Ultrasonic-assisted Sol Gel Method Research Articles

Improvement of wood properties by impregnation with TiO2via ultrasonic-assisted sol–gel process

Wood with improved properties was successfully prepared by impregnation with TiO2viaultrasonic-assisted sol–gel method which is an innovative, simple, and time-saving technology.

Synthesis of SnO2 nanostructures by ultrasonic-assisted sol–gel method

Fluorine doped SnO2 nanostructures were grown using ultrasonic assisted sol–gel method. The gel was obtained by dissolving stannous chloride in methanol with ammonium fluoride as dopant followed by irradiation with ultrasonic vibrations. Obtained samples were characterized by structural, morphological and optical studies. All the peaks in the X-ray diffractograms are identified and indexed as tetragonal cassiterite structure. Negative slope of Williamson–Hall plots indicates compressive strain. Particle size of SnO2 nanostructures is decreases with increases in concentration of fluorine doping. Atomic force microscopy, scanning electron microscopy and transmission electron microscopy studies confirm the formation of ring like porous structures and then hollow tube like growth with increase in the fluorine concentration. Peaks in Raman spectra also indicate strong confinement in SnO2 particles. Distinct peaks in the PL spectra make the structure suitable for photovoltaic applications.

Li2FeSiO4/C with good performance as cathode material for Li-ion battery

Li2FeSiO4/C has been prepared by the ultrasonic-assisted sol–gel method with about 50nm Fe2O3 particle as Fe source. The structures, morphologies, and carbon content of the product are characterized. Li2FeSiO4/C owns pure phase and the particle size of Li2FeSiO4 is close to Fe2O3 nanoparticle. As the cathode material of Li-ion battery, the product shows stable cycle performance at the wide range of rate and good rate performance. The discharge capacities of the 100th cycle are 140mAhg−1, 125mAhg−1, 120mAhg−1, 110mAhg−1, and 90mAhg−1 at 0.1C, 0.5C, 1C, 2C, and 5C rate, respectively.

Photocatalytic Activity of Sm, Zr Co-Doped TiO<sub>2</sub> Synthesized by Ultrasonic Assisted Sol-Gel Method

Sm, Zr doped nanocrystalline TiO2 powers were prepared successfully by a facile ultrasonic assisted sol-gel method. The products were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. X-ray diffraction peaks could be assigned to anatase TiO2, which confirms the crystallinity of the as-prepared samples. The SEM images demonstrated that the crystalinity is formed with spherical aggregates with average diameters ranging from 10 to 20 nm. The photocatalytic activity was studied on the photocatalytic degradation of methyl orange (MO) aqueous solution irradiated with UV-visible light. Under UV-visible light irradiation, the photocatalytic performances of the doped samples were much better than that of pure TiO2, and the co-dopant showed highest. It demonstrated that a strong Sm-Zr synergistic interaction might play a decisive role in driving the excellent photocatalytic performance of TiO2.

Synthesis and electrochemical properties of polyhedron-shaped Li3V2−xSnx(PO4)3 as cathode material for lithium-ion batteries

Sn-doped Li3V2−xSnx(PO4)3/C (x=0, 0.02, 0.04, 0.08) composites are prepared using an ultrasonic-assisted sol–gel method under a static inert atmosphere. The effects of Sn-doping on the structure and electrochemical performance of Li3V2(PO4)3/C are investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical measurements. The XRD patterns demonstrate that Sn-doping affects the preferred crystal growth direction of Li3V2(PO4)3. The SEM results show that the particles of the Sn-doped samples have a polyhedron shape. The particles are micron-size and present high crystallinity. The Li3V1.98Sn0.02(PO4)3/C sample, which has initial capacities of 122.7 and 117.2mAhg−1 at 0.2 and 5C between 3.0 and 4.3V, respectively, shows the best electrochemical performance among obtained samples. During Li+ de-intercalation and intercalation processes, Sn4+ could functions as a cushion bracket to protect the Li3V2(PO4)3 crystal lattice from shrinking, which greatly improves the rate performance and cycling performance of Li3V2(PO4)3.

