Gogotsi Y. (Ed.) Nanotubes and Nanofibers

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dye-sensitized solar cells. Titania nanotubes have been obtained by treating anatase or rutile struc-

ture TiO

with NaOH at 120°C, and subsequent washing with HCl solution [69,70]. The resulting

titania nanotubes (nanoscrolls) are 50 to 200 nm long and their diameter is about 10 nm. TEM images

of such nanotubes reveal lattice fringes with 0.78 nm spacing. Frequently, the number of molecular

layers is not the same on both sides of the nanotube, indicating that the nanotube is made of a con-

tinuous molecular sheet which is wound like a folded carpet or a scroll, and hence is termed nano-

scroll

(Figure 4.7). Indeed, a recent series of works [16,71] concluded that the NaOH treatment leads

to recrystallization of the anatase and exfoliation of individual Na

2⫺x

molecular sheets, which

fold into an open-ended nanoscroll. The driving force for the exfoliation of the titanate sheets was

attributed to the NaOH, which extracts protons from the exposed surface. This process produces a

charge imbalance between the two sides of the solution-exposed H

nanosheet. Consequently,

detachment of the nanosheet from the crystal surface and subsequent folding leads to the formation

of the nanoscroll [72]. Similarly, nanotubes (nanocrolls) of the lamellar compound K

were

obtained by exfoliation of the parent crystallites with tetra (n-butyl) ammonium hydroxide [73]. The

radius of the nanoscrolls is determined by a very delicate balance between the van der Waals inter-

actions and the elastic energy, which explains the size uniformity of these self-assembled structures.

Nanotubes from various layered metal-silicates were recently prepared via hydrothermal syn-

thesis, i.e., under moderate temperatures (generally ⬍ 200°C) and pressure of a few MPa [74].

These nanotubes were shown to exhibit high surface area, appreciable hydrogen storage capacity,

and when loaded with Pd metal, high catalytic reactivity toward CO and C

oxidation. Nanotubes

of δ-MnO

were synthesized by hydrothermal conversion of the layered

-NaMnO

compound [75].

The importance of this advance is in the possibility of using such nanotubular phases as cathodes

in high performance Li intercalation batteries.

Nanotubular and fullerene-like structures of various rare-earth hydroxides have been prepared

by hydrothermal synthesis [76]. Furthermore, dehydration and subsequent reactions led to the for-

mation of nanotubular structures of rare earth oxides, oxisulfides and oxifluorides. Nanotubes of

the ferroelectric materials BaTiO

and SrTiO

with perovskite structure were obtained by a two-step

hydrothermal synthesis [77]. In the preliminary step, TiO

(or titanate) nanotubes were prepared by

hydrothermal synthesis with NaOH and subsequent wash with HCl solution. In the following step,

the BaTiO

and SrTiO

were synthesized by hydrothermal reaction between the titanate nanotubes

142 Nanotubes and Nanofibers

FIGURE 4.6 Schematic representation of C

aza-fullerene. (Adapted from Hultman, L., et al., Phys.

Rev. Lett., 87, 225503, 2001.)

and Ba(OH)

and SrCl

, respectively. Although the XRD and TEM analyses suggest that the nan-

otubes are crystalline, a more thorough analysis is needed in order to understand the morphology

of the nanotubes. Nested fullerene-like nanoparticles of the layered compound Tl

O were synthe-

sized from TlCl

solutions using a sonochemical method [78]. Tl

O possesses the relatively rare

anti-CdCl

structure. Here, each molecular sheet consists of an oxygen layer in the center, sand-

wiched between two outer thalium layers. Numerous metal hydroxides afford a layered structure and

can therefore be transformed into nanoscrolls. Thus, Cu(OH)

nanoscrolls were obtained by simply

dipping the metal foil in a basic ammonical solution [79].

Various oxide nanotubes have also been obtained via high-temperature syntheses. Nanotubes of

the cubic compound In

were synthesized by heating In and In

powders under vacuum in an

induction furnace at 1300°C [80]. The nanotubes were crystalline, with one of their tips closed and

much of their hollow core filled with indium. Mg

nanotubes with polyhedral cross sections

were synthesized by heating Si wafer coated with thin film of boron in the presence of magnesium

vapor under mixed oxygen–argon atmosphere [81]. Magnesium borate is a thermoluminescing

material, which also possesses excellent tribological properties as an additive to lubricants.

