Laser Ablated Carbon Thin Film from Carbon Nanotubes and Their Property Studies

Sharon, Maheshwar,Rusop, M.,Soga, T.,Afre, Rakesh A. Korean Carbon Society 2008 Carbon Letters Vol.9 No.1

A carbon nanotube (CNT) of diameter ~20 nm has been synthesized by spray pyrolysis of turpentine oil using Ni/Fe catalyst. Pellet of CNTs has been used as a target to produce semiconducting carbon thin film of band gap 1.4 eV. Presence of oxygen pressure in the pulse laser deposition (PLD) chamber helped to control the $sp^3/sp^2$ ratio to achieve the desired band gap. Results are discussed with the help of Raman spectra, SEM TEM micrographs and optical measurements suggest that semiconducting carbon thin film deposited by PLD technique has retained its nanotubes structure except that its diameter has increased from 20 nm to 150 nm.

Development of Supercapacitors Using Porous Carbon Materials Synthesized from Plant Derived Precursors

Vilas Khairnar,Sandesh Jaybhaye,Chi-Chang Hu,Rakesh Afre,Tetsu Soga,Madhuri Sharon,Maheshwar Sharon 한국탄소학회 2008 Carbon Letters Vol.9 No.3

Porous carbon materials synthesized from various plant derived precursors i.e. seeds of [Castor (Ricinus communis), Soap nut (Sapindus sp.), Cashew-nut (Semecarpus anacardium), Jack fruit (Artocarpus heterophyllus), Safflower (Carthamus tinctorius), Ambadi (Crotolaria juncea), Neem (Azadirachta indica), Bitter Almond (Prunus amygdalus), Sesamum (Sisamum indicum), Date-palm (Phoenix dactylifera),Canola (Brassica napus), Sunflower (Helianthus annulus)] and fibrous materials from [Corn stem- (Zea mays), Rice straw (Oryza sativa), Bamboo (Bombax bambusa) and Coconut fibers (Cocos nucifera)] were screened to make supercapacitor in 5M KOH solution. Carbon material obtained from Jack fruit seeds (92.0 F/g), Rice straw (83.0 F/g), Soap nut seeds (54.0 F/g), Castor seeds (44.34 F/g) and Bamboo (40.0 F/g) gave high capacitance value as compared to others. The magnitude of capacitance value was found to be inversely proportional to the scan rate of measurement. It is suggested that carbon material should possess large surface area and small pore size to get better value of capacitor. Moreover, the structure of carbon materials should be such that majority of pores are in the plane parallel to the plane of electrode and surface is fluffy like cotton ball.

Photocatalytic Degradation of E. coli and S. aureus by Multi Walled Carbon Nanotubes

Madhuri Sharon,Suprama Datta,Sejal Shah,Mahesh War Sharon,T. Soga,Rakesh Afre 한국탄소학회 2007 Carbon Letters Vol.8 No.3

Carbon Nano Tubes could be either metallic or semi-conducting in nature, depending on their diameter. Its photocatalytic behavior has given an impetus to use it as an anti-microbial agent. More than 95% Escherichia coli and Staphylococcus aureus bacteria got killed when exposed to Carbon Nano Tubes for 30 minutes in presence of sunlight. Carbon Nano Tubes are supposed to have smooth surface on to which it accumulates positive charges when exposed to light. The surface that is non illuminated has negative charge. At the cellular level microorganisms produce negative charges on the cell membrane, Therefore damaging effect of multi walled carbon nano tubes (exposed to light) on the microorganisms is possible. In this paper, photo catalytic killing of microbes by multi walled carbon nano tubes is reported. Killing was due to damage in the cell membrane, as seen in SEM micrographs. Moreover biochemical analysis of membrane as well as total cellular proteins by SDS PAGE showed that there was denaturation of membrane proteins as well as total proteins of both the microbes studied. The killed microbes that showed a decrease in number of protein bands (i.e. due to breaking down of proteins) also showed an increase in level of free amino acids in microbes. This further confirmed that proteins got denatured or broken down into shorter units of amino acids. Increased level of free amino acids was recorded in both the microbes treated with multi walled carbon nano tubes and sunlight.

