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A STUDY PROJECT

ON

NANOTECHNOLOGY

FOR SUSTAINABLEFUTURE

DURING MAY-JUNE 2009 AT IISc BANGALORE

Submitted By

ANUP MAHESH SAVALE

KVPY Reg. No. 1071213

2nd yr Integrated M.S.,

IISER, Pune.

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CERTIFICATE

This is to certify that Mr. Anup Mahesh Savale has

successfully completed the summer project on the topic

Nanotechnology for sustainable future, under my

guidance during May-June 2009.

Dr. P Balachandra

Principal Research Scientist

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ACKNOWLEDGEMNE

NT

It is my honour to express my gratitude and sincere thanks to Dr. P.

Balachandra, Principal Research Scientist, Department of

Management Studies, Indian Institute of Science, Bangalore for

giving me an opportunity to pursue my summer project under his

valuable guidance.

I further want to extend my gratitude to the Chairman,

Department of Management Studies, Indian Institute of Science for

granting me the library and the computer facilities in the department

which greatly helped me in grasping some valuable knowledge under

my belt.

Last but not the least; I want to thank my parents for theirimmense love, faith and moral support at each and every instant of my

life.

Anup Mahesh Savale

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CONTENTS

Introduction 5

Nanotechnology- A birds eye view 6

1 An insight into the global problems 8

2 Nanotechnology: A key to energy crisis 10

2.1 Advancements in fossil fuels 10

2.2 Advancements in Li batteries 11

2.3 Applications in Renewable energy utilization 12

2.3.1 Electricity generation with solar energy 13

2.3.2 Hydrogen production with solar energy 14

2.3.3 Solid state hydrogen storage 16

2.3.4 Utilization of hydrogen with fuel cells 19

3 Nanotechnology: A step towards better environment 21

3.1 Water purification 22

3.1.1 Ceramic membranes 22

3.1.2 Nanocatalysts

3.1.3 Iron remediation 24

4 Barriers to the nanotechnology advancements 25

4.1 Nano-hazards 26

4.2 Nano-regulation 27

5 Conclusion 29

References

Bibliography

Internet sources

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INTRODUCTION

In the present world, everyone one of us wants to improve our ownliving standards in the society and simultaneously wants to have a

greener habitat. We crave to earn more money but still wish to have a

hygienic environment. Basically, what we desire is nothing but

sustainability. As such, sustainability can be defined as Improving

the quality of human life while living within the carrying capacity of

supporting eco-systems. Crudely speaking, when all the three

societal, environmental and economical factors are considered fordevelopment, we are directing to sustainable development.

Efforts have been made to handle all the three factors effectively

by science and technological research, efficient management skills

and also by some law amendments i.e. introducing some new rules

and regulations along with relaxing others. None of these have

completely succeeded in giving hopes of a sustainable tomorrow. But

advancements in the field of nanotechnology have given all of us thehope of a better tomorrow. Nanotechnology is continuously being

portrayed as a force that will help to materialize ultimate solutions to

todays economical and technological problems. To put into words

the power of nanotechnology the following citation is the best.

Never before has any civilization had the unique opportunity to

enhance human performance on the scale that we will face in the

future. The convergence of nanotechnology, biotechnology,information technology, and cognitive science (NBIC) is creating a

set of powerful tools that have the potential to significantly enhance

human performance as well as transform society, science, economics,

and human evolution.[1]

NANOTECHNOLOGY- A BIRDS EYE VIEW

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The naive and direct answer to the frequently posed question what

exactly is Nanotechnology? is to say that it is a technology

concerning processes which are relevant to physics, chemistry and

biology taking place at a length scale of one divided by 100 million ofa metre. Maybe a little bit more enlightening although equally naive is

to say that nanotechnology is the art of producing little devices and

machines, somewhat at the molecular scale [2]. However the

scientific definition which I admit may be slightly involved for a non-

specialized person is to say that nanotechnology is a technology

applied in the grey area between classical mechanics and quantum

mechanics.

Classical mechanics is the mechanics governing the motion of

all the objects we can see with our naked eye. This is a mechanics

which obeys deterministic laws and which we can control to a very

far extent. For example, falling of an apple; if we know the height

from which the apple fell, we can find the time after which it will

reach the ground and also the speed at that very time. By contrast,

quantum mechanics which is the mechanics controlling the motion of

things like the electron, the proton, the neutron and the like is

completely probabilistic [I]. We know nothing about the motion of the

electron except that there is a probability that the electron may be here

or there. Even crazier than this, if we know the exact location of an

electron, it is impossible to know its speed, and if we know the exact

speed of the electron it is impossible to know its exact location. This

is well stated as the Heisenberg uncertainty principle. The question

then which poses itself is when does a classical object like an apple

or so changes its nature to a quantum object like an electron?

Somewhere between these two scales these changes happen, but this

does not happen suddenly. There is a grey area between these two

scales which is neither classical nor quantum. Theoretical physicists

call it the mesoscopic system [3]. This is what is called by non-

physicists the nanoworld. A nanosystem is therefore something which

is sufficiently small that we could not see with our naked eye and not

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even with an ordinary microscope [3]. However it is sufficiently

larger than an electron so that we can control it in principle if we have

a very fine tool to manipulate the system.

