Surface properties of SnO2 nanolayers prepared by spin-coating and thermal oxidation.

In this work, comparative studies of the surface morphology and surface chemistry of SnO2 nanolayers prepared by spin coating with subsequent thermal oxidation (SCTO) in the temperature range of 400-700 °C using scanning electron microscopy (SEM), atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS) methods, are presented. The SEM images show that SCTO SnO2 nanolayers contain partly connected irregular structures strongly dependent on the final oxidation temperature, with interconnected single grains of longitudinal shape and size, resulting in a flatter surface morphology with respect to the commonly used three-dimensional (3D) SnO2 thin films. In turn, AFM studies additionally confirm that SCTO SnO2 nanolayers after post-oxidation annealing at higher temperatures contain isolated grains of average lateral dimensions in the range of 20-50 nm having a rather flat surface morphology of average surface roughness defined by the root mean square factor at the level of ∼2 nm. From the XPS experimental research it can be concluded that, for our SCTO SnO2 samples, a slight surface nonstoichiometry defined by the relative [O]/[Sn] concentration at the level of 1.8-1.9 is observed, also depending on the final post-oxidation temperature, being an evident contradiction to recently published literature using x-ray diffraction data. Moreover, XPS experiments show that there is also a permanent small amount of carbon contamination present at the surface of internal grains of our SCTO SnO2 nanolayers, creating an undesired potential barrier for interactions with gaseous species when they are used as the active materials for gas sensing devices.

Bottle-brush-shaped heterostructures of NiO-ZnO nanowires: growth study and sensing properties.

We present here heterostructured ZnO-NiO nanowires (NWs), constituted by a core of single crystalline ZnO NWs, covered by poly-crystalline NiO nanorods (NRs). The bottle-brush shape was investigated by scanning electron microscopy and transmission electron microscope, confirming that a columnar growth of NiO occurred over the ZnO core, with a preferred orientation of NiO over ZnO NWs. The heterostructured devices are proposed for gas sensing application. Bare ZnO NWs and heterostructured sensors with two different thicknesses of NiO poly-crystalline NRs were analysed for acetone, ethanol, NO2 and H2 detection. All sensors maintained n-type sensing mechanism, with improved sensing performance for lower thickness of NiO, due to high catalytic activity of NiO. The sensing dynamic is also strongly modified by the presence of heterojunction of NiO/ZnO, with a reduction of response and recovery times towards ethanol and acetone at 400 °C.

Nickel oxide nanowires: vapor liquid solid synthesis and integration into a gas sensing device.

In the field of advanced sensor technology, metal oxide nanostructures are promising materials due to their high charge carrier mobility, easy fabrication and excellent stability. Among all the metal oxide semiconductors, nickel oxide (NiO) is a p-type semiconductor with a wide band gap and excellent optical, electrical and magnetic properties, which has not been much investigated. Herein, we report the growth of NiO nanowires by using the vapor liquid solid (VLS) technique for gas sensing applications. Platinum, palladium and gold have been used as a catalyst for the growth of NiO nanowires. The surface morphology of the nanowires was investigated through scanning electron microscopy to find out which catalyst and growth conditions are best for the growth of nanowires. GI-XRD and Raman spectroscopies were used to confirm the crystalline structure of the material. Different batches of sensors have been prepared, and their sensing performances towards different gas species such as carbon monoxide, ethanol, acetone and hydrogen have been explored. NiO nanowire sensors show interesting and promising performances towards hydrogen.

Visible electroluminescence from a ZnO nanowires/p-GaN heterojunction light emitting diode.

In the current paper we apply catalyst assisted vapour phase growth technique to grow ZnO nanowires (ZnO nws) on p-GaN thin film obtaining EL emission in reverse bias regime. ZnO based LED represents a promising alternative to III-nitride LEDs, as in free devices: the potential is in near-UV emission and visible emission. For ZnO, the use of nanowires ensures good crystallinity of the ZnO, and improved light extraction from the interface when the nanowires are vertically aligned. We prepared ZnO nanowires in a tubular furnace on GaN templates and characterized the p-n ZnO nws/GaN heterojunction for LED applications. SEM microscopy was used to study the growth of nanowires and device preparation. Photoluminescence (PL) and Electroluminescence (EL) spectroscopies were used to characterize the heterojunction, showing that good quality of PL emission is observed from nanowires and visible emission from the junction can be obtained from the region near ZnO contact, starting from onset bias of 6V.

Thermally oxidized zinc oxide nanowires for use as chemical sensors.

Zinc oxide (ZnO) mat-based conductometric devices were fabricated using a thermal oxidation technique. A metallic zinc layer was deposited on the alumina transducer and then oxidized in a controlled atmosphere, in order to obtain ZnO nanostructures. Two different batches of sensors have been prepared, and their sensing performances have been evaluated towards oxidizing and reducing gases. Functional measurements showed very good sensing performances towards ethanol and acetone at 500 °C, and NO2 at 200 °C, indirectly confirming the n-type behaviour of the material. The influence of the humidity on the response has been explored. In practical conditions the interference of humidity is very small, and could be neglected in many applications. Simultaneous measurements on different devices from the same batch confirm the high reproducibility of the response within the batch.

Co3O4/ZnO nanocomposites: from plasma synthesis to gas sensing applications.

