Preparation of Mesoporous Silica Films with Fully Aligned Large Mesochannels Using Nonionic Surfactants

Miyata, Hirokatsu; Noma, Takashi; Watanabe, Masatoshi; Kuroda, Kazuyuki

doi:10.1021/cm010412m

Cited by 105 publications

(133 citation statements)

References 90 publications

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“…One of the most successful techniques to date for aligning mesochannels on a global scale (centimetre) has originated from a technique known as 'rubbing', pioneered by researchers at Cannon and Waseda University, and initially demonstrated for mesoporous particles in 1999 and for films in 2000 [5,[75][76][77][78][79][80]. The technique entails using a 10 nm thin polyimide coating to induce preferred unidirectional alignment and orientation of the mesochannels in the overlaying film.…”

Section: Chemical Epitaxymentioning

confidence: 99%

Self-assembled templates for the generation of arrays of 1-dimensional nanostructures: From molecules to devices

Farrell

Petkov²,

Morris

et al. 2010

Journal of Colloid and Interface Science

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Self-assembled nanoscale porous architectures, such as mesoporous silica films (MPS), block copolymer films (BCP) and porous anodic aluminas (PAAs), are ideal hosts for templating one dimension (1 D) nano-entities for a wide range of electronic, photonic, magnetic and environmental applications. All three templates offer dimensional scalability and tunability over a wide range, with critical pore sizes for each system well below the 20 nm threshold [1][2][3]. Recently, research has progressed towards controlling the pore direction, orientation and long range order of these nanostructures through so called directed self-assembly (DSA). Significantly, the introduction of a wide range of top-down chemically and physically pre-patterning substrates has facilitated the DSA of nanostructures into functional device arrays. The following review begins with an overview of the fundamental aspects of self-assembly and ordering processes during the formation of PAAs, BCPs and MPS films. Special attention is given to the different ways of directing self-assembly, concentrating on properties such as uni-directional alignment, precision placement and registry of the self-assembled structures to hierarchal or top down architectures. Finally, to distinguish this review from other articles we focus on research where nanostructures have been utilised in part to fabricate arrays of functioning devices below the sub 50 nm threshold, by subtractive transfer and additive methods. Where possible, we attempt to compare and contrast the different templating approaches and highlight the strengths and/or limitations that will be important for their potential integration into downstream processes. ACCEPTED MANUSCRIPT 3 SECTION 1.0: SELF ASSEMBLY AND NANO-ARCHITETCURESThe diversity of self-assembled nanostructures and more importantly, their precise orientation within a thin film (fixed to a substrate) ultimately determines their function and overall application. A large population of research reports to date have focused on identifying these orientations and related periodicities, using x-ray and microscopy tools, as well the development of methods for readily manipulating nanostructures, such as pre-patterning of silicon substrates for the alignment of block copolymers (BCPs) [4] and mesoporous thin films (MTFs) [5] and altering the growth direction of porous anodic alumina (PAA) templates [6]. In this section, a brief synopsis of the mechanisms behind the self-assembly/organisation of each system and highlight nanoscale architectures (and orientations), which are important from a device perspective. Templated mesoporous thin filmsOrdered mesoporous powders were first discovered by researchers at the Mobil Petrochemical Corporation in 1992 and shortly after, sol-gel derived mesoporous silica films were fabricated [1,7].The first series of ordered mesoporous films were reported by Yang et al. in 1996 [8], prepared using initial surfactant concentrations above their critical micelle concentration (CMC). However the films prepared fil...

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Section: Chemical Epitaxymentioning

confidence: 99%

Self-assembled templates for the generation of arrays of 1-dimensional nanostructures: From molecules to devices

Farrell

Petkov²,

Morris

et al. 2010

Journal of Colloid and Interface Science

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“…It is confirmed that the mesochannels in the MPS films are aligned perpendicularly to the rubbing direction (º = 0°). FWHM values of the peaks in the rocking curves are 11.3°for C 10 EO 10 and 7.8°for C 12 EO 10 . These values are larger than the value for C 16 EO 10 (2.8°), indicating that the degrees of the mesochannel alignment for C 10 EO 10 and C 12 EO 10 are lower than that for C 16 EO 10 .…”

Section: ¹1mentioning

confidence: 93%

“…This implies that the alkyl chains of the surfactants are slightly folded in the mesochannels. Figure 2 summarizes the in-plane XRD study of the MPS films synthesized using C 10 EO 10 and C 12 EO 10 . Figure 2a shows the º2ª» scanning profiles of the MPS films.…”

Section: ¹1mentioning

confidence: 99%

Control of Periodicity in Mesoporous Silica Films with Aligned Mesochannels Prepared by a Sol–Gel Process

