Three-Dimensional Structure of Large-Pore Mesoporous Cubic Ia[text removed]d Silica with Complementary Pores and Its Carbon Replica by Electron CrystallographyThis work was supported by the Swedish Natural Science Council (VR) and the Japan Science and Technology Agency (JST).

نویسندگان

  • Yasuhiro Sakamoto
  • Tae-Wan Kim
  • Ryong Ryoo
  • Osamu Terasaki
چکیده

Large-pore three-dimensional (3D) mesoporous silicas are among the most interesting mesoporous materials discovered in recent years, and they have attracted much attention for potential applications requiring easily accessible, uniform, large pores. Examples of these are SBA-15 (p6mm) and SBA16 (Im3̄m), which have cylindricaland cage-type structures, respectively. It has been reported that hexagonally ordered large-pore mesoporous SBA-15 silica made by using a block copolymer contains complementary pores, while such pores were not found in MCM-41 with the same 2D hexagonal p6mm symmetry. These complementary pores are arranged in a disordered way between the hexagonally ordered largepore channels. Recently, large-pore mesoporous silicas with a cubic Ia3̄d structure were synthesized by using triblock copolymers as structure-directing agent under various synthesis conditions. The mesoporous silica with a bicontinuous cubic structure of Ia3̄d symmetry is composed of an enantiomeric pair of 3D mesoporous networks that are interwoven, as observed in the MCM-48 structure. The structures of these highly ordered mesoporous materials can hardly be determined from powder XRD patterns alone, because the few reflections that are observed at low scattering angles are especially broad and overlap. Electron microscopy is the main tool for characterization of such structures. The advantage over XRD is the stronger interaction of electrons with matter, which enables us to obtain structural information from a single crystal with only a few hundred unit cells. In electron crystallography (EC) the phases and amplitudes of the structure factors are obtained by Fourier transformation of high-resolution TEM (HRTEM) images. By calculating the inverse Fourier transform of the structure factors, a 3D electrostatic potential distribution of the structure can be obtained. This is another advantage compared to traditional single-crystal XRD. Based on the 3D electrostatic potential distribution of the structure, direct information on the detailed structures inside the mesoporous crystals such as diameter, shape, and connectivity of the pores can be obtained. Herein we report on the structure of the large-pore mesoporous silica with cubic Ia3̄d symmetry after removal of the surfactant by calcination and, in particular, on its ordered complementary pores between two independent channel systems, determined by using EC methods. Furthermore, the structure of its carbon replica, made by using this large-pore mesoporous silica as a hard template and then removing the template, is reported. Figure 1 shows HRTEM images of mesoporous silica with Ia3̄d symmetry taken with the incident beam parallel to the

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

بررسی قابلیت جذب هیدروژن در ماده مرکب نانو‌ساختار SBA-16-Pd

The purpose of this work was to study the hydrogen adsorption on the surface of mesoporous materials based on silica (SBA-16) modified with palladium via temperature. Since mesoporous silica materials have a high specific surface area, and the ordered mesoporous size of 2-10nm, they are suitable for adsorption and storage of hydrogen. SBA-16 is suitable for this purpose due to its cubic crystal...

متن کامل

Synthesis and Characterization of Functionalized SBA-15 Mesoporous Silica by N, N´-Bis(salicylidene)ethylenediamine Schiff-Base

In this work, BSEA-SBA-15 was prepared for the first time, which was prepared by covalently anchoring Schiff-base compound (N,N´-bis(salicylidene)ethylenediamine (BSEA) on SBA-15 by hydrothermal method. The structure and physicochemical properties were determined by elemental analysis, XRD, nitrogen adsorption–desorption, thermogravimetric analysis and FTIR spectroscopy, SEM, BET surface area a...

متن کامل

Mesoporous Silica Nanoparticles as a Nanocarrier for Delivery of Vitamin C

Background: In the last decades, mesoporous silica nanoparticles (MSN) are improved for drug delivery, imaging, and biomedical applications due to their special properties such as large surface area, high drug loading capacity, tunable pore size, and modification of surface area by functional groups. Objectives: The aim of this study was to evaluate MSNs as carriers for oral colon-specific and...

متن کامل

MCM-48-like large mesoporous silicas with tailored pore structure: facile synthesis domain in a ternary triblock copolymer-butanol-water system.

Assembly of mesostructured silica using Pluronic P123 triblock copolymer (EO(20)-PO(70)-EO(20)) and n-butanol mixture is a facile synthesis route to the MCM-48-like ordered large mesoporous silicas with the cubic Iad mesostructure. The cubic phase domain is remarkably extended by controlling the amounts of butanol and silica source correspondingly. The extended phase domain allows synthesis of ...

متن کامل

Synthesis and Charaterization of Magensium Oxide Mesoporous Microstructures Using Pluronic F127

Mesoporous  MgO  microstructures  were  synthesized  using magnesium  acetate  tetrahydrate,  ammonium  oxalate  monohydrate and  Pluronic  F127  via  heating  at  40  °C  for  24  h  and  subsequent calcination. The mesoporous structure of magnesium oxide with the specific  surface  area  of  47m2 /g,  pore  volume  0.30  cm3 /g  and  the average pore size 24 nm is produced. According to ...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2004