Fabrication of nanosized Pt on rutile TiO2 using a standing wave sonochemical reactor (SWSR) – observation of an enhanced catalytic oxidation of CO

Fine particles of rutile TiO₂ supporting nanosized particles of Pt were prepared by a simultaneous in situ sonochemical reduction and deposition method using a standing wave sonochemical reactor (SWSR). The mean diameter of sonochemically obtained Pt particles are of 2 nm. Following this sonochemical technique, rutile TiO₂ was also deposited with different weight percentages of Pt. Catalytic function of the prepared composite catalysts were tested by the oxidation of CO to CO₂. From the catalytic activity results, it has been found out that the catalysts prepared by the sonochemical method exhibited higher catalytic activity for CO oxidation, probably attributed to the higher Pt particle distribution achieved under sonication. Transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), and diffuse reflectance spectroscopy (DRS) were employed to characterize the resulting material.     

Ultrasonic assisted synthesis of Bikitaite zeolite: A potential material for hydrogen storage application

Li containing Bikitaite zeolite has been synthesized by an ultrasound-assisted method and used as a potential material for hydrogen storage application. The Sonication energy was varied from 150 W to 250 W and irradiation time from 3 h to 6 h. The Bikitaite nanoparticles were characterized by X-ray diffraction (XRD), infrared (IR) spectral analysis, and field-emission scanning electron microscopy (FESEM) thermo-gravimetrical analysis and differential thermal analysis (TGA, DTA). XRD and IR results showed that phase pure, nano crystalline Bikitaite zeolites were started forming after 3 h irradiation and 72 h of aging with a sonication energy of 150 W and nano crystalline Bikitaite zeolite with prominent peaks were obtained after 6 h irradiation of 250 W sonic energy. The Brunauer–Emmett–Teller (BET) surface area of the powder by N₂ adsorption–desorption measurements was found to be 209 m²/g. The TEM micrograph and elemental analysis showed that desired atomic ratio of the zeolite was obtained after 6 h irradiation. For comparison, sonochemical method, followed by the hydrothermal method, with same initial sol composition was studied. The effect of ultrasonic energy and irradiation time showed that with increasing sonication energy, and sonication time phase formation was almost completed. The FESEM images revealed that 50 nm zeolite crystals were formed at room temperature. However, agglomerated particles having woollen ball like structure was obtained by sonochemical method followed by hydrothermal treatment at 100 °C for 24 h. The hydrogen adsorption capacity of Bikitaite zeolite with different Li content, has been investigated. Experimental results indicated that the hydrogen adsorption capacities were dominantly related to their surface areas as well as total pore volume of the zeolite. The hydrogen adsorption capacity of 143.2 c.c/g was obtained at 77 K and ambient pressure of (0.11 MPa) for the Bikitaite zeolite with 100% Li, which was higher than the reported values for other zeolites. To the best of our knowledge, there is no report on the synthesis of a Bikitaite zeolite by sonochemical method for H₂ storage.     

Dependence of sonochemical parameters on the platinization of rutile titania – An observation of a pronounced increase in photocatalytic efficiencies

Using a standing wave sonochemical reactor (SWSR), the influences of parameters of ultrasonic power input, sonication time, sonication temperature and the amount of propanol (which generates the reducing radicals) were systemically investigated to ascertain and optimize the best conditions for the sonochemical reduction of Pt from its precursor hexachloroplatinic acid and then its deposition on rutile TiO₂ (platinization of rutile titania) catalysts. Catalytic activity of the prepared platinized catalysts was tested in the reaction of methyl orange degradation. The results of photocatalytic activity study in the degradation of methyl orange further demonstrate that sonochemically as-prepared Pt/TiO₂ catalysts show a pronounced increase (～2 times) in photodegradation, even with a deposition of small amounts of platinum (1.4 wt.%), as compared to the unsupported or naked rutile titania. Although there are various parameters that influence the sonochemical platinization of rutile titania, the present optimization results clearly indicate that the best photocatalytic degradation of methyl orange can be obtained when the experimental conditions of the preparation were with an input power of 50 W, an initial hexachloroplatinic acid volume of 70 ml (which results into 1.4 wt.% Pt on TiO₂), sonication time of 90 min, 0.18 g of propanol and a temperature of 10 °C were adopted. The method of ultrasound application to prepare metal supported semiconductors has many advantages such as convenience, safety and high efficiency. Furthermore, it is hopeful that this optimization study can also be extended to the generation of similar metal supported semiconductors.     

