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Measured absolute optical absorption cross sections of 2-6 nm Ge nanocrystals embedded in SiO2 in the near-infrared-ultraviolet spectral range are reported. Thin layers of Ge sandwiched between SiO2 layers were prepared in a multilayered configuration, which upon heat treatment at 800 °C led to multilayers of Ge nanocrystals with a narrow size distribution. Four samples with different nanocrystal average sizes were prepared by this technique. In addition, samples containing Ge nanocrystals randomly distributed in SiO2 films were also prepared in order to clarify the effects of the multilayer configuration on the optical properties. The size distribution and density of the nanocrystals were obtained from transmission electron microscopy investigations and Rutherford backscattering spectrometry measurements. In combination with this structural information the nanocrystal absorption cross sections were obtained from optical transmission measurements, which were corrected for thin film interference effects by a self-consistent procedure. The measurements clearly show that the nanocrystal absorption per atom in the 1.5-5 eV spectral range is smaller than in bulk Ge atoms regardless of the nanocrystal size and that the absorption cross sections per atom for the nanocrystals are largely independent of the nanocrystal size. Moreover, we find that the absorption cross sections for small concentrations of Ge nanocrystals embedded in SiO2 are quantitatively well described by the Mie theory using bulk values for the dielectric function of Ge in the spectral range investigated. Hence quantum confinement effects have only minor if any influence on the dominant features of the absorption spectra for spherical Ge nanocrystals embedded in SiO2. For Ge nanocrystals ordered in multilayers we find that the experimental absorption cross section for the larger and more close packed nanocrystals exceeds that for similar concentrations of nanocrystals randomly distributed in the films, whereas this effect is not observed for multilayered samples with smaller and less densely packed nanocrystals. The combined results show that for all the Ge nanocrystals studied the nanocrystal shape and the matrix in which the nanocrystals are embedded, as well as the nanocrystal configuration play an important role in the optical response of the Ge nanocrystals and that these effects dominate the effects of quantum confinement in the absorption from spherical Ge nanocrystals embedded in SiO2. [ABSTRACT FROM AUTHOR]

Tin-containing nanocrystals, embedded in silicon, have been fabricated by growing an epitaxial layer of Si1-x-ySnxCy, where x = 1.6 % and y = 0.04 % on a silicon substrate, followed by annealing at various temperatures ranging from 650 °C to 900 °C. The nanocrystal density and average diameters are determined by scanning transmission-electron microscopy to ≈ 1017 cm-3 and ≈ 5 nm, respectively. Photoluminescence spectroscopy demonstrates that the light emission is very pronounced for samples annealed at 725 °C, and Rutherford back-scattering spectrometry shows that the nanocrystals are predominantly in the diamond-structured phase at this particular annealing temperature. The origin of the light emission is discussed. [ABSTRACT FROM AUTHOR]

Abstract: In this work we demonstrate that InSb nanocrystals embedded in display a substantial melting-point hysteresis. Transmission electron microscopy was performed after heat treatment on the 500nm-thick films doped with 10at.% of In and Sb atoms in order to verify the presence of the nanocrystals, identify their crystalline form, and obtain their size distribution. The crystalline zinc-blende structure of the InSb nanocrystals was further confirmed with X-ray diffraction characterization. The planar distances and the cubic structure were derived from the X-ray diffraction spectrum. Furthermore, it showed that the nanocrystals have a planar distance slightly smaller than for the bulk crystals, indicating that the nanocrystals are exposed to a compressive stress which we estimate to be 14kbar. Both superheating and supercooling of the nanocrystals could be observed by following the diffraction pattern of the nanocrystals using TEM. The melting-point hysteresis was measured to be about 19% of the melting temperature of bulk InSb. [Copyright &y& Elsevier]

