Absence Of Sn Research Articles

Growing MASnI3 perovskite single-crystal films by inverse temperature crystallization

Perovskite single-crystal films are promising candidates for high-performance perovskite optoelectronic devices due to their optoelectrical properties. However, there are few reports of single-crystal films of tin based perovskites. Here, for the first time, we realize the controllable growth and preparation of lead-free tin perovskite MASnI3 single crystals via inverse temperature crystallization (ITC) strategy with γ–butyrolactone (GBL) as solvent. The solubility characteristics of MASnI3 in GBL are clarified by quantitative analytical method. Highly repeatability experiments are further demonstrated using this unique solubility and ITC properties. Sequentially, using space limiting method, tin perovskite MASnI3 single-crystal thin films are fabricated with micron-scale thickness, which is highly desired for efficient tin perovskite solar cells. Our MASnI3 single-crystal thin films show typical single-crystalline features including strongly optical absorbance with sharp absorption edges, pure-phase x-ray diffraction patterns, and absence of Sn(IV) x-ray photoelectron spectroscopy. We believe that our findings will further broaden the application prospects of tin perovskite MASnI3 single crystals and cause a new upsurge in exploring the field of lead-free perovskite single-crystal growth.

Developmental immaturity of sialic acid recognition mediates neonatal susceptibility to GBS pneumonia

Abstract Group B Streptococcus (GBS) is a major neonatal pathogen but rarely causes disease in adults. We previously showed in mice that GBS escapes killing in the neonatal lung via its heavily sialylated capsule. Immune cells detect sialic acid moieties via expression of a repertoire of Siglec receptors. Combinatory expression of proinflammatory and anti-inflammatory Siglec receptors allows differentiation between host and pathogenic microbial sialic acid modifications. We test here the hypothesis that neonatal alveolar macrophages (AMs) fail to detect and kill GBS due to developmental immaturity of Siglec receptor expression. Adult AMs express the proinflammatory sialic acid receptor Sialoadhesin (Sn, Siglec-1) and the anti-inflammatory receptors Siglec-E and Siglec-F. However, real time PCR, immunofluorescence, and FACS detected only Siglec-E in neonatal lung macrophage populations. Sn expression increased soon after birth and was restricted to AMs. The timing of increased Sn expression in newborn mice correlated with susceptibility to GBS. Mice infected with GBS on day 1 suffered early onset mortality, while mice infected on day 2 displayed late onset disease. Mice infected on day 3 survived GBS infection. Further implicating AM immaturity, Csf2−/− mice, which have defects in AM differentiation, lacked Sn expression and had reduced GBS clearance following infection. The presence of Siglec-E but absence of Sn in newborn AMs appeared to promote tolerance to GBS. Newborn SigE−/− mice had increased GBS phagocytosis and killing compared to WT controls. We therefore conclude that GBS exploits developmental immaturity of Siglec expression in AMs via its sialic acid capsule in causing neonatal disease.

Non-destructive characterization of Egyptian Blue cakes and wall painting fragments from the east of Lake Van, Turkey.

A total of five Urartian blue cakes and two wall painting fragments, from excavations in different regions of the east of Lake Van, were analyzed by means of X-ray diffraction (XRD), micro-X-ray fluorescence spectrometry (μ-XRF), scanning electron microscopy combined with energy dispersive spectrometry (SEM-EDS) and Fourier-transform infrared spectroscopy (FT-IR). All the studies were performed non-destructively considering the great archaeological importance of the samples. The results indicate the presence of Egyptian Blue, which is the first synthetic pigment, consists of crystals of calcium-copper tetrasilicate (cuprorivaite, CaCuSi4Ol0) along with unreacted quartz (SiO2) and in some cases. Comparison of the elemental compositions of the samples from Egypt and Mesopotamia suggests that EB cakes may be local products due to the presence of zinc. The absence of Sn on the other hand, indicates that the source of the copper may be a copper ore not bronze scrap.

Effect of Sn on Isobutane Dehydrogenation Performance of Ni/SiO2 Catalyst: Adsorption Modes and Adsorption Energies of Isobutane and Isobutene.

