The Visible Light Activity of the TiO 2 and TiO 2 :V 4+ Photocatalyst

Transcription

1 Nnomterils n Nnotehnology ARTICLE The Visile Light Ativity of the TiO 2 n TiO 2 :V 4+ Phototlyst Regulr Pper Nguyen Minh Thuy 1,*, Duong Quo Vn 1 n Le Thi Hong Hi 2 1 Deprtment of Physis, Hnoi Ntionl University of Eution, Hnoi, Vietnm 2 Deprtment of Chemistry, Hnoi Ntionl University of Eution, Hnoi, Vietnm * Corresponing uthor: thuynm@hnue.eu.vn Reeive 18 Septemer 212; Aepte 16 Nov Thuy et l.; liensee InTeh. This is n open ess rtile istriute uner the terms of the Cretive Commons Attriution Liense ( whih permits unrestrite use, istriution, n reproution in ny meium, provie the originl work is properly ite. Astrt TiO2 n vnium ope TiO2 nnoprtiles were synthesize y using the hyrotherml metho. The V oping ontents re.;.1;.3;.5;.7 n.9% molr. The vnium ope TiO2 nnoprtiles hve ientil ntse phse with n verge rystl size of 1 2nm. The olei i n ethnol solvents with ifferent molr onentrtions n mke spheril nnogrins, or stik form grins, whih influene the photo tivity of the mterils. The sorption spetr of ope smples exhiite longtile sorption in the visile light region ove 38nm. The visile light phototlyti tivity ws evlute y the egrtion of phenol queous solutions; fter 36 min. uner the visile irrition, the normlize onentrtion of phenol erese to 9%. Keywors Semionutors, Nnorystls, Phototlysts, Asorption, Irrition. 1. Introution Titnium ioxie (TiO2) is n importnt ompoun, the eletroni struture of whih ontinues to ttrt onsierle experimentl n theoretil ttention for oth funmentl interest n potentil moern tehnologil pplitions (see [1,2,3]). In reent yers, gret el of interest hs een evote to the phototlyti egrtion of orgni wter pollutnts on semionutor prtiles (see [4,5,6]). TiO2 n e pplile for the eomposition of unesire ompouns in ir s well s wste wter, solr energy onversion n the proution of len energy resoures through the wter splitting retion. In prtiulr, pplitions for environmentl issues suh s purifition of wste wter using nturl solr light re of gret prtil interest. However, the pplition of TiO2 s phototlyst for visile light inue hemil retions hs een hmpere y its lrge n gp energy (3.2eV for ntse TiO2), whih requires ultrviolet (UV) light to tivte n les to the lower energy effiieny. Wiening the sorption ege of TiO2 from the UV to the visile spetrl rnge oul provie the grounwork to evelop TiO2 tlysts with visile light tivity. Mny stuies h een ttriute to the oping of trnsition metls into TiO2 to evelop vis phototlysts, suh s V, Cr, Mo, Fe (see [1,3,7]). Among the trnsition metl ions, vnium ion is ttrtive euse vnium Nguyen Nnomter. Minh Thuy, nnotehnol., Duong Quo 212, Vn n Vol. Le 2, Thi Art. Hong 14:212 Hi: The Visile Light Ativity of the TiO 2 n TiO 2 :V 4+ Phototlyst 1

2 oping n inrese rrier lifetime n pprently lso exten the sorption rnge of TiO2. Different methos h een hosen to prepre V ope TiO2 tlysts, suh s the sol gel metho, the metl ion implnttion metho, the o preipittion metho, the hyrotherml metho n so on (see [3 6]). It is promising to synthesize V ope TiO2 powers eonomilly n prtilly y using the hyrotherml metho euse of its low ost, effetiveness n esy exeution. The performne of TiO2 phototlyst is strongly epenent on numer of other struturl ftors, suh s rystl phse, s well s grin forms n the egree of rystllinity of the TiO2 prtiles. The tehnique prmeters of the hyrotherml