They are stronger than steel, lighter than most materials in use so far, and very good when it comes to conductivity. They are sort of a future treasure-trove for applications still waiting to unlocked – specially in areas where solar innovations, quantum computing and clean energy market are moving deeper ahead. Gadhadar Reddy, Co-Founder & CEO, NoPo Nanotechnologies, a deep-tech company (pioneering the large-scale manufacturing of single-walled carbon nanotubes (SWCNTs) helps us to understand why these nano-materials are going to get big while he also addresses some environmental dimensions of these star-ingredients.
How strong and scalable is the use of silicon nanomaterials in clean energy, lithium batteries, etc.?
It has been found that the only way to stabilise silicon is by using single-walled carbon nanotubes; they are an essential ingredient, no longer just an optional add-on. It has reached a point where you cannot achieve good life and performance from silicon without single-walled nanotubes. They play a significant role, and that role is growing rapidly. We have seen that any high-performance battery today makes use of this combination, which is an exciting development. When it comes to fuel cells, people have reported using nanotubes as thinner membrane structures, but it is not an area with much ongoing work. There are only older publications where people have stored hydrogen using nanotubes, but the weight percentage achieved is very small, at about 3 weight percent. That has largely been the extent of the work in that area.
Can you share something on platinum nanomaterials for hydrogen fuel cells; supercapacitors in energy storage; and quantum dot solar cells?
In terms of quantum dots, we have not seen a specific use case for nanotubes in solar cells. Quantum dots have mostly been explored as devices for photon detection. However, we have seen applications combining nanotubes with perovskites, which have shown very high performance and made for a very cheap solar cell material. Perovskites and nanotubes together have demonstrated good performance improvements, but this area is still at the R&D stage and has not advanced as far as batteries have.
Is it easy to maintain environmental responsibility and cognizance when nanomaterials are pursuing innovative breakthroughs?
Yes, it is definitely possible, and we are an example of that. In fact, when we go to the pollution control boards for the licenses required to operate, they often want to know what we are polluting so they can issue us a license. We have the opposite problem: we are not releasing anything into the atmosphere, and all our effluents are completely treated. We often debate whether we even need a PCB license, but the law is the law, so we comply regardless. We have been very conscious of our environmental impact.
Can you elaborate how?
For our nanotube production, we use a gas called carbon monoxide, which is quite straightforward to produce from carbon dioxide in the atmosphere, making it an excellent example of sequestration, which we have demonstrated internally through our experiments.
All the raw materials we use come from readily available systems. For example, we use iron, which is widely available in the country, to create our raw materials. At the same time, we have built our own technical capabilities for constructing the reactors and systems we need, and we use green energy sources. These are some of the major initiatives we have undertaken at NoPo to ensure that the product we create is completely recycled and reused. It is also made of carbon, the same element that all life on the planet is made of, which makes it a very environmentally friendly and capable process.
How serious are their own side-effects like biocompatibility issues, toxicity, environmental stress etc.?
It is still something that has been under study for quite some time. What has been found is that, when it comes to nanotubes, size plays a major role. Larger tubes have been known to have properties that are not very safe. NoPo’s tubes are almost 20 times smaller than the tubes that have been reported to have such effects. We have also seen that, in the wild, nanotubes bundle together, collecting into larger tubules, which makes it very difficult for them to enter the human body because human nostrils are very good at filtering out nanotubes and other carbon particles. Along with that, in our water experiments, where we create RO membranes from nanotubes, we have studied their leaching properties.
What turned out here?
Leaching is when nanotubes come out of the system, and we have not observed any such effect. Some experiments we have done with silkworms have shown that nanotubes actually improve their health and protect them from fungal infections. Toxicity is something we take very seriously and study closely.
So far, what has been found is that nanotubes, through natural processes, do not enter the human body. Studies that have reported toxicity have involved completely unnatural processes, such as surgically inserting nanotubes directly into the lungs, a pathway that never occurs naturally. If any compound is introduced into the body that way, it can create toxicity. When it comes to removing nanotubes from the environment, normal bleaching powder used for cleaning is sufficient to destroy them completely. Washing anything containing nanotubes with bleach is enough to completely eliminate them and safely convert them into carbon dioxide.