Free-standing TiO2 nanograssy tubular hybrid membrane for polysulfide trapping in Li-S battery.

During the growth of anodic TiO2 nanotubes with a high layer thickness of greater than 20 µm, "nanograss" structures are typically formed on the outermost surface. This happens due to the fact that the engraving of the oxide tubes arises during prolonged exposure to an F- ion containing electrolyte. These TiO2 nanotubular layers have a high aspect ratio with astonishing bundles of nanograss structures on the tube top and especially a high surface area with anatase crystallites in the tubes. By two-step anodization in synergy with the hybridization of a rubber polymer binder, freestanding nanotubular layers consisting of nanograssy surfaces with nano-crystalline particles in the tubes were successfully obtained. Under the highly efficient polysulfide trapping and electrolyte perturbation, this nanotubular hybrid membrane could deliver an enriched performance with a capacity of 618 mA h g-1 after 100 cycles at 0.1C in Li-S batteries.

Multimodal Capturing of Polysulfides by Phosphorus-Doped Carbon Composites for Flexible High-Energy-Density Lithium-Sulfur Batteries.

The widespread adoption of Li-ion batteries is currently limited by their unstable electrochemical performance and high flammability under mechanical deformation conditions and a relatively low energy density. Herein, high-energy-density lithium-sulfur (Li-S) batteries are developed for applications in next-generation flexible electronics and electric vehicles with long cruising distances. Freestanding high-S-loading carbon nanotubes cathodes are assembled with a phosphorus (P)-doped carbon interlayer coated on commercial separators. Strategies for the active materials and structural design of both the electrodes and separators are highly efficient for immobilizing the lithium polysulfides via multimodal capturing effects; they significantly improve the electrochemical performance in terms of the redox kinetics and cycling stability. The foldable Li-S cells show stable specific capacities of 850 mAh g-1 over 100 cycles, achieving high gravimetric and volumetric energy densities of 387 Wh kgcell -1 and 395 Wh Lcell -1 , respectively. The Li-S cells show highly durable mechanical flexibilities under severe deformation conditions without short circuit or failure. Finally, the Li-S battery is explored as a light-weight and flexible energy storage device aboard airplane drones to ensure at least fivefold longer flight times than traditional Li-ion batteries. Nanocarbon-based S cathodes and P-doped carbon interlayers offer a promising solution for commercializing rechargeable Li-S batteries.

Vertically Aligned Binder-Free TiO2 Nanotube Arrays Doped with Fe, S and Fe-S for Li-ion Batteries.

Vertically aligned Fe, S, and Fe-S doped anatase TiO2 nanotube arrays are prepared by an electrochemical anodization process using an organic electrolyte in which lactic acid is added as an additive. In the electrolyte, highly ordered TiO2 nanotube layers with greater thickness of 12 µm, inner diameter of approx. 90 nm and outer diameter of approx. 170 nm are successfully obtained. Doping of Fe, S, and Fe-S via simple wet impregnation method substituted Ti and O sites with Fe and S, which leads to enhance the rate performance at high discharge C-rates. Discharge capacities of TiO2 tubes increased from 0.13 mAh cm-2(bare) to 0.28 mAh cm-2 for Fe-S doped TiO2 at 0.5 C after 100 cycles with exceptional capacity retention of 85 % after 100 cycles. Owing to the enhancement of thermodynamic and kinetic properties by doping of Fe-S, Li-diffusion increased resulting in remarkable discharge capacities of 0.27 mAh cm-2 and 0.16 mAh cm-2 at 10 C, and 30 C, respectively.

Effect of Enhanced Recovery After Surgery program on hospital stay and 90-day readmission after pancreaticoduodenectomy: a single, tertiary center experience in Korea.

