Undoped and doped PbTe nanoparticles with neodymium (Nd) and ytterbium (Yb) ions were hydrothermally synthesized and deposited on anodized TiO2 nanotube (TNT) arrays to form hybrid binder-free TNT electrodes for supercapacitor. The as-prepared TNT electrodes were characterized by XRD, SEM, and XPS. Besides, BET method was used to confirm the surface area of as-synthesized nanoparticles. Among TNT electrodes, the one with Yb-doped PbTe exhibited enhanced capacitance (0.93 mF/cm(2) at 10 mV/s, 2.16 mF/cm(2) at 5 mu A/cm(2)) and low resistance (4.68 Omega), along with good stability (similar to 93%). Overall, TNT in combination with Yb-doped PbTe nanoparticles could provide an ideal platform for efficient delivery of capacitance. (c) 2020 Elsevier B.V. All rights reserved.

This work reports highly selective phosphopeptide enrichment using amorphous TiO2 nanotubes (TiO2NTs) and the same material decorated with superparamagnetic Fe3O4 nanoparticles (TiO2NTs@Fe3O4NPs). TiO2NTs and TiO2NTs@Fe3O4NPs materials were applied for phosphopeptide enrichment both from a simple peptide mixture (tryptic digest of bovine serum albumin and α-casein) and from a complex peptide mixture (tryptic digest of Jurkat T cell lysate). The obtained enrichment efficiency and selectivity for phosphopeptides of TiO2NTs and TiO2NTs@Fe3O4NPs were increased to 28.7 and 25.3%, respectively, as compared to those of the well-established TiO2 microspheres. The enrichment protocol was extended for a second elution step facilitating the identification of additional phosphopeptides. It further turned out that both types of amorphous TiO2 nanotubes provide qualitatively new physicochemical features that are clearly advantageous for highly selective phosphopeptide enrichment. This has been confirmed experimentally resulting in substantial reduction of non-phosphorylated peptides in the enriched samples. In addition, TiO2NTs@Fe3O4NPs combine high selectivity and ease of handling due to the superparamagnetic character of the material. The presented materials and performances are further promising for applications toward a whole range of other types of biomolecules to be treated in a similar fashion.

Anodic TiO2 nanotube layers (TNTs) of different thicknesses (approximate to 1, 5 and 20 mu m) were homogeneously decorated with Pt nanoparticles using atomic layer deposition (ALD) and explored for the electrocatalytic activity in methanol oxidation reaction (MOR). Six different numbers of ALD cycles (N-ALD) - 24, 40, 56, 72, 88 and 104 - were used. Pt nanoparticles with diameter in the range of 1.3-4.6 nm were obtained for the first five N-ALD) and a complete coating was achieved for the highest N-ALD) (1 04). The SEM/TEM analyses revealed that Pt nanoparticles uniformly decorated exteriors and interiors of TNTs. A linear increase of the particle diameter of Pt was observed with increasing N-ALD). Highest electrocatalytic activities of Pt/TNTs electrodes represented by current density of 74 mA/cm(2) were obtained for N-ALD) = 88 and for thickest TNTs (20 mu m). The electrooxidation performance of Pt-decorated TiO2 nanotube layers was thoroughly compared to reference substrates: Pt-decorated graphite sheets and TiO2 flat layers (on annealed Ti foils) as well as for a commercial Pt/C catalyst attached on graphite sheets. From chronoamperometric measurements it turned out that the catalytic activity of Pt-loaded nanotube layers is superior and long lasting compared to other substrates, where significant degree of catalyst poisoning takes place. The presented ALD decoration approach is an effective strategy for the homogeneous distribution of precious Pt nanoparticles on a high surface area catalyst support for high-performance electrocatalysis. (C) 2018 Elsevier Inc. All rights reserved.

Ti substrate surface is modified into two-dimensional (2D) TiO 2 nanoplatelet or one-dimensional (1D) nanorod/nanofiber (or a mixture of both) structure in a controlled manner via a simple KOH-based hydrothermal technique. Depending on the KOH concentration, different types of TiO 2 nanostructures (2D platelets, 1D nanorods/nanofibers and a 2D+1D mixed sample) are fabricated directly onto the Ti substrate surface. The novelty of this technique is the in-situ modification of the self-source Ti surface into titania nanostructures, and its direct use as the electrochemical microelectrode without any modifications. This leads to considerable improvement in the interfacial properties between metallic Ti and semiconducting TiO 2 . Since interfacial states/defects have profound effect on charge transport properties of electronic/electrochemical devices, therefore this near-defect-free interfacial property of Ti-TiO 2 microelectrode has shown high supercapacitive performances for superior charge-storage devices. Additionally, by hydrothermally tuning the morphology of titania nanostructures, the electrochemical properties of the electrodes are also tuned. A Ti-TiO 2 electrode comprising of a mixture of 2D-platelet+1D-nanorod structure reveals very high specific capacitance values (~7.4 mF.cm −2 ) due to the unique mixed morphology which manifests higher active sites (hence, higher utilization of the active materials) in terms of greater roughness at the 2D-platelet structures and higher surface-to-volume-ratio in the 1D-nanorod structures.

