Ultrathin SnO2 Nanosheets Research Articles

Surface chemistry altering electronic behaviour of liquid metal-derived tin oxide nanosheets.

Possessing excellent electronic properties and high chemical stability, semiconducting n-type two-dimensional (2D) tin dioxide (SnO2) nanosheets have been featured in sensing and electrocatalysis applications recently. Derived from non-layered crystal structures, 2D SnO2 has abundant unsaturated dangling bonds existing at the surface, providing interfacial activity. How the surface chemistry alters the electronic properties of 2D SnO2 nanomaterials remains unexplored. In this study, we synthesised ultra-thin 2D SnO2 nanosheets using a liquid metal (LM) touch printing technique and investigated experimentally and theoretically how the interactions of organic solvents composed of alkyl and hydroxyl groups with the surface of LM-derived 2D SnO2 modulate the electronic properties. It was found that alkane solvents can physically absorb onto the SnO2 surface with no impact on the material conductivity. Alcohol-based solvents on the other hand interact with the SnO2 surface via chemical absorptions primarily, in which oxygen atoms of hydroxyl groups in the alcohols form bonds with the surface atoms of SnO2. The binding stability is determined by the length and configuration of the hydrocarbon chain in alcohols. As representative long-chain alcohols, 1-octanol and 1-pentanol attach onto the SnO2 surface strongly, lowering the binding energy of Sn4+ and reducing the electron transfer ability of SnO2 nanosheets. Consequently, the electronic properties, i.e. conductivity and electronic mobility of SnO2 nanosheet-based electronic devices are decreased significantly.

Unveiling Hierarchical Dendritic Co3O4–SnO2 Heterostructure for Efficient Water Purification

The construction of a desirable, environmentally friendly, and cost-effective nanoheterostructure photoanode to treat refractory organics is critical and challenging. Herein, we unveiled a hierarchical dendritic Co3O4-SnO2 heterostructure via a sequential hydrothermal process. The time of the secondary hydrothermal process can control the size of the ultrathin SnO2 nanosheets on the basis of the Ostwald solidification mass conservation principle. Ti/Co3O4-SnO2-168h with critical growth size demonstrated a photoelectrocatalysis degradation rate of ∼93.3% for a high dye concentrate of 90 mg/L with acceptable long-term cyclability and durability over reported Co3O4-based electrodes because of the large electrochemically active area, low charge transfer resistance, and high photocurrent intensity. To gain insight into the photoelectric synergy, we proposed a type-II heterojunction between Co3O4 and SnO2, which prevents photogenerated carriers' recombination and improves the generation of dominant active species •O2-, 1O2, and h+. This work uncovered the Ti/Co3O4-SnO2-168 as a promising catalyst and provided a simple and inexpensive assembly strategy to obtain binary integrated nanohybrids with targeted functionalities.

Tailoring microenvironment for enhanced electrochemical CO2 reduction on ultrathin tin oxide derived nanosheets

Electrocatalytic CO2 reduction powered by renewable electricity has been considered as a promising approach for sustainable energy storage and chemicals production. Herein, ultrathin few-layer SnO2 nanosheets exposed with (001) facets were synthesized and exhibited a rather broad potential window (0.8 V) for selective CO2 conversion to formate. Both DFT calculations and operando spectroscopic characterizations were carried out to identify key intermediate *OCHO. Systematically tailoring microenvironment in the catalyst layer of gas diffusion electrode (GDE) indicate that both flexible Nafion and solid polytetrafluoroethylene (PTFE) nanoparticles are essential to create abundant and robust triple-phase boundaries (TPB) with more active sites, where CO2 and H2O meet at nanosheet surface to output a high formate partial current density of 380 mA·cm-2 with the selectivity of 88.4%. Moreover, such novel Nafion/PTFE/SnO2 TPB porous structures above largely enhance the single-pass carbon efficiency up to 29.3% in 1 M KOH. This study implies that engineering TPB active sites is an effective approach to the design of advanced CO2 electrolyzers.

