WO2015170331A2 - Nanomatériaux inorganiques - Google Patents

Nanomatériaux inorganiques Download PDF

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WO2015170331A2
WO2015170331A2 PCT/IL2015/050479 IL2015050479W WO2015170331A2 WO 2015170331 A2 WO2015170331 A2 WO 2015170331A2 IL 2015050479 W IL2015050479 W IL 2015050479W WO 2015170331 A2 WO2015170331 A2 WO 2015170331A2
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nanostructure
nanomaterial
las
crs
formula
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WO2015170331A3 (fr
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Reshef Tenne
Leela Srinivas PANCHAKARLA
Gal RADOVSKY
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Yeda Research And Development Co. Ltd.
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Definitions

  • the present invention concerns inorganic nanostructures, and specifically layered tubular structures, comprising mixed metal-chalcogenides and specifically layered tubular structures comprising lanthanide-chalcogenide and transition metal chalcogenide.
  • van der Waals bonded materials have extra advantage compared to other materials in that, it show less different between bulk and their surface.
  • Lot of interest is to bring down these materials to low dimensions due to the new properties offered by reduced dimension.
  • carbon nanotubes, S 2 and M0S 2 nanotubes as one- dimensional materials and most recently graphene, MoS 2 monolayers as two- dimensional materials showed their unique structure and dimensionality relate properties.
  • One common method to screen for promising new materials is to systematically exploring the periodic table, by replacing one element in an existing material with another element in the same group. This strategy lead to the discovery of silicene.
  • MLC metal-chalcogenide "misfit" layer compounds
  • the present invention concerns synthesis of nanomaterials, typically layered nanostructures, from misfit compounds based on lanthanides.
  • the growth mechanism of these nanostructures differs radically from the previously reported misfit nanotubes.
  • Various many-body effects like topological insulators and phase slip have been recently observed by measuring the transport properties of nanowires at cryogenic temperatures.
  • the nanostructures of the present invention are free of surface defects and consequently are expected to reveal truly unique many-body physical phenomena in 1-D. It is thus an object of the present invention to provide novel misfit materials being of a nanometric scale.
  • this invention provides novel methods to produce misfit layered structures with high yield. Methods of this invention allow the formation of a novel class of misfit layered materials that may find applications in electronics, photonics and in thermo-electric devices. The novel methods of this invention produces misfit layered materials with high yield.
  • the invention provides a nanomaterial being of the formula [(MiX (P )X' -p))i «(M 2 X , (q )X' ⁇ ) y ]-(TX , t )X'' (2t) ) > wherein M x being a metal, M 2 being a metal, T being a transition metal, each of X' and X" being independently S or Se, 0 ⁇ p ⁇ l , 0 ⁇ q ⁇ l, 0 ⁇ k ⁇ 2, 0 y ⁇ 0.2, 0 ⁇ z ⁇ 0.3, and M ⁇ M 2 , provided that when y is zero than ⁇ , and when z is zero than y ⁇ 0.
  • the nanomaterial described by the formula [(M 1 X' (p) X" (1 - p ))i + z(M 2 X' (q) X" (1 - q ))y]-(TX' (k) X" (2 _ k) ), is a misfit layered nanomaterial.
  • Mi, M 2 or a combination thereof is a lanthanide metal.
  • the nanomaterial described by the formula [(M ! X' (p) X" (1 . p) ) 1+z (M 2 X' (q) X" (1 . q) ) y ]-(TX' (k) X" (2 . k) ), is a misfit tubular layered nanomaterial.
  • the layered nanomaterial comprising layer(s) of [(M 1 X' (p) X" (1 . p) ) 1+z (M 2 X' (q) X" (1 . q) ) y ] and layer(s) of [TX (k) X" (2 _ k) ] wherein the layers are misfit layers.
  • the invention provides a nanomaterial being of the formula [(MiX)i+z(M 2 X)y](TX"2), wherein Mi being a lanthanide metal, M 2 being a metal, T being a transition metal, each of X' and X" being independently S or Se, 0 ⁇ ⁇ 0.2, 0 ⁇ z ⁇ 0.3, and Mi ⁇ M 2 , provided that when y is zero than ⁇ , and when z is zero than y ⁇ 0.
  • this invention provides a nanomaterial of formula [(M ! X' (p) X" (1 . p) ) 1+z (M 2 X' (q) X" (1 . q) ) y ](TX' (k) X" (2 . k) ), wherein M x being a metal, M 2 being a metal, T being a transition metal, each of X' and X" being independently S or Se, 0 ⁇ y ⁇ 0.2, 0 ⁇ z ⁇ 0.3, 0 ⁇ p ⁇ l, 0 ⁇ q ⁇ l, Q ⁇ k ⁇ 2, and Mi ⁇ M 2 , provided that when y is zero than ⁇ , and when z is zero than y ⁇ 0.
  • this invention provides a nanomaterial being of the formula [( ⁇ ') ⁇ + ⁇ ( ⁇ 2 ⁇ ') ⁇ ]( ⁇ " 2 ), wherein Mi being a lanthanide metal, M 2 being a metal, T being a transition metal, each of X' and X" being independently S or Se, 0 ⁇ ⁇ 0.2, 0 ⁇ z ⁇ 0.3, and Mi ⁇ M 2 , provided that when y is zero than ⁇ , and when z is zero than y ⁇ 0.
  • this invention provides a layered nanostructure comprising at least one first sublayer having the formula [(MiX' (P) X" ( i_ P) )i +z (M 2 X' (q) X" ( i_ q) ) y ] m and at least one second sublayer having the formula (TX' (k) X" (2 _ k) ) n , wherein Mi being a metal, M 2 being a metal, T being a transition metal, each of X' and X" being independently S or Se, 0 ⁇ p ⁇ l , 0 ⁇ q ⁇ l, 0 ⁇ k ⁇ 2, 0 ⁇ ⁇ 0.2, 0 ⁇ z ⁇ 0.3, m and n being integers, independently selected from 1 to 10, and Mi ⁇ M 2 , provided that when y is zero than ⁇ , and when z is zero than y ⁇ 0 .
  • m and n represent the number of layers of each type in one periodic unit (one periodic superlayer).
  • the different types being: first type [(MiX' (P) X"(i_ P ))i +z (M 2 X'( q )X"(i-q))y]m and second type (TX' (k )X" (2 -k))n, according to some embodiments.
  • this invention provides a layered nanostructure comprising at least one first layer having the formula [(MiX')i +z (M 2 X') y ]m and at least one second layer having the formula (TX" 2 ) n , wherein Mi being a lanthanide metal, M 2 being a metal, T being a transition metal, each of X' and X" being independently S or Se, 0 ⁇ ⁇ 0.2, 0 ⁇ z ⁇ 0.3, m and n being integers, independently selected from 1 to 10, and Mi ⁇ M 2 , provided that when y is zero than ⁇ , and when z is zero than y ⁇ 0 .
  • this invention provides a layered nanostructure comprising a plurality of superlayers.
  • Superlayers comprise alternating layers of [(MiX')i +z (M 2 X')y] m and of (TX" 2 ) n , In each super layer a misfit exists between the layers of type [(MiX')i +z (M 2 X') y ] m and the adjacent layers of type (TX" 2 ) n .
  • the number of layers in each superlayer and the number of superlayers controls the properties of the layered material in some embodiments.
  • Superlayer is defined as a unit comprising (MX) m and (TX 2 ) n coupled together.
  • (MX) m is the short description of [(MiX')i +z (M 2 X) y ] m and (TX 2 ) n is the short description for (TX" 2 ) n .
  • Each superlayer is being composed of a first layer of the formula [(MiX')i +z (M 2 X') y ] m and a second layer of formula (TX" 2 ) n , or vice versa (i.e.
  • a plurality of superlayers is being stacked, wherein Mi being a lanthanide metal, M 2 being a metal, T being a transition metal, each of X' and X" being independently S or Se, 0 ⁇ y ⁇ 0.2, 0 ⁇ z ⁇ 0.3 , and Mi ⁇ M 2, provided that when y is zero than ⁇ , and when z is zero than y ⁇ 0.
  • the integers m and n range between 1-10.
  • this invention provides a layered nanostructure comprising at least one first layer of the formula [(MiX'( P )X"(i-p))i +z (M 2 X'(q)X"(i- q))y]m, having a first crystallographic cell unit, and at least one second layer of formula (TX' (k )X" (2 -k))n, having a second crystallographic cell unit, said first and second layers being alternately stacked, wherein said first and second crystallographic cell units having a misfit defined by the ratio (ai-a 2 /ai) having a value of between 0.3 and 0.5, wherein Mi being a metal, M 2 being a metal, T being a transition metal, each of X' and X" being independently S or Se, 0 ⁇ p ⁇ l, 0 ⁇ q ⁇ l, 0 ⁇ k ⁇ 2, 0 ⁇ ⁇ 0.2, 0 ⁇ z ⁇ 0.3, and Mi ⁇ M 2 , provided that when y is zero
  • this invention provides a layered nanostructure comprising at least one first layer of the formula [(MiX')i +z (M 2 X')y] m having a first crystallographic cell unit, and at least one second layer of formula (TX" 2 ) n having a second crystallographic cell unit, said first and second layers being alternately stacked, wherein said first and second crystallographic cell units having a misfit defined by the ratio ⁇ ai-a 2 /ai) having a value of between 0.3 and 0.5, wherein Mi being a lanthanide metal, M 2 being a metal, T being a transition metal, each of X' and X" being independently S or Se, 0 ⁇ ⁇ 0.2, 0 ⁇ z ⁇ 0.3, and Mi ⁇ M 2 , provided that when y is zero than ⁇ , and when z is zero than y ⁇ 0.
