Hierarchical SnO2 Nanostructures Research Articles

Schottky junction based solar cell behavior of trichome hierarchical SnO2 nano-structures

Hydrothermally grown SnO2 hierarchical trichome nano-flowers (T-NFLs) have been examined for their device performance compared to nano-flakes (NFs), in part to meet the growing need for metal-oxide based solar cells. The structural analyses reveal superior lattice strain and free energy in the tetragonal phase of the T-NFLs over NFs. The band gap widening and oxygen defect-dominated luminescence in the visible range are observed from photoluminescence measurements. Compared to NFs, the Schottky current-voltage characteristics of the T-NFLs show improved Schottky barrier height (0.82 eV) with an ideality factor of 3.52 under dark and better solar cell properties with a conversion efficiency of 1.78 ± 0.03% under 1 sun illumination. The observed high open-circuit voltage of 1.56 V resulted from the decrement rate of carrier recombination, making the transparent metal oxide nano-material SnO2 T-NFLs suitable for solar cells and fast electronic applications.

Hydrothermal Synthesis of Hierarchical SnO2 Nanostructures for Improved Formaldehyde Gas Sensing.

The indoor environment of buildings affects people’s daily life. Indoor harmful gases include volatile organic gas and greenhouse gas. Therefore, the detection of harmful gas by gas sensors is a key method for developing green buildings. The reasonable design of SnO2-sensing materials with excellent structures is an ideal choice for gas sensors. In this study, three types of hierarchical SnO2 microspheres assembled with one-dimensional nanorods, including urchin-like microspheres (SN-1), flower-like microspheres (SN-2), and hydrangea-like microspheres (SN-3), are prepared by a simple hydrothermal method and further applied as gas-sensing materials for an indoor formaldehyde (HCHO) gas-sensing test. The SN-1 sample-based gas sensor demonstrates improved HCHO gas-sensing performance, especially demonstrating greater sensor responses and faster response/recovery speeds than SN-2- and SN-3-based gas sensors. The improved HCHO gas-sensing properties could be mainly attributed to the structural difference of smaller nanorods. These results further indicate the uniqueness of the structure of the SN-1 sample and its suitability as HCHO- sensing material.

Preparation of Coral-like SnO2 Hierarchical Nanostructures and Its Application in Ethanol Gas-sensing Performance

Coral-like SnO2 hierarchical nanostructures were successfully fabricated by a simple hydrothermal route. By means of a comprehensive analysis of microstructures and morphologies of the hierarchical SnO2, we found that the coral-like nanostructures were comprised of irregular nanorods and nanosheets. Considering the essential advantages of hierarchical architectures, its gas sensitivity and the formation mechanism have been further explored. The sensor response to 100 ppm ethanol is about 25 at the optimum working temperature of 240 °C, and the response and recovery time are about 17 s and 7 s, respectively. Based on the experimental results, a possible morphology-dependent sensing mechanism are speculated.

Rational Design and Controllable Synthesis of Multishelled Fe2O3@SnO2@C Nanotubes as Advanced Anode Material for Lithium-/Sodium-Ion Batteries

Hierarchical Fe2O3 and SnO2 nanostructures have shown great potential for applications in high-performance ion batteries because of their superiority, including wide resources, facile preparation, environmental friendliness, and high energy density. However, some severe challenges, such as rapid capacity decay due to volume expansion upon cycling and poor conductivity, limit their rate performance. To address this issue, multishelled Fe2O3@SnO2@C (FSC) nanotubes were designed and synthesized by using a template method and Ostwald interaction. The as-prepared FSC nanotubes can deliver a high capacity of 1659 mA h g-1 at a current density of 200 mA g-1 and a high reversible capacity of 818 mA h g-1 at 2000 mA g-1 for lithium-ion batteries. Particularly, a high specific capacity of 1024 mA h g-1 is still maintained after 100 charging/discharging cycles at 200 mA g-1. Applied in sodium-ion batteries, the multishelled FSC nanotubes manifest a high specific capacity of 449 mA h g-1 after 180 cycles at 50 mA g-1. Such excellent performances of the as-fabricated FSC nanotubes may be due to the unique multishelled tubular structure, porous characteristics, and high specific surface area. Therefore, the present work provides an outstanding method to improve the energy storage performance of metal oxide composites and other types of nanocomposites.

