FIBER OPTIC EVANESCENT WAVE BIOSENSORdspace.cusat.ac.in/jspui/bitstream/123456789/10134/1/FIBER OPTIC... · CONTENTS 1. Introduction 1 1.1Optical Fiber 2 1.2 Fiber Optic Sensor 4

FIBER OPTIC EVANESCENT WAVE BIOSENSOR

Project report submitted in partial fulfillment of the requirement of the award of

degree

MASTER OF TECHNOLOGY

IN

OPTOELECTRONICS AND LASER TECHNOLOGY

Submitted by

Smrithi.V

Register No. 95713009

Under the guidance of

Dr. P. Radhakrishnan,

International School of Photonics

Cochin University of Science & Technology

Cochin‐ 682022

ACKNOWLEDGEMENT

With deep sense of gratitude, I express my heartfelt thanks to

Dr. P. Radhakrishnan, Professor, ISP for the guidance, motivation, support and

encouragement given throughout my project work. I express my sincere gratitude to Dr.

M. Kailasnath, Director, ISP for the help rendered . I also express my sincere thanks to

Dr. V.P.N Nampoori Emeritus Professor, ISP for his help. I am thankful to all the

research scholars of ISP especially Mr. Bobby Mathews. C , Ms. Roopa Venkataraj and

Sister Rosmin for their constant support and help. I extend my sincere thanks to the

teaching and non‐ teaching staff of ISP for all the help and assistance. I would like to

remember my friends who helped me and supported me. I am extremely grateful to my

family who were a constant source of encouragement. Last, but most important of all, I

thank Almighty God.

Smrithi.V

ABSTRACT

Biosensors are analytical devices that can detect chemical or biological species or a

microorganism. A biosensor utilizes a biological recognition element that senses the presence

of an analyte ie; the species to be detected and creates a physical or chemical response that is

converted by a transducer to a signal. Biosensors can be used in clinical diagnostics, drug

development, environmental monitoring air, water, soil and food quality control.

Fiber Optic Biosensors (FOBS) are optical fiber derived devices which use optical field to

measure biological species. Because of their chemical inertness, their compatibility to a wide

range of surface modification, the potential for remote sensing, efficiency, accuracy, low cost,

and the ready availability of inexpensive lasers and photodetectors, FOBS are promising

alternatives to traditional methods for biomolecule measurements. One reliable and sensitive

optical method is evanescent sensing. A sensor based on evanescent field absorption relies on

the interaction of a target substance with the evanescent field adjacent to the fibre core.

Removing the cladding from a portion of an optical fibre permits the evanescent field to

interact with the substances in‐which the fibre is immersed. The objective of this project work

is to develop a Fiber Optic Biosensor based on evanescent wave to detect the microorganisms

such as Yeast molecule and to evaluate their activity in the presence of Curcumin and Neera.

CONTENTS

1. Introduction 1

1.1Optical Fiber 2

1.2 Fiber Optic Sensor 4

1.2.1 Classification of Fiber‐Optic Sensors 5

1.3 Biosensors 5

1.3.1 Introduction 5

1.3.2 Principles of Optical Biosensors 7

1.3.3 Optical Transduction 8

1.3.4 Immobilization of Biorecognition elements 9

1.4 Fiber Optic Biosensors 11

1.4.1 Different types of FOBS 12

1.5 Evanescent Wave Fiber Optic Biosensors 13

1.6 Yeast 171.7 Curcumin 181.8Neera 18

2. Measurement of absorption spectrum of yeast in curcumin 19

3. Measurement of absorption spectrum of yeast in neera 30

4. Measurement of absorption spectrum of curcumin in neera 38

5. Measurement of absorption spectrum of yeast in curcumin and neera 48

6. Conclusions 61

References 62

1

CHAPTER 1

INTRODUCTION

The field of biosensors has emerged as a topic of great interest because of the great

need in medical diagnostics and, more recently, the worldwide concern of the threat of

chemical and bioterrorism. The constant health danger posed by new strands of microbial

organisms and spread of infectious diseases is another concern requiring biosensing for

detecting and identifying them rapidly. Conventional laboratory methods for the detection of

microorganisms and biological toxins in food, water, and human specimens are often time

consuming, require extensive training in microbiology and give delayed results. Various rapid

methods have also been attempted. These methods, while rapid, require sophisticated,

expensive, non portable equipment, thus limiting their usefulness as real‐world detection

systems. These sensitivities also are often limited. Optical biosensors utilize optical techniques

to detect and identify chemical or biological species. They offer a number of advantages such as

the ability for principally remote sensing with high selectivity and specificity and the ability to

use unique biorecognition schemes.

