G. R. Ahmed Jamal

Generation of usable electric power from available random sound energy

In this work, a relatively less explored source of green energy is proposed. Random sound energy around us can be treated as a source of electric power after their efficient conversion using suitable transducer. An effective way of producing usable electric power from available random sound energy is presented here. Piezoelectric transducers are used for conversion of sounds into electric energy. The produced electric energy from multiple piezoelectric transducers are stored in multiple supercapacitors which are then summed up and amplified through adder and voltage multiplier circuits. The resultant electric power was used to charge a rechargeable DC battery so as to store this energy. A small 9 volt DC battery was found to be fully recharged within half an hour from fully discharged stage using medium sound source through the proposed conversion circuit. In this way, random sound energy from numerous sources around us can be stored as electric energy which can be used later to deliver electric power to drive compatible small loads. The proposed idea can give a new source of green energy and can contribute in global search for renewable energy.

A novel battery charger operated from random sound sources or air pressure

Design and implementation of a novel cell phone charger using renewable energy is reported in this work. Conventional cell phone charger takes main line ac source as input, then rectify it and step it down to charge the battery. The cumulative power taken per day from the main line by all the mobile phone users over the world or in a single country is not a small amount. So, if there is alternative way of charging mobile batteries, a significant amount of power can be saved. Here, random sound energy or air pressure is proposed as a new source of renewable energy which can be easily used to charge a mobile phone battery through suitable energy conversion circuit. Piezoelectric material is used here as the transducer to convert sound energy or air pressure into electric energy. The produced electric energy is then processed through simple circuit to make suitable output which can directly charge any commonly used cell phone battery. The proposed set up is simple, portable and especially useful in rural areas where there is no electric power at all. It is also helpful during natural disaster when electric power may not be available in a particular area. The performance of the circuit for different frequencies of sound was tested. Some ways to improve the overall performance of this circuit were also prescribed.

Chirality Dependence of Gas Adsorption Property of Single Wall Carbon Nanotubes

In this work, effect of chirality on gas adsorption property of semiconducting single-wall carbon nanotubes (SWCNTs) is reported for the first time. First principles simulation of the interaction of three different chirality SWCNTs with different gas molecules is performed maintaining equilibrium tube–molecule distance. Results are obtained employing density functional theory, using the Atomistic toolkit simulation package (ATK-DFT). Nanotube density of states is observed to vary significantly due to interaction with different types of gases as well as for same gas if chirality of SWCNTs varies. The most significant finding is, the change in DOS near Fermi level is highest in mod 2 type semiconducting SWCNT for different gas molecules irrespective of donor or acceptor. Thus, proper selection of chirality of SWCNT is important to make nanotube based gas sensor and mod 2 types semiconducting SWCNTs should get preference over mod 1 type as a sensing element so as to get better sensitivity.

An Improved Technique for Chirality Assignment of SWCNTs Exploiting their (2n+m) Family Behavior

In this work, an improved technique for chirality assignment of single wall carbon nanotubes (SWCNT) is proposed which work for both isolated and bundles SWCNTs. The technique exploits the (2n+m) family pattern both in optical transitions vs diameter plot and Raman G-mode frequency vs diameter plot of SWCNTs. Using two different plots can give accurate value of the family of unknown SWCNTs that can be used to find chiral index (n, m) of unknown SWCNT unambiguously in most of the cases. Unlike existing methods, graphical comparison or pattern recognition with an existing Kataura plot is not required here. Chirality of 13 SWCNTs are assigned here using this technique. Validity of assigned chirality is cross checked from previous experimental reports. The technique is especially useful for determining chirality of isolated SWCNT.

Many body corrections for higher optical transitions in semiconducting SWCNTs

In this work, Coulomb effect on determining optical transition energies of semiconducting single wall carbon nanotubes is discussed. Due to their quasi-one-dimensional structure, electron-electron and electron-hole interaction and corresponding self energy and exciton binding energy are important in SWCNTs and the difference between these two energies gives many body effect. Here, at first, a brief review of nature of correction in the conventional single particle electronic picture of SWCNTs to include many body effect in first four optical transitions is presented. Then, many body corrections needed for next three higher optical transitions i.e. 5th, 6th and 7th transitions of semiconducting SWCNTs are investigated. Experimental values of these higher transitions are collected from recent experimental reports so as to explain those data by extending single-particle picture corrected for nanotube curvature and chirality effect along with many body corrections. Our result shows that these three transitions excellently follow the proposed corrected picture with less than 0.5% average absolute error which proves that excitonic behaviour is strong in 5th, 6th and 7th optical transitions of semiconducting SWCNTs unlike 3rd and 4th transitions as reported in some recent works.

Chirality dependence of Single Wall Carbon nanotube based gas sensor

In this work, effect of chirality on gas sensing property of semiconducting single-wall carbon nanotubes (SWCNTs) is reported for the first time. First principles simulation of the interaction of three different chirality SWCNTs with different gas molecules is performed maintaining equilibrium tube-molecule distance. Results are obtained employing density functional theory, using the Atomistic toolkit simulation package (ATK-DFT). Nanotube density of states is observed to vary significantly due to interaction with different types of gases as well as for same gas if chirality of SWCNTs varies. The most significant finding is, the change in DOS near Fermi level is highest in mod 2 type semiconducting SWCNT for different gas molecules irrespective of donor or acceptor. Thus, proper selection of chirality of SWCNT is important to make nanotube based gas sensor and mod 2 types semiconducting SWCNTs should get preference over mod 1 type as a sensing element so as to get better sensitivity.

Empirical prediction of optical transitions in metallic armchair SWCNTs

In this work, a quick and effective method to calculate the second and third optical transition energies of metallic armchair single wall carbon nanotubes (SWCNT) is presented. In this proposed method, the transition energy of any armchair SWCNT can be predicted directly just by knowing one of its chiral index. The predicted results are compared with recent experimental data and found to be accurate over a wide diameter range. The empirical equation proposed here is also compared with that proposed in earlier works. The proposed way may help the research works or applications where information of optical transitions of armchair metallic nanotubes is needed.