Sahyadri Journal of Research

TM

JULY 2016VOL.2 ISSUE 1

SIJRJournal

Research

Research Papers

Review Papers

Scientific Articles

International

ISSN 2456-186X

Advisors

Editorial Board

Members

Dr. D L Prabhakara - Director

Dr. Manjappa Sarathi - Director-Consultancy

Dr. Umesh M Bhushi - Principal

Dr. Siddhartha. P. Duttagupta - IIT Bombay

Dr. Achanta Venu Gopal - TIFR, Mumbai

Dr. Shriganesh Prabhu - TIFR, Mumbai

Dr. Dinesh Kabra - IIT Bombay

Dr. Richard Pinto - Editor-in-Chief

Dr. Jayarama A - Editor

Mr. Arjun S. Rao - Dept. of ECE

Dr. Rathishchandra Gatti - Dept. of ME

Dr. Ashwath Rao - Dept. of ECE

Dr. Navin N. Bappalige - Dept. of Phy.

Dr. Niraj Joshi - Dept. of Phy.

Dr. Sarvesh Vishawakarma - Dept. of CSE

Mr. Shamanth Rai - Dept. of CSE

Mr. Harisha, - Dept. of CSE

Ms. Srinidhi - Dept. of CSE

Mr. Duddela Sai Prashanth - Dept. of CSE

Mr. Vasudeva Rao P V - Dept. of CSE

Mr. Naitik S T - Dept. of ISE

Mr. Steven L Fernandes - Dept. of ECE

Mr. Sunil Kumar - Dept. of Civil E

Mr. Bharath Bhushan - Dept. of MCA

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parties. The views expressed are those of the authors. Facts

and opinions published in SIJR express solely the opinions of

the respective authors. Authors are responsible for citing of

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Contents

SAHYADRI International Journal of Research | Vol 2 | Issue 1 | July 20162

Contents

Research Articles

Scientific Articles

Editorial 3

Optical, Structural and Catalytic Studies of

Silver Nanoparticle Embedded PVA Films 4-6

Preparation, Electrical and Optical Studies of

ZnO Nanoparticles and Fe Doped ZnO Nanocomposites 7-10

Synthesis, Growth and XRD Studies of

New Nonlinear Optical L-tyrosine Hydrochloride

Single Crystals 11-13

Dielectric and ó Conductivity Studies of Sodiumac

Alginate/FeCl and Carboxy Methyl3

Cellulose/FeCl Composites 14-173

Synthesis of CTAB Assisted NanoCrystalline

BiFeO as Acetone Sensor 18-203

Hypoenergetic and Strongly Hypoenergetic Trees 21-23

The Expanding Universe and the

Enigma of Dark Energy 24-25

General Guidelines 26

Vol. 2, Issue 1ISSN 2456-186X (Online)ISSN Pending (Print)

Mailing Address:Editor Sahyadri International Journal of ResearchSahyadri campus, Adyar, Mangalore - 575 007, IndiaE-mail: editor@sijr.inWebsite: www.sijr.in

SAHYADRIInternational Journal of Research

It gives us immense pleasure to bring out Volume 2, Issue 1 of Sahyadri

International Journal of Research (SIJR). We are happy to state that we have got

good response for the first volume. Recently we have obtained ISSN for online

version; we are expecting to receive ISSN for print version very soon.

There are lots of challenges in bringing out a high quality research journal. Being in

a technological institute, our focus is multidisciplinary; the most important

disciplines in which we would focus are Physics, Chemistry, Applied mathematics,

Electronics and Communications, Mechanical Engineering, Civil Engineering and

Computer science and Engineering. Apart from research papers, the journal also

would attempt to publish articles on important scientific discoveries. Future issues

will also have review papers on exciting fields of current interest.

Editorial team would like to thank the contributors and reviewers of the first issue.

- Editorial Board

Editorial

3SAHYADRI International Journal of Research | Vol 2 | Issue 1 | July 2016

Optical, Structural and Catalytic Studies of

Silver Nanoparticle Embedded PVA Films

E. V. Chandan, Kirthesh Kumar, B. Madhura and K. Sanath Shetty

Materials Science Dept., Mangalore University, Mangalagangothri - 574 199, Karnataka

Abstract

Stable silver nanocomposite �lms were synthesized bymixing aqueous solutions of AgNO3 and PVA which actsas both reducing and stabilizing agent, without using anytoxic chemicals. Composite �lms of appropriate weightpercentage with di�erent contents of inorganic phase wereobtained by heating, followed by solvent evaporation. Thee�ect of temperature and the duration of heat treatmentwere explored.The synthesized composite �lms, characterized by UV-visible spectroscopy, revealed the increase in number ofAg nanoparticles with heating time and the intensity plotsshowed a red shift. Scanning electron microscopy (SEM)revealed the increase in average diameter of particleswith increase in the duration of heating. Energy disper-sive X-ray spectroscopy (EDS) authenticates the pres-ence of Ag whose concentration increased with increasein the duration of heat treatment as well as increasingweight percentage of AgNO3. Catalytic activity of thenanocomposite �lms for the reduction of the organic dyeRhodamine B and Methylene Blue was investigated inthe presence of excess NaBH4 and good catalytic activ-ity towards the reduction of Rhodamine B was observed.The simple and fast preparation methodology makes theAg-PVA �lms cost-e�ective catalysts in the decolouriza-tion of organic dyes.

Keywords: In-situ and ex-situ methods, Rhodamine,UV-Vis spectroscopy.

1 Introduction

Nanoscale study of noble metals such as silver and gold areof great signi�cance due to their attractive optical, elec-trical and catalytic properties. Nanoparticles (NPs) �ndwide applications in catalysis, drug delivery, data stor-age, non-linear optics, microelectronics and bio-imaging.Synthesis of silver nanoparticles is of research interest notonly due to its size dependent properties but also due toits antimicrobial and antifungal activity. For the prepa-rations of AgNPs, polymers like PVA, PVP are beingused as the matrix due to its easy processability, highoptical clarity, biocompatibility, and reducing ability ofsecondary alcohol groups[1, 2]. Ag-PVA nanocompos-ite �nds applications as catalytic agents, biosensors, Sur-face Enhanced Raman Spectroscopy (SERC) detectorsetc. There are various physical and chemical methodsto produce AgNPs like chemical reduction, laser abla-tion, UV irradiation, gamma irradiation, microwave and

photochemical methods [3]. Basically, a metal-polymernanocomposite can be made by both in-situ and ex-situmethods. In in-situ techniques, metal particles are gen-erated inside a matrix by dissolving the precursor in thepolymer. In ex-situ, the metal particles are produced sep-arately �rst and then dispersed into the polymeric matrix.The aim of this work is to synthesize silver nanoparticlesin PVA matrix by simple heat treatments and to inves-tigate the catalysis property of silver in the reduction ofrhodamine in the presence of NaBH4. Synthetic dyes areused in many industries such as textile, paper and chem-ical industries etc. Rhodamine is one of these toxic andcarcinogenic chemicals found in waste water from theseindustries. It is necessary to separate this dye from waterbefore they get into our environment[4, 5].Several samples were prepared by varying the weight ra-tios of precursor to matrix and the time of reaction.The nanocomposites were characterized by various tech-niques such as UV-Vis spectroscopy, Scanning ElectronMicroscopy and EDS.

2 Experimental

2.1 Preparation of Ag-PVA nanocompos-

ite

PVA solution was initially prepared by dissolving 1.2gof PVA (M.W 125000) in 25ml of distilled water withcontinuous stirring until the polymer is completely dis-solved. AgNO3 solution is prepared by dissolving 0.144gof AgNO3 in 10ml of distilled water. 5ml of aqueousAgNO3 solution was then pipetted out into a beaker con-taining PVA solution (0.384mM) to obtain weight ratio of0.06%. The AgNO3 solution was added dropwise and thesolution was constantly stirred for two hours. Care wastaken to protect the solutions from sunlight until heattreatment. Similarly, weight ratio of 0.1% is obtained bytaking 0.240g of AgNO3 and 1.2g PVA [6, 7].The colloidal solution was then poured on to glass sub-strates and dishes and then heated in an oven. Ag-PVAcomposite �lms were maintained at 100◦C and samples(�lms) were removed at the intervals of 1hr, 2hrs and3hrs.

2.2 Reduction of rhodamine

0.01mM of rhodamine solution was prepared by dissolving0.005g of rhodamine in 1000ml of distilled water. 10mgof nanocomposite were placed into 12.5ml of rhodaminesolution. As a reducing agent, 1ml of aqueous NaBH4

4

(0.05M) was added to the same solution drop wise, underconstant stirring [8]. The reduction of rhodamine withsilver nanocomposite as the catalyst was monitored usingUV-Vis spectrophotometer.

