Title of Invention	SYNTHESIZED CARBON NANOTUBES AND ITS PROCESS OF MANUFACTURE
Abstract	Synthesized CNTs comprising of CNTs directly electro-deposited in pure form on wafer/substrates preferably selected from Si and Sn02 coated glass substrates. Also disclosed is the selective process for synthesis of carbon nanotubes by direct electro-deposition on substrates comprising electrolyting bath involving selectively acetonitrile (CH3CN) and water as the electrolyte. The above would provide for directly synthesized CNTs onto the wafer/substrate which would be simple and cost-effective. The manufacture of CNTs directly onto the wafer/substrate in the purest form which would be capable of industrial use and in particular large  scale synthesis of CNTs by way of a simple and cost effective process. It would thus be possible for  large scale synthesis of CNTs directly onto the Si and Sn02 coated glass substrates by way of a simple and cost effective electro deposition technique which can be importantly further used to achieve coating even on irregular surfaces. Carbon nanotubes are effective for use in flat panel displays and also in strategic areas using light weight and high impact resistance coatings. The synthesized carbon nanotubes of the invention can be applied as materials for sensor applications, materials for scanning probe microscope tips and light weight high strength materials for defense and space applications.

Title of Invention

SYNTHESIZED CARBON NANOTUBES AND ITS PROCESS OF MANUFACTURE

Abstract

Synthesized CNTs comprising of CNTs directly electro-deposited in pure form on wafer/substrates preferably selected from Si and Sn02 coated glass substrates. Also disclosed is the selective process for synthesis of carbon nanotubes by direct electro-deposition on substrates comprising electrolyting bath involving selectively acetonitrile (CH3CN) and water as the electrolyte. The above would provide for directly synthesized CNTs onto the wafer/substrate which would be simple and cost-effective. The manufacture of CNTs directly onto the wafer/substrate in the purest form which would be capable of industrial use and in particular large  scale synthesis of CNTs by way of a simple and cost effective process. It would thus be possible for  large scale synthesis of CNTs directly onto the Si and Sn02 coated glass substrates by way of a simple and cost effective electro deposition technique which can be importantly further used to achieve coating even on irregular surfaces. Carbon nanotubes are effective for use in flat panel displays and also in strategic areas using light weight and high impact resistance coatings. The synthesized carbon nanotubes of the invention can be applied as materials for sensor applications, materials for scanning probe microscope tips and light weight high strength materials for defense and space applications.

