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NoPo’s Single-Walled Carbon Nanotubes Exceeds Previously Established R&D Standard

NoPo’s Single-Walled Carbon Nanotubes Exceeds Previously Established R&D Standard 1

Amritsar, NFAPost News Service: NoPo Nanotechnologies India, a Bengaluru headquartered startup, has come up with single-walled carbon nanotubes (SWCNTs) have long been heralded as a wonder material in terms of potential properties exceeding that of any other known material, especially when it comes to electrical and mechanical properties.

They have been a subject of research for nearly three decades, and have stepped past the lab-scale in the recent few years when it comes to applications ranging from 4G/5G antennas, flexible displays for smart devices, solar cells, sports equipment, and even automotive bodies and engines. A lot of the research that has gone into this, and continues to be, utilizes Rice University’s developed high-pressure carbon monoxide process, known as HiPco.

HiPco SWCNTs were made available to researchers around the world for years via the nano Carbon Center at Rice University. This gas-phase process was developed by the 1996 Nobel Laureate in Chemistry, the late Prof. Richard Smalley.

However, the center ceased to continue operations in the mid- 2010s, and there were no established plans for future HiPco production from the 3rd-party entity which purchased the assets. The expiration of the core patents for the HiPco process also meant that there was a growing scarcity of high-quality SWCNTs, and worry on whether future research and development could be consistent or comparable to previously used materials.

NoPo Nanotechnologies India is proudly claiming independent analysis done by scientists at the Energy Safety Research Institute (ESRI) at Swansea University in collaboration with researchers at Rice University (USA) shows that the NoPo HiPCO commercially available samples can be directly compared to that of the Rice “standard”, often exceeding the requisite properties when it comes to sample purity and uniformity. The NoPo HiPCO SWCNTs are manufactured in Bengaluru, Karnataka, using an improved reactor design and a scalable process enabling the needs of the industry again.

Gadhadar Reddy, the CEO of NoPo Nanotechnologies India, formed the company in 2011 and said that making nanotubes has been a dream he has pursued since he was a kid.

“It’s nice to see it becoming a reality. My goal has been to show that something of this magnitude can be achieved in India, and corroboration of NoPo HiPCO® SWCNTs is testament to this,” said Gadhadar Reddy.

Lead author and Indian-origin scientist Dr Varun Shenoy Gangoli stated that it is in the interest of all researchers to understand how the presently available product compares to historically available Rice CNT materials that have been the subject of a great range of academic studies, and also to those searching for a commercial replacement to continue research and development in this field.

Anto Godwin, a scientist at NoPo Nnaotechnologies and co-author on the peer-reviewed article reporting this work, expressed his excitement to be contributing “to a day in the near future where the carbon nanotubes we are making would make a huge difference in people’s lives.”

“Since variability in carbon nanotube sources is known to be a significant issue when comparing output from various groups. What is worse is that being able to correlate high-quality literature results with scaled processes is still difficult,”  said Prof. Andrew Barron, the project lead.

Dr Varun Shenoy Gangoli is a research scientist in the Chemistry Department at Rice University in Houston, Texas, USA. Co-authors of this work are M. Anto Godwin, Gadhadar Reddy of NoPo Nanotechnologies (India), and Prof. Robert Kelley Bradley of Lamar University (USA). Prof. Andrew R. Barron is the Sêr Cymru Chair of Low Carbon Energy and Environment, and Director of ESRI at Swansea University and professor emeritus of chemistry, materials science and nanoengineering at Rice. The Office of Naval Research and the Welsh Government Sêr Cymru National Research Network in Advanced Engineering and Materials supported the research.

High-pressure carbon monoxide (HiPco)-synthesized single-walled carbon nanotubes (SWCNTs) have been a widely studied carbon nanomaterial for nearly two decades. It has been the de facto standard for SWCNT research, be it functionalisation, separation and purification, or composites, as a result of the consistent, high-quality material that was made available at an affordable price to researchers worldwide.
The recent shutdown of the HiPco reactor at Rice University has resulted in a scarcity of HiPco material available to the research community, and a new source of similar SWCNTs is desperately needed. Continued research and development on the design, materials used, and the overall process have led to a new HiPco material, referred to as NoPo HiPCO®, as an alternative to the erstwhile Rice HiPco SWCNTs.
Carbon nanotubes have been at the forefront of materials research for the better part of three decades now, with single-walled carbon nanotubes (SWCNTs) taking precedence over their multi-walled variants. Indeed, a major part of this interest has been due to the unique electronic properties possessed by SWCNTs, dictated by the chirality of the individual carbon nanotube that has led to potential applications including solar power, fuel cells, water filtration, and thin-film transistors.
As-synthesized SWCNTs have also been further analyzed via various methods of separation to develop enriched ensembles of metallic- and semiconducting-SWCNTs, to further facilitate research and a move from the lab to the retail market. Synthesis of SWCNTs has thus always been key in progressing this field of research, with various techniques having been developed for this, including arc discharge, laser ablation, and chemical vapor deposition (CVD).

NoPo HiPco Growth

The modified NoPo HiPco reactor was designed to be the first all-metal HiPco reactor (the reaction zone is also made of metals), which operates at a high pressure (30–50 atm) and temperature (900–1100 °C). Carbon monoxide was used as the carbon source for the process. Iron and/or nickel carbonyl was used as the catalyst precursor such that, when the catalyst is introduced to the high temperature, it starts to decompose and forms the metal catalyst particles. The metal catalyst acts as the SWCNT seed via the Boudouard reaction, which led to the growth of nanotubes via disproportionation.
Since both the catalyst and source are in the gas phase, the reactor can be run continuously for long periods of time, which helps in industrial scale production on the order of 0.5 g-SWCNT/hour/reactor, with scaling coming in the form of multiple such reactors running in parallel as needed.
Raman spectroscopy of the two as-produced HiPco SWCNT samples revealed a mixed bag of information, but again, it must be noted that the slightly lower average diameter for the NoPo SWCNTs compared to those from Rice University would play a role in resonance. This, combined with bundle interference of a detailed analysis of the radial breathing modes (RBMs) in the absence of a liquid Raman spectroscopy holder, also meant it is prudent to limit discussions on the nature of the carbon content and the diameter distribution, rather than chirality distribution.
A back-to-back analysis of typical Rice University and NoPo HiPco SWCNT samples has been performed using AFM, TEM, SEM/EDS, Raman spectroscopy, and UV-vis-NIR spectrometer. Although the samples are similar, the NoPo sample comprised smaller average diameter SWCNTs, lower catalyst content, and lower amorphous carbon content.
Furthermore, the Raman IG/ID ratio suggested that NoPo samples have fewer defects overall for the smaller-diameter metallic-SWCNTs. The overall result is that, as far as the further use or functionalization of NoPo SWCNTs in comparison to previously published work with Rice HiPco SWCNTs, the former represents a suitable replacement for the latter.
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