Imaging of trapped ions with a microfabricated optic for quantum information processing

Trapped ions are a leading system for realizing quantum information processing (QIP). Most of the technologies required for implementing large-scale trapped-ion QIP have been demonstrated, with one key exception: a massively parallel ion-photon interconnect. Arrays of microfabricated phase Fresnel lenses (PFL) are a promising interconnect solution that is readily integrated with ion trap arrays for large-scale QIP. Here we show the first imaging of trapped ions with a microfabricated in-vacuum PFL, demonstrating performance suitable for scalable QIP. A single ion fluorescence collection efficiency of 4.2±1.5% was observed. The depth of focus for the imaging system was 19.4±2.4 μm and the field of view was 140±20 μm. Our approach also provides an integrated solution for high-efficiency optical coupling in neutral atom and solid-state QIP architectures.     

Floating carpets and the delamination of elastic sheets

We investigate the deformation of a thin elastic sheet floating on a liquid surface and subject to a uniaxial compression. We show that at a critical compression the sheet delaminates from the liquid over a finite region forming a delamination "blister." This blistering regime adds to the wrinkling and localized folding regimes that have been studied previously. The transition from wrinkled to blistered states occurs when delamination becomes energetically favorable compared with wrinkling. We determine the initial blister size and the evolution of blister size with continuing compression before verifying our theoretical results with experiments at a macroscopic scale.     

A 2,6‐Bis(phenylamino)pyridinato Titanium Catalyst for the Highly Regioselective Hydroaminoalkylation of Styrenes and 1,3‐Butadienes

The C? C bond forming catalytic hydroaminoalkylation of terminal alkenes, 1,3‐dienes, or styrenes allows a direct and highly atom efficient (100 %) synthesis of amines which can result in the formation of two regioisomers, the linear and the branched product. We present a new titanium catalyst with 2,6‐bis(phenylamino)pyridinato ligands for intermolecular hydroaminoalkylation reactions of styrenes and 1‐phenyl‐1,3‐butadienes that delivers the corresponding linear hydroaminoalkylation products with excellent regioselectivities.     

Transient excited-state absorption of the liquid crystal CB15 [4-(2-methylbutyl)-4-cyanobiphenyl] in its isotropic phase

Liquid crystals are known to possess large electronic optical non-linearities. Transient photoinduced absorption is not commonly applied to liquid crystals, but it is a powerful technique by which to examine the excited-state absorption (ESA) and hence the non-linear absorption of molecular systems. We show that measurements of this kind can give an insight into the dominant mechanisms of picosecond non-linear optical response in liquid crystals, and together with semi-empirical quantum chemical calculations appropriate assignments of the absorptions can be made. In particular, we report measurements of the transient ESA of the liquid crystal CB15 [4-(2-methylbutyl)-4-cyanobiphenyl] in its isotropic phase using femtosecond pump-probe spectroscopy in the wavelength range from 400 to 1000 nm. By pumping directly into the first excited state (S₁) we identify at least four transient ESAs which contribute to the non-linear response up to a time of 1 ns after excitation. These features show a linear dependence with pump intensity. There also exists weak two-photon absorption (TPA) into S₁ at 650 nm, giving a similar ESA. Furthermore, we show that a semi-empirical quantum-chemical treatment of a single molecular unit of CB15 using the AMI Hamiltonian gives good agreement with the observed spectra, and implies that the dominant ESA in the picosecond regime can be attributed principally to singlet-singlet transitions from monomer units; but there is also a possible contribution to the ESAs by excimer absorption. On the time scale of our experiment we see no evidence of triplet-triplet absorptions, and we have also measured a fluorescence quantum yield of 20%.     