Approaching nanotechnology from another point of view,namely that of industrial production, we can say that the majority of

our industrial products are so far bulk industry or bulk production. To

produce a wooden chair, we take a large trunk of a tree and cut it

down to smaller sizes and fit these pieces together until we produce a

chair. However nature operates in a very different way. To produce

the trunk of a tree, nature grows a tree. It starts with a very small seed.

This seed has all the information needed to grow a tree. Innanotechnology, we are trying partially to imitate nature and to build

things starting with atoms. So we have moved now from the

traditional bulk industry which is wasteful and accompanied by a

great deal of pollution to the atomic scale industry which we call

nanotechnology [II].

Nanotechnology has immense potential. In fact, nanotechnology

discoveries are currently causing a domino effect of innovation acrossnearly every science and engineering field. As more and more

technologists learn the fundamentals of nanotechnology, and more

unusual nanoscale properties are understood, more powerful uses are

being imagined. Perhaps the most globally exciting nano application

is in the area of energy. Humanitys future prosperity and energy

availability, as well as the quality of the global environment, is the

most important area that will be affected by nano applications.

1. AN INSIGHT INTO THE GLOBAL PROBLEMS

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Prior to the deep investigation of the technological road of nano to

the much desired sustainable environment, I would like to first state

the problems which humanity faces today, which have to be sought

out at any cost to reach to the pleasing future.

TABLE-1*

Ranking Problem

1 Energy

2 Clean Water

3 Food4 Environment

5 Population

6 Disease

7 War/Terrorism

8 Poverty

9 Education

10 Land

(*Source: Williams, 2006)

Table 1 shows the top ten problems in front of humanity today.

As we can see energy tops the list. To justify energy crisis as the

biggest problem, I would just ask this question What would happen

if quantities of inexpensive, environmentally friendly, and widely

available energy were in abundant supply? As to everyonesagreement the answer is that it would solve a lot of societys material

problems. Solving the problem of energy, deals with the problems of

war, poverty and land issues to an extent. Another big problem is the

availability of clean water. Theres a lot of water on this planet (over

70 percent of the Earths surface, in fact), but its salty and not always

accessible. Solving this problem and energy crisis solves the problem

of food as theres a lot of arable land (land fit for cultivation) in the

world, but we dont have water to irrigate crops and energy to provide

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clean water everywhere. Simultaneously, solving the above problems

can take care of the population explosion and certainly can fulfil

needs of all the people.

Another important hurdle in our path is pollution and otherenvironmental problems. Noticeably, a lot of our environmental

problems result from the kind of energy we use, now mostly fossil

fuels, like oil, natural gas, and coal, but also wood and animal waste

for heating or cooking. These fuels produce a lot of CO2, soot, and

other atmospheric contaminants that pollute the air and are a major

cause of global warming [III].

Thus, to get the pleasure of a sustainable environment, we have

to overcome the hurdles of energy crisis and environmental problems.

Since, nanomaterials have several intriguing properties that may be

exploited for technological applications; hopes of many are tied with

them.

2. NANOTECHNOLOGY: A KEY TO ENERGY CRISIS

2.1 Advancements in Fossil Fuels

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Today about 80% of global energy use is ingrained in chemical

energy stored in fossil fuel reserves. With the increase in global

requirements of fossil fuels and our failure in keeping in pace with the

energy needs of the world; has made it necessary to maximize the profits from the available resources. Hence, improvement in the

performance of both gas and diesel engines is needed. To enable the

production of more super ultra-low emission vehicles, higher quality

fuels are needed. This requires advances in catalyst technology to:

Improve catalyst reactivity, selectivity, and yield.

Optimize and reduce active species loading levels.

Improve catalyst durability and stability under exposure to theoperating environment.

Reduce reliance on precious-metal-based and corrosive

catalysts.

Produce lower cost, less energy-intensive and more

environmentally friendly catalysts. ( *source: www.nano.gov)

In essence, catalytic processes are nanoscale because reactions take

place on the surface. An interesting property of some particularnanomaterials is their unusually high chemical reactivity. This has led

to the widespread use of metal and metal oxide nanoparticles as

commercial catalysts in the chemical and petrochemical industries.

Metal nanoparticles are also currently employed within catalytic

converters in automobiles as three-way catalysts. Three-way catalysts

catalyze the following three reactions:

Oxidation of unburned hydrocarbons

Oxidation of CO

Reduction of nitrogen oxides

Envirox, Cerium oxide containing nanoparticle is studied a lot and

it has been recognised for some time that cerium oxide could give a

cleaner burning fuel. It increases fuel efficiency only by 5% or so.

Currently research is going on to search for other nanoparticles that

can be used as catalysts. But the main problem faced is that until

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nanoparticles could be manufactured, the catalyst simply settles down

to the bottom of the gas tank. Nanoparticles are small enough to stay

in solution.

2.2 Advancements in Li Batteries

Ultra-capacitors and various batteries are getting benefitted from

moving to the nanoscale. Breakthroughs in the performance of

thermoelectrics have already occurred as a result of advancements at

the nanoscale. Lithium ion batteries have now become ubiquitous due

to their high voltage (

3.6V), high energy density and long life cycle(>1000 cycles) relative to other battery types, such as Ni-Cd, Ag-Zn,

Ni-hydride and lead acid batteries. Applications are widespread in

portable consumer electronics, including notebook computers, cellular

telephones, MP3 players and camcorders. Like other batteries, Li ion

batteries are composed of a cathode and anode separated by an

electrolyte. Significant research efforts have been undertaken to find

new materials for cathode, anode and electrolyte to improve the life

cycle and increase the energy density of the Li ion battery. Many of

these efforts have involved the development of nanomaterials, in large

part due to their higher internal surface area [4].