metho, suh s the solvent n tempertures, n iretly ffet the ove properties of the TiO2 nnoprtiles. In this work, V ope TiO2 nnopowers were synthesize y using the hyrotherml metho. We investigte the solvent influene on morphology n prtile size in the smple in orer to otin high visile phototivity of TiO2:V nnorystls. The solvents re wter or olei i with ethnol, whih hve ffete the forms n sizes of the grins in the smples. The photoegrtion of phenol (C6H5OH) in queous suspension ws use s proe retion to evlute the phototlyti tivity. As shown in previous works, the metl oping in nnosize TiO2 hs no ientify effet on the phototlysti tivity of titn: ref. [7] illustrte tht the visile light phototivity of ope vnium is lower thn tht of unope titni prepre y the solution omustion metho. However ref. [5], using the hyrotherml metho, otine n effetively improve retion rte for the egrtion of isoutnol y smll mounts of vnium oping into TiO2. The phototlyst of ope nnosize titn is strongly relte to the smple preprtion metho [4,5,7]. In our previous work [8], we foun tht y using the hyrotherml metho the.5%vope TiO2 ntse nnorystls hve the highest visile light tivity; unope TiO2 hs phototlyst only uner UV ritive exittion. This result is in goo greement with [9,1] in methyl ornge phototlyti egrtion. However, the smple prepre with the wter solvent h low egrtion rte (fter 36 min. of visile irrition, the normlize onentrtion of phenol erese to 3%). In this work we inten to improve the grin form n size y hnging the polrity of the solvent. Olei i (C17H33COOH) n ethnol (C2H5OH) solvent n e use for this. The ifferent rtios of olei i/ethnol were me to ontrol the morphology n grin form in the smples, hene their phototlysti tivity n e improve. After 36 min. of visile irrition with TiO2:V nnoprtile tretment, the normlize onentrtion of phenol erese to 9% n the onentrtion of phenol erese to.3mg/l, whih is less thn the llowle phenol vlue on inustril wste wter y ishrge stnrs. The visile light phototlysti tivity of V ope TiO2 suggeste n pplition for n environmentl tretment of wste wter. 2. Experiment The use hemils were TiCl4, i itri (CA), NH4NO3, NH3 1%, V2O5/HCl.3M, olei i (OA) C17H33COOH (pk=9.85 [11]) n C2H5OH. All hemils were of nlytil regent gre. Pure titnium tlyst ws prepre using the hyrotherml metho with the following proeure: firstly 3.ml TiCl4 ws e rop y rop to 1ml of solvent (istille wter or OA), whih ws ontinuously stirre for 2 min. Afterwrs, mmoni queous solution NH3 (25%) ws e to just the ph vlue to 7 8, n then stirre for 3 min. Then the mixture ws trnsferre into n utolve n kept t 2 C for 5h. After entrifugtion n wshing, the smples were rie in the ir. A series of V ope TiO2 hyrosols were prepre y hnging the V/Ti rtio. The vnium oping ontent ws lulte y the following eqution: %V = nv/(nv + nti) where nv n nti were the mole of vnium n titnium, respetively. The V oping ontents re.;.1;.3;.5;.7 n.9 molr %. For stuying the influene of the solvents, we hose the smple TiO2:.5%V. The ifferent proportions of the TiCl4: OA: C2H5OH re 1:4:2; 1:5:2; 1:6:2 n 1:8:2. We nme the otine smples s T 142 5; T 152 5; T n T 182 5, respetively. The struture n rystlline hrters were nlyse y X ry iffrtion (XRD) SIEMENS D55, selete re eletron iffrtion (SEAD), n y Rmn sttering mesurements with LABRAM miro Rmn spetrosopy. X ry photoeletron spetrosopy (XPS) mesurements were performe in ommeril Mirol 35 XPS system equippe with n Al Kα soure, in UHV hmer (~1 9 Torr) with 6 o tke off ngle. The morphology ws investigte y using snning eletron mirosope (SEM), trnsmission eletron mirosope (TEM) n high resolution TEM (HR TEM). Asorption mesurements were otine with JASCO V 67 spetrometer. 2 Nnomter. nnotehnol., 212, Vol. 2, Art. 14:212