Synthesis of Hollow SiO2 Nanoparticles from Dy2O3@SiO2 Core–Shell Nanocomposites via a Recyclable Sonochemical Method

Hollow silica nanoparticles were prepared from Dy2O3@SiO2 core–shell nanocomposites, for the first time, by a simple ultrasonic assisted sol–gel method. The Dy2O3@SiO2 core–shell nanocomposites were prepared by the deposition of a SiO2 layer onto the surface of Dy2O3 nanoparticles using a three-step coating process. The hollow SiO2 nanostructures were obtained by selective removal of the Dy2O3 cores. The structure, morphology and composition of the products were determined by the techniques of X-ray diffraction, Fourier transfom infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. The results indicated that hollow SiO2 nanostructures were sphere-like shape with the average size of 20 nm and had an amorphous crystal structure. The important advantage of this process is the recyclability of the Dy2O3 nanoparticles as the starting material of the reaction.

Photocatalytic Activity of La, Y Co-Doped TiO<SUB>2</SUB> Nanoparticles Synthesized by Ultrasonic Assisted Sol–Gel Method

Bare TiO2 (T), La-doped TiO2 (LT), Y-doped TiO2 (YT), La, Y co-doped TiO2 (LYT) were successfully prepared by facile ultrasonic assisted sol-gel synthesis using Ti(OC4H9)4 as the precursor. The products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), UV-visible diffuse reflectance spectra (DRS), and X-ray photoelectron spectroscopy (XPS), respectively. The photocatalytic activities of anatase samples, with the average particle diameters ranging from 14 nm to 21 nm, were evaluated for photodegradation of methyl orange (MO). The XPS results indicated that Y atoms were incorporated into titania lattice, while La atoms existed on the crystal surface. Due to doping, the optical absorption edges of LT, YT, and LYT shifted to the visible light region by 21 nm, 29 nm and 35 nm, respectively. The photocatalytic performances of the doped samples, such as LT, YT and LYT, were much higher than that of bare TiO2 under UV-visible light irradiation. And the photoreactivity efficiency of the LYT was the highest. It indicated that a strong La-Y synergistic interaction appeared to play a decisive role in driving the excellent photocatalytic performance of titania.

Ultrasonic-assisted synthesis and solar photoactivity investigation of Ce, B co-modified TiO2 nanoparticles

► Ce, B co-modified titania nanoparticles synthesized by ultrasonic assisted sol–gel method. ► The preparation processes are all under mild condition (low temperature). ► The samples exhibited high photocatalytic activity under solar light irradiation. In this study, Ce and B co-modified TiO 2 nanoparticles were prepared using an ultrasonic-assisted sol–gel method. The prepared sample was characterized by X-ray diffraction, scanning electron microscopy, UV–vis diffuse reflectance spectroscopy and BET analysis. In order to detect the effect of dopants on the titania, the photocatalytic activity of these as-prepared titania nanoparticles was determined by following the degradation of the reactive dye methylene blue under solar light irradiation. The activity was compared to that of pure titania. It was revealed that the photocatalytic activity of the Ce and B co-modified titania nanoparticles produced a significant enhancement compared to pure titania. The apparent rate constant of the as-prepared co-modified titania was 3 times higher than that of pure titania.

