Tin Oxide Nanocrystals Research Articles

Reversible Tuning of the Surface Plasmon Resonance of Indium Tin Oxide Nanocrystals by Gas-Phase Oxidation and Reduction

Heavily doped oxide nanocrystals exhibit a tunable localized surface plasmon resonance (LSPR) in the infrared, a property that is promising for applications in photonics, spectroscopy, and photochemistry. Nanocrystal carrier density and, thus, spectral response are adjustable via chemical reaction; however, the fundamental processes that govern this behavior are poorly understood. Here, we study the time dependence of the LSPR supported by indium tin oxide (ITO) nanocrystals during O2 and N2 annealing with in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). We show that the LSPR red-shifts upon oxidation in O2 and blue-shifts to its original position upon reduction in N2. A reaction–diffusion model allows us to rationalize the underlying physicochemical processes and quantitatively connect nanocrystal redox chemistry, solid-state diffusion, carrier density, and the LSPR.

Enhancement of room temperature ferromagnetism in tin oxide nanocrystal using organic solvents

The effect of organic solvents (ethanol & ethylene glycol) on the room temperature ferromagnetism in nanocrystalline tin oxide has been studied. The samples were synthesized using sol-gel method with the mixture of water & organic liquid as solvent. It is found that pristine SnO2 nanocrystal contain two different types of paramagnetic centres over their surface:(i) surface chemisorbed oxygen species and (ii) Sn interstitial & oxygen vacancy defect pair. The magnetic moment induced in the as-prepared samples is mainly contributed by the alignment of local spin moments resulting from these defects. These surface defect states are highly activated by the usage of ethylene glycol solvent rather than ethylene in tin oxide nanostructure synthesis. Powder X-ray diffraction, transmission electron microscope imaging, energy dispersive spectrometry, Fourier transformed infrared spectroscopy, UV–vis absorption spectroscopy, photoluminescence spectroscopy, vibrating sample magnetometer measurement and electron spin resonance spectroscopy were employed to characterize the nanostructured tin oxide materials.

A Solution-Processed Ultrafast Optical Switch Based on a Nanostructured Epsilon-Near-Zero Medium.

All the optical properties of materials are derived from dielectric function. In spectral region where the dielectric permittivity approaches zero, known as epsilon-near-zero (ENZ) region, the propagating light within the material attains a very high phase velocity, and meanwhile the material exhibits strong optical nonlinearity. The interplay between the linear and nonlinear optical response in these materials thus offers unprecedented pathways for all-optical control and device design. Here the authors demonstrate ultrafast all-optical modulation based on a typical ENZ material of indium tin oxide (ITO) nanocrystals (NCs), accessed by a wet-chemistry route. In the ENZ region, the authors find that the optical response in these ITO NCs is associated with a strong nonlinear character, exhibiting sub-picosecond response time (corresponding to frequencies over 2 THz) and modulation depth up to ≈160%. This large optical nonlinearity benefits from the highly confined geometry in addition to the ENZ enhancement effect of the ITO NCs. Based on these ENZ NCs, the authors successfully demonstrate a fiber optical switch that allows switching of continuous laser wave into femtosecond laser pulses. Combined with facile processibility and tunable optical properties, these solution-processed ENZ NCs may offer a scalable and printable material solution for dynamic photonic and optoelectronic devices.

Phosphorus Enhanced Intermolecular Interactions of SnO2 and Graphene as an Ultrastable Lithium Battery Anode.

SnO2 suffers from fast capacity fading in lithium-ion batteries due to large volume expansion as well as unstable solid electrolyte interphase. Herein, the design and synthesis of phosphorus bridging SnO2 and graphene through covalent bonding are demonstrated to achieve a robust structure. In this unique structure, the phosphorus is able to covalently "bridge" graphene and tin oxide nanocrystal through PC and SnOP bonding, respectively, and act as a buffer layer to keep the structure stable during charging-discharging. As a result, when applied as a lithium battery anode, SnO2 @P@GO shows very stable performance and retains 95% of 2nd capacity onward after 700 cycles. Such unique structural design opens up new avenues for the rational design of other high-capacity materials for lithium battery, and as a proof-of-concept, creates new opportunities in the synthesis of advanced functional materials for high-performance energy storage devices.