The reaction of isobutane over Ni/SiO2 catalyst changes from hydrogenolysis to dehydrogenation when Sn is introduced. The adsorption modes and energies of isobutane and isobutene over the Ni/SiO2 catalyst with and without Sn addition were determined by in situ FTIR and a novel transient response adsorption approach. In the absence of Sn, isobutane is adsorbed in a double-site mode with H atoms in two methyl groups of isobutane, facilitating hydrogenolysis of isobutane. After the addition of Sn, a single-site adsorption mode with the H atom in the methylidyne group is speculated instead, which is beneficial to the rupture of the C-H bond rather than the C-C bond. Moreover, the double-site adsorption mode of isobutene with the C═C bond and the H atom in a methyl group is turned into single-site mode with the C═C bond after the introduction of Sn. As for the adsorption energy of isobutene, the introduction of Sn leads to an obvious decrease from 74 to 50 kJ mol-1 and facilitates the prompt desorption of isobutene, resulting in a high selectivity of 81.9 wt %.

Compositional Dependence of Chemical and Electrical Properties in Cu2ZnSnS4Thin Films

Photovoltaic-grade thin-film solar cell absorber layers composed of Cu2ZnSnS4 are most often prepared under nonstoichiometric compositions, in particular Cu-poor and Zn-rich conditions. The effects of compositional deviations on chemical and electrical properties of this material are under investigation and are expected to have a strong influence on final device performance. Herein, a study of variation in the cationic ratios (Cu/Zn, Cu/Sn) across a broad range and their effect on the properties of thin films is presented. After etching to remove the ZnS phase, the ratio of Cu/Zn is nearly constant between all the films, while there are significant variations in the ratio of Cu/Sn. This is correlated with changes in the chemical and electrical properties of these films, as determined by variable temperature conductivity measurements. The postetching composition and absence of Sn–S secondary phases points to multivalency of Sn in this material, in addition to other potential factors such as differences in grain size and defect formation. The Cu/Sn ratio is shown to strongly affect the electrical properties of films, in particular of the conductivity, grain boundary barriers, and localization length.

Role of Sn in the Regeneration of Pt/γ-Al2O3 Light Alkane Dehydrogenation Catalysts.

Alumina-supported Pt is one of the major industrial catalysts for light alkane dehydrogenation. This catalyst loses activity during reaction, with coke formation often considered as the reason for deactivation. As we show in this study, the amount and nature of carbon deposits do not directly correlate with the loss of activity. Rather, it is the transformation of subnanometer Pt species into larger Pt nanoparticles that appears to be responsible for the loss of catalytic activity. Surprisingly, a portion of the Sn remains atomically dispersed on the alumina surface in the spent catalyst and helps in the redispersion of the Pt. In the absence of Sn on the alumina support, the larger Pt nanoparticles formed during reaction are not redispersed during oxidative regeneration. It is known that Sn is added as a promoter in the industrial catalyst to help in achieving high propene selectivity and to minimize coke formation. This work shows that an important role of Sn is to help in the regeneration of Pt, by providing nucleation sites on the alumina surface. Aberration-corrected scanning transmission electron microscopy helps to provide unique insights into the operating characteristics of an industrially important catalyst by demonstrating the role of promoter elements, such as Sn, in the oxidative regeneration of Pt on γ-Al2O3.

Low-temperature oxidation of methane on Pd-Sn/ZrO2 catalysts

Pd/ZrO2, Pd-Sn/ZrO2 and Sn/ZrO2 were prepared by incipient wetness using Pd(NO3)2·XH2O and SnC4H4O6·XH2O as precursors, dried and calcined in static air at 500°C, 800°C or 1100°C. The influence of Sn species in the oxygen storage capacity of the catalysts, distribution of Pd particle sizes and CH4 oxidation reaction were investigated. Pd particle size was larger on Sn-containing catalysts and showed lower mobility than those in the absence of Sn. Sn oxide species act as an oxygen reservoir that are easily transferred to Pd surfaces promoting the oxidation reaction of methane. For Pd-Sn-containing solids calcined at 1100°C, the contribution of Sn in the CH4 oxidation reaction is negligible.

