The organic template moiety in the sample was determined using a Mettler TGA SDTA851 instrument (Mettler-Toledo, Columbus, OH, USA) with a heating rate of 10°C·min−1 under nitrogen flow. Nitrogen adsorption-desorption analysis was conducted using a Micromeritics ASAP 2010 instrument (Norcross, GA, USA). The template-free PI3K Inhibitor Library sample was first degassed at 250°C for 3 h followed by
nitrogen adsorption measurement at −196°C. The surface physicochemical properties were then calculated using the Brunauer-Emmett-Teller (BET) and the Barrett-Joyner-Halenda (BJH) models . Solid-state 29Si-MAS-NMR spectra were recorded using a Bruker Ultrashield 300 spectrometer (Madison, WI, USA) operating at 300 MHz with tetramethylsilane as a reference. The measurement
was carried out at 79.4 MHz and single-contact cross-polarization 4EGI-1 pulse program was used. The spectra were acquired with a pulse length of 2.7 μs, a repetition time of 6 s, and a contact time of 4 ms. The FTIR spectra of the as-synthesized solid products were obtained with a PerkinElmer spectrometer (System 2000) using the KBr pellet technique (KBr/sample weight ratio = 150:1). Results and discussion The chemical composition of the initial and re-used solutions characterized by dry mass, AAS, and TG/DTA analyses is summarized in Table 1. As can be seen, large amounts of silicate solution (approximately 15 g) and CTABr (approximately 3.5 g) were consumed for three subsequent synthesis cycles of MCM-41. Initially, the CTABr was dissolved in distilled water, and silica was precipitated out after sodium silicate was added into the CTABr solution. At this stage, silicate oligomers act as multidentate ligands with high charge density at head groups, which leads to a lamellar organization of the surfactant . As the acid is introduced, polycondensation and polymerization of silica take place, resulting in the dissolution of lamellar phase. At pH close to 11.0, this dissolution is followed by the formation Gemcitabine datasheet of the hexagonal Ilomastat research buy MCM-41 material [22, 23]. Table 1 Compensated chemicals added into non-reacted mother liquor for MCM-41 synthesis
cycles and MCM-41 solid yield MCM-41 synthesis 1st cycle 2nd cycle 3rd cycle Non-reacted mother liquor (g) 0 54.404a 63.337a Added reagents Na2SiO3 (g) 21.206 15.664 15.560 CTABr (g) 5.772 3.750 3.251 H2O (g) 79.916 31.882 27.110 H2SO4 (g) 0.603 2.082 0.9881 pH 10.78 10.80 10.80 Solid yield, gram (wt.%)b 8.034 g (73.6%) 7.851 (71.9%) 7.694 (78.3%) aAfter evaporating water at 55°C for 16 h. b . pH was determined to be the most important of the investigated synthesis parameters in affecting pore ordering and mesophase. The solubility and the rate of dissolution of silica increases with the increasing pH resulted in a decrease of the total interfacial area and a more long-range pore ordering [24, 25]. High pH results in fast and complete hydrolysis where polymerization can occur within a few minutes .