Sonochemical Deposition Research Articles

Solar-Heated Sustainable Biodiesel Production from Waste Cooking Oil Using a Sonochemically Deposited SrO Catalyst on Microporous Activated Carbon

A novel catalyst, SrO on microporous activated carbon (SrO/C), was synthesized by sonochemical deposition of SrO on carbon. The SrO/C demonstrated high catalytic performance in solar-heated transesterification reactions of canola oil, soybean oil, and waste cooking oil (WCO). The catalytic activity increased more than 5-fold (corresponding to 81% less catalyst compared to pristine SrO), using soybean oil as a feedstock. Similar enhancement was also observed with canola oil and WCO, where the catalytic activity improved more than 4-fold, corresponding to 76% less catalyst compared to pristine SrO. A yield of 98.5 wt % fatty acid methyl esters (FAME) was obtained from WCO in 60 min using a 1:6 oil:methanol molar ratio and 7.1 wt % SrO/C catalyst (24% SrO loading) at 46 °C (solar heating). The SrO/C catalyst was used for four consecutive transesterification reactions of WCO without any significant decrease in its catalytic activity (only 3% decrease in FAME yield and less than 5 ppm leaching). The results co...

Sonochemical co-deposition of antibacterial nanoparticles and dyes on textiles.

The sonochemical technique has already been proven as one of the best coating methods for stable functionalization of substrates over a wide range of applications. Here, we report for the first time on the simultaneous sonochemical dyeing and coating of textiles with antibacterial metal oxide (MO) nanoparticles. In this one-step process the antibacterial nanoparticles are synthesized in situ and deposited together with dye nanoparticles on the fabric surface. It was shown that the antibacterial behavior of the metal oxides was not influenced by the presence of the dyes. Higher K/S values were achieved by sonochemical deposition of the dyes in comparison to a dip-coating (exhaustion) process. The stability of the antibacterial properties and the dye fastness was studied for 72 h in saline solution aiming at medical applications.

Synthesis and photocatalytic performance of ZnO hollow spheres and porous nanosheets

ZnO hollow spheres and porous nanosheets were prepared by sonochemical deposition approach and hydrothermal method, respectively. Their photodegradation efficiencies for rhodamine B dye aqueous solutions under UV light irradiation were investigated in detail. Compared with ZnO porous nanosheets, the ZnO hollow spheres exhibited a relatively higher photocatalytic activity. Both absorption and photoluminescence results testified that the synergistic effects of absorption capacity and intrinsic defects finally determined the photocatalytic activity of ZnO hollow spheres.

Can r-graphene oxide replace the noble metals in SERS studies: the detection of acrylamide

Environmental context The need for detecting and sensing hazardous materials that can contaminate our food and water is growing each and every year. Regulation of these contaminants to safeguard human health depends on the ability to detect them at ultra-low concentrations in the environment. This work proposes a simple and efficient substrate preparation for detecting acrylamide, a toxic and carcinogenic material usually found in drinking water. Abstract Polyacrylamide acts as a very common water purifier worldwide. Unfortunately, it leaves hazardous and toxic residues of its monomer, acrylamide (C3H5NO), in water sources. The World Health Organization (WHO), the Food and Agriculture Organisation of the United Nations (FAO) and the European Union (EU) set the maximum contaminant level of acrylamide in drinking water to 0.1–0.5µgL–1. This environmental risk encouraged our efforts to develop surface-enhanced Raman spectroscopy (SERS) probes that are easy and simple to fabricate, and also have superb detection ability. We report down to 0.071µgL–1 acrylamide detection with good reproducibility, which is even lower than the WHO, FAO and EU requirements, and may be used as a powerful analytical alternative for detection. In this manuscript, we present a practical route to fabricate these detection substrates for detection of ultra-low concentrations of aqueous acrylamide solutions. The facile method is based on deposition of graphene oxide on Si wafers by ultrasonication, followed by surface reduction. These substrates require no adhesion layer or pretreatment with O2 plasma or aminopropyl triethoxysilane for the coating process. Sonochemical deposition of silver nanoparticles on the substrates is also carried out and the product compared with the proposed Si–reduced graphene oxide wafers.

