Anna Lisowska-Oleksiak

Novel nitrogen precursors for electrochemically driven doping of titania nanotubes exhibiting enhanced photoactivity

Nitrogen doped titania nanotubes were successfully sensitized by the electrochemical method, i.e. as-anodized titania was immersed in different amine (diethylenetriamine – DETA, triethylamine – TEA, and ethylenediamine – EDA) and urea (U) solutions and a constant potential was applied. The highly ordered morphology of fabricated N-TiO2 was investigated by scanning electron microscopy. Spectroscopic techniques, i.e. UV-Vis spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and photoluminescence spectroscopy, were utilized to characterize absorbance capability and the crystalline phase, to confirm the presence of nitrogen atoms and to study charge recombination, respectively. The highest photocurrent under both UV-Vis and visible illumination (λ > 420 nm) was registered for the N-TiO2 sample obtained from diethylenetriamine solution, used as a nitrogen precursor. The photocurrent density exhibited during UV-Vis irradiation by the most active nitrogen doped titania was 2.83 times higher compared to pure TiO2 nanotubes. The photocatalytic activity studies demonstrated a significant improvement when N-TiO2–DETA (52%) and N-TiO2–U samples (49%) where used instead of undoped TiO2 (27%). The presented results show that electrochemical doping with 0.5 M amine or urea solutions is a simple, cheap and effective strategy to introduce nitrogen atoms into the titania structure without affecting its morphology.

Enhanced photoelectrochemical and photocatalytic performance of iodine-doped titania nanotube arrays

The paper discusses the synthesis and performance of iodine doped titania nanotube arrays exhibited under irradiation. The doping procedure was performed as an additional, electrochemical process carried out after formation of nanotube arrays via anodization of the Ti substrate. The optical and structural properties were characterized using Raman, UV-vis, photoluminescence and X-ray photoelectron spectroscopy. The surface morphology and cross-section studies performed by means of scanning electron microscopy show that the ordered tubular architecture is not influenced by the doping method. However, iodine doping causes a reduction of bandgap energy and photoluminescence intensity. The nanotubular TiO2 electrodes have been monitored by electrochemical (using cyclic voltammetry and electrochemical impedance spectroscopy) and in situ UV-vis spectroelectrochemical measurements in contact with an aqueous electrolyte. Collected results show significant differences in electrochemical activity between pure and doped titania exhibited as i.e. change of Mott–Schottky relation or shift in the onset potential when a decrease in reflectance is initiated. The photocurrent density reached 155.2 and 142.2 μA cm−2 for iodine doped materials when KI and HIO4 were used as iodine precursors whereas only 25.6 μA cm−2 was registered for pure titania nanotubes under UV-vis illumination. Moreover, doped samples are far more efficient for the photodegradation progress than undoped material leading to decomposition of over 70% of methylene blue used as a model organic pollutant. The reported studies demonstrate for the first time the detailed optical, electrochemical and photoelectrochemical studies of iodine doped nanotube arrays.

Highly stable organic–inorganic junction composed of hydrogenated titania nanotubes infiltrated by a conducting polymer

A poly(3,4-ethylenedioxythiophene) conducting polymer doped with poly(2-styrene sulfonate) (pEDOT:PSS) was efficiently electrodeposited on a layer composed of ordered titania nanotubes. TiO2 nanotubes were formed during an anodization process and, after calcinations, a layer was subjected to hydrogen plasma. Hydrogenation leads to Ti(III) formation, a decrease in resistance, and a huge increase of donor density when compared with pure titania. According to a detailed structure analysis, the coverage by the polymer matrix is uniform on the entire titania surface as well as along the tubes. The composite material exhibits highly enhanced anodic photocurrent (106 μA cm−2) when compared with hydrogenated titania H–TiO2 (54 μA cm−2) or pure polymer film (2 μA cm−2). Moreover, H–TiO2/pEDOT:PSS is characterized with high photostability displayed during prolonged illumination. The proposed hydrogenation approach could be regarded as a facile titania modification for further electrochemical modifications.

Aquatic biomass containing porous silica as an anode for lithium ion batteries

A composite electrode was manufactured by pyrolysis of Red Algae (Polysiphonia fucoides) covered by diatoms (Diatomophyceae). Electrodes were tested as a half cell with capacity of 500 mA h g−1 after 80 cycles. XPS analysis shows formation of lithium silicate under reduction of silica in an aprotic electrolyte containing LiPF6 salt.