Microtubes and nanotubes of pure elements like Te [82,83] and Se [84], have been synthesized

as well. A variety of techniques, including wet [82,84] and simple thermal evaporation [83], were

successfully used for this purpose. Bi nanotubes were synthesized by solvothermal reduction of

with ethylene glycol [85], or alternatively by reduction of BiCl

with Zn at room temperature

[86]. Similar processes have been used by the same group for the synthesis of Sb nanotubes [87].

An interesting case is that of InS nanotubes [88], which have been synthesized by a “chemie

douce” process. While the stable crystalline structure of InSe and GaS is lamellar, the more ionic InS

compound crystallizes in an orthorhombic lattice structure. Using a low-temperature solution-based

Inorganic Nanotubes and Fullerene-Like Materials of Metal Dichalcogenide 143

(a) (b)

[0 0 1] normal

[0 0 1]

[1 0 0] normal

[0 0 1]

9 nm

FIGURE 4.7 TEM image and schematic representation of H

nanotubes: (a) axial direction;

(b) cross section showing clearly the winding of the sheets into nanoscroll structure; (c) schematic rendering of

the cross section; and (d) schematic rendering of the winding of the nanosheet into a nanoscroll. (Adapted from

Chen, Q. et al., Adv. Mater., 14, 1208, 2002.)

synthesis with benzenethiol (C

SH) as a catalyst, InS nanotubes were obtained. This work shows

that kinetic control could lead to the preferential growth of an otherwise metastable layered structure,

which does not exist in the bulk InS material.

Nanotubes of various III–V compounds with zincblende structure, like GaN and AlN nan-

otubes, were recently reported [20,89]. Clearly, simple folding of a molecular sheet is not possible

in this case. Here uniaxial growth along an easy axis is promoted resulting in a highly faceted nan-

otube morphology. The faceted faces of the nanotube are chemically very reactive. Therefore, pro-

tection of the facets’ surfaces with respect to the ambient atmosphere remains a great challenge for

various applications like field emission, etc.

In summary, over the past few years, a large chemical apparatus has been conceived in order to

synthesize new nanotubular and fullerene-like structures; part of this effort has been summarized in

this rather noncomprehensive listing.

4.3 INORGANIC NANOTUBES AND FULLERENE-LIKE STRUCTURES

STUDIED BY COMPUTATIONAL METHODS

Computational methods play a major role in the progress of materials science in general, and nanoma-

terials in particular. Pioneering efforts in this direction were undertaken by the Cohen–Louie group,

who studied various B

nanotubes [90–92] (see also Table 4.2). Following this preliminary work,

Seifert and coworkers [94–96,101] undertook a systematic approach to elucidate the structural aspects

and the physical behavior of metal-dichalcogenide nanotubes [102]. These studies indicated that the

strain in the nanotube increases like 1/R

, where R is the radius of the nanoubes. Furthermore, due to

the bulky structure of the multiple atom S–M–S layer, the strain energy of an MS

nanotube was found

to be about an order of magnitude larger than that of carbon nanotubes with the same diameter. These

calculations clearly indicated that in agreement with the experiment, multiwall WS

(MoS

) nanotubes

consisting of 4 to 7 layers, with an inner radius of 6 to 12 nm, are the most stable moities [101].

Generally, the formation of a polyhedral nanoparticle by folding the molecular sheet in two direc-

tions is more demanding in terms of elastic energy than folding the lamella in one direction to obtain

a nanotube. One manifestation of this conjecture is the fact that the number of defects and irregulari-

ties in nested fullerene-like nanoparticles of WS

is appreciably higher than those observed in WS

nanotubes. Furthermore, while the cross section of WS

nanotubes is in general circular, fullerene-like

nanoparticles of WS

have been shown to exhibit a phase transformation from an evenly curved sur-

face into polyhedral (faceted) configuration, when the number of molecular layers (i.e., the thickness)

exceeds a critical number (3 to 4 layers) [125]. This principle has been confirmed also in the case of

black phosphorous, where a stable configuration could be calculated for the nanotubes, while

fullerene-like nanoparticles of similar dimensions have been found to be unstable [117–119].

