Controllable growth of SnO2 nanoparticles by citric acid assisted hydrothermal process

A facile sol–gel method based on urea–SnCl2 deep eutectic solvents for the synthesis of SnO2/SiO2 with high oxidation desulfurization activity

The n%-SnO2/SiO2 (n = 2, 4, 6) supported catalyst was prepared by the sol–gel and calcination method. Compared with the traditional impregnation method, the catalyst prepared by sol–gel method has higher oxidative desulfurization activity.

Acid-Induced, Oxygen-Atom Defect Formation in Reduced Polyoxovanadate-Alkoxide Clusters

Here, we present the first example of acid-induced, oxygen-atom abstraction from the surface of a polyoxometalate cluster. Generation of the oxygen-deficient vanadium oxide, [V₆O₆(OC₂H₅)₁₂]^1-, was confirmed via independent synthesis. Spectroscopic analysis using infrared and electronic absorption spectroscopies affords resolution of the electronic structure of the oxygen-deficient cluster (oxidation state distribution = [V^IIIV^IV₅]). This work has direct implications toward the elucidation of possible mechanisms of acid-assisted vacancy formation in bulk transition metal oxides, in particular electron-proton codoping that has recently been described for vanadium oxide (VO₂). Ultimately, these molecular models deepen our understanding of proton-dependent redox chemistry of transition metal oxide surfaces.

A lanthanide ion-doped Ba3Sc2F12 phosphor: hydrothermal synthesis, morphological control, energy transfer, and temperature-sensing performance

Ba₃Sc₂F₁₂ crystals were synthesized by a facile one-step hydrothermal method with Ba/Sc raw material in a ratio of 3 : 2. With the F/Sc ratio increasing from 4 to 8, the obtained crystal's morphology evolved gradually from a strip to a chocolate shape; further, the use of the additives, such as CTAB and EDTA, the obtained crystal's morphology changed from strip to cubic. The energy transfer of Ce³⁺→ Tb³⁺ in the Ba₃Sc₂F₁₂ host was also explored, and it was found to belong to a dipole-dipole interaction mechanism; the color of the light could be adjusted from blue-violet to green due to the different energy transfer efficiencies at different Ce³⁺ and Tb³⁺ ion-doping concentrations. Because of the thermal coupling level of Er³⁺ (²H_11/2→⁴I_15/2 and ⁴S_3/2→⁴I_15/2), Ba₃Sc₂F₁₂:14%Yb³⁺,2%Er³⁺ phosphors showed an excellent temperature-sensing ability with S_A(max) = 0.0043 K^-1 and T_max = 523 K, which are much better than the previously reported values for Yb³⁺/Er³⁺ co-doped systems. The as-prepared lanthanide ion-doped phosphors might have potential to serve as color light/displays and temperature control/sensors.

Facile Synthesis and Characterization of Two Dimensional SnO2-Decorated Graphene Oxide as an Effective Counter Electrode in the DSSC

SnO2-decorated graphene oxide (SnO2/GO) was synthesized by the modified Hummers’s method, followed by a chemical incorporation of SnO2 nanoparticles. Then, the nanocomposite was used as anon-precious counter electrode in a dye-sensitized solar cell (DSSC). Although GO has a relatively poor electrical conductivity depending essentially on the extent of the graphite oxidation, presence of SnO2 enhanced its structural and electrochemical properties. The Pt-free counter electrode exhibited a distinct catalytic activity toward iodine reduction and a low resistance to electron transfer. Moreover, the decorated GO provided extra active sites for reducing I3− at the interface of the CE/electrolyte. In addition, the similarity of the dopant in the GO film and the fluorine-doped tin oxide (FTO) substrate promoted a strong assimilation between them. Therefore, SnO2-decorated GO, as a counter electrode, revealed an enhanced photon to electron conversion efficiency of 4.57%. Consequently, the prepared SnO2/GO can be sorted as an auspicious counter electrode for DSSCs.

A honeycomb-like ZnO/SnO2 nanocomposite on nickel foam for high-performance asymmetric supercapacitors

In this work, a honeycomb-like ZnO/SnO₂ nanocomposite was synthesized on nickel foam (NF) using a single-step hydrothermal route for achieving good electrochemical performance.

