Gun'ko V M, Turov V V, Myronyuk I F, Goncharuk O V, Pakhlov E M, Bezruka N A, Skwarek E, Janusz W, Blitz J P
Chuiko Institute of Surface Chemistry, 17 General Naumov Street, 03164 Kyiv, Ukraine.
Chuiko Institute of Surface Chemistry, 17 General Naumov Street, 03164 Kyiv, Ukraine.
J Colloid Interface Sci. 2014 Nov 15;434:28-39. doi: 10.1016/j.jcis.2014.08.008. Epub 2014 Aug 14.
Unmodified pyrogenic silica PS300 and partially silylated nanosilica samples at a degree of substitution of surface silanols by trimethylsilyl (TMS) groups Θ(TMS)=27.2% and 37.2% were studied to elucidate features of the interfacial behavior of water adsorbed alone, or co-adsorbed with methane, hydrogen, or trifluoroacetic acid (TFAA). In the aqueous suspension modified PS300 at Θ(TMS)=37.2% forms aggregates of 50-200 nm in size and can bind significant amounts of water (up to ∼5 g/g). Only 0.5 g/g of this water is strongly bound, while the major fraction of water is weakly bound. The presence of surface TMS groups causes the appearance of weakly associated water (WAW) at the interfaces. The adsorption of methane and hydrogen onto TMS-nanosilica with pre-adsorbed water (hydration degree h=0.05 or 0.005 g/g) increases with increasing temperature. In weakly polar CDCl3 medium, interfacial water exists in strongly (SAW, chemical shift δ(H)=4-5 ppm) and weakly (δ(H)=1-2 ppm) associated states, as well as strongly (changes in the Gibbs free energy -ΔG>0.5-0.8 kJ/mol) and weakly (-ΔG<0.5-0.8 kJ/mol) bound states. WAW does not dissolve TFAA but some fraction of SAW bound to TMS-nanosilica surface can dissolve TFAA.
研究了未改性的热解硅石PS300以及三甲基硅烷基（TMS）基团对表面硅醇的取代度分别为27.2%和37.2%的部分硅烷化纳米硅石样品，以阐明单独吸附的水或与甲烷、氢气或三氟乙酸（TFAA）共吸附的水的界面行为特征。在水悬浮液中，取代度为37.2%的改性PS300形成尺寸为50 - 200 nm的聚集体，并且能够结合大量的水（高达约5 g/g）。其中只有0.5 g/g的水是强结合的，而大部分水是弱结合的。表面TMS基团的存在导致在界面处出现弱缔合水（WAW）。甲烷和氢气在预吸附水（水合度h = 0.05或0.005 g/g）的TMS - 纳米硅石上的吸附随温度升高而增加。在弱极性的CDCl3介质中，界面水以强（SAW，化学位移δ(H)=4 - 5 ppm）和弱（δ(H)=1 - 2 ppm）缔合状态存在，以及强（吉布斯自由能变化-ΔG>0.5 - 0.8 kJ/mol）和弱（-ΔG<0.5 - 0.8 kJ/mol）结合状态存在。WAW不溶解TFAA，但与TMS - 纳米硅石表面结合的部分SAW可以溶解TFAA。