The electronic structure of MS

nanotubes have been studied in considerable detail. It was

found that semiconducting materials, like MoS

and WS

[94,95], form nanotubes with forbidden

gaps, which shrink with decreasing diameter of the nanotubes. It is clear then that in contrast to

the ubiquitous semiconducting quantum dots and nanowires, the quantum size effect in MS

nan-

otubes is not particularly large. The diminutive nature of the quantum size effect in IF nanoparti-

cles can be attributed to the confinement of their electronic states within the molecular sheet. On

the other hand, the lattice distortion induced by the bending of the molecular layer, which increases

with the shrinkage of the nanoparticle radius, leads to an opposite effect, i.e., reduction of the

bandgap. Many of the semiconducting layered compounds possess an indirect transition and there-

fore exhibit a weak luminescence, if any. While (n,n) armchair nanotubes also possess an indirect

gap, (n,0) zigzag nanotubes were shown to be direct bandgap semiconductors, suggesting a vari-

ety of optical effects in such nanotubes. Nanotubes of materials with metallic character, like NbS

remain metallic in nature, irrespective of their diameter and chirality [96,98]. The high density of

states near the Fermi level suggests that such nanotubes may become superconductors at low tem-

peratures.

144 Nanotubes and Nanofibers

Inorganic Nanotubes and Fullerene-Like Materials of Metal Dichalcogenide 145

TABLE 4.2

Summary of First-Principle Calculations for Inorganic Nanotubes

Compound Method Used References Comment

BN DFT–LDA [90] Insulator

N DFT–LDA [91] Chiral; metals or semiconductors

DFT–LDA [92]

GaSe DFT–LDA [93] Semiconductor

DFT–TB [94] Semiconductor — Z Z, direct; AC indirect;

bandgap shrinks with decreasing diameter

MoS

DFT–TB [95] Like WS

NbS

DFT–TB [96] Metal, possibly superconductor

TiS

DFT–TB [97]

NbSe

TB [98] Metal, possibly superconductor

ZrS

TB [99] Semiconductor––Z Z, direct;

AC, indirect; bandgap shrinks with

decreasing diameter stability: ZZ>AC

MoS

1/3

bundles DFT [100] Stable mostly as bundles; metallic

, MoS

DFT–TB [101] Stability of the nanotubes was confirmed

, MoS

DFT–TB [102] Bandgap of the nanotubes as a function of

diameter was determined

(MS

)

TB [103] Stable nanooctahedra; metallic

(M=Mo, Nb, Zr, S)

nanooctahedra

Ca(AlSi)

and Sr(GaSi)

TB [104] Metallic, possibly superconducting;

CaSi

LDA–DFT [105] metallic

TB [106] Semiconductors; bandgap shrinks with

decreasing diameter

ZrNCl TB [107] ZZ — metal; AC — semiconductor

(becomes metal upon removal of 30%

chlorine)

B HF–SCF [108–110] Nanotubes are stable nanostructures,

metallic character

AlB

HF–SCF [111] Metallic

Bi DFT [112] Semiconductors

TB [113–115] Metallic, possibly superconducting

(M=Mg,Be,Sc,Ca,

Al,Ti,,Cr,Mo,Ta,Zr)

TB [116] Semiconductors; bandgap shrinks with

decreasing diameter –– effect is

stronger with ZZ as compared with AC

nanotubes

Black-P, As DFT–TB [117–119] Nanotubes –– stable; fullerenes ––

unstable

GaN DFT [120] Folded graphite-like GaN; bandgap

decreases with shrinking diameter;

ZZ –– direct gap; AC –– indirect gap

AlN DFT [121–123] Folded graphite-like AlN; bandgap

decreases with shrinking diameter;

ZZ –– direct gap; AC — indirect gap.

Fullerene-like structures –– stable

InP SCF–MO [124]

TB, tight binding; DFT, density functional theory; HF-SCF, Hartree-Fock self-consistent field; LDA, local density approxi-

mation; SCF-MO, Self-consistent–field-molecular orbital; ZZ, zigzag; AC, armchair.

