Solution-Route Inkjet Fabrication of CeO2 Thin Films with Tunable Microstructure.

We report the fabrication and characterization of solution-route CeO2 thin films with a tunable porosity and microstructure. Films were deposited by means of inkjet printing technique using 0.2 M, 0.4 M and 0.6 M concentration inks prepared from Ce(NO3)3·6H2O precursor. Printing was performed at two different temperatures of 60 °C and 300 °C to study the variation in structure. Printing parameters were adjusted for the consecutive deposition of layers, resulting in ≈140 nm and ≈185 nm thick single layers for 60 °C and 300 °C printing temperatures, respectively. We compared the microstructure of printed films for different concentrations, printing temperatures, solvents and substrates. The formation of the cubic fluorite structure of the printed films was confirmed via XRD characterization. We suggest this technique as an advanced method for high-quality film fabrication with a controlled microstructure and with a minimal waste of materials. Through adjusting printing parameters, both dense and porous films can be produced for use in different applications.

Pattern shape control for heat treatment purification of electron-beam-induced deposition of gold from the Me2Au(acac) precursor.

Gold structures can be created in a scanning electron microscope (SEM) from the Me(2)Au(acac) precursor by direct writing with the electron beam. The as-deposited purity is usually poor, and a common purification approach is a post-annealing step that indeed is effective but also induces a volume reduction because of carbon loss and an undesirable reconfiguration of the gold structure, resulting in the loss of the original shape. We studied the shape change as a result of such purification, and to minimize this effect, the application of a tantalum and chromium buffer layer was investigated. These buffer materials are well-known for their good adhesion properties. We confirm by dedicated SEM, atomic force microscopy (AFM), and transmission electron microscopy (TEM) analysis that, for the creation of a uniform Au structure, tantalum is a better buffer layer material than chromium. Post-annealing of the Au electron-beam-induced deposition (EBID) patterns for 1 h at 600 °C in air resulted in a dramatic purity increase (from 8-12 atomic % Au to above 92 atomic % Au). The uncovered part of the tantalum layer can be easily etched away, resulting in a well-defined, high-purity, gold structure.

Particle size and magnetic properties dependence on growth temperature for rapid mixed co-precipitated magnetite nanoparticles.

Magnetite nanoparticles have been prepared by co-precipitation using a custom-designed jet mixer to achieve rapid mixing (RM) of reactants in a timescale of milliseconds. The quick and stable nucleation obtained allows control of the particle size and size distribution via a more defined growth process. Nanoparticles of different sizes were prepared by controlling the processing temperature in the first few seconds post-mixing. The average size of the nanoparticles investigated using a Tecnai transmission electron microscope is found to increase with the temperature from 3.8 nm at 1 ± 1 °C to 10.9 nm for particles grown at 95 ± 1 °C. The temperature dependence of the size distribution follows the same trend and is explained in terms of Ostwald ripening of the magnetite nanoparticles during the co-precipitation of Fe(2+) and Fe(3+). The magnetic properties were studied by monitoring the blocking temperature via both DC and AC techniques. Strikingly, the obtained RM particles maintain the high magnetization (as high as ∼88 A m(2) kg(-1) at 500 kA m(-1)) while the coercivity is as low as ∼12 A m(-1) with the expected temperature dependence. Besides, by adding a drop of tetramethylammonium hydroxide, aqueous ferrofluids with long term stability are obtained, suggesting their suitability for applications in ferrofluid technology and biomedicine.

Ordered coalescence of nanocrystals: a path to strong macroporous nanoceramics.

A versatile approach for integrating two apparently conflicting physical properties, high porosity and high mechanical strength, in polycrystalline bulks is established and demonstrated for the case of alumina ceramics. Macroporous alumina nanoceramics are synthesized by stimulating coalescence-mediated necking, which enables the formation of strong crystallographically coherent necks between adjacent grains. The work places a general emphasis on manipulating crystal growth on the nanoscale and on preparing highly porous polycrystalline bulk ceramics with improved mechanical rigidity.

