Highly Sensitive Sub-ppm CH3COOH Detection by Improved Assembly of Sn3O4-RGO Nanocomposite

Detection of sub-ppm acetic acid (CH₃COOH) is in demand for environmental gas monitoring. In this article, we propose a CH₃COOH gas sensor based on Sn₃O₄ and reduced graphene oxide (RGO), where the assembly of Sn₃O₄-RGO nanocomposites is dependent on the synthesis method. Three nanocomposites prepared by three different synthesis methods are investigated. The optimum assembly is by hydrothermal reactions of Sn⁴⁺ salts and pre-reduced RGO (designated as RS nanocomposite). Raman spectra verified the fingerprint of RGO in the synthesized RS nanocomposite. The Sn₃O₄ planes of (111), (210), (130), (13¯2) are observed from the X-ray diffractogram, and its average crystallite size is 3.94 nm. X-ray photoelectron spectroscopy on Sn3d and O1s spectra confirm the stoichiometry of Sn₃O₄ with Sn:O ratio = 0.76. Sn₃O₄-RGO-RS exhibits the highest response of 74% and 4% at 2 and 0.3 ppm, respectively. The sensitivity within sub-ppm CH₃COOH is 64%/ppm. Its superior sensing performance is owing to the embedded and uniformly wrapped Sn₃O₄ nanoparticles on RGO sheets. This allows a massive relative change in electron concentration at the Sn₃O₄-RGO heterojunction during the on/off exposure of CH₃COOH. Additionally, the operation is performed at room temperature, possesses good repeatability, and consumes only ~4 µW, and is a step closer to the development of a commercial CH₃COOH sensor.     

Uber das bei der Disproportionierung von SnO entstehende Zinnoxid,Sn2O3

On the Tin Oxide Sn₂O₃, which is formed by Disproportionation of SnO When tin monoxide disproportionates at >300°C, together with SnO₂ an unstable tin oxide is formed, which further decomposes under the same conditions. By chemical analysis and a modified method of X-ray analysis, its formula is determined as Sn₂O₃.     

Synthesis,open-framework structure and thermal behaviour of ammonium tin oxalate,Sn2(NH4)2(C2O4)3·3H2O

A new mixed ammonium tin oxalate trihydrate, Sn₂(NH₄)₂(C₂O₄)₃·3H₂O, has been prepared from evaporation of a solution of tin and ammonium oxalates. Its crystal structure has been solved from single-crystal diffraction data. The symmetry is orthorhombic, space group Pnma (No. 62), cell dimensions a=15.1821(5) Å, b=11.7506(2) Å, c=10.8342(3) Å, and Z=4. The structure consists of macroanionic layers built from [Sn(C₂O₄)₃]^2– groups. The SnO₆ polyhedron can be described as a pseudo pentagonal bipyramid, with the lone pair of electrons presumably occupying one apex. The resulting framework displays holes in which the water molecules and ammonium groups are located. The thermal behaviour of the mixed ammonium tin oxalate has been investigated with temperature-dependent X-ray powder diffraction and conventional thermal analysis. The degradation process has been completely explained, as well as that of oxammite, a phase always obtained in the preparations. The thermal decomposition of oxammite leads to (NH₄)₂C₂O₄ and a new acid salt, NH₄HC₂O₄. The mixed ammonium tin oxalate decomposes successively into the amorphous compounds, Sn₂(NH₄)₂(C₂O₄)₃·H₂O and Sn₂(NH₄)₂(C₂O₄)₃, SnC₂O₄ and, finally, cassiterite SnO₂.     

Phase equilibria,thermal analysis,and reactivity of tin tungsten bronzes and related phases

Crystal chemistry and phase relations of the bronze forming region of the SnWO system have been investigated. Above 780°C the tin bronzes Sn_xWO₃ are shown to be thermally unstable and an equilibrium diagram is established at 700°C which shows that the composition limits of the tetragonal phase are 0.21 ? x ? 0.29. Below x = 0.21 a series of single and two phase regions containing orthorhombic bronzes exists for which the composition limits have been established. In the range 0.29 ? x ? 0.76 the system comprises the tetragonal bronze, Sn₂W₃O₈ and SnWO₄, while above 0.76 there is no bronze, only Sn₂W₃O₈, SnWO₄ and free Sn. The phase Sn₂W₃O₈ has been isolated and shown to have a hexagonal unit cell, a = 7.696 Å, c = 18.654 Å. The evidence of differential thermal analysis and X-ray studies suggests that this hexagonal phase arises from the decomposition of the tungsten bronze phase and is itself decomposed to cubic SnWO₄ above 700°C. Small thermal effects observed in the DTA scans of tin-containing tetragonal bronzes are interpreted in terms of an order-disorder phenomenon arising from asymmetric tunnel occupancy by Sn²⁺ ions caused by the presence of the lone pair of electrons. Hydrogen reduction of Sn_xWO₃ has been shown to result in complete removal of oxygen, producing Sn + α-W in the range 600–850°C. Some activation energy data are given for the reduction process.     

