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Morphology Control Self Assembly and Site Selective Deposition of Nanocrystals

Nanocrystalsacicular crystals TiO2 films consistedfilms showed high c-axis orientation Acicular BaTiO particles were prepared usingorphology control of BaC2O405H2O They were prepared in aqueous solutions andannealed with co-precipitated amorphous phase to form acicular BaTiO particlen this chapter, we will mainly fen"liquid phase morphology control of metal oxidesnanocrystals of Znot, TiO and BaTiO particles, and"liquid phase site-selectivef metal oxide nanocrystals" of TiO2 and Eu: YzO352 Liquid Phase Morphology Control of Metal Oxide NanocrystalsStand-alone Zno films were fabricated using aqueous solutions The filmsof sheet shaped nanocrystals They had gradient structure, higlntation, higlof solutions withobstrate Air-liquid interface was used as a template in this process60 C Ethylenediamine(H2NCH CH NH2)(15 mM)was added to the solution to induce theZno1 Thekept at60°Cter bath6 h withstirring The solution was then left42 h in the bath Polyethylene terephthalat(PET) film, glass(S-1225, Matsunami Glass Ind, Ltd )andafer(p-type Si [100], NKPlatz Co, Ltd )were used as substrates

The solution color was changed from transparent tfter the addition ofThe solution became transparent again after 6h The supersaturation degree of thee rowthethy lenediamine Zno particles were formed by the homogeneous nucleationas high at the initial stage of the reaction for the first 1 h and decreased as theution changed Ethylenediamine accelerated deposition of ZnO, Zinc-ethylenediaminemplex forms in the solution as shown by eq 16Zn2++3H2NCH CHNHLn(H2NCH2CH2NHz)2+the left and the zinetheZn *at elevated temperatureOH- concentration increases by the hydrolysis of ethylenediamine as shown2H2NCHICH2NH2 2H20--H3NCH2 CH2NH32++ 2OHZnO and Zn(OH)z are thus formed in the aqueous solution as shown by eq 3n2+ +2OHfilms had sufficiently high strength to be obtained as stand-alone films Additionally, a filmhoped to past onto a desired substrate such PET film, Si wafer, glass plated thepasted ZnO film was then dried to bond it to the substrate Both sides of the film can be pastedon substrate The film physically adheredsubstrate The film maintained its adhesitrong ultrasonication The film can be handled easily from substrate to other substrate It alsontechopen

Morphology control, self-assembly and site-selective deposition of metal oxide nanocrystalsof pores-28 and-36 nmectively Additionally, the analyses susof micropores of -1 nm Crystallization and self-assembly oftilized to fabricate nanocrystal assembled TiO particles having high surfacearea and nanorelief surface structurePoe wdh nmDv @og oFig

5 (a): N2 adsorption-desorption isotherm of anatase TiO2 particles(b: BET surface areaof anatase TiO2 particles (c): Pore size distribution calculated from N2 adsorption data ofusing B]H equation (d): Nz adsorption-desorption isotherm andDFT/Monte-Carlo fittingdistributioalculated from N2 adsorption data of anatase TiO2 particles using DFT/ Monte-Carlouationntechopen

Nanocrystalsf crystallization in the solution(1 M) and distillet while the volume of the soludjustedml by thesditions The aqueouson⑤50m) with barium(393mg)d with thexalic acid solution The mixed solutioling barium acetate (0 77 mM), butyl tit(2 mM) and oxalic acid (10 mM)was kept at room temperature for several hourswith no stirring, and the solution gradually became cloudy Stirring causes the collision ofaction of large greoided in thisof the precipitateeasily controlled froreterorder to micrometer order by changing the growth period Large particles were grown byimmersion for several hours to evaluate the morphology and crystallinity in detailOxalate ions (C2O42)react with barium ions(Ba2)to form barium oxalate (BaC2005H2O) BaC204 05H2O is dissolved in weak acetate acid provided by barium acetate((CH3 COO)2Ba),hcan be deposited at pH 7 which is adjusted by adding NaoHBaC2O4 05H2O was thus successfully precipitated from the solutionAcicular particles were homogeneously nucleated and precipitated from the solution(Fig6a) They wereerage 23 um(ranging from 19 to 27 um)in width and 167 um(rangingfrom 144 to 189 um)in length, giving a high aspect ratio of 72 They had sharp edges andXRD diffraction patterns for the mixture of acicular particles and gel-like solid showedsharp diffraction peaks of crystalline BaC2O:0

