Zengyan Wei

Magnetic iron oxide–fluorescent carbon dots integrated nanoparticles for dual-modal imaging, near-infrared light-responsive drug carrier and photothermal therapy

Multifunctional hybrid nanoparticles (NPs, ∼100 nm) that combine magnetic Fe3O4 nanocrystals and fluorescent carbon dots (CDs) in porous carbon (C) were successfully synthesized using a one-pot solvothermal method by simply increasing the H2O2 concentration. The resultant Fe3O4@C-CDs hybrid NPs not only demonstrate excellent magnetic responsive properties (Ms = 32.5 emu g-1) and magnetic resonance imaging ability (r = 674.4 mM-1 s-1) from the Fe3O4 nanocrystal core, but also exhibit intriguing photoluminescent (quantum yield ∼6.8%) properties including upconversion fluorescence and excellent photostability from the CDs produced in the porous carbon. The hybrid NPs can enter the intracellular region and illuminate mouse melanoma B16F10 cells under different excitation wavelengths. Meanwhile, the mesoporous carbon shell and hydrophilic surface functional groups endow the hybrid NPs with high loading capacity (835 mg g-1) for the anti-cancer drug doxorubicin and excellent stability in aqueous solutions. More importantly, the hybrid NPs can absorb and convert near-infrared (NIR) light to heat due to the existence of CDs, and thus, can realise NIR-controlled drug release and combined photothermo/chemotherapy for high therapeutic efficacy. Such nanostructured Fe3O4@C-CDs hybrid NPs demonstrate great promise towards advanced nanoplatforms for simultaneous imaging diagnostics and high efficacy therapy.

Fe3O4/carbon quantum dots hybrid nanoflowers for highly active and recyclable visible-light driven photocatalyst

Water dispersible Fe3O4@carbon quantum dots (CQDs) hybrid nanoflowers show highly efficient photocatalytic activities because of their strong absorption in the visible light range and upconversion photoluminescence. The magnetic Fe3O4 nanocrystals not only allow efficient magnetic separation and recycling of the photocatalyst, but also promote the photocatalytic activities of the CQDs.

Porous carbon protected magnetite and silver hybrid nanoparticles: morphological control, recyclable catalysts, and multicolor cell imaging.

A simple and facile synthetic strategy is developed to prepare a new class of multifunctional hybrid nanoparticles (NPs) that can integrate a magnetic core with silver nanocrystals embedded in porous carbon shell. The method involves a one-step solvothermal synthesis of Fe3O4@C template NPs with Fe3O4nanocrystals in the core protected by a porous carbon shell, followed by loading and in situ reduction of silver ions in the carbon shell in water at room temperature. The core-satellite and dumbbell-like nanostructures of the resulted Fe3O4@C-Ag hybrid NPs can be readily controlled by loading amount of silver ions. The hybrid NPs can efficiently catalyze the reduction reaction of organic dyes in water. The easy magnetic separation and high stability of the catalytically active silver nanocrystals embedded in the carbon shell enable the hybrid NPs to be recycled for reuse as catalysts. The hybrid NPs can also overcome cellular barriers to enter the intracellular region and light up the mouse melanoma B16F10 cells in multicolor modal, with no cytotoxicity. Such porous carbon protected Fe3O4@C-Ag hybrid NPs with controllable nanostructures and a combination of magnetic and noble metallic components have great potential for a broad range of applications in the catalytic industry and biomedical field.

Scanning Electrochemical Microscopy Study of Permeability of a Thiolated Aryl Multilayer and Imaging of Single Nanocubes Anchored to It.

Electroreduction of diazonium salts is a widely used technique for grafting organic films on various surfaces. In this paper, scanning electrochemical microscopy (SECM) was used for high-resolution characterization of a thiolated aryl multilayer film obtained by electrografting of thiophenol diazonium on highly ordered pyrolytic graphite (HOPG). The blocking properties of the film were evaluated, and the origins of incomplete surface passivation were elucidated by comparing current-distance curves and surface reactivity maps obtained with nanometer- and micrometer-sized tips. In this way, one can distinguish between different pathways of charge transport in the film, e.g., pinhole defects versus rate-limiting charge transfer through the film. Pd nanocubes were anchored to the film by thiol groups and imaged by SECM. The applicability of SECM to in situ visualization of the geometry of non-spherical nanoparticles has been demonstrated.

Near-Infrared- and Visible-Light-Enhanced Metal-Free Catalytic Degradation of Organic Pollutants over Carbon-Dot-Based Carbocatalysts Synthesized from Biomass.