Study on the oxygen exchange capacities of Ce<Subscript>2</Subscript>Sn<Subscript>2</Subscript>O<Subscript>7</Subscript> pyrochlore

Ce₂Sn₂O₇ pyrochlore was synthesized by a hydrothermal method. X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the composition and valence state of the sample. The oxygen exchange property of the Ce₂Sn₂O₇ phase was measured by an oxidation reaction in sealed air atmosphere and a followed reduction reaction in 5% H₂-95% N₂ atmosphere. Gas chromatography (GC) was used to analyze the oxygen change in the reaction. The results show that Ce₂Sn₂O₇ sample has excellent oxygen absorption capacity at 250°C as Ce³⁺ ions are oxidized to Ce⁴⁺ ions. The oxidized sample can be reduced by 5% H₂-95% N₂. The refreshed sample remains the capacity of oxygen absorption, while the oxygen exchange capacity degrades with the reduction times.     

Mössbauer diagnosis of the electronic structure and local environment of <Superscript>119</Superscript>Sn in MgTiO<Subscript>3</Subscript>

Annealing of a hydroxide precursor containing equimolar amounts of Mg²⁺ and Ti⁴⁺ and small additions of Sn⁴⁺ (0.1 at %) in air at 900°C leads to titanate MgTiO₃ with an ilmenite structure. The ¹¹⁹Sn Mössbauer spectrum of the sample (unresolved doublet with the isomer shift δ = 0.10 ± 0.01 mm/s and the quadrupole splitting Δ = 0.49 ± 0.02 mm/s) is evidence that the tin atoms are still in the oxidation state +4. Annealing of the precursor at the same temperature in a hydrogen atmosphere yields MgTiO₃ containing Sn²⁺ ions (a doublet at δ = 2.82 ± 0.01 mm/s and Δ = 1.66 ± 0.03 mm/s) (the Sn²⁺/MgTiO₃ sample). According to the spectral parameters, the ¹¹⁹Sn²⁺ ions have a low coordination number (CN ? 6) and are abnormally resistant to reduction to the metal. Analogous features of the crystal-chemical behavior of ¹¹⁹Sn²⁺ were previously observed during the Mössbauer study of the samples containing tin on the surface of Cr₂O₃, α-Al₂O₃, and MgO crystallites. The conclusion drawn from analysis of the ¹¹⁹Sn²⁺ Mössbauer parameters that tin in the Sn²⁺/MgTiO₃ sample has surface localization was supported by X-ray photoelectron spectroscopy. Mössbauer measurements show that the tin of Sn²⁺/MgTiO₃ when in contact with air is oxidized much more slowly than on the surface of Cr₂O₃, α-Al₂O₃, or MgO crystallites. The inhibition of the oxidation reaction is explained to be due to passivation of adsorbed O₂ molecules caused by their interaction with mobile t _2g electrons of Ti³⁺ forming in titanate during high-temperature annealing in H₂. In addition to the Sn²⁺ doublet, the ¹¹⁹Sn spectrum shows a spectral component with parameters (δ ～ 1.6 mm/s, Δ ≤ 0.2 mm/s) not fitting the known tin species that can form in MgTiO₃. This component is explained by persistence in titanate of some Sn⁴⁺ ions immobilizing the mobile t _2g electron at one of their neighboring Ti⁴⁺ cations.     

Mössbauer-Messungen an Sn2O3

Mössbauer Studies on Sn₂O₃ Mössbauer data for ¹¹⁹Sn in Sn₂O₃ show this compound to contain bivalent and tetravalent tin. Whereas tin(IV) is coordinated in a similar way in Sn₂O₃ and SnO₂, a rather large quadrupole splitting indicates an environment of low symmetry for tin(II).     