The structure of the stable polyhedral clusters of metal dichalcogenide and other layered com-

pounds was first discussed in [6]. It was hypothesized that instead of pentagons, which occur in carbon

fullerenes and carbon nanotubes, rhombi and triangles would be the stable elements among IF nanopar-

ticles. Later work provided the first evidence for the existence of nanooctahedra (six rhombi) and nan-

otetrahedra (four triangles) in MoS

[126]. More decisive evidence in support of the existence and

stability of MoS

nanooctahedra was obtained by laser ablation of an MoS

target [55]. Figure 4.8 shows

an HRTEM image of one such MoS

nanooctahedron (left) and its Fourier transform filtered image

(right). These images clearly reveal the precise arrangement of the Mo atoms in the cluster. Recently,

the IF nanooctahedra of metal dichalcogenide compounds have been theoretically analyzed and their

atomic and electronic structure evaluated [103,127]. Figure 4.9 shows the structure of an (MoS

)

nanooctahedron calculated by tight binding (TB) theory. The structures of similar nanooctahedra of Nb,

Zr, and Sn disulfides were also investigated. Most interestingly, all the nanooctahedra studied were

found to be metallic, irrespective of the electronic structure of the parent compound. This conclusion,

which remains to be verified experimentally, shows the importance of elucidating the structure of IF

nanoparticles and their properties. Also, more accurate first-principle calculations have to be carried out

in order to verify the proposed stable structure of such nanooctahedra.

146 Nanotubes and Nanofibers

FIGURE 4.8 HRTEM image (right) and its Fourier filtered image (left) of an MoS

nanooctahedron prepared

by laser ablation of an MoS

target. (Courtesy of M. Bar-Sadan and S.Y. Hong.)

FIGURE 4.9 Schematic representation of the structure of (MoS

)

. (Adapted from Enyashin, A.N. et al.,

Inorg. Mater., 40, 395, 2004.)

The structure, stability, and properties of GaN and AlN nanotubes were studied as well [120–122].

In analogy to the semiconducting MS

nanotubes, and in sharp contrast to carbon nanotubes, the

bandgap shrinks with a decreasing diameter of the nanotubes. Furthermore, while (n,n) armchair nan-

otubes were found to exhibit an indirect transition, direct transition was seen for (n,0) zigzag nanotubes.

An interesting case is presented by nanotubes of the layered compound

-ZrNCl (see Figure

4.10a). This compound is a semiconductor with a bandgap of 2 eV in the bulk. It was converted into

a superconductor (T

= 13 to 15 K) by intercalating such electron donors as alkali atoms, or by dein-

tercalation of some of the lattice chlorine atoms. The structure and electronic properties of

β-ZrNCl nanotubes were investigated in detail in [107] (Figure 4.10b). The (n,n) armchair nanotubes

were shown to be semiconductors, but (n,0) zigzag nanotubes with diameter larger than 2.8 nm are

found to be all metallic. Furthermore, while the (29,0) nanotube is metallic, its unfolded stripe is a

semiconductor with a bandgap of 1.2 eV. As in semiconducting MS

nanotubes [93,94], the bandgap

Inorganic Nanotubes and Fullerene-Like Materials of Metal Dichalcogenide 147

(a)

(b)

Zn(N)

N(Zn)

Cl(cl)

−

1 2

FIGURE 4.10 (a) Crystal structure of a

-ZrNCI lattice; 1, Zigzag (12,0); 2, armchair (12,12) ZrNCI nan-

otube. (Adapted from Enyashin, A.N. et al., Chem. Phys. Lett., 387, 85, 2004.)

of the armchair nanotubes shrinks with decreasing nanotube diameter. Moreover, intrinsic or extrin-

sic doping may lead to significant variation of the electronic properties of nanotubes. Thus, dein-

tercalation of 30% of chlorine atoms endows metallic character to the ZrNCl nanotubes [107],

suggesting that they may become superconductors at sufficiently low temperatures.

In conclusion, the structure and electronic properties of various inorganic nanotubes have been

investigated in some detail. While some of the properties could be confirmed by experiment, much

more work is needed to elucidate the electronic and optical properties of these novel nanomaterials.

4.4 STUDY OF THE PROPERTIES OF INORGANIC NANOTUBES IN

RELATION TO THEIR APPLICATIONS

The properties of inorganic nanotubes and IF nanoparticles have been studied only recently (see

Table 4.3). In spite of that, a major application area for the IF nanoparticles in solid lubrication has

emerged from these studies. It was initially hypothesized that the quasi-spherical nanoparticles

148 Nanotubes and Nanofibers

TABLE 4.3

Summary of Potential Applications of Inorganic Nanotubes and Fullerene-Like

Nanoparticles

Properties and

Compound Proposed Applications References Comment

MoS

,WS

Tribology: additives to [51,128,129] Oils, greases, machining

lubricating fluids fluids, etc.