Experimental evidence for Mo isotope fractionation between metal and silicate liquids

Stable isotope fractionation of siderophile elements may inform on the conditions and chemical consequences of core–mantle differentiation in planetary objects. The extent to which Mo isotopes fractionate during such metal–silicate segregation, however, is so far unexplored. We have therefore investigated equilibrium fractionation of Mo isotopes between liquid metal and liquid silicate to evaluate the potential of Mo isotopes as a new tool to study core formation. We have performed experiments at 1400 and 1600 °C in a centrifuging piston cylinder. Tin was used to lower the melting temperature of the Fe-based metal alloys to <1400 °C, while variable Fe-oxide contents were used to vary oxygen fugacity in graphite and MgO capsules. Isotopic analyses were performed using a double spike technique. In experiments performed at 1400 °C, the 98Mo/95Mo ratio of silicate is 0.19±0.03‰ (95% confidence interval) heavier than that of metal. This fractionation is not significantly affected by the presence or absence of carbon. Molybdenum isotope fractionation is furthermore independent of oxygen fugacity in the range IW −1.79 to IW +0.47, which are plausible values for core formation. Experiments at 1600 °C show that, at equilibrium, the 98Mo/95Mo ratio of silicate is 0.12±0.02‰ heavier than that of metal and that the presence or absence of Sn does not affect this fractionation. Equilibrium Mo isotope fractionation between liquid metal and liquid silicate as a function of temperature can therefore be described as ΔMoMetal–Silicate98/95=−4.70(±0.59)×105/T2. Our experiments show that Mo isotope fractionation may be resolvable up to metal–silicate equilibration temperatures of about 2500 °C, rendering Mo isotopes a novel tool to investigate the conditions of core formation in objects ranging from planetesimals to Earth sized bodies.

Colouring glasses using nanoparticles synthesized within polyelectrolyte layer-by-layer films

In this work polyelectrolyte multilayers (PEMs) produced through the layer-by-layer (LbL) method were used for the in situ synthesis of Au and Ag metal nanoparticles on the surface of float glass in order to colour it. The samples were characterized by UV–Vis absorption spectroscopy, Scanning Electron Microscopy (SEM), Rutherford Backscattering Spectrometry (RBS) and Particle Induced X-Ray Emission (PIXE). The use of temperatures slightly above the glass transition temperature (Tg) during the thermal treatment allowed the fixing of the nanoparticles, colouring the glass surface. Pink and blue colours were obtained from Au nanoparticles, yellow colour from Ag, and orange from a mixture of both Au nanoparticles and Ag nanoparticles. Variables such as the pH value during film assembly, the number of layers used to form the PEMs, the time duration of thermal treatment, and the presence or absence of Sn in the surfaces of float glass, all influence its colouration. Thermal treatments shorter than 1h already promote the diffusion of Ag into the glass and therefore fix it, while longer times are necessary to fix the Au metal. The Ag colour intensity in the glass is easily controlled through the number of layers while in the case of Au this variable influences not only the colour intensity but also the tone.

Inner-Sphere Structure of Rhodium Complexes with Tin(II) Chloride in Concentrated Hydrochloric Acid Solution

Abstract The coordination properties of highly concentrated rhodium complexes (Rh: ca. 10 g L−1) in concentrated hydrochloric acid solution upon addition of tin(II) chloride were investigated using Rh and Sn K-edge XAFS spectra. For Rh solutions in the absence of Sn, the Rh ion shows no inner-sphere H2O complexation for [HCl] ≥ 6 M. The coordination structure of Rh in 3 M HCl solution (ca. 1 O(H2O) at 2.06(3) Å and ca. 5 Cl− at 2.321(8) Å) drastically changes with increasing amount of tin(II) chloride added; the Sn directly coordinates to Rh by replacing the H2O/Cl−. At [Sn]/[Rh] = 12.4, the inner coordination sphere of Rh is occupied only by Sn (ca. 5 Sn at 2.510(7) Å). The curve fits of the Sn K-edge EXAFS spectra for the Rh–Sn system show that the Sn has ca. 3 Cl− and ca. 1 Rh in the inner coordination sphere. XANES analysis reveals that the Rh ion is reduced from trivalent to monovalent with concomitant oxidation of the Sn ion, divalent to tetravalent. These results demonstrate that the Rh complexes in 3 M HCl solution transform from [RhIIICl5(H2O)]2− to [RhI(SnIICl3)5]4− through the [RhIIICln(H2O)m(SnIICl3)6−n−m]n−3 complex (1 ≤ n ≤ 5, 0 ≤ m ≤ 1) with an increase in the Sn concentration.