Carbon Material from Natural Sources as an Anode in Lithium Secondary Battery

Sunil Bhardwaj,Maheshwar Sharon,T. Ishihara,Sandesh Jayabhaye,Rakesh Afre,T. Soga,Madhuri Sharon 한국탄소학회 2007 Carbon Letters Vol.8 No.4

Carbon materials of various morphologies were synthesized by pyrolysis of Soap-nut seeds (Sapindus mukorossi), Jack Fruit seeds (Artocarpus heterophyllus), Date-seeds (Phoenix dactylifera), Neem seeds (Azadirachta indica), Tea leaves (Ehretia microphylla), Bamboo stem (Bambusa bambus) and Coconut fiber (Cocos nucifera), without using any catalyst. Carbon materials thus formed were characterized by SEM XRD and Raman. Carbon thus synthesized varied in size (in μm) but all showed highly porous morphology. These carbon materials were utilized as the anode in Lithium secondary battery. Amongst the various precursors, carbon fibers obtained from Soap-nut seeds (Sapindus mukorossi) and Bamboo stem (Bambusa bambus), even after 100th cycles, showed the highest capacity of 130.29 mAh/g and 92.74 mAh/g respectively. Morphology, surface areas and porosity of carbon materials obtained from these precursors were analyzed to provide interpretation for their capacity to intercalate lithium. From the Raman studies it is concluded that graphitic nature of carbon materials assist in the intercalation of lithium. Size of cavity (or pore size of channels type structure) present in carbon materials were found to facilitate the intercalation of lithium.

Laser Ablated Carbon Thin Film from Carbon Nanotubes and Their Property Studies

Maheshwar Sharon,M. Rusop,T. Soga,Rakesh A. Afre 한국탄소학회 2008 Carbon Letters Vol.9 No.1

A carbon nanotube (CNT) of diameter ~20 nm has been synthesized by spray pyrolysis of turpentine oil using Ni/Fe catalyst. Pellet of CNTs has been used as a target to produce semiconducting carbon thin film of band gap 1.4 eV. Presence of oxygen pressure in the pulse laser deposition (PLD) chamber helped to control the sp3/sp2 ratio to achieve the desired band gap. Results are discussed with the help of Raman spectra, SEM TEM micrographs and optical measurements suggest that semiconducting carbon thin film deposited by PLD technique has retained its nanotubes structure except that its diameter has increased from 20 nm to 150 nm.

Photocatalytic Degradation of E. coli and S. aureus by Multi Walled Carbon Nanotubes

Sharon, Madhuri,Datta, Suprama,Shah, Sejal,Sharon, Mahesh War,Soga, T.,Afre, Rakesh Korean Carbon Society 2007 Carbon Letters Vol.8 No.3

Carbon Nano Tubes could be either metallic or semi-conducting in nature, depending on their diameter. Its photocatalytic behavior has given an impetus to use it as an anti-microbial agent. More than 95% Escherichia coli and Staphylococcus aureus bacteria got killed when exposed to Carbon Nano Tubes for 30 minutes in presence of sunlight. Carbon Nano Tubes are supposed to have smooth surface on to which it accumulates positive charges when exposed to light. The surface that is non illuminated has negative charge. At the cellular level microorganisms produce negative charges on the cell membrane, Therefore damaging effect of multi walled carbon nano tubes (exposed to light) on the microorganisms is possible. In this paper, photo catalytic killing of microbes by multi walled carbon nano tubes is reported. Killing was due to damage in the cell membrane, as seen in SEM micrographs. Moreover biochemical analysis of membrane as well as total cellular proteins by SDS PAGE showed that there was denaturation of membrane proteins as well as total proteins of both the microbes studied. The killed microbes that showed a decrease in number of protein bands (i.e. due to breaking down of proteins) also showed an increase in level of free amino acids in microbes. This further confirmed that proteins got denatured or broken down into shorter units of amino acids. Increased level of free amino acids was recorded in both the microbes treated with multi walled carbon nano tubes and sunlight.

Carbon Material from Natural Sources as an Anode in Lithium Secondary Battery

Bhardwaj, Sunil,Sharon, Maheshwar,Ishihara, T.,Jayabhaye, Sandesh,Afre, Rakesh,Soga, T.,Sharon, Madhuri Korean Carbon Society 2007 Carbon Letters Vol.8 No.4