MoS

,WS

Tribological coatings [129–131] Medical applications

(metallic, polymers)

MoS

,WS

Tribology: self-lubricating [132] Sliding bearings

porous structures

MoS

, WS

Impact resistance [133]

(M=W, Mo) Mechanical properties [134–136]

(nanocomposites, etc.)

(M=Mo,Ti) Rechargeable batteries [40,137–139]

(M=Mo, Ti) Hydrogen storage [40,41]

MoS

Catalysis [140] CO+3H

→ CH

MoS

Field emission [141]

BN Mechanical properties [142,143] Young’s modulus of

700–1200 GPa

BN H

storage [144] Up to 4.2 wt%

BCN Field emission [145] Comparable to multiwall

carbon nanotubes

Cathodes for rechargeable [146–148] 100 cycles; >200 mAh/g

Li batteries

Optical limiting [149]

(OH)

storage; catalyst support [150]

CuSiO

O for CO oxidation

Rare earth oxisulfides Non-linear optics [76]

Titanates Dye sensitized solar cells [151] Solar to electrical

(e.g., H

) efficiency of 5%

GaN Optical nanodevices [89]

:Eu Optical nanodevices [152]

Silicate Catalysis, H

stoarge [74] Catalytic CO and

oxidation

would exhibit facile rolling and sliding. Coupled with its mechanical stability and chemical inert-

ness it was thought that IF-WS

(MoS

) nanoparticles could become very efficient nanoball bear-

ings, especially under high loads, where lubricating fluids tend to be squeezed out of the contact

region between the two moving pieces. This hypothesis was invariably confirmed [51,128].

Apparently, the favorable role played by IF nanoparticles in alleviating friction and wear is a much

more complex phenomenon than initially believed. A number of studies have indicated that during

friction tests under load, the IF nanoparticles gradually deform and exfoliate, depositing molecular

(MoS

) nanosheets on the underlying surfaces. These transferred molecular sheets (third body)

provide easy shear for the mating metal pieces, further alleviating friction [129]. Recent technical

tests of IF-WS

in various industrial environments demonstrated the large potential of such

nanoparticles for numerous tribological applications in the automotive, aerospace, electronics, and

many other industries.

Figure 4.11 shows the detrimental effect of addition of a minute amount of

IF-WS

nanoparticles on the friction coefficient between a ceramic pair, i.e., a Si

ball and alu-

mina flat. The effect of the IF-WS

nanoparticles on the wear rate of the ball was similar. The large-

scale application of IF-WS

(MoS

) would not be possible, should scaling of the production and its

cost effectiveness would not be proved. Indeed, a fluidized-bed reactor with a capacity of more than

100 g/day of a pure IF-WS

phase was realized sometime ago [153], and the construction of a

mock-up system for full-scale production is in progress. The feedstocks for the present process are

quite cheap and notwithstanding the small amount of the nanomaterials needed to alleviate both

friction and wear, the cost effectiveness of the IF-WS

nanolubricant seems to have been realized.

Many of the proposed applications of inorganic nanotubes are in their infancy stage and thus

they are not expected to reach the marketplace before a decade or so. Recent work has indicated the

large impact resistance of WS

nanotubes to shockwaves, suggesting numerous applications for

nanocomposites formulated with such nanoparticles [133].

One of the most appealing applications of inorganic nanotubes is in the field of cathode material

for rechargeable lithium batteries. Two of the most demanding requirements for host material are a

large capacity to accommodate significant amounts of the foreign lithium atoms and the reversibility

with respect to charge/discharge cycles. Intercalation of the lithium and hydrogen atoms have been

accomplished within the van der Waals gap between two layers of the nanotube [138,139]. An extra

capacity of the alkali atoms may exist also in the cylindrical hollow core of the nanotube, but the

mechanism of charge transfer in this case may be quite different from that of the alkali atoms interca-

lated between each two layers. The metal atoms in the core may not be in direct contact with the wall

Inorganic Nanotubes and Fullerene-Like Materials of Metal Dichalcogenide 149

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 50 100 150 200 250 300 350 400 450 500 550

Number of cycles

Friction coefficient

FIGURE 4.11 Friction coefficient vs. number of cycles for alumina Al

plat –– Si

ball pair. Load

P = 0.75 N. Open circles –– non-lubricated part; full circles –– IF lubricated pair.

of the nanotube to permit a fast charge transfer from the alkali atoms to the host, and take part in the

electrochemical reaction effectively. The other property that makes inorganic nanotubes an intrigu-

ing cathode material for rechargeable batteries is their inherent stability, which in general is not com-

mon to nanostructured materials. The inherent stability of inorganic nanotubes coupled with their large

internal surfaces accessible to small molecules, also suggests that inorganic nanotubes can serve as

efficient and selective catalysts, which so far was realized in a few cases only [74,140].

