Properties Of Sol Research Articles

Impact of thiourea concentration on the properties of sol–gel derived Zn(O,S) thin films and Cu(In,Ga)Se2 solar cells

A novel approach based on sol–gel spin coating method to deposit Zn(O,S) thin film using thiourea(TU) as a sulfur source replacing CdS as buffer layer was developed and the influence of TU concentration on the properties of Zn(O,S) thin films and Cu(In,Ga)Se2(CIGS) solar cells were investigated in this paper. It was found by X-ray diffraction and X-ray photoelectron spectroscopy that sol–gel derived Zn(O,S) thin films were amorphous and composed of ZnS, ZnO as well as Zn(OH)2. The variation of the optical band gap as a function of the S/(S+O) ratio was determined by energy-dispersive spectroscopy and UV-VIS-NIR. The results indicated that the minimum value for band gap of approximate 3.72 eV was obtained when the S/(S+O) = 0.44. Efficiency of up to 7.28% was achieved for a CIGS solar cell with Zn(O,S) buffer layer from 0.2M TU, which was attributed to the optimized conduction band offset (CBO) of +0.45 eV at the CIGS/Zn(O,S) interface.

Properties of silica sol bonded corundum‐spinel castables for steel ladles

AbstractIn order to overcome the shortcoming of the calcium aluminate cement (CAC) bonded castables, we prepared corundum‐spinel castables using silica sol as binder and tabular corundum, sintered magnesia‐alumina spinel, and reactive alumina as raw materials in this study. The effect of spinel grain size and solid content of silica sol on the flow value, sintering, mechanical strength and microstructure of the specimens treated at varying temperature of 400, 1000, 1500, and 1650°C for 5 hours in an air atmosphere were studied by SEM and EDS analyses. The results indicate that silica sol is suitable as a binder for corundum‐spinel systems. And silica sol with solid content of 25% bonded samples containing ≤90 μm spinel perform quite better than the others. At the same time, silica sol bonded samples had high strength in medium temperature. This is because that the closer proximity of silica sol and alumina powder and the high activity of nanometer SiO2 in silica sol are beneficial for the reaction of SiO2 and Al2O3 to generate mullite needed for reinforcement of castables matrix.

Effect of Ultra-Sonication Temperature on Photocatalytic Properties of Sol–Gel TiO2 Thin Films

Effect of Ultra-Sonication Temperature on Photocatalytic Properties of Sol–Gel TiO₂ Thin Films

Influence of erbium on the structural, optical and magnetic properties of sol–gel Ce: YIG films

Sol–gel Y2.8-xCe0.2Er x Fe5O12 (x = 0.0, 0.2, 0. 4, 0.6, 0.8 and 1.0) nanofilms were successfully prepared for their potential use in nonreciprocal magneto-optical devices, such as isolators and circulators. The effect of Er-doped Ce-substituted yttrium iron garnet (Ce:YIG) was investigated using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), UV–vis spectrophotometry and vibrating sample magnetometry (VSM). Analysis of the diffractograms indicated a cubic garnet structure and the incorporation of the Er3+ ions into the Ce: YIG. The absorption bands in IR spectra revealed the fingerprint of the YIG structure in the obtained films. The optical transparency of the Er-doped Ce:YIG samples was above 98% in the visible and near infrared region wavelengths. All samples were soft ferrimagnetic films, as indicated by their hysteresis loops and low magnetic coercivity fields (~50 Oe). As more erbium ions were introduced, the saturation magnetisation decreased and the magnetic coercivity increased. These findings suggest that Er-doped Ce:YIG films may have a promising role in magneto-optical applications.

Нелинейно-оптические свойства квантовых точек CdS/ZnS в матрице из высокомолекулярного поливинилпирролидона

AbstractSols containing core/shell CdS/ZnS semiconductor quantum dots are synthesized and their nonlinear properties, which are interesting for a large variety of applications in nanophotonics, are studied. The quantum dots produced are smaller in dimensions than the exciton Bohr radius and, therefore, exhibit a well-pronounced quantum-confinement effect. The nonlinear optical properties of low-concentration sols are studied upon exposure to laser pulses with an emission wavelength of 532 nm and a duration of 5 ns by the z-scan technique. The dependences of nonlinear optical coefficients on the concentration of CdS/ZnS quantum dots are obtained. The intensity dependence of two-photon absorption coefficients is presented. The dependence determines the boundary of the influence of high-order nonlinearities on the nonlinear transmittance of the samples. The mechanisms of optical limitation exhibited by sols, specifically, two-photon absorption, nonlinear refraction, and nonlinear scattering are discussed.