PURPOSE: Despite increasing number of reports on Enhanced Recovery After Surgery program (ERAS) and readmission after pancreaticoduodenectomy (PD) from Western countries, there are very few reports on this topic from Asian countries. This study aimed to evaluate the effects of ERAS on hospital stay and readmission and to identify reasons and risk factors for readmission after PD. METHODS: This retrospective cohort study included 670 patients who underwent open PD from January 2003 to December 2017. The patients were classified into ERAS (n = 352) and non-ERAS (n = 318) groups. Patients' characteristics, perioperative outcomes, and readmission rates were compared. RESULTS: There were no significant differences in the postoperative complication rates between the groups. The mean postoperative hospital stay was significantly shorter in the ERAS group (24.5 vs. 18.0 days, P < 0.001), but the 90-day readmission rate was similar in the 2 groups (9.1% vs. 8.5%, P = 0.785). Complications associated with pancreatic fistula (42.4%) were the most common cause for readmission. In the multivariate analysis, diabetes mellitus (odds ratio [OR], 1.84; 95% confidence interval [CI], 1.05-3.24; P = 0.034), preoperative non-jaundice (OR, 0.45; 95% CI, 0.25-0.82; P = 0.009) and severe postoperative complications (OR, 4.12; 95% CI, 2.34-7.26; P < 0.001) were identified as risk factors for readmission. CONCLUSION: The results confirmed that the ERAS program for PD was beneficial in reducing postoperative stay without increasing readmission risks. To decrease readmission rates, prudent discharge planning and medical support should be considered in patients who experience severe complications.

Enhanced osteogenic differentiation of human mesenchymal stem cells on Ti surfaces with electrochemical nanopattern formation.

Titanium (Ti) and its alloys are mainly used for dental and orthopedic applications due to their excellent biocompatibility and mechanical properties. However, their intrinsic bioinertness often quotes as a common complaint for biomedical applications. Herein, we produced nanopattern Ti surfaces with 10 nm nanopores in 120 nm dimples by electrochemical nanopattern formation (ENF), and evaluated the osteogenic differentiation of human mesenchymal stem cells (hMSCs) on the nanopattern Ti surfaces. The ENF surfaces were obtained by removing the TiO2 nanotube (NT) layers prepared by an anodization process. To determine the in vitro effects of the ENF surface, cell proliferation assay, alkaline phosphatase activity assay, alizarin red staining, western blotting, and immunocytochemistry were performed. Atomic force microscopy and scanning electron microscopy analysis show that the ENF surface has an ultrafine surface roughness with highly aligned nanoporous morphology. hMSCs on ENF surfaces exhibit increased proliferation and enhanced osteogenic differentiation as compared to the ordered TiO2 nanotubular and compact TiO2 surfaces. Surface modification with the ENF process is a promising technique for fabricating osteointegrative implant materials with a highly bioactive, rigid and purified nano surfaces.

Anodic WO3 mesosponge @ carbon: a novel binder-less electrode for advanced energy storage devices.

A novel design for an anodic WO3 mesosponge @ carbon has been introduced as a highly stable and long cyclic life Li-ion battery electrode. The nanocomposite was successfully synthesized via single-step electrochemical anodization and subsequent heat treatment in an acetylene and argon gas environment. Morphological and compositional characterization of the resultant materials revealed that the composite consisted of a three-dimensional interconnected network of WO3 mesosponge layers conformally coated with a 5 nm thick carbon layer and grown directly on top of tungsten metal. The results demonstrated that the carbon-coated mesosponge WO3 layers exhibit a capacity retention of 87% after completion of 100 charge/discharge cycles, which is significantly higher than the values of 25% for the crystalline (without carbon coating) or 40% for the as-prepared mesosponge WO3 layers. The improved electrochemical response was attributed to the higher stability and enhanced electrical conductivity offered by the carbon coating layer.

Comparative electrochemical analysis of crystalline and amorphous anodized iron oxide nanotube layers as negative electrode for LIB.

