Co-doped SnO2 Research Articles

Effect of cobalt concentration on morphology of Co-doped SnO2 nanostructures synthesized by solution combustion method

Cobalt (Co) doped SnO2 nanostructures were synthesized by solution combustion synthesis and structural and optical properties were investigated. The morphology of SnO2 nanostructure was changed from nanoflakes to nanospheres via nanorods and crystallite size was reduced from 4.7 nm to 2.7 nm as increase of Co doping concentration. The obvious diffraction peaks of X-ray diffraction and clear lattice fringes confirmed the formation of rutile phase of SnO2. The absorption edge transfers to upper wavelengths and energy bandgap was found to be decreasing by increase of Co concentration. The observed absorption band shows the characteristic band of d–d transitions of Co2+ ions in octahedral site symmetry. Vibrational spectroscopy shows the characteristic absorption peaks of Sn–O and confirms the incorporation of Co ions in SnO2 lattice.

Physical, Electrical and Optical Properties of F/Sb Codoped SnO2 Synthesized Via Sonochemical Process

F/Sb-codoped SnO2 nanoparticles were synthesized via sonochemical process using stannic chloride pentahydrate (SnCl4·5H2O) as host precursor while antimony(III) chloride (SbCl3) and ammonium fluoride (NH4F) were chosen as Sb and F dopant precursors, respectively. Their physical properties and morphologies were investigated using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscope while their electrical and optical properties were investigated by Hall measurement and diffuse reflectance spectroscopy. As-synthesized powder of polycrystalline phase SnO2 nanoparticles can be obtained by one-step sonochemical process and its crystallinity can be improved by calcination process. The formation of crystalline phase of SnO2 is assisted by cavitation effect provided by intense ultrasonic radiation via rapid collision. The characterization results disclose that Sb dopant has strong influence on both physical and electrical properties while F dopant provide considerable effect on electrical property of the samples. It is noticed that the codoping of both elements with certain contents can significantly heighten its electrical conductivity.

Synthesis and properties of (Fe, Al) co-doped SnO2 nanoparticles

Un-doped and (Fe, Al) co-doped SnO2 nano powders have been successfully synthesized by chemical co-precipitation method using SnCl2 2H2O, Fe (NO3)2 and AlCl3 as raw materials and PEG (poly ethylene glycol) as stabilizer. The prepared samples have been annealed at 600°C for 4 hours under ambient condition in order to improve the crystallinity. Powder XRD results show that the prepared samples are in tetragonal rutile type SnO2 phase. The average crystalline size of pure and (Fe, Al) co-doped SnO2 are found to be around 20-27 nm. The crystal structure of the SnO2 does not change with the co-doping of Fe and Al, but crystalline size increases by increasing from 3 mol% to 5 mol% of Fe at 5 mol% Al kept constant. These results have been confirmed by the transmission electron microscopy (TEM) studies. The crystalline size of the samples from TEM is 30-50 nm, which is in good agreement with the XRD results. The Raman studies reveal that the obtained peaks 300, 478, 633,779 cm-1 are good agreement with standard peaks of rutile phase SnO2. The SEM micro graphs of the (Fe, Al) co-doped nanoparticles result in agglomeration with near spherical shape. The EDAX Spectra show the chemical composition of samples to be uniform. UV-VIS diffusion reflectance spectroscopy (DRS) studies show that the band gap energy is 3.7 eV for pure, and 3.6 and 3.5 eV for (Fe, Al) co-doped (3 mol% and 5 mol%) SnO2 nanoparticles respectively. Photoluminescence (PL) has been studied with excitation wavelength of 350 nm. The un-doped sample exhibit one broad emission peak at 449 nm and relatively sharp emission peaks at 491 nm and 500 nm respectively. Co-doped SnO2 samples also exhibit the broad emission peaks at 442 nm and 444 nm with decreasing intensity. The magnetic measurements reveal that all pure and co-doped nanoparticles exhibit room temperature Ferromagnetism (RTFM) and weak Ferro magnetism due to lattice defects such as O-vacancies and play an important role in activating the observed ferromagnetism based on the bound polaron model (BMP). As a result weak Ferromagnetism and Ferromagnetism is developed.