  • this invention provides a process for obtaining a nanomaterial of the formula [(MiX' (p) X" ( i-p))i + z(M2X( q )X"(i- q )) y ](TX , (k) X" ( 2-k)), wherein Mi being a metal, M 2 being a metal, T being a transition metal, each of X' and X" being independently S or Se, 0 ⁇ p ⁇ l, 0 ⁇ q ⁇ l, ⁇ k ⁇ 2, 0 ⁇ y ⁇ 0.2, 0 ⁇ z ⁇ 0.3, m and n being integers, independently selected from 1 to 10, and Mi ⁇ M 2 , provided that when y is zero than ⁇ , and when z is zero than y ⁇ 0, the process comprising:
  • hydrogen H 2
  • N 2 hydrogen
  • the addition of nitrogen facilitates the process.
  • the addition of nitrogen gas to hydrogen gas is not necessary.
  • the nitrogen is essential for establishing a proper hydrodynamic regime in some embodiments.
  • inert gasses can be used instead of the H 2 /N 2 gas mixture.
  • He, Ar or a combination thereof are used with or without hydrogen gas instead of the H 2 /N 2 gas mixture.
  • this invention provides a process for obtaining a nanomaterial of the formula [(MiX')i +z (M2X)'y] m (TX"2)n, wherein Mi being a lanthanide metal, M 2 being a metal, T being a transition metal, each of X' and X" being independently S or Se, 0 ⁇ ⁇ 0.2, 0 ⁇ z ⁇ 0.3, m and n being integers, independently selected from 1 to 10, and Mi ⁇ M 2 , provided that when y is zero than ⁇ , and when z is zero than y ⁇ 0, the process comprising:
  • this invention provides a nanomaterial of the formula [(M 1 X' (p) X" (1 _p ) ) 1+z (M2X , (q )X" ( i- q )) y ] m (TX (k) X" ( 2-k))n, wherein M x being a metal, M 2 being a metal, T being a transition metal, each of X' and X" being independently S or Se, 0 ⁇ y ⁇ 0.2, 0 ⁇ z ⁇ 0.3, 0$p ⁇ l, Q3 ⁇ 4 ⁇ 1, 0 ⁇ k ⁇ 2, m and n being integers, independently selected from 1 to 10, and Mi ⁇ M 2 , provided that when y is zero than ⁇ , and when z is zero than y ⁇ 0, obtained by a process comprising:
  • this invention provides a nanomaterial of the formula
  • Mi being a lanthanide metal
  • M 2 being a metal
  • T being a transition metal
  • each of X' and X" being independently S or Se, 0 ⁇ ⁇ 0.2, 0 ⁇ z ⁇ 0.3
  • m and n being integers, independently selected from 1 to 10, and Mi ⁇ M 2 , provided that when y is zero than ⁇ , and when z is zero than y ⁇ 0, obtained by a process comprising:
  • this invention provides a composition comprising the nanomaterials or the layered nanostructure described herein above.
  • this invention provides an article comprising the nanomaterials or the layered nanostructure described herein above.
  • Fig. 1 shows SEM images of LaS-CrS2 nanoscrolls and nanotubes (a) low (b) and (c) high magnification images. Insets in (b) and (c) show single nanotube and single nanoscrolls images respectively.
  • Fig. 2(a) shows high resolution TEM image of LaS-CrS 2 nanoscroU along with the line profile (c) obtained from the region enclosed in the white rectangle. Low magnification TEM image of the corresponding nanoscroU is shown as an inset.
  • Fig. 2(b) is an SAED pattern taken from the area shown in Fig. 2(a). Tube axis (i) and basal reflection (ii) are shown. Spots relevant to the same interplanar spacing are marked with segmented circles and measured values with corresponding Miller indices are assigned. (LaS and GS 2 subsystems and combined -spacing)
  • Fig. 3 shows: (a) Schematic model of single layer of CrS 2. Panels (b), (c) and (d) are single LaS layers: panel (c) and (d) are rotated by 60° and 120° along the c-axis relative to panel (b). (e) and (f) show respectively schematic of (LaS)i .2 CS 2 in b and a viewing directions, (g) shows the LaS and CrS 2 layers orientation within a single nanoscroU with corresponding projected 020 electron diffraction patterns. All the layers together give the observed 020 reflection in electron diffraction as shown in Fig. 2(b). [0034] Fig. 4 shows a high resolution TEM image of 20% Gd substituted LaS- CrS 2 .
  • Fig. 5 shows low (a) and high (b) magnification SEM images of CeS- CrS 2 nanotubes and nanoscroUs. Inset in (b) shows the formation of nanoscroU by bending the nanosheet. (c) and (d) respectively, show the low and high magnification SEM images of GdS-CrS 2 nanotube/nanoscrolls.
  • Fig. 6 shows (a) High resolution TEM image of CeS-CrS 2 nanotube along with the line profile (c) obtained from the region enclosed in the white rectangle. Low magnification TEM image of the corresponding nanoscroU is shown as an inset, (b) SAED pattern obtained from the nanotube shown in (a), (d) high resolution TEM image along with low magnification images (inset) of GdS-CrS 2 nanotube and with the line profile (f) obtained from the region enclosed in the white rectangle, (e) SAED pattern obtained from the nanotube shown in (d). Tube axis (i) and basal reflection (ii) are shown. Spots relevant to the same interplanar spacing are marked with segmented circles and measured values with corresponding Miller indices are assigned. (CeS (GdS) and CrS 2 subsystems and combined -spacing)
  • Fig. 7 shows (a) high resolution TEM image of CeS-CrS 2 nanotube along with the line profile (c) obtained from the region enclosed in the white rectangle. Low magnification TEM image of the corresponding nanoscroUs are shown as an inset, (b) SAED pattern obtained from the nanotube shown in (a). Spots relevant to the same interplanar spacing are marked with segmented circles and measured values with corresponding Miller indices are assigned. (CeS and CrS 2 subsystems and combined subsystems) [0038] Fig. 8 shows SEM images of products obtained at different temperatures by treating mixture of lanthanum and chromium hydroxides in the presence of H 2 /H 2 S.
  • Fig. 9 shows SEM images of products obtained at different durations at 825 °C by treating mixture of lanthanum and chromium hydroxides in the presence of H 2 /H 2 S.
  • Fig. 10 shows (a) high resolution TEM image of LaS-CrS 2 nanotube (synthesized from nanowhiskers precursor) along with the line profile (c) obtained from the region enclosed in the white rectangle. Low magnification TEM image of the same tube is shown as an inset. SAED pattern (b) is taken from the area shown in (a). Tube axis (i) and basal reflection (ii) are shown. Miller indices are assigned. (LaS and CrS 2 subsystems )
  • Fig. 11 shows (a) High resolution TEM image of LaS-CrS 2 nanoscroll along with the line profile (c) obtained from the region enclosed in the white rectangle. Low magnification TEM image of the corresponding nanoscrolls are shown as an inset. SAED pattern (Fig. lib) is taken from the area shown in (Fig. 11a). Tube axis (i) and basal reflection (ii) are shown. Spots relevant to the same interplanar spacing are marked with segmented circles and measured values with the corresponding Miller indices are assigned. (LaS and CrS 2 subsystems and combined -spacing )
  • Fig. 12 shows a growth model for a LnS-CrS 2 nanoscroll. Models along with SEM images in different stages of the reaction are shown to illustrate the growth of the nanoscroll.
  • Fig. 13-14 show growth models for a LnS-CrS 2 layered nanotubes. Models along with SEM images in different stages of the reaction are shown to illustrate the growth of layered nanotubes.
  • Fig. 15 is an image of a nanotubular structure from the family of misfit compounds LnS-TaS2-
  • the solid arrow represents the b-axis with respect to the ortho-pseudohexagonal unit cell, coincides with the tube axis.
  • the two dashed arrows represent crystaUographically equivalent directions rotated by 60° and 120° relative to the direction marked by the solid arrow, c) Initiation of bending around the b-axes of the LnX and TaX 2 layers that comprise an LnX- TaX 2 slab, d) A concentric tubule whose axis (perpendicular to the plane of the paper) coincides with the b-axes of LnX and TaX 2 . e) Partially unfolded sheets, demonstrating the scrolling process for the NdS-TaS 2 MLC case.
  • Fig. 17 a) SEM image of LaS-TaS 2 tubular structures and common byproducts. Scrolling steps are visible on the tubular crystals, b) TEM images of a LaS-TaS 2 nanotube, with LaS and TaS 2 layers stacked in an alternating sequence, c) SAED pattern taken from the area shown in (b). The tubule axis is marked by the double arrow. Spots corresponding to the same interplanar spacing are marked by large segmented circles (TaS 2 and LaS). The Miller indices of the MO in- plane reflections are indicated. Basal OOn reflections are marked by small arrows. A chiral angle of 3.1° was determined for both the LaS and the TaS 2 layers from the splitting of the spots, as discussed in the text, d) Line profile perpendicular to the tubule axis extracted from the region marked in b).
  • Fig. 19 presents a Raman spectra of single LaS-TaS 2 and NdS-TaS 2 tubular crystals. A spectrum recorded from a TaS 2 platelet is also shown for comparison.
  • Fig. 20 presents a schematic diagram showing the possible stacking of the LnS and TaS 2 layers along their common c-axis and their in-plane orientations for tubules containing rotational variants of the LnS and TaS 2 layers.
  • Two types of TaS 2 layers are denoted “1 " and “2”.
  • Three types of LnS layers are denoted “ ⁇ ", "2' " and “3' “.
  • ⁇ head-on view along the c-axis
  • the tubule axis is marked by smaller arrows.
