Time-Dependent Controlled Release of Ferulic Acid from Surface-Modified Hollow Nanoporous Silica Particles

Release of ferulic acid from surface-functionalized hollow nanoporous silica particles (HNSPs) was investigated in deionized water (DI water) and in ethanol. The host material, an HNSP, was synthesized in the presence of polymer and surfactant templates, and the pore as well as the surface were modified with either pentyltriethoxysilane (PTS) or octyltriethoxysilane (OTS) through silane coupling reactions. The inner hollow space occupied a volume of ~45% of the whole HNSP with a 2.54 nm pore channel in the wall. The pore size was estimated to decrease to 1.5 nm and 0.5 nm via the PTS and OTS functionalization, respectively. The encapsulation efficiencies of the HNSP (25 wt%), PTS-functionalized HNSP (PTS-HNSP, 22 wt%) and OTS-functionalized HNSP (OST-HNSP, 25 wt%) toward ferulic acid were similar, while the %release in DI water and ethanol varied following HNSP > PTS-HNSP > OTS-HNSP. Release kinetic analyses with Korsmeyer-Peppas fitting suggested a trade-off relationship between the solvent's ability to access the HNSP and the affinity of ferulic acid to the surface, allowing us to understand the solvent's controlled release rate and mechanism.

Design strategies, surface functionalization, and environmental remediation potentialities of polymer-functionalized nanocomposites

Inorganic nanoparticles (NPs) have a tunable shape, size, surface morphology, and unique physical properties like catalytic, magnetic, electronic, and optical capabilities. Unlike inorganic nanomaterials, organic polymers exhibit excellent stability, biocompatibility, and processability with a tailored response to external stimuli, including pH, heat, light, and degradation properties. Nano-sized assemblies derived from inorganic and polymeric NPs are combined in a functionalized composite form to import high strength and synergistically promising features not reflected in their part as a single constituent. These new properties of polymer/inorganic functionalized materials have led to emerging applications in a variety of fields, such as environmental remediation, drug delivery, and imaging. This review spotlights recent advances in the design and construction of polymer/inorganic functionalized materials with improved attributes compared to single inorganic and polymeric materials for environmental sustainability. Following an introduction, a comprehensive review of the design and potential applications of polymer/inorganic materials for removing organic pollutants and heavy metals from wastewater is presented. We have offered valuable suggestions for piloting, and scaling-up polymer functionalized nanomaterials using simple concepts. This review is wrapped up with a discussion of perspectives on future research in the field.

Efficient Negative Photochromism by the Photoinduced Migration of Photochromic Merocyanine/Spiropyran in the Solid State

Efficient negative photochromism was achieved by the photoinduced migration of merocyanine in mesoporous silica to an organophilic clay as spiropyran. Depending on the nature of the organophilic clays (dioctadecyldimethylammonium and dioleyldimethylammonium clays), important differences in the negative photochromisms and the thermal coloration were observed; the dioleyldimethylammonium clay gave a higher yield (98%) and faster reaction (half-life t_1/2 = 2.8 h) than the dioctadecyldimethylammonium clay (94% and t_1/2 = 3.2 h) of the negative photochromism, indicating the important role of the surfactant assembly to control the molecular diffusion.

Designing nanoarchitecture for environmental remediation based on the clay minerals as building block

Nanoarchitecture of hybrids materials based on clay minerals as nano building blocks for the environmental remediation is summarized with the emphasis on the utilization of layered clay minerals, especially smectite group of clay minerals, as nano building blocks for designing functional nanostructures for the adsorption of molecular contaminants from the environments. Smectites are well-known adsorbents of cationic contaminants, while surface modification of smectites with organoammonium ions has given hydrophobic and microporous characters to uptake nonionic organic contaminants from environments. Not only on the designed interactions between adsorbent-adsorbate for efficient and higher capacity adsorption, the states of the adsorbed nonionic organic compounds have been altered and varied by the modification of smectites as shown by the controlled release and specific catalytic reactions. The organically modified clays are classified from the nanoarchitecture, and the functions derived from the nanoarchitectures are discussed based on the structure-property relationship.

Acceleration of photochromism and negative photochromism by the interactions with mesoporous silicas

The adsorption of merocyanine dye onto mesoporous silicas with varied pore sizes (5.5, 9.4 and 2.2 nm) from the toluene solution of 1,3,3-trimethylindolino-6'-nitrobenzopyrylospiran under UV irradiation was investigated quantitatively. The photoinduced adsorption of merocyanine onto SBA-15 with the pore diameter of 9.4 nm followed the pseudo-second order kinetics and the rate constant was larger than that observed for MCM-41 (pore size of 2.2 nm) owing to the efficient diffusion of merocyanine. The maximum adsorbed amounts of the merocyanine dye was 152 mg g-1 of SBA-15, which corresponded to the sufficiently high concentration of merocyanine in the pores (0.376 mol L-1 of pore). The resulting red-colored hybrids (SBA-15 containing merocyanine) showed decoloration in the solid-state by visible light irradiation (negative photochromism). The conversion was high (about 80% at the photostationary state) under visible light irradiation at room temperature using a solar simulator (100 W). The red color was re-generated by storing the photochemically formed colorless samples in the dark at room temperature. The half-lives of the thermal coloration process were 2.6, 1.9 and 1.3 h for the MCM-41, SBA-15s with the BJH pore sizes of 5.5 and 9.4 nm, respectively. Since the coloration was affected by the diffusion of the molecules in the pores, larger pores provided the efficient molecular diffusion, leading to faster reactions.