WST-EM14241R1 (1)

ta

er

ter

nt T

d w

s w

ro

ure

una

e hi

lowUniversidad de Buenos Aires,

Instituto de Fsica,UNAM, Mxico D.F.

Q1Q2

Q3

lead to hole-electron recombination, which increases with

Q4

rfac 5pr

sedung

c6ffer

sed(W 7

gan et al. Q8), electrochemical anodic oxidation (Neupaneet al. ) and hydrothermal treatment (Wang et al. ;Nakahira et al. Q9; Asiah et al. ). Hydrothermal treat-ment of TiO particles in alkaline solutions is one of the

roduce 1D-layered titanate struc-hemical process, more favourable

d production of low cost materialnanotubes-nanorods compared tos surfactant-assisted templatingt al. ). The hydrothermal syn-

thesis of TiO2 nanotubes involve several steps where the

1 IWA Publishing 2014 Water Science & Technology | in press | 2014

Uncorrected Proofsuch as nanotubes, nanorods, nanowires, nanobelts, etc. of

inorganic materials have attracted great attention becausethe presence of surface defects or trapping sites. Severalapproaches were explored to increase the photoefciency

of TiO2, being the modication of the particle morphologyand dimensionality one of the newest (Lai et al. ).During the last years one-dimensional (1D) nanostructures

2

simplest techniques to ptures. It is a simple wet c

for large-scale reaction anfor the formation of TiO2other methods, such a(Adachi et al. ; Liu e(as water oxidation, oxygen reduction, etc). One of the maindrawbacks of TiO2 nanoparticles is the random pathway ofthe electrons during the photocatalytic reactions that mayINTRODUCTION

TiO2 nanomaterials are well-studied and commonly usedmaterials for liquid and gas-phase applications due to itshigh performance as photocatalysts for degradation of

organics, water splitting and solar cells, within others(Ollis et al. ; Cowan et al. ; Yan & Zhou ; Renet al. ). Under UV illumination, electrons from theTiO2 valence band jump to the conductive band leaving oxi-dant positive holes behind (Ibhadon & Fitzpatrick ). Theelectrons and holes diffuse to the surface of TiO2 particles,where they can participate in oxidative-reduction processes

they could offer larger suparticles (Yamin et al.nanotubes exhibit unique

for photocatalysis. Theenhanced light adsorptioneter, (ii) rapid and lo

capability, (iii) large speciability (Liu et al. ). Diin order to get TiO2-baassisted-template methoddoi: 10.2166/wst.2014.312e area in comparison to nano- Q). In the case of TiO2, theoperties that may be benecial

unique features include: (i)e to the high ratio length/diam-distance electron transport

surface area, (iv) ion exchangeQent routes have been developed

1D nanostructures such asu & Chi-Chung Q; Maiyala-P-25 can be associated with the lower crystallinity of 1D TiO2 in both materials.

Key words | hydrothermal treatment, 1D TiO2 nanostructures, photocatalytic activityHowever, the rod like nanostructures obtained from SG-TiO2 displayed slightly higher efciency than

the sol gel prepared powders. The lower photocatalytic activity of the nanostructures with respect toArgentina

Dwight AcostaSynthesis, characterization and photoca

of 1 D TiO2 nanostructures

Julieta Cabrera, Hugo Alarcn, Alcides Lpez, Rob

Dwight Acosta and Juan Rodriguez

ABSTRACT

Nanowire/nanorods TiO2 structures of approximately 8 nm in diame

were synthesized by alkaline hydrothermal treatment of two differe

precursor was TiO2 obtained by sol gel process (SG-TiO2); the secon

commercial TiO2 P-25 (P25-TiO2). Anatase like 1D TiO2 nanostructure

The 1D nanostructures synthesized from SG-TiO2 powders turned on

annealing at 400 WC during 2 hours. On the other hand the nanostruct

preserved the tubular structure after annealing, displaying higher Br

area than the rst system (279 and 97 m2/g respectively). Despite th

the 1D nanostructures, in both cases the photocatalytic activity waslytic activity

to Candal,

and around 1000 nm long

iO2 nanopowders. The rst

as the well-known

ere obtained in both cases.

d like nanostructures after

s synthesized from P25-TiO2

uerEmmettTeller surface

gher surface area shown by

er than P25-TiO2 powder.