  • pseudohexagonal and ortho- pseudohexagonal unit cells are shown in as in Fig.
  • FIG. 16 b Representative EDS spectra recorded from LnS-TaS 2 tubular structures, for which LnS is: (a) LaS, (b) CeS, (c) NdS, (d) HoS and (e) ErS.
  • LnS is: (a) LaS, (b) CeS, (c) NdS, (d) HoS and (e) ErS.
  • the (unmarked) peaks appearing at 8.65 keV and 8.92 keV in (a)-(e) are ⁇ ⁇ ⁇ and CuK i, originate from the TEM grid.
  • the peaks at 6.42 keV and 6.93 keV in (b) are FeKai and CoK a i, respectively. They are attributed to the mechanical aperture in the TEM column, (f) and (g) are representative spectra recorded from LaSe- TaSe 2 tubular structures synthesized by the catalytic action of TaCls and TaBrs, respectively.
  • FIG. 22 SEM images of the tubular structures and common by-products from (a) ErS-TaS 2 , (b) NdS-TaS 2 , (c) HoS-TaS 2 , (d) CeS-TaS 2 and (e) LaSe- TaSe 2 MLC. Scrolling steps are visible on the tubular crystals.
  • Fig. 23 Representative XRD patterns recorded from the total products obtained during the synthesis of (a) LaS-TaS 2 , (b) NdS-TaS 2 and (c) ErS-TaS 2 tubular structures. Different orders of peaks associated with the LnS/TaS 2 (1 :1) superstructure along the common c-axis are marked [(001)-(009)]. The corresponding interplanar spacings are also marked.
  • Fig. 24 presents a TEM images of (a) ErS-TaS 2 and (b) LaSe-TaSe 2 tubular crystals, with the LnS(Se) and TaS 2 (Se) layers stacked periodically. Top:
  • Middle SAED patterns acquired from the areas shown in the upper images. Spots corresponding to the same interplanar spacings are marked by large segmented ellipses or circles (TaS 2 (Se) and LnS(Se)) and the respective Miller indices are indicated. The tubule axes are marked by double arrows. Basal refiections are marked by small arrows. Chiral angles of 7.2° and 5.4° for the tubules shown in (a) and (b), respectively, were determined from the splitting of the spots, as discussed in the text.
  • Bottom Line profiles integrated along the rectangles marked in the upper images.
  • Fig 25 presents TEM images of (a) NdS-TaS 2 and (b) HoS-TaS 2 nanotubes, with the LnS and TaS 2 layers stacked periodically.
  • Top High magnification images, with low and medium magnification images shown as insets.
  • Middle SAED patterns recorded from the areas shown in the upper images. Spots corresponding to the same interplanar spacings are marked by large segmented circles (TaS 2 and LnS) and the respective Miller indices are indicated.
  • the tubule axes are marked by double arrows. Basal reflections are marked by small arrows. Chiral angles of 6° and 2.5° for the tubules shown in (a) and (b), respectively, were determined from the splitting of the spots, as discussed in the text.
  • Bottom Line profiles integrated along the rectangles marked in the upper images.
  • Fig 26 presents TEM images of CeS-TaS 2 tubular crystals, a) LnS and TaS 2 layers stacked periodically according to the (1: 1) superstructure.
  • Top High, medium and low (insets) magnification images. (The high magnification image was taken from the area marked by the circle in the inset).
  • Middle SAED pattern taken from the area shown in the upper image. Spots corresponding to the same interplanar spacing are marked by the large segmented circles (TaS 2 and LnS) and Miller indices are indicated.
  • Tubule axis is marked by the double arrow. Basal reflections are marked by the small arrows.
  • the chiral angle (4°) for the tubule shown in a) was determined from the splitting of the spots as discussed in the text.
  • Fig. 27 a) High magnification and (inset) low magnification TEM images of a NdS-TaS 2 tubular crystal with disordered stacking of the LnS and TaS 2 layers along the c-axis. b) Line profile integrated along the rectangle marked in a), c) SAED pattern recorded from the area shown in a). Spots corresponding to the same interplanar spacings are distributed on ring-like patterns. Their interplanar spacings and Miller indices are indicated (TaS 2 and NdS). The tubule axis is marked by a double arrow.
  • Fig. 28 Density of states calculated for isolated LaS and NbS 2 monolayers, (a) shows the local density of states (LDOS) of all S atoms in the NbS 2 monolayer, (b) the LDOS of the Nb atoms in the same layer, (c) the LDOS of the S atoms in the LaS monolayer and (d) the LDOS for the La atoms in this layer.
  • the Fermi energy is displayed as a dashed black line and the total DOS of the monolayer is represented by the black curve.
  • the individual projected orbitals are drawn as greyscale areas: medium grey for s, light grey for p and dark grey for d states. The energy is given relative to "vacuum zero".
  • FIG. 29 LaS x Se ! _ x - TaS y Se 2 - y tubular structures, (a) SEM image, (b) High magnification TEM image of a single LaS x Sei_ x - TaS y Se 2 - y nanotube, with LaS x Sei_ x and TaS y Se 2 - y layers stacked in an alternating sequence with 1.16 nm periodicity along the common c-axis.
  • the insets are low magnification image and line profile integrated along the rectangle marked in the high magnification image.
  • Fig. 30 (a) high, (b) low-magnification SEM images of LaS-CrS 2 nanoscrolls and nanotubes. (c) HRTEM image of a LaS-CrS 2 nanotube, shown alongside a line profile (d) obtained from the region indicated by the white rectangle. A low-magnification TEM image of the same tube is shown as an inset [0060]
  • Fig. 31 (a) SEM images of CrS2 coated LaS-CrS 2 nanotubes.
  • a low-magnification TEM image of the same tube is shown as an inset.
  • nanomaterial refers to matter or material having at least one dimension in the nanometric scale.
  • a nanomaterial is meant to have at least one dimension being of up to 500 nm. Namely, when the nanomaterial is of particulate form, the average diameter of the particles is up to 500 nm; in other cases, when the nanomaterial is, for example, a nanotube, the diameter of the nanotubes is up to 500 nm.
  • the nanomaterial of this invention comprising layer(s) of [(MiX' (p) X" a _ p) )i +z (M 2 X' (q) X" ( i_ q) ) y ] and layer(s) of (TXV ) X" ( 2- k) ),
  • Mi is a metal.
  • Mi is a lanthanide metal.
  • Mi is Bi or Y.
  • Mi is any metal from groups IIIA and VA of the periodic table.
  • Mi is any metal that is capable of donating three electrons.
  • Mi is selected from B, Al, Ga, In, Tl, N, P, As, Sb or Bi.
  • Mi is a lanthanide metal, i.e. is selected from metals having atom numbers 57 through 71 of the Periodic Table of Elements.
  • Mi is selected from Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.
  • Mi may be selected from La, Ce, Gd and Tb, Y.
  • M-2 when present (i.e. when y ⁇ 0) is a metallic element being different than Mi, which, in some embodiments, may be selected from Ca, Sr, Ba, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.
  • M 2 atoms when present, are introduced into the lattice structure of ⁇ ' as substitution atoms, i.e. substituting up to 20 at% of the Mi atoms in the MiX' lattice structure. Therefore, the pairing of Mi and M2 metals should be such that will allow up to 20 at% of Mi atoms to be substituted by M2 atoms without hindering the MiX' lattice structure.
  • T in the nanomaterials of the invention, is a transition metal, i.e. a metal that may be selected from Groups IIIB, IVB, VB, VIB, VIIB, VIIIB of block d the Periodic Table of Elements.
  • T is selected from Ti, V, Cr, Mn, Fe, Co, Ni, Nb, Ta, W, and Mo.
  • y and z designate atomic fractions of M 2 and Mi, respectively.
  • M 2 when y is zero M 2 is absent and z ⁇ 0; while when z is zero than y ⁇ 0, and therefore M 2 is present.
  • Mi In any case, according to the present invention Mi ⁇ M 2 .
  • p, q and k designate atomic fractions of the chalcogenides present in the formula (e.g. of S, Se or Te).
  • the ranges of p, q and k are: 0 ⁇ p ⁇ l , 0 ⁇ q ⁇ l , 0 ⁇ k ⁇ 2.
  • the nanomaterial of the invention is a layered nanomaterial, i.e. a layered nanostructure.
  • the nanomaterial may comprise at least one first layer having the formula [(MiX' (P) X" ( i_ P) )i +z (M 2 X' (q) X" ( i_ q) ) y ] and at least one second layer having the formula (TX' (k )X"(2-k)) wherein 0 ⁇ p ⁇ l, Q3 ⁇ 4 ⁇ 1, 0 ⁇ k ⁇ 2, 0 ⁇ y ⁇ D2, 0 ⁇ z ⁇ 0.3.
  • the nanomaterial of the invention has the formula [(MiX' (P) X" ( i_ p) )i +z (M 2 X' (q) X" ( i. q) ) y ] m [TX (k) X" (2 . k) ] n or [(MiX')i +z (M 2 X') y ] m (TX" 2 ) n , wherein m and n being integers, independently selected from 1 to 10. [0071 ] m and n values indicate the number of layers in each sublayer respectively. By changing the values of m and n, one can tune the electrical and thermal properties of the materials.
  • a “sublayer” in the context of this invention is a layer of the formula [(MiX'( P )X"(i_p))i +z (M2X'(q)X"(i-q))y]m or a layer of the formula [TX'(k X"( 2 -k)]n (with M, X, y, z, p, q, k parameter definition as described herein above).
  • a sublayer of formula [(MiX' (P) X" ( i_ p) )i +z (M 2 X'(q)X"(i- q )) y ] m or [(M l X) l+z QA 2 X)y] m is herein designated as "Z m "
  • a sublayer having the formula [TX' (k )X"( 2 -k)] n or (TX" 2 ) n is herein designated as r n .