Difference in structural and chemical properties of sol-gel spin coated Al doped TiO2, Y doped TiO2 and Gd doped TiO2 based on trivalent dopants.

In this research, pure titanium dioxide (TiO2) and doped TiO2 thin film layers were prepared using the spin coating method of titanium(iv) butoxide on a glass substrate from the sol–gel method and annealed at 500 °C. The effects on the structural and chemical properties of these thin films were then investigated. The metal doped TiO2 thin film which exists as trivalent electrons consists of aluminium (Al), yttrium (Y) and gadolinium (Gd). The anatase phase of the thin films was observed and it was found that the crystal size became smaller when the concentration of thin film increased. The grain size was found to be 0.487 to 13.925 nm. The types of surface morphologies of the thin films were nanoporous, with a little agglomeration and smaller nanoparticles corresponding to Al doped TiO2, Y doped TiO2 and Gd doped TiO2, respectively. The trivalent doping concentration of the thin films increased with a rising of thickness of the thin film. This can contribute to the defects that give advantages to the thin film when the mobility of the hole carriers is high and the electrons of Ti can move easily. Thus, Ti3+ existed as a defect state in the metal doped TiO2 thin film based on lattice distortion with a faster growth thin film that encouraged the formation of a higher level of oxygen vacancy defects.

Chemical substitution-induced structure transition and enhanced magnetic and optical properties of sol–gel synthesized multiferroic BiFeO3 nanoparticles

Substitution-induced modifications in structural, magnetic and optical properties of Nb doped and Sm–Nb co-doped BiFeO3 nanoparticles are reported. X-ray diffraction and Raman analyses indicate that the phase transforms from a rhombohedral to orthorhombic one due to Nb doping and Sm–Nb co-doping. The Nb doping and Sm–Nb co-doping both can lead to a decrease in particle size and an enhancement in magnetic properties, but there is a much stronger effect for the Sm–Nb co-doping than for the Nb doping. With increasing doping concentration of Nb and Sm, the maximum and remanent magnetizations first increase and then drop down, i.e., there is a maximum value in both maximum and remanent magnetizations. The optimal maximum and remanent magnetizations are obtained as 0.601 and 0.155 emu/g, respectively, at y = 0.05 for BiFe1 - y Nb y O3 nanoparticles, while they are 0.954 and 0.206 emu/g at x = 0.15 for Bi1 - x Sm x Fe0.95Nb0.05O3 nanoparticles. Meanwhile, the corresponding optical energy band gap of these samples decreases from 2.16 to 2.02 eV with increasing Sm–Nb co-doping concentration, indicating a strong absorption of visible light. Consequently, the magnetic and optical properties of BiFeO3 nanoparticles can be improved considerably by doping high-valence transition and rare earth elements.

High humidity response property of sol–gel synthesized ZnFe2O4 films

The high humidity response of the sol–gel-synthesized ZnFe2O4 films was discovered, which was characterized through the relative humidity (RH) influence on the electric parameters of capacitance, impedance and resistance. As the RH increased from 30% to 90%, both the impedance and resistance of the ZnFe2O4 films, decreased by ∼2–3 orders of magnitude. This might be due to the physical adsorption and polarization of water molecules on the ZnFe2O4 surface. The high humidity response of ZnFe2O4 films has potential application in humidity sensitive devices.

Enhanced Field-Emission Properties of Sol–Gel-Derived Nanostructured $$\hbox {SnO}_{2}$$ SnO 2 :F Thin Film for Vacuum Microelectronics

Nanocrystalline fluorine-doped tin oxide thin film is synthesized by sol–gel-dip-coating technique. Hydrofluoric acid is used as the F-source, which has performed a simultaneous dual activity: (1) it has improved the conductivity by F-doping and (2) has increased the surface roughness via mild etching, both of which have improved the field-emission performance of the doped film over the undoped film. Electron microscopic image of $$\hbox {SnO}_{2}$$ :F film has revealed highly sharp emitter tips at the film surface, which has provided a very high geometrical field enhancement factor ( $$\beta \sim 760$$ ) and a very low turn-on field ( $$\sim $$ 4.8 V $$\upmu \hbox {m}^{-1})$$ . The field-emission process follows the Fowler–Nordheim tunnelling of cold-electron emission. This simple and cost-effective approach can be very useful for surface nanostructuring of thin film-based field emitters with improved field-emission characteristics for vacuum microelectronics applications.