Julieta CabreraHugo AlarcnAlcides LpezJuan Rodriguez (corresponding author)Universidad Nacional de Ingeniera,Lima, PerE-mail: [email protected]

Alcides LpezInstituto Peruano de Energa Nuclear,IPEN, Lima,Per

Roberto CandalINQUIMAE,Facultad de Ciencias Exactas y Naturales,

HS WorkCross-Out

HS WorkCross-Out

HS WorkCross-Out

HS WorkCross-Out

HS WorkCross-Out

HS WorkCross-Out

HS WorkCross-Out

HS WorkInserted TextYu

HS WorkCross-Out

HS WorkCross-Out

HS WorkCross-Out

HS WorkCross-Out

HS WorkInserted Text,

HS WorkInserted Textthe

HS WorkCross-Out

HS WorkInserted Text-

HS WorkCross-Out


HS WorkCross-Out

HS WorkInserted Textinto

HS WorkCross-Out

HS WorkInserted Textfor

HS WorkCross-Out

HS WorkInserted TextConversely,

HS WorkInserted Texta


HS WorkInserted Textfor the

HS WorkCross-Out


HS WorkInserted Text1D TiO2 nanostructures,

HS WorkCross-Out

HS WorkCross-Out

HS WorkInserted Text is

HS WorkCross-Out


HS WorkCross-Out

HS WorkCross-Out

HS WorkInserted Textamong


HS WorkInserted Textsuch

HS WorkCross-Out

HS WorkInserted Textone of the newest

HS WorkInserted Texts

HS WorkCross-Out

HS WorkCross-Out

HS WorkHighlight

HS WorkSticky NoteAQ1: This phrase did not quite make sense; I have tried to guess at your meaning, but please check carefully and provide new wording if necessary.

HS WorkCross-Out

HS WorkInserted Textrecent


HS WorkInserted Text.

HS WorkInserted Text(

HS WorkInserted Text)

HS WorkCross-Out

HS WorkInserted Textconsiderable

HS WorkCross-Out


HS WorkCross-Out



HS WorkCross-Out

HS WorkInserted Textcreate

HS WorkCross-Out



ing suspension was heated at 70 WC for 2 h to peptize the

persion of TiO2 particles and adsorption of RhB on the

2 J. Cabrera et al. | Photocatalityc activity of 1 D TiO2 nanostructures Water Science & Technology | in press | 2014

Uncorrected Proofaggregates of particles and, in order to get the nanoparticles,

it was auto-cleaved in a stainless steel chamber at 220 WC for12 h. After the hydrothermal treatment a transparent sol-ution and a white precipitate was obtained. The white

precipitated was washed and dried at 100 WC overnight ina dry oven.

The obtained nanostructures were characterized by X-ray diffraction (XRD) in a Rigaku diffractometer using

CuK radiation ( 1.54056 ). The morphology wasstudied by Field Emission Scanning Electron Microscopy(FE-SEM SUPRA 40 Carl Zeiss) and High Resolution Trans-

mission Electron Microscopy (HRTEM, JEOL JEM-2010Fstructure of the TiO2 precursor changes completely. These

steps include acid wash and thermal treatment. The natureof the TiO2 use as precursor in the alkaline hydrothermalsynthesis affects the quality and properties of the nal pro-

duct (Liu et al. ). In this work, we report the synthesisof rod and tube-like TiO2 nanostructures by hydrothermalsynthesis using as precursors TiO2 nanopowders syn-thesized in our laboratory by solgel method and

commercial TiO2 P-25. Their photocatalytic efciency wascompared by means of the Rhodamine B (RhB) photocataly-tic degradation.

MATERIAL AND METHODS

All reagents were used as received without further puri-

cation. Titanium isopropoxide, NaOH and HCl werepurchased from Merck. Commercial TiO2 powder P25 wasobtained from Degussa.

Synthesis and characterization of TiO2 nanostructures

Nanotubes/nanorods were synthetized by hydrothermaltreatment of 1 g of TiO2 powder (commercial P25: P25-

TiO2, or solgel synthetized TiO2: SG-TiO2) in a 10 MNaOH solution at 130 WC for 18 and 24 h. After hydrother-mal treatment, the obtained white powder was vacuum-

ltered, washed with HCl solution for ionic exchange andthen washed with distilled water until a neutral pH wasreached. Finally, the samples were annealed at 400 WC for2 h to crystallize the material.

In the synthesis of nanoparticles from solgel method acolloidal solution was obtained adding slowly drops of tita-nium isopropoxide to a vigorous stirred concentrated

acidic solution (HCl 0.1 M) at room temperature. The result-transmission electron microscope [TEM] operating atcatalysts. 4 mL samples of the suspension were taken just

before illumination and after illumination at periods of 5or 15 minutes. The samples were centrifuged at10,000 rpm for 8 min using a 5804R Eppendorf Ultracentri-

fuge to separate the photocatalyst from the solution. Theconcentration of RhB in the solution was determined byUV-Vis spectroscopy. The evolution of the RhB concen-tration was determinate as a function of the irradiation

time from the change in absorbance at 564 nm. The ef-ciency of the nanotubes and nanorods was compared withtheir respective precursor TiO2 powders.