  • the layered nanostructure is meant to encompass a structure comprising multiple (i.e. at least 2) layers, having at least one dimension in the nanometric scale (typically having a thickness of between 0.1 and 250 nm).
  • Such nanostructure may be, by some embodiments, selected from a sheet, a distorted sheet, a fullerene-like nanoparticle, or a tubular nanostructure.
  • the layers may be stacked along a direction perpendicular to surface of the structure. While the atoms within each layer are held by strong chemical bonds, weak van der Waals and/or charge transfer interactions hold the first and second layers together.
  • the term distorted sheet refers, within the context of the present disclosure, to a sheet having at least one portion which is curved (i.e. concaved or convexed) or folded.
  • the nanostructure may be a nanotube and/or a nanoscroU.
  • nanotube denotes an elongated tubular structure composed of discrete closed layers, i.e. each layer is substantially devoid of dangling, edge bonding sites.
  • Such nanotubes may be selected in a non-limited fashion from single -walled nanotubes (i.e. of l ⁇ -t ⁇ structure), multi-walled nanotubes (of various l m -t a arrangements, as will be described below), double-walled nanotubes (i.e. of l ⁇ -t ⁇ -l ⁇ -t ⁇ structure), few-walled nanotubes, etc.
  • nanoscroU refers to a single, continuous sheet, which is rolled onto itself to form a tubular structure.
  • the sheet may be rolled once, twice or a plurality of times about a longitudinal axis of the nanoscroU, thereby forming a single, double or multi-walled nanoscroU, respectively. Therefore, a nanoscroU of the invention may be formed out of a continuous sheet having, for example, a multi-walled l m -t a layered structure.
  • the diameter of the tubular nanostructures of the invention is between about 20 and about 500 nm.
  • the diameter of the tubular nanostructure is between 20 and 450 nm, between 20 and 400 nm, between 20 and 350 nm, between 20 and 300 nm, between 20 and 250 nm, between 20 and 200 nm, between 20 and 150 nm, or even between 20 and 100 nm.
  • the diameter of the tubular nanostructure is between about 25 and about 500 nm, between about 50 and about 500 nm, between about 100 and about 500 nm, between about 150 and about 500 nm, between about 200 and about 500 nm, between about 250 and about 500 nm, or even between about 300 and about 500 nm.
  • the diameter of the tubular nanostructure is between about 25 and about 400 nm, between about 50 and about 350 nm, or between about 100 and about 250 nm.
  • the nanomaterial of the invention may comprise, in some embodiments, at least one first layer having the formula [( ⁇ ') ⁇ + ⁇ ( ⁇ 2 ⁇ )' ⁇ ] ⁇ and at least one second layer having the formula (TX" 2 ) n .
  • the nanomaterial of the invention may comprise, in some embodiments, at least one first layer having the formula [(MiX' (P) X" ( i_ p))i +z (M 2 X'(q)X"(i-q))y] and at least one second layer having the formula
  • the nanostructure comprises one [(MiX')i +z (M2X)'y]m sublayer, onto which one (TX"2) n sublayer is stacked (i.e. l m - t a structure), or vice versa (t n -l m structure).
  • the term stacked relates to the arrangement of the layers one on top of the other to form the nanomaterial, e.g. layered nanostructures, of the invention.
  • 1 and t are sublayers.
  • the nanostructure comprises one [(MiX' (P) X" ( i_ p) )i +z (M 2 X'( q )X"(i- q ))y]m sublayer, onto which one [TX' (k) X" ( 2-k)]n sublayer is stacked (i.e. l m -t a structure), or vice versa (t a -l m structure).
  • the term stacked relates to the arrangement of the layers one on top of the other to form the nanomaterial, e.g. layered nanostructures, of the invention.
  • m and n may be the same or different, i.e. each of m and n may be independently selected from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.
  • Such a nanostructure will be, then, composed of a plurality (i.e. m) of first sublayers each being of the formula [(MiX')i +z (M 2 X)' y ], and a plurality (i.e. n) of second sublayers each being of the formula (TX' 2 ).
  • a nanomaterial may have the following, exemplary layered structures: (.. .l-t-l-t-l- t.. .), (.. ll-t-ll-t-ll-t.. .), (.. .l-tt-l-tt-l-tt.. .), (.. .lll-tt-lll-tt-lll-tt.. .), etc (or vice versa such that t and 1 are interchanged).
  • the nanostructure comprises any random order of sublayers, for example ⁇ .. .l-ttt-ll-t.. .), ⁇ .. .ll-t-lll-tt-l-tttt.. .), ⁇ .. .), (.. .), etc.
  • the nanostructure comprises any random order of superlayers, for example (.. .1-t-ll-tt-lll-ttt.. .), (.. .11-tt-lll-ttt-l-t.. .), (.. .1-t-l-t-lll- ttt.. .), (.. .11-tt-l-t-ll-tt.. .), etc.
  • the nanostructure comprises an alternating order of layers as follows: (.. .liti liti Uti liti liti liti liti liti).
  • Such nanostructure will be, then, composed of a plurality (i.e. m) of first layers each being of the formula [(MiX' (p) X" ( i_ P) )i +z (M 2 X' (q) X" ( i- q) ) y ], and a plurality (i.e. n) of second layers each being of the formula [TX' (k) X" (2 - k) ]-
  • a nanomaterial may have the following, exemplary layered structures: ⁇ .. .l-t-l-t-l-t.. .), ⁇ .. .ll-t-ll-t-ll-t.. .), ⁇ ..
  • both m and n are 1. In some other embodiments, m is 2n. In further embodiments, m and n may be independently between 1 and 3.
  • the nanomaterial comprises a plurality of said first layer and a plurality of said second layer, which may be stacked in various configurations.
  • the first layers and the second layers are alternately stacked; meaning that in such an arrangement, the layered nanostructure is of alternating stacked [(M 1 X')i +z (M 2 X)' y ] m and (TX" 2 ) n layers or [(MiX (p) X" ( i_ p) )i +z (M 2 X' (q) X" ( i- q )) y ] and [TX' (k) X" (2 - k) ]n layers.
  • the invention provides a layered nanostructure comprising at least one first layer having the formula [(MiX')i +z (M 2 X')y] m or [(MiX'( P )X"(i_p))i +z (M2X'(q)X"(i-q))y]m and at least one second layer having the formula (TX"2) n or [TX'(k)X"(2-k)]n , wherein Mi being a lanthanide metal, M2 being a metal, T being a transition metal, each of X' and X" being independently S or Se, 0 ⁇ ⁇ 0.2, 0 ⁇ z ⁇ 0.3, m and n being integers, independently selected from 1 to 10, and Mi ⁇ M 2 , provided that when y is zero than ⁇ , and when z is zero than y ⁇ 0.
  • Mi, M 2 , T, X', X", x, y, z, m and n are defined
  • Another aspect of the invention provides a layered nanostructure comprising a plurality of superlayers, each superlayer in said plurality of superlayers being composed of a first sublayer of the formula [(MiX)i +z (M 2 X) y ] m or [(MiX' (p) X" ( i.
  • the superlayer is defined to comprise at least one layer of the formula [(MiX)i + z(M 2 X)y] and at least one layer of the formula (TX" 2 ), thereby constituting a repeating layered unit.
  • a superlayer therefore, has a repeating unit of l m -t a .
  • the plurality of superlayers comprises between 2 and 100 superlayers; namely, having the structure (Z m -in)2-ioo- [0096]
  • the superlayer is defined to comprise at least one layer of the formula [(MiX (p) X" ( i_ p) )i +z (M 2 X' (q) X" ( i_ q) ) y ] or [(MiX)i +z (M 2 X)' y ] and at least one layer of the formula (TX" 2 ) or [TX' (k) X" (2 _ k) ], thereby constituting a repeating layered unit.
  • a superlayer therefore, has a repeating unit of l m -t a .
  • the plurality of superlayers comprises between 2 and 100 superlayers; namely, having the structure (Z m -in)2-ioo-
  • said plurality of superlayers comprises between 2 and 20 superlayers, i.e. 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 repeating units, each repeating unit constituted by at least one first layer of the formula [(MiX')i +z (M 2 X') y ] and at least one second layer of the formula (TX" 2 ).
  • said plurality of superlayers comprises between 2 and 20 superlayers, i.e. 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 repeating units, each repeating unit constituted by at least one first layer of the formula [(MiX' (p )X" ( i_ P) )i +z (M 2 X'( q )X" ( i_ q ))y] and at least one second layer of the formula [TX' (k) X" (2 _ k) ].
  • each of the first and second layers may comprise a plurality of sub-layers.
  • the first layer may comprise between 1 and 10 sub-layers of the formula [(MiX')i +z (M 2 X') y ], while the second layer may comprise, independently, between 1 and 10 sub-layers of the formula (TX" 2 ), i.e., having the structure ( ⁇ _ ⁇ - ⁇ - ⁇ )2- ⁇ -
  • each of the first and second layers may comprise a plurality of sub-layers.
