Synthesis and characterization of nanocrystalline tin oxide by sol–gel method

Tin Oxide Based Hybrid Nanostructures for Efficient Gas Sensing

Tin oxide as a semiconductor metal oxide has revealed great potential in the field of gas sensing due to its porous structure and reduced size. Especially for tin oxide and its composites, inherent properties such as high surface areas and their unique semiconducting properties with tunable band gaps make them compelling for sensing applications. In combination with the general benefits of metal oxide nanomaterials, the incorporation of metal oxides into metal oxide nanoparticles is a new approach that has dramatically improved the sensing performance of these materials due to the synergistic effects. This review aims to comprehend the sensing mechanisms and the synergistic effects of tin oxide and its composites in achieving high selectivity, high sensitivity and rapid response speed which will be addressed with a full summary. The review further vehemently highlights the advances in tin oxide and its composites in the gas sensing field. Further, the structural components, structural features and surface chemistry involved in the gas sensing are also explained. In addition, this review discusses the SnO2 metal oxide and its composites and unravels the complications in achieving high selectivity, high sensitivity and rapid response speed. The review begins with the gas sensing mechanisms, which are followed by the synthesis methods. Further key results and discussions of previous studies on tin metal oxide and its composites are also discussed. Moreover, achievements in recent research on tin oxide and its composites for sensor applications are then comprehensively compiled. Finally, the challenges and scope for future developments are discussed.

SnO2 Nanoparticles: Green Synthesis, Characterization, and Water Treatment

The green synthesis approach was utilized to synthesize tin dioxide (SnO2) nanoparticles (NPs) using Ocimum Basilicum leaves extract with different concentrations (10, 15, 20 ml) and different reaction temperatures (30, 60, 90 °C). The green synthesis method is considered economical, environmentally friendly, and non-toxic. X-ray diffraction patterns of the synthesized SnO2 NPs have displayed a tetragonal crystalline structure. The crystallite size of SnO2 NPs increased from 15.12 to 17.9 nm with increasing reaction temperature while decreasing from 20.68 to 17.9 nm with increasing extract concentrations. The morphology of the synthesized SnO2 NPs was investigated using high-energy transmission electron microscopy (HR-TEM). The optical energy gap was determined using the diffuse reflectance UV–vis spectra range (300–1200) nm of SnO2 NPs at different reaction temperatures and different extract concentrations. UV/Visible Spectrophotometer was used for studying the photodegradation of methylene blue dye (MB) dye. The photocatalytic degradation of MB revealed that SnO2 NPs at reaction temperature 90 °C degraded 69% of MB solution when exposed to UV illumination for 90 min while the degradation reaches 90% for 180 min of exposure. It was obvious that the degradation rate of MB was increased with the increase of reaction temperature, and the extract concentration.

Application of lead oxide electrodes in wastewater treatment: A review

Electrochemical oxidation (EO) based on hydroxyl radicals (·OH) generated on lead dioxide has become a typical advanced oxidation process (AOP). Titanium-based lead dioxide electrodes (PbO₂/Ti) play an increasingly important role in EO. To further improve the efficiency, the structure and properties of the lead dioxide active surface layer can be modified by doping transition metals, rare earth metals, nonmetals, etc. Here, we compare the common preparation methods of lead dioxide. The EO performance of lead dioxide in wastewater containing dyes, pesticides, drugs, landfill leachate, coal, petrochemicals, etc., is discussed along with their suitable operating conditions. Finally, the factors influencing the contaminant removal kinetics on lead dioxide are systematically analysed.

