Cole T. Duncan

Recent advances in nanostructured chemosensors and biosensors.

Over the past few decades the fabrication of nanoscale materials for use in chemical sensing, biomedical and biological analyses has proven a promising avenue. Nanomaterials show promise in such chemical and biological analysis mainly due to their highly tunable size- and shape-dependent chemical and physical properties. Furthermore, they exhibit unique surface chemistry, thermal stability, high surface area and large pore volume per unit mass that can be exploited for sensor fabrication. This review will discuss the chemical and physical properties of nanomaterials necessary for use as chemosensors and biosensors. It will also highlight some noteworthy recent avenues using nanoscale materials as scaffolds for chemosensing and biosensing. Nanomaterials that have proven to be useful for the fabrication of sensors, as reviewed herein, have compositions including metals, metal oxides, chalcogenides and polymers. Their structures range from nanoparticles, nanorods, and nanowires to nanoporous and core-shells. Examples of the different types of structures and compositions as well as sensors and biosensors fabricated from them will be described. Some nanomaterials are functionalized with various kinds of ligands and bioactive groups to produce sensitive and selective sensors for specific analytes. The combination of two or more types of nanostructures with core-shell type nanoassemblies and other composite structures, in addition to advantageous features enhancing sensitivity and response time of related sensors, are also discussed.

Mesoporous Silica Nanoparticles Inhibit Cellular Respiration

We studied the effect of two types of mesoporous silica nanoparticles, MCM-41 and SBA-15, on mitochondrial O 2 consumption (respiration) in HL-60 (myeloid) cells, Jurkat (lymphoid) cells, and isolated mitochondria. SBA-15 inhibited cellular respiration at 25-500 microg/mL; the inhibition was concentration-dependent and time-dependent. The cellular ATP profile paralleled that of respiration. MCM-41 had no noticeable effect on respiration rate. In cells depleted of metabolic fuels, 50 microg/mL SBA-15 delayed the onset of glucose-supported respiration by 12 min and 200 microg/mL SBA-15 by 34 min; MCM-41 also delayed the onset of glucose-supported respiration. Neither SBA-15 nor MCM-41 affected cellular glutathione. Both nanoparticles inhibited respiration of isolated mitochondria and submitochondrial particles.

Controlled Synthesis of Water-Dispersible Faceted Crystalline Copper Nanoparticles and Their Catalytic Properties

We report a solution-phase synthetic route to copper nanoparticles with controllable size and shape. The synthesis of the nanoparticles is achieved by the reduction of copper(II) salt in aqueous solution with hydrazine under air atmosphere in the presence of poly(acrylic acid) (PAA) as capping agent. The results suggest that the pH plays a key role for the formation of pure copper nanoparticles, whereas the concentration of PAA is important for controlling the size and geometric shape of the nanoparticles. The average size of the copper nanoparticles can be varied from 30 to 80 nm, depending on the concentration of PAA. With a moderate amount of PAA, faceted crystalline copper nanoparticles are obtained. The as-synthesized copper nanoparticles appear red in color and are stable for weeks, as confirmed by UV/Vis and X-ray photoemission (XPS) spectroscopy. The faceted crystalline copper nanoparticles serve as an effective catalyst for N-arylation of heterocycles, such as the C--N coupling reaction between p-nitrobenzyl chloride and morpholine producing 4-(4-nitrophenyl)morpholine in an excellent yield under mild reaction conditions. Furthermore, the nanoparticles are proven to be versatile as they also effectively catalyze the three-component, one-pot Mannich reaction between p-substituted benzaldehyde, aniline, and acetophenone affording a 100% conversion of the limiting reactant (aniline).

Aminotroponiminate–Zinc Complex-Functionalized Mesoporous Materials: Efficient and Recyclable Intramolecular Hydroamination Catalysts

The formation of nitrogen heterocycles is of considerable interest in the production of fine chemicals, pharmaceuticals, and synthetic natural products. To avoid lengthy synthetic methods, there has been a wealth of research toward these products through intramolecular hydroamination using organoRh, -Pt, , and -Zr complexes, as well as organolanthanides and group three metal complexes as catalysts; such catalysts generally help in generating moderate to excellent yields with good reaction times (7–48 h) for a broad range of reagent functionalities. These materials, however, are generally air sensitive, costly to produce, and lack recyclability necessary for industrial scale syntheses. Zinc-based zeolites have been very effective in the cyclization of 6-aminohex-1-yne, but they have not proven useful with more bulky non-activated alkenes or alkynes, nor have they been shown recyclable. Herein, we report the synthesis and characterization of a zinc-aminotroponiminate (ATI) complex immobilized on mesoporous silica for use as a recyclable catalyst in the intramolecular hydroamination of a non-activated alkene, which to our knowledge, is the first of this kind on functionalized mesoporous silica. Recent studies performed by Roesky and Blechert have shown homogenous zinc aminotroponiminates (ATIs) and zinc amintroponates (ATOs) to be very effective intramolecular hydroamination catalysts for non-activated alkenes and alkynes with a broad range of functional group compatibility. 7] Furthermore, these compounds may easily be modified to alter the steric/electronic nature of the catalyst, are relatively stable in air and moisture at various pH levels, and utilize a nontoxic metal. Owing to its bidentate anionic nature, the ATI ligand forms very stable chelate complexes with a variety of metals. Such chelating properties make it an excellent material for heterogeneous catalysis to aid in the prevention of metal (active site) leaching over multiple uses. Synthesis of the ATI ligand was accomplished in a multistep process on highly ordered mesoporous silica SBA-15 with a surface area of 727 m g and pore diameter of 85 by grafting and post-synthesis modification (Scheme 1). Briefly, 3-aminopropyltrimethoxysilane in isopropanol was grafted to serve as the amine source toward imine formation of the ATI com-

Solvent-washable polymer templated synthesis of mesoporous materials and solid-acid nanocatalysts in one-pot

We report a new and simple one-pot synthetic method to produce mesoporous silica and nanoporous solid acid catalyst capable of catalyzing pinacole-pinacolone rearrangement and esterification reactions, by preparing a solvent washable phosphonated triblock copolymer template and self-assembling it in the presence of alkoxysilane.