PROJECT REPORT ON NANOPARTICLES

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PROJECT REPORT ON

OPTICAL OPTICA L STUDY OF CO-PRECI CO- PRECIPITA PITATED TED CERIUM MOLYBDO IODATE AND CERIUM MOLYBDO PHOSPHATE NANOPARTICLES

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CHAPTER 1 NANOSTRUCTURED MATERIAL-A BRIEF INTRODUCTION

1.1. Nanotechnology an Nano!ate"#al$ % An #nt"o&ct#on #nt"o&ct#on  The roots of Nanotechnology and Nanomaterials can be traced to a lecture deliv deliver ered ed by Richar Richard d Feymann eymann(No (Nobel bel Laure Laureate ate)) in 1959 1959 in a mee meetin ting g of  American hysical society! "hen he seculated this future scientists and engineers "ould build structures from atoms and molecules(1)# $e gave a tal%! &There's lenty of Room at the ottom!& at an American hysical *ociety meeting at caltech# Nanotechnology shortened to &nanotech&! is the study of  maniulating matter on an atomic atomic   an and molecular sca scale# le# +enera +enerally lly!! nanotechnology deals "ith structures si,ed bet"een 1 to 1-- nanometre in at leas leastt one one dime dimens nsio ion! n! and and invo involv lves es deve develo loi ing ng mate materi rial alss or devi device cess osses ossessin sing g at least least one dimens dimension ion "ithin "ithin that si,e# si,e# .uantum mechanical e/ects are very imortant at this scale! "hich is in the 0uantum realm#The realm#The

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+ree% "ord nano2 refers to a dimension !one thousand times smaller than a micron#

R#cha" Fey!ann

Although nanotechnology is a relatively relatively recent develoment in scienti3c research! the develoment of its central concets haened over a longer eriod of time# The emergence of nanotechnology in the 194-s "as caused by the convergence of eerimental advances such as the invention of

the sc scann annin ing g

tunn tu nnel elin ing g

micr mi cros osco coe e in

1941

and

the

discovery

of fullerenes fullerenes in  in 1945! "ith the elucidation and oulari,ation of a concetual . fram frame" e"or or% % for for the the goal goalss of nano nanote tech chno nolo logy gy begi beginn nnin ing g "ith "ith the the 1946 1946 ublication of the boo% 7ngines of 8reation#

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 The scanning tunneling microscoe! microscoe! an instrument for imaging surfaces at the the atom atomic ic leve level! l! "as "as deve develo loe ed d in 1941 1941 by +er +erd d in innig nig and  and $einrich Rohrer at Rohrer  at : ;urich Research Laboratory! Laboratory! for "hich they received the Nobel ri ri,e ,e in h hys ysic icss in 1946 1946## Fullerenes "er "ere disc discov over ered ed in 1945 1945 by $arry
of

nanotechnology

and

founded

the

3eld

of molecular

nanotechnology## n 19>9! =reler encountered Richard Fe nanotechnology Feynman ynman's 's 1959 tal% &The &T here re's 's len lenty ty of Roo oom m at the the ott ottom om&# &# The The term term &nano &nanote tech chnol nolog ogy& y&!! originally coined by Norio Taniguchiin Taniguchiin 19>?! "as un%no"ingly aroriated by =reler in his 1946 boo% Engines of Creation: @ne of the roblems facing nanotechnology is the confusion about its de3nition# :ost de3nitions revolve around the study and control of henomena and materials at length scales belo" 1--nm and 0uite often they ma%e a comarison "ith a human hair! "hich is about 4----nm "ide# de# The There has has been been much uch deba debate te on the the fut future ure

imli licati ations ons of 

nanote nanotechn chnolo ology gy## Nanote Nanotechn chnolo ology gy has the otent otential ial to creat create e many many ne" mate materi rial alss and and devi device cess "ith "ith a vast vast rang range e of al alic icat atio ions ns!! such such as in medicine!electronics medicine!electronics and energy roduction# sciencebased aroach to Nano!ate"#al$ is a 3eld that ta%es a materials sciencebased nanotechnology## t studie nanotechnology studiess materi materials als "ith "ith morho morholog logica icall featur features es on the nanoscale!! and esecially those that have secial roerties stemming from nanoscale their nanoscale dimensions# Nanoscale is usually de3ned as smaller than a one tenth of a micrometer in at least one dimension! BC D though this term is sometimes also used for materials smaller than one micrometer# micrometer# Nanomateria Nanomaterials ls (nanocryst (nanocrystallin alline e materials materials ) are materials materials ossessing ossessing grain si,es of the order of a billionth of ammeter#A nanocrystalline material

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has grains of the order of 11-- nm#The average si,e of an atom is of the order of 1 to C Angstroms in radius# 1 nanometer comrises 1- AngstromsE hence in one nm there may be  to 5 atoms!deending on their radii# Nanocrystalline materials are ecetionally ecetionally strong!hard! and ductile at high tem temer erat atur ures es!" !"ea earr

res esis ista tant nt!c !cor orro rosi sion on

resi resist stan ant! t!

eros erosio ion n

res esis ista tant nt

G

chemically very active#

1.'. Cla$$#(cat#on Cla$$#(cat#o n o) nano!ate"#al$ #

1.'.1. On the *a$#$ o) #!en$#on Nanostructured materials are 8lassi3ed into four di/erent

categories deending on their hysical dimensions#

 They are

a. Nano!ate"#al$ #n +e"o #!en$#on,cl&$te"$

This is the recent tye of the nanostructured materials# The ,ero dimensional clusters are being investigated to tailor otical roerties# *olgel rocess has been commonly used to generated clusters#The tyical method of synthesi synthesiss of the the recent recent ,ero ,ero dimensio dimensional nal nanostruc nanostructure tured d materials materials are are the solgel rocess#They are also called 0uantum dots# *. Nano!ate"#al$ #n one #!en$#on%

@ne dimension dimensional al nano structure structure has been called called by a variety variety of  name namess incl includ udin ing g "his "his% %ers!3 ers!3br bres es or 3bri 3brids ds!n !nan ano" o"ir ires es or nano nanoro rods# ds#@n @ne e

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dimensional nanostructured materials there "ill be a layered structure or a lamell lamellar ar struct structure ure#H #Haou aourr deosi deositio tion! n! sutte sutterin ring g techni techni0ue 0uess and ele electr ctro o deosition techni0ues have been used to synthesi,e the one dimensional layered nanostructured materials#The magnitude of length G "idth are much greater than the thic%ness of the layered nanocrystals# :onolayerIs(layers that are one atom or molecule) are also routinely mace G used in chemistry# c. Nano!ate"#al$ #n to #!en$#on%

n this nanostructur nanostructured ed materials materials synthesi, synthesi,ed ed are 3lamentary 3lamentary in natu naturre#Th e#The e leng length th subs substa tanc ncia iall lly y lar larger ger than than the the "idt "idth h or dime dimete terr in 3lamentary nanocrystals# T"o dimensional nanomaterials includes tubes G "ires#ecause of 3lamentary nature!this tye of nanostructured materials is refer referre red d to as t"o dimens dimension ional# al#The The tyica tyicall method method of synthe synthesis sis of

t"o

dimensional nanostructured material is chemical vaour deosition#(8H=)

Nano#"e$

Nano"ires are ultra3ne "ires or linear arrays of dots!formed by self  assembly#They can be made from a "ide range of materials#*emiconductor Nano Na no"i "irres made made of sili silico con! n!ga gall lliu ium m nitr nitrid ide e G indi indium um hos hosh hid ide e have have demonstrated remar%able otical!electronic G magnetic characteristics#

. Nano!ate"#al$ #n th"ee #!en$#on

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The nanostructured materials are basically in e0uiaed in and are hence called as nanocrystallites or three dimensional nanostructured#The methods commonlyemloyed to synthesis nanocrystalline hase in a variety of mate materi rial alss

are are gas gas

cond co nden ensa sati tion on!m !mec echa hani nica call allo alloyi ying ng G

chem chemic ical al

reciitation and sray conversion rosessing technJ0ues# 1 Nano/a"t#cle$.

Nanoarticles are si,ed bet"een 1G1--nms# Nanorticles may or may not ehibit ehibit si,e related related roerties that di/er di/er signi3cantly from from those observed in 3ne articles or bul% materials# Nanoclusters have atleast one dimension bet"een 1G1-nms and anarro" si,e si,e distribution#Nanoo"ders are agglomerates agglomerates of ultra3ne articles! nanoarticles or nanoclusters#Nanometer si,ed single crystals!or single single domain domain ultra3 ultra3ne ne articl articles es are are often often refer referre red d to as nanocr nanocryst ystals als # Nanoarticles research is currently an area of intense scienti3c interest due to a "ide variety variety of otential alications in biomedical!otical biomedical!otical G electronic 3elds# ' F&lle"ene

A fullerene is any molecule comosed entirely of carbon! in the form of ahollo" shere !ellised!or tube#*herical fullerenes are also called 8arbon 8arbon nanotu nanotubes bes or buc%y buc%ytub tubes# es# Fuller ullerene eness are are simil similar ar in structu structure re to grahite!"hich is comosed of stac%ed grahine sheets of lin%ed heagonal rings #

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F#g.1.1

F&lle"ene

0 Den "#!e"$

=en drimers drimers are sherical olymeric molecules!formed molecules!formed through a nanoscale !hierarchial self assembly rocess#There are many tyes of den drimers E the smallest is several several nanometers in si,e# si,e# =en drimers are used inconventional alications such as coatings G lin%s#  2&ant&! ot$.

