Szymon Wojtyła

Photocatalytic Carbon Dioxide Reduction at p-Type Copper(I) Iodide.

A p-type semiconductor, CuI, has been synthesized, characterized, and tested as a photocatalyst for CO2 reduction under UV/Vis irradiation in presence of isopropanol as a hole scavenger. Formation of CO, CH4 , and/or HCOOH was observed. The photocatalytic activity of CuI was attributed to the very low potential of the conduction band edge (i.e., -2.28 V vs. NHE). Photocurrents generated by the studied material confirm a high efficiency of the photoinduced interfacial electrontransfer processes. Our studies show that p-type semiconductors may be effective photocatalysts for CO2 reduction, even better than extensively studied n-type titanium dioxide, owing to the low potential of the conduction band edge.

An Efficient CuxO Photocathode for Hydrogen Production at Neutral pH: New Insights from Combined Spectroscopy and Electrochemistry.

Light-driven water splitting is one of the most promising approaches for using solar energy in light of more sustainable development. In this paper, a highly efficient p-type copper(II) oxide photocathode is studied. The material, prepared by thermal treatment of CuI nanoparticles, is initially partially reduced upon working conditions and soon reaches a stable form. Upon visible-light illumination, the material yields a photocurrent of 1.3 mA cm(-2) at a potential of 0.2 V vs a reversible hydrogen electrode at mild pH under illumination by AM 1.5 G and retains 30% of its photoactivity after 6 h. This represents an unprecedented result for a nonprotected Cu oxide photocathode at neutral pH. The photocurrent efficiency as a function of the applied potential was determined using scanning electrochemical microscopy. The material was characterized in terms of photoelectrochemical features; X-ray photoelectron spectroscopy, X-ray absorption near-edge structure, fixed-energy X-ray absorption voltammetry, and extended X-ray absorption fine structure analyses were carried out on pristine and used samples, which were used to explain the photoelectrochemical behavior. The optical features of the oxide are evidenced by direct reflectance spectroscopy and fluorescence spectroscopy, and Mott-Schottky analysis at different pH values explains the exceptional activity at neutral pH.

Is 3D printing safe? Analysis of the thermal treatment of thermoplastics: ABS, PLA, PET, and nylon

ABSTRACT The fast development of low-cost desktop three-dimensional (3D) printers has made those devices widely accessible for goods manufacturing at home. However, is it safe? Users may belittle the effects or influences of pollutants (organic compounds and ultrafine particles) generated by the devices in question. Within the scope of this study, the authors attempt to investigate thermal decomposition of the following commonly used, commercially available thermoplastic filaments: acrylonitrile-butadiene-styrene (ABS), polylactic acid (PLA), polyethylene terephthalate (PET), and nylon. Thermogravimetric analysis has shown the detailed thermal patterns of their behavior upon increasing temperature in neutral atmosphere, while GC analysis of organic vapors emitted during the process of heating thermoplastics have made it possible to obtain crucial pieces of information about the toxicity of 3D printing process. The conducted study has shown that ABS is significantly more toxic than PLA. The emission of volatile organic compounds (VOC) has been in the range of 0.50 µmol/h. Styrene has accounted for more than 30% of total VOC emitted from ABS, while for PLA, methyl methacrylate has been detected as the predominant compound (44% of total VOCs emission). Moreover, the authors have summarized available or applicable methods that can eliminate formed pollutants and protect the users of 3D printers. This article summarizes theoretical knowledge on thermal degradation of polymers used for 3D printers and shows results of authors’ investigation, as well as presents forward-looking solutions that may increase the safety of utilization of 3D printers.

The quenching effect of chitosan crosslinking on ZnO nanoparticles photocatalytic activity

Zinc oxide (ZnO), the main component of several suntan lotions, generates highly oxidizing, cytotoxic and genotoxic reactive oxygen species (ROS) upon UV light absorption. In order to increase safety combined with ZnO use as a sunscreen, its photocatalytic activity should be efficiently quenched. In our studies commercial samples of zinc oxide nanoparticles were hybridized by ionotropic gelation with a natural biopolymer, chitosan (CS). The chemical crosslinking of the polymer in the presence of ZnO nanoparticles was performed. Significantly, in contrast to several CS–ZnO hybrid materials described in the literature, the obtained composites maintained the UV light absorption ability, while the photocatalytic activity towards chemical and biological substrates was totally quenched. Furthermore, a complete lack of photoelectrochemical response observed for the chitosan modified semiconductors confirmed the total inhibition of photoinduced interfacial electron transfer processes. Additionally, antibacterial activity against selected bacterial strains, Staphylococcus aureus and Escherichia coli was observed, although there was no cytotoxic effect against human keratinocytes. The nanocomposites resolve the problem of the risk associated with using semiconductor nanoparticles as ingredients of suntan lotions, cosmetics and dermatological formulations. The transparent polymeric coating allows the absorption of UV irradiation by ZnO particles and simultaneously blocks photogeneration of reactive radicals and oxygen species.

Photosensitization and photocurrent switching effects in wide band gap semiconductors: CuI and TiO2 functionalized with iron and nickel complexes: from semiconductors to logic devices

Materials obtained by immobilization of nickel and iron complexes on the surface of n-type titanium dioxide and p-type copper iodide have interesting photoelectrochemical properties. Fe(NA)Cl2@TiO2, Fe(NA)Cl2@CuI, Ni-rutin@CuI and Ni-rutin@TiO2 exhibit pronounced photosensitization towards visible light and photoelectrodes prepared from these materials generate photocurrents over a broad light wavelength window. The polarity of the generated photocurrents varies with change of the applied potential. Photocurrent switching phenomena can be described in terms of photoinduced charges transfer involving semiconductor and excited metal complex. Various types of interaction between semiconductor and adsorbed complex reflected in different mechanism of photosensitization. The studied materials has been characterized using various spectroscopic, crystallographic and electrochemical methods. Based on the photochemical measurements and diffuse reflectance spectroscopy the mechanism of photosensitization as well as mechanism of photocurrent generation in various conditions have been suggested. Due to interesting photoelectrochemical properties, studied materials are promising for optoelectronic logic devices such as demultiplexer. Studied materials are particularly attractive due to high stability and photostability.