Here - Physics - Indian Institute of Science

WORKSHOP PROGRAMME
Monday January 9
8:30 - 9:30 Registration
9:00-9:30 Inauguration
Hybrid and coherent coupling in nanostructures
9:45-10:45 Prof. Gregory Salamo, Coherent Coupling between Quantum
Dots and a Quantum well
10:45-11:15 Break(Tea/coffee)
11:15-12:15 Dr. Sushil Mujumdar, Coherent optical emission from a
disordered nanostructured amplifier
12:15-13:15 Dr. Stephen Gray, Optical Interactions of Metal
Nanoparticlesand Quantum Dots
13:15-14:15 Lunch
Nanophotonics
14:15-15:15 Prof. Galina Khitrova, Quantum Metaphotonics
15:15-16:15 Poster Session, Tea/Coffee
16:15-17:15 Prof. S. K. Ray, Silicon based Nanophotonic Devices
Tuesday January 10
Molecule-plasmon coupling and sensor approaches
9:30- 10:30 Prof. Lasse Jensen, Understanding the molecule-plasmon
coupling
10:30-11:30 Prof. D. N. Rao, Preparation of Metal Nanoparticle Deposited
Substrates for SERS and Optical Limiting Studies
11:30-12:00 Break (Tea/Coffee)
12:00-13:00 Prof. N. R. Jana, Gold Nanoparticle based Hybrid Cellular Probe
with Multifunctional Properties
13:00-14:00 Lunch
Optical properties of complex systems
14:00-15:00 Prof. S. Anantha Ramakrishna, Broadband extra-ordinary
transmission of light in plasmonic nano-checkerboards
15:00-16:00 Poster Session,Tea/Coffee
16:00-17:00 Prof. Prashant Kamat, Excited State Interactions of Graphene-
Metal Nanocomposites
19:00- Conference Dinner

Wednesday January 11
Exciton-Plasmon Interaction and Chiral plasmonics
9:30- 10:30 Prof. George K. Thomas, Coupled and Chiral Surface Plasmons
in Metal Nanostructures
10:30-11:30 Prof. Alexander Govorov, Optically-active hybrid
nanostructures: Exciton-plasmon interaction, Fano effect, and
plasmonic chirality
11:30-12:00 Break (Tea/Coffee)
12:00-13:00 Prof. J. K. Basu, Exciton plasmon interaction in hybrid nano
assemblies
13:00-14:00 Lunch
Self-assembled nanostructures and Nanophotonics
14:00-15:00 Prof. R. Vijaya, Spontaneous and stimulated emission from selfassembled
photonic structures
15:00-16:00 Poster Session, Tea/Coffee
16:00-17:00 Dr. G.Vijaya Prakash, Template-assisted and naturally selfassembled
nanophotonic structures
Thursday January 12
Optical properties and Solar applications of nanostructures
9:30- 10:30 Dr. Victor Klimov, How Nano Can Help Solar
10:30-11:30 Prof. Amitava Patra, Design and Development of Metal-
Nanoparticles Based Energy Transfer
11:30-12:00 Break (Tea/Coffee)
12:00-13:00 Prof. D. D. Sarma, Optical properties of complex semiconductor
nanocrystal and their internal structures
13:00-14:00 Lunch
Optical properties and Solar applications of nanostructures (continued)
14:00-15:00 Dr. Gary Wiederrecht, Cavity-mode and plasmonic
enhancement of solar energy concentration and conversion
15:00-15:30 Tea/Coffee
Contributed Talks
15:30-16:00 Dr. Debansu Chaudhuri (Contributed Talk),Long-range exciton
migration in H-aggregated molecular nanowires
16:00-16:30 Dr. Sameer Sapra (Contributed Talk),The importance of surface
for semiconductor
16:45-17:45 Panel Discussion/Concluding Session
January 13
Excursion to Mysore

Invited Talks

T01
Coherent Coupling between Quantum Dots and a Quantum well
Gregory J. Salamo
Department of Physics, University of Arkansas, Physics Building,
Fayetteville, AR, 72701, USA
salamo@uark.edu
We present experimental results and corresponding discussion of coupling between a
photo-excited quantum-dot layer and quantum well. The coupling is understood by
investigating the dependence of quantum-dot photoluminescence as a function of dot-well
barrier thickness. For small thickness of the dot-well barrier, the signal shows an anomalous low
intensity behavior. This behavior is explained by sub-picosecond tunneling between the
quantum dot layer and quantum well. As the barrier thickness increases the quantum-dot
photoluminescence signal increases at first but then again decreases. This and other unusual
behavior of the communication between a quantum-dot layer and quantum well will be
discussed.

T02
Coherent optical emission from a disordered nanostructured
amplifier.
Sushil Mujumdar
Nano-optics and Mesoscopic Optics Laboratory,
Tata Institute of Fundamental Research,
Homi Bhabha Road, Colaba,
Mumbai 400005. India
When classical waves scattered within a disordered medium undergo self- interference, several
mesoscopic phenomena are realized, the most popular of them being Anderson localization. In
the optical wave scenario, when propagation in the disordered medium is accompanied by
amplification, a new paradigm is created, one that has not been treated in any of the traditional
mesoscopic studies. Coherent emission, with strong statistical fluctuations, can be obtained
from such a structurally 'dirty' system. In this talk, I shall give a brief introduction to this
research field, and follow up with a description of our own activities focused on the frequency
fluctuations in nanostructured amplifying systems.

T03
Optical Interactions of Metal Nanoparticles and Quantum Dots
Stephen K. Gray
Center for Nanoscale Materials
Argonne National Laboratory
Argonne, Illinois 60439
I discuss theoretical predictions of how quantum dots (QDs) interact with plasmonic systems
(e.g. metal nanoparticles). The QD is treated either as a dipole emitter, as an effective,
polarizable medium, or with a quantum mechanical density matrix approach. The combined
system is modeled with computational electrodynamics. The presence of the quantum dot can
significantly alter the optical response of the system. I show how quantum dot emission can
excite dark plasmon modes, i.e., modes that cannot be excited by ordinary light [1], how a
system's overall photoluminescence can be actively changed by altering the distance between
the quantum dot and nanoparticle [2], and how the quantum dot can induce a transparency in the
system [3].
1 M. Liu et al., Phys. Rev. Lett. 102, 107401 (2009).
2 D. Ratchford et al., Nano Letters 11, 1049 (2011).
3 X. Wu, S. K. Gray, and M. Pelton, Opt. Exp. 18, 23633 (2010).

T04
Quantum Metaphotonics
Galina Khitrova
College of Optical Sciences, The University of Arizona, Tucson,
AZ 85749 USA
The observation of accelerated decay (Purcell) of the resonant near-field coupling between two
“oscillators”, one the typical gain of a single quantum well and the other the very strong
absorption of an array of silver split ring resonators with very large dipole moments, will be
described. The observation of this coupling is possible because of the giant vacuum field
produced by the split ring resonator having a mode volume V a thousand times smaller than the
minimum for a dielectric cavity. Those data indicate that one should be able to see coupling
between a single stationary quantum dot and such a resonator, opening up a new regime of lightmatter
(resonator-emitter) interaction. Usually Purcell enhancement, proportional to Q/V, is
achieved in a dielectric cavity of very high quality factor Q; thus enhancement occurs only for
an emitter lying within the very narrow range of frequencies of the cavity peak. In contrast here,
the Q of the split ring resonator is only of order 10; nonetheless, the Purcell enhancement is still
large because of the metallic resonator's very tiny mode volume. Consequently, emitters with
transitions lying anywhere within the very broad resonance are subjected to a very large
vacuum field and have their spontaneous emission accelerated, resulting in overlap of their
radiatively broadened spectra. This makes quantum dots with different transition energies
effectively behave as identical (indistinguishable), opening up the possibility of coupling a few
dots in a volume much smaller than a cubic wavelength into one collective dot having an
increased dipole moment and saturation by a single photon, i.e., anti-bunching. Such a
collective dot can absorb at most one photon from the field, higher order excitations being
forbidden since they are shifted out of resonance by the interdot interactions. In fact, this would
be the first time in the optical domain where Dicke superradiance could be studied in a
systematic way for the type of system originally envisioned by Dicke in which all the atoms
were confined to a transition wavelength.
Ÿ N.Meinzer, M. Ruther, S. Linden, C. M. Soukoulis, G. Khitrova, J. Hendrickson, J. D.
Olitzky, H. M. Gibbs, and M. Wegener, “Arrays of Ag split-ring resonators coupled to
InGaAs single-quantum-well gain,” Opt. Express 18, 24140-24151 (2010).
Ÿ N. Meinzer, M. König, M. Ruther, S. Linden, G. Khitrova, H. M. Gibbs, K. Busch, and M.
Wegener, “Distance dependence of the coupling between split-ring resonators and singlequantum-well
gain”, Appl. Phys. Lett. 99, 111104 (2011).
Ÿ M. M. Glazov, E. L. Ivchenko, A. N. Poddubny, and G. Khitrova, “Purcell factor in small
metallic cavities”, Physics of the Solid State 53, 1753-1760 (2011).