Full Text	Field of the Invention The present invention relates to synthesized carbon nanotubes and to the process of manufacture of such carbon nanotubes by way of a simple and cost effective manner of manufacture. Carbon nanotubes are effective for use in flat panel displays and also in strategic areas using light weight and high impact resistance coatings. The synthesized carbon nanotubes of the invention can be applied as materials for sensor applications, materials for scanning probe microscope tips and light weight high strength materials for defense and space applications. Background Art Carbon nanotubes were first discovered in 1991 by lijima et al. (Nature 354, 56 (1991). Since its development there has been continued research and developmental activities on carbon nanotubes. Importantly, the encouraging physical and chemical properties of carbon nanotubes have lead to development of nanoscale devices several of which are discussed in various references [ S.Saito, Science 278, 77 (1977); S.J. Tans, A. R. M. Verschueren and C. Dekker, Nature 393, 49 (1998); T.W. Tombler, C. Zhou, L. Alexseyev, J. Kong, H. Dai, L. Liu, C. S. Jayanthi, M. Tang and S. Y. Wu, Nature 405, 769 (2000), A. Bachtold, P. Hadley, T. Nakanishi and C. Dekker, Science 294, 1317 (2001) ; G. Zhou, W. Duan and B. Gu, Phys. Rev. Lett. 87, 095504 (2001); F. Leonard and J. Tersoff, Phys. Rev. Lett. 88, 258302 (2002) ]. The synthesis of carbon nanotubes commonly involve method such as arc discharge [ C. Journet, W. K. Maser, P/ Bernier, A. Loiseau, M. L. De La Chapelle, S. Lefrant, P. Deniart, R. Lee, J. E. Fischer, Nature 388, 756 (1997), ] laser ablation [ A. Thess, R. Lee, P. Nikolaev, H. Dai, P. Petit, J. Robert, C. Xu, Y. H. Lee, S. G. Kim, A. G. Rinzler, D. T. Colbert, G. E. Scuseria, D. Tomanek, J.E. Fischer and R.E. Smalley, Science 273, 483 (1996) ] and CVD processes [ M. Ge and K. Sattler, Science 260, 515 (1993) ]. However, it has been found that all such presently known synthesis techniques inherently produced carbon nanotubes alongwith various impurities in the form of amorphous carbon, metal catalyst and many carbonaceous particle:; etc. Thus such carbon nanotubes obtained following conventional processes required further purification and suspension to produce high quality CNTs for device applications. Moreover, such processes required the suspension in-solvent before depositing them on suitable substrates. Also, it is found that all such purification and suspension procedures further lead to the CNTs containing various defects on their surfaces which again affect the electronic property and in turn the device performance. Objects of the Invention It us thus the basic object of the present invention to provide for directly synthesized CNTs onto the wafer/substrate which would be simple and cost- effective. Another object is to provide for the process for manufacture of CNTs directly onto the wafer/substrate in the purest form which would be very cost-effective and simple. Yet another object of the present invention is directed to provide for manufacture of CNTs directly onto the wafer/substrate in the purest form which would be capable of industrial use and in particular large scale synthesis of CNTs by way of a simple and cost effective process. Yet further object is directed to large scale synthesis of CNTs directly onto the Si and Sn02 coated glass substrates by way of a simple and cost effective electro deposition technique which can be further used to achieve coating even on irregular surfaces. Yet another object of the present invention is directed to large scale synthesis of CNTs directly onto irregular surfaces/substrates by way of a simple and cost- effective electro deposition technique. Summary of the Invention Thus according to the basic aspect of the present invention there is provided synthesized CNTs comprising of CNTs directly electro-deposited in pure form on wafer/substrates. In the above synthesized CNTs the wafer/substrates can be selected from Si and Sn02 coated glass substrates. In accordance with a another aspect of the present invention there is provided a process for synthesis of carbon nanotubes by direct electro-deposition on substrates comprising: - providing an electrolyting bath comprising acetonitrile (CH3CN) and water as the selective electrolyte; - said electrolytic bath having as one of its electrodes the substrate for deposition of the CNTs and a graphite counter electrode; - means to carry out electrolysis such as to deposit the CNTs directly on to the said substrates. In the above process of the invention, the selective use of acetonitrile and water as the electrolyte provided for the desired concentration of methyl radicals and hydrogen ions due to electrolyte dissociation. Such methyl radicals and hydrogen ions present in the solvent importantly provide for the desired formation of films i.e. the direct deposition of CNTs on the substrate. The above electro deposition technique apart from being simple, is cost-effective and is industrially applicable for large scale production of the CNTs. In accordance with a preferred aspect the process for direct synthesis of CNTs in accordance with the invention comprise; - providing the electrolyte bath comprising acetonitrile (CH3CN) and water as the selective electrolyte and using a graphite anode as the counter electrode and the substrate selected from Si wafers and Sn02 coated glass as the other cathode electrode; - carrying out the electrolysis at atmospheric pressure and a bath temperature of about 273 K .to 350 K, preferably 300K. In accordance with yet further aspect the process for direct synthesis of carbon nanotubes on Si wafer/Sn02 coated glass comprise: - providing the electrolytic bath comprising acetonitrile and water as the selected electrolyte and using a graphite anode electrode and a selected substrate for direct deposition thereon of CNTs as the cathode electrode; - carrying out the electrolysis at atmospheric pressure and bath temperature of 273 K to 350 K, preferably 300 K in the presence of an applied magnetic field. The application of magnetic field during electro-deposition was found to have a special effect on the alignment of carbon nanotubes. When the deposition was carried out at different magnetic field applied perpendicular to the electric