Programming nanostructured soft biological surfaces by atomic layer deposition

Here, we present the first successful attempt to programme the surface properties of nanostructured soft biological tissues by atomic layer deposition (ALD). The nanopatterned surface of lotus leaf was tuned by 3-125 nm TiO2 thin films. The lotus/TiO2 composites were studied by SEM-EDX, XPS, Raman, TG-DTA, XRR, water contact angle and photocatalysis measurements. While we could preserve the superhydrophobic feature of lotus, we managed to add a new property, i.e. photocatalytic activity. We also explored how surface passivation treatments and various ALD precursors affect the stability of the sensitive soft biological tissues. As we were able to gradually change the number of nanopatterns of lotus, we gained new insight into how the hollow organic nanotubes on the surface of lotus influence its superhydrophobic feature

Micronutrient status in lactating mothers before and after introduction of fortified flour: cross-sectional surveys in Maela refugee camp

Background Deficiency of micronutrients is common in refugee populations. Objectives Identify deficiencies and whether provided supplements and wheat flour fortified with 10 micronutrients impacts upon status among breast-feeding women from Maela refugee camp. Methods Two sequential cross-sectional studies were conducted in different groups of lactating mothers at 12 weeks postpartum. The first survey was before and the second 4-5 months after micronutrient fortified flour (MFF) had been provided to the camp (in addition to the regular food basket). Iron status and micronutrients were measured in serum, whole blood, and in breast milk samples. Results Iron and zinc deficiency and anemia were highly prevalent while low serum retinol and thiamine deficiency were rarely detected. Iron and zinc deficiency were associated with anemia, and their proportions were significantly lower after the introduction of MFF (21 vs. 35% with soluble transferrin receptor (sTfR)>8.5 mg/L, P = 0.042, and 50 vs. 73% with serum zinc<0.66 mg/L, P = 0.001). Serum sTfR, whole-blood thiamine diphosphate (TDP) and serum β-carotene were significant predictors (P<0.001) of milk iron, thiamine and β-carotene, respectively. Lower prevalence of iron deficiency in the MFF group was associated with significantly higher iron and thiamine in breast milk. Conclusions High whole-blood TDP and breast milk thiamine reflected good compliance to provided thiamine; high prevalence of iron deficiency suggested insufficient dietary iron and low acceptance to ferrous sulfate supplements. MFF as an additional food ration in Maela refugee camp seemed to have an effect in reducing both iron and zinc deficiency postpartum. © Springer-Verlag 2012

Entwicklung von elektronenleitenden Schutzschichten gegen die anodische Auflösung von Stromsammlern in neuartigen „Dual-Ionen“-Energiespeichern

In times of the energy revolution, electrochemical storage systems gain in importance to balance the fluctuating electricity generation from renewable energies. Dual-ion batteries represent a cost-efficient and environmentally friendly concept for the application as stationary and local energy storage system, because graphite is used as the only material for both electrodes. In these batteries cations and anions of a novel electrolyte intercalate simultaneously into the graphite electrodes. This reversible principle provides a cell voltage above 5 V. However the electrolyte anions (bis(trifluoromethanesulfonyl)imide – TFSI-) do not form a passivation layer in contact with the aluminum current collector. Therefore further oxidation of the metal surface is not prevented and leads to a degradation of the current collector. Since even noble metals like gold are not sufficiently electrochemically stable at such high potentials, the aim is to develop an electronically conductive ceramic layer to prevent the anodic dissolution of the aluminum current collector. The applied sol-gel process is easily scalable and enables the deposition of the selected oxide ceramics using a few coating steps. Necessarily, the deposited thin films need to be thermally treated at a temperature below the melting temperature of aluminum. Therefore aluminum doped zinc oxide (ZnO:Al) and lanthanum doped strontium titanate (SLT) were selected as materials since they crystallize at low temperatures. The developed sol synthesis routes yielded appropriate sols with good long-term stability and film formation properties. Even on the rough surface of aluminum substrates homogenous coatings were possible, after optimizing the wettability of the surface by a pretreatment. Calcined thin films of both materials showed single phase crystal structures and a crack-free morphology of densely packed particles. However the conductivity of SLT was too low for the application as artificial protective coating and this material was not considered further on. Electrochemical measurements showed a significantly reduced anodic dissolution of aluminum for the protected current collector. Furthermore it was observed, that the protection effect increased with the homogeneity of the protection layers. In additional tests, aluminum plates were used to avoid typical cracking effects of the brittle ceramic protection layer at the edge of the samples due to mechanical stress. Using this setup, the electrochemical stability of ZnO:Al and the protection effect of the layer was demonstrated by a 120 times reduced anodic dissolution. Herein the occurrence of only few corrosion spots indicated that the corrosive attack of TFSI anions on the aluminum surface was mainly prevented. In conclusion, the developed protection layer will contribute to an improved dual-ion cell by maintaining the contact of the aluminum current collector to the positive electrode

