Hierarchical Self-Assembly of pH-Responsive Nanocomposites with Molecular-Scale and Mesoscale Periodicities

Abstract

We have demonstrated a novel synthesis of mesoscopically ordered stimulus-responsive silica-based hybrid materials through a hierarchical self-assembly process. Two cationic surfactants with a special functional chromophoric group at one end of a carbon chain and a trimethylammonium headgroup at the other end were synthesized and used as both structure-directing agents and functional nano building blocks. Using these two cationic ammonium surfactants with different chromophoric groups at their hydrophobic tails, the micrometer-sized particles with a two-dimensional hexagonal mesostructure and spherical particles with a wormlike mesostructure were produced, respectively. Both of the mesostructured composite particles exhibit strongly fluorescent and pH-responsive behaviors with a rapid and recyclable signal response. Significantly, the symmetry of the self-assembled architecture demonstrated here not only guarantees a high filling and total homogeneous distribution of organic functionalities but also affords precise molecular-scale control over the spatial distribution of the organic component in the mesoscopically ordered inorganic network, which endows the hierarchical materials with mechanical robustness, improved thermal stability, and faster responses to chemical stimuli.

Functional-template directed self-assembly (FTDSA) of mesostructured organic-inorganic hybrid materials

“…We exploited the utility of the FTDSA approach in driving the optically active functionalities within the periodical nanoscale silica channels and reported a novel mesoscopically ordered pH responsive nanocomposite ( Figure 5) [59] . Two cationic ammonium surfactants that have special functional chromophoric groups at the ends of their hydrophobic tails are designed and synthesized and then used as both structuredirecting agents and functional nanobuilding blocks.…”

“…Such fluorescent mesostructured materials for pH detection in aqueous media can be of particular use, including medical, biological, and environmental applications. This ability to rapidly arrive at self-assembled structures with diverse morphologies will obviously be important in the production of a family of Figure 5 Functional-template directed self-assembly (FTDSA) of the mesoscopically ordered pH responsive nanocomposites and the representation of the external (pH) stimulus-responsive process [59] . optoelectronic materials, such as sensors, optical switches, and other devices.…”

Fabrication, structural characterization and sensing properties of polydiacetylene nanofibers templated from anodized aluminum oxide

“…The conjugated PDA backbone has two major spectroscopically distinct phases designated as the "blue phase" and the "red phase" [1]. Upon external perturbation, such as temperature change [2][3][4], pH [5,6] or mechanical stress [7,8], ligand-receptor interaction [9,10], the conjugated poly(ene-yne) backbone can undergo a drastic reversible or irreversible change in the relative intensity of these two phases, which is even visible to naked eyes. By making use of this sharp blue to red color change, PDAs have been extensively explored as chemical or biological sensors to monitor species ranging from small organic molecules, bio-macromolecules and even to virus and bacteria [11][12][13][14][15][16][17].…”

Hierarchical Self-Assembly of Superlattice Hybrids Consisting of Periodic and Alternating Cores of Porphyrin Molecules Separated by Nanoscale Silica Walls

“…The invention of the surfactant-directed self-assembly of mesoporous materials has sparked worldwide attention for mesostructured materials because of their intriguing structural characteristics and fascinating applications . Recently, mesoporous materials have attracted considerable interest as hosts that encapsulate organic functional groups, thus elaborating on organic−inorganic hybrid materials . These host−guest materials not only could provide both useful functionality and mechanical integrity but also could serve to protect the organic entities inside and allow their optical properties to be probed from outside because of the chemical inertness and optical transparency of silica .…”

“…Recently, mesoporous materials have attracted considerable interest as hosts that encapsulate organic functional groups, thus elaborating on organic−inorganic hybrid materials . These host−guest materials not only could provide both useful functionality and mechanical integrity but also could serve to protect the organic entities inside and allow their optical properties to be probed from outside because of the chemical inertness and optical transparency of silica . Two general methods, postloading and co-condensation, have already been developed for the inclusion of optically active guests such as organic dyes or conjugated polymers into the mesostructure, which led to a number of advanced optical applications such as optical switches and sensors, micrometer-sized lasers or optical data storage, and controlled drug-delivery systems .…”