Dielectric and magnetic properties of (Zn, Co) co-doped SnO2 nanoparticles**Project supported by the National Basic Research Program of China (Grant Nos. 2015CB921004, 2012CB821404, and 2011CBA00103) and the National Natural Science Foundation of China (Grant Nos. 11374261 and 11204059).

Polycrystalline samples of (Zn, Co) co-doped SnO2 nanoparticles were prepared using a co-precipitation method. The influence of (Zn, Co) co-doping on electrical, dielectric, and magnetic properties was studied. All of the (Zn, Co) co-doped SnO2 powder samples have the same tetragonal structure of SnO2. A decrease in the dielectric constant was observed with the increase of Co doping concentration. It was found that the dielectric constant and dielectric loss values decrease, while AC electrical conductivity increases with doping concentration and frequency. Magnetization measurements revealed that the Co doping SnO2 samples exhibits room temperature ferromagnetism. Our results illustrate that (Zn, Co) co-doped SnO2 nanoparticles have an excellent dielectric, magnetic properties, and high electrical conductivity than those reported previously, indicating that these (Zn, Co) co-doped SnO2 materials can be used in the field of the ultrahigh dielectric material, high frequency device, and spintronics.

Structural characterization and properties of nanocrystalline Sn1−xCoxO2 based dilute magnetic semiconductors

Abstract

Investigation of optical and structural properties of Fe, Cu co-doped SnO2 nanoparticles

The undoped Sn0.98Fe0.02O2 and Cu-doped Sn0.98Fe0.02O2 nanoparticles have been synthesized by a simple chemical co-precipitation method. Structural and optical properties of the synthesized samples have been studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–visible spectrophotometer and photoluminescence (PL) spectroscopy. The tetragonal rutile structure was confirmed by XRD with no other phases observed. The crystallite size of the nanoparticles calculated from the XRD peaks was in the nanometer range (5–6nm) which is in good agreement with the transmission electron microscopy (TEM) results. Substitution of Cu into the Sn0.98Fe0.02O2 nanoparticles can be confirmed by the shifting of peaks in XRD patterns. Sudden decrease in crystallite size at Cu=6% doped sample could have resulted in blue shift in energy gap which revealed the domination of quantum confinement effect. The shift of lattice mode around 637–693cm−1 and the change in shape of the band confirmed the presence of Cu in Sn–Fe–O. A strong violet peak around 391nm and a weak blue photoluminescence peak around 459nm were observed, while a blue peak appeared only after introducing Cu into the Fe–SnO2 host.

Effects of cobalt doping on nitric oxide, acetone and ethanol sensing performances of FSP-made SnO2 nanoparticles

In the present work, gas-sensing properties of flame-spray-made Co-doped SnO2 nanoparticles are systematically studied for detection of nitric oxide (NO), acetone (C3H6O) and ethanol (C2H5OH) gases occurred in human breathe. Structural characterizations by electron microscopy and X-ray analysis confirmed the formation of loosely agglomerated SnO2 nanoparticles (5–20nm) with highly crystalline tetragonal-cassiterite SnO2 structure and Co substitutional doping with Co2+ and Co3+ oxidation states. The gas-sensing properties of unload SnO2 and Co-doped SnO2 sensors were systematically tested towards NO, acetone and ethanol. Tested results indicated that small Co-doping levels in the range of 0.2–0.5wt% led to enhanced sensing properties toward NO, acetone and ethanol compared with undoped one. In particular, 0.2wt% Co-doped SnO2 sensor showed very high response of ∼1637–1000ppm NO at 350°C while 0.5wt% Co-doped SnO2 one exhibited high responses of ∼660–2000ppm acetone and ∼806–1000ppm ethanol. Thus, Co-doped SnO2 sensors are potential for responsive detections of NO, acetone and ethanol at ppm-level but with limited selectivity and may be useful for general environmental, industrial and biomedical applications.