Influence of Binders and Solvents on Stability of Ru/RuOx Nanoparticles on ITO Nanocrystals as Li-O2 Battery Cathodes.

Fundamental research on Li-O2 batteries remains critical, and the nature of the reactions and stability are paramount for realising the promise of the Li-O2 system. We report that indium tin oxide (ITO) nanocrystals with supported 1-2 nm oxygen evolution reaction (OER) catalyst Ru/RuOx nanoparticles (NPs) demonstrate efficient OER processes, reduce the recharge overpotential of the cell significantly and maintain catalytic activity to promote a consistent cycling discharge potential in Li-O2 cells even when the ITO support nanocrystals deteriorate from the very first cycle. The Ru/RuOx nanoparticles lower the charge overpotential compared with those for ITO and carbon-only cathodes and have the greatest effect in DMSO electrolytes with a solution-processable F-free carboxymethyl cellulose (CMC) binder (<3.5 V) instead of polyvinylidene fluoride (PVDF). The Ru/RuOx /ITO nanocrystalline materials in DMSO provide efficient Li2 O2 decomposition from within the cathode during cycling. We demonstrate that the ITO is actually unstable from the first cycle and is modified by chemical etching, but the Ru/RuOx NPs remain effective OER catalysts for Li2 O2 during cycling. The CMC binders avoid PVDF-based side-reactions and improve the cyclability. The deterioration of the ITO nanocrystals is mitigated significantly in cathodes with a CMC binder, and the cells show good cycle life. In mixed DMSO-EMITFSI [EMITFSI=1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide] ionic liquid electrolytes, the Ru/RuOx /ITO materials in Li-O2 cells cycle very well and maintain a consistently very low charge overpotential of 0.5-0.8 V.

Microwave-synthesized tin oxide nanocrystals for low-temperature solution-processed planar junction organo-halide perovskite solar cells

Tin oxide nanoparticles prepared by microwave-assisted non-aqueous sol–gel were used to cast an electron transporting layer for organohalide perovskite solar cells showing, in average, high efficiencies thanks to the good optoelectronic properties of the material.

Nanoparticle enhanced spectral filtration of insolation from trough concentrators

A nanoparticle fluid filter consisting of gold nanoparticles and indium tin oxide nanocrystals was fabricated and the optical properties were assessed. Results were integrated against the AM 1.5 solar spectrum to determine solar weighted efficiency of the filter for light energies transmitted above the bandgap to a photovoltaic cell for direct electrical generation while absorbing light below the bandgap that is converted to heat for thermal storage or processing. Temperature dependent bandgaps for both GaAs and cSi were used for optimization of the filter design. GaAs is preferred based upon its higher IR reflectivity, lower temperature coefficient, and greater high-temperature efficiency. However, cSi is significantly cheaper than current and projected GaAs costs. It was found that the experimental filter efficiency was 62% for GaAs and 56% for cSi which was within 6% of previous theoretical predictions.

Room temperature ferromagnetism of tin oxide nanocrystal based on synthesis methods

The experimental conditions used in the preparation of nanocrystalline oxide materials play an important role in the room temperature ferromagnetism of the product. In the present work, a comparison was made between sol–gel, microwave assisted sol–gel and hydrothermal methods for preparing tin oxide nanocrystal. X-ray diffraction analysis indicates the formation of tetragonal rutile phase structure for all the samples. The crystallite size was estimated from the HRTEM images and it is around 6–12nm. Using optical absorbance measurement, the band gap energy value of the samples has been calculated. It reveals the existence of quantum confinement effect in all the prepared samples. Photoluminescence (PL) spectra confirms that the luminescence process originates from the structural defects such as oxygen vacancies present in the samples. Room temperature hysteresis loop was clearly observed in M–H curve of all the samples. But the sol–gel derived sample shows the higher values of saturation magnetization (Ms) and remanence (Mr) than other two samples. This study reveals that the sol–gel method is superior to the other two methods for producing room temperature ferromagnetism in tin oxide nanocrystal.