Snx[BPO4]1−x composites as negative electrodes for lithium ion cells: Comparison with amorphous SnB0.6P0.4O2.9 and effect of composition

A comparative study of two Sn-based composite materials as negative electrode for Li-ion accumulators is presented. The former SnB_0.6P_0.4O_2.9 obtained by in-situ dispersion of SnO in an oxide matrix is shown to be an amorphous tin composite oxide (ATCO). The latter Sn_0.72[BPO₄]_0.28 obtained by ex-situ dispersion of Sn in a borophosphate matrix consists of Sn particles embedded in a crystalline BPO₄ matrix. The electrochemical responses of ATCO and Sn_0.72[BPO₄]_0.28 composite in galvanostatic mode show reversible capacities of about 450 and 530 mAh g⁻¹, respectively, with different irreversible capacities (60% and 29%). Analysis of these composite materials by ¹¹⁹Sn Mössbauer spectroscopy in transmission (TMS) and emission (CEMS) modes confirms that ATCO is an amorphous Sn^II composite oxide and shows that in the case of Sn_0.72[BPO₄]_0.28, the surface of the tin clusters is mainly formed by Sn^II in an amorphous interface whereas the bulk of the clusters is mainly formed by Sn⁰. The determination of the recoilless free fractions f (Lamb-Mössbauer factors) leads to the effective fraction of both Sn⁰ and Sn^II species in such composites. The influence of chemical composition and especially of the surface-to-bulk tin species ratio on the electrochemical behaviour has been analysed for several Sn_x[BPO₄]_1−x composite materials (0.17<x<0.91). The cell using the compound Sn_0.72[BPO₄]_0.28 as active material exhibits interesting electrochemical performances (reversible capacity of 500 mAh g⁻¹ at C/5 rate).     

Deeper insight on the lithium reaction mechanism with amorphous tin composite oxides

Lithium reaction mechanism in amorphous tin composite oxide SnB_0.6P_0.4O_2.9 is characterized by X-ray diffraction, ¹¹⁹Sn Mössbauer spectroscopy and X-ray absorption fine structure. The analysis of the experimental data concerning SnB_0.6P_0.4O_2.9 shows that Sn^II is highly ionic and is surrounded by three oxygen atoms. The detailed analysis of lithium insertion mechanism shows a complex reduction mechanism in two steps. During the first one the main reaction corresponds to a partial Sn^II reduction, involving a mixed valence system. It is accompanied by modifications of tin environments, while lithium acts as a network modifier inducing the formation of nonbridging oxygen atoms. The second step corresponds to LiSn alloying process, with the formation of LiSn bonds. It is worth noting the persistence of SnO interactions in this second step. The reversible part of the mechanism can be explained from the formation of small particles of lithium–tin alloys in strong interaction with the oxygen atoms in the glass matrix, while the vitreous support presents an interesting dispersal effect.     

Indium oxide co-doped with tin and zinc: A simple route to highly conducting high density targets for TCO thin-film fabrication

Indium oxide co-doped with tin and zinc (ITZO) ceramics have been successfully prepared by direct sintering of the powders mixture at 1300 °C. This allowed us to easily fabricate large highly dense target suitable for sputtering transparent conducting oxide (TCO) films, without using any cold or hot pressing techniques. Hence, the optimized ITZO ceramic reaches a high relative bulk density (∼ 92% of In₂O₃ theoretical density) and higher than the well-known indium oxide doped with tin (ITO) prepared under similar conditions. All X-ray diagrams obtained for ITZO ceramics confirms a bixbyte structure typical for In₂O₃ only. This indicates a higher solubility limit of Sn and Zn when they are co-doped into In₂O₃ forming a solid-solution. A very low value of electrical resistivity is obtained for [In₂O₃:Sn_0.10]:Zn_0.10 (1.7 × 10⁻³ Ω cm, lower than ITO counterpart) which could be fabricated to high dense ceramic target suing pressure-less sintering.     

Coordinatively Unsaturated Polynuclear Mixed-Valent Sn<Superscript>II</Superscript>–Sn<Superscript>IV</Superscript> and Cu<Superscript>II</Superscript>–Sn<Superscript>IV</Superscript> Oxo-Centered Carboxylates