Synthesis of high performance Li3V2(PO4)3/C cathode material by ultrasonic-assisted sol–gel method

A novel ultrasonic-assisted sol–gel method is proposed to prepare Li3V2(PO4)3/C cathode material. X-ray diffraction analyses show that both Li3V2(PO4)3/C(A) synthesized by the ultrasonic-assisted sol–gel method and Li3V2(PO4)3/C(B) synthesized by a traditional sol–gel method have monoclinic structure. Scanning electron microscopy images indicate that the Li3V2(PO4)3/C(A) composite has a more uniform morphology than that of the Li3V2(PO4)3/C(B) composite. In the voltage range of 3.0–4.3 V (vs. Li/Li+), the initial specific discharge capacities of the Li3V2(PO4)3/C(A) and Li3V2(PO4)3/C(B) samples are 129.8 and 125.9 mAh g−1 at 1C rate (1C = 133 mA g−1), respectively. Furthermore, at 2-C charge/10-C discharge rate, the specific discharge capacity of the Li3V2(PO4)3/C(A) composite retains 113.2 mAh g−1 after 50 cycles, but the Li3V2(PO4)3/C(B) composite only presents a capacity of 94.8 mAh g−1.

TiO2 supported on SiO2 photocatalysts prepared using ultrasonic-assisted sol-gel method

TiO2-SiO2 (TiO2 supported on SiO2) photocatalysts were prepared using an ultrasonic-assisted sol-gel method. These photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and photoluminescence spectra (PL). Their photocatalytic activities were investigated by the method of methyl orange oxidation. It was found that the photocatalytic activity of TiO2-SiO2 was optimal when the molar ratio of hexadecyl trimethyl ammonium bromide to titanium butoxide was 1:10. The average crystallite size of TiO2-SiO2 was smaller than that prepared by the stirring method. Furthermore, for pure anatase phase samples, it was shown that the lower the photoluminescence intensity, the higher the photocatalytic activity.

A review on nano-TiO2 sol–gel type syntheses and its applications

Nanomaterials, defined as particles ranging from 1 to 100 nm diameter, have become widely utilized because of their unique physicochemical properties. Among those nanoparticles, titanium dioxide (TiO2) is frequently used in the production of paints, paper, plastics, welding rod-coating material, cosmetics, etc. TiO2 is the most commonly used semiconductor photocatalyst. Among the different nanomaterials, it is the most studied. Activated by UV-A irradiation, its photocatalytic properties have been utilized in various applications. A wealth of information on TiO2 photocatalytic in activation of bacteria has been acquired over the last 20 years. Hence, in this review article we have described synthesis methods mainly sol–gel type method like sol–gel method, ultrasonic-assisted sol–gel method, microemulsion method, colloidal synthesis, and also other method are discussed like solvo-thermal method, thermal plasma process, supersonically expanded plasma jet method, induction plasma torch, reactive plasma processing, plasma electrolytic oxidation, hydrolysis method, thermohydrolysis method, coprecipitation method, citrate–nitrate autocombustion method, etc. Also applications of TiO2 like medical applications, environmental application, sensor application, photocatalytic applications, and also its health impact for long-term exposure are discussed.

Preparation and characterization of magnetic TiO2 nanoparticles and their utilization for the degradation of emerging pollutants in water

Magnetic TiO2/Fe3O4 and TiO2/SiO2/Fe3O4 nanoparticles (NPs) were prepared by an ultrasonic-assisted sol–gel method using a commercial nanosized magnetic iron oxide as a support. Magnetic NPs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption (BET surface area) and SQUID magnetometer. Structure analyses indicated that TiO2/Fe3O4 NPs presented a core–shell structure with a TiO2 (anatase) coating wrapped around the magnetic iron oxide surface. TiO2/SiO2/Fe3O4 NPs showed a ternary structure with a core of Fe3O4, a SiO2 mesosphere and a TiO2 (anatase) crust. Both types of NPs exhibited magnetic properties with saturation magnetization about 40emu/g and low remanent magnetization and coercivity. Stability of TiO2/SiO2/Fe3O4 NPs in an aqueous solution under UV illumination was better than that of TiO2/Fe3O4 NPs as the presence of the insulation SiO2 layer prevented photodissolution of iron. Both catalysts showed the ability to catalyze the photodegradation of acetaminophen and other four pharmaceutical and personal care products (PPCPs) (antipyrine, caffeine, metoprolol and bisphenol A) from an aqueous solution. In terms of catalytic activity the synthesized magnetic NPs were almost comparable to the commercial Degussa P25 TiO2 photocatalyst. In addition, the easily recoverable magnetic photocatalysts showed good reusability, especially in the case of TiO2/SiO2/Fe3O4 NPs.