Single-step preparation of indium tin oxide nanocrystals dispersed in ionic liquids via oxidation of molten In-Sn alloys.

Oxidation of molten In-Sn alloys was carried out in ionic liquids by heat treatment with vigorous stirring, resulting in the formation of indium tin oxide (ITO) nanocrystals. The ITO nanocrystals exhibited a plasmon peak, the peak wavelength of which was blue-shifted with an increase in the Sn fraction in ITO.

Solvothermal synthesis of Sb:SnO2 nanoparticles and IR shielding coating for smart window

The buildings in tropical climate like Singapore get excessive heat gain throughout the year. Passive cooling can be achieved with IR-shielding coating by blocking the IR radiation from solar light. In this work, antimony-doped tin oxide (ATO) nanocrystals with diameter of 10nm were synthesized by solvothermal method. The Sb dopant concentration in ATO nanoparticles was optimized towards enhanced IR shielding properties. Sol–gel precursor was formulated with silanes and ATO nanocrystals. Transparent IR shielding coatings were coated on glass for smart window. The optical and IR shielding performance of the coatings were evaluated. By incorporating smaller ATO nanocrystals synthesized by solvothermal synthesis, the IR shielding performance of the coating was greatly improved as compared to that using larger commercial ATO nanoparticles. The IR shielding coating with synthesized ATO nanocrystals can block more than 90% IR while it can maintain more than 80% transmittance at the visible range. The solar heat gain coefficient (SHGC or G-value) of the coating with 10wt.% synthesized ATO nanocrystals is 0.68 for single layer structure, and decreases to 0.53 with double glazing structure while maintaining good visible transmittance of 60%.

High Rate Capability Core–Shell SnO2/Multiwall Carbon Nanotube Nano Composite Electrodes for Li-Ion Batteries

In this study, core-shell SnO2/MWCNT nanocomposites were produced as a high rate anode material for Li-ion batteries via two steps. Firstly, MWCNT based buckypapers were produced via vacuum filtration techniques. Then, a uniform layer of tin oxide nanocrystals which consist of highly homogenous SnO2 having average mean grain sizes of 7-14 nm was deposited onto the surfaces of buckypapers. The as-prepared nanocomposites were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), galvanostatic charging and discharging and electrochemical impedance spectroscopy (EIS) tests. As anode materials for Li-ion batteries, the nanocomposites showed excellent cyclic retention, with the high specific capacity of 314 mAh g(-1) up to 100 cycles. The special hybrid core-shell structure of the as produced nanocomposites are served as electron conductors and volume buffers in the anode electrodes.

Influence of Ti addition on the room temperature ferromagnetism of tin oxide (SnO2) nanocrystal

Nano-crystalline Sn1−xTixO2 (x=0.00, 0.02, 0.05 and 0.07) particles were synthesized by the sol–gel method without any surfactant and dispersant material. The X-ray diffraction (XRD) pattern shows the formation of the tetragonal rutile phase structure for the undoped SnO2 nanoparticle and Ti doping does not alter the structure of undoped tin oxide. Due to quantum confinement effect, a larger optical band gap for as-synthesized materials was found. Vibrating sample magnetometer (VSM) result demonstrates the undoped and 2% Ti doped SnO2 samples exhibit perfect room temperature ferromagnetism (RTFM) but 5% and 7% of Ti doped samples show a weak ferromagnetism with diamagnetic contribution. The ferromagnetic property of the material was initiated with the help of oxygen vacancy. The amount of oxygen vacancy present in the samples were identified from the photoluminescence spectra and the value of oxygen vacancy decreased with increasing Ti concentration.

