Nuclear magnetic resonance study of borate- polyborate equilibria in aqueous solution

Colorimetric Humidity Sensor Based on Liquid Composite Materials for the Monitoring of Food and Pharmaceuticals

“…Since during the course of the reaction orthoborate concentrations rise (at ~850 cm -1 ), -OH containing groups were attributed to said borate species and considered to be responsible for the changes in bonding environment arising from the aging process. Increases in pH of the solution from about 7.5 to 9 were measured in the course of sensing material aging (from day 1 to day 9), which is in agreement with the formation of polyborates during the course of aging 29 . Distribution of borates species (mainly B(OH) 3 It is important to note that the aging of the sensing solution not only brings chemical changes, but also significant changes in physical properties.…”

“…This specific type of shift has been reported to be characteristic of very polar bonding environments in aqueous systems [25][26] . In addition, Figure 1A shows that the characteristic peaks of sodium borohydride diminished at 1105 cm -1 , 2220 cm -1 , and 2275 cm -1 , and new peaks appeared between 1800 cm -1 -2300 cm -1 , indicating the presence of the hydrogen-bridged boron structures of diborane [27][28][29][30][31] .…”

“…In simple aqueous systems, borate ion solutions can contain over a dozen components, since the composition depends on temperature, pH, concentration of species, and counter-ions [28][29][30]32 . The aqueous borate solution is then coated on silica gel and dehydrated.…”

Amineborane Based Chemical Hydrogen Storage - Final Report

“…A similar induction period was previously observed for NaBH 4 catalyzed by Ru supported on carbon (2-wt% Ru). 97 [98][99][100] With more concentrated solutions of 1 (Figure 6.6b (4.9-wt%) and 6.6c (22.7-wt%)), the signals for the condensed-borates B 3 O 3 (OH) 4 ! and B 5 O 6 (OH) 4 !…”

“…were dominant. [98][99][100] Thus, although the 5-wt% Rh/Al 2 O 3 showed extended catalytic activity for the hydrolysis of the diluted solution of 1, more concentrated solutions will probably not exhibit such extended activity because the borates will precipitate from the solutions and coat the catalyst surface. Similar to the results previously observed for the catalyzed NaBH 4 80,97,101 and NH 3 BH 3 83,85 hydrolysis reactions, the H 2 -release rate appeared to be independent of the concentration of 1 with, for example, identical rates observed for 4.9-wt% and 22.7-wt% solutions of 1 with 5-wt% Rh/Al 2 O 3 (1.1 mol% Rh).…”