Morphologically controlled preparation of CuO nanostructures under ultrasound irradiation and their evaluation as pseudocapacitor materials

Various morphologies of copper oxide (CuO) nanostructures have been synthesized by controlling the reaction parameters in a sonochemical assisted method without using any templates or surfactants. The effect of reaction parameters including molar ratio of the reactants, reaction temperature, ultrasound exposure time, and annealing temperature on the composition and morphology of the product(s) has been investigated. The prepared samples have been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDAX), and thermogravimetric analysis (TGA). It has been found that Cu₂(OH)₃NO₃ nanoplatelets are achieved in mild conditions which can be then converted to various morphologies of CuO nanostructures by either using high concentrations of OH⁻ (formation of nanorods), prolonging sonication irradiation (nanoparticles), or thermal treatment (nanospheres). Application of the prepared CuO nanostructures was evaluated as supercapacitive material in 1 M Na₂SO₄ solution using cyclic voltammetry (CV) in different potential scan rates ranging from 5 to 100 mV s⁻¹. The specific capacitance has been calculated using CV curves. It has been found that the pseudocapacitor performance of CuO can be tuned via employing morphologically controlled samples. Accordingly, the prolonged sonicated sample (nanoparticles) showed the high specific capacitance of 158 F.g⁻¹.     

Ultrasound-assisted synthesis of ZnO photocatalysts for gas phase pollutant remediation: Role of the synthetic parameters and of promotion with WO3

The synthesis of ZnO photocatalysts by ultrasound-assisted technique was here investigated. Several experimental parameters including the zinc precursor (acetate, chloride, nitrate), sonication conditions (amplitude, pulse) and post-synthetic thermal treatment (up to 500 °C) were studied. Crystalline ZnO samples were obtained without thermal treatments due to the adopted reactant ratios and synthesis temperature. Sonication plays a major role on the morphological oxide features in terms of particle size and surface area, the latter showing a 20-fold increase with respect to conventional synthesis. Interestingly, 1 and 3 s sonication pulses led to morphological properties similar to continuous sonication. A thermal treatment at moderate temperatures (400–450 °C) promoted the loss of surface hydroxylation and the formation of lattice defects, while higher temperatures were detrimental for the sample morphology. The prepared ZnO was decorated with WO₃ particles comparing an ultrasound-assisted technique using 1 s pulses with a conventional approach, giving rise to composites with promoted visible light absorption. Samples were tested towards the photocatalytic degradation of nitrogen oxides (500–1000 ppb) in humidified air under both UV and visible light. By carefully controlling the synthetic procedure, better performance were observed with respect to the commercial benchmark. Samples from ultrasound-assisted syntheses, also in the case of pulsed sonication, showed consistently better results than conventional references, in particular for ZnO-WO₃ composites. The composite by ultrasound-assisted synthesis showed > 95% degradation in 180 min and doubled NO_x degradation under visible light with respect to the conventional composite.     

Sonochemical synthesis and anchoring of zinc oxide on hemin-mediated multiwalled carbon nanotubes-cellulose nanocomposite for ultra-sensitive biosensing of H2O2

