Presence Of Sn2 Research Articles

Is the Presence of Sn2+ a Crucial Factor for the Generation of Low Thermal Conductivity in Tin-Based Sulfides?

Comprehending the relationship between crystal structures and transport properties is crucial to develop materials with improved electrical and thermal properties for thermoelectric applications. In this article, we report on the complex crystal structure and physical properties of Cr2Sn3S7, a n-type magnetic semiconductor with a low energy band gap and low thermal conductivity. Importantly, we demonstrate that the high level of structural complexity is related to the coexistence of two sublattices: a host lattice, [Cr4Sn2S11]2-, characterized by a mixed Sn4+/Cr3+ occupancy of its cationic sites, and a guest lattice characterized by [Sn4S3]2+ chains, containing Sn2+ cations only, closely related to the ones encountered in the orthorhombic SnS compound. By combining experiments including X-ray diffraction with ab initio calculations of electrons and phonons, we succeeded to elucidate the origin of the low thermal conductivity in Cr2Sn3S7. We demonstrate that the low dimensionality of the [Sn4S3]2+ chains, which generates weak Sn···S interactions with the 3D host lattice, is induced by the lone pair stereochemical activity of Sn2+. This lattice softening favors strong anisotropic vibrations at low frequencies, highlighting the primordial role played by Sn2+ cations in both crystal structure dimensionality and low thermal conductivity in tin-based sulfides.

Surface Chemistry and Band Engineering in AgSbSe2: Toward High Thermoelectric Performance.

AgSbSe2 is a promising thermoelectric (TE) p-type material for applications in the middle-temperature range. AgSbSe2 is characterized by relatively low thermal conductivities and high Seebeck coefficients, but its main limitation is moderate electrical conductivity. Herein, we detail an efficient and scalable hot-injection synthesis route to produce AgSbSe2 nanocrystals (NCs). To increase the carrier concentration and improve the electrical conductivity, these NCs are doped with Sn2+ on Sb3+ sites. Upon processing, the Sn2+ chemical state is conserved using a reducing NaBH4 solution to displace the organic ligand and anneal the material under a forming gas flow. The TE properties of the dense materials obtained from the consolidation of the NCs using a hot pressing are then characterized. The presence of Sn2+ ions replacing Sb3+ significantly increases the charge carrier concentration and, consequently, the electrical conductivity. Opportunely, the measured Seebeck coefficient varied within a small range upon Sn doping. The excellent performance obtained when Sn2+ ions are prevented from oxidation is rationalized by modeling the system. Calculated band structures disclosed that Sn doping induces convergence of the AgSbSe2 valence bands, accounting for an enhanced electronic effective mass. The dramatically enhanced carrier transport leads to a maximized power factor for AgSb0.98Sn0.02Se2 of 0.63 mW m-1 K-2 at 640 K. Thermally, phonon scattering is significantly enhanced in the NC-based materials, yielding an ultralow thermal conductivity of 0.3 W mK-1 at 666 K. Overall, a record-high figure of merit (zT) is obtained at 666 K for AgSb0.98Sn0.02Se2 at zT = 1.37, well above the values obtained for undoped AgSbSe2, at zT = 0.58 and state-of-art Pb- and Te-free materials, which makes AgSb0.98Sn0.02Se2 an excellent p-type candidate for medium-temperature TE applications.

Nopol Production Over Sn‐MCM‐41 Immobilized in a Wall‐Coated Microreactor using Formaldehyde Generated Ex‐Situ

AbstractThe kinetic study of the synthesis of nopol from β‐pinene and formaldehyde generated ex‐situ was carried out in a continuous flow process using Sn‐MCM‐41 wall‐coated microreactors of 1/8“ stainless steel tubes. The presence of Sn2+ and Sn4+ species was identified through XPS and TEM; the homogeneous distribution of tin on the support throughout the surface of the coating was verified by SEM analysis. Taylor flow regime and the kinetic control of the reaction were verified with hydrodynamic studies. A determination coefficient of 0.92 was obtained for the mathematical adjustment of the equation that described the reaction pathway obtained under the assumption of a dual‐site Langmuir‐Hinshelwood formalism with product desorption as the limiting step.

