Polarizability of DNA Block Copolymer Nanoparticles Observed by Electrostatic Force Microscopy

In this study, DNA block copolymer (DBC) micelles with a polystyrene (PS) core and a single‐stranded (ss) DNA shell were doped with ferrocene (Fc) molecules. Tapping mode atomic force microscopy (AFM) was used to study the morphology of the doped and undoped block copolymer aggregates. We show that introducing Fc molecules into the hydrophobic core does not affect the structural properties such as shape or size. In contrast, doping with Fc significantly changes the micelles' electrical properties, namely their polarizability. Electrostatic force microscopy (EFM) measurements reveal that the undoped micelles show no significant polarization signal, while the Fc‐doped aggregates exhibit strongly enhanced polarizability. Furthermore, the nucleic acid moieties were utilized in combination with complementary ssDNA strands to assemble single particles into linear arrays of DBC nanoobjects. The ability to tune the electrostatic properties of the polymer core and the presence of nucleic acids might open the way for using these bioorganic nanoparticles as building blocks for nanoelectronic or biosensing devices.

     

Fluorescence Spectroscopy Study of Polyoxyethylene Surfactant Micellar Systems

The systems investigated by fluorescence spectroscopy and atomic force microscopy were water/ethoxylated mono, di-glyceride/oil + ethanol. The oils were R (+)-limonene and isopropylmyristate. The mixing ratio (w/w) of ethanol/oil equals unity. The fluorescent probes auramine-O and 8-anilino-1-naphthalenesulfonic acid were used to determine the minimum ω′ value for the transition of reverse micelles to microemulsions in the systems based on the two oils, as well as at different surfactant contents. The fluorescence quenching of Safranine-T (3,6-diamino-2,7-dimethyl-5 phenyl phenazinium chloride) by the inorganic ions Fe²⁺, Fe³⁺ and Cu²⁺ was studied in reverse micelles and microemulsions. The Stern–Volmer quenching constants at different water/surfactant molar ratios (ω values) were calculated from the data of the quenching process. Atomic force microscopy was used to image the systems based on the two oils for different water to surfactant molar ratios below and above the minimum ω′ value.     

Transition from Micelles to Microemulsions in Sugar-Based Surfactant Systems Probed by Fluorescence Spectroscopy and Atomic Force Microscopy

The systems investigated by fluorescence spectroscopy and atomic force microscopy were water/sucrose laurate/oil + ethanol. The oils were R (+)-limonene and isopropylmyristate. The mixing ratio (w/w) of ethanol/oil equals unity. The fluorescent probes auramine-O and 8-anilino-1-naphthalenesulfonic acid were used to determine the minimum ω′ value for the transition of reverse micelles to microemulsions in the systems based on the two oils, as well as at different surfactant contents. The fluorescence quenching of Safranine-T (3, 6-diamino-2,7-dimethyl-5 phenyl phenazinium chloride) by the inorganic ions Fe²⁺, Fe³⁺, and Cu²⁺ was studied in reverse micelles and microemulsions. The Stern-Volmer quenching constants at different water/surfactant molar ratios (ω values) were calculated from the data of the quenching process. Atomic force microscopy was used to image the systems based on the two oils for different water to surfactant molar ratios below and above the minimum ω′ value.