field it is expected that the radicals (ChV) and (ions) (H+;OH-) would experience Lorentz force. Thus the ions move in the direction of the cathode in a helical path whose diameter depend on the magnitude of both the electric and magnetic field. In this way the carbon nanotubes grow in bunches and align with longer length than those obtained without the application of magnetic field. The nanotubes could be seen to be aligned parallel to the substrate surface. Order of the magnetic field applied can be in the range of 0.2 to 1 K Gauss, preferably, the order of the magnetic field applied perpendicular to the electro field can be higher in the range of 0.8 to 0.9 K Gauss for better results. Detailed Description of the Invention In the above process of the invention selective use of acetonitrile and water as the electrolyte has been carried out. As explained above, such selective electrolyte provide for certain concentration of methyl radicals and hydrogen ions due to electrolytic dissociation. The methyl radicals and hydrogen ions in the solvents play a critical role in the formation of the CNTs films. The carbon nanotubes can be the result of folding graphite layers into carbon cylinders of single shell (single-walled nanotubes) or of multishells (multi-walled nanotubes). Therefore, by suitably choosing the electrolyte and the deposition parameters it is possible to deposit carbon nanotubes by the electro deposition technique. The carbon nanotubes were deposited preferably onto Si (wafers) resistivity approximately 5 to 20 ohm cm preferably 15 ohm-cm ; size approx. 6 mm to 15 mm x6 mm to 10mm x 0.1mm to 0.4 mm preferably 10mm x 8mm x 0.3 mm and SnC>2 coated glass size approximately 8 mm to 15.mm x 6 mm .to 12 mm x 2 mm .to 5 mm preferably 10mm x 8 mm x 4mm) which were attached to a copper cathode. As discussed above, the graphite was used as the counter electrode (anode). Before mounting the substrates on the cathode, they were thoroughly cleaned and rinsed with deionized water and ethanol solution respectively. In accordance with a further aspect of the invention, the electrodes were separated by a distance of approximately 6 mm .to. 10 mm preferably 8 mm. The applied DC voltage between the electrodes was kept at 15..to 25. V preferably 20V by using a DC power supply capable of generating stabilized voltage (30V, 2A). The deposition was carried out for about 10-20 hours. The substrates in the process used is required to be cleaned thoroughly before use in deposition. The optimum voltage, time of deposition and composition of the electrolyte need to be appropriately maintained to achieve the desired objects and advantages. The details of the invention its objects and advantages are explained hereunder in greater detail in relation to non-limiting exemplary illustrations hereunder: EXAMPLES Example - 1: Process according to the invention To carryout the process of the invention, an electrolytic bath was used with water and acetonitrile (1% v/v) as the selective electrolyte solution. Graphite was used as the anode while a low resistive (15 ohm cm) Si and Sn02 coated glass substrate was used at the cathode for depositing the carbon nanotubes. The electrolysis was carried out at an applied DC potential of about 20V. The electrolysis for a period of 12 hours resulted in deposition of carbon nanotubes as films on the substrates in both the Si and SnO2 coated substrates. The growth of CNTs on the substrate achieved in the two cases (Examples 1 & 2) were monitored and the results illustrated in accompanying figures 1-6 The growth of CNTs on the substrate in case of the process of the Example I was confirmed by XRD, SEM, Raman, Optical absorbance, FTIR and ESR measurements. The results of which are illustrated by way of accompanying figures 1-6. In particular, the XRD Spectra (figure 2) of the films shown (002), (100) and (004) reflections which could be assigned to the hexagonal ring structure of graphite sheets forming the carbon nanotubes. The UV - VIS - NIR optical reflectance spectra of CNT deposits showed two stronger reflection peaks at 1880 nm and 935 nm alongwith a weaker and broader one at 700 nm. The stronger peak is assigned to the first and second interband optical transitions of the CNTs and the one at 700 nm to the metallic CNTs respectively. This indicated the presence of higher content of the semiconducting CNT bundles in the films than the metallic CNT bundles. The Raman Spectra generated contained the confirmative signature of the presence of carbon nanotubes in the films obtained following Example 1. The films showed a sharp feature 1354 cm"1 (D-Band) and 1600 cm"1 (G-Band). The photoluminescence specter are dominated by a sharp peak centre 0.95 eV which could be related to the band-edge transition (figure 7a and 7b). The field emission properties of the CNTs films were further analyzed using the Fowler Nordheim Model. The values of effective work function ( Øe = Øß) and ß derived from FN plots of the films varied between 130-150 meV and 2000-2200 respectively for the films presented under Example 1. Thus these films obtained following the Example 1 serve as good materials for flat panel display devices. FTIR and ESR measurements also indicated the growth of carbon nanotubes in the films. lit is thus possible by way of the present invention to provide for large scale synthesis of CNTs directly onto the wafer onto the substrates in their purest form and very cost-effective and scalable technique. The present invention further provides to synthesis CNTs directly onto the Si and (SnO2 coated glass substrates) by simple electro deposition technique. Importantly, the process of the invention apart from being scalable is also found to provide for cost competitive coating on irregular surfaces. WE CLAIM 1. Synthesized CNTs comprising of CNTs obtained of direct electro- deposition in pure form on wafer/substrates. 2. The synthesized CNTs as claimed in claiml wherein the wafer/substrates are selected from Si and Sn02 coated glass substrates. 3. The synthesized CNTs as claimed in anyone of claimsl or 2 wherein the thickness of the CNT films deposited is 45 to 65,nm. 4. The synthesized CNTs as claimed in anyone of claimsl to 3 wherein the carbon nonotube structures comprise interconnected single -walled nonotube bundles in a web like network and/or multi shells comprising multi-walled nanotubes. 