Magnetic properties,anticancer and antibacterial effectiveness of sonochemically produced Ce3+/Dy3+ co-activated Mn-Zn nanospinel ferrites

Some new types of Ce³⁺ and Dy³⁺ co-doped manganese-zinc nanospinel ferrites (CDMZNSFs) of the form (Mn_0.5Zn_0.5)[Fe_2-2xCe_xDy_x]O₄ (with 0.0 ≤ x ≤ 0.1) were sonochemically produced and characterized. The structure, morphology, optical and magnetic properties of these NSFs were determined as a function of co-dopant (Ce³⁺ and Dy³⁺) contents. The direct optical band gap energies of the studied NSFs were ranged from 1.54 to 1.85 eV. The measurements of magnetization versus magnetic field of the prepared NSFs disclosed a superparamagnetic (SPM) behavior at room temperature (RT). The measurements of temperature-dependent magnetizations revealed a transition from superparamagnetic (SPM) state above blocking temperature T_B to a ferromagnetic (FM) state below T_B. The saturation magnetization and T_B decreased with the increase in co-dopant contents. In addition, the bactericidal (on the gram-positive and gram-negative bacterial strains) and anti-cancerous effectiveness of these NSFs were assessed. The cancer cells' growth inhibitory action of these NSFs was tested against both normal (HEK-293) and cancerous (HCT-116) human cells. After 48 h of treatment of the cancerous cells with the NSFs, their population was significantly dropped as shown by the MTT assay, indicating the selective inhibition of the cancer cells growth by the proposed NSFs. Conversely, the non-cancerous cells (HEK-293) population remained unaffected. The IC₅₀ values of the NSFs-treated cancerous cells (HCT-116) were in the range of 0.74–2.35 µg/mL. The results of the MIC and MBC assays revealed the reasonable antibacterial efficacy (growth inhibitory activity) of these NSFs when tested against the E. coli and S. aureus bacterial strains. It is established that the proposed Ce³⁺/Dy³⁺ co-activated CDMZNSFs may be beneficial for the anti-cancerous and bactericidal applications.     

The effect of high-intensity ultrasound on the ring-opening polymerisation of cyclic lactones

High-intensity ultrasound has been applied to the ring-opening polymerisation of δ-valerolactone and ε-caprolactone catalysed by dibutyl tin dilaurate. Sonication was found to accelerate the polymerisation. In the case of δ-valerolactone, sonication also promoted a depolymerisation reaction so that the molecular weight fell during later stages of the reaction. Co-polymers of the two monomers were synthesised and the use of ultrasound led to preferential incorporation of ε-caprolactone into the material, probably due to degradation of the valerolactone sequences.     

The effect of heterogeneous solvent systems on sonochemical reactions: accelerated degradation of alkyl thiols in emulsion

Sonochemical reactions of alkyl and aryl thiols in water–organic mixed solvent systems were kinetically investigated. The reaction in the liquid–liquid interface apparently depends on the polarities, surface activities, vapor pressures and hydrophobicities of organic solvents and thiols. Interestingly, the rate jump in sonochemical disappearance of alkyl thiols was observed under emulsified conditions.     

Ultrasound promoted synthesis of Nile Blue derivatives

Ultrasound irradiation was used for the first time towards the synthesis of new Nile Blue related benzo[a]phenoxazinium chlorides possessing isopentylamino, (2-cyclohexylethyl)amino and phenethylamino groups at 5-position of the heterocyclic system. The efficacy of sonochemistry was investigated with some of our earlier reported synthesis of benzo[a]phenoxazinium chlorides. This newer protocol proved competent in terms of reaction times and enhanced yields. Photophysical studies carried out in ethanol, water and simulated physiological conditions, revealed that emission maxima occurred in the range 644–656 nm, with high fluorescent quantum yields. Other attractive feature exhibited by these materials includes good thermal stability. These properties might be useful in the development of fluorescent probes for biotechnology.     

Thermal and sonochemical synthesis of porous (Ce,Zr)O2 mixed oxides from metal β-diketonate precursors and their catalytic activity in wet air oxidation process of formic acid

Porous (Ce_0.5Zr_0.5)O₂ solid solutions were prepared by thermolysis (T = 285 °C) or sonolysis (20 kHz, I = 32 W cm⁻², P_ac = 0.46 W mL⁻¹, T = 200 °C) of Ce(III) and Zr(IV) acetylacetonates in oleylamine or hexadecylamine under argon followed by heat treatment of the precipitates obtained in air at 450 °C. Transmission Electron Microscopy images of the samples show nanoparticles of ca. 4–6 nm for the two synthetic approaches. The powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray and μ-Raman spectroscopy of solids obtained after heat treatment indicate the formation of (Ce_0.5Zr_0.5)O₂ solid solutions with a metastable tetragonal crystal structure for the two synthetic routes. The specific surface area of the samples varies between 78 and 149 m² g⁻¹ depending on synthesis conditions. The use of Barrett–Joyner–Halenda and t-plot methods reveal the formation of mixed oxides with a hybrid morphology that combines mesoporosity and microporosity regardless of the method of preparation. Platinum nanoparticles were deposited on the surface of the mixed oxides by sonochemical reduction of Pt(IV). It was found that the materials prepared by sonochemistry exhibit better resistance to dissolution during the deposition process of platinum. X-ray photoelectron spectroscopy analysis shows the presence of Pt(0) and Pt(II) on the surface of mixed oxides. Porous (Ce_0.5Zr_0.5)O₂ mixed oxides loaded with 1.5 %wt. platinum exhibit high activity in catalytic wet air oxidation of formic acid at 40 °C.     

