SnO2 Quantum Dots Research Articles

Growth of size-controllable tetragonal rutile stannic oxide nanostructures by co-precipitation route for eosin Y dye degradation under solar radiation

A simple one step co-precipitation route was employed to synthesize the size controlled quantum dots (size ~ 3 nm) by maintaining the pH value at 6, without addition of capping agent. The effect of different annealing temperatures on the structural and optical properties of as synthesized sample have been explained. XRD analysis of sample showed the formation of pure rutile SnO2 quantum dots with tetragonal rutile structure for all the prepared samples. The SnO2 sample prepared by co-precipitation route was annealed at different temperatures and photo catalytic activities of annealed samples at various temperatures were investigated under direct solar irradiation. The obtained prepared sample with smallest size (3 nm) annealed at 300 °C displayed excellent degradation of Eosin Y (EY) dye. This is attributed to small grain size, tuned band gap, high crystallinity and high interfacial surface area. Quantum confinement effect enhanced the catalyst performance by creating oxygen vacancies and enabling the efficient charge transportation through discrete energy levels. Synthesized samples of SnO2 was subjected to the photocatalysis experiment to determine their photodegradation efficiency and was found to be lower for annealed samples than that shown by SnO2 quantum dots. QDs showed 73% degradation efficiency for EY dye when illuminated under sunlight for an hour.

Ultrahigh Reversibility of SnO2 in SnO2@C Quantum Dots/Graphene Oxide Nanosheets for Lithium Storage

AbstractAmong promising substitutions for commercial graphite anodes for lithium ion batteries, SnO2 has a fourfold theoretical capacity of graphite (if the O element is completely reversible), while the oxygen reutilization is seriously hampered by poor conductivity of both the electron and Li+ ions. This work proposes a novel ternary architecture of SnO2@C quantum dots (QDs, with average diameter of 3.37 nm) grafted on graphene oxides, denoted as SnO2@C/G, via a facile and scalable one‐pot hydrothermal method. The SnO2@C/G show extraordinary long‐term cycling performance (1080 mAh g−1 at 200 mA g‐1 after 300 cycles) and rate capability (∼840 mAh g−1 at 2 A g−1). If excluding the contribution of carbon, the specific capacity of SnO2 is 1447 mAh g−1 at 200 mA g‐1, 96.9% of its theoretical capacity. The extraordinary performance is ascribed to ultrahigh reversibility of SnO2 QDs, good structural stability, and much better ionic/electronic diffusions confirmed by XPS, TEM, EIS, respectively.

Structural and optical properties of Fe-doped SnO2 quantum dots

Fe-doped SnO2 quantum dots (QDs) were synthesized by a time-efficient solution combustion synthesis with various concentration of Fe ions. The structural and optical properties are keenly investigated through various characterization techniques like XRD, HR-TEM, XPS, UV–vis, EPR, and FT-IR spectroscopies. The structural description gives an information that the SnO2 QDs are having a particle size below 5 nm with the tetragonal crystal structure. The Fe doping increases the absorption capability of SnO2 QDs via tuning of the bandgap. The bandgap of SnO2 QDs is decreased with increasing the content of Fe. The XPS study clearly confirms the existence of Fe in 3+ state as octahedral sites in SnO2 QDs which was further strongly supported by EPR. The FT-IR analysis gives the information of Fe doping effect on vibrational modes of SnO2.

Magnetically engineered SnO2 quantum dots as a bimodal agent for optical and magnetic resonance imaging

