Micro/nano structures of colloidal nanoparticles attached to an electret substrate and method for producing such micro/nano structures

Patent metadata

Field	Value
Publication number	US-9975764-B2
Application number	US-201414772980-A
Country	US
Kind code	B2
Filing date	Feb 27, 2014
Priority date	Mar 8, 2013
Publication date	May 22, 2018
Grant date	May 22, 2018

Abstract

Method for producing a directed monolayer or multilayer assembly of colloidal nanoparticles attached to an electret substrate, including imparting a surface electric potential to an electret substrate according to a pattern of positive and/or negative electric charges, and contacting an electret substrate with a colloidal dispersion. The colloidal dispersion has electrically neutral or near neutral and electrically polarizable colloidal nanoparticles, and a nonpolarizing or weakly polarizing dispersion medium. The absolute value of the surface electric potential and the concentration of polarizable nanoparticles are no lower than a first surface electric potential threshold and no lower than a second concentration threshold, respectively, such as to obtain an assembly having a desired geometric shape, at least the first layer of which is compact in terms of the absence of undesired gaps having sizes greater than the size of two adjacent nanoparticles, preferably not greater than the size of one nanoparticle.

First claim

The invention claimed is:

1. A process for the manufacture of a micro/nanostructure formed of colloidal nanoparticles comprising a monolayer or multilayer assembly of colloidal nanoparticles which are attached to an electret substrate, having a freely chosen and predetermined geometric shape, at least the first layer of which is compact in terms of absence of undesired gaps with sizes of greater than or equal to the size of two adjacent nanoparticles, optionally greater than or equal to the size of one nanoparticle, comprising the stages consisting of:
in a first stage, providing the electret substrate, composed of an electret material and having a free receiving surface, then
in a second stage, writing a surface electric potential on the receiving surface of the electret substrate according to a predetermined pattern of positive and/or negative electric charges corresponding to the monolayer or multilayer assembly of nanoparticles, then
in a third stage, bringing the electret substrate having the receiving surface written with the surface potential according to the desired pattern of electric charges into contact with a colloidal dispersion for a contacting time which is less than or equal to fifteen minutes,
wherein:
the colloidal dispersion comprises electrically neutral or quasineutral colloidal particles which are electrically polarizable under the action of an external electric field and a dispersing medium, in the form of a liquid solvent or a gas which is substantially devoid of an electrical polarization action, in which the colloidal nanoparticles are dispersed, and
the absolute value of the surface electric potential and the concentration of polarizable nanoparticles are respectively greater than or equal to a first surface electric potential threshold and to a second concentration threshold, the first and second thresholds each depending on the nature of the dispersing medium and on the nature of the polarizable nanoparticles, so that
after the first contacting time, the micro/nanostructure obtained is a monolayer or multilayer micro/nanostructure having the desired geometric shape, at least the first layer of which is compact in terms of absence of undesired gaps with sizes greater than or equal to the size of two adjacent nanoparticles, optionally greater than or equal to the size of one nanoparticle, the nanoparticles being bonded to one another and/or to the substrate under the action of dielectrophoretic forces created from the interaction between the polarizable nanoparticles and the written surface potential.

2. The process as claimed in claim 1 , in which:
the assembly of colloidal nanoparticles which are attached to the electret substrate, having a freely chosen and predetermined geometric shape, is a multilayer assembly, at least the first layer of which is compact, and
the absolute value of the surface electric potential and the concentration of polarizable nanoparticles are respectively greater than or equal to a third surface electric potential threshold and greater than or equal to a fourth concentration threshold, the third and fourth thresholds each depending on the nature of the dispersing medium and on the nature of the polarizable nanoparticles, so that
after the contacting time, the micro/nanostructure obtained is the multilayer micro/nanostructure having the desired geometric shape, at least the first layer of which is compact in terms of absence of undesired gaps with sizes of greater than or equal to the size of two adjacent nanoparticles, optionally with sizes greater than or equal to the size of one nanoparticle, the nanoparticles being bonded to one another and/or to the substrate under the action of dielectrophoretic forces created from the interaction between the neutral and electrically polarizable nanoparticles and the written surface potential.