Nanoarticles of semiconductors(0uantum dots) "ere theori,ed in the 19>-s and initially created in early 194-s#f semiconductors articles are made small enough! 0uantum e/ects come into lay !"hich limit the energies at "hich electrons G holes can eist in the articles# F#g 1.'

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Fig1#C# reresents the schematic reresentation of the four di/erent tyes of nanostructured materials#

1.'.' Pha$e co!/o$#t#on According to hase comosition nanostructured materials are classi3ed into  grous#They are *ingle hase solids

8rystalline !amorhous articles G

:ulti hase solids

Layers etc# :atri comosites!coated articles

:ulti hase systems

etc# 8olloids!aerogels!ferro Kuids etc

Table 1#C#C#8lassi3cation based on hase comosition#

1.'.0 Man&)act&"#ng /"oce$$ +as hase reaction

Flame

Li0uid hase reaction

synthesis!condensation!8H= etc *olgel!reciitation!hydrothermal

:echanical rocedures

rocessing etc# all milling!lasyic deformation etc

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Table 1#C##8lassi3cation based on manufacturing rocess#

1.0. P"o/e"t#e$ o) Nano$t"&ct&"e Mate"#al$ @"ing to the very 3ne grain si,e! nanostructured materials ehibit a variety of roerties that are di/erent and often considerably imroved in com co mari ariso son n "ith "ith thos those e of co conv nven enti tion onal al co coar arse serr grai graine ned d oly olycr crys ysta tall llin ine e materi materials als## f the si,e of the atomi atomicc ensem ensemble ble become becomess comar comarabl able e to or smaller than the tyical length scale of a hysical henomenon! then the satia satiall con3ne con3nemen mentt can a/ect any roerty roerty##

*ome *ome of the roer roertie tiess of 

nanostructured materials are given belo"#

,a. Mechan#cal P"o/e"t#e$ 7lasti 7lasticc consta constants nts of nanocry nanocrytst tstall alline ine materi materials als have have been been reduc reduced ed cons co nsid ider erabl ably y co com mar ared ed to thos those e of bul% bul% mater materia ials ls##

This This is due due to the

comara comarativ tivel ely y higher higher inter interat atomi omicc sacin sacing g in the boundar boundary y regio regions# ns# The streng strength th of nanocr nanocryst ystall alline ine materi material al incre increase asess consid considera erably bly than than that that of  coarsegrained material# $ardness also increases "ith decreasing grain si,e in conventional conventional coarser grained materials# materials# This relationshi relationshi is called called Hallmaterials hardness decreases "ith Petch "elat#on$h#/3# For nanocrystalline materials decrease in grain si,e# si,e# t is referred referred to as inverse $alle $alletch tch e/ect# n some grains! direct relationshi bet"een oungIs modulus and hardness has been established# Reducing the grain si,e can lo"er lo"er the ductileMbrittle ductileMbrittle transition temeratur temerature# e# The fracture fracture stress of nanocrystal nanocrystalline line material material is lo"er than that of convention conventional al coarsegraine coarsegrained d material# material# +rain si,e si,e and shae! their their

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distribution! ores and their distribution! surface condition! all a/ect the mechanical behaviour of nanocrystalline materials#

,*.The"!al P"o/e"t#e$  The thermal eansion coecient of nanocrystalline material is greatly enhanc enhanced ed due to the rese resence nce of large large amount amount of grain grain boundarie boundaries# s# The sec seci3 i3cc heat heat of a mat materia eriall is clos closel ely y relat elated ed to the the vibr vibrat atio iona nall and and con3gu con3gurat ration ional al entro entroy y of the materi material! al! "hich "hich is direct directly ly relat related ed to the near neares estt neig neighbo hbour ur co con3 n3gur gurat atio ion# n#

The The seci seci3c 3c heat heat in nano nanocr crys ysta tall llin ine e

mate materi rial al is much much high higher er than than that that in the the co coars arser er grai graine ned d mate materi rial al## The The increase in seci3c heat in nanocrystalline material is art attributed to the comli comlicat cated ed struct structur ure e of grain grain and hase hase bounda boundarie ries# s# The enthal enthaly y and entroy of nanocrystalline material is very high#

,c. Elect"#cal P"o/e"t#e$  The electrical resistivity of nanocrystalline na nocrystalline metal is higher than in both coarsegrai coarsegrained ned olycrystall olycrystalline ine metal and alloys# The residual residual resistivi resistivity ty of  nanocrystalline metals of --< decreases decreases "ith an increase in in grain si,e# f the crystal si,e is smaller than the electron mean free ath! grain boundary scat sc atte teri ring ng domi domina nate tess and and henc hence e elec electr tric ical al res esis isti tivi vity ty as "ell "ell as the the tem temer erat atur ure e co coe eci cien entt is increa increase sed# d#

t has has been been sho" sho"n n that that the A8

conducting of nanocrystalline Ti@C doed "ith about 1O t is reversible "ith tem temer erat atur ure# e#

The The magn magnit itud ude e of elec electr tric ical al resi resist stiv ivit ity y and and henc hence e the the

condu co nduct ctiv ivit ity y in co com mos osit ites es can be chan change ged d by alte alteri ring ng the the si,e si,e of the the electrically conducting comonent#

,. Magnet#c P"o/e"t#e$. :agnetic roerties of nanocrystalline materials deend on the grain si,e si,e##

t "as "as noted noted that "ith "ith incr increa easi sing ng grai grain n si,e si,e d! the the co coer erci civi vity ty $ c

increases follo"ing d6 o"er la" u to 5-nm! runs through maimum of the

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$c -AMcm and then decreases decreases for grain si,es of about 5-nm decoding to the "ell %no"n %no"n 1Md la" for olycrystall olycrystalline ine magnets# magnets# Nanostructur Nanostructured ed materials materials sho" sho" a reduc reducti tion on in the the sa satu tura rati tion on magn magnet eti, i,ati ation on and ferr ferrom omag agne neti ticc transition temerature! due to the deviations of interatomic sacing in the interfacial region#3 Nano Na noccryst rystal allline ine iron iron base based d allo alloys ys are are used used for for so sofft magne agneti ticc al alic icati ation onss due due to thei theirr sec seci3 i3cc char charac acte ters rs li% li%e lo" lo" co coer erci civi vity ty!! high high ermeability! ,ero magnetostriction! lo" core losses due to high electrical recetiv recetivity ity and good thermal thermal stability stability# :agnetic :agnetic calori3c calori3c e/ect is another another imortant magnetic roerty of nanocomosites5# The magnetic roerty of  nanosi,ed article deends on the large surface to volume ratio# Pnli%e bul% mater ateriials als

cons co nsiistin sting g

of

multi ultil le e

magne agneti ticc

dom domains ains!!

sev se veral ral

smal sm alll

ferromagnetic articles can form single magnetic domains! giving rise to sur suram amagn agnet etis ism# m# This This beha behavi viou ourr oen oenss the the ossi ossibl bly y for for al alic icati ation on in information storage#

,e. O/t#cal P"o/e"t#e$ Qhen Qhen the the diam diamet eter er of the the nano nanost stru ruct ctur ured ed mate materi rial al is decr decrea ease sed! d! discrete discrete electroni electronicc energy states states are formed# The eciton eciton ohr radius lay the central role in the otical roerties of semiconductor nanostructures! "hen "hen the si,e si,e of nanost nanostruc ructur ture e comon comonent ent aroac aroache hess the ohr ohr radius radius electronic and otical absortion changes and the integrated absortion can incre increase ase##

f the crystal crystallit lite e si,e si,e of a nanocry nanocrystal stallin line e materi material al becomes becomes

comarable or smaller than deroglie "avelength of the charge carriers generated by the absorbed light! the con3nement increases energy re0uired for absortion# absortion#

This energy energy increase increase shifts shifts the absortionM absortionMlumi luminesce nescence nce

sectra to"ards shorter "avelength "avelength (blue)# The blue shift shift is a 0uantum si,e

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e/ect# e/ect#

7aml 7amle e lue shift shift is observed observed in the lumine luminesce scence nce sectra sectra of 

nanocrystalline ;n@ as a function of crystal si,e# 8ontrolling article si,e can change otical roerties of nanostructure samle samles# s#

y controll controlling ing the cluster cluster si,e of 8d*e! 8d*e! *teiger" *teiger"ald ald and urs

