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 10⁵ with higher values from 10⁹ to 10¹¹ 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 10⁷. 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 (<i>e.g.</i>, phenylketonuria, tyrosinaemia type II and tyrosinosis)

Fenton-Hydroxyl Radical Antioxidant Efficiency of Ibuprofen-Fe₃O₄‑GO Nanospheres

A feasible one-step “solvent-antisolvent” oil-free acoustic emulsification method is demonstrated for the complexation of pristine ibuprofen with Fe3O4-GO in the form of nanospheres with a core–shell structure (∼50 nm). The ultrasonic complexation occurs via the H-bond formation with the ibuprofen side chains (CH, CH2, and CH3) and C–O–H involving the interaction of carboxylic groups and Fe–O bonds. Synthesized ibuprofen-Fe3O4-GO nanospheres are efficient antioxidants with hydroxyl radical (·OH) scavenging and iron inactivation properties in the electro-Fenton process exhibiting ∼24 times higher diminishing rate than free ibuprofen per se and ∼161 times higher than pristine ibuprofen nanoparticles in aqueous medium. This pronounced antioxidant efficiency of ibuprofen-Fe3O4-GO nanospheres is due to the increased concentration of inactive protonated Fe(II) centers in Fe–O, C–Fe, and CO–Fe bonds (FeO+, CFe+, and COFe+) of complexed drug molecules and increased concentration of CHO2+, OH+, and CO+ ions on the surface of nanospheres. The demonstrated method discloses the conditions of enhanced antioxidant efficiency of ibuprofen and defines the roles of Fe3O4 and GO in two basic fundamental COX-independent mechanisms

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

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 Er₂O₃ in the bulk with (ii) hexagonal and (iii) spherical geometries. Each type of ultrasonically formed nanoparticle reveals Er³⁺ 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 (⁴S_3/2–⁴I_15/2), which is not observed for spherical nanoparticles. Our work is unique because it combines for the first time spectroscopy of Er³⁺ 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