Jin-woo Cheon

Current biomedical imaging techniques including magnetic resonance imaging (MRI), positron emission tomography (PET), and computed X-ray tomography (CT) are vital in the diagnosis of various diseases. Each imaging modality has its own merits and disadvantages, and a single technique does not possess all the required capabilities for comprehensive imaging. Therefore, multimodal imaging methods are quickly becoming important tools for state-of-the-art biomedical research and clinical diagnostics a

Mesoporous silica nanoparticles are useful nanomaterials that have demonstrated the ability to contain and release cargos with mediation by gatekeepers. Magnetic nanocrystals have the ability to exhibit hyperthermic effects when placed in an oscillating magnetic field. In a system combining these two materials and a thermally sensitive gatekeeper, a unique drug delivery system can be produced. A novel material that incorporates zinc-doped iron oxide nanocrystals within a mesoporous silica framew

Magnetic nanoparticles have been extensively explored as a versatile platform for magnetic resonance imaging (MRI) contrast agents due to their strong contrast enhancement effects together with the platform capability for multiple imaging modalities. In this tutorial review, we focus on recent progress in the use of magnetic nanoparticles for MRI contrast agents and multi-mode imaging agents such as T1-T2 MRI, MRI-optical, and MRI-radioisotopes. This review also highlights emerging magnetic imag

The preparation of 2D layered SnS2 nanoplates with nanoscale lateral confinement (less than 150 nm) is described (see figure). Their unique nanoscale characteristics, including finite lateral 2D morphology, make the discharge capacity of Li ion batteries remarkably high-almost close to the theoretical possible value.

We demonstrate a novel synthetic scheme that can be used to differentially guide the shape of PbS semiconductor nanocrystals. Our study first demonstrates the discovery of single-crystalline star-shaped nanocrystals as novel transient species. We then carefully probe their shape evolution toward other novel nanostructures (e.g., tadpole-, L-, T-, cross-shapes, highly faceted star shapes, truncated octahedrons and cubes, etc.) and systematically elucidate the key parameters that control these fin

With the aim of controlling nanoscale magnetism, we demonstrate an approach encompassing concepts of surface and exchange anisotropy while reflecting size, shape, and structural hybridization of nanoparticles. We visualize that cube has higher magnetization value than sphere with highest coercivity at 60 nm. Its hybridization into core-shell (CS) structure brings about a 14-fold increase in the coercivity with an exceptional energy conversion of magnetic field into thermal energy of 10600 W/g, t

Shape- and dopant-controlled magnetic semiconductor nanocrystals have been achieved by the thermolysis of nonpyrophoric and less reactive single molecular precursors under a monosurfactant system. Reaction parameters governing both the intrinsic crystalline phase and the growth regime (kinetic vs thermodynamic) are found to be important for the synthesis of various shapes of MnS nanocrystals that include cubes, spheres, 1-dimensional (1-D) monowires, and branched wires (bipods, tripods, and tetr

Shape- and size-controlled synthesis of single-crystalline maghemite (gamma-Fe2O3) nanocrystals are performed by utilizing a solution-based one-step thermolysis method. Modulating the growth parameters, such as the type and amount of capping ligands as well as the growth time, is shown to have a significant effect on the overall shape and size of the obtained nanocrystals and on the ripening process itself. The resulting shapes of the novel structures are diverse, including slightly faceted sphe

Achieving high accuracy in the imaging of biological targets is a challenging issue. For MRI, to enhance imaging accuracy, two different imaging modes with specific contrast agents are used; one is a T1 type for a "positive" MRI signal and the other is a T2 type for a "negative" signal. Conventional contrast agents respond only in a single imaging mode and frequently encounter ambiguities in the MR images. Here, we propose a "magnetically decoupled" core-shell design concept to develop a dual mo

Magnetic nanoparticles exhibit unique nanoscale properties and their utilization for various magnetic systems is of significant interest. Especially, heterostructured magnetic nanoparticles are emerging as next-generation materials due to their synergistically enhanced magnetism and potential multifunctionalities. Herein, we overview the recent advances in the development of magnetic nanoparticles with a focus on multicomponent heterostructured nanoparticles including alloys, core-shells, and bi

Since inorganic nanocrystals exhibit unique shape-dependent nanoscale properties and can be utilized as basic building blocks for futuristic nanodevices, a systematic study on the shape control of these nanocrystals remains an important subject in materials and physical chemistry. In this feature article, we overview the recent progress on the synthetic development of symmetry-controlled colloidal nanocrystals of semiconductor and metal oxide, which are prepared through nonhydrolytic chemical ro

Despite various approaches to immunoassay and chromatography for monitoring cortisol concentrations, conventional methods require bulky external equipment, which limits their use as mobile health care systems. Here, we describe a human pilot trial of a soft, smart contact lens for real-time detection of the cortisol concentration in tears using a smartphone. A cortisol sensor formed using a graphene field-effect transistor can measure cortisol concentration with a detection limit of 10 pg/ml, wh