Tag Archives: nanographene

Quick and efficient nanographene synthesis

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Thank you to Nagoya University (Japan) for making this image available.

Caption: APEX reactions are carried out on the K, M and bay regions of the polycyclic aromatic hydrocarbon, synthesizing multiple nanographenes. These reactions can then be repeated, further increasing the number of potential nanographene structures that can be synthesized. Credit: Issey Takahashi

From a June 28, 2021 Nagoya University press release (also on EurekAlert),

A group of researchers at Nagoya University, Japan, have developed a new method for quickly and efficiently synthesizing nanographenes, a type of nanocarbon with great potential as a next generation material.

Nanographenes are the part structures of graphene, which is a sheet of carbon atoms around 3 nanometers thick with particular potential for use in semiconductor development, having electron mobility several hundred times better than current generation materials. Graphene was first isolated in 2004, a discovery which received the 2010 Nobel Prize in physics, making it a very new material which is currently the subject of a great deal of research.

With magnetic and electric characteristics beyond those of graphene, nanographenes are equally of interest to scientists in the nanocarbon research field. The biggest obstacle, albeit an exciting one, faced by researchers is the sheer number of potential nanographenes. The number of potentially possible nanographene structures increases with the number of benzene rings (6 atoms of carbon in a hexagonal formation) to make them. For example, even a relatively small 10 benzene ring nanographene may have up to 16,000 variants. As each nanographene has different physical characteristics, the key to applied nanographene research is to identify the relationship between the structure and characteristics of as many nanographenes as possible.

Thus, scientists’ task is to create a nanographene library, containing data on the properties of as many nanographenes as possible. However, the current method of nanographene synthesis, known as a coupling reaction, is a multi-step process which produces one single nanographene. Thus, to create a 100-nanographene library, 100 separate coupling reactions would have to be carried out. Even this would be a significant undertaking, rendering the construction of a truly comprehensive nanographene library practically impossible.

To solve this problem, the Nagoya University research group, led by Professor Kenichiro Itami, have been working on the APEX reaction, a reaction which uses polycyclic aromatic hydrocarbons as templates to synthesize nanographenes. Polycyclic aromatic hydrocarbons have three areas of their structure – known as the K region, M region and bay region – which can be elongated in an APEX reaction, producing three nanographenes. These nanographenes can then be further elongated in a second reaction, meaning that a large number of nanographenes can be synthesized from a single polycyclic aromatic hydrocarbon template molecule.

With Professor Itami’s group having already developed the K region APEX reaction, and another group of scientists having done so for the bay region, they turned their attention to the M region. They activated the M region using the 1950 Nobel Prize winning Diels-Alder reaction, and succeeded in carrying out an elongation reaction on the activated M region, thus rendering all three possible sites on the polycyclic aromatic hydrocarbons capable of synthesizing nanographenes.

The researchers were able to produce 13 nanographenes with three APEX reactions, with most of these being previously unseen structures, thus proving both the efficiency and usefulness of this new method.

This exciting new piece of research and its potential to accelerate the creation of nanographene libraries is a step towards the development of the next generation of materials, which have the potential to revolutionize semiconductors and solar energy and improve lives all around the world.

Here’s a link to and a citation for the paper,

Diversity-oriented synthesis of nanographenes enabled by dearomative annulative π-extension by Wataru Matsuoka, Hideto Ito, David Sarlah & Kenichiro Itami. Nature Communications volume 12, Article number: 3940 (2021) DOI: https://doi.org/10.1038/s41467-021-24261-y Published 24 June 2021

This paper is open access.

Better bioimaging accuracy with direct radiolabeling of nanomaterials

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Even I can tell the image is improved when the chelator is omitted,

Courtesy: Wiley

A Feb. 9, 2017 news item on phys.org describes a new, chelator-free technique for increased bioimaging accuracy,

Positron emission tomography (PET) plays a pivotal role for monitoring the distribution and accumulation of radiolabeled nanomaterials in living subjects. The radioactive metals are usually connected to the nanomaterial through an anchor, a so-called chelator, but this chemical binding can be omitted if nanographene is used, as American scientists report in the journal Angewandte Chemie. The replacement of chelator-based labeling by intrinsic labeling significantly enhances the bioimaging accuracy and reduces biases.

A Feb 9, 2017Wiley press release (also on EurekAlert), which originated the news item, provides more detail,

Nanoparticles are very promising substances for biodiagnostics (e.g., detecting cancerous tissue) and biotherapy (e.g., destroying tumors by molecular agents), because they are not as fast [sic] metabolized as normal pharmaceuticals and they particularly enrich [sic] in tumors through an effect called enhanced permeability and retention (EPR). Chelators, which have a macrocyclic structure, are used to anchor the radioactive element (e.g., copper-64) onto the nanoparticles’ surface. The tracers are then detected and localized in the body with the help of a positron emission tomography (PET) scanner. However, the use of a chelator can also be problematic, because it can detach from the nanoparticles or bias the imaging. Therefore, the group of Weibo Cai at University of Wisconsin-Madison, USA, sought for chelator-free solutions—and found it in nanographene, one of the most promising substances in nanotechnology.