3 Characterization

Figure 1(a) shows UV-Vis spectra of a sample withAgNO3:PVA (0.06 weight ratio) heated at 100◦C for 1hr,2hr and 3hr. The peak of samples heated for 1hr appearsat ≈418nm which reveals the formation of silver nanopar-ticles. Lesser absorbance value indicates the formation ofsmaller amount of nanoparticles. Futher heat treatmentresults in the formation of more amount of nanoparticlesof increased diameter,which is con�rmed by SEM images.Figure 1(b) shows the absorption spectra of the sample0.1 wt% heated for di�erent time intervals.

Figure 1: UV-Vis spectra of samples with (a) 0.06wt%(AgNO3:PVA) and (b) 0.1wt%.

Figure 2: SEM photographs of (a) 0.06wt% with 1 hrheating. (b) 0.06wt% with 3hr heating. (c) 0.1wt% with1hr heating.

SEM photographs of above mentioned weight percent-ages are shown in Figure 2(a), (b) and (c). It can be seenthat the particle size increases with increase in heating

time and also with increase in weight percentage. Par-ticles with average diameter of ≈ 8nm and ≈ 25nm areobserved in samples of 0.06wt% heated for 1hr and 3hrrespectively. Nanoparticles with average diameter of ≈46nm are seen in nanocomposites of 0.1wt%.

Table 1: Correlation of λmax and Particle sizeWeightpercentage

Heating time(hrs)

λmax

(nm)Avg Particle size(nm)

0.06 1 415.7 80.06 3 424.0 300.1 1 430.9 46

The presence of Ag in the samples was veri�ed withEnergy Dispersive Spectroscopy (EDS). Figure 3 showsEDS image of sample 0.1wt% with 1hr heating.

Figure 3: EDS Photograph of 0.1wt% sample with 1hrheating.

Catalytic activity of Ag nanocomposite �lms withRhodamine was monitored by UV-Vis Spectrophotome-try. Figure 4 shows catalytic activity of �lms with 0.1wt%of AgNO3:PVA with heating time 1hr. The absorptionpeak at 554 nm, corresponding to rhodamine dye de-creases to a very small value within 5 minutes, after whichthe decrease is not very signi�cant. The inset shows thedecrease in the rhodamine peak at 554 nm monitored after5 minutes. It is seen that a very low intense peak corre-sponding to Ag nanoparticles also appears after 15 min-utes . This may indicate slow dissolution of the nanopar-ticles from the �lm. We also observed faster dissolution ofAg particles from the sample with a smaller weight ratioof AgNO3:PVA. E�orts are being made to impede this be-haviour by varying the rate of heating or by crosslinkingthe polymer.

5

Figure 4: Catalytic activity of Ag nanocomposite withRhodamine.

4 Conclusion

This work shows a simple and cost e�ective method forthe synthesis of silver nanoparticles embedded on a PVAmatrix by heat treatment. The study also demonstratesthe catalytic activity of nano silver in the reduction ofrhodamine using NaBH4. AgNO3 was used as the precur-sor. PVA acted not only as the polymer supporting tem-plate but also as stabilizing and reducing agent. Resultsfrom UV-Vis spectrophotometer, EDS and SEM analysisproved the presence of silver in the composite.

References

[1] Z. I. Ali, H. H. Saleh and T. A. A�fy, "Optical,structural and catalytic evaluation of gamma-irradiation synthesized Ag/PVA nanocomposite�lms", Chem.Mater. Vol. 4, pp. 1527-1538, 2014.

[2] M. Ghanipour and D. Dorranian, "E�ect of Ag-nanoparticles doped in polyvinyl alcohol on the struc-

tural and optical properties of PVA �lms", J. Nano-Mater. pp. 1-10, 2013.

[3] Guozhong Cao, "Nanostructures and nanomaterials;synthesis, properties & application", Published by Im-perial College Press, London, 2004.

[4] J. Y. Cheon, Y. O. Kang and W. H. Park, "Forma-tion of Ag nanoparticles in PVA solution and cat-alytic activity of their electrospun PVA nano�bers",Chem.Poly. Vol. 4, pp. 840-849, 2015.

[5] Y. Meng, "A sustainable approach to fabricating Agnanoparticles/PVA hybrid nano�ber and its catalyticactivity", NanoMater, Vol. 5, pp. 1124-1135, 2015.

[6] S. Porel, S. Singh, S. S. Harsha, D. N. Rao andT. P. Radhakrishnan, "Nanoparticle-embedded poly-mer: In-situ synthesis, free-standing �lms with highlymonodisperse silver nanoparticles and optical limit-ing", Chem. Mater. Vol. 17, pp. 9-12, 2005.

[7] M. Pattabi, R. M. Pattabi and G. Sanjeev, "Studieson the growth and stability of silver nanoparticles syn-thesized by electron beam irradiation", J. Mater. Sci:Mater. Electron. Vol. 20, pp. 1233-1238, 2009.

[8] L. Ai, C. Zeng and Q. Wang, "One step solvother-mal synthsis of Ag-Fe3O4 composite as a magneti-cally recyclable catalyst for reduction of rhodamine",B. Cat.Com. Vol. 14, pp. 68-73, 2011.

[9] Z. H. Mbhele, M. G. Salemane, C. G. C. E. van Sit-tert, J. M. Nedeljkovic, V. Djokovic and A. S Luyt,"Fabrication and characterization of silver-polyvinylalcohol nanocomposites", Chem. Mater. Vol. 15, pp.5019-5024, 2003.

[10] M. Venkatesham, D. Ayodhya, A. Madhusudhan, N.V. Babu and G. Veerabhadram, "A novel green one-step synthesis of silver nanoparticles using chitosan:catalytic activity and antimicrobial studies", ApplNanosci. Vol. 4, pp. 113-119, 2014.

6

Preparation, Electrical and Optical Studies of ZnO

Nanoparticles and Fe Doped ZnO Nanocomposites

A. Manjunath, Mohammed Irfan∗, K. A. Asha and E. Yamuna

PG Studies Dept. in Physics, Government Science College, Chitradurga, Karnataka, India∗Email: irfan.bse@gmail.com

Abstract

ZnO nanoparticles and ZnO(1−x) Fe(x) (x = 0, 0.25,0.5, 0.75, 1gram) have been synthesized by chemicalmethod. The pellets of ZnO nanoparticles and Fe dopedZnO nanocomposites were used for electrical and opticalstudies. The AC conductivity studies and dielectric stud-ies were carried out in the frequency range from 50Hz to5MHz by using HIOKI 3532-50 LCR HITESTER Version2.4. AC conductivity of the ZnO nanoparticle increasesslightly in the low frequency region and it is almost aconstant for a wide range of frequencies. At very highfrequencies in the upper MHz region there is an abruptincrease in the conductivity. We observed that the dielec-tric constant decreases with the increase in concentrationof Fe, the dielectric constant has high values in the low fre-quency regions for the nanomaterials. The structural andmorphological studies of ZnO nanoparticles and Fe dopedZnO nanocomposites were carried out using XRD andFTIR (3700-650cm−1) analysis. In XRD pattern somepeaks appear in pure ZnO at higher angles disappear inthe ZnO-Fe samples. This is because of the reduction ofgrain size and development of strain in the ZnO lattice byinducing Fe atoms. The calculated crystallite size for allthe samples ranges from 20-30nm. FTIR studies suggestthat the micro structural changes take place as a resultof Fe doping in ZnO.

Keywords: Nanocomposites, AC conductivity, Di-electric, XRD, FTIR.

1 Introduction

Nanotechnology is de�ned as the study of manipulatingmatter on the atomic and molecular scale [1]. In General,nanotechnology deals with structures whose sizes vary be-tween 1 to 100 nm in one dimension at least, and involvesdeveloping materials having at least one dimension withinthat size range. It is able to create many new materialswith a vast range of applications, such as in medicine,biomaterials, electronics, and production of energy. How-ever, nanotechnology raises many concerns about toxicityand impact of nanomaterials on environment, and theire�ects on global economics.

Nanoparticles are particles that have one dimensionthat is 100 nanometers or less in size.The properties ofmany conventional materials change when formed fromnanoparticles. This is typically because nanoparticleshave a greater surface area per weight than larger par-ticles; this causes them to be more reactive to certain

other molecules. Nanoparticles are used, or being evalu-ated for use, in many �elds. Nanoparticles are of greatscienti�c interest as they are e�ectively a bridge betweenbulk materials and atomic or molecular structures [2].