5. The synthesized CNTs as claimed in anyone of claimsl to 4 wherein diameters of the CNT bundles range from 20-30 nm for deposits on Si and 30-40 nm for deposits on Sn02 coated glass substrates. 6. The synthesized CNTs as claimed in anyone of claims 1 to 5 wherein the carbon nanotubes deposited are aligned parallel to the substrate plane. 7. A process for synthesis of carbon nanotubes by direct electro-deposition on substrates comprising: - providing an electrolyting bath comprising acetonitrile (CH3CN) and water as the selective electrolyte; - said electrolytic bath having as one of its electrodes the substrate for deposition of the CNTs and a graphite counter electrode; - means to carry out electrolysis such as to deposit the CNTs directly on to the said substrates. 8. A process for synthesis of carbon nanotubes by direct electro-deposition on substrates as claimed in claim 8 wherein the methyl radicals and 9 hydrogen ions present in the solvent provide for the desired formation of films by the direct deposition of CNTs on the substrate. 9. A process for synthesis of carbon nanotubes by direct electro-deposition on substrates as claimed in anyone of claims 8 or 9 comprising : - providing the electrolyte bath comprising acetdnitrile (CH3CN) and water as the selective electrolyte and using a graphite anode as the counter electrode and the substrate selected from Si wafers and Sn02 coated glass as the other cathode electrode; - carrying out the electrolysis at atmospheric pressure and a bath temperature of about 273K to 350 K .preferably 300K. 10. A process for synthesis of carbon nanotubes by direct electro-deposition on Si wafer/Sn02 coated glass as claimed in anyone of claims 8 to 10 comprising : - providing the electrolytic bath comprising acetonifrile and water as the selected electrolyte and using a graphite anode electrode and a selected substrate for direct deposition thereon of CNTs as the cathode electrode; - carrying out the electrolysis at atmospheric pressure and bath temperatures of 273 K to 350 K .preferably 300 K in the presence of an applied magnetic field. 11. A process for synthesis of carbon nanotubes by direct electro-deposition on substrates as claimed in claim 11 comprising of application of magnetic field during electro deposition for desired alignment of carbon nanotubes and/or the growth in bunches. 12. A process for synthesis of carbon nanotubes by direct electro-deposition on substrates as claimed in anyone of claims 8 to 12 wherein the nanotubes are aligned parallel to the substrate surface. 10 13. A process for synthesis of carbon nanotubes by direct electro-deposition on substrates as claimed in anyone of claims 8to 13 wherein the magnetic field applied is in the range of 0.2 .to 1.0 K Gauss, preferably in the range of 1 K Gauss. 14. A process for synthesis of carbon nanotubes by direct electro-deposition on. substrates as claimed in anyone of claims 8 to 14 wherein the carbon nanotubes are generated as a result of folding graphite layers into carbon cylinders of single shell (single-walled nanotubes) or of multishells (multi- walled nanotubes). 15. A process for synthesis of carbon nanotubes by direct electro-deposition on substrates as claimed in anyone of claims 8 to 15 wherein the carbon nanotubes are deposited preferably onto Si (wafers) resistivity approximately 5 to 20 ohm cm preferably 15 ohm-cm ; size approx. 6 mm to 15 mm x 6 mm to 10 mm x 0.1 to 0.4 mm preferably 10mm x 8mm x 0.3 mm and SnC>2 coated glass size approximately 8 mm to 15.mm x 6 mm .to 12 mm x 2 mm .to 5 mm preferably 10mm x 8 mm x 4mm which were attached to a copper cathode. 16. A process for synthesis of carbon nanotubes by direct electro-deposition on substrates as claimed in anyone of claims 8 to 16 wherein before mounting the substrates on the cathode the same is thoroughly cleaned and rinsed with deionized water and ethanol solution respectively. 17. A process for synthesis of carbon nanotubes by direct electro-deposition on substrates as claimed in anyone of claims 8 to 17 wherein the electrodes are separated by a distance of approximately 6 to 10 mm preferably 8 mm. 18. A process for synthesis of carbon nanotubes by direct electro-deposition on substrates as claimed in anyone of claims 8 to 18 wherein the applied DC voltage between the electrodes is kept at 15 to 25 V preferably 20V. 11 19. A process for synthesis of carbon nanotubes by direct electro-deposition on substrates as claimed in anyone of claims 8 to 19 wherein the deposition is carried out for about 10-20 hours. 20. A process for synthesis of carbon nanotubes by direct electro-deposition on substrates as claimed in anyone of claims 8 to 21 wherein the electric field applied between the electrodes is. 15 to 25 V. 21. Synthesized CNTs and its process of manufacture substantially as hereindescribed and illustrated with reference to the accompanying examples and figures. ABSTRACT Synthesized CNTs comprising of CNTs directly electro-deposited in pure form on wafer/substrates preferably selected from Si and Sn02 coated glass substrates. Also disclosed is the selective process for synthesis of carbon nanotubes by direct electro-deposition on substrates comprising electrolyting bath involving selectively acetonitrile (CH3CN) and water as the electrolyte. The above would provide for directly synthesized CNTs onto the wafer/substrate which would be simple and cost-effective. The manufacture of CNTs directly onto the wafer/substrate in the purest form which would be capable of industrial use and in particular large scale synthesis of CNTs by way of a simple and cost effective process. It would thus be possible for large scale synthesis of CNTs directly onto the Si and Sn02 coated glass substrates by way of a simple and cost effective electro deposition technique which can be importantly further used to achieve coating even on irregular surfaces. Carbon nanotubes are effective for use in flat panel displays and also in strategic areas using light weight and high impact resistance coatings. The synthesized carbon nanotubes of the invention can be applied as materials for sensor applications, materials for scanning probe microscope tips and light weight high strength materials for defense and space applications.

