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In this present study, we explored the catalytic behaviors of the in situ generated metal nanoparticles, i.e., Pt/Ni, embedded in laser-induced carbon nanofibers (LCNFs) and their potential for H2O2 detection under physiological conditions. Furthermore, we demonstrate current limitations of laser-generated nanocatalyst embedded within LCNFs as electrochemical detectors and possible strategies to overcome the issues. Cyclic voltammetry revealed the distinctive electrocatalytic behaviors of carbon nanofibers embedding Pt and Ni in various ratios. With chronoamperometry at +0.5 V, it was found that modulation of Pt and Ni content affected only current related to H2O2 but not other interfering electroactive substances, i.e., ascorbic acid (AA), uric acid (UA), dopamine (DA), and glucose. This implies that the interferences react to the carbon nanofibers regardless of the presence of metal nanocatalysts. Carbon nanofibers loaded only with Pt and without Ni performed best in H2O2 detection in phosphate-buffered solution with a limit of detection (LOD) of 1.4 µM, a limit of quantification (LOQ) of 5.7 µM, a linear range from 5 to 500 µM, and a sensitivity of 15 µA mM−1 cm−2. By increasing Pt loading, the interfering signals from UA and DA could be minimized. Furthermore, we found that modification of electrodes with nylon improves the recovery of H2O2 spiked in diluted and undiluted human serum. The study is paving the way for the efficient utilization of laser-generated nanocatalyst-embedding carbon nanomaterials for non-enzymatic sensors, which ultimately will lead to inexpensive point-of-need devices with favorable analytical performance. Graphical abstract

in: Angew. Chem. Int. Ed.: https://doi.org/10.1002/anie.201805239

A reinvestigation of the alkali metal thiosulfates has led to the new phase Cs2S2O3 center dot H2O. At first cesium thiosulfate monohydrate was obtained as a byproduct of the synthesis of Cs4In2S5. Further investigations were carried out using the traditional synthesis reported by J. Meyer and H. Eggeling. Cs2S2O3 center dot H2O crystallizes in transparent, colorless needles. The crystal structure of the title compound was determined by single crystal X-ray diffraction at room temperature: space group C2/m (No. 12), unit cell dimensions: a = 11.229(4), b = 5.851(2), c = 11.260(5) angstrom, beta = 95.89(2)degrees, with Z = 4 and a cell volume of V = 735.9(5)angstrom(3). The positions of all atoms including the hydrogen atoms were located in the structure refinement. Cs2S2O3 center dot H2O is isotypic with Rb2S2O3 center dot H2O. Isolated tetrahedra [S2O3](2-) are coordinated by the alkali metal cations, and in addition they serve as acceptors for hydrogen bonding. For both Cs atoms the shortest distances are observed to oxygen atoms of the S2O32- anions where as the terminating sulfur atom has its shortest contacts to the water hydrogen atoms. Thus, an extended hydrogen bonding network is formed. The title compound has also been characterized by IR spectroscopy. IR spectroscopy reveals the vibrational bands of the water molecules at 3385 cm(-1). They show a red shift in the OH stretching and bending modes as compared to free water. This is due both to the S center dot center dot center dot H hydrogen bonding and to the coordination of H2O molecules to the cesium atoms.

The light gray selenogallate CsGaSe2-mC64 was obtained by reaction of stoichiometric amounts of CsN3, GaSe, and Se at elevated temperatures. Its crystal structure was determined by single-crystal X-ray diffraction. The compound crystallizes in the monoclinic space group C2/c (No. 15) with a = 11.043(2) Å, b = 11.015(4) Å, c = 16.810(2) Å, β = 99.49(1) °, V = 2016.7(8) Å3, and Z = 16 (powder data, ambient temperature). Its crystal structure features anionic layers ∞ 2 [Ga4Se8 4−] consisting of corner-sharing Ga4Se10 supertetrahedra. The compound undergoes a first-order phase transition at temperatures of 610 ± 10 °C. The hightemperature phase CsGaSe2-mC16 also crystallizes in the monoclinic space group C2/c (No. 15) with a = 7.651(3) Å, b = 12.552(4) Å, c = 6.170(3) Å, β = 113.62(4)°, V = 542.9(5) Å3, and Z = 4 (powder data, ambient temperature). The crystal structure of the high-temperature phase consists of SiS2 analogous chains ∞ 1 [GaSe2 −]. In situ high-temperature X-ray diffraction experiments were performed to study this phase transition. The crystallization kinetics of the phase transitions were studied using Johnson−Mehl−Avrami−Kolmogorov (JMAK) theory for isothermal crystallization processes. The activation energy of the phase transition was determined using the Arrhenius equation. Furthermore, the compound was studied by vibrational and diffuse reflectance spectroscopy.

The reaction of CsN3 with GaS and S at elevated temperatures results in Cs2Ga2S5. Its crystal structure was determined from single-crystal X-ray diffraction data. The colorless solid crystallizes in space group C2/c (no. 15) with V=1073.3(4) Å3 and Z=4. Cs2Ga2S5 is the first compound that features one-dimensional chains equation image[Ga2S3(S2)2−] of edge- and corner-sharing GaS4 tetrahedra. The vibrational band of the S22− units at 493 cm−1 was revealed by Raman spectroscopy. Cs2Ga2S5 has a wide bandgap of about 3.26 eV. The thermal decomposition of CsN3 yields elemental Cs, which reacts with sulfur to provide Cs2S6 as an intermediate product. The crystal structure of Cs2S6 was redetermined from selected single crystals. The red compound crystallizes in space group equation image with V=488.99(8) Å3 and Z=2. Cs2S6 consists of S62− polysulfide chains and two Cs positions with coordination numbers of 10 and 11, respectively. Results of DFT calculations on Cs2Ga2S5 are in good agreement with the experimental crystal structure and Raman data. The analysis of the chemical bonding behavior revealed completely ionic bonds for Cs, whereas Ga[BOND]S and S[BOND]S form polarized and fully covalent bonds, respectively. HOMO and LUMO are centered at the S2 units.

Cs2Ga2Se5 was obtained by the reaction of CsN3 with stoichiometric amounts of GaSe and Se at elevated temperature. It forms yellow crystals embedded in a pure orange microcrystalline powder. The crystal structure of Cs2Ga2Se5 was determined by single-crystal X-ray diffraction at 123 K. The compound crystallizes monoclinically in the space group C2/c (No. 15) with a = 15.3911(5) Å, b = 7.3577(2) Å, c = 12.9219(3) Å, β = 126.395(3)°, V = 1177.89(7) Å3, and Z = 4. The structure features one-dimensional chains 1∞[Ga2Se3(Se2)2–], consisting of edge- and corner sharing GaSe4 tetrahedra. Raman spectroscopic measurements reveal vibrational bands of the Se22– units at 236 cm–1, and the bands of Ga–Se vibrations at 254 and 273 cm–1. UV/Vis diffuse reflectance spectroscopy shows the bandgap at about 1.95 eV.

Zur Mikro- und Nanostruktur der neuen ternären Chalkogenide RbIn3S5, CsIn3S5 und K2In12Se19 Präparation, Röntgenstrukturanalyse und Elektronenmikroskopie PDF-Dokument. On the Micro- and Nanostructure of the New Ternary Chalcogenides RbIn3S5, CsIn3S5 and K2In12Se19 Preparation, X-Ray Structure Analysis, Electron Microscopy PDF-Abstract.