Combining more than one imaging technique into a single system can outweigh the limitations of conventional imaging techniques. Pairing optically active quantum dots (QDs) with superparamagnetic MRI agent is an adorable way to develop probes for bimodal imaging. Tiny SnO2 quantum dot embedded iron oxide (IO) nanocomposite (SQD-IO) is synthesized. This combines the superparamagnetic property of IO nanoparticles (NPs) and special optical properties of SnO2 QDs, and is explored as a bimodal imaging agent. Morphological studies of the nanocomposite reveal that 3 nm tiny SnO2 QDs are embedded in ~30 nm γ-Fe2O3 NPs. The SQD-IO preserves the intrinsic superparamagnetic behaviour of its constituent IO NPs with a magnetization ~21.4 emu g−1 measured at an applied field of 20k Oe. The emission colour of the nanocomposite is tuned by simply varying the excitation wavelength. The centre of the emission band shifts from 570 to 600 nm as the excitation alters from 488 to 535 nm. The cytotoxicity assessment indicates that the nanocomposite is suitable for its in vitro use. Transverse proton relaxivity (141 mM−1 s−1) of the nanocomposite is higher than the widely used negative contrast agent Feridex (R2 = 98.3 mM−1 s−1). The confocal laser scanning microscope images give evidence of the cellular uptake behaviour of SQD-IO in HeLa cells and it is seen that QDs retain their optical properties within the intracellular environment. The high R2 value for MRI and the tunable florescence images of HeLa cells essentially establish SQD-IO as a potential probe for bimodal imaging.

Enhancement of visible-light-driven photoresponse of Mn-doped SnO2 quantum dots obtained by rapid and energy efficient synthesis

Mn-doped SnO2 quantum dots (QDs) with different Mn concentrations were prepared by solution combustion synthesis. The crystallite size was under 5nm was confirmed from XRD and HR-TEM. A considerable decrease in band gap energy was observed with the increase in Mn content. The PL spectra show orange emission at about 590nm due to the ultra-small crystallite size and crystal defects of SnO2 QDs. The photocatalytic degradation of MO dye was measured under visible light irradiation using the Mn-doped SnO2 QDs as catalysts. 3mol% Mn-doped SnO2 QDs showed the 17 times higher photocatalytic performance than SnO2 QDs within 240min.

SnO2 quantum dots for nano light emitting devices

SnO2 quantum dots for nano light emitting devices

Sunlight-driven photocatalytic activity of SnO2 QDs-g-C3N4 nanolayers

Herein, we reported a sunlight driven photocatalyst, SnO2 quantum dots (QDs)-g-C3N4 nanolayers (NLs) for the abatement of water pollution. SnO2 QDs were prepared in the presence of g-C3N4 NLs and the average crystallite size of SnO2 QDs was achieved below 3 nm. The interactions between both SnO2 QDs and g-C3N4 NLs are strong, as established by differences in binding energies. The sunlight driven photocatalytic activity of SnO2-g-C3N4 composite was carried out by the degradation of methyl orange (MO) and it shows 94% degradation under sunlight within 180 min. The improved photocatalytic activity under sunlight is attributed to the synergetic effect of SnO2 QDs and layered g-C3N4.

One pot synthesis of Ag-SnO2 quantum dots for highly enhanced sunlight-driven photocatalytic activity

Herein, we reported a plasmonic photocatalyst, Ag-SnO2 quantum dots (QDs) for the abatement of water pollution by a simple and one pot synthesis in water. The Ag-SnO2 QDs were prepared with various concentrations of Ag loading. The as synthesized plasmonic photocatalysts were systematically investigated by X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), and nitrogen adsorption-desorption isotherm, diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and photoluminescence spectroscopy (PL). The average crystallite size of pristine SnO2 QDs was achieved below 3 nm. The band gap of Ag-SnO2 QDs plasmonic photocatalyst was shifted from UV to visible region i.e. from 3.02 to 2.54 eV. The surface plasmon resonance (SPR) band of Ag-SnO2 QDs is blue shifted in the visible region and the PL intensity of Ag-SnO2 QDs composites decreases with the increase of Ag loading. The sunlight driven photocatalytic activity of Ag-SnO2 QDs composites was carried out by the degradation of Rhodamine B (RhB) solution and the optimized amount of Ag was significantly enhances the photocatalytic activity. The Ag-SnO2 QDs composite with optimized Ag amount showed the highest photocatalytic performance with 98% degradation of the dye under sunlight within 180 min. The improved photocatalytic activity under sunlight is attributed to the tuning of band gap to visible region, SPR of Ag and its synergetic effect of metal and semiconductor quantum dot. The plausible photocatalytic mechanism was suggested for the degradation of the pollutant under sunlight irradiation.

Hydrothermal synthesis of TiO2 hollow spheres adorned with SnO2 quantum dots and their efficiency in the production of methanol via photocatalysis.

