Particles with a dimension that is 100nm or less in size are considered nanomaterials.\u00a0 But, size is not what provides the unique nanomaterial properties that are being observed. Consider the following:\u00a0 80nm aluminum particles are dangerous as a possible inhalant.\u00a0 30nm aluminum particles are very reactive (explosive) when they come in contact with air\/oxygen.\u00a0 70nm gold particles are fine dust, but below 20nm, these particles when added to glass change the color of the glass. \u00a0Just because a particle is less than 100nm does not give it special properties just because it is less than 100nm.<\/p>\n
There are other interesting changes in behavior in the sub-100nm range that can impact how materials behave.\u00a0 One example is that the adhesion forces of particles to surfaces change as the particles get smaller.\u00a0 Below roughly 70nm, van der Waals forces become the dominate adhesion mechanism.\u00a0 Most changes in material property and behavior start to occur somewhere in the 30nm to 70nm size region.\u00a0 (Part of this reason for change is that the size of a particle diminishes into the region where a significant portion of the atoms have \u201caccess\u201d to the particle\u2019s surface with the resultant increased opportunity to react with other material.)<\/p>\n
Currently, research in the nanotechnology realm work with basic elements and combinations of nano-scaled materials, which has created some materials with interesting properties.\u00a0 Carbon has been the most researched with single walled nanotubes and multi-walled nanotubes having a lot of early interest.\u00a0 The ability of the carbon nanoteubes to increase strength of other materials with a decrease in weight has been utilized in automotive and sports industries to name a couple areas.\u00a0 Depending on the chirality of the carbon nanotubes, the resultant material can be either conducting or semi-conducting.\u00a0 \u201cUnrolling\u201c a single walled carbon nanotube results in the material called graphene, which is called a \u201ctwo-dimensional\u201d material due to being only one atom thick.\u00a0 It is conductive.\u00a0 Contaminating the surface with oxygen produces a material called graphane, which is non-conducting (different name, different properties \u2013 graphane not graphene). [Ref. 1, 2, & 3]<\/p>\n
What if we are not considering all the possibilities?<\/strong><\/p>\n The current published research focuses on using various bulk materials to develop experiments and find the new properties of the nanomaterial.\u00a0 But, what if, nano-scale material is also different from bulk material due to the various isotopes of the material?<\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Bulk material containing various isotopes<\/strong><\/p>\n Bulk material consists of various isotopes of the specific element(s) in a ratio that has been determined through various techniques and has been quantified. [Ref. 4] \u00a0In general, one makes an assumption that the nano-scale material has the same isotope ratios as the bulk.\u00a0 One also assume that the different isotopes of the bulk material have identical properties when present together.\u00a0 Is it possible that individual isotopes are different from the bulk containing various isotopes?\u00a0 Is this possible?<\/p>\n One example that shows there is a different in isotopes is uranium.\u00a0 A specific form of the element (isotope) uranium is 235<\/sup>U, which makes up 0.07% of typical uranium in the mined ore.\u00a0 238<\/sup>U is the predominant form on the element and has a half-life of 4.5 billion years, while 235<\/sup>U is more reactive and can be split to produce energy. [Ref. 5] \u00a0The isotope that is useful, 235<\/sup>U, is separated from other isotopes of that material.\u00a0 It might be expensive and challenging, but if a specific isotope is useful, it will be obtained.<\/p>\n Another example of different properties of isotopes involves water.\u00a0 A water molecule consists of two hydrogen atoms and one oxygen atom.\u00a0 However, there are other forms (isotopes) of hydrogen that have one or two extra neutrons.\u00a0 Water molecules that consist of oxygen and deuterium (hydrogen with one extra neutron) are called heavy-water and are employed in damping nuclear radiation.\u00a0 So, one form of hydrogen has properties that the other does not.<\/p>\n It can be stated that in this case, the extra neutron causes a significant percentage increase in the atom\u2019s mass.\u00a0 Work has been done that states the impact of additional neutrons are the greatest on the elements with the lowest mass.\u00a0 Some projections imply that the additional of extra neutrons does not have a significant, if any, impact on the material properties.\u00a0 Is this true?\u00a0 What about 235<\/sup>U?<\/p>\n Consider Lithium with two stable isotopes, 6<\/sup>Litium and 7<\/sup>Lithium, with 7<\/sup>Lithium accounting for over 92% of the material.