A facile synthesis of highly water-soluble, core–shell organo-silica nanoparticles with controllable size via sol–gel process

A series of highly water-soluble organo-silica nanoparticles, ranging from 2 to 10 nm in diameter, were synthesized by the cohydrolysis and copolycondensation reactions. ω-methoxy(polyethyleneoxy)propyltrimethoxysilane (PEG6-9) and hydroxymethyltriethoxysilane (HMTEOS) mixtures were catalyzed by sodium hydroxide in the presence of surfactant benzethonium chloride (BTC) with various ratios of PEG6-9/HMTEOS at room temperature. The synthesized organo-silica nanoparticles possess a core–shell structure with a core of organo-silica resulting from HMTEOS and a monolayer shell of PEG6-9. The chemo-physical characteristics of the particles were studied by gel permeation chromatography (GPC), Fourier transform infrared (FTIR) spectroscopy, ²⁹Si nuclear magnetic resonance (NMR), dynamic light scattering (DLS), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The molecular weight and particle size of the particles increased with increasing HMTEOS molar ratios. The richest HMTEOS composition for the water-soluble particles was found to be HMTEOS:PEG6-9 = 80:20, where the particles had a 6 nm diameter core and a 0.8 nm thick shell. We propose that these water-soluble organo-silica nanoparticles will be suitable for biomedical applications.     

Two-photon absorption enhancement of polymer-templated porphyrin-based J-aggregates

Supramolecular structures based on organized assemblies of macrocyclic chromophores, particularly porphyrin-based dyes, have attracted widespread interest as components of molecular devices with potential applications in molecular electronics, artificial light harvesting, and pharmacology. We report the formation of J-aggregates of two porphyrin-based dyes, 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TSPP, 4) and an amino tris-sulfonate analogue (5) in water using a functionalized norbornene-based homopolymer, synthesized by ring-opening metathesis polymerization (ROMP). Ionic interactions of the cationic side chains (ammonium groups) of the polymer under acidic conditions with the negatively charged sulfonate groups of the porphyrins facilitated polymer template enhanced J-aggregation of the porphyrin dyes. J-Aggregation behavior was investigated photophysically by UV-vis absorption along with steady-state and time-resolved fluorescence studies. Two-photon absorption (2PA) was enhanced by about an order of magnitude for the J-aggregated TSPP relative to its free base. Significantly, the 2PA cross section of the polymer-templated TSPP J-aggregate was up to three times higher than the J-aggregated TSPP in the absence of the polymer template while the 2PA cross section for polymer-templated J-aggregates of 5 increased substantially, up to ca. 10,000 GM, suggesting a prominent role of polymer-templating to facilitate porphyrin aggregation and greatly enhance nonlinear absorption.     

Two-dimensional supramolecular assembly of phenylmercury(II) and cadmium(II) complexes with a tridentate thiohydrazone NNS donor ligand: Synthesis,coordination behavior and crystal structure

The reaction of phenylmercury(II) acetate and cadmium(II) acetate with a refluxed solution of diacetylmonoxime and morpholine N-thiohydrazide formed a novel phenylmercury(II) complex, [PhHg(Hdammthiol)] (1) and a cadmium(II) complex, [Cd(Hdammthiol)₂] (2), respectively (where H₂dammthiol is the thiol form of diacetylmonoximemorpholine N-thiohydrazone (Hdammth) formed by the condensation of diacetylmonoxime and morpholine N-thiohydrazide in the presence of phenylmercury(II) and cadmium(II) ions). The complexes were characterised by elemental analyses and spectral data (electronic, infrared and ¹H NMR) and also by X-ray crystal structure analysis. The X-ray crystallography shows that the phenylmercury(II) complex attained a tricoordinated distorted T-shaped structure, while the cadmium(II) complex attained a trapezoidal bipyramidal geometry. The phenylmercury(II) complex forms a two-dimensional sheet via C–H?O and O–H?N hydrogen bonding and also forms a two-dimensional supramolecular dimer, having C–H?π synthons. Intermolecular C–H?O and O–H?O hydrogen bonding of the cadmium(II) complex forms a two-dimensional supramolecular sheet along the bc plane and posses an impressively short intermolecular C(sp³)?O(sp³) contact.     