The role of neutral and ionized oxygen defects in the emission of tin oxide nanocrystals for near white light application

Tin oxide (SnO2) nanocrystals (NCs) based phosphor was synthesized by a green chemistry microwave-assisted hydrothermal method at different reactor pressures. The x-ray diffraction analysis showed that a single rutile SnO2 phase with a tetragonal lattice structure was formed. The photoluminescence emission was measured for He–Cd laser excitation at 325 nm and it showed a broad band emission from 400 to 800 nm for all the synthesized reactor pressures. The broad emission spectra were due to the creation of various oxygen and tin defects as confirmed by x-ray photoelectron spectroscopy data. The origin of the emission in the SnO2 NCs is discussed with the help of an energy band diagram. Analysis suggests that the visible emission of SnO2 NCs is due to a transition of an electron from a level close to the conduction band edge to a deeply trapped hole in the SnO2 NCs. The NCs were found to be suitable for warm near white light emission device applications.

Fabrication and characterization of Er+3 doped SiO2/SnO2 glass-ceramic thin films for planar waveguide applications

Glass-ceramics are a kind of two-phase materials constituted by nanocrystals embedded in a glass matrix and the respective volume fractions of crystalline and amorphous phase determine the properties of the glass-ceramics. Among these properties transparency is crucial in particular when confined structures, such as, dielectric optical waveguides, are considered. Moreover, the segregation of dopant rare-earth ions, like erbium, in low phonon energy crystalline medium makes these structures more promising in the development of waveguide amplifiers. Here we are proposing a new class of low phonon energy tin oxide semiconductor medium doped silicate based planar waveguides. Er3+ doped (100-x) SiO2-xSnO2 (x= 10, 20, 25 and 30mol%), glass-ceramic planar waveguide thin films were fabricated by a simple sol-gel processing and dip coating technique. XRD and HRTEM studies indicates the glass-ceramic phase of the film and the dispersion of ~4nm diameter of tin oxide nanocrystals in the amorphous phase of silica. The spectroscopic assessment indicates the distribution of the dopant erbium ions in the crystalline medium of tin oxide. The observed low losses, 0.5±0.2 dB/cm, at 1.54 μm communication wavelength makes them a quite promising material for the development of high gain integrated optical amplifiers.

A transparent flexible z-axis sensitive multi-touch panel based on colloidal ITO nanocrystals.

Bottom-up fabrication of a flexible multi-touch panel prototype based on transparent colloidal indium tin oxide (ITO) nanocrystal (NC) films is presented. A series of 7% Sn(4+) doped ITO NCs protected by oleate, octanoate and butanoate ligands are synthesized and characterized by a battery of techniques including, high resolution transmission electron microscopy, X-ray diffraction, (1)H, (13)C and (119)Sn nuclear magnetic resonance spectroscopy, and the related diffusion ordered spectroscopy. Electrical resistivities of transparent films of these NCs assembled on flexible polyethylene terephthalate substrates by convective self-assembly from their suspension in toluene decrease with the ligand length, from 220 × 10(3) for oleate ITO to 13 × 10(3)Ω cm for butanoate ITO NC films. A highly transparent, flexible touch panel based on a matrix of strain gauges derived from the least resistive film of 17 nm butanoate ITO NCs sensitively detects the lateral position (x, y) of the touch as well as its intensity over the z-axis. Being compatible with a stylus or bare/gloved finger, a larger version of this module may be readily implemented in upcoming flexible screens, enabling navigation capabilities over all three axes, a feature highly desired by the display industry.

Assembly of antimony doped tin oxide nanocrystals into conducting macroscopic aerogel monoliths.

We present the assembly of preformed antimony doped tin oxide nanobuilding blocks into centimeter sized aerogels with surface areas exceeding 340 m(2) g(-1). After calcination, the resistivity of the aerogels was decreased by 4 orders of magnitude to a few kΩ cm, with the primary conducting structures measuring only a few nanometers.

