past article

The size of Elementary Particles of Detonation Nanodiamond (EPDND) decided at 2.6±0.5nm!

 The only mass-produced artificial nanodiamond is being manufactured by a novel method of ‘detonation’. This method has been known since 1963, but the true size of elementary particles of detonation nanodiamond (EPDND) remained unknown until recently. As the diamond crystals are basically isometric, they are usually quasi-spherical. If diameter is known, then we can estimate their surface area, and predict important properties originating from the surface. Hence it is desirable to know reliable diameter of EPDND.
 When we prematurely thought to have isolated the EPDND in 2005, we obtained an average DLS diameter of 4.8±0.8nm. In view of the large uncertainty in the DLS method, we used to express the diameter as 4〜5nm.Although many people use this expression still now, the size of EPDND kept decreasing since then with the advance in isolation technique, and finally reached a seemingly final value of 2.6±0.5nm a few years ago. Needless to say, but the size of EPDND is fixed at a certain value when it is formed and we cannot change it during the disintegration-isolation process. However the observed size is profoundly affected by the ad hoc aggregation. Especially strong is the interparticle bonding in dimers which persists till the end of disintegration process. Unless we completely cleave off every dimer bond to leave only the monomers (namely elementary particles alone), the observed diameter exceeds the true diameter.
 Is the diameter of 2.6nm correct?We need a good proof. The first proof came from unexpected direction. Highly reliable scientific report on the discovery of nanodiamond appeared in 1989 Nature written by R. N. Lewis and his group (Univ. Chicago), much later than the discovery of detonation nanodiamond. They isolated and confirmed nanodiamond from the famous Allende meteorite, believed to have been formed before the birth of solar system. They measured the size by TEM images to be exactly 2.6nm, perfectly identical with our DLS value! This coincidence is amazing but does not give a perfect proof because the relation between meteorite and detonation nanodiamonds is missing.
 The only acceptable proof, even though still indirect, would be to show by experiments that we always obtain exclusively those having average diameters within the 2.6±0.5nm size-range but never smaller ones. We recently finished an early stage of this endeavor and now it seems highly likely that we are right. Although we cannot disclose the details at this moment in order to protect our intellectual properties right, but will publish the results in due course.
 The surprisingly small diameter of EPDND suggests high potential in the future applications in various fields of material industry. For example, the surface density calculated from the diameter by using sphere approximation is 4,000 /g, comparable with that of the best activated charcoal. In contrast, detonation nanodiamonds having diameters 4〜5 nm are composed of dimers and should have an effective surface area one digit smaller than the true EPDND.