This work is a comparative study of the electrochemical performance of crystalline and amorphous anodic iron oxide nanotube layers. These nanotube layers were grown directly on top of an iron current collector with a vertical orientation via a simple one-step synthesis. The crystalline structures were obtained by heat treating the as-prepared (amorphous) iron oxide nanotube layers in ambient air environment. A detailed morphological and compositional characterization of the resultant materials was performed via transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and Raman spectroscopy. The XRD patterns were further analyzed using Rietveld refinements to gain in-depth information on their quantitative phase and crystal structures after heat treatment. The results demonstrated that the crystalline iron oxide nanotube layers exhibit better electrochemical properties than the amorphous iron oxide nanotube layers when evaluated in terms of the areal capacity, rate capability, and cycling performance. Such an improved electrochemical response was attributed to the morphology and three-dimensional framework of the crystalline nanotube layers offering short, multidirectional transport lengths, which favor rapid Li(+) ions diffusivity and electron transport.

Electrically exploded silicon/carbon nanocomposite as anode material for lithium-ion batteries.

In this work, silicon (Si) containing carbon coated core-shell nanostructures were synthesized by electrical explosion of Si wires in ethanol solution followed by high energy mechanical milling (HEMM) process. Material characterization was carried-out using transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analysis. HEMM led to very fine and amorphous Si particles in the presence of carbon and inactive Silicon-Carbide (SiC) matrix. These Si based nanocomposites, obtained through electrical explosion followed by HEMM (milled sample), exhibited enhanced electrochemical performance than unmilled nanocomposites, when evaluated as anode material for lithium-ion batteries (LIBs). On completion of (the) 1st cycle, milled and unmilled sample(s) showed specific discharge capacities around 825 mAh/g and 717 mAh/g, respectively. Interestingly, the coulombic efficiencies of milled and unmilled samples were 98.5% and 97% after 60th cycle respectively. The enhanced electrochemical performance is attributed to fine and amorphous Si based nanocomposite obtained through HEMM process.

Extended self-ordering regime in hard anodization and its application to make asymmetric AAO membranes for large pitch-distance nanostructures.

We report here a fast and reliable hard anodization process to make asymmetric anodic aluminum oxide (AAO) membranes which can serve as a template for large pitch-distance nanostructures. In order to make larger pitch distances possible, the common burning failure associated with the high current density during the conventional constant voltage hard anodization, especially at a voltage higher than a known limit, i.e., 155 V for oxalic acid, was effectively suppressed by using a burning-protective agent. A new self-ordering regime beyond the voltage limit was observed with a different voltage-interpore distance relationship of 2.2 nm V(-1) compared to the reported 2.0 nm V(-1) for hard anodization. Combining a sulfuric acid mild anodization with this new regime of hard anodization, we further demonstrate a scalable process to make an asymmetric membrane with size up to ~47 mm in diameter and ~60 µm in thickness. This free-standing membrane can be used as a template for novel nanopatterned structures such as arrays of quantum dots, nanowires or nanotubes with diameters of a few tens of nanometers and pitch distance of over 400 nm.

Surface-assisted laser desorption-ionization mass spectrometry on titanium dioxide (TiO2) nanotube layers.

The paper reports on the use of a titanium oxide (TiO(2)) nanotube layer as a sensitive substrate for surface-assisted laser desorption-ionization mass spectrometry (SALDI-MS) of peptides and small molecules. The nanotube layers were prepared by electrochemical anodization of titanium foil. The optimized TiO(2) nanotubes morphology coupled to a controlled surface chemistry allowed desorption-ionization (D/I) of a peptide mixture (Mix1) with a detection limit of 10 femtomoles for the neurotensin peptide. The performance of the TiO(2) nanotubes for the D/I of small molecules was also tested for the detection of sutent, a small tyrosine kinase inhibitor, and verapamil. A detection limit of 50 fmol was obtained for these molecules, as compared to 500 fmol using classical matrix-assisted laser desorption-ionization mass spectrometry (MALDI-MS). Both amorphous and anatase TiO(2) layers displayed a comparable performance for D/I of analyte molecules. In a control experiment, we have performed D/I of analyte molecules on a flat TiO(2) layer. The absence of signal emphasizes the role of the nanostructured substrate in the D/I process.