Relaxation of the rigid backbone of an oligoamide-foldamer-based α-helix mimetic: identification of potent Bcl-xL inhibitors

By conducting a structure-activity relationship study of the backbone of a series of oligoamide-foldamer-based α-helix mimetics of the Bak BH3 helix, we have identified especially potent inhibitors of Bcl-x(L). The most potent compound has a K(i) value of 94 nM in vitro, and single-digit micromolar IC(50) values against the proliferation of several Bcl-x(L)-overexpressing cancer cell lines.     

Insertion of arynes into thioureas: a new amidine synthesis

Arynes, generated from trimethylsilyl phenyltriflate precursors, have been found to react with thioureas via a formal π-insertion into the C═S bond. The reaction contrasts with that of ureas, which proceeds via benzyne σ-insertion into the C-N bond, and represents a new, operationally simple route to functionalized amidines.     

Characterization and deposition of various light-harvesting antenna complexes by electrospray atomization

Photosynthetic organisms have light-harvesting complexes that absorb and transfer energy efficiently to reaction centers. Light-harvesting complexes (LHCs) have received increased attention in order to understand the natural photosynthetic process and also to utilize their unique properties in fabricating efficient artificial and bio-hybrid devices to capture solar energy. In this work, LHCs with different architectures, sizes, and absorption spectra, such as chlorosomes, Fenna–Matthews–Olson (FMO) protein, LH2 complex, and phycobilisome have been characterized by an electrospray-scanning mobility particle-sizer system (ES-SMPS). The size measured by ES-SMPS for FMO, chlorosomes, LH2, and phycobilisome were 6.4, 23.3, 9.5, and 33.4?nm, respectively. These size measurements were compared with values measured by dynamic light scattering and those reported in the literature. These complexes were deposited onto a transparent substrate by electrospray deposition. Absorption and fluorescence spectra of the deposited LHCs were measured. It was observed that the LHCs have light absorption and fluorescence spectra similar to that in solution, demonstrating the viability of the process.     

Optimization and characterization of a biosensor assembly for detection of <Emphasis Type="Italic">Salmonella</Emphasis> Typhimurium

The performance of biosensors depends directly on the strategies adopted during their development. In this paper, a fast and sensitive biosensor for Salmonella Typhimurium detection was assembled by using optimization studies in separate stages. The pre-treatment assays, biomolecular immobilization (primary antibody and protein A concentrations), and analytical response (hydroquinone and hydrogen peroxide concentrations) were optimized via voltammetric methods. In the biosensor assembly, a gold surface was modified via the self-assembled monolayer technique (SAM) using cysteamine thiol and protein A for immobilization of anti-Salmonella antibody. The analytical response of the biosensor was obtained through the use of a secondary antibody labeled with a peroxidase enzyme, and the signal was evaluated by applying the chronoamperometry technique. The biosensor was characterized by infrared spectroscopy and cyclic voltammetry. Optimization of protein A and primary antibody concentrations enabled higher analytical signals of 7.5 and 75 mg mL^?1, respectively, to be achieved. The hydroquinone and H₂O₂ concentrations selected were 3 and 300 mM, respectively. The biosensor developed attained a very low detection limit of 10 CFU mL^?1 and a fast response with a final detection time of 125 min. These results indicate that this biosensor is very promising for the food safety and emergency response applications.     

Effect of N-doping on hard carbon nano-balls as anode for Li-ion battery: improved hydrothermal synthesis and volume expansion study

Using an improved single-step hydrothermal method, mesoporous hard carbon nano-balls, with nitrogen doping, have been successfully synthesized. These materials exhibit good reversible charge capacity during half-cell tests. Gravimetric capacity for undoped nano-sized and micron-sized mesoporous hard carbon balls is 506 and 475 mAh g^?1, respectively. After nitrogen doping, the specific gravimetric capacities of both nano- and micron-sized carbon balls increase by 6.9 and 8%, respectively. Nitrogen doping enhances retention in specific capacity of both anode materials, particularly in nano-sized carbon balls with capacity retention of 83.9% after 100 cycles. The enhancement is attributed to a significant decrease in volume expansion due to the nitrogen doping. Density functional theory-based computation confirms the reduction of volume expansion by 60%. Improved electrochemical performance of nitrogen-doped hard carbon is due to the drop in volume expansion rate during lithiation along with increased porosity and electronic conductivity. Furthermore, this one-step synthesis can be extended to other carbon sources to get nitrogen-doped hard carbon with sizes varying from micro to nano.