Discovery of surface-enhanced Raman scattering (SERS) followed by evolution of optical systems and nanoengineering approaches has paved a path to detection of essential organic molecules on solid SERS-active substrates from solutions at concentrations attributed to single-molecule ones, i. e. below 10 À 15 M. However, in practical terms confident SERS-imaging of single molecules is still quite a challenge. In present work, we fabricated and comprehensively characterized tightly-packed 3D silver dendrites with prevalent chevron morphology that demonstrated ultrahigh sensitivity as SERS-active substrates resulted in 10 À 18 M detection limit. Using these substrates we achieved SERSimaging of single 5-thio-2-nitrobenzoic acid (TNB) molecule released from the attomolar-concentrated solution of of 5,5'dithio-bis-[2-nitrobenzoic acid] (DTNB), which is vital compound for chemical and biomedical analysis. In contrast to generally accepted belief about adsorption of only uniform monomolecular TNB layer on surface of silver nanostructures, we showed formation of a coating constituted by TNB layer and DTNB nanoclusters on the dendrites' surface at 10 À 6-10 À 12 M DTNB concentrations confirmed by presence/absence of disulfide bonds signature in the SERS-spectra and by scanning electron microscopy. DTNB concentrations below 10 À 14 M resulted in adsorption of TNB molecules in separated spots on the surface of silver nanostructures.
A single-step ultrasonic
method (20 kHz) is demonstrated for the
formation of acetylsalicylic acid-Fe3O4-graphene
oxide nanocomposites (∼80 nm) in aqueous solution. The electronic
molecular structure of these nanocomposites is stable in acidic or
basic aqueous medium. Coating of these nanocomposites with poly(vinyl
alcohol) (PVA) occurs through increased binding with drug, magnetite,
Fe(II)–C–O and carbonaceous network of graphene oxide.
PVA-coated-acetylsalicylic acid-Fe3O4-GO nanocomposites
substantially improve acetylation of pristine ascorbic acid than free
unmodified drug or uncoated acetylsalicylic acid-Fe3O4-GO nanoparticles because of enhanced electron density through
the presence of magnetite and graphene oxide, and specific binding
of PVA with drug and ascorbic acid.
In this study, we developed a filtering material for facial masks, which is capable of trapping and subsequent inactivation of bacteria under white light emitting diodes (LED) or sunlight irradiation. Such a functionality is achieved via the modification of the composite membrane based on porous polymer with photocatalytic (TiO2) and plasmonic (Ag) nanoparticles. The porous polymer is produced by means of a computer numerical control machine, which rolls a photoresist/thermoplastic mixture into a ~20-µm-thick membrane followed by its thermal/ultraviolet (UV) hardening and porosification. TiO2 nanoparticles are prepared by hydrothermal and sol-gel techniques. Colloidal synthesis is utilized to fabricate Ag nanoparticles. The TiO2 photocatalytic activity under UV excitation as well as a photothermal effect generated by plasmonic Ag nanoparticles subjected to LED irradiation are studied by the assessment of methylene blue (MB) decomposition. We demonstrate that, in contrast to the filter of the standard facial medical mask, the polymer membrane modified with spray-coated TiO2 and Ag nanoparticles prevents the penetration of bacillus subtilis from its top to bottom side and significantly inhibits bacterial growth when exposed to LED or sunlight.
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.
In this work, surface enhanced Raman scattering (SERS) spectra of aspirin and ibuprofen molecules adsorbed on the surface of silver nets sputtered on porous silicon were collected and analyzed. The bands in the SERS-spectra were correlated in accordance with the type of molecular vibration. Predominantly chemical adsorption of the indicated drugs on the SERS-active substrate through oxygen was observed. It was established that the Raman spectroscopy combined with the SERS-active silver nets makes it possible to detect the aspirin and ibuprofen at 10-6 M concentration.
A single-step
ultrasonic method (20 kHz) is demonstrated for the
complexation of acetylsalicylic acid (ASA)–ZnO–graphene
oxide (GO) nanoparticles with an average size of <70 nm in aqueous
solution. ASA–ZnO–GO more efficiently inhibits the growth
of probiotic Escherichia coli strain
M-17 and exhibits enhanced antioxidant properties than free ASA and
ASA–ZnO in neutralization of hydroxyl radicals in the electro-Fenton
process. This improved function of ASA in the ASA–ZnO–GO
can be attributed to the well-defined cone-shaped morphology, the
surface structure containing hydroxyl and carboxylate groups of ZnO–GO
nanoparticles, which facilitated the complexation with ASA.
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