In this work, the metal oxide and biopolymer nanocomposites on multiwalled carbon nanotubes (MWCNT) were prepared using a simple sonochemical method. The hexagonal nanorods of zinc oxide (ZnO NR) were synthesized by probe sonication (frequency = 20 kHz, amplitude = 50) method and were integrated on ultrasonically functionalized MWCNT-cellulose nanocrystals (MWCNT-CNC) for the first time. The stable hemin bio-composites also were prepared using the bath sonication (37 kHz of frequency, 150 W of power) method, and was used for the selective and ultrasensitive electrochemical detection of H₂O₂. The UV–Vis spectroscopy studies confirmed the presence of native hemin on MWCNT-CNC/ZnO NR nanocomposite. Cyclic voltammetry studies revealed that an enhanced redox electrochemical behaviour of hemin was observed on hemin immobilised MWCNT-CNC/ZnO NR nanocomposite than that of other hemin modified electrodes. Also, the MWCNT-CNC/ZnO NR/hemin modified SPCE showed 2.3 folds higher electrocatalytic activity with a lower reduction potential (−0.2 V) towards H₂O₂ than that of other investigated hemin modified electrodes including hemin/MWCNT and hemin/CNC-ZnO. The fabricated biosensor displayed a stable amperometric response (-0.2 V vs Ag/AgCl) in the linear concentration of H₂O₂ ranging up to 4183.3 µM with a lower detection limit of 4.0 nM.     

Sonochemical synthesis and structural characterization of a new nanostructured Co(II) supramolecular coordination polymer with Lewis base sites as a new catalyst for Knoevenagel condensation

A new Co(II) mixed-ligand coordination supramolecular polymer with composition [Co₂(ppda)(4-bpdh)₂(NO₃)₂]_n (1) (where, ppda = p-phenylenediacrylic acid, 4-bpdh = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene) was synthesized using solvothermal, mechanochemical and sonochemical methods. Compound 1 and the new nanostructure have been characterized by single-crystal X-ray, infrared spectroscopy (IR), powder X-ray diffraction (PXRD) analysis and scanning electron microscopy (SEM). The thermal stability of compound 1 was also studied by thermal gravimetric analysis (TGA). The surface area of these compounds was determined by BET. The single-crystal X-ray data shows a new interesting two-dimensional coordination polymer (CP). In addition, the effect of various sonication concentrations of initial reagents, power of ultrasound irradiation and also the time on the size and morphology of nano-structured coordination polymer 1 were evaluated. Moreover, it has been demonstrated that the nanostructure of the CP1 can be used as a catalyst in Knoevenagel condensation reaction.     

Synthesis of a new Hg(II) coordination polymer: Ultrasonic-assisted synthesis and mechanical preparation of nanostructure

A new mercury(II) coordination polymer, [Hg(4-bpmo)I₂]_n (1), (4-bpmo = N,N′-bis(pyridin-4-ylmethyl)oxalamide), was synthesized, by branched tube method, and structurally characterized by single-crystal X-ray diffraction. Compound 1 is a polymer with a distorted tetrahedral HgN₂I₂ coordination environment. The thermal stability of 1 was studied by thermal gravimetric (TG) and differential thermal (DTA) analyses. Also 1 was prepared by a sonochemical process at ambient temperature. Reaction time and concentration of initial reagents effects on the size and morphology were studied. Nanoparticles of 1, was synthesized easily by a mechanical method (neat grinding). The resulting structures were characterized by scanning electron microscopy (SEM), IR spectroscopy and X-ray powder diffraction (XRD).     

Sonochemical syntheses of binuclear lead(II)-azido supramolecule with ligand 3,4,7,8-tetramethyl-1,10-phenanthroline as precursor for preparation of lead(II) oxide nanoparticles

The new neutral binuclear lead(II) azido coordination compound, [Pb₂(tmph)₂(μ-N₃)₂(CH₃COO)₂] (1) [tmph = 3,4,7,8-tetramethyl-1,10-phenanthroline], has been synthesized by a sonochemical method. Single crystal X-ray structure shows that the overall structure of 1 is binuclear unit. Complex 1 has a bridging azido pathway, end-to-end bridging azides between a pair of lead(II) centers. This is further extended into a one-dimensional (1D) and three-dimensional (3D) supramolecular structure by Pb⋯C and π–π weak directional intermolecular interactions. The coordination number of lead(II) ions is seven, PbN₄O₃, with two N-donor atoms from tmph ligands and three O-donors from acetate anions and two N-donors from two azide anions. It has a “stereo-chemically active” electron lone pair, and the coordination sphere is hemidirected. The PbO nanoparticles were obtained by thermolysis of 1 at 180 °C with oleic acid as a surfactant. The morphology and size of the prepared PbO samples were further observed using scanning electron microscopy (SEM).     

