Amphiphilic block copolymer nanotubes and vesicles stabilized by photopolymerization

We report on a new method to stabilize nanotube and vesicle structures created from amphiphilic diblock copolymers by means of photopolymerization. Cross-linking with UV light exposure minimizes fluid disruption during stabilization. Additionally, the spatial control afforded by focusing or masking the initiating light source enables stabilization of distinct segments of individual nanostructures. This contribution demonstrates (1) that vesicles and nanotubes formed from poly(ethylene oxide)-block-polybutadiene are stabilized by exposure to UV light in the presence of a water-soluble photoinitiator and (2) that new nanotube geometries can be constructed by means of spot-curing, and (3) it reveals an application for photopolymerized nanotubes by showing electrophoresis of DNA through a UV-stabilized nanotube.     

Photofunctional Nanomodulators for Bioexcitation

A single organism comprises diverse types of cells. To acquire a detailed understanding of the biological functions of each cell, comprehensive control and analysis of homeostatic processes at the single‐cell level are required. In this study, we develop a new type of light‐driven nanomodulator comprising dye‐functionalized carbon nanohorns (CNHs) that generate heat and reactive oxygen species under biologically transparent near‐infrared (NIR) laser irradiation. By exploiting the physicochemical properties of the nanohorns, cellular calcium ion flux and membrane currents were successfully controlled at the single‐cell level. In addition, the nanomodulator allows a remote bioexcitation of tissues during NIR laser exposure making this system a powerful tool for single‐cell analyses and innovative cell therapies.     

Cross‐Cultural Issues Arising for Four Science Teachers During Their International Migration to Teach in U.S. High Schools

U.S. schools have experienced a perennial shortage of teachers. Recently, many school districts have been inviting foreign veteran teachers to help mitigate such teacher shortages. This study describes the initial cross‐cultural issues four international science teachers encountered when they immigrated to teach in U.S. high schools. In‐depth, semistructured interviews of four science teachers (from Ghana, Britain, and Germany) produced the main source of data. The international teachers faced a variety of support system problems, which were not directly classroom related, but nevertheless had an impact on their instructional effectiveness. They also faced teaching‐related issues, including differences in school organization and structure, assessment and philosophical beliefs, communication, textbooks, teaching methods, and teacher‐student relations. They all expressed a need to become active learners in order to function effectively in their new teaching contexts. The implications are discussed based on the findings.     

Hopping transport in conductive heterocyclic oligomers: reorganization energies and substituent effects

Molecular scale charge motion in disordered organic materials at ambient temperature occurs via a hopping-type mechanism with rates dictated both by the charge transfer integral and by the reorganization energy due to geometric relaxation. This contribution presents a systematic theoretical analysis of cation internal reorganization energies for a broad family of organic oligoheterocycles-variation of reorganization energy with oligomer chain length, heteroatom identity, and a range of heterocycle substituents provides key information on important structural properties governing internal reorganization energies. At room temperature, the range in reorganization energies induced by substituent variations corresponds to a >10(2)-fold variation in intrinsic hole transfer rate, suggesting that changes in reorganization energy dominate variations in charge-transfer rates for many semiconducting/conducting oligomers.     

Electrodeposited quantum dots IV. Epitaxial short-range order in amorphous semiconductor nanostructures

The structure of diffraction-amorphous CdSe (a-CdSe) quantum dots (QDs) electrodeposited on evaporated Pd substrate was studied by high resolution transmission electron microscopy (HRTEM), and compared with epitaxial (crystalline) QDs obtained by the same procedure on Au, as well as with a simulated image of random a-CdSe. Digital analysis of HRTEM images established the existence of repeating ordered motifs in a-CdSe QDs on Pd substrates, in the form of epitaxial sub-nanometre to nanometre size clusters. The QDs are shown to be intermediate between crystalline and random amorphous material. Digital Fourier analysis indicated epitaxial relationship with the 111inPd substrate, rotated 30° relative to the orientational relationship on 111_Au.     

Synthesis and post-processing of nanomaterials using microreaction technology

A critical barrier to the routine use of nanomaterials is the tedious, expensive means of their synthesis. Microreaction technology takes advantage of the large surface area-to-volume ratios within microchannel structures to accelerate heat and mass transport. This accelerated transport allows for rapid changes in reaction temperatures and concentrations leading to more uniform heating and mixing which can have dramatic impacts on macromolecular yields and nanoparticle size distributions. Benefits of microreaction technology include higher yield and reactant conversion, better energy efficiency and less by-product generation. Microreactors can help minimize the environmental impact of nanoproduction by enabling solvent free mixing, integrated separation techniques and reagent recycling. The possibility of synthesizing nanomaterials in the required volumes at the point-of-use eliminates the need to store and transport potentially hazardous materials and provides the flexibility for tailoring complex functional nanomaterials. Recognizing these benefits for nanosynthesis, continuous flow microreactors have been used by several research groups to synthesize and characterize nanomaterials. An overview of these efforts and issues related to scale up and other post synthesis processes such as separation and deposition are presented in this paper.     

In situ 54Mn NMRON Studies of the Mixed Halide Mn(Br X Cl1−X )2 · 4H2O in Applied Magnetic Fields

⁵⁴Mn NMRON in the mixed halide antiferromagnet, Mn(Br _X Cl_1−X )₂ · 4H₂O, for varying external field, is reported. Significant qualitative differences are found between these NMRON transitions and those of the two terminal compounds, especially in respect to line widths. A tentative assignment is made to most of the observed NMRON transitions out to 0.8 T. An unidentified lower frequency inhomogeneous signal, present only at the lowest temperatures, with no counterpart in the terminal compounds, is also reported.     

Quantitative Absorption spectra via photoacoustic phase angle spectroscopy (ΦAS)

By measuring the phase angle of the photoacoustic signal it is possible to calculate the quantitative absorption spectrum of a condensed phase sample, if in addition only the sample thermal diffusivity is known. The technique also extends the upper limit of absorptivity which may be usefully studied photoacoustically by a factor of 10.