Synthesis of hybrid amorphous/crystalline SnO2 1D nanostructures: investigation of morphology, structure and optical properties

The aim of the study was to prepare SnO₂ nanowires via a combination of electrospinning and the sol–gel method from a polyvinylpyrrolidone (PVP)/dimetylformamide (DMF)/ethanol(EtOH)/tin(IV) chloride pentahydrate (SnCl₄·5H₂O) solution. The morphology, structure and chemical composition of the obtained PVP/SnO₂ nanofibers and SnO₂ nanowires were examined using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) as well as a scanning electron microscope (SEM) with an energy dispersive spectrometer (EDX). The optical property analysis was performed on the basis of UV–Vis spectra of absorbance as a function of the wavelength, based on which the rated values of band gaps of the fabricated 1D nanostructures were determined. The morphology analysis showed that the obtained amorphous SnO₂ nanowires with crystalline protuberances were characterized by a diameter of 50 to 120 nm. Results demonstrated that nanowires with a ratio of 1:1 precursor to polymer in the spinning solution were characterized by the smallest diameter after calcination and the smallest energy gap of 3.3 eV among all investigated samples. The rest of the studied materials were characterized by a larger energy gap (3.8 and 3.9 eV).

Facile sealing treatment with stannous citrate complex to enhance performance of electrodeposited Ti/SnO2-Sb electrode

Ti/SnO₂-Sb is a promising anode for electrochemical advanced oxidation process with advantages of low cost and no secondary pollution, while suffers from low work economy due to the short service life. In this study, a facile strategy was proposed to fabricate Ti/SnO₂-Sb electrode with high oxidation ability and long service life based on novelly sealing electrodeposited Sn-Sb coating with stannous citrate complex. The treated Ti/SnO₂-Sb electrode exhibited an accelerated service life of 41.5 h (100 mA cm^-2; 0.5 M H₂SO₄) and a degradation rate constant for methylene blue dye of 1.02 h^-1 which were respectively 11.9 and 2.5 times as that of the untreated electrode. It was found out that the complex could well repair the coating defects inside or outside and form a covering film to tighten the coating, and was then mineralized during the following calcination process to achieve a uniform, rough and highly active SnO₂-Sb catalytic layer. The distinctive structure was confirmed by XRD, SEM, XPS and FT-IR. The sealing treatment could be achieved by in situ electrodepositing Sn-Sb coating from or ex situ dipping Sn-Sb coating in solution containing stannous citrate complex followed by drying in air. This study provided a novel, facile and effective strategy to enhance performance of Ti/SnO₂-Sb electrode that could be easily achieved in both laboratory and industrial scales and combined with other strategies.

Undoped SnO2 as a Support for Ni Species to Boost Oxygen Generation through Alkaline Water Electrolysis

In this study, the synergistic behavior of Ni species and bimodal mesoporous undoped SnO₂ is investigated in oxygen evolution reactions (OERs) under alkaline conditions without any other modification of the compositional phases or using noble metals. An efficient and environmentally friendly hydrothermal method to prepare bimodal mesoporous undoped SnO₂ with a very high surface area (>130 m² g^-1) and a general deposition-precipitation method for the synthesis of well-dispersed Ni species on undoped SnO₂ are reported. The powders were characterized by adsorption-desorption isotherms, TG-DTA, XRD, SEM, TEM, Raman, TPR-H₂, and XPS. The best NiSn composite generates, under certain experimental conditions, a very high TOF value of 1.14 s^-1 and a mass activity higher than 370 A g^-1, which are remarkable results considering the low amount of Ni deposited on the electrode (3.78 ng). Moreover, in 1 M NaOH electrolyte, this material produces more than 24 mA cm^-2 at an overpotential value of approximately +0.33 V, with only 5 wt % Ni species. This performance stems from the dual role of undoped SnO₂, on the one hand, as a support for active and well-dispersed Ni species and on the other hand as an active player through the oxygen vacancies generated upon Ni deposition.