RESULTS AND DISCUSSION

Figure 1 shows FE-SEM and TEM images of the SG-TiO2nanoparticles (NP). The images show that the NP displayeda radius of approximately 7 nm and formed relatively largeand compact aggregates. Figure 2 shows the morphology

and structure of the materials formed after 18 h of exposingthe SG-TiO2 powder to alkaline hydrothermal treatment.The images indicate that the NP turned to tube-like nanos-

tructures with an average inner and external diameter ofapproximately 5.6 and 8 nm respectively. After the hydro-thermal treatment the samples were acid treated toexchange Na by H. Figure 2(b) shows that the tubular

structure was conserved in spite of the acid treatment.Figure 2(c) shows the morphology and structure of thesamples after annealing at 400 WC. The images clearly

shows that as consequence of the annealing the tube like200 kV). TEM samples were prepared by dispersing a

small amount of the sample in ethanol with the help of anultrasonic bath. Small droplets of the freshly prepared dis-persion were placed onto a cupper grid covered with

carbon to improve the conduction of the electrons. Alsothe surface area was estimated by BrunauerEmmettTeller (BET) method in a Gemini VII 2390 instrument.

Measurement of photocatalytic activity

Photocatalytic efciency for degradation of RhB was carriedout under the radiation of 220 WOSRAM ultravitalux lamp,with a measured radiation Intensity of 60 W/m2 in the UV-A

range. An aqueous solution with initial volume of 150 mLwas prepared with an amount of 0.05 g of catalyst andRhB 10 ppm, the solution was sonicated rst for 30 min

and then stirred in the dark for 30 min to ensure a good dis-nanostructures turned into short rod-like particles. Most of

HS WorkInserted Textd


HS WorkInserted Texton

HS WorkInserted Textcreated

HS WorkCross-Out

HS WorkInserted Text as precursors


HS WorkCross-Out


HS WorkCross-Out

HS WorkInserted Text (New Jersey, US)

HS WorkInserted Text (Germany)

HS WorkCross-Out



HS WorkCross-Out


HS WorkInserted Textby slowly

HS WorkCross-Out

HS WorkInserted Textly


HS WorkCross-Out

HS WorkCross-Out

HS WorkInserted Textf

HS WorkCross-Out

HS WorkInserted Texte

HS WorkCross-Out


HS WorkCross-Out


HS WorkCross-Out

HS WorkInserted Textm

HS WorkCross-Out

HS WorkInserted Texth

HS WorkCross-Out

HS WorkInserted Textr

HS WorkCross-Out

HS WorkInserted Textt

HS WorkCross-Out


HS WorkCross-Out

HS WorkInserted Textm

HS WorkCross-Out


HS WorkCross-Out


HS WorkSticky NoteAQ: Please provide manufacturer, city and country for all equipment mentioned.

HS WorkHighlight

HS WorkCross-Out

HS WorkInserted Texto

HS WorkCross-Out

HS WorkInserted TextIn addition,


HS WorkCross-Out

HS WorkInserted Textusing

HS WorkHighlight



HS WorkHighlight

HS WorkCross-Out

HS WorkInserted Texti

HS WorkInserted Textan

HS WorkCross-Out

HS WorkInserted TextThen,

HS WorkHighlight

HS WorkCross-Out

HS WorkInserted Texted



HS WorkCross-Out

HS WorkCross-Out

HS WorkInserted Textto

HS WorkHighlight

HS WorkSticky NoteAQ3: Do you mean 'to'?

HS WorkCross-Out



HS WorkCross-Out


HS WorkCross-Out


Q10

taine


Uncorrected Proofthese particles remained attached one to the other, resem-bling the original morphology of the tubes. These resultssuggest that during the annealing the structure of the tubes

collapsed, cutting the tubes in smaller pieces but preservingin part their original morphology. Longer hydrothermaltreatment was also performed, but not appreciable changesin morphology were detected. Figure 2(d) shows examples

of tubular TiO2 nanostructures obtained after 24 h oftreatment.

Figure 3 shows TEM images of TiO2 nanostructures

obtained by alkaline hydrothermal treatment of P25-TiO2powder during 18 or 24 h, followed by acid exchange and2 h annealing at 400 WC. As in the previous case, tubes

were obtained by both hydrothermal treatment times (18and 24 h). But in this case the tubular 1D structure wasmaintained after annealing. The insets shown in Figure 3

are diffraction patterns obtained by Fast Fourier Transform(DPFFT). The patterns showed well dened points, somecorresponding to (101) planes distances typical of anatase.

The growth mechanism of 1D TiO2 nanostrucures syn-

Figure 1 | FE-SEM and TEM images (left and right, respectively) for TiO2 nanoparticles obthesized by alkaline hydrothermal method from TiO2nanoparticles is still under discussion. It was suggestedthat it take place by the rolling of hydrogen titanate laminar

structures during the ion exchange step (Kasuga et al. ;Capula ) But others authors suggested the 1D structureformation during the treatment of TiO2 in NaOH aqueous

solution (Du et al. ; Zhang et al. ; Zhao et al.). Our results seem to be in agreement with the lastauthors because the tubes were well formed before the

acid treatment was applied.Figure 4 shows the XRD patterns of nanoparticles

obtained by solgel method and the products obtainedafter hydrothermal treatment for 18 h, with further acid

treatment and the nal product obtained after annealing at400 WC for 2 h. The SG-TiO2 NP used as precursorsshowed a XRD pattern typical of low crystalline anatase.After hydrothermal treatment the structure of the solidchanged to another displaying reection peaks at 10, 24.5,

