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This work aims to demonstrate that the Fe 2 O 3 nanocrystals' adsorptive and photocatalytic properties can be adjusted by exposing the crystal facets that are functionalized. To this end, cube- and disc-like structures were synthesized using a metal ion-mediated hydrothermal route. Thereafter, some of the samples were annealed at 500 °C for 3 h. Our paper combines the experimental part with theoretical calculations of the obtained materials' band edge positions. The results reveal that-aside from hematite-the as-synthesized discs also contain γ-FeOOH and β-Fe 2 O 3 phases, which transform into α-Fe 2 O 3 during annealing. The hydrodynamic diameter, zeta potential, and adsorption kinetics measurements show that the cube-like samples exhibit the highest affinity for cationic, whereas the discs have an affinity for anionic dye. Measurements of the wall zeta potential also reveal that annealing the discs modifies their surface state and ability to adsorb molecules. Photocatalytic tests show that the as-synthesized powders have better photocatalytic performance toward methylene blue decomposition than the annealed ones. The observed small changes in the concentration of the MO during illumination result from the energy band structure of the cube-like crystal orientation.

Upconversion as a modification strategy to enhance the utilization of sunlight in titanium dioxide photoanodes with an internal upconverter was investigated. TiO 2 thin films containing an Er activator and Yb sensitizer were deposited in the magnetron sputtering process on conducting glass, amorphous silica, and silicon. Scanning electron microscopy, energy dispersive spectroscopy, grazing incidence X-ray diffraction, and X-ray absorption spectroscopy allowed assessment of the thin film composition, structure, and microstructure. Optical and photoluminescence properties were measured by means of spectrophotometry and spectrofluorometry. Changing the content of Er 3+ (1, 2, 10 at%) and Yb 3+ (1, 10 at%) ions allowed us to achieve thin film upconverters with a crystallized and amorphous host. Upon 980 nm laser excitation Er 3+ exhibits upconversion with the main emission in green ( 2 H 11/2 → 4 I 15/2 , λ em ≈ 525 nm) and weak emission in red ( 4 F 9/2 → 4 I 15/2 , λ em ≈ 660 nm). For a thin film with a higher ytterbium content (10 at%) a significant increase in red emission and upconversion from NIR to UV was observed. The average decay times of green emission for TiO 2 :Er and TiO 2 :Er,Yb thin films were calculated based on time-resolved emission measurements., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Heterostructures of TiO 2 @Fe 2 O 3 with a specific electronic structure and morphology enable us to control the interfacial charge transport necessary for their efficient photocatalytic performance. In spite of the extensive research, there still remains a profound ambiguity as far as the band alignment at the interface of TiO 2 @Fe 2 O 3 is concerned. In this work, the extended type I heterojunction between anatase TiO 2 nanocrystals and α-Fe 2 O 3 hematite nanograins is proposed. Experimental evidence supporting this conclusion is based on direct measurements such as optical spectroscopy, X-ray photoemission spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), and the results of indirect studies of photocatalytic decomposition of rhodamine B (RhB) with selected scavengers of various active species of OH • , h • , e - , and • O 2 - . The presence of small 6-8 nm Fe 2 O 3 crystallites at the surface of TiO 2 has been confirmed in HRTEM images. Irregular 15-50 nm needle-like hematite grains could be observed in scanning electron micrographs. Substitutional incorporation of Fe 3+ ions into the TiO 2 crystal lattice is predicted by a 0.16% decrease in lattice parameter a and a 0.08% change of c, as well as by a shift of the Raman E g(1) peak from 143 cm -1 in pure TiO 2 to 149 cm -1 in Fe 2 O 3 -modified TiO 2 . Analysis of O 1s XPS spectra corroborates this conclusion, indicating the formation of oxygen vacancies at the surface of titanium(IV) oxide. The presence of the Fe 3+ impurity level in the forbidden band gap of TiO 2 is revealed by the 2.80 eV optical transition. The size effect is responsible for the absorption feature appearing at 2.48 eV. Increased photocatalytic activity within the visible range suggests that the electron transfer involves high energy levels of Fe 2 O 3 . Well-programed experiments with scavengers allow us to eliminate the less probable mechanisms of RhB photodecomposition and propose a band diagram of the TiO 2 @Fe 2 O 3 heterojunction.

