Layered TiO2: PVK nano-composite thin films for photovoltaic applications. TiO2: PVK nano-composite thin films.

The influence of the solvent used for spin-coating on the homogeneity of poly(N-vinylcarbazole) (PVK) films is investigated. Homogenous films are obtained only by the use of toluene, solution in tetrahydrofuran (THF) and chloroform results in radially oriented inhomogeneities and films prepared by use of N-methylpyrrolidone and dimethylacetamide show particle formation during spin-coating. Layered nano-composite thin films are prepared by spin-coating a PVK film on top of a nano-structured titanium dioxide ( TiO2) layer. The TiO2 thin films are prepared by a sol-gel process using an amphiphilic copolymer as structure-directing agent. Structural characterisation of the TiO2 :PVK nano-composite films is done by field emission scanning electron microscopy (FESEM) and grazing-incidence small-angle scattering (GISAXS). Bare TiO2 films are probed for comparison. Light is basically only absorbed in the ultraviolet regime and absorption slightly increases upon addition of PVK, which makes the layered TiO2 :PVK nano-composite thin films good candidates for UV photovoltaic devices. Furthermore, absorption remains stable over a period of several days.

In situ GISAXS investigation of gold sputtering onto a polymer template.

Microphase-separation structures in mixed diblock-triblock copolymer thin films are used for the incorporation of gold atoms inside the polymer matrix via sputtering of gold. Polystyrene (PS) spheres are arranged in a liquidlike type with a well defined nearest neighbor distance inside a polyisoprene matrix acting as a template for directing the gold atoms. Sputtering conditions are selected with a very low sputtering rate to avoid clustering in the atmosphere so that gold reaches the polymer surface in its atomic state. Due to the mobility of the gold atoms and the selective interaction with the PS parts of the microphase separation structure, gold is accumulated inside the polymer film in the PS spheres, as probed in situ with grazing incidence small-angle X-ray scattering (GISAXS). Nominally 4.3 A of gold is deposited, which by diffusion is spread out vertically over a thickness of 280 nm. UV-vis spectroscopy reveals a small blue shift for the gold sputtered polymer film. Atomic force microscopy proves the absence of gold clusters on the film surface. For low sputtering rate, GISAXS proves good sensitivity for gold migration inside the polymer film and opens new possibilities for studying polymer-metal interaction.

Aumento del daño en el ADN y estrés oxidativo en espermatozoides de pacientes con oligozoospermia idiopática y antecedentes de criptorquidismo / Extent of sperm DNA damage in spermatozoa from men examined for infertility. Relationship with oxidative stress

Background: Cryptorchidism and oligozoospermia are clinical conditions closely associated with impaired fertility. Oxidative stress and related sperm DNA damage have been identified as significant causes of male infertility. Aim: To determine the extent of sperm nuclear DNA damage in patients affected with idiopathic oligozoospermia or undescended testes and to examine its relationship with oxidative stress. Patients and methods: We studied 20 patients with idiopathic oligozoospermia and 18 with undescended testes (who previously underwent orchiopexy) and 25 normozoospermic healthy controls. All subjects underwent semen analysis. Sperm DNA damage was evaluated by the sperm chromatin structure assay/flow cytometry (SCSA-FCM) and by the dUTP-biotin nick end labeling (TUNEL) assay. Levels of reactive oxygen species (ROS) and total antioxidant capacity (TAC) were assessed by a chemiluminescence assay. Results: DFI (percentage of sperm with denatured DNA) values and percentage of TUNEL positive cells were significantly greater in patients with oligozoospermia (DFI: 28.8±5.6; TUNEL+: 26.9±3.0) or cryptorchidism (DFI: 26.4±10.1; TUNEL+: 29.1±3.9), compared with controls (DFI: 7.1±0.9; TUNEL+: 14.2±1.2). Similarly, both groups of patients had significantly higher (p <0.01) levels of ROS. TAC levels did not differ between control and patient groups, suggesting that the DNA damage occurs before spermiation. Conclusions: Sperm DNA damage is significantly increased in men with idiopathic oligozoospermia and in cryptorchid subjects. The finding of increased ROS levels may indicate that seminal oxidative stress may be involved in the pathogenesis of sperm DNA damage in these patients.