High surface area TiO2 nanotubes (TNTs) were used as a catalyst support for well dispersed, stable and ultra-small (3-5 nm) Pt nanoparticles (Pt@TNTs) for the reduction of olefins. Pt@TNT catalyst was synthesized by a simple soaking of anodized TNTs in the chloroplatinic (H2PtCl6) acid solution. Various techniques such as XRD, SEM, TEM, and XPS were used to characterize the materials and its catalytic property for the olefin reduction has been described along with a proposed mechanism. The Pt@TNT catalyst showed moderate to high catalytic conversions of styrene and its derivative to ethyl benzene-based products using hydrazine hydrate as a reducing agent. An excellent catalytic activity along with high product selectivity was achieved using low amount (10 mg) of Pt@TNT catalyst containing similar to 2.2 wt.% Pt and short reaction time (45 min). (C) 2017 Elsevier Ltd. All rights reserved.

Titania nanotubes is synthesized by an anodization process were used as a basic substrate material to create different morphologies of nanoribbon, nanoflake and nanoparticle structuresviaan alkali-controlled hydrothermal route.

A simple co-precipitation method was developed to synthesize the zinc oxide (ZnO) nanoparticles (NPs) anchored graphitic carbon nanofiber (GCN) hybrid. X-ray diffraction (XRD) analysis revealed the good crystalline nature of hybrids. The attached ZnO NPs to the GCN was identified by transmission electron microscopy (TEM). The purity of the GCN and GCNZnO hybrids were examined by micro Raman studies. In vitro cytotoxicity of the hybrid was carried out using HeLa cell culture system with different dosages. The enhanced growth inhibition and cell death was observed as a function of concentration of hybrid. Evidently, the hybrid has shown potent cytotoxicity against HeLa cells than that of the pristine ZnO and functionalized GCN. This is manifested because of the higher reactive surface area and synergistic effect of the hybrid, which leads to greater interactions with the cells.

Zinc oxide (ZnO) nanoparticles (NPs) anchored to carbon nanofiber (CNF) hybrids were synthesized using a facile coprecipitation method. This report demonstrates an effective strategy to intrinsically improve the conductivity and supercapacitive performance of the hybrids by inducing oxygen vacancies. Oxygen deficiency-related defect analyses were performed qualitatively as well as quantitatively using Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. All of the analyses clearly indicate an increase in oxygen deficiencies in the hybrids with an increase in the vacuum-annealing temperature. The nonstoichiometric oxygen vacancy is mainly induced via the migration of the lattice oxygen into interstitial sites at elevated temperature (300 °C), followed by diffusion into the gaseous phase with further increase in the annealing temperature (600 °C) in an oxygen-deficient atmosphere. This induction of oxygen vacancy is corroborated by diffuse reflectance spectroscopy, which depicts the oxygen-vacancy-induced bandgap narrowing of the ZnO NPs within the hybrids. At a current density of 3 A g(-1), the hybrid electrode exhibited higher energy density (119.85 Wh kg(-1)) and power density (19.225 kW kg(-1)) compared to a control ZnO electrode (48.01 Wh kg(-1) and 17.687 kW kg(-1)). The enhanced supercapacitive performance is mainly ascribed to the good interfacial contact between CNF and ZnO, high oxygen deficiency, and fewer defects in the hybrid. Our results are expected to provide new insights into improving the electrochemical properties of various composites/hybrids.

We report the fabrication of self-organized titania (TiO2) nanotubes (TNTs) with controlled pore diameters (140-20 nm) by anodization for the application of electrochemical capacitor electrodes. The areal capacitances obtained for 140 nm TNTs as 0.23/0.13 mF cm(-2) at a scan rate of 1/5 mV s(-1) and it is enhanced to 5.5/2.9 mF cm(-2) (at the same scan rates) by controlling the pore diameter to 20 nm. In this study, role of pore diameter in the capacitance behavior of TNTs is explained on the basis of effective surface area and presence of oxygen vacancies/titanium interstitials. With a decrease in the pore diameter, the surface area-to-volume ratio (and hence, active surface sites) increases, which leads to greater dissociation of Ti4+ into Ti3+ under high temperature annealing and thus brings more nonstoichiometric defects like Ti3+ interstitials and oxygen deficiency within the lower dimensional TNTs. This manifests higher charge conductivity and greater electrochemical performance of TNTs with lower diameters. The simplicity of anodization method and the excellent electrochemical properties make these vertical TNTs as an alternative candidate for use in energy storage applications.