\u00a0 There are also a number of short lived lithium isotopes. [Ref. 6 & 7]\u00a0 It is known that 6<\/sup>Lithium has a greater affinity than 7<\/sup>Lithium for the element mercury.\u00a0 This fact is used in the separation of the two isotopes of Lithium.\u00a0 How is this possible if the extra neutron does not change the material properties?\u00a0 Maybe it does!<\/p>\n Is it possible that we need to think about research that works with specific isotopes of \u201ccommon\u201d materials?\u00a0 If various isotopes have different reactions with other materials, is it possible that \u201clumping\u201d all isotopes of an element into an experiment actually degrades the performance that a single isotope might have? At a minimum, research that works with specific isotopes of \u201ccommon\u201d materials should clearly state the isotopes used, including any percentage of other isotopes that may be present, which may impact performance.<\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Material purity<\/strong><\/p>\n There are various levels of material purity that can be purchased.\u00a0 Very high purity copper can be obtained that at 99.9999% pure.\u00a0 That is one part per million pure material.\u00a0 Other materials are not available in purities of greater than 99.99% and some are not even close to 99%.<\/p>\n It is known that doping of semiconductors with a very small percentage of different elements can change the properties of the combined material.\u00a0 Doping in silicon (semiconductors to increase the charge carrier concentration) can range from lightly doped (parts per billions) to heavily doped (parts per thousands) of the doping material.\u00a0 Depending on the materials employed, other effects besides carrier concentrations can be impacted.\u00a0 Lithium can be employed for increasing the resistance of solar material (solar cells) to the sun\u2019s radiation.<\/p>\n Has anyone examined the percentage impurity of isotopes in common materials, like carbon or copper?\u00a0 In order to conduct that experiment it would be necessary to have pure material and then add impurities.\u00a0 How difficult is that?\u00a0 Consider that conventional computer hard drives require more than 1 million atoms per bit and over \u00bd billion atoms per byte! \u00a0Consider a 2\u00b5m copper sphere.\u00a0 Calculations yield that it should have 3.56 x 1011<\/sup> atoms.\u00a0 If the material is six 9s pure, it contains 356,000 contaminant atoms! [Ref. 8 & 9] Do we really know the true properties of materials?<\/p>\n When the materials are in the nano-scale region, the total quantity of atoms is smaller.\u00a0 A 30nm aluminum particle has roughly 850,000 atoms in it.\u00a0 \u201cSuper pure\u201d aluminum can be as much as five 9s pure.\u00a0 That would still leave 9 contaminant atoms.\u00a0 Is that enough to modify material properties?<\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Material isotope homogeneity <\/strong><\/p>\n Another question is whether anyone has worked with a pure isotope of common materials.\u00a0 Granted that there are techniques for separating the isotopes, e.g., uranium, which can produce high purity materials.\u00a0 But, when the desired isotope exists as a very small percentage of the total material, it takes many passes through a process to achieve the desired concentration and that concentration is not 100%.\u00a0 It may be enough to be effective, but it is not 100%.<\/p>\n Copper has 29 isotopes with the two predominant being 63<\/sup>Cu (69%) and 65<\/sup>Cu (30.8%).\u00a0 That implies that the pure copper one can acquire will typically be 69% of one type and 31% of the other.\u00a0 Aluminum is interesting in the that for all practical purposes, 100% of aluminum is 27<\/sup>Al.\u00a0 So any changes to the properties would be due to contaminants and not isotopes of aluminum.<\/p>\n Thoughts<\/strong><\/p>\n If we have found that different isotopes of materials may have different properties in the bulk, is it not reasonable to anticipate that there will be different properties in the nano realm?\u00a0 Maybe we should start to investigate the properties of various isotopes of nanomaterials?\u00a0 Are we missing some potentially important properties when we do not investigate the isotopes on various nanomaterials?\u00a0 Do we have the concept of nanotechnology research mis-focused or just misunderstood?\u00a0 Any thoughts?\u00a0 Send to: Ideas at nano-blog.com<\/strong> (The email address has been written with \u201cat\u201d in place of the \u201cat symbol\u201d to avoid spam filling the mail box.)<\/p>\n Acknowledgements: <\/strong><\/p>\n Special thanks to Deb, Evelyn, and Harold for critical review and suggestions to improve this blog.<\/p>\n References:<\/strong><\/p>\n Particles with a dimension that is 100nm or less in size are considered nanomaterials.\u00a0 But, size is not what provides the unique nanomaterial properties that are being observed. 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