5H2O withditional phase aciculararticles were crystalline BaC2O405H2O and the gel-like solid would beFortunately, BaC2O4 05H2o has a triystal structure as shown by thealculated from structure data 14(Fig 6b XRD first step) and thus anisotropic crystal growthas allowed to proceedn acicular shape Each crystal face has a diffeurface energy and surface nature such as zeta potential and surface groups Anisotrcrystal growth is induced by minimizing the total surface energy in ideal crystal growthditionally, site-selective adsorption of ions or molecules on specific crystal facesPresses crystal growth perpendicular to the faces and so induces anisotropic crystgrowth These factors wuse anisotropic crystal growth of BaC2O405H2O andow us to control morphologybricate acicular BaC2O4 05H2O particles, Thepositions of diffraction peaksnded with that of CPDSthird step)and that calculated from crystal structure data 14(Fig 6b XRD second step)were enhanced strongystal faces would be related to anisotropic crystal growth; a large crystal size in a specificntechopen

Morphology control, self-assembly and site-selective deposition of metal oxide nanocrystalsorientation increases the x-ray diffraction intensithe crystal face perpendicularto the crystal orientationEDX elemental analysis indicated the chemical ratio of the precipitate, which includedacicular particles and gel-like solid, to be about Ba/ Ti- l to 15 The chemical ratiodicated that the coprecipitated amorphous gel contained Ti ions Additional Ba ions canbe transformed into BacO by annealing and removed by HCl treatment in the next stephe ratio was thus controlled to slightly above Ba/Ti-1 by adjusting the volume ratio oficular particles and gel-like solid Consequently, acicular particles of crystalline BaC2on comparison, isotropic particles of barium titanyl oxalate (BaTio(Cecipitated at pH 2 TiOC2 O4 was formed by the following reaction in which the reactionxalic acid (H2C2O4 2H2O)with butyl titaner((CaHyO)aTi) and hydrolysisn take place simultaneously 15(C4HOi+HC2O4·2H2O→TOC2O4+4C4HOH+HOlO(C2OA)was then converted to oxalotitanic acid (H2TiO(CO4)2) by the reactionriO(CAO4)+H2C2O4·2Ho→H2ioC2O)2+2H2Oxalotitanic acid (H2TIO(C2O4)2) formed bysubjected to the following cation exchange reaction by rapidly adding an aqueous solutionof barium acetate atH2TIO(C2O4)2+ Ba(CH3COO)2- BaTiO(C2OCH3COOH (c)BaTiO(C O4)z isotropic particles were formed by reaction(c)On the other hand, neither BaC2O405H2O nor BaTiO(C2Oa)2 was precipitated at pH 3 toH 6 Gel-like solid was formed in the solution and their XRD spectra showed nodiffraction peaks The amorphous gel that precipitated at pH =3 to 6 would be theThese comparisons show that the crystal growth and morphology control of Bac05H2OonditionsThe precipitate was annealed at 750C for 5 h in air Acicular05H2O particleining amorphous gelIntoystalline BaTiO3

X-ray diffraction of the annealed precipitatecrystalline BaTiOnd an additional barium carbonate phase(BacO3) Excess precipitation of BaC2O405H2Oused the generation of barium carbonate phase(BaCOs) as expectedThe annealed precipitate was further immersed in HCl solution (1 M) to dissolve bariumcarbonate(BaCO3) Acicular particles of crystalline BaTiO3 were sucally fabricatedwith no additional phase Particles showed acicular shape with 28x10x50 um and x-radiffraction of sinhigh aspect ratio of the parti(17 8=50/28)would be provided by that of BaC2O405H2O particles The particle size ofacicular BaTiO3 can be easily controlled by the growth period and solution concentrationfor BaC2 05H2O precipitation which decides the particle size of BaC2O405H2Ontechopen

Nanocrystalsacicular particlesICH,OLTi750℃CH CHIOH)CH (-CH,OHTriclinic BaCz 0,5H20 Tetragonal BaTiOa(b)(c)10 uTriclinic BaC2O405H20Tetragonal BaTiO3BaCO05Ho ca⊥⊥Llution at pH-7