1.1 ZnO nanoparticles

ZnO, an inorganic compound also known as zincite, occursrarely in nature, generally in a crystalline form. It usuallyappears as a white crystalline powder, which is nearly in-soluble in water. This has several favorable properties likehigh electron mobility, good transparency, wide bandgapfor semi-conductivity, high room-temperature lumines-cence, etc. These properties are used in applications forelectrodes in liquid crystal displays as well as in energy-saving and heat-protecting windows, electronic applica-tions of ZnO as thin-�lm transistors and light-emittingdiodes Zinc oxide has a stable wurtzite structure.

Zinc oxide has the wurtzite hexagonal crystal struc-ture. Commercial zinc oxides show this crystal structureonly under electron microscopic examination. The pre-cise shape of the crystal depends on the method of forma-tion. In regular zinc oxide these vary between a cicularneedles and plate shaped crystals. Zinc oxide can be in-duced to form a very large variety of crystalline shapesusing specialized deposition methods, which is currentlya very active area of research. Zinc oxide usually crystal-lizes in three di�erent forms: hexagonal wurtzite, cubiczincblende and cubic rocksalt. The latter is the mostrarely found. The wurtzite structure is most stable atambient conditions and is hence most common [3].

2 Experimental: Materials and

Preparation

2.1 Synthesis of ZnO nanoparticles(Chemical method)

The chemical reagents used in this work were Zn(CH3COO)2.2H2O, NaOH and TEA of analytical gradepurity. Zinc acetate solution was prepared by dissolving0.001 mole of CH3COO)2.2H2O in 50 ml of water. Thealkaline solution was prepared by dissolving NaOH (0.002mole) and TEA (0.003 mole) in 250ml of absolute ethanolunder stirring until a homogeneous solution is formed.The zinc salt solution was added into the alkaline solu-tion under magnetic stirring at 60-70◦C and this solutionwas continuously heated for 2h at temperature 70◦C. Itwas then allowed to cool naturally at room temperature.

7

After the reaction was complete, the resulting white prod-uct was washed with ethanol to remove the organic agentTEA and hydroxide ions. The product was �ltered anddried in oven at 60-70◦C [4].

2.2 Synthesis of Fe doped ZnO nanocom-posites

The chemical reagents used in this work wereZn (CH3COO)2.2H2O, Fe(NO)3.9H2O, NaOH andTEA of analytical grade purity. The solu-tion was prepared by dissolving 0.001 mole ofZn(CH3COO)2.2H2O+Fe(NO)3.9H2O in 50 ml of water.The alkaline solution was prepared by dissolving NaOH(0.002 mole) and TEA (0.003 mole) in 250 ml of absoluteethanol under stirring until the homogeneous solution.The iron doped zinc salt solution was added into the al-kaline solution under magnetic stirring at 60-70◦C andthis solution was continuously heated for 2h. It was thenallowed to cool naturally at room temperature. After thereaction was complete, the resulting white product waswashed with ethanol to remove the organic agent TEAand hydroxide ions. The product was �ltered and driedin oven at 60◦C for 2hr [4, 5].

2.3 Preparation of ZnO, ZnO-Fe pellet

For electrical conductivity measurements, the powdersamples of ZnO nano particles/ZnO-Fe nano compositeswere pressed uniaxially into pellet of thickness 1-2mm andof diameter 12mm by applying pressure of 3 tons for 3min using the device Polymerpress. The pellets weresintered at 100◦C for 1h to get the thermal stability. Finequality silver paste was applied on both sides of the pelletsfor good electrical contacts.

3 Instrumentation

The pellets of ZnO nanoparticles and Fe doped ZnOnanocomposites were used for electrical and optical stud-ies. The AC conductivity studies and dielectric studieswere carried out in the frequency range from 50Hz to5MHz by using HIOKI 3532-50 LCR HITESTER Version2.4. The structural and morphological studies of ZnOnanoparticles and Fe doped ZnO nanocomposites werecarried out using XRD and FTIR (3700-650cm−1) analy-sis.

4 Results and Discussion

4.1 Electrical Studies

The electrical properties of ZnO nanoparticles/ZnO-Fenanocomposites pellets are in�uenced mainly by thesynthesis technique, grain size, cation distribution etc.In the present studies, dielectric and AC conductiv-ity studies have been undertaken on the prepared ZnOnanoparticles/ZnO-Fe nanocomposites. In particular,measurement of AC conductivity studies and dielectricconstant (ε

′) have been undertaken [6].

4.1.1 AC Conductivity

AC conductivity and Dielectric studies on the preparedZnO nanoparticles has been undertaken using impedanceanalyzer model. The measurements were carried out atroom temperature in between the range 100Hz-5MHz.Figure 1 shows the plots of AC vs frequency.

Figure 1: Plot of Conductivity versus Frequency of ZnO,ZnO-Fe Nanocomposite

4.1.2 Dielectric Studies

Figure 2 and Figure 3 show the variation of dielectric con-stant with log frequency for ZnO nano particle and ZnO-Fe nano composites. Pellets of ZnO and ZnO-Fe nanocomposite powders of thickness around 1.0 mm were madeby applying a pressure of 3 ton in a polymer press. Themeasurements were carried out in the range from 50Hzto 5MHz. The dielectric constant (εr) of the ZnO andZnO-Fe nano composite sample was determined by usingthe relation,

εr =Cd

εoA

Where C is the capacitance, d is the thickness, εo is thepermittivity of the free space (8.854 × 10−12 F/m) andA is the surface area of the sample.

As the concentration of Fe increases dielectric constantdecreases. The dielectric constant has high values in thelow frequency regions for the nanomaterials than for theconventional materials. The very high values of dielectricconstant at low frequencies may be due to the presence ofdi�erent types of polarization mechanisms [7]. Because ofthe presence of interfaces in the nano materials, the appli-cation of an electric �eld creates dipole moments and ro-tates them along the applied �eld direction which is calledas rotation direction polarization. Space charge polariza-tion and rotation direction polarization are responsible forthe high value of dielectric constant for ZnO and ZnO-Fenanomaterials at low frequencies [8].

8

Figure 2: Plot of Dielectric constant versus Frequency ofPure ZnO nanoparticles.

Figure 3: Plot of dielectric constant Versus Frequency ofZnO+1 Fe nanocomposite.

Table 1: Details of XRD data and crystallite size ofZnO+ 0.75 Fe nanocomposite.

4.2 XRD Studies

Figure 4 shows XRD patterns of ZnO-Fe sample. Withincreasing Fe concentration, the (1 0 1) or third peak ex-hibits an increase in line broadening.It is also observed from the XRD patterns that impuritypeak appears at higher angles in the ZnO-Fe samples.

This is because of the reduction of grain size and devel-opment of strain in the ZnO lattice in inducing Fe atoms.The crystallite size (D) for all the samples was calculatedusing Scherrer's formula.

Figure 4: Plot of intensity versus 2θ of ZnO+0.75 Fenanocomposite.

4.3 FTIR Studies

FTIR spectra were recorded in solid phase using ATRtechnique in the wave number region 650-4000 cm−1 forZnO and ZnO-Fe samples and are shown in Figure 5.This spectral region is very important because of severalstretch modes involving hydroxyl bond, carbon-oxygenand metal oxide bonds are obtained clearly in this range.

Due to absorption of CO band at 1166.31 cm−1 (C-O) and a symmetric stretching vibration at 1388.86 cm−1

(COO−) is observed. The band found at 1620.06 cm−1 isdue to OH bond of water. The bending around 2838 cm−1

is because of absorption of CO2 molecule present in air.The OH vibrations in ZnO lie in the range from 3000 to3500 cm−1 depending on the con�guration and number ofhydrogen atoms absorbed by ZnO. Shifting of this bandas a result of Fe doping suggests microstructural changestaking place in the ZnO matrix.

5 Conclusion

The AC electrical conductivity study shows that at con-stant temperature, for an increase in frequency, there isa slight increase in the electrical conductivity of the ZnOnanocomposite at the low frequency region and it is al-most a constant for a wide range of frequencies and atvery high frequencies there is an abrupt increase in theconductivity. As the Fe concentration increases, AC con-ductivity increases as shown in Figure 6.

9

Figure 6: Plot of conductivity of ZnO-Fe nanocompositesat 5 MHz.

Table 2: Conductivity data of ZnO, ZnO-Fe nanocom-posites at 5 MHz for all samples.