Biofouling suppression of modified feed spacers: Localized and long-distance antibacterial activity

Abstract Biofouling hindering activity of two modified feed spacers was assessed. A ‘short-distance’ modification was attained by covalently binding polymeric quaternary ammonium groups (pQAs) to the spacer by atom transfer radical polymerization (ATRP). A ‘long-distance’ modification was based on embedding silver nanoparticles (nAg) in the polymeric spacer by sonochemical deposition. Cross-flow experiments in planar-membrane filtration cells using ultrafiltration membranes exposed to a mixed microbial enrichment were performed at conditions simulating spiral wound modules (0.15 m·s− 1 channel flow velocity). Physical properties of the modified spacers were evaluated using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. Microscopic analysis of the membranes adjacent to the modified spacers indicated the presence of a sporadic monolayer structure compared to a developed biofilm in the untreated spacers. SEM imaging and total organic carbon analysis of the attached layer revealed a low number of bacteria near the modified spacers and adjacent membranes. Both modified spacers displayed improved permeate fluxes compared to the control. nAg modified spacers displayed a somewhat steadier permeate flux profile within the length of the experiments probably due to the release of antibacterial active species. pQA modified spacers are assumed to have a more localized influence by direct contact on their surface.

Sonochemically synthesized Ag nanoparticles as a SERS active substrate and effect of surfactant

Abstract Surface enhanced Raman scattering (SERS) enables the detection of substances at low concentrations using silver or gold nanostructure. The SERS technique has many applications, such as environmental detection and biosensing. Sonochemistry is an excellent and cheap deposition technique for coating substrates in a form of nanostructure at ambient temperature. It can also be utilized to prepare large SERS substrates. Here, we used the advantages of sonochemistry to deposit solid SERS substrates immobilized on GaN nanostructure. Morphology was studied by scanning electron microscopy. The elemental composition and the spatial distribution were examined by energy dispersive X-ray spectroscopy. The crystal structure and atomic presence was confirmed by X-ray diffraction. SERS substrates were examined with the analytes crystal violet (10 −5 M) and rhodamine 6G (10 −6 M), they showed prominent characteristic peaks. We discovered that the SERS intensity of poly-vinyl-pyrrolidinone aided sonochemical deposition of Ag nanoparticles was increased. The reason for the effect is morphological changes of the Ag nanoparticles. Smaller nanoparticles were fabricated, which increase their SERS intensity.

Hydrothermal growth of hierarchical Ni3S2 and Co3S4 on a reduced graphene oxide hydrogel@Ni foam: a high-energy-density aqueous asymmetric supercapacitor.

Ni foam@reduced graphene oxide (rGO) hydrogel-Ni3S2 and Ni foam@rGO hydrogel-Co3S4 composites have been successfully synthesized with the aid of a two-step hydrothermal protocol, where the rGO hydrogel is sandwiched between the metal sulfide and Ni foam substrate. Sonochemical deposition of exfoliated rGO on Ni foam with subsequent hydrothermal treatment results in the formation of a rGO-hydrogel-coated Ni foam. Then second-time hydrothermal treatment of the dried Ni@rGO substrate with corresponding metal nitrate and sodium sulfide results in individual uniform growth of porous Ni3S2 nanorods and a Co3S4 self-assembled nanosheet on a Ni@rGO substrate. Both Ni@rGO-Ni3S2 and Ni@rGO-Co3S4 have been electrochemically characterized in a 6 M KOH electrolyte, exhibiting high specific capacitance values of 987.8 and 1369 F/g, respectively, at 1.5 A/g accompanied by the respective outstanding cycle stability of 97.9% and 96.6% at 12 A/g over 3000 charge-discharge cycles. An advanced aqueous asymmetric (AAS) supercapacitor has been fabricated by exploiting the as-prepared Ni@rGO-Co3S4 as a positive electrode and Ni@rGO-Ni3S2 as a negative electrode. The as-fabricated AAS has shown promising energy densities of 55.16 and 24.84 Wh/kg at high power densities of 975 and 13000 W/kg, respectively, along with an excellent cycle stability of 96.2% specific capacitance retention over 3000 charge-discharge cycles at 12 A/g. The enhanced specific capacitance, stupendous cycle stability, elevated energy density, and a power density as an AAS of these electrode materials indicate that it could be a potential candidate in the field of supercapacitors.

