SnO2 Nanoribbons Research Articles

Metastable Hexagonal Phase SnO2 Nanoribbons with Active Edge Sites for Efficient Hydrogen Peroxide Electrosynthesis in Neutral Media.

Electrochemical two-electron oxygen reduction reaction (2 e- ORR) to produce hydrogen peroxide (H2 O2 ) is a promising alternative to the energetically intensive anthraquinone process. However, there remain challenges in designing 2 e- ORR catalysts that meet the application criteria. Here, we successfully adopt a microwave-assisted mechanochemical-thermal approach to synthesize hexagonal phase SnO2 (h-SnO2 ) nanoribbons with largely exposed edge structures. In 0.1 M Na2 SO4 electrolyte, the h-SnO2 catalysts achieve the excellent H2 O2 selectivity of 99.99 %. Moreover, when employed as the catalyst in flow cell devices, they exhibit a high yield of 3885.26 mmol g-1 h-1 . The enhanced catalytic performance is attributed to the special crystal structure and morphology, resulting in abundantly exposed edge active sites to convert O2 to H2 O2 , which is confirmed by density functional theory calculations.

Metastable Hexagonal Phase SnO2 Nanoribbons with Active Edge Sites for Efficient Hydrogen Peroxide Electrosynthesis in Neutral Media

AbstractElectrochemical two‐electron oxygen reduction reaction (2 e− ORR) to produce hydrogen peroxide (H2O2) is a promising alternative to the energetically intensive anthraquinone process. However, there remain challenges in designing 2 e− ORR catalysts that meet the application criteria. Here, we successfully adopt a microwave‐assisted mechanochemical‐thermal approach to synthesize hexagonal phase SnO2 (h‐SnO2) nanoribbons with largely exposed edge structures. In 0.1 M Na2SO4 electrolyte, the h‐SnO2 catalysts achieve the excellent H2O2 selectivity of 99.99 %. Moreover, when employed as the catalyst in flow cell devices, they exhibit a high yield of 3885.26 mmol g−1 h−1. The enhanced catalytic performance is attributed to the special crystal structure and morphology, resulting in abundantly exposed edge active sites to convert O2 to H2O2, which is confirmed by density functional theory calculations.

Nanoribbons of SnO2 as a high performance Li-ion battery anode material

Here, SnO2 nanoribbons (NRs) synthetized on the catalyst-free stainless steel (SS) substrate as a possible anode for Li-ion batteries (LIBs) have been reported. SnO2 NRs were synthesized on catalyst-free SS substrate via vapor-solid (VS) growth approach. Morphological and structural characterizations of the SnO2 NRs were confirmed using scanning electron microscopy (SEM), transmission electron microscopy (TEM) microscopes and x-ray diffraction (XRD) respectively. The prepared binder-free electrode demonstrated high initial discharge/charge capacities of 1818/929 mAh g−1 at current density of 300 mA g−1. A reversible capacity of 676 mAh g−1 with a coulombic efficiency of 98.5% has been achieved after 20 cycles. High specific capacity, superior rate capability and good cycling performance resulting from the SnO2 NRs electrode propose this nanostructure as an excellent anode for advanced LIBs.

Room temperature ppb level H2S detection of a single Sb-doped SnO2 nanoribbon device

Sb-doped SnO2 nanoribbons (NRs) with a single crystal structure are synthesized via thermal evaporation. H2S gas sensor is developed based on a single Sb-SnO2 NR through dual-ion beam sputtering deposition with a mask template. The response of the Sb-SnO2 NR sensor has been measured up to 56–100ppm of H2S at 150°C. More importantly, this sensor shows a response of 10(1.6) toward 100ppb of H2S at 150°C(25°C), which promotes the detection limit of H2S. The NR-based sensor also exhibits a high sensitivity, good selectivity and long-term stability with a prompt response time, demonstrating good sensing capabilities at room temperature. The mechanism for enhanced sensing performance of Sb-doped SnO2 nanoribbon is discussed.

Synthesis and high sensing properties of a single Pd-doped SnO2 nanoribbon.