Energy response and thermoluminescence properties of lithium potassium borate Glass co-doped with Cu and SnO2 nanoparticles

SnO2 nanoparticles doped lithium potassium borate with Cu-doped was prepared by melt-quenching technique. The field emission scanning electron microscope was used to examine morphology of samples. The TLD-Reader 4500 was used to measurement of thermoluminescence. The glow curves position of Cu-doped and co-doped SnO2 glass were recorded at about 205 °C and 215 °C respectively. The linear relationship of dose-TL intensity was observed for both samples. The TLD sensitivity shows that the co-doped SnO2 glass has almost 6 time higher sensitivity compared to Cu-doped glass. It was found that the theoretical calculations are in good agreement with the experimental results for relative energy response. The activation energy and frequency factor of TL glow peak are determined by using the peak shape method.

Modification of crystal anisotropy and enhancement of magnetic moment of Co-doped SnO2 thin films annealed under magnetic field.

Co-doped SnO2 thin films were grown by sputtering technique on SiO2/Si(001) substrates at room temperature, and then, thermal treatments with and without an applied magnetic field (HTT) were performed in vacuum at 600°C for 20 min. HTT was applied parallel and perpendicular to the substrate surface. Magnetic M(H) measurements reveal the coexistence of a strong antiferromagnetic (AFM) signal and a ferromagnetic (FM) component. The AFM component has a Néel temperature higher than room temperature, the spin axis lies parallel to the substrate surface, and the highest magnetic moment m =7 μB/Co at. is obtained when HTT is applied parallel to the substrate surface. Our results show an enhancement of FM moment per Co+2 from 0.06 to 0.42 μB/Co at. for the sample on which HTT was applied perpendicular to the surface. The FM order is attributed to the coupling of Co+2 ions through electrons trapped at the site of oxygen vacancies, as described by the bound magnetic polaron model. Our results suggest that FM order is aligned along [101] direction of Co-doped SnO2 nanocrystals, which is proposed to be the easy magnetization axis.

Construction of 3D Pt Catalysts Supported on Co-Doped SnO2 Nanourchins for Methanol and Ethanol Electrooxidation

Pt nanoparticles on Co-doped SnO2 nanostructures have been synthesized and used for methanol and ethanol electrooxidation. The hierarchical Co-SnO2 nanostructure with urchin-like morphology, self-assembled from numerous thin nanoneedles, provides a three-demensional (3D) frame for supporting Pt nanoparticles. The as-prepared Pt/Co-SnO2(urchin) nanocatalyst was characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), field effect scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry were carried out to comparatively investigate electrochemical properties of Pt/Co-SnO2(urchin), Pt/Co-SnO2(flower), Pt/SnO2 and Pt/C electrocatalysts. The urchin-shaped Pt/Co-SnO2 electrocatalyst shows better catalytic activity and higher catalytic stability compared with the other electrocatalysts.

Study of structural, morphological and optical properties of S and Cu co-doped SnO2 nanostructured thin films prepared by spray pyrolysis

Abstract We have established the effect of copper dopant concentration (Cu/Sn = 0–30 at.%) on the structural, morphological and optical properties of SnO2 : S films grown on glass substrate using a spray pyrolysis technique. According to the experimental evidence and data analysis, we found that the polycrystalline layers in undoped condition mainly consist of mixed phases such as SnS2 and SnO2, whilst in doped ones, Cu2SnS3 and Cu4SnS4 phases are dominant. With increasing Cu concentration, a decrease in the grain size with a change in the shape of the grains is observed. Optical measurement analysis showed that these films have a direct band gap energy of about 2.98–3.59 eV.

Structural, electrical and magnetic properties of (Fe, Co) co-doped SnO2 diluted magnetic semiconductor nanostructures

