Effects of hydroxylation and silanization on the surface properties of ZnO nanowires.

Silanization is commonly used to form bonds between inorganic materials and biomolecules as a step in the surface preparation of solid-state biosensors. This work investigates the effects of silanization with amino-propyldiethoxymethylsilane on hydroxylated sidewalls of zinc oxide (ZnO) nanowires (NWs). The surface properties and electrical characteristics of NWs are analyzed by different techniques after their hydroxylation and later silanization. Contact angle measurements reveal a stronger hydrophobic behavior after silanization, and X-ray photoelectron spectroscopy (XPS) results show a reduction of the surface dipole induced by the replacement of the hydroxyl group with the amine terminal group. The lower work function obtained after silanization in contact potential measurements corroborates the attenuation of the surface dipole observed in XPS. Furthermore, the surface band bending of NWs is determined from surface photovoltage measurements upon irradiation with UV light, yielding a 0.5 eV energy in hydroxylated NWs, and 0.18 eV, after silanization. From those results, a reduction in the surface state density of 3.1 × 10(11) cm(-2) is estimated after silanization. The current-voltage (I-V) characteristics measured in a silanized single NW device show a reduction of the resistance, due to the enhancement of the conductive volume inside the NW, which also improves the linearity of the I-V characteristic.

Conducting properties of nearly depleted ZnO nanowire UV sensors fabricated by dielectrophoresis.

ZnO nanowires (NWs) with different radii (rNW) have been aligned between pre-patterned electrodes using dielectrophoresis (DEP) for the fabrication of high gain UV sensors. The DEP conditions (voltage amplitude and frequency) and electrode material, geometry and size were optimized to enhance the efficiency during the DEP process. To understand the alignment mechanism of the ZnO NWs, the dielectrophoretic force (FDEP) was analyzed as a function of the DEP conditions and NW dimensions. These studies showed that the DEP alignment process tends to trap NWs with a smaller radius. The effects of NW size on device performance were analyzed by means of I-V measurements in darkness and under illumination (200 nm < λ < 600 nm). In darkness, the NW resistance increases as rNW decreases due to the reduction of the conduction volume, until saturation is reached for rNW < 65 nm. On the other hand, the NW spectral photoresponse shows high values around 10(8) A W(-1) (measured at 5 V and λ < 370 nm) and follows a linear trend as a function of the NW cross section. In addition, the cut-off wavelength depends on rNW, presenting a clear blue-shift for NWs with a lower radius (rNW < 50 nm). Transient photoresponse studies show that NWs with lower radii have longer rise times and shorter decay times mainly due to surface trapping effects. Regardless of NW size, passivation of the surface using a dielectric capping layer of SiO2 reduces the dynamic range of the photoresponse due to a strong increase of the dark current.

[Passive smoking as a cerebrovascular risk factor]. / El fumador pasivo como factor de riesgo cerebrovascular.

INTRODUCTION: Stroke is one of the main causes of morbidity and mortality in developed countries today. Smoking is a risk factor that is associated with arteriosclerotic disease. AIM: To evaluate the risk of having a stroke associated to both active and passive smoking in a case-control study. PATIENTS AND METHODS: A case-control study was conducted which included 151 stroke patients who were admitted to hospital in the Neurology Service at the Hospital General Universitario in Alicante over a 12-month period. The control group (302) was obtained from patients who visited the emergency department at the hospital with no history of strokes and who reported clinical signs and symptoms that were not compatible with a stroke. The cases and controls were paired according to age and sex, including two controls of the same sex and whose ages were within a year of that of each case which was obtained. RESULTS: The mean age of the patients was 70.6 years (range: 59-81 years). Males predominated in the sample (57.6%). Stroke patients had a significantly higher percentage of hypertension, peripheral arterial disease, heart disease and dyslipidemia than the control group. The most frequently affected vascular territory was the carotid (33.8%). The most frequent presenting symptom of the stroke was motor syndrome together with language disorders (39.4%). The risk of suffering a stroke associated to active smoking was 1.40 (CI 95% = 0.91-2.15) and in the case of passive smoking it was 1.45 (CI 95% = 0.82-2.58). CONCLUSIONS: The findings from this study suggest there is a relevant association between environmental exposure to tobacco smoke and increased vascular risk (which confirms other results that have been published in the literature) and stress how important it is for non-smokers to find smoke-free zones.

El fumador pasivo como factor de riesgo cerebrovascular / Passive smoking as a cerebrovascular risk factor

El ictus es actualmente una de las principales causas de morbimortalidad en los países desarrollados.El tabaco es un factor de riesgo que está relacionado con la enfermedad arterioesclerótica. Objetivo. Valorar el riesgo de presentación de ictus asociado al tabaquismo tanto activo como pasivo en un estudio de casos y controles. Pacientes y métodos.Se realizó un estudio de casos y controles en el que se incluyó a 151 pacientes con ictus que fueron ingresados en el Servicio de Neurología del Hospital General Universitario de Alicante durante un período de 12 meses. El grupo control (302 sujetos) se obtuvo de pacientes que acudieron a urgencias del hospital sin antecedentes de ictus y que referían una clínica no compatible con un ictus. Los casos y controles se aparearon por edad y sexo, incluyendo dos controles del mismo sexo y ± un año que cada caso obtenido. Resultados. La edad media de los pacientes fue de 70,6 años (rango: 59-81 años). El 57,6% correspondíaa varones. Los pacientes con ictus tenían de forma significativa un porcentaje mayor de hipertensión, arteriopatía periférica, cardiopatía y dislipemia que el grupo control. El territorio vascular más afectado fue el carotídeo (33,8%). La clínica de presentación más frecuente del ictus fue el síndrome motor junto con alteración del lenguaje, con un 39,4%. El riesgode ictus asociado al tabaquismo activo fue de 1,40 (IC 95% = 0,91-2,15) y al tabaquismo pasivo fue de 1,45 (IC 95% = 0,82-2,58). Conclusión. Los datos obtenidos en este estudio sugieren una asociación relevante entre la exposición ambiental al tabaco y un aumento del riesgo vascular, confirmando otros trabajos publicados, y recalcan la importancia de que los no fumadoresencuentren espacios libres de humo

Introduction. Stroke is one of the main causes of morbidity and mortality in developed countries today. Smoking is a risk factor that is associated with arteriosclerotic disease. Aim. To evaluate the risk of having a stroke associated to both active and passive smoking in a case-control study. Patients and methods. A case-control study was conducted which included151 stroke patients who were admitted to hospital in the Neurology Service at the Hospital General Universitario in Alicante over a 12-month period. The control group (302) was obtained from patients who visited the emergency department at the hospital with no history of strokes and who reported clinical signs and symptoms that were not compatible with a stroke. Thecases and controls were paired according to age and sex, including two controls of the same sex and whose ages were within a year of that of each case which was obtained. Results. The mean age of the patients was 70.6 years (range: 59-81 years).Males predominated in the sample (57.6%). Stroke patients had a significantly higher percentage of hypertension, peripheral arterial disease, heart disease and dyslipidemia than the control group. The most frequently affected vascular territory wasthe carotid (33.8%). The most frequent presenting symptom of the stroke was motor syndrome together with language disorders (39.4%). The risk of suffering a stroke associated to active smoking was 1.40 (CI 95% = 0.91-2.15) and in the case of passive smoking it was 1.45 (CI 95% = 0.82-2.58). Conclusions. The findings from this study suggest there is a relevantassociation between environmental exposure to tobacco smoke and increased vascular risk (which confirms other results that have been published in the literature) and stress how important it is for non-smokers to find smoke-free zones

Accidente Cerebrovascular