28.4 and 48.3 degrees 2. These peaks can be assigned tothe diffraction of sodium titanates with chemical formulaas Na2TinO2n1 (n 3, 6, 9). In agreement with JCPDS NW311,329 and 331,293 we could describe it as a mix of Na2-Ti3O7 and Na2Ti9O19 designed as sodium titanates. Afteracid treatments the features corresponding to titanatealmost disappeared, being replaced by poor dened peaks

that may be associated with anatase. After the annealingprocess only anatase TiO2 crystalline phase was observedsince the samples showed well dened peaks around 25.3,

37.8, 48.0 2 degrees characteristics of (101), (004) and(200) respectively of anatase TiO2. It should be noted thatbefore annealing the samples were poorly crystalline since

the X-ray reections were slightly dened. After annealingthe crystal structure of the samples was well dened, inagreement with the DPFFT analysis (Figure 3). The crystal-line structures correspond mainly to anatase, although a

d by solgel method.small amount of brookite could be detected in all thecases. Analyzing the width at half maximum of the reec-tions employing Scherrers equation, in the direction of

(101) plane in the Figure 4(b), Q15crystallite sizes about 5 and16 nm around were found for the SG-TiO2 precursor andfor the rod-like structures, respectively. This result shows

that the crystallite size increased when the rod-like shapestructures were formed. Table 1 shows the BET surfacearea values of the different samples. In the case of the

TiO2 nanostructures obtained from SG-TiO2 there was aclear diminution of surface area as consequence of the mor-phological transformation. These results suggest that theconversion from particles to nanorods occurred by a dissol-

ution-precipitation process that involved the transformationof TiO2 to sodium titanate, followed by proton exchange to

HS WorkCross-Out

HS WorkCross-Out

HS WorkCross-Out

HS WorkCross-Out

HS WorkCross-Out

HS WorkInserted Textng

HS WorkCross-Out

HS WorkCross-Out

HS WorkCross-Out

HS WorkCross-Out

HS WorkInserted Textone an

HS WorkCross-Out



HS WorkCross-Out

HS WorkCross-Out

HS WorkInserted Textin


HS WorkCross-Out


HS WorkCross-Out

HS WorkInserted Textt

HS WorkCross-Out


HS WorkCross-Out


HS WorkCross-Out

HS WorkInserted Text, b

HS WorkCross-Out

HS WorkCross-Out

HS WorkCross-Out


HS WorkInserted Textthat

HS WorkCross-Out

HS WorkInserted Texttter

HS WorkCross-Out


HS WorkSticky NoteAQ4: I think you mean 'latter' (that is, Du et al ...). Please check and advise.

HS WorkCross-Out



HS WorkInserted Textn




HS WorkCross-Out


HS WorkHighlight

HS WorkSticky NoteAQ5: Please write in full on first use. International Centre for Diffraction Data?


HS WorkInserted Textly



HS WorkCross-Out



HS WorkCross-Out




HS WorkCross-Out

HS WorkCross-Out

HS WorkCross-Out

HS WorkInserted TextBy a



HS WorkCross-Out


Figure 2 | FE-SEM and TEM images (left and right, respectively) of 1D nanoestructures obtained from SG-TiO2 powders, hydrothermally treated for 18 h (a), after acid treatment (b) and afterannealing at 400

W

C (c), TEM images of tubular TiO2 nanostructures obtained after 24 h of hydrothermal treatment (d).


Uncorrected Proof

Q11


Uncorrected Proofproduce titanic acid and, nally, crystallization to anataseafter thermal treatment. The crystalline structure evolved

through all this steps given more crystalline compoundswith lower surface area.

Figure 5 shows XRD patterns of P25-TiO2 powder andthe TiO2 nanostructures obtained after alkaline hydrother-

mal treatment, acid exchange and annealing at 400 WC. P-25 showed the typical reection peaks corresponding toanatase and rutile. After hydrothermal treatment the diffrac-

tion pattern shows peaks at 10, 24.5, 28.4 and 48.3 degrees2. As discussed before, these features correspond to a mixof sodium titanate described by Na2Ti3O7 and Na2Ti9O19.

After acid treatment the intensity of 10 and 28.4 degreepeaks was practically negligible while the correspondingpeak to 24.5 degrees increased to similar intensity than the

48 degree peak. These reections are usually assigned ashydrogen titanates H2Ti3O7 (Kolenko et al. ). Itshould be noted that both products display better dened

Figure 3 | FE-SEM and TEM images (left and right, respectively) of 1D nanostructures obtained ftreatment and nally annealed at 400

W

C. The insets are DPFFT of the area highlighpeaks than in the previous case. The main crystallinephase of the nal annealed product was also anatase, but

in contrast to the rod shaped structures obtained from SG-TiO2, the crystallite size for nanotubes were in the 810 nm range, which was much less than the crystallite sizeof the P-25-TiO2: 21.5 nm. Besides, as shown in Table 1,

the specic surface area of the P25-TiO2 powders is muchlower than its corresponding 1D TiO2 nanostructures. TheP-25 seeds are more crystalline than the nanostructures

obtained by hydrothermal treatment and even displayedsome amount of rutile. This difference is due to the hightemperature synthesis used in the preparation of P25-TiO2.

