiar growth mode of anatase on LaAlO3 and SrTiO3 characterized by the formation of an epitaxial layer at the film/substrate interface, due to cationic diffusion from the substrate into the film region. Pure TiO2 anatase growth occurs in both specimens above a critical thickness of about 20 nm. The microstructural and chemical characterization of the samples is presented and discussed in the framework of oxide interface engineering.

A simple synthesis was applied and tested for the preparation of boron-doped titanium dioxide [TiO2(B)] nanocrystals using titanium tetraisopropoxide (TTIP) together with boric acid (H3BO3) and benzyl alcohol as reaction solvent. Changes in the TTIP/H3BO3 molar ratio allowed a scalable synthetic protocol with a significant B-dopant control. In particular, this approach does not need surfactants or a final calcination step. X-ray diffractometry (XRD), low- and high-resolution transmission electron microscopy (TEM and HRTEM), and micro Raman spectroscopy revealed that the TiO2 nanocrystals produced have diameters up to about 10 nm and are mainly of the anatase phase but that a brookite phase was progressively formed with increased dopant level. The amount of boron was measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES), and the presence of boron inside the crystals was determined by 11B cross-polarized magic-angle spinning nuclear magnetic resonance (11B CP-MAS NMR) spectroscopy. X-ray photoelectron spectroscopy (XPS) revealed the presence of boron on the nanocrystal surfaces, confirming the trend in the dopant concentration already observed with ICP-AES elemental analysis. Microphotoluminescence studies indicated the formation of three different typical luminescent defect states in correlation with the amount of added boron in the titania. UV/Vis absorption spectra showed a boron-dependent redshift of the absorption edge.

An iron-molybdenum alloy powder was extensively deformed by high energy milling, so to refine the bcc iron domain size to nanometer scale (similar to 10 nm) and introduce a strong inhomogeneous strain. Both features contribute to comparable degree to the diffraction peak profile broadening, so that size and strain contributions can be easily separated by exploiting their different dependence on the diffraction angle. To assess the reliability of Line Profile Analysis, results were compared with evidence from other techniques, including scanning and transmission electron microscopy and X-ray small angle scattering. Results confirm the extent of the size broadening effect, whereas molecular dynamics simulations provide insight into the origin of the local atomic, inhomogeneous strain, pointing out the role of dislocations, domain boundaries and interactions among crystalline domains.

Despite the great interest that cocrystals are currently gaining for their application to the design of new supramolecular structures with desired functional properties, studies concerning new experimental strategies capable of controlling polymorphism phenomena of a given system are scarcely reported. We propose herein the use of polymer-assisted grinding (POLAG) as a new method for the selective control of the product polymorphic form in a mechanochemical cocrystallization reaction. Specifically, to the model system selected in this study formed by caffeine and glutaric acid, we demonstrate that the polymorphic outcome can be controlled by modifying the number of monomer units of the catalyst from the shortest dimer to a polymer with chains of approximately 1000 units. The characteristics of each polymorphic form were investigated by low-dose high-resolution TEM, and the mechanistic aspects of the cocrystal formation were studied through a series of ex situ and interconversion experiments. The results suggest that for this system the modification of the catalyst chain length and, consequently, modification of polarity drives cocrystal formation toward the more stable polymorph. The approach proposed in this paper can be readily applied to each system, where polarity is the main issue for polymorph control without the risk of solvate formation.

High angle annular dark field (HAADF) scanning transmission electron microscopy has demonstrated the capability to achieve sub-Angstrom resolution in the study of the structure of materials Furthermore, the sensitivity of HAADF imaging to fine variations of the chemistry of the specimen allows one to derive the relevant chemical map from the intensity distribution in an image Here, a general approach to calculate the HAADF image intensity for an alloy is derived and applied to experimental images to measure quantitatively the distribution of the chemical species The calculations of HAADF image contrast have been performed by multi-slice methods in the framework of the frozen-phonon approximation by developing and using a parallel code to strongly reduce the computing time necessary to obtain a reliable simulation of realistic specimens The parameters that influence the HAADF image contrast have been studied and their role has been quantified Experimental examples of quantification of the chemistry of semiconducting heterostructures will be shown Attention will be focused on the different parameters that influence the HAADF image contrast depending on the material system and on the specimen composition