Regioselective Friedel-Crafts Acylation Reaction Using Single Crystalline and Ultrathin Nanosheet Assembly of Scrutinyite-SnO2.

Peculiar physicochemical properties of two-dimensional (2D) nanomaterials have attracted research interest in developing new synthetic technology and exploring their potential applications in the field of catalysis. Moreover, ultrathin metal oxide nanosheets with atomic thickness exhibit abnormal surficial properties because of the unique 2D confinement effect. In this work, we present a facile and general approach for the synthesis of single crystalline and ultrathin 2D nanosheets assembly of scrutinyite-SnO2 through a simple solvothermal method. The structural and compositional characterization using X-ray diffraction (Rietveld refinement analysis), high-resolution transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and so on reveal that the as-synthesized 2D nanosheets are ultrathin and single crystallized in the scrutinyite-SnO2 phase with high purity. The ultrathin SnO2 nanosheets show predominant growth in the [011] direction on the main surface having a thickness of ca. 1.3 nm. The SnO2 nanosheets are further employed for the regioselective Friedel–Crafts acylation to synthesize aromatic ketones that have potential significance in chemical industry as synthetic intermediates of pharmaceuticals and fine chemicals. A series of aromatic substrates acylated over the SnO2 nanosheets have afforded the corresponding aromatic ketones with up to 92% yield under solvent-free conditions. Comprehensive catalytic investigations display the SnO2 nanosheet assembly as a better catalytic material compared to the heterogeneous metal oxide catalysts used so far in the view of its activity and reusability in solvent-free reaction conditions.

Reduced graphene oxide-SnO2 nanosheets hybrid nanocomposite for improvement of formaldehyde sensing properties

Two-dimensional (2D) nanomaterials and their composites have become a popular area among researchers owing to their superior properties which can be attributed to the planar structure. In this work, we used a hydrothermal method to generate ultrathin SnO2 nanosheets with thickness of ~ 5 nm on the reduced graphene oxide (rGO) layer to construct sheet-on-sheet heterostructured architectures. The sensor response of rGO/SnO2 nanosheets composites is 11.9 to 100 ppm formaldehyde at the optimal operating temperature of 220 °C. Besides of the superior sensor response at lower working temperature, the rGO/SnO2 nanosheets composites sensor exhibited good selectivity and fast response/recover performance. These strengths revealed the promising applications of the rGO/SnO2 nanosheets composites in practical detection. The present work definitely reveals the advantages of rGO/SnO2 nanosheets composites featured with a sheet-on-sheet architecture between two different nanosheets in gas sensing applications.

Ultrathin SnO2 nanosheets anchored on graphene with improved electrochemical kinetics for reversible lithium and sodium storage

SnO2 is regarded to be promising for both Li-ion and Na-ion batteries. Thus, it is imperative to fabricate SnO2-based anode with improved lithiation reaction kinetics using simple but effective method. Herein, we develop a one-pot hydrothermal route to fabricate two-dimensional SnO2 nanosheets and the graphene supported SnO2 nanosheet composite with decreased SnO2 nanosheet of about 5–10 nm. The ultrathin nanosheet structure anchored on graphene supporting can effectively accelerate the conversion/alloying reaction. Electrochemical researches demonstrate that the reaction kinetics of the lithiation/delithiation reaction can be significantly enhanced by the graphene supported SnO2 nanosheets. As a result, a capacity of 817.2 mAh g−1 after 100 cycles in the potential window of 0.01 to 3 V are achieved at 500 mA g−1. The full cell performance and the sodium storage performance are both demonstrated to be good. These promising results suggest that such strategy to fabricate two-dimensional SnO2-based anode is of great interest for next-generation Li-ion and Na-ion batteries.

