Sonoprocessing: From Concepts to Large-Scale Reactors.

Intensification of ultrasonic processes for diversified applications, including environmental remediation, extractions, food processes, and synthesis of materials, has received attention from the scientific community and industry. The mechanistic pathways involved in intensification of ultrasonic processes that include the ultrasonic generation of cavitation bubbles, radical formation upon their collapse, and the possibility of fine-tuning operating parameters for specific applications are all well documented in the literature. However, the scale-up of ultrasonic processes with large-scale sonochemical reactors for industrial applications remains a challenge. In this context, this review provides a complete overview of the current understanding of the role of operating parameters and reactor configuration on the sonochemical processes. Experimental and theoretical techniques to characterize the intensity and distribution of cavitation activity within sonoreactors are compared. Classes of laboratory and large-scale sonoreactors are reviewed, highlighting recent advances in batch and flow-through reactors. Finally, examples of large-scale sonoprocessing applications have been reviewed, discussing the major scale-up and sustainability challenges.

Leveraging new opportunities and advances in high-pressure homogenization to design non-dairy foods.

High-pressure homogenization (HPH) and ultrahigh-pressure homogenization (UHPH) are emerging food processing techniques for stabilizing emulsions and food components under the pressure range from 60 to 400 MPa. Apart from this, they also support increasing nutritional profile, food preservation, and functionality enhancement. Even though the food undergoes the shortest processing operation, the treatment leads to modification of physical, chemical, and techno-functional properties, in addition to the formation of micro-sized particles. This study focuses on recent advances in using HPH/UHPH on plant-based milk sources such as soybeans, almonds, hazelnuts, and peanuts. Overall, this systematic review provides an in-depth analysis of the principles of HPH/UHPH, the mechanism of action, and their applications in other nondairy areas such as fruits and vegetables, meat, fish, and marine species. This work also deciphers the role of HPH/UHPH in modifying food components, their functional quality enhancement, and their provision of oxidative resistance to many foods. HPH is not only perceived as a technique for size reduction and homogenization; however, it does various functions like microbial inactivation, improvement of rheologies like texture and consistency, decreasing of lipid oxidation, and making positive modifications to proteins such as changes to the secondary structure and tertiary structure thereby enhancing the emulsifying properties, hydrophobicity of proteins, and other associated functional properties in many nondairy sources at pressures of 100-300 MPa. Thus, HPH is an emerging technique with a high throughput and commercialization value in food industries.

Ultrasonic Transformation of Antibiotic Molecules into a Selective Chemotherapeutic Nanodrug.

Ultrasound-based engineering of carrier-free nanodrugs by supramolecular self-assembly has recently emerged as an innovative and environmentally friendly synthetic approach. By applying high-frequency sound waves (490 kHz) in aqueous solutions, the transformation of small chemotherapeutic and antibiotic drug molecules into carrier-free nanodrugs with anticancer and antimicrobial activities was recently achieved. The transformation of the antibiotic drug molecules, i.e., doxycycline, into stable nanodrugs (~130 nm) with selective anticancer activity was achieved without requiring organic solvents, chemical agents, or surfactants. The obtained nanodrug exhibited reactive oxygen species (ROS)-mediated cytotoxicity on human breast cancer (MDA-MB 231 cells) but a negligible antiproliferative effect on healthy fibroblast cells. Imaging by super-resolution microscopy (STORM) provided insights into the intracellular trafficking and endosomal escape of the nanodrugs. Overall, these findings suggest that small antibiotic drugs can be transformed into chemotherapeutic nanodrugs with high selectivity against cancer cells.

Ultrasonic and homogenization: An overview of the preparation of an edible protein-polysaccharide complex emulsion.