The tetranuclear mixed-valent oxo-cluster [Sn^IISn^IVO(O₂CCF₃)₄]₂ (1) has been prepared by reacting SnCl₂ with AgO₂CCF₃ in a sealed ampoule at 90 °C. Alternatively, 1 was obtained by acidolysis of Ph₃SnSnPh₃ with trifluoroacetic acid in solution. The X-ray diffraction study of 1 revealed the presence of a Sn^IIOSn₂^IVOSn^II core comprised of the penta-coordinated divalent and six-coordinated tetravalent tin atoms. The ¹¹⁹Sn NMR studies confirmed the stability of the cluster in solution and the presence of two different oxidation states of tin. An acidolysis of Ph₃SnSnPh₃ in the presence of [Cu₂^II(O₂CCF₃)₄] followed by sublimation of the resulting product at 90 °C afforded the first trinuclear mixed metal Sn–Cu cluster [(C₆H₅)₂Sn₂^IVCu^IIO(O₂CCF₃)₆] (2). The X-ray diffraction analysis of 2 revealed the presence of two phenyl groups attached to the six-coordinated tin(IV) atoms and the tetragonal pyramidal environment of the copper(II) atom. Both complexes have been obtained free of exogenous ligands.     

Hydrothermal Synthesis of Mixed Oxide Compositions of Cobalt-Zirconium and their Catalytic Activity in the Decomposition of Hydrogen Peroxide

The article presents the results of research on the hydrothermal synthesis of nanoscale oxide of cobalt and zirconium and their mixed oxide compositions. The synthesized samples have been characterized by the X-ray phase, scanning electron microscopy and nitrogen adsorption-desorption methods; the composition of the samples has been determined by chemical analysis methods, and their catalytic activity in the decomposition of hydrogen peroxide has been studied. It has been shown that during synthesis, highly dispersed cobalt and zirconium oxide are formed, and the sample of the composition (mol %): Co₃O₄(88)−ZrO₂(12) has the highest specific surface area (181.2 m²/g) and the highest activity (K=6.18 ⋅ 10⁻² s⁻¹) against the decomposition of hydrogen peroxide. The increasing of the ZrO₂ content in oxide compositions reduces their catalytic activity. The particle size in the synthesized samples is 7–38 nm.     

Mössbauer effect at <Superscript>119</Superscript>Sn<Superscript>4+</Superscript> nuclei in fine crystalline MnO

The hyperfine structure of the low-temperature Mössbauer spectra of dopant ¹¹⁹Sn⁴⁺ ions (0.4 at. %) in a fine crystalline MnO sample, characterized by X-ray diffraction and magnetic measurements, has been studied. The ¹¹⁹Sn spectra show that tin is distributed over positions with an inhomogeneous cationic environment. The appearance of such positions is explained by the local compensation for the excess charge of Sn⁴⁺ by manganese vacancies V _Mn and segregation of defects resulting in precipitation of MnSnO₃ clusters. The non-uniform distribution of Sn⁴⁺ and the related dependence of the number of broken magnetic bonds on the local tin concentration are responsible for the fluctuation of the T _N values, which is “perceived” by ¹¹⁹Sn in different MnO crystallites. The ¹¹⁹Sn spectra exclude the possibility that tin enters into the composition of superpara-magnetic particles.     

A tetranuclear metal system in nitratotris(triphenylstannyl)tin(IV)

A new organotin nitrato compound of formula [Sn^IV(NO₃){(C₆H₅)₃Sn^IV}₃], has been obtained and its crystal structure is reported; this represents the first X-ray characterization of a tetranuclear system of tin atoms.     

Tin trifluoroacetylacetonate [Sn(C<Subscript>5</Subscript>H<Subscript>4</Subscript>O<Subscript>2</Subscript>F<Subscript>3</Subscript>)<Subscript>2</Subscript>] as a precursor of tin dioxide in APCVD process

A new method of synthesis of volatile complex, tin trifluoroacetylacetonate [Sn(C₅H₄O₂F₃)₂], was proposed. The prepared compound was identified by IR spectroscopy, CH analysis, X-ray powder diffraction, and DTA/TGA, the composition was confirmed by MALDI-TOF mass spectrometry, crystal structure was established. Thin films of tin dioxide on silicon were obtained by atmospheric pressure chemical vapor deposition using [Sn(C₅H₄O₂F₃)₂] as a precursor. The morphology and composition of the films were studied by scanning electron microscopy, EDX elemental analysis, and X-ray powder diffraction. Surface resistance and light transmission in visible and near IR region were studied.     

Syntheses and Crystal Structures of Two New Open‐Framework Tin(II) Phosphates: Sn5O2(PO4)2 and Sn4O(PO4)2

Two new three‐dimensional neutral open‐framework tin(II) phosphates, Sn₅O₂(PO₄)₂ and Sn₄O(PO₄)₂, were synthesized under hydrothermal conditions with different ratio of tin(II) oxalate, phosphoric acid and 4,4′‐diaminodiphenylmethane. Their crystal structures have been solved by single‐crystal X‐ray diffraction methods. Sn₅O₂(PO₄)₂ crystallizes in the space group and contains six‐membered ring and twelve‐membered ring channels running parallel to the b axis. Sn₄O(PO₄)₂ crystallizes in the space group P2₁/n and contains intersecting eight‐membered ring channels. These two compounds have rare trigonal‐planar Sn₃O.     