T05
Silicon based Nanophotonic Devices
Samit K. Ray
Department of Physics & Meteorology, IIT Kharagpur 721 302 India
e.mail : physkr@phy.iitkgp.erent.in
Light emission in bulk silicon-based devices is constrained in the infrared wavelength range
with very weak quantum efficiency due to their indirect bandgap. Ge nanostructures have
potential applications for light emitters and quantum dot infrared photodetectors, making the
indirect gap Ge attractive for novel optical devices. We observed infra-red photoluminescence
signal from Ge islands, associated with the radiative recombination of holes confined in the Ge
islands and electrons localized in the Si buffer layer. The photoluminescence peak position and
intensity were found to be influenced by the islands size and intermixing of Si and Ge. The
photoresponse characteristics of quantum dot infrared photodetectors fabricated using Ge
islands will be discussed. The light emission in the visible wavelength range from Ge
nanocrystals embedded in different high band gap oxide matrices has also been studied. The
observed electroluminescence (EL) around 730 nm was attributed to electron hole
recombination in quantum confined Ge nanocrystals. The dependence of integrated EL
intensity on drive currents was observed. The optical properties of erbium doped Si/Ge
4 4
nanostructures have been extensively studied due to the intra-4f I13/2 → I15/2
transition (first
excited state to the ground state), which overlaps with the optical communication wavelength
(1.53 µm). We shall present the results on optical emission from Er doped Ge nanocrystals and
Er doped Ge nanowires

T06
Understanding the molecule-plasmon coupling
Lasse Jensen
Department of Chemistry
The Pennsylvania State University
104 Chemistry Building
University Park, PA 16803 USA
jensen@chem.psu.edu
Controlling the optical behavior of molecules near the vicinity of noble metal nanoparticles
continues to be an active research area in nanoscience. A molecular level understanding of the
optical properties of such metal-molecule complexes is important for many applications such as
energy harvesting, nanoscale optical circuits, and ultra-sensitive chemical and biological
sensors. In this talk we will discuss our recent theoretical studies aimed at understanding the
coupling between molecules and plasmons. We will show how electrodynamics simulations
can be used to describe the optical properties of mixed exciton-plasmon states arising when
strongly absorbing dyes interact with plasmons. Electronic structure methods will be used to
explore the chemical coupling in surface-enhanced Raman scattering (SERS), and resonance
effects in SERS and surface-enhanced hyper-Raman scattering.

T07
Preparation of Metal Nanoparticle Deposited Substrates for SERS and
Optical Limiting Studies
D. Narayana Rao
School of Physics, University of Hyderabad, Hyderabad, India
We are going to present our recent efforts on the preparation of metal nanoparticles on different
substrates to enhance the Raman signals from organic molecules. Surface Enhanced Raman
Scattering (SERS) spectra were recorded with the cluster deposited Ag and Au nanoparticles,
laser irradiated silver and aluminium sheets for Rhodmine 6G and Cresyl Violet dyes. The
results show that we can obtain good SERS signals even at very low concentrations. We will
also present our in-situ investigation of the formation of silver nanoparticles in polyvinyl
alcohol through Raman spectroscopy. In addition to the Raman signals indicating the formation
of the nanoparticles, we also carried out the scattering experiments to monitor the formation of
the nanoparticles. We will also present the results on SERS studies using inverse opal photonic
crystal embedded with Ag nanoparticles. We also demonstrate the application of these metal
nanoparticle embedded polymer films for optical limiting

T08
Gold Nanoparticle based Hybrid Cellular Probe with
Multifunctional Properties
Nikhil R. Jana
Centre for Advanced Materials, Indian Association for the Cultivation
of Science, Kolkata-700032 India
Hybrid nanoparticles having multimodal imaging/detection options are considered as powerful
probe in understanding cellular function. Here we will summarize our effort in synthesizing
gold nanoparticle based plasmonic-fluorescent, plasmonic-magnetic and plasmonicfluorescent-magnetic
cellular probes and show their potential for dual imaging or imagingseparation
applications. The synthetic designs are optimized so that optical property of each
component nanoparticle is retained. In hybrid probes the gold nanoparticle component acts as
dark field contrast agent, quantum dot/fluorophore acts as fluorescent probe and magnetic iron
oxide offers for magnetic separation. Hybrid nanoparticles have good colloidal stability in
physiological condition and option for further functionalization with different affinity
molecules. Different functionalized hybrid nanoprobes have been synthesized and used as dual
imaging cellular probes and for magnetic cell separation.

T09
Spontaneous and stimulated emission from self-assembled photonic
Structures
R. Vijaya
Department of Physics, Indian Institute of Technology, Kanpur, India
Photonic crystals are grown within 3 hrs in ambient conditions from dye-doped polystyrene
colloids using the method of self-assembly. These highly ordered periodic dielectric structures
show a systematic angle-dependent suppression of spontaneous emission within the
wavelength range of the photonic stop band, an enhanced emission at the band edge, directional
spectral narrowing as well as a threshold effect when excited within their absorption spectrum.
These features of emission from the photonic crystal-based microcavities are discussed with
support from experimental results.

T10
Coupled and Chiral Surface Plasmons in Metal Nanostructures
K. George Thomas
Indian Institute of Science Education and Research
Thiruvananthapuram, 695016, India
kgt@iisertvm.ac.in
The presentation will provide examples of modulating the optical properties of
nanomaterials by integrating them into higher order assemblies using electrostatic,
1-7
supramolecular and covalent approaches. Various approaches to organize metal nanoparticles
by varying the distance and geometry will be discussed in the first part of the presentation,
2-6
highlighting the role of plasmon coupling. Raman signal enhancement of different analyte
molecules, when placed at various locations of these assemblies (such as junctions and edges)
6
will be presented. In the second part of the presentation, a novel strategy for inducing chirality
7
to metal nanoparticles, by growing them on peptide nanotube surfaces will be discussed. The
surface plasmon coupled circular dichroism in these systems originates from the asymmetric
organization of Au nanoparticles, resulting in bisignated CD signals. The chiral information and
asymmetry at the molecular level on the D- and L-isomers of peptide nanotubes are transferred
to gold nanoparticles.
1 K. George Thomas and P. V. Kamat, Acc. Chem. Res., 2003, 36, 888.
2 P. K. Sudeep, S. T. S. Joseph and K. George Thomas, J. Am. Chem. Soc.,
2005, 127, 6517.
3 S. T. S. Joseph, B. I. Ipe, P. Pramod and K. George Thomas, J. Phys. Chem. B 2006, 110,
150.
4 P. Pramod, S. T. S. Joseph and K. George Thomas, J. Am. Chem. Soc., 2007, 129, 6712.
5 P. Pramod and K. George Thomas, Adv. Mater., 2008, 20, 4300.
6 Jatish Kumar and K. George Thomas, J. Phys. Chem. Lett., 2011, 2, 610.
7 Jino George and K. George Thomas, J. Am. Chem. Soc., 2010, 132, 2502.

T11
Optically-active hybrid nanostructures:
Exciton-plasmon interaction, Fano effect, and plasmonic chirality
Alexander Govorov
Department of Physics and Astronomy, Clipinger Research Labs,
Ohio University, Athens, USA
Hybrid nanostructures are assembled from metal nanocrystals, semiconductor nanoparticles,
and molecules. They exhibit interesting optical properties, such as Fano resonances, energy
transfer between components and related light harvesting, new mechanisms of nonlinearity,
plasmonic chirality and plasmonic circular dichroism. This talk will review our recent results
on hybrid nanomaterials including both theory and experiment.

T12
Exciton-plasmon Coupling in Hybrid Nanoassemblies
Jaydeep K Basu
Department of Physics,
Indian Institute of Science, Bangalore, India.
e-mail: basu@physics.iisc.ernet.in
We present results of optical measurements on hybrid nanoassemblies consisting of quantum
dots and metal nanoparticles either embedded in a polymer based photonic medium as well as in
the form of a close packed monolayer. We discuss how the coupling between the excitons in the
quantum dots and the plasmons in the metal nanoparticles along with the photonic density of
states can be tuned by controlling the dispersion of such nanoscale objects in the embedding
medium. Both spectral enhancement and quenching regimes can be obtained as a result of the
exciton-plasmon coupling. More interestingly, we also discuss how the photoluminescence
lifetime can also be enhanced and quenched in these hybrid arrays.
Ÿ M. Haridas, J. K. Basu, D. J. Gosztola and G. P. Wiederrecht, Appl. Phys. Lett, 97, 083307
(2010 ).
Ÿ M Haridas and J K Basu, Nanotechnology, 21 , 415202 (2010).
Ÿ M. Haridas, L. N. Tripathi and J. Basu, Appl. Phys. Lett ,98, 063305 (2011).