A biosensor is an analytical device that combines a biological sensing element with a

transducer to produce a signal proportional to the analyte concentration. This signal can result

from a change in protons concentration, release or uptake of gases, light emission, absorption

and so forth, brought about by the metabolism of the target compound by the biological

recognition element. The transducer converts this biological signal into a measurable response

such as current, potential or absorption of light through electrochemical or optical means,

which can be further amplified, processed and stored for later analysis. Fiber Optic Biosensors

(FOBS) use optical fibers as the transduction element, and rely exclusively on optical

transduction mechanisms for detecting target biomolecules. Evanescent wave FOBS are

biosensors that utilize evanescent wave detection techniques. Electromagnetic waves

propagate within an optical fiber by total internal reflection at the exposed surface. Light

propagating through an optical fiber consists of two components: the guided field in the core

and the exponentially decaying evanescent field in the cladding. In evanescent wave FOBS the

cladding of a fiber is reduced or removed, the evanescent wave can interact with the

surroundings. Thus evanescent wave FOBS can identify such target analytes in minutes directly

from complex matrix samples, significantly improving the detection sensitivity, selectivity, and

speed.

The detection of chemical and biological agents is a key problem in environment

protection and food monitoring. Traditional laboratory methods can accurately detect the

chemical and biological agents. But the need for expensive devices, special operators, and also

long time for detection limit their wide applications. Thus, it is an urgent demand to develop a

simple, rapid, economical, portable and accurate detection device based on biological agent.

2

This project aims to investigate the properties of evanescent waves and to explore their novel

applications as sensing devices for detecting Yeast molecules, because the rapid detection and

identification of Yeast molecules are necessary for the assessment of their beneficial and

harmful roles in the production and spoilage of foods respectively

Fiber‐optic communication systems are light wave systems that employ optical fibers for

information transmission. Such systems have been deployed worldwide since 1980 and have

indeed revolutionized the technology behind telecommunications. Indeed, the light wave

technology, together with microelectronics, is believed to be a major factor in the advent of the

“information age.”

1.1 OPTICAL FIBER

An optical fiber is a dielectric waveguide that operates at optical frequencies. An optical

fiber is cylindrical in form consisting of the core, the cladding and the buffer. The basic structure

is shown in figure 1.1.

Fig 1.1 Basic structure of an optical fiber

The core is a cylindrical rod of dielectric material and is generally made of glass. Light

propagates mainly along the core of the fiber. The cladding layer is made of a dielectric material

with an index of refraction less than that of the core material. The cladding is usually made of

glass or plastic. The cladding reduces scattering loss that results from dielectric discontinuities

at the core surface, it adds mechanical strength to the fiber, and it protects the core from

absorbing surface contaminants with which it could come in contact. The coating or buffer is a

layer of material used to protect an optical fiber from physical damage. The material used for a

buffer is a type of plastic. The buffer is elastic in nature and prevent abrasions.

The light propagates through the fiber by total internal reflection. The angle at which

total internal reflection occurs is called the critical angle of incidence. At any angle of incidence,

3

greater than the critical angle, light is totally reflected back into the glass medium. The critical

angle of incidence is determined by Snell’s Law.

