major contributions

Mesostructured Fluids in oil rich regions: Structural and templating approaches.

In this feature article, a phase diagram of a divalent surfactant is presented and discussed. The formation of the thermodynamically stable state of self-assembled supra-aggregates is demonstrated. Two different types of mesostructured fluids are described with either formation of a lamellar phase, containing and surrounded by a bicontinuous microemulsion, or interdigitated reverse micelles. These microstructures are used as templates where the control of the shape of copper nanocrystals is related to that of the microstructure. However, the template is not the only parameter which controls the shape of nanocrystals.

Source : Mesostructured Fluids in oil rich regions: Structural and templating approaches. M.P. Pileni Langmuir, 2001, 17, 7476-7487.

major contributions

Ferrite Magnetic Fluids: A New Fabrication Method and Magnetic Properties of Nanocrystals differing by their size and composition.

In this paper we outline different ways to make magnetic fluids from colloidal selfassemblies (normal and reverse micelles) and describe the preparation of both ferrite nanocrystals with various compositions and cobalt metal nanocrystals. The general magnetic behaviors are described but it is found that these are not applicable to the whole variety of ferrites produced. Ferrite and cobalt magnetic fluids are organized in 3D superlattices to form various mesoscopic structures. Within a number of limitations, the magnetic properties of both the above nanocrystals and these fluids have been determined and described.

Source : Ferrite Magnetic Fluids: A New Fabrication Method and Magnetic Properties of Nanocrystals differing by their size and composition. M.P. Pileni Advanced Functionalized Material, 2001, 11 , 323- 336.

major contributions

Role of soft colloidal templates in the control of size and shape of inorganic nanocrystals.

In the past decade, colloidal solutions have been assumed to be very efficient templates for controlling particle size and shape. A large number of groups have used reverse micelles to control the size of spherical nanoparticles. This makes it possible to determine the various parameters involved in such processes, and demonstrates that nanoparticles can be considered to be efficient nanoreactors. However, some discrepancies arise. There are few reports concerning the control of particle shape, and it is still rather difficult to determine the key parameters, such as the adsorption of salts and other molecules, and the synthesis procedure. Here, we discuss these controls of the size and shape of inorganic nanomaterials.

Source : Role of soft colloidal templates in the control of size and shape of inorganic nanocrystals. M.P. Pileni Nature Materials, 2003, 2, 145-150.

major contributions

Control of the size and shape of inorganic nanocrystals at various scales from nano to macrodomains.

Control of the size and shape of inorganic nanocrystals at various scales from nano to macrodomains.
M.P. Pileni J. Phys. Chem. C 111, 2007, 9019-9038.

In this paper, we propose the hypothesis that, in highly pure media, the cluster shape can be retained at various scales. Impurities and/or the additives can control the shape of the developing crystals by adsorption on selective sites. We demonstrate that the shape of clusters is retained at the nanoscale. This is supported by structural studies and both experiment and simulated optical properties of nanocrystal assemblies. We compare the data to those obtained by using a large variety of techniques and observation of crystal growth in nature.

Source : Control of the size and shape of inorganic nanocrystals at various scales from nano to macrodomains. M.P. Pileni J. Phys. Chem. C 111, 2007, 9019-9038.

major contributions

Self-assembly of inorganic nanocrystals: Fabrication and collective intrinsic properties.

In this Account, we demonstrate that the ordering of nanocrystals over long distances in 3D superlattices, called supracrystals, can lead to unexpected results: the emergence of collective intrinsic properties. The shape of the nanocrystal organization at the mesoscopic scale also induces new physical properties. In addition, we show that nanocrystals can be used as masks for lithography.

Source : Self-assembly of inorganic nanocrystals: Fabrication and collective intrinsic properties. M.P. Pileni Acc. of Chem. Res., 2007, 40, 685-693.

major contributions

Supracrystals of inorganic nanocrystals: An open challenge for new physical properties

When naturally occurring spherical objects self-organize, the physical properties of the material change. For example, a colorless opal is the result of a disordered aggregate of silica particles. When the silica particles are ordered, however, the opal takes on color, which is determined by the size of the self-assembled particles. In this Account, we describe how these 3D arrangements of nanomaterials can self-organize in 3D arrays called supracrystals; the 3D arrays can fall into the familiar categories of face-centered cubic (fcc), hexagonal compact packing (hcp) crystals, and body-centered (bcc) crystals. The collective properties of these 2D and 3D arrangements are different from the properties of individual nanoparticles and from particles in bulk. Comparison between the approach to saturation of the magnetic curve for supracrystals and disordered aggregates produced from the same batch of nanocrystals is similar to that observed with films or nanoparticles, either highly crystallized or amorphous. We also demonstrate by two various processes and with two types of nanocrystals (silver and cobalt) that when nanocrystals are self-ordered in 3D superlattices, they exhibit a coherent breathing mode vibration of the supracrystal, analogous to a breathing mode vibration of atoms in a nanocrystal. Furthermore, we used 10 nm γ-Fe2O3 nanocrystals to gain new insight into the scaling law of crack patterns. We found that isotropic and directional crack patterns follow the same universal scaling law over a film height varying by 3 orders of magnitude. These data have led us to propose general analogies between supracrystals of nanocrystals, individual nanocrystals, and the molecules in the bulk phase for certain physical properties based on the ordering of the material. As we continue to study the physical properties of the ordered and disordered arrangements of nanomaterials, we will be able to go further in these analogies. And this exploration leads to new questions: first and foremost, is this behavior general ?

Source : Supracrystals of inorganic nanocrystals: An open challenge for new physical properties. M.P.Pileni Acc. Chem. Res., 2008,  41, 1799-1809.