ESCA and optical emission study of the inductively coupled RF plasma copolymerization of naphthalene and octafluoronaphthalene mixtures

Plasma polymerization of octafluoronaphthalene, naphthalene, and 1 : 1 mixtures of the two yielded thin films which were then analyzed by ESCA. Optical emission was recorded during deposition and the resultant spectra are shown. Deposition of the copolymer at 150°C resulted in a film whose composition was different from that deposited at room temperature and from the single plasma polymers. Copolymerization resulted in a lowering of CF₂ functionalities and an increased retention of the aromatic nature of the monomers. Optical emission of CF₂ during copolymerization was greatly reduced as was a peak at about 510 nm.     

Purification and characterization of commercial NADH and accompanying dehydrogenase inhibitors.

The anion-exchange chromatography of commercial NADH using a potassium bicarbonate solution as eluent yields highly pure NADH with good stability. Twelve compounds are also separated which act as dehydrogenase inhibitors. The main impurities are further characterized. The compound mainly responsible for residual optical density in commercial NADH preparations is probably a stereoisomer of NADH which is in reversible equilibrium with NADH at pH values in the range 5-7. A method of thin-layer chromatography, to check commercial NADH preparations for impurities, is described.     

Hollow,pH-Sensitive Microgels as Nanocontainers for the Encapsulation of Proteins

Depending on their architectural and chemical design, microgels can selectively take up and release small molecules by changing the environmental properties, or capture and protect their cargo from the surrounding conditions. These outstanding properties make them promising candidates for use in biomedical applications as delivery or carrier systems. In this study, hollow anionic p(N-isopropylacrylamid-e-co-itaconic acid) microgels are synthesized and analyzed regarding their size, charge, and charge distribution. Furthermore, interactions between these microgels and the model protein cytochrome c are investigated as a function of pH. In this system, pH serves as a switch for the electrostatic interactions to alternate between no interaction, attraction, and repulsion. UV–vis spectroscopy is used to quantitatively study the encapsulation of cytochrome c and possible leakage. Additionally, fluorescence-lifetime images unravel the spatial distribution of the protein within the hollow microgels as a function of pH. These analyses show that cytochrome c mainly remains entrapped in the microgel, with pH controlling the localization of the protein – either in the microgel's cavity or in its network. This significantly differentiates these hollow microgels from microgels with similar chemical composition but without a solvent filled cavity.     

A Simple,Transition Metal Catalyst-Free Method for the Design of Complex Organic Building Blocks Used to Construct Porous Metal–Organic Frameworks

The design of metal–organic frameworks (MOFs) having large pore sizes and volumes often requires the use of complex organic ligands, currently synthesized using costly and time-consuming palladium-catalyzed coupling chemistry. Thus, in the present work, a new strategy for ligand design is reported, where piperazine and dihydrophenazine units are used as substitutes for benzene rings, which are the basic building block of most MOF ligands. This chemistry, which is based on simple, nucleophilic aromatic substitution (S_NAr) reactions, is used for the transition metal catalyst-free construction of 21 new, carboxylate-based ligands with varying sizes, shapes, and denticity and 15 linear di- and tetra-nitriles. Moreover, to demonstrate the utility of the ligands as building blocks, 16 new structurally diverse MOFs having surface areas up to 3100 m² g⁻¹ were also synthesized.     

Identifying the Interfacial Polarization in Non-stoichiometric Lead-Free Perovskites by Defect Engineering

Recent advances in perovskite ferroelectrics have fostered a host of exciting sensors and actuators. Defect engineering provides critical control of the performance of ferroelectric materials, especially lead-free ones. However, it remains a challenge to quantitatively study the concentration of defects due to the complexity of measurement techniques. Here, a feasible approach to analyzing the A-site defect and electron in alkali metal niobate is demonstrated. The theoretical relationships among defect concentration, conductivity, and oxygen partial pressure can be established based on the defect chemistry equilibria. The type and concentration of defects are reflected through the conductivity variation with oxygen partial pressure. As a result, the variation of defect concentration gives rise to defect-driven interfacial polarization, which further leads to distinct properties of the ceramics. e.g., abnormal dielectric behavior. Furthermore, this study also suggests a strategy to manipulate defects and charges in perovskite oxides for performance optimization.