The Removal of Pertechnetate from Aqueous Solution by Synthetic Hydroxyapatite: The Role of Reduction Reagents and Organic Ligands.

The use of knowledge from technetium radiochemistry (even from nuclear medicine applications) allows us to select an sorbent for 99mTc radionuclide sorption, which is hydroxyapatite. Using radioisotope indication, the 99mTcO₄- sorption process on synthetic hydroxyapatite was studied by the batch method in the presence of SnCl2 and FeSO4 reducing agents. The complexing organic ligands' effect on the 99mTcO₄- sorption under reducing conditions was investigated. In the presence of Sn2+ ions without the addition of organic ligand, the sorption percentage reached above 90% independently of the environment. In the presence of Fe2+ ions without the addition of organic ligand, the sorption of 99mTcO₄- was significantly lower and was at approximately 6%, depending on the concentration of Fe2+ ions in solution. The effect of complexing organic ligands on the 99mTcO₄- sorption on hydroxyapatite from the aqueous solution, acetate buffer and phosphate buffer decreases in the following order for Sn2+: oxalic acid > ethylenediaminetetraacetic acid > ascorbic acid. In the presence of Fe2+ ions without organic ligands, the sorption reached up to 15% depending on the composition of the solution. The addition of oxalic acid and ascorbic acid increased the sorption up to 80%. The ethylenediaminetetraacetic acid had no significant effect on the sorption of technetium on hydroxyapatite.

A Fluorescence Turn On-off-on Method for Sensitive Detection of Sn2+ and Glycine Using Waste Eggshell Membrane Derived Carbon Nanodots as Probe.

Changes in Sn2+ and glycine levels are relevant to many important physiological procedures in human health. However, investigation of their physiological functions is limited because few versatile methods towards Sn2+ and glycine detection have been developed. In this work, a fluorescence turn on-off-on strategy was firstly constructed for rapid and sensitive detection of Sn2+ and glycine through the specific binding between Sn2+ and glycine. Carbon nanodots (CDs) with a quantum yield of 19.5% were synthesized by utilizing inner film of waste eggshell as carbon source and employed as fluorescent probe. In the presence of Sn2+, the fluorescence of CDs was quenched by Sn2+ via the primary inner filter effect (IFE). However, the binding between Sn2+ and glycine prevented the IFE between Sn2+ and CDs, resulting in fluorescence recovery of CDs. Under optimized conditions, the fluorescent response of CDs displayed good linear relationships with the concentrations of Sn2+ in the range of 10-200µM and 200-5000µM, and the limit of detection (LOD) was 2.4µM. For glycine detection, a good linear relationship was obtained in the concentration range of 5-1000µM with a low LOD down to 0.76µM. Moreover, the practicability of the assay was also demonstrated by measuring glycine content in human serum samples. This work provides an economical, green and fast method for biological analysis of Sn2+ and glycine.

Photocatalytic activity of Sn-doped ZnO synthesized via peroxide route

ZnO*ZnO2 mixture was prepared by thermal hydrolysis of a zinc peroxo-complex precursor in presence of Sn2+ and Sn4+ ions. The effect of different tin valence states on structure and photocatalytic properties of the resulting products was investigated. All samples before annealing contained ZnO2 and except one sample also SnO2. Microstructural analysis showed a difference in morphology between the two sets of samples. A difference was also observed for the specific surface area. The photocatalytic decolorization of Orange II dye was employed to determine the photocatalytic activity of the samples; Sn2+ doped samples were more active than Sn4+ doped ZnO samples. Temperature 600 °C was optimal for annealing - the sample ZnP150Sn2 annealed at 600 °C had the highest rate constant (0.0730 min−1) among the samples. Additional increase of Sn2+ amount led to further increase in rate constant (0.0937 min−1 for the sample ZnP200Sn2) up to a certain point.