  • the first layer may comprise between 1 and 10 sub-layers of the formula [(MiX' (p) X" ( i_ p) )i +z (M 2 X'( q )X"(i- q) )y]
  • the second layer may comprise, independently, between 1 and 10 sub-layers of the formula [TX' (k) X" ( 2-k)], i-e., having the structure ( ⁇ 1 _ ⁇ 0 - ⁇ - ⁇ )2- ⁇ -
  • Another aspect of the invention provides a layered nanostructure comprising at least one first layer of the formula [(MiX')i +z (M 2 X') y ] or [(MiX'( P )X"(i_p))i +z (M2X'(q)X"(i-q))y] having a first crystallographic cell unit, and at
  • misfit is defined as the following ratio (ai-a 2 /ai), wherein ai is the fl-axis value of the crystallographic unit cell of [(MiX')i +z (M 2 X') y ] or [(MiX'(p)X"(i-p))i +z (M2X'(q)X"(i-q))yL and ci2 is the a-axis value of the crystallographic unit cell of TX" 2 or [TX' (k) X" (2 _ k) ]. Frequently, the b-axis is common to the two subunits.
  • the a-axis is different for the two crystallographic lattices and often the ratio between the two a-directions is irrational.
  • the strain between the two incommensurate a-sublattices may lead to folding and scrolling. In addition this difference can lead to structural modulation of the two sublattices. Therefore, often the common tube (scroll) axis for the two layers is the b-axis in many cases.
  • the nanomaterials i.e. layered nanostructures
  • the nanomaterials may be of the formula (LaS)i +z CrS 2 , (LaS) 1+z VS 2 , (CeS) 1+z CrS 2 , (CeS) 1+z VS 2 , (GdS) 1+z CrS 2 , (GdS) 1+z VS 2 , wherein 0 ⁇ z ⁇ 0.3.
  • the nanomaterials may be of the formula LaS(SrS) y CrS 2 , LaS(SrS) y VS 2 , LaS(CeS) y CrS 2 , LaS(CeS) y VS 2 , LaS(GdS) y CrS 2 , LaS(EuS) y CrS 2 , LaS(GdS) y VS 2 , CeS(SrS) y CrS 2 , CeS(SrS) y VS 2 , CeS(GdS) y CrS 2 , CeS(GdS) y VS 2 , CeS(GdS) y VS 2 , wherein 0 ⁇ y ⁇ 0.2.
  • the top-most layers or the external layers or the outermost layers of a layered nanostructure of this invention comprises more than one "t" sublayer. According to this aspect and in one embodiment, these top “t” layers are not intercalated. In one embodiment, the conductivity of the top “t” layers is higher than the conductivity of intercalated inner “t” layers.
  • such layers are defined as [TX' 2 ] r @[[(MiX' (p) X" ( i_p ) )i +z (M 2 X' (q) X" ( i_ q) ) y ](TX' (k) X" (2 _ k) )] wherein Mi being a lanthanide metal, M 2 being a metal, T being a transition metal, each of X' and X" being independently S or Se, where r is an integer, and wherein "@ " indicates that [TX' 2 ] r layers are covered on top of the [[(M!X' (p) X" (1 .
  • the invention provides a process for obtaining nanomaterial of the invention as herein defined, the process comprising:
  • the substrate is contacted with H 2 gas and with H 2 S gas in step (iii) of the process.
  • H 2 may be used instead of H 2 /N 2 gas mixture in some embodiments.
  • the nanomaterial is a layered nanostructure, comprising at least one first layer having the formula [(MiX')i +z (M 2 X)' y ] m and at least one second layer having the formula (TX" 2 ) n .
  • Mi, M 2 , T, X', X", x, y, z, m and n are defined hereinabove.
  • the nanomaterial is a layered nanostructure, comprising at least one first layer having the formula [(MiX' (P) X" ( i_ p))i +z (M 2 X'(q)X"(i-q))y] and at least one second layer having the formula [TX'(k)X"( 2 -k)]- Mi, M 2 , T, X', X", x, y, z, k, p, q, m and n are defined hereinabove [00113]
  • said Mi -precursor, T-precursor and M 2 precursor are oxides or hydroxides of Mi, M 2 and T, respectively.
  • the substrate is typically, though not exclusively, provided as a homogenous mixture of the precursors.
  • the substrate is in the form of a slab, a block, a particle, a flake, a powder, or a nano whisker composed of a homogenous mixture of Mi -precursor, T-precursor and M 2 precursor.
  • the substrate may be formed from mixing Mi-precursor, T- precursor and M 2 precursor, each being independently in the form of a slab, a block, a particle, a flake, a powder, or a nanowhisker.
  • the ratio between Mi-precursor and T-precursor is non-stoichiometric.
  • the T-precursor is used in processes of the invention in molar excess compared to the Mi-precursor. In such embodiments, the T-precursor is taken at 5-20 % mol in excess compared to the Mi-precursor.
  • the ratio (mol/mol) between Mi- precursor and T-precursor is 1 :1.
  • the ratio (mol/mol) between Mi-precursor and M 2 -precursor, when present, is at most 1 :0.2.
  • the ratio (mol/mol) between Mi -precursor and M 2 -precursor is at most 1 :0.15, at most 1 :0.1, at most 1 :0.05 or even at most 1:0.01.
  • the substrate is heated to an elevated temperature, which in some embodiments, may be between about 800 and 1200°C.
  • said elevated temperature may be between about 800 and 1150°C, between about 800 and 1100°C, between about 800 and 1050°C or even between about 800 and 1000°C.
  • said elevated temperature may be between about 850 and 1200°C, between about 900 and 1200°C, between about 950 and 1200°C or even between about 1000 and 1200°C
  • said elevated temperature may be between about 800 and 950°C.
  • Heating to the required elevated temperature is carried out, by some embodiments, at a heating rate of between 10 and 20 °C/min. In some embodiments, the heating is carried out at a rate of between about 12 and 18 °C/min In other embodiments, the heating rate may be 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 °C/min.
  • the relatively large heating rate is a special feature of the present invention, which allows the formation of the nanomaterials, i.e. layered nanostructures, of the present invention.
  • the substrate is contacted with a gas atmosphere comprising a H 2 /N 2 gas mixture and H 2 S gas for a period of time permitting obtaining the layered nanostructure (the nanomaterial of the invention).
  • the volumetric ratio between said H 2 /N 2 gas mixture and said H 2 S gas is between about 8:1 and 6:1. This is another feature of the process of the present invention.
  • the period of time the substrate is contacted with the gas atmosphere is between about 5 minutes and 2 hours. In some other embodiments, said period of time is between about 5 minutes and 1.5 hours, between about 5 minutes and 60 minutes, between about 5 minutes and 45 minutes, between about 5 minutes and 30 minutes, between about 5 minutes and 20 minutes, between about 5 minutes and 15 minutes, or even between about 5 minutes and 10 minutes.
  • the relatively short reaction time is another feature of the present invention which allows the formation of the nanomaterials, i.e. layered nanostructures, of the invention.
  • the Mi -precursor may be a hydroxide or an oxide of these metals.
  • M 2 when present, may selected from Ca, Sr, Ba, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, the M 2 -precursor being a hydroxide or an oxide of these metals; while in other embodiments, T may be selected from Ti, V, Cr, Mn, Fe, Co, Ni, Nb, Ta, W, and Mo. the T-precursor being a hydroxide or an oxide of these metals.
  • the layered nanostructures obtained by a process of the invention may be selected from a sheet, a distorted sheet, a fullerene-like nanoparticle, or a tubular nanostructure.
  • the tubular nanostructure may be selected from a nanotube and a nanoscroll, which may have a diameter of between about 20 and about 500 nm.
  • Another aspect of the invention provides a nanomaterial of the formula [(MiX')i + z(M 2 X')y]m(TX"2) n , wherein Mi being a lanthanide metal, M 2 being a metal, T being a transition metal, each of X' and X" being independently S or Se, 0 ⁇ ⁇ 0.2, 0 ⁇ z ⁇ 0.3, m and n being integers, independently selected from 1 to 10, and Mi ⁇ M 2 , provided that when y is zero than ⁇ , and when z is zero than y ⁇ 0, obtainable by the process as herein described.
  • Mi, M 2 , T, X', X", x, y, z, m and n are defined hereinabove.
  • Another aspect of the invention provides a nanomaterial of the formula [(MiX' (p) X" ( i-p))i + z(M 2 X' (q) X" ( i- q ))y]m[TX (k )X" (2 - k )] n , wherein Mi being a lanthanide metal, M 2 being a metal, T being a transition metal, each of X' and X" being independently S or Se, 0 ⁇ p ⁇ l, 03 ⁇ 4 ⁇ 1, 0 ⁇ k ⁇ 2, 0 ⁇ ⁇ 0.2, 0 ⁇ z ⁇ 0.3, m and n being integers, independently selected from 1 to 10, and Mi ⁇ M 2 , provided that when y is zero than ⁇ , and when z is zero than y ⁇ 0, obtainable by the process as herein described.
  • Mi, M 2 , T, X', X", x, y, z, m and n are defined hereinabove.
  • p, q and k designate atomic fractions of the chalcogenides present in the formula as X' or X" (e.g. of S, Se or Te).
  • the ranges of p, q and k are: 0 ⁇ p ⁇ l, 0 ⁇ q ⁇ , 0 ⁇ k ⁇ 2.
  • 20 superlayers comprise 20 repetitions of (MS) m - (TS 2 ) n -
  • the number of layers of MS and of TS 2 in each superlayer each ranges between 1-10 (i.e. m and n range between 1-10).
  • the invention provides a composition (i.e. composition of matter) comprising the layered nanostructure as herein described.
  • the composition is selected from a lubricant composition, a shock absorbing composition, nanostructured electrical conductor, additives composition to lubricating fluids, a self-lubricating coating composition, and coatings.
  • Another aspect of the invention provides an article comprising the layered nanostructure of the invention as herein described.
  • the article being selected from a thermoelectric component, a transistor, a solar cell, an electrode, and photo-catalyst.
  • Lubrication properties of nanostructures, e.g. nanotubes, of the invention are expected to be higher than their bulk counterparts, due to large interlayer spacing in nanotubes.