T13
Broadband extra-ordinary transmission of light in plasmonic nanocheckerboards
S.A. Ramakrishna
Department of Physics, Indian Institute of Technology, Kanpur, India
Intersecting corners and checkerboards of ideal non-dissipative negative refractive index
materials (NRIM) represent highly singular electromagnetic systems. Large local field
enhancements, cavity effects and drastic modifications of the local density of modes in these
systems have been theoretically predicted. Since plasmonic metals mimic the behaviour of
NRIM at small lengthscales, opaque gold films structured at sub-micron scales in a
checkerboard fashion were fabricated using focussed-ion-beam technologies and their
scattering spectra measured. Subwavelength square holes in a thick gold film placed in
checkerboard fashion show a broadband extra-ordinary transmission of light in the visible
spectrum (from 450nm to 950nm). We find that the smaller the square holes, the larger the
transmission which suggests such structured meta-surfaces display very unusual effective
properties. This is confirmed by band diagrams computed with finite elements. Theoretical
results also confirm that the experimentally measured transmission is well over 80 percent from
750nm to 950nm for a checkerboard with 150nm à 150nm square holes. These structures are
seen to have enhanced interaction of light at the edges, corners and at inclusions, and are also
found to give rise to an enhancement of florescence by imbedded dye molecules.

T14
Excited State Interactions of Graphene-Metal Nanocomposites
Prashant V. Kamat
University of Notre Dame Radiation Laboratory, Departments of Chemical &
Biomolecular Engineering, and Chemistry & Biochemistry,
Notre Dame, Indiana 46556 USA
Graphene based carbon nanostructures serve as a two-dimensional carbon support
and they offer an opportunity to harness graphene's redox properties for energy conversion.
Efforts are being made to employ graphene oxide sheets as conducting scaffolds by anchoring
photoactive semiconductor and metal
nanoparticles. For example, the interaction of
semiconductor particles (TiO and CdSe) and
2
metal nanoparticles (Au and Ag) with reduced
graphene oxide enables the development of new
type of light energy harvesting assemblies.
Enhanced surface plasmon effect has been
observed with graphene-Ag composites. In
addition the graphene oxide which facilitates
electron storage can be tailored to drive selective
catalytic reduction and oxidation processes
(Scheme 1). The photoinduced electron transfer
processes of graphene oxide semiconductor and
semiconductor assemblies will be discussed.
Scheme 1. Reduced graphene
oxide as a 2D conducting support
to carry out selective catalysis at
different sites.
Acknowledgement: The research described herein was supported by the Office of Basic
Energy Sciences of the US Department of Energy.
References:
Ÿ Kamat, P. V. Graphene-based Nanoassemblies for Energy Conversion.
J. Phys. Chem. Lett. 2011, 2, 242–251.
Ÿ Kamat, P. V. Graphene based Nanoarchitectures. Anchoring Semiconductor and Metal
Nanoparticles on a 2-Dimensional Carbon Support.
J. Phys. Chem. Lett. 2010, 1, 520-527.
Ÿ Ng, Y. H.; Lightcap, I. V.; Goodwin, K.; Matsumura, M.; Kamat, P. V. To What Extent
Do Graphene Scaffolds Improve the Photovoltaic and Photocatalytic Response of TiO
2
Nanostructured Films?
J. Phys. Chem. Lett. 2010, 1, 2222–2227.
Ÿ Muszynski, R.; Seger, B.; Kamat, P. Decorating Graphene Sheets with Gold
Nanoparticles. J. Phys. Chem. C 2008, 112, 5263 - 5266.
Ÿ Williams, G.; Seger, B.; Kamat, P. V. TiO -Graphene Nanocomposites.
2
UV-Assisted Photocatalytic Reduction of Graphene Oxide. ACS Nano 2008, 2, 1487-
1491.
Ÿ Seger, B.; Kamat, P. V. Electrocatalytically Active Graphene-Platinum Nanocomposites.
Role of 2-D Carbon Support in PEM Fuel Cells. J. Phys. Chem. C 2009, 113, 7990-7995.

T15
Template-assisted and naturally self-assembled nanophotonic
structures
G. Vijaya Prakash
Nanophotonics Lab, Physics Department,
Indian Institute of Technology Delhi
New Delhi – 110016 India
Email: prakash@physics.iitd.ac.in
Recent progress in the fabrication technologies has revolutionised the science and applications
of multi-functional materials. The ability of preparing materials with structures, down to few
nanometres and/or to wavelength scales, is an important basic on which many opto/electronic
properties strongly dependent.
Self-assembly is one of the most versatile, low-cost and recently emerged methods for the
creation of interconnected nano and mesa structured materials: structure sizes typically
between nano to even to the macroscopic world. These structures can be 1D, 2D and 3D both in
ordered and disordered forms. The techniques based on natural self-assembly, usually making
use of chemical and colloidal techniques, are proved to be readily integratable onto a chip for
large scale integration.
This talk provides a review of the major lines of development in this growing research area. It
covers a broad spectrum of templated materials, methods and a variety of possible photonic
applications.
More details in our research group website : http://nanophotonics.iitd.ac.in/

T16
How Nano Can Help Solar
Victor I. Klimov
Center for Advanced Solar Photophysics, Chemistry Division, Los Alamos
National Laboratory, Los Alamos, New Mexico 87545, USA
This presentation provides a brief overview of research activities in the Center for Advanced
Solar Photophysics with focus on nanoscale phenomena of relevance to solar energy
conversion. One topic of my talk will be “active” nanoplasmonic structures in which
semiconductor nanocrystals are combined with nanoscale metals. We use these hybrid
structures to exploit plasmonic effects for enhancing the range of excitonic transport and
controlling carrier dynamics in semiconductor nanocrystals. I will also review the status of
research on carrier multiplication (multiple exciton generation by single photons) and describe
some of the challenges concerning experimental measurements of multiexciton yields and
understanding the mechanisms for multiexciton generation and competing energy relaxation
processes. Finally, I will talk about our studies of nanocrystal-based exploratory devices such as
optical field-effect transistors, which we use to elucidate the nature of conducting states in dark
and under illumination. These studies illustrate how key insights into the performance of
nanoscale materials are gained through close integration of spectroscopic, materials and device
efforts across the Center

T17
Design and Development of Metal-Nanoparticles Based Energy
Transfer
Amitava Patra
Department of Materials Science
Indian Association for the Cultivation of Science,
Kolkata 700 032, India
e-mail: msap@iacs.res.in
Recent advances on Au nanoparticles based surface energy transfer (SET) in the past few years
1-10
using Au nanoparticles as efficient quencher in SET process have been demonstrated. It is
4
evident that the efficiency of surface energy transfer follows 1/d distance dependence between
donor and acceptor. Therefore, SET process is capable of measuring distances nearly twice as
compared to FRET which will help to understand the large scale complex biomolecules. Thus,
the energy transfer between Au nanoparticles and dye provides a new paradigm for design of an
optical–based molecular ruler for long distance measurement. Recent research has established
that PL quenching and energy transfer efficiency are sensitive to the shape, size and assembled
nanoparticles. The distance dependence of the rate of energy transfer as a function of shape,
size, assembled Au nanoparticles, Au-semiconductor (core-shell) and Au-conjugated
semiconductor nanoparticles has been discussed. Results reveal that the surface energy transfer
(SET) process is very elegant method to measure the molecular coverage on the nanoparticle,
shell thickness of core-shell nanoparticles and conformation of BSA protein. Finally, the
designing of nanostructures materials with unidirectional energy transfer for the application of
energy storage system has been discussed. Analysis suggests that such energy transfer between
dye and Au nanoparticles could pave the way for designing new optical based materials for the
application in chemical sensing or light harvesting system.
References
1 T. Sen, S. Sadhu and A. Patra, Appl. Phys. Lett. 2007, 91, 1043104–1.
2 T. Sen and A. Patra, J. Phys. Chem. C 2008, 112, 3216-3222.
3 K. K. Haldar and A. Patra, Chem. Phys. Lett. 2008, 462, 88–91.
4 K.K. Haldar, T. Sen and A. Patra, J. Phys. Chem. C 2008, 112, 11650–11656.
5 T. Sen, K. K. Haldar and A. Patra, J. Phys. Chem. C 2008, 112, 17945–17951.
6 T. Sen and A. Patra, J. Phys. Chem. C 2009, 113, 13125-13132.
7 T. Sen, S. Jana, S. Koner and A. Patra, J. Phys. Chem. C 2010, 114, 707–714.
8 K. K. Haldar, T. Sen and A. Patra, J. Phys. Chem. C 2010, 114, 4869–4874
9 T. Sen, S. Jana, S. Koner and A. Patra , J. Phys. Chem. C, 2010 114,
19667-19672.
10 T. Sen, K. K. Haldar, and A. Patra, J. Phys. Chem. C, 2010, 114, 11409-11413.

