Polymeric Micelle Assembly for Preparation of Large-Sized Mesoporous Metal Oxides with Various Compositions

Here we report the synthesis of mesoporous metal oxide materials with various compositions by assembly of spherical polymeric micelles consisting of triblock copolymer poly­(styrene-<i>b</i>-2-vinyl pyridine-<i>b</i>-ethylene oxide) (PS-<i>b</i>-PVP-<i>b</i>-PEO) with three chemically distinct units. The PVP block interacts strongly with the inorganic precursors for the target compositions. The hydrophobic PS block is kinetically frozen in the precursor solutions, enabling the spherical micelles to remain in a stable form. The frozen PS cores serve as templates for preparing robust mesoporous materials. The PEO corona helps the micelles to stay well dispersed in the precursor solutions, which plays a key role in the orderly arrangement of the micelles during solvent evaporation. This approach is based on assembly of the stable micelles using a simple, highly reproducible method and is widely applicable toward numerous compositions that are difficult for the formation of mesoporous structures

Synthesis of Hierarchical Micro/Mesoporous Structures via Solid–Aqueous Interface Growth: Zeolitic Imidazolate Framework‑8 on Siliceous Mesocellular Foams for Enhanced Pervaporation of Water/Ethanol Mixtures

A new hierarchical micro/mesoporous composite is synthesized via direct growth of microporous zeolitic imidazolate framework-8 (ZIF-8) on siliceous mesocellular foams (MCF). Depending on different synthetic conditions, ZIF-8 with two different particle sizes, i.e., ZIF-8 microparticles and ZIF-8 nanoparticles, were successfully formed on the external surface of amine-functionalized MCF (denoted as microZIF-8@MCF and nanoZIF-8@MCF, respectively). The synthesized hierarchical micro/mesoporous ZIF-8@MCF structures were characterized with several spectroscopic techniques including X-ray diffraction (XRD), solid-state NMR, and FT-IR and electron microscopic techniques (scanning electron microscope, SEM, and transmission electron microscopy, TEM). In addition, the pervaporation measurements of the liquid water/ethanol mixture show that nanoZIF-8@MCF/PVA (poly­(vinyl alcohol) mixed-matrix membrane exhibits enhanced performance both on the permeability and separation factor. Compared to conventional routes for chemical etching, this study demonstrates a promising and simple strategy for synthesizing novel hierarchical porous composites exhibiting both advantages of mesoporous materials and microporous materials, which is expected to be useful for gas adsorption, separation, and catalysis

Cellulose Framework Directed Construction of Hierarchically Porous Carbons Offering High-Performance Capacitive Deionization of Brackish Water

We demonstrate a cellulose-templating method for synthesizing a hierarchically porous carbon electrode that is capable of high-performance capacitive deionization (CDI). Hierarchically porous carbons (denoted as HPC-<i>X</i>, <i>X</i> = 500–900 °C) of an exceptionally high surface area up to 2535 m² g^–1 and wide-range pore size distribution (macro-, meso-, and micropores) were obtained via the pyrolysis of macroporous cellulose fibrous-templated resorcinol-formaldehyde-triaminopyrimidine (RF-TPF) polymers. The improved electrosorption performance of HPC-800 electrode can be ascribed to the enhanced specific surface area, favorable hierarchical structure, and excellent capacitive electric double layer behaviors

Multimodal Superparamagnetic Nanoparticles with Unusually Enhanced Specific Absorption Rate for Synergetic Cancer Therapeutics and Magnetic Resonance Imaging