TiO2-based thin films and nanomaterials have been fabricated via physical and solution-based techniques by various research groups around the globe. Generally, most applications of TiO2 involve photocatalytic activity for water and air purification, self-cleaning surfaces, antibacterial activity, and superhydrophilicity. As a wide-bandgap semiconductor, modified TiO2 belongs to a class of materials called transparent semiconducting oxides (TSOs), which are simultaneously optically transparent and electrically conductive. TSOs continue to be in high demand for a variety of applications ranging from transparent electronics and sensor devices to light detecting and emitting devices in telecommunications. However, reports on TiO2 applications as an effective TSO for transparent electronics applications have been limited. In general, TiO2 is intrinsically an n-type semiconductor but can be doped to have p-type semiconductivity. This provides a very important opportunity to fabricate all-transparent homojunction devices for light harvesting and energy storage. P-type TSOs have recently attracted tremendous interest in the field of active devices for emerging transparent electronics for potential use in ultra-violet light-based solar cells. Therefore, a detailed overview of the synthesis, band structure modification via doping, properties, and applications of modified TiO2 as n- and p-type TSOs is warranted. This article comprehensively reviews the latest developments. The discussion includes solution-based wet chemical techniques and vacuum-based dry physical techniques fabricating TiO2–TSOs. The synthesis of p-TiO2 in particular is discussed in detail as it may provide interesting breakthroughs in emerging transparent electronics applications. Also, the structural, optical, and electrical properties of TiO2 are discussed in the context of TSO applications, specifically the defect chemistry of TiO2 to obtain n- and p-type semiconductivity, which could provide interesting insights into the band structure engineering of TiO2 for conductivity reversal. Applications of both n- and p-type TiO2 have been reviewed in detail in relation to thin film transparent homo/heterojunction devices, dye-sensitized solar cells, electrochromic displays, and other energy-related applications.

Titania (TiO2) nanotube arrays (TNAs) with different pore diameters (140 - 20 nm) are fabricated via anodization using hydrofluoric acid (HF) containing ethylene glycol (EG) by changing the HF-to-EG volume ratio and the anodization voltage. To evaluate the effects of different pore diameters of TiO2 nanotubes on bacterial biofilm formation, Shewanella oneidensis (S. oneidensis) MR-1 cells and a crystal-violet biofilm assay are used. The surface roughness and wettability of the TNA surfaces as a function of pore diameter, measured via the contact angle and AFM techniques, are correlated with the controlled biofilm formation. Biofilm formation increases with the decreasing nanotube pore diameter, and a 20 nm TiO2 nanotube shows the maximum biofilm formation. The measurements revealed that 20 nm surfaces have the least hydrophilicity with the highest surface roughness of ∼17 nm and that they show almost a 90% increase in the effective surface area relative to the 140 nm TNAs, which stimulate the cells more effectively to produce the pili to attach to the surface for more biofilm formation. The results demonstrate that bacterial cell adhesion (and hence, biofilm formation) can effectively be controlled by tuning the roughness and wettability of TNAs via controlling the pore diameters of TNA surfaces. This biofilm formation as a function of the surface properties of TNAs can be a potential candidate for both medical applications and as electrodes in microbial fuel cells.

A facile three-step co-precipitation method is developed to synthesize graphitic carbon nanofibers (CNFs) decorated with ZnO nanoparticles (NPs). By interchanging intermediate steps of the reaction processes, two kinds of nanohybrids are fabricated with stark morphological and physicochemical differences. The morphologies differ because of the different chemical environments of the NP/nanocluster formation. The hybrid with larger and non-uniform ZnO nanocluster size is formed in liquid phase and resulted in considerable interfacial defects that deteriorate the charge-transfer properties. The hybrid with smaller and uniform ZnO NPs was formed in a dry solid phase and produced near-defect-free interfaces, leading to efficient charge transfer for superior photocatalytic performance. The results broaden the understanding of the anchoring/bonding mechanism in ZnO/CNF hybrid formation and may facilitate further development of more effective exfoliation strategies for the preparation of high-performance composites/hybrids.

Hierarchical (HC) porous titania (TiO2) nano-networks are developed via a two-step anodization method in a mixed viscous electrolyte of hydrofluoric acid (HF) and glycerol. An ordered imprint was generated on metallic titanium (Ti) substrate and subsequently anodized this imprint in aged HF/glycerol at different conditions to create HC nanostructures. The optimal HF/glycerol volume ratio, conductivity, and initial water/glycerol content of the electrolyte are 1:5, 10 to 12μS/cm, and 17/83vol%, respectively, for obtaining HC structures. Also, ruthenium-based dye adsorption analysis demonstrates better dye adsorption on HC–TiO2 as compared to conventional TiO2 nanotubes (TNAs), due to the enhanced active surface area of the HC nano-network.

