We report on the synthesis, characterization, and optoelectronic properties of the novel trimethylsulfonium lead triiodide perovskite, (CH)SPbI. At room temperature, the air-stable compound adopts a hexagonal crystal structure with a 1D network of face-sharing [PbI] octahedra along the c axis. UV-vis reflectance spectroscopy on a pressed pellet revealed a band gap of 3.1 eV, in agreement with first-principles calculations, which show a small separation between direct and indirect band gaps. Electrical resistivity measurements on single crystals indicated that the compound behaves as a semiconductor. According to multi-temperature single-crystal X-ray diffraction, synchrotron powder X-ray diffraction, Raman spectroscopy, and differential scanning calorimetry, two fully reversible structural phase transitions occur at -5 and ca. -100 °C with reduction of the unit cell symmetry to monoclinic as temperature decreases. The role of the trimethylsulfonium cation regarding the chemical stability and optoelectronic properties of the new compound is discussed in comparison with APbI (A = Cs, methylammonium, and formamidinium cation), which are most commonly used in perovskite solar cells.

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In this study we show that nanoparticles of various ferric oxides (hematite, maghemite, amorphous Fe 2 O 3 , b-Fe 2 O 3 and ferrihydrite) incorporated into carbon paste exhibit electro-catalytic properties towards hydrogen peroxide reduction. The modified paste electrode performances were evaluated and compared with those obtained with Prussian Bluemodified carbon paste electrode, which represents an excellent chemical mediator towards the H 2 O 2 redox reaction (as widely described in literature). The best catalytic activity was found for carbon paste modified by amorphous ferric oxide with 2 -4 nm particle size, which was further tested for possible application as hydrogen peroxide sensor. At pH 7, the limit of detection was 2 Â 10 À5 M H 2 O 2 (S/N ¼ 3), the calibration curves were linear upto 8.5 mM H 2 O 2 (R 2 ¼ 0.998), the measurement reproducibility (RSD ¼ 97%, n ¼ 4), the interelectrode reproducibility (RSD ¼ 16%, n electrodes ¼ 5) and < 3 s response time.Keywords: Nanoparticles, Ferric oxide, Iron oxide, Hydrogen peroxide, Sensors, Biosensors, Modified electrodes DOI: 10.1002/elan.200703938 Electrochemical sensing of hydrogen peroxide is an attractive alternative to spectrophotometric [1,2] and chemiluminescence techniques [3,4] for hydrogen peroxide detection. It is also utilized in design of many oxidase-based biosensors [5]. Platinum is the usual material of choice for anodic determination of hydrogen peroxide, due to the relatively rapid electrode kinetics of hydrogen peroxide reduction on platinum oxides [6,7]. Cathodic regime is convenient especially for hydrogen peroxide determinations in biological matrices, since this potential region is usually free from interferences caused mainly by ascorbate and urate, often present in high quantities in biological samples, e.g. body fluids, tissue homogenates, cell lysates etc. [8,9]. In the negative potential region, carbon, in various forms, is one of a few materials which can be successfully used as solid electrode material. Among different carbon materials the carbon nanotubes have been recognized as excellent material for both hydrogen peroxide electroreduction and electrooxidation [10,11]. Recently it has been reported that carbon bamboo structured nanotube paste electrode is more than 20 more sensitive towards hydrogen peroxide compared to the paste which utilize ordinary hollow structure carbon nanotubes [12]. Electrodes made of other carbon forms generally exhibit slow charge transfer kinetics for hydrogen peroxide reduction, therefore high overpotentials are required, in many cases oxygen reduction precedes the onset of hydrogen peroxide reduction wave. To overcome this obstacle, carbon surfaces are modified by various electrocatalytical layers in the case of solid carbon electrodes, or bulk modification is used for carbon paste, screen printed and composite electrodes. While Prussian blue is one of the most frequently used modifier materials for hydrogen peroxide amperometric sensors construction [13] [16]. The aim of this work is to ...

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