TiO2 hollow spheres and TiO2 hollow spheres adorned with SnO2 quantum dots were synthesized successfully under mild temperature and autogenous pressure using the hydrothermal route. X-ray diffraction, field emission scanning electron microscopy, scanning electron microscopy, transmission electron microscope, photoluminescence spectroscopy, and UV-vis spectroscopy were used to characterize the physical and chemical nature of the synthesized sample. The characterized samples were used in the photocatalytic applications to reduce the concentration of carbon dioxide in the presence of water under the influence of visible light. Our observation confirmed that with increasing SnO2 content there is a tremendous change in the photocatalytic performance of the samples, due to free mobility of the electrons and holes and decline in charge recombination centers formed with the formation of nano-heterojunction between SnO2 and TiO2. The greater photocatalytic production of methanol was achieved using 2ST sample, i.e., 1.61μmol/g/h which tends to decrease with an increase in SnO2 content.

Rapid microwave-assisted synthesis of SnO2 quantum dots/reduced graphene oxide composite with its application in lithium-ion battery

SnO2 quantum dots/reduced graphene oxide (SnO2/rGO) composite has been successfully prepared by a rapid microwave-irradiation process and subsequent annealing treatment. SEM and TEM results reveal that SnO2 quantum dots with the sizes of 1–5nm are uniformly anchored on rGO nanosheets. The SnO2/rGO composite as an anode material presents a high initial discharge capacity of 1628mAh/g and maintains a reversible capacity of 797mAh/g after 100 cycles. After being cycled at various rates for 100 cycles, the capacity can recover to 777mAh/g at 100mA/g. The high reversible capacity, long cycling life and good rate performance can be attributed to the size effect of SnO2 quantum dots and the synergistic effect from rGO nanosheets.

Multiwalled carbon nanotubes@C@SnO2 quantum dots and SnO2 quantum dots@C as high rate anode materials for lithium-ion batteries

The SnO2 quantum dots anchored on amorphous carbon coated multiwalled carbon nanotubes (CNTs@C@SnO2) and SnO2 quantum dots embedded in amorphous carbon network (SnO2@C) have been designed and fabricated by a solvothermal process accompanied by a high temperature calcination treatment. Such unique structured electrodes exhibit excellent cycle stability and high rate capability. At the current density of 5Ag−1, the capacities of 515 and 364mAhg−1 are achieved after 300 cycles for CNTs@C@SnO2 and SnO2@C, respectively.

Synthesis of Cr-doped SnO2 quantum dots and its enhanced photocatalytic activity

Chromium (Cr)-doped SnO2 quantum dots (QDs) with various doping concentration have been successfully synthesized using a simple combustion method. The QDs have been characterized by using various techniques. The X-ray diffraction patterns revealed that the prepared QDs have monophasic tetragonal rutile-type crystallite structure with an average crystallite size of ∼3nm. The optical band gap energies of QDs increased with increasing the Cr ion concentration. The XPS spectra reveal the presence of Sn4+, Cr3+, and O respectively. Cr (0.03mol%)-doped SnO2 QDs are exhibited the greater photocatalytic activity compared with other photocatalysts, which is attributed mainly due to quantum confinement effect and an increase in specific surface area. The existence of a Cr3+ as shown from XPS spectra, act as an electron acceptor and/or hole donor, which enhancing longer survived charge carrier separation in Cr-doped SnO2 QDs as confirmed by PL spectroscopy.

Improving the electrochemical properties of Cr-SnO2 by multi-protecting method using graphene and carbon-coating

Designing heteroatom doped metal oxides and modifying them with carbonaceous materials can grant metal oxides with good Li+ storage performance because of the improved structure stability and enhanced electric conductivity. Herein, monodispersed Cr-doped SnO2 quantum dots fixed by graphene nanosheets and carbon layers (C/Cr-SnO2/G) were successfully assembled, which showed excellent cyclic stability, high reversible capacity and remarkable rate capability for Li+ storage. According to the characteristics results, 3.8wt% Cr were uniformly incorporated into SnO2 lattice in form of Cr3+, resulting the decrease of SnO2 diameters. The C/Cr-SnO2/G electrodes displayed an excellent reversible capacity of 672mAhg−1 after 200cycles at 100mAg−1 without apparent capacity fading throughout the test, and still retained a stable specific capacity of 296mAhg−1 even at 5Ag−1. The enhanced electrochemical performances of C/Cr-SnO2/G can be related to incorporation of Cr into lattice of SnO2 and the double structure protections by graphene nanosheets and carbon layers, which can easily obtain quantum dots structure, increase the conductivity, and keep the structure stability.

