It was discovered a few decades ago how to obtain diamond nanoparticles in large quantities, during the utilization of explosives. Since then, tremendous efforts have been put into finding the real world applications for this unique form of carbon.
It is now clear that nanodiamonds could be considerably beneficial to many areas of industry. However, more work is still required to fully adapt this material from the laboratory to meet the requirements of different industries.
The RUSNANOPRIZE Award nomination process helps in the evolution of the nanodiamond story from interesting scientific finding to large scale commercial material. Indeed, three applications to the RUSNANOPRIZE 2013 were dedicated to nanodiamonds. Some recent developments in the area of nanodiamonds are further described below.
Tons, Kilograms, Grams – Three Scales of Refinement
To understand possible nanodiamond (ND) applications, there are two extremes to be considered. Some applications may require large quantities of ND, and in some cases no serious modification is needed. In the first instance, it is possible to significantly strengthen electrochemical coatings with nanodiamonds as an additive to the electrolyte. Tons of ND yearly is used in industries dealing with Cr, Ni, Zn, Sn or even Au coatings.
In contrast, in the pharmaceutical sector, nanodiamonds were shown to be effective drug carriers, as well as promising intracellular tracers. Now, the avalanche-like wave of researches requires ND related chemicals on a gram scale.
Between these two extremes there are a large number of applications with a kilogram-scaled consumption with specific demands for the size, purity, controlled imperfections in the crystal lattice, homogeneity, surface characteristics and so on.
Professor Valery Dolmatov and his team in the "FGUP SKTB "Technolog" company (Russia) are studying the next step after one obtains tons of nanodiamonds in a detonation chamber. It is obvious that chemical purification must be performed to remove large amounts of carbon and non-carbon contaminations from the crude ND-containing mix.
A number of technologies have been suggested and optimized for such refinement. Prof. Dolmatov's team has been constructing the industrial equipment to separate ND in ton-scaled quantities. Any purification technology makes sense only if they are scalable to industrial quantities with reasonable costs.
In "FGUP SKTB "Technolog" engineers developed a wide line of industrial equipment for different refinement technologies to obtain nano diamonds of 95% or 99% purity, focusing on getting rid of certain contaminations (e.g., Cr or Fe) or on getting nanodiamonds with a modified surface.
Down to Single Crystals
World renowned Japanese scientist EijiOsawa was the first to predict the fullerene form of carbon, or the C60 molecule. He understood the prospects of ND as soon as this kind of material could be obtained in large quantities. He discovered that detonation synthesis gives nanodiamonds in a highly aggregated form. Professor Osawa spent several years trying to disintegrate the aggregates down to single crystals. The technology was finally developed that allowed obtaining nanodiamonds in the form of simple pure nanoparticles in large quantity on a kilogram scale.
Computational modeling done by Dr Amanda Barnard from Australia complimented purifying efforts. It was shown that "bare" ND crystal has several charge localization zones with opposite polarity on its surface and this can be a main cause of the aggregation.
Prof. Dean Ho from USA validated the safety of disintegrated ND crystals for internal use in humans and animals. Nanodiamonds are not just non-toxic, but also improve some important pharmaceuticals. Prof. Ho worked on the issue of drug delivery systems for anti-cancer therapies. According to him, liver and breast cancers that are normally resistant to chemotherapy can be cured if given along with drugs delivered by ND.
Modifications: On the Surface and Inside the Crystal
A large number of industries benefit from using nanodiamonds, including the following:
•Microelectronics – Nanodiamonds are used in the fine polishing compositions, moreover ND serve as a seeding for CVD growth of diamond films
•Heavy engineering industries – Nanodiamonds are used as additives to lubricating oils provide up to x10 decrease in friction coefficient and up to 50% decrease in wear.
•New materials – Nanodiamonds are used in polymer composites and can result in enhanced thermal stability, thermal conductivity, radiation stability, UV protection and radar absorption properties. Different applications need different characteristics of ND.
Dr. Olga Shenderova from USA has made considerable progress in adopting NDs to specific industry demands, mostly by ND surface modification and size selection. The line of Adamas Nanotechnologies commercial products includes many types of functionalized NDs with sizes ranging from primary particles up to 100nm aggregates: carboxylated, hydroxylated, aminated, PEGylated, fluorinated, hydrogenated, NDs with silane groups, etc. These products are regularly delivered to respective industrial customers.
Another method of modification is related to controlled defects in the ND crystal. Dr. Huan-Cheng Chang from Taiwan separated primary ND particles from grinded synthetic microdiamond powder. Dr. Chang developed the automated ion-beam-based technology for implementation of controlled defect centers into crystal lattice (e.g., nitrogen vacancies).
The story of nanodiamonds underlines how important scientific collaboration is. The groups mentioned represent just a section of the intellectual forces focused on nanodiamonds. It is now clear that this material has really high potential for industrial exploitation.
The progress in further commercialization is possible because of the high level of cooperation between different specialists worldwide. Enthusiasm and faith in success are the main common traits of the people who have developed the ND-related theory and practice.
The RUSNANOPRIZE Award nomination has also been most advantageous, acting as a searchlight to catch the most interesting technologies for commercialization. The real prospect lies in transcontinental integration of many different approaches which could lead to an important industrial break-through in the very near future.
About Rusnano Prize Directorate
The Rusnano Prize is awarded to researchers, scientists and developers (up to three people) being the authors of scientific-technological discovery or discoveries in the field of nanotechnologies, and to the company being the first to apply the discovery (discoveries) to mass production with the annual turnover of at least $10 million and reached business success through the application of the discovery (discoveries).