(1949) "ere able to synthesi,e clusters of very narro" si,e distributions and sho" sho" that that they they indi indica cate te vary varyin ing g degr degree eess of 0uan 0uantu tum m co con3 n3ne neme ment nt and and di/erent band gas# 8lusters of 1#C1#5nm 1#C1#5nm diameter have a band ga of eH and those having diameter of #5nm have a band ga of C#eH "hile the bul% material have a band ga ga of 1#4eH# 1#4eH# =ue to three dimensional con3nements! con3nements! the me mecha chanis nisms ms for reson resonant ant band band edge edge otic otical al nonli nonlinea nearit ritie iess in nano crystalli crystallites tes are di/erent di/erent from those in bul% materials# materials# @tical @tical and infrared infrared absortion measurements have been erformed for nano crystalline *i 3lm at di/erent di/erent temer temeratu ature res# s# A rono ronounc unced ed red shift of the absort absortion ion "as noticed "ith increasing temeratures u to 5- -8# f deosition temerature "as increased to ?---8 blue shift "as observed "hich sho"s the relation bet"een crystal si,e and deosition temerature

1. Cha"acte"#$t#c )eat&"e$ o) nano$t"&ct&"e nano$t"&ct&"e !ate"#al$ n nano nanost stru ruct ctur ured ed mate materi rial als! s! t"o t"o tye tyess of atom atomss ca can n be distinguished crystal atoms and boundary atoms. *chematic reresentation of hard shere model of an e0uiaed nanocrystalline metal is sho"n in F#g&"e 1.0. and t"o tyes of atoms can be distinguished! of these the 3rst

one

contain ains

crysta stal

atoms

"ith

neare arest

neighbor bor

con3g n3gurati ation

corresonding to the lattice and boundary atoms "ith a variety of inter

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atomic sacing di/ering from boundary to boundary# boundary# A nanocrystaline metal metal contains a large number of interfaces (S61-C5m)"ith random orientation relationshis and conse0uently a substantial fraction of atoms lie in the interfaces interfaces## Assuming Assuming that grains grains have the shae shae of sheres sheres or cubes the volume fraction of the nanocrystaline materials associated "ith the boundary can be calculated as  UMd! "here U is the average grain boundary thic%ness and d the average grain diameter diameter## Thus the volume fraction fraction of atoms in the grain boundaries can be as much as 5-O for 5nm grains and decrease to about -O for 1-nm grains and O for 1--nm grains#

Figure 1#

1.3 A//l#cat#on$ o) nanotechnology Qith nanotechnology! a large set of materials and imroved roducts rely on a change in the hysical roerties "hen the feature si,es are shrun%# Nanoarticles! for eamle! ta%e advantage of their dramatically incr increa ease sed d surf surfac ace e area area to volu volume me rati ratio# o# Thei Theirr oti otica call ro roer erti ties es!! e#g# e#g# Kuorescence!! become a function of the article diameter# Qhen brought into Kuorescence a bul% bul% mate materi rial al!! nano nanoart artic icle less ca can n stro strong ngly ly inKu inKuen ence ce the the me mech chani anica call roerties of the material! li%e sti/ness or elasticity# For eamle! traditional olymers   can be reinforced by nanoarticles resulting in novel materials olymers "hich can be used as light"eight relacements for metals# Therefore! an incre increasi asing ng soc socie ietal tal bene3t bene3t of such such nanoa nanoarti rticle cless can be eec eected ted## *uch *uch

15

nanote nanotechn chnolo ologic gicall ally y enhanc enhanced ed materi materials als "ill "ill enabl enable e a "eigh "eightt reduc reductio tion n accomanied by an increase increase in stability stability and imroved imroved functionality# functionality# There are many alicatons of nanotechnology! fe" of them are sho" here#

a Tissu issue e engi engine neeri ering ng Nanotechnology can hel to reroduce or to reair damaged tissue# Tissue engineering2 ma%es use of arti3cially stimulated cell roliferation by using using suitab suitable le nanoma nanomater terial ialba based sed sca sca/ol /olds ds and gro"t gro"th h factor factors# s# Tissu Tissue e engi engine neer erin ing g migh mightt rel relac ace e today todayIs Is co conv nven enti tion onal al trea treatm tmen ents ts li% li%e orga organ n translants or arti3cial imlants# Advanced forms of tissue engineering may lead to life etension# etension#

b Che!#$t"y an en4#"on!ent 8hem 8hemic ical al ca cata taly lysi siss and and 3ltr 3ltrat atio ion n tech techni ni0u 0ues es are are t"o t"o rom romin inen entt eamles "here nanotechnology already lays a role# The synthesis rovides novel materials "ith tailored features and chemical roerties for eamle! nanoa nanoarti rticle cless "ith "ith a distin distinct ct chemic chemical al surro surroundi unding ng (ligand (ligands)! s)! or seci3 seci3cc otical roerties# n this sense! chemistry is indeed a basic nanoscience# n a shortterm ersective! chemistry "ill rovide novel nanomaterials2 and in the long long run! run! sueri suerior or roce rocesse ssess such such as se self lfass assem embly bly22 "ill "ill enabl enable e energy and time reserving strategies# n a sense! all chemical synthesis can be unde unders rsto tood od in ter terms of nano nanote tech chno nolo logy gy!! beca becaus use e of its its abil abilit ity y to manuf anufac actu turre ce cert rtai ain n molec olecul ule es# Thus Thus!! chem hemistry stry for forms a base base for for nanotechnology roviding tailormade molecules! olymers! etcetera! as "ell as clusters and nanoarticles# nanoarticles#

c 8atalysis 8hemical catalysis ben3ts esecially from nanoarticles! due to the etre treme mely ly larg large e surf surfac ace e to volu volume me rati ratio o#

The The ali alica cati tion on ote otent ntia iall of 

nanoarticles in catalysis ranges from fuel cell to catalytic converters and

16

hotoc hotocatal atalyti yticc device devices# s#

8ataly 8atalysis sis is als also o imort imortant ant for the roduct roduction ion of 

chemicals#

d :edicine  The biological and medical research communities have eloited the uni0ue roerties of nanomaterials for various alications# Terms such as biomedical nanotechnology! nanobiotechnology! and nanomedicine are used to describe this hybrid 3eld# Functionalities can be added to nanomaterials by interf interfaci acing ng them them "ith "ith biolog biologica icall molecu molecules les or struct structur ures# es# The si,e si,e of  nanomaterials is similar to that of most biological molecules and structuresE ther theref efor ore! e! nano nanoma mate teri rial alss ca can n be usef useful ul for for both both in vivo vivo and and in vitr vitro o biom biome edica dicall rese sear arch ch and and al aliicati ations# ons# Thus Thus far! far! the integ ntegra rati tion on of  nanomaterials "ith biology has led to the develoment of diagnostic devices! contrast agents! analytical tools! hysical theray alications! and drug delivery vehicles#

e F#lt" #lt"at at#o #on n A strong strong inKuen inKuence ce of nanoch nanochem emist istry ry on "aste "aste"at "ater er treatm treatment ent!! air uri3cation and energy storage devices is to be eected# :echanical or chemical methods can be used for e/ective 3ltration techni0ues# @ne class of 3ltration techni0ues is based on the use of membranes "ith suitable hole si,es! "hereby the li0uid is ressed through the membrane# Nanoorous membranes are suitable for a mechanical 3ltration "ith etremely small or ores sm smal alle lerr than than 1- nm (na (nano no3l 3ltr trat atio ion n2) and and may be comos comosed ed of  nanotubes# nanotubes# Nano3ltration is mainly used for the removal of ions or the searation of di/erent Kuids# @n a larger scale! the membrane 3ltration techni0ue is named ultra3ltration! "hich "or%s do"n to bet"een 1- and 1-nm# @ne imortant 3eld of alication for ultra3ltration is ultra3ltration is medical uroses as can be found in renal dialysis# :agnetic nanoarticles o/er an e/ective and reliable method to remove heavy metal contaminants from "aste "ater by ma%ing use of magnetic searation techni0ues# Psing nanoscale articles

17

increases the eciency to absorb the contaminants and is comaratively ineensive comared comared to traditional reciitation and 3ltration methods5

f  In)o"!at#on an co!!&n#cat#on 8urrent hightechnology roduction rocesses are based on traditional to do"n strategies! "here nanotechnology has already been introduced sile silent ntly ly## The The crit critic ical al leng length th sc scal ale e of integrated integrated circuits circuits   is already at the nanoscale (5- nm and belo") regarding the gate length of transistors in 8Ps or 8Ps or =RA: devices# =RA: devices#

g Novel Novel semicon semiconduc ductor tor device devicess An eam amle of such novel devices is based on sintronics#The sintronics#The deendence of the resistance of a material (due to the sin of the electrons) on an eternal 3eld is called magnetoresistance# magnetoresistance# This e/ect can be signi3 signi3can cantly tly amli3 amli3ed ed (+:R (+:R  +iant +iant :agnet :agnetoR oResi esista stance nce)) for nanosi nanosi,e ,ed d obJects! for eamle "hen t"o ferromagnetic layers are searated by a nonmagnetic layer! "hich is several nanometers thic% (e#g# 8o8u8o)# The +:R e/ect has led to a strong increase in the data storage density of hard dis% dis%ss and made made the the gigab gigabyt yte e rang range e oss ossib ible le## The The so ca call lled ed tunn tunnel elin ing g magnetoresistance (T:R) is very similar to +:R and based on the sin deendent deendent tunneling tunneling of electron electronss through through adJacent adJacent ferromagne ferromagnetic tic layers# layers# oth oth +:R +:R and and T:R T:R e/ e/ec ects ts ca can n be used used to crea create te a non nonvo vola lati tile le main main memo me mory ry for for co com mut uter ers! s! such such as the the so ca call lled ed magn magnet etic ic rando random m ac acce cess ss memory or :RA:# :RA:# n 1999! the ultimate 8:@* transistor develoed at the Laboratory for 7lectronics and nformation Technology in +renoble! France! tested the limits of the the rin rinci cil les es of the the :@*F :@*F7T 7T tran transi sist stor or "ith "ith a diam diamet eter er of 14 nm (aroimately >- atoms laced side by side)# This "as almost one tenth the si,e of the smallest industrial transistor in C-- (1- nm in C--! 9- nm in C--? C--?!! 65 nm in C--5 C--5 and and ?5 nm in C--> C-->)# )# t enab enable led d the the theo theorretic etical al

