Exploring Photothermal Pathways via in Situ Laser Heating in the Transmission Electron Microscope: Recrystallization, Grain Growth, Phase Separation, and Dewetting in Ag0.5Ni0.5 Thin Films.

A new optical delivery system has been developed for the (scanning) transmission electron microscope. Here we describe the in situ and "rapid ex situ" photothermal heating modality of the system, which delivers >200 mW of optical power from a fiber-coupled laser diode to a 3.7 µm radius spot on the sample. Selected thermal pathways can be accessed via judicious choices of the laser power, pulse width, number of pulses, and radial position. The long optical working distance mitigates any charging artifacts and tremendous thermal stability is observed in both pulsed and continuous wave conditions, notably, no drift correction is applied in any experiment. To demonstrate the optical delivery system's capability, we explore the recrystallization, grain growth, phase separation, and solid state dewetting of a Ag0.5Ni0.5 film. Finally, we demonstrate that the structural and chemical aspects of the resulting dewetted films was assessed.

Cobalt-catalyzed asymmetric olefin aziridination with diphenylphosphoryl azide.

The cobalt(II) complexes of D2-symmetric chiral porphyrins, such as 3,5-Di(t)Bu-ChenPhyrin P5, can catalyze asymmetric olefin aziridination with diphenylphosphoryl azide (DPPA) as a nitrene source. Acceptable asymmetric inductions were observed for the [Co(P5)]-based catalytic system, forming the desired N-phosphorus-substituted aziridines in moderate to high yields and good enantioselectivities.

A metal-organic framework as a flask: photophysics of confined chromophores with a benzylidene imidazolinone core.

Photophysics and dynamics of chromophores with a benzylidene imidazolinone core, responsible for emission of green fluorescent protein variants, were studied as a function of host topology by three approaches. Coordinative, non-coordinative, and "fastened" immobilization were utilized to study chromophore emission. Variable-temperature quadrupolar spin-echo 2H NMR spectra are reported.

Laser-Assisted Focused He+ Ion Beam Induced Etching with and without XeF2 Gas Assist.

Focused helium ion (He+) milling has been demonstrated as a high-resolution nanopatterning technique; however, it can be limited by its low sputter yield as well as the introduction of undesired subsurface damage. Here, we introduce pulsed laser- and gas-assisted processes to enhance the material removal rate and patterning fidelity. A pulsed laser-assisted He+ milling process is shown to enable high-resolution milling of titanium while reducing subsurface damage in situ. Gas-assisted focused ion beam induced etching (FIBIE) of Ti is also demonstrated in which the XeF2 precursor provides a chemical assist for enhanced material removal rate. Finally, a pulsed laser-assisted and gas-assisted FIBIE process is shown to increase the etch yield by ∼9× relative to the pure He+ sputtering process. These He+ induced nanopatterning techniques improve material removal rate, in comparison to standard He+ sputtering, while simultaneously decreasing subsurface damage, thus extending the applicability of the He+ probe as a nanopattering tool.

A rapid microfluidic synthesis of [18F]fluoroarenes from nitroarenes.

Microfluidic radiofluorodenitrations have been successfully performed using a commercially available microfluidic synthesis system. Reactions of nitroarenes with para-substituted electron withdrawing groups provide incorporation yields ranging from 43 to 97%. Ortho- and meta-substituted nitroarenes provided incorporation yields up to 35%. The reactions were conducted using dry, no-carrier-added [(18)F]-fluoride and K(2)CO(3)/K(222) dissolved in N,N-dimethylformamide or dimethyl sulfoxide with total synthesis times of less than five min. The methodology developed in these studies can be applied to the synthesis of a variety of fluorine-18 labeled radiotracers and radiolabeled prosthetic groups from nitroarene precursors.