Ultrasound assisted chitosan coated iron oxide nanoparticles: Influence of ultrasonic irradiation on the crystallinity,stability, toxicity and magnetization of the functionalized nanoparticles

Due to unique reaction conditions of the acoustic cavitation process, ultrasound-assisted synthesis of nanoparticles has attracted increased research attention. In this study, we demonstrate the effect of ultrasonic irradiation on the crystallinity, stability, biocompatibility, and magnetic properties of chitosan-coated superparamagnetic iron oxide nanoparticles (CS-SPIONs). CS solution and colloidal suspension of SPIONs were mixed and sonicated using an ultrasonic probe of 1.3 cm tip size horn, frequency (20 kHz), and power (750 W). Different samples were sonicated for 1.5, 5, and 10 min with corresponding acoustic powers of 67, 40 and 36 W, and the samples were denoted S_1.5, S_5, and S₁₀, respectively. The samples were characterized using X-ray diffractometer (XRD), Energy dispersive X-ray (EDX), Transmission electronic microscope (TEM), Fourier transform infrared spectroscopy (FTIR), Zeta sizer, and vibrating sample magnetometer (VSM). Cell cytotoxicity and cell uptake were investigated with human embryonic kidney 293 (HEK-293) cells through MTT assay and Prussian blue staining, respectively. The sharp peaks of the XRD pattern were disappearing with an increase in the sonication period but a decrease in acoustic power. EDX analysis also demonstrates that atomic and weight percentages of the various elements in the samples were decreasing with an increase in the sonication period. However, the Zeta potential (ζ) values increase with an increase in the sonication period.The saturation magnetization (M_s) of the S_1.5 before and after the coating is 62.95 and 86.93 emu/g, respectively. Cell cytotoxicity and uptake of the S_1.5 show that above 70% of cells were viable at the highest concentration and the longest incubation duration. Importantly, the CS-SPIONs synthesized by the sonochemical method are non-toxic and biocompatible.     

Impact of sonochemical synthesis condition on the structural and physical properties of MnFe2O4 spinel ferrite nanoparticles

Herein, we report sonochemical synthesis of MnFe₂O₄ spinel ferrite nanoparticles using UZ SONOPULS HD 2070 Ultrasonic homogenizer (frequency: 20 kHz and power: 70 W). The sonication time and percentage amplitude of ultrasonic power input cause appreciable changes in the structural, cation distribution and physical properties of MnFe₂O₄ nanoparticles. The average crystallite size of synthesized MnFe₂O₄ nanoparticles was increased with increase of sonication time and percentage amplitude of ultrasonic power input. The occupational formula by X-ray photoelectron spectroscopy for prepared spinel ferrite nanoparticles was (Mn_0.29Fe_0.42)[Mn_0.71Fe_1.58]O₄ and (Mn_0.28Fe_0.54) [Mn_0.72Fe_1.46]O₄ at sonication time 20 min and 80 min, respectively. The value of the saturation magnetization was increased from 1.9 emu/g to 52.5 emu/g with increase of sonication time 20 min to 80 min at constant 50% amplitude of ultrasonic power input, whereas, it was increased from 30.2 emu/g to 59.4 emu/g with increase of the percentage amplitude of ultrasonic power input at constant sonication time 60 min. The highest value of dielectric constant (ε′) was 499 at 1 kHz for nanoparticles at sonication time 20 min, whereas, ac conductivity was 368 × 10⁻⁹ S/cm at 1 kHz for spinel ferrite nanoparticles at sonication time 20 min. The demonstrated controllable physical characteristics over sonication time and percentage amplitude of ultrasonic power input are a key step to design spinel ferrite material of desired properties for specific application. The investigation of microwave operating frequency suggest that these prepared spinel ferrite nanoparticles are potential candidate for fabrication of devices at high frequency applications.     