Emulsion systems are extensively utilized in the food industry, including dairy products, such as ice cream and salad dressing, as well as meat products, beverages, sauces, and mayonnaise. Meanwhile, diverse advanced technologies have been developed for emulsion preparation. Compared with other techniques, high-intensity ultrasound (HIUS) and high-pressure homogenization (HPH) are two emerging emulsification methods that are cost-effective, green, and environmentally friendly and have gained significant attention. HIUS-induced acoustic cavitation helps in efficiently disrupting the oil droplets, which effectively produces a stable emulsion. HPH-induced shear stress, turbulence, and cavitation lead to droplet disruption, altering protein structure and functional aspects of food. The key distinctions among emulsification devices are covered in this review, as are the mechanisms of the HIUS and HPH emulsification processes. Furthermore, the preparation of emulsions including natural polymers (e.g., proteins-polysaccharides, and their complexes), has also been discussed in this review. Moreover, the review put forward to the future HIUS and HPH emulsification trends and challenges. HIUS and HPH can prepare much emulsifier-stable food emulsions, (e.g., proteins, polysaccharides, and protein-polysaccharide complexes). Appropriate HIUS and HPH treatment can improve emulsions' rheological and emulsifying properties and reduce the emulsions droplets' size. HIUS and HPH are suitable methods for developing protein-polysaccharide forming stable emulsions. Despite the numerous studies conducted on ultrasonic and homogenization-induced emulsifying properties available in recent literature, this review specifically focuses on summarizing the significant progress made in utilizing biopolymer-based protein-polysaccharide complex particles, which can provide valuable insights for designing new, sustainable, clean-label, and improved eco-friendly colloidal systems for food emulsion. PRACTICAL APPLICATION: Utilizing complex particle-stabilized emulsions is a promising approach towards developing safer, healthier, and more sustainable food products that meet legal requirements and industrial standards. Moreover, the is an increasing need of concentrated emulsions stabilized by biopolymer complex particles, which have been increasingly recognized for their potential health benefits in protecting against lifestyle-related diseases by the scientific community, industries, and consumers.

Ultrasound-induced protein restructuring and ordered aggregation to form amyloid crystals.

Amyloid crystals, a form of ordered protein aggregates documented relatively recently, have not been studied as extensively as amyloid fibres. This study investigates the formation of amyloid crystals with low frequency ultrasound (20 kHz) using ß-lactoglobulin, as a model protein for amyloid synthesis. Acoustic cavitation generates localised zones of intense shear, with extreme heat and pressure that could potentially drive the formation of amyloid structures at ambient bulk fluid temperatures (20 ± 1 °C). Thioflavin T fluorescence and electron microscopy showed that low-frequency ultrasound at 20 W/cm3 input power induced ß-stacking to produce amyloid crystals in the mesoscopic size range, with a mean length of approximately 22 µm. FTIR spectroscopy indicated a shift towards increased intermolecular antiparallel ß-sheet content. An increase in sonication time (0-60 min) and input power (4-24 W/cm3) increased the mean crystal length, but this increase was not linearly proportional to sonication time and input power due to the delayed onset of crystal growth. We propose that acoustic cavitation causes protein unfolding and aggregation and imparts energy to aggregates to cross the torsion barrier, to achieve their lowest energy state as amyloid crystals. The study contributes to a further understanding of protein chemistry relating to the energy landscape of folding and aggregation. Ultrasound presents opportunities for practical applications of amyloid structures, presenting a more adaptable and scalable approach for synthesis.

Nanoarchitectonics of Congo red dye to biocompatible fluorescent carbon dots for highly sensitive Fe3+ and ferritin detection.

In this work, we have meticulously tuned the carcinogenic Congo red dye to environmentally benign fluorescent carbon dots (CDs) by adopting a typical hydrothermal method without any additives. The as-synthesized CDs were extremely water soluble, exhibited an excitation wavelength independent emission with a high fluorescence quantum yield (46%) and were biocompatible. The microscopy results revealed that the CDs were quasi-spherical with a particle diameter of ∼5 nm. The structure and functional groups of the CDs were comprehensively investigated using Fourier-transform infrared, X-ray photoelectron and Raman spectroscopy analyses. These studies show that the CDs were intrinsically functionalized with -OH, N-H and CO groups. In the sensing experiments, the CDs selectively responded to Fe3+ ions over other analytes with a detection limit of 12 nM. The time-resolved fluorescence quenching measurements were used to decipher the sensing mechanism. For the onsite 'equipment-free' detection of iron, we have developed a CD adsorbed paper-based analytical tool. Furthermore, the selective nature of CDs was highly beneficial for detecting Fe3+ in non-heme metalloprotein (ferritin) and real water samples. Thus, the CDs produced from the Congo red dye could be a prospective asset to the bio-imaging and biosensing research fields.

Revealing the stability of CuWO4/g-C3N4 nanocomposite for photocatalytic tetracycline degradation from the aqueous environment and DFT analysis.