The present study presents an experimental evidence for amorphization of rf sputtered MoSx films by ion bombardment. Even at low doses (3×1015 ions/cm2) of 400 keV argon ions a complete amorphization was confirmed by x-ray diffraction analysis and transmission electron microscopy. As a result of the ion bombardment the film density increased 100% to almost the bulk value for MoS2. The friction coefficient for ion beam amorphized MoSx was measured to be 0.04 in agreement with the values reported for crystalline films but disagreeing considerably with the friction coefficient of 0.4 previously reported for amorphous films. [ABSTRACT FROM AUTHOR]

Solid lubricant films of MoS2 with improved adhesion to a stainless-steel substrate have been deposited by a combination of rf sputtering and ion implantation with inert gas ions in the 100-keV region. When the sputter film had obtained a thickness of 500 Å, it was subjected to the ionic bombardment prior to completion of the sputter deposition. Dependent on the ion dose an adhesion improvement and a sliding life enhancement of approximately a factor of 2 were obtained for the solid lubricant film. [ABSTRACT FROM AUTHOR]

Abstract: New open-framework of zinc phosphate materials, [CH3NH3][(Co x Zn1−x )4(PO4)3], were synthesised under hydrothermal conditions in the presence of the organic additive 3-dimethylamino-1-propylamine, (CH3)2NH(CH2)3NH2. This amine was found to decompose to methyl amine and a brown oil upon hydrothermal heating to T >200 °C. Thereby the structure-directing agent (methyl amine) is prepared in situ prior to crystallisation of the product. This approach is further explored by systematic syntheses performed in order to study the phase stability of the different phosphate materials found in the system, 1Zn(CH3COO)2:mH3PO4:2.0(CH3)2NH(CH2)3NH2:∼140H2O. Furthermore, this new approach is utilised to substitute cobalt into the framework of zinc phosphate materials by a study of the synthesis system, nCo(CH3COO)2:(1− n)Zn(CH3COO)2:3.5H3PO4:2.1(CH3)2NH(CH2)3NH2:∼140H2O. The amount of Co is varied in the range 5–100mol%, i.e. 0.05⩽ n ⩽1. One to four phases are identified in each synthesis product and the phase distribution as a function of the relative amount of cobalt and zinc is determined. Energy dispersive X-ray fluorescence is used to measure the amount of Co incorporated into the framework as a function of the amount of cobalt present in the synthesis mixture, n. A relatively broad substitution range was observed, 0< x <0.35. The structure of [CH3NH3][Co1.35Zn2.65(PO4)3] was determined by single-crystal X-ray diffraction: orthorhombic, space group Pbca (no. 61), a =14.687(1), b =10.111(1), c =16.612(2)Å, V =2466.7(4)Å3, Z =8, μ =7.37cm−1, D cal =3.071gcm−3. The structure has a three dimensional open framework structure built from PO4 and (Zn/Co)O4 tetrahedra and (Zn/Co)O5 trigonal bipyramids. The methyl ammonium template was found in the one-dimensional seven-ring channels and interacts with the inorganic framework by hydrogen bonds. Cobalt has a preference for the higher coordination numbers demonstrated here where the trigonal bipyramid sites are found to have significantly more Co(II) than the tetrahedral sites. [Copyright &y& Elsevier]

Abstract: The adsorption of human fibrinogen on tantalum oxide, titanium oxide and gold surfaces has been studied by quartz crystal microbalance with dissipation (QCM-D) at 37  C. Two different protein concentrations have been used, one close to physiological concentration (1 mg/ml) and one significantly lower (0.033 mg/ml). To further characterize the adsorbed fibrinogen layer, the subsequent binding of both polyclonal and monoclonal antibodies of fibrinogen is studied. We found that the viscoelastic properties of the fibrinogen layer depends strongly on the initial protein concentration. The trend is generally seen for all three surfaces. The fibrinogen layer on gold and tantalum oxide is found to have the same viscoelastic properties, which are different from those found for the fibrinogen layer adsorbed on titanium oxide. The dependency of the surface chemistry on the viscoelastic properties of the fibrinogen layer is observed directly for the 0.033 mg/ml solution, and indirectly through the antibody response for the 1 mg/ml solution. From this we conclude that the orientation and/or denaturation of fibrinogen on a surface depends on the surface chemistry and the protein concentration in the solution, and that the binding of antibodies is a useful way to detect this difference. [Copyright &y& Elsevier]