Synthesis and structural investigation of a new oxide fluoride of composition Ba2SnO2.5F3·xH2O (x≈0.5)

The preparation of a new oxide fluoride of composition Ba₂SnO_2.5F₃·xH₂O (x≈0.5) from the low-temperature (240 °C) reaction between Ba₂SnO₄ and ZnF₂ is reported. X-ray and neutron powder diffraction showed fluorination to result in a significant enlargement along the c-axis (by ca. 3 Å) of the unit cell of the precursor oxide. A structural model based on the perovskite-related K₂NiF₄-type structure of this oxide is proposed in which there is direct replacement of oxygen in octahedral SnO₆ units by fluorine, as well as the presence of F^- at interstitial sites between BaO rock salt layers. Atomistic computer modelling indicates that apical fluorine substitution is favoured. The structural model is supported by the results of ¹⁹F and ¹¹⁹Sn MAS NMR spectroscopy as well as tin K- and barium K-edge EXAFS. Thermal analysis revealed the presence of water in the synthesized material and this is assigned to interstitial sites. ¹¹⁹Tin Mössbauer spectroscopy and tin K-edge XANES are consistent with enhanced withdrawal by substituted fluorine of electron density from Sn⁴⁺.     

Bi@Bi2Sn2O7/TiO2等离子体复合纤维的制备及增强的光催化产氢活性

以电纺TiO_2纳米纤维为基质,采用一步水热法合成了Bi@Bi_2Sn_2O_7/TiO_2等离子体复合纤维光催化剂。利用X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、高分辨透射电镜(HRTEM)、紫外-可见漫反射(UV-Vis DRS)和光致发光光谱(PL)等分析测试手段对样品的物相、形貌和光电性能等进行表征。以三乙醇胺为电子给体,研究了Bi@Bi_2Sn_2O_7/TiO_2复合纤维光催化裂解水制氢的反应过程。结果表明:在水热过程中,Bi_2Sn_2O_7构筑在TiO_2纳米纤维表面形成p-n结的同时,部分Bi3+被葡萄糖还原成金属Bi沉积在Bi_2Sn_2O_7上。金属Bi的等离子体共振效应与p-n结的协同作用,有效提高了样品的光催化活性,产氢速率达到7.26 mmol·h~(-1)·g~(-1)。     

Low temperature sintering and color of a new compound Sn1.24Ti1.94O3.66(OH)1.50F1.42

Nanopowder of a new tin(II) titanium(IV) oxide hydroxide fluoride, Sn_1.24Ti_1.94O_3.66(OH)_1.50F_1.42 with the pyrochlore-type structure (cubic a = 10.3777(7) Å, space group Fd-3m) was prepared by using a microwave-assisted solvothermal reaction. The grain size of the nanopowder was 20–30 nm in diameter. Sn_1.24Ti_1.94O_3.66(OH)_1.50F_1.42 decomposed above 300 °C, but could be sintered to relative density greater than 99% by a hydrothermal hot-pressing (HHP) method at 270 °C and 80 MPa for 4 h. The synthesized powder and solidified body obtained using HHP showed significantly different color, probably due to the difference in water content.     

Hydrothermal synthesis and structure of the first tin(II) squarate Sn2O(C4O4)(H2O)—comparison with Sn2[Sn2O2F4]

A tin(II) squarate Sn₂O(C₄O₄)(H₂O) was synthesized by hydrothermal technique. It crystallizes in the monoclinic system, space group C2/m (no. 12) with lattice parameters a=12.7380(9) Å, b=7.9000(3) Å, c=8.3490(5) Å, β=121.975(3)°, V=712.69(7) Å³, Z=4. The crystal structure determined with an R=0.042 factor, consists of [(Sn₄O₁₀)(H₂O)₂] units connected from one another in the [101] and [010] directions via squarate groups to form layers separated by Sn(II) lone pairs. This compound presents the same remarkable structural arrangement as observed in the tin-oxo-fluoride Sn₂[Sn₂O₂F₄] inorganic compound with Sn(II) lone pairs E(1) and E(2) concentrated in large rectangular-shape tunnels running along [001] direction.