Ultrathin SnO2 nanosheets with dominant high-energy {001} facets for low temperature formaldehyde gas sensor

Semiconducting metal oxides (SMO) have been investigated as important gas sensing materials for detecting various inflammable and toxic gases; however most of them are suffered from low response and high operation temperature. Ultrathin SnO2 nanosheets with dominant high-energy {001} facets were synthesized by a facile hydrothermal method, and the gas sensing properties to formaldehyde (HCHO) were systemically studied. The structure, morphology, specific surface area, band gap and chemical state of the ultrathin SnO2 nanosheets were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), N2 adsorption–desorption, UV–Vis diffuse reflectance spectrum and X-ray photoelectron spectroscopy (XPS), respectively. Sensors based on SnO2 nanosheets show outstanding gas sensing properties to HCHO vapor at the optimum operating temperature (OOT) of 200 °C. The nanosheet sensor exhibit a response of 207.7 to 200 ppm HCHO at 200 °C with the response-recovery time of 30 s and 57 s, respectively. Notably, as low as 1 ppm HCHO can be readily detected with a high response value (Sr = 6.1). The excellent HCHO sensing performance is mainly originated from the structural sensitization of large specific surface area, characteristically small thickness and dominant high-energy {001} facets.

Two-dimensional SnO2/graphene heterostructures for highly reversible electrochemical lithium storage

The ever-growing market demands for lithium ion batteries have stimulated numerous research efforts aiming at the exploration of novel electrode materials with higher capacity and long-term cycling stability. Two-dimensional (2D) nanomaterials and their heterostructures are an intense area of study and promise great potential in electrochemical lithium storage owing to their unique properties that result from structural planar confinement. Here we report a microwave chemistry strategy to integrate ultrathin SnO2 nanosheets into graphene layer to construct surface-to-surface 2D heterostructured architectures, which can provide unique structural planar confinement for highly reversible electrochemical lithium storage. The as-synthesized 2D SnO2/graphene heterostructures can exhibit high reversible capacity of 688.5 mA h g−1 over 500 cycles with excellent long-term cycling stability and good rate capability when used as anode materials for lithium ion batteries. The present work definitely reveals the advantages of 2D heterostructures featured with a surface-to-surface stack between two different nanosheets in energy storage and conversion devices.

Self-accelerated electrochemiluminescence emitters of Ag@SnO2 nanoflowers for sensitive detection of cardiac troponin T

Metal oxide semiconductor nanocrystals (NCs), which emerged as a novel class of electrochemiluminescence (ECL) emitters with low cost and good biocompatibility, have attracted particular research interests in ECL biosensors. However, their analytical applications still remained a substantial challenge of relatively low ECL intensity. Herein, the novel self-accelerated ECL emitters of silver nanoparticles functionalized SnO2 nanoflowers (Ag@SnO2 NFs) were first prepared by in situ generating silver nanoparticles on the surface of SnO2 nanoflowers via silver mirror reaction, which exhibited high-intensity ECL emission with the maximum emission peak at 542 nm in the case of S2O82− as a co-reactant. It was worthy to note that compared with traditional ECL emitters of SnO2 NCs with diameters below 10 nm, the obtained Ag@SnO2 NFs with diameters about 1–2 μM showed a stronger ECL emission. The ECL enhancement was supposed to derive from 1) the strong size effect of flower-like nanostructure aggregating by ultrathin SnO2 nanosheets, which would offer large amount of tin interstitials or oxygen vacancies; 2) the in situ generated silver nanoparticles (Ag NPs) as co-reaction accelerator, which would generate more oxidizing intermediate (▪) to significantly self-promote the ECL emission of Ag@SnO2 NFs. Given these attributes, we developed a sensitive ECL immunosensor for the detection of cardiac troponin T (cTnT) utilizing Ag@SnO2 NFs as efficient signal probes, which showed outstanding sensitivity with a favorable linear range from 1 fg/mL to 100 pg/mL and relatively low detection limit of 0.11 fg/mL. This work efficiently offered insights into the promising applications of Ag@SnO2 NFs as a low toxicity and superior ECL emitter in ECL bioanalysis.