Superparamagnetic nanoparticles (SPMNPs) used for magnetic resonance imaging (MRI) and magnetic fluid hyperthermia (MFH) cancer therapy frequently face trade off between a high magnetization saturation and their good colloidal stability, high specific absorption rate (SAR), and most importantly biological compatibility. This necessitates the development of new nanomaterials, as MFH and MRI are considered to be one of the most promising combined noninvasive treatments. In the present study, we investigated polyethylene glycol (PEG) functionalized La_1–<i>x</i>Sr_<i>x</i>MnO₃ (LSMO) SPMNPs for efficient cancer hyperthermia therapy and MRI application. The superparamagnetic nanomaterial revealed excellent colloidal stability and biocompatibility. A high SAR of 390 W/g was observed due to higher colloidal stability leading to an increased Brownian and Neel’s spin relaxation. Cell viability of PEG capped nanoparticles is up to 80% on different cell lines tested rigorously using different methods. PEG coating provided excellent hemocompatibility to human red blood cells as PEG functionalized SPMNPs reduced hemolysis efficiently compared to its uncoated counterpart. Magnetic fluid hyperthermia of SPMNPs resulted in cancer cell death up to 80%. Additionally, improved MRI characteristics were also observed for the PEG capped La_1–<i>x</i>Sr_<i>x</i>MnO₃ formulation in aqueous medium compared to the bare LSMO. Taken together, PEG capped SPMNPs can be useful for diagnosis, efficient magnetic fluid hyperthermia, and multimodal cancer treatment as the amphiphilicity of PEG can easily be utilized to encapsulate hydrophobic drugs

Mesoporous TiO₂ Embedded with a Uniform Distribution of CuO Exhibit Enhanced Charge Separation and Photocatalytic Efficiency

Mixed metal oxide nanoparticles have interesting physical and chemical properties, but synthesizing them with colloidal methods is still challenging and often results in very heterogeneous structures. Here, we describe a simple method to synthesize mesoporous titania nanoparticles implanted with a uniform distribution of copper oxide nanocrystals (CuO@MTs). By calcining a titanium-based metal–organic framework (MIL-125) in the presence of Cu ions, we can trap the Cu in the TiO₂ matrix. Removal of the organic ligand creates mesoporosity and limits phase separation so that tiny CuO nanocrystals form in the interstices of the TiO₂. The CuO@MTs exhibits superior performance for photocatalytic hydrogen evolution (4760 μmol h^–1) that is >90 times larger than pristine titania

A Glucose-Assisted Hydrothermal Reaction for Directly Transforming Metal–Organic Frameworks into Hollow Carbonaceous Materials

Hollow micro-/nanostructures with controllable shape, size, and composition are an intriguing class of porous materials with a promising potential for various applications. Metal–organic frameworks (MOFs) have been attractive as promising precursors for preparing carbon materials with various kinds of nanoartchitectures owing to the rich variety in their composition, morphology, and structure. Herein, we report a glucose-assisted hydrothermal method for directly transforming MOFs into hollow carbonaceous materials. During the hydrothermal reaction, the MOF particles (zeolitic imidazolate frameworks-8, ZIF-8) are decomposed, which is induced by the acid generated from the hydrolysis of glucose. At the same time, the species released from the decomposed MOF continuously diffuse out and react with the glucose-derived polymers, resulting in the formation of hollow Zn-containing carbonaceous composites. Following calcination at 900 °C and 500 °C under a nitrogen atmosphere, hollow carbon and zinc oxide/carbon (ZnO/C) materials can be obtained, respectively. The obtained ZnO/C materials with hollow interiors exhibit more active sites, which are supported by their superior electrochemical performance for supercapacitor applications. The proposed method in this work provides a pathway for synthesizing a variety of multicompositional inorganic hollow structures from MOFs, which would facilitate their potential use in practical applications

Cosynthesis of Cargo-Loaded Hydroxyapatite/Alginate Core–Shell Nanoparticles (HAP@Alg) as pH-Responsive Nanovehicles by a Pre-gel Method

