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T. PradeepDepartment of Chemistry and Sophisticated Analytical Instrument Facility

Indian Institute of Technology MadrasChennai 600 036

pradeep@iitm.ac.in

CUSAT, Cochin, September 29, 2006

mailto:pradeep@iitm.ac.in

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Alchemy

Nano

Lavoisier

Faraday

van’t Hoff Pauling

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400+ papers

Electro-magnetic rotations (1821)

Benzene (1825)

Electro-magnetic induction (1831)

The laws of electrolysis and coining words such as electrode, cathode, ion (early 1830s)

The magneto-optical effect and diamagnetism (both 1845)

Field theory of electro-magnetism

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Divided Metals, 1857

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The ruby red colour of gold colloid is due to the small size of the metal particles and not due to some peculiar state of the gold metal.

Michael Faraday

64th Century AD, RomansLycurgus Cup

Silicon dioxide in Lycurgus cup = 73%Silicon dioxide in Modern Glass = 70%Sodium oxide in Lycurgus cup = 14%Sodium oxide in Modern Glass = 15%Calcium oxide in Lycurgus cup = 7%Calcium oxide in Modern Glass = 10%

So why is it coloured? The glass contains very small amounts of gold ( about 40 parts permillion) and silver ( about 300 parts per million)

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These are the materials of tomorrow….

They offer new properties.

How any atoms are needed for metallicity?

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Photoelectron spectroscopy ofmass selected copper clusters

R. E. Smalley et. al. Phys. Rev. Lett. 64 (1990) 1785

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A magnetotactic bacterium in TEMMagnetospirillum magnetotacticum

Even nature uses nanoparticles!

11Morphology of magnetite crystals in bacteria

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1000 nm500 nm

Even buttermilk makes nanoparticles!

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The world we live: 2004

Population – 6.37 b (July 2004)Energy use – 14.93 (Trillion kWh electricity, 2001)Food – 1827 M tons (2003 estimate)

The world we live: 2050

Population – 10 bFood –Water –Air –

Why do we look at nano today?

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Most challenging problems

EnergyWaterPopulation and associated issuesLandFood and agriculturePollutionBiodiversityWeaponsDiseasesNatural calamities

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2000 1,838 1,855 -162001 1,870 1,898 -272002 1,819 1,910 -912003 1,827 1,932 -105

Food production and consumption in (Mtones)

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World EnergyMillions of Barrels per Day (Oil Equivalent)

300

200

100

01860 1900 1940 1980 2020 2060 2100

Source: John F. Bookout (President of Shell USA) ,“Two Centuries of Fossil Fuel EnerInternational Geological Congress, Washington DC; July 10,1985. Episodes, vol 12, 257-262 (1989).

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Solutions?

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Nano is THE solutionAt least for some problems…

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Very new technologies are needed

Can we reach there with our present knowledge?

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Did we reach the limits of technology?

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Our common assumptions

· Industrial development is the only alternative to poverty. · Many people must work in factories. · Greater wealth means greater resource consumption. · Logging, mining, and fossil-fuel burning must continue. · Manufacturing means polluting. · Third World development would doom the environment.

Industry as we know it cannot be replaced.

Eric Drexler and Chris Peterson, Unbounding the Future: the Nanotechnology Revolution

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· The twenty-first century will basically bring more of the same. · Today's economic trends will define tomorrow's problems. · Spaceflight will never be affordable for most people. · Forests will never grow beyond Earth. · More advanced medicine will always be more expensive. · Even highly advanced medicine won't be able to keep people healthy. · Solar energy will never become really inexpensive. · Toxic wastes will never be gathered and eliminated. · Developed land will never be returned to wilderness. · There will never be weapons worse than nuclear missiles. · Pollution and resource depletion will eventually bring war or collapse.

Technology as we know it will never be replaced

There will never be water in Chennai.

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All wrong!

We must look into history.

