Dynamics of the rutile structure. III. Lattice dynamics, infrared and Raman spectra of SnO2

Ultrafine Mix-Phase SnO-SnO2 Nanoparticles Anchored on Reduced Graphene Oxide Boost Reversible Li-Ion Storage Capacity beyond Theoretical Limit

Tin-based materials with high specific capacity have been studied as high-performance anodes for Li-ion storage devices. Herein, a mix-phase structure of SnO-SnO₂@rGO (rGO = reduced graphene oxide) was designed and prepared via a simple chemical method, which leads to the growth of tiny nanoparticles of a mixture of two different tin oxide phases on the crumbled graphene nanosheets. The three-dimensional structure of graphene forms the conductive framework. The as-prepared mix phase SnO-SnO₂@rGO exhibits a large Brunauer-Emmett-Teller surface area of 255 m² g^-1 and an excellent ionic diffusion rate. When the resulting mix-phase material was examined for Li-ion battery anode application, the SnO-SnO₂@rGO was noted to deliver an ultrahigh reversible capacity of 2604 mA h g^-1 at a current density of 0.1 A g^-1. It also exhibited superior rate capabilities and more than 82% retention of capacity after 150 charge-discharge cycles at 0.1 A g^-1, lasting until 500 cycles at 1 A g^-1 with very good retention of the initial capacity. Owing to the uniform defects on the rGO matrix, the formation of LiOH upon lithiation has been suggested to be the primary cause of this very high reversible capacity, which is beyond the theoretical limit. A Li-ion full cell was assembled using LiNi_0.5Mn_0.3Co_0.2O₂ (NMC-532) as a high-capacity cathodic counterpart, which showed a very high reversible capacity of 570 mA h g^-1 (based on the anode weight) at an applied current density of 0.1 A g^-1 with more than 50% retention of capacity after 100 cycles. This work offers a favorable design of electrode material, namely, mix-phase tin oxide-nanocarbon matrix, exhibiting adequate electrochemical performance for Li storage applications.

The tin sulfates Sn(SO4)2 and Sn2(SO4)3: crystal structures, optical and thermal properties

We report the crystal structures of two tin(IV) sulfate polymorphs Sn(SO4)2-I (P2₁/c (no. 14), a = 504.34(3), b = 1065.43(6), c = 1065.47(6) pm, β = 91.991(2)°, 4617 independent reflections, 104 refined parameters, wR₂ = 0.096) and Sn(SO4)2-II (P2₁/n (no. 14), a = 753.90(3), b = 802.39(3), c = 914.47(3) pm, β = 92.496(2)°, 3970 independent reflections, 101 refined parameters, wR₂ = 0.033). Moreover, the first heterovalent tin sulfate Sn2(SO4)3 is reported which adopts space group P1̄ (no. 2) (a = 483.78(9), b = 809.9(2), c = 1210.7(2) pm, α = 89.007(7)°, β = 86.381(7)°, γ = 73.344(7)°, 1602 independent reflections, 152 refined parameters, wR₂ = 0.059). Finally, SnSO4 - the only tin sulfate with known crystal structure - was revised and information complemented. The optical and thermal properties of all tin sulfates are investigated by FTIR, UV-vis, luminescence and ¹¹⁹Sn Mössbauer spectroscopy as well as thermogravimetry and compared.

Nanomixture of 0-D ternary metal oxides (TiO2- SnO2-Al2O3) cooperating with 1-D hydroxyapatite (HAp) nanorods for RhB removal from synthetic wastewater and hydrogen evolution via water splitting

This work was carried out to devise a feasible alternative to remove cationic dyes from industrial wastewater. A nanomixture of (TiO₂-SnO₂-Al₂O₃) cooperating with Hydroxyapatite (HAp) nanorods was synthesized in this regard as a catalyst to degrade Rhodamine B (RhB) dye from aqueous medium. The physicochemical properties of the hydrothermally prepared Hydroxyapatite Nano Mixture (HNM) were revealed through XRD, FESEM, TEM, XPS, FTIR, BET-BHJ, UV-Vis, and Raman spectroscopy techniques. The synthesized material which was found to be nanorods of average crystallite size 12.53 nm and BET Specific Surface area 60.81 m² g^-1 proved to be very effective for the removal of RhB at various pH conditions (acid, basic, and neutral). Maximum removal of 97% was achieved within 30 min of UV irradiation using 5 ppm RhB in acidic medium while at a higher concentration (20 ppm), it takes just 90 min to achieve 98% degradation of RhB under the same reaction conditions. A further catalytic potential of the prepared nanomixture for hydrogen (H₂) evolution via water splitting was explored where 129.45 μmol g^-1 of H₂ was evolved within 60 min. Our findings suggest that the prepared nanomixture could be used as an efficient catalyst for removing spent dyes used in industrial processes and also as a catalyst for hydrogen gas production.