T18
Optical properties of complex semiconductor nanocrystal and their
internal structures
D. D. Sarma
Solid State and Structural Chemistry Unit
Indian Institute of Science, Bangalore 560012 India
Controlling the size, composition or dopant concentration is a well known route to tailor
properties of semiconductor nanocrystals. Specifically, photophysical properties of
semiconductor nanocrystals are strongly influenced by such manipulations. It has been realised
in more recent times that the nature of the internal structure of semiconductor nanocrystals may
also have profound influences on optical properties. However, the relationship between the
internal structure and optical properties has remained less obvious due to the lack of suitable
probes to investigate details of internal structures of complex nanocrystal systems. We discuss
here the unexpected and counter-intuitive ability of photoelectron spectroscopy to investigate
such complex internal structures and show that in some cases, such structures can lead to a
differential collapse of the electron and the hole wave-functions towards the core of the
nanocrystal. We further discuss the importance of these results in determining optical
properties.
Based primarily on:
Ÿ P. K. Santra et al., J. Am. Chem. Soc., 131, 470 (2009);
Ÿ D. D. Sarma et al., J. Phys. Chem. Lett., 1, 2149 (2010).
Ÿ S. Sengupta et al., Adv. Mater., 23, 1998 (2011).
Earlier relevant publications:
Ÿ S. Sapra and D. D. Sarma, Phys. Rev. B 69, 125304 (2004); R. Viswanatha,
Ÿ S. Sapra, T. Saha-Dasgupta and D. D. Sarma, Phys. Rev. B 72, 045333 (2005);
Ÿ R.Viswanatha and D. D. Sarma, Chem. - A European J. 12, 180 (2006).
Ÿ J. Nanda, B. A. Kuruvilla, and D. D. Sarma, Phys. Rev. B 59, 7473 (1999);
Ÿ J. Nanda and D. D. Sarma, J. Appl. Phys. 90, 2504 (2001); and S. Sapra et al., J. Phys. Chem.
B 110, 15244 (2006).

T19
Cavity-Mode and Plasmonic Enhancement of Solar Energy
Concentration and Conversion
Gary P. Wiederrecht
Center for Nanoscale Materials, Argonne National Laboratory,
Argonne, IL 60439 USA
Efficient and affordable solar energy remains a critical challenge in our quest for a sustainable
and reduced-carbon energy source. In this talk, the application of cavity modes in bilayer films
for solar concentration and conversion is introduced, and new methods to monitor
photoinduced charge separation on an ultrafast time scale in organic heterostructures are
described. Beginning with solar concentration, a bilayer cavity is used to improve upon
traditional luminescent solar concentrator (LSCs) designs. LSCs have been proposed for
concentrating energy without costly tracking optics. However, absorption losses limit the
concentration ratios to about a factor of 10. Here, a new bilayer cavity produces a cavity-mode
that is evanescently coupled to the underlying substrate, resulting in directional emission into
the substrate.[1] By changing the cavity thickness as a function of position, the cavity resonance
is altered so that the emitted light reflected back to the bilayer can no longer interact with the
absorptive molecules in the cavity. Near lossless propagation of emission is demonstrated. We
further use the cavity-mode concept to develop a planarized dye-sensitized solar cell (DSSC)
with dramatically reduced dark counts relative to conventional DSSCs with nanostructured
TiO
2.[2] Finally, the use of an ultrafast Stark shift in excitonic molecular aggregates as a probe
to time-resolve charge separation and photovoltaic field formation in organic heterostructures
is described. Ultrafast photoexcitation into the plasmon modes of the underlying Au film
initiates the charge separation process.
1 Resonance-shifting to circumvent reabsorption loss in luminescent solar concentrators,”
N. C. Giebink, G. P. Wiederrecht, and M. R. Wasielewski, Nature Photon., Advanced
Online Publication (2011), DOI:10.1038/nphoton.2011.236.
2 Planar dye-sensitized photovoltaics through cavity mode enhancement,”
A. B. F. Martinson, N. C. Giebink, G. P. Wiederrecht, D. Rosenmann, and
M. R. Wasielewski, Energy Environ. Sci. 4, 2980 (2011).

Contributed Talks

T20
Long-range exciton migration in H-aggregated molecular nanowires
Debansu Chaudhuri
Assistant Professor
Department of Chemical Science, IISER-Kolkata
Mohanpur-741252, Nadia, WB India
Excitonic transitions in organic semiconductors are associated with large oscillator strength
that limits the excited-state lifetime and can in turn impede long-range exciton migration. We
present perylene-based emissive H-aggregate nanowires where the lowest energy excited state
is only weakly coupled to the ground state, thus dramatically enhancing its lifetime. Exciton
migration occurs by thermally activated hopping, leading to luminescence quenching on
topological wire defects. An atomic force microscope tip can introduce local topological
quenchers by perturbing the H-aggregate structure, demonstrating long-range exciton
migration at room temperature and offering a potential route to writing fluorescent
“nanobarcodes” and excitonic circuits.

T21
The importance of surface for semiconductor
Sameer Sapra
Assistant Professor
Indian Institue of Technology Delhi
Hauz Khas, New Delhi 110016 India
It has been known for quite some time now that the luminescence properties are strongly
affected by the surface atoms. However, for core-shell structures it was presumed that the
surface atoms on the shell material do not have any role to play for the luminescence properties
of the core. The role of surface atoms on the emission from core-shell nanocrystals depends on
whether the surface atom is anionic or cationic. Our recent findings suggest that a cation-rich
surface enhances the emission intensity, while an anion-rich surface leads to deterioration of the
fluorescence signal as shown in the figure below. However, the correspondence of surface
coverage to emission intensity is not so straightforward and depends on that kind of surface sites
are being talked about. The role of different facets of the crystal seem to be very important in
deciding the final properties of the particles. In the present talk, I will discuss our study of CdSe-
CdS and CdSe-ZnS core-shell nanocrystals and see the effect of surface composition on the
luminescence of these materials.
The variation of fluorescence as a function of the anion/cation monolayer coverage on CdSe
core nanocrystals
Reference:
Ÿ U. Soni and S. Sapra, J. Phys. Chem. C 114, 22514 (2010)

Poster presentation

P01
Effect of a substrate on the localized Plasmon resonances of single and
coupled particles
Abhay Kumar Tiwari and Murugesan Venkatapathi*
Supercomputer Education and Research Center, Indian Institute of Science,
Bangalore – 560012, India
Email: murugesh@serc.iisc.ernet.in
Substrates can significantly alter the localized plasmon resonance of particles on it and this
effect is shown using computational models; substrates can be exploited for shifting, tempering
or enhancing plasmon resonances of particles. The localized plasmon resonances of particles
with various geometries and material properties have been studied for more than two decades.
While methods like Discrete Dipole Approximations (DDA) are useful in modelling extinction
by arbitrary shaped nano structures, the interaction with a substrate is difficult to include either
due to lack of separable co-ordinates or the inability to compute Fresnel coefficients for the near
field sources. An isolated sphere on a substrate was initially studied using bispherical
coordinates in the electrostatic limit and so was the change in polarizability of a spheroid due to
contact with a surface. Marginal effects on the optical properties of dielectric nano particles due
to a substrate were observed in some experiments. Later significant enhancement of coupling
between gold particles on indium-tin-oxide (ITO) substrate has been observed. With many
parameters to vary it is difficult to experimentally elucidate all the effects of the interaction of
isolated and coupled particles and different surfaces. A method of images was recently reported
to approximate plasmon resonances of arbitrary shaped particles on a substrate; a method to
compute the polarizability of sphere clusters on a substrate was derived earlier. We have used
the traditional DDA method in conjunction with the Sommerfeld integral relations to compute
the Fresnel coefficients and the surface interaction. Coupling of nano structures/particles on a
substrate are common in many applications that exploit plasmon resonances. The computed
extinction curves are shown to be very different from that of the single/coupled particles in the
absence of the substrate. We have numerically studied the extinction of small gold cylinders on
dielectric substrates to demonstrate this effect.

P02
Microsphere-enhanced Raman scattering and photoluminescence of
nanomaterials
Arindam Dasgupta, G.V. Pavan Kumar*
Photonics and Spectroscopy Laboratory, Division of Physics and Chemistry,
Indian Institute of Science Education and Research (IISER), Pune
India – 411008
e-mail: pavan@iiserpune.ac.in
When a lossless dielectric microsphere or microcylinder is illuminated with light of wavelength
shorter than the radius of the sphere, a narrow, high-intensity light beam emerges out of the
shadow surface of the sphere. This light beam is known as photonic nanojet, and can be
harnessed to enhance optical processes such as Raman scattering and photoluminescence.
Herein we present enhanced-Raman scattering and photoluminescence studies of various
nanomaterials by imaging an isolated dielectric sphere deposited on a glass surface. Further, we
explore the effect of conjugated spheres on the enhancement of Raman scattering and
photoluminescence. We validate our experimental results with finite-element method
simulations.

P03
Infrared photo detectors based on reduced grapheme oxide and
grapheme nanoribbons
1 2 1 2
Basant Chitara , L. S. Panchakarla , S. B. Krupanidhi * and C. N. R. Rao *
1 Materials Research Centre, Indian Institute of Science, Bangalore 560012, India
2 Chemistry and Physics of Materials Unit, New Chemistry Unit and CSIR Centre
of Excellence in Chemistry, Jawaharlal Nehru Centre for Advanced Scientific
Research, Jakkur P.O., Bangalore 560064, India
Optical and electronic properties of graphene make it an important material for future
technologies. Its potential use in photonics and optoelectronics potential is evident from some
of the recent results dealing with solar cells, light emitting devices, photodetectors and ultrafast
lasers. In this context, we have explored the use of reduced graphene oxide and graphene
nanoribbons as infrared photodetectors. The results have been most encouraging. Thus, IR
detection is demonstrated by both reduced graphene and grapheme nanoribbons in terms of
time the resolved photocurrent as well as photoresponse. The responsivity of the detectors is
found to be 4 mA/W and 1 A/W respectively for reduced graphene oxide and graphene
nanoribbons.

