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Dr. Aleksandar Tomović

Dna translocations

Determination of genetic code embedded in DNA molecules is fundamental to molecular biology and medicine. Alternative, fast and low-cost methods for DNA sequencing are in high demand. We report on DNA translocations experiments through the solid state nanopores, a technique that has potential to meet those demands. We measured translocation of ?-DNA through 5 and 10 nm silicon nitride nanopores. DNA translocation is shown to result in the decrease in the ionic current. Possibility of using macro-fluidics and related sources of noise in such systems and ways of improving it were also studied.

Physical Vapor Deposition (PVD)

Physical Vapor Deposition by Knudsen cell is suitable for deposition of thin films of organic compounds. Most of these materials are solid at room temperature, and sublimate when they are heated. Our system consists of a vacuum chamber, which can be divided in two parts, both of them are equipped with Knudsen evaporators. In that way we can deposit two different materials simultaneously. Working pressure is 10-6 mbar if entire volume is pumped, while reducing the volume around only one Knudsen evaporator we can go down to 10-7mbar. Temperature of the evaporation boat can be controlled to precision of 1 °C and go up to 500 °C.

Films made by this method can have thickness gradient (image 1): we successfully made TPD and Pentacene thin films with different thicknesses usually around 100 nm in the thickest part of the film.


A custom spectrophotometer was made to measure absorption spectra. It is especialy suitable for thin organic films made by PVD, because of its capability to measure thickness at different parts of film. It consists of box with UV-Vis light sources and sample holder, spectrometer and CCD camera.


Raman spectroscopy

Our system for Raman spectroscopy is custom made and consist of He-Ne laser, sample holder with 3D movement capability, spectrometer and CCD camera (or/and PMT detector coupled with lock-in amplifier). The precision of our system is 5 cm-1, we study thin films, liquids and powders.

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