The combination of Au-metallic-NPs and CNTs are a new class of hybrid nanomaterials for the development of electrochemical biosensor. Concentration of Au(nanoparticles [NPs]) in the electrochemical biosensor is crucial for the efficient charge transfer between the Au-NPs-MWCNTs modified electrode and electrolytic solution.Methods: In this work, the charge transfer kinetics in the glassy carbon electrode (GCE) modified with Au(NPs)-multiwalled carbon nanotube (MWCNT) nanohybrid with varied concentrations of Au(NPs) in the range 40-100 nM was studied using electrochemical impedance spectroscopy (EIS). Field emission scanning electron microscopy and transmission electron microscopy confirmed the attachment of Au(NPs) on the surface of MWCNTs.Results: The cyclic voltammetry and EIS results showed that the charge transfer mechanism was diffusion controlled and the rate of charge transfer was dependent on the concentration of Au(NPs) in the nanohybrid. The formation of spherical diffusion zone, which was dependent on the concentration of Au(NPs) in nanohybrids, was attributed to result in 3 times the increase in the charge transfer rate ks, 5 times increase in mass transfer, and 5% (9%) increase in Ipa (Ipc) observed in cyclic voltammetry in 80 nM Au(NP) nanohybrid-modified GCE from MWCNT-modified GCE. The work was extended to probe the effect of charge transfer rates at various concentrations of Au(NPs) in the nanohybrid-modified electrodes in the presence of Escherichia coli. The cyclic voltammetry results clearly showed the best results for 80 nM Au(NPs) in nanohybrid electrode.Conclusion: The present study suggested that the formation of spherical diffusion zone in nanohybrid-modified electrodes is critical for the enhanced electrochemical biosensing applications.

In this paper, a method to synthesize anatase TiO2 nanorods by hydrolysis of titanium(IV) isopropoxide(TTIP) in the presence of benzyl alcohol and acetic acid at 210 °C was tested. The novelty of the presentapproach relies on the evaluation of the shape-controlled synthesis of anatase TiO2 nanocrystals via amicrowave-solvothermal method in 45 min. The different TiO2 nanocrystals were obtained by tuningthe TTIP/acetic acid ratio under optimized synthetic conditions and were characterized in detail by X-raydiffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), micro Raman(together with microphotoluminescence) and FT-IR spectroscopies. The acetic acid coordinated on thenanocrystal surface was removed by the reduction of its carboxyl group via a "super-hydride reaction",and the photocatalytic activity of bare TiO2 nanocrystals, under visible light irradiation, was alsoevaluated: the best performing TiO2 anatase nanocrystals exhibited a discrete photoactivity, completelydegrading Rhodamine B solution in five hours.

The fabrication of flexible multilayer graphene oxide (GO)membrane and carbon nanotubes (CNTs) using a rare form of high-puritynatural graphite, vein graphite, is reported for the first time. Graphite oxideis synthesized using vein graphite following Hummer's method. Byfacilitating functionalized graphene sheets in graphite oxide to selfassemble,a multilayer GO membrane is fabricated. Electric arc discharge isused to synthesis CNTs from vein graphite. Both multilayer GOmembrane and CNTs are investigated using microscopy and spectroscopyexperiments, i.e., scanning electron microscopy (SEM), atomic forcemicroscopy (AFM), high-resolution transmission electron microscopy(HRTEM), Fourier transform infrared spectroscopy (FTIR), X-raydiffraction (XRD), thermogravimetric analysis (TGA), core level photoelectronspectroscopy, and C K-edge X-ray absorption spectroscopy(NEXAFS), to characterize their structural and topographical properties. Characterization of vein graphite using differenttechniques reveals that it has a large number of crystallites, hence the large number of graphene sheets per crystallite,preferentially oriented along the (002) plane. NEXAFS and core level spectra confirm that vein graphite is highly crystalline andpure. Fourier transform infrared (FT-IR) and C 1s core level spectra show that oxygen functionalities (-C-OH, -C?O,-C-O-C-) are introduced into the basal plane of graphite following chemical oxidation. Carbon nanotubes are produced from veingraphite through arc discharge without the use of any catalyst. HRTEM confirm that multiwalled carbon nanotube (MWNTs)are produced with the presence of some structure in the central pipe. A small percentage of single-walled nanotubes (SWNTs)are also produced simultaneously with MWNTs. Spectroscopic and microscopic data are further discussed here with a view tousing vein graphite as the source material for the synthesis of carbon nanomaterials.

We report on the unprecedented direct observation of spin-polarization transfer across colloidal magneto-plasmonic Au@Fe-oxide core@shell nanocrystal heterostructures. A magnetic moment is induced into the Au domain when the magnetic shell contains a reduced Fe-oxide phase in direct contact with the noble metal. An increased hole density in the Au states suggested occurrence of a charge-transfer process concomitant to the magnetization transfer. The angular to spin magnetic moment ratio, m(orb)/m(spin) for the Au 5d states, which was found to be equal to 0.38, appeared to be unusually large when compared to previous findings. A mechanism relying on direct hybridization between the Au and Fe states at the core/shell interface is proposed to account for the observed transfer of the magnetic moment.

Well-defined sized (5-10 nm) metallic iron nanoparticles (NPs) with body-centered cubic structure encapsulated inside the tip of millimeter-long vertically aligned carbon nanotubes (VACNTs) of uniform length have been investigated with high-resolution transmission electron microscopy and soft X-ray spectroscopy techniques. Surface-sensitive and chemically-selective measurements have been used to evaluate the magnetic properties of the encapsulated NPs. The encapsulated Fe NPs display magnetic remanence up to room temperature, low coercivity, high chemical stability and no significant anisotropy. Our surface-sensitive measurements combined with the specific morphology of the studied VACNTs allow us to pinpoint the contribution of the surface oxidized or hydroxidized iron catalysts present at the VACNT-substrate interface.