18

inte integra grati tion on of se seve ven n bill billio ion n Junc Juncti tion onss on a V1 co coin in## $o $o"e "eve ver! r! the the 8:@* 8:@* transistor! "hich "as created in 1999! "as not a simle research eeriment to study ho" 8:@* technology functions! but rather a demonstration of ho" this technology functions no" that "e ourselves are getting ever closer to "or%ing on a molecular scale# Today it "ould be imossible to master the coordinated assembly of a large number of these transistors on a circuit and it "ould also be imossible to create this on an industrial level6#

h Co$!e o$!et# t#c$ c$ @ne 3eld of alication is in sunscreens# The traditional chemical PH rotection aroach su/ers from its oor longterm stability# A sunscreen base based d on mine mineral ral nano nanoa art rtic icle less such such as tita titani nium um dio dioide ide o/er o/er se seve veral ral advantages# Titanium oide nanoarticles have a comarable PH rotection ro roer erty ty as the the bul% bul% mater ateria ial! l! but but lose lose the the co cosm smet etic ical ally ly unde undesi sira rabl ble e "hitening as the article si,e is decreased#

# Ene"gy  The most advanced nanotechnology roJects related to energy are storage! conversion! manufacturing imrovements by reducing materials and rocess rates! energy saving and enhanced rene"able energy sources#

 J Reduction of energy consumtion A reduction of energy consumtion can be reached by better insulation systems! by the use of more ecient lighting or combustion systems! and by use of lighter and stronger materials in the transortation sector# 8urrently used light bulbs only convert aroimately 5O of the electrical energy into light# light# Nanote Nanotechno chnolog logica icall aroa aroache chess li%e li%e lightemi lightemitting tting diodes diodes (L7= (L7=s) s) or 0uantum caged atoms (.8As) atoms (.8As) could lead to a strong reduction of energy consumtion for illumination#

19

1.5 P"e$ent P"e$ent 7o"8  Nanomaterials have fascinated scienti3c community in recent ast# Nanosi,ed materials are those "hich have articlesorganic! inorganic or combinatio combinations ns that are of nanometer nanometer si,e# si,e# These material materialss ehibit ehibit unusual ro roer erti ties es co com mar ared ed to thei theirr bul% bul% co coun unte ter rar arts ts##

The The synt synthe hesi siss of 

nanomaterials "ith uniform article si,e is a subJect of intensive research in recent times because of their fundamental scienti3c interest as "ell as for technological imortance# Acid Acid sa salt ltss of me meta tals ls (T:A (T:A sa salt lts) s) are are obta obtain ined ed in amor amorho hous us and and crys crysta tall llin ine e form# form#

Thes These e co com mou ounds nds have the gene general ral formu formula la :(H :(H))

($W@?)Cn$C@ "here! "here! :(H)X8e!;r!Th!Ti :(H)X8e!;r!Th!Ti etc WX!:o!Q etc# The roerties roerties of  the @$ grou of above materials can be echanged for several cations and thus thus these these material materialss are are terme termed d inorg inorgani anicc ion echa echange ngers# rs# A number number of  cation can be echanged "ith $Y due to "hich the material ossess cation echange echange roerti roerties es deending deending on the stoitiomet stoitiometry ry of the reagent used! used! temerature at "hich they are mied! rate of addition! mode of miing!  $ etc# etc#

The The resu result ltan antt mate materi rial alss vary vary in "ate "aterr co cont nten ent! t! co com mos osti titi tion on and and

crysta crystalli llinit nity y#

Liter Literatur ature e sho"s sho"s that these these materi materials als are "ell "ell studie studied d in

crystalline and amorhous forms# n the the res resen entt "or%! "or%! nano nanoa art rtic icle less of 8e 8eri rium um moly molybdo bdoio ioda date te and and 8eri 8e rium um moly molybdo bdoh hos osha hate te are are synt synthe hesi si,e ,ed d by co cont ntro roll lled ed che!#c che!#cal al coco7=TA as the organic temlating temlating agent# The as /"ec#/#tat#on !etho using 7=TA reared samles are annealed at 5---8 for C hours# hours# The average average crystalline crystalline

20

si,e of both samles are determined from 9-"ay #:"act#on line broadening by using Sche""e" The surf surfac ace e mor morho holo logy gy and and chem chemic ical al Sche""e" e;&at#on e;&at#on# The comosition of both samles are obtained from SEM #th EDA9 techni0ues#  The FTR  $/ect"&! of both both sa sam mle less are are reco record rded ed for for dete determ rmin inin ing g the the di/er di/erent ent stretc stretchin hing g and bendin bending g fre0u fre0uenc encies ies of molecu molecular lar grou grouss in the samles#

1.6 Re)e"e Re)e"ence nce 1# ($ +leiter!rog#:ater#*ci#(1944)CC#) C#8ristina u,ea! van acheco! and )# Nanomaterials and Nanoarticles *ources and Toicity2# #N# Taniguchi (19>?)# On the ‘Basic Concept of Nano-Technology’ # roc# ntl# 8onf# rod# rod# London! art  ritish *ociety of recision recision 7ngineering# ?#
(1996) 609#

6#*ergey # +ubin (C--9)# Magnetic nanoparticles# QileyH8$# QileyH8$#

21

CHAPTER-'  

CHARACTERI
TECHNI2UES

22

'.1. Int"o&ct#on  The nanomaterials can be investigated and characteri,ed using di/erent techni0ues li%e Wray di/raction di/ract ion (WR=)! PHHisible PHHisible *ectroscoy(PH *ectroscoy(P H His)!nfrared *ectroscoy(R)! *canning 7lectron :icroscoy(*7:)! Tunneling Tunneling 7lectron :icroscoy(T7:) etc# This chater brieKy describes the theory and instrumentation of Wray di/raction analysis! *7: "ith 7=AW techni0ue and PHvisible PHvisible *ectroscoy *ectros coy##

'.'. 9-Ray D#:"act#on D#:"act# on '.',a.Int"o&ct#on Wray ray =i/r =i/rac acti tion on (WR= (WR=)) is one one of the the most most vers versat atil ile e and and "ide "idely ly emlo em loyed yed eer eerime imenta ntall techni techni0ue 0uess for the struct structural ural charac character teri, i,ati ation on of  crystalline materials

# Wray di/raction attern of the samle rimarily give

1-0

information about the di/erent crystalline hases resent=3 # Therefore! the 3rst ste after synthesi,ing the crystalline samle is to record its Wray di/raction attern# Wray di/raction is the most convenient indirect method

23

for the determination of average crystallite si,e of nanocrystalline samles

5-

#

6

'.',*.Theo"y an In$t"&!entat#on Wray o"der di/raction has been used in t"o main areas! for the 3nge nger

rin rint

chara aracteri,ation

of

dete determ rmin inati ation on of thei theirr stru struct ctur ure# e#

crystall alline

materia rials

and

for

the

7ach 7ach crys crysta tall llin ine e so soli lid d has has its its uni0 uni0ue ue

characteri characteristic stic Wray Wray o"der o"der attern! attern! "hich "hich may be used as a

I3nger

rint rintII for for its its iden identi ti3c 3cat atio ion# n# Wray ray crys crysta tall llog ogra rahy hy ca can n also also be used used to dete determ rmin ine e crys crysta tall stru struct ctur ure# e# The The me measu asure reme ment nt of crys crysta tall llin ine e si,e si,e of a olycrystalline secimens by means of Wray is based on the broadening of  di/raction lines "hen the crystallite si,e is very 3ne i#e#! less than 1- >m =3 #  The broadening of di/raction ea% can be used to determine the si,e of the crystalline samle using the *cherrer e0uation#

*cherr errer e0uation is!

t X -#9 #9λM\h%l8os θh%l

raggIs la" is given by! Cdsin] X n^ ___________## (1) For 3rst order di/raction! Cdsin] X ^_____________ ^_____________ (C) :ultilying both sides by an integer m such that md Xt! thic%ness of the crystal Ctsin] Xm ^________########## () 70n(C 70n(C)! )! can also also be inter interre reted ted as the the mth order reKection from a set of  lanes "ith interlanar distanceItI# =ifferentiating both sides of ()! remembering m ^ is a constant# Ctcos] ` ] YCsin ] ` t X-____ (?)