Template-free synthesis of nanosheets-assembled SnO2 hollow spheres for enhanced ethanol gas sensing

The specific structure of hollow sphere with hierarchical structure is beneficial to facilitate the gas diffusion and supply more active sites for improving gas sensing performance. In this paper, we report the fabrication of hierarchical SnO2 hollow spheres assembled by ultrathin nanosheets (SnO2 NSHSs) via a template-free hydrothermal method. The formation mechanism and microstructures of the SnO2 NSHSs were discussed and characterized in detail. The SnO2 NSHSs sensor shows a high response and ultrafast response time (5 s) towards ethanol. Furthermore, the SnO2 NSHSs gas sensor also exhibits a low detection limit of ppb level. The enhanced sensing performance can be attributed to the unrestricted gas diffusion in the hierarchical hollow spheres and plenty of active sites on the ultrathin SnO2 nanosheets.

Gold electrode modified with ultrathin SnO2 nanosheets with high reactive exposed surface for electrochemical sensing of As(III)

Here we report a system using ultrathin SnO2 nanosheets with high reactive exposed (110) surface modified gold electrode for sensitive detection of As(III) by Square wave anodic stripping voltammetry (SWASV) with a mild acid condition (pH 5.0). Ultrathin SnO2 nanosheets have been synthesized via a hydrothermal process successfully with the thickness of about 0.52nm (four atomic layers thick). This oxide is used as electrode modifier, and the modified electrode exhibits good performance in stripping determination of As(III). The LOD actually measured is 5μgL−1 and below the guideline value given by the World Health Organization (WHO). As compared with SnO2 bulks, ultrathin SnO2 nanosheets are found to exhibit stronger adsorption capability and better detection performance toward As(III), it may be due to the atomic thickness and extremely huge percentage of (110) facet ultrathin nanosheets materials exposed. Finally, this system is successfully applied for the analysis of a real sample collected from Inner Mongolia, China. Most importantly, we pose a potential for the use of ultrathin materials to improve the electrochemical performance of bare gold electrode in mild acid condition.

Electric-Field-Driven Dual Vacancies Evolution in Ultrathin Nanosheets Realizing Reversible Semiconductor to Half-Metal Transition.

Fabricating a flexible room-temperature ferromagnetic resistive-switching random access memory (RRAM) device is of fundamental importance to integrate nonvolatile memory and spintronics both in theory and practice for modern information technology and has the potential to bring about revolutionary new foldable information-storage devices. Here, we show that a relatively low operating voltage (+1.4 V/-1.5 V, the corresponding electric field is around 20,000 V/cm) drives the dual vacancies evolution in ultrathin SnO2 nanosheets at room temperature, which causes the reversible transition between semiconductor and half-metal, accompanyied by an abrupt conductivity change up to 10(3) times, exhibiting room-temperature ferromagnetism in two resistance states. Positron annihilation spectroscopy and electron spin resonance results show that the Sn/O dual vacancies in the ultrathin SnO2 nanosheets evolve to isolated Sn vacancy under electric field, accounting for the switching behavior of SnO2 ultrathin nanosheets; on the other hand, the different defect types correspond to different conduction natures, realizing the transition between semiconductor and half-metal. Our result represents a crucial step to create new a information-storage device realizing the reversible transition between semiconductor and half-metal with flexibility and room-temperature ferromagnetism at low energy consumption. The as-obtained half-metal in the low-resistance state broadens the application of the device in spintronics and the semiconductor to half-metal transition on the basis of defects evolution and also opens up a new avenue for exploring random access memory mechanisms and finding new half-metals for spintronics.

Microwave-assisted and gram-scale synthesis of ultrathin SnO2 nanosheets with enhanced lithium storage properties.

