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Progress in Understanding Fluids in Mesopores

• Introduction to the phenomenon
• Theoretical
• shortcomings of standard thermodynamics for
  confined systems
• new concept
• Applications
• control of negative pressure (static, dynamic)
• molecular
  conformation, reaction rate, solvent properties,
  separation
• bioanalytics

Harald Morgner Wilhelm Ostwald Institute for
Physical and Theoretical Chemistry Leipzig
University, Linnéstrasse 2, D-04103 Leipzig,
hmorgner_at_rz.uni-leipzig.de
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Introduction Theoretical
Applications behavior of
fluids in mesopores

• natural phenomena
• hydrology of ground water
• natural purification and pollution
• industrial activities
• oil extraction
• mixture separation, filtering
• catalysis
• sensor development
• basic research
• bioanalytics

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Introduction Theoretical
Applications adsorption from
vapor phase
Adsorption Hysteresis in Porous Material
SBA-15 silica pores with two open ends narrow
pore size distribution
R.Rockmann PhD Thesis 2007 U Leipzig
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Introduction Theoretical
Applications adsorption from
vapor phase
Adsorption Hysteresis in Porous Material
H.Morgner 2010 J.Phys.Chem.C in press
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Introduction Theoretical
Applications computer
simulation
shape of pore isotherm of pores with two open
ends crossing of grand potential curves
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Introduction Theoretical
Applications shortcomings
of TD

• observations
• switching points decoupled from grand potential
  crossing
• switching points reproducibly stable in
  experiment and simulation
• metastable states are stable in simulation and
  in experiment for any trial time (up to gt 6
  weeks)

grand potential
shape of pore isotherm of pores with two open
ends crossing of grand potential curves
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Introduction Theoretical
Applications new concept,
confined TD
grand canonical boundary conditions
canonical boundary conditions
COS and concept of applying canonical boundary
conditions COS allow to retrieve isotherm
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Pore with bottom
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Pore with bottom, constant radius
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Introduction Theoretical
Applications new concept,
confined TD
Pore with bottom, narrow mouth
curves of states (COS)
homogeneous volume 3nm x31nm expanded
liquid ?neg. pressure, Plt -100 bar
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Introduction Theoretical
Applications
control of negative pressure

• negative pressure exerts pull onto embedded
  molecule
• negative pressure is known for macroscopic
  systems, but metastable
  (e.g. A. R. Imre On the existence of
  negative pressure states, Phys. Stat. Sol. (b)
  244 (2007) 893-9)
• in the nanoworld negative pressure states are
  stable and can be controlled, homogeneous
  negative pressure is taken on in volumes large
  enough to handle big (bio-)molecules
• for comparison positive pressure of 80bar turns
  CO2 into polar solvent!
• what can -140bar do to influence molecular
  properties?
• molecular conformation
• reaction rate (large reaction volume)
• solvent properties
• separation of mixtures by inducing phase
  separation at neg. pressure Indirect
  methods to study liquid-liquid miscibility in
  binary liquids under negative pressure
  Imre, Attila R. et al. NATO Science Series,
  II Mathematics, Physics and Chemistry  (2007),
  242 (Soft Matter under Exogenic
  Impacts), 389-398

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Introduction Theoretical
Applications
negative pressure in stationary
flow?
for high throughput continuous flow of solvent
desirable can situation of negative pressure
exist under stationary flow? the answer
requires the ability to handle a velocity field
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Introduction Theoretical
Applications generalized
diffusion
Transport of Matter
Common Treatment of Diffusion and Convection by
generalized Diffusion
single component
only one common driving force
binary system
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Introduction Theoretical
Applications
negative pressure in stationary
flow
the answer negative pressure can be held up
under stationary flow!
v0.018cm/s gt residence
time in 100nm pore is 500?s
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Introduction Theoretical
Applications


Bioanalytics
Simulation ejection of nanodroplet from mesopore
t1.21ms vol?610-21l