Figure 1.2 Total Internal Reflection in an Optical Fiber

Optical fibers are divided into two groups called single mode and multimode. Single

mode fiber is optical fiber that is designed for the transmission of a single ray or mode of light

as a carrier and is used for long‐distance signal transmission. Single mode fiber has a much

smaller core than multimode fiber. Multimode fiber is optical fiber that is designed to carry

multiple light rays or modes concurrently, each at a slightly different reflection angle within the

optical fiber core. Multimode fiber transmission is used for relatively short distances because

the modes tend to disperse over longer lengths (this is called modal dispersion).For longer

distances, single mode fiber sometimes called monomode) fiber is used. In classifying the index

of refraction profile, we differentiate between step index and graded index. Step index fibers

have a constant index profile over the whole cross section. Graded index fibers have a

nonlinear, rotationally symmetric index profile, which falls off from the center of the fiber

outwards. Figure 1.3 shows the different types of optical fibers

19

Chapter 2

MEASUREMENT OF ABSORPTION SPECTRUM OF YEAST IN CURCUMIN

This section deals with the determination of the absorption spectrum of

(a) Curcumin in ethanol,

(b) Yeast and Curcumin dissolved in ethanol

using Jasco V‐570 UV/ Visible/ NIR Spectrophotometer and Ocean Optics Spectrometer.

2.1. Measurement of absorption spectrum of Curcumin in ethanol and different

concentrations 0.2, 0.4, 0.6 and 0.8 gms of yeast in curcumin using

Spectrophotometer.

Preparation of the sample

(i) Curcumin

40 ml of ethanol is taken in a beaker. 10‐4 molar curcumin is weighed and

dissolved well in ethanol.

(ii) Yeast in Curcumin

Take four 100ml beakers and label them as 0.2, 0.4, 0.6 and 0.8 gms. Add

20 ml of sterilized water into each of these beakers. Then weigh 0.2, 0.4, 0.6

and 0.8 gms of Yeast using a weighing balance and dissolved well into the

sterilized water. Divide the curcumin solution into four equals parts and pour

into the four beakers containing yeast extract.

Experimental procedure

Absorption spectrum of the samples are taken using UV Visible NIR Spectrophotometer.

Graph showing absorption spectrum for curcumin and different concentrations of Yeast

in curcumin are shown in figures below.

20

(a)

(b)

(c)

21

(d)

(e)

Fig 2.1 Absorption spectrum for curcumin and different concentrations of yeast in curcumin.

Variation in the wavelength of peak 3 for different concentrations of yeast is plotted below.

0.2 0.3 0.4 0.5 0.6 0.7 0.8

425

426

427

428

429

Wav

elen

gth (nm

)

Concentration of yeast (gms)

Conc Vs wavelength

Fig 2.2 Graph showing the variation in wavelength of peak 3 for different concentrations of

yeast in the presence of constant amount of curcumin

22

Conclusions

1. Absorption spectrum was well defined at lower concentrations.

2. As the concentration of yeast in curcumin is increased peak 3 showed a blue shift in

wavelength.

3. The experiment was repeated for lower concentrations 0.0005, 0.001, 0.005, 0.01, 0.05,

0.1 and 0.2 gms and for higher concentrations 1, 3 and 5 gms of yeast. The above

result was repeated for lower concentrations. For higher concentrations structure

of the absorption spectrum changes with the addition of yeast.

2.2 Measurement of evanescent wave absorption spectrum of Curcumin in ethanol

and different concentrations of yeast in curcumin.

Absorption spectrum is obtained using evanescent wave sensor and ocean optics

spectrometer. Experimental layout is as follows. Here the variation in intensity of output light is

determined for different concentrations of yeast in curcumin.

Equipments required are

(i) White light LED source

(ii) Sensing cell : Made of glass, 15 cm long, 2.5 cm wide

(iii) Sensing fiber: Multimode, 400 μm core diameter, 430 μm cladding diameter

(iii) Ocean optics spectrometer: HR 4000, responsive from 200‐

1100 nm.

Preparation of Sensing Fiber

Take Plastic Clad Silica fiber of length 30 cm. The ends of the fiber should be polished for

maximum coupling of light from source to fiber and also from fiber to detector. A small portion

of the fiber is removed from both the ends of the fiber. These ends are then cut with a

diamond cutter. Hand polishing is done by drawing figure "8" patterns on a polishing sheet.

After determining the desired sensor length, it is marked at the middle portion of the fiber. The

sheath as well as the cladding of the marked portion is then removed using a razor blade. The

remaining cladding is removed by dipping that portion in acetone.

Preparation of Sensing Cell

The sensing cell is made from cylindrical glass tube of length 15cm and of diameter 2.5 cm.

The two ends of the tubes are closed and a hole is made at each ends through which the fiber

is passed.