The diversity of materials proposed for non-enzymatic glucose detection and the lack of standardized protocols for assessing sensor performance have caused considerable confusion in the field. Therefore, methods for pre-evaluation of working electrodes, which will enable their conscious design, are currently intensively sought. Our approach involved comprehensive morphologic and structural characterization of copper sulfides as well as drop-casted suspensions based on three different polymers-cationic chitosan, anionic Nafion, and nonionic polyvinylpyrrolidone (PVP). For this purpose, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy were applied. Subsequently, comparative studies of electrochemical properties of bare glassy carbon electrode (GCE), polymer- and copper sulfides/polymer-modified GCEs were performed using electrochemical impedance spectroscopy (EIS) and voltammetry. The results from EIS provided an explanation for the enhanced analytical performance of Cu-PVP/GCE over chitosan- and Nafion-based electrodes. Moreover, it was found that the pH of the electrolyte significantly affects the electrocatalytic behavior of copper sulfides, indicating the importance of OH ads in the detection mechanism. Additionally, diffusion was denoted as a limiting step in the irreversible electrooxidation process that occurs in the proposed system.

Titanium dioxide photoanodes for hydrogen generation suffer from a profound mismatch between the optical absorption of TiO 2 and the solar spectrum. To solve the problem of low solar-to-chemical efficiency, optically active materials are proposed. In this work, TiO 2 thin films containing erbium were deposited by radio frequency RF magnetron sputtering under ultrahigh vacuum conditions UHV. Morphology, structural, optical and electronic properties were studied. TiO 2 :Er thin films are homogenous, with uniform distribution of Er ions and high transparency over the visible VIS range of the light spectrum. However, a profound 0.4 eV blue shift of the fundamental absorption edge with respect to undoped TiO 2 was observed, which can be attributed either to the size effect due to amorphization of TiO 2 host or to the onset of precipitation of Er 2 Ti 2 O 7 nanocrystals. Near-infrared NIR to VIS up-conversion is demonstrated upon excitation at 980 nm, while strong green photoluminescence at 525 and 550 nm occurs upon photon absorption at 488 nm.

A TiO 2 @Cu 2 O semiconductor heterostructure with better photochemical response compared to TiO 2 was obtained using an electrochemical deposition method of Cu 2 O on the surface of TiO 2 nanotubes. The choice of 1D nanotubes was motivated by the possibility of achieving fast charge transfer, which is considered best suited for photochemical applications. The morphology and structural properties of the obtained heterojunction were determined using standard methods -SEM and Raman spectroscopy. Analysis of photoelectrochemical properties showed that TiO 2 @Cu 2 O heterostructures exhibit better properties resulting from an interaction with sunlight than TiO 2 . A close relationship between the morphology of the heterostructures and their photoproperties was also demonstrated. Investigations representing a combination of photoelectrochemical cells for hydrogen production and photocatalysis-photoelectrocatalysis-were also carried out and confirmed the observations on the photoproperties of heterostructures. Analysis of the Mott-Schottky plots as well as photoelectrochemical measurements (I ph -V, I ph -t) showed that TiO 2 as well as, unusually, Cu 2 O exhibit n-type conductivity. On this basis, a new energy diagram of the TiO 2 @Cu 2 O system was proposed. It was found that TiO 2 @Cu 2 O n-n type heterostructure prevents the processes of photocorrosion of copper(I) oxide contained in a TiO 2 -based heterostructure.

The constant progress in novel nanomaterials synthesis has contributed to the rapid development of nonenzymatic glucose sensors. For working electrodes preparation, drop casting proved to be the most convenient and thus most widely applied method. However, appropriate interpretation of obtained electrochemical signal requires in-depth knowledge of limitations related to this technique. In this study, we prepared solutions based on commonly reported polymers for nanostructures immobilization and investigated their influence on copper sulfides distribution on the electrode. Characterization of suspensions properties and behavior of particles during droplet drying revealed that nonionic polyvinylpyrrolidone (PVP) was favorable for electrodes modification with copper sulfides in comparison with Nafion and chitosan. It ensured homogeneity of the suspension as well as the uniform coverage of the electrode surface with particles, what resulted in increased active surface area and, therefore, higher signal from glucose addition. On the other hand, when cationic chitosan was used as a binder, suspensions were agglomerated and, within dry deposits, a coffee-ring effect was observed. Appropriate adjustment of material and polymer interactions led to enhanced electrode electrochemical performance.

