Growth mechanism of gold nanoparticles decorated on polystyrene spheres via self-regulated reduction

Uniform polystyrene (PS) microspheres prepared for deposition of metallic nanoparticles were synthesized using the surfactant-free emulsion polymerization based on styrene/potassium persulfate/water (St/KPS/H₂O) system. Owing to the presence of sulfate groups, the PS microspheres can be utilized to reduce gold nanoparticles without adding extra reducing agent into the mixture. The synthesis and characterization of metal-polystyrene nanocomposites are reported, and a possible reduction mechanism is proposed: by heating the aqueous solution in the presence of metal ions and PS, the sulfate chain end groups of the PS hydrolyzed and transformed to hydroxyl groups firstly. The hydroxyl groups function as a reducing agent, and carboxylic groups provide a site to adsorb the gold nuclei. The Au nanoparticles grow in size with the coalescence and dissolving of nuclei through the Ostwald ripening process. The PS microspheres and Au nanoparticles were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, X-ray power diffraction, and thermal gravimetric analysis.     

The fascinating noncentrosymmetric copper(II) phosphates synthesized via CsCl salt-inclusion

Two new noncentrosymmetric (NCS) solids were isolated via high-temperature, salt-inclusion reactions, Cs(2)Cu(7)(P(2)O(7))(4).6CsCl (1, CU-9) and Cs(2)Cu(5)(P(2)O(7))(3).3CsCl (2, CU-11). These copper(II) phosphates exhibit novel open-framework structures conceptually templated by extended Cs-Cl salt. The latter resides cooperatively in the channels upon the formation of the NCS Cu-P-O frameworks, leading to the formation of fascinating salt lattices centered by the NaCl-type core. These new discoveries are significant for they may give rise to a new route for the templated synthesis of NCS solids. We are to show here the structural correlation of the newly discovered hybrid solids, and the role of the chlorine atoms in the "intergrowth" of covalent/ionic sublattices.     

Photochemical Activities of N‐Nitroso Carboxamides and Sulfoximides and Their Application to DNA Cleavage

N‐Nitroso compounds containing benzene, fluorene or fluorenone rings were synthesized. Photolysis of these compounds with 312‐nm UV light provided the NO ^. species, the presence of which was corroborated by use of an EPR method and of 2‐phenyl‐4,4,5,5‐tetramethylimidazolin‐1‐oxyl 3‐oxide (PTIO) as a trapping agent. During irradiation of N‐methyl‐N‐nitroso‐9‐fluorenone carboxamide ( 14 c ) in the absence of PTIO, it underwent decomposition followed by recombination to give the heterocyclic nitric oxide radical 15 . Incorporation of intercalating moieties endowed the N‐nitroso compounds with DNA‐cleaving ability through single‐strand scission upon UV irradiation in a phosphate buffer (pH 5.0–8.0) under aerobic conditions.     

Atomic scale oxidation of a complex system: O2/alpha-SiC(0001)-( 3 x 3)

The atomic scale oxidation of the alpha-SiC(0001)-(3 x 3) surface is investigated by atom-resolved scanning tunneling microscopy, core level synchrotron radiation based photoemission spectroscopy, and infrared absorption spectroscopy. The results reveal that the initial oxidation takes place through the relaxation of lower layers, away from the surface dangling bond, in sharp contrast to silicon oxidation.     

Deoxygenative olefination reaction as the key step in the syntheses of deoxy and iminosugars

Just a spoonful of sugar! A new synthetic strategy involving the use of a deoxygenative olefination reaction as the key step was developed for the preparation of deoxy and iminosugars in their optically active form (see scheme). This strategy has been proven successful by the use of a pentose, hexose, heptose, and disaccharide as the starting materials. Furthermore, it was applied in a formal total synthesis of iminosugar (-)-1-deoxy-L-fuconojirimycin, which can inhibit α-L-fucosidase.     

High throughput label-free platform for statistical bio-molecular sensing

Sensors are crucial in many daily operations including security, environmental control, human diagnostics and patient monitoring. Screening and online monitoring require reliable and high-throughput sensing. We report on the demonstration of a high-throughput label-free sensor platform utilizing cantilever based sensors. These sensors have often been acclaimed to facilitate highly parallelized operation. Unfortunately, so far no concept has been presented which offers large datasets as well as easy liquid sample handling. We use optics and mechanics from a DVD player to handle liquid samples and to read-out cantilever deflection and resonant frequency. Also, surface roughness is measured. When combined with cantilever deflection the roughness is discovered to hold valuable additional information on specific and unspecific binding events. In a few minutes, 30 liquid samples can be analyzed in parallel, each by 24 cantilever-based sensors. The approach was used to detect the binding of streptavidin and antibodies.