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Photophysics of nanomaterials (for renewable energy)

Among the physical deposition methods of preparation of thin layers (called physical vapour deposition - PVD) in our department we use a PLVD (pulsed laser vapour deposition) technique based on the use of ablation of the material under influence of pulsed laser beam. This technique is particularly useful for research purposes, because of possible selection and control of the experimental conditions and process parameters in a wide range. Selectable process parameters are: substrate temperature, base pressure, the intensity of the vapour stream (system geometry, the distance the substrate from vapour source, the rate of evaporation), the energy of the vapour stream (depending on the density of pulse energy, laser wavelength and pulse rate), the type of material used pair production (solid or powder/nanopowder pressed), and type and pressure of buffer gas.

Obtained nanoporous layers with the new surface properties and controlled porosity can be applied in various fields of production, e.g. for the production of surface hydrophobic, hydrophilic, catalytic and photocatalytic.

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The pressure dependence of the anatase (A) and rutile (R) Raman band intensities
for the pressure range of 5.4×10-4 < p < 1.2×10-2 hPa

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The XRD spectra of the TiO2 films deposited at pressure 1.2x10-2 and 1.6x10-3 hPa;
A, R and Si correspond to the anatase, rutile and silicon peak intensities

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The SEM image of the sample deposited at 4.6x10-3 hPa (a),
and EDX line scan of Ti by cross-section of the sample (b)

In our laboratory we also study the particle size distribution, morphology and optical properties of the Au nanoparticle structures in dependence on their preparation conditions. The structures are produced from thin Au films sputtered on SiO2 glass substrate and annealed with several pulses of laser radiation. The SEM inspection reveals nearly homogeneously distributed, spherical gold particles. From peak intensities of the Raman spectra recorded for Rhodamine 6G in the range of 300 – 1800 cm-1 it is confirmed that the obtained structures are suitable for SERS (surface enhanced raman spectroscopy) measurements and sensing.

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SEM images of Au nanoparticles obtained for the films of a thickness of d ~ 10nm, irradiated with (a) 5,
and (b) 10 laser pulses at 266 nm and fixed fluence of 100 mJ/cm2

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Comparison between the Raman spectra of R6G deposited on:
glass- NR, (a) - Au non-structured film,
and (b), (c) - gold nanoparticle structures; samples excited at λ = 785 nm

 

Laboratory - Stand for spectroscopic and ablation studies

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