Leaders in Pharmaceutical Business Intelligence (LPBI) Group

Advanced Nanospectroscopy

Larry H. Bernstein, MD, FCAP, Curator

LPBI

 

Graphene Enables Nanoelectromechanical Systems Integration

http://www.photonics.com/Article.aspx?AID=58224&refer=Spectroscopy&utm_source=Spectroscopy_2016_02_03

BARCELONA, Spain, Jan. 21, 2016 — Combining nanoelectromechanical (NEMS) systems with on-chip optics holds promise as a method to actively control light at the nanoscale, and now a hybrid system has overcome the challenges of integrating such nanoscale devices with optical fields thanks to the material graphene.

Researchers from the Institute of Photonic Sciences (ICFO) have demonstrated an on-chip graphene NEMS suspended a few tens of nanometers above nitrogen-vacancy centres (NVCs), which are stable single-photon emitters embedded in nanodiamonds. The work confirms that graphene is an ideal platform for both nanophotonics and nanomechanics, the researchers said.

Due to its electromechanical properties, graphene NEMS can be actuated and deflected electrostatically over a few tens of nanometers with modest voltages applied to a gate electrode, the researchers found. The graphene motion can thus be used to modulate the light emission by the NVC, while the emitted field can be used as a universal probe of the graphene position. The optomechanical coupling between the graphene displacement and the NVC emission is based on near-field, dipole-dipole interaction.

http://www.photonics.com/images/Web/Articles/2016/1/21/PIC_ICFO.jpg

False color scanning electronic micrograph of a hybrid graphene-nitrogen-vacancy nearfield nano-optomechanical system. Courtesy of ICFO.

The researchers observed that the coupling strength increased strongly for shorter distances and was enhanced because of graphene’s 2D character and linear dispersion. These achievements hold promise for selective control of emitter arrays on-chip, optical spectroscopy of individual nano-objects, and integrated optomechanical information processing. The ICFO team also said the hybrid device could advance quantum optomechanics.

The research was published in Nature Communications (doi: 10.1038/ncomms10218).

Electromechanical control of nitrogen-vacancy defect emission using graphene NEMS

Antoine Reserbat-Plantey, Kevin G. Schädler, Louis Gaudreau, Gabriele Navickaite, Johannes Güttinger, et al.

Nature Communications 2016; 7(10218)      http://dx.doi.org:/10.1038/ncomms10218

Despite recent progress in nano-optomechanics, active control of optical fields at the nanoscale has not been achieved with an on-chip nano-electromechanical system (NEMS) thus far. Here we present a new type of hybrid system, consisting of an on-chip graphene NEMS suspended a few tens of nanometres above nitrogen-vacancy centres (NVCs), which are stable single-photon emitters embedded in nanodiamonds. Electromechanical control of the photons emitted by the NVC is provided by electrostatic tuning of the graphene NEMS position, which is transduced to a modulation of NVC emission intensity. The optomechanical coupling between the graphene displacement and the NVC emission is based on near-field dipole–dipole interaction. This class of optomechanical coupling increases strongly for smaller distances, making it suitable for nanoscale devices. These achievements hold promise for selective control of emitter arrays on-chip, optical spectroscopy of individual nano-objects, integrated optomechanical information processing and open new avenues towards quantum optomechanics.

 

Graphene is ideal substrate for brain electrodes, researchers find

February 1, 2016  http://www.kurzweilai.net/graphene-is-ideal-substrate-for-brain-electrodes-researchers-find

This illustration portrays neurons interfaced with a sheet of graphene molecules in the background (credit: Graphene Flagship)

An international study headed by the European Graphene Flagship research consortium has found that graphene is a promising material for use in electrodes that interface with neurons, based on its excellent conductivity, flexibility for molding into complex shapes, biocompatibility, and stability within the body.

The graphene-based substrates they studied* promise to overcome problems with “glial scar” tissue formation (caused by electrode-based brain trauma and long-term inflammation). To avoid that, current electrodes based on tungsten or silicon use a protective coating on electrodes, which reduces charge transfer. Current electrodes are also rigid (resulting in tissue detachment and preventing neurons from moving) and generate electrical noise, with partial or complete loss of signal over time, the researchers note in a paper published recently in the journal ACS Nano.

Electrodes are used as neural biosensors and for prosthetic applications — such as deep-brain intracranial electrodes used to control motor disorders (mainly epilepsy or Parkinson’s) and for brain-computer interfaces (BCIs), used to recover sensory functions or control robotic arms for paralyzed patients. These applications require an interface with long-term, minimal interference.

Interfacing graphene to neurons directly

Scanning electron microscope image of rat hippocampal neurons grown in the lab on a graphene-based substrate, showing normal morphology characterized by well-defined round neural soma, extended neurite arborization (branching), and cell density similar to control substrates (credit: A. Fabbro et al./ACS Nano)

“For the first time, we interfaced graphene to neurons directly, without any peptide-coating,” explained lead neuroscientist Prof. Laura Ballerini of the International School for Advanced Studies (SISSA/ISAS) and the University of Trieste.

Using electron microscopy and immunofluorescence, the researchers found that the neurons remained healthy, transmitting normal electric impulses and, importantly, no adverse glial reaction, which leads to damaging scar tissue, was seen.