A dual-mode fluorescent probe based on perylene for the detection of Sn2+

A dual-mode fluorescent probe based on perylene, namely N,N'-bis[(2-salicylaldehyde)-ethyl]-3,4,9,10-perylene tetracarboxylicdiimide (SEPTD), has been constructed and synthesized for the detection of Sn2+ in DMF solution. SEPTD exhibited excellent selectivity and sensitivity for detecting Sn2+. The color change of SEPTD was from colerless to yellow in the presence of Sn2+ in DMF solution under 365 nm UV light. The fluorescent intensity of SEPTD was increasing gradually with adding Sn2+. The superior linear response of SEPTD for the concentration of Sn2+ ranged from 50 to 100 μM. The limit of detection (LOD) of SEPTD for the detection of Sn2+ was low to 0.168 μM. The reversibility behavior of SEPTD was investigated. Finally, the mechanism of SEPTD for detecting Sn2+ was investigated by 1H NMR titration and IR spectra.

Improved dielectric properties of CaCu3−xSnxTi4O12 ceramics with high permittivity and reduced loss tangent

The structural and electrical parameters of sintered CaCu3−xSnxTi4O12 ceramics (x = 0, 0.05, and 0.10) were systematically investigated. Single-phase CaCu3Ti4O12 was detected in all-ceramic samples. The grain size in the CaCu3−xSnxTi4O12 ceramics decreased as x increased. A high dielectric permittivity of ~ 6736–19,992 and a reduced loss tangent of ~ 0.028–0.033 was obtained in the ceramics with x = 0.05 and 0.10. In addition, the temperature stability of the dielectric permittivity and loss tangent also improved by doping with Sn ions. The dielectric response of the CaCu3−xSnxTi4O12 ceramics was closely associated with an internal barrier layer capacitor model. X-ray photoelectron spectroscopy indicated the existence of mixed Cu+/Cu2+ and Ti3+/Ti4+ in all ceramic samples, which promoted the hopping of electrons between Cu+ ↔ Cu2+ and Ti3+ ↔ Ti4+ and was the possible origin of semiconducting grains in the samples. The presence of Sn2+ was detected by X-ray photoelectron spectroscopy indicated a reduction in the oxidation state of the Sn ions due to the charge compensation that occurred for the replacement of Cu host sites.

Electrical properties of barium titanate in presence of Sn2+ dopant

The properties of BaTiO3 based ferroelectrics can be enhanced by appropriate doping. BaTiO3 and Sn doped BaTiO3 were synthesized using sol–gel route and characterized by X-ray diffraction technique. Microstructural evaluation was done by scanning electron microscopy. On doping with Sn, the dielectric permittivity of the material is increased 3 times to that of the pure BaTiO3 and a very low dielectric loss of < 1 was observed. Tin doped BaTiO3 can act as a promising material for piezoelectric applications because of high Tc (292 °C).

Peroxidase from Coleus Forskohlii: Purification and Biochemical Characterization

In this study, a peroxidase from new source was purified using ion exchange and gel filtration techniques. The recovery for peroxidase activity was 19% with 11-fold purification and specific activity of 749 unit/mg protein. Purified peroxidase demonstrated a molecular mass of 39 kDa using gel filtration and was confirmed as a single band on SDS-PAGE. The purified peroxidase revealed a broad optimum pH activity at 6.0-6.5 and 50°C temperature. The kinetic parameters for purified peroxidase toward H2O2 and guaiacol as substrates were found to be Km = 3.355, 5.395 mM, Kcat = 99.52, 79.56 s-1 and Vmax =1.531, 1.242 µmole ml-1 min-1, respectively. The catalytic efficiency (kcat/Km) of the purified peroxidase was 14.75 and 29.66 s−1 mM−1 for guaiacol and H2O2, respectively. Peroxidase activity was observed to be enhanced by Cu2+, Co2+, Ni2+ and inhibited in the presence of Sn2+, Al3+, Hg2+, NaN3, EDTA and urea. Characterization showed that peroxidase purified from C. forskohlii has the ability to be used for food industrial applications.