Monocrystal SnO2 and Pd-SnO2 nanoribbons have been successfully synthesized by thermal evaporation, and novel ethanol sensors based on a single Pd-SnO2 nanoribbon and a single SnO2 nanoribbon were fabricated. The sensing properties of SnO2 nanoribbon (SnO2 NB) and Pd-doped SnO2 nanoribbon (Pd-SnO2 NB) sensors were investigated. The results indicated that the SnO2 NB showed a high sensitivity to ethanol and the Pd-SnO2 NB has a much higher sensitivity of 4.3 at 1,000 ppm of ethanol at 230°C, which is the highest sensitivity for a SnO2-based NB. Pd-SnO2 NB can detect ethanol in a wide range of concentration (1 ~ 1,000 ppm) with a relatively quick response (recovery) time of 8 s (9 s) at a temperature from 100°C to 300°C. In the meantime, the sensing capabilities of the Pd-SnO2 NB under 1 ppm of ethanol at 230°C will help to promote the sensitivity of a single nanoribbon sensor. Excellent performances of such a sensor make it a promising candidate for a device design toward ever-shrinking dimensions because a single nanoribbon device is easily integrated in the electronic devices.

SnO2 nanoribbons: excellent field-emitters

Nanoribbon structures have the feature of sharp edges, providing the marked geometrical field enhancement for field emitters even in a randomly arranged thin film structure. In this work, the field emission of SnO2 nanoribbons with thin walls (10–30 nm) prepared on a large scale via a rapid oxidation reaction is investigated. It is found that macroscopically, thin films made of SnO2 nanoribbons have an extremely low electron threshold field as low as 1.23 V μm−1. The SnO2 nanoribbon field emitter also exhibits excellent emission stability, with a degradation lower than 2.7% and a huge field enhancement factor as high as 2680. Furthermore, the emission current decrease slightly, while the stability remains excellent even for a poor vacuum of 10−4 Pa. These field emission properties of the present SnO2 nanoribbons surpass any other reported SnO2 nanostructures. This work opens the avenues for SnO2 nanoribbon structures as promising thin film field emitters.

Air-Assisted Growth of Tin Dioxide Nanoribbons

SnO2 nanoribbons have been synthesized by annealing of a milled SnO2 powder, which is able to evaporate efficiently at the temperature as low as 1100 degrees C due to the metastable structure created by ball milling treatment. When the milled powder was annealed in an assembly of two combustion boats, SnO2 nanoribbons formed on the surface of the milled powder. The nanoribbons tend to grow along the [101] crystallographic direction and their side surfaces are represented by +/- (010) and +/- (101) facets. The oxygen plays an important role in enhancing their formation.

Synthesis of Sb-additivated SnO2 nanostructures and dependence of photoluminescence properties on Sb additivation concentration

Single crystalline Sb-additivated SnO2 nanorods, beaklike nanorods, and nanoribbons were synthesized by an in situ catalyst-assisted thermal evaporation process on single-crystal Si substrates. As the Sb:Sn weight ratios were increased, the morphologies of Sb-additivated SnO2 nanostructures would progressively transform from nanorods to beaklike nanorods and to the mixture of nanowires and nanoribbons. The SnO2 nanorods grow along the [02¯0] direction and with lateral facets defining a square column consisting of {100} and {001} planes. The Sb-additivated SnO2 beaklike nanorods initially grow along the [01¯1¯] direction and then switch to the [031¯] direction to form the beak, while the nanoribbons grow along the [110] direction. The Sb atoms were found to uniformly distribute over the whole Sb-additivated SnO2 nanostructures and that it would not affect the single crystallinity of SnO2 nanostructures. The photoluminescence spectra of the nonadditivated and Sb-additivated SnO2 nanostructures exhibited multipeaks with peak positions centered at 403, 453, 485, 557, and 622 nm. When Sb atoms were additivated into SnO2 nanostructures, the luminescence intensities would significantly decrease and photoluminescence at 557 and 622 nm would almost disappear. These can be explained by the replacements of the six- and fivefold coordinated Sn atoms on low-index facets by five- and fourfold coordinated Sb atoms, respectively, leading to the cancellation of 100° tin coordinated on-plane oxygen bridging vacancies and 130° tin coordinated in-plane oxygen vacancies.