Design and tailoring of inks for inkjet patterning of metal oxides.

Inkjet printing has become a promising, efficient, inexpensive, scalable technique for materials deposition, mask-less and digital patterning in many device applications. Meanwhile, the ink preparation remains a challenge especially for printing functional oxide materials. Based on the principles of inkjet printing (especially relevant for piezoelectric drop-on-demand inkjet printer) and the process of the conversion of liquid ink into solid thin films of oxide materials, we present two approaches to the design and tailoring of inks: (i) oxide particle suspensions (e.g. SiO2, TiO2, Fe3O4) and (ii) metal-acetates precursor solutions for directly printing oxide thin films (e.g. ZnO, MgO, ITO and so forth). The solution inks are stable and produce tunable oxide films with high density and smooth surface. For some of the inks containing multi-type acetates with possible phase separation even before calcinations, we have developed a chelating procedure in order to tailor the films into single-phase homogeneity. The work lays a foundation for inkjet printing of oxides films for functional applications in electronic, photonic and energy devices.

Basal cell carcinoma invasion depth determined with 30 and 75 MHz high-frequency ultrasound and histopathology - a comparative study.

AIM: To compare the depth spread of basal cell carcinoma (BCC) measured by histological examination and high-frequency ultrasound (HFUS) imaging with 30-MHz and 75-MHz probes. MATERIALS AND METHODS: HFUS skin imaging was used to examine 27 BCCs. A specialized high-resolution digital ultrasound imaging system DUB (TPM GmbH, Germany) with 75-MHz and 30-MHz probes was used. After HFUS scanning, the BCCs biopsy samples were collected by punch biopsy or surgical excision for the morphological examination. Based on the histomorphology results obtained, the tumors were divided into thin (≤1 mm invasion depth) and thick (>1 mm invasion depth). Each BCC spread depth was measured during the HFUS examination with 75-MHz and 30-MHz ultrasound probes and morphological examination. RESULTS: Thin BCCs average invasiondepth measured histologically was 0.494±0.212 mm. Its average depth obtained with HFU examination with 75-MHz and 30-MHz probes was 0.591±0.265 and 0.734±0.123 mm, respectively. High, statistically significant correlation betweenthe histological and 75 MHz HFU measurements was obtained (r=0.870). The correlation was weak (r=0.290) when using a 30 MHz transducer. The average thick BCC invasion depth values obtained with the histological examination and 30 MHz HFUS scanning was 1.845±0.718 mm and 1.995±0.699 mm, respectively. High, statistically significant (r=0.951) correlation between the thick BCC spread depth measured with 30 MHz transducer and histomorphological examination was obtained. CONCLUSIONS: In cases of BCCs with thickness of ≤1 mm, there was a high correlation (r=0.870) of the tumor spread depth between micromorphological measurements and the results obtained using a 75 MHz transducer and in cases of BCCs with thickness of >1 mm, a very high correlation (r=0.951) of the tumor spread depth was observed between histomorphometry and30 MHz transducer measurements.

Intermediate filament-like proteins in bacteria and a cytoskeletal function in Streptomyces.

Actin and tubulin cytoskeletons are conserved and widespread in bacteria. A strikingly intermediate filament (IF)-like cytoskeleton, composed of crescentin, is also present in Caulobacter crescentus and determines its specific cell shape. However, the broader significance of this finding remained obscure, because crescentin appeared to be unique to Caulobacter. Here we demonstrate that IF-like function is probably a more widespread phenomenon in bacteria. First, we show that 21 genomes of 26 phylogenetically diverse species encoded uncharacterized proteins with a central segmented coiled coil rod domain, which we regarded as a key structural feature of IF proteins and crescentin. Experimental studies of three in silico predicted candidates from Mycobacterium and other actinomycetes revealed a common IF-like property to spontaneously assemble into filaments in vitro. Furthermore, the IF-like protein FilP formed cytoskeletal structures in the model actinomycete Streptomyces coelicolor and was needed for normal growth and morphogenesis. Atomic force microscopy of living cells revealed that the FilP cytoskeleton contributed to mechanical fitness of the hyphae, thus closely resembling the function of metazoan IF. Together, the bioinformatic and experimental data suggest that an IF-like protein architecture is a versatile design that is generally present in bacteria and utilized to perform diverse cytoskeletal tasks.

