Activation of Ibuprofen via Ultrasonic Complexation with Silver in N-Doped Oxidized Graphene Nanoparticles for Microwave Chemotherapy of Cervix Tumor Tissues.

An ultrasonic method (20 kHz) is introduced to activate pristine ibuprofen organic molecular crystals via complexation with silver in nitrogen-doped oxidized graphene nanoplatforms (∼50 nm). Ultrasonic complexation occurs in a single-step procedure through the binding of the carboxylic groups with Ag and H-bond formation, involving noncovalent πC=C → πC=C* transitions in the altered phenyl ring and πPY → πCO* in ibuprofen occurring between the phenyl ring and C-O bonds as a result of interaction with hydroxyl radicals. The ibuprofen-silver complex in ≪NrGO≫ exhibits a ∼42 times higher acceleration rate than free ibuprofen of the charge transfer between hexacyanoferrate and thiosulfate ions. The increased acceleration rate can be caused by electron injection/ejection at the interface of the ≪Ag-NrGO≫ nanoplatform and formation of intermediate species (Fe(CN)5(CNSO3)x- with x = 4 or 5 and AgHS2O3) at the excess of produced H+ ions. Important for microwave chemotherapy, ibuprofen-silver complexes in the ≪NrGO≫ nanoplatform can produce H+ ions at ∼12.5 times higher rate at the applied voltage range from 0.53 to 0.60 V. ≪Ibu-Ag-NrGO≫ NPs develop ∼105 order higher changes of the electric field strength intensity than free ibuprofen in the microwave absorption range of 100-1000 MHz as revealed from the theoretical modeling of a cervix tumor tissue.

Ultrasonic Formation of Fe3O4-Reduced Graphene Oxide-Salicylic Acid Nanoparticles with Switchable Antioxidant Function.

We demonstrate a single-step ultrasonic in situ complexation of salicylic acid during the growth of Fe3O4-reduced graphene oxide nanoparticles (∼10 nm) to improve the antioxidant and antiproliferative effects of pristine drug molecules. These nanoparticles have a precisely defined electronic molecular structure with salicylic acid ligands specifically complexed to Fe(III)/Fe(II) sites, four orders of magnitude larger electric surface potential, and enzymatic activity modulated by ascorbic acid molecules. The diminishing efficiency of hydroxyl radicals by Fe3O4-rGO-SA nanoparticles is tenfold higher than that by pristine salicylic acid in the electro-Fenton process. The H+ production of these nanoparticles can be switched by the interaction with ascorbic acid ligands and cause the redox deactivation of iron or enhanced antioxidation, where rGO plays an important role in enhanced charge transfer catalysis. Fe3O4-rGO-SA nanoparticles are nontoxic to erythrocytes, i.e., human peripheral blood mononuclear cells, but surpassingly inhibit the growth of three cancer cell lines, HeLa, HepG2, and HT29, with respect to pristine salicylic acid molecules.

Sonochemical Formation of Copper/Iron-Modified Graphene Oxide Nanocomposites for Ketorolac Delivery.

A feasible sonochemical approach is described for the preparation of copper/iron-modified graphene oxide nanocomposites through ultrasonication (20 kHz, 18 W cm-2 ) of an aqueous solution containing copper and iron ion precursors. Unique copper-, copper/iron- and iron-modified graphene oxide nanocomposites have a submicron size that is smaller than that of pristine GO and a higher surface area enriched with Cu2 O, CuO, and Fe2 O3 of multiform phases (α-, ß-, ϵ-, or γ), FeO(OH), and sulfur- or carbon-containing compounds. These nanocomposites are sonochemically intercalated with the nonsteroidal anti-inflammatory drug ketorolac, which results in the formation of nanoscale carriers. Ketorolac monotonically disintegrates from these nanoscale carriers in aqueous solution upon adjustment of the pH from 1 to 8. The disintegration of ketorolac proceeds at a slower rate from the copper/iron-modified graphene oxide at increased pH, but at a faster rate from the iron-modified graphene oxide under acidic conditions.

Sonochemically Assembled Photoluminescent Copper-Modified Graphene Oxide Microspheres.