3 The phototlyti tivity of smples ws evlute y egrtion of phenol (C6H5OH) ilute in wter. All phenol ilute wter smples were prepre s follows: 8ml phenol solution (5.1 5 mol/l) ws stirre in rk onitions. Then 2mg of TiO2 se phototlysts ws e to the phenol solution n the mixture ws stirre for 6 min. uner rk onitions. Next visile light irrition ws rrie out using 1W Wolfrm lmp with n emission spetrl rnge from 4 to 8nm. The progress of the retions ws monitore y high performne liqui hromtogrphy HPLC for 36 min. selete for nlysing y Gtn igitl mirogrph (DM) 1.5. Fig.2 is n imge of the inverse fst Fourier trnsform (IFFT) of the selete regulr region in fig.2 otine y Gtn DM (see [12]). Fig.2 is the IFFT profile of the selete region in fig.2 fter msk pplition, whih shows the sping of the oserve lttie plne is..354nm. This vlue is onsistent with the seprtion of (11) plnes of TiO2 ntse. 3. Result n isussions 3.1 Smple hrteriztion Fig.1 presente the XRD ptterns of V oping TiO2 powers. For ll oping smples, the XRD ptterns show only ntse TiO2 peks. (11) Reltive Intensity (.u) 3 Reltive Intensity (.u) thet (Degree) (2) (15) (211) (4) 1 B nm 5 nm 6 2thet (Degree) Figure 1. The XRD ptterns of TiO2 ();.3% () n.5% () V ope smples. The inset shows (11) pek in etil. Trnsmission eletron mirosopy (TEM) ws use to exmine the rystllite/prtile size, the rystllinity n morphology of the smples. TEM oservtion (fig.2) revele tht the prepre smples onsiste of prtiles of 1 3 nm in size. The selete re eletron iffrtion (SEAD) pttern (fig.2 insert) shows the three iffrtion rings, whih re perfetly inexe to the sme position s those from ntse TiO2. Moreover, the HR TEM imges (fig.2) show the regulr struture in the grin, whih is Intensity The verge rystllite size ws lulte using the Sherer s formul giving vlue of out 1nm, whih is in goo greement with the vlue etermine y TEM. In the XRD ptterns, there is one light pek (B) t 31.2 n its intensity is inrese with the V oping ontent. This XRD pek my e relte to the existene of the rookite TiO2 in the smples. A more etile piture of the (11) XRD pek (in the inset) shows systemtilly pek position shift to the higher 2Thet with the inresing vnium oping onentrtion, whih inites vnium inorportion in the ntse TiO2..354nm nm Figure 2. TEM (); SEAD ( inset) n HR TEM () imges of TiO2:.5%V4+ nnoprtiles; () is the imge of inverse fst Fourier trnsform of the selete region in (); n () is the profile of IFFT of the selete region in (), otine from Gtn DM nlysing. Fig.3 presents the Rmn sttering ptterns of unope TiO2 n V ope TiO2. In generl, the Rmn spetrum of TiO2 is hrterize y strong n t 146m 1 (virtion moe Eg), three ns t 396, 517 n 639 m 1 (moes Eg, B1g/A1g n Eg), n wek n t 196m 1 (moe Eg). Nguyen Minh Thuy, Duong Quo Vn n Le Thi Hong Hi: The Visile Light Ativity of the TiO2 n TiO2:V4+ Phototlyst 3

