it explains the role of metal nano particles in bio appkictions

1. PONDICHERRY UNIVERSITY
CENTRE FOR NANOSCIENCE AND TECHNOLOGY
NANOPHOTONICS AND BIOPHOTONICS
TOPIC :Metallic nanoparticles and nanorods for Biosensing
SUBMITTED TO SUBMITED BY
DR P. THANGADURAI VENKATA KISHORE .PERLA
M.TECH II YEAR

2. What is a Biosensor?

3. Nano sensors
Nanotechnology opened doors to new
ways of identifying and quantifying
biomolecules through use of nanosensors
and nanoprobes.
• Tools are capable of monitoring
biomolecular processes within single
cells.
• Use in biological and medicinal
research.
• Two major categories,
(i) biosensors (consists of biological
recognition element called
bioreceptor (Ab, NA or enzyme, cell)
and a signal transducer
(ii) chemical sensors (chemical
recognition element eg pH sensitive
dye and a signal transducer).

4. Why Nanosensors ???
 Particles that are smaller than the characteristic lengths associated with the specific
phenomena often display new chemistry and new physics that lead to new properties
that depend on size
 When the size of the structure is decreased, surface to volume ratio increases
considerably and the surface phenomena predominate over the chemistry and physics
in the bulk
 The reduction in the size of the sensing part and/or the transducer in a sensor is
important in order to better miniaturise the devices
 Science of nano materials deals with new phenomena, and new sensor devices are
being built that take advantage of these phenomena
 Sensitivity can increase due to better conduction properties, the limits of detection
can be lower, very small quantities of samples can be analysed, direct detection is
possible without using labels, and some reagents can be eliminated.

5. Why metal nano particles as sensors
• The unique optical and electromagnetic
properties of metal nanoparticles can be
utilized in several areas including biosensing.
• The plasmonic resonance created in metal
nanoparticles is extremely sensitive for
changes in their surroundings, making them
suitable elements for sensing applications.

6. Nobel metal nano particles
• In particular, the unique properties of noble metal
nanoparticles have allowed for the development of new
biosensing platforms with enhanced capabilities in the
specific detection of bioanalytes.
• Noble metal nanoparticles show unique
physicochemical properties (such as ease of
functionalization via simple chemistry and high
surface-to-volume ratios) that allied with their unique
spectral and optical properties have prompted the
development of a plethora of biosensing platforms.

7. • Several researchers have focused on biosensor for monitoring
of biological interaction. Moreover, the detection of
bimolecular is an extremely significant problem. Hence, the
development of optical biosensors based on optical properties
of noble metal nanoparticles using Surface Plasmon
Resonance was considered.
• Surface plasmon resonance (SPR) is a powerful technique to
retrieve information on optical properties of biomaterial and
nanomaterials. Biosensor based on SPR is a versatile
technique for biological analysis applications. Essentially,
SPR depends on the optical properties of metal layer and
enviromental changes so it is related to charge density
oscillation at the interface between them .
• One advantage of SPR is, the light beam never passes through
the dielectric medium of interest and hence the effect of
absorption of the light in the analyte can be ignored. Hence,
the main potential of surface plasmon resonance is
characterization of medium after the metal layer.

8. • Biomolecular interaction are determined and predicted via angular
modulation sensor; hence, the out put of SPR biosensor sensor is angle shift
(θspr), associated with the point of minimum reflected light intensity and is
very sensitive to the changes in the dielectric constant of the medium.
• Fundamentally, the base of the biosensor is the coupling of a ligand-receptor
binding reaction to a signal transducer. Moreover, angular, phase and
polarization modulations are the various methods applicable for
distinguishing the interaction of bimolecular with the receptor.
• Essentially, SPR is a quantum electromagnetic phenomenon that appears at
the interface of the dielectric and the metal. Under certain conditions, the
energy of the light beam is absorbed by collective excitation of the free
electrons called surface Plasmon (SP), which lies between the interface of
the dielectric and the metal.
• On the other hand, when the momentum of the photon matches that of the
Plasmon, the resonance appears as an interface of two two media with
dielectric constants of opposite signs, and the SP wave propagates along the
interface. In accordance with the SP wave properties, the SPR is classified as
propagating the SPR, the long-range SPR and the localized SPR.

9. METAL NANO RODS FOR BIOSENSOR
Synthesis of metal nano rods
Thermo-vapor transport method
A general setup for thermal-vapor transport method

11. Catalyst-assisted fabrication
Deposition of a catalyst layer, e.g. thermal evaporation of a 10 nm thick metal film
or injection of a precursor which decomposes into particles
ZnO nanorods on Au and NiO catalysts

13. Template-based Methods

14. Kim k. et al.

15. A schematic summary of the kinds of quasi-one-dimensional
metaloxide nanostructures
(A) nanowires and nanorods; (B) core-shell structures with metallic inner core,
semiconductor, or metal-oxide; (C) nanotubules/nanopipes and hollow nanorods;
(D) heterostructures; (E) nanobelts/nanoribbons; (F) nanotapes, (G) dendrites,
(H) hierarchical nanostructures; (I) nanosphere assembly; (J) nanosprings.

16. • Gold nanoparticles have a long history as optical
or electron microscopy labels. More recently, their
plasmon resonance has been employed for more
elaborate optical nanoscopic-sensing schemes.
• Rod-shaped nano-particles remain popular for
plasmonic applications. Some reasons for this are
the ability to fabricate gold nanorods in high
quality using seeded crystallization from solution,
the adjustability of the plasmon resonance by
varying the aspect ratio, the strong scattering
efficiency, and the low plasmon damping in
nanorods

17. • There are several different quantities that describe
the performance of a plasmonic structure for
sensing applications on a single particle level—and
all of them have their merits for certain
applications. We will discuss the most important of
them in the following Paragraphs — the plasmonic
sensitivity to refractive index change as well as
various ‘figures of merit’—and present their
dependency on nanorods
• In practice, one would normally detect a spectral
shift of a resonance as a relative intensity change
dl/l at a fixed wavelength λ0induced by a small
index change dn. We can therefore define an
alternative dimensionless figure of merit:

18. • Bio-sensing applications are even more complex. In this case, one seeks to detect
the binding of small (organic) molecules to the nanoparticle surface instead of
exchanging the entire embedding medium. The spectral shift now depends on the
relative size of the molecules to the volume the plasmon field penetrates into the
medium.

19. • Furthermore, the sensitivity is reduced with increasing distance to the particles
surface. A‘figure of merit’ trying to capture the different sensing volumes of
various nanostructures can be defined as the FOM layer * for a homogeneous
coating of molecules with a specific refractive index (for example, n=1.5, typical
for organic molecules) in a layer of thickness l around the particle normalized to
this layer thickness. The formal definition of this ‘ figure of merit for thin
layers’FOM layer*is therefore

20. References
• The Optimal Aspect Ratio of Gold Nanorods
for Plasmonic Bio-sensing.
• BIOSENSOR by Pier Andrea Serra Intech.
• Application of Surface Plasmon Resonance
Based on a Metal Nanoparticle.
• http://dx.doi.org/10.5772/512191.