• Prepare a 7 nm thick graphene based coating on an Inconel 625 substrate. • A low temperature, molecular polymerisation recipe prevents substrate degradation. • Coating reduces corrosion current by two orders of magnitude in acidic conditions. The use of graphene materials as protective coatings for metallic substrates has received much attention because of graphene's ability to seal a metal and prevent the diffusion of most corrosive species to the metal surface. The application of graphene-based coating technology to industrially relevant samples, however, is hindered by the high growth temperatures required to prepare functional and efficient protective graphene layers. The growth temperatures typical for popular catalysts and precursors are incompatible with most relevant alloys. Here, we present a low-temperature synthesis route to a graphene-based coating, using a complex metallic alloy, Inconel 625, as an example substrate. We demonstrate that the coating reduces the sample corrosion current by two orders of magnitude and also shifts the open circuit potential from −308 mV to + 129 mV. We present an extensive characterisation of the coating and the coating synthesis procedure. The procedure relies on a surface-activated, thermally-induced polymerisation reaction and the method should be transferable to other metallic alloys. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Laser-induced optical-change threshold of GST depends strongly on film thickness. • Amorphization requires slightly higher laser fluences. • Two distinct low- and high-fluence ablation thresholds are present for thick films. Abstract Modifications induced by ultrashort laser pulses have been investigated in crystalline Ge 2 Sb 2 Te 5 thin films. The observations comprise optical and structural changes, amorphization, and ablation. By combining optical microscopy and cross-sectional scanning- and transmission electron microscopy, it is found that the threshold for permanent change of the optical properties of Ge 2 Sb 2 Te 5 – responsible for the reduced optical reflectivity – is slightly lower than that for amorphization; no further change in reflectivity is seen upon amorphization. The laser-fluence thresholds for amorphization and change of the optical properties both show a strong dependence on film thickness that can be explained thermally by two-temperature simulations. In the case of sufficiently thick films, two distinct low- and high-fluence ablation thresholds are found. The mechanisms of the ablation thresholds are discussed, and it is concluded that ablation in the low-fluence regime proceeds by photomechanical spallation. [ABSTRACT FROM AUTHOR]

A novel fast‐setting calcium silicate cement containing fluoride (novel‐CSC) has been developed for applications in tooth crowns. The aim of this study was to assess the ability of the novel‐CSC to close the experimental gaps at the dentin–cement interface. The novel‐CSC was tested against Vitrebond and GC Fuji II LC. Experimental gaps of 50 or 300 μm width were created between the materials and dentin. Specimens with the 300‐μm‐wide gap were immersed in phosphate‐buffered saline and the closed gap area was measured during 96 h. All specimens with 50 or 300 μm gap width were analyzed by scanning electron microscopy equipped with energy dispersive X‐ray spectroscopy (SEM/EDX) to assess the morphology and chemical composition of the precipitates after 96 h immersion in phosphate‐buffered saline. High‐resolution micro‐computed tomography (μCT) was used to evaluate the integrity and continuity of the precipitiates after 96 h and 180 d. In all novel‐CSC samples, precipitates closed the gap area completely after 96 h. The SEM/EDX revealed that the globular precipitates closing the gap area were mainly composed of calcium and phosphorus. After 180 d, μCT indicated thicker precipitates compared with initial precipitates only in the novel‐CSC group, whereas no precipitates were observed in resin‐modified glass ionomers. Novel‐CSC promoted continuous precipitation of calcium phosphate, including apatite, and closed the experimental gaps. [ABSTRACT FROM AUTHOR]