Clearly, the P25-TiO2 particles were also exposed to dissol-ution-precipitation processes that leaded to thedisappearance of the rutile phase. The new solid phases dis-

played a more disorganized structure with lower crystallitesizes and higher surface area than the precursor powder.It is remarkable that in this system the nanotubes did not

rom P25-TiO2 powders hydrothermally treated for 18 h (a) and 24 h (b) with subsequent acid

ted in red.

HS WorkCross-Out

HS WorkCross-Out

HS WorkInserted Text2

HS WorkCross-Out


HS WorkCross-Out


HS WorkCross-Out

HS WorkCross-Out

HS WorkInserted Textese


HS WorkCross-Out

HS WorkInserted Texting



HS WorkCross-Out

HS WorkInserted Textearlier



HS WorkCross-Out

HS WorkInserted Textas

HS WorkCross-Out


HS WorkCross-Out


HS WorkCross-Out


HS WorkCross-Out

HS WorkInserted TextIn addition

HS WorkCross-Out


Uncorrected Proofcollapse after annealing, preserving the high surface area.Although the reasons are still not clear, it was reportedthat the thermal and structure stability depend on the type

of precursor (Preda et al. ). The low thermal stabilityof the TiO2 NP, may be consequence of the presence of ana-tase seeds after acid wash. These seeds may trigger thecrystallization of anatase, leading to the rearrangement

and collapse of the structure.The photocatalytic activities of the obtained samples

were tested via degradation of aqueous RhB under UVA

irradiation. It is important to notice that in the literature itis very common to report the beginning of the degradation

Figure 4 | XRD patterns of Sol Gel nanoparticles (NP) and the product obtained from itafter 18 h of hydrothermal treatment, sample with further acid treatment and

nally annealed at 400W

C (18 h/400W

C). Also the nal product obtained with

24 h of hydrothermal treatment is shown (24 h/400W

C) (A anatase, Bbrookite, T Sodium titanate).

Table 1 | BET Surface area of the different samples

TiO2 nanostructures

Surfacearea BET(m2/g) TiO2 nanostructures

Surfacearea BET(m2/g)

TiO2 NPs-Sol Gel 201 TiO2 P 25 NPs 60

1D Nanostructures18 h/400 WCa

97 1D Nanostructures18 h/400 WCa

279

aHidrotermal treatment time/annealing temperature.curve as 0% of degradation at 0 time. However adsorption

on the photocatalyst should be considered. In this case thedegradation curve was drafted considering the initialdecrease of RhB due to adsorption of the dye on TiO2 photo-

catalyst. As is shown in Figures 6 and 7 before theirradiation (t 0), an adsorption process of RhB on the

Figure 5 | XRD patterns of P25-TiO2 powder and the product obtained from it after 24 h ofhydrothermal treatment, sample with further acid treatment and nally

annealed at 400W

C (24 h/400W

C). Also the nal product obtained with 18 h of

hydrothermal treatment is shown (18 h/400W

C) (A anatase, R rutile, TSodium titanate, H Hydrogen titanate).

Figure 6 | RhB degradation for sample obtained from P25 hydrothermally treated for 18 hwith further acid treatment () and after annealing process at 400 WC ().

HS WorkSticky NoteTS: Please delete the top two boxes



HS WorkCross-Out



HS WorkCross-Out


HS WorkCross-Out


HS WorkCross-Out

HS WorkInserted TextT

HS WorkInserted Textalso

HS WorkCross-Out

HS WorkInserted TextT

HS WorkInserted Textalso

HS WorkCross-Out

HS WorkInserted Texty

HS WorkInserted Texth

12

1314

ures obtained from it (a) and P25 nanoparticles and the 1D nanostructures obtained from it (b).


Uncorrected ProofTiO2 nanostructures were observed. The adsorption on com-

mercial P25-TiO2 was measured to be 4% and 5 and 2% fornal 1D structures obtained with 18 and 24 h of hydrother-mal treatment respectively. On the other hand, absorption

was approximately 1 and 2% for samples obtained fromSG-TiO2 after 18 and 24 h of thermal treatment respectively,and practically negligible for the SG-TiO2 precursor. Theadsorption amount could be ascribed to the high surface

area of the TiO2 nanotubes and nanorods.Figure 6 shows the evolution of RhB concentration in

