Optical properties of (SrMnO3)n/(LaMnO3)2n superlattices: an insulator-to-metal transition observed in the absence of disorder.


We measure the optical conductivity of (SrMnO3)n/(LaMnO3)2n superlattices (SL) for n=1, 3, 5, and 8 and 10<T<400 K. Data show a T-dependent insulator to metal transition (IMT) for n≤3, driven by the softening of a polaronic mid-infrared band. At n=5 that softening is incomplete, while at the largest period n=8 compound the MIR band is independent of T and the SL remains insulating. One can thus first observe the IMT in a manganite system in the absence of the disorder due to chemical doping.  Unsuccessful reconstruction of the SL optical properties from those of the original bulk 

materials suggest that (SrMnO3)n/(LaMnO3)2n heterostructures give rise to a novel electronic state.

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Optical properties of (SrMnO3)n/(LaMnO3)2n superlattices: an insulator-to-metal transition observed in the absence of disorder.
A. Perucchi, L. Baldassarre, A. Nucara, P. Calvani, C. Adamo, D.G. Schlom, P. Orgiani, L. Maritato, and S. Lupi

Nano Letters 10, 4819 (2010).

A Microscopic view on the Mott transition in Cr-doped V2O3

V2O3 is the prototype system for the Mott transition, one of the most fundamental phenomena of electronic correlation. Temperature, doping or pressure induce a metal-to-insulator transition (MIT) between a paramagnetic metal (PM) and a paramagnetic insulator. This or related MITs have a high technological potential, among others, for intelligent windows and field effect transistors. However the spatial scale on which such transitions develop is not known in spite of their importance for research and applications. Here we unveil for the first time the MIT in Cr-doped V2O3 with

submicron lateral resolution: with decreasing temperature, microscopic domains become metallic and coexist with an insulating background. This explains why the associated PM phase is actually a poor metal.

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A microscopic view on the Mott transition in chromium-doped V2O3;
S. Lupi, L. Baldassarre, B. Mansart, A. Perucchi, A. Barinov, P. Dudin, et al. 
Nature Communications 1, 105 (2010)

A multiple-screening platform for investigating single-cell biochemical perturbations upon prion infection

SR-IRMS was employed to investigate the biochemical perturbations undergone by prion infected mouse hypothalamic GT1-1 cells at the cellular and subcellular level. A decrement in total cellular protein content upon prion infection was identified by whole-cell IR microspectra and validated by bicinchoninic acid assay as well as single-cell volume analysis by atomic force microscopy (AFM). Hierarchical cluster analysis (HCA) of IR data discriminated between infected (Sc-GT1) and uninfected (GT1) cells and allowed to deduce an

increment of lysosomal bodies within the cytoplasm of infected GT1-1 cells, a hypothesis further confirmed by SR-IRMS at subcellular spatial resolution and fluorescent microscopy.

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Infrared Microspectroscopy: A Multiple-Screening Platform for Investigating Single-Cell Biochemical Perturbations upon Prion Infection.
A. Didonna, L. Vaccari, A. Bek, G. Legname.
ACS Chem. Neurosci. 2, 160 (2011)

Effects on antigen-presenting cells of short-term interaction with the human host defence peptide β-defensin 2


hBD2 (human β-defensin 2) is an antimicrobial peptidethat plays a role in alerting and enhancing cellular components of innate and adaptive immunity. In the present study, SR-IRMS was employed for studying the peptide interaction with iDCs (immature dendritic cells). A different iDC response to short-term exposure to hBD2 was elicited and correlated with a peculiar cellular morphology and internal complexity, as revealed also by flow cytometry. Prominent differences in lipid order and composition were detected between responsive iDCs; in particular, a relevant decrease in the IR-signal of carbonyl ester of phospholipids, below the detection limit, was observed in the cytoplasmic region as a consequence of hBD2 exposure and related

to cellular degranulation upon activation. These events were associated with the chemotaxis of iDCs, which appears to occur not only via CCR6 (CC chemokine Receptor 6)-dependent mechanism but also via a CCR6-independent one, involving a meaningful re-organization of the endomembrane system.

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Effects on antigen-presenting cells of short-term interaction with the human host defence peptide β-defensin 2.

F. Morgera, S. Pacor, L. Creatti, N. Antcheva, L. Vaccari.
Biochem. J. 436, 537-546 (2011)

New biocompatible CaF2 fluidic device for FTIRM based on SU-8 resist
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