A new core–shell nanostructure consisting of inorganic hydroxyapatite (HAP) nanoparticles as the core and organic alginate as the shell (denoted as HAP@Alg) was successfully synthesized by a pre-gel method and applied to pH-responsive drug delivery systems (DDS). HAP@Alg nanoparticles have the advantages of hydroxyapatite and alginate, where hydroxyapatite provides pH-responsive degradability, and alginate provides excellent biocompatibility and COOH functionality. Through the subsequent addition of CaCl₂ and phosphate solutions to the alginate solution, HAP@Alg nanoparticles with controllable particle sizes (ranging from 160 to 650 nm) were obtained, and their core–shell structure was confirmed through transmission electron microscopy (TEM) observation. Rhodamine 6G (R6G), a positively charged dye, was selected as a model drug for pH-sensitive DDS. R6G was encapsulated in the HAP/Alg nanoparticles upon synthesis, and its loading efficiency could reach up to approximately 63.0%. The in vitro release behavior of the loaded R6G at different pH values was systematically studied, and the results indicated that more R6G molecules were released at lower pH conditions. For example, after releasing for 8 h, the release amount of R6G at pH 2.0 was 2.53-fold the amount at pH 7.4. We attributed this pH-sensitive release behavior to the dissolution of the HAP core in acidic conditions. The results of the MTT assay and confocal laser scanning microscopy indicated that the HAP@Alg were successfully uptaken by liver cancer cells (HepG2) without apparent cytotoxicity. The synthesized HAP@Alg nanoparticles show great potential as drug nanovehicles with high biocompatibility, enhanced drug loading, and pH-responsive features for future intracellular DDS

Shielding against Unfolding by Embedding Enzymes in Metal–Organic Frameworks via a <i>de Novo</i> Approach

We show that an enzyme maintains its biological function under a wider range of conditions after being embedded in metal–organic framework (MOF) microcrystals via a <i>de novo</i> approach. This enhanced stability arises from confinement of the enzyme molecules in the mesoporous cavities in the MOFs, which reduces the structural mobility of enzyme molecules. We embedded catalase (CAT) into zeolitic imidazolate frameworks (ZIF-90 and ZIF-8), and then exposed both embedded CAT and free CAT to a denature reagent (i.e., urea) and high temperatures (i.e., 80 °C). The embedded CAT maintains its biological function in the decomposition of hydrogen peroxide even when exposed to 6 M urea and 80 °C, with apparent rate constants <i>k</i>_obs (s^–1) of 1.30 × 10^–3 and 1.05 × 10^–3, respectively, while free CAT shows undetectable activity. A fluorescence spectroscopy study shows that the structural conformation of the embedded CAT changes less under these denaturing conditions than free CAT

Trifunctional Fe₃O₄/CaP/Alginate Core–Shell–Corona Nanoparticles for Magnetically Guided, pH-Responsive, and Chemically Targeted Chemotherapy

Chemotherapy of bladder cancer has limited efficacy because of the short retention time of drugs in the bladder during therapy. In this research, nanoparticles (NPs) with a new core/shell/corona nanostructure have been synthesized, consisting of iron oxide (Fe₃O₄) as the core to providing magnetic properties, drug (doxorubicin) loaded calcium phosphate (CaP) as the shell for pH-responsive release, and arginylglycylaspartic acid (RGD)-containing peptide functionalized alginate as the corona for cell targeting (with the composite denoted as RGD-Fe₃O₄/CaP/Alg NPs). We have optimized the reaction conditions to obtain RGD-Fe₃O₄/CaP/Alg NPs with high biocompatibility and suitable particle size, surface functionality, and drug loading/release behavior. The results indicate that the RGD-Fe₃O₄/CaP/Alg NPs exhibit enhanced chemotherapy efficacy toward T24 bladder cancer cells, owing to successful magnetic guidance, pH-responsive release, and improved cellular uptake, which give these NPs great potential as therapeutic agents for future in vivo drug delivery systems

Imparting Functionality to Biocatalysts via Embedding Enzymes into Nanoporous Materials by a <i>de Novo</i> Approach: Size-Selective Sheltering of Catalase in Metal–Organic Framework Microcrystals

We develop a new concept to impart new functions to biocatalysts by combining enzymes and metal–organic frameworks (MOFs). The proof-of-concept design is demonstrated by embedding catalase molecules into uniformly sized ZIF-90 crystals via a <i>de novo</i> approach. We have carried out electron microscopy, X-ray diffraction, nitrogen sorption, electrophoresis, thermogravimetric analysis, and confocal microscopy to confirm that the ∼10 nm catalase molecules are embedded in 2 μm single-crystalline ZIF-90 crystals with ∼5 wt % loading. Because catalase is immobilized and sheltered by the ZIF-90 crystals, the composites show activity in hydrogen peroxide degradation even in the presence of protease proteinase K