Nanomaterials that have been proposed as an anode material in

Li ion batteries are mainly metal nanoparticles, carbon nanotubes and

nano-composites that combine these two materials. High Li capacity

has been obtained for numerous elements, including Ag, Sn, Al, Si,

Sb, Bi and Pb, as an alternative to graphite [5]. Some of the widely

studied lithium storage materials are Sn nanoparticles and Si

nanoparticles, both of which have high storage capacity arising from

the stoichiometry Li22Sn5 and Li22Si5 respectively.

2.3 Applications in Renewable Energy Utilization

Due to excessive increase in the energy demands and the lack of

potential of current energy sources to fulfil it, has brought a pressing

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need for alternative energy sources that are both renewable and

environmentally benign. Among a limited number of options, solar

energy represents an important renewable energy resource that can be

directly converted into electricity using photovoltaic (PV) devices.Solar radiation is also a renewable energy for splitting water to

produce hydrogen, which is regarded as the cleanest transportation

fuel. The oxidation of hydrogen through the use of fuel cells generates

electricity, where water constitutes the only emission. Fuel cells

represent an effective and practical approach to convert hydrogen

produced from solar and other sources into electricity. While solar

energy is virtually inexhaustible, it is limited in the amount of the

energy that can be converted and stored for practical utilization at a

given time. In order for solar energy to be the major contributor to the

generation of electricity and clean transportation fuel (hydrogen), the

efficiencies of PV and solar water-splitting devices need to be

improved. Likewise, high performance fuel cells as well as high

capacity hydrogen-storage materials have to be realized, in order for

hydrogen to become the primary fuel for transportation systems.

Technological breakthroughs and revolutionary developments

are needed in order to achieve effective conversion, storage, and

utilization of renewable energy resources. Nanotechnology,

particularly the developments of nanoscale materials and structures,

including the methods to create them, offers a new paradigm for

realizing the goals of renewable energy research.

2.3.1 ELECTRICITY GENERATION WITH SOLAR ENERGY

Harvesting energy from sunlight using PV technology has been

considered an essential pathway to energy sustainability. Typically, a

photo-voltage is generated when light-induced excess charge carriers

in a semiconductor are separated in space, so the process is

determined by the fundamental properties of light absorption and

carrier transport of the semiconductor material. A PV device, or solar

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cell, converts absorbed photons directly into electrical charges that are

used to energize an external circuit. Large scale manufacturing of

these devices would enable a significant fraction of future energy

needs to be supplied by solar energy. Current production of PVdevices is dominated by a p-n junction type, single crystalline and

polycrystalline silicon modules termed as first-generation

technology and occupy 90% of the current market. While the second

generation technologies based on CdS, CdTe and other types of

multiple semiconductor layers are still under development, nano-

structured third generation PV technologies have gained much

attention due to their potential of achieving competitive cost/

efficiency ratios [6].

One class of nano-structured PV devices that may have

significant benefits at a low cost alternative to conventional p-n

junction type modules is the dye- sensitized solar cells (DSSC), also

known as Gratzel cell. Central to DSSC is a nano-structured network

of a wide band gap semiconductor, usually TiO2 (titanium dioxide),

which is covered with a monolayer of organic dye molecules.

Deposited on a transparent conductive oxide layer and in contact with

a redox electrolyte or an organic hole-conductor, the TiO2,

nanomaterial offers a large surface area for the adsorption of light-

harvesting molecules. While pure TiO2, absorbs light only in the UV

region, when modified with dye molecules it can absorb light in the

visible wavelengths. In addition, synthesis and modification of

various types of TiO2 nanomaterials have attracted significant

attention recently due to the improvement of material processing

techniques. For instance, ordered mesoporous TiO2 nanocrystalline

film improves the solar conversion efficiency by about 50% compared

to that of traditional films of same thickness made from randomly

oriented nanocrystals [7]. Other than nanocrystals, TiO2 nanotube-

based DSSCs are found to display higher efficiency, possibly due to

increase of electron density in nanotube electrodes.

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Various elements have been used as dopants to modify the

physical properties of TiO2 nanostructures and extend optical

absorption into the visible region. For example, it was found that TiO2

nanocrystals can take up to 8% of nitrogen atoms into the lattice,compared to 2% in thin films and micro-scale TiO2powders [8]. Such

doped nanomaterials absorb well into the visible spectrum of light as

compared to the pure TiO2 material that only absorbs in the UV

region. Additionally, the photo-current due to visible light at moderate

bias is increased to about 200 times or so compared to the case when

pure TiO2 electrodes are used [9].

Different from DSSCs, semiconductor quantum dots (QDs) based solar cells represent another category of nano-structured PV

devices. Significant progress is being made in forming 3-D arrays of

QDs. Hybrid solar cells consisting of QDs and organic

semiconductors polymers have also been reported, for example, with

CdSe QDs embedded in a hole-conducting polymer (MEH-PPV)

[10].Although the conversion efficiency of hybrid QD solar cells is

relatively low, improvements are being made over time to time.