P04
Highly enhanced fluorescence from Rhodamine-6G dye doped PMMA
film prepared on porous alumina template
*
Dheeraj Pratap, P. Mandal, S. A. Ramakrishna
Department of Physics
Indian Institute of technology Kanpur, India
Porous alumina templates are attractive class of templates being used to fabricate plasmonic
photonic and metamaterial structures. These templates are also used for surface enhanced
fluorescence and surface enhanced Raman scattering. In the present study we have fabricated
alumina templates with anodization of 99.9% pure aluminium foil and using these templates
surface enhanced fluorescence are investigated. The structures are also investigated to explore
the effect of surface plasmon on surface enhanced fluorescence. The observed fluorescence
signal from the alumina template is highly enhanced of about 8 times the signal from sample on
plane quartz as well as gold coated flat quart. Interestingly the fluorescence signal is completely
quenched when gold coated alumina template being used as substrate. The very large enhanced
fluorescence signal from alumina template is ascribed due to the effect of large scattering and
efficient excitation of fluorophores. Quenching of fluorescence from gold coated alumina
template is due to the effect of local electromagnetic field.

P05
Integrated fabrication of plasmonic Nanostructures and its novel
optical properties
Gangadhar Behera and S. Anantha Ramakrishna
Department of Physics
Indian Institute of technology Kanpur, India
The strong coupling between light and surface plasmons in nanostructures leads to novel
phenomena of optical field enhancement and improvement of the optical absroption. The
optical response of noble metal can be tuned by controlling their size, shape and physical
environment, providing a strarting point for the emerging field of research in solar cells. In
recent advanced solar cell research, organic solar cells (OSC) are of great interest as they have
a strong potential in reducing the cost of photovoltaics. However, the efficiency of the OSC is
still low of upto 5-6 %. In this regard, plasmonic nanostructures are expected to be a leading
candidate. We have fabricated some plasmonics nanostructures by using laser interference
lithography ,electron beam lithography and also measure its novel optical properties of these
respective structures. In the present poster presentation , we will show how these novel
plasmonic nanostructures can be fabricated through various lithographic tools (LIL,EBL)and
also its novel optical properties.

P06
Synthesis of sandwich nanoparticles and Raman markers for surface
enhanced Raman spectroscopy applications
Gayatri Kumari*, Erode N Prabhakaran† and Chandrabhas Narayana*
* Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore
† Indian Institute of Science, Bangalore, India
Nanoparticles show fascinating properties owing to the existence of surface plasmons
(collective oscillation of surface free electrons). Surface plasmons can interact with the electric
field of light and enhance the Raman signal of analyte adsorbed on them, the phenomenon
known as surface enhanced Raman scattering. We have synthesized silver silica gold sandwich
nanoparticles by multi-step seeded growth process and characterized by UV-Vis spectroscopy,
Transmission Electron Microscopy, X-Ray diffraction. This structure shows high SERS
enhancement factor due to light transmission and multiple reflections through it. Light incident
on the surface of sandwich nanoparticles bearing gold island will be transmitted through the
silica layer and can undergo reflections from the silver core. The interference between incident
and transmitted light will result in regions of high and low intensity on the surface of
nanoparticles. It has been shown that sandwich nanoparticles show SERS enhancement factor
of 106, which is 100 fold larger than that observed by silica gold core shell particles under same
experimental conditions. Raman markers are compounds with high density of pi electrons and
mostly have some charge. Benzotriazole is one such molecule with strong Raman signal. We
have synthesized benzotriazolyl-acetate and acetic acid derivatives and studied their SERS
properties. Benzotriazolyl-acetic acid shows different SERS spectra at different Ph conditions.
This is attributable to the change in active site on the molecule through which interaction with
nanoparticles occur at different pH conditions. So the orientation of molecule on the
nanoparticles change as the pH is changed, which is reflected in SERS signal.

P07
Spontaneous emission control of quantum dots in photonic crystal slab
using plasmonic nanoantena
1 1 2 2
M. Haridas , J. K. Basu , D. J. Gosztola and G. P. Wiederrecht
1
Department of Physics, Indian Institute of Science, Bangalore, India
Center for Nanoscale Materials, Argonne National Laboratory, Argonne, USA
2
We present the emission properties of a hybrid films consisting of cadmium selenide quantum
dots (CdSe QDs) and gold nanoparticles(Au NPs), arranged in di block copolymer (Di-BCP)
template. Di-BCP structures are known to behave as a two dimensional photonic crystals, under
sufficient optical contrast between the two blocks. Here dispersion of CdSe QDs inside
minority block and Au NPs in the majority block increases the optical contrast between the
block and allows them use as a effective band gap materials. The films were prepared using two
types CdSe QDs – the smaller QDs with their emission spectra overlapping with surface
Plasmon resonance of Au NPs and larger QDs with red shifted emission peak. The
photoluminescence measurements (PL) from such hybrid system shows enhancement in
emission with increase in volume fraction of Au NPs compared to the CdSe QD film, both for
small and large CdSe QD films. However we observed significant changes in the PL decay
profile between the small and large CdSe QD films. The exciton lifetime for the hybrid films
with small CdSe QDs are lower than the corresponding CdSe film . However for the similar
films with larger CdSe QDs shows non monotonic behavior with respect to the volume fraction
of Au NPs. The films with lower volume fraction of Au NPs shows increase in lifetime
compared to the corresponding CdSe QD films whereas the higher volume fraction of Au NPs
shows reduced lifetime. The observed phenomena has been explained considering the excitonplasmon
interaction and the variation of emission rates introduced by the change in the local
density of states of Di-BCP photonic crystals.

P08
Surface enhanced Raman spectroscopy at nanorod dimer and quartet
junction
a
a,b
Jatishkumar and K. George Thomas *
a
Photosciences and Photonics, National Institute for Interdisciplinary Science and
Technology (NIIST), CSIR, Thiruvananthapuram, 695 019, India
and
b
School of Chemistry,
Indian Institute of Science Education and Research-Thiruvananthapuram (IISER-
TVM), CET campus, Thiruvananthapuram, 695 016, India
Email: kgt@iisertvm.ac.in
Surface Enhanced Raman Spectroscopy (SERS), using noble metal nanoparticles as substrates,
has emerged as one of the most powerful tools for the detection and identification of chemically
1
and biologically important molecules. One of the major challenges in SERS is the fabrication
of simple and reproducible SERS substrates capable of producing enhanced signal intensities.
Most of the chemical methods utilizes spherical metal nanoparticles for designing SERS
2
substrate. However random aggregation and poor reproducibility due to their isotropic nature
is one of the limiting factors. Herein, we utilize the anisotropic features of Au nanorods for
producing enhanced Raman signals of analyte molecules by placing them at junctions of (i)
nanorod dimers formed through their longitudinal assembly and (ii) nanorod dimer and quartet
assemblies formed through their lateral organization. When two Au nanorods are brought
3
together, their plasmon oscillations couple each other, creating regions of high electric field
4
(hot spots) at the junctions resulting in enhancement of Raman signals. These aspects will be
discussed in the poster.
References:
1 (a) Kneipp, K.; Kneipp, H.; Itzkan, I.; Ramachandra R. Dasari, R. R.; Feld, M. S.
Chem. Rev. 1999, 99, 2957. (b) Campion, A.; Kambhampati, P. Surface-enhanced
Raman scattering. Chem. Soc. Rev. 1998, 27, 241.
2 (a) Camden, J. P.; Dieringer, J. A.; Wang, Y.; Masiello, D. J,; Marks, L. D.; Schatz, G. C.;
Van Duyne, R. P. J. Am. Chem. Soc. 2008, 130, 12616. (b) Li, W.; Camargo, P. H. C.; Au,
L.; Zhang, Q.; Rycenga, M.; Xia, Y. Angew. Chem. Int. Ed. 2010, 49, 164.
3 (a) Pramod, P.; Thomas K. G. Adv. Mater. 2008, 20, 4300. (b) Joseph, S. T. S.; Ipe, B. I.;
Pramod, P.; Thomas, K. G. J. Phys. Chem. B 2006, 110, 150–157. (c) Sudeep, P. K.;
Joseph, S. T. S.; Thomas, K. G. J. Am. Chem. Soc. 2005, 127, 6516.
4 Kumar, J: Thomas, K. G. J. Phys. Chem, Lett. 2011, 2, 610.

P09
Design, Fabrication and Characterization of Photonic Sculptured
thin film
Jhuma Dutta and S.Anantha Ramakrishna
Department of Physics
Indian Institute of technology Kanpur, India
Sculptured thin films are a class of nanostructured materials that can give rise to large optical
anisotropy and chirality in the films. Large oblique angle deposition and substrate motion
during the physical or chemical vapor deposition process are used to formed different
morphologies ranging from columnar, zig-zag to helical. Due to the multi-scale porous nature of
the structures, these have been used for various sensor applications. The large control possible
on the structure enables the construction of optical filters and even switches by incorporating
nonlinearities. By depositing periodic seed layers on substrates, we have fabricated periodically
patterned sculptured thin films. These anisotropic or chiral photonic crystals that have two-scale
spatial variation have the potential for many interesting photonic applications. The interfaces of
such PPSTF and metals are expected to support new kinds of surface plasmon modes.