Fe–Ni metal–organic frameworks with prominent peroxidase-like activity for the colorimetric detection of Sn2+ ions

Fe-Ni-MOFs with different amounts of Fe are synthesized through a two-step template etching method. Kinetic analysis indicates that Fe-Ni-MOF exhibits prominent intrinsic peroxidase-like activity, which could catalytically oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to produce oxidized TMB (oxTMB) with a blue color. As a peroxidase-mimicking MOF, Fe-Ni-MOF with its efficient stable catalysis properties is demonstrated to allow a sensitive colorimetric assay for Sn2+ ions. The mechanism is explored, whereby Sn2+ ions could reduce the peroxidase-like activity of Fe-Ni-MOF based on a redox interaction, making the oxTMB color lighter and decreasing the absorbance intensity at 652 nm. The linear determination of the Sn2+ ion concentration using a UV-vis spectrometer ranges from 0.01 mM to 1.0 mM and from 1.0 mM to 4.0 mM. The presented Fe-Ni-MOF-based assay of Sn2+ ions was successfully applied to real water samples.

Rapid and room temperature synthesis of MAPb1−xSnxBr3−2xCl2x perovskite quantum dots with enhanced lifetime in warm WLEDs: A step towards environmental friendly perovskite light harvester

In this work, a facile approach to develop nontoxic CH3NH3PbBr3 perovskite quantum dots (PQDs) by substituting tin (Sn2+) ion instead of lead (Pb2+) ion and chloride (Cl−) ion instead of bromide (Br−) ion has been reported. Synchronized cation and anion substitution in CH3NH3Pb1−xSnxBr3−2xCl2x PQDs has resulted in commercial-friendly properties like fine-tuning of bandgap, shifting of color emission from green to cyan region (523 nm–490 nm), enhancing structural stability, excitonic lifetime, and color gamut. Presence of Sn2+ cations in +2 state, Cl− anions in −1 state, and ion exchange was confirmed from various spectroscopic and morphological analyses. Photoluminescence quantum yield (PLQY) for unsubstituted CH3NH3PbBr3 was observed as 97.50% and it is reduced to >50% for 15% SnCl2 substituted CH3NH3PbBr3 PQDs because of the presence of defect-related nonradioactive recombination centres while cation and anion changeover. Warm white LED prototype with 123% color gamut encircling as per National Television System Committee Standard was achieved using as prepared CH3NH3Pb1−xSnxBr3−2xCl2x PQDs and commercial red phosphor on the blue LED chip. The inflated colour-gamut, promising PLQY, and slender FWHM of as-synthesized CH3NH3Pb1−xSnxBr3−2xCl2x PQDs illustrate great prospect to explore their utilization in display applications. Reduction in toxicity in perovskite material was confirmed by the biological study.

Toothpaste factors related to dentine tubule occlusion and dentine protection against erosion and abrasion.

To investigate the effect of toothpastes on dentine surface loss and tubule occlusion, and the association of toothpaste-related factors to each of the outcomes. One hundred and sixty human dentine specimens were randomly distributed into 10 groups, according to different toothpastes. The specimens were submitted to artificial saliva (60min), citric acid (3min), and brushing abrasion (25s; totalizing 2min in toothpaste slurries). This was repeated five times and two outcome variables were analyzed: dentine surface loss (dSL; μm) and tubule occlusion by measurement of the total area of open tubules (Area-OT; μm2). Data were analyzed with Kruskal-Wallis and Mann-Whitney tests (α= 0.05); bivariate and multivariate regressions were used to model the association of the chemical (pH, concentration of F-, Ca2+, and PO43- and presence of Sn2+) and physical (% weight of solid particles, particle size, and wettability) factors of the toothpastes to both outcome variables. Toothpastes caused different degrees of dSL and did not differ in Area-OT. All chemical and physical factors, except the presence of Sn2+, were associated with dSL (p< 0.001). Area-OT was associated only with the presence of Sn2+ (p= 0.033). Greater dSL was associated with lower pH, lower concentration of F-, higher concentration of Ca2+ and PO43-, greater % weight of solid particles, smaller particle size, and lesser wettability, whereas tubule occlusion was associated with the presence of Sn2+. Depending on their chemical and physical composition, toothpastes will cause different degrees of dentine tubule occlusion and dentine surface loss. This could, in turn, modulate dentine hypersensitivity.

