Standardization News

Nanomaterials: What’s in a Name?

That which we call a nanomaterial, by any other name, would smell as sweet.
By: 
John Rumble, Debra Kaiser, Frederick Klaessig, and Kathleen Chalfin

Over the last two decades, nanoscience has developed thousands of nanomaterials that promise to revolutionize many aspects of science and technology. From nanomedicines to quantum dots to nanomachines, the possibilities seem endless. Because of their tiny size (nanomaterials have one or more dimensions in the range of 1 to 100 nanometers), nanomaterials are complex, typically much larger than individual molecules, yet much less complicated than bulk materials such as metals, ceramics, and polymers. 

A major challenge is how to describe a nanomaterial so we know exactly which one is being discussed. Helping to meet this challenge are the members of the committee on nanotechnology (E56), which has recently published three standard guides on topics related to establishing a nomenclature system for nanomaterials. 

Naming the Object

Shakespeare was correct — names identify rather than define an object. But we still find using names more convenient to refer to an object rather than having to specify all of its attributes. Names are useful to help us remember or recall a particular object. For instance, the name “Charlie Brown” immediately brings to mind Charles M. Schulz’s famous cartoon character and usually even conjures up his image. However, when there are billions of objects with names (for example, people on earth), our memories fail us. Even if we learned all 7-8 billion personal names, our brains would not be able to process them fast enough to remember the person associated with each one. 

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The same situation arises with material objects we encounter — the millions of chemicals, metals, ceramics, polymers, composites, wood, concrete, birds, trees, etc. While we have specific names for many of them, we need help to remember what they really are. For scientific and technical contexts, we have devised several methods to help us. 

One approach is to develop a detailed system that carries identifying information in the name itself, with chemical nomenclature as the most prominent example. For instance, 2,4,6-trinitrotoluene (TNT) denotes a chemical structure where a benzene molecule (C6H6) has a methyl (CH3) group substituting for one benzene hydrogen atom and three nitro (NO2) groups substituting for three other benzene hydrogen atoms at the specified positions. Here the name carries specific detailed information. 

A second approach, often used for bulk materials such as metals, ceramics, and polymers, is to enumerate the characteristics of a material and specify its name in the document that defines it. For example, the specification for chromium-iron sealing alloys with 18 or 28% chromium (F256). These alloys are known as UNS K91800 or ASTM F256 Type I (18% chromium) and UNS K92501 or ASTM F256 Type II (28% chromium). In this case, the name refers backs to a document with the detailed specification. 

Neither approach presently works for nanomaterials. There is not yet a nomenclature system for assigning names nor are there detailed specification documents that associate characteristics with individual particles or nanomaterial categories beyond a few international standards for size and shape such as nanoscale, nanoplate, and nanofiber. Yet the variety of nanomaterials and the subtle differences between many of them make it almost impossible to come up with a naming system similar to chemical nomenclature that systematically assigns names that can be deconstructed into a specific structure or set of characteristics. 

The Guides

The nanotechnology committee (E56) has published three standard guides focused on providing detailed information about nanomaterials and their production. These guides describe the information categories and specific descriptors needed to identify a nano-object uniquely. Uniqueness is defined as the ability of a description system to differentiate one object from every other object and to establish which specific object is being described within the broad range of disciplines and user communities, including guides for reporting the: 

  • Physical and chemical characteristics of nano-objects (E3144); 
  • Physical and chemical characteristics of a collection of nano-objects (E3206); and 
  • Production information and data for nano-objects (E3172). 

Describing a nanomaterial uniquely is accomplished at three levels: the individual nano-object (the smallest nanomaterial unit); collections of nano-objects (which are very important because of the strong affinity that nano-objects have to associate with or adhere to one another); and the production of individual nano-objects and their collections. 

  • Each of the guides defines several categories of important information, including: 
  • Chemical composition, size, and shape of a nano-object; 
  • Physical structure and distribution of sizes in a collection of nano-objects; and 
  • Starting materials, conditions, and methods for producing nano-objects and their collections.  

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Each information category contains many specialized descriptors, and the guides provide clear definitions and examples for each. The guides are designed to be useful in many situations, as outlined in the sidebar. We also anticipate that the guides will be updated as our knowledge of what makes a nanomaterial unique reveals new categories and descriptors that reflect those advances. 

To answer the question: What is in a nanomaterial name? These three guides from the committee on nanotechnology are an important step to systematically defining and categorizing the information that allows us to know which nanomaterial we are really talking about. When the time comes for creating a nanomaterial naming system, E56 has developed powerful tools to ensure that such a naming system is based on science – and not Shakespeare.■

John Rumble is a long-time member of several ASTM International committees, including the committee on nanotechnology (E56). Retired from the U.S. National Institute of Standards and Technology, he is a chemical physicist and CEO and president of R&R Data Services, Gaithersburg, Maryland. 

Debra Kaiser is chair of the committee on nanotechnology and a long-time materials scientist at the U.S. National Institute of Standards and Technology, Gaithersburg, Maryland. 

Frederick Klaessig is chair of the subcommittee on informatics and terminology (E56.01). He is a chemist and does consulting work as Pennsylvania Bio Nano Systems LLC, Doylestown, Pennsylvania. 

Kathleen Chalfin is staff manager for the committee on nanotechnology and a director, technical committee operations, at ASTM International. She also manages seven other committees.

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Issue Month: 
September/October
Issue Year: 
2020
COMMITTEE: 
E56