Source: School of Physics & Engineering

Written by: School of Physics & Engineering

Edited by: Wang Dongmei

Guowei Yang's group of School of Materials Science & Engineering, School of Physics & Engineering, Nanotechnology Research Center and State Key Laboratory of Optoelectronic Materials and Technologies of Sun Yat-sen University published their important scientific advance and great technical breakthrough about carbon in Science Advances on October 30, 2015. (Paper link: advances.sciencemag.org/content/1/9/e1500857)

As we know, the discovery of fullerene in 1985 pioneered an exciting new age of research on allotropes of carbon including carbon nanotubes and more recently graphene and significant scientific discoveries and technological advances have made on these new carbon materials. There are the three forms of carbon in terms of carbon-atom hybridization. The first and second well-established forms of carbon are diamond with the three-dimensional sp3-hybridized carbon atoms, and graphite with the two-dimensional sp2-hybridized carbon atoms. The third carbon is carbyne with the one-dimensional sp-hybridized carbon atoms. In 1960s, astrophysicists proposed carbyne might exist in interstellar dust, meteorites and as a by-product of shock-fused graphite by observing a new hexagonal phase of carbon in meteorite. Following the astrophysicists’ finding, a lot of scientists have tried to synthesize carbyne in the laboratory. However, on all accounts, the resulting products or materials are ill-defined, definitive evidence for carbyne remains elusive, and the specific properties of carbyne remain unrealized to this day. Is carbyne really a myth?

Right now, “Myth into reality” in Yang’s laboratory! Carbyne crystals with one-dimensional sp-hybridized carbon atoms have, for the first time, synthesized under ambient conditions in the laboratory by using a novel process of laser ablation in liquid. They reported the systemically and originally experimental data for carbyne as follows.

(i) The first entire Raman spectrum of carbyne, in which two sharp peaks at 1050 and 2175 cm-1 are characteristic of carbon-carbon single bond and triple bonds of carbyne, respectively. Note that researchers have never observed the characteristic peak 1050 cm-1 of carbon-carbon single bond in Raman spectrum of the resulting products, so far.

(ii) The strong purple-blue fluorescence from the intrinsic emission of carbyne. Up to date, there have not been any reports involved in fluorescence of carbyne.

(iii) The carbyne crystals with the hexagonal structure, i.e. the condensed phase of carbyne, the white powders (so-called white carbon), from the synthesized solution of carbyne.

Therefore, these investigations showed that, now, researchers have synthesized the well-defined products of carbyne.

Yang's group has demonstrated novel nature of the carbyne crystals, which pushes us to a new era of carbyne science and technology.

(1) Potential applications of carbyne in biomedicine

Well known, fullerenes, carbon nanotubes, and graphene are not luminescent, while diamond with a wide bandgap has little practical applications in biomedicine. Interestingly, carbyne molecules are proven to be intrinsically luminescent, and the wavelength can be modulated by the chain length. As a fire-new pure carbon probe, the carbyne molecule can be regarded as the fluorescent probe to detect biomacromolecule and tumor cell due to its small size and low toxicity.

(2) Potential applications of carbyne in microelectronics and integrated photonics

As the thinnest nanowire, luminescent molecular wire, carbyne molecules are expected to play a significant role in integrated photonics as a nanolights source, and microelectronics as connected wires. Additionally, carbyne molecules have potential applications in the exploration of single molecular laser.

All carbon materials cannot emit the visible light, and there have not been any optoelectronic devices made from pure carbon. In other words, carbon materials have little practical applications in optoelectronics. Their studies have showed that the carbyne crystals possess the intrinsic photoluminescence, which paves the way to develop a fire-new research field, the optoelectronics of carbon.

All carbon materials have no intrinsic magnetic property, so they have much little practical applications in the field of magnetism. Interestingly, the carbyne crystals are consisted of linear carbyne molecules. The kinked carbyne chains are unexpectedly deformed into a helix in the crystalline structure; consequently, the carbyne crystal resembles parallel arrays of helices. These kinks may result in intrinsic magnetic property due to the deformation of structure. Therefore, the carbyne crystals may appear as a novel magnetic materials. These discoveries will develop a fire-new research field, the carbon magnetism.