Carbon-supported binary Li-Sn catalyst for acetylene hydrochlorination

The study of a novel catalyst containing LiCl and SnCl2 (LiSn/AC) for acetylene hydrochlorination has been reported in this paper. Furthermore, the performance of both high activity (98.3%) and selectivity (>98.0%) are achieved by LiSn/AC catalysts under the reaction temperature of 200 °C and C2H2 hourly space velocity of 30 h−1. The structural characteristics of the Sn based catalysts were deeply researched via BET, XRD, TEM, TPR, C2H2-TPD, XPS and TG techniques. According to these characteristic results, we proposed that the presence of Sn2+ exhibited better activity and stability than that of Sn4+ in Sn based catalysts. Additionally, LiCl additives not only can restrain the oxidation of Sn2+ and the loss of Sn4+ in fresh Sn based catalysts but also make the Snδ+ (δ = 2,4) species dispersed well on the surface of support. Therefore, the adsorption capacity of C2H2 and HCl was enhanced in LiSn/AC, which exhibited the better catalytic performance than that of Sn based catalyst.

Synthesis, Structure, and Electronic Properties of Sn(CN2) and Sn4Cl2(CN2)3.

A solid-state metathesis reaction between equimolar amounts of Li2(CN2) and SnCl2 revealed the formation of two new compounds, Sn4Cl2(CN2)3 and Sn(CN2). Thermal analysis of this reaction indicated that Sn4Cl2(CN2)3 forms exothermically near 200 °C and subsequently transforms into Sn(CN2) at higher temperatures. The crystal structures of both compounds are presented. According to optical measurements and band structure calculations, Sn(CN2) can be considered as a semiconductor with a band gap on the order of 2 eV. The presence of Sn2+ ions in the structure of Sn(CN2) with a toroidally shaped lone pair is indicated by electron localization function calculations. The structure of Sn(CN2) is shown to be related to the structures of FeS2 and CaC2.

Inhibition of Anodic Dissolution of Steel by Sn2+ in Perchloric Acid Solution

The inhibition effect of Sn2+ on the anodic dissolution of Fe-0.05C steel was investigated electrochemically in a solution of 0.2 M HClO4. Anodic currents were suppressed in the presence of Sn2+, and the suppression behavior depended on the concentration of Sn2+ and the electrode potentials. The experimental condition for the current suppression is explained by the theory of underpotential deposition (UPD). X-ray photoelectron spectroscopy (XPS) depth analysis revealed the deposition of metallic Sn on the steel, while inductively coupled plasma-mass spectrometry (ICP-MS) analysis demonstrated that the Sn layer thickness was monolayer-level. This strongly suggests that the anodic dissolution of iron was suppressed by the UPD of Sn. The proposed mechanism for corrosion inhibition by Sn-UPD also explains the superior corrosion resistance of Sn-bearing steel under atmospheric environments.