Sample Conductivity at 5MHz (S/Cm)PureZnO+0Fe 1.07719E-05ZnO+0.25 Fe 1.75122E-05ZnO+0.50,Fe 1.66475E-05ZnO+0.75,Fe 1.90873E-05ZnO+1,Fe 1.92952E-05

As the concentration of Fe increases, dielectric con-stant decreases. The very high values of dielectric con-stant at low frequencies may be due to the presence ofdi�erent types of polarization mechanisms. XRD patternshows that the reduction of grain size and developmentof strain in the ZnO lattice in inducing Fe atoms. FTIRspectra show the C-O bond and OH bond vibrations inZnO nanoparticles and Fe doped ZnO nanocomposites.Shifting of the bands of Fe doped ZnO nanoparticles sug-

gests microstructural changes taking place in the ZnO ma-trix.

References

[1] Omkar Behera and Subhankar Paul, "Syn-thesis and characterization of ZnO nanopar-ticles of various sizes and Applications"http://www.aadet.com/article/nanoparticle,Nanoparticle.

[2] Kamal Singh Rathore, S. S. Sisodia, M.S. Ranawat and R. K. Nema, "Ophthalmicnanoparticles drug delivery systems", Arti-clesbase, http://www.articlesbase.com/vision-articles/ophthalmic-nanoparticles-drug-delivery-systems 1273176.html, Sept 26, 2009.

[3] P. M. Aneesh, K. A.Vanaja and M. K. Ja-yaraj, "Nanophotonic materials IV", edited by ZenoGaburro, Stefano Cabrini, Proc. of SPIE, 6639,66390J, 0277-786X/07/18, doi:10.1117/12.730364,2007.

[4] M. M. Hassan, A. S. Ahmed, M. Chaman, W. Khan,A. H. Naqvi and A. Azam, Materials research bulletin,Vol. 47, pp. 3952, 2012.

[5] C. R. Ayre and R. J. Madix, "Allyl and Trimethylene-methane complexes derived from isobutylene adsorp-tion on oxygen-activated Ag(110)", Surf. Sci. Vol. 262,pp. 51, 1992.

[6] S. Z. Hanani, R. Adnan, A. F. A. Latip and C. S.Sipaut, Sains Malaysiana, Vol. 40, no. 9, pp. 999-1006,2011.

[7] A. Djelloul, M. S. Aida and J. Bougdira, Journal ofLuminescence, Vol. 130, pp. 2113-2117, 2010.

[8] E. V. Lavrov, J. Weber, F. Borrnert, C. G. VandeWalle and R. Helbig, Physical Review.B, Vol. 66, pp.165205, 2002.

10

Synthesis, Growth and XRD Studies of New Nonlinear

Optical L-tyrosine Hydrochloride Single Crystals

K. Ravindraswami1∗, Jayaprakash Gowda1, Chitharanjan Rai2 and B. Narayana Moolya11St. Aloysius College (Autonomous) Mangaluru, Karnataka, India-5750032Kalpataru First Grade Science College, Tiptur, Karnataka, India- 572 202

∗Email: swamiphysics@gmail.com

Abstract

Nonlinear optics deals with the study of phenomenathat take place due to the modi�cation of the opticalproperties of a material in the presence of intense laserlight. Most of the organic and inorganic crystals inves-tigated so far have failed to meet the standards set bydevice applications used in the �eld of telecommunica-tions and Optoelectronics. Hence, there is a need tosynthesize various new materials and to grow good qual-ity single crystals for NLO applications. In this context, anew class of materials called semiorganics have come intoexistence. L-tyrosine hydrochloride, a new semiorganicmaterial was synthesized and bulk single crystals of thismaterial have been grown by solution growth method.Grown crystals were characterized by Powder XRD andSingle Crystal XRD techniques. Second harmonic conver-sion e�ciency of the synthesized material was measuredin powder form and compared with that of KDP.

Keywords: Nonlinear optics, second harmonic gen-eration, bulk crystals.

1 Introduction

With unprecedented developments that are taking placein the �eld of telecommunications and data processing,photonics which employs the 'photon' to acquire, store,process and transmit data has become a potent �eld of re-search. The design of devices that utilize photons insteadof electrons in the transmission of information has createda need for new materials with unique optical properties[1]. Materials possessing nonlinear optical (NLO) suscep-tibility are of particular interest [2]. Second HarmonicGeneration (SHG) is the conversion of coherent light offrequency ω into light of frequency 2ω. One practical ap-plication of second harmonic generation is the conversionof relatively inexpensive (yet powerful) infrared laser lightinto visible laser light. Self-focusing e�ect allows one tochange the refractive index of a material by applying aDC electric �eld to the material; thus, one can utilize themodulation of an electrical signal to activate an opticalswitch [3].Since, it is impossible to get a crystal which satis�es, thestandards set by device applications for the fabricationof nonlinear optical devices, the search for new materi-als satisfying most of those conditions is still continuing.

The inherent limitations of the maximum attainable non-linearity in inorganic materials and the moderate successin growing device grade organic single crystals have madescientists to adopt alternate strategies. The obvious onewas to develop hybrid organic-inorganic materials withsome tradeo� in their respective advantages. This newclass of materials has come to be known as semiorganics.One approach to high e�ciency optical quality organicbased NLO materials in this class is to form compoundsin which a polarizable organic molecule is stochiometri-cally bonded to an inorganic host. They have better me-chanical properties as compared to organic molecules, likewide transparency range, higher laser damage threshold;and at the same time, like organic crystals, their proper-ties can be controlled by the wide variation of chemicalcomposition. Keeping this in view, experiments were car-ried out so as to develop new salts of amino acids. Somerepresentative amino acids are selected and made to reactwith inorganic acids. The resulting materials were inves-tigated for their NLO properties since; they will have theproperties of ionic as well as, hydrogen bond and Vanderwalls force. L-tyrosine hydrochloride (L-THCl), a salt ofamino acid L-tyrosine is synthesized, characterized andbulk single crystals are grown, and presented in this pa-per.

2 Experimental

2.1 Synthesis

A saturated solution of L-tyrosine prepared in 4N HCl(pH<1) was heated for 12 hrs at 40◦C to evaporate. Theresulting pale yellow solid was dried and puri�ed by re-peated crystallization in concentrated HCl. The mate-rial thus prepared was analyzed by physical and chemicalmethods and con�rmed to be L-THCl. This compoundwas used to grow bulk crystals. Following chemical reac-tion yields L-THCl:

2.2 Crystal Growth

A saturated solution of L-THCl at 40◦C was preparedand subjected to slow vaporization by cooling at a rate

11

of 0.5◦C per day. Optically transparent seed crystalswere suspended in the supersaturated solution when thetemperature reached 32◦C. The growth temperature wasmaintained at 32◦C in the crystal growth apparatus. Bulkcrystals of maximum size 30mm × 10mm × 4mm wereharvested after a month. L-THCl crystal grows in theshape of prism elongated in the c direction. L-THCl isstable at room temperature and non hygroscopic. Figure1 is the photograph of grown crystals.

Figure 1: Single Crystals of L-THCl.

2.3 Powder X-Ray Di�raction Studies

Powder X-ray di�raction patterns of the grown L-THClwas recorded using BRUKER D8 ADVANCE powderdi�ractometer with Cu Kα radiation (λ =1.5406Å). Thesample was scanned at a rate of 1◦ per minute in the range10◦ to 70◦. The Powder XRD di�ractogram of L-THCl isshown in Figure 2.

Figure 2: Powder XRD di�ractogram of L-THCl.

2.4 Unit Cell Parameters

Unit cell parameters of the grown crystals were obtainedusing ENRAF, NONIUS CAD-4 di�ractometer. The re-sults obtained are presented in Table 1. These valuesagree quite well with the reported values.

Table 1: Unit cell parameters of L-THCl

ParameterPresent work

Single crystal powderLiterature

[4]Space Group P21 P21 P21

a(A) 11.0704 11.0822 11.41b(B) 9.0556 9.0327 9.11c(A) 5.0877 5.0912 5.17B 91.7243◦ 91.7902◦ 91.00◦

V(A3) 509.8124 509.3915 537.5

2.5 Second Harmonic Generation

The second harmonic generation (SHG) e�ciency wasdetermined by the modi�ed version of the powder tech-nique developed by Kurtz and Perry [5] using a QuantaRay Spectra Physics model Prolab170 Nd: YAG 10 nslaser with a pulse repetition rate of 10Hz working at1064 nm. The sample was ground into �ne powder andtightly packed in a micro-capillary tube. It was mountedin the path of the laser beam of 9.6 mJ pulse energyobtained by splitting the original laser beam. The out-put light was passed through a monochromator (TRI-ACS 550) transmitting only the second harmonic (green)light at 532 nm. The green light intensity was registeredby a photomultiplier tube (PMT-Philips Photonics XP2020) and converted into an electrical signal. This sig-nal was displayed on the oscilloscope (Tektronics TDS3052B) screen. Potassium dihydrogen phosphate (KDP)ground into samples of identical size was used as referencematerial in the SHG measurement. SHG conversion e�-ciency was computed by the ratio of signal amplitude ofthe L-THCl sample to that of the KDP signal amplituderecorded for the same input power. The SHG e�ciencyof the L-THCl was found to be 1.2 times that of KDP.

