Zhaofu Fei

Targeted delivery and controlled release of doxorubicin to cancer cells using modified single wall carbon nanotubes

A targeted drug delivery system that is triggered by changes in pH based on single wall carbon nanotubes (SWCNTs), derivatized with carboxylate groups and coated with a polysaccharide material, can be loaded with the anticancer drug doxorubicin (DOX). The drug binds at physiological pH (pH 7.4) and is only released at a lower pH, for example, lysosomal pH and the pH characteristic of certain tumor environments. By manipulating the surface potentials of the modified nanotubes through modification of the polysaccharide coating, both the loading efficiency and release rate of the associated DOX can be controlled. Folic acid (FA), a targeting agent for many tumors, can be additionally tethered to the SWCNTs to selectively deliver DOX into the lysosomes of HeLa cells with much higher efficiency than free DOX. The DOX released from the modified nanotubes has been shown to damage nuclear DNA and inhibit the cell proliferation.

Cycloaddition of CO2 to epoxides catalyzed by imidazolium-based polymeric ionic liquids

A series of cross-linked ionic polymers based on styrene-functionalized imidazolium salts with chloride, hexafluorophosphate, or tetrafluoroborate counter anions have been prepared and characterized using a range of analytical and spectroscopic techniques and electron microscopy. The polymer with the chloride anion is an efficient catalyst for the cycloaddition of carbon dioxide with epoxides to afford cyclic carbonates. The cross-linked polymer is insoluble in organic solvents and is highly stable and therefore can be easily recycled and reused.

Biphasic Hydrogenation over PVP Stabilized Rh Nanoparticles in Hydroxyl Functionalized Ionic Liquids

Polyvinyl pyrrolidone stabilized rhodium nanoparticles are highly soluble in hydroxyl-functionalized ionic liquids, providing an effective and highly stable catalytic system. In hydrogenation reactions, excellent results were obtained, and transmission electron microscopy, solubility determinations, and leaching experiments were employed to quantify the advantages of this catalytic system.

Highly selective hydrogenation of aromatic chloronitro compounds to aromatic chloroamines with ionic-liquid-like copolymer stabilized platinum nanocatalysts in ionic liquids

Platinum nanoparticles (PtNPs stabilized by an ionic-liquid-like-copolymer (IP) immobilized in various ionic liquids (ILs)) effectively catalyze the selective hydrogenation of aromatic chloronitro compounds to aromatic chloroamines, a reaction of considerable commercial significance. The preparation of 2,4-dichloro-3-aminophenol (DAP) has been primarily studied due to its important industrial applications. DAP is usually prepared from 2,4-dichloro-3-nitrophenol (DNP) by reduction with hydrogen using Ni- or Pt-based catalysts. Compared to reactions in molecular (organic) solvents, the ILs system provides superior selectivity with functionalized ILs containing an alcohol group demonstrating the best recyclability, and ultimately achieving a turnover number of 2025 which is 750 fold higher than Raney nickel catalyst. A universal catalyst–ionic liquid system for the conversion of aromatic chloronitro compounds to aromatic chloroamines was also established. TEM, XPS, IR spectroscopy were used to characterize the morphology of the nanocatalysts allowing their structure to be correlated to their activity.

Fabrication of gold nano- and microstructures in ionic liquids—A remarkable anion effect

Gold nano- and microstructures such as polyhedral crystals, large single-crystalline nanoplates, hollow trapeziform crystals, holey polyhedra, and dendrites were produced via microwave heating of HAuCl(4).4H(2)O in a variety of ionic liquids (ILs) in the absence of capping agents (polymers or surfactants) or additional reducing agents. The influence of the IL anions and cations on the topology (size, shape, etc.) of gold materials was studied in detail. The anions of the ILs control the topology of materials, whereas the cations used in the experiments exert less influence. It was also found that the HAuCl(4) concentration, reaction temperature, and heating method are key parameters that help to control the topological structures of the gold materials. For example, the thickness of the large single-crystalline nanoplates could be adjusted from 16 to 320 nm by varying the HAuCl(4) concentration and reaction temperature. This easy synthetic approach to gold nano- and microstructures is a seedless, one-step, fast, template-free route that shows good reproducibility and may be further developed to produce other types of metal nanostructures that satisfy specific applications.