Full Text

Field of the Invention
The present invention relates to synthesized carbon nanotubes and to the
process of manufacture of such carbon nanotubes by way of a simple and cost
effective manner of manufacture. Carbon nanotubes are effective for use in flat
panel displays and also in strategic areas using light weight and high impact
resistance coatings. The synthesized carbon nanotubes of the invention can be
applied as materials for sensor applications, materials for scanning probe
microscope tips and light weight high strength materials for defense and space
applications.
Background Art
Carbon nanotubes were first discovered in 1991 by lijima et al. (Nature 354, 56
(1991). Since its development there has been continued research and
developmental activities on carbon nanotubes. Importantly, the encouraging
physical and chemical properties of carbon nanotubes have lead to development
of nanoscale devices several of which are discussed in various references [
S.Saito, Science 278, 77 (1977); S.J. Tans, A. R. M. Verschueren and C. Dekker,
Nature 393, 49 (1998); T.W. Tombler, C. Zhou, L. Alexseyev, J. Kong, H. Dai, L.
Liu, C. S. Jayanthi, M. Tang and S. Y. Wu, Nature 405, 769 (2000), A. Bachtold,
P. Hadley, T. Nakanishi and C. Dekker, Science 294, 1317 (2001) ; G. Zhou, W.
Duan and B. Gu, Phys. Rev. Lett. 87, 095504 (2001); F. Leonard and J. Tersoff,
Phys. Rev. Lett. 88, 258302 (2002) ].
The synthesis of carbon nanotubes commonly involve method such as arc
discharge [ C. Journet, W. K. Maser, P/ Bernier, A. Loiseau, M. L. De La
Chapelle, S. Lefrant, P. Deniart, R. Lee, J. E. Fischer, Nature 388, 756 (1997), ]
laser ablation [ A. Thess, R. Lee, P. Nikolaev, H. Dai, P. Petit, J. Robert, C. Xu,
Y. H. Lee, S. G. Kim, A. G. Rinzler, D. T. Colbert, G. E. Scuseria, D. Tomanek,
J.E. Fischer and R.E. Smalley, Science 273, 483 (1996) ] and CVD processes [
M. Ge and K. Sattler, Science 260, 515 (1993) ]. However, it has been found that
all such presently known synthesis techniques inherently produced carbon
nanotubes alongwith various impurities in the form of amorphous carbon, metal
catalyst and many carbonaceous particle:; etc. Thus such carbon nanotubes
obtained following conventional processes required further purification and

suspension to produce high quality CNTs for device applications. Moreover,
such processes required the suspension in-solvent before depositing them on
suitable substrates. Also, it is found that all such purification and suspension
procedures further lead to the CNTs containing various defects on their surfaces
which again affect the electronic property and in turn the device performance.
Objects of the Invention
It us thus the basic object of the present invention to provide for directly
synthesized CNTs onto the wafer/substrate which would be simple and cost-
effective.
Another object is to provide for the process for manufacture of CNTs directly onto
the wafer/substrate in the purest form which would be very cost-effective and
simple.
Yet another object of the present invention is directed to provide for manufacture
of CNTs directly onto the wafer/substrate in the purest form which would be
capable of industrial use and in particular large scale synthesis of CNTs by way
of a simple and cost effective process.
Yet further object is directed to large scale synthesis of CNTs directly onto the Si
and Sn02 coated glass substrates by way of a simple and cost effective electro
deposition technique which can be further used to achieve coating even on
irregular surfaces.
Yet another object of the present invention is directed to large scale synthesis of
CNTs directly onto irregular surfaces/substrates by way of a simple and cost-
effective electro deposition technique.
Summary of the Invention
Thus according to the basic aspect of the present invention there is provided
synthesized CNTs comprising of CNTs directly electro-deposited in pure form on
wafer/substrates.

In the above synthesized CNTs the wafer/substrates can be selected from Si and
Sn02 coated glass substrates.
In accordance with a another aspect of the present invention there is provided a
process for synthesis of carbon nanotubes by direct electro-deposition on
substrates comprising:
- providing an electrolyting bath comprising acetonitrile (CH3CN) and water as
the selective electrolyte;
- said electrolytic bath having as one of its electrodes the substrate for
deposition of the CNTs and a graphite counter electrode;
- means to carry out electrolysis such as to deposit the CNTs directly on to the
said substrates.
In the above process of the invention, the selective use of acetonitrile and water
as the electrolyte provided for the desired concentration of methyl radicals and
hydrogen ions due to electrolyte dissociation. Such methyl radicals and
hydrogen ions present in the solvent importantly provide for the desired formation
of films i.e. the direct deposition of CNTs on the substrate.
The above electro deposition technique apart from being simple, is cost-effective
and is industrially applicable for large scale production of the CNTs.
In accordance with a preferred aspect the process for direct synthesis of CNTs in
accordance with the invention comprise;
- providing the electrolyte bath comprising acetonitrile (CH3CN) and water as
the selective electrolyte and using a graphite anode as the counter electrode
and the substrate selected from Si wafers and Sn02 coated glass as the other
cathode electrode;
- carrying out the electrolysis at atmospheric pressure and a bath temperature
of about 273 K .to 350 K, preferably 300K.