2.3.2 HYDROGEN PRODUCTION WITH SOLAR ENERGY

Besides direct generation of electricity using PV devices, another path

of utilizing solar energy, especially for energy supply to the

transportation systems, is the production of hydrogen by splitting

water. Solar-driven water splitting through the use of photo-electrochemical (PEC) cells has many attractive features over other

hydrogen production approaches; both the energy source and the

reactive medium (water) are renewable and readily available, and the

resultant fuel product (hydrogen) as well as the emissions (water)

from the utilization of the fuel is environmentally benign.

TiO2 nanomaterials represent the most important semiconductor

catalysts for splitting water and producing hydrogen. When TiO2

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absorbs light with energy larger than its band gap, electrons and holes

are generated in the conduction and valence bands, respectively. The

photo-generated electrons and holes induce redox reactions- water

molecules are reduced by the electrons to form H2 and oxidized by theholes to form O2, leading to overall water splitting. The width of the

band gap and the potentials of the conduction and valence bands are

critical to the efficiency of solar water splitting. The bottom level of

the conduction band has to be more negative than the reduction

potential of H+/H2 (0 V vs. normal hydrogen electrode), while the top

level of the valence band has to be more positive than the oxidation

potential of O2/H2O (1.23V). The photo-catalytic characteristics of

TiO2 are strongly affected by the surface properties, such as surface

states, surface chemical groups, surface area, and active reaction sites,

as well as charge separation mobility, and lifetime of photo-generated

carriers [11].

Well-dispersed metal nanoparticles can act as mini-

photocathode trapping electrons, while addition of carbonate salts to

Pt-loaded TiO2

suspensions yields efficient water splitting. A bare n-

TiO2 nanocrystalline film electrode is actually unstable during water-

splitting reactions under illumination, but its stability could be

significantly improved when covered with Mn2O3. The overvoltage

for the evolution of oxygen is of the order 0.6eV for n-TiO2 electrodes

loaded with RuO2. The morphology of TiO2 nanomaterials affects

their photo-catalytic activities. Highly ordered TiO2 nanotube arrays

are actually found out to be able to efficiently decompose water under

UV irradiation [12].The nanotube wall thickness is actually

considered to be a key factor influencing the magnitude of the photo-

anodic response and the overall efficiency of the water-splitting

reaction.

In order to improve the efficiency of solar water splitting by

semiconductor nanostructures, it is also necessary to shift the

wavelength of light absorption away from UV (2% of sunlight) to

the visible range of the solar spectrum. A variety of dopants have

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been employed to modify the optical properties of TiO2 nanomaterial

for solar hydrogen production. Water splitting is induced with visible

light in colloidal solutions of Cr-doped TiO2 nanoparticles deposited

with ultrafine Pt or RuO2. Br and Cl co-doped nanocrystalline TiO2with the absorption edge shift to a lower energy region displays

higher efficiency for water splitting than pure TiO2.

Composite nanostructured semiconductors have also been

developed for visible-light water-splitting. A self-driven system for a

water-splitting reaction under illumination was achieved with the

combination of single crystal p SiC and nanocrystalline n-TiO2

photo-electrodes [13]. A nanocomposite polycrystalline Si/ dopedTiO2 solar water-splitting structure was proposed for high efficiency

and low cost by combining the advantages of Si and doped TiO2. An

n-Si electrode with surface alkylation and metal nanoparticle coating

offers an efficient and stable PV characteristic, and TiO2 doped with

other elements, such as nitrogen and sulphur, could induce water

photo-oxidation (oxygen photo evolution) by visible light

illumination. A high solar-to-chemical conversion efficiency of more

than 10% was predicted for such a system [14].

2.3.3 SOLID-STATE HYDROGEN STORAGE

Among the various alternative energy strategies is the building of an

energy infrastructure that uses hydrogen as the primary energy carrier.

The energy produced by the Sun can be converted, stored, anddistributed in the form of hydrogen. A major challenge to realizing

hydrogen economy is the development of high capacity and safe

hydrogen-storage materials. In general, hydrogen may be stored in the

form of pressurized gas, liquefied hydrogen, or can be chemically or

physically bonded to a suitable solid-state material. Of the three

hydrogen-storage approaches, solid-state storage has the highest

volumetric density of hydrogen. While gaseous and liquid state

storage requires extremely high pressure or low temperature, solid

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state hydrogen-storage materials could store hydrogen at near-ambient

temperatures and pressures. Particularly for transportation

applications, storing pressurized or liquefied hydrogen requires a

large footprint container that is not only a safety concern but alsoeasily takes up a significant fraction of space in the vehicle.

Therefore, solid-state storage is potentially the most convenient and

the safest method for storing and distributing hydrogen for

transportation systems.

The use of nanostructured solid-state materials serves multiple

functions; they improve the kinetics by increasing the diffusivity,

reducing the reaction distance, and increasing the reaction surfacearea. The fundamental mechanisms for solid-state hydrogen storage in

nanomaterials include chemisorption and physisorption [11].

Chemisorption starts with dissociation of hydrogen molecules and

chemical bonding of the hydrogen atoms by integration in the lattice

of a solid material, e.g. metal hydrides. This process inherently

involves large enthalpy changes and normally requires high operation

temperature and a catalyst for fast hydrogen uptake and release. In

contrast, physisorption mainly involves the adsorption of hydrogen

molecules on the surface of nanomaterials through weak

intermolecular forces- the van der Waals interaction. As a

consequence, the force is less material specific compared to the case

of chemisorption. Since the Van der Waals forces between the

hydrogen molecule and the surface is in the lower kJ mol-1 range, it is

necessary to apply low temperatures to achieve a sufficient amount of

adsorbed hydrogen. Nevertheless, release of physiosorbed hydrogen

can be fast because of the weak molecular forces.