Graphitic carbon nitride (g-C3N4) is an emerging metal-free photocatalyst, however, engineering the photocatalytic efficiency for the effective degradation of hazardous molecules is still challenging. An unstable and low bandgap CuWO4 was composited with g-C3N4 to achieve synergistic benefits of tuning the visible light responsiveness and stability of CuWO4. CuWO4/g-C3N4 nanocomposite exhibited a relatively high visible light absorption region and the bandgap was modified from 2.77 to 2.53 eV evidenced via UV-DRS. Moreover, the fast electron transfer rate was observed with CuWO4/g-C3N4 nanocomposite as confirmed using PL and photocurrent studies. XRD, FT-IR, and HR-TEM analyses signified the formation of CuWO4/g-C3N4 nanocomposite. CuWO4/g-C3N4 nanocomposite showed enhanced photocatalytic degradation of Tetracycline (TC) about ∼7.4 fold greater than pristine g-C3N4 in 120 min. Notably, the OH• and •O2- radicals played a most significant role in photocatalytic TC degradation. Furthermore, the energy band structure, density of state, and Bader charge analyses of these molecules were performed.

Enrichment of hydrogen production from fruit waste biomass using ozonation assisted with citric acid.

In this study, the impact of ozonation abetted with the citric acid pretreatment (OZCAP) method on fruit waste was investigated for ameliorating hydrogen production. Initially, the ozonation pretreatment (OZP) method was performed by varying ozone (O3) dosage and disintegration time. At optimized conditions (O3 dosage (0.04 g/g suspended solid; SS) and disintegration time (40 minutes)), 17.6% of liquefied organics emancipate rate (LER) and 13.5% of SS reduction were perceived. Further augmenting LER of fruit waste, OZCAP method was proceeded by varying citric acid dosage and disintegration time at an optimized OZP dosage (0.04 g/g SS). A higher LER (24.4%) and SS reduction (19%) were described at an optimal citric acid dosage (0.03 g/g SS) and disintegration time (20 minutes). Then, the hydrogen production potential of OZCAP, OZP and raw fruit waste were evaluated in which OZCAP method exhibited a higher cumulative hydrogen production (30 mL/g volatile solids). Energy valuation reveals that OZCAP method exhibited a net energy of 3.7 kWh/kg of fruit waste.

Ultrasound-Assisted Microencapsulation of Soybean Oil and Vitamin D Using Bare Glycogen Nanoparticles.

Ultrasonically synthesized core-shell microcapsules can be made of synthetic polymers or natural biopolymers, such as proteins and polysaccharides, and have found applications in food, drug delivery and cosmetics. This study reports on the ultrasonic synthesis of microcapsules using unmodified (natural) and biodegradable glycogen nanoparticles derived from various sources, such as rabbit and bovine liver, oyster and sweet corn, for the encapsulation of soybean oil and vitamin D. Depending on their source, glycogen nanoparticles exhibited differences in size and 'bound' proteins. We optimized various synthetic parameters, such as ultrasonic power, time and concentration of glycogens and the oil phase to obtain stable core-shell microcapsules. Particularly, under ultrasound-induced emulsification conditions (sonication time 45 s and sonication power 160 W), native glycogens formed microcapsules with diameter between 0.3 µm and 8 µm. It was found that the size of glycogen as well as the protein component play an important role in stabilizing the Pickering emulsion and the microcapsules shell. This study highlights that native glycogen nanoparticles without any further tedious chemical modification steps can be successfully used for the encapsulation of nutrients.

Sono-Fenton Chemistry Converts Phenol and Phenyl Derivatives into Polyphenols for Engineering Surface Coatings.

We report a sono-Fenton strategy to mediate the supramolecular assembly of metal-phenolic networks (MPNs) as substrate-independent coatings using phenol and phenyl derivatives as building blocks. The assembly process is initiated from the generation of hydroxyl radicals (. OH) using high-frequency ultrasound (412 kHz), while the metal ions synergistically participate in the production of additional . OH for hydroxylation/phenolation of phenol and phenyl derivatives via the Fenton reaction and also coordinate with the phenolic compounds for film formation. The coating strategy is applicable to various phenol and phenyl derivatives and different metal ions including FeII , FeIII , CuII , and CoII . In addition, the sono-Fenton strategy allows real-time control over the assembly process by turning the high-frequency ultrasound on or off. The properties of the building blocks are maintained in the formed films. This work provides an environmentally friendly and controllable method to expand the application of phenolic coatings for surface engineering.

A simple and ubiquitous device for picric acid detection in latent fingerprints using carbon dots.