3 Results and Discussion

L-tyrosine hydrochloride (L-THCl) was synthesized byconducting reactions with hydrochloric acid. Single crys-tals of L-THCl of dimension up to some centimeters couldbe grown by slow evaporation of saturated solutions of L-THCl in 2N hydrochloric acid. These crystals grow in theshape of prisms elongated in c-direction bounded by sixmajor planes. The crystals are yellowish and optically notvery transparent.

The crystallinity of the synthesized L-THCl was con-�rmed by the powder XRD pattern. The cell parametersof the grown crystals were determined using the singlecrystal X-ray di�ractometer as well as from powder datausing the standard software. Close agreement of the de-termined cell parameters with the reported values con-�rmed the identity of the grown crystals. L-THCl crys-tallizes in noncentrosymmetric system with space groupP21 making the materials as an eligible candidates forsecond harmonic generation.

4 Conclusions

L-Tyrosine hydrochloride is synthesized and bulk singlecrystals are grown by slow evoporisation of solution in

12

2N hydrochloric acid. Crystallinity of the sample is an-alyzed by powder XRD and single crystal XRD experi-ments. Cell parameters of the grown single crystals foundto agree quite well with the reported literature. Secondharmonic conversion e�ciency of the crystal is measuredby modi�ed version of the powder technique developed byKurtz and Perry, and found to be 1.2 times that of KDP.

References

[1] N. Bloembergen, "Nonlinear Optics", Benjamin, NewYork, 1965.

[2] D. S. Chemla and J. Zyss, Eds, "Nonlinear OpticalProperties of Organic Molecules and Crystals", Acad.Press, Vols. 1 and 2, 1987.

[3] M. S. Lyons, "Materials for Nonlinear Optics andElectro Optics, Inst. of physics Conf. Series", pp. 103,1989.

[4] M. N. Frey, T. F. Koetzle, M. S. Lehmann and W. C.Hamilton, Journal of Chemical Physics, Vol. 58, pp.2547-2556, 1973.

[5] S. K. Kurtz, T. T. Perry, J. Appl. Phys., Vol. 39, pp.3798-3813, 1968.

13

Dielectric and σac Conductivity Studies of Sodium

Alginate/ FeCl3 and Carboxy Methly Cellulose/

FeCl3 CompositesS. Suresha1, R. Ashok Lamani2∗, H. S. Jayanna2, V. S. Chathurmukha2, B. S. Avinash2 and B. M. Harish2

1Physics Dept., Govt. First Grade College, Holalkere Karnataka, India2PG Studies Dept. and Research in Physics, Kuvempu University, Shankaraghatta-577451.Shimoga. Karnataka, India

∗Email: Ashok1571972@gmail.com

Abstract

The Sodium alginate(NaAlg), Carboxy methyl Cellu-lose (CMC), ferric chloride (FeCl3) doped sodium alginateand Carboxy methyl Cellulose were prepared separately inthe weight percent ratios (90:10) by solution casting. The�lms were characterized by X-ray di�ractometer. For-mations of single phase cubic structure of the �lms werecon�rmed by X-ray di�raction (XRD) technique. The di-electric measurements of all the samples were measured inthe frequency range 100Hz-1MHz at room temperature.The AC conductivity obeys the power law of frequencyand dielectric constant, dielectric loss of CMC/FeCl3 in-creases. The dielectric constant of NaAlg/FeCl3 decreasesand dielectric loss increases, while AC conductivity in-creases with increase in frequency with substitution ofFeCl3 with Carboxy methyl cellulose and Sodium Algi-nate.

Keywords: Composites, Dielectric, Sodium Algi-nate, Carboxy methyl Cellulose.

1 Introduction

In polymer thin �lms, e�ects due to con�nement and in-terfacial interactions are responsible for di�erent physi-cal phenomena that change with �lm thickness. Theyhave high conductivity, and are light in weight, inexpen-sive and �exible[1]. The interaction of biopolymers withconducting polymers may generate interesting biopoly-mer/conducting polymer composites, which �nd applica-tions where electrical conductivity is desirable, such as inarti�cial nerves, sensors and actuators [2]. Sodium Algi-nate (NaAlg) is a biopolymer sodium salt of Alginic acid,and it is a water-soluble anionic polymer. Alginate oc-curs in the cell wall of brown seaweed. Sodium Alginate(NaAlg) is a polyelectrolyte with good biocompatibility;however, it su�ers from limitations in fabrication. Theirmechanical properties are often poor. In recent years, themodi�cation of such natural polymers has received muchattention for the production of new biomaterials withspeci�c properties [3]. Carboxy methyl cellulose (CMC)is a polysaccharide comprising �brous tissue of plants.Also, it has a number of sodium Carboxy methyl groups(eCH2COONa) which aids its solubility in water [4]. ADielectric Study of Sodium Alginate and carboxy methylcellulose in aqueous solution were reported by the authors

[5-6]. Thus these properties of CMC and NaAlg have en-couraged us to study dielectric properties of CMC/ FeCl3and NaAlg/FeCl3. Composites are synthesized separatelyby solution casting method and then they are structurallycharacterized using XRD.

2 Experimental

2.1 Materials

Carboxy methyl cellulose, Sodium Alginate of analyticalgrade reagents were procured from S.D �ne chemicals,Mumbai, India and ferric chloride was purchased fromNice Chemicals, Kerala, India.

2.2 Preparation of CMC/ FeCl3 andNaAlg/FeCl3 composites

Films of Sodium Alginate (NaAlg) doped with ferric chlo-ride (FeCl3) and Carboxy methyl cellulose (CMC) dopedwith ferric chloride (FeCl3) with weight percentage of90:10 each were prepared separately by using solutioncasting technique. NaAlg, CMC, FeCl3 were dissolvedseparately in distilled water and the mixtures were stirredat room temperature for 3 days. The stirred solution wascast in di�erent Petri dishes and allowed to evaporateslowly at room temperature for �lms to form. Finally�lms were carefully separated from the dishes.

3 Results and Discussion

3.1 X-ray Di�raction Studies

XRD pattern of Carboxy methyl cellulose (CMC) shows abroad peak at 2θ=20◦ indicating the amorphous nature ofCMC which is well established by the published literature[4]. The XRD spectrum of NaAlg shows a broad hump at2θ=28◦ which indicates the amorphous nature of NaAlgwhich is also well established by the literature [2]. TheXRD patterns of the composites show peak at 2θ=32◦ in-dicating the single phase cubic structure of CMC/ FeCl3and NaAlg/FeCl3 as shown in Figure 1.

3.2 Dielectric Studies

The dielectric measurement is a powerful tool for obtain-ing information about the ion-polymer interaction and

14

conduction mechanism of polymer composites. Based onthe concept of polarization, dielectric materials get elec-trically polarized when an electric �eld is applied. Thedielectric loss factor can be used to measure the strengthand frequency of relaxation, depending on the character-istic properties of unipolar/dipolar relaxation [7].

Figure 1: XRD patterns of (a) CMC/ FeCl3 and (b)NaAlg/FeCl3.

Figure 2 (a), (b) and (c) presents the frequency de-pendent dielectric constant (ε

′), dielectric loss (ε

′′) and

dielectric loss tangent (tan δ ) of CMC/FeCl3 at roomtemperature. In dielectric dispersion curves for CMC inaqueous solution at di�erent concentrations, a high fre-quency increment is obtained. The cause of the high fre-quency increment is not known but several explanationshave been discussed [8, 9]. It is evident from the Figure2(a), (b) and (c) that the values of dielectric constants,dielectric loss and dielectric loss tangent are low in thelow frequency region. As the frequency increases ε

′, ε

′′

and tan δ increase; and at lower frequencies the dielectricconstants are almost independent of frequency, becauseat lower frequencies the charge carriers are able to orientthemselves in �eld direction.

In the frequency dependence of the dielectric constant(ε

′) of Sodium Alginate, two kinds of relaxation processes

were observed. The higher relaxation process is due to the�uctuation of the bound counter ion(Ikeda et al., 1997),The experimental data were in good agreement with thebest �t curves using the Cole-Cole equation.

Figure 2: Variation of (a) dielectric constant (b) dielectricloss and (c) tan δ with frequency at room temperature forCMC/ FeCl3.