The ideal material for hydrogen storage would achieve a

compromise between having the hydrogen too weakly bonded to the

storage material, resulting in a low storage capacity at room

temperature and too strong a bonding, thus requiring high

temperatures to release the hydrogen. Solid-state nanomaterials

currently being investigated for hydrogen storage include carbon

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nanomaterials, metal-organic frameworks, and nanocrystalline metal

and complex hydrides, among others.

Physisorption of hydrogen molecules in nanostructured

materials has been explored extensively; examples include variousforms of carbon, clathrates, and metal-organic frameworks.

Significant storage capacity was initially reported for hydrogen

storage using carbon nanotubes [15]. Later investigations suggested

that desorption of hydrogen appear to originate from Ti alloy particles

introduced during the ultrasonic treatment rather than from the CNTs.

For hydrogen chemisorption, the most studied materials are

metal hydrides and related complex hydrides. Small hydrogen atoms

can readily enter the interstitials of many metals and alloys to form

hydrides. Since a high weight fraction of hydrogen in the solid-state

hydrogen-storage materials are required for practical transportation

system applications, research to enhance the hydrogen capacity in

metal hydrides has been focussed on those based on light weight

elements such as magnesium.

A complete class of nanostructured all-inorganic materials, the

nanoporous metal inorganic (oxide) networks, for solid-state

hydrogen storage has been developed. The nanoporous metal-

inorganic materials have a linked 3-D network of M: SiO2 and similar

nanostructures that include a monolayer or nanoparticles of

metal/alloys (denoted M), implemented into a nanoporous oxide

network. Current research is focussed on the particular nanoparticles

of M which provides maximum storage capacity for solid-state

hydrogen.

2.3.4 UTILIZATION OF HYDROGEN WITH FUEL CELLS

One effective way to use chemical energy stored in hydrogen is to

directly convert it into electricity through the use of a fuel cell. Fuel

cells harness the chemical energy of hydrogen to generate electricity

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without combustion and pollution. The development of fuel cells as a

clean, environmentally friendly energy source is widely anticipated.

The use of hydrogen as a fuel is particularly attractive, since the main

product produced would be water, with effectively zero emissions.Even the economical use of other hydrocarbon fuels beyond petrol,

diesel and CNG may have global benefits, as this may reduce the

demands for hydrocarbon fuels.

Fuel cells operate by converting chemical potential energy

directly into a current or voltage by coupling an electrochemical

oxidation reaction with an electrochemical reduction reaction. There

are numerous number of fuel-cells formed till date. Some of them are: proton exchange membrane, direct methanol, molten carbonate,

phosphoric acid and solid oxide fuel cells.

High-temperature fuel cells such as molten carbonate, solid

oxide and phosphoric acid fuel cells have recently been employed for

several applications, particularly those where waste heat can be

employed to reach and maintain the operating temperature. For e.g.

waste heat is widely generated throughout industrial chemical plants,sometimes making fuel cells an economical energy source. At the

operating temperature of these fuel cells, the anode and cathode

reactions are typically fairly facile, making the use of electrocatalysts,

which are often in the form of nanoparticles, unnecessary. In addition,

nanomaterials may subject to grain growth, sintering, dissolution and

other unwanted chemical reactions at high temperature.

On the other hand, nanomaterials are much more compatible

with low temperature fuel cells, which are needed for many

transportation and consumer applications where intermittent operation

is typical and power requirements are relatively modest. The most

common low temperature fuel cells are the polymer electrolyte

membrane fuel cell (PEMFC) and the direct methanol fuel cell

(DMFC), where the following reactions occur:

Anode (PEMFC): H2 2H+ + 2e-

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Anode (DMFC): CH3OH + H2O CO2 + 6H+ + 6e-

Cathode (PEMFC and DMFC): O2 + 4H+ + 4e- 2H2O

When considering the use of nanomaterials in fuel cells, manyobservers would first consider the use of nanoparticle catalysts in both

anode and cathode. Hydrogen reduction takes place at the anode of a

PEMFC. This process is most facile due to its simple reaction

mechanism and Pt nanoparticles are widely used as electrocatalysts

for this reaction. The main problem is that Pt catalysts can be easily

poisoned by trace CO in the H2 fuel, and so far the best performance

has been attained by PtRu bimetallic nanoparticle catalysts, preferably

with a 1:1 ratio of Pt: Ru, that facilitate CO desorption. Ternary and

quaternary catalysts have also been widely investigated in laboratories

[IV]. The methanol reduction at anode of DMFC and O2 reduction at

cathode of both DMFC and PEMFC, involve more complex

mechanisms and multi-step electron transfer, making electrocatalysts

more difficult. O2 Reduction is most facile on Pt nanoparticle

catalysts, and the use of Pt alloys with transition metals such as Co,

Cr, Ti and Zr has been thoroughly investigated. Similarly, methanoloxidation has been widely studied on Pt nanoparticle catalysts alloyed

with a wide variety of different transition metals, including Ru, Os

and Sn. Given that the expensive Pt catalyst contributes significantly

to the overall fuel cell cost, non-Pt catalyst materials are also under

intensive investigation for both PMFCs and DMFCs [16]. However,

Pt and its alloys in nanoparticle form remain the best catalysts for the

reactions in low-temperature fuel cells. [IV]

In addition to this, carbon nanotubes and carbon nanofibres have

been widely investigated for possible application into the catalyst

supports for the operating PEMFCs and DMFCs [17]. The main

improvement that is envisioned is increased utilization for the Pt

catalyst supported on carbon nanotubes. Currently, for long term

usage and better commercialization of both PEMFCs and DMFCs,

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catalyst agglomeration, catalyst dissolution and carbon corrosion are

the primary barriers from which the researchers want to get rid of.

