Silver Nitrate/Oligo(ethylene Oxide) Surfactant/Mesoporous Silica Nanocomposite Films and Monoliths

Abstract

A lyotropic, liquid crystalline (LC) phase of a silver nitrate/ oligo(ethylene oxide), water, and acid mixture was used for onepot synthesis of mesoporous silica materials in which Ag + ions are uniformly distributed. We established that the AgNO 3 -to-surfactant mole ratio is very important in a 50 wt% surfactant/water system to preserve the hexagonal LC phase before and after the addition of the silica source. Below a 0.6 AgNO 3 -to-surfactant mole ratio, the mixture is liquid crystalline and serves as a template for silica polymerization. However, between 0.6 and 0.8 AgNO 3 -to-surfactant mole ratios, one must control the composition of the mixture during the polymerization processes. Above a 0.8 mole ratio, Ag + ions undergo phase separation from the reaction mixture by complexing with the surfactant molecules. The resulting silica materials obtained from AgNO 3 /surfactant ratios above 0.8 have anisotropy but without a hexagonal mesophase. Here, we establish a AgNO 3 concentration range in which the LC phase is preserved to template the synthesis of mesoporous silica, and we discuss the structural behavior of the mixtures at AgNO 3 /surfactant mole ratios of 0.00-2.00, using POM, PXRD, FTIR, and UV-Vis absorption spectroscopy. C 2001 Academic Press

The synthesis of mesostructured silica films and monoliths functionalised by noble metal nanoparticles

“…5,23,24 A key question is how much AgNO 3 , HAuCl 4 and H 2 PtCl 6 can be introduced into the hexagonal mesophase of C 12 EO 10 : H 2 O (50 w/w%) : HNO 3 without affecting the mesostructure? 24 The mesophases that exist in silver nitrate-C 12 EO 10 : H 2 O (50 w/w%) : HNO 3 mixtures were defined by studying a range of 0.0 ¡ r ¡ 2.0 samples, where r is the AgNO 3 -C 12 EO 10 mole ratio. To visualise mesophases heated samples were monitored by POM.…”

“…A strong electrostatic interaction between the surface O 3 Si(CH 2 ) 3 N(CH 3 ) 3 1 cationic sites and MCl m n2 anions (where M is Pt or Au) promoted ion exchange between Cl 2 of the surface O 3 Si(CH 2 ) 3 N(CH 3 ) 3 Cl groups and MCl m n2 ions in the solution. 22 The LC templating with the non-ionic surfactant C n H 2n 1 1 -(CH 2 CH 2 O) m OH, (C n EO m ) was first used in a one-pot synthesis to incorporate Li 1 and Ag 1 ions 23,24 into mesoporous silica materials. This surfactant has the advantage of dissolving metal salts and maintaining the integrity of the liquid crystalline (LC) phase during the synthesis of the mesoporous silica.…”

Liquid Crystalline Mesophases of Pluronics (L64, P65, and P123) and Transition Metal Nitrate Salts ([M(H2O)6](NO3)2)

“…Most likely, the function of metal aqua complexes in the salt:Pluronic systems is similar to silica or other metal oxide species in the true liquid crystalline templating systems of metal oxides. 17,30,31 Note also that the synthesis of mesostructured silica [30][31][32] or titania 16 in the LLC mesophase of a nonionic surfactant produces an intermediate silicatropic or titaniatropic LC mesophase just before the phase becomes solid with the further polymerization of silica or titania species, respec- tively. The salt:Pluronic systems could be categorized in the same group as silicatropic [30][31][32] 6 ]-(NO 3 ) 2 :Pluronic systems have also been investigated using FTIR, micro-Raman spectroscopy, and XRD methods, Figures 8-10, respectively, using the same samples for each measurement.…”

The role of charged surfactants in the thermal and structural properties of lyotropic liquid crystalline mesophases of [Zn(H2O)6](NO3)2?CnEOm?H2O

“…The water-C n EO m LLCM can accommodate transition metal salt (TMS) without disturbing the mesophase, denoted as TMS-water-C n EO m mesophase [6][7][8][9][10]. However, the TMS-water-C n EO m mesophase is only stable at low salt concentrations [11]. The TMS-C 12 E 10 [12] and TMS-Pluronics (TMS-EO x-PO y EO x ) [13] were introduced to the literature by our group in 2001 and 2005, respectively.…”

“…Note also that a 6-7 SiO 2 /C 12 EO 10 mole ratio is required to mimic an LLC mesophase that can be converted to stable mesostructured silica films or monoliths [11,18]. Therefore the salt-surfactant mesophase still needs to be further improved on the metal ion concentration to overcome the problem of an insufficient metal ion density in the LLC media.…”