Defect mediated ferromagnetism in cluster free Zn1−xNixO nanopowders prepared by combustion method

Structural, optical, vibrational and magnetic properties of sol–gel auto-combustion assisted Zn1−xNixO (x=0–3mol%) nanoparticles have been characterized. The X-ray diffraction (XRD) studies show hexagonal wurtzite phase formation upto 1mol% doping, confirming the substitution of Ni2+ ions. Photoluminescence and Raman spectroscopy confirm existence of zinc interstitials (Zni) and oxygen vacancies (Vo). Both extrinsic Ni doping and intrinsic oxygen vacancy contribute to the observed ferromagnetism. Magnetization values derived from bound magnetic polaron (BMP) model match the observed changes in magnetization. Temperature dependent magnetization characteristics of 1mol% Ni doped ZnO exhibits distinct zero field cooled (ZFC) and field cooled (FC) curves.

Pretreating temperature controls on structural, morphological and optical properties of sol–gel ZnO thin films

ZnO thin films on glass substrates were synthesised by sol–gel method with different pretreating temperature. The thermal behaviours of dried gel were firstly tested and found the relationship between organics evaporation and pretreating temperature. Then the structural, morphological and optical properties of thin films were investigated. X-ray diffraction patterns showed the phase with hexagonal wurtzite structure, and the preferred orientation growth at (0 0 2) plane increased as rising pretreating temperature. Atomic force microscope was used to measure the surface morphology of films and found the wrinkle-like at low pretreating temperature. Transmittance spectra of ZnO thin films prepared at higher pretreating temperature revealed the steeper absorption edge and the larger transmittance values, and the deduced optical energy gap increased. Meanwhile, with increasing pretreating temperature, photoluminescence spectra showed the stronger ultraviolet peak and weaker visible peaks which, respectively, originated from intrinsic emission and various defect emissions.

Enhanced cytocompatibility and osteoinductive properties of sol-gel-derived silica/zirconium dioxide coatings by metformin functionalization.

The aim of this study was to evaluate the pro-osteogenic properties of sol-gel-derived silica/zirconium dioxide coatings functionalized with 1 mM of metformin. The matrices were applied on 316L stainless steel using dip-coating technique. First of all, physicochemical properties of biomaterials were evaluated. Surface morphology and topography was determined using energy-dispersive X-ray spectroscopy and atomic force microscopy. The chemical composition was evaluated using Fourier transform infrared spectroscopy. Further, wettability and surface free energy were characterized. Cytocompatibility of biomaterials was tested invitro using model of human multipotent mesenchymal stromal cells isolated from adipose tissue. The influence of biomaterials on cells morphology and proliferation was determined. Osteogenic effect of obtained biomaterials was evaluated in terms of their influence on secretory activity of human multipotent mesenchymal stromal cells isolated from adipose tissue and matrix mineralization. Analysis was performed in relation to the control cultures i.e. maintained on pure SS316L substrate and SS316L covered with silica/zirconium dioxide. Obtained results indicate that silica/zirconium dioxide_metformin coatings ameliorated metabolic and proliferative activity of human multipotent mesenchymal stromal cells isolated from adipose tissue, as well as promoted their proper growth and adhesion. The human multipotent mesenchymal stromal cells isolated from adipose tissue cultured on biomaterials were characterized by typical fibroblast-like morphology. The addition of metformin to the silica/zirconium dioxide coatings improved functional differentiation of human multipotent mesenchymal stromal cells isolated from adipose tissue. Osteogenic cultures on silica/zirconium dioxide_metformin were characterized by formation of well-developed osteonodules rich in calcium and phosphorous. Moreover, human multipotent mesenchymal stromal cells isolated from adipose tissue cultured on silica/zirconium dioxide_metformin synthesized increased amount of alkaline phosphatase, bone morphogenetic protein 2 and osteopontin, both on messenger RNA and protein level. Obtained biomaterials modulate cellular plasticity of human multipotent mesenchymal stromal cells isolated from adipose tissue promoting their osteogenic differentiation, thus may find application in broadly defined tissue engineering.