3. NANOTECHNOLOGY: A STEP TOWARDS BETTER

ENVIRONMENT

Environment is one of the pillars of sustainability. We all have to take

care of it. It is our responsibility to keep it clean and healthy.

Sometimes it seems that the ills of the environment are too big to

handle. Some people give up in the face of these looming giant

problems. However, nanotechnologists believe that this difficult taskcan be accomplished with the help of nanotechnology. The design and

manipulation of atomic and molecular scale materials offers great

possibilities for environmental cleanup. Unique properties of new

nanoscale materials can produce advances in cleaner energy

production, energy efficiency, water treatment, and environmental

remediation. Researchers are trying to determine how different kinds

of environmental contaminants bind to or could be transported withnanomaterials through groundwater systems or how cell

interactions/toxicity might occur.

3.1 Water Purification

As the population of the world is increasing at a rapid pace we require

greater volumes of potable water for both drinking and agriculture

purpose. Thus, the needs for better purification methods have become particularly important. The use of nanomaterials may offer big

improvements to existing water purification techniques and materials

and may well bring about new ones. Furthermore, nanomaterials have

the potential supplying water treatment and purification in remote

areas where electricity is not available.

Engineered nanomaterials are a new class of materials, relatively

unknown to most environmental engineers and water treatmentworkers. However, this is changing. With more and more research on

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safe, improved, low-cost, and efficient ways to treat water, general

water treatment methods will begin to change, too.

3.1.1 CERAMIC MEMBRANES

Membranes and filters of all sizes are used to separate various

compounds and chemicals. Depending on their properties, they have

greater or lesser success. In ultrafiltration, pressure pushes against one

side of an ultrafiltration membrane, forcing water and low molecular

weight compounds through its pores. Larger molecules and suspended

solids move across the membrane, getting more concentrated as they

are blocked because of their larger size.

Centre for Biological and Environmental Nanotechnology

(CBEN) researchers at Rice University have developed a reactive

membrane from iron oxide ceramicmembranes (ferroxanes). Due to

irons unique chemistry, these reactive membranes provide a platform

for removing contaminants and organic waste from water and

cleaning them up. Ferroxane materials have even been found to

decompose the contaminant benzoic acid [III].When using aluminium oxide ceramic membranes (alumoxanes)

as the ceramic nanomembrane material, membrane thickness, pore

size scattering, permeability, and surface chemistry can be altered by

changing the first layering of alumoxane particles. Membrane thermal

properties can be changed to create a range of pore sizes.

Nanostructured ceramic membranes treat and purify water both

actively and passively. Ceramic membranes could be placed inlinewithin conventional treatment systems for final cleaning of polluted

water and air.

3.1.2 NANO CATALYSTS

Although nanofiltration membranes are important in water

purification, nanoparticles either in solution or attached to membranes

can help ensure that pollutants chemically degrade and dont just

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travel somewhere else. Nano-catalysts are currently being studied for

their environmental applications. Catalytic treatments can lower

polluted water treatment costs by making it possible for purification

methods to be specifically designed to treat chemicals at a particularsite.

Dr. Daniel R. Strongin, chemistry professor at Temple

University in Philadelphia, has used protein structures to design and

assemble metal oxide nanoparticles that could be used in

environmental remediation. By using nanoparticles made from

biological components as nanocatalysts, Strongin and others have

been looking at how nanoparticles may be used in environmentalremediation (cleaning up polluted areas). Reactions that would make

polluting metals clump or separate out of solution so they arent

transported downstream or soak into groundwater are also studied

[III].

3.1.3 IRON REMEDIATION

Wei-Xian Zhang of Pennsylvanias Lehigh University has shown the

potential of iron nanoscale powder that is able to clean up soil and

groundwater previously contaminated by industrial pollutants.

Iron, one of the most abundant metals on Earth, thus might prove to

be the cleaning agent of various contaminated industrial sites,

underground storage tank leakages, landfills, and abandoned mines.

The answer seems to come from the fact that iron oxidizes easily andforms rust. However, when metallic iron oxidizes around

contaminants such as trichloroethylene, carbon tetrachloride, dioxins,

or PCBs, these organic molecules are broken down into simple, far

less toxic carbon compounds. Similarly, with toxic heavy metals such

as lead, nickel, mercury, or even uranium, oxidizing iron reduces

them to an insoluble form that is locked within the soil, rather than

being mobile, so they could become part of the food chain and their

impacts could be more widespread. Since iron has no known toxic

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effect and is plentiful in rocks, soil, water, and nearly everything on

the planet, several companies now use a ground iron powder to clean

up their industrial wastes before releasing them into the environment.