Experimental characterization and numerical simulation of the anti-biofuling activity of nanosilver-modified feed spacers in membrane filtration

The antibiofouling activity of nanosilver-coated feed spacers was investigated in a crossflow membrane filtration-cell system simulating the conditions in spiral wound modules. Silver ions distribution in the feed channel and near the membrane was estimated by numerical simulation. Nanosilver was embedded into the polypropylene network using sonochemical deposition. The ability of the modified spacer to hinder biofilm development on the adjacent membranes was studied at 0.15 ms−1 crossflow velocity, using polysulfone ultrafiltration membrane exposed to a mixed microbial enrichment. The physical properties of the modified spacer and biofilm development were evaluated using scanning electron microscopy and confocal laser scanning microscopy imaging (HRSEM and CLSM). HRSEM images depicted significantly less bacteria attached to the membranes near the modified spacer, mainly scattered with a sporadic monolayer structure. Dead/live staining assay by CLSM indicated a significantly higher percentage of dead bacteria cells attached to the membranes adjacent to the modified spacer in comparison to untreated spacers (control). The silver modified spacers displayed improved and steadier permeate flux along the 10 days of the run compared to the control. Flow and mass transfer simulations showed increased silver ions concentration near the membrane as a function of the spacer configuration. The life span of the modified spacer was evaluated as well.

Silver/titania nanocomposite-modified photoelectrodes for photoelectrocatalytic methanol oxidation

Silver deposited titania (Ag/TiO2) nanocomposite thin films were fabricated by the simple sonochemical deposition of Ag on preformed aerosol-assisted chemical vapor deposited TiO2 thin films. The photelectrocatalytic performance of a newly fabricated Ag/TiO2-modified photoelectrode was studied for methanol oxidation under simulated solar AM 1.5G irradiation (100 mW/cm2). The Ag/TiO2-modified photoelectrode showed a photocurrent density of 1 mA/cm2, which is four times that of an unmodified TiO2 photoelectrode. The modification of Ag on the TiO2 surface significantly enhanced the photoelectrocatalytic performance by improving the interfacial charge transfer processes, which minimized the charge recombination. Density functional theory (DFT) calculation studies revealed that methanol could be easily adsorbed onto the Ag surfaces of Ag/TiO2 via a partial electron transfer from Ag to methanol. The newly fabricated Ag/TiO2-modified photoelectrode could be a promising candidate for photoelectrochemical applications.

Fe3O4/TiO2 core/shell nanocubes: Single-batch surfactantless synthesis, characterization and efficient catalysts for methylene blue degradation

Amorphous titania coated magnetite (Fe3O4/TiO2) nanocubes were successfully synthesized through hydrolysis and condensation of titanium isopropoxide and iron sulfate heptahydrate using single reaction sonochemical process for catalytic applications. X-ray diffractometry, transmission electron microscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy were used to characterize the crystal structure, size and morphology, elemental composition, metal–metal and metal–oxygen bonds of the core/shell nanocubes. Magnetic properties of the samples were measured by a vibrating sample magnetometer at room temperature. Catalytic measurements on the samples showed an excellent efficiency for the degradation of methylene blue, and this efficiency was further promoted remarkably by addition of hydrogen peroxide (H2O2) within only 5 min of reaction time in the absence of ultraviolet irradiation. Even after recycling the sample for six times, the introduced catalyst was found to retain as much as 90% initial efficiency. A possible reaction mechanism for the sonochemical deposition of titania on the surface of magnetite nanocubes and also for the degradation process of methylene blue by the introduced catalyst was discussed.

Sonochemical Coating of Textiles with Hybrid ZnO/Chitosan Antimicrobial Nanoparticles

Textiles are good substrates for growth of microorganisms especially under moisture and temperature conditions found in hospitals. Microbial shedding from the body occurs continuously at contact of the patient with textile materials used in medical practices, contributing to the occurrence of hospital acquired infections. Thus, the use of efficient antimicrobial textiles is necessary to prevent the transfer of pathogens and the infection incidence. In this work, hybrid antimicrobial coatings were generated on cotton fabrics by means of a one-step simultaneous sonochemical deposition of ZnO nanoparticles (NPs) and chitosan. The process was further optimized in terms of reagents concentration and processing time in order to improve the antibacterial properties of the fabric and ensure their biocompatibility. The highest antibacterial activity of the fabrics against two medically relevant bacterial species was achieved in a 30 min sonochemical coating process using 2 mM ZnO NPs suspension. When chitosan was simultaneously deposited with the same amount of ZnO, the obtained hybrid NPs coating displayed higher by 48 and 17% antibacterial activity against Staphylococcus aureus and Escherichia coli, respectively. The presence of biopolymer also improved the durability of the antimicrobial effect of the coatings by 21% for Staphylococcus aureus and 40% for Escherichia coli, evaluated after applying multiple washing cycles at hospital laundering regimes. Finally, 87% biocompatibility improvement supported by fibroblast viability was observed for the hybrid ZnO/chitosan coating compared to the steady decrease of cells viability over one week in contact with the fabrics coated with ZnO alone.