Origin of Magnetite- and Ilmenite-series Granitic Rocks in Sulawesi, Indonesia: Magma Genesis and Regional Metallogenic Constraint

Lateral and spatial variations magnetic susceptibilities of the granitic rocks from Sulawesi, Indonesia were studied to constrain its implication for their magma genesis and regional metallogenic. The magnetic susceptibility of the granitic rocks varies between 0.08 x 10-3 SI to 18.58 x 10-3 SI, corresponding respectively to ilmenite series (< 3x 10-3 SI; oxidized type) and magnetite series (> 3x 10-3 SI; reduced type) granite. This wide range result is due to large variation of rock types within one suite which cause a variety of magnetic minerals content in the rocks. Although regionally, Sulawesi granitic rocks are dominated by ilmenite series granites, the ratio of ilmenite/magnetite series granites decreases substantially from the southern part to the northern part of the island. The occurrence of the ilmenite-series with I-type characteristic granitic rocks in Sulawesi Island may be explained by assimilation process between magma and crustal material that containing a various quantity of reduced C- and S-bearing sediments. The ilmenite series granitic rocks are characterised by the occurrences of ilmenite and hematite, higher Sn – W, U – Th, V and total REE+Y, whereas the magnetite series are characterized by abundance of hematite and sulphide minerals but lower Sn – W, U – Th, V and total REE+Y. The absence of Sn and W mineralization in ilmenite-series granitic rocks could be explained by the high oxidation state of the granitic magma.

Sn-doped bismuth telluride nanowires with high conductivity

Bismuth telluride (Bi(2)Te(3)) nanowires with sub-100 nm diameters were synthesized by Au-Sn co-catalyzed chemical vapor deposition. These Bi(2)Te(3) nanowires were single crystals with a hexagonal lattice. The Sn catalyst played a key role in achieving the one-dimensional nanowire structures, while the absence of Sn resulted in other morphologies such as nanoplates, nanooctahedrons and nanospheres. Raman spectra revealed that compared to the Bi(2)Te(3) bulk materials, the Bi(2)Te(3) nanowires displayed an A(1u) spectral peak, implying the breaking of symmetry. The temperature-dependent electrical measurement indicated that these Sn-doped Bi(2)Te(3) nanowires were metallic, with a high conductivity of 1.6 × 10(5) S m(-1) at 300 K.

Poly(&lt;i&gt;Ethylene Oxide&lt;/i&gt;)-B-Poly(&lt;i&gt;ε-Caprolactone&lt;/i&gt;) Amphiphilic Block Copolymers: Synthesis and Self-Assembly

A series of amphiphilic block copolymers mPEO-b-PCL with different PCL molecular weight were successfully prepared by combination of anionic ring-opening polymerization with coordination-insertion ring-opening polymerization. Firstly, the linear mPEO was prepared by anionic ring-opening copolymerization of EO with 2-(2-methoxyethoxy) ethoxide potassium as the small molecule initiators, then the mPEO as the macroinitiator was used to initiate the ring-opening polymerization of CL, in the absence of Sn(Oct)2 as the catalyst, and amphiphilic block copolymers mPEO-b-PCL were obtained. By changing the ratio of monomer and macroinitiator, prepared a series of different molecular weight mPEO-b-PCL. The structure of intermediates and final products were characterized by 1H NMR and GPC. The critical micelle concentration (cmc) of the final copolymer was measured. In addition, the sizes and morphologies of the obtained micelles at different PCL chains were studied with Laser nano-particle size analyzer and transmission electron microscopy (TEM).

Synthesis and Characterization of Ti1−xSnxO2 Nanoparticles and Nanotubes and their Photovoltaic Properties as Dye-Sensitized Solar Cell Photoelectrodes

Ti1−xSnxO2 nanoparticles with different Ti/Sn ratios (x=0–0.1 and 1.0) were successfully synthesized by the coprecipitation method, and its nanotubes were prepared from low-temperature chemical synthesis in NaOH solution. The influence of Sn dopant on the structures and the photovoltaic properties as dye-sensitized solar cells for these nanostructured TiO2 were investigated. The photovoltaic performance of Ti1−xSnxO2 nanoparticle photoelectrodes degraded with the addition of Sn. However, regardless of the absence of Sn, a conversion efficiency of TiO2 nanotubes made from Ti1−xSnxO2 (x=0–0.05) nanoparticles increased depending on the x value and reached to 5.98% for x=0.05.