A new accessible sonochemical assembly method is developed for the preparation of photoluminescent oil-filled silica@CuS/Cu2O/CuO-graphene oxide (GO) microspheres that emit light of green, yellow, and red colors. This method is based on the ultrasonic emulsification of a biphasic mixture consisting of CuS/Cu2O/CuO-graphene oxide (GO) nanocomposites with poly(vinyl alcohol) (PVA) (aqueous phase) and tetraethyl orthosilicate with sunflower oil (organic phase). CuS/Cu2O/CuO-GO nanocomposites are composed of sonochemically formed three phases of copper: covellite CuS (p-type semiconductor), cuprite Cu2O (Bloch p-type semiconductor), and CuO (charge-transfer insulator). The photoluminescence properties of microspheres result from H-bridging between PVA and CuS/Cu2O/CuO-GO nanostructures, light absorption ability of Cu2O, and charge-transfer insulation by CuO. Substitution of PVA by S-containing methylene blue quenches fluorescence by enhanced dye adsorption on CuS/Cu2O/CuO-GO because of CuS and induced charge transfer. Non-S-containing malachite green is in a nonionized form and tends to be in the oil phase, prohibiting the charge transfer on CuS/Cu2O/CuO-GO.

Ultrasonically treated liquid interfaces for progress in cleaning and separation processes.

Ultrasound and acoustic cavitation enable ergonomic and eco-friendly treatment of complex liquids with outstanding performance in cleaning, separation and recycling of resources. A key element of ultrasonic-based technology is the high speed of mixing by streams, flows and jets (or shock waves), which is accompanied by sonochemical reactions. Mass transfer across the phase boundary with a great variety of catalytic processes is substantially enhanced through acoustic emulsification. Encapsulation, separation and recovery of liquids are fast with high production yield if applied by ultrasound. Here we discuss the state of knowledge of these processes by ultrasound and acoustic cavitation from a perspective of a physico-chemical model in order to predict and control the outcome. We focus on the physical interpretation and quantification of ultrasonic parameters and properties of liquids to understand the chemistry of liquid/liquid interfaces in acoustic fields. The roles of thermodynamic enthalpy and entropy (incl. Laplace and osmotic pressure) in the context of sonochemical reactions (separation, catalysis, degradation, cross-linking, ion exchange and phase transfer) are outlined. The synergy of ultrasound and electric fields or continuous flow chemistry for cleaning and separation via emulsification is highlighted by specific strategies involving polymers and ultrasonic membranes.

Ultrasonic Mastering of Filter Flow and Antifouling of Renewable Resources.

Inadequate access to pure water and sanitation requires new cost-effective, ergonomic methods with less consumption of energy and chemicals, leaving the environment cleaner and sustainable. Among such methods, ultrasound is a unique means to control the physics and chemistry of complex fluids (wastewater) with excellent performance regarding mass transfer, cleaning, and disinfection. In membrane filtration processes, it overcomes diffusion limits and can accelerate the fluid flow towards the filter preventing antifouling. Here, we outline the current state of knowledge and technological design, with a focus on physicochemical strategies of ultrasound for water cleaning. We highlight important parameters of ultrasound for the delivery of a fluid flow from a technical perspective employing principles of physics and chemistry. By introducing various ultrasonic methods, involving bubbles or cavitation in combination with external fields, we show advancements in flow acceleration and mass transportation to the filter. In most cases we emphasize the main role of streaming and the impact of cavitation with a perspective to prevent and remove fouling deposits during the flow. We also elaborate on the deficiencies of present technologies and on problems to be solved to achieve a wide-spread application.

Surpassingly competitive electromagnetic field enhancement at the silica/silver interface for selective intracellular surface enhanced Raman scattering detection.