4.5 CONCLUSIONS

Building upon the analogy between the structure of graphite and inorganic layered compounds, nan-

otubes and fullerene-like nanoparticles of various compounds have been synthesized and investi-

gated in some detail. The versatility in choosing the starting material coupled with the structural

complexity of inorganic layered compounds led to numerous intriguing observations, and some

important potential applications. Many fundamental issues remain to be addressed; most funda-

mental among them is the elucidation of the detailed structure of inorganic nanotubes and fullerene-

like particles. In order to study the physical properties and chemically modify these nanotubes,

macroscopic amounts of the nanotubes must first be synthesized, which in some cases has proved

to be an illusive goal. Finally, by careful characterization of these nanophases, new applications may

emerge with time.

ACKNOWLEDGMENTS

R.T. is supported by the Helen and Martin Kimmel Center for Nanoscale Science and holds the

Drake Family Chair in Nanotechnology. The support of the Israel Science Foundation and

“Nanomaterials Ltd.” is acknowledged.

REFERENCES

1. Kroto, H.W., Heath, J.R., O’Brien, S.C., Curl, R.F., and Smalley, R.E., C

: Buckminsterfullerene,

Nature, 318, 162, 1985.

2. Iijima, S., Helical microtubules of graphitic carbon, Nature, 354, 56, 1991.

3. Wilson, J.A. and Yoffe A.D., Transition metal dichalcogenides discussion and interpretation of

observed optical, electrical and structural properties, Adv. Phys. 269, 193–335, 1969.

4. Lévy, F., Structural Chemistry of Layer-Type Phases, Vol. 5, D. Reidel, Dordrecht,

1976.

5. Tenne, R., Margulis, L., Genut, M., and Hodes, G., Polyhedral and cylindrical structures of tungsten

disulphide, Nature, 360, 444, 1992.

6. Margulis, L., Salitra, G., Tenne, R., and Talianker, M., Nested fullerene-like structures, Nature, 365,

113, 1993.

7. Rosenfeld, H.Y. et al., Cage structures and nanotubes of NiCl

, Nature, 395, 336, 1998.

8. Ajayan, P.M. et al., Carbon nanotubes as removable templates for metal oxide nanocomposites and

nanostructures, Nature, 375, 564, 1995.

9. Patzke, G.R., Krumeich, F., and Nesper, R., Oxidic nanotubes and nanorods — anisotropic modules

for a future nanotechnology, Angew. Chem. Int. Ed. 41, 2446, 2002.

10. Chen, Q. et al., Tritanate nanotubes made via a single alkali treatment, Adv. Mater., 14, 1208, 2002.

11. Tenne, R., Advances in the synthesis of inorganic nanotubes and fullerene-like nanoparticles, Angew.

Chem. Int. Ed., 42, 5124, 2003.

12. Nath, M. and Rao, C.N.R., Inorganic nanotubes, Dalton Trans., 1, 1, 2003.

13. Pauling, L., The structure of the chlorites, Proc. Natl. Acad. Sci., 16, 578, 1930.

14. Wiegers, G.A. and Meerschut, A., Structures of misfit layer compounds (MS)

(MSn, Pb, Bi, rare

earth metals; TNb, Ta, Ti, V, Cr; 1.08 ⬍ n ⬍ 1.23), J. Alloys Comp., 178, 351, 1992.

150 Nanotubes and Nanofibers

15. Suzuki, K., Enoki,T., and Imaeda, K., Synthesis, characterization and physical properties of incom-

mensurate layered compounds/(RES)

TaS

(RE=Rare earth metal), Solid State Commun. 78, 73,

1991.

16. Kresge, C.T. et al., Control of metal radial profiles in alumina supports by carbon-dioxide, Nature,

259, 710, 1992.

