Abnormal graphene sensor "sensitive" can be wrapped in a machine

Due to the unique properties of graphene, many basic research areas are very interested in it. Graphene is a single-stranded carbon structure that is light and extremely strong. In addition, graphene is an excellent thermal and conductive material. Although graphene has such a clear and widespread potential use, so far, its practical application is still very scarce. Researchers from the biofuelsystem laboratory (BIOS) at the Federal Institute of Technology in Lausanne (EPFL) and researchers at the Institute of Photonic Science (ICFO) in Spain are now showing an example of how graphene can be used. Because of the unique electro-optical properties of graphene, researchers have developed a reconfigurable, highly sensitive molecular sensor.

Improve detection sensitivity by focusing

Researchers use graphene to improve this molecular detection method, namely infrared absorption spectroscopy. In the standard detection method, the beam can stimulate the molecules, these molecules according to their own characteristics and make different vibrations. This is like a string, different lengths of the strings make different sounds. By observing the vibration of a molecule, one can obtain a variety of information about the molecule.

However, the effect of infrared absorption spectroscopy is not obvious for nanostructured molecules. Infrared photons have a wavelength of about 6 microns (6,000 nanometers - 0.006 millimeters), while the molecules to be measured are only a few nanometers (about 0.000001 millimeter). Therefore, trying to detect the vibration of such small molecules by reflecting light is a challenging task.

This is where graphene works. If the structure of graphene is properly designed, it can focus the beam precisely on the surface, thus detecting the vibration of the nano-molecules attached to the surface. Daniel Rodrigo, one of the authors of the paper, said: First, nanostructures are attached to the surface of graphene by electron beam irradiation or oxygen ion beam etching. When the light beam strikes the nanostructures, the electrons in the graphene nanostructures begin vibration. This phenomenon is known as local surface plasmon resonance, which condenses the light beam into extremely fine spots of the size of the molecule of interest. Thus facilitating the detection of nanostructures.

Real-time reconstruction of graphene, the detection of molecular structure

There are many uses of graphene. In addition to being useful in discerning the appearance of nanomolecules, this method can also reveal the nature of atomic bonding in molecules.

When a molecule vibrates, it does not vibrate at a single frequency, but rather a superposition of all vibrational frequencies. Just like a guitar: Each string vibrates at a different frequency, and only the individual strings can be combined to form a single musical instrument that can play different notes. These nuances provide information for understanding the nature of atomic bonds and the state of the entire molecule. Odeta Limaj, another author of the paper, said: These vibrations are just like fingerprinting, through which we can distinguish molecules such as proteins and even their health.

In order to clarify the sound emitted by each string, it must be capable of discerning the entire frequency range. And this is the strength of graphene. By applying different voltages, researchers can adjust the frequency of graphene, which is currently unavailable for all types of sensors. Hatice Altug said: We tested the feasibility of this method by attaching proteins to the surface of graphene. At the same time, we also get all the information of protein molecules.

A big step towards graphene molecular sensing

For researchers, the study is a breakthrough in the field of graphene molecular sensing. This is mainly due to the following reasons: First, this method can reduce the use of equipment, and only one instrument can complete this series of complex analyzes. Often, however, multiple different instruments are required to conduct a complex analysis. Second, the whole process of biological samples is non-destructive testing analysis. In addition, this study shows the potential use of graphene in molecular detection. Altug thinks: Graphene is used in a wide variety of applications. Our research has focused mainly on the field of biomolecules. However, this method should be equally applicable to the detection of polymers and many other substances.