In accordance with yet further aspect the process for direct synthesis of carbon
nanotubes on Si wafer/Sn02 coated glass comprise:
- providing the electrolytic bath comprising acetonitrile and water as the
selected electrolyte and using a graphite anode electrode and a selected
substrate for direct deposition thereon of CNTs as the cathode electrode;
- carrying out the electrolysis at atmospheric pressure and bath temperature of
273 K to 350 K, preferably 300 K in the presence of an applied magnetic field.
The application of magnetic field during electro-deposition was found to have a
special effect on the alignment of carbon nanotubes. When the deposition was
carried out at different magnetic field applied perpendicular to the electric field it
is expected that the radicals (ChV) and (ions) (H+;OH-) would experience Lorentz
force. Thus the ions move in the direction of the cathode in a helical path whose
diameter depend on the magnitude of both the electric and magnetic field. In
this way the carbon nanotubes grow in bunches and align with longer length than
those obtained without the application of magnetic field. The nanotubes could be
seen to be aligned parallel to the substrate surface. Order of the magnetic field
applied can be in the range of 0.2 to 1 K Gauss, preferably, the order of the
magnetic field applied perpendicular to the electro field can be higher in the range
of 0.8 to 0.9 K Gauss for better results.
Detailed Description of the Invention
In the above process of the invention selective use of acetonitrile and water as
the electrolyte has been carried out. As explained above, such selective
electrolyte provide for certain concentration of methyl radicals and hydrogen ions
due to electrolytic dissociation. The methyl radicals and hydrogen ions in the
solvents play a critical role in the formation of the CNTs films.
The carbon nanotubes can be the result of folding graphite layers into carbon
cylinders of single shell (single-walled nanotubes) or of multishells (multi-walled
nanotubes). Therefore, by suitably choosing the electrolyte and the deposition
parameters it is possible to deposit carbon nanotubes by the electro deposition
technique.

The carbon nanotubes were deposited preferably onto Si (wafers) resistivity
approximately 5 to 20 ohm cm preferably 15 ohm-cm ; size approx. 6 mm to 15
mm x6 mm to 10mm x 0.1mm to 0.4 mm preferably 10mm x 8mm x 0.3 mm and
SnC>2 coated glass size approximately 8 mm to 15.mm x 6 mm .to 12 mm x 2 mm
.to 5 mm preferably 10mm x 8 mm x 4mm) which were attached to a copper
cathode.
As discussed above, the graphite was used as the counter electrode (anode).
Before mounting the substrates on the cathode, they were thoroughly cleaned
and rinsed with deionized water and ethanol solution respectively.
In accordance with a further aspect of the invention, the electrodes were
separated by a distance of approximately 6 mm .to. 10 mm preferably 8 mm. The
applied DC voltage between the electrodes was kept at 15..to 25. V preferably
20V by using a DC power supply capable of generating stabilized voltage (30V,
2A). The deposition was carried out for about 10-20 hours.
The substrates in the process used is required to be cleaned thoroughly before
use in deposition. The optimum voltage, time of deposition and composition of
the electrolyte need to be appropriately maintained to achieve the desired objects
and advantages.
The details of the invention its objects and advantages are explained hereunder
in greater detail in relation to non-limiting exemplary illustrations hereunder:
EXAMPLES
Example - 1: Process according to the invention
To carryout the process of the invention, an electrolytic bath was used with water
and acetonitrile (1% v/v) as the selective electrolyte solution. Graphite was used
as the anode while a low resistive (15 ohm cm) Si and Sn02 coated glass
substrate was used at the cathode for depositing the carbon nanotubes.

The electrolysis was carried out at an applied DC potential of about 20V. The
electrolysis for a period of 12 hours resulted in deposition of carbon nanotubes as
films on the substrates in both the Si and SnO2 coated substrates.
The growth of CNTs on the substrate achieved in the two cases (Examples 1 & 2)
were monitored and the results illustrated in accompanying figures 1-6
The growth of CNTs on the substrate in case of the process of the Example I was
confirmed by XRD, SEM, Raman, Optical absorbance, FTIR and ESR
measurements. The results of which are illustrated by way of accompanying
figures 1-6.
In particular, the XRD Spectra (figure 2) of the films shown (002), (100) and (004)
reflections which could be assigned to the hexagonal ring structure of graphite
sheets forming the carbon nanotubes. The UV - VIS - NIR optical reflectance
spectra of CNT deposits showed two stronger reflection peaks at 1880 nm and
935 nm alongwith a weaker and broader one at 700 nm. The stronger peak is
assigned to the first and second interband optical transitions of the CNTs and the
one at 700 nm to the metallic CNTs respectively. This indicated the presence of
higher content of the semiconducting CNT bundles in the films than the metallic
CNT bundles.
The Raman Spectra generated contained the confirmative signature of the
presence of carbon nanotubes in the films obtained following Example 1. The
films showed a sharp feature 1354 cm"1 (D-Band) and 1600 cm"1 (G-Band). The
photoluminescence specter are dominated by a sharp peak centre 0.95 eV which
could be related to the band-edge transition (figure 7a and 7b).
The field emission properties of the CNTs films were further analyzed using the
Fowler Nordheim Model. The values of effective work function ( Øe = Øß) and ß
derived from FN plots of the films varied between 130-150 meV and 2000-2200
respectively for the films presented under Example 1. Thus these films obtained
following the Example 1 serve as good materials for flat panel display devices.