Study of erbium (III) doped titanium dioxide nanoparticles by photoacoustic spectroscopy

Nanocrystalline titania as photocatalyst has attracted considerable attention for its potential use in environmental cleaning. Recently, lanthanide ions doped titania samples have been shown to increase the photocatalytic efficiency of selected reactions. In this work, TiO 2 nanoparticles doped with Er 3+ were prepared via an ultrasonic assisted sol-gel method. The optical properties of the samples were determined by photoacoustic (PA) spectroscopy. It was found that the absorption edge shifted to lower wavelength when the particle size fell into nanometer range, which is the evidence of a quantum size effect. The nature of ligand bonding to Er 3+ and the structural properties were investigated with the PA absorptions of the f-f transitions of Er 3+, which are sensitive to the local environment. The results showed that TiO 2 gel heated at 70 °C still contained abundant trapped water and ethanol, and the environment around Er 3+ was similar to the one in the aqueous ion. The “degree of covalency” for Er 3+ bonding increased continuously during the gel-to-anatase transition. For the sample calcined at 1100 °C, however, the f-f transitions of Er 3+ showed blue shifts and the intensity of the hypersensitive transition decreased, indicating an increase of ionicity in the Er 3+ bonding. This can be attributed to the segregation of Er 3+ ions to the external surface, forming Er 2Ti 2O 7 during the anatase-to-rutile transition, which was confirmed with XRD and TEM measurements.

Synthesis of high power type LiMn 1.5Ni 0.5O 4 by optimizing its preparation conditions

LiMn 1.5Ni 0.5O 4 has been synthesized by an ultrasonic-assisted sol–gel method. The precursor is heat treated at a series of temperatures from 650 °C to 1000 °C. The structure and physical–chemical properties of the as-prepared powder are investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV) thermal gravimetric and galvanostatic charge–discharge tests in detail. As temperature goes up, the particle size increases, the reactivity of the material in 4 V region becomes more obvious, the structure of the samples become more stable and it behaves optimal electrochemical properties as the material is heat treated at 850 °C. When it is used as cathode active material in a lithium battery, it delivers high initial capacity of 134.5 mAh g −1 (corresponding to 91.7% of the theoretical capacity), and high rate discharge capability, e.g., 133.4, 120.6, 111.4, 103.2 and 99.3 mAh g −1 as discharged at 0.5, 1, 5, 10 and 15 C (1 C = 148 mA g −1)-rates, respectively. It also shows satisfactory capacity retention even at high rate of 5 C, which is about 99.83% of the capacity retention per cycle.

Structure and electrochemical properties of LiLa xMn 2– xO 4 cathode material by the ultrasonic-assisted sol-gel method

Powders of spinel LiLa x Mn 2— x O 4 were successfully synthesized by the ultrasonic-assisted sol-gel (UASG) method. The structure and properties of LiLa x Mn 2— x O 4 were examined by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electronic microscopy (SEM), galvanostatic charge-discharge test, and cyclic voltammetry (CV). XRD results show that the La 3+ can partially replace Mn 3+ in the spinel and the doped materials with La 3+ have a larger lattice constant compared with pristine LiMn 2O 4. FT-IR indicates that the absorption peak of Mn 3+−O and Mn 4+− O bonds has a red and blue shift with the increase of doping lanthanum in LiLa x Mn 2— x O 4, respectively. The charge-discharge test exhibits that the initial discharge capacity of LiLa x Mn 2— x O 4 drops off, and the capacity retention increases gradually at C/5 discharge rate with the increase of doping lanthanum, and LiLa 0.01Mn 1.99O 4 has a higher discharge capacity and a better cycling performance at 1C discharge rate. CV reveals that the doping La 3+ is beneficial to the reversible extraction and intercalation of Li + ions.