Hydrothermal Synthesis of Novel Hierarchical Flower-Like SnO₂ with Enhanced Visible-Light-Driven Photocatalytic Activity.

The novel hierarchical flower-like SnO₂ (HFL-SnO₂) nanostructures with the diameter of about 500 nm, which are composed of regular-shaped nanosheets, are synthesized with a solvothermal method in the presence of 1 ml of Triethylamine (TEA) and the 0.2 mmol of Hexamethylene tetraamine (HMT) at 160 °C for 6 h. The SnO₂ has a high specific surface area of about 38.5 m²g-1. Based on the nucleation and self-assembly process, possible formation process of the new hierarchical flower-like nanostructures can be presented. The effects of TEA and HMT on the product are also studied. In addition, the product exhibits excellent photocatalttic activity to Methyl orange (MO) aqueous solution and possess good stability and reusability under visible light. This study will provide valuable experimental data for further study of nanomaterials and their photocatalytic properties.

How Cu doping improves the interfacial wettability between Ag and SnO2 of Ag/SnO2 contact material

In order to explore how Cu doping improves the wettability between Ag and SnO2 of Ag/SnO2 contact material, the physical and chemical changes of pure SnO2 and Cu-doped SnO2 powders at a high temperature were studied using a laser simulated arc. The results show that some of the SnO2 grows preferentially along the (211) and (101) crystal planes, and the other part changes to SnO preferentially growing along the (101) crystal plane. SnO2 particles with SnO make contact with each other under the action of the simulation arc to form large agglomerate particles. Meanwhile, the deposition of gasified SnO2 during the arc process aggravates the formation of SnO2 agglomerates. However, Cu doping reduces the gasified deposition of SnO2 during the arc process, and inhibits the preferred growth of SnO2 along the (211) and (101) crystal planes and the change from SnO2 to SnO at a high temperature. Furthermore, Cu doping induces SnO2 grains to redistribute along a specific direction to form nanoneedle assembled Cu-doped SnO2 hierarchical nanostructures during the arc process. Finally, a mechanism of Cu doping which improves the interfacial wettability between Ag and SnO2 of Ag/SnO2 contact material is proposed.

Highly sensitive formaldehyde gas sensors based on Y-doped SnO2 hierarchical flower-shaped nanostructures

In this work, we have successfully prepared Y-doped SnO2 hierarchical flower-like nanostructures through a facile one-step hydrothermal method for the purpose of improving the formaldehyde gas sensing performance of conventional SnO2 semiconductor nanomaterials. The products were characterized by diverse techniques, which revealed that trivalent Y cations have been introduced into the crystal lattice of SnO2 and they exhibited lots of regular flower-like nanostructures consisting of several layers of rough and porous flakes. At an optimal working temperature of 180 °C, the fabricated gas sensor based on Y-doped SnO2 shown much better gas sensing properties to formaldehyde compared with SnO2 due to the combination of this distinctive three-dimensional hierarchical flower-like nanostructures and doping of Y ions. In particular, the detectable formaldehyde minimum limit has been reduced to 1 ppm. Consequently, Y-doped SnO2 hierarchical flower-like nanostructures are expected to become ideal gas sensing materials of highly sensitive gas sensors for formaldehyde detection due to their excellent gas sensing performance.