FTIR and ESR measurements also indicated the growth of carbon nanotubes in
the films.
lit is thus possible by way of the present invention to provide for large scale
synthesis of CNTs directly onto the wafer onto the substrates in their purest form
and very cost-effective and scalable technique. The present invention further
provides to synthesis CNTs directly onto the Si and (SnO2 coated glass
substrates) by simple electro deposition technique. Importantly, the process of
the invention apart from being scalable is also found to provide for cost
competitive coating on irregular surfaces.
WE CLAIM
1. Synthesized CNTs comprising of CNTs obtained of direct electro-
deposition in pure form on wafer/substrates.
2. The synthesized CNTs as claimed in claiml wherein the wafer/substrates
are selected from Si and Sn02 coated glass substrates.
3. The synthesized CNTs as claimed in anyone of claimsl or 2 wherein the
thickness of the CNT films deposited is 45 to 65,nm.
4. The synthesized CNTs as claimed in anyone of claimsl to 3 wherein the
carbon nonotube structures comprise interconnected single -walled
nonotube bundles in a web like network and/or multi shells comprising
multi-walled nanotubes.
5. The synthesized CNTs as claimed in anyone of claimsl to 4 wherein
diameters of the CNT bundles range from 20-30 nm for deposits on Si and
30-40 nm for deposits on Sn02 coated glass substrates.
6. The synthesized CNTs as claimed in anyone of claims 1 to 5 wherein the
carbon nanotubes deposited are aligned parallel to the substrate plane.
7. A process for synthesis of carbon nanotubes by direct electro-deposition
on substrates comprising:

- providing an electrolyting bath comprising acetonitrile (CH3CN) and
water as the selective electrolyte;
- said electrolytic bath having as one of its electrodes the substrate for
deposition of the CNTs and a graphite counter electrode;
- means to carry out electrolysis such as to deposit the CNTs directly on
to the said substrates.
8. A process for synthesis of carbon nanotubes by direct electro-deposition
on substrates as claimed in claim 8 wherein the methyl radicals and

9
hydrogen ions present in the solvent provide for the desired formation of
films by the direct deposition of CNTs on the substrate.
9. A process for synthesis of carbon nanotubes by direct electro-deposition
on substrates as claimed in anyone of claims 8 or 9 comprising :
- providing the electrolyte bath comprising acetdnitrile (CH3CN) and
water as the selective electrolyte and using a graphite anode as the
counter electrode and the substrate selected from Si wafers and Sn02
coated glass as the other cathode electrode;
- carrying out the electrolysis at atmospheric pressure and a bath
temperature of about 273K to 350 K .preferably 300K.
10. A process for synthesis of carbon nanotubes by direct electro-deposition
on Si wafer/Sn02 coated glass as claimed in anyone of claims 8 to 10
comprising :
- providing the electrolytic bath comprising acetonifrile and water as the
selected electrolyte and using a graphite anode electrode and a
selected substrate for direct deposition thereon of CNTs as the cathode
electrode;
- carrying out the electrolysis at atmospheric pressure and bath
temperatures of 273 K to 350 K .preferably 300 K in the presence of an
applied magnetic field.

11. A process for synthesis of carbon nanotubes by direct electro-deposition
on substrates as claimed in claim 11 comprising of application of
magnetic field during electro deposition for desired alignment of carbon
nanotubes and/or the growth in bunches.
12. A process for synthesis of carbon nanotubes by direct electro-deposition
on substrates as claimed in anyone of claims 8 to 12 wherein the
nanotubes are aligned parallel to the substrate surface.

