General Physics Institute Russian Academy of Sciences A.M. Prokhorov General Physics Institute Russian Academy of Sciences 119991, Moscow, Vavilov Str., 38 Non-invasive laser diagnostics of swelling Nafion in water and aqueous solutions of salts Nikolai Bunkin

Motivation of the study (1) RSO3H + Н2О  RSO3- + H3О+ EXCLUSION ZONE G.H. Pollack, The Fourth Phase of Water; Ebner and Sons Publishers: Seattle, WA, USA, 2013.

ABSORPTION COEFFICIENT OF NAFION AND WATER Optical density, arb. units lum = 460 - 650 nm Wavelength, nm

EXPERIMENT WITH LUMINESCENCE SPECTROSCOPY N.F. Bunkin, V.S. Gorelik, V.A. Kozlov, A.V. Shkirin, and N.V. Suyazov, Colloidal Crystal Formation at the “Nafion−Water” Interface, J. Phys. Chem. B, 118, 3372−3377, 2014. λ = 376 nm, Δλ = 3 nm,  = 50 m, NA = sin  = 0.3   = 17; h = 4 mm

LUMINESCENCE SPECTRUM OF DRY NAFION PLATE SHIFT BETWEEN TWO SUBSEQUENT SPECTROGRAMS is 25 m LUMINESCENCE SPECTRUM OF NAFION PLATE SWOLLEN IN LIGHT AND HEAVY WATER WITHIN 1 Hr

LUMINESCENCE SPECTRUM OF COLLOID SUSPENSION OF 100 nm NAFION PARTICLES IN LIGHT WATER

DYNAMICS OF SWELLING NAFION IN LIGHT AND HEAVY WATER; SPECTRAL INTENSITY OF LUMINESCENCE AT  = 508 nm vs. TIME Nafion plate Colloid suspension of 100 nm Nafion particles

3 hrs after start of swelling – luminescence is absent IMPORTANT CONCLUSION: ABSENCE OF THE LUMINESCENCE DOES NOT MEAN THE ABSENCE OF NAFION IN LIQUID 3 hrs after start of swelling – luminescence is absent

INITIALLY SWOLLEN NAFION AFTER COMPARISON BETWEEN DRY AND SWOLLEN NAFION,  = 508 nm Dry Nafion  = 508 nm Nafion after soaking within 3 hrs INITIALLY SWOLLEN NAFION AFTER DRYING WITHIN 48 hrs

PROCESSING OF DATA FOR NAFION, SWOLLEN IN ORDINARY WATER FOR 1 hr; LUMINESCENCE INTENSITY AT  = 508 nm

1 Hr SWELLING OF NAFION IN AQUEOUS SOLUTIONS NaCl and KCl,  = 508 nm

1 Hr SWELLING OF NAFION IN AQUEOUS SOLUTIONS CsCl and LiCl,  = 508 nm

DISTRIBUTION OF ELECTROSTATIC POTENTIAL IN AQUEOUS SOLUTIONS OF NaCl and KCl

DISTRIBUTION OF BULK CHARGE DENSITY in AQUEOUS NaCl and KCl SOLUTIONS L >> L0 Lc L0 KCl Lc

The emergence of specific ionic effects when interacting Nafion with aqueous solutions of NaCl and KCl NaCl I(x) ~ (x),  = 508 nm KCl   Lc

REFRACTIVE INDEX ANISOTROPY; QUASI-CRYSTALLINE STRUCTURE? Nafion C = 0.01 M NaCl X = L0  40 m 175 m  = 532 nm

FORMATION OF PHOTONIC CRYSTAL CLOSE TO NAFION INTERFACE Z

 = 270 nm  a = /2 = 135 nm

EXTRACELLULAR MATRIX Fig. 6.3 from “The Machinery of Life”, David S. Goodsell, Springer New York, 2009 5 nm Green color - a lipid bilayer of membrane. Twisted fibers – glycocalyx.

UV irradiation of dry and swollen plate of Nafion results in the luminescence in the visible range. If Nafion is swollen in light water, the luminescence sources are located not only on the Nafion interface, but in the bulk of liquid. That is due to disentangling of polymeric fibers from the Nafion surface toward the liquid. Luminescence is terminated after 1.5 – 2 hr of soaking; as was shown in experiments with the colloidal suspension of Nafion particles, despite the absence of luminescence, the Nafion particles still remain in the bulk of liquid. After drying the plates of Nafion, the effect of luminescence is completely restored. In case of swelling Nafion plate in heavy water, the effect of unwinding the polymeric fibers is no longer observed. The density distribution of Nafion particles in the bulk of water has a gradient-like behavior; the scale of the gradient area coincides with the EZ size. Thus, the Nafion particles should contribute to the formation of EZ close to the Nafion surface. The regimes of swelling Nafion are different for aqueous solutions of Na+ and K+ ions: for high ionic concentrations the disentangled fibers prevent the penetration of ions Na+ into the membrane, but promote the penetration of K+ ions.

OUR TEAM N.F. Bunkin, professor in physics, team leader M.E. Astashev, PHD in biology V.A. Kozlov, post-graduate student in physics S.V. Gudkov, professor in biology

Thank you

SPECIFIC EFFECTS OF CATIONS ARE NOT DUE TO QUENCHING OF LUMINESCENCE

PROCESSING OF EXPERIMENTAL DATA FOR DRY NAFION; LUMINESCENCE INTENSITY AT  = 508 nm (x) is Heaviside function d = 175 m, а = 100 m