2012

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Periodicity of mesoporous silica films with aligned cylindrical pores formed on a substrate with a rubbing-treated polyimide through a solgel process can be finely controlled using nonionic surfactants with different alkyl chains. The degree of alignment increases with the alkyl-chain length of the surfactant due to increase in anisotropic hydrophobic interaction between the oriented polyimide chains and the alkyl groups, which is responsible for the alignment.Mesoporous silica (MPS) films are promising materials for application in optical and electronic molecular devices because they have highly ordered nanostructures and are synthesized through a simple self-assembly process.15 Especially, MPS films with highly aligned cylindrical mesochannels are expected to be used for anisotropic accommodation of various guest species, e.g., metals, 6 dyes, 7 and polymers. 8,9 Several methods to control the alignment of the mesochannels have been reported. 1017 Among them, the method in our previous report using a substrate with a rubbing-treated polyimide layer combined with evaporation-induced self-assembly (EISA) can control the mesochannel direction within the º distribution of 3°at macroscopic scales.11 The method, however, has not achieved to control the periodicity of the MPS films, which associates with the pore size. The optimum conditions for the preparation of aligned MPS films using different surfactants have been difficult to find because it is necessary to take the interactions between the oriented polyimide chains and the surfactant molecules into account in addition to the self-assembly of the surfactant. The control of the pore size of the aligned mesochannels enables the fine tuning of the properties of the guest species in the mesochannel through changes of the amount and the conformation. In view of this situation, we report the control of the periodicity and the pore size of the MPS films with aligned mesochannels by varying alkyl-chain length of nonionic surfactants.The MPS films with the aligned mesochannels were prepared based on our previous method 11 after careful optimization for each surfactant. The polyimide with a 8-nm thickness on a Si wafer underwent rubbing treatment using a cottoncovered cylindrical roller. Nonionic surfactant (poly(oxyethylene)-10-alkyl ether, C n EO 10 , n = 10, 12, and 16) was dissolved in 2-propanol (IPA), and then ultrapure water (Milli-Q), 0.1 M HCl, and tetraethoxysilane (TEOS) were added to the solution. The final molar ratio of the chemicals was C n EO 10 8.00 © 10 ¹2 0.120/TEOS 1.00/IPA 16.7/H 2 O 5.00/HCl 4.00 © 10 ¹3. After stirring and aging the solution for 0.53.0 h, the Si wafer was dip-coated with the solution at withdrawal speed of 1.5 mm s ¹1 at 25°C and 3943% RH and subsequently dried at 25°C and 40% RH over 16 h. The surfactants were removed by calcination at 400°C for 10 h in air. Structural analysis of the synthesized films was performed by X-ray diffractometry (XRD). Conventional ª2ª scanning XRD and in-plane XRD were performed with Philips X'Pert Pr...

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“…This alignment is passed on to the micellar structure of the surfactant molecules and can lead to a macroscopic alignment of the mesopores. The exact formation mechanism that leads to the alignment seems to depend on the matching of the chain length of the hydrophobic part of the surfactant to the chemical structure of the polyimide underlayer [44,45]. Zhao et al [41] and Naik et al [42] demonstrated that the shear flow exerted on films during dip coating can also influence mesopore alignment to some degree, but the correlation length of the obtained mesostructure might be low in these cases.…”

Section: Thin Film Deposition and Functionalization Techniquesmentioning

confidence: 99%

Review. Fluorescence Microscopy Studies of Porous Silica Materials

Rühle

Davies

Bein

et al. 2013

Zeitschrift Für Naturforschung B

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In this article, we discuss how fluorescence microscopy techniques are used to investigate important characteristics of porous silica materials. We start with a discussion of the synthesis, formation mechanism and functionalization of these materials. We then give an introduction to single molecule microscopy and show how this technique can be used to gain deeper insights into some defining properties of porous silica, such as pore structure, host-guest interactions and diffusion dynamics. We also provide examples from the literature demonstrating how fluorescence microscopy is used for elucidating important aspects of porous silica materials and heterogeneous catalysis, e. g. diffusion properties, reactivity, morphology, intergrowth, accessibility, and catalyst deactivation. Finally, a short outlook on the scope of porous silica hosts in drug delivery applications is given.

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Preparation of Mesoporous Silica Films with Fully Aligned Large Mesochannels Using Nonionic Surfactants

Cited by 105 publications

References 90 publications

Self-assembled templates for the generation of arrays of 1-dimensional nanostructures: From molecules to devices

Self-assembled templates for the generation of arrays of 1-dimensional nanostructures: From molecules to devices

Control of Periodicity in Mesoporous Silica Films with Aligned Mesochannels Prepared by a Sol–Gel Process

Review. Fluorescence Microscopy Studies of Porous Silica Materials

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