Figure 3(a) shows that the values of (ε′) is high in the

low frequency region, con�rming the non-Debye type be-havior due to the contribution of charge accumulation atelectrode-electrolyte interface. As the frequency increasesthe dielectric constant decreases. The dependence of theε′′and tan δ on frequency of NaAlg/FeCl3 is shown in

Figure 3(b) and (c) which shows that ε′′and tan δ value

increases with increasing frequency. This indicates thatthe probability per unit time increases with salt concen-tration. The dispersion observed at low frequencies couldbe attributed to the interfacial-polarization mechanism.

15

3.3 AC Conductivity

The dielectric measurements were carried out at roomtemperature using high precision LCR meter/impedenceanalyser over a wide frequency range (model N4L-numetriq PSM 1735) In Figure 4(a) and 4(b) are the de-pendence of AC conductivity on the frequency for CMC/FeCl3 and NaAlg/FeCl3, AC conductivity behavior of allthe prepared samples was investigated over the frequencyrange 100Hz-1MHz. σac = 2πfε◦ε

′′, where f is frequency,

ε◦ is the permittivity of free space, and ε is the dielectricloss.

Figure 3: Variation of (a) dielectric constant (b) dielectricloss and (c) tan δ with frequency at room temperature forNaAlg/FeCl3.

Figure 4: Dependence of AC conductivity on frequencyat room temperatures. (a), (c) CMC/ FeCl3 and (b),(d)NaAlg/FeCl3.

16

The diagrams σac versus logf of the �lms exhibit sim-ilar behavior. The conductivity is lower at lower frequen-cies. The plateau region appeared, as shown in Figure4(a) and 4(b). This behavior suggests that the hoppingmechanism might be playing an important role in theconduction process.

The frequency dispersion of σac has been observed tofollow a universal power law of ac conductivity.

σac(ω) = AωS

where ω is the angular frequency, A and s are exper-imentally determined material constants, and σac(ω) isthe frequency dependent conductivity, measured takingthe logarithm of Eq. σac(ω) = AωS . In Figure 4(c) and(d) values of the exponent (s) were calculated from theslopes of these lines from the relation between logσac ver-sus logf of the higher frequencies. According to the abovemeasurements, it can be noticed that AC conductivity in-creases with increase in frequency. Hence the study hascon�rmed the AC conductivity obeyed the power law offrequency.

4 Conclusion

In the present work, CMC/ FeCl3 and NaAlg/FeCl3 com-posites were prepared separately in the weight ratios(90:10) by solution casting. The single phase cubic struc-ture of composites were con�rmed by XRD spectra. Thefrequency dependent dielectric constant (ε

′), dielectric

loss (ε′′) and dielectric loss tangent tan δ of CMC/FeCl3

are low in the low frequency region. As the frequency in-creases ε

′, ε

′′and tan δ increase and at lower frequencies

they are almost independent of frequency. The dielectricconstant (ε

′) of NaAlg/FeCl3 is high in the low frequency

region and ε′′and tan δ value increase with increasing fre-

quency. The study has shown that the AC conductivityobeyed the power law of frequency.

References

[1] K. Sreelalitha and K. Thyagarajan, "Electrical prop-erties of pure and doped (KNO3 & MgCl2) polyvinylalcohol polymer thin �lms", IJETCAS, Vol. 4, no. 3,pp. 308-312, 2013.

[2] Y. T. Ravikiran, S. Kotresh, S. C. Vijaya Kumari,K. C. Sajjan, B. S. Khened and S. Thomas, "ACconductivity studies of p-toluenesulfonic acid dopedpolyaniline-sodium alginate composites", CelluloseChemistry and technology, Vol. 49, no. 1, pp. 24-28,2015.

[3] T. Sheela, R.F. Bhajantri, V. Ravindrachary, SunilG. Rathod, P.K. Pujari, Boja Poojary and R.Somashekar, "E�ect of UV irradiation on opti-cal, mechanical and microstructural properties ofPVA/NaAlg blends", Radiation Physics and Chem-istry, Vol. 103, pp. 45-52, 2014.

[4] Y.T. Ravikiran, S. Kotresh, S.C. Vijayakumari and S.Thomas, "Liquid petroleum gas sensing performanceof polyaniline-carboxymethyl cellulose composite atroom temperature", Current Applied Physics, Vol. 14,pp. 960-964, 2014.

[5] L. G. Allgen and Siw Roswall, "A dielectric study ofsodium alginate in aqueous solution", Journal of Poly-mer Science, Vol. 23, no. 104, pp. 635-650, 1957.

[6] L. G. Allgen and Siw Roswall, "A dielectric study of acarboxymethylcellulose in aqueous solution", Journalof Polymer Science, Vol. 12, pp. 229-236, 1954.

[7] S. G. Rathod, R. F. Bhajantri, V. Ravindrachary,P. K. Pujari and T. Sheela, "Ionic conductivity anddielectric studies of LiClO4 doped poly (vinylalco-hol)(PVA)/chitosan (CS) composites", Journal of Ad-vanced Dielectrics, Vol. 4, no. 4, pp. 1450033(1-7),2014.

[8] I. Jungner, "Dielectric Determination of MolecularWeight and Dipole Moment of Sodium Thymonucle-ate", Acta Physiol. Scand. 20, Supp. 69, 1950.

[9] L. G. Allgen, "A Dielectric Study of Nucleohistonefrom Calf Thymus", ibid. 22, Suppl. 76, 1950.

[10] Shinya Ikeda and Hitoshi Kumagai, "Scaling Be-havior of Physical Properties of Food PolysaccharideSolutions:� Dielectric Properties and Viscosity ofSodium Alginate Aqueous Solutions", J. Agric. FoodChem., Vol. 45, no. 9, pp. 3452-3458, 1997.

17

Synthesis of CTAB Assisted Nanocrystalline BiFeO3

as Acetone SensorP. A. Ghadage1, U. R. Ghodake2, J.Y. Patil1, and S.S. Suryavanshi1

1Ferrite Material Laboratory, Department of Physics, Solapur University, Solapur2Electronics Dept., Shri. Shivaji Mahavidyalaya, Barshi - 413411, Dist-Solapur, Maharashtra, India

1Email: sssuryavanshi@redi�mail.com, ghadagepa@gmail.com2Email: urghodake@gmail.com

Abstract

The e�ect of CTAB addition on acetone sensing prop-erties of BiFeO3 (BFO) multiferroic semiconductor areinvestigated in this report. The material was synthe-sized by simple glycine combustion method. The sinteredsample was studied by X-ray di�raction analysis (XRD),Scanning Electron Microscope (SEM) and element com-position of material was determined by using EDAX.The experimental results indicate that the sensor basedon the sample BFO/CTAB shows excellent gas sensingproperties towards acetone gas at lower operating tem-perature. The response of the BFO/CTAB sample is 90for acetone gas; while to other test gases the response islower than 50. With increasing concentration of acetone,the resistance of the sensor based on sample BFO/CTABincreases. The response and recovery times of the sampletowards acetone gas are 20 sec and 45 sec.

Keywords: BiFeO3, Glycine combustion method,Gas Sensor .

1 Introduction

In recent years, a rhombohedrally distorted perovskitetype BFO have been investigated for the multiferroicproperties. Due to the interesting physical properties ofBFO, it acts as a potential candidate for future techno-logical applications [1, 2, 3]. For the formation of BFOnanoparticles we adopted the time consuming glycinecombustion technique. Here, we discuss the e�ect of sur-factant cetyltrimethylammonium bromide (CTAB) on thestructural, morphological and gas sensing properties ofBFO.

2 Experimental Details

For the facile synthesis of BFO nanoparticlesFe(NO3)3·9H2O, Bi (NO3)3·5H2O and glycine wereused as starting materials. Then a cationic surfactantcetyltrimethylammonium bromide (CTAB) was added tothe solution with molar ratio of surfactant/Bismuth: 0.1.This mixture was dissolved in 100ml distilled water withvigorous magnetic stirring for 30min. at 70◦C constanttemperature. While another solution without surfactantwas also prepared. The precursor solution was kept onthe heater, which undergoes a �ameless combustion and

the �u�y foam of our �nal product was obtained. Thegrinded calcined powder was used for the pellet forma-tion. The �nal pellet samples are sintered at 550◦C andsilver contacts are drawn from it for the measurement ofgas sensing properties.