23


(i) Curcumin



(ii) Yeast in Curcumin

Take seven 100ml beakers and label them as 0.0005, 0.001, 0.005, 0. 01, 0.05,

0.1 and 0.2 gms. Add 20 ml of sterilized water into each of these beakers. Then

weigh 0.0005, 0.001, 0.005, 0. 01, 0.05, 0.1 and 0.2 gms of Yeast using a

weighing balance and dissolved well into the sterilized water. Divide the

curcumin solution into seven equals parts and pour into the seven beakers

containing yeast extract.

Experimental Set Up

24

Fig 2.3 Experimental set up for Evanescent wave biosensor


Fix the components required for the sensing on the optical bench. Switch on the white

light source. Align the components in such a way that light coming out from the fiber falls on

the ocean optics spectrometer. Take the spectrum of the cell. Then pour the different

concentrations of sample into the glass cell one by one and note the corresponding intensity of

output light in terms of wavelength. Ensure that each time before adding the new

concentration of sample into the glass cell, the sensing cell must be cleaned using the

sterilized water.

25

Absorption spectrum of source, cell, curcumin and different concentrations of yeast in

curcumin are shown below . The first peak is obtained at 453 nm.

Second peak is obtained at 545 nm.

(a)

Second peak is at 549 nm

(b)

26

Second peak for curcumin is at 555 nm.

(c)

200 400 600 800 1000 1200600

800

1000

1200

1400

1600Yeast 0.0005 gm + Curcumin

Intens

ity

Wavelength

Wavelength of the second peak is at 591 nm.

(d)

200 400 600 800 1000 1200700

800

900

1000

1100

1200


Intensity

Wavelength


(e)

200 400 600 800 1000 1200700

800

900

1000

1100

1200

Yeast 0.005 gm + Curcumin

Intensity

Wavelength

27


(f)

200 400 600 800 1000 1200700

800

900

1000

1100

1200


Intensity

Wavelength


(g)

200 400 600 800 1000 1200700

800

900

1000

1100

1200


Intensity

Wavelength


(h)

200 400 600 800 1000 1200

800

1000

1200

1400

1600

Intensity

Wavelength

Yeast 0.1 gm + Curcumin


28

(i)

200 400 600 800 1000 1200600

800

1000

1200

1400

1600


Intensity

Wavelength


(j)

Fig 2.4 Evanescent wave absorption spectrum for different concentrations of yeast in

curcumin

Graph showing the variation in relative intensity and wavelength of the second peak

with concentration of yeast are shown below.

0.00 0.05 0.10 0.15 0.201.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

2.0Conc. Vs Relative intensity

Rela

tive in

tens

ity

Conc. oc yeast in gms

(a)

29

0.00 0.05 0.10 0.15 0.20

800

1000

1200

1400

1600

Inte

nsi

ty o

f firs

t pea

k

Conc. of yeast in gms

Y+C

(b)

0.00 0.05 0.10 0.15 0.20540

550

560

570

580

590

600

610

Wave

leng

th (

nm

)

Concentration of Yeast (gms)

Conc. Vs Wavelength

(c)

Fig 2.5 Graph showing the variation in (a) relative intensity , (b) Intensity of peak 1 and (c)

wavelength of peak 2 for different concentrations of yeast

Conclusions

1. It was observed that when yeast was added to curcumin,

there was a red shift in wavelength for peak 2 .

2. When concentration of yeast was increased further there is a

blue shift followed by saturation.

3. In the presence of curcumin, the first peak gets suppressed

especially at lower concentrations of yeast.

30

4. Thus yeast can be detected in the presence of curcumin

especially at low concentrations .

30

Chapter 3

MEASUREMENT OF ABSORPTION SPECTRUM OF YEAST IN NEERA

This section deals with the determination of the absorption spectrum of Yeast

dissolved in sterilized water in neera using Jasco V‐570 UV/ Visible/ NIR Spectrophotometer

and Ocean Optics Spectrometer.

3.1 Measurement of absorption spectrum of different concentrations 0.1, 0.5, 1

and 2 gms of yeast in neera.


