Molecular ruler based on concurrent measurements of enhanced Raman scattering and fluorescence.

We report a way to assess the separation between a molecule and a metal surface on account of both Raman scattering and fluorescence intensities measured simultaneously. This approach has no need for an accurate quantity of molecules and bears 1 nm resolution. Its distance sensitivity is experimentally demonstrated in the case of dye molecules lying on a gold surface with a polymer spacer layer in between and is compared with theoretical prediction.

An approach to conductometric immunosensor based on phthalocyanine thin film.

A new approach to conductometric biosensors utilizing iodine-sensitive phthalocyanine thin films has been proposed. The excellent sensitivity of the tetra-tert-butyl copper phthalocyanine (ttb-CuPc) to free iodine was used for the first time to detect a peroxidase-initiated reaction in an aqueous medium. To minimize the interfering effect of aqueous electrolytes on the impedance responses of the ttb-CuPc film itself, Au/Cr interdigitated planar electrodes bearing ttb-CuPc thin films were protected with hydrophobic gas-permeable membranes, namely thermally evaporated calixarene or plasma polymerized hexamethyldisiloxane films. Impedance spectroscopy data were analyzed in order to define the optimal operating frequency. An enzyme sensor with peroxidase immobilized in a cross-linked albumin matrix was tested. Its impedance responses were studied under variation of the substrate concentration, pH, ionic strength and buffer capacity. These results were used to define conditions for peroxidase-linked immunoassay in subsequent tests. With the developed sensor, concentrations of IgG in 0.2-2 micrograms/ml range were measured in a competitive mode with satisfactory accuracy. The detection of IgG in both test solutions and blood serum samples has been demonstrated.