3 Results and Discussion

X-ray di�raction (XRD) pattern revealed that pure BFOsamples have rhombohedral structure with some sec-ondary phases like Bi2Fe4O9 [1], where as the CTAB as-sisted BFO samples show hexagonal phase without sec-ondary phases as shown in Figure 1. The XRD patternsshow the di�raction peaks corresponding to rhombohedralstructure and hexagonal phase which match well with theJCPDS card No. 71-2494 [2].

Figure 1: XRD pattern of BFO and BFO-CTAB sinteredat 550◦C.

Scanning electron microscope (SEM) images shows the

18

agglomeration of small particles having irregular shape,size and porous structure, which forms the non uniformgrains. A change in porosity provides more surface areafor gas adsorption and hence, it exhibits enhanced gassensing properties.

Figure 2: EDAX and SEM images.

Electron di�raction spectrum (EDAX) spectrumshows the con�rmation of elemental composition whichis shown in Figure 2. The reducing gases were tested onthe CTAB assisted BFO sample for gas sensing properties(Figure 3). The response of reducing gas is determinedby [3]:

S(%) = [Rg −Ra

Ra]× 100

Where, Ra is resistance of sensor in air and Rg resis-tance after the exposure of test gas.

Figure 3: Gas sensing properties of BFO-CTAB sampleSintered at 550◦C.

The CTAB assisted BFO sample shows selective high-est response (90%) for acetone gas at optimal operatingtemperature 300◦C as shown in Figure 4. The sensitiv-ity of the sensor with increasing gas concentration is also

plotted on the graph as shown in Figure 5.The responseand recovery time observed in CTAB assisted BFO sensoris shown in Figure 6.

Figure 4: Selectivity of the BFO-CTAB sensor Sinteredat 550◦C.

Figure 5: Sensitivity vs Gas concentration.

Figure 6: Transient response of the BFO-CTAB sensor.

19

4 Conclusion

The CTAB assisted BFO nanoparticles were successfullysynthesized by glycine combustion method. XRD con-�rms the formation of hexagonal structure single phaseBFO. EDAX technique identi�es the chemical composi-tion of Bi, Fe and O. The CTAB assisted BFO sensorshowed highest response towards acetone gas at optimaloperating temperature which was mainly attributed to itsporous structure.

References

[1] S. N. Tripathy, B.G. Mishra, M. M. Shirolkar, S. Sen,S. R. Das, D. B. Janes and D. K. Pradhan, "Struc-

tural, microstructural and magneto-electric proper-ties of single-phase BiFeO3 nanoceramics preparedby auto-combustion method", Journal of MaterialsChemistry and Physics, Vol. 141, pp. 423-431, 2013.

[2] J. Yang, X. Li , J. Zhou, Y. Tang, Y. Zhang and Y.Li, "Factors controlling pure-phase magnetic BiFeO3

powders synthesized by solution combustion synthe-sis", Journal of Alloys and Compounds, Vol. 509, pp.9271- 9277, 2011.

[3] M. Dziubaniuk, R. B. Koro'nska, J. Suchanicz, J.Wyrwa and M. Rekas, "Application of bismuth ferriteprotonic conductor for ammonia gas detection", Sen-sors and Actuators B, Vol. 188, pp. 957- 964, 2013.

20

Hypoenergetic and Strongly Hypoenergetic trees

Sunita Priya D'Silva

Mathematics Dept., Sahyadri College of Engineering & Management.

Email: sunita.math@sahyadri.edu.in

Abstract

In the past few decades, much scienti�c research hasbeen focused on how to capture and convert by a the-oretical pathway the information encoded in a molecu-lar structure of a chemical compound into one or morenumbers used to establish quantitative relationships be-tween structures and properties, biological activities, orother experimental properties. Mathematical represen-tations of a molecule, called Molecular Descriptors, areobtained by a well-speci�ed algorithm, and are applied toa de�ned molecular representation or a well-speci�ed ex-perimental procedure. Molecular descriptors are derivedby applying principles from several di�erent theories, suchas quantum-chemistry, information theory, organic chem-istry and graph theory. One such molecular descriptoris the parameter energy of the molecular graph of a con-jugated hydrocarbon. The energy E(G) of a graph G isde�ned as the sum of the absolute values of the eigenvalues of G.

The motivation for the introduction of the this invari-ant comes from chemistry, where results on E(G) wereobtained already in the 1940's. A graph G with n verticesis said to be "hyperenergetic" if E > 2n-2, and to be "hy-poenergetic" if E(G) < n. In this paper we outline themain hitherto obtained results related to Hypoenergeticand strongly Hypoenergetic trees.

Keywords: Energy of the graphs, Hypoenergeticgraphs, strongly Hypoenergetic graphs.

1 Introduction

The energy E(G) of a graph G is de�ned as the sum ofthe absolute values of the eigen values of G. If λ1, λ2,λ3,............,λn are the eigen values of a graph G of n ver-

tices, then energy of G is given by E(G)=n∑

i=1

|λi|. A

n-vertex graph is said to be Hypoenergetic if E(G) < nand strongly Hypoenergetic if E(G)<n-1. Here we char-acterize the existence of both Hypoenergetic and stronglyHypoenergetic trees of order n and maximum degree ∆.

2 Hypoenergetic and strongly Hy-

poenergetic trees

We outline the results for Hypoenergetic and stronglyHypoenergetic trees and study for what conditions of

vertices(n) the trees are Hypoenergetic and strongly Hy-poenergetic.

1. For Hypoenergetic trees we have the follow-

ing results :

(i) There exist Hypoenergetic trees for any number of ver-tices and any value of maximum vertex degree ∆, exceptfor the case ∆ = 4 and n ≡ 2 ( mod 4).

(ii) There exist Hypoenergetic trees of order n withmaximum degree ∆ ≤ 3 only for n = 1, 3, 4, 7.For e.g.:

For n=1 S1: • E(S1) = 0.For n=3 S3: E(S3) = 2.8284.

For n=4 S4: E(S4) = 3.4640.

For n=7 G: E(G) = 6.8280.

(iii) If ∆ ≥ 4, then there exist Hypoenergetic trees forall n ≥ ∆ + 1.E.g.: For n = 7 and ∆ = 4G:

0 1 0 0 0 0 01 0 1 0 1 0 10 1 0 1 0 1 00 0 1 0 0 0 00 1 0 0 0 0 00 0 0 0 0 1 00 1 0 0 0 0 0

The associated matrix is given above and the eigen

values are: ± 2.0743, ± 0.8350, 1, 0, 0.

21

The energy of the graph is E(G) = 6.8186 < 7 , so itis hypoenergetic graph.

2. For Strongly Hypoenergetic trees we have

the following results :

(i) There do not exist Strongly Hypoenergetic trees withmaximum degree atmost 3.(ii)For ∆ = 4e, there exist Strongly Hypoenergetic treesfor n > 5 such that n ≡ 1(mod 4)Eg: For n = 9 and ∆ = 4G:

0 1 0 0 0 0 0 0 01 0 1 0 0 0 1 0 10 1 0 1 0 0 0 0 00 0 1 0 1 0 0 1 00 0 0 1 0 1 0 0 00 0 0 1 0 0 0 0 00 1 0 0 0 0 0 0 00 0 0 0 0 0 0 0 00 1 0 0 0 0 0 0 0

The associated matrix is given above and Eigen values

are: 2.829, 1.6673, -1.3417 , -0.3859, 0, 0, 0, 0.

The energy of the graph, E(G) = 7.7005 < 8 =(n - 1),so it is strongly hypoenergetic graph.

(iii) If ∆ = 5 , then there exit n vertex strongly hy-poenergetic trees for n = 6 and all n â�¥ 9 but there donot exit any strongly hypoenergetic trees for n = 7 and8.

Eg: For ∆ = 5 and n = 6,S6:

0 1 1 1 1 11 0 0 0 0 01 0 0 0 0 01 0 0 0 0 01 0 0 0 0 01 0 0 0 0 0

The associated matrix for the graph S6 is given above.

The energy, E(S6) = 4.4721 < 5 = (n-1), and hence it isstrongly hypoenergetic graph.

(iv) For ∆ = 5 and n = 9 ,we have the graph G,G:

0 1 1 1 1 1 0 0 01 0 1 0 0 0 0 0 01 0 0 0 0 0 0 0 01 0 0 0 0 0 0 0 01 0 0 0 0 0 0 0 01 0 0 0 0 0 1 1 10 0 0 0 0 1 0 0 00 0 0 1 0 1 0 0 00 0 0 0 0 1 0 0 0

The associated matrix is given above and Eigen values

are : ±2.4495, ±1.4142, 0, 0, 0, 0, 0.

The energy, E(G) = 7.7274 < 8 = (n-1), its stronglyhypoenergetic graph.