XRd diffraction measurement data(first step), Xrd pattern calculatedfrom crystaldata6(second step)and XRD pattern of JCPDS No 20-134(third stepe shown for triclinic BaC2O405H2O (c) SEM micrograph and XRD diffraction pattern ofacicular BaTiO3 particles after annealing at 750C for 5 h and HCl treatment XRDent data( first step) and XRD pattern of JCPDS No 05-0626(step) are shown for tetragonal BaTiOntechopen

Morphology control, self-assembly and site-selective deposition of metal oxide nanocrystalsBaTiO3 has a cubic crystal structure at high temperature above phase transition and has arystal structure at room temperature The cubisotropic and the tetragonal crystal structure results from stretching alattice alongf its lattice vectors For both of the crystal structures it is difficult to control anisotroptaluld successfully controthe morphology and fabricate acicular particles This was achieved by controlling themorphology of triclinic BaC05HO to acicular shape and the phase transition trecipitated amorpnovelfabricate acicular BaTiO particles was developedphology control of crystalline BaC2O405H2O to acicular shape was realized inqueous solution The particles were then transformed into crystalline BaTiO bytroducing Ti ions from the coprecipitated amorphous gel phase during the annealingeveral key technologies Morphology control in this system has high scientific value forcrystal growth,cicular particles of crystalline BaTiO may have a great imptra-thin mlcc in future3 Liquid Phase Site-selective Deposition of Metal Oxide NanocrystalsNucleation and crystal growth of TiO were accelerated on super hydrophilic surfaces Itallowed us to formatterns of TiO2 nanocrystalsparent conductive substrate of F doped SnO2(FTO, SnO2: F, Asahi Glass Co, Ltd6×50×11mm) was blown by air to rposed to ultraviopressure mercury lamp PL16-110, air flow, 100 V, 200 W, SEN Lights Co ) formin through a photomask (Test-chart-No 1-N tubstrate, 1524 mm thicknessToppan Printing Co,, Ltd )(Fig

7) The initial SnO2: F substrateed a water contactngle of 96 The UV-irradiated surface was, however, wetted completely (contact angle O°) The contact angle decreased with irradiation time96°,70°54°,35°,14,5°and0°for0nin and 5 min, respectively) This suggests thated molecules on the SnOz: F substrate was removed completely by Uirradiation The surface of the SnO2: F substrate would be covered by hydrophilicfter irradiation Consequently, the SnO2: F substramodified to have apatterned surface with hydrophobic regions and super-hydrophilic regionswere separately dissolved in deionized water (100 mL) at 50C Boricddedexafluorotitanate0 15 M and 005 M,pectively The SnO2: F substrate having a patterned surface with hydrophobicered by a silicon rubbeshR-SG-s5mmt ra grade, Shin-etsu Finetech Co, Ltd to suppress deposition of Tio at theinitial stage The substrate was immersed perpendicularly in the middle of the solutionntechopen

NanocrystalsFig 7) The solution was kept at 50C with no stirring The silicon rubber sponge sheeted from the SnO F substrate after 25 h, thenat 50 C The substrate wered by the sheet insteaemersion of substrate at 25h tagitation of the solution0 min after thehexafluorotitanate solution and boric acid solution The particles were homogeneousnucleated in the solution and made the solution white They then gradually precipitatednd fell to the bottom ofessel, so the solution became transparent over a period ofurs Ti ions were consumed for crystallization of TiO2 particles, thus decreasing thelow to realize slow heterogeneous nucleation without homogenforms TiOz particles The silicon rubber sponge sheetremoved from the SnOzsubstrate after 25 h, then the substrate was kept for a further 2 h at 50C Consequently, theatterned surface on the SnO2: F substrate was exposed to the transparent solutioncluding Ti ions at aconcentration for 2 h Heterogeneous nucleation and slowystallization of TiO2sed only on the substrateDeposition of anatase TiOz proceeds by the following mechanisms:TiF62+ 2H,O=TiO2+4H++6BO3+ 4F

