6 research outputs found
Supplementary document for Photon-pair production at the nanoscale with hybrid nonlinear/plasmonic antennas - 6444377.pdf
Supplementary -
Supplementary document for Photon-pair production at the nanoscale with hybrid nonlinear/plasmonic antennas - 6444377.pdf
Supplemental document
Impact of Polyethylenimine Conjugation Mode on the Cell Transfection Efficiency of Silica Nanovectors
The
conjugation of polyethylenimine (PEI) to silica nanoparticles has
emerged as a useful strategy in gene delivery. Here we investigate
the influence of the PEI conjugation mode on the transfection ability
of plain silica nanoparticles. Surface functionalization with sulfonate-
and chloride-bearing silanes modulates the amount and conformation
of PEI and therefore the particlesâ affinity for the plasmid,
without impacting on cytotoxicity. However, transfection efficiency
in both immortalized and primary cells is more directly correlated
to the nature and strength of the particleâPEI interactions.
It suggests that PEI detachment from the particle surface at the stage
of endosomal escape is a key event in the plasmid delivery process.
These data should provide fruitful guidelines for the fine tuning
of colloidal surfaces intended for intracellular delivery of bioactive
molecules
Hydrothermal Carbon from Biomass: Structural Differences between Hydrothermal and Pyrolyzed Carbons via <sup>13</sup>C Solid State NMR
The objective of this paper is to better describe the structure of the hydrothermal carbon (HTC) process and put it in relationship with the more classical pyrolytic carbons. Indeed, despite the low energetic impact and the number of applications described so far for HTC, very little is known about the structure, reaction mechanism, and the way these materials relate to coals. Are HTC and calcination processes equivalent? Are the structures of the processed materials related to each other in any way? Which is the extent of polyaromatic hydrocarbons (PAH) inside HTC? In this work, the effect of hydrothermal treatment and pyrolysis are compared on glucose, a good model carbohydrate; a detailed single-quantum double-quantum (SQ-DQ) solid state <sup>13</sup>C NMR study of the HTC and calcined HTC is used to interpret the spectral region corresponding to the signal of furanic and arene groups. These data are compared to the spectroscopic signatures of calcined glucose, starch, and xylose. A semiquantitative analysis of the <sup>13</sup>C NMR spectra provides an estimation of the furanic-to-arene ratio which varies from 1:1 to 4:1 according to the processing conditions and carbohydrate employed. In addition, we formulate some hypothesis, validated by DFT (density functional theory) modeling associated with <sup>13</sup>C NMR chemical shifts calculations, about the possible furan-rich structural intermediates that occur in the coalification process leading to condensed polyaromatic structures. In combination with a broad parallel study on the HTC processing conditions effect on glucose, cellulose, and raw biomass (Falco, C.; Baccile, N.; Titirici, M.-M. <i>Green Chem.</i>, <b>2011</b>, DOI: 10.1039/C1GC15742F), we propose a broad reaction scheme and in which we show that, through HTC, it is possible to tune the furan-to-arene ratio composing the aromatic core of the produced HTC carbons, which is not possible if calcination is used alone, in the temperature range below 350 °C
How High Concentrations of Proteins Stabilize the Amorphous State of Calcium Orthophosphate: A Solid-State Nuclear Magnetic Resonance (NMR) Study of the Casein Case
Understanding how proteins stabilize
amorphous calcium <i>ortho</i>-phosphate (ACP) phases is
of great importance in biology
and for pharmaceutical or food applications. Until now, most of the
former investigations about ACPâprotein stability and equilibrium
were performed under conditions where ACP colloidal nanoclusters are
surrounded by low to moderate concentrations of peptides or proteins
(15â30 g L<sup>â1</sup>). As a result, the question
of ACPâprotein interactions in highly concentrated protein
systems has clearly been overlooked, whereas it corresponds to actual
industrial conditions such as drying or membrane filtration in the
dairy industry for instance. In this study, the structure of an ACP
phase is monitored in association with one model phosphorylated protein
(casein) using solid-state nuclear magnetic resonance (ssNMR) under
two conditions of high protein concentration (300 and 400 g L<sup>â1</sup>). At both concentrations and at 25 °C, it is
found that the caseins maintain the mineral phase in an amorphous
form with no detectable influence on its structure or size. Interestingly,
and in both cases, a significant amount of the nonphosphorylated side
chains interacts with ACP through hydrogen bonds. The number of these
interacting side chains is found to be higher at the highest casein
concentration. At 45 °C, which is a destabilizing temperature
of ACP under protein-free conditions, the amorphous structure of the
mineral phase is partially transformed at a casein concentration of
300 g L<sup>â1</sup>, while it remains almost intact at a casein
concentration of 400 g L<sup>â1</sup>. Therefore, these results
clearly indicate that increasing the concentration of proteins favors
ACPâprotein interactions and stabilizes the ACP clusters more
efficiently
Nanostructured Ultrafast Silicon-Tip Optical Field-Emitter Arrays
Femtosecond ultrabright electron
sources with spatially structured
emission are an enabling technology for free-electron lasers, compact
coherent X-ray sources, electron diffractive imaging, and attosecond
science. In this work, we report the design, modeling, fabrication,
and experimental characterization of a novel ultrafast optical field
emission cathode comprised of a large (>100â000 tips), dense
(4.6 million tips·cm<sup>â2</sup>), and highly uniform
(<1 nm tip radius deviation) array of nanosharp high-aspect-ratio
silicon columns. Such field emitters offer an attractive alternative
to UV photocathodes while providing a direct means of structuring
the emitted electron beam. Detailed measurements and simulations show
pC electron bunches can be generated in the multiphoton and tunneling
regime within a single optical cycle, enabling significant advances
in electron diffractive imaging and coherent X-ray sources on a subfemtosecond
time scale, not possible before. At high charge emission yields, a
slow rollover in charge is explained as a combination of the onset
of tunneling emission and the formation of a virtual cathode