The rational design and fabrication of SnO2-based anode materials could offer a powerful way of effectively alleviating their large volume variation and guaranteeing excellent reaction kinetics for electrochemical lithium storage. Herein, we present an ultrarapid, low-cost, and simple microwave-assisted synthesis of ultrathin SnO2 nanosheets at the gram-scale. The two-dimensional (2D) anisotropic growth depends on microwave dielectric irradiation coupled with surfactant structural direction, and is conducted under low-temperature atmospheric conditions. The ultrathin 2D nanostructure holds a great surface tin atom percentage with high activity, where the electrochemical reaction processes could be facilitated that highly dependent on the surface. Compared with 1D SnO2 nanorods, the ultrathin SnO2 nanosheets exhibit remarkably improved electrochemical lithium storage properties with a high reversible capacity of 757.6 mAh g(-1) at a current density of 200 mA g(-1) up to 40 cycles as well as excellent rate capability and cycling stability. Specifically, the ultrathin 2D nanosheet could significantly reduce ion diffusion paths, thus allowing faster phase transitions, while the sufficient external surface interspace and interior porous configuration could successfully accommodate the huge volume changes. Even more importantly, we develop a promising strategy to produce ultrathin SnO2 nanosheets to tackle their intrinsic problems for commercial applications.

A new way for synthesizing SnO2 nanosheets

Two-dimensional SnO2 nanomaterials hold great potential for new advanced applications, such as solar cells, batteries, and gas sensors. Here, we report a large-scale synthesis of high-quality ultrathin SnO2 nanosheets from ball-milled commercial SnO2 powder under mild hydrothermal conditions. These nanosheets show a graphene-like morphology with large planar area, ultrathin thickness (2–5nm), and high percentage of surface atoms. Dissolution/hydrolysis/precipitation is proposed as a growth mechanism.

TiO2-Coated Ultrathin SnO2 Nanosheets Used as Photoanodes for Dye-Sensitized Solar Cells with High Efficiency

Ultrathin SnO2 nanosheets were prepared by a hydrothermal method using SnF2 and methenamine as precursor and morphology controlling agent, respectively. Structural characterizations indicate that these ultrathin SnO2 nanosheets having a thickness of approximately 4–6 nm can assemble into a three-dimensional, flowerlike architecture. Due to the higher electron mobility and enhanced light-scattering effect of these hierarchical structures, the dye-sensitized solar cells (DSSCs) based on such SnO2 architectures exhibit much higher cell performance than that of SnO2 nanoparticles. Furthermore, coating a TiO2 layer on these ultrathin SnO2 nanosheets can also significantly improve the short-circuit current, open-circuit voltage, and fill factor. Compared with the plain SnO2 nanosheets, the TiO2 coating on these ultrathin SnO2 nanosheets can lead to more than 7 times improvement in the energy conversion efficiency. With a thin layer of TiO2 coating, the highest overall photoconversion efficiency of DSSCs based o...

Ultrathin SnO2 Nanosheets: Oriented Attachment Mechanism, Nonstoichiometric Defects, and Enhanced Lithium-Ion Battery Performances

We successfully synthesized large-scale and highly pure ultrathin SnO2 nanosheets (NSs), with a minimum thickness in the regime of ca. 2.1 nm as determined by HRTEM and in good agreement with XRD refinements and AFM height profiles. Through TEM and HRTEM observations on time-dependent samples, we found that the as-prepared SnO2 NSs were assembled by “oriented attachment” of preformed SnO2 nanoparticles (NPs). Systematic trials showed that well-defined ultrathin SnO2 NSs could only be obtained under appropriate reaction time, solvent, additive, precursor concentration, and cooling rate. A certain degree of nonstoichiometry appears inevitable in the well-defined SnO2 NSs sample. However, deviations from the optimal synthetic parameters give rise to severe nonstoichiometry in the products, resulting in the formation of Sn3O4 or SnO. This finding may open new accesses to the fundamental investigations of tin oxides as well as their intertransition processes. Finally, we investigated the lithium-ion storage of...