In a previous work, we discovered a new set of growth parameters for fabricating (100) homoepitaxial phosphorusdoped n-type diamond with unique properties: full incorporation of phosphorus donors in substitutional sites together with a low surface roughness. In this work, a planar type Schottky barrier diode has been fabricated on the epilayer and C-V characteristics were measured. From the capacitance properties, the net donor density and the Schottky barrier height were experimentally determined to be ~3.1 × 1016 cm-3 and ~4.65 eV, respectively. The phosphorus electrical activity in our (100) n-type diamond epilayer is discussed in comparison with previous works on the (100) and (111) orientations. [ABSTRACT FROM AUTHOR]

Upconversion in radio frequency magnetron sputtered Er-doped zinc oxide thin films on Si substrate has been demonstrated using 1550 nm cw laser excitation. As-sputtered thin films did not show any upconversion emission, and annealing was required to optically activate the Er3+-ions. Emissions at 985, 809, and 665-675 nm were observed in annealed thin films, corresponding to transitions from 4I11/2, 4I9/2, and 4F9/2 to the ground state 4I15/2, respectively. The emission from 4I11/2 was the dominant one, whereas emission from 4I9/2 was the weakest. The highest intensity at 985 nm was obtained with 2.4 at.% of Er by annealing the film at 700 ℃. Annealing at higher temperatures causes Er to diffuse and segregate to the Si-ZnO interface between the Si substrate and the ZnO film. [ABSTRACT FROM AUTHOR]

Abstract: A hybrid biofuel cell has been constructed based on the Zn anode and O2 biocathode, exploiting fungal Cerrena maxima and Choriolus hirsutus laccases cross-linked onto graphite and microstructured graphitized carbon cloth (GCC) electrodes. Immobilized at the graphite electrodes, laccases exhibited a high similarity in the reaction of direct (in the absence of any mediators) bioelectrocatalytic reduction of O2 starting from 0.7V vs. Ag/AgCl, pH 5, which was consistent with a 94% structural homology of the laccases. The efficiency of the bioelectrocatalytic reaction was enhanced by immobilizing laccases on the high-surface area GCC, due to the increased surface concentration of the laccase molecules properly orientated for the direct electron transfer reaction within the micro-structured electrode. The hybrid biofuel cell, based on the battery-type Zn anode and oxygen laccase/GCC biocathode yielded the open-circuit voltage V oc of 1.76V and the short-circuit current density j sc of 4mAcm−2 in quiescent aerated solutions. A maximum power density of the cell was 0.44mWcm−2 at the cell voltage of 0.5V, pH 5. The hybrid biofuel cell exploiting cross-linked stabilized laccases at GCC was able to power a 1.5V domestic device for 38 days. [Copyright &y& Elsevier]

Abstract: Controlling cellular responses on biomaterial surfaces is crucial in biomedical applications such as tissue engineering and implantable prosthetics. Since cells encounter various nanoscale topographic features in their natural environment, it has been postulated that surface nanotopography may be an alternative route to fabricate biomaterials with a desirable cellular response. In this framework, we investigated the responses of primary human fibroblasts to platinum substrates with different levels of surface roughness at the nanoscale. The nanorough surfaces were fabricated by using the glancing angle deposition technique (GLAD). We found that levels of cellular responses depended on the surface roughness and the size of the nanoscale features. We showed that in response to nanotopography cells spread less and have an elongated morphology, displaying signs of actin cytoskeleton impairment and reduced formation of focal adhesion complexes. Although cell growth and adhesion were impaired on the nanorough substrates, cell viability was not affected by topography. To a minor extent our results also indicate that cell migration might be reduced on the nanorough surfaces, since a significantly lower gene expression of migration related genes were found on the roughest surfaces as compared to the flat reference. The results presented here demonstrate that surface nanotopography influences fibroblasts responses on platinum, which may be used to reduce cellular adhesion on platinum implant surfaces such as implantable neural electrodes. [Copyright &y& Elsevier]