Nanostructures (NSs) of basic composition Sn1−xFex/2Cox/2O2 with x=0.00, 0.04, 0.06, 0.08 and 0.1 were synthesized by citrate-gel route and characterized to understand their structural, electrical and magnetic properties. X-ray diffraction and Raman spectroscopy were used to confirm the formation of single phase rutile type tetragonal structure. The crystallite sizes calculated by using Williamson Hall were found to decrease with increasing doping level. In addition to the fundamental Raman peaks of rutile SnO2, the other three weak Raman peaks at about 505, 537 and 688cm−1 were also observed. Field emission scanning electron microscopy studies showed the emergence of structural transformation. Electric properties such as dc electrical resistivity as a function of temperature and ac conductivity as a function of frequency were also studied. The variation of dielectric properties with frequency reveals that the dispersion is due to Maxwell–Wagner type of interfacial polarization in general. Hysteresis loops were clearly observed in M–H curves of Fe and Co co-doped SnO2 NSs. However, pure SnO2 nanoparticles (NPs) showed paramagnetic behaviour which vanished at higher values of magnetic field. The grain and grain boundary contribution in the conduction process is estimated through complex impedance plot fitted with non-linear least square (NLLS) approach which shows that the role of grain boundaries increases rapidly as compared to the grain volume with the increase of Fe and Co ions in to system.

Electrochemical Degradation of Methyl Orange by Samarium and Antimony Codoped SnO<sub>2</sub> Electrodes

In this work, samarium and antimony (Sm–Sb) codoped tin oxide (SnO2) films have been successfully prepared on titanium (Ti) substrate by a facile sol gel method. The samples were characterized by X–ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The composite film materials were used as anode for the electro-degradation of methyl orange solution. Two effective factors of electro–catalytic properties namely, the content of Sm in the SnO2 samples and the calcination temperature, have been optimized based on the electro-degradation experiments. A moderately calcination temperature of 873 K and 1.0% Sm doping owned the best performance. The smaller grain sizes and optical band gap of the SnO2 by introduction of the Sm improved electro-catalytic activity.

Structural, optical and morphological properties of La, Cu co-doped SnO2 nanocrystals by co-precipitation method

Sn0.96−xLa0.04CuxO2 (0⩽x⩽0.03) nanocrystals have been successfully synthesized by employing a simple co-precipitation method. The crystal structure of the synthesized nanocrystals was found to be tetragonal rutile of tin oxide by using X-ray diffraction technique and was not affected by doping. The change in lattice parameters was discussed based on the secondary phase formation and presence of Cu2+/Cu3+ in LaSnO2 lattice. The variation in size and shape of the nanocrystals by Cu-doping was discussed using scanning electron microscope. The chemical stoichiometry of Sn, Cu, La and O was confirmed by energy dispersive X-ray spectra. The best optical transparency and lower absorption observed at Sn0.97La0.02Cu0.01O2 nanocrystals seems to be optimal for industrial applications especially as transparent electrode. The initial blue shift of energy gap from 3.65eV (Cu=0%) to 3.78eV (Cu=1%) (ΔEg≈0.13eV) is due to the distortion in the crystal structure of the host compound and generation of defects. The red shift of energy gap after Cu=1% is due to the charge-transfer transitions between the metal ions d-electrons and the SnO2 conduction or valence band. Lattice mode of SnO2 at 686cm−1 in Sn0.98La0.02O2 nanocrystals and anti-symmetric SnOSn stretching mode of the surface bridging oxide around 634–642cm−1 in Cu doped Sn0.98La0.02O2 nanocrystals was confirmed by Fourier transform infrared spectra.

Synthesis of sub-5 nm Co-doped SnO2 nanoparticles and their structural, microstructural, optical and photocatalytic properties

A swift chemical route to synthesize Co-doped SnO2 nanopowders is described. Pure and highly stable Sn1−xCoxO2−δ (0 ≤ x ≤ 0.15) crystalline nanoparticles were synthesized, with mean grain sizes <5 nm and the dopant element homogeneously distributed in the SnO2 matrix. The UV–visible diffuse reflectance spectra of the Sn1−xCoxO2−δ samples reveal red shifts, the optical bandgap energies decreasing with increasing Co concentration. The samples' Urbach energies were calculated and correlated with their bandgap energies. The photocatalytic activity of the Sn1−xCoxO2−δ samples was investigated for the 4-hydroxylbenzoic acid (4-HBA) degradation process. A complete photodegradation of a 10 ppm 4-HBA solution was achieved using 0.02% (w/w) of Sn0.95Co0.05O2−δ nanoparticles in 60 min of irradiation.