24

` ] can be ositive or negative# 8onsidering magnitude only (?) leads to tX`tsin]M ` ]cos] *ince the smallest increment increment in in tI is d! using using ` tXd! and substituting ^MC for dsin] Bfrom (C)D! "e get tX ^MC`]cos]_________## (5)

A



I

AI 8>

8 =

]Y`]

=I

1 C

:I N

:

L ]

tXmd LI

NI

25

#

F#g&"e %'.1

Let ]1  X ] Y` ]! be the highest ossible angle that can be got before comlete destructive interference and let ] CX] [` ] be lo"est angle that can be got before comlete destructive interference# No" "e can interret C`] as the angular "idth of the Wray di/raction line# n the Wray di/ractome di/ractometer ter "hat is recorde recorded d is the variation variation in intensity of the diffraction lines "ith C]! so in the Wray diffractogram "e can see diffracted Wrays over all scattering angles bet"een C] 1andC]C# f "e assume a triangular shae for the ea%! the full "idth at half maimum (FQ$:) "ill be! \

X

X

]1]C

(C]1  C]C ) MC

X (] Y` ]) [ (] [` ]) \

X

C ` ]____________ (6)

ma  

ntensity maMC#

_#\_#

26

C]C

C]

C]1

F#g&"e%'.'

=iffraction from finite thic%ness crystal! substituting \ for C`] on (5)! "e get t

X

^M\ 8os]___________## (>)

 This is essentially the *cherrer *cherrer e0uation# A more more rigo rigoro rous us trea treatm tmen entt (usi (using ng a +aus +aussi sian an func functi tion on!! rathe ratherr than than a triangular function) gives! t

X

-#9^ M\ 8os]_______ (4)!

for

sherical

crystal of diameter t# t

X

%^ M\h%l 8os]h%l

$ere!t is the average crystallite si,e normal to the reKecting lanes !% is the shae factor! "hich lies bet"een -#95 and 1#15 deending uon the shae of  the grains in the "ave length of Wray used and \ h%l is the Full Qidth at $alf  :aimum(FQ$:) of the diffraction in radians and ] h%l  is the ragg angle corresonding to the di/raction line arising from the lanes designated by the :iller :iller indices(h%l indices(h%l))6#
27

F#g&"e%'.0.E?/e"#!ental F#g&"e%'.0.E?/e"#!e ntal $et &/ )o" 9RD

9-Ray #:"acto!ete"

28

'.0. Scann#ng Elect"on M#c"o$co/e #th EDA9 '.0.1. Int"o&ct#on *7: *7: stan stand ds for for sc scan anni ning ng elect lectrron mic micros osco coe e##

The The *7: *7: is a

microscoe that uses electrons electrons instead of light to form an image# *ince their deve develo lom men entt in the the ea earl rly y 195195-'s! 's! sc scan anni ning ng elec electr tron on micr micros osco coe ess have have deve develloe oed ne" ne" area areass of stu study in the the medic dical and and hy hysic sical sc sciienc ence communiti communities# es# The *7: has allo"ed allo"ed researchers researchers to eamine eamine a much bigger bigger variety of secimens#  The scanning electron microscoe has many advantages over traditional traditional microsc microscoes# oes# The *7: has a large large deth of 3eld! "hich allo"s allo"s more more of a secime secimen n to be in focus at one time# time# The *7: also also has much higher resolution! so closely saced secimens can be magni3ed at much higher levels# ecause the *7: uses electromagnets electromagnets rather than lenses! lenses! the resea researc rcher her has much much more more contr control ol in the degree degree of magni3 magni3cat cation ion## All of  these advantages! as "ell as the actual stri%ingly clear images! ma%e the scanning electron microscoe one of the most useful instruments in research today#

29

 

F#g&"e%'.

:orhological studies of the samles are done using scanning electron microscoy# *7: is a very ecient tool to study the surface tetures of  materials# $ere the surface of the samle is irradiated "ith a beam of  accelerated electrons# *ince electrons have shorter "avelengths comared to hotons! the resolution obtained in *7: is very high comared to that in conventional otical microscoy# Furthermore! the deth of focus in *7: is much greater than that achieved in otical microscoy# n addition to the above t"o factors! it has the advantage of greater magnifying o"er and henc hence e *7: *7: has has beco become me a very very o"e o"erf rful ul tech techni ni0u 0ue e to elo lore re the the free free surfaces of materials# The energy disersive sectrum of the samle are also sho"n along "ith the *7: image#  The *7: is an instrument that roduces a largely magni3ed image by using electr electrons ons instead instead of light to form an image# A beam of electrons electrons is rodu roduced ced at the to of the micros microsco coe e by an electro electron n gun# gun# The electr electron on beam follo"s a vertical ath through the microscoe! "hich is held "ithin a vacuum# The beam travels through electromagnetic electromagnetic 3elds and lenses! lenses! "hich focus the beam do"n do"n to"ard to"ard the samle# @nce the beam beam hits the samle! samle! electrons and Wrays are eJected from the samle#

F#g&"e%'.3

30

=etect =etectors ors collec collectt these these Wrays! rays! bac%sc bac%scatt atter ered ed ele electr ctrons ons!! and sec second ondary ary electrons and convert them into a signal that is sent to a screen similar to a television screen# This roduces the 3nal image# image#

'.0.'.In$t"&!entat#on%

F#g&"e%'.5 SEM o/ene $a!/le cha!*e"

 The *7: micrograhs of our samles are obtained "ith a $itachi :odel *---$ electron microscoe# The electron beam is focused on selected area areass of the the sa sam mle less ac acco cord rdin ing g to the the re0ui e0uirrem emen ents ts and and at di/e di/errent ent magni3 magni3cat cation ion## The %ineti %ineticc energ energy y ac0uir ac0uired ed by ele electr ctrons ons in an elect electro ron n column! "hen they are accelerated through an electric 3eld! is transferred to the samle and its dissiation yields a variety of signals available for analysis of elec electr tron on from from the the high highes estt oc occu cui ied ed mole molecu cula larr orbi orbita tall to the the lo"e lo"est st available un3lled molecular orbital# n most of the cases! several transitions occur resulting in the formation of several s everal bands#

31

 The most most imor imortan tantt roer roerty ty of a sem semico icondu nducto ctorr nanost nanostruc ructur ture e is its its otical behavior to crystallite si,e# @tical roerties may be absortion! sectral s ectral resonse!

hotoluminescence!

hotoluminescence

ecitation!

electroluminescence and Raman scattering "hose otical roerties resond to crys crysta tall llin ine e si,e si,e## As the the si,e si,e is decr decrea ease sed! d! the the elec electr tron onic ic stat states es are are disc discre reti ti,e ,ed d and and resu result ltss in "ide "ideni ning ng of the the band band ga and and incr increa ease sess the the oscillator strength# The radiative recombination life time of carrier is lo"ered from nanosecond to icoseconds# These features %no"n as 0uantum si,e e/ect (.*7) are observed in semiconductor nanocrystals#

'.. Fo&"#e" T"an$)o"! In)"a"e S/ect"o$co/y '..1. Int"o&ct#on

*ectroscoy is the study of interaction of electromagnetic radiation

"ith matter# nfrared *ectroscoy is one of the most o"erful analytical techni0ues "hich "hich o/er the ossibility of of chemical identi3cation# @ne of the most imortant advantages of R sectroscoy over the other usual methods of structural analysis is that it rovides useful information about the structure of molecul molecule e 0uic%ly 0uic%ly## This This techni techni0ue 0ue is based on the fact that that a chemi chemical cal substance sho"s selective selective absortion in in the infrared region# After After absortion of R radiation! the molecule of a chemical substance vibrate at many rate of  vibration giving rise to ac%ed absortion band! called R absortion sectra# Harious bands "ill corresond to the characteristic functional grous and bond resent resent in a chemical chemical substance# substance# Thus an R sectrum sectrum of a chemical chemical substance is 3ngerrint for its identi3cation# A mole molecu cule le abso absorb rbss radi radiati ation on only only "hen "hen the the natu natural ral fre0 fre0ue uenc ncy y of  vibration of some art of a molecule is the same as the fre0uency of the radiation# The molecules molecules vibrate at increased increased amlitude# This occurs at the eense of the energy of R radiation "hich "hich has been absorbed# n nfrared sectroscoy! the absorbed energy brings about redominant changes in the vibrational energy "hich deend uon

32

(a) :ass of the atom resent in the molecule (b) *trength of the bond (c) The arrangement of atom "ithin the molecule# t has been found that no t"o comounds ecet the enantiomers can have have similar similar nfrare nfrared d sectr sectra# a#

Qhen Qhen infrar infrared ed light is assed through through

sam sa mle le!! the the vibr vibrat atio iona nall and and rota rotati tion onal al ener energi gies es of the the mole molecu cule le are are increased# T"o tyes of fundamental vibrations vibrations are stretching and bending# bending# n stretching vibrations! the distance bet"een the t"o atoms increases or decre decrease asess but the atom remain remain in the same same bond ais# ais#

ut in bending bending

vibrations the osition of atoms changes "ith resect to the original bond ais# There are t"o tyes tyes of stretching vibrations# Also there there are four tyes of bending vibrations scissoring! roc%ing! "agging and t"isting# Another condition for a molecule to absorb R radiation is its electric diole# A molecule can only absorb R radiation "hen "hen its absortion causes causes a change in its electri electricc diole# diole# A molecule molecule is said to have an electric electric diole! diole! "hen there is a slight ositive charge and a slight negative charge on its comonent atoms#