4 Intensity (.u.) e W venumer, m -1 Figure 3. The Rmn spetr of TiO2 () n V ope TiO2 ( e) n their etile Eg 146m 1 Rmn peks (insert). The oserve spetrum showe tht the nnoprtiles were omplete ntse phse. The typil peks of nno ntse TiO2 re light lue shift (out 5 m 1 ) from tht of the ulk smple, whih n e ttriute to the quntum size effet tht omes from the smll prtile size. Detile Eg 146m 1 Rmn peks of unope TiO2 n V ope TiO2 re presente in fig.3 insert. Compre with the unope smple, the Eg virtions t 146 n 197 m 1 presente light lue shift fter V oping, whih inite the vnium inorportion into the TiO2 host lttie. All peks eme wie n slightly unsymmetril fter V oping. In this stuy the lue shift n e srie to the TiO2 lttie struture istortion ue to V oping. This lue shift n e lso prtly ttriute to the oxygen efets (see [9]). The lttie struture istortion ue to V oping n lso e seen in the sorption spetr. Asorne ( h ) ,5 3, 2,5 2, 1,5 1,,5 e Intensity (.u.) W v e n u m e r ( m - 1 ) W ve len gth (n m ), 2,5 3, 3,5 Figure 4. UV Vis sorption spetr of TiO2 () n V ope TiO2 ( e). The optil sorption spetr of TiO2 n V ope TiO2 smples re presente in fig.4. Pure TiO2 (urve ) Photon Energy (ev) e B C 3 D 5 E 7 F 9 B C3 E5 G7 H9 e e exhiite the sorption ege t roun 3.2 ev (38nm), whih orrespone to the n gp of ntse type of TiO2. The V ope TiO2 exhiite the re shift of the n ege n the long tile sorption in the visile light ove 38nm. Compre with the spetrum of unope TiO2 (urve ), the n eges re shifte systemtilly towr smller energy in the ope smples. V opnts in TiO2 host hve een etermine to preferentilly sustitute Ti +4 ions, where one V n six Os onstitute lol symmetry D2 [13,14]. The re sorption shift is ttriute to the hrge trnsfer etween vlene ns to the t2g level of vnium (splitting of 3 oritls of V +4 in otherl TiO2 host [1]), whih lies just elow the onution n [1,13]. The tiling of the sorption n in the ope smples n e ssigne to the hrge trnsfer trnsition from the oritl of V 4+ to the onution n of TiO2 (see [6,7]). The wek sorption n roun 2.5eV (65 7nm) n e ue to the trnsitions of V3 eletrons. Besies the trnsition, the gp sttes introue y V oping were nother importnt reson for the visile light sorption (see [7]). Aoring to ref. [9], the wek sorption n til of unope TiO2 omes from the momentry loliztion of exitons ue to the phonon intertion, n the strong n til of the V ope TiO2 nnoprtiles minly ontriute to the impurities n lttie isorer, whih lso inite the formtion of gp sttes, in orne with the result of the lultion in [13,15]. In the present work, we suppose tht the strong n til in the visile light of V oping TiO2 nnopowers is relte to the trnsition of V 4+ in the host TiO2 n lso to the lttie istortion. The eviene of the V 4+ in host TiO2 n lttie struture istortion ue to V oping n lso e seen y the XPS spetr. Fig 5.. shows the Ti 2p ore level spetr of unope n vnium ope smples. As is well known, the Ti 2p pek splits into Ti 2p3/2 (~459 ev) n Ti 2p1/2 (~464.5 ev) ue to the self oritl oupling effet. For the unope smple, these peks were symmetril, initing tht Ti +4 were minly presente in the unope smple. The Ti 2p pek eme wie n unsymmetril fter V oping, whih my e relte to more oxygen efets fter V oping (it n le to Ti2O3 formtion). Fig 5. illustrtes the O 1s ore level XPS spetr of unope n vnium ope smples. The O 1s pek (~ 53 to 532 ev for unope TiO2) is often elieve to e ompose of severl ifferent oxygen speies, suh s Ti O ons in TiO2 or Ti2O3, hyroxyl groups, C O ons n sore H2O. In the XPS spetr of the ope smple, this pek is roene, whih n e nlyse to three omponents (see fig.5. n ): (i) the min pek (~ 53 ev for unope n ~ ev for ope smples) oul e srie to the lttie oxygen in TiO2 (Ti O Ti); (ii) the light shouler t ev oul e ssoite to surfe hyroxyl (Ti OH) groups ([9,16]); n (iii) for the oping smples there oul e nother pek t ~534 ev of 4 Nnomter. nnotehnol., 212, Vol. 2, Art. 14:212