A thin plasmonic nanofilm is formed by preformed silver nanoparticles (30 nm) in the matrix of poly(vinyl alcohol) adsorbed on silica microparticles (1.5 µm) (SiO2@Ag-PVA). By applying finite element method (FEM) analysis the surface enhanced Raman spectroscopy (SERS) enhancement factors (EFs) can reach 10(5) with higher values from 10(9) to 10(11) in the silver layer of 5 nm thickness. Nanoparticles in the SiO2@Ag-PVA nanofilm need at least 15 nm radius to exhibit SERS EFs greater than 10(7). High values of this enhancement at the silver/silica interface of spherical geometry can be reached faster by using a 532 nm compared to 785 nm excitation wavelength. By this approach different SERS spectral features can be distinguished between live fibroblasts with spread ("healthy" state) or round ("unhealthy" state) shapes. Characteristic features of secondary protein structures, detection of different acidic conditions and cholesterol with at least a 3-fold higher sensitivity are examined. Moreover, a greater amount of glucose (glucogen) and also tyrosine can be monitored in real time. This is important in identification of higher risk of diabetes as well as in several genetic metabolic disorders (e.g., phenylketonuria, tyrosinaemia type II and tyrosinosis).

Prospects for plasmonic hot spots in single molecule SERS towards the chemical imaging of live cells.

Single molecule surface enhanced Raman scattering (SM-SERS) is a highly local effect occurring at sharp edges, interparticle junctions and crevices or other geometries with a sharp nanoroughness of plasmonic nanostructures ("hot spots"). The emission of an individual molecule at SM-SERS conditions depends on the local enhancement field of the hot spots, as well as the binding affinity and positioning at a hot spot region. In this regard, the stability of near-field nano-optics at hot spots is critical, particularly in a biological milieu. In this perspective review, we address recent advances in the experimental and theoretical approaches for the successful development of SM-SERS. Significant progress in the understanding of the interaction between the excitation electromagnetic field and the surface plasmon modes at the metallic or metallic/dielectric interface of various curvatures are described. New knowledge on methodological strategies for positioning the analytes for SM-SERS and Raman-assisted SERS or the SERS imaging of live cells has been acquired and displayed. In the framework of the extensive development of SM-SERS as an advancing diagnostic analytical technique, the real-time SERS chemical imaging of intracellular compartments and tracing of individual analytes has been achieved. In this context, we highlight the tremendous potential of SERS chemical imaging as a future prospect in SERS and SM-SERS for the prediction and diagnosis of diseases.

Highly effective hot spots for SERS signatures of live fibroblasts.

Pre-formed silver-boron nanoparticles of 22 nm form pearl-like necklace nanostructures with interparticle junctions of less than 10 nm length in the matrix of polyethylene glycol (8000 Da). The silver necklace nanostructure is stable at 37 °C or 70 °C and also inside a live cell medium. A polyethylene glycol matrix with a shorter chain length (1000 Da) does not protect the nanoparticles against attraction, and random aggregates are formed. Silver necklace nanostructures exhibit strong Raman enhancement by more than ∼10(9) which is much higher than for silver-citrate or random silver-boron aggregates. The polymeric matrix of 8000 Da contributes strongly to the electromagnetic field enhancement and removes the chemical contribution to the surface Raman scattering increase. The stable interparticle junctions act as local hot spots for strong Raman scattering signals collected from live fibroblasts and allow systematic in situ studies.

Single bubble perturbation in cavitation proximity of solid glass: hot spot versus distance.

A systematic study of the energy loss of a cavitation bubble in a close proximity of a glass surface is introduced for the first time in a low acoustic field (1.2-2.4 bar). Single bubble sonoluminescence (SBSL) is used as a tool to predict the temperature and pressure decrease of bubble (µm) versus surface distance. A glass as a model system is used to imitate the boundary conditions relevant for nano- or micromaterials. SBSL preequilibrated with 5% argon is perturbed by a glass rod with the tip (Z-perturbation) and with the long axis (X-perturbation) at a defined distance. From 2 mm to 500 µm argon-SBSL lines monotonically narrow and the effective emission temperature decreases from 9000 K to 6800 K comparable to multiple bubbles. The electron density decreases by two orders of magnitude in Z-perturbation and is by a factor of two higher in X-perturbation than the unperturbed cavitating bubble. The perturbed single bubble sonoluminescence pressure decreases from 2700 atm to 1200 atm at 2.4 bar. In water new non-SBSL SiO molecular emission lines are observed and OH emission disappears.

Ultrasonic approach for formation of erbium oxide nanoparticles with variable geometries.