Cost-efficient nanoparticle carbocatalysts composed of fluorescent carbon dots (CDs) embedded in carbon matrix were synthesized via one-step acid-assisted hydrothermal treatment (200 °C) of glucose. These as-synthesized CD-based carbocatalysts have excellent photoluminescence (PL) properties over a broad range of wavelengths and the external visible or NIR irradiation on the carbocatalysts could produce electrons to form electron-hole (e(-)-h(+)) pairs on the surface of carbocatalysts. These restant electron-hole pairs will react with the adsorbed oxidants/reducers on the surface of the CD-based carbocatalysts to produce active radicals for reduction of 4-nitrophenol and degradation of dye molecules. Moreover, the local temperature increase over CD-based carbocatalyst under NIR irradiation can enhance the electron transfer rate between the organic molecules and CD-based carbocatalysts, thus obviously increase the catalytic activity of the CD-based carbocatalyst for the reduction of 4-nitrophenol and the degradation of dye molecules. Such a type of CD-based carbocatalysts with excellent properties and highly efficient metal-free photocatalytic activities is an ideal candidate as photocatalysts for the reduction of organic pollutants under visible light and NIR radiation.

Biomimetic assembly of proteins into microcapsules on oil-in-water droplets with structural reinforcement via biomolecular-recognition-based cross-linking of surface peptides.

By mimicking the stabilization of bacterial membranes with S-layer proteins, a novel process to fabricate highly stable protein microcapsules is introduced. In this strategy, engineered collagen peptides with site-specific biotinylation are assembled into microcapsules on the oil-in-water droplets, and the resulting microcapsules are reinforced by biomolecular-recognition-based cross-linking with the protein. Furthermore the microcapsules are shown to be versatile scaffolds for developing functionalized hierarchical colloidosomes for important biotechnological applications.

Rational strategy for shaped nanomaterial synthesis in reverse micelle reactors

The shape-controlled synthesis of nanoparticles was established in single-phase solutions by controlling growth directions of crystalline facets on seed nanocrystals kinetically; however, it was difficult to rationally predict and design nanoparticle shapes. Here we introduce a methodology to fabricate nanoparticles in smaller sizes by evolving shapes thermodynamically. This strategy enables a more rational approach to fabricate shaped nanoparticles by etching specific positions of atoms on facets of seed nanocrystals in reverse micelle reactors where the surface energy gradient induces desorption of atoms on specific locations on the seed surfaces. From seeds of 12 nm palladium nanocubes, the shape is evolved to concave nanocubes and finally hollow nanocages in the size ~10 nm by etching the center of {200} facets. The high surface area-to-volume ratio and the exposure of a large number of palladium atoms on ledge and kink sites of hollow nanocages are advantageous to enhance catalytic activity and recyclability.

Discovery of Catalytic Peptides for Inorganic Nanocrystal Synthesis by a Combinatorial Phage Display Approach

Nature tends to find the easiest way to grow materials with high efficiency and selectivity at room temperature, and thus biomimetic approach is a potential pathway to break through novel room-temperature inorganic nanocrystal synthesis because enzymes can catalyze the growth of materials in desired structures at low temperature. Recently, several promising peptides and proteins were demonstrated to catalyze the growth of semiconductors[1], however a successful discovery of the catalytic peptide sequences needed to go through trial-and-error processes[2], and the development of the systematic methodology with combinatorial selection is desirable for future materials chemistry. Here, we report a novel evolutionary approach to identify catalytic peptides for the room-temperature growth of target semiconductor materials. The conventional phage display technique is limited to find peptide sequences that bind specific target surfaces, however our combinatorial phage display approach directly screens peptides that catalyze the target material growth. The unique feature in this technique is that the panning process of peptides undergoes in precursor solutions where no reactions are expected to occur without catalysts. Thus, the product is observed only when there are phages in the solution which display peptides to catalyze the target reactions. Our methodology provides a simple and convenient route to discover a catalytic peptide for ZnO nanocrystal growth at room temperature and the ZP-1 peptide induces non-classical crystallization process which conventional ZnO synthetic methods cannot match. The broad impact is highly expected from this outcome since this novel screening technology can be applied to generate a wide range of new catalyses.

One-pot crystalline ZnO nanorod growth in mineralizing peptide gels

A new biomimetic approach for the one-pot synthesis of ZnO nanorods at neutral pH and room temperature is introduced; self-assembly of the ZnO-mineralzing peptides (CN111, PAGLQVGFAVEV-GGGSC) with Zn ions as bundles of nanofibers in the gel form leads to the growth of ZnO nanorod (NRD) inside the gel. This new nanomaterial synthesis may open a new strategy by using the catalytic peptide gels as nanomaterial reactors.