In situ synthesis of ultrasmall SnO2 quantum dots on nitrogen-doped reduced graphene oxide composite as high performance anode material for lithium-ion batteries

SnO2 is considered as one of the anode material for Li-ion batteries in terms of its superiority in high theoretical capacity (1494 mAh g−1), low cost and environmental friendly. However, it is suffered from several issues such as rapid capacity deterioration, undesirable aggregation of tin particles and pesky expansion of volume. To conquer these shortcomings, a novel composite of ultrasmall SnO2 quantum dots with an average particle size of 4–5 nm anchored on nitrogen-doped reduced graphene oxide (SnO2@NRGO) was first in situ synthesized By means of hydrothermal method. The results show that as-prepared SnO2@NRGO electrode exhibits a greater enhancement in its initial discharge capacity (1678.4 mAh g−1) and reversible capacity (1333.5 mAh g−1 after 450 cycles) at a current density of 500 mA g−1, implying a long cycle life. Furthermore, the high rate capability of SnO2@NRGO is superior to SnO2@RGO and SnO2 electrodes. The excellent electrochemical reversibility of SnO2@NRGO electrode can be ascribed to the great conductivity, ultrahigh specific surface area and the synergetic effect between ultrasmall SnO2 quantum dots and NRGO.

Structural, optical and magnetic properties of SnO2 quantum dot

High crystalline rutile nano sized tin oxide SnO2 nanoparticles have been synthesized by microwave irradiation technique with the assistance of Cetyl Tributyl Ammonium Bromide (CTAB). The addition of surfactant CTAB resulted in a strong variation of particle size. The presence of CTAB during the solvothermal synthesis considerably affects the morphology, band gap, fluorescence emission and magnetic property. The X-ray diffraction patterns reveal pure rutile-type tetragonal phase SnO2 nanoparticles. The transmission electron microscopy result shows the formation of spherical shaped SnO2 quantum dots of size about 4 nm. Noticeable morphological changes were observed by scanning electron microscopy. The functional groups were analyzed using Fourier Transform Infrared Spectroscopy studies. Optical studies were carried by UV–Visible Spectroscopy and Fluorescence Spectroscopy. Electron Paramagnetic resonance was used to calculate the Lande splitting factor ‘g’. The magnetic properties of the nanoparticles were studied by using Vibrating Sample Magnetometer.

Enhanced visible light photocatalytic activity of Cu-doped SnO2 quantum dots by solution combustion synthesis

Copper (Cu)-doped tin oxide (SnO2) quantum dots (QDs) were prepared using energy-efficient solution combustion synthesis. The synthesized nanoparticles were characterized by XRD, TEM, XPS, UV–Vis DRS, and FT-IR. The X-ray diffraction (XRD) pattern shows that the QDs have tetragonal rutile-like structure. HR-TEM shows modification in the growth inhibition of the SnO2 lattice parameters with Cu doping. When increasing the Cu concentration, the optical band gap energy of SnO2 decreases. X-ray photoelectron spectroscopy (XPS) reveals the presence of copper and tin as Cu2+ and Sn4+, respectively. Fourier transform infrared (FT-IR) spectroscopy confirmed the fundamental vibrational modes of SnO2. The photocatalytic degradation of methyl orange dye was measured under visible light irradiation using the QDs as catalysts. The QDs with 0.03 mol % Cu doping showed the highest photocatalytic performance with 99% degradation of the dye under visible light within 180 min, which means they could be used to treat polluted water.

