Enhanced Photocatalytic Activity of 3,4,9,10-Perylenetetracarboxylic Diimide Modified Titanium Dioxide Under Visible Light Irradiation

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1 Phototlyti Ativity of Sensitizer/Ti 2 Bull. Koren Chem. So. 2010, Vol. 31, No DI /ks Enhned Phototlyti Ativity of 3,4,9,10Perylenetetrroxyli Diimide Modified Titnium Dioxide Under Visile Light Irrdition Ji Won Kim, * Hee Sung Kim, Kook Hyun Yu, Akir Fujishim, nd Young Soon Kim Deprtment of Chemistry, Dongguk University, Seoul 10071, Kore. * Emil: jwkim1234@dongguk.edu SmMyung Bio Chem Co., Ltd., Chunguk 36392, Kore Kngw Ademy of Siene nd Tehnology, 321 Skdo, Tktsuku, Kwskishi, Kngw , Jpn Reeived August 9, 2010, Aepted August 18, 2010 A method to improve the phototlyti tivity of titnium dioxide y modifition with sensitizer nd metl oxide is proposed. To hieve this gol, we used metl oxides s dopnts. In prtiulr, CW 4 nd Gd 2 2S:T were used euse their 2.6 ev nd 2.2 ev nd gp energy nd optil properties hve lrge positive effet on phototlysis. The improvement in the phototlyti tivity of Ti2 modified with Gd22S:T under ultrviolet light irrdition is desried in previous study. The present work fouses on the sensitiztion of metl oxidemodified Ti 2. Hving oserved the ultrvioletvisile sorption spetr of 3,4,9,10Perylenetetrroxyli diimide in the wide visilelight region from 400 nm to 60 nm nd the rod peks in its photoluminesene spetr t 69 nm nd 717 nm, we deided to use this perylene dye to sensitize modified Ti 2 to enhne its tivity s visilelight hrvesting phototlyst. We lso explored the positive effets thinfilm surfe hnges stemming from ultrviolet pretretment hve on phototlyti tivity. Finlly, we sujeted severl metl oxidemodified Ti 2 produts sensitized y the perylene dye to ultrviolet pretretment, otining the most tive phototlysts. Key Words: Titnium dioxide, Ti 2, Phototlyst, Sensitizer, 3,4,9,10Perylenetetrroxyli diimide Introdution With inresing lls for lener environment, phototlyti pplitions used y industry re ttrting renewed interest. For exmple, mny onerned sientists see deomposition of orgni pollutnts y phototlysis s one wy to hieve the gol of n eofriendly eonomy. And nother dvntge of phototlyti tehnology is tht it n e very ost effetive euse sunlight n e used s n energy soure. 1 Semiondutor mterils, suh s Ti 2, Zn, Sn 2, CdS, GP, nd W 3, re pplied in phototlysis. Among them, Ti 2 is the most populr for this purpose euse it is nontoxi, hemilly stle, inexpensive, nd very effiient. In ft, Ti 2 phototlysts re frequently employed in environmentl lenups. However, their phototlyti tivity is restrited y the wide nd gp of Ti 2 (3.03 ev for rutile nd 3.18 ev for ntse) nd fst eletronhole reomintion. 69 Ti 2 n sor only out 3% 4% of solr light in the ultrviolet, or UV, region. To inrese the mount of visile light (to out 4%) Ti 2 sors from the sun, reserhers re working on the development of Ti 2 visilelight hrvesting phototlysts. 10 The visilelight sensitivity of Ti 2xN x is result of the nrrowing of the nd gp y mixing the 2p sttes of nitrogen nd 2p sttes of oxygen.,11 In semiondutor phototlysis the visile or UV light forms eletrons nd holes in the semiondutor mteril, whih re essentil to the tlyti retions. We investigted metloxide doping euse of its ility to nrrow the nd gp. Under UV light irrdition, the phototlyti tivity of metl oxidemodified Ti 2, or Ti 2 /metl oxide, ws 13% 3 % higher thn tht of Ti 2 (P2) under UV light irrdition; however, the tivity ws still low under visile light ( 400 nm) irrdition. This mkes prtil use diffiult. We ddressed these drwks y sensitizing Ti 2/ metl oxide to otin visilelight hrvesting phototlyst. The fluoresent dye 3,4,9,10Perylenetetrroxyli diimide or PTCDI ws used s the sensitizer euse of its high therml stility nd photostility. PTCDI is used extensively s n industril pigment, nd its derivtives re effetive ntype orgni semiondutors with vrious pplitions. For exmple, they re used s tunle lser dyes, lighthrvesting mterils, trnsistors, solr ells, nd optoeletroni devies, suh s lightemitting diodes, euse of their unique optil nd eletrohemil properties. 12,13 In the present work, we report the enhned phototlyti tivity under visilelight irrdition of metl oxidemodified Ti 2 sensitized with PTCDI. We lso propose n effiient method for the preprtion of phototlyst thin film. Experimentl Mteril. Titnium dioxide powder (Deguss, P2) ws used s the phototlyst se mteril. It ws omposed of 80% ntse nd 20% rutile, with speifi surfe re of BET 60 ± m 2 g 1. The metl oxides were Ag 2, CW 4, Fe 2 3 (Aldrih Co.,USA; nlyti regent grde), nd Gd 2 2S:T. 3,4,9,10 Perylenetetrroxyli diimide (Tokyo Chemil Industry Co., first grde regent) ws used s the sensitizer. Ethnol (Wko Chemil, USA) ws used s the dispersion medium. The thinfilm sustrte ws petri dish (8.6 m 1.7 m). Methylene lue nd formldehyde (Aldrih Co., first grde regent) were used s is. Wterorne polyurethne dispersion (SmMyung Biohem Co., Kore, ph 7, M.W 8000, MTU06) ws used s inder. We used furne (Muffle112, Dongyng Siene Co.) to prepre the Ti 2/metl oxide. The thin films were prepred y spry oting (NCF 03CC, Air Mker, Kore) under pre