  • electrical properties and without wishing to be bound by theory, mobility of electrons is expected to be higher in the nanostructure of the present invention.
  • nanostructures of the invention could be useful for magnetic resonance imaging purpose.
  • the fact that the nanomaterials, e.g. nanotubes of the invention, contain lanthanide atoms make them suitable for optical and magnetic applications, i.e. tagging, marking of pathogenic tissues, magnetic sorting of pathogenic cells, optomagnetic sensors and actuators.
  • the (LaS)i. 2 CrS 2 (sometimes named LaCrS 3 or LaS-CrS 2 ) is a misfit compound made of an alternating LaS and GS 2 layers, the latter phase (hexagonal CrS 2 ) is metastable and is not known in the pristine form in the bulk phase.
  • the PbS-NbS 2 system is different from the lanthanide-based systems described in the present invention.
  • PbS cannot form a stable misfit structure with either GS 2 or VS 2 .
  • the lanthanides-based nanomaterials of this invention form misfit structures comprising &S 2 or comprising VS 2 in some embodiments.
  • the lanthanide nanotubes possess unique structural properties and therefore may be used for applications where systems based on PbS-TS 2 are not applicable.
  • this invention provides nanomaterials of the formula
  • this invention provides nanomaterials of the formula [(MiX' (P) X" ( i_ p) )i +z (M 2 X' (q) X" ( i- q))y]m[TX'(k>X"(2-k)]n, wherein [TX'(k>X"(2-k)] does not exist in the pristine form in the bulk phase.
  • this invention provides nanomaterials of the formula [(M!X ⁇ pjX-d-p ⁇ i+zCMzXiqjX-d-q ⁇ ylmtTXVkjX ⁇ ln wherein [TX'(k)X"(2-k)] does not exist in a pure bulk phase.
  • this invention provides nanomaterials of the formula [(MiX)i +z (M 2 X') y ] m (TX" 2 )n, wherein (TX” 2 ) is metastable. In some embodiments, this invention provides nanomaterials of the formula [(MiX')i +z (M 2 X')y] m (TX" 2 )n, wherein (TX" 2 ) does not exist in the pristine form in the bulk phase. In some embodiments, this invention provides nanomaterials of the formula [(MiX')i +z (M 2 X')y] m (TX" 2 )n, wherein (TX” 2 ) does not exist in a pure bulk phase.
  • Nanoparticles of layered materials are known to minimize the internal energy of the unsaturated rim atoms by folding into seamless hollow-cage structures (kinetically controlled products), i.e. nanotubes and fullerene-like nanoparticles.
  • MLCs like (LaS)i. 2 CrS 2 , suffer from a misfit strain along the a-axis, which promotes their scrolling.
  • the combination of these two independent stimuli promotes the formation of nanotubes (and nanoscrolls) from misfit layered compounds (MLC), as shown in Fig. la.
  • Nanostructures of this kind have not been explored until recently when nanotubes of the misfit compound SnS-SnS 2 and (PbS)i.i 4 NbS 2 were reported.
  • the present invention concerns synthesis of LnS-MS 2 nanotubes, where Ln is lanthanide atom, like La, Ce, Gd, Y and M is an early transition atom like Cr, V, etc. Partial substitution (up to 20 at ) of the La atom by Sr, Ce, and Gd atoms in (LaS)i. 2 CrS 2 nanotubes was also confirmed.
  • the hexagonal phase (CrS 2 and VS 2 ) in the nanotubes do not exist in the bulk form and becomes stable upon charge transfer from the LnS lattice. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to decipher the crystalline structure of the nanotubes. The growth mechanism of these nanotubes was elucidated through careful temperature and time-dependence observations.
  • Three precursors are used to synthesize nanotubes/nanoscrolls of LaS- CrS 2 : (1) amorphous hydroxide mixtures, (2) LaCrC>3 powder and (3) hydroxide or oxide nanowhiskers.
  • Hydroxide mixture or oxide precursors are subjected to anneal at different temperatures in the presence of 40 seem (standard cubic centimeter per minute) of 5% H 2 +95 N 2 and 5 seem H 2 S. Temperatures used are 650, 750, 825, 850 and 900 °C. Reactions with different annealing times at 825 °C are also conducted to understand the growth of the nanotubes.
  • Quaternary nanotubular structures are prepared by substituting lanthanum by up to 20 at% with gadolinium, cerium or strontium.
  • the corresponding hydroxide mixtures are annealed at 850 °C in 40 seem of 5% H 2 +95 N 2 and 5 seem of H 2 S atmosphere to obtain the corresponding nanotubes.
  • SEM analysis is done by Zeiss Ultra model V55 SEM.
  • TEM analysis is done by Philips CM120 TEM, operating at 120 kV and FEI Technai F20 operating at 200 kV, equipped with HAADF detector for STEM and also with FEI Technai F30- UT high-resolution transmission electron microscopy (HRTEM) operating at 300 kV.
  • HRTEM transmission electron microscopy
  • the TX 2 and MX layers have different crystallographic structure and they are stacked periodically.
  • TX 2 is a three-atom thick sandwich layer with a pseudo-hexagonal structure, in which the metal atoms are surrounded by six chalcogen atoms, either in octahedral or in trigonal prismatic coordination.
  • this invention provides nanotubes from a new family of LnS-TaS 2 (LaSe-TaSe 2 ) MLC. These nanotubes exhibit unique structural characteristics not described hitherto, and potentially have interesting magnetic and electrical properties.
  • the b-axis of the LnS layer can therefore be superimposed on TaS 2 in three rotational variants, which are rotated azimuthally by 60° about their common c-axis, as shown in Figure 20.
  • the 3 ⁇ 4-axis of TaS 2 can be superimposed onto either the 3 ⁇ 4-axis or the a-axis of LnS, which differ by 90°, as shown in Fig. 20.
  • this invention provides meta-stable compounds in stable form on top of lanthanide based misfit compounds.
  • such compounds comprise nanotubes comprising chromium disulfide and chromium diselenide (CrS 2 @LaCrS 3 and CrSe 2 @LaCrS 3 _ x Se x ) as shown in Example 3 herein below.
  • other compounds such as LaVS 3 _ x Se x , VS 2 @LaVS 3 , VSe 2 @LaVS 3 - x Se x , CeCrS 3 - x Se x , NdCrS 3 - x Se x , GdCrS 3 _ x Se x , TbCrS 3 _ x Se x and tellurium (Te) based compounds are synthesized according to the same procedure.
  • Transition-metal dichalcogenides such as M0S 2 and WS 2 have been the subjects of a wealth of studies in nanotubular form and most recently as single layers. Chromium belongs to same group as Mo and W but doesn't form stable dichalogenide, which is theoretically predicted to be good electronic and optical as well as piezoelectric material.
  • this invention tubular structures comprising GS 2 which is earlier imagined to be not possible to realize in the stable form.
  • Metastable GS 2 forms a stable hexagonal layered structure upon intercalating alkali, Cu, or Ag atoms or with intercalating two-dimensional layers such as LaS, CeS or GdS. Intercalated GS 2 show insulating behavior.
  • Fig. 1 shows the low (a) and high (b and c) magnification SEM images of as synthesized nanotubes. Clearly, the nanotubes grow vertically from the substrate. In this procedure nanotubes, nanoscrolls, as well as unfolded or semi-folded sheets of LaS-CrS 2 , are observed as well.
  • LaS-CrS2 nanotubes were characterized by TEM and high-resolution TEM (HRTEM).
  • HRTEM high-resolution TEM
  • Fig. 2a shows a typical high-resolution TEM (HRTEM) image of LaS-CrS 2 nanoscroll synthesized at 900°C.
  • the superstructure of alternating LaS and CrS 2 layers with 1.14 nm periodicity can be clearly seen (see line profile in the bottom of Fig. 2a).
  • Low magnification TEM image of the same nanoscroll is shown as an inset to Fig. 2a.
  • the basal reflections (ii) in the selected area electron diffraction (SAED) also confirm the superstructure periodicity (Fig. 2b).
  • the growth axis of the tube (i) is shown with the arrow in the SAED pattern.
  • the refiections of the LaS sublattice and the refiections of the CrS 2 sublattice are marked in segmented circles.
  • the interplanar spacings reported here are in good agreement with the one reported for bulk (LaS)i .2 CrS 2 (see Table 1).
  • Table 1 Nanotubes lattice parameters obtained from electron diffraction and their possible properties. Lattice parameters of the same bulk misfit compound subunits are given in parenthesis. Note: the (1+z) values in first five compounds is not shown. The formulas are given in a general form.
  • the multiplicity factor of these planes is four, which indicates that there are two types of LaS sheets with different rolling vectors present in a same nanoscroll. Chiral folding of the layers results in splitting of the diffraction spots.
  • the eight sets of each 110 and 220 spots are splintered by 12° (chiral angle of 6°).
  • the multiplicity factor of this plane is six which indicates that there are two CrS 2 layers within the same nanoscroll with different rolling vectors.
  • the multiplicity factor of the ⁇ 020 ⁇ planes in LaS sublattice is four (assuming that a and b parameters are almost same) and for GS 2 sublattice is six. This observation confirms the existence of 020 reflections of both GS 2 and LaS on the same circle and further eight higher intensity spots are combination of both LaS and GS 2 layers (see Fig. 3).
  • the one-to-one stacking order of the LnS-CrS2 (VS2) superstructure in the nanotube is necessary for securing the stability of the hexagonal layered structure of CrS 2 by charge transfer from the LnS layer (in the case of 20% Gd substituted LaCrS 3 , new type of periodicities like O-T-O-T-T are observed, see Fig. 4).