Yeast in neera

Take four 100ml beakers and label them as 0.1, 0.5, 1 and 2 gms. Add 20 ml of sterilized water

into each of these beakers. Then weigh 0.1, 0.5, 1 and 2 gms of Yeast using a weighing

balance and dissolve well into the sterilized water. Add 30 ml neera into these beakers and stir

well.



Graph showing absorption spectrum for neera, 0.1 gm concentration of Yeast and

different concentrations of yeast in neera are shown in figures below.

200 400 600 800 1000 1200

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Abso

rbanc

e (A

U)

Wavelength (nm)

Neera

(a)

31

(b)

Downward peak is observed at 298 nm and upward peak at 360 nm.

(c)

Upward peak is observed at 338 nm.

(d)

32


(e)


(f)

Fig 3.1 Absorption spectrum for neera, yeast and yeast in neera

Graph showing the variation in wavelength of the absorption peak with concentration of

yeast in neera is shown below.

33

-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2325

330

335

340

345

350

355

360

365

Wav

eleng

th (nm

)


Y+N

Fig 3.2 Graph showing variation in wavelength for the peak with concentration of yeast

Conclusions

1. Peak absorption spectrum of neera is at 238 nm.

2. Addition of yeast shifts the absorption maximum of yeast from around 220 nm to

360 nm at low concentration.

3. With increase in concentration of yeast, the peak shifts to blue side.

4. In the presence of neera, there is a switch over from negative values of absorption to

positive values at lower concentrations of yeast.

5. This enables the measurement of concentration of yeast in the presence of neera.

3.2 Measurement of evanescent wave absorption spectrum of different

concentrations of yeast in neera.

Evanescent wave absorption spectrum is obtained using evanescent wave sensor and ocean

optics spectrometer. Experimental layout and set up is explained in section II of chapter 2.

Here the variation in intensity of output light is determined for different concentrations of

yeast in neera.

Evanescent wave absorption spectrum of of source, cell, neera and different

concentrations of yeast in neera are given below. For all cases first peak is obtained at 453 nm.

34


(a)


(b)

Wavelength of second peak is 556 nm.

(c)

35

Peak is obtained at 569 nm.

(d)

Second Peak is obtained 568 nm.

(e)

Peak obtained at and 568 nm.

(f)

36

Peaks is obtained at 568 nm.

(g)

Fig 3.3 Evanescent wave absorption spectrum for different concentrations of yeast in neera

Variation in wavelength of second peak with increase in the concentration of yeast is

shown below.

0.0 0.5 1.0 1.5 2.0

568.0

568.2

568.4

568.6

568.8

569.0Conc. Vs Wavelength

Wa

vele

ngth

(n

m)

Conc. of yeast in gms

Fig 3.4 Concentration of yeast Vs wavelength of second peak

37

Conclusions

1. In the presence of neera with increase in concentration of yeast, the relative intensity

increases.

2. There is no appreciable change in the evanescent wave absorption spectrum of yeast in

neera at higher concentrations. The first peak was immersed in noise.

3. Absorption spectrum gives a better signature regarding the measurement of yeast in the

presence of neera.

4. Experiment was performed for higher concentrations of yeast (upto 20 gms). But there

was not much variation in the output and hence has not been presented here.

38

Chapter 4

MEASUREMENT OF EVANESCENT WAVE ABSORPTION SPECTRUM OF CURCUMIN IN

NEERA


spectrometer. Experimental layout and set up is explained in section II of chapter 2. Here the

variation in intensity of output light is determined for different concentrations of curcumin in

neera.

4.1Measurement of Evanescent wave absorption spectrum of 10 ‐3 molar

curcumin in neera.


Curcumin in neera

Take four 100ml beakers and label them as 0.25*10 ‐3molar curcumin,

0.33*10 ‐3 molar, 0.5*10 ‐3 molar curcumin and 10 ‐3 molar curcumin,. Take 80ml,

60ml, 40ml and 20ml ethanol in the above beakers. Weigh 10 ‐3 molar curcumin using a

weighing balance and add into the beakers and dissolve well in ethanol. Add 30 ml

neera into these beakers and stir well.

Graph showing evanescent wave absorption spectrum for neera, different

concentrations of curcumin in neera are shown in figure below. The first peak was at

453 nm for all the cases.

(a)

The second peak is at 545 nm.

39

(b)

Second peak is observed at 547 nm.