Development of Corrosion Protection Layers for Current Collectors in Dual-Ion Batteries

In novel dual-ion cells graphite intercalation compounds will be used for both electrodes. The consequent intercalation of both, cations and anions, in the respective electrodes enables voltage values above 5 V. Established liquid electrolytes do not resist these conditions. Therefore those are replaced by ionic liquids having a good electrochemical performance also at higher temperatures. Now the challenge is to overcome the corrosion of the aluminium current collector triggered by fluorinated anions like bis(trifluoromethylsulfonyl)imide (TFSI). Our approach to protect the metal against corrosion is the deposition of an only electronically conductive, defect free and mechanically as well as electrochemically stable layer. Different material compositions in the range of oxidic ceramics are tested, first of all doped semiconductors, e. g. alumina doped zinc oxide. The preparation is based on a sol-gel route combined with several wet-chemical coating methods, because these are easily adjustable to different substrate sizes. Cyclic voltammetry is used to investigate the electrochemical performance of the protection layers on aluminium substrates

Processing of Al-doped ZnO protective thin films on aluminum current collectors for lithium ion batteries

In this work, aluminum current collectors for Li-ion batteries were coated with protection layers made of Al-doped ZnO (ZnO:Al) to prevent the corrosion of aluminum caused by bis(trifluoromethylsulfonyl)imide (TFSI−) at 5 V. These thin films of ~ 100 nm thickness were prepared with a facile and scalable sol-gel coating process with subsequent heat treatment by rapid thermal processing (RTP) at 500 °C. The ZnO:Al films exhibited the usual hexagonal phase, a homogeneous morphology and a sufficient electronic conductivity. In electrochemical testing, chronoamperometry demonstrated that the protection layer reduces the corrosion of the aluminum current collector 120 times compared with conventional unprotected aluminum

Development of electronically conductive corrosion protection layers for current collectors in innovative dual-ion cells

Due to the intercalation of both cations and anions in this new type of battery, the voltage can reach values above 5 V. This can lead to the corrosion of the aluminum current collector if the electrolyte containing fluorinated anions is used. However, the advantages of ionic liquid over organic solvent based solutions overbalance and there is no useful option to replace them. Therefore it is necessary to protect the aluminum current collector with an electronically conductive, defect free and stable coating. Several coating methods and material compositions were tested and the performance of the coatings are investigated in long term cell tests with cyclic voltammetry

Anodic Dissolution in Dual-Ion Batteries: Development of Protection Layers for Current Collectors

One aspect of the current research on lithium ion batteries is the increase of the cell voltage to improve the energy density. In innovative dual-ion cells, graphite intercalation compounds are used for both electrodes. Consequently, a simultaneous intercalation of lithium ions into the anode and the corresponding salt anions into the cathode is possible and enables voltage values above 5 V vs. Li/Li+. Established liquid electrolytes, consisting of carbonates and lithium hexafluorophosphate, do not resist these conditions. Therefore, we replace this mixture by ethyl methanesulfonate and organic lithium salts, having a good electrochemical performance also at higher temperatures. Now, it is the challenge to overcome the anodic dissolution of the aluminum current collector triggered by fluorinated anions like bis(trifluoromethylsulfonyl)imide (TFSI-). Our approach to protect the metal against anodic dissolution is the deposition of an only electronically conductive, defect-free and mechanically as well as electrochemically stable layer. We test different material compositions in the range of oxidic ceramics. First of all semiconductors like alumina doped zinc oxide show promising results to meet the requirements. The preparation is based on a sol-gel route combined with several wet-chemical coating methods, because these are easily adjustable to different substrate dimensions. Ceramic thin layers of around 100 nm thickness are deposited on aluminum foil and mainly investigated by scanning electron microscopy, X-ray diffraction and secondary ion mass spectrometry. Additionally, we present conductivity measurements and the electrochemical performance tested with cyclic voltammetry