Synthesis and physicochemical properties of LiLa 0.01Mn 1.99O 3.99F 0.01 cathode materials for lithium ion batteries

Spinel lithium manganese oxide cathode materials were synthesized using the ultrasonic-assisted sol-gel method. The synthesized samples were investigated by differential thermal analysis (DTA) and thermogravimetry (TG), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), and the charge-discharge test. TG-DTA shows that significant mass loss occurs in two temperature regions during the synthesis of LiLa 0.01Mn 1.99O 3.99F 0.01. XRD data indicate that all samples exhibit the same pure spinel phase, and LiLa 0.01Mn 1.99O 3.99F 0.01 and LiLa 0.01Mn 1.99O 4 samples have a better crystallinity than LiMn 2O 4. SEM images indicate that LiLa 0.01Mn 1.99O 3.99F 0.01 has a slightly smaller particle size and a more regular morphology structure with narrow size distribution. The charge-discharge test reveals that the initial capacities of LiMn 2O 4, LiLa 0.01Mn 1.99O 4, and LiLa 0.01Mn 1.99O 3.99F 0.01 are 130, 123, and 126 mAh·g 1, respectively, and the capacity retention rates of the initial value, after 50 cycles, are 84.8%, 92.3%, and 92.1%, respectively. The electrode coulomb efficiency and CV reveal that the electrode synthesized by the ultrasonic-assisted sol-gel (UASG) method has a better reversibility than the electrode synthesized by the sol-gel method.

Ultrasonic-assisted sol-gel method of preparation of TiO2 nano-particles: Characterization, properties and 4-chlorophenol removal application

Nano-size TiO2 photocatalysts were prepared by sol-gel and ultrasonic-assisted sol-gel methods using two different sources of ultrasonicator, i.e., a bath type and tip type. The physicochemical characteristics of the catalysts were investigated by BET, XRD and TEM analyses and the photocatalytic properties of the TiO2 catalysts prepared by three different methods were compared. The intrinsic and extrinsic properties of TiO2, such as the particle size, surface area, pore-volume, pore-diameter, crystallinity as well as anatase, rutile and brookite phase ratios, could be controlled by the ultrasonic-assisted sol-gel method. During this preparation method, the effect of such important operating variables as the ultrasonic irradiation time, power density, the ultrasonic sources (bath-type and tip-type), magnetic stirring during synthesis, initial temperatures and size of the reactors are discussed here. It was found that each of the parameters played a significant role in controlling the properties of the TiO2 nano-particles. Among the three different methods, TiO2 photocatalysts prepared by ultrasonic (tip-US) assisted sol-gel possessed the smallest particle size, highest surface area and highest pore-volume than the catalysts prepared by the other two methods. 4-Chlorophenol was used as a pollutant to observe the photocatalytic degradation ability of the prepared photocatalysts and the TiO2 catalysts prepared by the bath-US ultrasonic-assisted sol-gel method were shown to be the most highly active. This is due to their high surface area and high pore-diameter. This study clearly demonstrates the importance and advantages of ultrasonication in the modification and improvement of the photocatalytic properties of mesoporous nano-size TiO2 particles.