Application of non-metal doped titania for inverted polymer solar cells

Inverted bulk-heterojunction polymer solar cells have been fabricated applying non-metal doped TiO2 as electron extraction buffer layers. Spin-coated films from nitrogen, sulphur, and iodine doped TiO2 nanoparticles dispersed in dimethyl sulphoxide showed comparable roughness and uniformity as those from the pure TiO2 nanoparticles. The highest power conversion efficiency (PCE) of 1.67% was obtained for N-doped TiO2, whereas in the case of pure TiO2, PCE was around 1%. The highest short circuit current density (Jsc = 10.66 mA cm−2) was achieved for I-doped TiO2. Moreover, it was observed that devices with doped TiO2 exhibit better stability under constant illumination comparing to the control devices with pure TiO2.

Investigation of some taste substances using a set of electrodes with lipid-modified membranes

Abstract A five-channel taste module based on ion-selective electrodes (ISE) with lipid-polymer membranes was constructed. Five different kinds of lipids or their derivatives were used inPVC membranes as substances transforming taste information into electric signals: benzylcetyldimethylammoniurn chloride monohydrate, hexadecylamine, elaidic acid, 1-dodecanol and oleic acid. The electrode potential in response to sour taste substances — citric, hydrochloric and acetic acids — was examined. It was found that sensitivity of the potential of electrodes containing elaidic acid, 1 -dodecanol or oleic acid in the membrane to citric and hydrochloric acid is very good. Lower sensitivity was observed in the case of acetic acid present in the system. New types of electrodes with conducting PEDT/PSS polymers and oleic acid were tested for sour taste. It was found that stability and reproducibility of electrodes used were very good. The obtained results show that lipid-polymer membranes can be successfully applied as sour taste sensors.

Titania nanotubes infiltrated with the conducting polymer PEDOT modified by Prussian blue – a novel type of organic–inorganic heterojunction characterised with enhanced photoactivity

A highly ordered p–n heterojunction was formed based on titania nanotubes containing a conducting polymer with Prussian blue matrix. The study demonstrates, for the first time, cases when a composite based on titania array scaffolding and Prussian blue embedded in PEDOT exhibits reversible FeII/FeIII redox activity. Highly enhanced photoactivity and capacitance of the obtained material are depicted in comparison to pristine titania. To the best of our knowledge this is the first report showing a heterojunction with titania nanotubes containing redox active species that may take part in efficient photocurrent generation.

Tin oxide nanoparticles from laser ablation encapsulated in a carbonaceous matrix – a negative electrode in lithium-ion battery applications

This report concerns carbonaceous electrodes doped with tin(II) oxide nanoparticles. Tin nanoparticles are obtained by pulsed laser ablation in water. Crystalline nanoparticles have been encapsulated in a carbonaceous matrix formed after pyrolysis of a mixture consisting of tin/tin(IV) oxide nanoparticles and gelatine. The obtained material is characterized by means of X-ray diffraction, selected area diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray analysis. Battery charging/discharging tests exhibit a capacity of 580 mA h g−1 for current densities of 100 mA g−1. The cycling performance of the material suggests that the tested nanocomposite can be used as an anode for lithium-ion batteries.

HETERO-JUNCTION COMPOSED OF POLY(3, 4-ETHYLENEDIOXYTHIOPHENE) WITH POLY(STYRENESULPHONATE) AND IODINE DOPED TITANIUM DIOXIDE

This work presents new bulk p-n hetero-junction where iodine doped TiO2 (I-TiO2) acts as n and poly(3, 4-ethylenedioxy- thiophene):polystyrenesulphonate (pEDOT:PSS) as p-element. Heterogeneous films were obtained by means of potentiostatic polymerization of monomer on the metal electrode in presence of suspended I-TiO2 particles in the electrolyte, (applied potentials in a range of 0.8–1.1 V versus Ag/AgCl/0.1 M KCl). The procedure brings about hybrid films where I-TiO2 particles are uniformly incorporated into the bulk polymer matrix. An incorporation of I-TiO2 into the pEDOT:PSS matrix causes increase in the measured current under visible light illumination.

Biosilica from sea water diatoms algae—electrochemical impedance spectroscopy study

Here, we report on an electrochemical impedance study of silica of organic origin as an active electrode material. The electrode material obtained from carbonized marine biomass containing nanoporous diatoms has been characterised by means of XRD, IR, SEM and EIS. Different kinds of crystallographic phases of silica as a result of thermal treatment have been found. The electrode is electrochemically stable during subsequent cyclic voltammetry measurements taken in the potential range from 0.005 up to 3.0 V vs. Li/Li+. The material has been found to exhibit high charge capacitance of 521 mAh g−1 being cycled at a rate C/20 with capacity retention of about 97%. Electrochemical impedance spectroscopy performed at an equilibrated potential E = 0.1 V in the temperature range 288–294 K discloses low charge transfer resistivity and low diffusional impedance.