UVA illuminated solution containing TiO2 nanotubes

obtained from P-25. The results indicate that the annealednanotubes display much higher photocatalytic activity thanthe raw nanotubes. This phenomenon can be associated

with the different nature of the TiO2 nanotubes before andafter annealing. Only after ring the structure of the nano-tubes became anatase (see Figure 5), which is thecrystalline TiO2 phase with well known photoicatalytic

activity.Figure 7-a shows the photocatalytic degradation of

RhB in solutions containing SG-TiO2 NP, and annealed

1D TiO2 obtained from TiO2-SG NP precursor. Clearly,

Figure 7 | Degradation of RhB solutions with Sol Gel nanoparticles and the 1D nanostructthe photocatalytic activity of the 1D TiO2 samples ishigher than that displayed by the precursor material,

being more active the sample expose to longer hydrother-mal treatment. This phenomenon can be a consequenceof the different crystallite size displayed by the systems. It

was reported that a highly crystalline structure lead tomore active photocatalysts due to a diminution in therecombination of the photogenerated carriers (Liu et al.). In this case, as showed in Figure 4, the annealed

nanotubes displayed a well crystallized anatase structure.Figure 7(b) allows comparing the photocatalytic activityof P-25 with the activity of 1D TiO2 obtained by hydrother-

mal treatment of P-25 followed by annealing. In this case,the precursor material displayed higher photocatalyticactivity than the 1D TiO2 structures, even thought the

1D nanostructures had larger surface area. This resultmay consequence of different phenomena. By one hand,it was proposed that the presence of both crystalline

phases (anatase and rutile) in the P25-TiO2 particles mayimprove the photocatalytic response of this material (Suet al. Q). By the other, the crystalline domines of the1D TiO2 nanostructures are quite small (611 nm) hin-

dered the photo activity of the material. This effect maybe consequence of the presence of dangling bonds or dis-torted lattice structures that may act as electron-hole

recombination sites (Henderson ). Also the 1D nanos-tructures were not pure in morphology but were mixedwith particles of different shapes and even amorphous

TiO2. Despite the 1D nanostructures showed lower photo-catalityc activity than P25-TiO2, these nanostructuresdisplayed a reasonable good photocatalytic activity forRhB degradation since we have gotten the complete degra-

dation of a concentrate solution in 6080 min(shorterthan reporter by other authors (Zhao et al. Q; Thennar-asu et al. Q)).CONCLUSIONS

TiO2 anatase 1D nanostructures, with high surface area and

photocatalytic activity, were synthesized by hydrothermaltreatment. The structure of the systems depended on theTiO2 precursor powder used in the synthesis. P25-TiO2 pro-duced nanotubes that were not altered by the thermal

treatment, but the structures produced from SG-TiO2 col-lapsed after annealing at 400 WC. This phenomenon may beconsequence of the presence of anatase seeds in the TiO2nanotubes after acid washing. All the synthesized 1D TiO2nanostructures were effectively used in the photocatalytic

HS WorkCross-Out


HS WorkCross-Out

HS WorkInserted Textbe a

HS WorkCross-Out


HS WorkCross-Out

HS WorkCross-Out

HS WorkCross-Out



HS WorkCross-Out

HS WorkInserted TextConversely


HS WorkInserted Text did

HS WorkCross-Out

HS WorkInserted Texto

HS WorkCross-Out


HS WorkSticky NoteTS: Please include (a) in the link.

HS WorkInserted Textthan




HS WorkCross-Out

HS WorkInserted Textn

HS WorkCross-Out


HS WorkCross-Out



HS WorkCross-Out

HS WorkInserted Textson of

HS WorkCross-Out


HS WorkCross-Out

HS WorkInserted TextFor instance

HS WorkCross-Out

HS WorkInserted TextAlternatively

HS WorkHighlight

HS WorkSticky NoteAQ6: Please check this word as it does not appear to be English.


HS WorkCross-Out

HS WorkInserted TextMoreover,

HS WorkCross-Out


HS WorkCross-Out

HS WorkInserted Texty

HS WorkCross-Out

HS WorkInserted Textachieved

HS WorkCross-Out


HS WorkCross-Out

HS WorkInserted Text


cations. For example, TiO2 nanotubes can be use to

FINCYT-IB-2013, the Peruvian-Argentinean 201102-CON-CYTEC OAJ Project and MINCYT-CONCYTEC PE/09/01,


Uncorrected ProofCONICET-PIP 11220080102533, UBACyT X003 and20020090100297 and the Pacic Alliance Program 20132through the SRE-Mxico. RJC is member of CONICET.

DO UBA fellowship is acknowledged. We are grateful toCentral Laboratory of Microscopy of Physic Institute ofUNAM from Mexico and Dr. F. Chandezon for fruitful

discussions.

REFERENCES

Adachi, M., Murata, Y., Okada, I. & Yoshikawa, S. Formation of titania nanotubes and applications fordye-sensitized solar cells. J. Electrochem. Soc. 150 (8), G488G493.

Asiah, M. N., Mamat, M. H., Khusaimi, Z., Achoi, M. F., Abdullah, S.& Rusop, M. Thermal stability and phase transformation ofTiO2 nanowires at various temperatures. Microelectron. Eng.108, 134137.