Heterogeneous Photocatalytic Degradation of Chlorophenols over Ag-TiO<sub>2</sub> Nano Particles in an Aqueous Suspension

In the present work, TiO2 and Ag-TiO2 catalysts were prepared by an ultrasonic assisted sol-gel method. The physico-chemical characteristics studies of the newly synthesized catalysts were carried out by XRD, TEM, EDX, XPS, UV-Visible absorption spectra and an optical ellipsometry. In order to find out the optical absorption properties of the catalysts, theoretical simulations have been carried out by using the Tauc-Lorentz oscillator model. Photodegradation and mineralisation of the chlorophenols were confirmed by the HPLC and TOC measurements. The rate of a mineralisation trend was observed in the order of P < 2-CP < 2,4-DCP < 2,6-DCP < 4-CP < 2,4,6-TCP by using the Ag-TiO2 catalyst. The concentration of the main aromatic intermediate products was considerably lower for the Ag-TiO2 photocatalysts than for pure TiO2. This experiment demonstrated that the presence of Ag on TiO2 catalysts could enhance the photocatalytic oxidation of chlorophenols in an aqueous suspension. It was found that the degradation of the chlorphenols by these catalysts followed the pseudo- first order kinetic model.

Synthesis and physicochemical properties of LiAl 0.05Mn 1.95O 4 cathode material by the ultrasonic-assisted sol–gel method

Spinel LiAl 0.05Mn 1.95O 4 has been successfully synthesized by a new ultrasonic-assisted sol–gel (UASG) method. The structure and physicochemical properties of this as-prepared powder compared with the pristine LiMn 2O 4 and LiAl 0.05Mn 1.95O 4 synthesized by the traditional sol–gel method were investigated by differential thermal analysis (DTA) and thermogravimetery (TG), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), cyclic voltammetry (CV), and galvanostatic charge–discharge testing in detail. The results show that all samples have high phase purity, and ultrasonic process plays an important role in controlling morphology; LiAl 0.05Mn 1.95O 4 has higher Mn oxidation state, and the absorption peak of Mn(III) O and Mn(IV) O bonds has blue shift because of the doped Al. CV confirms that the LiAl 0.05Mn 1.95O 4 sample (UASG) has a good reversibility and its structure is very advantageous for the transportation of lithium ions. The charge–discharge tests indicate that LiAl 0.05Mn 1.95O 4 (UASG) has nearly equal initial capacity with LiMn 2O 4 (sol–gel) at 1 C discharge rate, but LiAl 0.05Mn 1.95O 4 (UASG) has higher discharge potential than that of LiMn 2O 4 (sol–gel). In addition, LiAl 0.05Mn 1.95O 4 (UASG) has higher discharge potential and capacity than that of LiAl 0.05Mn 1.95O 4 (sol–gel) at 1 C discharge rate, and LiAl 0.05Mn 1.95O 4 (UASG) has high capacity retention at C/3 and 1 C discharge rate among three samples after 50 cycles, which reveals that the sample obtained via UASG method, has the best electrochemical performance among three samples.

Photocatalytic degradation of bisphenol A as an endocrine disruptor in aqueous suspension using Ag-TiO<SUB align=right>2 catalysts

A novel photocatalyst, titanium dioxide (TiO2) deposited with silver (Ag), was prepared by an ultrasonic-assisted sol–gel method and studied for the photocatalytic degradation of endocrine disrupting chemicals such as bisphenol A (BPA) under UV illumination, in order to determine its photocatalytic properties. A series of Ag-TiO2 catalysts prepared with different Ag dosage were characterised by SEM, EDX, XRD, XPS, and UV–Visible absorption spectroscopy and their photocatalytic activity was evaluated in the degradation of BPA in aqueous suspension. The experiment demonstrated that the presence of Ag in TiO2 catalysts could enhance the photocatalytic oxidation of BPA in aqueous suspension. It was found that the degradation of BPA by these catalysts followed the first-order kinetic model. The enhanced reduction of oxygen through better electron-hole separation in Ag-TiO2 particles compared to pure TiO2 particles increased the rates of BPA degradation. In the reaction of BPA degradation, the presence of two methyl groups in the BPA structure were initially attacked with OH and/or OOH radicals which have strong oxidising power, and then followed by the cleavage of the two phenyl moieties. Finally, the photomineralisation to CO2 gas occurred via oxidative processes involving carboxylic acids and aldehydes.