+ 6HBF4+ 3HOEquation(a) is described in detail by the following two equations-TiF-(OH -+nF-6-D0HTi(OH2-+6FOH若—→TiO2+2H2O+2OHFluorinated titanium complex ions gradually change into titanium hydroxide complex ionssolutionEq (c) Thea)and(c)to the left,the produced f can benged by H3 BO3(BO)asshown in Eq (b) to displace Eqs (a)and (c)to the right Anatase TiO formed from titaniumhydroxide complex ions(Ti(OH)2)in Eq (d)Liquid phase patterning was not realized in the initial solution but realized in the solutionaluated as function of time to clarify thisafter thehexafluorotitanatelution and boric acid solution, became clouded after 05 h and showed maximumwhiteness after 1 h Anatase TiO2 particles nucleated homogeneously in the solution angrew to form large particles, which gradually precipitated and made the bottom of theessel white The solution became slightly white after 5 h and transparent after 25 h Thesolutions changed to transparent by the filtrations Precipitated particles from the residuallution and particles from the supernatant solution trapped by filters were determined byXRD evaluatigle phase of anatase TiO2ntechopen

Morphology control, self-assembly and site-selective deposition of metal oxide nanocrystalsPrecipitated particles from the residual solution increased as 0 mg, 1651 mg, 2309 mg andatO h,2 h, 5 h and 25 htation increased rapidly at theinitial stage and moderately after 2 h, reflecting the decrease of crystal growth ratehe weight of particles >25 um in diameter was estimated to be 28 mg, 497 mg, 95 mg, 0mg and 0 mg at 05 h, 1 h, 2 h, 5 h and 25 h, respectively Particlestage and precipitated, making the bottom of the vessel white This is consistent with thechange of the solution3 precipitate from the filtrate collected by all of the filtersmg, 1345 mg and 1341 mg at 05 h, 1 h, 2h, 5 h andectively This indicated that thcontained a highntration oftial stage, which then decreasedfunctif tind decreasby the crystallization and precipitation of anatase TiO This result is consistent with thtion of precipitated particles, weight variation of suspended partiution color change shown in the photographLiquid phase patterning was not realized in the initial clouded solution but realized in theafter 25 h Evaluation of solutin

TiO2 particles formed at the initial stage around 1 h andprecipitated gradually lons were consumed for crystallization of TiOz and decreased as aunction of time, Heterogeneous nucleation predominantly progressed after 5 hConsequently, TiOz was formed on super hydrophilic regions selectively to realize liquidFrO substrate was immersed in the solution for 25 h to form a thick film and ultrasonicatedas constructed of two layUnderwith 200thickness was a polycrystalline film of anatase TiO Upper layer with 300 nm thicknessas an assembly of acicular TiO crystals which grew perpendicular to the substrate Thefilm was shown by electron diffraction pattern to be a single phase ofse Tio, electdiff

raction from the 004 plane was stronger than that of the 101, 200, 211 planes, etc to showanisotropic crAdditionally, 004 diffractistrongperpendicular to the substrate, showing that the c-axis orientation of acicular crystals wasperpendicular to the substrate The FTO layer was shown to be a single phase of SnOz withgh crystallinity Acicular TiOz crystals hadshape, being-300 nm in length and 10100 nm in diameter A lattice image of anatase TiO2 was observed from the crystalsThe film deposited on the substrevaluated by XRD analysis Strong X-ray diffractionrere observed for films deposited on FTO substrates and assigned to SnO of FTo films The4 diffraction peak of anatase TiOz was not observed clearly for TiO film on FTO substratesbecause both of the weak 004 diffraction peak of TiO and the strong diffraction peak of FTowere observed at the same angle Glass substrates with no FTO coating627 for the films deposited on glass substrates They were assigned to 101, 004, 200, 105, 211nd 204 diffraction peaks of anatase TiO(ICSD No 9852)(Fig 7) A broad diffraction peakfrom the glass substrate was also observed at about 28=25ntechopen

