Targeted delivery to single cells in precisely controlled microenvironments.

The heterogeneous nature of cells can be an issue for in vitro analysis of cell function due to cell type differences within a population. Observations are most often averaged and dependent on the homogeneity or lack thereof for most cell types. Patterning of features at the sub-cellular scale (< 10 μm) allows for single cell manipulation.

Multi-ink pattern generation by dip-pen nanolithography.

Multiplexed patterns of hydrogels and phospholipids with fluorescent dyes are accomplished by dip-pen nanolithography (DPN). For example, four different dye-labeled hydrogel dot arrays are DPN patterned within 50x50 microm(2) area, and two different dye-doped phospholipids dots and letters with less than 1 microm line-width are also DPN patterned. We demonstrate that multi-ink patterns with precise alignment are able to be printed by DPN within a micron-scale.

Depositing ordered arrays of metal sulfide nanoparticles in nanostructures using supercritical fluid carbon dioxide.

Silver sulfide and cadmium sulfide nanoparticles of controllable sizes are synthesized using a water-in-hexane microemulsion method and stabilized by dodecanethiol. The stabilized metal sulfide nanoparticles can be deposited homogenously on flat substrates forming ordered 2-D arrays in supercritical fluid carbon dioxide (Sc-CO(2)). The use of Sc-CO(2) leaves the particles unaffected by dewetting effects caused by traditional solvents and produces uniform arrays.

Biocidal activity of nanocrystalline silver powders and particles.

While the activity of the SMAD powders is lower than that of pure silver nitrate, it has the ability to kill bacteria very effectively and over long periods of time.

Fine-tuning size of gold nanoparticles by cooling during reverse micelle synthesis.

By lowering the reaction temperature during metal ion reduction in a reverse micelle system, gold nanoparticle size can be subtly tuned from 6.6 to 2.2 nm in diameter.

Synthesis and characterization of a new Tiara Pd(II) thiolate complex, [Pd(SC12H25)2]6, and its solution-phase thermolysis to prepare nearly monodisperse palladium sulfide nanoparticles.

A new tiara Pd(II) thiolate complex, [Pd(SC12H25)2]6, has been synthesized and fully characterized by X-ray single crystal analysis, elemental analysis, MALDI, 1H NMR, powder XRD, IR, Raman, and UV/vis. It was found that, in each complex cluster, the six palladium atoms form a nearly planar hexagonal ring and the adjacent palladium atoms are bridged by sulfur atoms from both sides. Then the complex was further used as a single-source precursor to prepare nearly monodisperse palladium sulfide (PdS) nanoparticles through the high-temperature-induced decomposition in diphenyl ether.

Gram-scale synthesis of aqueous gold colloids stabilized by various ligands.

We have developed a method for the large-scale synthesis of gold nanoparticles (Au NPs) in an aqueous medium stabilized by various water-soluble ligands. Significantly, the narrow size-distribution of the particles is achieved without employing size-selective procedures. The versatility of the procedure is demonstrated for the preparation of three colloidal systems stabilized by different ligands.

Low-temperature metallic alloying of copper and silver nanoparticles with gold nanoparticles through digestive ripening.

We describe a remarkable and simple alloying procedure in which noble metal intermetallic nanoparticles are produced in gram quantities via digestive ripening. This process involves mixing of separately prepared colloids of pure Au and pure Ag or Cu particles and then heating in the presence of an alkanethiol under reflux. The result after 1 h is alloy nanoparticles.

Synthesis of spherical silver nanoparticles by digestive ripening, stabilization with various agents, and their 3-D and 2-D superlattice formation.

Capped nanoparticles of silver were synthesized via the solvated metal atom dispersion (SMAD) technique followed by a digestive ripening procedure producing gram quantities of monodisperse spherical nanoparticles. This shows for the first time that a digestive ripening protocol is possible for an element other than gold. The particle size and optical spectra were found to be dependent on the capping agent used.