Herein, we describe the design, fabrication and gas sensing tests of p-Co(3)O(4)/n-ZnO nanocomposites. Specifically, arrays of (001) oriented ZnO nanoparticles were grown on alumina substrates by plasma enhanced-chemical vapor deposition (PECVD) and used as templates for the subsequent PECVD of Co(3)O(4) nanograins. Structural, morphological and compositional analyses evidenced the successful formation of pure and high-area nanocomposites with a tailored overdispersion of Co(3)O(4) particles on ZnO and an intimate contact between the two oxides. Preliminary functional tests for the detection of flammable/toxic analytes (CH(3)COCH(3), CH(3)CH(2)OH, NO(2)) indicated promising sensing responses and the possibility of discriminating between reducing and oxidizing species as a function of the operating temperature.

Deregulation of Aurora kinase gene expression in human testicular germ cell tumours.

The Aurora kinases regulate chromosome segregation and cytokinesis, and alterations in their expression associate with cell malignant transformation. In this study, we demonstrated by qRT-PCR analysis of 14 seminomas that Aurora-A mRNA was, with respect to control tissues, augmented in five of 14 tumour tissues by 2.17 +/- 0.30 fold (P < 0.05) and reduced in 9 to 0.38 +/- 0.10 (P < 0.01). Aurora-B mRNA was increased in 11 tumour tissues by 4.33 +/- 0.82 fold (P < 0.01) and reduced in 3 to 0.41 +/- 0.11 fold. Aurora-C mRNA was reduced to 0.20 +/- 0.32 fold (P < 0.01) in 13 seminomas and up-regulated in one case. Western blot experiments, performed on protein extracts of nine seminomas and six normal testes, showed an up-regulation of Aurora-B protein by 10.14 +/- 3.51 fold (P < 0.05), while Aurora-A protein was found increased in four seminomas by 2.16 +/- 0.43 (P < 0.05), unchanged in three and reduced in two tumour tissues. Aurora-C protein was increased by 9.2 +/- 2.90 fold (P < 0.05), suggesting that post-transcriptional mechanisms modulate its expression. In conclusion, we demonstrated that expression of Aurora kinases is deregulated in seminomas, suggesting that they may play a role in the progression of testicular cancers.

Recombination dynamics of deep defect states in zinc oxide nanowires.

The recombination dynamics of defect states in zinc oxide nanowires has been studied by developing a general expression for time-resolved photoluminescence intensity based on a second-order approximation for the radiative and non-radiative recombination rates. The model allows us to determine the parameters that characterize the recombination from deep defect states (defect concentration, unimolecular lifetime and bimolecular coefficient) through multi-fitting analysis of time-resolved photoluminescence measurements. Analyses conducted on zinc oxide nanowires gave deep state concentrations of the order of 10(18) cm(-3) and unimolecular lifetimes and bimolecular recombination coefficient comparable to those typical of interband recombination in direct gap semiconductors. The consistency of a 'two-channel decay' model (double exponential decay) has been tested by means of a similar analysis procedure. The results suggest that double exponential fitting of time-resolved photoluminescence data of zinc oxide nanowires may be just a mere phenomenological tool which does not reflect the real recombination dynamics of the visible emission band.

Effect of human alpha-fetoprotein on native and in vitro-stimulated NK activity.

We have examined the effect of human alpha-fetoprotein (h-alpha FP), at concentrations ranging from the physiological to pathological circulating levels, on the native and alpha IFN- and IL2-boosted NK activity of normal peripheral blood lymphocytes (PBL). The cytotoxic function of unstimulated PBL was unchanged after a 16 hr incubation with 200 to 8000 ng/ml h-alpha FP. By contrast, this treatment significantly reduced the responsiveness of PBL to the NK-enhancer factors IFN and Interleukin 2. Optimal inhibition was observed when cells were pre-incubated with h-alpha FP before being stimulated with IFN. The sensitivity of PBL to the h-alpha FP mediated inhibition was restricted to the very early times (30 min) of incubation with the stimulating agents.

Immunological studies in patients with mumps orchitis.

Seventy patients with mumps orchitis were investigated. Serological tests for antitesticular antibodies, using four different techniques showed positive results in 25 patients. Antivirus antibodies were detected and they reached higher values during the remission period of acute cases. Delayed hypersensitivity was studied by means of skin tests using homologous antigenic material. Several patients gave definite positive reactions. Testicular biopsies performed in some patients showed a histological picture similar to that obtained in experimental human or animal auto- or iso-sensitization. All patients in whom testicular damage was present also showed positive skin tests, ascertained by histology of the site of reaction, but none of them exhibited circulating antibodies in meaningful titers. The skin hypersensitivity suggest some correlation between this type of reaction and the development of the testicular lesions as shown in several other diseases in which an immune mechanism could be involved.

Immunologic response to A and B erythrocytic antigen.

Immunologic response to A and B erythrocytic antigen stimulation was studied in patients with pemphigus, in patients with systemic lupus erythematosus (SLE), and in normal subjects. Patients with pemphigus and normal subjects demonstrated a similar specific response (isohemagglutinins). A comparison between patients with pemphigus and SLE showed higher titers in the latter. Intercellular antibody titers increased after stimulation; corresponding titers were unaffected by isohemagglutinin absorption. Direct immunofluorescent studies showed IgG deposits in the intercellular spaces of the skin of the patients with pemphigus. However, C3 was found in the same sites in only three cases of pemphigus erythematosus. Immunofluorescent studies for IgG at the basal membrane were positive in only two cases of pemphigus erythematosus. Immunologic response of patients with pemphigus was similar to that of controls; however, it differed from that of patients with SLE.