Abstract: In this study, the experimental techniques scanning electron microscopy (SEM) including energy-dispersive X-ray analysis, atomic force microscopy (AFM) and scanning small angle X-ray scattering (SAXS) have been exploited to characterize the organization of large molecules and nanocrystallites in and around the neurocentral growth plate (NGP) of a pig vertebrae L4. The techniques offer unique complementary information on the nano- to micrometer length scale and provide new insight in the changes in the matrix structure during endochondral bone formation. AFM and SEM imaging of the NGP reveal a fibrous network likely to consist of collagen type II and proteoglycans. High-resolution AFM imaging shows that the fibers have a diameter of approximately 100 nm and periodic features along the fibers with a periodicity of 50–70 nm. This is consistent with the SAXS analysis that yields a cross-sectional diameter of the fibers in the range of 90 to 112 nm and a predominant orientation in the longitudinal direction of the NGP. Furthermore, we find inhomogeneities around 7 nm in the NGP by SAXS analysis. Moving towards the bone in the direction perpendicular to the growth plate, a systematic change in apparent thickness is observed, while the large-scale structural features remain constant. In the region of bone, the apparent thickness equals the mean mineral thickness and increases from 2 nm to approximately 3.5 nm as a function distance from the NGP. The mineral particles are organized as plates in a rather compact network structure. We have demonstrated that SEM, AFM and SAXS are valuable tools for the investigation of the organization of large molecules and nanocrystallites in the NGP and adjacent trabecular bone. Our findings will be an important basis for future work into identifying the defects on nanometer length scale responsible for idiopathic scoliosis and other growth-plate-related diseases. [Copyright &y& Elsevier]

Abstract: Highly crystalline anatase TiO2 nanoparticles have been synthesised in less than 1min in a supercritical propanol–water mixture using a continuous flow reactor. The synthesis parameter space (T, P, concentration) has been explored and the average particle size can be accurately controlled within 10–18nm with narrow size distributions (2–3nm). At subcritical conditions amorphous products are obtained, whereas a broad range of T and P in the supercritical regime gives 11–14nm particles. At high temperature and pressure, the particles size increase to 18nm. The nanoparticles have been extensively characterised with powder X-ray diffraction (PXRD), transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) with excellent agreement on size and size distribution parameters. The SAXS analysis suggests disk-shaped particles with diameters that are approximately double the height. For comparison, a series of conventional autoclave sol–gel syntheses have been carried out. These also produce phase-pure anatase nanoparticles, but with much broader size distributions and at much longer synthesis times (hours). The study demonstrates that synthesis in supercritical fluids is a very promising method for manipulating the size and size distribution of nanoparticles, thus removing one of the key limitations in many applications of nanomaterials. [Copyright &y& Elsevier]

Abstract: The quartz crystal microbalance with dissipation (QCM-D) technique was employed to characterize initial cell adhesion in terms of attachment and spreading of pre-osteoblastic MC3T3-E1 cells on Ta and Cr surfaces. Evaluation of initial cell adhesion established a correlation between input cell number and the shifts in frequency and dissipation (D). The f-shift was found to be much larger in serum-free medium as compared to a medium including serum; hence, initial cell adhesion was subsequently evaluated in serum-free medium. During the first hour of adhesion, we found a positive correlation between the QCM-D f-shift and the average area of the spread cells, as measured by cryo-scanning electron microscopy (cryo-SEM). Finally, the QCM-D technique was used to study cell adhesion on different metal oxide surfaces. Initial cell adhesion on Ta was found to induce a larger f-shift as compared to Cr, indicating larger spreading of cells on Ta. Cryo-SEM data confirmed that spreading of cells on Cr was on average only two-thirds the spreading on Ta. Our results demonstrate that the QCM-D technique is a versatile technique to quickly distinguish initial cell–surface interactions on different biomaterials. [Copyright &y& Elsevier]