(c)

The second peak is at 555 nm.

(d)


40

(e)


c

(f)


(g)


Fig 4.1 Evanescent wave absorption spectrum for different concentrations of curcumin

in neera.

41

Variation in the intensity of peak 1 and wavelength of peak 2 for different concentrations

of curcumin are plotted below.

0.25*10-3 0.33*10-3 0.5*10-3 10-3

1000

1500

2000

2500

3000

3500

C+N

Inte

nsity

(A

U)

Molar conc of curcumin

(a)

0.25*10-3 0.33*10-3 0.5*10-3 10-3544

546

548

550

552

554

Wave

length

(nm

)

Molar concentration of curcumin

C+N

(b)

Fig 4.2 Graphs showing (a) Concentration of curcumin Vs intensity of peak 1 & (b)

Concentration of curcumin Vs wavelength of peak 2 for 0.25 10‐3 to 10‐3 Molar

curcumin in the presence of neera.

42

4.2 Measurement of evanescent wave absorption spectrum of 10 ‐6, 10 ‐5,

10 ‐4molar curcumin in neera.


Curcumin in neera

Take three 100ml beakers and label them as 10 ‐6molar curcumin,

10 ‐5 molar curcumin and 10 ‐4 molar curcumin. Take 40 ml ethanol in the

above beakers. Weigh 10 ‐6 molar curcumin, 10 ‐5 molar curcumin and 10 ‐4

molar curcumin using a weighing balance and add into the respective beakers

and dissolve well in ethanol. Add 10 ml neera into these beakers and stir well.

Add 10 ml ethanol to the above three samples to obtain the next sample to

obtain 0.8 molar concentrations. 10 ml ethanol is again added to obtain the 0.67

molar concentrations.


concentrations of curcumin in neera are shown in figure below. The first peak was at

453 nm for all the cases.

(a)


43

(b)


(c)


(d)


44

(e)


(f)


(g)


45

(h)


(i)


(j)


46

(k)


Fig 4.3 Evanescent wave absorption spectrum for different concentrations of curcumin

in neera.

0.67*10-6 0.8*10-6 10-6 0.67*10-4 0.8*10-4 10-43600

3800

4000

4200

4400

4600

C+N

Inte

nsity

(AU)

Molar conc. of Curcumin

(a)

47

0.67*10-6 0.8*10-6 10-6 0.8*10-5 10-5 0.8*10-4 10-4548

550

552

554

556

558

560

C+N

Wave

length

(nm

)

Molar conc. of Curcumin

(b)

Fig 4.4 Graphs showing (a) Concentration of curcumin Vs intensity of peak 1 & (b)

Concentration of curcumin Vs wavelength of peak 2 in the presence of neera.

Conclusions

1. When neera is added to curcumin there was a blue shift in wavelength for the

second peak when the concentration of curcumin was increased.

2. Also the amplitude of the first peak decreased with the concentration of curcumin.

3. The device performs in a linear fashion at lower concentrations and shows

saturation at higher concentrations.

4. Hence neera can be used to measure the concentration of curcumin.

48

Chapter 5

MEASUREMENT OF ABSORPTION SPECTRUM OF YEAST IN CURCUMIN AND NEERA

This section deals with the determination of the absorption spectrum of Yeast dissolved in

sterilized water in neera and curcumin using Jasco V‐570 UV/ Visible/ NIR Spectrophotometer

and Ocean Optics Spectrometer‐HR 4000 ( 200‐1100 nm).

5.1 Measurement of absorption spectrum of different concentrations 0.001, 0.01, 0.1

and 1 gm Yeast in curcumin and neera.


(i) Curcumin



(ii) Yeast in Curcumin and Neera

Take four 100ml beakers and label them as 0.001, 0.01, 0.1 and 1 gms. Add 20

ml of sterilized water into each of these beakers. Then weigh 0.001, 0.01, 0.1 and

1 gms of Yeast using a weighing balance and dissolved well into the sterilized

water. Divide the curcumin solution into four equal parts and pour into the four

beakers containing yeast extract. Add 30 ml of neera into four beakers and stir

well.



Graph showing absorption spectrum for curcumin and different concentrations of Yeast

in curcumin are shown in figures below.