Sonochemical synthesis of two new nano lead(II) coordination polymers: Evaluation of structural transformation via mechanochemical approach

Two new lead(II) mixed-ligand coordination polymers, [Pb(PNO)(SCN)]_n (1) and [Pb(PNO)(N₃)]_n (2), (HPNO = picolinic acid N-oxide) were synthesized by a sonochemical method and characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and elemental analysis. Compounds 1 and 2 were structurally characterized by single crystal X-ray diffraction. The thermal behavior of 1 and 2 were studied by thermal gravimetric analysis. Structural transformations of compounds 1 and 2 were evaluated through anion-replacement processes by mechanochemical method. Moreover, the effect of sonication conditions including time, concentrations of initial reagents and power of irradiation were evaluated on size and morphology of compounds 1 and 2.     

Sonochemical dissolution of nanoscale ThO2 and partial conversion into a thorium peroxo sulfate

The influence of the sample morphology and experimental conditions towards the sonochemical dissolution of nanoscale ThO₂ samples in sulfuric acid media is described. Significant sonochemical dissolution rates and yields are observed at 20 kHz under Ar/O₂ atmosphere in dilute 0.5 M H₂SO₄ at room temperature, contrasting with the generally-reported high refractory behavior for ThO₂. The dissolution of ThO₂ combines the physical effects driven by acoustic cavitation phenomenon, the complexing affinity of Th(IV) in sulfuric medium and the sonochemical generation of H₂O₂. These sonochemical conditions further allow the observation of the partial conversion of ThO₂ into a scarce Th(IV) peroxo sulfate with 1D morphology resulting from one or both following processes: dissolution/reprecipitation or formation of an intermediate Th(IV) surface complex.     

Effect of switching ultrasonic amplitude in preparing a hybrid of fullerene (C60) and gallium oxide (Ga2O3)

In this study, we proposed ‘switching ultrasonic amplitude’ as a new strategy of applying ultrasonic energy to prepare a hybrid of buckminsterfullerene (C₆₀) and gallium oxide (Ga₂O₃), C₆₀/Ga₂O₃. In the proposed method, we switched the ultrasonic amplitude from 25% to 50% (by 5% amplitude per 10 min, within 1 h of ultrasonic irradiation) for the sonochemical treatment of a heterogeneous aqueous mixture of C₆₀ and Ga₂O₃ by a probe-type ultrasonic horn operating at 20 kHz. We found that compared to the conventional techniques associated with high amplitude oriented ultrasonic preparation of functional materials, switching ultrasonic amplitude can better perform in preparing C₆₀/Ga₂O₃ with respect to avoiding titanium (Ti) as an impurity generating from the tip erosion of a probe-type ultrasonic horn during high amplitude ultrasonic irradiation in an aqueous medium. Based on SEM/EDX analysis, the quantity of Ti (wt.%) in C₆₀/Ga₂O₃ prepared by the proposed technique of switching ultrasonic amplitude was found to be 1.7% less than that prepared at 50% amplitude of ultrasonic irradiation. The particles of C₆₀/Ga₂O₃ prepared by different modes of amplitude formed large (2–12 μm) aggregates in their solid phase.Whereas, in the aqueous medium, they were found to disperse in their nano sizes. The minimum particle size of the as-synthesized C₆₀/Ga₂O₃ in an aqueous medium prepared by the proposed method of switching ultrasonic amplitude reached to approximately 467 nm. Comparatively, the minimum particle sizes were approximately 658 nm and 144 nm, using 25% and 50% amplitude, respectively. Additionally, Ga₂O₃ went under hydration during ultrasonic irradiation. Moreover, due to the electron cloud interference from C₆₀ in the hybrid structure of C₆₀/Ga₂O₃, the vibrational modes of Ga₂O₃ were Raman inactive in C₆₀/Ga₂O₃.     