P10
Opto-electrical properties of ultrathin MoS2 and Graphene/MoS2
hybrids.
Kallol Roy
Indian institute of Science, Bangalore, India
Molybdenum disulphide (MoS
2) is an interesting semiconductor whose bandgap depends on
the number of atomic layers in the system. We present a systematic study of the optical response
of the two-point resistance of MoS 2 flakes as a function of number of layers. We also investigate
the opto-electronic properties of MoS2-graphene hybrid devices. A procedure for transferring
MoS 2 flakes onto CVD grown graphene will be presented. In these devices, we find that the
optical response of grapheme is modified by the presence of MoS 2 flakes on the surface. Our
results can be useful in developing various optoelectronic devices including solar cells.

P11
Tuning the parameters to establish Quenching and enhancement
regimes in hybrid Gold nanoparticles and CdSe Quantum dots
monolayer
L. N. Tripathi, M.Praveena, J K Basu
Department of Physics, Indian Institute of Science, Bangalore, India.
The multi-component nanomaterials combines the individual properties and give rise to
emergent phenomenon. Optical excitations in such hybrid nanomaterials (for example
Exciton in semiconductor quantum dots and Plasmon in Metal nanomaterials ) undergo strong
/weak electromagnetic coupling. Such exciton-plasmon interactions allow design of
absorption and emission properties, control of nanoscale energy-transfer processes, creation of
new excitations in the strong coupling regime.\cite{Achermann2010a}.This Exciton plasmon
interaction in hybrid nanomaterial can lead to both enhancement in the emission as well as
quenching .The enhancement comes due to Electric field amplified by the plasmon resonance
.The Quenching Comes from the energy transfer from semiconductor to metal nanoparticles.
emission enhancement was observed mostly in experiments with extended systems (rough
metal surface, nanowires, largeAu NPs) where the plasmon-induced field amplification can be
especially strong. In most experiments with a few/several small Au NPs, the emission intensity
decreases because of the energy transfer effect\cite{Govorov2006, Kulakovich2002}.
In this work we prepared close-packed hybrid monolayer of thiol capped CdSe and
gold nanoparticles . They exhibit both the Quenching and enhancements the in PL emission
.The systematic variance of PL from such hybrid nanomaterials monolayer is studied by tuning
the Number ratio of Gold per Quantum dots, the surface density of QDs and the spectral overlap
of emission spectrum of QD and Absorption spectrum of Gold nanoparticles. Role of Localized
surface Plasmon which not only leads to quenching but strong enhancements as well, is
explored.
References
Ÿ M. Achermann, The Journal of Physical Chemistry Letters 1, 2837 (2010).
Ÿ A. O. Govorov, G. W. Bryant, W. Zhang, T. Skeini, J. Lee, N. A. Kotov, J. M.
Slocik, and R. R. Naik Nano Letters 6, 984 (2006)..
Ÿ O. Kulakovich, N. Strekal, A. Yaroshevich, S. Maskevich, S. Gaponenko, I.
Nabiev, U. Woggon, and M. Artemyev, Nano Letters 2, 1449 (2002),
Ÿ M. Haridas, L. N. Tripathi, and J. K. Basu, APPLIEDPHYSICS LETTERS 98,
063305 (2011).
Ÿ M. Kawai, A. Yamamoto, N. Matsuura, and Y. Kanemitsu,Phys. Rev. B 78,
153308 (2008).
Ÿ K. Hosoki, T. Tayagaki, S. Yamamoto, K. Matsuda, andY. Kanemitsu, Phys. Rev.
Lett. 100, 207404 (2008).
Ÿ L. N. Tripathi, M. Haridas, and J. K. Basu, AIP ConferenceProceedings 1147, 415
(2009).

P12
Fabrication and optical analysis of artificial opal films
M. Srinivas Reddy
Indian Institute of Technology, Bombay, India
The artificial opal 3D-photonic crystals have been fabricated by horizontal self assembly using
mono-dispersed polystyrene colloids with an average diameter of 264nm. Structural as well as
optical characterization of these crystals has been carried out. Theoretical calculations of the
angle-resolved reflection and transmission spectra using Korringa-Kohn-Rostoker (KKR)
wave method, incorporating optical extinction show good agreement with the experimental
results. The complex band structure was calculated and compared with the band structure of a
perfect fcc lattice and the effect of the extinction was studied in the high energy region.

P13
Distance dependent Plasmon coupling in Ag-Sio2 Nanostructures and
its relevance in SERS
† ‡,*
M. Shanthil and K. George Thomas
†Photosciences and Photonics, National Institute for Interdisciplinary Science and
Technology (NIIST), CSIR, Thiruvananthapuram, 695 019, India
‡School of Chemistry, Indian Institute of Science Education and Research-
Thiruvananthapuram (IISER-TVM), CET Campus, Thiruvananthapuram, 695 016,
India
Surface Plasmons on metal nanoparticles can amplify various spectroscopic signals
of molecules (for e.g., Raman scattering, absorption, fluorescence etc.) due to intense electric
1
field prevailing on the surface. Intensity of electric field can be enhanced many folds by
bringing two or more metal nanoparticles close by which allow the detection of even single
2
molecules. We have synthesized core-shell nanoparticle having silver as core, over coated
with silica of varying thickness (3- 25 nm) and various analyte molecules were linked on their
surface. It was found that the electric field experienced by the analyte molecules can be tuned by
varying the thickness of silica shell and their Raman signal intensities were investigated.
Further we could selectively bring two core-shell nanoparticles and create dimeric structures.
The enhanced electric field and Raman signal intensity of analytes at the junctions were
investigated as a function of shell thickness and these aspects will be presented in the poster.
References:
1 Rycenga, M.; Cobley, C. M.; Zeng, J.; Li, W.; Moran, C. H.; Zhang, Q.; Qin, D.; Xia, Y.;
Chem. Rev. 2011, 111, 3669.
2 Haran, G. Acc. Chem. Res. 2010, 43, 1135.

P14
Electrochemical integration of Graphene with light absorbing copperbased
alloys
Medini Padmanabhan
Indian Institute of Science, Bangalore, India
We present an electrochemical route for the integration of grapheme with light sensitive copperbased
alloys used in optoelectronic applications. Graphene grown using chemical vapor
deposition (CVD) transferred to glass is found to be a robust substrate on which
photoconductive Cu_{x}S films of 1-2 micron thickness can be deposited. The effect of
growth parameters on the morphology and photoconductivity of Cu_{x}S films is presented.
Current-voltage characterization and photoconductivity decay experiments are performed with
graphene as one contact and silver epoxy as the other. The initial stages of electrochemical
growth might involve the nucleation of nanostructures whose interaction with the underlying
graphene layer will be explored.

P15
Mapping local surface Plasmon resonant modes using
cathodoluminescence in scanning electron microscope.
Pabitra Das
Saha Institute of Nuclear Physics, Kolkata, India
When an energetic electron is incident from vacuum onto the boundary of a material it perturbs
the electrons in the uppermost layers due to its external field and creates a polarization charge.
This charge together with the incoming electron can be considered as an effective dipole. In
case of a metal substrate the dipole can decay into two channels: direct emission into the far field
(transition radiation) and generation of surface plasmons (SP). Cathodoluminescence in a
Scanning electron microscope (SEM) is a very promising technique for the spectroscopic
1
investigation of localized surface plasmons . In CL, photon emission of the metal nanostructure
under investigation is induced via high energy electron beam, and collected using a suitable
2
detection system . A unique feature of this is that by scanning the electron beam over the particle
surface the spatial profile of the optical modes can be mapped by collecting the light at the
3
respective peak wavelength .
We have prepared Au nanoparticles of different shape and size by chemical route and then
studied them in our CL-SEM system (for details of system see Ref (ii)). The images (Fig. 1(b),
1(c)) indicate that we have been able to image the resonant plasmonic modes from Au
nanoparticles with spatial resolutions of a few tens of nanometers which is possible only if we
employ a local probe technique like CL. These emission maps at a particular wavelength can be
simulated by solving Maxwell Equations using Finite Difference Time Domain (FDTD)
method. Experimental as well as FDTD simulated results of different metallic structures will be
presented.
1 F. J. García de Abajo, Rev. Mod. Phys., 82, 209 (2010).
2 P. Das and T. K. Chini, Current Science, 101, 849 (2011).
3 P Chaturvedi, H Hsu Keng, A Kumar, K H Fung, J C Mabon, and N X Fang, ACS Nano,
3, 2965 (2009).

P16
Nanoplasmonic architectures for single molecule SERS
Partha Pratim Patra, Danveer Singh, Rohit Chikkareddy,
G.V. Pavan Kumar*
Photonics and Spectroscopy Laboratory, Division of Physics and Chemistry,
Indian Institute of Science Education and Research (IISER), Pune
India – 411008 e-mail: pavan@iiserpune.ac.in
Single molecule detection and characterization is vital in my disciplines of science. For various
nano- and bio-photonic applications, it is desirable to probe the structure of single molecules on
the surface of a plasmonic nanomaterial. Surface enhanced Raman scattering (SERS) has
emerged as a unique technique with single molecule sensitivity and molecular specificity. The
geometry, shape and composition of plasmonic nanomaterials play a critical role in single
molecule SERS studies and hence their design and fabrication are vital. Herein we present a
variety of architectures such as plasmonic nano-core-shells, nanorings and nanowires
fabricated by bottom-up and top-down approaches. We demonstrate how these nanoarchitectures
can be harnessed for single molecule SERS and validate them with numerical
simulations.