Ultrasound assisted ambient temperature synthesis of ternary oxide AgMO2 (M=Fe, Ga)

The application of ultrasound for the synthesis of ternary oxide AgMO₂ (M=Fe, Ga) was investigated. Crystalline α-AgFeO₂ was obtained from the alkaline solutions of silver and iron hydroxides by sonication for 40 minutes. α-AgFeO₂ was found to absorb optical radiation in the 300-600 nm range as shown by diffuse reflectance spectroscopy. The Raman spectrum of α-AgFeO₂ exhibited two bands at 345 and 638 cm⁻¹. When β-NaFeO₂ was sonicated with aqueous silver nitrate solution for 60 minutes, β-AgFeO₂ possessing orthorhombic structure was obtained as the ion-exchanged product. The Raman spectrum of β-AgFeO₂ showed four strong bands at 295, 432, 630 and 690 cm⁻¹. Sonication of β-NaGaO₂ with aqueous silver nitrate solution for 60 minutes resulted in olive green colored, α-AgGaO₂. The diffuse reflectance spectrum and the EDX analysis confirmed that the ion-exchange through sonication was complete. The Raman spectrum of α-AgGaO₂ had weak bands at 471 and 650 cm⁻¹.     

Sonochemistry and sonoluminescence in ionic liquids, molten salts, and concentrated electrolyte solutions

Ionic liquids have favorable intrinsic properties that make them of interest as solvents for various chemical reactions. The same properties that make the liquids effective solvents also make them interesting liquids for studies involving sonochemistry, acoustic cavitation, and sonoluminescence. Recent interest in using ultrasound to accelerate chemical reactions conducted in ionic liquids necessitates an understanding of the effects of acoustic cavitation on these solvents. Here, we review our previous results on the effects of cavitation on some room-temperature ionic liquids, including the sonoluminescence spectra of molten salt eutectics and concentrated aqueous electrolyte solutions. In all cases, regardless of the essentially nonexistent vapor pressure of the solution atomic and small molecule emitters are observed in the spectra which arise from sonolysis of the ionic liquids.     

Enhancement and quenching of high-intensity focused ultrasound cavitation activity via short frequency sweep gaps

This letter reports on the use of frequency sweeps to probe acoustic cavitation activity generated by high-intensity focused ultrasound (HIFU). Unprecedented enhancement and quenching of HIFU cavitation activity were observed when short frequency sweep gaps were applied in negative and positive directions, respectively. It was revealed that irrespective of the frequency gap, it is the direction and frequency sweep rate that govern the cavitation activity. These effects are related to the response of bubbles generated by the starting frequency to the direction of the frequency sweep, and the influence of the sweep rate on growth and coalescence of bubbles, which in turn affects the active bubble population. These findings are relevant for the use of HIFU in chemical and therapeutic applications, where greater control of cavitation bubble population is critical.     

Preparation of metal–ceramic composites by sonochemical synthesis of metallic nano-particles and in-situ decoration on ceramic powders

Copper and nickel nanoparticles were synthesized using reducing agents in the presence of direct high energy ultra-sonication. The metallic nanoparticles were decorated on various ceramic substrates (e.g. α-Al₂O₃, and TiO₂) leading to metal reinforced ceramics with up to 45% metallic content. Different parameters, such as the amount of precursor material or the substrate, as well as the intensity of ultrasound were examined, in order to evaluate the percentage of final metallic decoration on the composite materials. All products were characterized by means of Inductively Coupled Plasma Spectroscopy in order to investigate the loading with metallic particles. X-ray Diffraction and Scanning Electron Microscopy were also used for further sample characterization. Selected samples were examined using Transmission Electron Microscopy, while finally, some of the powders synthesized, were densified by means of Spark Plasma Sintering, followed by a SEM/EDX examination and an estimation of their porosity.     

Imparting superhydrophobic and biocidal functionalities to a polymeric substrate by the sonochemical method

Multifunctional substrates with superhydrophobic and biocidal properties are gaining interest for a wide range of applications; however, the production of such surfaces remains challenging. Here, the sonochemical method is utilized to impart superhydrophobicity and antimicrobial properties to a polyethylene (PE) sheet. This is achieved by sonochemically depositing nanoparticles (NPs) of a hydrophobic fluoro-polymer (FP) on the PE sheets. The polymer is a flexible, transparent fluoroplastic composed of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride in the form of a powder. The NPs of polymers are generated and deposited on the surface of the PE using ultrasound irradiation. Optimizing the process results in a homogeneous distribution of 110–200 nm of NPs on the PE surface. The coated surface displays a water-contact angle of 160°, indicating excellent superhydrophobicity. This superhydrophobic surface shows high stability under outdoor conditions for two months, which is essential for various applications. In addition, metal-oxide nanoparticles (CuO or ZnO NPs) were integrated into the polymer coating to achieve antibacterial properties and increase the surface roughness. The metal oxides were also deposited sonochemically. The antibacterial activity of the FP@ZnO and FP@CuO PE composites was tested against the bacterium Staphylococcus aureus, and the results show that the FP@CuO PE can effectively eradicate the bacteria. This study highlights the feasibility of using the sonochemical method to deposit two separate functions, opening up new possibilities for producing “smart” novel surfaces.