Different Strategies of Stabilization of Vanadium Oxidation States in Lagao3 Nanocrystals

The spectroscopic properties of LaGaO₃, doped with V ions, were examined in terms of the possibility of the stabilization of particular vanadium oxidation states. It was shown that three different approaches may be applied in order to control the ionic charge of vanadium, namely, charge compensation, via incorporation of Mg²⁺/Ca²⁺ ions, citric acid (CA)-assisted synthesis, with various CA concentrations and grain size tuning through annealing temperature regulation. Each of utilized method enables the significant reduction of V⁵⁺ emission band at 520 nm associated with the V⁴⁺→ O^2- CT transition in respect to the ²E→ ²T₂ emission band of V⁴⁺ at 645 nm and ¹E₂ → ³T_1g emission band of V³⁺ at 712 nm. The most efficient V oxidation state stabilization was obtained by the use of grain size modulation, which bases on fact of different localization of the V ions of given charge in the nanoparticles. Moreover, the CA-assisted synthesis of LaGaO₃:V determines V valence states but also provides significant separation of the nanograins. It was found that superior charge compensation was achieved when Mg²⁺ ions were introduced in the matrix, due the more efficient lability, resulting from the comparable ionic radii between Mg²⁺ and V ions.

Effect of Oxygen Vacancy on Structural, Optical and Magnetic Behavior of Tin Oxide Nanoparticles

Nanocrystalline SnO2powder has been successfully synthesized by using tin(II) chloride dihydrate (SnCl[Formula: see text]H2O), distilled water and liquid ammonia by the simple chemical co-precipitation method at room temperature using different SnCl[Formula: see text]H2O molar concentration of 0.3[Formula: see text]M, 0.4[Formula: see text]M and 0.5[Formula: see text]M. The structural properties of the prepared SnO2and transition metal doped SnO2nanoparticles has been studied using X-ray diffraction method and scanning electron microscope. The composition of the powders has been analyzed using energy dispersive X-ray analysis. The XRD pattern of the SnO2nanoparticles indicates the formation of single-phase rutile tetragonal structure. The grain size is found to be in the range of 3–7[Formula: see text]nm and is found to increase with increasing SnCl2molar concentration. The absorption spectra revealed that the bandgap decreased from 3.74[Formula: see text]eV to 3.59[Formula: see text]eV with increasing SnCl2molar concentration. The photoluminescence spectra of SnO2nanoparticles showed a visible broad luminescence band in the region of 385–430[Formula: see text]nm. The magnetic studies have been carried out using the hysteresis loop obtained from a vibrating sample magnetometer. The SnO2samples using 0.3 and 0.4 SnCl2molar concentration exhibited ferromagnetic behavior whereas the SnO2sample prepared using 0.5[Formula: see text]M SnCl[Formula: see text]H2O exhibited paramagnetic nature.

Cytotoxicity study of Piper nigrum seed mediated synthesized SnO2 nanoparticles towards colorectal (HCT116) and lung cancer (A549) cell lines

Different sized tetragonal tin oxide nanoparticles (SnO₂ NPs) were synthesized using Piper nigrum seed extract at three different calcination temperatures (300, 500, 900°C) and these nanoparticles (NPs) were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), dynamic light scattering (DLS) and Fourier transform infrared spectrophotometry (FT-IR). The optical properties were studied using UV-Vis and photoluminescence (PL) spectrophotometers. The generation of reactive oxygen species (ROS) was monitored by using a fluorescence spectrophotometer and fluorescence microscope. The cytotoxicity of the synthesized SnO₂ NPs was checked against the colorectal (HCT116) and lung (A549) cancer cell lines and the study results show that SnO₂ NPs were toxic against cancer cell lines depending on their size and dose. IC₅₀ values of SnO₂ NPs having average particle sizes of 8.85±3.5, 12.76±3.9 and 29.29±10.9nm are 165, 174 and 208μgL^-1 against HCT116, while these values are 135, 157 and 187μgL^-1 against A549 carcinoma cell lines, respectively. The generated ROS were responsible for the cytotoxicity of SnO₂ NPs to the studied cancer cells and smaller size NPs generated more ROS and hence showed higher cytotoxicity over larger size NPs. The results of this study suggest that the synthesized stable nanoparticles could be a potent therapeutic agent towards cancerous cell lines.