Vertically aligned mixed V2O5-TiO2 nanotube arrays for supercapacitor applications.

Highly ordered mixed V(2)O(5)-TiO(2) nanotubes can be formed by self-organizing anodization of Ti-V alloys with vanadium content of up to 18 at%. In the resulting oxide nanotube arrays, the vanadium is electrochemically switchable leading to a specific capacitance that can reach up to 220 F g(-1) and an energy density of 19.56 Wh kg(-1) with perfect reversibility and long-term stability. Thus these mixed oxide nanotubes may be considered as a promising candidate for supercapacitors.

Highly self-ordered nanochannel TiO2 structures by anodization in a hot glycerol electrolyte.

In the present work, we report on the self-organized growth of TiO(2) layers consisting of a highly aligned nanochannel morphology. We show that an electrochemical anodization process of Ti in a hot glycerol/K(2)HPO(4) electrolyte can be adjusted to yield these self-organized TiO(2) structures. The channel diameter and length are controllable by the anodization parameters. This directional structure can, for example, find application in dye-sensitized solar cells.

Nb doping of TiO2 nanotubes for an enhanced efficiency of dye-sensitized solar cells.

Nb-doped TiO(2) nanotube (with C(Nb) < 1 wt%) layers were successfully fabricated by self-ordered electrochemical anodization of Ti-Nb alloys. When used in dye-sensitized solar cells the efficiency enhanced by up to 30% compared to non-doped TiO(2) nanotubes. IMVS measurements indicate the beneficial effect to be due to lower recombination losses.

TiO2 nanotubes and their application in dye-sensitized solar cells.

The present article reviews the current status of using TiO(2) nanotubes in Grätzel-type, dye-sensitized solar cells and extends the overview with the latest results and findings. Critical factors in tube geometry (length, diameter, top morphology), crystal structure (amorphous, anatase, rutile) as well as factors affecting dye loading or electron mobility are addressed. The highest solar cell efficiencies today for pure nanotube systems reach approximately 4% while for some mixed systems, around 7% has been reported. For both systems significant room for enhancement is anticipated and some key points and strategies for improvement are outlined.

Size-selective separation of macromolecules by nanochannel titania membrane with self-cleaning (declogging) ability.

We report on a simple and self-organizing process for the fabrication of TiO(2) nanochannel membranes with a channel width of 8-10 nm that can be used for size selective separation of macromolecules (proteins). The membrane, consisting of self-aligned oxide channels, is formed by complete anodization of a thin Ti foil under specific electrochemical conditions in a glycerol-phosphate electrolyte. Due to self-cleaning properties of TiO(2), clogged membranes (for example due to extended use) can easily be fully reopened and thus are reusable. As the TiO(2) after anodic formation directly contains anatase crystallites (the most photoactive TiO(2) crystal form) no thermal treatment of the membrane is required (avoiding the danger of thermally induced cracking).

Anodic formation of thick anatase TiO2 mesosponge layers for high-efficiency photocatalysis.

We report a process for the fabrication of an anatase TiO(2) mesosponge (TMS) layer by an optimized Ti anodization process in a hot glycerol electrolyte followed by a suitable etching process. Such layers can easily be grown to >10 microm thickness and have regular channels and structural features in the 5-20 nm range. The layers show high photocatalytic activity and are mechanically very robust. The layers therefore open new pathways to the wide field of TiO(2)(anatase) applications.

TiO2 nanotubes in dye-sensitized solar cells: critical factors for the conversion efficiency.

Particle vs tube: The present paper systematically investigates a range of fundamental geometrical and structural features of TiO(2) nanotube layers and their effect on the dye-sensitized solar cell conversion efficiency, to deduce the most promising strategies for improvement. It is found that the performance of the cells strongly depends on the morphology and crystalline structure of the nanotubes.