Tailoring Pore Size, Structure, and Morphology of Hierarchical Mesoporous Silica Using Diblock and Pentablock Copolymer Templates

Mesoporous materials of tailored pore size, structure, and morphology are of interests for a wide range of applications. It is important to develop synthetic methods that will allow for easy processing and facile structure modification. Here, we present the preparation of hierarchically structured bimodal mesoporous silicas using water-soluble poly­(lactic acid-<i>co</i>-glycolic acid)-<i>b</i>-poly­(ethylene oxide) (PLGA-<i>b</i>-PEO) diblock copolymer and poly­(lactic acid-<i>co</i>-glycolic acid)-<i>b</i>-poly­(ethylene oxide)-<i>b</i>-poly­(propylene oxide)-<i>b</i>-poly­(ethylene oxide)-<i>b</i>-poly­(lactic acid-<i>co</i>-glycolic acid) (PLGA-<i>b</i>-PEO-<i>b</i>-PPO-<i>b</i>-PEO-<i>b</i>-PLGA) pentablock copolymers as templates. The block copolymers were synthesized through a step-growth polymerization method using a commercial Pluronic F68 macroinitiator. Mesoporous silica samples were obtained by sol–gel chemistry in acidic aqueous solutions. Hexagonally (<i>p</i>6<i>mm</i>) ordered mesoporous silica particles were obtained in the presence of a PLGA-PEO diblock copolymer and exhibited bimodal pore size distributions in the range of 2–9 nm. Core–shell type mesoporous silica particles were obtained in the presence of the PLGA-PEO-PPO-PEO-PLGA pentablock copolymer and exhibited a large pore diameter up to 20 nm with distinct bimodal pore size distributions. The pore size increased when using a longer pentablock copolymer template in strong acid. The physicochemical properties were investigated using small-angle X-ray scattering (SAXS), nitrogen adsorption–desorption, transmission electron microscope (TEM), solid-state ²⁹Si nuclear magnetic resonance (NMR), and scanning electron microscope (SEM), respectively

Socio-demographic characteristics of respondents according to age groups.

Socio-demographic characteristics of respondents according to age groups.</p

Prevalence of underweight, right weight, overweight, and obese perceptions according to body mass index deciles for age groups.

Prevalence of underweight, right weight, overweight, and obese perceptions according to body mass index deciles for age groups.</p

Active {001} Facet Exposed TiO₂ Nanotubes Photocatalyst Filter for Volatile Organic Compounds Removal: From Material Development to Commercial Indoor Air Cleaner Application

TiO₂ nanotubes (TNT) have a highly ordered open structure that promotes the diffusion of dioxygen and substrates onto active sites and exhibit high durability against deactivation during the photocatalytic air purification. Herein, we synthesized {001} facet-exposed TiO₂ nanotubes (001-TNT) using a new and simple method that can be easily scaled up, and tested them for the photocatalytic removal of volatile organic compounds (VOCs) in both a laboratory reactor and a commercial air cleaner. While the surface of TNT is mainly composed of {101} facet anatase, 001-TNT’s outer surface was preferentially aligned with {001} facet anatase. The photocatalytic degradation activity of toluene on 001-TNT was at least twice as high as that of TNT. While the TNT experienced a gradual deactivation during successive cycles of photocatalytic degradation of toluene, the 001-TNT did not exhibit any sign of catalyst deactivation under the same test conditions. Under visible light irradiation, the 001-TNT showed degradation activity for acetaldehyde and formaldehyde, while the TNT did not exhibit any degradation activity for them. The 001-TNT filter was successfully scaled up and installed on a commercial air cleaner. The air cleaner equipped with the 001-TNT filters achieved an average VOCs removal efficiency of 72% (in 30 min of operation) in a 8-m³ test chamber, which satisfied the air cleaner standards protocol (Korea) to be the first photocatalytic air cleaner that passed this protocol

Weight status based on self-reported height and weight, weight perceptions, and correctness of weight perceptions among respondents according to age groups.

Weight status based on self-reported height and weight, weight perceptions, and correctness of weight perceptions among respondents according to age groups.</p

Agreement of body mass index classification based on self-reported height and weight with self-perceptions of weight.

Agreement of body mass index classification based on self-reported height and weight with self-perceptions of weight.</p

Accuracy of body weight perceptions according to age groups.

Accuracy of body weight perceptions according to age groups.</p

Stage of adoption of breast cancer screening according to sociodemographic characteristics of the population (n = 2364; Korea, 2013).

<p>NCSP, National Cancer Screening Program</p><p>Stage of adoption of breast cancer screening according to sociodemographic characteristics of the population (n = 2364; Korea, 2013).</p

Multinomial logistic analysis of factors associated with each stage of adoption for breast cancer screening in Korea, 2013^a.

<p>^a Comparison to the pre-contemplation group</p><p>Multinomial logistic analysis of factors associated with each stage of adoption for breast cancer screening in Korea, 2013<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0132351#t004fn001" target="_blank">^a</a>.</p