'..'. In$t"&!entat#on  The aaratus for measuring infrared sectra is di/erent from that for visible and ultraviolet regions because the otical materials li%e glass and 0uar 0uart, t, absorb absorb stron strongl gly y in the infr infrar ared ed regio region# n#

The The main main arts arts of an R

sectrometer sectrometer are as follo"s#1a b c d

The The R radi radiat atio ion n sour source ce## The The mon monoc ochr hrom omat ator ors# s# The samle samle cells cells and and sam samlin ling g of subs substan tance ces# s# =etectors#

33

F#g&"e% '.6 ,a The IR "a#at#on $o&"ce

 The various oular sources of R radiations are! i

ncandescent la lam n the near infrared instruments an ordinary incandescent lam is

generally used! "hich fails in the far infrared# ii Ne Nerrnst nst glo" glo"er er t consist of a hollo" rod "hich is about Cmm in diameter and -mm in length! "hich is non conducting at room temerature and must be heated by eternal means to bring it to a conducting conducting state# The main disadvantage disadvantage of  Nernst glo"er is that it emit R radiation over "ide "avelength range! the intensity of radiation constant over long eriod of time# iii +lo"er +lo"er source source t is a rod of sintered silicon carbide "hich is about 5-mm in length length and ?mm in diameter diameter##

Pnli% Pnli%e e the Nernst Nernst glo"er glo"er it is self 

starting starting and more satisfactory satisfactory## The main disadvantage disadvantage is that it is a less intense source than the Nernst glo"er#

34

(iv) :ercury arc t is used in far infrared instrument# ,* Monoch"o!ato"

 The radiation source emits radiation of various fre0uencies as the samling electron electronss absorbs at certain certain fre0uency fre0uency## t is necess necessary ary to sel select ect desired desired fre0 fre0ue uenc ncy y from from the the radi radiat atio ion n so sour urce ce##

This This se sele lect ctio ion n is advi advise sed d by

monochromators! "hich are mainly of t"o tyes! rism monochromator and grating monochromator# ,c Sa!/le cell$ cell$ an $a!/l#ng o) $&*$tance$

*amle can be solid! li0uid or gas# ut it should should be contained in a cell transaren transarentt to R radiation# *amle *amle cells are are usually made made of al%ali metal metal halides such as sodium chloride! otassium bromide etc# Sa!/l#ng o) $ol#$

Four techni0ues are generally emloyed for rearing solid samles#  These are *olid run in solution f the solution of solid can be reared in a suitable solvent then the solution is run in one of the cells for li0uids# li0uids# ut this method cannot cannot be used for all solids because suitable solvent are limited in number and there is no single solvent "hich is transarent throughout the R region# (ii) *olid 3lms f the solid is amorhous in nature! the samle is deosited on the surface of <r or Na8l cell by evaoration of a solution of the solid# iv :ull techni0ue techni0ue n this techni0ue! the 3nely ground solid samle is mied "ith nuJol (mineral oil) to ma%e a thic% aste "hich is then made to sread bet"een R transmitting "indo"s# Qhen R sectrum of a solid samle samle is ta%en ta%en in nuJol mull! absortion bands of the samle that haen to coincide "ith the absortion band of the nuJol mull "ill be hidden! but others "ill be clearly

35

seen in the R sectrum# This method is good for 0ualitative analysis analysis but not for 0uantitative analysis# v ress ressed ed ell ellet et techni techni0ue 0ue n this techni0ue a small amount of 3nely ground solid samle is intimately mied "ith about 1-- times its "eight of o"dered otassium bromide# The 3nely ground ground miture is is then assed under very high ressure in a ress to form a small ellet (about 1Cmm thic% and 1cm in diameter)#  The resulting ellet ellet is transarent to R radiation and is run as such# A4antage$

1 <r ell ellets ets can can be stor stored ed for for long eri eriod od of time# time# C As the conce concent ntrat ratio ion n of the saml samle e can be suit suitabl ably y adJu adJust sted ed in the ellets! it can be used for 0uantitative analysis#  The reso resolut lution ion of the sect sectrum rum in the <r <r is suerior suerior to that that obtaine obtained d "ith mulls# D#$a4antage$

1 The The high high res ressu sure re invol involve ved d duri during ng the the form format atio ion n of ell ellet etss may may brin bring g about olymorhi olymorhicc changes changes in crystallin crystallinity ity in the samles! samles! "hich may cause comlication in R sectrum# C This This method method is not succes successfu sfull for some oly olymer merss "hich "hich are dicul dicultt to grind "ith <r# From the above discussion "e %no"s that one may emloy the NuJol method for running crystalline comounds in the solid and may reserve the <r ellet method for remaining solid samles#  Detecto"$

 T"o  T"o main tyes are in common use! one sensing the heating e/ect of  radiation! the other deending u on hotoconductivity hotoconductivity## n the near infrared regi region on hot hotoc ocon ondu duct ctiv ivit ity y ce cell ll is gene genera rall lly y used used that that is the the radi radiat atio ion n is allo"ed to fall on hoto conducting material and conductivity of material meas me asur ured ed co cont ntin inuo uous usly ly by a brid bridge ge net" net"or or%# %#

Psual Psual R dete detect ctor orss are are

thermocoule! thermisters! golay cell! hotoconductivity cell! bolo meters etc#

36

'.3. Re)e"ence$ 1# Z * lac%more! in oli! state "hysics! *econd 7dition! 8ambridge Pniversity ress! 8ambridge (1945)# C# Z  *rivasthava! in Ele#ents of oli! tate physics rentice$all rentice$all ndia! Ne" =elhi (C--1)# # 8#4)# 6# *uryanarayana 8#! ull#:at#*ci# 1> (199?) (0)# ># A 8ervellnio! 8 +iannini! A +uagliardi and : Ladisa* "hy+,e+B+>C (C--5) 0(./1# (7lectronic version)#

4# R Zamuto"s%i!Z#R#F Zamuto"s%i!Z#R#Ferraro! erraro! and =#8 Lans%i! *ectroscoy!>(199C) *ectroscoy!>(199C) 11E #R! Altemose! Z#8hem#7duc! 6 6 (1946) (1946) 216! AC6C#

9# *%oog! $oller and Nieman! in "rinciples of $nstr%#ental 2nalysis ! Fifth edition#

37

a n! pectroscopy* pectroscopy* II (C-->)194C--# 1-# +#Aruldhas! Molec%lar tr%ct%re an!

#

CHAPTER-0 S@NTHESIS AND CHARACTERI
38

0.1. Int"o&ct#on 8hemistry has layed a maJor role in develoing the materials "ith ne" and technologically imortant roerties# The advantage of chemical synthesis is its versatility in designing and synthesi,ing ne" materials that can be re3ned re3ned into 3nal roducts# roducts# The rimary rimary advantage advantage is that chemical chemical methods o/ers miing at molecular level# $o"ever the bene3ts of emloying sim simle le and and co cost st e/ e/ec ecti tive ve chem chemic ical al roc roces essi sing ng me meth thod odss are are "ide "idely ly recogni,ed and a areciated

1-3

#The #The ro roe erti rties and and al alic icat atio ion n of 

nanoa nanoarti rticle cless are largel largely y deend deendent ent on their their si,e! si,e! shae shae and tet teture uress5# 8ons 8o nsid ider erab able le atte attent ntio ion n has has been been dra" dra"n n to"a to"arrds the the si,e si,e and and sha shae e contr controll olled ed synthe synthesis sis of nanost nanostruc ructur tured ed materi materials als

# =eending uon the

1-0

seci3c re0uirements such as material to be synthesi,ed! the grain si,e and maimum ermissible si,e distribution! urity of samle re0uired! 0uality of  samle samle gener generate ated d etc#! etc#! di/er di/erent ent me metho thods ds are em emlo loye yed d for synthe synthesi, si,ing ing nanohase materials# n the resent study! nanocrystalline cerium molybdate and cerium cerium molybdoiod molybdoiodate ate "ere "ere synthesi,e synthesi,ed d through through controlle controlled d chemical chemical reciitation method#

0.'. 0.'. Sa!/ Sa!/le le /"e/ /"e/a" a"at at#o #on n an an E?/e E?/e"# "#!e !ent ntal al P"oce&"e Nanoart Nanoarticl icles es of 8erium 8erium :olybd :olybdoio oiodate date "ere "ere rea reare red d by contr controll olled ed co reciitation method using analytical grade chemicals# *odium :olybdate! ottasi o ttasium um odate odate and Ammonium Ammonium ceric sulhate sulhate "ere "ere used as the starting materials# 7=TA "as used as the stabili,er# A0ueous solutions of *odium