(a)

49

200 400 600 800 1000 1200

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Abs

orba

nce (AU)

Wavelength (nm)

Neera

(b)

(c)

(d)

50

(e)

(f)

(g)

51

(h)

(i)

(j)

Fig 5.1 Absorption spectrum for yeast in curcumin and neera

52

Graph showing the variation in wavelength of the absorption peak with concentration of

yeast in neera and curcumin is shown below.

0.0 0.2 0.4 0.6 0.8 1.0

340

360

380

400

420

440

Wave

leng

th o

f pea

k (n

m)

Conc. of yeaast in gms

YNC

Fig 5.2 Absorption peak Vs concentration of yeast

Conclusions

1. With increase in concentration of yeast, the peak shifts to blue side.

2. This enables the measurement of concentration of yeast in the presence of neera and

curcumin.

5.2 Measurement of evanescent wave absorption spectrum of different

concentrations of yeast in curcumin and neera.


spectrometer. Experimental layout and set up is explained in section II of chapter 2. Here the

variation in intensity of output light is determined for different concentrations of yeast in

curcumin and neera. Preparation of the sample is explained in section I.

Absorption spectrum using ocean optics spectrometer is shown below.

53


(a)


(b)


(c)

54


(d)


(e)


(f)

55


(g)

Fig 5.3 Evanescent wave absorption spectrum of yeast in neera and curcumin

Variation in wavelength of second peak with increase in the concentration of yeast is shown

below.

0.0 0.2 0.4 0.6 0.8 1.0568

569

570

571

572

573YNC

Wave

leng

th (nm

)


Fig 5.4 Concentration of yeast Vs wavelength of the second peak

56

Conclusions

1. First peak was suppressed when neera and curcumin are added to yeast.

2. For lower concentrations of yeast, there is blue shift in wavelength of the second

peak .

3. For higher concentrations wavelength saturates so sensitivity is low.

4. This enables the measurement of lower concentration of yeast in the presence of

neera and curcumin.

5.3 Measurement of absorption spectrum of different concentrations of

curcumin in Yeast and neera.


spectrometer. Experimental layout and set up is explained in section II of chapter 2.

Here the variation in intensity of output light is determined for different

concentrations of yeast in curcumin and neera.


a) Curcumin in neera

Take four 100ml beakers and label them as 10 ‐4, 5* 10 ‐4, 10 ‐3 and 5* 10 ‐3

molar .Take 40ml ethanol into each of these beakers. Then weigh 10 ‐4, 5* 10 ‐4,

10 ‐3 and 5* 10 ‐3 molar curcumin using a weighing balance and add into the

beakers and dissolve well into the ethanol.

b) Yeast in neera

Take a 100ml beaker and add 20 ml of sterilized water into it. Then weigh 0.01 gm

of Yeast using a weighing balance and dissolve well into the sterilized water. Add 30ml

neera into this beaker and stir well. Now the solution is divided into four and poured

into the four beakers containing curcumin.

Evanescent wave absorption spectrum of the samples are determined using Ocean Optics

Spectrometer


concentrations of curcumin in neera and yeast are shown in figure below.

57


(a)


(b)


(c)

58


(d)


(e)


(f)

59


(g)


(h)

Fig 5.5 Evanescent wave absorption spectrum of curcumin in yeast and neera

Variation in wavelength of second peak with increase in the concentration of curcumin is

shown below.

60

10-4 5*10-4 10-3 5*10-3

550

555

560

565

570

575

580

585

Wave

length

(nm

)

Molar Concentration of curcumin

Y+N+C

Fig 5.6 Concentration of Curcumin Vs wavelength of second peak

Conclusions

1. There is complete elimination of first peak in the presence of neera and yeast.

2. Signal strength is comparatively high and noise is also absent.

3. When concentration of curcumin was increased, spectrum shows red shift which is a

concentration related feature.

4. This enables the detection of curcumin in the presence of neera and yeast .

Comparison

In Evanescent wave absorption

1. When concentration of curcumin in the presence of yeast and neera is increased, there

was red shift in wavelength of peak 2 from 552 nm to 585 nm.

2. When concentration of yeast in the presence of curcumin and neera was increased,

there was blue shift in wavelength of peak 2 from 573 nm to 569nm.