5 V O groups (see [9]). The lst (V O) pek is inrese with the oping effet. The V oping le to the O 1s pek shifting to higher ining energy, whih inite the O vlene inrese [9]. T i 2 p 3 /2 Ti 3 Intensity Ti T i 2 p 1 /2 Ti 1 nme the otine smples s T1425; T1525; T1625 n T1825, respetively. 3+ unope T io 2 :. 5 V B.E ( e V ) Figure 6. TEM imges of the TiO2:.5% V4+ with ifferent OA solvent: the rtios of TiCl4: OA: C2H5OH re 1:4:2 (); 1:5:2 (); 1:6:2 () n 1:8:2 (). Figure 6 present TEM imges of T1425 (), T1525 (), T1625 () n T1825 (), respetively. The TEM imges showe tht the ifferent OA solvents h n influene on the morphology of the smples. The smples hve rnom spheroi like (,), ui like () or similr ro like () morphologies. The grin size in the smples is lso relte to the onentrtion of the solvent. The proportions TiCl4: OA: C2H5OH of solvents of 1:8:2 () le to the smllest grin size, whih is 1nm. This result my e relte to the polrity of the solvent. As is well known, OA (C17H33COO ) onsists from two prts: the polr prt (COO ) hyrophilous n the other non polr prt (C17H33 ) hyrophoi. Due to the non polr prt, the polrity of the OA solvent is lower thn tht of wter; hene, the grin formtion n e ontrolle y hnging the rtio of C17H33 COO /C2H5OH. The morphology n grin form in the smple relte very losely to the phototlyti tivity of the smple. 3.3 Phototlyti tivity mesurement Figure 5. The Ti 2p () n O 1s () XPS spetr of unope n.5 vnium ope smples; The Gussin fits of O 1s of pure () n.5v ope TiO2 (). 3.2 Influene of the solvent on the struture properties of smples Figure 6 presents TEM imges of.5%v ope TiO2 with ifferent solvents. In this work we use olei i (OA), pk=9.85 [11] n ethnol solvent smples to stuy the solvent effet. The ifferent proportions of the TiCl4: OA:C2H5OH re 1:4:2; 1:5:2; 1:6:2 n 1:8:2. We The phototlysti egrtion of phenol hs een hosen s moel retion to evlute the phototlysti tivities of the otine TiO2 se tlysts. Phenol (C6H5OH) is ommon hemil tht is use extensively in vriety of inustril pplitions. Phenol ws selete s moel pollutnt for the phototlyti oxition experiments. All phenol ilute wter smples were prepre s follows: 8ml (C6H5OH) solution (5.1 5 mol/l) ws stirre in rk onitions. Then 2mg of TiO2 se phototlysts ws e to the phenol solution n the mixture ws stirre for 6 min. uner rk onitions. Next, visile light irrition ws rrie Nguyen Minh Thuy, Duong Quo Vn n Le Thi Hong Hi: The Visile Light Ativity of the TiO2 n TiO2:V4+ Phototlyst 5

6 out using 1W Wolfrm lmp with n emission spetrl rnge from 4 to 8nm. mv 2 Detetor A:275nm min mv Detetor A:275nm min Figure 7. Chromtogrphs of phenol egrtion using TiO2:,5%V uner vis irrition t (over) n 36 min. (elow). Fig.7 presents the hromtogrphs of the phenol egrtion of phenol pollution wter using TiO2:.5%V s phototlysts, whih were reore y HPLC t n 36 min. fter visile irrition. By lulting n ompring the squres of phenol peks (t trent.