Facile sonochemical method for preparation of Cs2HgI4 nanostructures as a promising visible-light photocatalyst

Attempts are continuing to discover novel and efficient solutions to promote water grade and industrial sewage treatment. For the first time, we present a novel Cs₂HgI₄ photocatalyst functional below visible radiation. Cs₂HgI₄ nano photocatalyst has been prepared via an accelerated sonochemical approach to examine its photocatalytic progression. Several construction circumstances, including variations of power and time of sonication and performance of different surfactant types, were conducted to produce fine particles with uniform morphology. FESEM images attested that the presence of surfactant had an adverse and destructive effect on the morphology of products. The bandgap for Cs₂HgI₄ nanostructures was determined to be approximately 2.3 eV, making these nanostructures desirable for photocatalytic applications. The photocatalytic data confirmed that Cs₂HgI₄ could destroy acidic coloring agents greater than basic ones. The highest photodegradation was observed for methyl orange with 76.8%.     

Superior selectivity of high-frequency ultrasound toward chorine containing-pharmaceuticals elimination in urine: A comparative study with other oxidation processes through the elucidation of the degradation pathways

This work considered the sonochemical degradation (using a bath-type reactor, at 375 kHz and 106.3 W L^-1, 250 mL of sample) of three representative halogenated pharmaceuticals (cloxacillin, diclofenac, and losartan) in urine matrices. The action route of the process was initially established. Then, the selectivity of the sonochemical system, to degrade the target pharmaceuticals in simulated fresh urine was compared with electrochemical oxidation (using a BDD anode, at 1.88 mA cm⁻²), and UVC/H₂O₂ (at 60 W of light and 500 mol L^-1 of H₂O₂). Also, the treatment of cloxacillin in an actual urine sample by ultrasound and UVC/H₂O₂ was evaluated. More than 90% of the target compounds concentration, in the simulated matrix, was removed after 60 min of sonication. However, the sono-treatment of cloxacillin in the real sample was less efficient than in the synthetic urine. The ultrasonic process achieved 43% of degradation after 90 min of treatment in the actual matrix. In the sonochemical system, hydroxyl radicals in the interfacial zone were the main degrading agents. Meanwhile, in the electrochemical process, electrogenerated HOCl was responsible for the elimination of pharmaceuticals. In turn, in UVC/H₂O₂ both direct photolysis and hydroxyl radicals degraded the target pollutants. Interestingly, the degradation by ultrasound of the pharmaceuticals in synthetic fresh urine was very close to the observed in distilled water. Indeed, the sonodegradation had a higher selectivity than the other two processes. Despite the sono-treatment of cloxacillin was affected by the actual matrix components, this contrasts with the UVC/H₂O₂, which was completely inhibited in the real urine. The sonochemical process led to 100% of antimicrobial activity (AA) elimination after 75 min sonication in the synthetic urine, and ∼ 20% of AA was diminished after 90 min of treatment in the real matrix. The AA decreasing was linked to the transformations of the penicillin nucleus on cloxacillin, the region most prone to electrophilic attacks by radicals according to a density theory functional analysis. Finally, predictions of biological activity confirmed that the sono-treatment decreased the activity associated with cloxacillin, diclofenac, and losartan, highlighting the positive environmental impact of degradation of chlorinated pharmaceuticals in urine.     

Simple sonochemical synthesis,characterization of TmVO4 nanostructure in the presence of Schiff-base ligands and investigation of its potential in the removal of toxic dyes

Thulium vanadate (TmVO4) nanorods were successfully prepared by a simple sonochemical approach using Schiff-base ligands. Additionally, TmVO₄ nanorods were employed as a photocatalyst. The most optimal crystal structure and morphology of TmVO4 have been determined and optimized by varying Schiff-base ligands, the molar ratio of H2Salen, the sonication time and power, and the calcination time. A Eriochrome Black T (EBT) analysis revealed that the specific surface area was 24.91 m2/g. A bandgap of 2.3 eV was determined by diffuse reflectance spectroscopy (DRS) spectroscopy, which makes this compound suitable for visible photocatalytic applications. In order to assess the photocatalytic performance under visible light, two anionic dyes (EBT) and cationic dyes (Methyl Violet (MV)) were used as models. A variety of factors have been studied in order to improve the efficiency of the photocatalytic reaction, including dye type, pH, dye concentration, and catalyst loading. Under visible light, the highest efficiency was achieved (97.7%) when 45 mg TmVO4 nanocatalysts were present in 10 ppm Eriochorome Black T at pH = 10.     

