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ANNOTATION on the research


of Anna.V. Zatseva (Shishlova),
Ph.D. student (on the second year of the program)

Research title:
Formation and physicochemical properties investigation of ordered metal
nanostructures on the surface of polymer films.

Physics department of M.V. Lomonosov Moscow State University


Objectives:
Investigation of surface morphology, thermo-mechanical and optical
properties, as well as catalytic activity of the system: semiconductor
(dielectric) substrate - polymer film - ordered ensemble of metal
nanoparticles embedded in polymer surface layer.

Statement of work:
1. Scanning tunneling (STM) and atomic-force microscopy (AFM)
investigation of silicon substrates. Nanolithography and patterning on
silicon surfaces. Nanostructures surface morphology and optical
properties exploration.
2. Atomic-force microscopy study of the glassy polymer surface layers
mechanical and thermomechanical properties and AFM-based
nanoindentering.
3. Fabrication of model systems: semiconductor (dielectric) substrate -
polymer film - ordered ensemble of metal nanoparticles embedded in
polymer surface layer;
4. Surface morphology, catalytic activity and optical (Rayleigh
scattering, absorption) as well as non-linear optical (Raman
Scattering, Surface Enhanced Raman Scattering) properties
investigation of fabricated systems (see p. 3).
5. Evaluation of the fabricated systems (see p. 3) as prototypes of novel
type model catalysts and gas sensors.

Scientific novelty:
1. Induced oxidation of the silicon monocrystal surface and its
applicability for nanolithography was investigated. The role of
elastic interactions in tunnel contact was clarified and the
corresponding forces were estimated.
2. A novel original AFM-based method of glassy polymer surface layers
investigation was elaborated.
3. Using this method it was demonstrated for the first time that polymer
"surface" (Tg,s) and "bulk" (Tg,b) vitrifying temperature are
essentially different (Tg,s lower vitrifying temperature was measured.
4. A new method of metal nanoparticles stabilization in glassy polymer
surface layer was developed allowing formation of "two-dimensional"
ordered nanostructures.
5. Catalytic activity of fabricated nanostructures is being analyzed. A
new type catalytic coatings (economic, effective, simple-fabricated)
for heterogeneous catalysis and gas sensors are being developed.
6. Optical properties of the system: semiconductor (dielectric) substrate
- polymer film - ordered ensemble of metal nanoparticles embedded in
polymer surface layer is being investigated. Their applicability to
optical gas sensors development is under exploration.

Results obtained during the first year of post-graduate course:

. A novel original method of glassy polymer surface layer thermo-
mechanical properties investigation was elaborated.
(The method essence follows: monodisperse metal nanoparticles are
deposited from hydro- or organosols onto polymer film surface, the
system is annealed at temperatures close to the bulk polymer
vitrifying temperature, the depth of nanoparticles immersion into
the polymer surface layer after annealing is measured with the help
of atomic-force microscope; thus the temperature range is
determined in which only the thin surface layer of polymer is
devitrified.)
. Using this method it was demonstrated for the first time that the
polymer "surface" and "bulk" vitrifying temperatures are
essentially different (Tg,s . The influence of annealing conditions and chemical treatment (photo
oxidation by UV-irradiation) on thermo-mechanical properties of
polystyrene (PS) surface layer was investigated.
. The thickness of the layer with lower vitrifying temperature was
measured.
. The local mechanical polystyrene surface properties were
investigated by the novel AFM-based nanoindentation method. The PS
surface is proved to have viscoelastic properties.
. Systems consisting of silicon (glass) substrate - polymer (PS) film
- ordered ensemble of metal nanoparticles (Au, Ag, Pt) embedded in
polymer surface layer were fabricated and investigated by AFM.
Hydro- and organosols with different of particles stabilization
method were used. The possibility to create "two-dimensional"
densely packed ensemble of nanoparticles embedded in polystyrene
surface layer was demonstrated.
. The first model polystyrene-Pt catalysts were made. Their catalytic
properties investigation on test reactions was started. The
acceleration of some reducing reactions was already shown.
. The first samples for optical and non-linear optical investigations
are prepared.

RESEARCH PLAN ON YEAR 2002

1. Further Atomic-force microscopy (AFM) investigation of the sample
preparation conditions (way of polymer film deposition, metal used,
method of sol stabilization and its deposition on polymer surface,
annealing temperature and duration etc.) influence on the polymer
surface morphology (sizes of nanoparticles, distribution density and
immersion depth into polymer surface), as well as mechanical and
thermomechanical properties.
Polystyrene (PS), as well as polyvinylpyridine (PVP) films will be
used as matrix for nanoparticles. Along with sols containing Au, Ag
and Pt palladium sols will be used.

2. Catalytic activity investigation of systems polymer - metal
nanoparticles on different test reactions will be continued.
Correlation between reaction rate and sample surface morphology, metal-
catalyst used, nanoparticles sizes and distribution density will be
determined.
The effective model catalysts will be designed based on the evaluation
results of the sample systems.

3. Optical and non-linear optical properties of systems silicon or glass
substrate - polymer (PS, PVP) film - ordered ensemble of metal
nanoparticles (Ag, Pt) embedded in polymer surface layer will be
investigated:
а) The dependence of Rayleigh light scattering on the sample
preparation conditions, sizes and distribution density of used
nanoparticles will be studied.
The surface heterogeneity value obtained from optical data and from
direct atomic-force microscopy measurements will be compared.
б) The dependence of light absorption on the sample preparation
conditions, sizes and distribution density of used nanoparticles will
be investigated.
(Effects caused by plasmon resonance in metal nanoparticles are
expected to take place).
б) Raman Light Scattering will be studied.
(Effect of Surface Enhanced Raman Scattering (SERS) is expected to be
registered). The following systems will be explored:
. Silicon substrate + polyvinylpyridine (PVP) film + Ag
nanoparticles embedded in polymer surface layer;
. Silicon substrate + polymer (PS, PVP) film + Ag nanoparticles
embedded in polymer surface layer + adsorbed pyridine molecules.
The following researches will be conducted:
. The dependence of SERS signal intensity on excitation laser
wavelength.
. Dimensional effects exploration: the dependence of SERS signal
intensity on nanoparticles sizes and their distribution density
on the polymer surface.
. Developing of effective gas sensor prototype based on SERS-
effect.