This is great for new wastes, but wastes that have already soaked intothe soil and water must be taken care of as well. Here we use the

nanoscale iron particles which are 10 to 1000 times more reactive

than commonly used iron powders. Smaller size also gives nano-iron

a much larger surface area, allowing it to be mixed into slurry and

pumped straight into the centre of a contaminated site, like a giant

injection. Upon arrival, the particles flow along with the groundwater,

decontaminating the environment as they go [IV].

Iron particles are not changed by soil acidity, temperature, or

nutrient levels. Their size (1100 nm in diameter and 101000 times

smaller than most bacteria) allows them to move between soil

particles. Laboratory and field tests have shown that nanoscale iron

particles treatment drops contaminant levels around the injection well

within a day or two and nearly eliminates them within a few weeks,

bringing the treated area back into compliance with federal

groundwater quality standards [V]. Results have also indicated thatthe nanoscale iron stays active in the soil for six to eight weeks before

the nanoscale particles become dispersed completely in the

groundwater and become less concentrated than naturally occurring

iron. This method is also a lot cheaper than digging up contaminated

soil and treating it a little at a time, as has been done in the past at

highly polluted sites.

4. BARRIERS TO THE NANOTECHNOLOGY

ADVANCEMENTS

Technology cuts both ways is a phrase commonly associated to

almost every technology. Nanotechnology is not an exception to this.

Signs of nanotechnologys continuing maturation abound. Most

experts focus on the continuing surge in nanotechnology research anddevelopment (R&D). Perhaps most surprising is the fact that

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nanotechnology commercialization is moving forward at a lightning

speed. Thousands of tons of nanomaterials are already being produced

each year. The nanomaterials now being manufactured, marketed and

purchased are inevitably finding their way into the naturalenvironment. Entry can occur accidentally or intentionally over the

course of a nanomaterials lifecycle, during manufacturing,

transportation, use, recycle, or disposal. The current wave of nano-

products includes an inordinate number of sunscreens, cosmetics, and

other personal care products, as the personal care industry is the

leading sector in the manufacturing and marketing of nano-products.

These products enter the environment via the household waste

streams and other nanomaterials, such as those used in electronics,

fuel cells, and tires, will be worn off or leak out over a period of use

or after product disposal. Still other nanomaterials will reach the

environment through landfills or other methods of disposal (e.g.

residual sunscreens or cosmetics in containers). Finally, some

nanomaterials may be introduced deliberately into the natural

environment for environmental remediation purposes. For example, I

have earlier indicated that iron nanoparticles could be used to clean upcontaminated soil by neutralizing contaminants (e.g. DDT and

dioxin). As many industries involved in nanotechnology expand, and

increase in number and variety of nano-enhanced products available;

both industrial and domestic nano-waste will also logically increase in

quantity [VI].

4.1 Nano-Hazards

Humans and animals have been encountering naturally

occurring nanomaterials for millions of years. Nature produces some

nanoparticles, like salt nanocrystals found in ocean air or carbon

nanoparticles emitted from fire. Thus, one could feel that there is no

danger as such in the nanoscale. However, it is only recently that

scientists have developed the techniques for synthesizing and

characterizing many new materials with at least one dimension on the

nanoscale. The concern is that nanomaterials now in development are

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different than anything that exists in nature. The materials engineered

or manufactured to the nanoscale can exhibit different fundamental

physical, biological and chemical properties from bulk materials of

the same substance. Just as the size and physics properties ofengineered nanoparticles can give them exciting properties, those

same new properties- tiny size, high surface area/volume ratio; high

reactivity- can also create unique and unpredictable human health and

environmental risks. Swiss insurance giant Swiss Re noted that:

Never have before the risk and opportunities of new technology been

as closely linked as they are in nanotechnology. It is precisely those

characteristic which make nanoparticles so valuable that give rise toconcern regarding hazards to human beings and environment

alike.[VI]

These new properties create numerous human health risks. For

starters, due to their size, nanoparticles have unprecedented mobility:

they are more easily taken up by the human body and can cross

biological membranes, cells, tissues and organs more efficiently than

larger particles. Once in the blood stream, nanomaterials can circulatethroughout the body and can be taken up by the organs and tissues,

including the brain, kidney, liver, heart, bone marrow, spleen and

nervous system. When inhaled, they reach all regions of the

respiratory tract, and can move out of it via different pathways and

mechanisms. When in contact with the skin, there is an evidence of

penetration of the dermis and subsequent translocation via the lymph

nodes .When ingested, systematic uptake can occur [V].

Second, the change in the physicochemical and structural

properties of engineered nanoparticles can also be responsible for a

number of material interactions that can lead to toxicological effects.

Once inside the cells, they can interfere with the cell signalling, cause

structural damage and cause harmful damage to DNA. There is a

dependant relationship between size and surface area and nanoparticle

toxicity; as particles are engineered smaller on the nanoscale, they are

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more likely to be toxic [V]. Many relatively inert and stable chemicals

(e.g. carbon) pose toxic risk in their nanoscale form.

4.2 Nano-Regulation

Due to over publicity and hype of the term nano, everyone is having

an eye on the advancements in nanotechnology. Nanotechnology

though being touted as the future solution for almost all our

technological requirements, has to be assessed carefully and with

regard to safety, health and environmental issues so that we do not

repeat the mistakes made in the past with regards to asbestos andCFCs. [18]

However, there is no universal assessment of nanotechnologys

risks or of its hazards and opportunities. Nano-products, materials,

applications and devices are governed today within the existing

framework of statutes, laws, regulations and policies. The main

question is whether current regulatory controls are adequate to meet

the many concerns posed by the ability of nanotechnology to createproducts whose structures, devices and systems have novel properties

and structures because of their size. This question still remains

unanswered [VI]. Yet, the most pressing issue may be not in the

creation of new, but in the enforcement of old, regulations on the

industries that create and process these new materials.

