Jung-Tak Jang

Critical Enhancements of MRI Contrast and Hyperthermic Effects by Dopant-Controlled Magnetic Nanoparticles†

Doped up: The incorporation of Zn(2+) dopants in tetrahedral sites leads to the successful magnetism tuning of spinel metal ferrite nanoparticles (see picture). (Zn(0.4)Mn(0.6))Fe(2)O(4) nanoparticles exhibit the highest magnetization value among the metal ferrite nanoparticles. Such high magnetism results in the largest MRI contrast effects (r2=860 mm(-1) s(-1)) reported to date and also huge hyperthermic effects.

Well-Defined Colloidal 2-D Layered Transition-Metal Chalcogenide Nanocrystals via Generalized Synthetic Protocols

While interesting and unprecedented material characteristics of two dimensionality (2-D) layered nanomaterials are emerging, their reliable synthetic methodologies are not well developed. In this study we demonstrate general applicability of synthetic protocols to a wide range of colloidal 2-D layered transition-metal chalcogenide (TMC) nanocrystals. As distinctly different from other nanocrystals, we discovered that 2-D layered TMC nanocrystals are unstable in the presence of reactive radicals from elemental chalcogen during the crystal formation. We first introduce the synthesis of titanium sulfide and selenide where well-defined single crystallinity and lateral size controllability are verified, and then such synthetic protocols are extended to all of group IV and V transition-metal sulfide (TiS(2), ZrS(2), HfS(2), VS(2), NbS(2), and TaS(2)) and selenide (TiSe(2), ZrSe(3), HfSe(3), VSe(2), NbSe(2), and TaSe(2)) nanocrystals. The use of appropriate chalcogen source is found to be critical for the successful synthesis of 2-D layered TMC nanocrystals. CS(2) is an efficient chalcogen precursor for metal sulfide nanocrystals, whereas elemental Se is appropriate for metal selenide nanocrystals. We briefly discuss the effects of reactive radical characteristics of elemental S and Se on the formation of 2-D layered TMC nanocrystals.

Magnetic nanoclusters for ultrasensitive magnetophoretic assays.

Assays of metabolites and disease biomarkers with high sensitivity are most demanding in the fields of medical and biological sciences. Toaccomplish this goal, theuseofmagnetic particles (MPs) has been attractive mainly due to their distinct advantages, including facile control by magnetism, high biocompatibility, and high detection sensitivity. In particular, integration with microfluidic systems endowed the MPbased assay with significantly enhanced sensitivity and selectivity in detecting target analytes. In addition to the combination of a microfluidic system, modulations in the structure and shape of MPs are expected to confer enhanced analytical performance on theMP-based assay. It was reported that multimeric form or self-assembly of magnetic nanoparticles (MNPs) can improve the sensitivity of the bioassay due to the amplified transverse relaxation time.