オゾンを援用したSnO<sub>2</sub>量子ドットの合成

SnO2 quantum dot was successfully synthesized at ambient temperature via ozone bubbling to suspension including Sn6O4(OH)4 under pH of 12. It was clarified that use of SnF2 as starting material enables to obtain clear and stable SnO2 quantum dot suspension. Possible formation mechanism of quantum dot was proposed and shift of fluorescence was predicted with use of varied basic solution for neutralization and pH adjustment based on the hypothesis that shift of fluorescence is attributed to change in size. And this prediction was confirmed by experiment. Finally addition of Zn as dopant gave improved luminescence intensity without shift of fluorescence.

Highly efficient photocatalytic performances of SnO2-deposited ZnS nanorods based on interfacial charge transfer

SnO2/ZnS nanocomposites of SnO2 quantum dots (QDs)-deposited ZnS nanorods having highly enhanced photocatalytic activity and photostability have been fabricated via a facile two-step hydrazine-assisted hydrothermal process without involving any surface treatments. The photocatalytic activity of SnO2/ZnS nanocomposites with a Sn-to-Zn molar ratio (RSn/Zn) of 0.1 is 3 times higher than that of pristine ZnS nanorods and 17 times higher than that of commercial ZnS. The incorporation of SnO2 QDs increases the photocatalytic efficiency of ZnS nanorods due to the following reasons: photogenerated charge carriers are readily separated owing to type II band configuration and direct contact at interfaces without having any linker molecules; active surface sites are increased to adsorb more dye molecules; the light absorption range is extended to the visible region, generating more charge carriers on the surfaces of heterojunction structures. The decay time, as well as the intensity, of the band-edge emission of SnO2/ZnS nanocomposites at 325nm decreases progressively and rapidly with the increase of RSn/Zn, indicating that fast electron transfer takes place from photoexcited ZnS nanorods to SnO2 QDs. Thus, the higher photocatalytic degradation efficiencies of SnO2/ZnS nanocomposites are considered to result mainly from the increased separation rates of photogenerated charges. The photostability of SnO2/ZnS nanocomposites is also improved due to the protection and charge-separation effects of decorating SnO2 QDs. Our prepared SnO2/ZnS nanocomposites are suggested to have great potential for photodegradation nanocatalysts in the field of waste-water treatment.

SnO2 quantum dots/graphene aerogel composite as high-performance anode material for sodium ion batteries

A three-dimensional SnO2 quantum dots/graphene aerogel (SnO2 QDs/GA) composite was prepared using a facile and scalable strategy without adding any surfactant and reducing agent .This as-prepared nanocomposite, with zero-dimensional SnO2 QDs (2–5nm) anchoring and dispersing on the surface of three-dimensional graphene aerogel, exhibits better properties as anode material for sodium ion batteries than bare SnO2 for its higher reversible capacity (319mAhg−1 at 50mAg−1 after 50 cycles) and stability (rate capacity still remains 150mAhg−1 at 800mAg−1). Such three-dimensional graphene aerogel could not only act as an electronic conductive matrix for the fast transportation of sodium ion and electrons, but also provide double protection against the aggregation and volume changes of SnO2 QDs during cycling.

There-dimensional porous carbon network encapsulated SnO2 quantum dots as anode materials for high-rate lithium ion batteries

SnO2 quantum dots have attracted enormous interest, since they have been shown to effectively minimize the volume change stress, improve the anode kinetic and shorten the lithium ion migration distance when used as anode materials for lithium ion battery. In this work, we report a facile strategy to fabricate nanostructure with homogenous SnO2 quantum dots anchored on three-dimensional (3D) nitrogen and sulfur dual-doped porous carbon (NSGC@SnO2). Characterization results show that the obtained SnO2 quantum dots have an average critical size of 3–5nm and uniformly encapsulated in the porous of NSGC matrix. The as-designed nanostructure can effectively avoid the aggregation of SnO2 quantum dots as well as accommodate the mechanical stress induced by the volume change of SnO2 quantum dots and thus maintain the structure integrity of the electrode. As a result, the obtained NSGC@SnO2 composite exhibits a specific reversible capacity as high as 1118mAhg−1 at a current of 200mAg−1 after 100 cycles along with a high coulombic efficiency of 98% and excellent rate capability.