The effect of the surface of SnO2 nanoribbons on their luminescence using x-ray absorption and luminescence spectroscopy

X-ray excited optical luminescence (XEOL) and x-ray absorption near-edge structure in total electron, x-ray fluorescence, and photoluminescence yields at Sn M5,4-, O K-, and Sn K-edges have been used to study the luminescence from SnO2 nanoribbons. The effect of the surface on the luminescence from SnO2 nanoribbons was studied by preferential excitation of the ions in the near-surface region and at the normal lattice positions, respectively. No noticeable change of luminescence from SnO2 nanoribbons was observed if the Sn ions in the near-surface region were excited selectively, while the luminescence intensity changes markedly when Sn or O ions at the normal lattice positions were excited across the corresponding edges. Based on the experimental results, we show that the luminescence from SnO2 nanoribbons is dominated by energy transfer from the excitation of the whole SnO2 lattice to the surface states. Surface site specificity is not observable due to its low concentration and weak absorption coefficient although the surface plays an important role in the emission as a luminescence center. The energy transfer and site specificity of the XEOL or the lack of the site specificity from a single-phase sample is discussed.

Time-resolved x-ray excited optical luminescence from SnO2 nanoribbons: Direct evidence for the origin of the blue luminescence and the role of surface states

Time-resolved x-ray excited optical luminescence (XEOL) and x-ray absorption near edge structures have been employed to study the origin of the multicolor luminescence from SnO2 nanoribbons. The authors find that the yellow-green luminescence has a long lifetime while the blue luminescence a short one. The luminescence is attributed to the radiative decay of trapped electrons in oxygen vacancies just below the conduction band and electrons in the conduction band to intrinsic surface states in the band gap.

Processing and Characterization of Nanostructured Metal Oxides for Gas Sensing Applications

Nanoscience and nanotechnology involve materials and systems with at least one dimension in the range of 1-100nm that exhibit novel and size-dependent properties. This article reviews the main processing techniques used to fabricate nanomaterials, ranging from sol-gel to vapor deposition to electrospinning. Emphasis is given to metal oxide nanostructures, such as SnO2 nanoribbons and MoO3 nanowires. Their electronic properties and their gas detection behavior are presented and discussed. The high surface-to-volume ratio of metal oxide nanostructures has been exploited to develop gas sensors with higher stability, faster response, and higher sensitivity to the analytes of interest than their conventional counterparts. Commonly observed p-n type transition phenomena in nanostructured metal oxides are explained on the basis of the sensing mechanism involved in gas detection by semiconducting oxides and the size-related effects of nanomaterials in the concentration of free charge carriers. Insights are given on the future challenges in resistive gas sensing and how nanotechnology may be helpful in overcoming these burdens

Cathodoluminescence spectroscopy of single SnO2 nanowires and nanobelts

Abstract1D semiconducting SnO2 nanoribbons in form of nanowires and nanobelts with a lateral size ranging from 50 to 700 nm and length of several hundreds of micrometers are studied by Cathodoluminescence in the Scanning Electron Microscope and Transmission Electron Microscopy.Experimental High Angle Annular Dark Field imaging suggests compositional modulations along the 〈100〉 direction in agreement with recent theoretical predictions. Single nanobelt and nanowire cathodoluminescence spectroscopy reveals the presence of a broad emission made of two sub‐bands centered at about 460 nm and 580 nm at room temperature. No near band edge emission is found. This result is assigned to a major role of surface effects with respect to bulk properties. CL spectroscopy carried out at different temperatures and Sn vapour pressure, before and after thermal treatments in Oxygen atmosphere and under electron beam irradiation show that the integrated intensity of the sole emission at 580 nm changes. A red and blue shift of about 20 nm are found respectively for the two bands by decreasing the temperature. A correlation between Oxygen vacancies and the cathodoluminescence emission peak at 580 nm is discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