P17
Synthesis and Photophysical Properties of II-IV Semiconductor
Nanostructures
Pratheesh V. Nair and K. George Thomas
Photosciences and Photonics Group, National Institute for Interdisciplinary
Science and Technology, Trivandrum, 695 019, India
and School of Chemistry, Indian Institute of Science Education and Research,
Thiruvananthapuram, 695016, India
E-mail: kgt@iisertvm.ac.in
Among the various organic and inorganic nanostructured materials, semiconductor quantum
dots (QDs) have attracted attention in recent years due to their remarkable optical and electrical
properties that are distinctly different from bulk materials. Two aspects will be discussed in the
poster: (i) synthesis and characterization of various II-VI semiconductor nanostructures (type I
and II quantum dots and, one dimensional nanowires) and (ii) investigations of their
electrochemical, photophysical and structural properties. A series of type 1 (CdSe/ZnS) and
type II (CdTe/CdSe) core-shell QDs with varying shell thickness was synthesized and their
electrochemical and photophysical properties were investigated. A good correlation between
1
the optical band gap and electrochemical band gap were observed. Photoinduced charge
transfer processes between these core-shell QDs and surface adsorbed electron acceptors were
studied as a function of shell thickness. A steady increase in photoluminescence quenching
efficiency was observed with increase in CdSe shell thickness and these aspects will be
2, 3
discussed. We have carried out a detailed investigation on the morphological changes and
variation in the optoelectronic properties of CdTe QDs in the presence of a common reducing
agent, hydrazine monohydrate. At low concentration, hydrazine induces a drastic enhancement
in PL intensity of CdTe QDs whereas one dimensional growth of luminescent CdTe QDs to
crystalline nanowires has been observed at higher concentrations. Growth process was
followed by various microscopic and spectroscopic techniques and these aspects will be
4
discussed.
References
1 Pratheesh V. Nair, Ganesh Markhand, Santosh. K. Haram and K. George Thomas (To be
submitted).
2 Pratheesh V. Nair, Saranya P. S. and K. George Thomas (Chem. Commn. 2011, under
submission)
3 Vinayakan, R., Shanmugapriya, T., Pratheesh V. Nair, P. Ramamurthy and K. George
Thomas, J. Phys. Chem. C 2007, 111, 10146-10149.
4 Pratheesh V. Nair and K. George Thomas, J. Phys. Chem. Lett. 2010, 1, 2094-2098.

P18
All optical actuation and interrogation of NEMS resonant mode
sensors
1, 2 4 1, 3 1, 2
P. Prakash , C. Venkatesh , M. Varma , R. Pratap
1 Centre for Nano Science and Engineering (CeNSE), IISc Banagore-12, India
2 Department of Mechanical Engineering, IISc Banaglore-12, India
3 Electronics and Communication Engineering, IISc Banaglore-12, India
4 School of EE&CE, University of Western Australia, Perth, Australia
There have been spectacular developments in Micro Electro-Mechanical Systems (MEMS)
which have enabled the exploration of transduction modes. As a result an innovative family of
chemical and biological sensors has emerged. Mechanical resonators are widely used as inertial
balances to detect small quantities of adsorbed mass through shifts in oscillation frequency.
Guided wave Optics in combination with micromachining technology offers immense potential
for sensor applications. Conventional electrical schemes have limited bandwidth and Optical
methods are fast, super sensitive and achieve unlimited bandwidth but subject to the diffraction
limit.
We present a fabrication and characterization process for 260 nm thick SOI based beams to be
used in making optical waveguides for mass sensing applications. Focused Ion beam (FIB) is
used to mill micro scale beams into coupled single-mode waveguides cantilevers separated by
100 nm for cantilever-based sensing. The bending up of such beams due to process related
residual stresses have been successfully reduced by FIB annealing. A combination of high
current, less width and lower depth of milling has been found to do local annealing in structures
that result in releasing stress effectively. Our experimental result is supported by analytical
modeling using MATLAB and Coventorware simulation done by us. We also demonstrated the
impact of FIB induced stress variation in 260 nm thick beams.
Reference:
Ÿ Lavrik, N.; Sepaniak, M.; Datskosa, G.; Review of Scientific Instrument. 2004, 75, 7.
Ÿ Jensent, k.; Kimi, K.; Zettel, A.; Nano Nanotechnology. 2008, Volume 3,
Ÿ Pattnaik, P.; Selvarajan, A; Srinivas, T.; 2005, Sensors for Industry Conference

P19
Statistical regimes of emission from disordered nanostructured media
with gain
Ravitej Uppu and Sushil Mujumdar
Nano-optics and Mesoscopic Optics Laboratory,
TIFR, Homi Bhabha Road, Colaba, Mumbai-400005. India.
Random lasers, disordered amplifying media, are known to emit ultranarrow coherent
peaksthrough a synergy between multiple scattering and optical amplification[1]. They also
undergo a laser-like threshold behaviour in emission intensity on variation of the pump
energy[2]. Emission before and after this threshold is expected to show markedly different
statistical nature[3]. Owing to the exponential dependance of amplification on the path length
that a photon traverses in the medium, and that the distribution of the path lengths of this
diffusing photon in the random medium is exponentially decaying, the emission above the
threshold is expected to show very strong fluctuations in intensity[4]. Due to the absence of
frequency selectivity in amplification, the random lasing peaks appear at random frequencies in
the emission profile under conditions of strong inversion. This frequency insensitive
amplification also causes the emission spectrum to self-average under strong excitation of the
system, hence, reducing the fluctuations[5].
In our current work, we present the first measurement of these statistical regimes of random
lasers. The experimental data was collected from a suspension of 10 nm ZnO nanoparticles in
2.5mM solution of Rhodamine-6G in methanol(l* = 1060 μm). The system was excited with a
30ps frequency-doubled Nd:YAG laser pulse(λ = 532.8 nm). The emission intensity at 558 nm,
which is close to the emission maximum, was collected over 1000 spectra. The distribution of
these intensities was fit with an α -stable L´evy distribution to find the tail exponent. Under
weak excitation, the distribution is Gaussian due to the pump and the detector noise. The
appearance of ultranarrow peaks under stronger excitation makes the distribution leptokurtic
and the right tail has a power-law nature with an α = 1.11. The reduction in fluctuations under
stronger pump energies weakens the power-law nature of the tail (α = 1.85). In summary, the
system presents an abrupt transition from the pre-lasing Gaussian regime to a strongly L´evy
regime followed by a continuous asymptotic crossover back to the Gaussian regime.
References
1 S. Mujumdar, et. al., Phys. Rev. Lett. 93, 053903 (2004).
2 N. M. Lawandy, et. al., Nature 368, 436 (1994).
3 S. Lepri, et. al., Phys. Rev. A 75, 063820 (2007).
4 R. Uppu & S. Mujumdar, Opt. Lett. 35, 2831 (2010).
5 R. Uppu & S. Mujumdar, Appl. Opt. 50, E13 (2011).

P20
Optical effects near metal nanostructures: Towards surface enhanced
spectroscopy
Reshmi Thomas and R. S. Swathi*
School of Chemistry,
Indian Institute of Science Education and Research Thiruvananthapuram (IISER-
TVM), CET campus, Thiruvananthapuram, 695 016, India
Email: swathi@iisertvm.ac.in
The trapping of light at the surfaces of nanomaterials gives rise to regions of enhanced electric
fields around the nanostructures, leading to enormous optical cross-sections for molecules in
1 2
vicinity .We use the Finite Difference Time Domain (FDTD) method to calculate the near field
as well as the far field optical properties of spherical Au nanoparticles and Au nanorods as a
function of their size. Au nanoparticles are found to give rise to about an order of magnitude
enhancement in the electric field of the incident light. For Au nanorods we find three orders of
magnitude enhancement under resonant conditions for the longitudinal polarization of the
incident light. Edges of nanorods are found to possess large electric fields in comparison with
3
the lateral faces. We also consider dimers formed by these Au nanostructures i.e., spheresphere,
rod-rod and sphere-rod dimers. The dimer junctions show higher orders of enhancement
of the incident light as compared to the individual monomers.The results thus obtained from the
FDTD calculations provide important insights in designing better geometries for surface
enhanced spectroscopy studies.
References
1 Stiles, P. L.; Dieringer J. A.; Shah, N. C.; Van Duyne,R. P. Annu. Rev. Anal. Chem.2008,
1, 601-626.
2 A. Taflove and S. C. Hagness, Computational Electrodynamics: The Finite-Difference
Time-Domain Method, Norwood, MA: Artech House, 2005.
3 Thomas, R., Kumar, J., Swathi, R. S., Thomas, K. G., Current Sciences, 2011 (invited
article; under revision).