Capula, S. Synthesis, characterization and photocatalyticactivity evaluations of Pt-Ir nanoparticles soported ontotitania nanotubes. Master in Science Thesis, Institutoprepare ltration membranes with self cleaning properties

under UVA illumination (preventing membrane fooling).TiO2 nanotubes are also easily lterable than NP and canbe easily removed from solutions. In other words the possi-bility to produce a photocatalytic material with different

shapes makes it more versatile for the photocatalytic appli-cation by itself or in the form of composite materials.

ACKNOWLEDGEMENTS

This work was supported by the Fincyt Project No 140-degradation of Rhodamine B. The efciency of the TiO2nanotubes as photocatalyst was lower than that of P-25(under similar condictions), although was high enough tobe successfully use as photocatalyst. It should be mentioned

that the rod-like nanostructures displayed higher efciencythan that of its SG TiO2 precursor. The lower photocatalyticactivity of the nanostructures with respect to P25 can berelated with the lower crystallinity of 1D TiO2 in both

materials and the absence of rutile as minor phase. Due toits photocatalytic activity, aspect ratio and tubular structure,this material is very attractive as a component for the

synthesis of functional materials for environmental appli-Politcnico Nacional, Mexico D.F. Mexico.Cowan, A., Tang, J., Leng, W., Durrant, J. & Klug, D. Mechanism of water splitting by TiO2. J. Phys. Chem. C 114(9), 42084214.

Du, G. H., Chen, Q., Che, R. C., Yuan, Z. Y. & Peng, L. M. Preparation and structure analysis of titanium oxidenanotubes. Appl. Phys. Lett. 79 (22), 37023704.

Henderson, M. A. A surface science perspective on TiO2photocatalysis. Surf. Sci. Rep. 66, 185297.

Ibhadon, A. O. & Fitzpatrick, P. Heterogeneous photocatalysis:recent advances and applications. Catalysts 3, 189218.

Kasuga, T., Hiramatsu, M., Hoson, A., Sekino, T. & Niihara, K. Formation of titanium oxide nanotube. Langmuir 14(12), 31603163.

Kolenko, Y. V., Kovnir, K. a, Gavrilov, A. I., Garshev, A. V.,Frantti, J., Lebedev, O. I. & Yoshimura, M. Hydrothermal synthesis and characterization of nanorods ofvarious titanates and titanium dioxide. J. Phys. Chem. B 110(9), 40304038.

Lai, C. W., Juan, J. C., Bae Ko, W. & Hindawi, S. B. Anoverview: recent development of titanium oxide nanotubes asphotocatalyst for dye degradation. Publishing Corporation.Int. J. Photoenergy 2014, 14, Article ID 524135.

Liu, N., Chen, X., Zhang, J. & Schwank, J. W. A reviewon TiO2-based nanotubes synthesized via hydrothermalmethod: Formation mechanism, structure modication,and photocatalytic applications. Catal. Today 225, 3451.

Maiyalagan, T., Viswanathan, B. & Varadaraju, U. Fabrication and characterization of uniform TiO2 nanotubearrays by sol-gel templating method. Bull. Mater. Sci. 29 (7),705708.

Nakahira, A., Kubo, A. & Numako, C. TiO2-derived titanatenanotubes by hydrothermal process with acid treatments andtheir microstructural evaluation. Appl. Mater. Interfaces 2 (9),26112616.

Neupane Madhav, P., Song Park, I., Sung Bae, T., Keun Yi, H.,Watari, F. & Ho Lee, M. Synthesis and morphology ofTiO2 nanotubes by anodic oxidation using surfactant basedFluorinated electrolyte. J. Electrochem. Soc. 158 (8),C242C245.

Ollis, D. F., Pelizetti, E. & Serpone, N. Destruction of watercontaminants. Environ. Sci. Technol. 25, 15221529.

Preda, S., Teodorescu, V. S., Musuc, A. M., Andronescu, C. &Zaharescu, M. Inuence of the TiO2 precursors on thethermal and structural stability of titanate-based nanotubes.J. Mater. Res. 28 (03), 294303.

Ren, Y., Zheng, L., Pourpoint, F., Armstrong, A., Grey, C. & Bruce,P. Nanoparticulate TiO2 (B): anode for lithium-ionbatteries. Angew. Chem. Int. Ed. 51, 21642167.

Su, R., Bechstein, R., S, L., Vang, R. T., Sillassen, M., Palmqvist,A. & Besenbacher, F. How the anatase-to-rutile ratioinuences the photoreactivity of TiO2. J. Phys. Chem. 115(49), 2428724292.

Thennarasu, S., Rajasekar, K. & Balkis Ameen, K. Hydrothermal temperature as a morphological controlfactor: Preparation, characterization and photocatalyticactivity of titanate nanotubes and nanoribbons. J. Mol. Struct.

1049, 446457.

HS WorkCross-Out

HS WorkCross-Out

HS WorkInserted TextY

HS WorkCross-Out


HS WorkCross-Out


HS WorkCross-Out


HS WorkCross-Out

HS WorkCross-Out

HS WorkCross-Out

HS WorkInserted TextAbd Hamid

HS WorkInserted Text Nos.

