Haoquan Zheng

One-pot Synthesis of Metal-Organic Frameworks with Encapsulated Target Molecules and Their Applications for Controlled Drug Delivery.

Many medical and chemical applications require target molecules to be delivered in a controlled manner at precise locations. Metal-organic frameworks (MOFs) have high porosity, large surface area, and tunable functionality and are promising carriers for such purposes. Current approaches for incorporating target molecules are based on multistep postfunctionalization. Here, we report a novel approach that combines MOF synthesis and molecule encapsulation in a one-pot process. We demonstrate that large drug and dye molecules can be encapsulated in zeolitic imidazolate framework (ZIF) crystals. The molecules are homogeneously distributed within the crystals, and their loadings can be tuned. We show that ZIF-8 crystals loaded with the anticancer drug doxorubicin (DOX) are efficient drug delivery vehicles in cancer therapy using pH-responsive release. Their efficacy on breast cancer cell lines is higher than that of free DOX. Our one-pot process opens new possibilities to construct multifunctional delivery systems for a wide range of applications.

Coordination Polymer Coated Mesoporous Silica Nanoparticles for pH‐Responsive Drug Release

Coordination polymer coated mesoporous silica nanoparticles for drug delivery are successfully synthesized. The system ensures that drugs are stored in the mesopores under a physiological environment. Upon H(+) stimulus in the endosomal and lysosomal compartments, the drugs are released into the intracellular organelles of cancer cells, effectively killing the cells.

Porous Au–Ag Nanospheres with High-Density and Highly Accessible Hotspots for SERS Analysis

Colloidal plasmonic metal nanoparticles have enabled surface-enhanced Raman scattering (SERS) for a variety of analytical applications. While great efforts have been made to create hotspots for amplifying Raman signals, it remains a great challenge to ensure their high density and accessibility for improved sensitivity of the analysis. Here we report a dealloying process for the fabrication of porous Au-Ag alloy nanoparticles containing abundant inherent hotspots, which were encased in ultrathin hollow silica shells so that the need of conventional organic capping ligands for stabilization is eliminated, producing colloidal plasmonic nanoparticles with clean surface and thus high accessibility of the hotspots. As a result, these novel nanostructures show excellent SERS activity with an enhancement factor of ∼1.3 × 10(7) on a single particle basis (off-resonant condition), promising high applicability in many SERS-based analytical and biomedical applications.

Hierarchical Co(OH)F Superstructure Built by Low-Dimensional Substructures for Electrocatalytic Water Oxidation

The development of new materials/structures for efficient electrocatalytic water oxidation, which is a key reaction in realizing artificial photosynthesis, is an ongoing challenge. Herein, a Co(OH)F material as a new electrocatalyst for the oxygen evolution reaction (OER) is reported. The as-prepared 3D Co(OH)F microspheres are built by 2D nanoflake building blocks, which are further woven by 1D nanorod foundations. Weaving and building the substructures (1D nanorods and 2D nanoflakes) provides high structural void porosity with sufficient interior space in the resulting 3D material. The hierarchical structure of this Co(OH)F material combines the merits of all material dimensions in heterogeneous catalysis. The anisotropic low-dimensional (1D and 2D) substructures possess the advantages of a high surface-to-volume ratio and fast charge transport. The interconnectivity of the nanorods is also beneficial for charge transport. The high-dimensional (3D) architecture results in sufficient active sites per the projected electrode surface area and is favorable for efficient mass diffusion during catalysis. A low overpotential of 313 mV is required to drive an OER current density of 10 mA cm-2 on a simple glassy carbon (GC) working electrode in a 1.0 m KOH aqueous solution.

Explaining the Size Dependence in Platinum-Nanoparticle-Catalyzed Hydrogenation Reactions.