P21
Galvanic Exchange on Reduced Graphene Oxide. Designing
Multifunctional Two-Dimensional Nano assembly
Sachidananda Krishnamurthy and Prashant V. Kamat
Department of Chemistry and Biochemistry,
University of Notre Dame,
Notre Dame, IN 46556, USA
The two-dimensional conductive network of reduced graphene oxide (RGO) acts as a support to
selectively anchor semiconductor and metal nanoparticles. We have succeeded in designing a
multifunctional catalyst mat by anchoring semiconductor nano particles (TiO ) and metal nano
2
particles (silver and gold) on RGO. Photogenerated electrons from UV-irradiated TiO are
2
transported across RGO network to reduce silver ions into silver nanoparticles. These silver
nanoparticles are then galvanically exchanged with gold ions forming gold nanoparticles. Such
interesting chemical transformation on RGO surface demonstrates RGO's versatile ability to
anchor a wide array of nano-particles. This coupled with RGO's unique ability to capture and
conduct electrons has been used to contrive a two-dimensional catalyst nanomat. Furthermore,
Raman studies show that metal nanoparticles anchored in such a fashion give stronger
enhancement of RGO Raman signal than that of a physical mixture of RGO and matal
nanoparticles, indicating such assemblies can be used as effective SERS agents. These findings
pave the way for the development of graphene-based multifunctional composites for “detect
and destroy” applications.

P22
Localized surface Plasmon resonance based u-shaped fiber optic
biosensor for detection of blood
1,* 2 2 1
Sachin K. Srivastava , Vikas Arora , Sameer Sapra , and Banshi D. Gupta
1
Department of Physics, Indian Institute of Technology Delhi, New Delhi, India
2
Department of Chemistry, Indian Institute of Technology Delhi, New Delhi, India
Email: sachinchitransh@gmail.com
In the present study, we report the fabrication and characterization of a U shaped fiber optic
glucose sensor utilizing localized surface plasmon resonance (LSPR) of metal nanoparticles.
Localized surface plasmons are the quanta of charge density oscillations in metal nanoparticles
and get resonantly excited by a radiation of suitable frequency [1]. The probe was prepared by
first attaching gold nanoparticles on the U bent portion of the optical fiber core and then
immobilizing glucose oxidase (GOx) over it [1]. The sensor works in the intensity modulation
scheme in which the absorbance is measured with respect to the change in the concentration of
glucose around the sensing region. Due to the presence of glucose in the vicinity of the sensing
region, the refractive index of the GOx film changes due to the following chemical reaction [1]
Glucose + O
GlucoseOxidase
¾¾¾¾ ¾® GluconicAcid + H O
2 2 2
As a result of local refractive index change, the absorbance of the metal nanoparticle changes
significantly. Fiber optic U-shaped sensing probes of different bending radii were fabricated to
optimize the performance with respect to the bending radius. It has been found that the probe of
around 1mm bending radius possesses the maximum sensitivity. The response of the sensor is
fast and requires very small volume of sensing sample, as it can be used as a point sensor. Only
the tip of the sensor is needed to be in the contact. The concentrations of glucose in aqueous
solutions were kept in the range of blood glucose level to mimic the human blood. The
selectivity and specificity of GOx to glucose have already been established [2]. The present
study is useful in the fabrication of new optical sensors for detection of blood glucose and other
clinical parameters. The use of optical fiber in U- shaped design makes the sensor advantageous
in terms of low sample volumes, enhanced sensitivity and online monitoring, which is not
possible in present commercial glucose sensors.
References:-
1. Srivastava et. al., Plasmonics (Accepted for publication, 2011).
2. Yoo, E.-H. and Lee, S.-Y., Sensors 10, 4558 (2010)

P23
Photonic Crystal devices: demultiplexing and filtering
Sandeep Ummethala
Indian Institute of Science, Bangalore, India
Photonic Integrated Circuits have recently become important for communication & sensor
application due to their chip-level integration with their electronic counterparts. Photonic Band
Gap structures have periodic variation of refractive index profile and promise to provide
compact devices. These have become increasingly popular from the past 5-7 years because of
their ability to control light precisely. It is expected to have huge applications in devices at nanoscale.
The current research involves the study of resonators and more particularly ring
resonators in Photonic Band Gap structures. The resonating characteristics of the ring and its
dependence on various parameters like size, shape and the sharp change in the resonance and
Free Spectral Range (FSR) for different scattering radius has been analyzed. Also, the
application of Photonic Crystal Ring Resonators (PCRR) for adddrop filtering and
demultiplexing has been studied.

P24
Photophysics of Er3+ doped silica embedded Ge nanocrystals prepared
by sol gel technique
1 1 2 3 3 1ǂ
S. Manna , R Aluguri , S Das , N Prtljaga , N Daldosso , S K Ray and L
3
Pavesi
1
Department of Physics and Meteorology, Indian Institute of Technology
Kharagpur, Kharagpur -721 302, India
2
Tyndall National Institute, University College Cork Lee Maltings, Prospect Row,
Cork, Ireland
3
Dipartimento di Fisica, Laboratorio di Nanoscienze, Università di Trento, Via
Sommarive 14, 38100 Povo (Trento), Italy
Rare earth doped silica glasses are of great interest for a range of applications in fiber optics,
3+
waveguide devices and solid-state lasers. Particularly, Er ions in an appropriate host matrix
emit ~1.54 μm near infrared signal, which is the low loss window for modern fiber-optics
3+
telecommunication. The origin of Er luminescence at 1.54 μm is due to intra-4f transition from
4 4
the first excited to the ground state ( I 13/2 → I 15/2) [1]. But this transition is parity forbidden for the
free ion or in a host with inversion symmetry. The partially allowed transition requires a noncentro-symmetric
environment. It has been put forward that the luminescence may be enhanced
3+
by energy transfer from silicon nanocrystals to the Er ions [2]. In this context, germanium with
a larger excitonic Bohr radius (~26 nm) might be a conspicuous alternate material since
quantum confinement is more articulated in Ge than in Si. Here we present the synthesis and
photo-physical process of Er-doped silica glass matrix embedded Ge nanocrystals (NCs)
prepared by the sol–gel method [3]. Different sets of sol-gel glasses have been prepared with
different Ge and Er percentage annealed at different temperatures. Photoluminescence (PL) and
photoluminescence decay times of different sol gel derived glasses have been measured. Strong
photoluminescence at 1.54 µm has been observed from the different sol gel derived glasses and
decay time has been observed to be as high as 9 ms. The PL enhancement was observed
correspondingly with Ge proportion and temperature. Here, Ge NCs acting as strong sensitizers
3+ 3+
for Er ions is explained to elucidate the emission. Energy transfer from Ge NCs to Er ions has
3+
been confirmed by radiatively and non-radiatively (to Er ions) exciting the glasses and
measuring the decay times.
1 Polman A 1997 J. Appl. Phys. 82 1.
2 Pacifici D, Franzo G, Priolo F, Iacona F and Negro L D 2003 Phys. Rev. B 67 245301.
3 Das K, Nagarajan V, NandaGoswami M L, Panda D, Dhar A, and Ray S K 2007
Nanotechnology 18 095704.

P25
Modulation of optical properties of GaN nanowall network by Ag
nanoparticle deposition
Varun Thakur
Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India
In this work, we demonstrate enhancement and quenching of photoluminescence (PL) from
GaN by the deposition of silver nanoparticles. Growing GaN on a c-plane Al2O 3 (0001) surface
in a nitrogen rich ambient yields a fine GaN three-fold nanowall network structure, which forms
as a consequence of lattice-mismatch strain relaxation. The network matrix is formed of wedgeshaped
20-30nm wide nanowalls which show a large surface area and a strong band-edge PL
peak at 362nm. Deposition of metal nanoparticles on such a surface enables one to modify the
opto-electronic properties of the GaN surface. Silver is chosen since it shows the highest
efficiency of plasmon excitation and has a large diffusion coefficient among the three metals
that display plasmon resonance in the visible spectrum. Electroless deposition is used to deposit
silver onto the GaN network structure. A sharp quenching of the GaN PL peak at 362nm is
observed, but as the system was annealed to higher temperatures, new peaks are observed in the
PL spectrum. We use FESEM, XPS and PL as the characterization techniques to progressively
study the system. As the temperature increases from RT to 600°C, we observe that silver
diffuses on the GaN nanowalls and also forms nanoparticles which adsorb on the wall surfaces.
The PL during this temperature change shows some interesting features, starting from the initial
quenching at RT upon Ag adsorption. The PL starts increasing slowly as the system is annealed
to 200°C, but shoots up to almost 10 times the initial intensity when we reach 600°C. Also, new
peaks are observed in the PL spectrum at 382nm, 398nm and 424nm along with a slight red shift
of the 362nm peak to 367nm. However, further annealing to 700°C quenches the whole
emission, concurrent with the observation of silver spreading and covering the nanowalls. This
is also supported by XPS studies; Ag 3d peak increases in intensity when annealed from RT to
600°C, showing that Ag clusters dissociate into mobile Ag nanoparticles. The decrease in
intensity at 700°C is attributed to the layering of silver on the surface, which attenuates the GaN
emission. The valence band spectra obtained from XPS shows the appearance of metallic states
near the Fermi level. The results are understood in terms of the coupling between the GaN bandedge
emission and the surface plasmons of the Ag nanoparticles