Constructing hierarchical SnO2 nanofiber/nanosheets for efficient formaldehyde detection

SnO2 nanofiber/nanosheets with hierarchical nanostructures were successfully synthesized via a facile hydrothermal method by using hollow SnO2 nanofibers as the backbone. The microstructure, morphology, chemical composition, oxidation states and surface areas of SnO2 nanofibers, SnO2 nanofiber/nanosheets and SnO2 nanosheets were comparatively studied by X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET). The characterization results indicated that the hierarchical SnO2 nanofiber/nanosheets were constructed by nanosheets arrays uniform growth on the surface of nanofibers. Sensing performances of SnO2-based nanomaterials were investigated utilizing formaldehyde (HCHO) as a target gas. Compared to SnO2 nanofibers, nanosheets and the physical mixture of nanofibers and nanosheets, the gas sensor based on SnO2 nanofiber/nanosheets exhibited better response, more excellent selectivity, transient response and trace detection ability to HCHO gas. The response (Ra/Rg) of the gas sensor is 57 toward 100 ppm HCHO at 120 °C, which is about 300% and 200% higher than that of pure SnO2 nanofibers sensors and SnO2 nanosheets sensors, respectively. Furthermore, the sensor has an excellent response/recovery performance with 4.7 s and 11.6 s for detecting 100 ppm HCHO. Both the growth process and the gas sensing mechanism of SnO2 hierarchical nanostructures were discussed. Successful preparation of SnO2 nanofiber/nanosheets is attributed to uniform decoration of seeds on the nanofibers and suitable growth conditions of nanosheets. Enhanced sensing performance mainly result from the synergistic effect of nanofibers and nanosheets, hierarchical structures and larger specific surface areas. The synthetic strategy can also be applied in preparing hierarchical materials of different constituent materials.

Preparations of Bi-doped SnO2 hierarchical flower-shaped nanostructures with highly sensitive HCHO sensing properties

In order to improve the gas sensing performance of traditional SnO2 semiconductor nanomaterials, Bi-doped SnO2 hierarchical flower-shaped nanostructures had been synthesized by a one-step hydrothermal route. Diverse techniques characterization results collectively revealed that Bi ions have been successfully doped into SnO2 lattice and samples present numerous uniform flower-shaped nanostructures composed of many layered petal-like thin nanosheets. Benefiting from such unique 3D hierarchical flower-shaped nanostructures and Bi doping, the sensors based on Bi-doped SnO2 exhibited superior gas sensing performance concluding higher response value, faster response/recovery time, good stability and excellent selectivity to HCHO at the optimum operating temperature of 170 °C. Therefore, Bi-doped SnO2 hierarchical flower-shaped nanostructures could be used as a candidate semiconductor gas sensing materials for manufacturing highly sensitive HCHO gas sensors in the future.

Surfactant-free synthesis of novel hierarchical dahlia-like SnO2 nanostructures with enhanced visible-light-driven photocatalytic activity

A facile hydrothermal method is developed to prepare hierarchical dahlia-like SnO2 nanostructures (HDSNs). They have been successfully synthesized without using any templates or surfactants. We find that the hierarchical architectures of SnO2 are assembled by a number of regular-shaped nanosheets and nanoparticles, which are cross-linked in the interior of the micro-flower. Based on the nucleation and self-assembly process, a possible formation mechanism is proposed. The effect of NaCl on the product is also studied. In addition, the product exhibits excellent photocatalytic activity to Rhodamine B (RhB) aqueous solution and possess good stability and reusability under visible light. This study will provide valuable experimental data for further study of nanomaterials and their photocatalytic properties.

Hierarchical SnO2 nanostructures as high efficient photocatalysts for the degradation of organic dyes

Hierarchical SnO2 flower-like structures are synthesized successfully through a simple and effective hydrothermal method. The morphology, microstructure, specific surface area, and photocatalytic property of the as-prepared products are characterized in detail by various analytical techniques. The results show that the as-prepared products possess flowers-shaped morphologies, and each flower is assembled by many nanorods with a diameter of 60 nm and a length of 300 nm. The effects of reaction temperature and time on the morphology of SnO2 nanoflowers are studied and the growth mechanism of the nanoflower is proposed. The products possess excellent photocatalytic activity for several organic dyes. The degradation rates of methylene blue, rhodamine B and methyl orange are 99.6, 99.5, and 96.8%, respectively after 40 min. The as-prepared SnO2 nanoflowers might possess potential applications in wastewater treatment. Hierarchical SnO2 flower-like structures are synthesized successfully through a simple and effective hydrothermal method. The results show that the as-prepared products possess excellent photocatalytic activity for several organic dyes, demonstrating their potential applications in wastewater treatment.