Temperature effect over structure and photochemical properties of nanostructured SnO2 powders

We successfully synthesized tin dioxide nanoparticles with polyhedral morphology via an ethylene glycol assisted sol-gel approach. The structural characteristics of three tin dioxide samples were investigated after being thermally treated at 400°C, 600°C and 800°C. X-ray diffraction (XRD) patterns clearly show the formation of single phase tin dioxide nanoparticles, with crystallite size of 6–20 nm, in good correlation with Fourier transform infrared (FTIR) spectra. Transmission electron microscopy (TEM) analysis confirms the formation of 6nm polyhedral nanoparticles for the 400°C sample. Ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectra suggest a high concentration of oxygen vacancies. The oxygen vacancy concentration increases with temperature, due to the combined action of the formation of VO and the energetic O compensation. X-ray photoelectron spectroscopy (XPS) analysis also confirms the formation of single phase tin dioxide and the presence of oxygen vacancies in good agreement with UV-VIS and PL data.

Surfactant effects on the synthesis of durable tin-oxide nanoparticles and its exploitation as a recyclable catalyst for the elimination of toxic dye: a green and efficient approach for wastewater treatment

A green synthesis of SnO₂ nanoparticles was successfully developed using urea by a microwave heating method.

Influence of SiO2 on the structure-controlled synthesis and magnetic properties of prismatic MnO2 nanorods

Silicon dioxide-doped tetragonal MnO2 single crystalline prismatic nanorods have been successfully synthesized through a facile hydrothermal route at a temperature of 250 ° C with a reaction time as quick as 5 h. The synthesized MnO2 prismatic nanorods were characterized by x-ray diffraction, field emission scanning electron microscopy, energy dispersive x-ray analysis, transmission electron microscopy, high resolution transmission electron microscopy with selected area electron diffraction and Raman spectroscopy. Experimental results show that single crystalline tetragonal MnO2 nanorods have been successfully synthesized at all doping concentrations and that nanorods with a prismatic surface morphology have been obtained at 20 mass% of SiO2. The diameter of as-prepared MnO2 nanorods increases from 125 to 250 nm on increasing the dopant concentration. X-ray photoelectron spectroscopy analysis confirms the presence of valence Si (2p) of SiO2 in the as-prepared MnO2 nanostructures. The intensity of Raman modes clearly increases with increasing doping concentration, indicating an improvement in the structural aspects of the MnO2 nanorods. The magnetic properties of the products have been evaluated using a vibrating sample magnetometer, revealing that the as-prepared MnO2 nanorods exhibit weak ferromagnetic behavior at room temperature. The Néel temperature of the as-obtained products is calculated as 97 K. On the basis of the structural information, a growth mechanism is proposed for the formation of prismatic-like 1D MnO2 nanorods.

Effect of Sintering Temperatures on the Synthesis of SnO2 Nanospheres

In this communication we report the rapid nanostructure of SnO2 with a spherical morphology which has been prepared in large scale via sol-gel method. The products were characterized with scanning electron microscopy, X-ray powder diffraction, transmission electron microscopy, FTIR, and photoluminescence spectroscopy. The strong photoluminescence of the nanosphere in visible region suggested possible application in nanoscaled optoelectronic devices. A possible growth mechanism for the SnO2 nanosphere in terms of solvation, hydrolysis, and polymerization was proposed.

Effect of tin oxide nanoparticle binding on the structure and activity of α-amylase from Bacillus amyloliquefaciens

Proteins adsorbed on nanoparticles (NPs) are being used in biotechnology, biosensors and drug delivery. However, understanding the effect of NPs on the structure of proteins is still in a nascent state. In the present paper tin oxide (SnO2) NPs were synthesized by the reaction of SnCl4·5H2O in methanol via the sol-gel method and characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). The binding of these SnO2-NPs with α-amylase was investigated by using UV-vis, fluorescence and circular dichroism (CD) spectroscopic techniques. A strong quenching of tryptophan fluorescence intensity in α-amylase was observed due to formation of a ground state complex with SnO2-NPs. Far-UV CD spectra showed that the secondary structure of α-amylase was changed in the presence of NPs. The Michaelis-Menten constant (K(m)), was found to be 26.96 and 28.45 mg ml(-1), while V(max) was 4.173 and 3.116 mg ml(-1) min(-1) for free and NP-bound enzyme, respectively.