Chaedong Lee

One-Step Facile Solvothermal Synthesis of Copper Ferrite–Graphene Composite as a High-Performance Supercapacitor Material

In this work, we reported a facile approach to prepare a uniform copper ferrite nanoparticle-attached graphene nanosheet (CuFe2O4-GN). A one-step solvothermal method featuring the reduction of graphene oxide and formation of CuFe2O4 nanoparticles was efficient, scalable, green, and controllable. The composite nanosheet was fully characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), which demonstrated that CuFe2O4 nanoparticles with a diameter of approximately 100 nm were densely and compactly deposited on GN. To investigate the formation mechanism of CuFe2O4-GN, we discussed in detail the effects of a series of experimental parameters, including the concentrations of the precursor, precipitation agent, stabilizer agent, and graphene oxide on the size and morphology of the resulting products. Furthermore, the electrochemical properties of the CuFe2O4-GN composite were studied by cyclic voltammetry and galvanostatic charge-discharge measurements. The composite showed high electrochemical capacitance (576.6 F·g(-1) at 1 A·g(-1)), good rate performance, and cycling stability. These results demonstrated that the composite, as a kind of electrode materials, had a high specific capacitance and good retention. The versatile CuFe2O4-GN holds great promise for application in a wide range of electrochemical fields because of the remarkable synergistic effects between CuFe2O4 nanoparticles and graphene.

Facile Synthesis of Oxidation-Resistant Copper Nanowires toward Solution-Processable, Flexible, Foldable, and Free-Standing Electrodes

Oxidation-resistant copper nanowires (Cu NWs) are synthesized by a polyol reduction method. These Cu NWs show excellent oxidation resistance, good dispersibility, and have a low sintering temperature. A Cu NW-based flexible, foldable, and free-standing electrode is fabricated by filtration and a sintering process. The electrode also exhibits high electrical conductivity even bending, folding, and free-standing.

Synthesis of Cu3Sn alloy nanocrystals through sequential reduction induced by gradual increase of the reaction temperature.

Cu3Sn alloy nanocrystals are synthesized by sequential reduction of Cu and Sn precursors through a gradual increase of the reaction temperature. By transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), UV/Vis spectroscopy, and X-ray diffraction (XRD) analyses, the alloy formation mechanism of Cu3Sn nanocrystals has been studied. The incremental increase of the reaction temperature sequentially induces the reduction of Sn, the diffusion of Sn into the preformed Cu nanocrystals, resulting in the intermediate phase of Cu-Sn alloy nanocrystals, and then the formation of Cu3Sn alloy nanocrystals. We anticipate that the synthesis of Cu3Sn alloy nanocrystals encourages studies toward the synthesis of various alloy nanomaterials.

A magnetically recoverable photocatalyst prepared by supporting TiO2 nanoparticles on a superparamagnetic iron oxide nanocluster core@fibrous silica shell nanocomposite

A magnetically recoverable photocatalyst was prepared by supporting TiO2 nanoparticles on a superparamagnetic iron oxide nanocluster (SION) core@fibrous silica shell (FSS) nanocomposite. Using the raspberry-shaped magnetic iron oxide nanocluster core as a seed, FSS with uniform thickness was grown directly on the core surface by a sol–gel process. The preparation method was optimized to have a single core for each nanoparticle by adjusting the amount of the silica source. The FSS has a fanning structure of radial pores, which enable large amounts of TiO2 nanoparticles to be supported easily on the pore surface. SION@FSS with amorphous TiO2 loaded on the pores (SION@FSS@Am-TiO2) was crystallized to the anatase phase (SION@FSS@A-TiO2), which shows good photocatalytic effect. When used for water purification, SION@FSS@A-TiO2 shows faster dye degradation kinetics than that of commercial P25 nanoparticles. The as-prepared SION@FSS@A-TiO2 photocatalyst could be magnetically recovered easily from water after decolorization of the dye.

One pot synthesis of amine-functionalized and angular-shaped superparamagnetic iron oxide nanoparticles for MR/fluorescence bimodal imaging application

Herein, we report the simple preparation of water dispersible angular-shaped amine-functionalized super-paramagnetic iron oxide nanoparticles (A-SPIONs). A-SPIONs were synthesized by heating iron(III) acetylacetonate in a mixture of solvents containing polyethyleneglycol (PEG) and branched polyethyleneimine (b-PEI) under vigorous stirring. Both PEG and b-PEI provided high water dispersibility by competitively surface coating the A-SPIONs. In addition, b-PEI controlled the overall morphology of the A-SPIONs, producing polyhedral nanocrystals in combination with the added halide ions. Due to the amine functional group from b-PEI, the A-SPIONs are proven to have both a positively charged surface (+29.1 mV) and active sites, which enable facile functionalization. Using A-SPIONs of 9.42 ± 2.93 nm (TEM observation), a high saturation magnetization value of 75.61 emu g−1 was obtained using a superconducting quantum interface device (SQUID). The A-SPIONs sustained a stable dispersion in aqueous media with various pH, and their hydrodynamic size was about 13.97 nm in 0.10 M NaCl solution. Through the MTT assay, the A-SPIONs were proven to have negligible cellular toxicity in SKOV-3, U87-MG, and U251 cell lines. The angular-shaped iron oxide nanoparticles also exhibited high relaxivity for magnetic resonance imaging (MRI), which originated from their high magnetization. Cyanine 5.5 dye-functionalized A-SPIONs (Cy 5.5@A-SPIONs) were prepared and serial experiments were conducted to investigate their fluorescence imaging applications. According to the results, the A-SPIONs are expected to have potential applications in bimodal imaging.

In vivo delineation of glioblastoma by targeting tumor-associated macrophages with near-infrared fluorescent silica coated iron oxide nanoparticles in orthotopic xenografts for surgical guidance

Glioblastoma multiforme (GBM) is the most aggressive and lethal type of human brain cancer. Surgery is a current gold standard for GBM treatment but the complete surgical resection of GBM is almost impossible due to their diffusive characteristics into surrounded normal brain tissues. There is an urgent need to develop a sensitive imaging tool for accurate delineation of GBM in the operating room to guide surgeons. Here we illustrate the feasibility of using near-infrared fluorescent silica coated iron oxide nanoparticles (NF-SIONs) with high water dispersion capacity and strong fluorescence stability for intraoperative imaging of GBM by targeting tumor-associated macrophages. Abundant macrophage infiltration is a key feature of GBM margins and it is well associated with poor prognosis. We synthesized NF-SIONs of about 37 nm to maximize endocytosis activity for macrophage uptake. The NF-SIONs selectively visualized tumor-associated macrophage populations by in vitro live-cell imaging and in vivo fluorescence imaging. In the orthotopic GBM xenograft models, the NF-SIONs could successfully penetrate blood-brain barrier and delineated tumor burden specifically. Taken together, this study showcased the potential applications in GBM treatment for improved intraoperative staging and more radical surgery as well as dual modality benefit in order to circumvent previous clinical failure.