Ultrasound (20 kHz, 29 W·cm(-2)) is employed to form three types of erbium oxide nanoparticles in the presence of multiwalled carbon nanotubes as a template material in water. The nanoparticles are (i) erbium carboxioxide nanoparticles deposited on the external walls of multiwalled carbon nanotubes and Er(2)O(3) in the bulk with (ii) hexagonal and (iii) spherical geometries. Each type of ultrasonically formed nanoparticle reveals Er(3+) photoluminescence from crystal lattice. The main advantage of the erbium carboxioxide nanoparticles on the carbon nanotubes is the electromagnetic emission in the visible region, which is new and not examined up to the present date. On the other hand, the photoluminescence of hexagonal erbium oxide nanoparticles is long-lived (µs) and enables the higher energy transition ((4)S(3/2)-(4)I(15/2)), which is not observed for spherical nanoparticles. Our work is unique because it combines for the first time spectroscopy of Er(3+) electronic transitions in the host crystal lattices of nanoparticles with the geometry established by ultrasound in aqueous solution of carbon nanotubes employed as a template material. The work can be of great interest for "green" chemistry synthesis of photoluminescent nanoparticles in water.

Acoustic cavitation for engineering of gold sols in silver nitrate solutions.

Binary gold-silver nanostructures of preformed gold nanoparticles (25nm) in silver nitrate solutions are produced by a two step sonication (20kHz). Ultrasonic treatment of gold-silver mixtures is carried out in the presence of sodium dodecyl sulfate in water or 2-propanol, and poly(vinyl pyrrolidone) in ethylene glycol solutions. Gold-silver nano-worms, which consist of ripened gold particles connected by ultrasonically reduced silver, are formed after 1h of sonication in the presence of sodium dodecyl sulfate aqueous solution. In 2-propanol bimetallic nano-worms have a well defined core-shell structure. Polygonal alloy nanoparticles with gold as a core material and a silver shell are produced after 180min of sonication in the presence of poly(vinyl pyrrolidone) in ethylene glycol solution. Bimetallic gold-silver nanostructures have defected face centered cubic structure and represent polycrystals with a large number of crystallites randomly oriented. For the first time, the mechanism of gold particle design by ultrasound is examined in detail. The role of additives (sodium dodecyl sulfate, polyvinyl pyrrolidone, ethylene glycol and 2-propanol) as reductants of silver at the gold contact surface or stabilizers of particles is highlighted.

Ultrasonic alloying of preformed gold and silver nanoparticles.

Alloyed gold/silver nanoparticles with a core/shell structure are produced from preformed gold and silver nanoparticles during ultrasonic treatment at different intensities in water and in the presence of surface-active species. Preformed gold nanoparticles with an average diameter of 15 + or - 5 nm are prepared by the citrate reduction of chloroauric acid in water, and silver nanoparticles (38 + or - 7 nm) are formed after reduction of silver nitrate by sodium borohydride. Bare binary gold/silver nanoparticles with a core/shell structure are formed in aqueous solution after 1 h of sonication at high ultrasonic intensity. Cationic-surfactant-coated preformed gold and silver nanoparticles become gold/silver-alloy nanoparticles after 3 h of sonication in water at 55 W cm(-2), whereas only fusion of isolated gold and silver nanoparticles is observed after ultrasonic treatment in the presence of an anionic surfactant. As the X-ray diffraction profile of alloyed gold/silver nanoparticles reveals split, shifted, and disappeared peaks, the face-centered-cubic crystalline structure of the binary nanoparticles is defect-enriched by temperatures that can be as high as several thousand Kelvin inside the cavitation bubbles during ultrasonic treatment.

Synthesis of silver nanoparticles for remote opening of polyelectrolyte microcapsules.

Silver nanoparticles of 10, 18, and 23 nm were synthesized in aqueous medium by chemical reduction of silver nitrate in excess of sodium borohydride. Modification of polyelectrolyte shells with synthesized silver nanoparticles was performed using the layer-by-layer approach. Remote opening of the polyelectrolyte/silver capsules was performed with a CW Nd:YAG FD laser with an average incident power output up to 70 mW. Capsules with a mixture of 10 and 18 nm silver nanoparticles in its polyelectrolyte shell were ruptured after less than 7 s of laser irradiation, while microcapsules with 23 nm silver nanoparticles in the shell were broken after 11 s of laser treatment and 10 nm silver nanoparticles were broken after 26 s.