=5.6 min.) in the hromtogrphs, we otine the phenol egrtion rte (C/Co) in the phototlyti proess. In our work we foun tht unope TiO2 hs phototlyst only uner UV ritive exittion [8]. By using the hyrotherml metho, the optiml vnium oping onentrtion for visile light phototlyst is.5% molr. The photoegrtion of phenol using TiO2:V nnorystls n e expline s follows. The unope TiO2 ntse hs only UV optil n gp (3,2eV), hene it nnot e exite uner visile irrition. The exittion ehviour of V TiO2 uner visile irrition might e relte to V 3 oritl. Due to the ft tht the t2g level of V 3 oritl lies little elow the onution n ege of TiO2 [1,13], eletrons n e exite from the vlene n of TiO2 to the t2g level of V 3 oritl uner visile light irrition (Eqs.(1)), n further migrte to sore O2 to form O 2. Menwhile, holes migrte to the surfe hyroxyl group to proue hyroxyl rils (OH ). Both of O2 n OH n further egre phenol. Thus, phenol ws egre uner visile light irrition. The phototlyti egrtion proesses n e esrie y Eqs. (1) (7). V 4+ ions, ting s oth eletron n hole trps, n turn into V 3+ n V 5+ ions y trpping photogenerte eletrons n holes, respetively (Eqs. (2) n (3)). TiO2 :V (+Visile Light) e +h + (1) V 4+ +e V 3+ (2) V 4+ +h + V 5+ (3) Then, the trppe eletrons n holes re relese (Eqs. (4) n (5)) n migrte to the surfe of TiO2. By epting n eletron, the sore O2 on the surfe of TiO2 is reue to O2 (Eq. (6)), while the surfe hyroxyl group trnsltes into hyroxyl ril (OH ) y epting hole (Eq. (7)). V 3+ V 4+ +e (4) V 5+ V 4+ +h + (5) V 3+ + O2 (s) V 4+ +O 2 (6) V 5+ + OH (s) V 4+ +OH (s) (7) So, the inorportion of V 4+ ions in TiO2 lttie n restrin the reomintion rte of photogenerte eletrons n holes, enhning the phototlyti tivity of TiO2. However, too high V onentrtion (more thn.5%) n le to erese of phototlyti tivity. This tren n e relte to severl effets: (i) if the onentrtion of V 4+ ions is too high, they n eome the reomintion entres of photogenerte eletrons n holes; (ii) the speifi surfe re ereses with the inrese of V onentrtion whih is unfvourle for otining high phototlyti tivity. C/C (%) C/C (%) Irr tio n tim e ( m in.) B - W te r s o lv e n t - O A s o lv e n t Figure 8. Phototlyti phenol egrtion urves of the.5% V ope TiO2 phototlyst prepre with ifferent solvents. Fig.8 esries the phototlysti tivity of the.5%vope TiO2 smples prepre with ifferent solvents. One n see tht the smple prepre with the OA solvent ( urve in fig.8a) exhiite higher phototlysti tivity thn tht with the wter solvent. This tren my e relte to the lower polrity of the OA A Ir r i tio n tim e ( m in.) T T T T Nnomter. nnotehnol., 212, Vol. 2, Art. 14:212

7 solvent; hene the grin size of OA smples is smller. Among the smples prepre with the OA n ethnol solvent (fig.8b), the smple with the proportions TiCl4: OA: C2H5OH of 1:6:2 h the est phototlysti tivity. After 36 min. irrition, the urrent normlize phenol onentrtion erese to 9.%. This result my e relte to the ro like morphology of the smple, whih is shown in the fig.6. The ro like morphology of the smples n le to inresing speifi surfe res, hene improving their phototivity. 4. Conlusions The pure n vnium oping TiO2 nnorystls were suessfully prepre y using hyrotherml methos with ifferent solvents. The oping V onentrtion ws in rnge from.1% to.9%. All otine smples were single ntse rystl phse. The verge rystl size ws out 1 2nm. The vnium ope smples exhiite long tile sorption in the visile light ove 38nm. This n e relte to the hrge trnsfer trnsitions from the oritl of V to the onution n of TiO2 n lttie isorer. The grin form n size re epenent on the polrity of the solvent. Olei i n ethnol n e use