Undoped SnO2 as a Support for Ni Species to Boost Oxygen Generation through Alkaline Water Electrolysis

In this study, the synergistic behavior of Ni species and bimodal mesoporous undoped SnO₂ is investigated in oxygen evolution reactions (OERs) under alkaline conditions without any other modification of the compositional phases or using noble metals. An efficient and environmentally friendly hydrothermal method to prepare bimodal mesoporous undoped SnO₂ with a very high surface area (>130 m² g^-1) and a general deposition-precipitation method for the synthesis of well-dispersed Ni species on undoped SnO₂ are reported. The powders were characterized by adsorption-desorption isotherms, TG-DTA, XRD, SEM, TEM, Raman, TPR-H₂, and XPS. The best NiSn composite generates, under certain experimental conditions, a very high TOF value of 1.14 s^-1 and a mass activity higher than 370 A g^-1, which are remarkable results considering the low amount of Ni deposited on the electrode (3.78 ng). Moreover, in 1 M NaOH electrolyte, this material produces more than 24 mA cm^-2 at an overpotential value of approximately +0.33 V, with only 5 wt % Ni species. This performance stems from the dual role of undoped SnO₂, on the one hand, as a support for active and well-dispersed Ni species and on the other hand as an active player through the oxygen vacancies generated upon Ni deposition.

Stanosilicates based on Sn-magadiites applied in conversion of fructose at moderate temperatures

Sn-Magadiite stanosilicates were successfully synthesized by the hydrothermal method.

3D Multi-Branched SnO2 Semiconductor Nanostructures as Optical Waveguides

Nanostructures with complex geometry have gathered interest recently due to some unusual and exotic properties associated with both their shape and material. 3D multi-branched SnO₂ one-dimensional nanostructrures, characterized by a “node”—i.e., the location where two or more branches originate, are the ideal platform to distribute signals of different natures. In this work, we study how this particular geometrical configuration affects light propagation when a light source (i.e., laser) is focused onto it. Combining scanning electron microscopy (SEM) and optical analysis along with Raman and Rayleigh scattering upon illumination, we were able to understand, in more detail, the mechanism behind the light-coupling occurring at the node. Our experimental findings show that multi-branched semiconductor 1D structures have great potential as optically active nanostructures with waveguiding properties, thus paving the way for their application as novel building blocks for optical communication networks.

U-Pb Ages, O Isotope Compositions, Raman Spectrum, and Geochemistry of Cassiterites from the Xi’ao Copper-Tin Polymetallic Deposit in Gejiu District, Yunnan Province

: The Xi’ao Cu-Sn polymetallic deposit is located in the inner alteration zone of the Laoka granite. The ore bodies extend to 400 m in the granite rock and primarily occur with fluorite and potassic alterations. Two cassiterite samples of altered rock-type ore and one tourmaline vein-type ore in the Xi’ao Cu-Sn polymetallic deposit yielded U-Pb ages of 83.3 ± 2.1 Ma, 84.9 ± 1.7 Ma, and 84.0 ± 5.6 Ma, respectively. The Raman spectrum peak values of A1g were shifted to a lower frequency, possibly due to the substitution of Sn with Nb, Ta, Fe, and Mn. Measured δ18O values of cassiterite samples and calculated δ18OH2O values for the ore-forming fluid indicate that the latter was mostly derived from magma. The high Fe and Mn abundances for cassiterite are consistent with those of hydrothermal origin. The Nb, Ta, and Ti contents indicate that cassiterites in the Xi’ao deposit likely formed in a metallogenic environment that was largely affected by granitic magmatism. Therefore, we conclude that the Xi’ao deposit is a magmatic hydrothermal deposit.