Effect of different solvents on the key structural, optical and electronic properties of sol–gel dip coated AZO nanostructured thin films for optoelectronic applications

Transparent conducting aluminum (i.e. 2 at.%) doped zinc oxide (AZO) thin films were prepared on glass substrates by sol–gel dip coating technique using different solvents. This inexpensive dip coating method involves dipping of substrate consecutively in zinc solution and tube furnace for required cycles. Prepared films were investigated by XRD, SEM, PL, Raman spectroscopy optical and electrical studies. From the XRD studies, it confirmed the incorporation of aluminum in ZnO lattice. The prepared samples are polycrystalline nature, and these films reveal hexagonal wurtzite arrangement with (002) direction. The structural parameters such as crystallite size, dislocation density, micro strain, texture coefficient and lattice constant were investigated. SEM study showed well defined smooth and uniformed ganglia shaped grains are regularly distributed on to the entire glass substrate without any pinholes and cracks, and the average grain size is 75 nm. From the optical studies, the observed highest transmittance is 93% in the visible range and the band gap (Eg) is 3.26 eV. Room temperature PL spectra exhibited strong UV emission peak located at 386 nm for all the films. The electrical properties of the AZO thin films were studied by Hall-Effect measurements and found as n-type conductivity with high carrier concentrations (n), 2.76 × 1019 cm− 3 and low resistivity (ρ), 7.56 × 10− 3 Ω cm for the film deposed using methanol as solvent.

Investigation of sensing properties of sol–gel processed 4 at%Sb:SnO2/TiO2 thin films

In this work we investigate the gas and photo sensing properties of the antimony doped tin oxide and titanium oxide (4 at%Sb:SnO2/TiO2) nanocrystalline thin films deposited by sol–gel dip-coating. Photoconductivity measurements are carried out under solar light spectra irradiation at different powers. These results show a photo sensitivity of the films in a lateral junction due to interfacial defects. Gas sensitivity was studied at different pressures, and higher conductivity is presented at lower pressure compared to oxygen-rich atmosphere. It occurs due to absence of oxygen adsorption on the semiconductors surface. TiO2 films are also investigated concerning its properties to gas sensing under photo-excitation with InGaN LED light source with wavelength centered in 450 nm. The decay of photo-induced current evaluated under O2 and vacuum atmospheres shows that the sample illumination may contribute to higher gas-sensitivity. This measurement allows determining the charge carrier capture energy, that is related to trapping dominated by distinct defects in each atmosphere.

Electrochromic properties of sol–gel prepared hybrid transition metal oxides – A short review

This short review paper revisits the progress achieved in the last 10-15 years in the field of hybrid electrochromic materials, synthesized through sol-gel methods.During the recent decade, new avenues have been opened, exploring new concepts and particularly interesting applications of electrochromism. In this paper, we will discusssome of the new research directions in the field of electrochromism, together with novel applications of many electrochromic hybrid oxides. The most important incentive for enhanced properties of traditional materials has been the advent of nanotechnology. The discoveries in the field of synthesis of nanomaterials enabled to expand the materials and connect the morphological features of nanoparticles to the electrochromic properties at the macro level. This was possible because of the emergence of the new and more elaborate characterization methods, enabling to unveil hitherto unknown structural and morphological properties of electrochromic materials.It is important to mention the development of novel hybrid materials with significantly improved EC properties, where tungsten oxide is associated with carbonaceous materials such as MWCNT or graphene. These hybrid materials with enhanced EC properties, compared to the inorganic hybrids, will be remarkable in the future,for a series of novel applications.Retracing briefly the history of EC hybrid materials and summarizing the principal achievements will be useful not only for researchers in the field but for a wider readership as well.

Magnetic and DC electric properties of sol–gel-synthesized Ce-doped BiFeO3 nanoflakes

In this work, Bi1−x Ce x FeO3 (x = 0.0, 0.04, 0.06, 0.08, 0.1) mesoporous nanoflakes with average thickness 36–122 nm have been synthesized using the sol–gel method. The effect of Ce doping on the structural, morphological, magnetic, and electrical properties was investigated. The samples were characterized by the X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and scanning electron microscopy. The magnetic measurements show that the Bi1–x Ce x FeO3 nanoflakes have weak ferromagnetic ordering which can be attributed to the oxygen vacancies and Ce4+ substitution in the Bi sites. The DC electric transport properties were studied in the temperature range (300–700) K by the two-probe method. The materials show typical semiconductor features and the conduction mechanisms are governed by the hopping process. The Ce doping results in a significant enhancement in the electrical conductivity and the magnetic features of the BFO nanoflakes.