Advocating for regulation of nanotechnological innovation with

yet uncertain and inconclusive demonstrated risks, without clearly

understanding how the regulatory system are designed to work,

dilutes the very purpose for which they were intended while

simultaneously impairing the progress of transformative, disruptive,

emerging, converging or enabling technologies [VI].

How can one regulate something that cannot be seen, and that is

not even here yet? Even more, why impose such an unnecessary

restraint on its advance and choke the very opportunities

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nanotechnology may present? Ultimately, will promulgating

regulation diminish that alleged risks, produce different risks, deprive

the end users of expected benefits, or simply silence the political

reaction of the nano-twisting activists?To reduce uncertainties and ensure a sustainable introduction of

nanotechnology, efforts must be made to establish a common

discussion platform that facilitates an open dialogue on risk analysis,

risk management, and acceptable options for risk transfer.

5. CONCLUSION

There is no doubt that nanotechnology-enabled environmental

remediation and renewable energy technologies are starting to scale

up dramatically. As they become mature and cost effective in the

decades to come, we will have a greener environment and then

eventually renewable energy could replace the traditional,environmentally unfriendly, fossil fuels; thus providing us a

sustainable environment to live in.

However, these developments are only at the beginning stage

and the insecurity that is connected with the production of these new

materials currently outweigh their possible advantages. The optimal

commercial use of nanotechnology is crucially dependent on cross-

disciplinary dialogue, which should address the full scope of the twosides of the risk: potential hazards and inherent opportunities. As

unexpected losses can destroy economic investments, far-sighted

thinking is necessary. I personally, think that the principal prerequisite

for successful risk assessment in a technology as multifaceted as

nanotechnology is finding a harmony among the industry

representatives, policy makers, and research institutes concerned. It is

one that must extend across national borders, regulatory

discrepancies, and different perceptions of risks and benefits.

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Summing up, Nanotechnology is a field where neither the

probability nor the extent of potential benefits and losses can be

calculated precisely. To analyse these benefits and to measure those

against their possible losses along with providing a crystal clearpicture before everyone still seems to be a huge challenge in front of

us.

REFERENCES:

PAPERS:

1. Canton J. Designing the future: NBIC technologies and human

performance enhancement. In Roco M.C and Montemagno

C.D. The co-evolution of human potential and converging

technologies New York: Annals of the New York Academy of

Sciences; 2004.pp. 186-198.

2. Drexler KE.Engines of creation. Fourth Estate, London, 1990.

3. Ando.T et al .1998. Mesoscopic physics and electronics

Heidelberg: Springer

4. Liu H.K, Wang G.X, Guo.Z, Wang.J, Konstantinov.K.2006

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TiO2 films exhibiting greatly enhanced performance in DSSC.

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8. Chen et al . 2005b. Formation of oxynitride as the

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9. Lindgren et al . 2003. Photoelectrochemical and optical

properties of nitrogen doped TiO2 films prepared by reactive

DC magnetron sputtering. Journal of Physical Chemistry

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renewable energy applications.Int. J. Energy Res. 31:619.

12.Mor et al. 2005. Enhanced photocleavage of water using

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hydrogen in p-SiC/Pt and p-SiC/n-TiO2. Int. J. Hydrogen

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14.Takabayeshi et al. 2004. A nano-modified Si/TiO2 composite

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Photobiol. 166:107.

15.Dillon et al. 1997. Storage of hydrogen in SWNTs. Nature386:377.

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18.Hansen H.F, Maynard .A, Baun.A, Tickner.J.A. 2008. Nature

Nanotechnology 3:444.

BOOKS:

I. Ball P. (1994) Designing the molecular world, New Jersey:

Princeton.

II. Foster LE. (2006)Nanotechnology,New York: Prentice Hall.

III.Williams L. (2007). Nanotechnology Demystified, Tata

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IV.Krug HF (2008). Nanotechnology: Environmental aspects

Vol.2, John Wiley and sons.

V. Kumar C. (2006). Nanomaterials-Toxicity, Health and

Environmental Issues, John Wiley and sons.VI.Cameron NMS, Mitchell M.E., (2007) Nanoscale: Issues and

perspectives for the Nano Century, John Wiley and sons.

INTERNET REFERENCES:

1.

Wikipedia: www.wikipedia.org2. National Nanotechnology Initiative: http://www.nano.gov

3. Nano Science and Technology Institute: http://www.nsti.org

4. EnvironmentalChemistry.com site on periodic table:

http://environmentalchemistry.com/yogi/periodic/Pb.html

5. National Institute of Standards and Technology:

http://www.nist.gov

6. Environmental Protection Agency Nanotechnology page:

http://es.epa.gov/ncer/nano

7. National Centre for Environmental Research:

http://es.epa.gov/ncer/publications/nano/index.html

8. Department of Energy, Energy Efficiency and Renewable

Energy: http://www.eere.energy.gov

9. Richard E. Smalley Institute for Nanoscale Science and

Technology at Rice University: http://www.cnst.rice.edu

10. Small Times news: http://www.smalltimes.com

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