This work addresses the synthetic optimization of carbon dots (CDs) and their application in sensing picric acid from latent fingerprints by exploiting a smartphone-based RGB tool. The optimization of the synthesis of CDs is investigated towards achieving shorter reaction time, better product yield and fluorescence quantum efficiency. Precursors such as citric acid and thiourea were chosen for the synthesis of CDs. Among the various synthetic methodologies, it is found that the pyrolysis method offers ∼50% product yield within 15 min. The morphology and optical properties of the prepared CDs are characterized using the typical microscopic and spectroscopic techniques, respectively. The synthesized CDs exhibit quasi-spherical shape with an average particle size of 1.7 nm. The excitation dependent emissive properties of CDs are investigated by time resolved fluorescence spectroscopy. Furthermore, the excellent fluorescence properties (φ = 11%) of CDs are explored as a fluorescent fingerprint powder for the identification of latent fingerprints on various substrates. In addition, the presence of picric acid in latent fingerprints was detected. Furthermore, this study is extended to perform real time detection of fingerprints and harmful contaminants in fingerprints by utilizing a smartphone-based RGB color analysis tool. Based on these investigations, the prepared CDs could be a prospective fluorescent material in the field of forensics.

Ultrasound and Sonochemistry for Radical Polymerization: Sound Synthesis.

The use of ultrasound as an external stimulus for promoting polymerization reactions has received increasing attention in recent years. In this Review article, the fundamental processes that can lead to either the homolytic cleavage of polymer chains, or the sonolysis of solvent (or other) small molecules, under the application of ultrasound are described. These reactions promote the production of reactive radicals, which can be utilized in chain-growth radical polymerizations under the right conditions. A full historical overview of the development of ultrasound-assisted radical polymerization is provided, with special attention given to the recently described systems that are "controlled" by methods of reversible (radical) deactivation. Perspectives are shared on what challenges still remain in polymer sonochemistry, as well as new areas that are yet to be explored.

Exploring New Applications of Lysozyme-Shelled Microbubbles.

This feature article provides a review of recent work on the synthesis of biopolymer-shelled microbubbles using various techniques with a particular focus on ultrasonic methodology that offers advantages over other conventional methods for tuning their physical and functional properties. A detailed discussion on the role of surface chemistry in fabricating functional lysozyme-shelled microbubbles has also been presented. Highlights on the applications of lysozyme-shelled microbubbles, particularly recent findings on their use for potential theranostic applications in lung diseases, have also been presented.

Ultrasonically synthesized organic liquid-filled chitosan microcapsules: part 2: characterization using AFM (atomic force microscopy) and combined AFM-confocal laser scanning fluorescence microscopy.

Atomic Force Microscopy (AFM) is used to measure the stiffness and Young's modulus of individual microcapsules that have a chitosan cross-linked shell encapsulating tetradecane. The oil filled microcapsules were prepared using a one pot synthesis via ultrasonic emulsification of tetradecane and crosslinking of the chitosan shell in aqueous solutions of acetic acid. The concentration of acetic acid in aqueous solutions of chitosan was varied from 0.2% to 25% v/v. The effect of acetic acid concentration and size of the individual microcapsules on the strength was probed. The deformations and forces required to rupture the microcapsules were also measured. Three dimensional deformations of microcapsules under large applied loads were obtained by the combination of Laser Scanning Confocal Microscopy (LSCM) with Atomic Force Microscopy (AFM). The stiffness, and hence the modulus, of the microcapsules was found to decrease with an increase in size with the average stiffness ranging from 82 to 111 mN m-1 and average Young's modulus ranging from 0.4 to 6.5 MPa. The forces required to rupture the microcapsules varied from 150 to 250 nN with deformations of the microcapsules up to 62 to 110% relative to their radius, respectively. Three dimensional images obtained using laser scanning confocal microscopy showed that the microcapsules retained their structure and shape after being subjected to large deformations and subsequent removal of the loads. Based on the above observations, the oil filled chitosan crosslinked microcapsules are an ideal choice for use in the food and pharmaceutical industries as they would be able to withstand the process conditions encountered.

Ultrasonically synthesized organic liquid-filled chitosan microcapsules: part 1: tuning physical & functional properties.

This study reports the synthesis of tetradecane-filled chitosan microcapsules in acetic acid aqueous solutions using high intensity ultrasound at 20 kHz. The size, size distribution, and stability of microcapsules were tuned by varying the concentration of acetic acid from 0.2% to 25% v/v. After long-time storage at room temperature (more than 3 months), the microcapsules maintained their shell-core structure where the volume of the microcapsules at 0.2% acetic acid concentration increased by 8.3% due to leaking and coalescence. Microcapsules were consistently spherical and had a smooth shell surface, however, their shell thickness varied with acetic acid concentration. The relaxation behavior of individual microcapsules to an applied constant stress was measured by atomic force microscopy (AFM) to probe the shell strength and extent of crosslinking. The effect of acetic acid on the relative viscosity of chitosan aqueous solutions played a major role in microcapsule size control at low acid concentrations. With constant addition of acetic acid, amino groups in chitosan chains were acetylated partially under ultrasonic irradiation. This reduced the amphiphilicity of the shell material and therefore influenced the size, size distribution, stability and mechanical strength of the microcapsules. Apart from the acetylation effect, the counter-ion effect and the formation of covalent bond crosslinks also made contributions to the formation of stable chitosan microcapsules.