Highly Soluble Ligand Stabilized Tin Oxide Nanocrystals: Gel Formation and Thin Film Production

Highly soluble ligand stabilized tin oxide nanocrystals have been prepared by the postsynthetic modification of hydrous tin oxide with the simple short-chain carboxylic acids, acetic acid and trifluoroacetic acid. The surface modified nanoparticles are soluble in common organic solvents at concentrations of up to 2 g/mL and may be stored indefinitely in the solid-state with no loss of solubility. The nature and role of the surface carboxylate groups has been assessed through a combination of thermogravimetric analysis and infrared spectroscopy. The effect of surface modification on the sintering behavior of the nanomaterials has also been investigated. Tuning the surface chemistry of the hybrid nanocrystals allows the generation of monolithic gels, while their high solubility permits the preparation of high quality thin films using simple solution processing techniques.

Synthesis and application of non-agglomerated ITO nanocrystals via pyrolysis of indium–tin stearate without using additional organic solvents

Indium–tin stearate precursor was successfully synthesized by a direct reaction between metals (indium and tin) and molten stearic acid under a nitrogen atmosphere at 260 °C for 3 h for the first time. Nearly, monodisperse ~7 nm indium tin oxide (ITO) nanocrystals without any agglomeration were efficiently synthesized by pyrolysis of the as-synthesized precursors without using additional organic solvents under different conditions. It was found that both pyrolysis temperature and Sn doping level significantly influenced the particle size and size distribution of the ITO nanocrystals. A lower pyrolysis temperature and a higher Sn doping level resulted in a smaller particle size of the ITO nanocrystals. Addition of 1-octadecene solvent in the pyrolysis reaction could lead to a narrow particle size distribution of the ITO nanocrystals. In addition, all the as-synthesized ITO nanocrystals could be dispersed homogeneously in non-polar solvents such as n-hexane and chloroform without using surfactants forming optically clear solutions, which were used to prepare ITO/PVB nanocomposite film as interlayer for making laminated glass in solar control glazing.

Fast detection of low concentration carbon monoxide using calcium-loaded tin oxide sensors

Solid state sensors with noble metal-loaded tin oxide as sensing elements are widely used for the detection of flammable and toxic gases and volatile organic compounds (VOCs). Apart from rendering high cost, incorporation of noble metals often increases the preconditioning time and introduces a drift in baseline properties of the sensors. Herein, we report on the development of stable and economically viable sensor modules for fast and efficient detection of carbon monoxide (CO) in air. The sensing layer comprises sonochemically synthesized calcium-loaded tin oxide (Ca-SnO2) nanocrystals, in which calcium primarily gets segregated at the SnO2 grain boundaries as calcium oxide (CaO) and thereby restricts the growth of SnO2 particles. Due to larger ionic radius of Ca2+ as compared to that of Sn4+, a minute quantity of calcium can be doped as well into the SnO2 lattice. The variation of calcium concentration in SnO2 has a prominent effect on the sensor performance, where 5wt% calcium loading shows the highest sensor response. The sensors exhibit a lower detection limit of 1ppm CO in air. The response time (10–12s) and recovery time (30–45s) of our sensors, for different concentrations of CO, are equivalent or less compared to those of commercially available metal-oxide sensors. Additionally, a highly stable baseline with minimal drift even after being operational for over 1.5 years is observed.

Synthesis and Characterization of Fluorine-Doped Tin Oxide Nanocrystals Prepared by Sol-Gel Method

Fluorine-doped tin dioxide (FTO) nanocrystals were prepared with sol–gel method using SnCl4·5H2O and NH4F as precursor material. The FTO was characterized with X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Differential Thermal Analysis and Thermal Grativity (DTA-TG) and Infrared Radiation (IR) respectively. The electrical property was measured with Hall Effect Sensor. The result of XRD and SEM shows that FTO nanocrystal size is about 20 nm and the dimension of the grain is about 300 nm. IR spectrum analysis proves fluorine doping. The crystal phase transformation was discussed with DTA-TG curve. When the sintering temperature is 450°C, the sintering time is 60 min, and the molar ratio of F to Sn is 2:10, the sheet resistance of FTO film is 107Ω/□.