Role of Synthesis Method on Luminescence Properties of Europium(II, III) Ions in β-Ca2SiO4: Probing Local Site and Structure

The europium ion probes the symmetry disorder in the crystal structure, although the distortion due to charge compensation in the case of aliovalent dopant remains interesting, especially preparation involves low and high temperatures. This work studies the preparation of the β-Ca₂SiO₄ (from here on C₂S) particle from Pechini (C₂SP) and hydrothermal (C₂SH) methods, and its luminescence variance upon doping with Eu²⁺ and Eu³⁺ ions. The blue shift of the charge-transfer band (CTB) in the excitation spectra indicates a larger Eu³⁺-O^2- distance in Eu³⁺ doped C₂SH. The changes in vibrational frequencies due to stretching and bending vibrations in the FTIR and the Raman spectra and binding energy shift in the XPS analysis confirmed the distorted SiO₄^4- tetrahedra in C₂SH. The high hydrothermal temperature and pressure produce distortion, which leads to symmetry lowering although doping of aliovalent ion may slightly change the position of the Ca atoms. The increasing asymmetry ratio value from C₂SP to C₂SH clearly indicates that the europium ion stabilized in a more distorted geometry. It is also supported by Judd-Ofelt analysis. The concentration quenching and site-occupancy of Eu³⁺ ions in two nonequivalent sites of C₂S were discussed. The charge state and concentration of europium ions in C₂SP and C₂SH were determined using X-ray photoelectron spectroscopy measurements. The C₂S particles were studied by X-ray powder diffraction, FTIR, Raman, BET surface area, TGA/DTA, electron microscopy, XPS, and luminescence spectroscopy. The impact of citrate ion on the morphology and particle size of C₂SH has been hypothesized on the basis of the microscopy images. This study provides insights that are needed for further understanding the structure of C₂S and thereby improves the applications in optical and biomedical areas and cement hydration.

Effect of both deposition temperature and indium doping on the properties of sol-gel dip-coated SnO2 films

Using indium chloride as an In source, In-doped SnO(2) films were fabricated by sol-gel method through dip-coating on borofloat glass substrates. The undoped SnO(2) films were deposited in air between 400 and 600 °C to get optimum deposition temperature in terms of crystal quality and hence In-doped SnO(2) films were deposited in air at 600 °C. The effect of both deposition temperature and In content on structural, morphological, optical and electrical properties was investigated. The crystalline structure and orientation of the films were investigated by X-ray diffraction (XRD) and surface morphology was studied by a field emission scanning electron microscope (FESEM). The compositional analysis of the films was confirmed by energy dispersive X-ray spectrometer (EDS). The absorption band edge of the SnO(2) films shifted from 3.88 to 3.66 eV with In content. The van der Pauw method was used to measure the sheet resistance of the films. The sheet resistance was affected significantly by deposition temperature and In content.

Effect of alumina incorporation on restricting grain growth of nanocrystalline tin(IV) oxide

In this project, nanocrystalline SnO2 powders were successfully prepared by (a) citrate sol-gel and (b) direct precipitation methods. Powders were characterized using thermal analysis techniques (DTA-TG-DSC), X-ray powder Diffraction (XRD), surface area (BET) and electrical conductivity measurements. XRD patterns showed the presence of the cassiterite structure. SnO2 particles, prepared through sol-gel method exhibit crystallite sizes in the range from 3.1 to 22.3 nm when the gel is heat treated at different temperatures up to 900°C. SnO2 nanocrystallites prepared by the precipitation method are comparatively larger in size. The higher specific surface area was obtained for the powder prepared using sol-gel method and the obtained average grain size (d) is relatively large compared with that of the average crystallite size. The powders show a semiconducting behavior with increasing temperature. The higher conductivity obtained for SnO2 prepared by sol-gel method can be attributed to their smaller average crystallite size. XRD of alumina doped powder exhibits finer particles than pure SnO2. TEM images showed that the particles are spherical in shape and consist of a core of SnO2 surrounded by a coating of alumina. The calculated surface area was found to decrease with temperature increases. Due to the effective role of Al2O3 additive as a grain growth inhibitor for the matrix grains, the observed surface area for the coated materials are predominantly higher than for the uncoated materials.