Supporting Information
Experimental.
S.1 Silica particles from formic acid and TMOS (0.01M)
TMOS (0.015 g, 0.1 mmol) was dissolved in a mixture of anhydrous toluene:
tetrahydrofuran (THF) (4:1) such that the final solution was approximately 5 mL in
volume. A second 5 mL solution was prepared by adding formic acid (0.015 mL, 0.4
mmol) to anhydrous toluene:THF (4:1). The two solutions were combined (10 mL total
volume) and mixed for 30 s then left without stirring for 24 h after which time the
opalescent suspension of particles was observed. The resulting particles were isolated by
centrifugation (3 times, 6000 rpm) with THF washes (0.006 g, yield = 106%).
S.2 Silica particles from formic acid and TMOS (0.05M)
TMOS (0.075 g, 0.5 mmol) was dissolved in a mixture of anhydrous toluene:
tetrahydrofuran (THF) (4:1) such that the final solution was approximately 5 mL in
volume. A second 5 mL solution was prepared by adding formic acid (75L, 2.0 mmol)
to anhydrous toluene:THF (4:1). The two solutions were combined (10 mL total volume)
and mixed for 30 s then left without stirring for 24 h after which time the opalescent
suspension of particles was observed.
The resulting particles were isolated by
centrifugation (3 times, 6000 rpm) with THF washes (0.033 g, yield = 112%).
S.3 Silica particles from formic acid and TMOS (0.1M)
TMOS (0.152 g, 1.0 mmol) was dissolved in a mixture of anhydrous toluene:
tetrahydrofuran (THF) (4:1) such that the final solution was approximately 5 mL in
volume. A second 5 mL solution was prepared by adding formic acid (150L, 4 mmol)
to anhydrous toluene:THF (4:1). The two solutions were combined (10 mL total volume)
and mixed for 30 s then left without stirring for 24 h after which time the opalescent
suspension of particles was observed.
The resulting particles were isolated by
centrifugation (3 times, 6000 rpm) with THF washes (0.0610 g, yield 106%).
S.4 Silica particles from formic acid and TMOS (1M)
Tetramethoxysilane (1.52 g, 10 mmoles) and diluted with anhydrous toluene bringing the
total volume to 5 mL. A second solution containing formic acid (1.49 mL, 80 mmol) was
diluted to 5 mL with anhydrous toluene. The molar ratio of monomer to formic acid to
toluene for the preparation of silica particles was 2:8:3.8. The two solutions were poured
into a scintillation vial, the volume adjusted to 10 mL then vigorously mixed for 30 s.
The solution was left without stirring for 24 h when it was noticed to have phase
separated into an translucent, opalescent gel composed of particles. The solid was
isolated by centrifugation (3 times, 6000 rpm) with THF washes. After centrifugation and
drying, a fine white powder was obtained (0.632 g, yield = 105%).
S.5 Silica particles from formic acid and TMOS (1.5M)
Tetramethoxysilane (2.28 g, 15 mmol) and diluted with anhydrous toluene bringing the
total volume to 5 mL. A second solution containing formic acid (2.76, 60 mmol) was
diluted to 5 mL with anhydrous toluene. The molar ratio of monomer to formic acid to
toluene for the preparation of silica particles was 2:8:3.8. The two solutions were poured
into a scintillation vial, the volume adjusted to 10 mL then vigorously mixed for 30 s.
The solution was left without stirring for 24 h when it was noticed to have phase
separated into an translucent, opalescent gel composed of particles. The solid was
isolated by centrifugation (3 times, 6000 rpm) with THF washes. After centrifugation and
drying, a fine white powder was obtained (0.979 g, yield = 109% based on SiO2).
S.6 Silica particles from formic acid and TMOS (2M)
Tetramethoxysilane (3.04 g, 2.97 mL, 19.7 mmoles) and diluted with anhydrous toluene
bringing the total volume to 5 mL. A second solution containing formic acid (3.68 g,
2.98 mL, 80 mmoles) was diluted to 5 mL with anhydrous toluene. The molar ratio of
monomer to formic acid to toluene for the preparation of silica particles was 2:8:3.8.
The two solutions were poured into a scintillation vial, the volume adjusted to 10 mL
then vigorously mixed for 30 s. The solution was left without stirring for 24 h when it
was noticed to have phase separated into an translucent, opalescent gel composed of
particles. The solid was isolated by centrifugation (3 times, 6000 rpm) with THF washes.
After centrifugation and drying, a fine white powder was obtained (1.33 g, yield = 111%
29
based on fully condensed silica). Si CP MAS-NMR (100 MHz) δ -93 (Q2), -100 (Q3) 111 (Q4); IR (KBr) 3432, 1651, 1127, 931, 808, 595 cm-1; Hydrodynamic diameter =
2435 ± 204 nm; No stirring: Surface area = 539 m2/g; Pore diameter = 0.5 nm. Stirring
at 200 rpm: Surface area = 829 m2/g; Pore diameter = 0.6 nm.
Surface area = 408 m2/g; Pore diameter = 0.5 nm.
Stirring at 1000 rpm:
S.7 Methyltrimethoxysilane (1M) with formic acid
MTMS (1.78g, 0.01 moles), dissolved in 5mL anhydrous toluene, was mixed with
anhydrous formic acid (1.38 g, 0.03 moles) in 5 ml toluene.
As with the reaction at
lower concentration, phase separation of a liquid phase was observed and no particles
were obtained.
Figure S1. Solid state Si-29 CP MAS NMR spectrum of silica particles made from
TMOS and formic acid.
- 80
- 90
- 100
- 110
- 120
ppm
Figure S2. Silica precipitate from reaction of TEOS and formic acid in toluene/THF.