One-dimensional (1D) and two-dimensional (2D) titania/titanate nanostructures are fabricated directly on a self-source metallic titanium (Ti) surface via in situ surface re-construction of a Ti substrate using potassium hydroxide (KOH) under a hydrothermal (HT) condition. The effect of temperature and the concentration of KOH on the variations in morphology and titania-to-titanate phase changes are studied and explained in detail. A growth model is proposed for the formation process of the platelet-to-nanorod conversion mechanism. The field emission (FE) properties of titania/titanate nanostructures are studied, and the effects of the morphologies (such as 1D nanorods, 2D nanoplatelets, and a mixture of 1D nanorods and 2D platelets) on the FE properties of the samples are investigated. The samples depict a reasonable low turn-on field and emission stability. The FE mechanism is observed to follow standard Fowler-Nordheim (FN) electron tunneling. The geometrical field enhancement factor (β) is measured to be very high, and is compared with theoretical values calculated from various existing models to explore the feasibility of these models. The surface modification of metallic Ti by a simple non-lithographic bottom-up method and the low-macroscopic FE properties can provide a potential alternative to field emission displays for low-power panel technology.

Single and multi-stage Y-branched TiO2 nanotube arrays (TNAs) have been fabricated by a voltage ramping down process using potentiostatic two-step anodization in 0.5 wt% hydrofluoric acid (HF)/glycerol (1:2 volume ratio) electrolyte. Initially, the voltage is kept at 40V for 3 h and then it is ramped down to different voltages (e.g. 30V, 34V, 36V, 38V and 39V) at a ramping rate of either -1.0V s(-1) or -0.5V s(-1) in one time and two-time aged electrolytes. The growth mechanism of Y-branching of TNAs is modeled and explained in terms of unequal interfacial movements of the two interfaces across the barrier oxide layer (BOL) under non-steady-state growth regime. The 'pinched off area of the BOL at the nanotube propagation front can be controlled effectively with the relative ramping voltage levels and electrolyte's conductivity to obtain Y-branched TNAs. (C) 2015 Elsevier B.V. All rights reserved.

An important aspect of orthopedic implant integration is the enhancement of functional activity of osteoblasts at the tissue-implant interface without any fibrous tissue intervention. Nanostructured implant surfaces are known to enhance osteoblast activity. Previously, we have reported a simple hydrothermal method for the fabrication of non-periodic nanostructures (nanoscaffold, nanoleaves and nanoneedles) on titanium implants showing good biocompatibility and a distinct osteoblast response in vitro in terms of osteoblast adhesion to the surface. In the present work, these nanostructures have been evaluated for their detailed in vitro cellular response as well as in vivo osteointegration. Our studies showed that a specific surface nanomorphology, viz. nanoleaves, which is a network of vertically aligned, non-periodic, leaf-like structures with thickness in the nanoscale, provided a distinct increase in osteoblast cell proliferation, alkaline phosphatase (ALP) activity and collagen synthesis compared to several other types of nanomorphology, such as nanotubes, nanoscaffold and nanoneedles (rods). Gene expression analysis of ALP, osteocalcin, collagen, decorin and Runx2 showed ~20- to 40-fold up-regulation on the leaf-like topography. Cytoskeletal arrangement studies on this substrate again revealed a unique response with favorable intracellular protein expressions of vinculin, FAK and src. In vivo osteointegration study over 12 weeks on rat model (Sprague-Dawley) showed early-stage bone formation (60% bone contact by week 2 and ~85% by week 8, p<0.01) in the leaf-like nanopattern, without any inflammatory cytokine production.

Hydroxyapatite-reinforced polyamide 6,6 nanocomposites were prepared for load-bearing bone implant applications. Nanoparticles of hydroxyapatite (nHAp) were synthesized through a wet chemical reaction and were incorporated into the polymer melt at different loading fractions by melt compounding so as to sensitively modulate the mechanical properties of the latter. Tensile properties of the nanocomposites were found to be substantially improved at filler loading fractions as low as 3wt%. Theoretical calculations also confirm the improved extent of reinforcement for nanocomposites over the predicted data for conventional micro counterparts. Differential scanning calorimetry studies revealed that the melting and crystallization characteristics of the polyamide matrix were unaltered with the incorporation of nHAp. However, the addition of nanohydroxyapatite considerably influenced the thermal stability of the nanocomposites.