3. The process as claimed in claim 1 , in which:
the assembly of colloidal nanoparticles which are attached to an electret substrate, having a freely chosen and predetermined geometric shape, is a multilayer assembly of a certain number NI of layers, each of the layers of which is compact in terms of absence of undesired gaps with sizes greater than the size of two adjacent nanoparticles, optionally greater than the size of one nanoparticle, and
the absolute value of the surface electric potential and the concentration of polarizable nanoparticles are respectively greater than or equal to a fifth surface electric potential threshold and to a sixth concentration threshold, the fifth and sixth thresholds each depending on the nature of the dispersing medium, on the nature of the polarizable nanoparticles and on the number of layers, so that
after the contacting time, the micro/nanostructure obtained is the multilayer micro/nanostructure having the desired geometric shape, all the layers of which are compact in terms of absence of undesired gaps with a size greater than or equal to the size of two adjacent nanoparticles, optionally greater than or equal to the size of one nanoparticle, the nanoparticles being bonded to one another and/or to the substrate under the action of dielectrophoretic forces created from the interaction between the polarizable nanoparticles and the written surface potential.

4. The process as claimed in claim 1 , in which the stage of writing the surface electric potential on the receiving surface of the electret substrate according to a pattern of charges is carried out according to preference,
by a process of sequential writing of positive and/or negative charges on the electret substrate included within the group formed by inscription of electric charges by a beam of focused ions, inscription of electric charges by a beam of focused electrons, inscription of electric charges by atomic force microscopy (AFM) and inscription of electric charges by electrophotography, by a process of writing in parallel of positive and/or negative charges on the electret substrate included within the group formed by electrical nanoimprinting and electrical microcontact.

5. The process as claimed in claim 1 , in which:
the electret material is a material included within the group formed by polymethyl methacrylates (PMMA), cyclic olefin copolymers (COC), polyethylene terephthalates (PET), polydimethylsiloxanes (PDMS), polypropylenes (PP), polycarbonates (PC), polystyrenes (PS), polyvinyl chlorides (PVC), polytetrafluoroethylenes (PFTE), triglycine sulfate (TGS), polyvinylidene fluoride (PVDF), silicon nitride (Si 3 N 4 ), silicon oxide (SiO 2 ), or the compound Si 3 N 4 /SiO 2 /Si (NOS);
the substantially neutral and electrically polarizable colloidal nanoparticles are compounds stabilized by themselves or by ligands and/or charges, having physical properties included within the group formed by plasmonic, conducting, magnetic, luminescent, catalytic, electrochromic or photochromic properties, rendered substantially neutral and electrically polarizable, produced from base colloidal nanoparticles,
the base colloidal nanoparticles having a solid core and, if appropriate, a shell and being included within the group formed by the latex, SiO 2 , TiO 2 , ZrO 2 ; CdS, CdSe, PbSe, GaAs, GaN, InP, In 2 O 3 , ZnS, ZnO, MoS 2 , Si, C, ITO, Fe 2 O 3 , Fe 3 O 4 , Co, Fe—Co, Fe 3 C, Fe 5 C 2 , Ni; Au, Ag, Cu, Pt, and the bimetallic nanoparticles; WO 3 ; NaLnF 4 , lanthanide fluorides (LnF 3 ), lanthanide oxides (Ln 2 O 3 ), zirconates, silicates, hydroxides (Ln(OH) 3 ) and sulfides of oxides doped or not doped with one or more different lanthanides (Ln denoting a lanthanide), mixtures of these compounds, and dispersing medium for the polarizable nanoparticles is selected from the group consisting of a liquid solvent or a nonpolarizing gas, the liquid solvent being included within the group formed by pentane, isopentane, hexane, heptane, octane, n

Assignees

• Institut Nat Des Sciences Appliquees De Toulouse
• Centre Nat Rech Scient
• Univ Toulouse 3 Paul Sabatier

Inventors

• Ressier Laurence
• Neralagatta Munikrishnaiah Sangeetha
• Moutet Pierre

Classifications

• B82Y30/00

  Nanotechnology for materials or surface science, e.g. nanocomposites · CPC title

• G03G5/024

  Photoelectret layers · CPC title

• B05D3/14

  by electrical means · CPC title

• B81C1/00373 Primary

  Selective deposition, e.g. printing or microcontact printing · CPC title

• H01G7/02

  Electrets, i.e. having a permanently-polarised dielectric · CPC title