10
13. A process for synthesis of carbon nanotubes by direct electro-deposition
on substrates as claimed in anyone of claims 8to 13 wherein the magnetic
field applied is in the range of 0.2 .to 1.0 K Gauss, preferably in the range
of 1 K Gauss.
14. A process for synthesis of carbon nanotubes by direct electro-deposition
on. substrates as claimed in anyone of claims 8 to 14 wherein the carbon
nanotubes are generated as a result of folding graphite layers into carbon
cylinders of single shell (single-walled nanotubes) or of multishells (multi-
walled nanotubes).
15. A process for synthesis of carbon nanotubes by direct electro-deposition
on substrates as claimed in anyone of claims 8 to 15 wherein the carbon
nanotubes are deposited preferably onto Si (wafers) resistivity
approximately 5 to 20 ohm cm preferably 15 ohm-cm ; size approx. 6 mm
to 15 mm x 6 mm to 10 mm x 0.1 to 0.4 mm preferably 10mm x 8mm x 0.3
mm and SnC>2 coated glass size approximately 8 mm to 15.mm x 6 mm .to
12 mm x 2 mm .to 5 mm preferably 10mm x 8 mm x 4mm which were
attached to a copper cathode.
16. A process for synthesis of carbon nanotubes by direct electro-deposition
on substrates as claimed in anyone of claims 8 to 16 wherein before
mounting the substrates on the cathode the same is thoroughly cleaned
and rinsed with deionized water and ethanol solution respectively.
17. A process for synthesis of carbon nanotubes by direct electro-deposition
on substrates as claimed in anyone of claims 8 to 17 wherein the
electrodes are separated by a distance of approximately 6 to 10 mm
preferably 8 mm.
18. A process for synthesis of carbon nanotubes by direct electro-deposition
on substrates as claimed in anyone of claims 8 to 18 wherein the applied
DC voltage between the electrodes is kept at 15 to 25 V preferably 20V.

11
19. A process for synthesis of carbon nanotubes by direct electro-deposition
on substrates as claimed in anyone of claims 8 to 19 wherein the
deposition is carried out for about 10-20 hours.
20. A process for synthesis of carbon nanotubes by direct electro-deposition
on substrates as claimed in anyone of claims 8 to 21 wherein the electric
field applied between the electrodes is. 15 to 25 V.
21. Synthesized CNTs and its process of manufacture substantially as
hereindescribed and illustrated with reference to the accompanying
examples and figures.

ABSTRACT
Synthesized CNTs comprising of CNTs directly electro-deposited in pure form on wafer/substrates preferably selected from Si and Sn02 coated glass substrates. Also disclosed is the selective process for synthesis of carbon nanotubes by direct electro-deposition on substrates comprising electrolyting bath involving selectively acetonitrile (CH3CN) and water as the electrolyte.
The above would provide for directly synthesized CNTs onto the wafer/substrate

which would be simple and cost-effective. The manufacture of CNTs directly onto the wafer/substrate in the purest form which would be capable of industrial use and in particular large scale synthesis of CNTs by way of a simple and cost effective process. It would thus be possible for large scale synthesis of CNTs directly onto the Si and Sn02 coated glass substrates by way of a simple and cost effective electro deposition technique which can be importantly further used to achieve coating even on irregular surfaces. Carbon nanotubes are effective for use in flat panel displays and also in strategic areas using light weight and high impact resistance coatings. The synthesized carbon nanotubes of the invention can be applied as materials for sensor applications, materials for scanning probe microscope tips and light weight high strength materials for defense and space applications.

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Patent Number

270285

Indian Patent Application Number

459/KOL/2003

PG Journal Number

50/2015

Publication Date

11-Dec-2015

Grant Date

09-Dec-2015

Date of Filing

29-Aug-2003

Name of Patentee

INDIAN ASSOCIATION FOR THE CULTIVATION OF SCIENCE

Applicant Address

JADAVPUR, KOLKATA - 700 032, STATE OF WEST BENGAL, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	ROY RITWIK K.	DEPARTMENT OF MATERIALS SCIENCE, INDIAN ASSOCIATION FOR THE CULTIVATION OF SCIENCE, JADAVPUR, KOLKATA - 700 032, STATE OF WEST BENGAL, INDIA
2	GUPTA SNIGDHA	DEPARTMENT OF MATERIALS SCIENCE, INDIAN ASSOCIATION FOR THE CULTIVATION OF SCIENCE, JADAVPUR, KOLKATA - 700 032, STATE OF WEST BENGAL, INDIA
3	DEB BISWAPRIYA	DEPARTMENT OF MATERIALS SCIENCE, INDIAN ASSOCIATION FOR THE CULTIVATION OF SCIENCE, JADAVPUR, KOLKATA - 700 032, STATE OF WEST BENGAL, INDIA
4	PAL ARUN K.	DEPARTMENT OF MATERIALS SCIENCE, INDIAN ASSOCIATION FOR THE CULTIVATION OF SCIENCE, JADAVPUR, KOLKATA - 700 032, STATE OF WEST BENGAL, INDIA
5	MANDAL SWAPAN K.	DEPARTMENT OF MATERIALS SCIENCE, INDIAN ASSOCIATION FOR THE CULTIVATION OF SCIENCE, JADAVPUR, KOLKATA - 700 032, STATE OF WEST BENGAL, INDIA

PCT International Classification Number

C01B31/02

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA