Mariusz Szkoda

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.

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.

Ordered titanium templates functionalized by gold films for biosensing applications – Towards non-enzymatic glucose detection

Recently, metal nanostructures evoke much interest due to application potential in highly sensitive detectors in biochemistry and medical diagnostics. In this work we report on preparation and characteristics of thin (1-100nm) Au films deposited onto highly ordered structured titanium templates for SERS (Surface Enhanced Raman Spectroscopy) and electrochemical sensing. The Ti templates are formed by selective removal of TiO2 nanotubes out of as-anodized titanium substrate. The surface of the obtained material reproduce precisely the bottom layer of the nanotubes and consists of a uniformly distributed dimples with diameter of ~100nm. For all structures covered with Au films the measured average SERS signal is markedly higher than the one observed for bare Ti templates. This is due to strong electromagnetic field in the vicinity of the film grains. Moreover, such nanostructured gold surface exhibits also attractive electrochemical and electrocatalytic properties, which should be attributed to enhancement of the electron transfer at the Au-Ti interface formed without any linker molecules. It is shown that prepared material can be used as an enzyme-free sensor for glucose detection in air-saturated neutral media especially in case of low sugar concentrations present in human body liquids, such as saliva, sweat and interstitial fluid.

Corrigendum to “Ordered titanium templates functionalized by gold films for biosensing applications – Towards non-enzymatic glucose detection” [Talanta 166 (2017) 207–214]

Corrigendum to “Ordered titanium templates functionalized by gold films for biosensing applications – Towards non-enzymatic glucose detection” [Talanta 166 (2017) 207–214] Katarzyna Grochowskaa,, Mariusz Szkoda, Jakub Karczewski, Gerard Śliwiński, Katarzyna Siuzdak a Centre for Plasma and Laser Engineering, The Szewalski Institute of Fluid-Flow Machinery, Polish Academy of Sciences, Fiszera 14 St., 80-231 Gdańsk, Poland b Faculty of Chemistry, Gdańsk University of Technology, Narutowicza 11/12 St., 80-233 Gdańsk, Poland c Faculty of Applied Physics and Mathematics, Gdańsk University of Technology, Narutowicza 11/12 St., 80-233 Gdańsk, Poland