HS WorkInserted Textit


HS WorkInserted Textstill



HS WorkCross-Out

HS WorkInserted Textthose from the

HS WorkCross-Out


HS WorkCross-Out

HS WorkInserted Textin the

HS WorkHighlight

HS WorkSticky NoteAQ7: Do you mean 'in the'?


HS WorkCross-Out

HS WorkInserted Textould

HS WorkCross-Out


HS WorkCross-Out

HS WorkInserted Textu

HS WorkInserted Textmore

HS WorkCross-Out

HS WorkInserted TextHence,

HS WorkCross-Out


HS WorkCross-Out

HS WorkInserted Textup

HS WorkCross-Out

HS WorkInserted TextA.

HS WorkCross-Out


Wang, D., Zhou, F., Liu, Y. & Liu, W. Synthesis andcharacterization of anatase TiO2 nanotubes with uniformdiameter from titanium powder. Mater. Lett. 62, 18191822.

Wu, J. & Chi-Chung, Yu, Aligned TiO2 nanorods andnanowalls. J. Phys. Chem. B 108 (11), 33773379.

Yamin,Y., Keller,N.&Keller, V. WO3-modiedTiO2 nanotubesfor photocatalytic elimination ofmethylethylketone under UVAand solar light irradiation. J. Photochem. Photobiol. A: Chem.245, 4357.

Yan, J. & Zhou, F. TiO2 nanotubes: Structure optimization forsolar cells. J. Mater. Chem. 21, 9406.

Zhang, Z. J., Zhang, J. W., Guo, X. Y., Jin, Z. S., Zhang, S. L. &Zhou, J. F. TEM study on the formation processof TiO2 nanotubes. Chin. Chem. Lett. 14 (4), 419422.

Zhao, D., Zhang, R. & Tu, B. Synthesis of highly stable andcrystalline mesoporous anatase by using a simple surfactantsulfuric acid carbonization method. Chem. Eur. J. 16,99779981.

First received 28 February 2014; accepted in revised form 30 June 2014. Available online 12 July 2014


Uncorrected Proof

HS WorkInserted Text J.

HS WorkCross-Out

HS WorkInserted TextC. C.

HS WorkCross-Out


HS WorkCross-Out

HS WorkInserted Text & Zhao, D.

HS WorkHighlight

HS WorkSticky NoteTS: Please move this reference underneath the one below (now that the author order has altered).

Author QueriesJournal: Water Science & Technology

Manuscript: WST-EM14241R1

Q1 Please confirm the change of citation from Ollis (1991) to Ollis et al. (1991) as per the reference list.

Q2 Please confirm the change of citation from Yan (2011) to Yan & Zhou (2011) as per the reference list.

Q3 Please confirm the change of citation from Ibhadon (2013) to Ibhadon & Fitzpatrick (2013) as per the referencelist.

Q4 Please confirm the change of citation from Lai (2014) to Lai et al. (2014) as per the reference list.

Q5 Please confirm the change of citation from Yamin (2012) to Yamin et al. (2012) as per the reference list.

Q6 Please confirm the change of citation from Liu (2014) to Liu et al. (2014) as per the reference list.

Q7 Please confirm the change of citation from Wu (2004) to Wu & Chi-Chung (2004) as per the reference list.

Q8 Please confirm the change of citation from Maiyalagan (2006) to Maiyalagan et al. (2006) as per the referencelist.

Q9 Please confirm the change of citation from Nakahira (2010) to Nakahira et al. (2010) as per the reference list.

Q10 Please confirm the change of citation from Zhao (2010) to Zhao et al. (2010) as per the reference list.

Q11 Please confirm the change of citation from Kolenko (2006) to Kolenko et al. (2006) as per the reference list.

Q12 Please confirm the change of citation from Su (2011) to Su et al. (2011) as per the reference list.

Q13 Please confirm the change of citation from Zhao (2010) to Zhao et al. (2010) as per the reference list.

Q14 Please confirm the change of citation from Thennarasu (2013) to Thennarasu et al. (2013) as per the referencelist.

Q15 Figure 4(b) is cited in text. But respective part label is not given in figure. Please check.

HS WorkCross-Out

Synthesis, characterization and photocatalytic activity of 1 D TiO2 nanostructuresINTRODUCTIONMATERIAL AND METHODSSynthesis and characterization of TiO2 nanostructuresMeasurement of photocatalytic activity

RESULTS AND DISCUSSIONCONCLUSIONSThis work was supported by the Fincyt Project No 140-FINCYT-IB-2013, the Peruvian-Argentinean 2011-02-CONCYTEC OAJ Project and MINCYT-CONCYTEC PE/09/01, CONICET-PIP 112-200801-02533, UBACyT X003 and 20020090100297 and the Pacific Alliance Program 2013-2 through the SRE-Mxico. RJC is member of CONICET. DO UBA fellowship is acknowledged. We are grateful to Central Laboratory of Microscopy of Physic Institute of UNAM from Mexico and Dr. F. Chandezon for fruitful discussions.REFERENCES

Documents

WST-EM14241R1 (1)