Ultrasonographic features of superficial and nodular basal cell carcinoma.

AIM: To describe the ultrasonographic findings of surface and nodular basal cell skin cancer (BCC) using high frequency ultrasonography. MATERIALS AND METHODS: We examined 60 primary BCCs in different locations with the High Frequency Ultrasound (HFU) system DUB Skin Scanner using 75 MHz and 30 MHz probes. Epidermis, dermis, and depth of tumors spread in the region of interest (ROI) were measured. Visually unchanged, contralateral skin areas were examined as the control. Results: The surface BCC most often had elongated contours, clear margins and hypoechoic structure, while the nodular BCC had round or oval outlines and diffusely hypo-heterogeneous structure with clear margins. Sclerodermiform BCCs were visualized as hypoechoic areas of irregular shape penetrating in the dermis, with wavy fuzzy margins. The average thickness of the surface BCC in the US examination was 556.28±136.95 µ, the nodular BCC thickness was 2439.71±865.92 µ and the sclerodermiform thickness was 1500±325.33 µ. A statistically significant increase in the average thickness of tumors of the nodularand scleroderma forms was observed in comparison with the surface clinical variant (p<0.05). Hyperechoic inclusions were observed in 11% of the surface BCC's and in the 100% of the nodular BCC's. Their average number was 2±0.57 and 4±4.8, with the average area of 0.03±0.02 mm2 and 0.04±0.03 mm2 (p>0.05), respectively. In the surface BCC, they were mainly located along the periphery of the hypoechoic zones. In nodular BCC, the inclusions had a peripheral and combined (center and peripheral) distribution. CONCLUSIONS: Ultrasound allows differentiating BCC as diffuse-heterogeneous, hypoechoic, formations in the dermis with distinct contours. Depending on the clinical picture, they differ in form, depth of bedding, as well as in the quantitative ratio and distribution of the point hyperechoic structures in them.

Roles of curli, cellulose and BapA in Salmonella biofilm morphology studied by atomic force microscopy.

BACKGROUND: Curli, cellulose and the cell surface protein BapA are matrix components in Salmonella biofilms. In this study we have investigated the roles of these components for the morphology of bacteria grown as colonies on agar plates and within a biofilm on submerged mica surfaces by applying atomic force microscopy (AFM) and light microscopy. RESULTS: AFM imaging was performed on colonies of Salmonella Typhimurium grown on agar plates for 24 h and on biofilms grown for 4, 8, 16 or 24 h on mica slides submerged in standing cultures. Our data show that in the wild type curli were visible as extracellular material on and between the cells and as fimbrial structures at the edges of biofilms grown for 16 h and 24 h. In contrast to the wild type, which formed a three-dimensional biofilm within 24 h, a curli mutant and a strain mutated in the global regulator CsgD were severely impaired in biofilm formation. A mutant in cellulose production retained some capability to form cell aggregates, but not a confluent biofilm. Extracellular matrix was observed in this mutant to almost the same extent as in the wild type. Overexpression of CsgD led to a much thicker and a more rapidly growing biofilm. Disruption of BapA altered neither colony and biofilm morphology nor the ability to form a biofilm within 24 h on the submerged surfaces. Besides curli, the expression of flagella and pili as well as changes in cell shape and cell size could be monitored in the growing biofilms. CONCLUSION: Our work demonstrates that atomic force microscopy can efficiently be used as a tool to monitor the morphology of bacteria grown as colonies on agar plates or within biofilms formed in a liquid at high resolution.

Understanding the magnetic interaction between intrinsic defects and impurity ions in room-temperature ferromagnetic Mg1-xFexO thin films.