One-step synthesis of novel hierarchical flower-like SnO2 nanostructures with enhanced photocatalytic activity

Novel hierarchical flower-like SnO2 (HFL-SnO2) nanostructures are successfully synthesized through the hydrothermal method. We find that the hierarchical architectures of SnO2 is assembled by a number of regular-shaped nanosheets, which are cross-linked in the interior of the micro-flower. The product also has a high specific surface area of about 78.8 m2g−1. Based on the nucleation and self-assembly process, a possible formation mechanism is proposed. The effects of SDS and NaCl on the product are also studied. Moreover, the product exhibits excellent photocatalytic activity and take possession of good stability and reusability under visible light. This study provides valuable experimental data for further study of nanomaterials and their photocatalytic properties.

Hierarchical Morphology-Dependent Gas-Sensing Performances of Three-Dimensional SnO2 Nanostructures.

Hierarchical morphology-dependent gas-sensing performances have been demonstrated for three-dimensional SnO2 nanostructures. First, hierarchical SnO2 nanostructures assembled with ultrathin shuttle-shaped nanosheets have been synthesized via a facile and one-step hydrothermal approach. Due to thermal instability of hierarchical nanosheets, they are gradually shrunk into cone-shaped nanostructures and finally deduced into rod-shaped ones under a thermal treatment. Given the intrinsic advantages of three-dimensional hierarchical nanostructures, their gas-sensing properties have been further explored. The results indicate that their sensing behaviors are greatly related with their hierarchical morphologies. Among the achieved hierarchical morphologies, three-dimensional cone-shaped hierarchical SnO2 nanostructures display the highest relative response up to about 175 toward 100 ppm of acetone as an example. Furthermore, they also exhibit good sensing responses toward other typical volatile organic compounds (VOCs). Microstructured analyses suggest that these results are mainly ascribed to the formation of more active surface defects and mismatches for the cone-shaped hierarchical nanostructures during the process of thermal recrystallization. Promisingly, this surface-engineering strategy can be extended to prepare other three-dimensional metal oxide hierarchical nanostructures with good gas-sensing performances.

Mesoporous SnO2 Nanostructures of Ultrahigh Surface Areas by Novel Anodization.

Here we report a novel type of hierarchical mesoporous SnO2 nanostructures fabricated by a facile anodization method in a novel electrolyte system (an ethylene glycol solution of H2C2O4/NH4F) followed by thermal annealing at a low temperature. The SnO2 nanostructures thus obtained feature highly porous nanosheets with mesoporous pores well below 10 nm, enabling a remarkably high surface area of 202.8 m2/g which represents one of the highest values reported to date on SnO2 nanostructures. The formation of this novel type of SnO2 nanostructures is ascribed to an interesting self-assembly mechanism of the anodic tin oxalate, which was found to be heavily impacted by the anodization voltage and water content in the electrolyte. The electrochemical measurements of the mesoporous SnO2 nanostructures indicate their promising applications as lithium-ion battery and supercapacitor electrode materials.

A novel low temperature gas sensor based on Pt-decorated hierarchical 3D SnO2 nanocomposites

A novel gas sensor composed of Pt nanoparticles-decorated hierarchical SnO2 nanostructures (Pt–SnO2) was synthesized via a facile dipping-precipitation strategy. Pt nanoparticles with small sizes (avg. 4nm) were successfully dispersed onto our pre-synthesized 3D hierarchical SnO2 nanoflowers supports by using lysine as both capping and linking agents. The morphology, structure and composition of the as-prepared samples were characterized by means of field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Comparisons of the gas sensing performance between pure SnO2 and Pt–SnO2 nanocomposites revealed that after supporting Pt nanoparticles, the decorated sensor not only got an optimal working temperature of as low as 100°C, but also exhibited faster response and recovery speeds and higher response than the pristine one at such low temperature. Moreover, good selectivity and excellent stability were also shown for the hybrid sensor. Sensing mechanisms were illustrated to help explain the strong spillover effect of the Pt nanoparticles and the Schottky barriers at the interface of metal and semiconductor, both of which facilitated the low temperature sensing performance. The Pt–SnO2 sensors are considered to be a promising candidate for trace environmental gas detections in practical use.