Simplified sonochemical preparation of titania embedded with selected metals for purification of benzene and toluene

Titania (TiO₂) photocatalysts, each embedded with one of six metals (Ag, Ce, Co, Fe, Mg, and Mn), were prepared using a simplified ultrasonic process. The characteristics of the prepared metal-embedded TiO₂ (metal–TiO₂) were determined using transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, photoluminescence emission spectroscopy, UV–visible spectroscopy, and nitrogen adsorption–desorption. Except for Co–TiO₂, the metal–TiO₂ photocatalysts showed improved performance for the decomposition of gaseous benzene and toluene, which are two of the most problematic indoor air pollutants that can cause a variety of adverse health symptoms, under daylight lamp irradiation. Photocatalytic activity was greatest for the Mg–TiO₂ sample, followed by, in order, the Ag–TiO₂, Ce–TiO₂, Fe–TiO₂, Mn–TiO₂, unmodified TiO₂, and Co–TiO₂ samples. Although Mg–TiO₂ showed the least redshift in its light absorption and the highest electron–hole recombination rate among the metal–TiO₂ photocatalysts, it yielded the highest photocatalytic activity, likely because of its increased adsorption capacity and anatase composition. The degradation of benzene and toluene over Mg–TiO₂ improved as ultrasound treatment amplitude increased from 20 to 37 μm, then decreased gradually as amplitude was further increased to 49 μm. Degradation efficiency also improved as ultrasound operation time increased from 30 to 60 min, then decreased gradually as amplitude was further increased to 90 min. Overall, this process could be utilized to prepare metal–TiO₂ photocatalysts with improved performance for the decomposition of gas phase pollutants under daylight lamp irradiation.     

Sonochemical synthesis of LiNi0.5Mn1.5O4 and its electrochemical performance as a cathode material for 5 V Li-ion batteries

LiNi_0.5Mn_1.5O₄ was synthesized as a cathode material for Li-ion batteries by a sonochemical reaction followed by annealing, and was characterized by XRD, SEM, HRTEM and Raman spectroscopy in conjunction with electrochemical measurements. Two samples were prepared by a sonochemical process, one without using glucose (sample-S1) and another with glucose (sample-S2). An initial discharge specific capacity of 130 mA h g⁻¹ is obtained for LiNi_0.5Mn_1.5O₄ at a relatively slow rate of C/10 in galvanostatic charge–discharge cycling. The capacity retention upon 50 cycles at this rate was around 95.4% and 98.9% for sample-S1 and sample-S2, respectively, at 30 °C.     

Facile synthesis of mesoporous ZSM-5 aided by sonication and its application for VOCs capture

Application of ultrasound power to the mother liquor is popular pretreatment for zeolite synthesis which offers a simple way of accelerating crystallization process and finetuning the properties of nanocrystalline zeolites. In this work, sonication-aided synthesis of mesoporous ZSM-5 at low temperature and ambient pressure was systematically studied, in an attempt to reach efficient and benign synthesis of zeolites with hierarchical pore structure, which has wide applications as catalysts and sorbents. The effects of sonication duration, power density, sonication temperature and seeding on the crystallization of ZSM-5 were investigated. The obtained samples were characterized by XRD, SEM, BET and VOCs capture. High quality mesoporous ZSM-5 can be obtained by a facile 5 d synthesis at 363 K, much faster than conventional hydrothermal synthesis. The reduced synthesis time was mainly attributed to the enhanced crystallization kinetics caused by the fragmentation of seeds and nuclei, while sonication radiation had little impact on the nucleation process. Compared with control sample, mesoporous ZSM-5 prepared by sonochemical method had higher surface area and mesoporosity which demonstrated improved adsorption performance for the capture of isopropanol.