Liquid crystal alignment properties of 2-naphthoxymethyl-substituted polystyrenes

The liquid crystal (LC) alignment properties of LC cells fabricated with films of 2-naphthoxymethyl-substituted polystyrenes with different contents of naphthoxymethyl side groups were investigated. The polymer films exhibited good optical transparency in the visible light region (400–700 nm). The LC cells made from the unrubbed films of polymers having more than 57 mol%?of 2-naphthoxymethyl containing monomeric units showed homeotropic LC alignment with a high pretilt angle of about 90^o. Good electro-optical characteristics, such as the threshold voltage, response time, voltage holding ratio and residual DC voltage were observed for the LC cells fabricated with the polymer having 100 mol%?of 2-naphthoxymethyl containing monomeric units as an LC alignment layer.     

General Method to Increase Carboxylic Acid Content on Nanodiamonds

Carboxylic acid is a commonly utilized functional group for covalent surface conjugation of carbon nanoparticles that is typically generated by acid oxidation. However, acid oxidation generates additional oxygen containing groups, including epoxides, ketones, aldehydes, lactones, and alcohols. We present a method to specifically enrich the carboxylic acid content on fluorescent nanodiamond (FND) surfaces. Lithium aluminum hydride is used to reduce oxygen containing surface groups to alcohols. The alcohols are then converted to carboxylic acids through a rhodium (II) acetate catalyzed carbene insertion reaction with tert–butyl diazoacetate and subsequent ester cleavage with trifluoroacetic acid. This carboxylic acid enrichment process significantly enhanced nanodiamond homogeneity and improved the efficiency of functionalizing the FND surface. Biotin functionalized fluorescent nanodiamonds were demonstrated to be robust and stable single-molecule fluorescence and optical trapping probes.     

Demonstration of a surface plasmon-coupled emission (SPCE)-based immunoassay in the absence of a spacer layer

The technique of surface plasmon-coupled emission (SPCE) involves the coupling of light which is emitted from a fluorophore into the surface plasmon of an adjacent thin metal film, giving rise to highly directional emission. We have combined the advantages of SPCE with the high light collection efficiency of supercritical angle fluorescence by carrying out an immunoassay on a paraboloid array biochip in the absence of the conventional SPCE spacer layer normally used to minimize metal quenching of the fluorescence. In this work, we have successfully demonstrated an SPCE-based assay by utilizing the protein assay layer as the spacer layer. A novel 3 × 3 injection molded polymer biochip with paraboloid elements was used. The paraboloid elements served to enhance the light collection efficiency while the top surface was coated with a gold layer to use excitation of surface plasmons and detection of SPCE emission. Theoretical modeling of the gold-protein layer structure showed that the surface plasmon resonance angles were located in the detection range of the paraboloid biochip. The polarization dependence of SPCE emission was also demonstrated. Finally, a human IgG sandwich immunoassay was carried out which exhibited a limit of detection of ~10 ng/ml using 3σ. The results demonstrate the potential of the SPCE-based paraboloid array biochip as a novel platform for high-throughput analysis of biomolecular interactions.     

Integrated One‐Flow Synthesis of Heterocyclic Thioquinazolinones through Serial Microreactions with Two Organolithium Intermediates

The synthesis of pharmaceutical compounds via short‐lived intermediates in a microreactor is attractive, because of the fast flow and high throughput. Additionally, intermediates can be utilized sequentially to efficiently build up a library in a short time. Here we present an integrated microfluidic synthesis of biologically active thioquinazolinone libraries. Generation of o‐lithiophenyl isothiocyanate and subsequent reaction with aryl isocyanate is optimized by controlling the residence time in the microreactor to 16 ms at room temperature. Various S‐benzylic thioquinazolinone derivatives are synthesized within 10 s in high yields (75–98 %) at room temperature. These three‐step reactions involve two organolithium intermediates, an isothiocyanate‐functionalized aryllithium intermediate, and a subsequent lithium thiolate intermediate. We also demonstrate the gram‐scale synthesis of a multifunctionalized thioquinazolinone in the microfluidic device with a high yield (91 %) and productivity (1.25 g in 5 min).     

On the interaction of methyl azide (CH3N3) ices with ionizing radiation: formation of methanimine (CH2NH), hydrogen cyanide (HCN), and hydrogen isocyanide (HNC)

Methyl azide (CH(3)N(3)) might be a potential precursor in the synthesis of prebiotic molecules via nonequilibrium reactions on interstellar ices initiated by energetic galactic cosmic rays (GCR) and photons. Here, we investigate the effects of energetic electrons as formed in the track of cosmic ray particles and 193 nm photons with solid methyl azide at 10 K and the inherent formation of methanimine (CH(2)NH), hydrogen cyanide (HCN), and hydrogen isocyanide (HNC). We present a systematic kinetic study and outline feasible reaction pathways to these molecules. These processes might be also important in solar system analogue ices.     

Ring Opening Metathesis Polymerization of Bicyclic α,β‐Unsaturated Anhydrides for Ready‐to‐be‐grafted Polymers Having Tailored pH‐Responsive Degradability

Polymers having α,β‐unsaturated anhydrides as repeating units were synthesized by ring opening metathesis polymerization (ROMP). The anhydride moieties were ready‐to‐be‐grafted with amines to form acid‐labile cis‐α,β‐unsaturated acid amide linkages. The pH‐responsive reversible de‐grafting can be controlled by changing the intramolecular accessibility between acid and amide groups. The alendronate‐grafted ROMP polymers showed distinct pH‐dependent cytotoxicity according to the anhydride structures.     

Spectroscopic observation of atomic hydrogen radicals entrapped in icy hydrogen hydrate

A hydrogen molecule entrapped in the cages of icy hydrogen hydrate is confined in host water framework and thus behaves unlike pure solid or liquid hydrogen. The gamma-irradiated hydrogen radicals are for the first time observed from ESR and solid-state MAS 1H NMR spectra to stably exist in the icy hydrate channels without any collapse of the host framework, confirming the chemical shift consistency of ionized hydrogen derivatives. We discuss the confined icy hydrate channels, which can act as potential storage sites for simultaneously imprisoning both molecular and ionized hydrogen and further as icy nanoreactors.     

Flow‐Assisted Synthesis of [10]Cycloparaphenylene through Serial Microreactions under Mild Conditions

Cycloparaphenylene (CPP) has been recognized as an attractive template for the bottom‐up synthesis of carbon nanotubes with uniform diameter, and is important for the chemistry of graphitic as well as ring‐shaped macromolecules. However, the reported routes from halogenated benzenes have suffered from low yields even under time‐ and labor‐consuming multistep conditions. Herein we report a flow‐assisted synthesis of [10]CPP in four steps under mild conditions. For the synthesis, a selective nucleophilic addition of the unprotected diketone without the double‐added byproduct was achieved within 3 s in high yield. Subsequently, the obtained compound was reacted with dilithiated benzene at 25 °C to form a U‐shaped precursor for CPP in a separate microreactor, which was finally dimerized and aromatized to obtain [10]CPP by a two‐step in‐flask reaction. Precise control of time and flow facilitated by the flow‐assisted system enabled the development of an efficient synthetic route for [10]CPP.