Vitrified Liquid Water : a Comparison with Vapor Deposited Amorphous Solid Water

A new method for the vitrification of pure liquid water anddilute aqueous solutions is described which works as the only one without liquidcryomedium for heat transfer : rapid rooling of aqueous aerosol droplets on a solidcryoplate (1). The method can be applied in diverse fields such as cryobiology,crymicrosco~and low temperature spectroscopy of water and aqueous solutions orsuspensions to avoid the formation of crystalline ice during quenching to cryogenictemperatures, the elimination of a liquid crymedium being particularly helpful forin situ spectroscopic investigations.Until now vitrified liquid water prepared by this method has been investigated byinfrared spectroscopy (2) and by differential thermdL analysis (DTA)(3), and itsproperties compared with those of vapor deposited amorphous solid water, H@(as). Acomparison of infrared spectra shows two differences : first, in the vitrifiedaerosol the peak maximum of the decoupled 0-D stretching transition at 20 K is atlower wavenumkrs, at 2416 cm-l, whereas in H@(as) it is at 2440 an-l. Second, inthe coupled 0-H stretching band region of vitrified liquid water ,an additionalshoulder is observed at approximately 3120 cm-l. These spectrdareprobably related to structural differences, implying that the amorphous forms ofwater made from the liquid and the vapor have different structures.The devitrification of quenched aerosol droplets as observed by DTA occurs in twosteps, with peak maximum temperatures of 150 and 156 K. This stepwisedevitr ification has been observed previously for samples quenched in liquidcryamedium by high-pressure jet-freezing (4). To my knowledge water is the onlyvitrified pure liquid with this behaviour. The two exotherms are interpreted interms oftwo fractions of vitrified liquid water formed in the cooling process withdifferent properties, which devitrify during reheating at slightly differenttemperatures, and this interpretation is related to the anomdlous properties ofsupercooled liquid water. A comparison with the devitrification of H20(as)establishes a further difference, because H2O (as) prepared this way devitr ifies asexpected in one step, the DTA curve showing only one exotherm.References(1) Mayer, E., J. Appl. Phys., 2, (1985), 663.(2)-Mayer,E., J. Appl. Phys., 86, (1985), 3474.(3) Mayer, E., J. Microsc., in press(4) Mayer, E. and Briiggeller, P., J. Phys. Chem., 87, (1983), 4744.