Carbon materials of various morphologies were synthesized by pyrolysis of Soap-nut seeds (Sapindus mukorossi), Jack Fruit seeds (Artocarpus heterophyllus), Date-seeds (Phoenix dactylifera), Neem seeds (Azadirachta indica), Tea leaves (Ehretia microphylla), Bamboo stem (Bambusa bambus) and Coconut fiber (Cocos nucifera), without using any catalyst. Carbon materials thus formed were characterized by SEM XRD and Raman. Carbon thus synthesized varied in size (in ${\mu}m$) but all showed highly porous morphology. These carbon materials were utilized as the anode in Lithium secondary battery. Amongst the various precursors, carbon fibers obtained from Soap-nut seeds (Sapindus mukorossi) and Bamboo stem (Bambusa bambus), even after $100^{th}$ cycles, showed the highest capacity of 130.29 mAh/g and 92.74 mAh/g respectively. Morphology, surface areas and porosity of carbon materials obtained from these precursors were analyzed to provide interpretation for their capacity to intercalate lithium. From the Raman studies it is concluded that graphitic nature of carbon materials assist in the intercalation of lithium. Size of cavity (or pore size of channels type structure) present in carbon materials were found to facilitate the intercalation of lithium.

Functionalization of multi-walled carbon nanotubes (MWCNTs) with nitrogen plasma for photovoltaic device application

Golap Kalita,Sudip Adhikari,Hare Ram Aryal,Rakesh Afre,Tetsuo Soga,Maheshwar Sharon,Masayoshi Umeno 한국물리학회 2009 Current Applied Physics Vol.9 No.3

Multi-walled carbon nanotubes (MWCNTs) placed under nitrogen (N2) and argon (Ar) microwave plasma in order to functionalize covalently their side walls with nitrogen containing groups. X-ray photoelectron spectroscopy (XPS) study shows surface modification of the MWCNTs with imine, amine, nitride and amide groups grafted on the side walls. Due to the functional groups, homogenous distribution of MWCNTs in solvent could be obtained. For photovoltaic device fabrication MWCNTs film was casted over n-Si wafer and poly(3-octylthiophene) solution was infiltered. Devices with functionalized MWCNTs show short circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF) and power conversion efficiency (g) as 1.8 mA/㎠, 0.20 V, 24% and 0.086%, respectively. In the composite film functionalized MWCNTs facilitate photo induced charge separation and efficient holes transportation, suppressing recombination of photo generated charges. Multi-walled carbon nanotubes (MWCNTs) placed under nitrogen (N2) and argon (Ar) microwave plasma in order to functionalize covalently their side walls with nitrogen containing groups. X-ray photoelectron spectroscopy (XPS) study shows surface modification of the MWCNTs with imine, amine, nitride and amide groups grafted on the side walls. Due to the functional groups, homogenous distribution of MWCNTs in solvent could be obtained. For photovoltaic device fabrication MWCNTs film was casted over n-Si wafer and poly(3-octylthiophene) solution was infiltered. Devices with functionalized MWCNTs show short circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF) and power conversion efficiency (g) as 1.8 mA/㎠, 0.20 V, 24% and 0.086%, respectively. In the composite film functionalized MWCNTs facilitate photo induced charge separation and efficient holes transportation, suppressing recombination of photo generated charges.

Prosthetic misfit of implant-supported prosthesis obtained by an alternative section method

Rodrigo Tiossi,Hilmo Barreto Leite Falcão-Filho,Fábio Afrânio de Aguiar, Júnior,Renata Cristina Silveira Rodrigues,Maria da Gloria Chiarello de Mattos,Ricardo Faria Ribeiro 대한치과보철학회 2012 The Journal of Advanced Prosthodontics Vol.4 No.2

PURPOSE Adequate passive-fitting of one-piece cast 3-element implant-supported frameworks is hard to achieve. This short communication aims to present an alternative method for section of one-piece cast frameworks and for casting implant-supported frameworks. MATERIALS AND METHODS Three-unit implant-supported nickel-chromium (Ni-Cr) frameworks were tested for vertical misfit (n = 6). The frameworks were cast as one-piece (Group A) and later transversally sectioned through a diagonal axis (Group B) and compared to frameworks that were cast diagonally separated (Group C). All separated frameworks were laser welded. Only one side of the frameworks was screwed. RESULTS The results on the tightened side were significantly lower in Group C (6.43 ± 3.24 µm) when compared to Groups A (16.50 ± 7.55 µm) and B (16.27 ± 1.71 µm) (P<.05). On the opposite side, the diagonal section of the one-piece castings for laser welding showed significant improvement in the levels of misfit of the frameworks (Group A, 58.66±14.30 µm; Group B, 39.48±12.03 µm; Group C, 23.13±8.24 µm) (P<.05). CONCLUSION Casting diagonally sectioned frameworks lowers the misfit levels. Lower misfit levels for the frameworks can be achieved by diagonally sectioning one-piece frameworks.