(v) For ∆ = 5 and n = 10, we have the graph GG:

0 1 1 1 1 1 0 0 0 01 0 0 0 0 0 0 0 0 01 0 0 0 0 0 0 0 0 01 0 0 0 0 0 0 0 0 01 0 0 0 0 0 1 1 1 10 0 0 0 0 1 0 0 0 00 0 0 0 0 1 0 0 0 00 0 0 1 0 1 0 0 0 00 0 0 0 0 1 0 0 0 0

Eigen values are: ±2.5616, ±1.5616, 0, 0, 0, 0, 0, 0.

E(G) = 8.2462 < 9 = (n-1), its strongly hypoenergeticgraph.

3 De�nitions

Nullity: The number of zero eigen values in character-istic equation of the graph is termed as nullity.

Lemma: Let G be a graph with n vertices and m edges.If nullity of is n0 , then E(G) ≤

√2m(n− n0).

Note: If the graph is a star, E(G) =√

2m(n− n0). Wehave illustrated this below with an example.

22

Eg: S4:

0 1 1 11 0 1 10 1 0 00 1 0 0

Eigen values are : ±1.7321, 0, 0.

Nullity : 2E(G) =

∑|λi| = 3.4642.

E(G) =√

2 ∗ 3 ∗ (4− 2) = 3.4648.

4 Conclusion

We have characterized the trees which are Hypoenergeticand strongly Hypoenergetic with examples using param-eters, vertices (n) and maximum degree (∆).

Acknowledgement:

The author thank Dr. S. A. Mariadoss for his guidanceand constant supervision as well as for providing necessaryinformation about "Energy of the graph". My thanks andappreciations also go to my colleagues for their support.

References

[1] I. Gutman, "The energy of a graph: old and new re-sults, Algebraic Combinatorics and Applications", pp.196-211, Springer-Verlag, Berlin, 2001.

[2] R. Balakrishnan, "The energy of a graph", LinearAlgebra and its Applications, Vol. 387, pp. 287-295,2004.

23

The Expanding Universe and the Enigma of Dark EnergyN. Navin Bappalige1∗, S. Arjun Rao2, A. Jayarama1 and Richard Pinto2

1Physics Dept., Sahyadri College of Engineering & Management, Adyar, Mangalore-5750072E & C Dept., Sahyadri College of Engineering & Management, Adyar, Mangalore-575007.

∗Email: navin.phy@sahyadri.edu.in

For thousands of years our species has looked at thenight sky and wondered with fascinating curiosity. Re-cently we celebrated the 400th anniversary of Galileo's vi-tal contribution in the form of a path breaking instrumentto look at the heavens, the telescope. However, Universeand its existence are much more complex than what we seethrough the telescope. As we all know, the law of gravitywhich operates in astronomical distances and timescalesis the fundamental force in the universe. Einstein �rstproposed a `cosmological constant' as a mathematical �xto the theory of general relativity. In its simplest form,general relativity predicted that the universe must eitherexpand or contract. Einstein conjectured that the uni-verse was static; to overcome the gravitational collapse heproposed a counter-force in the form of `cosmological con-stant' to `stabilize' the universe. Friedmann, (a Russianmathematician) however, thought that this was an unsta-ble �x, and proposed an expanding universe model, whichwas later validated by the fantastic discovery of Dopplershift in Galaxies in 1927 by Edwin Hubble which showedthat the universe is indeed, expanding. To explain the ori-gin of the expanding universe, cosmologists came up witha `Big Bang' theory which postulates a �nite expandinguniverse that has not existed forever, and that all mat-ter, energy and space in the universe was once squeezedinto an in�nitesimally small volume, which erupted in acataclysmic `explosion' .

This in�nitely dense and in�nitely hot gravitationalsingularity occurred some 13.7 billion years ago, thoughestimates vary between 11 and 18 billion years. It is inter-esting that after the Big Bang theory was adopted by cos-mologists, Einstein regretted modifying his elegant theory

and viewed the cosmological constant term as his `greatestmistake' .

When the expansion theory was accepted, two scenar-ios were possible: Universe might have su�cient energydensity to stop its expansion and possibly re-collapse,(because the Universe is full of matter and the attractiveforce of gravity pulls all matter together); or it mighthave so little energy density that it would never stopexpanding. However, the new observation in 1998 withHubble Space Telescope created further complexity: thevery distant supernovae, a few billion light years away,indicated that the Universe then was actually expandingmore slowly than it is today; this opened up a window onmysterious dark energy, which lead to 2011 Nobel Prizein physics for three researchers (Saul Perlmutter, BrianP. Schmidt and Adam G. Riess) whose discovery helpedto unveil a Universe that to a large extent is unknown toscience. In other words, the expansion of the Universehas not been slowing due to gravity, but accelerating dueto a mysterious force. This introduced a new complexitywhich none expected. In order to explain the observedphenomena, cosmologists conjectured two possible ex-planations. First, a long-discarded version of Einstein'stheory of gravity which contained the `cosmological con-stant' ; and the second, some kind of �eld that createsthis cosmic acceleration which is called dark energy.

Shown above are three possible models of expanding uni-verse: at extreme left is the decelerating universe whichreaches current size with a least amount time. In the ab-sence of any other �eld deceleration occurs due to gravitywhich could eventually contract and collapse into a big

24

crunch. A coasting universe shown at the center is olderthan a decelerating universe because it takes more timeto reach its present size; unlike the previous case this ex-pands forever. At extreme right is the expanding universewith a �nite acceleration indicated by 1998 supernova ob-servation. The rate of expansion (acceleration) increasesdue to repulsive force caused by the dark energy.

If the acceleration is to be driven by dark energy, thendark energy itself remains an enigma - perhaps one of thegreatest in physics today. What is known is that dark en-

ergy constitutes about three quarters of the Universe, i.ealmost 68% of the Universe as per the present postulates;the dark matter makes up about 27%. The rest - every-thing ever observed with all our instruments, all normalmatter - adds up to less than 5% of the Universe!!.

References

[1] https://www.spacetelescope.org/images/opo9919k/.

25

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SAHYADRI International Journal of Research

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Sahyadri Journal of ResearchInternational

26SAHYADRI International Journal of Research

PublisherManjunath Bhandary - President

Bhandary Foundation, Sahyadri Campus, Adyar, Mangaluru - 575 007

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| Vol 2 | Issue 1 | July 2016

27SAHYADRI International Journal of Research

Sahyadri College of Engineering and Management (SCEM) organized a seminar on Pulsed Laser

Deposition (PLD) on the occasion of Inauguration of Coherent-Excimer Laser on July 20, 2016 at

Sahyadri Campus. The Chief Guest Dr. Burkhard Fechner and the Guest of honor Dr. Lalit Kumar

inaugurated the Excimer Laser. The seminar was organized by Center of Excellence in Nano-science &

Technology (CENT) in association with Departments of Mechanical Engineering and Electronics &

Communication Engineering of Sahyadri College of Engineering and Management.

Pulsed Laser deposition is a powerful technique for the growth of thin films of multi-component

complex materials. The importance of the technique is such that it is possible to realize

stoichiometry of elements of the complex material in the thin films grown by PLD. Further, PLD is a

powerful technique for research; especially, when a material cannot be stabilized in bulk either due

to the problem of ionic radius or due to variable valance state; such materials can be synthesized in

the form of thin films by PLD. PLD is also very useful for the formation of Nano-materials. Hence, the

inauguration of Excimer laser will act as nucleus for CENT and the research effort on thin films and

Nano-materials will make rapid progress, especially in collaboration with neighboring institutions

and industry partners.

Inauguration of Coherent-Excimer Laser

and a Seminar on Pulsed Laser Deposition at Sahyadri

Inauguration of Coherent-Excimer Laser @ Sahyadri CENT

Prof. Richard Pinto explained thegenesis of PLD

Dr. Burkhard Fechner spoke about thehistorical perspective of lasers

| Vol 2 | Issue 1 | July 2016

Sahyadri Campus, Adyar, Mangaluru - 575 007

COLLEGE OF ENGINEERING & MANAGEMENTSAHYADRI

(Affiliated to VTU, Belagavi and Approved by AICTE, New Delhi)

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Empowering young minds

+ 91-824-2277222 | + 91 96119 45201 | editor@sijr.in | www.sijr.in | www.sahyadri.edu.inSAHYADRI Journal of Research | December 2015 | 3

Sahyadri campus - The sprawling campus just off the Mangalore-Bangalore National

Highway 48 is situated on the banks of the river Nethravathi. Surrounded with natures pristine

beauty and an excellent infrastructure coupled with dedicated and experienced faculty has made the

Campus a much sought-after abode of learning.