  • Each lanthanide ion has one extra electron with high chemical potential which can be transferred to the GS 2 layer rendering it stable in the hexagonal form.
  • the pseudo-hexagonal layers of CrS 2 have three equivalent axes with 60° orientation angles (Fig. 3). Since the LaS layers have a common b-axis with the CrS 2 layer (commensurate direction), they experience similar chemical environment in the three directions of the CrS 2 layers. This strong interaction between the layers also explains the presence of the same chirality angle observed for the CrS 2 and LaS layers.
  • La in (LaS)i .2 CrS 2 with other lanthanides can also yield nanotubes from the corresponding misfit layered compounds.
  • different synthetic strategies have been used to synthesize the LaCrS 3 nanotubes, which demonstrate the robustness of the present approach.
  • MLC nanotubes were obtained by sulfurization of different precursors at 825-900°C.
  • the three kinds of precursors were: a. mixed hydroxide nanowhiskers which were prepared by hydrothermal synthesis; b.
  • Figs. 5-6 show the SEM and TEM analyses of CeS-CrS 2 and GdS- CrS 2 nanotubes obtained during this study.
  • Low and high magnification SEM images of CeS-CrS 2 nanotubular structures synthesized at 850°C are shown in Fig. 5a and 5b respectively. Nanotubular structures are observed to grow vertically from the substrate in a helical or tubular fashion.
  • High magnification SEM image which shows the formation of a semi-scroll from the folding of a nanosheet is shown as an inset in Fig. 5b.
  • 5c and 5d show the low and high magnification SEM images of GdS-CrS 2 nanotubes with diameters range from 25-100 nm and lengths of 2-5 ⁇ . These nanotubes are observed to have a high aspect ratio and high flexibility compared to the LaS-CrS 2 and CeS-CrS 2 tubes.
  • the two subunits, CeS and CrS 2 possess distorted NaCl and ortho-hexagonal structures, respectively.
  • the reflections of CeS and &S 2 sublattices are marked in segmented circles while the basal reflection (ii) is marked in small arrows and the tubule axis (i) is shown in large arrow.
  • the SAED pattern shows clearly two 12 sets of spots which are distributed in equal azimuthal angle of 30° on a circle at the -spacings 4.1 and 2.09 A corresponding to the (110) and (220) planes of CeS sublattice, respectively.
  • the multiplicity factor of these planes is four which indicates that there are three CeS layers in total which are tilted by 60° angle relative to each other around the c-axis.
  • the [110] direction of one of the CeS layers coincides with the nanotubule axis.
  • the [020] direction of this tube ( ⁇ -direction) is observed to be tilted with 15° angle with respect to the tubule axis.
  • One of the CeS-CrS 2 nanotubes where the [200] direction is coincident with the tubular axis is shown in Fig. 7.
  • TEM along with SAED analysis of GdS-CrS 2 nanotubes showed the similar (-6% higher) lattice spacing with single crystal studies.
  • a typical high resolution TEM image along with SAED pattern of one of the GdS-CrS 2 nanotube is shown in Fig. 6d and 6e, respectively.
  • Low magnification image of the same tubes is shown as an inset in Fig. 6d.
  • High contrast double layers of GdS which are sandwiched between CrS 2 layers can be clearly seen from the HREM image.
  • the periodicity in odirection is observed to be 2.2 nm (see line profile).
  • SAED pattern of the nanotube shows four pairs of each 110 and 220 reflections of GdS subpart which are distributed on the CeS (GdS) segmented circles with interplanar spacing of 4.12 and 2.12 A, respectively. Multiplicity factor of these planes is four which indicates the presence of only one type of GdS layers in the tube. Splitting of each of the spots further into two with an angle of 24.4° indicates the presence of chirality in the GdS layer with chiral angle of 12.2°. There are two pairs of 200 reflections of GdS with d- spacing of 2.91 A. The 020 reflections of both GdS and CrS 2 appear in the same place (commensurate direction) with -spacing of 3.13 A, in the SAED pattern.
  • the [020] direction also matches with the tubular direction in this case.
  • Two pairs of 200 and four pairs of 130 reflections of the CrS 2 appeared with d- spacing of 1.85 A and 1.81 A, respectively.
  • the chiral angle in the CrS 2 sublattice (-12.2°) appears to be similar to that of the GdS sublattice.
  • the hydroxide mixture converts to porous LaCrC>3 which serves as a substrate for further nanotube growth.
  • Reacting LaCr(3 ⁇ 4 with H 2 S converts the oxide to sulfide by a slow diffusion controlled process.
  • the misfit stress between LaS and CrS 2 sub-lattices further induce the scrolling, which is another stress release process.
  • the nanotubes/scrolls thus formed continuous to grow in length (root growth) as well as in diameter with increasing reaction time during the synthesis (see in Fig. 9).
  • the density of the nanotubes depends upon the number of grain boundaries available on the oxide substrate, which depends on the reaction temperature and annealing time. At higher temperature and longer durations, oxide grains grow bigger which decreases the number of grain bounders thus decreasing the nucleation centers which yield lesser nanotubes (see Fig. 8). Slow (prolonged) heating from room-temperature to the required temperatures also resulted in a reduced number of nanotubes due to the same reason.
  • the reflections of LaS related to the ⁇ 110 ⁇ and ⁇ 220 ⁇ planes are marked (Fig. 10b).
  • the reflections of CrS 2 corresponding to ⁇ 200 ⁇ and ⁇ 020 ⁇ planes are marked (Fig. 10b)while the basal reflections (ii) are marked with small arrows.
  • the interplanar spacings reported here are in good agreement with the one synthesized along the other procedure.
  • the multiplicity factor of these planes is four. It appears that in the same tube there are three LaS sheets with different rolling vector present which are oriented 60° angle with respect to each other. Twelve sets of spots are splintered by similar angle; such a splitting arises from the chiral folding of the layers and the chiral angle of 6°, which equals half of the azimuthal splitting of the spots 12° in this case.
  • TEM image along with low magnification TEM image as an inset of CeS-CrS 2 nanotube is shown in Fig. 7a.
  • the periodicity in the c-direction of the nanotube is 1.13 nm which can be seen from the line profile and also calculated from the basal reflections in SAED pattern (Fig. 26).
  • SAED pattern shows clearly two 12 sets of spots which are distributed in equal azimuthal angle on a circle at the (f-spacing of 4.1 and 2.13 A and which are corresponding to ⁇ 110 ⁇ and ⁇ 220 ⁇ planes of CeS sublattice, respectively.
  • the multiplicity factor of these planes is four which indicates that there are three CeS layers which are rotated by 60° angle relative to one another around the c-axis.
  • High resolutions TEM image of another LaS-CrS 2 nanoscroll is shown in Fig. 11.
  • Low magnification TEM image of the same nanoscroll is shown as an inset.
  • the long range periodic stacking of the alternating LaS double layers and CrS 2 layers can be clearly seen from the images, which is also evident from the line profile.
  • the periodicity in the c-axis (1.13 nm) can be seen from the image and calculated from the line profile (Fig. 11a) as well as from the SAED pattern in Fig. lib.
  • the SAED pattern shown in Fig. lib is indexed similar to the previous case.
  • the reflections related to LaS and CrS 2 are marked in segmented circles and basal reflections (ii) are indicated with small arrows whereas the tubule axis (i) is shown in large arrow.
  • the present nanoscroll contain 8 pairs of 110 and 220 reflections of LaS subunit which are distributed on the circle with interplanar spacing of 4.1 A and 2.1 A, respectively. Since the multiplicity factor of these planes is four, this indicates the existence of two different LaS layers with different rolling vectors in the same nanoscroll which are rotated by 60° angle with respect to each other. The chiral folding of these sheets have similar chiral angle which are close to 1° (the smeared spots do now allow calculating the exact values).
  • the present nanoscroll also contain eight high intensity spots and four weak spots (in total 12) with same interplanar spacing of 3.05 A and are attributed to combination of both LaS and CrS 2 (high intensity reflections) and CrS 2 layers alone respectively (four weak intensity spots).
  • Nanotubular structures from a new family of misfit compounds LnS- TaS2 with (Ln La, Ce, Nd, Ho, Er) and LaSe-TaSe2, were synthesized. Stress relaxation originating from the lattice mismatch between the alternating LnS(Se) and TaS 2 (Se) layers, combined with seaming of the dangling bonds in the rim lead to the formation of a variety of tubular structures. Their structures was studied via scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM) and selected area electron diffraction (SAED).
  • SEM scanning electron microscopy
  • HRTEM high-resolution transmission electron microscopy
  • STEM scanning transmission electron microscopy
  • SAED selected area electron diffraction
  • Tubules exhibiting a single folding vector for the LnS(Se) as well as TaS 2 (Se) layers were often found.
  • the small values of the c-axis periodicities are indicative of a strong interaction between the two constituent layers which was also supported by Raman spectroscopy and theoretical calculations.
  • This new family of lanthanide based tubular structures is expected to exhibit interesting magnetic properties.
  • the tubular phase constituted ⁇ 50% of the total product for the LaS- TaS 2 case, ⁇ 20% for NdS-TaS 2 and ErS-TaS 2 , -5% for HoS-TaS 2 and LaSe- TaSe 2 and merely 1 % for the CeS-TaS 2 case.
  • LnS-TaS 2 MLC superstructures with LnS and TaS 2 layers stacked periodically along the c-axis are indicated on the patterns. Their corresponding interplanar spacings are indicated.
  • Nanotubes exhibiting two folding vectors of the TaS 2 layers with one, two or three folding vectors of the LnS layers were also encountered as discussed herein above (see figure 20) .
  • the latter configuration is common in nanotubes formed from PbS-NbS 2 and PbS-TaS 2 MLC.
