Considerable Enhancement of Field Emission of SnO2Nanowires by Post-Annealing Process in Oxygen at High Temperature

The field emission properties of SnO2nanowires fabricated by chemical vapor deposition with metallic catalyst-assistance were investigated. For the as-fabricated SnO2nanowires, the turn-on and threshold field were 4.03 and 5.4 V/μm, respectively. Considerable enhancement of field emission of SnO2nanowires was obtained by a post-annealing process in oxygen at high temperature. When the SnO2nanowires were post-annealed at 1,000 °C in oxygen, the turn-on and threshold field were decreased to 3.77 and 4.4 V/μm, respectively, and the current density was increased to 6.58 from 0.3 mA/cm2at the same applied electric field of 5.0 V/μm

The estimation of weight-loss programmes and using of slimming preparations among young women

Celem pracy była ocena rodzaju metod stosowanych w celu utraty masy ciała oraz zachowań związanych ze stosowaniem suplementów wspomagających odchudzanie wśród młodych kobiet. Badania przeprowadzono metodą ankietową w okresie późnojesiennym 2009 roku wśród 300 studentek Zachodniopomorskiego Uniwersytetu Technologicznego w Szczecinie. Analizując uzyskane wyniki stwierdzono, że większość badanych kobiet odchudzała się kiedykolwiek, wiele z nich w ostatnim półroczu. Kobiety podejmowały decyzję o odchudzaniu niezależnie od wartości wskaźnika BMI, co może wskazywać na zaburzone postrzeganie własnego ciała. W celu redukcji masy ciała badane stosowały różnego rodzaju metody, najczęściej była to modyfikacja sposobu żywienia i stosowanie preparatów wspomagających odchudzanie. Wśród stosowanych preparatów najczęściej wymieniane były środki hamujące apetyt lub przyspieszające spalanie tłuszczu i wzmagające termogenezę. Wiele kobiet podczas stosowania środków wspomagających odchudzanie zmieniła też swój sposób odżywiania, nie zawsze były to jednak zmiany prawidłowe, co wskazuje na brak wiedzy badanych dotyczącej zasad prawidłowego żywienia (mających zastosowanie także podczas odchudzania), lub na zwolnienie ze stosowania się do tych zasad podczas stosowania środków wspomagających odchudzanie. Obserwowane zachowania żywieniowe badanych kobiet mogą przyczynić się do rozwoju chorób na tle nieprawidłowego żywienia w wieku średnim, mogą także skutkować rozwojem zaburzeń odżywiania w niedalekiej przyszłości.The aim of this study was to evaluate the range of weight-loss programmes and behaviours associated with the use of slimming supplements observed among young women. The study in the form of questionnaire survey was carried out among 300 female students of the West Pomeranian University of Technology in Szczecin during late autumn 2009. Analysis of the responses revealed that most of the women had tried to lose weight ever during their lives, many of them within the past six months. The respondents undertook weight-loss programmes regardless of their BMI, which may imply a disturbed perception of one’s own body. In order to reduce body weight, the women applied various methods, usually modified diet and use slimming preparations. Among the preparations, the women most frequently mentioned appetite inhibitors or fat burning and thermogenesis enhancers. During the use of slimming enhancers, many women also changed their dietary patterns; such alterations were not necessarily nutritionally correct, due to either lack of knowledge on the principles of proper nutrition (which apply also during a weight-loss action) or due to abandoning these rules when applying the slimming aids. The observed dietary behaviours of the women may underlie serious nutrition-related health problems when they reach their middle age, but can also result in nutritional disorders in the near future

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

Flower-like ZnO Nanostructures Local Surface Morphology and Chemistry

This work presents the results of comparative studies using complementary methods, such as scanning electron microscopy (SEM), X-ray photoemission spectroscopy (XPS), and thermal desorption spectroscopy (TDS) to investigate the local surface morphology and chemistry of flower-like ZnO nanostructures synthesized by the thermal oxidation technique on native Si/SiO2 substrates. SEM studies showed that our flower-like ZnO nanostructures contained mostly isolated and irregular morphological low-dimensional forms, seen as rolled-up floss flowers, together with local, elongated, complex stalks similar to Liatris flowers, which contained joined short flosses in the form of nanodendrites. Beyond this, XPS studies showed that these nanostructures exhibited a slight surface nonstoichiometry, mostly related to the existence of oxygen-deficient regions, combined with strong undesired C surface contamination. In addition, the TDS studies showed that these undesired surface contaminations (including mainly C species and hydroxyl groups) are only slightly removed from the surface of our flower-like ZnO nanostructures, causing an expected modification of their nonstoichiometry. All of these effects are of great importance when using our flower-like ZnO nanostructures in gas sensor devices for detecting oxidizing gases because surface contamination leads to an undesired barrier for toxic gas adsorption, and it can additionally be responsible for the uncontrolled sensor aging effect

Novel insight on the local surface properties of ZnO nanowires

Novel insight on the local surface properties of ZnO nanowires (NW) deposited by the evaporation-condensation method on Ag-covered Si substrates is proposed, based on the results of comparative studies by using the scanning electron microscopy (SEM), x-ray photoemission spectroscopy (XPS) and thermal desorption spectroscopy (TDS) methods, respectively. SEM studies showed that ZnO nanowires (nanoribbons) are mostly isolated and irregular, having the average length μm and the average at the level of tens nm, respectively. Our XPS studies confirmed their evident surface non-stoichiometry, combined with strong C surface contaminations, which was related to the existence of oxygen-deficient regions. Additionally, TDS studies showed that undesired surface contaminations (including C species and hydroxyl groups) on the surface of ZnO NWs can be removed almost completely, leading to an increase of the final non-stoichiometry. Both effects are of great importance when using ZnO NWs for the detection of oxidizing gases, because the undesired C contaminations (including C-OH species) play the role of undesired barriers for the gas adsorption, especially at the low working temperature, additionally affecting the uncontrolled sensor ageing effect

Surface chemistry of SnO2 nanowires on Ag-catalyst-covered Si substrate studied using XPS and TDS methods

In this paper we investigate the surface chemistry, including surface contaminations, of SnO2 nanowires deposited on Ag-covered Si substrate by vapor phase deposition (VPD), thanks to x-ray photoelectron spectroscopy (XPS) in combination with thermal desorption spectroscopy (TDS). Air-exposed SnO2 nanowires are slightly non-stoichiometric, and a huge amount of C contaminations is observed at their surface. After the thermal physical desorption (TPD) process, SnO2 nanowires become almost stoichiometric without any surface C contaminations. This is probably related to the fact that C contaminations, as well as residual gases from air, are weakly bounded to the crystalline SnO2 nanowires and can be easily removed from their surface. The obtained results gave us insight on the interpretation of the aging effect of SnO2 nanowires that is of great importance for their potential application in the development of novel chemical nanosensor devices