39

:olybdate (-#1:! 5- ml) Ammonium ceric sulhate (-#1:! 5-ml) ottasium iodate (-#1:! 5-ml) 5-ml) and 7=TA(-#-1C5:! 7=TA(-#-1C5:! 55- ml) "ere slo"ly mied mied dro "ise "ise into into a conical conical Kas% Kas% and it it is stirr stirred ed "ell "ell using using a magne magnetic tic stir stirre rerr # This rocess is to be done in one hour# The stabili,er 7=TA "as used to revent gro"th and agglomeration of the articles# n this rocess the article si,e is is gove goverrned ned by the the eer erim imen enta tall ara arame mete ters rs li% li%e co conc ncen entr trat atio ion n of the the reactants! rate of miing! $! Hiscosity of the solutions etc6# t is imortant to note that the stabili,ers used for controlling the reciitation reaction should be easily and comletely removable from the samle so as to avoid any ossible contamination of the samles#The metal molybdoiodate reciitate formed "as "ashed several times in distilled "ater to free it from ions and othe otherr imu imuri riti tie es# The "et re recii ciita tate te obta obtaiined ned "as dri dried at roo oom m temerature and thoroughly ground using an agate motor to obtain the 8erium 8erium :olybdoiodate :olybdoiodate recursor recursor in the form of a 3ne o"der# o"der# The 8erium :olybdoiod :olybdoiodte te recursor recursor material material "as treated treated "ith 1N $8l#The $8l#The acid treated treated 8erium 8erium :olybd :olybdoio oiodat date e recur recursor sor "as anneal annealed ed at 5-5--o8

for for C hour hourss to to

reare nanoarticles of 8erium :olybdoiodate# Nanoarticles of 8erium :olybdohoshate "ere reared by controlled co reciitation method using analytical grade chemicals# *odium :olybdate! =isodium hydrogen otho hoshate and Ammonium ceric sulhate "ere used as the starting materials# 7=TA "as used as the stabili,er# A0ueous soluti sol utions ons of *odium *odium :olybd :olybdate ate (-#1: (-#1:!! 5- ml) ml) Ammon Ammonium ium ceric ceric sulhat sulhate e (-#1 (-#1:! :! 5-ml 5-ml)) ! =iso =isodi dium um hydr hydrog ogen en otho othoh hos osh hat ate e (-#1 (-#1:! :! 5-ml 5-ml)) and and 7=TA(-#-1C5: 7=TA(-#-1C5:!! 5- ml) "ere slo"ly mied mied dro dro "ise "ise into a conical conical Kas% and it is stirred "ell using a magnetic stirrer # This rocess is to be done in one hour#The hour#The 8erium :olybdohoshate recursor recursor material "as treated treated "ith 1N $8l#The $8l#The acid acid treat treated ed 8erium 8erium :olybd :olybdoh ohos oshate hate recu recurso rsorr "as anneal annealed ed 5--o8 for C hours to reare reare nanoarticles of 8erium :olybdohoshate# :olybdohoshate#  The samle code "as assigned to the four samles along "ith annealing temerature and duration of annealing is sho"n in Ta*le.0.1 #

40

 

Ta*le.0.1

0.0.

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=uration of 

code

 Temerature  Temerature

annealing

CMI

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CMP

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Reco"#ng o) 9-"ay D#:"act#on /atte"n  The Wray Wray di/raction attern of the samles CMI=CMI 3=CMP  and CMP 3

"ere recorded using 9PERT-PRO o"d o"der er di/r di/rac acto tome mete terr (PAN

analytical! Netherlands) emloying C&-   radiation # Fitted curve

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41

File name 8W'ert =atageneral* N 8ollege8: 5--#rdml 8omment 8on3gurationXFlat *amle *tage! @"nerXPser1! 8reation dateX1-M9MC--4 C19 : +oniometerXQ-5-M6+oniometerXQ-5-M6- (ThetaMTheta)E :inimum ste si,e CTheta-#--1E :inimum ste si,e @mega-#--1 *amle stageXQ->1M stageXQ->1M rac%et =i/ractometer =i/ra ctometer systemXW7RT systemXW 7RTR@ R@ :easurement rogramX+eneral 1-9-! @"nerXPser1! 8reation dateX?MCMC--9 1C-19 : :eas :easur urem emen entt =at =ate e M Tim Time e 4M1> 4M1>MC MC-1 -11 1 1 11 111 11 : @erator N*T Ra" =ata @rigin WR= measurement (#WR=:L) *can Ais +onio *tart o osition B BCTh#D 1-#-19? 7nd osition BCTh#D 49#94>? *te *i,e BCTh#D -#-1>*can *te Time BsD 1-#>1 *can Tye 8ontinuous *= :ode *canning *= Length BCTh#D C#1C @/set BCTh#D -#---=ivergence *lit Tye Fied =ive =iverg rgen ence ce *li *litt *i,e *i,e BD BD -#? -#?5? 5? *ec *ecim imen en Len Lengt gth h BmmD BmmD 1-#1-#-:eas asu urement Te Temerature B B8D C5#-Anode :aterial 8u <Alha1 BD 1#5?-6+enerator *ettings - mA! ?- %H =i/ractometer Tye --------11-?551 =i/r =i/rac acto tome mete terr Numb Number er +oniometer Radius BmmD C?-#-=ist# Focus=i Focus=iver verg# g# *lit *lit BmmD 1--#-1--#-ncident eam :onochromator No *inning No

42

ounts  #$ 500

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43

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4

2

0 0

20

40

60

80

100

2

F#g&"e.0. 0.9RD /atte"n o) CMP

:easurement 8onditions =ataset Name 8: 5-File name 8W'ert =atageneral* N 8ollege8: 5--#rdml 8omment 8on3gurationXFlat *amle *tage! @"nerXPser1! 8reation dateX1-M9MC--4 C19 : +oniometerXQ-5-M6+oniometerXQ-5-M6- (ThetaMTheta)E :inimum ste si,e CTheta-#--1E :inimum ste si,e @mega-#--1 *amle stageXQ->1M stageXQ->1M rac%et =i/ractometer =i/ra ctometer systemXW7RT systemXW 7RTR@ R@ :easurement rogramX+eneral 1-9-! @"nerXPser1! 8reation dateX?MCMC--9 1C-19 : :eas :easur urem emen entt =at =ate e M Tim Time e 4M1> 4M1>MC MC-1 -11 1 C C6 6?6 ?6 : @erator N*T Ra" =ata @rigin WR= measurement (#WR=:L) *can Ais +onio *tart o osition B BCTh#D 1-#-19? 7nd osition BCTh#D 49#94>? *te *i,e BCTh#D -#-1>*can *te Time BsD 1-#>1 *can Tye 8ontinuous *= :ode *canning

44

*= Length BCTh#D C#1C @/set BCTh#D -#---=ivergence *lit Tye Fied =ive =iverg rgen ence ce *li *litt *i,e *i,e BD BD -#? -#?5? 5? *ec *ecim imen en Len Lengt gth h BmmD BmmD 1-#1-#-:eas asu urement Te Temerature B B8D C5#-Anode :aterial 8u <Alha1 BD 1#5?-6+enerator *ettings - mA! ?- %H =i/ractometer Tye --------11-?551 =i/r =i/rac acto tome mete terr Numb Number er +oniometer Radius BmmD C?-#-=ist# Focus=i Focus=iver verg# g# *lit *lit BmmD 1--#-1--#-ncident eam :onochromator No *inning No

ounts  #P 500

60

40

20

0

20

30

40

50

60

70

80

Position [°2Theta] (o!!er (u""

F#g&"e.0. .9RD /atte"n o) CMP 3

ea% List os# BCTh#D C5#1>C9 C4#495C 1#-1? ?1#9?56 ?4#146-

$eight BctsD 9#1C #?9 >#4? 1>#4? 1>#--

FQ$: BCTh#D -#9>9C 1#1?C? -#?496 -#65C4 -#65C4

dsacing BD #5?9#-4>?? C#455> C#15C1 1#4469>

Rel# nt# BOD C?#144#51 1--#-?>#1? ??#9

45

0.. DETERMINA DETER MINATION TION OF AERAE CR@ST CR@STALLITE ALLITE SI
Wray Wray di/raction line broadening! "ithout

ta%ing ta%ing instrumental instrumental correcti correction on to line broadenin broadening# g# *cherrer *cherrer e0uation e0uation is the simlest method of determining the average si,e of nanocrystalline samles from Wray di/raction line broadening# *cherrer e0uation4 is! t  8G ,h8l !ea$&"eco$ Jh8l

$ere! t is the average crystallite si,e normal to the reKecting lanes! % is the shae factor "hich lies bet"een -#95 and 1#15 deending on the shae of the grains (%X1 for sherical crystallites)! ^is the "avelength of Wray used and (\h%l)  measured is the measured FQ$: of the di/raction line in radians and h%l is the ragg angle corresonding to the di/raction line arising from the lanes designated by :iller indices (h%l)# K

Ta*le %0.'# Average crystalli crystallite te si,e si,e of CMI 3 determined using *cherrer

e0uation C] C4#C>C 56#?5 >?#>>4

]

1?#1146 C4#1>1>5 >#49

\h%l -#?-4 -#9>9C -#C-?

8rystallite *i,e(nm) C#-->>7 -4 9#C--67 -9 ?#9-1C7 -4

Average 8rystallite *i,e(nm)

C6#-9>?