The aim of the work was to develop innovative antibacterial hybrid coatings applied on implants that are used for anastomoses of animals' long bones and to assess their physicochemical and biological properties. Plates made of the titanium alloy were covered with composite hybrid layers so as to protect the implant surface against corrosion and to enhance it with antibacterial properties.The hybrid coatings were obtained electrochemical oxidation and sol-gel. First, a layer of titanium nanotubes was applied to the implants surface through anodization. Next, the sol-gel method was used to create the second layer with silver nanoparticles. The microstructure examination of the materials was performed with the SEM. The phase composition analysis was carried out via the X-ray diffraction. The surface parameters (roughness, contact angle and free surface energy) were assessed. Biological studies of implants were conducted, including the analysis of degradation processes, cell response and bactericidal activity. The results confirmed that the hybrid antibacterial layers effectively protected the implant surface against scratches and corrosion and eliminated bacteria, which in turn would promote bone healing. The advantageous physicochemical and biological properties of metallic implants with hybrid composite layers raise hopes for their applicability in the veterinary treatment of bone fractures., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)

The aim of this research is to study the role of nanocrystalline TiO 2 /SnO 2 n-n heterojunctions for hydrogen sensing. Nanopowders of pure SnO 2 , 90 mol % SnO 2 /10 mol % TiO 2 , 10 mol % SnO 2 /90 mol % TiO 2 and pure TiO 2 have been obtained using flame spray synthesis (FSS). The samples have been characterized by BET, XRD, SEM, HR-TEM, Mössbauer effect and impedance spectroscopy. Gas-sensing experiments have been performed for H 2 concentrations of 1-3000 ppm at 200-400 °C. The nanomaterials are well-crystallized, anatase TiO 2 , rutile TiO 2 and cassiterite SnO 2 polymorphic forms are present depending on the chemical composition of the powders. The crystallite sizes from XRD peak analysis are within the range of 3-27 nm. Tin exhibits only the oxidation state 4+. The H 2 detection threshold for the studied TiO 2 /SnO 2 heterostructures is lower than 1 ppm especially in the case of SnO 2 -rich samples. The recovery time of SnO 2 -based heterostructures, despite their large responses over the whole measuring range, is much longer than that of TiO 2 -rich samples at higher H 2 flows. TiO 2 /SnO 2 heterostructures can be intentionally modified for the improved H 2 detection within both the small (1-50 ppm) and the large (50-3000 ppm) concentration range. The temperature T max at which the semiconducting behavior begins to prevail upon water desorption/oxygen adsorption depends on the TiO 2 /SnO 2 composition. The electrical resistance of sensing materials exhibits a power-law dependence on the H 2 partial pressure. This allows us to draw a conclusion about the first step in the gas sensing mechanism related to the adsorption of oxygen ions at the surface of nanomaterials.

The present work aims at development of novel hybrid materials from genipin crosslinked collagen or collagen/chitosan hydrogels containing various types of TiO 2 nanoparticles characterized with different anatase/rutile ratios. Collagen and chitosan were selected as hydrogel components since they are biopolymers being, like collagen, the major compound present in extracellular matrix or exhibit structural similarity to glycosaminoglycans, like chitosan. TiO 2 nanoparticles were introduced to the hydrogel matrices to improve their mechanical properties as well as bioactivity. A series of twelve novel hybrid materials were prepared and their physicochemical, mechanical and biological properties were evaluated. It was found that TiO 2 nanostructures introduced to the hydrogels have significant influence on the swelling properties of the synthesized hybrids and their impact is strongly dependent on the type of matrices. The surfaces of hybrid materials were found to be more hydrophilic than these of corresponding hydrogel matrix. It was also observed that, the storage modulus values of the hybrids based on collagen-chitosan hydrogel are comparable to these for plain hydrogels what indicates that the mechanical properties of the materials obtained are satisfactory for possible biomedical application. The in vitro cell culture studies have shown that prepared materials are biocompatible as they can support mitochondrial activity of MEFs as well as MG-63 cells. In vitro experiments performed under simulated body fluid (SBF) conditions have revealed that all studied TiO 2 nanoparticles present in hydrogel matrices, regardless of anatase/rutile ratio, successfully induced formation of apatite-like structures. The hybrid materials developed here are promising candidates for preparation of bioactive, injectable scaffolds for tissue engineering., (Copyright © 2016 Elsevier B.V. All rights reserved.)