  • Figures 17b-d show the structure of a LaS-TaS 2 nanotube.
  • the LaS and TaS 2 layers are stacked in an alternating sequence along their common c- axis with a 1.15 nm periodicity, as determined from line profiles and from the distance between basal reflections in diffraction patterns.
  • Figure 17c six pairs of spots with interplanar spacings of 1.64A and2.83A are equally-azimuthally distributed on a circle and are marked by small circles. These spots are attributed to the (11.0) and (10.0) planes of TaS 2 ((200) and (020) in the ortho- pseudohexagonal indexing system). The multiplicity factor for these planes is six. This observation suggests the presence of a single folding vector for the TaS 2 layers.
  • the splitting of the hk.O diffraction spots indicates a small chiral angle (see chirality discussion herein below.
  • Two pairs of LaS 020 spots match the 10.0 spots of TaS 2 (020 when indexed in the ortho-pseudohexagonal system) parallel to the tubule axis. These coincident spots (marked withsmall circles) reveal the presence of a common commensurate in-plane direction b that coincides with the nanotube axis, as expected and as shown in Figure 17d. 200 LaS spots also appear and are marked by segmented small circles. As expected, these spots appear at azimuthal angles of 90° from the 020 spots, which is equal to the angle between the (200) and (020) planes in orthorhombic LaS. The fact that the LaS 200 spots are approximately on the same circle as the 020 spots indicates that the a and b lattice parameters of LaS are almost equal. The first order LaS 010 and 100 spots are absent from the pattern, in agreement with previous observations.
  • X-ray diffraction (XRD) patterns recorded from the LaS-TaS 2 , NdS- TaS 2 and ErS-TaS 2 tubular structures are shown in Figure 23.
  • For the 001 (first order) superstructure peaks corresponding values of 11.45 A, 11.28 A and 11.11 A were obtained for LaS-TaS 2 , NdS-TaS 2 and ErS- TaS 2 MLC, respectively.
  • Line profiles generated from (HRTEM) images yielded quite similar values of 11.5 A, 11.4 A and 11.1 A.
  • Table 2 Typically measured interplanar spacings in tubular structures from LnS-TaS 2 MLC. *For TaS 2 , (11.0) and (10.0) planes labeled in the pseudohexagonal system are equivalent to (200) and (020) planes, respectively, in the ortho-pseudohexagonal system. In-plane (hkO) spacings were deduced from SAED solely, while the c-axis periodicities of the superstructures were deduced from SAED and XRD patterns as well in several cases.
  • Table 2 and Figure 18 show that both the average interplanar periodicity along the c-axis corresponding to the LnS-TaS 2 (1 :1) superstructure and the in-plane interplanar spacings decrease with increasing atomic number of Ln (i.e., La, Ce, Nd, Ho, Er). Similar behavior was observed for bulk single crystals of LnS-TaS 2 MLC and for tubular structures of MLC that are based on LnS-CrS 2 - This trend can be attributed to a decrease in the size of the Ln +3 ion with increasing atomic number.
  • Ln i.e., La, Ce, Nd, Ho, Er
  • FIG. 21 Representative examples of EDS analysis of the synthesized LnS-TaS 2 tubes are shown in Figure 21.
  • a spectrum recorded from a LaSe-TaSe 2 tubule produced by the addition of TaBrs powder to the ampoule is also shown. Chlorine peaks are clearly visible in the EDS spectra of LnS-TaS 2 and bromine is visible for LaSe-TaSe 2 nanotubes, as shown in Figure 21.
  • a Br peak was clearly visible in EDS spectra recorded from LaSe-TaSe 2 nanotubes ( Figure 21g).
  • SAED patterns acquired from ErS-TaS 2 and LaSe-TaSe 2 tubules are shown in Figures 24a(a) and 24a(b).
  • the tubules are, in principle, isostructural to that shown in Figure 17c for LaS-TaS 2 counterpart except for the following:
  • NdS-TaS 2 tubular crystals are quite similar to their LaS-TaS 2 counterparts.
  • the mode at 400 cm “1 is in perfect agreement with the A ⁇ g (intralayer out-of-plane vibration) mode of 2H-TaS 2 -
  • the mode at 327 cm 4 is attributed to the Z3 ⁇ 4 g (intralayer in-plane vibration) mode, which occurs at 286 cm “1 in bulk 2H- TaS2-
  • the large upshift of the intralayer Z3 ⁇ 4 g mode of the TaS2 layer (41 cm “1 in this case) has been reported for various intercalation compounds of 2H-TaS 2 (and 2H-NbS 2 ), including the misfit compounds.
  • the mode at -149 cm “1 matches the A ⁇ g (intralayer out-of-plane vibration) mode at 148 cm “1 of LaS in a LaS-TaS 2 MLC single crystal.
  • An additional A ⁇ g mode at 122 cm “1 was previously observed, but was not observed here due to experimental limitations at lower wavenumbers.
  • the observed Raman modes of the LaS layers within LaS-TaS2 MLC are different from the modes observed in LaS bulk single crystals with NaCl structure.
  • the broad band between ⁇ 240 and 303 cm "1 is attributed to the two-phonon band.
  • the ampoules were held in a temperature gradient of 400 °C at the bottom (with the precursors) and 850 °C at the upper part for 1 hr.
  • the temperatures were tuned to 850 °C at the bottom (with the precursors) and 50 °C at the upper part. This step lasted for 4 -16 hr. Most of the product remained at the hot edge of the ampoules. The amount of the substance transported to the cold edge was negligible.
  • X-ray diffraction (XRD) patterns were recorded with a Rigaku TTRAXIII diffractometer (Cu- ⁇ radiation) operating in the Bragg-Brentano ( ⁇ - 2 ⁇ ) mode.
  • HRTEM transmission electron microscopy
  • a solution of the product in ethanol was dripped onto a lacey/holey carbon/collodion-coated Cu grids.
  • the resulting samples were examined by Philips CM120 TEM, operating at 120 kV equipped with EDS detector (EDAX- Phoenix Microanalyzer); JEOL JEM2100 operating at 200 kV and FEI Tecnai F30-UT HRTEM operating at 300 kV.
  • High-resolution scanning transmission electron microscopy (STEM) images and EDS chemical maps were taken on a probe-corrected FEI Titan 80-200 G2 ChemiSTEM instrument equipped with a Bruker Super-X detector at 200 kV.
  • LaS intercalated CrS2 (LaCrSs) nanotubes were synthesized by sulfurization of La(OHte and Cr(OHb mixture at high temperature.
  • Figure 30 shows the SEM (a and b) and TEM (c) image of typical LaCrS 3 nanotubes.
  • FIG. 31 a and b respectively show SEM and TEM images of GS 2 nanotubes on top of LaCrS 3 nanotubes. Line profile in bottom of Fig. 31b clearly show the presence of CrS 2 layers on top of LaCrS 3 nanotube.
  • Preliminary data on CrS 2 coated LaCrS 3 nanotube showed substantial increase in conductivity (about 3 orders of magnitude) compared to LaCrS 3 nanotubes. Se substituted LaCrS 3 nanotubes also found to show higher conductivity (about 3 orders of magnitude).
  • Table 6 summarizes the new nanotubes which were synthesized.
  • Table 6 Nanotubes and synthesis techniques
  • LaS x Sei_ x - TaS y Se 2 - y tubular structures were synthesized.
  • the tubular structures were produced in two ways: [00243] 1. Powder of the preformed LaS-TaS 2 tubular structures was mixed with Ta, La, Se and TaCls powders and sealed in a silica tube. The thermal treatment was similar to the described in the experimental part.
  • the ampoules were held in a temperature gradient of 400 °C at the bottom (with the precursors) and 850 °C at the upper part for 1 hr.
  • the temperatures were tuned to 850 °C at the bottom (with the precursors) and 50 °C at the upper part. This step lasted for 4 -16 hr. Most of the product remained at the hot edge of the ampoules. The amount of the substance transported to the cold edge was negligible.
  • LaS x Sei_ x - TaS y Se 2 - y tubular structures could be produced as well. These could be produced in two ways: [00251] 1. Powder of the preformed LaS-TaS 2 tubular structures (as described in the experimental part herein above) was mixed with Ta, La, Se and TaCls powders and sealed in a silica tube. The thermal treatment is similar to the described in the experimental part herein above.
  • Figure 29 LaS x Sei_ x - TaS y Se 2 - y tubular structures, (a) SEM image, (b) High magnification TEM image of a single LaS x Sei_ x - TaS y Se 2 - y nanotube, with LaS x Sei_ x and TaS y Se 2 - y layers stacked in an alternating sequence with 1.16 nm periodicity along the common c-axis.
  • the insets are low magnification image and line profile integrated along the rectangle marked in the high magnification image.

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Abstract

La présente invention concerne des nanostructures inorganiques, et plus spécifiquement des structures tubulaires en couches, comprenant des chalcogénures métalliques mixtes et plus particulièrement des structures tubulaires en couches comprenant du lanthanide-chalcogénure et du chalcogénure métallique de transition.
PCT/IL2015/050479 2014-05-07 2015-05-07 Nanomatériaux inorganiques WO2015170331A2 (fr)

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US8545991B2 (en) * 2009-01-23 2013-10-01 State Of Oregon Acting By And Through The State Board Of Higher Education On Behalf Of The University Of Oregon Low thermal conductivity misfit layer compounds with layer to layer disorder
EP2769006A2 (fr) * 2011-10-20 2014-08-27 Yeda Research and Development Co. Ltd. Feuilles empilées ordonnés de composés inorganiques en couches, nanostructures comprenant celles-ci, leurs procédés de préparation et utilisations de celles-ci

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