for the solvent polrity ontroller; hene, the phototivity properties of the smples n e improve. The phenol egrtion mesurements uner visile light showe tht the.5% vnium ope smple with the proportions TiCl4: OA: C2H5OH of 1:6:2 h the est phototlysti tivity. After 36 min. visile light irrition, the urrent normlize phenol onentrtion erese to 9% (the onentrtion of phenol erese to.3mg/l, whih is less thn the llowle phenol vlue on inustril wste wter y ishrge stnrs). The visile light phototlysti of the mteril suggeste n pplition for n environmentl tretment of wste wter. 5. Aknowlegements The uthors thnk the referees for helpful omments n suggestions. The uthors woul like to thnk the Hnoi Ntionl University of Eution n the Ministry of Eution n Trining (MOET). This reserh is fune y the Vietnm Ntionl Fountion for Siene n Tehnology Development (NAFOSTED) uner grnt numer Referenes [1] W.Choi, A.Termin n M.R. Hoffmnn, The Role of Metl Ion Dopnts in Quntum Size TiO2: Correltion etween Photoretivity n Chrge Crrier Reomintion Dynmis, J.Phys. Chem. 98 (1994) [2] E.Grugnr, J.S.King, S.Jin, C.J.Summers, Y.Zhng Willims n I.C.Khoo, Eletri fiel tuning of the Brgg pek in lrge pore TiO2 inverse shell opls, Phys.Rev.B 72 (25) [3] N.Vn Duy, N.Vn Hieu, P.Thnh Huy, N.Du Chien, M.Thmilselvn, J.Yi, Mixe SnO2/TiO2 inlue with ron nnotues for gs sensing pplition, Physi E: Low imensionl Systems n Nnostrutures, V.41, Iss.2 (28)pp [4] L.Wng n T.Egerton, The effet of trnsition metl on the optil properties n phototivity of nnoprtiulte titnium ioxie, J. of Mterils Siene Reserh v.1, N.4, 212. [5] T.Kmegw, J.Sono, K.Sugimur, K.Mori, H.Ymshit, Degrtion of isoutnol ilute in wter over visile light sensitive vnium ope TiO2 phototlyst, Journl of Alloys n Compouns 486, (29) pp [6] S.Liu, T.Xie, Z.Chen, J.Wu, Highly tive V TiO2 for phototlyti egrtion of methyl ornge, Applie Surfe Siene 255, (29) pp [7] K.Ngveni, M.S. Hege, G. Mrs, Struture n Phototlyti Ativity of Ti1 xmxo2 (M = W, V, Ce, Zr, Fe, n Cu) Synthesize y Solution Comustion Metho, J. Phys. Chem. B.18 (24) pp.224. [8] N.M.Thuy, L.T.H.Hi, T.M.Du n N.T.H.Thnh, A visile light tivity of TiO2 se phototlysts, The 5th Interntionl Workshop on Avne Mterils Siene n Nnotehnology (IWAMSN21) Hnoi, Vietnm Nov. 9 12, 21. [9] B. Liu, X.Wng, G.Ci, L.Wen, Y.Song, X.Zho, Low temperture frition of V ope TiO2 nnoprtiles, struture n phototlyti stuies, J. of Hzrous Mterils 169 (29) pp [1] B.Tin n C.Li, Flme sprye V ope TiO2 nnoprtiles with enhne phototlyti tivity uner visile light irrition, Chem. Engineering J. 29; 151; [11] J.R.Kniky n D.O.Shh, Effet of Degree, Type, n Position of Unsturtion on the pk of Long Chin Ftty Ais, Journl of Colloi n Interfe Siene 256 (22), [12] [13] Y.Wng n D.J. Doren, Eletroni strutures of V ope ntse TiO2, Soli stte Commun. 136 (25) pp [14] Y.Hwu, Y.D.Yo, N.F.Cheng, C.Y.Tung n H.M.Lin, X ry sorption of nnorystl TiO2, Nnostruture Mterils, V.9, I1 8 (1997) Nguyen Minh Thuy, Duong Quo Vn n Le Thi Hong Hi: The Visile Light Ativity of the TiO 2 n TiO 2 :V 4+ Phototlyst 7

8 [15] H.Tng, F.Levy, H. Berger n P.E. Shmi, Urh til of ntse TiO2, Phys.Rev. B 52 (1995) pp [16] J.Zhu, J.Yng, Z. F.Bin, J.Ren, Y. M.Liu, Y.Co, H. X.Li, H. Y.He, K. N.Fn, Nnorystlline ntse TiO2 phototlysts prepre vi file low temperture nonhyroti sol gel retion of TiCl4 n enzyl lohol., Appl. Ctl. B: Environmentl 76 (27) pp Nnomter. nnotehnol., 212, Vol. 2, Art. 14:212