17. Stöber, W., Fink, A., and Bohn, E., Controlled growth of monodisperse silica spheres in micron

size range, J. Colloid Interf. Sci., 26, 62, 1968.

18. Nakamura, M. and Matsui, Y., Silica gel nanotubes obtained by the sol–gel method, J. Am. Chem. Soc.,

117, 2651, 1995.

19. Satishkumar, B.C. et al., Oxide nanotubes prepared using carbon nanotubes as templates, J. Mater.

Res., 12, 604, 1997.

20. Wu, Q. et al., Synthesis and characterization of faceted hexagonal aluminum nitride nanotubes, J. Am.

Chem. Soc., 125, 10176, 2003.

21. Sharma, S. and Sunkara, M.K., Direct synthesis of gallium oxide tubes, nanowires, and nanopaint-

brushes, J. Am. Chem. Soc., 124, 12288, 2002.

22. Chianelli, R.R. et al., Molybdenum disuflide in the poorly crystalline “Rag” structure, Science, 203,

1105, 1979.

23. Sanders, J.V., Structure of catalytic particles, Ultramicroscopy, 20, 33, 1986; Sanders, J.V.,

Transmission electron-microscopy of catalysts, J. Electron Microsc. Tech., 3, 67, 1986.

24. Feldman, Y. et al., High rate gas phase growth of MoS

nested inorganic fullerene-like and nanotubes,

Science, 267, 222, 1995.

25. Rosentsveig, R., et al., WS

nanotube bundles and foils, Chem. Mater., 14, 471, 2002.

26. Coleman, K.S., The formation of ReS

inorganic fullerene-like structures containing Re

parallelo-

gram units and metal–metal bonds, J. Am. Chem. Soc., 124, 11580, 2002.

27. Remskar, M. et al., MoS

as micro tubes, Appl. Phys. Lett., 69, 351, 1996.

28. Remskar, M. et al., New crystal structures of WS

: microtubes, ribbons, and ropes, Adv. Mater., 10,

246, 1998.

29. Remskar, M. et al., Self-assembly of subnanometer-diameter single-wall MoS

nanotubes, Science,

292, 479, 2001.

30. Zelenski, C.M. and Dorhout, P.K., Template synthesis of near-monodisperse microscale nanofibers

and nanotubules of MoS

, J. Am. Chem. Soc., 120, 734, 1998.

31. Santiago, P., et al., Synthesis and structural determination of twisted MoS

nanotubes, Appl. Phys. A.,

78, 513, 2004.

32. Nath, M. and Rao, C.N.R., New metal disulfide naotubes, J. Am. Chem. Soc., 123, 4841, 2001.

33. Nath, M. and Rao, C.N.R., Nanotubes of group 4 metal disulfides, Angew. Chem. Int. Ed., 41, 3451,

2002.

34. Hsu, W.K. et al., An alternative route to molybdenum disulfide nanotubes, J. Am. Chem. Soc., 122,

10155, 2000.

35. Zhu, Y.Q. et al., Carbon nanotube template promoted growth of NbS

nanotubes/nanorods, Chem.

Commun., 2184, 2001.

36. Brorson, M., Hansen, T.W., Jacobsen, C.J.H., Rhenium(IV) sulfide nanotubes, J. Am. Chem. Soc., 124,

11582, 2002.

37. Tsuneta, T. et al., Formation of metallic NbSe

nanotubes and nanofibers, Curr. Appl. Phys., 3, 473,

2003.

38. Afansiev, P. et al., Molybdenum polysulfide hollow microtubules grown at room temperature from

solution, Chem. Comm., 1001, 2000.

39. Chen, J. et al., Synthesis and characterization of WS

nanotubes, Chem. Mater., 15, 1012, 2003.

40. Chen, J. et al., Titanium disulfide nanotubes as hydrogen-storage materials, J. Am. Chem. Soc., 125,

5284, 2003.

41. Chen J. et al., Electrochemical hydrogen storage in MoS

nanotubes, J. Am. Chem. Soc., 123, 11813,

2001.

42. Li, X.L. and Li, Y.D., Formation of MoS

inorganic fullerenes (IFs) by the reaction of MoO

nanobelts

and S, Chem. Eur. J., 9, 2726, 2003.

43. Li., Y.D. et al., Artificial lamellar mesostructures to WS

nanotubes, J. Am. Chem. Soc., 124, 1411,

2002.

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