Several authors authors have reported the formation of monodispersed nickel nanoparticles when nickel acetylacetonate is used as precursor using oleylamine, trioctylphosphine, triphenylphosphine etc, in most cases combining two of them at the most. Just recently Jaiveer Singh et al (Naturally self-assembled nickel nanolattice. J. Singh, N. Kaurav, N. P. Lalla and G. S. Okram. J. Mater. Chem. C (2014) DOI: 10.1039/c4tc01360c; http://arxiv.org/ abs/1406.6881; online version attached) have demonstrated rather critically and convincingly that TOP is the sole surfactant that enables the monodispersisty. Others help only marginally. Moreover, TOP enables the nickel nanoparticles of different sizes with fine monodispersity, and most importantly and interestingly TOP enanbles these nanoparticles the formation of 3D hexagonal closed packed nanolattice (i.e. lattice of nanoparticles) without using any other extra surfactant or external forces. These hcp nanolattices have c/a ratios identical to those of atomic lattices. The external forces were otherwise considered essential to enable the nanolattice formation. This work thereore seems to pave the way to natural nanolattice formability as in atomic lattices, which are presented in detail in this paper mentioned above. Similar situation is believed to happen in other metals, and compounds, including other magnetic nanopaticles (nanodots).
Some work has also been done in the rock magnetic community to create 2D arrays of magnetic nanodots using electron lithography (see http://dx.doi.org/10.1029/2008JB006017).
The grain sized produced here were aimed at spanning the SD to PSD region so are a few tens to a few hundreds of nanometers. With this method you can also control the grain spacing.
From what I understand, however, it is a difficult method to perfect.
What is your demand on degree of monodispersehood? What is your understanding of "dot"? Some people have investigated magnetic clusters in molecular beams with atomic mass resolution. That is monodisperse, but sub-nm particles flying in vacuum may not be what you consider as "dots"...
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