Facile Synthesis and Characterization of Two Dimensional SnO2-Decorated Graphene Oxide as an Effective Counter Electrode in the DSSC

SnO2-decorated graphene oxide (SnO2/GO) was synthesized by the modified Hummers’s method, followed by a chemical incorporation of SnO2 nanoparticles. Then, the nanocomposite was used as anon-precious counter electrode in a dye-sensitized solar cell (DSSC). Although GO has a relatively poor electrical conductivity depending essentially on the extent of the graphite oxidation, presence of SnO2 enhanced its structural and electrochemical properties. The Pt-free counter electrode exhibited a distinct catalytic activity toward iodine reduction and a low resistance to electron transfer. Moreover, the decorated GO provided extra active sites for reducing I3− at the interface of the CE/electrolyte. In addition, the similarity of the dopant in the GO film and the fluorine-doped tin oxide (FTO) substrate promoted a strong assimilation between them. Therefore, SnO2-decorated GO, as a counter electrode, revealed an enhanced photon to electron conversion efficiency of 4.57%. Consequently, the prepared SnO2/GO can be sorted as an auspicious counter electrode for DSSCs.

Synthesis of nitrogen-doped graphene wrapped SnO2 hollow spheres as high-performance microwave absorbers

Nitrogen-doped graphene (NG)/SnO₂ hollow sphere hybrids were synthesized in this work. The chemical composition, crystal structure and morphology have been characterized by FT-IR spectra, XRD, Raman spectra, XPS, SEM and TEM in detail. Reflection loss (RL) values of NG/SnO₂ hollow sphere hybrids less than −10 dB and −20 dB are found in the wide frequency range of 4.5–18 GHz and 5–16.2 GHz within 1.3–3.5 mm, and a minimum RL of −50.3 dB is achieved at 8.6 GHz with the matching thickness of only 2.3 mm. The results indicate that the NG/SnO₂ hollow sphere hybrids with high-performance microwave absorption properties have a promising future in decreasing electromagnetic wave irradiation and interference.

Nitrogen-doped graphene/SnO₂ hollow sphere hybrids were synthesized and show high-performance microwave absorption properties.

Efficient Planar Perovskite Solar Cells Using Passivated Tin Oxide as an Electron Transport Layer

Planar perovskite solar cells using low-temperature atomic layer deposition (ALD) of the SnO2 electron transporting layer (ETL), with excellent electron extraction and hole-blocking ability, offer significant advantages compared with high-temperature deposition methods. The optical, chemical, and electrical properties of the ALD SnO2 layer and its influence on the device performance are investigated. It is found that surface passivation of SnO2 is essential to reduce charge recombination at the perovskite and ETL interface and show that the fabricated planar perovskite solar cells exhibit high reproducibility, stability, and power conversion efficiency of 20%.

The effect of annealing temperature on the structure and optical properties of well-aligned 1D SnO2nanowires synthesized using template-assisted deposition

We report the observations on the structural characterization and optical properties of SnO₂nanowires post-treated under different annealing temperatures (300, 400, 500 & 600 °C) for 1 h.

Self-assembled SnO2 micro- and nanosphere-based gas sensor thick films from an alkoxide-derived high purity aqueous colloid precursor

Tin oxide is considered to be one of the most promising semiconductor oxide materials for use as a gas sensor. However, a simple route for the controllable build-up of nanostructured, sufficiently pure and hierarchical SnO2 structures for gas sensor applications is still a challenge. In the current work, an aqueous SnO2 nanoparticulate precursor sol, which is free of organic contaminants and sorbed ions and is fully stable over time, was prepared in a highly reproducible manner from an alkoxide Sn(OR)4 just by mixing it with a large excess of pure neutral water. The precursor is formed as a separate liquid phase. The structure and purity of the precursor is revealed using XRD, SAXS, EXAFS, HRTEM imaging, FTIR, and XRF analysis. An unconventional approach for the estimation of the particle size based on the quantification of the Sn-Sn contacts in the structure was developed using EXAFS spectroscopy and verified using HRTEM. To construct sensors with a hierarchical 3D structure, we employed an unusual emulsification technique not involving any additives or surfactants, using simply the extraction of the liquid phase, water, with the help of dry butanol under ambient conditions. The originally generated crystalline but yet highly reactive nanoparticles form relatively uniform spheres through self-assembly and solidify instantly. The spheres floating in butanol were left to deposit on the surface of quartz plates bearing sputtered gold electrodes, producing ready-for-use gas sensors in the form of ca. 50 μm thick sphere-based-films. The films were dried for 24 h and calcined at 300 °C in air before use. The gas sensitivity of the structures was tested in the temperature range of 150-400 °C. The materials showed a very quickly emerging and reversible (20-30 times) increase in electrical conductivity as a response to exposure to air containing 100 ppm of H2 or CO and short (10 s) recovery times when the gas flow was stopped.