Efficient photocatalytic removal of RhB using magnetic Fe3O4–SnO2 nanocomposites containing Sn2+ interstitial impurities

Fe3O4–SnO2 nanocomposites with SnO2 in the reduced form (without post-annealing) were prepared. X-ray diffraction, high resolution TEM microscopy, X-Ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy and magnetization measurements were used for sample characterizations. Additionally, nitrogen adsorption–desorption isotherms and surface area measurements (BET) were made for porosity and surface area determination. Depending on the amount of SnCl2 used in preparation, tetragonal tin oxide hydroxide Sn6O4(OH)4 or SnO secondary phases were also formed in various samples. XPS analysis shows the presence of surface Sn2+ states and as well as lack, or non-detectable, interstitial tin inside SnO2 nanocrystallites. The presence of Sn2+ surface states determines important changes of both magnetic and photocatalytic properties of samples. Thus Sn2+ surface states determine, on the one hand, an increased efficiency of photocatalytic processes and, on the other hand, a significant decrease of the saturation magnetization of Fe3O4 cores. Moreover, by using ESR spin trapping technique, the generation of reactive oxygen species (·OH, O2·−) resulted by light irradiation of samples was evidenced.

Sn-BEA zeolites prepared by two-step postsynthesis method: Physicochemical properties and catalytic activity in processes based on MPV reduction

Sn0.5SiBEA and Sn2.0SiBEA zeolites obtained by two-step postsynthesis method were characterized by several physicochemical techniques (namely, NMR, Mössbauer, XPS, DR UV-vis and IR spectroscopies) and used in the study of Meerwein–Ponndorf–Verley (MPV) reduction as well as with the subsequent reaction of etherification, that is, conversion of (i) cyclohexanone with 2-propanol, (ii) 4-methoxybenzaldehyde with 2-butanol, and (iii) HMF with butyl alcohols (1-butanol, 2-butanol or isobutanol). The results have shown that in the case of cyclohexanone, MPV reduction to cyclohexanol occurs on both Sn0.5SiBEA and Sn2.0SiBEA zeolite catalysts with a higher degree of conversion in the presence of Sn2.0SiBEA. For 4-methoxybenzaldehyde a tandem process was observed consisting of MPV reduction with 2-butanol to 4-methoxybenzylalcohol followed by its etherification with 2-butanol to 4-methoxybenzyl sec-butyl ether. Higher conversion of aldehyde was achieved on the catalyst with higher amount of tin. The zeolites were active in HMF conversion with butyl alcohols. However, a tandem process including MPV reduction with the next formation of furanic diether was achieved only in the presence of secondary alcohol at test conditions.

Sensitizing effects of Sn2+ ions on Tm3+ emissions for deep UV excitation in phosphate glasses

In the present work, Tm3+-doped strontium phosphate glasses modified by Sn2+ are investigated. Sn2+ and Tm3+ can be co-excited with the deep UV light to emit the tunable blue light. The reinforced and purified blue emission is obtained at the excitation bands toward the deep-UV part of the spectrum. Photoluminescence emission and excitation spectra, and emission decay curves indicate consistently that the improved Tm3+ emission is in association with the presence of Sn2+ in the host glass where energy transfer from Sn2+ to Tm3+ occurs. Relevant mechanism is discussed.

Acid–Base and Thermodynamic Properties ofd-Gluconic Acid and Its Interaction with Sn2+and Zn2+

In this paper, new potentiometric, calorimetric, and voltammetric measurements are reported to model the behavior of d-gluconic acid in aqueous NaCl(aq) and NaNO3(aq) ionic media at different ionic strengths and temperatures (283.15 ≤ T/K ≤ 318.15) also in the presence of Sn2+ and Zn2+. The protonation constants of d-gluconic acid (Gluc– in its deprotonated form) in NaCl(aq) and NaNO3(aq) are very similar. The dependence on ionic strength of the protonation constant was modeled by means of the extended Debye–Huckel type equation, the Specific ion Interaction Theory (SIT) and a weak interaction model. At infinite dilution and T = 298.15 K, the thermodynamic parameters for the proton binding reaction, determined by direct calorimetric titrations and temperature gradients of protonation constants, are log KH0 = 3.709 ± 0.004, ΔG0 = −21.18 ± 0.01 kJ mol–1, ΔH0 = −4.56 ± 0.04 kJ mol–1, and TΔS0 = 16.6 ± 0.1 kJ mol–1, indicating that the reaction is exothermic and entropic in nature. Potentiometric and voltamme...