SnO2 Nanoribbons Channel Light at the Nanoscale

SnO₂ Nanoribbons Channel Light at the Nanoscale

Electromechanical and Chemical Sensing at the Nanoscale: Molecular Modeling Applications

Atomistic modeling and simulations are becoming increasingly important in the design of new devices at the nanoscale. Of the myriad of potential application areas commonly associated with Nanotechnology, sensors based on carbon nanotubes (CNT) and metal-oxide nanoribbons are one of the closest to commercial reality. In this work, we review some recent molecular modeling investigations on: (1) CNT-based electromechanical sensors, and (2) gas-sensing properties of SnO2 nanoribbons. Simulation methods include: First-Principles Density Functional Theory (DFT), classical molecular mechanics, and Green's-function-based tight-binding transport.

Novel Synthesis of Tin Dioxide Nanoribbons via a Mild Solution Approach

Abstract Single crystalline tin dioxide nanoribbons have been synthesized in bulk quantity by a mild solution approach using cetyltrimethylammonium bromide surfactant as a soft template. The as-synthesized SnO2 nanoribbons have a length up to tens of micrometers, width of several hundred nanometers, and thickness of several tens of nanometers.

Dióxido de estanho nanoestruturado: síntese e crescimento de nanocristais e nanofitas

The objectives of this work are to supply a basic background on nanostructured materials and also to report about the obtaining of nanoparticles, mainly, tin dioxide nanocrystalline particles (obtained by using the polymeric precursor method) presenting a high stability against particle growth due to the usage of a metastable solid solution. The synthesis and growth of SnO2 nanoribbons by a carbothermal reduction process are also discussed.

SnO2 Nanoribbons as NO2 Sensors: Insights from First Principles Calculations

SnO2 nanoribbons with exposed (1 0 1) and (0 1 0) surfaces have recently been demonstrated to be highly effective NO2 sensors even at room temperature. The sensing mechanism is examined here through first principles density functional theory (DFT) calculations. We show that the most stable adsorbed species involve an unexpected NO3 group doubly bonded to Sn centers. Significant electron transfer to the adatoms explains an orders-of-magnitude drop in electrical conductance. X-ray absorption spectroscopy indicates predominantly NO3 species on the surface, and computed binding energies are consistent with adsorbate stability up to 700 K. Nanoribbon responses to O2 and CO sensing are also investigated.

Oxide‐Assisted Growth of Semiconducting Nanowires

AbstractIn this contribution, we outline oxide‐assisted growth (OAG) (distinct from the conventional metal‐catalytic vapor–liquid–solid (VLS) process) for the growth of nanostructured materials. This synthesis technique, in which oxides instead of metals play an important role in inducing the nucleation and growth of nanowires, is capable of producing large quantities of high‐purity silicon nanowires with a preferential growth direction, uniform size, and long length, without the need for a metal catalyst. The OAG 1D nanomaterials synthesis is complementary to, and coexistent with, the conventional metal‐catalyst VLS approach, and can be utilized to produce nanowires from a host of materials other than Si including Ge nanowires, carbon nanowires, silicon and SnO2 nanoribbons, and Group III–V and II–VI compound semiconductor nanowires.

Synthesis of SnO2 Nanoribbons by Direct Oxidation of Tin Powders

Abstract A new method has been successfully developed to synthesize SnO2 nanoribbons in a large scale by direct oxidation of tin powders. The lengths of the nanoribbons were up to several hundreds of micrometers, and the width and thickness were in the range of 20–150 nm and 10–50 nm, respectively. The as-synthesized SnO2 nanoribbons had preferred [001] growth direction.

Synthesis of SnO<SUB>2</SUB> Nanoribbons by a Carbothermal Reduction Process

This communication describes, for the first time, the growth of SnO2 nanoribbons by a controlled carbothermal reduction process. An analysis of the transmission electron microscopy image revealed that these nanoribbons have a well-defined shape, with a typical width in the range of 70-300 nm. In general, the nanostructured ribbons were more than 100 microns in length. The results reported here support the hypothesis that this ribbon-like nanostructured material grows by a vapor-solid process. This study introduces two hypotheses to explain the SnO2 nanoribbon growth process.