Morphology control, self-assembly and site-selective deposition of metal oxide nanocrystalsn be attached strongly to substrate by annealing or addition of chemical regents such as silanecoupling agent to form cherto a thickness of about 5 um after 48 h, i e, 60 C for 6 h, and was left toair-liquid interface(Fig 1-a1), whereas the liquid side of the film haugh surface(Figb1) The films consisted of zno nano- sheetsclearly observed from the liquidFig 1-b2)and the fracture edge-on profile of the film( Fig 1-c1, 1-c2) The nano-sheets hadhickness of 5-10 nm and1-5 um in size They mainly grew forward to the bottom ofliquid interface, such that the sheets stooderpendicular to the air-liquid interface Thus, the liquid side of the film hadsurrounded by nano-sheet and had a high specificce area the air sidethe film, on the other hand, had a flat surface that followed the flat shape of the air-liquidinterface The air-liquid interface was thus effectively utilized to form the flat surface of thefilm This flatnesscontribute to the strong adhesion strength to substrates forf the film The air-side surfaceared for 48 h had holes of 100-500 nm indiameter(Fig 1-a2), and were hexagonal, rounded hexagonal or round in shape The airside surface prepared for 6 h, in contrast, had no holes on the surface The air-side surfacece and Zno crystalshexagons were then etched to form holes on the surface by decrease in pH The growth

ohexagonal shape because of the hexagonal crystal structure Well-crystallized zndde zno nano sheets woulelarge Zno film bmechanism would contribute to the development of crystallography in thesome formationZn ion supply from the aqueous solution Further investigation of thetion systend the crn of novel zno fine structuresThe film showed adiffraction peak of hexagonal Zno at 20-34 andweak 0004 diffraction peak at 28=7216 with no other diffractions of Zno( Fig 2)(0002) planesand(0004)planes were perpendicular to the c-axis, and the diffraction peak only from (0002)nd(0004)planes indicates high c-axis orientation of ZnO film The inset figure shows that theystal structure of hexagonal ZnO stands on a substrate to make the c-axis perpendicular to theubstrate Crystallite size parallel to(0002) planes was estimated from the half-maximum fullwidth of the 0002 peak to 43This is similar to the threshold limit valueXRDquipment and thus the crystallite size parallel to(0002) planes is estimated to be greater than orequal to 43 nm Diffraction peaks from a silicon substrate were observed at 20=689 and 283243°, Weak diffractions at20=125°,240°276°,305°324°and576° were assigned to co-ecipitated zinc carbonate hydroxide(Zn(CO)(OH)6 JCPDS No 19-1458)Stand-alone zno film was further evaluated by tem and electron diffraction theushed to sheets and dispersed in an acetone The sheets at the air-liquid interface werea cupper gridnanoparticles(Fig 2b) Lattice image was clearly observed to show high crystallinity of theparticles The film was shown to be single phase of Zno by electron diffraction patternThese observations were consistent with xRD and seM evaluationntechopen

Nanocrystalsa210mbl圖b2-IAm100mmAir-side surface of ZnO film (a2)Magnified area of (al)

(bl)Liquid-side surface of Znofilm(b2) Magnifiedof (b2)(cl)Fracture cross section of ZnO film frorside(c2Magnifiedntechopen

Morphology control, self-assembly and site-selective deposition of metal oxide nanocrystalsC-axIsJCPDS No 19-1458000240200 deg (CuKo40 nm10 nmD diffraction pattern of high c-axis oriented stand-alone Zno self-assembled film

microgaZno nano-sheets,(b)Magnifiesf (a)(Insertion) Electronon pattern of Znontechopen

NanocrystalsThe film pasted on a silicon wafennealed at 500%C for 1 h in air to evaluate thtails of the films ZnO film maintained its structure during theling(Fig 3) The airwed a smooth surface(Fig 3-al)and the liquid side showed a reliefstructure having a high specific surface area(Fig 3-bl, 3-b2)

The air side showed the filminsisted of dense packing of small Zno nanosheets and the size of sheets increasedarface(Fig 3-a2) ZnO sheets would grow from thele, i e, the sheets would nucleate at the liquid-air interface and grow down towardm of the solution by the supply of Zn ions from the solution, Annealed filmduring the annealing without any phase transition Highas also maintained during the annealing, showing a very strong 0002 diffraction peak10m1=bIb2SEM micrographs of high c-axis oriented standno self-assembled filmedge-on profile of ZnO film from air side (a2)Cross-section profile of Zno film from air side(b1)Fracture edge-on profile of ZnO filmfrom liquidb2)Cross-section profile of Zno film frontechopen