Magnetic properties of Co-doped SnO2 at different carrier concentrations

Magnetic properties of Co-doped wide-gap semiconductor SnO2 were studied theoretically by using the PPLCAO first-principles computational scheme. Since the carrier plays an important role on magnetic properties about diluted magnetic semiconductors (DMS) materials, we discuss the origin of magnetic moments and the magnetic ordering mechanism with different carrier concentration in Co-doped SnO2 based on calculated spin density distribution. It is found that, the RKKY interaction is dominated in the magnetic coupling in Co-doped SnO2.

Design of ferromagnetism in Co-doped SnO2 nanosheets: a first-principles study

First-principles calculations are performed to study the structural, electronic and magnetic properties of Co-doped SnO2 nanosheets (NSs), using the generalized gradient approximation (GGA) plus Hubbard U method. We find that two Co atoms have a clustering tendency and the magnetic interactions between them exhibit a ferromagnetic (FM) coupling, while the appearance of an oxygen vacancy (VO) turns it into an antiferromagnetic (AFM) order. When the Li atom is codoped into Co-doped SnO2NS, the interactions between Co atoms are rehabilitated to FM coupling with a high Curie temperature (TC) of 850 K. The electronic structure analysis reveals that this is mainly attributed to the hole-induced double-exchange mechanism from s–d hybridizations between Li and Co, which finally activates a long-range FM coupling between two Co atoms. These findings could be very useful in nano-material design for spintronics.

Densification behaviour and sintering mechanisms of Cu- or Co-doped SnO2: A comparative study

Compared with the CuO–SnO2 system, there is a lack of experimental evidence of a eutectic liquid phase in the CoO–SnO2 system. It is therefore believed that the densification behaviour and sintering mechanisms of the two systems are completely different. However, our present study clearly demonstrated that the Co- and Cu-doped SnO2 ceramics exhibited a similar densification behaviour. The 1wt.% Cu- or Co-doped SnO2 ceramics could reach over 95% relative density when sintered to 1250°C with a heating rate of 5°Cmin−1. It was found that both CoO4/3- and CuO-doped SnO2 follow the same mass transport mechanism – viscous flow sintering during early-stage sintering. This was verified with the classic isothermal and constant-heating-rate models, as well as Frenkel’s viscous flow theory. The viscous flow mechanism dominated densification up to ∼73 and ∼78% relative density with the apparent activation energies of 362 and 440kJmol−1 for Co and Cu doping cases, respectively.

Enhanced Photoelectrical Performance of DSSC by Co-Doped SnO&lt;sub&gt;2&lt;/sub&gt; Nanoparticles

Investigation of the I-V characteristics of the DSSC based on interconnected with cobalt-doped SnO2 nanoparticles covered with a nano-scale thin layer which was absorbed by natural dyes are described. The presence of co-doped SnO2 has been confirmed by its characteristic XRD pattern and the shape of the particle is confirmed by SEM. The thickness of the protective layer can be conveniently controlled by the mole value of co-doped SnO2 used in the preparation of the thin film and the optimum conditions for best performance of the DSSC are presented together with possible explanation for the variations observed. An optimum light-to-electricity conversion efficiency of 0.37 % in the presence of a layer of co-doped SnO2 has been obtained which enhancement over the cell prepared with other natural dyes. The characterization of the sample using different techniques was explained (change the sentence).

Physical properties of SnO2: Co thin films prepared by chemical spray pyrolysis

In this research, Co-doped SnO2 thin films were prepared by chemical spray pyrolysis technique using SnCl4.5H2O and CoCl2.6H2O, with impurity percentage are (0%-3%-6%-9%) on glass substrates preheated at (450oC) with spray rate 5sec./1min, and thickness (400nm). The investigation of (XRD) indicates that the (SnO2) films are polycrystalline type of (tetragonal), the optical properties and band gap energy was observed and it`s found varied from (3.361-2.855 eV) when increasing in percentage impurity the energy band gap decreased. The Hall coefficient, concentration and mobility of charge carriers of SnO2:Co films studied, and their results observed that the increase in impurity of cobalt caused increase in electrical properties generally.