2 280 Bull. Koren Chem. So. 2010, Vol. 31, No. 10 Ji Won Kim et l. ssure of 7 r. The speifi surfe re ws mesured y BET (ASAP 2020, Miromeritis Ins., USA). The sorne of methylene lue ws investigted y ultrvioletvisile, or UVvis, spetrophotometry (DT 1000 CE, en optis In., USA), nd the deomposition rte of the formldehyde ws mesured y gs hromtogrphy (HP 6890 Series, USA). Sensitiztion of Ti 2 thin films g of PTCDI ws dded to Ti 2 nd Vortex mixer ws used to mix them for minutes. At this point the speifi surfe re rtio of the PTCDI to Ti 2 ws BET % 10%. Distilled wter (60 ml) s solvent ws dded to the mixture, whih ws stirred t room temperture for 16 hrs. The wter ws removed y drying the mixture for 22 hr in n oven (HST01VS, HST Co.) t 120 o C. Preprtion of the Ti 2 /metl oxide ws ording to our previous study, 14 with 0.00 g of metl oxide dded to 0.04 g ( 10 4 mol) of Ti 2. Using the identil proedure desried ove, we sensitized the Ti 2/metl oxide nd linted it t 400 o C for 4 minutes. Ethnol (1 ml) ws dded to eh of the powder mixtures s dispersnt nd then wterorn polyurethne ws dded to the dispersed solutions, fter whih they were sonited for 1 hr. The wterorn polyurethne ted s inder, immoilizing Ti 2 prtiles nd preventing the degrdtion of phototlyti potentil. Thin films were prepred from the dispersed solutions y spry oting tehnique. Phototlyti tivity mesurements. The phototlyti tivity of eh smple, inluding the PTCDImodified Ti 2, ws determined y the hnge in sorne. The hnge in sorne ws determined y mesuring the perent of deolortion of queous methylene lue solution y phototlysis. The phototlyst thin films were oted with 40 µm of queous methylene lue solution nd pled under UV utoff filter (N169 (400 nm )). Visile light ws irrdited with two fluoresent light lmps (20 W, 380 nm, 9 W/m 2 ) pled t distne of 20 m. During hr period, we took sorne mesurements one n hour. The photodegrdtion of formldehyde ws mesured y the method desried erlier. 14 We dded 0.1 M formldehyde to the phototlyst thin films nd mesured its deomposition rte during 2hr period of visilelight irrdition. Chrteriztion of thin film trnsmittne nd phototlyti tivity. Phototlyti tivity nd trnsmittne were mesured for eh of the thinfilm otings, whih were numered from 1 through 20. The mesurements, y UVvis spetrophotometry, disolored the methylene lue. Chrteriztion of UV pretretment effet. UV pretretment ws strted when the phototlyti tivity ws t its highest level. An erlier investigtion of hr through 28 hr of tivity showed the 16th hr to e optimum. UV pretretment ws rried out using two lk lmps (Snkyo denki lk light lue (20 W, 32 nm, 16 W/m 2 )) pled t distne of 1 m. Chrteriztion of photoluminesene. Mesurement of the photoluminesene of the sensitizermodified Ti 2/metl oxide ws performed s desried previously. 14 Results nd Disussion Asorption spetrum of 3,4,9,10perylenetetrroxyli Asorne HN Moleulr Weight : g/mol Wvelength (nm) Figure 1. The hemil struture nd UVvis spetrum of 3,4,9,10 perylenetetrroxyli diimide. NH Moleulr Weight: g/mol diimide. The level of phototlyti tivity of phototlyst depends on the numer of exited eletrons reted y the energy supplied. If the intensity of the supplied energy equls n intensity within the visilelight region, the phototlyst might e tive under visilelight irrdition. Sensitiztion n improve performne y expnding phototlyti tivity to the visilelight region. The hemil struture nd UVvis spetr of the sensitizer, PTCDI, re shown in Figure 1. Sine the UVvis sorption spetr of PTCDI re in the wide visilelight region (400 nm 60 nm), we expeted sensitiztion to enhne the tivity of visilelight hrvesting phototlysts. Moreover, PTCDI displys high degree of photostility, mking it even more effetive. Thin film trnsmittne nd methylene lue deolortion rte. The most importnt onsidertion in the preprtion of phototlyst thin films is how to effiiently optimized the phototlyti tivity. Although Ti 2 phototlyst powders hve identil properties, signifint differenes in phototlyti tivity rise mong them euse of vritions in the mount of Ti 2 dispersed in solution or the thikness of their