Morphology control, self-assembly and site-selective deposition of metal oxide nanocrystalsThe solution was further kept at 25 C for 1 month to evaluate the details of theechanism The film prepared at the air-liquid interface for 1 month was not hexZnO The film showed strong X-ray diffractions of zinc carbonate hydroxide single phaseZno would be dissolved by decrease in pH Zno would be crystallized at the initialreaction stage for the first 48 h Zno was then gradually etched and dissolved by nitric acind zinc carbonate hydroxide was crystallized using Zn ions which were supplied by theZno filnak The air side of the film had a flat surface, whereas the liquid side had a rough surfaceounded by Zno nano sheets The rough surface of theliquid sidedytized solar cells The film was also pasteda desired substrate such as per filmsbstrate or glass plates The surface of loheat-resistant flexiblted crystalline Znofilm without heat treatment This low-cost, low-temperature techniqding sensors, solar cells, electrical devices and opticalgtheproperties of highoriented crystalline Zno22 Morphology Control of Nanocrystal Assembled TiO2 ParticlesTiO2 particles were prepared in aqueous solutions at ordinary temperature The particlehigh surfacm?/g and unique morphology They are candidate material for dye-sensitized solar cellsAmmonium hexafluorotitanate (12372 g)and boric acid (11 1852 g) were dnized water (600 mL) at 50C2, Concentratie0

15005Mrespectively The solution was kept at 50 C for 30 min using a water bath with no stirringThe solution was centrifuged at 4000 rpm for 10 min(Model 8920, Kubota Corpcles were dried at 60%C for 12 h after removal ofThe solution became clouded about 10 min after mixing ammonium hexafluorotitanatesolution and boric acid solution The particles were homogeneously nucleated in thesolution, turning the solution whiteX-ray diffraction analysis indicated that the particles were single phase of anatase TiOz The251379,476542624,693,75,1,825and940°,Theassigned to the101,004,200,105+211,204,116+220,215303+224diffraction peaks of anatase TiO20CPSD No 21-1272, ICSD No 9852)(Fig 4)tensity Additionally, the integral intensity of the 004 diffraction was 0 18 times the 101diffractiof the paiPartioriented on the glass holder for XRDTherefore, TiO crystals would beanisotropic shape in which the crystaelongated along the c-axis The crystals wouldntechopen

Nanocrystalsf stacks of c planes such as (001) planesn intensity from the( 004)planes would be enhanced compared to thatfrom the(101)Ooo8311272102030456708s010020/0 deg /CuKaC100nmFig 4 XRD diffraction pattern of anatase TiO particles (a): TEMh of anataseTiOz particles (b): Magnified area of (a) showing morphology of acicular crystals Inserticin(b): FFT image of (b) anatase TiO2(c): Magnified area of (a) showing lattice imagesCrystallite size perpendicular to the(101)or(004)planes was estimated from the full-widthhalf-maximum of the 101 or 004 peak to be 39 nm or 6

3 nm, respectively Elongation ofcrystals in the c-axis direction was also suggested by the difference in crystallite sizeown to be assemblies of nano TiO2 crystals(Fig 4a) Particle diameter00-200 nm Relief structures had formed on the surfaces and openpores had formed inside because the particles were porous assemblies of nanocrystalsntechopen

Morphology control, self-assembly and site-selective deposition of metal oxide nanocrystalsNanocrystalsshown to have acicular shapes (Fig 4b) They were about 5-10 nm indirection of acicular Tio, is indicated by the black arrow The inserted FFTnage shows the 101 and 004 diffractions of anatase TiO, Nanocrystals are assigned to theingle phase of anatase TiO It is notable that the diffraction from the(101) planes has a ringshape due to random orientation but that from the (004)planes was observed only in thed lower left region in the FFtindicated the direction of the c-axis, which was perpendicular to the(004)planes, as shown bythe longer direction of acicularfilms Anisotropic crystal growth is one of the features of liquid phase crystal depositionAcicular nanocrystals showed lattice images of anatase TiO(Fig 4c) Theyconstructed ofanatase TiO crystals without amorphous or additional phases Anatase crystals werwered with amorphous or additional phases even at the tips Bare anatase crystal withnanosized structure is important to achieve high performance for catalysts and devicesCrystallization of TiO2 was effectively utilized to form assemblies of acicular nanocrystals in theand surface relief structures were successfully formed on the particed particles were dispersewater to evaluate zeta potential and particletion after evaluation of N2 adsorption The particles had positive zeta potential of 30H1 which decreased to 50,-06,-113 and -363 mv at pH 5070

