Eugenia has recently finished her Ph.D. and got a postoctoral
position in the group. Her research interests include
fundamentals of polyelectrolyte interactions with surfaces,
fabrication of responsive polyelectrolyte films and their
structural and compositional characterization with in situ
ATR-FTIR and neutron reflectivity.
Responsive films/hydrogels of polyelectrolyte multilayers,
synthesis of block copolymers, responsive polymeric micelles,
inclusion of functional molecules within multilayers
My research activities include designing of polymer coated
surfaces with controlled protein adsorption, synthesis of
silver nanoparticles to be used as substrates for
surface-enhanced raman spectroscopy (SERS) and SERS-based
detection of biomolecules.
Yun Han
Ph.D. Student
Email: yhan @ stevens.edu
Co-Advisors: Henry Du (CBME) and Svetlana Sukhishvili (CCB)
My research is focused on nano/micro core-shell particles
synthesis and surface modification for Surface Enhanced Raman
Scattering based chemical sensing.
My research includes chemical modification of surfaces; design
and synthesis of pH-, salt-, temperature-, magnetic
field-responsive layer-by-layer films and capsules which can
be used for encapsulation and release of functional molecules.
Her projects are related to chemical modification of hydrogel
films and capsules to render them useful under wider pH conditions.
Jessica (Siliu) Tan
Ph.D. Student
Email: stan @ stevens.edu
Co-Advisors: Henry Du (CBME) and Svetlana Sukhishvili (CCB)
My project is to establish effective strategies for and an
understanding of immobilization of uniform Au and Ag
nanostructures in the cladding air holes along the fiber
length of PCFs (Photonic crystal fibers), which could be
developed for rapid and reliable sensing of chemical and
biological warfare agents and explosives based on SERS
(surface enhanced Raman scattering).
Synthesis of co-polymers and search for synthetic approaches
to design polymers applicable for creating new drug carriers.
INSTRUMENTATION
FTIR-ATR
Fourier transform infra-red spectroscopy (FT-IR) is a prime tool
for the in situ analysis of chemical composition, charge
densities, and precise amounts of substances under study. An
absorbance peak in IR region might be exactly attributed to the
chemical bond responsible for the extinction of light at a given
wavelength. Equinox-55 is the elaborate FT-IR setup from Bruker
Optics which is working in the attenuated total reflection mode
(ATR). Multiple reflections of a light beam at the crystal
interface allow accumulation of signal so that even a single
monolayer adsorbed might be characterized. This setup is
equipped with a thermo stabilized flowthrough liquid cell from
Harrick Scientific. This ensures that polymer multilayer
structure growth might be constantly monitored and the
compositional response to the change of environment is recorded.
FCS
Fluorescent Correlaton Spectroscopy (FCS) allows us to measure
the concentration, the diffusion coefficient, and the dynamics
of different processes of fluorescent species in solution and on
surfaces. The advantages of FCS are its extreme sensitivity even
at nanomolar concentration and wide range of times scales. This
home-built setup is designed to work with the most popular
fluorescent dyes which are excited in a green wavelength
range. Dye molecules must be covalently attached to the
molecules under study. The measurement takes just a few minutes
and might be done with a single droplet of sample
solution. Single molecule sensitivity and the simplicity of the
correlated data analysis make FCS one of the most useful tools
for studying of polymer dynamics.
Ellipsometry
Phase-modulated ellipsometry is an advanced technique designed
to measure the thickness and the refraction coefficient of thin
films deposited on various flat surfaces. In contrast with other
ellipsometric methods, the high-frequency phase-modulation of
the incident laser beam allows measurement of fast changes of
thickness in 1ms. For most dry samples the precision of
measurement is less than 1 Ångström. This home-built
setup is equipped with a cylindrical liquid cell which is used
to measure film thickness in situ and vary the properties of the
solvent. Depending on the nature of the film and its thickness,
it is possibile to reconstruct the refraction coefficient and
the thickness simultaneously. Extensive data analysis allows
measurement of multilayered films as well.
HPLC
High pressure liquid chromatography (HPLC) is the method of
separation and purification of chemical compounds dissolved in
various mixtures of aqueous and organic solvents. The main
principle of the separation is the different affinity of
chemicals under study to the stationary phase which results in
different times every component takes to come through the
separation column. The solution is pumped through the column at
high pressure and after separation every single compound is
detected by UV-absorption, refractive index change, light
scattering, or fluorescent detection. The HPLC setup from Waters
is a flexible instrument comprising several units, each of them
is easily interchangeable and upgradeable. Gel permeation
chromatography (GPC) columns are mostly used for polymer
fractionation and purification.