Understanding the nature and characteristics of the intrinsic defects and impurities in the dielectric barrier separating the ferromagnetic electrodes in a magnetic tunneling junction is of great importance for understanding the often observed 'barrier-breakdown' therein. In this connection, we present herein systematic experimental (SQUID and synchrotron-radiation-based x-ray absorption spectroscopy) and computational studies on the electronic and magnetic properties of Mg1-xFexO thin films. Our studies reveal: (i) defect aggregates comprised of basic and trimer units (Fe impurity coupled to 1 or 2 Mg vacancies) and (ii) existence of two competing magnetic orders, defect- and dopant-induced, with spin densities aligning anti-parallel if the trimer is present in the oxide matrix. These findings open up new avenues for designing tunneling barriers with high endurance and tunneling effect upon tuning the concentration/distribution of the two magnetic orders.

Disorder-induced room temperature ferromagnetism in glassy chromites.

We report an unusual robust ferromagnetic order above room temperature upon amorphization of perovskite [YCrO3] in pulsed laser deposited thin films. This is contrary to the usual expected formation of a spin glass magnetic state in the resulting disordered structure. To understand the underlying physics of this phenomenon, we combine advanced spectroscopic techniques and first-principles calculations. We find that the observed order-disorder transformation is accompanied by an insulator-metal transition arising from a wide distribution of Cr-O-Cr bond angles and the consequent metallization through free carriers. Similar results also found in YbCrO3-films suggest that the observed phenomenon is more general and should, in principle, apply to a wider range of oxide systems. The ability to tailor ferromagnetic order above room temperature in oxide materials opens up many possibilities for novel technological applications of this counter intuitive effect.

Magnetism of Amorphous and Nano-Crystallized Dc-Sputter-Deposited MgO Thin Films.

We report a systematic study of room-temperature ferromagnetism (RTFM) in pristine MgO thin films in their amorphous and nano-crystalline states. The as deposited dc-sputtered films of pristine MgO on Si substrates using a metallic Mg target in an O2 containing working gas atmosphere of (N2 + O2) are found to be X-ray amorphous. All these films obtained with oxygen partial pressure (PO2) ~10% to 80% while maintaining the same total pressure of the working gas are found to be ferromagnetic at room temperature. The room temperature saturation magnetization (MS) value of 2.68 emu/cm³ obtained for the MgO film deposited in PO2 of 10% increases to 9.62 emu/cm³ for film deposited at PO2 of 40%. However, the MS values decrease steadily for further increase of oxygen partial pressure during deposition. On thermal annealing at temperatures in the range 600 to 800 °C, the films become nanocrystalline and as the crystallite size grows with longer annealing times and higher temperature, MS decreases. Our study clearly points out that it is possible to tailor the magnetic properties of thin films of MgO. The room temperature ferromagnetism in MgO films is attributed to the presence of Mg cation vacancies.

Maghemite nanocrystal impregnation by hydrophobic surface modification of mesoporous silica.

Here, we report the design of a hybrid inorganic/organic mesoporous material through simultaneous pore engineering and hydrophobic surface modification of the intramesochannels to improve the uptake of superparamagnetic maghemite nanocrystals via impregnation techniques. The mesoporous material of the SBA-15 type was functionalized in situ with thiol organo-siloxane groups. Restricting the addition of the thiol organo-siloxane to 2 mol % yielded an inorganic/organic hybrid material characterized by large pores and a well-ordered hexagonal p6mm mesophase. The hydrophobic surface modification promoted the incorporation of 7.5 nm maghemite (gamma-Fe2O3) nanocrystals, prepared through temperature-controlled decomposition of iron pentacarbonyl in organic solvents. The hydrophobic, oleic acid capped superparamagnetic maghemite nanocrystals were incorporated into the porous network via wet impregnation from organic suspensions. Combining diffraction, microscopy, and adsorption data confirmed the uptake of the nanocrystals within the intramesochannels of the silica host. Magnetization dependencies on magnetic field at different temperatures show a constriction in the loop around the origin, which indicates immobilization of maghemite nanocrystals inside the thiol-functionalized silica host.