Mesoporous nanorods

Briefly explain with an example how to synthesize a mesoporous nanorod. 

A mesoporous nanorod is a nanorod with pores in the mesopoie size region (2 nm to 50 nm) along the length of the nanorod. Mesoporous nanorods have been synthesized using polycarbonate membrane as the template (132), using ultrasound... 

Of the various semiconductors tested to date, Ti02 is the most promising photocatalyst because of its appropriate electronic band structure, photostability, chemical inertness and commercial availability. But currently, a variety of nanostmctured Ti02 with different morphologies including nanorods, nanowires, nanostmctured films or coatings, nanotubes, and mesoporous/nanoporous structures have attracted much attention. 

This review will discuss the possibility to control and improve the reactivity of Titania by design of new tailored nano-architecture. Specifically, analyses quasi-ID Ti02 nanostructures, e.g. nanorods, nanowires and nanofibres, nanotubes and nanopillars. 2D Titania nanostructures, e.g. columnar-type films, ordered arrays of nanotubes or nano-rods/-wires, nanobowl array, nanomembranes (called also nanohole array) and nanosponge, and Ti-based ordered mesoporous matrices will be instead discussed in a consecutive review paper. 

Figure 15.18 Proposed structures of (a) Pt nanorod wires in silica FSM-16 and (b) Pt nanonecklace wires in organosilica such as HMM-1 (Et-HMM) and HMM-p (Ph-HMM), which are used as the mesoporous templates for nanowire formation.

Bicrystalline nanowires of hematite (a-Fe,03) have been synthesized by the oxidation of pure Fe.207 Single-crystalline hexagonal u-Fe20, nanorods and nanobeits can be prepared by a simple iron-water reaction at 673 K.20 Mesoporous quasi-single crystalline... 

Nanorods of oxide can also be made using a template. In this case, the morphology of the nanorods would depend on the shape of the template. For example, WO3 can grow in mesoporous silica MCM-41 which consists of an array of cylindrical pores without intercormections [119]. The growing orientation of the nanorods is variable. 

CMK-5 is the first example of the ordered tube-type mesoporous carbons that can be characterized with well-defined Bragg diffractions by ordinary XRD instrument [6]. The XRD pattern of the CMK-5 carbon is distinguished from that of CMK-3 by the much lower intensity of the (100) diffraction. The structure of CMK-5 may be described by the substitution of the carbon nanorods in CMK-3 with nanopipes. The CMK-5 carbon is synthesized using SBA-IS, similar to CMK-3, but the carbon source and synthesis condition are somewhat different from those for CMK-3. The synthesis method for the tube-type carbon can be extended to the SBA-16 mesoporous template. The resultant CMK-7 carbon has a bicontinuous mesoporous structure [15]. 

F. Kleitz, S.H. Choi, and R. Ryoo, Cubic Ia3d Large Mesoporous Silica Synthesis and Replication to Platinum Nanowires, Carbon Nanorods and Carbon Nanotubes. Chem. Commun., 2003, 2136-2137. 

S. Giri, B.G. Trewyn, M.P. Stellmaker, and V.S.Y. Lin, Stimuli-responsive Controlled-release Delivery System Based on Mesoporous Silica Nanorods Capped with Magnetic Nanoparticles. Angew. Chem., Int. Ed., 2005, 44, 5038-5044. 

SnOa nanorods ca. 5 10 nm in diameter and 10-30 nm in length was incorporated into large pore, well-ordered mesoporous SBA-15 silica materials... 

F. Klertz, S. H. Choi, R. Ryoo, Cubic la3d large mesoporous silica synthesis and replication to platinum nanowires, carbon nanorods and carbon nanotubes, Chem. Commun., 17,2136-7 (2003). 

In another research report by Yoshikaw and his group, mesoporous anatase Ti02 nanopowder was synthesized at 130°C for 12 h (see Table 2) [106]. Titanium (IV) butoxide (Ci6H3604Ti) was mixed in a 1 1 molar ratio with acetylacetone (CH3-CO-CH2-CO-CH3) to slowdown the hydrolysis and the condensation reactions. 40 ruL of distilled water was added in the solution and stirred at room temperature for 5 min. The solution was put into a Teflon-hned stainless steel autoclave while stirring and heated at 130°C for 12 h. The final product was naturally cooled to room temperature and washed with 2-propanol and distilled water. This was then dried followed by drying at 100°C for 12 h. The synthesized sample had a narrow pore size distribution with an average pore diameter of about 3 nm. The specific surface area of the sample was about 193 m /g. Mesoporous anatase TiOz nanopowders showed higher photocatalytic activity than the nanorods, nanofibers and commercial 7702 nanoparticles. 

It is possible to synthesize nanorods inside a restricted space such as the pores in a mesoporous material. Mesoporous materials are different from conventional templates... 

---