Quantitative Changes of Sialoadhesin and CD163 Positive Macrophages in the Implantation Sites and Organs of Porcine Embryos/Fetuses During Gestation

Porcine reproductive and respiratory syndrome virus (PRRSV) crosses the placenta most easily in the last third of gestation. Further, PRRSV does not replicate in preimplantation embryos but does replicate in postimplantation embryos and fetuses. In the present study, it was aimed to find an explanation for these observations by localization and quantification of the macrophages carrying two entry mediators that play a crucial role in PRRSV replication, sialoadhesin (Sn) and CD163, in the implantation sites and organs of embryos/fetuses during gestation. Uterus and embryos or organs (liver, spleen, lungs) from fetuses were obtained from pregnant PRRSV negative sows at different days of gestation (20–35, 50–60, 70–80, 114) and the Sn+ and CD163+ macrophages were quantified. In endometrium and placentas, two macrophage subsets were observed: Sn−CD163+ and Sn+CD163+. The highest number of Sn+ and CD163+ macrophages was counted at 114days of gestation. In the mid-gestation fetal placentas (50–60days of gestation), most CD163+ macrophages were Sn negative. The number of Sn+ and CD163+ macrophages in organs increased during gestation. In the liver, the Sn+ and CD163+ macrophages were most abundant (Sn+: 8.1–48.7%; CD163+: 22.0–55.0%); the lowest number of Sn+ and CD163+ macrophages was observed in the lungs (Sn+: 0–15.2%; CD163+: 4.0–19.3%). Double immunofluorescence staining revealed three macrophage subsets in the spleen: Sn+CD163−, Sn−CD163+ and Sn+CD163+; and two macrophage subsets in the lungs: Sn−CD163+ and Sn+CD163+. In the liver, due to physiological presence of biotin, the double immune-fluorescence staining could not be performed. The present results show clear changes in the quantity of Sn+ and CD163+ macrophages in the placentas and organs of embryos/fetuses during gestation which most probably have a physiological basis. The absence of Sn on macrophages in the fetal placenta at mid-gestation might explain the difficulty for PRRSV to spread transplacentally at this stage of gestation.

The effect of tartrate on the morphological and structural characteristics of lead–tin electrodeposit from an alkaline bath

The electrodeposition of Pb–Sn alloys from a tartrate-alkaline plating bath can lead to a deposition of pure lead or a normal codeposition of lead–tin depending on the deposition potential. The percentage of tin in the Pb–Sn deposit obtained at ∼−1.15 V increases from 4.08 wt.% to 20.7 wt.% as the charge density rises from 2.5 C cm −2 to 5.0 C cm −2 and then decreases from 12.07 wt.% to 7.52 wt.% as the charge density rises from 7.5 C cm −2 to 10.0 C cm −2. SEM images show that the Pb and Pb–Sn deposits obtained from a tartrate-alkaline bath did not, in general, show dendritic growth. X-ray analysis of the deposits obtained at −0.83 V with 5.0 C cm −2 or 10.0 C cm −2 indicated the presence of Pb and Pb 2PtO 4 and the absence of Sn. However, those obtained at −1.15 V and the same charge densities ( q d) showed the presence of Pb, Pb 2SnO 4, PbSnO 3 and PtSn 4. The Pb 2PtO 4 and PtSn 4 compounds were formed because the electrodeposition process occurred onto Pt substrate.

Extraction and Structural Properties of Rhodium–Tin Complexes in Solution

The extraction and structural properties of rhodium complexes with stannous chloride using N,N‐dioctyl hexanamide (DOHA) were investigated by solvent extraction and Rh K‐edge X‐ray absorption fine structure (XAFS) spectroscopy. In the absence of Sn(II), Rh was hardly extracted from a 1 M HCl solution. However, the Rh extraction was enhanced with an increase in the Sn(II) concentration in the initial aqueous phase. The high extractability of Rh is achieved using the 1 M solution at [Sn(II)]/[Rh] ≥ 6 as the aqueous phase. At the [Sn(II)]/[Rh] = 12, the extraction of Rh was almost 100% over the HCl concentration range from 1 to 10.5 M. The X‐ray absorption near edge structure (XANES) spectra changed with an increase in the [Sn(II)]/[Rh] value in the 1 M HCl solution, suggesting that the Rh ion was reduced from trivalent to monovalent. In the DOHA complex prepared by solvent extraction from the [Sn(II)]/[Rh] = 12–1 M HCl solution, the XANES spectrum indicated that Rh(I) is predominant. The extended X‐ray absorption fine structure (EXAFS) spectra and the obtained structural parameters showed nearly the same result for the 1 M HCl solution at [Sn(II)]/[Rh] = 12 (Rh–Sn 5.3(6) at 2.54(1) Å) and the DOHA complex (Rh–Sn 4.7(8) at 2.56(1) Å). These results suggest that the [RhI(SnCl3)5]4− complex is the predominant species in both the organic and aqueous phases when the 1 M HCl solution at [Sn(II)]/[Rh] = 12 is used as the aqueous phase and that the [RhI(SnCl3)5]4− complex is highly extractable.