61

Chapter 6

CONCLUSIONS

This project started with the detection of yeast in the presence of curcumin. First

absorption spectrum for different concentrations of yeast in curcumin was studied.

Absorption spectrum was well defined at lower concentrations. As the concentration of

yeast in curcumin is increased peak 3 showed a blue shift in wavelength. Then the spectral

analysis of the samples was done using evanescent wave sensor and ocean optics

spectrometer. It was observed that as the concentration of yeast was increased there was a

small red shift in wavelength for peak 2 initially . When yeast concentration was increased

further there was a blue shift and subsequent saturation. Also the first peak gets

suppressed at lower concentrations of yeast.Thus yeast can be detected in the presence of

curcumin. For the next studies neera was added to yeast. With increase in concentration of

yeast, the second peak shifts to blue side. There was a switch over from negative values of

absorption to positive values of absorption at lower concentrations of yeast in the

absorption spectrum. This enables the measurement of concentration of yeast in the

presence of neera. There was no appreciable change in the evanescent wave absorption

spectrum of yeast in neera at higher concentrations. Next reaction between neera and

curcumin was studied using ocean optics spectrometer . When neera is added to curcumin

there was a blue shift in wavelength for the second peak when the concentration of

curcumin was increased. Also the amplitude of the first peak decreased with the

concentration of curcumin unlike in the case of reaction between curcumin and yeast where

there was an increase in the amplitude of the first peak. Hence neera can be used to

measure the concentration of curcumin. For the final studies yeast in the presence of

curcumin and neera was taken. Evanescent wave absorption spectrum for different

concentrations of yeast in curcumin and neera are taken using ocean optics spectrometer.

First peak was suppressed due to the presence of curcumin and neera. Second peak has a

blue shift and saturation, as concentration of yeast was increased. This enables the

measurement of concentration of yeast in the presence of neera and curcumin. Evanescent

wave absorption spectrum for different concentrations of curcumin in the presence of yeast

and neera was studied next. Here also the first peak was suppressed. As the concentration

of curcumin was increased, there was a red shift in wavelength. This enables the detection

of curcumin in the presence of neera and yeast . From this studies I conclude that even

small concentrations of yeast and curcumin can be detected in the presence of neera .

62

REFERENCES

[1] B.D.Gupta, “ Fiber Optic Sensors: Principles and Applications”, 3rd Edition, 2006, ( New India

Publishing Agency).

[2] Paras N Prasad, “ Introduction to Biophotonics”, 4th Edition, 2003, (published by John. Wile

and sons, Inc).

[3] Otto S Wolfbeis, “ Fiber optic chemical sensors and Biosensors”, Analytical Chemistry, 2004

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[4] Mehrab Mehrvar and Chris Bis, “Fiber Optic Biosensors‐Trends and Advances”, Analytical

Sciences, 2000, Vol. 16, pages 677‐692.

[5] Angela Leung, P. Mohana Shankar, Raj Mutharasan, “A Review of Fiber Optic Biosensors”,

Sensors and Actuators B Vol. 125, 2007 pages 688‐703.

[6] S. F. D’Souza, “Microbial Biosensors”, Biosensors and Bioelectronics Vol 16, 2001

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[7] Chunhui Dai, Seokheun Choi, “Technology and Applications of Microbial Biosensors”, Open

Journal of Applied Biosensor, 2013 Vol 2, pages 83‐93.

[8] Yu Lei, Wilfred Chen, Ashok Mulchandani, “Microbial Biosensors”, Analytica Chimica Acta

2006, pages 200‐210

[9] Daniel V. Lim, “ Detection of Microorganisms and Toxins with Evanescent Wave Fiber Optic

Biosensors”, Proceedings of the IEEE, 2003, Vol 91, pages 902‐907.

[10] Maria Espinosa Bosch, Antonio Jesus Ruiz Sanchez, Fuensanta Sanchez Rojas, Catalina

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FIBER OPTIC EVANESCENT WAVE BIOSENSORdspace.cusat.ac.in/jspui/bitstream/123456789/10134/1/FIBER OPTIC... · CONTENTS 1. Introduction 1 1.1Optical Fiber 2 1.2 Fiber Optic Sensor 4