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The more important fundamental laws and facts ofphysical science have all been discovered, and these arenow so firmly established that the possibility of theirever being supplanted in consequence of new discoveriesis exceedingly remote .. . Our future discoveries must belooked for in the sixth place of decimals.

Albert A. Michelson 1894

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Where should we look at?

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Highest known efficiency

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Nature Technology

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Look at two technologies

What is technology? Manipulating objects

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So, why so much of fuss about nano!

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5 nm x 5 nm

HOPG

Nano tools

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Scanning tunneling microscopy (STM)

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Tip Sample-E

nergy

EFEF

Vacuum level

φ1 φ2

Extension of electronic wave function

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Vacuum levelTip

Sample

-Energy

EFEF

φ1

φ2

Overlap of electronic wavefunctionsd, gap

Vacuum level

I α exp(-2Kd)K = √(8mφ)/h

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Vacuum levelTip

-Energy

EFEF

φ1

φ2

Tip

EF

EF

φ1φ2

Vacuum level+ve

+ve- ve

- veSampleSample

Electron jumps from sample to tipprobing occupied states of the sample

Electron jumps from tip to the sampleprobing unoccupied states of the sample

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Si (111) – 7x7

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Si (111) – 7x7

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Moving atoms is possible

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Fe on Cu surface, 4 K

14.3 nm

Imaging atomsManipulating atoms

Quantum Corral

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December 29th 1959 at the annual meeting of the American Physical Society at the California Institute of Technology (Caltech) was first published in the February 1960 issue of Caltech's Engineering and Science, which owns the copyright .

``There is Plenty of Room at the Bottom''

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Gordon E. Moore observed that at our rate of technological development and advances in the semiconductor industry, the number of transistors on integrated circuits (a rough measure of computer processing power) doubles every 18 months. We should expect thatin 10 years computers will be about 100 times more powerful than they are today.

Moore’s law

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There are several other new tools

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Immunoglobin (IgG)

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There are many forms of such new materials

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• Particle size 1-100 nm (10 to 106 atoms or molecules per particle )

• Size dependent propertiesChanges in electronic band structure

So, what are nanomaterials?

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Atoms

Molecules Clusters Bulk

Atoms

Molecules Clusters Bulk

Schematic representing the cluster position between atom or molecule and bulk materials

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Fullerenes discovered, 1985 Smalley, 1985

Cyanopolyynes

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Euler’s theorem, f + v = e + 2Consider polyhedra with p pentagonal faces and h hexagonal facesF = p + h2e = 5p +6h3v = 5p + 6hThese relations yield,6(f+v-e) = 12 = pOr we must have 12 pentagons and number of heaxagons is arbitrary

1.401.46

1.40

‘Single’ and ‘double’ bonds.

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M. S. Dresselhaus, G. Dresselhaus and P. C. Eklund, Science of Fullerenes and Nanotubes, Academic Press, New York, 1995.

Time of flight mass spectrum of carbon clusters produced in a supersonic beam by laser evaporation of a graphite target.

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A high resolution TEM of Pt309 cluster

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TEM image of nanorods with an average aspect ratio of 4.1

J. Phys. Chem. 2002

54Nano Lett. 2003

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Superlattices of clusters

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Molecular shuttles

59S. Ijima, 1991

Carbon nanotubes arrive!

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Long molecule

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WS2 nanotube, scale 10 nm

R. Tenne

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Novel properties

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Delivery vehicles

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Interaction of vancomycin with Au nanoparticlesBis(vancomycin) cystamide in water

is reacted with 4 – 5 nm sized Au nanoparticles in toluene.

Au@van dissolves in the aqueous phase and can be seperated.

Nearly 31 Vancomycin molecules are bound on the surface of the Au nanoparticle as calculated from UV-Visible studies.

Control Experiment:-• Au@cys was prepared and nearly 1800 molecules of Cysteine was found to bind onto the nanoparticle surface.

• The broadness of the peak in UV-Vis studies indicated aggregation.

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Sensors

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Chem. Mater. 2003, 15, 20-28

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Gold nanoparticle capped with Zn-porphyrin complex.