Phosphane- and phosphorane Janus Head ligands in metal coordination

Abstract Our principal strategy to include the substituent periphery of phosphanides and phosphoranates in metal coordination is outlined. Rather than providing merely bulk or stereo information like in classical phosphane ligands to d-block metal centres the 2-pyridyl substituted species supply a second coordination site. Additional to the found σ/π coordination site selectivity these Janus Head ligands might serve as anionic staples in mixed Group 13/d-block metal complexes in homogeneous catalysis. The classical NP(Ph2)N− chelating ligand is converted into a NP(Py2)N− tripodal ligand. The pyridyl substitution has not only considerable impact on the metal coordination but also on the reactivity, emphasising the fact that this heteroaromatic substituent cannot simply be regarded as eka-phenyl. It facilitates double PC bond cleavage and reduction of iminophosphoranes to phosphanamines in a one-pot reaction. Even PN bond cleavage is observed. Several new routes to multidentate ligands in metal side-arm coordination were established.

Application of ionic liquids containing tricyanomethanide [C(CN)3]- or tetracyanoborate [B(CN)4]- anions in dye-sensitized solar cells.

A series of novel ionic liquids composed of imidazolium, pyridinium, pyrrolidinium, and ammonium cations with tricyanomethanide or tetracyanoborate anions were prepared. The ionic liquids were characterized by NMR and IR spectroscopy and ESI-mass spectrometry, and their physical properties were investigated. Solid state structures of the N-propyl-N-methylpyrrolidinium and triethylpropylammonium tetracyanoborate salts were obtained by single crystal X-ray diffraction. The salts that are liquid at room temperature were evaluated as electrolyte additives in dye-sensitized solar cells, giving rise to efficiencies 7.35 and 7.85% under 100 and 10% Sun, respectively, in combination with the standard Z907 dye.

Enhanced Conversion of Carbohydrates to the Platform Chemical 5‐Hydroxymethylfurfural Using Designer Ionic Liquids

5-Hydroxymethylfurfural (HMF) is a key platform chemical that may be obtained from various cellulosic (biomass) derivatives. Previously, it has been shown that ionic liquids (ILs) facilitate the catalytic conversion of glucose into HMF. Herein, we demonstrate that the careful design of the IL cation leads to new ionic solvents that enhance the transformation of glucose and more complex carbohydrates into HMF significantly. In Situ NMR spectroscopy and computational modeling pinpoint the key interactions between the IL, catalyst, and substrate that account for the enhanced reactivities observed.

MnO2 nanosheets as an artificial enzyme to mimic oxidase for rapid and sensitive detection of glutathione

Nanozymes are increasingly used as components in assays and diagnostics. Here, we describe a rapid and highly sensitive colorimetric assay for the detection and quantification of glutathione (GSH) employing MnO2 nanosheets as an artificial oxidase. In the assay pale yellow 3,3´,5,5´-tetramethylbenzidine (TMB) is oxidized to a blue product (oxTMB) under catalyzing of MnO2 nanosheets with a significant change in absorption at 650nm. GSH selectively inhibits this reaction with a detection limit of 300nM. The high specificity of inhibition by GSH allows this system to be used to determine the GSH concentrations in human serum samples. The MnO2 nanosheet-based assay is simple, rapid, sensitive and selective for the quantification of GSH and surpasses detection methods based on other MnO2 nanomaterials.

Fabrication of Dendritic Gold Nanoparticles by Use of an Ionic Polymer Template.

A facile method for the fabrication of dendritic gold nanoparticles (NPs) by use of an ionic polymer template has been developed. In situ generation of an imidazolium-based (cationic) polymer, poly[1-methyl-3-(4-vinylbenzyl)imidazolium], with AuCl4- counteranions is achieved by addition of HAuCl4 into a solution containing poly[1-methyl-3-(4-vinylbenzyl)imidazolium chloride]. Subsequent reduction with NaBH4 in water or in a mixture of ethanol and water affords various NPs depending on the conditions, including large dendritic gold NPs that have been analyzed by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and selected area electron diffraction (SAED). The structures of the dendritic gold NPs were found to depend on the ethanol concentration. Scanning electron microscopy (SEM) images of the ionic polymer reveal that the solvent used to deposit the polymer strongly influences its structure and may be correlated to the structure of the resulting NPs.