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Probing Quantum Confinement within Single Core–Multishell Nanowires
Martix301,nez-Criado, Gema,Homs, Alejandro,Alé,n, Benito,Sans, Juan A.,Segura-Ruiz, Jaime,Molina-Sax301,nchez, Alejandro,Susini, Jean,Yoo, Jinkyoung,Yi, Gyu-Chul American Chemical Society 2012 NANO LETTERS Vol.12 No.11
<P>Theoretically core–multishell nanowires under a cross-section of hexagonal geometry should exhibit peculiar confinement effects. Using a hard X-ray nanobeam, here we show experimental evidence for carrier localization phenomena at the hexagon corners by combining synchrotron excited optical luminescence with simultaneous X-ray fluorescence spectroscopy. Applied to single coaxial n-GaN/InGaN multiquantum-well/p-GaN nanowires, our experiment narrows the gap between optical microscopy and high-resolution X-ray imaging and calls for further studies on the underlying mechanisms of optoelectronic nanodevices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2012/nalefd.2012.12.issue-11/nl303178u/production/images/medium/nl-2012-03178u_0007.gif'></P>
Felouat, Abdellah,D’Alé,o, Anthony,Charaf-Eddin, Azzam,Jacquemin, Denis,Le Guennic, Boris,Kim, Eunsun,Lee, Kwang Jin,Woo, Jae Heun,Ribierre, Jean-Charles,Wu, Jeong Weon,Fages, Frex301,dex301 American Chemical Society 2015 The Journal of physical chemistry A Vol.119 No.24
<P>Controlling photoinduced intramolecular charge transfer at the molecular scale is key to the development of molecular devices for nanooptoelectronics. Here, we describe the design, synthesis, electronic characterization, and photophysical properties of two electron donor–acceptor molecular systems that consist of tolane and BF<SUB>2</SUB>-containing curcuminoid chromophoric subunits connected in a T-shaped arrangement. The two π-conjugated segments intersect at the electron acceptor dioxaborine core. From steady-state electronic absorption and fluorescence emission, we find that the photophysics of the dialkylamino-substituted analogue is governed by the occurrence of two closely lying excited states. From DFT calculations, we show that excitation in either of these two states results in a distinct shift of the electron density, whether it occurs along the curcuminoid or tolane moiety. Femtosecond transient absorption spectroscopy confirmed these findings. As a consequence, the nature of the emitting state and the photophysical properties are strongly dependent on solvent polarity. Moreover, these characteristics can also be switched by protonation or complexation at the nitrogen atom of the amino group. These features set new approaches toward the construction of a three-terminal molecular system in which the lateral branch would transduce a change of electronic state and ultimately control charge transport in a molecular-scale device.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpcafh/2015/jpcafh.2015.119.issue-24/acs.jpca.5b03699/production/images/medium/jp-2015-03699g_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp5b03699'>ACS Electronic Supporting Info</A></P>
Blue-Shifting Intramolecular Charge Transfer Emission by Nonlocal Effect of Hyperbolic Metamaterials
Lee, Kwang Jin,Lee, Yeon Ui,Fages, Frex301,dex301,ric,Ribierre, Jean-Charles,Wu, Jeong Weon,D’Alé,o, Anthony American Chemical Society 2018 NANO LETTERS Vol.18 No.2
<P>Metallic nanostructures permit controlling various photophysical processes by coupling photons with plasmonic oscillation of electrons confined in the tailored nanostructures. One example is hyperbolic metamaterial (HMM) leading to an enhanced spontaneous emission rate of emitters located nearby. Noting that emission in organic molecules is from either pi-pi* or intramolecular charge-transfer (ICT) states, we address here how HMM modifies ICT emission spectral features by comparing them with a spectral shift dependent on the local polarity of the medium. The 7.0 nm blue shift is observed in ICT emission from 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran dispersed into a polymer matrix prepared on HMM multilayered structure, while no spectral shift is observed in pi-pi* emission from perylene diimide. In the frame of the Lippert-Mataga formalism, the blue shift is explained by the HMM nonlocal effects resulting from 8% decrease in refractive index and 18% reduction in dielectric permittivity. This phenomenon was also shown in a hemi-curcuminoid borondifluoride dye yielding 15.0 nm blue shift. Such a capability of spectral shift control in films by HMM structure opens new prospects for engineering organic light-emitting devices.</P>
Molecular link between auxin and ROS-mediated polar growth
Mangano, Silvina,Denita-Juarez, Silvina Paola,Choi, Hee-Seung,Marzol, Eliana,Hwang, Youra,Ranocha, Philippe,Velasquez, Silvia Melina,Borassi, Cecilia,Barberini, Marix301,a Laura,Aptekmann, Ariel Ale National Academy of Sciences 2017 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.114 No.20
<P>Root hair polar growth is endogenously controlled by auxin and sustained by oscillating levels of reactive oxygen species (ROS). These cells extend several hundred-fold their original size toward signals important for plant survival. Although their final cell size is of fundamental importance, the molecular mechanisms that control it remain largely unknown. Here we show that ROS production is controlled by the transcription factor RSL4, which in turn is transcriptionally regulated by auxin through several auxin response factors (ARFs). In this manner, auxin controls ROS-mediated polar growth by activating RSL4, which then up-regulates the expression of genes encoding NADPH oxidases (also known as RESPIRATORY BURST OXIDASE HOMOLOG proteins) and class III peroxidases, which catalyze ROS production. Chemical or genetic interference with ROS balance or peroxidase activity affects root hair final cell size. Overall, our findings establish a molecular link between auxin and ROS-mediated polar root hair growth.</P>