Surface Modification of Aerosol-Assisted CVD Produced TiO2Thin Film for Dye Sensitised Solar Cell

We report a simple and convenient method for the preparation of Ag/TiO2thin films supported on indium tin oxide, which was achieved by sonochemical deposition of Ag+on aerosol-assisted chemical vapour deposited TiO2thin films. Posttreatment was performed on the film by immersion in HCl. The as-prepared composite film was characterised by X-ray diffraction, ultraviolet-visible absorption spectroscopy, Raman spectroscopy, and field emission scanning electron microscopy. The photoelectrochemical measurements andJ-Vcharacterisation showed approximately fivefold increase in photocurrent density generation and approximately sevenfold enhancement in dye sensitiser solar cell (DSSC) conversion efficiency, which was achieved after modification of the TiO2film with HCl posttreatment and Ag particle deposition. The improved photocurrent density of 933.30 μA/cm2, as well as DSSC power conversion efficiency of 3.63% with high stability, is an indication that the as-synthesised thin film is a potential candidate for solar energy conversion applications.

Sonochemical Deposition of Sn, SnO2 and Sb on Spherical Hard Carbon Electrodes for Li-Ion Batteries

Sonochemical deposition of Sn, SnO2 and Sb nanoparticles on the surface of autogenically-prepared hard carbon spheres increases their capacity for accommodating lithium, thereby rendering these carbon composite materials promising negative electrodes for advanced lithium-ion electrochemical cells. Preliminary data indicate that the carbon spheres, which offer a base capacity of ∼250 mAh/g, can provide between 300 and 400 mAh/g with excellent cycling stability when decorated with 10–15 wt% Sn, SnO2 and Sb nanoparticles. The latter value exceeds the theoretical capacity of conventional graphite electrodes (LiC6, 372 mAh/g), suggesting that the Sn, SnO2 and Sb nanoparticles remain tethered to, and maintain electrical connectivity with, the carbon substrate during electrochemical cycling. Compositional, morphological, structural and electrochemical properties of these carbon composite materials are presented and discussed with respect to other types of previously reported architectures composed of carbon, tin and/or antimony.

CuGaS2 hollow spheres from Ga–CuS core–shell nanoparticles

A liquid gallium emulsion was prepared as a starting material using ultrasound treatment in ethylene glycol. Core-shell particles of Ga@CuS were successfully synthesized by deposition of a CuS layer on gallium droplets through sonochemical deposition of copper ions and thiourea in an alcohol media. The core and shell of Ga@CuS products were composed of amorphous gallium metal and covellite phase CuS, which transformed into chalcopyrite CuGaS2 hollow spheres after sulfurization at 450°C, which was the lowest crystallization temperature. The formation of hollow nanostructures was ascribed to the Kirkendall mechanism, in which liquid gallium particles play an important role as reactive templates. In conclusion, we obtained CuGaS2 hollow spheres with a 430 nm outer diameter and 120 nm shell thickness that had the same crystal structure and electrical properties as bulk CuGaS2.

Impact of ZnO embedded feed spacer on biofilm development in membrane systems

The concept of suppressing biofouling formation using an antibacterial feed spacer was investigated in a bench scale-cross flow system mimicking a spiral wound membrane configuration. An antibacterial composite spacer containing zinc oxide-nanoparticles was constructed by modification of a commercial polypropylene feed spacer using sonochemical deposition. The ability of the modified spacers to repress biofilm development on membranes was evaluated in flow-through cells simulating the flow conditions in commercial spiral wound modules. The experiments were performed at laminar flow (Re = 300) with a 200 kDa molecular weight cut off polysulfone ultrafiltration membrane using Pseudomonas putida S-12 as model biofilm bacteria. The modified spacers reduced permeate flux decrease at least by 50% compared to the unmodified spacers (control). The physical properties of the modified spacer and biofilm development were evaluated using high resolution/energy dispersive spectrometry-scanning electron microscopy, atomic force microscopy and confocal laser scanning microscopy imaging (HRSEM, EDS, AFM and CLSM). HRSEM images depicted significantly less bacteria attached to the membranes exposed to the modified spacer, mainly scattered and in a sporadic monolayer structure. AFM analysis indicated the influence of the modification on the spacer surface including a phase change on the upper surface. Dead-live staining assay by CLSM indicated that most of the bacterial cells attached on the membranes exposed to the modified spacer were dead in contrast to a developed biofilm which was predominant in the control samples.