thin films. Vrious methods re used to prepre thin films, inluding spry oting, dip oting nd spin oting. In the present study, we used spry oting, euse it is effetive regrdless of the hrteristis of the thinfilm sustrte. A oting speed of 2.0 ± 0.0 m/se ws dhered to s losely s possile. Figure 2 onfirms tht this oting tehnique optimized the thinfilm phototlyti tivity. Although inder in the dispersed solution deresed thinfilm trnsmittne, the deolortion rte of methylene lue indites tht phototlyti tivity did inresed (Figure 2). This result is explined y the ft tht phototlysis ours t the surfe of the thin films. Inresing the numer of otings enhnes phototlyti tivity euse of the dense distriution of phototlyst prtiles (Figure 3). But, exessive oting numer use the disturne of phototlyti tivity y inresed inder mount. For the reson, Eight otings showed the highest methylenelue deolortion rte, nd this numer mintined the trnsmittne of the thin films t more thn 8%. UV pretretment effet. The degree of unsturtion of surfe onds effets the photohydrophiliity of thin films. UV irrdition n produe hydroxyl groups, promoting photo

3 Trnsmittne (%) 100 Bull. Koren Chem. So. 2010, Vol. 31, No Seleted oting numer Deolortion rte of methylene lue (%) Phototlyti Ativity of Sensitizer/Ti2 Coting numer Figure 2. Reltions with thin film trnsmittne nd deolortion rte of methylene lue. Inresing the numer of oting, deolortion rte of methylene lue mens phototlyti tivity inrese to ertin portion ompred with deresed trnsmittne of thin film. (A) (B) Figure 3. Mirogrph of thin film surfe (Video mirosope (SV3, Someteh Co. ( 600))). (A) Chrterized Ti2 thin film with oting numer 1, (B) Chrterized Ti2 thin film with oting numer 8. Inresing the numer of oting, distriution of the Ti2 phototlysts prtiles is densely pked. hydrophiliity. This hnge on the thinfilm surfe inreses the numer of wter moleules sored on the surfe. The UVvis spetr, whih shifted to the shorter wvelength fter UV irrdition, indited the photohydrophiliity of the Ti2 1 thin films. This onfirmed the positive effet UV pretretment 281 hd on phototlyti tivity. Also, the inresed rte of deolortion of methylene lue y UV pretretment of the Ti2/ metl oxide thin films ws onfirmed, showing tht UV pretretment improved their phototlyti tivity. For Ti2 (P2), the deolortion of methylene lue inresed y perentge points, from 4.88% to 29.14% s result of UV pretretment. And the phototlyti tivity of the other Ti2/metl oxide thin films inresed y perentge points (Tle 1). The tivity of the PTCDImodified Ti2 inresed y 4.77 perentge points, from 36.73% to 41.0% s result of UV pretretment. And UV pretretment inresed the tivity of the PTCDImodified Ti2/metl oxide y perentge points (Tle 2). However, fter UV light irrdition, the phototlyti tivity of the Ti2 /Gd22S:T deresed despite PTCDI modifition. Perhps, this phenomenon n e explined y the disturne reted etween lterntions in the hrteristis of the thinfilm surfe nd the trnsition of n eletron from D3 stte to the ondution nd or to the D4 level in the identil nioni environments of the T3+ ion.14 Further theoretil study is neessry to eluidte the reson for the lower phototlyti tivity of Ti2 /Gd22S:T fter UV pretretment. Photodeolortion of methylene lue solution. Before mesuring phototlyti tivity, we ompred the initil sorne of the queous methlyene lue solution with its finl sorne fter phototlysis. Next, we ompred the results of the photodeolortion rte of methylene lue (%) shown in Tle 1 nd Tle 2. Tle 1 shows the phototlyti tivity of Ti2 (P2) nd Ti2/metl oxide. Ti2 (P2) ws nerly phototlytilly intive, ut the tivity of Ti2/metl oxide inresed y perentge points under visile light. In prtiulr, euse of their lower nd gp energy (2.6 ev nd 2.2 ev) CW4 nd Gd22S:T showed inresed phototlyti tivity ompred with the other metl oxides. In ddition, the ehvior of Gd22S:T ws gretly influened y its optil properties, suh s the trnsition of n eletron from the D3 stte to the ondution nd or to the D4 level in the 3+ identil nioni environments of the T ion. Tle 2 shows the phototlyti tivity of Ti2 sensitized with PTCDI. Tle 1. Confirmtion of the UV pretretment effet on metloxide modified Ti2 thin film Smple Non UV pretretment UV pretretment Photodeolortion of 1st order rte onstnt Phototlyti MB y visile light for photodeolortion degrdtion of sorption (%) formldehyde y GC (%) Photodeolortion of 1st order rte onstnt MB y visile light for photodeolortion sorption (%) Ti2 (P2) Ti2/Ag ± ± ± ± 0.23 Ti2/Fe ± ± ± ± 0.26 Ti2/CW ± ± ± ± 0.30 Ti2/Gd22S:T ± ± ± ± Derese in onentrtion (%), Rte onstnt ( 10 M hr ), Perentge of phototlyti degrdtion (%).