Nanographene offers the electronic system to provide special binding electrons for some transition metal ions. “π bonds of nanographene are able to provide the additional electron to stably incorporate the 64Cu2+ acceptor ions onto the surface of graphene,” the authors wrote. Thus, it was possible to directly and stably attach the copper isotope to reduced graphene oxide nanomaterials stabilized by poly(ethylene glycol) (PEG), and this system was used for several bioimaging tests including the detection of tumors in mice.

After injection in the mouse model, the scientists observed long blood circulation and high tumor uptake. “Prolonged blood circulation of 64Cu-RGO-PEG […] induced a prompt and persistent tumor uptake via EPR effect,” they wrote. Moreover, the directly radiolabeled nanographene was readily prepared by simply mixing both components and heating them. This simple chelator-free, intrinsically labeled system may provide an attractive alternative to the chelator-based radiolabeling, which is still the “gold standard” in bioimaging.

Here’s a link to and a citation for the paper,

Chelator-Free Radiolabeling of Nanographene: Breaking the Stereotype of Chelation by Sixiang Shi, Cheng Xu, Dr. Kai Yang, Shreya Goel, Hector F. Valdovinos, Dr. Haiming Luo, Emily B. Ehlerding, Dr. Christopher G. England, Dr. Liang Cheng, Dr. Feng Chen, Prof. Robert J. Nickles, Prof. Zhuang Liu, and Prof. Weibo Cai. Angewandte Chemie International Edition DOI: 10.1002/anie.201610649 Version of Record online: 7 FEB 2017

© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Grossly warped ‘nanographene’, a brand new type of carbon

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A new of form carbon sounds exciting although the naming convention escapes me. Why call it ‘nanographene’ (albeit grossly warped) when graphene is already nanoscale? (For anyone who can explain this to me, please do let me know.) A July 15, 2013 news release on EurekAlert (it’s also available as a July 15, 2013 news item on ScienceDaily) describes the new form of carbon,

Bucking planarity, contorted sheets of graphene alter physical, optical and electronic properties of new material

Chemists at Boston College and Nagoya University in Japan have synthesized the first example of a new form of carbon, the team reports in the most recent online edition of the journal Nature Chemistry.

The new material consists of multiple identical pieces of grossly warped graphene, each containing exactly 80 carbon atoms joined together in a network of 26 rings, with 30 hydrogen atoms decorating the rim. Because they measure slightly more than a nanometer across, these individual molecules are referred to generically as “nanocarbons,” or more specifically in this case as “grossly warped nanographenes.”

There’s an explanation of why this discovery is special and how it was made (from,the news release),

Until recently, scientists had identified only two forms of pure carbon: diamond and graphite. Then in 1985, chemists were stunned by the discovery that carbon atoms could also join together to form hollow balls, known as fullerenes. Since then, scientists have also learned how to make long, ultra-thin, hollow tubes of carbon atoms, known as carbon nanotubes, and large flat single sheets of carbon atoms, known as graphene. The discovery of fullerenes was awarded the Nobel Prize in Chemistry in 1996, and the preparation of graphene was awarded the Nobel Prize in Physics in 2010.

Graphene sheets prefer planar, 2-dimensional geometries as a consequence of the hexagonal, chicken wire-like, arrangements of trigonal carbon atoms comprising their two-dimensional networks. The new form of carbon just reported in Nature Chemistry, however, is wildly distorted from planarity as a consequence of the presence of five 7-membered rings and one 5-membered ring embedded in the hexagonal lattice of carbon atoms.

Odd-membered-ring defects such as these not only distort the sheets of atoms away from planarity, they also alter the physical, optical, and electronic properties of the material, according to one of the principle authors, Lawrence T. Scott, the Jim and Louise Vanderslice and Family Professor of Chemistry at Boston College.

“Our new grossly warped nanographene is dramatically more soluble than a planar nanographene of comparable size,” said Scott, “and the two differ significantly in color, as well. Electrochemical measurements revealed that the planar and the warped nanographenes are equally easily oxidized, but the warped nanographene is more difficult to reduce.”

… By introducing multiple odd-membered ring defects into the graphene lattice, Scott and his collaborators have experimentally demonstrated that the electronic properties of graphene can be modified in a predictable manner through precisely controlled chemical synthesis.

Here’s a link to and a citation for the paper,

A grossly warped nanographene and the consequences of multiple odd-membered-ring defects by Katsuaki Kawasumi, Qianyan Zhang, Yasutomo Segawa, Lawrence T. Scott, & Kenichiro Itami. Nature Chemistry (2013) doi:10.1038/nchem.1704  Published online 14 July 2013

This paper is behind a paywall. For those who would like more information but can’t get access to the paper at this time, there’s a brief July 15, 2015 news piece by Caryl Richards on the Chemistry World website.