90 and 11respectively The isoelectric point was estimated to be ph 67, slightly higher than that ofnatase TiO(pH 27-60) Zeta potential is very sensitive to the particle surface conditions,ns adsorbed on the particle surfaces, and the kind andThe variations in zeta potential were likely caused by the difference in the surface conditionsMean particle size was estimated to be 550 nm in diameter with a standard deviation (STD) ofH31 This was larger than that observed by TEM Slight aggregation occurred at pH3 because the particles were dried completely prior toincreased withPH and showed aof near the isoelectric point (550 nm at pH 31, 3150 nm at pH 5,H7, 5500 nm at pH 9 or 2400 nm at pH 11 1 ) Strong aggregation resulted from theof repulsion force between particles near the isoelectric pointThe particleted in the solution at ph 38 in this study It would be suitablebtain repulsion force between particles for crystallization without strong aggregationTiOz particles exhibited N2 adsorption-desorption isotherms of Type IV5a) TEisotherm differed from adsorption isotherm in the relative pirange from 04 to 07, showing mesopores in the particles BET surface area of the particlwas estimated to be 270 m?/g( Fig 5b) This is higher than that of TiOz nanoparticles suchde P25(BET 50 m2/g, 21 nm in diameter, anatase 80%+ rutile 20%, DegussaAeroxide P90(BET 90-100 m2/g, 14 nm in diameter, anatase 90%+ rutile 10%, Degussa)MT-01(BET 60 m2/g, 10 nm in diameter, rutile, Tayca Corp ) and Altair TiNano(BET 50cannot be obtained from particles having a smooth surface even if the particle size is lessntechopen

Nanocrystalsthan 100 nm A high BET surface area would be realized by the unique morphology of Tio2particles constructed of nanocrysTotal pore volume and average pore diameter were estimated from pores smaller than 23nm at P/Po99-0431 cc/g and 64 nm, respectively They were estimated to be 0 21g and 3 1 nm, respectively, from pores smaller than 11 nm at P/Po=080 Total porvolume was also estimated by the BJH method from pores smaller than 154 nm to be 0428Pore size distribution was calculated by the bJH method using adsorption isotherms( Figlarger than 10 nm are considered to be interparticle spaces The pore size distribution alsoggested thece of micronsmaller than 1Pore size distribution was further calculated by the dFt/ monte-Carlo method The modelagreement withion isotherms(Fig 5d) Pore size distribution showed ahat indicated the existence of-36size calculated by the DFT/Monte-Carlo methodfrom the BJH method because the latter method is considered to have produceddistribution also suggested the existence ofI nm, probably resulting from microspaces surrounded by nanocrystals and the unesurface structure of nanocrystalsThe particles were shown to have a large surface area as well as micropores of -1 nm,esopores of-28-36 nm and pores larger than 10 nm, by Nz adsorption characteristicsAssembly of acicular nanocrystals resulted in unique features and high surfaceTiOz particles were generated in the solutions at 90C for 1h using an oil bath with nostirring for comparison

The solutions became clouded after the addition of boric acidnate solutions, High temperature acceleratedcrystal growth of TiOz Hydrogen chloride of 06 ml was added into the solutions of 200mldecrease crystallization speed of TiO2, The pH of the solutions was 2 4 one hour afterixing thtions bet surfaceof the particles was estimated to 18 m2/g Thiswer than that of the particles prepared at 50C and slightlyer than thatpared at 90oC for 8 min in our previous work (44 m2/g)13 Formation of TiOaccelerated at high temperature and it decreased surfaceThe particlesin thefunction of time Crystallization of TiO2be strongly affected by growth conditions such as solution temperature and growth timen summary, anatase TiO particles, 100-200 nm in diameter, were successfully fabricatedutionassemblies oftals 5-10isotropically along the c-axis to form acicular shapes The particles thus had nanoreliefurface structures constructed of acicular crystals, They showed c-axis orientation due tohigh-intensity X-ray diffraction from the(004)crystal planes The particles had a high BETsurfaceof 270 m2/g Total pore volume and average pore diameter were estimatedfrom pores smaller than 230 nm at P/Po=099-043 cc/g and 64 nm, respectively Theywere also estimated from pores smaller than 11 nm at P/Po m080-021 cc/g and 31 nm,espectively B)H and DFT/ Monte-Carlo analysis of adsorption isotherm indicated thentechopen