Synthesis of thermally stable monodispersed Au@SnO2 core–shell structure nanoparticles by a sonochemical technique for detection and degradation of acetaldehyde

A simple ultrasound assisted chemical precipitation technique for the synthesis of Au@SnO2 core–shell structure nanoparticles is reported. Au nanoparticles were synthesized via chemical reduction of metal salt followed by sonochemical deposition of a tin dioxide shell with controlled shell thickness. The phase and morphology have been investigated by an X-ray diffraction technique (XRD) and transmission electron microscopy (TEM) respectively. Au@SnO2 core–shell nanocomposites have shown a distinct surface plasmon peak in the UV-visible spectrum at 540 nm. The core–shell morphology is confirmed from the TEM images. XRD patterns have suggested the formation of gold and tin dioxide in the face-centered cubic and Cassiterite form respectively. Our investigations suggested that the formation of a core–shell structure results in the enhanced thermal stability of the system. The synthesized material is used for the detection and oxidation of acetaldehyde gas. Our investigations suggest the potential application of sonochemically synthesized Au@SnO2 nanoparticles for realization of a sense and shoot device for indoor air purification.

Sonochemical deposition of platinum nanoparticles on polymer beads and their transfer on the pore surface of a silica matrix

This study reported the sonochemical deposition of platinum on the surface of polystyrene beads (PSBs) and the transfer of obtained Pt nanoparticles into a porous silica matrix using the PSB as a sacrificial template. Platinum nanoparticle deposition was ensured by the sonochemical reduction of Pt(IV) at room temperature in latex solutions containing polystyrene beads in the presence of formic acid under Ar or under Ar/CO atmosphere without any additives. After ultrasonic treatments for few hours, well dispersed Pt nanoparticles within the range of 3-5 nm deposited on PSB were obtained in both studied conditions. Samples were then mixed with TEOS, dried, and heated at 450°C to ensure the PSB removal from the silica matrix. TEM and SEM results clearly show that final silica pore size is within the same order of magnitude than initial PSB. Finally, platinum decorated silica matrix with chosen pore sizes was successfully prepared.

Fast synthesis, formation mechanism, and control of shell thickness of CuS–polystyrene core–shell microspheres

Abstract The silanol-modified polystyrene microspheres were prepared through dispersion polymerization. Then copper sulfide particles were grown on silanol-modified polystyrene through sonochemical deposition in an aqueous bath containing copper acetate and sulfide, released through the hydrolysis of thioacetamide. The resulting particles were continuous and uniform as characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Fourier transform infrared, thermogravimetric analysis and UV–vis absorption spectroscopy were used to characterize the structure and properties of core–shell particles. The results showed the coating thickness of CuS shell can be controlled by the amount of silanol and the UV–vis absorption intensity of PSt/CuS composite also changed with the coating thickness of CuS.

Preparation and Biomedical Applications of Core–Shell Silica/Magnetic Nanoparticle Composites

Core-shell structured silica/magnetic nanoparticle composites have recently been subjected to extensive research since the shells could offer protection to the cores and introduce new properties to the hybrid structures, which endue them with great application potentials in various fields. Several approaches have been studied for the synthesis of SiO2 coated on magnetic nanoparticles. These approaches include Stöber process, microemulsion, sodium silicate and tetraethoxysilane hydrolysis, aerosol pyrolysis, layer-by-layer strategy, polymer-templating and sonochemical deposition. This review is focused on describing state-of-the-art synthetic routes and methods for the preparation of silica/magnetic nanoparticle composites. Furthermore, we also introduce main applications of these nanoparticle composites in biomedical scopes and address some challenges in the synthesis of high-quality magnetic nanoparticles.

Decoration of multiwall carbon nanotubes with nickel nanoparticles: effect of deposition strategy on metal dispersion and performance in the hydrogenation of p-chloroacetophenone

The sonochemical deposition of nickel nanoparticles onto the multiwall carbon nanotube aggregates leads to a uniformly distributed metal phase at high loadings and an average nickel crystal size of 4–8 nm at a 25–50 wt% nickel content. Its application enhances the catalytic activity of Ni/multiwall carbon nanotube material in the selective hydrogenation of chloroacetophenone by factors of 2–18, as compared with that prepared by traditional decoration methods.