Annealing temperature-dependent microstructure and optical and electrical properties of solution-derived Gd-doped ZrO2 high-k gate dielectrics

In current work, the microstructure and optical and electrical properties of sol–gel-derived Gd-doped ZrO2 gate dielectric thin films as functions of annealing temperatures were systemically investigated. Analyzes by x-ray diffraction have indicated that the 240 °C-baked sample as well as those samples annealed at lower temperatures keep amorphous state. In the sample annealed at 500 °C, however, the amorphous phase disappears and tetragonal ZrO2 is formed. Measurements from ultraviolet-visible spectroscopy (UV/Vis) have demonstrated that transmittance of all samples in the visible region is approximately 80% and the increase in band gap energy has been found with increasing the annealing temperature. Electrical properties of all samples based on Al/Si/ZrGdOx/Al MOS capacitor have been investigated by using semiconductor device analyzer. Through the analysis and calculation of the electrical characteristic curves, solution-processed Al/ZrGdOx/Si/Al capacitor shows improved performances at a annealing temperature of 400 °C, such as high dielectric constant (k) of 16.56, lowest oxidation charge density (Q ox) of −0.74 × 1012 cm−2, and boundary trap oxidation charge density (N bt) of 3.17 × 1012 cm−2. In addition, the leakage current mechanism for 400 °C-annealed sample has been discussed in detail. solution-processed Gd-doped ZrO2 gate dielectric films were realized. Al/ZrGdOx/Si/Al capacitor shows optimized and improved performances at a annealing temperature of 400 °C.

Infrared properties of sol–gel derived zirconia film

We examined infrared transmission characteristics of a sol–gel derived zirconia film and the antireflective (AR) effect of this film for an Si substrate in the midinfrared region. The surface reflection loss of an Si plate is high (∼30%) because of the high refractive index (3.42) in the infrared region. We employed zirconia nanoparticle dispersion with 15 wt. % (1-butanol solvent) as starting sol solution. Then, the dispersion was coated with Si substrate at a spin-coating speed of 2000 rpm, and the substrate was heated to 150°C. The number of coatings was repeated seven times. As a result, the transmittance at 5.6-μm wavelength was enhanced to 66.2%, and we found that the coated film worked efficiently as the AR film up to 10-μm wavelength. Additionally, by heating the substrate to 800°C, the large absorptions at 2.9-, 6.4-, and 6.9-μm wavelengths could be suppressed because the hydroxy group in the film was reduced. Its peak transmittance was 67.9% at 4.9-μm wavelength.

A Novel Protocol to Monitor Trace Levels of Selected Polycyclic Aromatic Hydrocarbons in Environmental Water Using Fabric Phase Sorptive Extraction Followed by High Performance Liquid Chromatography-Fluorescence Detection

Fabric phase sorptive extraction (FPSE) combines the advanced material properties of sol–gel derived microextraction sorbents and the flexibility and permeability of fabric to create a robust, simple and green sample preparation device. It simultaneously improves the extraction sensitivity and the speed of the extraction by incorporating high volumes of sponge-like, porous sol–gel hybrid inorganic–organic sorbents into permeable fabric substrates that are capable of extracting target analytes directly from both simple and complex aqueous sample matrices. For the first time, this technique was applied to the trace-level determination of selected polycyclic aromatic hydrocarbons (PAHs) in environmental water samples using a non-polar sol–gel C18 coated FPSE media. Several extraction parameters were optimized to improve the extraction efficiency and to achieve a high detection sensitivity. Validation tests of spiked samples showed good linearity for four selected PAHs (R2 = 0.9983–0.9997) over a wide range of concentrations (0.010–10 ng/mL). Limits of detection (LODs) and quantification (LOQs) were measured at pg/mL levels; 0.1–1 pg/mL and 0.3–3 pg/mL, respectively. Inter- and intra-day precision tests showed variations of 1.1%–4.1% for four selected PAHs. Average absolute recovery values were in the range of 88.1%–90.5% with relative standard deviations below 5%, surpassing the values predicted by the recovery prediction model. Finally, the developed FPSE-HPLC-FLD protocol was applied to analyze 8 environmental water samples. Out of four selected PAHs, fluoranthene (Flu) and phenanthrene (Phen) were the most frequently detected in four samples, at concentrations of 5.6–7.7 ng/mL and 4.1–11 ng/mL, respectively, followed by anthracene (Anth) and pyrene (Pyr) in two samples. The newly developed FPSE-HPLC-FLD protocol is simple, green, fast and economical, with adequate sensitivity for trace levels of four selected PAHs and seems to be promising for routine monitoring of water quality and safety.

Magnetic and ferroelectric properties of sol – gel synthesized rhombohedral phase AlFeO3 nanoparticles

We report the preparation of a rhombohedral phase (space group ) AlFeO3 nanoparticles (NPs) and its magnetic and ferroelectric properties. The high purity rhombohedral phase AFO NPs of an average size 50 nm were prepared by sol – gel route followed by annealing at 700 °C. The NPs show antiferromagnetic nature at room temperature and near room temperature, weak ferroelectric properties. The coexistence of magnetic and ferroelectric features indicate that AFO NPs can be used as a prospective lead free multiferroic material for the spintronics applications.