46

Ta*le %0.0# Average crystallite si,e of CMP 3 determined using *cherrer

e0uation C] C5#1>C9 C4#495C 1#-1? ?1#9?56 ?4#146

]

1C#546?5 1?#??>6 15#65-> C-#9>C4 C?#-9

\h%l -#9>9C 1#1?C? -#?496 -#65C4 -#65C4

8rystallite *i,e(nm) 4#1C67 -9 >#14-9?7 -9 1#645-?7 -4 1#-C>7 -4 1#-57 -4

Average 8rystallite *i,e(nm)

11#>?1?

RESULTS RESULTS AND AN D DISCUSSION DISC USSION

 The WR= attern of the samles of both CMI and CMP sho"s no "ell de3ned ea%s! reveals the articles synthesi,ed "as amorhous in nature#  The annealed samles of both materials sho" some "ellde3ned ea%s in the the WR= WR= att atter ern! n! co con3r n3rms ms the the crys crystal talli line ne natur nature e of the the sa sam mle les# s#

The The

average crystallite si,es of CMI 3 and CMP 3 "ere calculated from W ray ray di/ra di/ract ctio ion n line line broa broade deni ning ng usin using g *che *cherr rrer er e0ua e0uati tion on## The The aver average age crysta crystalli llite te si,e si,e obtain obtained ed for 8erium 8erium molybd molybdoio oiodat date e heated heated at 3C for' hours(CMI 3) is is '5.K6 n!  and that for 8erium molybdohoshate heated at 3C for ' hours(CMP 3) is 11.61 n!.

47

0.3 0.3. SEM SEM #! #!age$ ge$ # #th ED EDA9  The surface morhology of the o"der samles "as characteri,ed characteri,ed by scanning electron microscoe (*7:) Z7@LM7@ Z*:69-# The energy disersive analysis of W rays (7=AW) "as carried out on the samles to ascertain the chemical comosition#

0.3.1. SEM #!age o) CMI

F#g&"e.0.3

0.3.'.

SEM #! #!age o) o) CM CMP

48

F#g&"e.0.5

0.3.0. EDA9 o) CMI

F#g&"e.0.6

0.3.0.

EDA9 o) o) CMP

49

F#g&"e.0. RESULTS RESULTS AND AN D DISCUSSION DISC USSION

 The *7: image of the CMI and CMP are reroduced in F#g&"e% 0.3  The mor morho holo logy gy obta obtain ined ed from from the the *7: *7: imag image e indi indica cate tess that that 0.5# The nanoarticles are agglomerated to sherical shae# The 7=AW sectrum of  the the samle samle CMI  and and CMP are are sho"n sho"n in F#g&"e% 0.6  0.# From the 3gure! it is clear that the reared samle contain no other imurities#  The SEM "ith EDA9 sectrum of CMI contains elements such as Ce= Mo= I an O but CMP contains elements such as Ce= Mo= O! and P#

0.5.RECORDIN OF FTIR SPECTRUM OF THE SAMPLES  The infrared sectroscoic (R) studies of the samles

CMI=CMI

3= 3 =CM CMP P and CMP 3  "ere maderecorded using er%in 7lmer FTR

*ectro hoto :eter in the "avenumber range 3 and c!-1 by <r disc method#

50

 100  90

 80

 70      8      0  )      6      4      4      1

 60

     9      2  )      7      0      4      1      7      6  )      6      9      9

 50      1      7  )      2      1      6      1

     T      +

 40

 30

     5      7  )      5      3      3      1

     5      0  )      1      8      1      1

     5      3  )      9      7      0      1

 20

 10

     1      6  )      9      0      8

     4      0  )      8      9      3      3

0

     5      0     1  )      2  )     2      3     8      4     4      5

*10 4000

3500

3000

2500

2000

1500

1000

 500

,avenu'-ers (c'*1"

F#g&"e.0.K.FTIR SPECTRUM OF CMI

 100

 90

 80

 70

     9      1  )      3      2      6      1

 60

 50      T      +

 40      6      8  )      2      0      4      3

 30

     8      3  )      7      3      1      1

     7      1  )      6      0      6

 20

 10

     0      9  )      8      3      8

 0 *10 4000

3500

3000

2500

2000 ,avenu'-ers ,avenu'-ers (c'*1"

1500

1000

 500

51

F#g&"e.0.1.FTIR SPECTRUM OF CMI 3

 1 00  90

      6       7  )       1       0       4       1

 80       3       2  )       2       6       3       2

 70

 60

 50

      8       2  )       2       5       4       1

      7       5  )       5       2       6       1

      6       7  )       5       2       9       2

      T       +

 40

      2       2  )       7       2       4       3

 30

 20

      3       6  )       9       9       7

 )

      5       4  )       0       4       5

F#g&"e.0.11.FTIR SPECTRUM OF CMP       4       2  )       1       5       0       1

 10

 100  0

      1       1  )       5       1       6

 90 *10 4000

3500

3000

2500

 80

2000

1500

1000

,avenu'-ers (c'*1"

 70      7      1  )      6      2      6      1

 60

 50      T      +

 40      1      6  )      7      0      4      3

 30

     2      4  )      8      4      8

 20

     5      9  )      7      3      5

     9      4  )      9      4      9

 10      6      2  )      7      4      0      1

 0

     0      8  )      4      1      6

     3      8  )      1      6      5

*10 4000

3500

3000

2500

2000

1500

1000

 500

,avenu'-ers (c'*1"

F#g&"e.0.1'.FTIR SPECTRUM OF CMP 3

 5 0 0

52

RESULTS RESULTS AND DISCUSSION

 The FTIR $/ect"&! of samles CMI and CMI 3 "as reroduced in Figures#0.  0.K.  The broad absortion bands in the region 00Kc!-1 !151' c!-1! 0'c!-1 G 15'0 c!-1 is due to the valance vibration of occludedM entraed "ater 1#  The bands around K c!-1!30 c!-1=' c!-1 ! and 55 c!-1  corresonds to the intrinsic stretching 1 c!1!0 c!-1  an vibration of the metal "ith oygen atoms 11#The additional "ea% bands and shou should lder erss

inth inthe e sec sectr trum um due due to the the micr micros ostr truc uctu tura rall form format atio ion n of the the

samles#  The FTIR $/ect"&! of samles CMP and CMP 3 "as reroduced in Figures#0.11  0.1'.  The broad absortion bands in the region 0'6c!-1 !15'3c!-1! 06c!-1 G 15'5 c!-1 is due to the valance vibration of occludedM entraed "ater 1#

 The bands around 13 c!-1!6KKc!-1=3 c!-1 ! c!-1!51c!-1 ! 351c!  and 306 c!-1 corresonds to the intrinsic stretching stretching vibration of the metal

1

"ith "ith oyge ygen n atoms atoms11#The #The addit additio ional nal "ea% "ea% bands bands and and shou should lder erss

inth inthe e

sectrum due to the microstructural formation of the samles#

0.6.Concl&$#on Nanoarticles of 8erium molybdoiodate and 8erium molybdohoshate "ere reared by the chemical coreciitation method using 7=TA as the organic temlating temlating agent# The as reared reared samles samles "as annealed annealed at 3C for to hour hours# s# The The 9RD /atte"n of the sam samle less of both both CMI and CMP sho" sho"ss no "ell "elld de3 e3ne ned d ea% ea%s! s! revea eveals ls the the art artic icle less synt synthe hesi si,e ,ed d "as "as amorhous amorhous in nature# nature# The annealed annealed samles samles of both both material materialss sho" some "ellde3ned ea%s in the WR= attern! con3rms the crystalline nature of the

53

samle samles# s#

3 and CMP 3  "ere The average average crysta crystalli llite te si,e si,ess of CMI 3

calculated from Wray di/raction line broadening using *cherrer e0uation#  The average crystallite si,e of CMI 3 is '5.K6 n! and that for CMP 3 is 11.61 11.61 n!.  Th SEM #th #th EDA9 EDA9 se The SEM sectru ctrum m of CMI contains

elem elemen ents ts such such as Ce= Mo= O  an and I but ! *7: "ith 7=AW sectrum 8: contains elements such as Ce= Mo= P and O# From the *7: *7: image image of both both samles reveals that the articles are agglomerated into sherical shaes and the as reared samles of 8:and 8: contains no other imurities#  The FTIR S/ect"&! of CMI=CMI 3=CMP  CMP 3  "ere recored and the bands "ere identi3ed#

0.. Re)e"ence 1#

$ +leiter! "rog+Mater+ci+ 00 (1949)11(#

C#

$ +leiter* 2!+Mater  (199C)  (199C)/)/+

#

8 *uryanarayana! B%ll+Mater+16 (199?)(0)#

?#

: :o3tt! $ Hali and A 7insenberg! 7insenbe rg! Che+Mater+1 (1994) 01#

5#

L rus! 3+"hys+Che+oli!s#3K (1994) /.9#

6#

ing ;hang! u Fang! *han Qang! *huya Lin! 3+Cis+Elseier ! '6'(C--?)!

(1-(1. #

>#

#ramani%! B%ll+Mater+ci #1 (1995)49#

4# $arol 
54

1-#

;a"arch : F : and 7 
,C--C) )#

11#

*#$afner! ;eit#