Hydrothermal synthesis of SnO2 hierarchical nanostructures and their gas sensing properties

Gas sensing performances of SnO2 can often be improved remarkably once the thickness of nanosheets shrinks to a critical value of 14 nm (2λD) or self-assembly of two-dimensional nanoscale building blocks into three-dimensional (3D) complex superstructures. Here, using the hydrothermal method, we synthesise the SnO2 3D hierarchical nanostructures assembled with ultrathin nanosheets with a thickness as thin as 9–12 nm by adding sodium oxalate (Na2C2O4). Wondrously, using oxalic and sodium hydroxide (H2C2O4+2NaOH) substitute for equimolar Na2C2O4, the dimensions of nanosheets decrease, which may be due to the active degree is different between the Na2C2O4 directly and indirectly obtained by H2C2O4. In property, the as prepared SnO2 hierarchical nanostructures display excellent gas sensing functions to ethanol gas due to their subsize and the plane to plane contacts.

Facile formation of a hierarchical TiO2–SnO2 nanocomposite architecture for efficient dye-sensitized solar cells

Hierarchical TiO2–SnO2 nano-architecture for efficient DSSC.

Hydrothermal synthesis of hierarchical SnO2 nanostructures made of superfine nanorods for smart gas sensor

We report synthesis of hierarchical SnO2 nanostructures by a facile hydrothermal method. Extensive structural characterizations demonstrate that the well-defined hierarchical nanostructures are composed of numerous one-dimensional nanorods, the diameter and density of which can be precisely tailored by adjusting the dosage of NaOH. Interestingly, with more NaOH added, smaller and denser nanorods are formed, which is consistent with the assumption. We proposed that the nucleation process was facilitated in such case leading to all-direction rapider growth. Moreover, the nucleation process could be started by the decomposition of preformed ZnSn(OH)6 induced by alkali etching. Based on the comparative experiments, a possible growth mechanism for hierarchical SnO2 nanostructures has been proposed and discussed in detail. The gas sensing properties of the as-prepared hierarchical SnO2 nanostructures were all tested. It was found that the S3 sample which assembled with smallest and densest nanorods showed the excellent sensitivities toward ethanol.

Synthesis of hierarchical flower-like SnO2 nanostructures and their photocatalytic properties

SnO2 nanostructures were prepared successfully through a template-free and surfactant-free hydrothermal method. The prepared SnO2 nanostructures were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectra and UV–vis absorption spectra. Photocatalytic activity was evaluated using the degradation of organic dye methyl orange. Furthermore, the possible growth and photodegradation mechanism of the as-prepared sample were also briefly discussed.

Synthesis, characterization, and comparative gas sensing properties of tin dioxide nanoflowers and porous nanospheres

Self-assembly of lower nanostructures into 3D superstructures is extensively investigated because of their excellent physicochemical properties. In this study, the hierarchical SnO2 nanostructures were prepared via two simple hydrothermal methods. The SnO2 nanostructures were characterized by X-ray diffraction (XRD), surface area analyzer (using BET method), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The SEM, TEM results revealed that the hierarchical SnO2 flowers were assembled by numerous one-dimensional tetragonal prism nanorods and the sphere architectures were formed by numerous smaller particles. The gas sensing results demonstrated that the different SnO2 nanostructures have great effect on the gas sensing behavior. The nanoflowers exhibited higher sensitivities to ethanol than the nanospheres, whereas the typical responses of these sensors to H2 and LPG indicated that the porous spheres demonstrated better sensing performance than the hierarchical flowers. This interesting phenomenon contributes to clearly understand about morphology-dependent gas sensing properties.