Ultrafast breathing humidity sensing properties of low-dimensional Fe-doped SnO2 flower-like spheres

It is demonstrated that the low-dimensional Fe-doped SnO₂ flower-like spheres with enhanced breathing sensing property are synthesized by a simple template- and surfactant-free hydrothermal method.

One-step synthesis of SnO2 nanoparticles-loaded graphitic carbon nitride and their application in thermal decomposition of ammonium perchlorate

SnO₂NPs/g-C₃N₄ hybrids can effectively catalyze NH₄ClO₄ molecules by the aid of a synergistic reaction of SnO₂.

Ab initio and shell model studies of structural, thermoelastic and vibrational properties of SnO2 under pressure

The pressure dependences of the structural, thermoelastic and vibrational properties of SnO2 in its rutile phase are studied, as well as the pressure-induced transition to a CaCl2-type phase. These studies have been performed by means of ab initio (AI) density functional theory calculations using the localized basis code SIESTA. The results are employed to develop a shell model (SM) for application in future studies of nanostructured SnO2. A good agreement of the SM results for the pressure dependences of the above properties with the ones obtained from present and previous AI calculations as well as from experiments is achieved. The transition is characterized by a rotation of the Sn-centered oxygen octahedra around the tetragonal axis through the Sn. This rotation breaks the tetragonal symmetry of the lattice and an orthorhombic distortion appears above the critical pressure P(c). A zone-center phonon of B1g symmetry in the rutile phase involves such rotation and softens on approaching Pc. It becomes an Ag mode which stabilizes with increasing pressure in the CaCl2 phase. This behavior, together with the softening of the shear modulus (C11-C12)/2 related to the orthorhombic distortion, allows a precise determination of a value for Pc. An additional determination is provided by the splitting of the basal plane lattice parameters. Both the AI and the experimentally observed softening of the B(1g) mode are incomplete, indicating a small discontinuity at the transition. However, all results show continuous changes in volume and lattice parameters, indicating a second-order transition. All these results indicate that there should be sufficient confidence for the future employment of the shell model.

Controlled fabrication of SnO(2) arrays of well-aligned nanotubes and nanowires

Highly oriented SnO(2) nanotubes and nanowires arrays have been selectively fabricated via a convenient one-step wet-chemical approach using anodic aluminium oxide (AAO) as a hard template. Wall thickness of the SnO(2) nanotubes was tunable. The as-prepared nanostructures were composed of fine particles with sizes as small as 5 nm. Formation mechanism of SnO(2) nanostructure arrays with different shape is also discussed based on the experimental results. The structure, morphology, composition properties of the as-prepared samples were characterized using X-ray powder diffraction, transmission electron microscopy, energy dispersive X-ray spectrometry, scanning electron microscopy and Raman spectrum.

Derivation of Force Field Parameters for SnO2−H2O Surface Systems from Plane-Wave Density Functional Theory Calculations

Plane-wave density functional theory (DFT-PW) calculations were performed on bulk SnO2 (cassiterite) and the (100), (110), (001), and (101) surfaces with and without H2O present. A classical interatomic force field has been developed to describe bulk SnO2 and SnO2-H2O surface interactions. Periodic density functional theory calculations using the program VASP (Kresse et al., 1996) and molecular cluster calculations using Gaussian 03 (Frisch et al., 2003) were used to derive the parametrization of the force field. The program GULP (Gale, 1997) was used to optimize parameters to reproduce experimental and ab initio results. The experimental crystal structure and elastic constants of SnO2 are reproduced reasonably well with the force field. Furthermore, surface atom relaxations and structures of adsorbed H2O molecules agree well between the ab initio and force field predictions. H2O addition above that required to form a monolayer results in consistent structures between the DFT-PW and classical force field results as well.