Laboratoire P.A.S.T.E.U.R

Printer-friendly version

Molecular Hydrodynamics from Memory Kernels

PRL 116, 147804 (2016)

 

The memory kernel for a tagged particle in a fluid, computed from molecular dynamics simulations, decays algebraically as t-3/2. We show how the hydrodynamic Basset-Boussinesq force naturally emerges from this long-time tail and generalize the concept of hydrodynamic added mass. This mass term is negative in the present case of a molecular solute, which is at odds with incompressible hydrodynamics predictions. Lastly, we discuss the various contributions to the friction, the associated time scales, and the crossover between the molecular and hydrodynamic regimes upon increasing the solute radius.

Unveiling nickelocene bonding to a noble metal surface

Physical Review B 93, 195403 (2016)

 

The manipulation of a molecular spin state in low-dimensional materials is central to molecular spintronics. The designs of hybrid devices incorporating magnetic metallocenes are very promising in this regard, but are hampered by the lack of data regarding their interactionwith ametal. Here, we combine low-temperature scanning tunneling microscopy and density functional theory calculations to investigate a magnetic metallocene at the single-molecule level—nickelocene. We demonstrate that the chemical and electronic structures of nickelocene are preserved upon adsorption on a copper surface. Several bonding configurations to the surface are identified, ranging from the isolated molecule to molecular layers governed by van der Waals interactions

 

Depopulation of Single-Phthalocyanine Molecular Orbitals upon Pyrrolic-Hydrogen Abstraction on Graphene

ACS Nano 2016, 10, 2010−2016

 

Single-molecule chemistry with a scanning tunneling microscope has preponderantly been performed on metal surfaces. The molecule− metal hybridization, however, is often detrimental to genuine molecular properties and obscures their changes upon chemical reactions. We used graphene on Ir(111) to reduce the coupling between Ir(111) and adsorbed phthalocyanine molecules. By local electron injection from the tip of a scanning tunneling microscope the two pyrrolic H atoms were removed from single phthalocyanines. The detachment of the H atom pair induced a strong modification of the molecular electronic structure, albeit with no change in the adsorption geometry. Spectra and maps of the diff erential conductance combined with density functional calculations unveiled the entire depopulation of the highest occupied molecular orbital upon H abstraction. Occupied π  states of intact molecules are proposed to be emptied via  intramolecular electron transfer to dangling σ states of H-free N atoms.

Interview Christian Amatore : The Electrochemical Society

Christian Amatore has given an interview at The Electrochemical Society in the ECS Podcast context.

 

Ultrafast, sensitive and large-volume on-chip real-time PCR for the molecular diagnosis of bacterial and viral infections

Lab Chip2016, Advance Article

 

To control future infectious disease outbreaks, like the 2014 Ebola epidemic, it is necessary to develop ultrafast molecular assays enabling rapid and sensitive diagnoses. To that end, several ultrafast real-time PCR systems have been previously developed, but they present issues that hinder their wide adoption, notably regarding their sensitivity and detection volume. An ultrafast, sensitive and large-volume real-time PCR system based on microfluidic thermalization is presented herein. The method is based on the circulation of pre-heated liquids in a microfluidic chip that thermalize the PCR chamber by diffusion and ultrafast flow switches. The system can achieve up to 30 real-time PCR cycles in around 2 minutes, which makes it the fastest PCR thermalization system for regular sample volume to the best of our knowledge. After biochemical optimization, anthrax and Ebola simulating agents could be detected in a 7-minute real-time PCR and a 7.5-minute reverse transcription real-time PCR (for 30 PCR cycles), respectively 6.4 and 7.2 times faster than with an off-the-shelf apparatus, while conserving real-time PCR sample volume, efficiency, selectivity and sensitivity. The highspeed thermalization also enabled us to perform sharp melting curve analyses in only 20s and to discriminate amplicons of different lengths by rapid real-time PCR. This real-time PCR microfluidic thermalization system is cost-effective, versatile and can be then further developed for point-of-care, multiplexed, ultrafast and highly sensitive molecular diagnoses of bacterial and viral diseases.