Hydrogenation reactions are industrially important reactions that typically require unfavorably high H2 pressure and temperature for many functional groups. Herein we reveal surprisingly strong size-dependent activity of Pt nanoparticles (PtNPs) in catalyzing this reaction. Based on unambiguous spectral analyses, the size effect has been rationalized by the size-dependent d-band electron structure of the PtNPs. This understanding enables production of a catalyst with size of 1.2 nm, which shows a sixfold increase in turnover frequency and 28-fold increase in mass activity in the regioselective hydrogenation of quinoline, compared with PtNPs of 5.3 nm, allowing the reaction to proceed under ambient conditions with unprecedentedly high reaction rates. The size effect and the synthesis strategy developed herein may provide a general methodology in the design of metal-nanoparticle-based catalysts for a broad range of organic syntheses.

pH-responsive mitoxantrone (MX) delivery using mesoporous silica nanoparticles (MSN)

The pH-responsive delivery of an anti-cancer drug, MX, has been successfully achieved by varying the strength of the electrostatic interaction between the negatively charged silicate and positively charged MX, using MSN.

Anionic-cationic switchable amphoteric monodisperse mesoporous silica nanoparticles.

Anionic-cationic switchable monodisperse mesoporous silica nanoparticles were synthesized by one-pot amino and carboxylic acid bifunctionalization based on the self-assembly of the surfactant, two types of co-structure-directing agents containing amino and carboxylic groups, and silica sources. These nanoparticles revealed properties of dispersity and reversibility, with the advantage of the pH-responsive anionic-cationic/acid-base switchability. It was demonstrated that the extracted materials achieved reutilization and controllable dispersity in aqueous solution by adjusting the static electric power among the particles during the switching process.

Amino/quaternary ammonium groups bifunctionalized large pore mesoporous silica for pH-responsive large drug delivery

Mesoporous nanoparticles functionalized with amino groups on the pore surface and quaternary ammonium groups on the particle surface with particle sizes of 500–800 nm in length and 300–500 nm in diameter and a pore size of 7.2–7.4 nm, have been obtained through a post-synthesis and co-condensation method. Bleomycin (BLM) has been chosen as a model anti-cancer drug with a large molecular size, and the iron essential for organisms has been utilized for constructing NH2–Fe–BLM coordination bond architecture in the pore surface. The BLM was released under mildly acidic pH conditions by cleavage of the Fe–BLM coordination bond triggered by pH reduction. Cell assays show that mesoporous nanoparticles have good dispersity and good cell penetrating properties due to the positively charged quaternary ammonium groups on the outer surface of the nanoparticles. These organic functionalized large pore mesoporous materials can be utilized as carriers in the pH-responsive delivery of an anti-cancer drug with a large molecular size, opening up new opportunities for their further application in controlled release of biomacromolecules.

A facile synthesis of Fe3C@mesoporous carbon nitride nanospheres with superior electrocatalytic activity

We report a colloidal amphiphile-templating approach to preparing nanosized Fe3C encapsulated within mesoporous nitrogen-doped carbon nanospheres (Fe3C@mCN). The obtained Fe3C@mCN hybrids having a high surface area and ultrafine Fe3C nanocrystals exhibited superior activity and durability for oxygen reduction.

A Crystalline Mesoporous Germanate with 48-Ring Channels for CO2 Separation†

One of the challenges in materials science has been to prepare crystalline inorganic compounds with mesopores. Although several design strategies have been developed to address the challenge, expansion of pore sizes in inorganic materials is more difficult compared to that for metal-organic frameworks. Herein, we designed a novel mesoporous germanate PKU-17 with 3D 48×16×16-ring channels by introducing two large building units (Ge10 and Ge7 clusters) into the same framework. The key for this design strategy is the selection of 2-propanolamine (MIPA), which serves as the terminal species to promote the crystallization of Ge7 clusters. Moreover, it is responsible for the coexistence of Ge10 and Ge7 clusters. To our knowledge, the discovery of PKU-17 sets a new record in pore sizes among germanates. It is also the first germanate that exhibits a good selectivity toward CO2 over N2 and CH4 .