Supramolecular Sn⋯Cl associations in diorganotin dichlorides and their influence on molecular geometry as studied by ab initio molecular orbital calculations

A number of supramolecular architectures based on hypervalent Sn⋯Cl interactions are observed in a series of eight R2SnCl2 structures ranging from tetrameric assemblies to a variety of polymeric motifs. The absence of Sn⋯Cl interactions in the crystal lattice of tBu2SnCl2 may be attributed to the bulky size of the tin-bound t-butyl groups that precludes such interactions. The influence of the supramolecular aggregation upon molecular geometry has been investigated using ab initio molecular orbital calculations. These show that invariably more symmetric structures are observed in the absence of hypervalent Sn⋯Cl interactions.

Acetylene Chemisorption on Sn/Pt(100) Alloys

Adsorption and reaction of acetylene on a hexagonally reconstructed (5 × 20)-Pt(100) surface and two ordered Sn/Pt(100) alloy surfaces were investigated using temperature programmed desorption spectrometry (TPD), Auger electron spectroscopy (AES), low energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS). Vapor deposition of Sn onto a Pt(100) single-crystal substrate was used to form two Pt−Sn alloys, the c(2 × 2) and (3√2×√2)R45° Sn/Pt(100) structures with θSn = 0.5 and 0.67 ML, respectively, depending on the initial Sn concentration and annealing temperature. Acetylene nearly completely decomposed during TPD on Pt(100) in the absence of Sn, forming hydrogen, which then desorbs as H2, and surface carbon. This decomposition, associated with irreversible dissociative adsorption, was strongly suppressed on the two Pt−Sn alloy surfaces, and a large acetylene desorption peak in TPD was observed. Additionally, 15% of the adsorbed acetylene monolayer was converted to gaseous benzene during TPD on the (3√2×√2)R45° Sn/Pt(100) alloy. No such benzene desorption occurred from the c(2 × 2) alloy. Alloyed Sn in the c(2 × 2) alloy decreased the initial sticking coefficient of acetylene on Pt(100) at 100 K by ∼40%, but additional Sn in the other alloy had no additional effect. The saturation coverage of C2D2 in the chemisorbed monolayer at 100 K decreased from that on Pt(100) by 35% on the c(2 × 2) alloy and 50% on the (3√2×√2)R45° Sn/Pt(100) alloy. However, the c(2 × 2)-Sn adlayer eliminates acetylene chemisorption, illustrating that the effectiveness of Sn to “block” sites depends crucially on its location as an adatom or alloyed atom on Pt surfaces. The acetylene chemisorption bond energy, estimated by the acetylene desorption activation energy measured in TPD, also decreased (45−65%) as the alloyed Sn concentration increased. Multiple TPD peaks for C2D2 desorption from both the c(2 × 2) and the (3√2×√2)R45°Sn/Pt(100) alloy surfaces indicate either several energetically distinguishable adsorption sites for acetylene or the rate-limiting influence of more complex surface reactions on these surfaces.

Influence of Alloyed Sn on Adsorption and Reaction of NO on Pt(100) Surfaces

Adsorption and reaction of NO on the (5 × 20)-Pt(100) surface and two Sn/Pt(100) surface alloys have been studied using temperature programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS). On the (5 × 20)-Pt(100) surface, in the absence of Sn, NO is primarily reversibly adsorbed, and most of the chemisorbed NO desorbs molecularly from the surface during TPD. Approximately 25% of the adsorbed NO monolayer decomposes at temperatures higher than 400 K, and this leads to N2 and O2 desorption from the surface. Alloying Sn into the surface layer of Pt(100) forms two ordered surface alloys having c(2 × 2) and (3√2 × √2)R45°Sn/Pt(100) surface structures with θSn = 0.5 and 0.67 ML, respectively. Alloying reduced the saturation coverage of NO in the chemisorbed monolayer from that on Pt(100) at 100 K, and it also reduced the adsorption energy of molecularly bound NO by more than a factor of 2. Alloyed Sn, which removes all pure-Pt 2-fold bridge and 4-fold hollow sites, completely ...