Photocatalytic properties of hierarchical CuO nanosheets synthesized by a solution phase method.

CuO nanomaterials were synthesized by a simple solution phase method using cetyltrimethylammonium bromide (CTAB) as a surfactant and their photocatalytic property was determined towards the visible-light assisted degradation of Reactive Black-5 dye. A detailed mechanism for the formation of CuO nanostructures has been proposed. The effect of various experimental parameters such as catalyst amount, dye concentration, pH and oxidizing agent on the dye degradation efficiency was studied. About 87% dye was degraded at pH2 in the presence of CuO nanosheets under visible light. The enhanced photocatalytic activity of CuO nanosheets can be ascribed to good crystallinity, grain size, surface morphology and a strong absorption in the visible region. CuO is found to be a promising catalyst for industrial waste water treatment.

A model for the effect of bulk liquid viscosity on cavitation bubble dynamics.

A new model of single cavitation bubble dynamics has been developed to include the effect of bulk liquid viscosity in addition to the effects of evaporation/condensation of water vapor, thermal conduction and the compressibility of a liquid. In this study, the liquid viscosity is divided into two parts: viscosity at the bubble interface (µ') and viscosity of the bulk liquid (µ). A set of numerical calculations with and without µ has been completed under different viscosities (0.001-0.014 Pa s) to quantitatively analyze the effect of µ on single cavitation bubble dynamics. The results show that the effect can be negligible for small viscosities, but it should be taken into account for relatively high viscosities.

A study of the effectiveness and energy efficiency of ultrasonic emulsification.

Three essential experimental parameters in the ultrasonic emulsification process, namely sonication time, acoustic amplitude and processing volume, were individually investigated, theoretically and experimentally, and correlated to the emulsion droplet sizes produced. The results showed that with a decrease in droplet size, two kinetic regions can be separately correlated prior to reaching a steady state droplet size: a fast size reduction region and a steady state transition region. In the fast size reduction region, the power input and sonication time could be correlated to the volume-mean diameter by a power-law relationship, with separate power-law indices of -1.4 and -1.1, respectively. A proportional relationship was found between droplet size and processing volume. The effectiveness and energy efficiency of droplet size reduction was compared between ultrasound and high-pressure homogenisation (HPH) based on both the effective power delivered to the emulsion and the total electric power consumed. Sonication could produce emulsions across a broad range of sizes, while high-pressure homogenisation was able to produce emulsions at the smaller end of the range. For ultrasonication, the energy efficiency was higher at increased power inputs due to more effective droplet breakage at high ultrasound intensities. For HPH the consumed energy efficiency was improved by operating at higher pressures for fewer passes. At the laboratory scale, the ultrasound system required less electrical power than HPH to produce an emulsion of comparable droplet size. The energy efficiency of HPH is greatly improved at large scale, which may also be true for larger scale ultrasonic reactors.

Sono-RAFT Polymerization in Aqueous Medium.

The ultrasonic irradiation of aqueous solution is demonstrated to be a suitable source of initiating radicals for a controlled radical polymerization when conducted in the presence of a thiocarbonylthio-containing reversible addition-fragmentation chain transfer (RAFT) agent. This allows for a highly "green" method of externally regulated/controlled polymerization with a potentially broad scope for polymerizable monomers and/or polymer structures.

Shape-Dependent Interactions of Palladium Nanocrystals with Hydrogen.

Elucidation of the nature of hydrogen interactions with palladium nanoparticles is expected to play an important role in the development of new catalysts and hydrogen-storage nanomaterials. A facile scaled-up synthesis of uniformly sized single-crystalline palladium nanoparticles with various shapes, including regular nanocubes, nanocubes with protruded edges, rhombic dodecahedra, and branched nanoparticles, all stabilized with a mesoporous silica shell is developed. Interaction of hydrogen with these nanoparticles is studied by using temperature-programmed desorption technique and by performing density functional theory modeling. It is found that due to favorable arrangement of Pd atoms on their surface, rhombic dodecahedral palladium nanoparticles enclosed by {110} planes release a larger volume of hydrogen and have a lower desorption energy than palladium nanocubes and branched nanoparticles. These results underline the important role of {110} surfaces in palladium nanoparticles in their interaction with hydrogen. This work provides insight into the mechanism of catalysis of hydrogenation/dehydrogenation reactions by palladium nanoparticles with different shapes.