Chem. Comm. 2004

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Smart, responsive materials

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Temperature dependent clear-opaque transition of the thermosensitive gold nanoparticle

JACS 2004

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New chemistry

Reduced size, large surface area, less amount of material, more reactivity

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Chlorpyriphos 50 ppb in water

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New tools make manipulations possible

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New propertiesQuantum confinement

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a

b

ab

a

b

Metal / Colloid Cluster Molecule

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Cluster size effects

Size dependent melting1871 Lord Kelvin asked “Does MP depend on size of the particle?”

1976, MP of gold was studied smallest gold melt at 300 K (Bulk 1336 K)

Variation in properties with size

Empirical scaling laws

General property, G(R) = G(∞) + a R-α Related to radiusG(R) = G(∞) + a N-β Related to number

G(R) is the property and G(∞) is the bulk limit

Ionization potential with size, K clusters.

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Schematic of plasmon oscillation for a sphere showing the displacement of the conduction electron charge cloud relative to nuclei.

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Shape dependence of the plasmon absportion

UV-Vis absorption spectrum of gold nanorods

It is not nanoparticle all the time!!

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Why do you study clusters?

Size effectsClusters are similar to surfacesNanoscience

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Quantum size effects

Variation of a generic cluster property with size

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Metal clusters

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Direct Observation of Band-Gap Closure in Mercury ClustersRam Busani, Mareike Folkers, and Ori Cheshnovsky

School of Chemistry, The Sackler Faculty of Exact Sciences, Tel-Aviv University, 69978 Israel

We have measured the photoelectron spectra of mass-selected negatively charged mercury clusters Hg-n in the size range n = 3–250. The spectra are characterized by gaps which shrink with increasing n. These gaps represent the s-p excitation band gaps of the corresponding neutral clusters. Extrapolation to higher cluster size indicates band gap closure at the size range of n = 400±30, a considerably larger value than previously reported (n = 80–100). This new evaluation indicates that previous experimental criteria for the band closure are not appropriate and calls for a refined theoretical formulation of the electronic structure of mercury clusters.

Phys. Rev. Lett. 81 (1998) 3836-3839

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500 1000 1500 2000 25000

20k

40k

60k

m/z (Da)

1000 1500 20000

2k4k6k8k

10kMo13S25

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Inten

sity (

arb.un

its)

m/z (Da)

Inten

sity (

arb.u

nits)

Mo13S28-Mo13S25

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DLDI mass spectrum of MoS2 nanoflakes in the negative mode. Inset: PSD mode DLDI mass spectrum of Mo13S25− showing no

fragmentation. (b) Mass spectrum when the laser is directed to the center where bulk MoS2 is present.

J. Phys. Chem. 2005

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What do nanomaterials offer?

Carbon nanotubes are the toughest materials known.Nanoparticle based solar cells are more efficient than conventional ones.Nanoparticles of gold are highly efficient oxidation catalysts.Nanodots are very good fluorescent dyes.Nanotubes and particles can be delivered right into the cell nuclei.Nanoparticles find their way into our food and drugs.Nanoparticle based methods can screen diseases quickly.Many nanoparticles break toxic chemicals.……..

So what?

Our clothing will have nanomaterials tomorrow.Our toothpaste, soaps and detergents already have nanoparticles.Our medicines carry nanomaterials.Future surgeries will be done by needles and will be bloodless.Our world outside is going to change with new materials and systems. Mind and matter may be linked.

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Let us look forward to that world…..Because ….

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The great Indian realities

25,00,00,000 not have enough to eat That many with not enough clothing, housing, electricity,…80,00,00,000 with not enough water

We need 91,000,000 tons of grains per year to feed the hungry

Our roads, our environment, our forests, …

If we live the way we live….the neighbours will perish.

Something needs to be done.And you must.

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I thank my students and collaborators for their hard work which made it possible to stand before you…

Thank you all.http://chem.iitm.ac.in/pradeep/home.htm

World Energy Shape dependence of the plasmon absportion