4 282 Bull. Koren Chem. So. 2010, Vol. 31, No. 10 Ji Won Kim et l. Tle 2. The enhned phototlyti tivity of metloxide modified Ti 2 fter sensitiztion with 3,4,9,10perylenetetrroxyli diimide nd onfirmtion of the UV pretretment effet Smple Ti 2 (P2) Ti 2/Ag 2 Photodeolortion of MB y visile light sorption (%) Non UV pretretment 1st order rte onstnt for photodeolortion Phototlyti degrdtion of formldehyde y GC (%) Photodeolortion of MB y visile light sorption (%) UV pretretment 1st order rte onstnt for photodeolortion ± ± ± ± ± ± 0.32 Ti 2/Fe ± ± ± ± 0.41 Ti 2/CW ± ± ± ± Ti 2/Gd 2 2S:T 9.02 ± ± ± ± 0.22 Derese in onentrtion (%), Rte onstnt ( 10 2 M hr 1 ), Perentge of phototlyti degrdtion (%). Compred with Tle 1, the phototlyti tivity of PTCDImodified Ti 2 is 31.8 perentge points higher thn tht of Ti 2 (P2). Furthermore, the tivity of PTCDImodified Ti 2/ metl oxide inresed y 7.67% 24.3% ompred with tht of Ti 2 /metl oxide. These results represent n improvement in phototlyti tivity through PTCDI nd metloxide modifition. The UVvis sorption spetr with PTCDI s sensitizer were oserved in the wide visilelight region, nd PTCDI properties, suh s high fluoresene quntum yields in solution (Φ F 9%), hemil inertness, nd photohemil stility, hd positive influene on phototlyti tivity. 16 Kinetis of photodeolortion for methylene lue through the 1st order rte onstnt. Tle 1 nd Tle 2 give the firstorder rte onstnts for the photodeolortion of methylene lue. These results were otined y lulting the orreltion etween the length of time of visilelight irrdition nd the deresing rtio of methylene lue. This orreltion is desried with the following eqution, using the firstorder rte onstnt (k) k = ln(c/c 0) / (t t 0) (1) C 0 is the initil onentrtion of methylene lue solution nd C is its onentrtion fter phototlysis. t t 0 is the time for phototlysis to proeed. The firstorder rte onstnt (k) shows liner reltionship with the photodeolortion of methylene lue solution. This shows tht the phototlysis rte vries with the type of prepred thin film. In the se of non UVpretretment, eh of the firstorder rte onstnts of PTCDImodified Ti 2 nd PTCDImodified Ti 2/metl oxide inresed ± M hr 1 more thn the rte onstnts of Ti 2 (P2) nd Ti 2/metl oxide inresed, whih ws ± M hr 1. And, the firstorder rte onstnts of the UV pretreted thin films showed more improvement thn the onstnts of the non UV pretreted thin films regrdless of PTCDI sensitiztion. Finlly, the present work shows tht mong the severl metl oxides studied, Ti 2/metl oxide pretreted with UV nd sensitized with PTCDI ws the kinetilly superior phototlyst. Photodegrdtion of formldehyde. The photodegrdtion of formldehyde ws studied with referene to the sik house syndrome, phrse used to desrie sitution in whih the residents of house eome ill nd their illness is linked to the house s ir qulity. Formldehyde is often ited s one use of suh mlise. ur investigtion ws performed in the drk euse of the low photostility of formldehyde. The deomposition rtes of formldehyde were mesured y gs hromtogrphy. In the proedure, 13.2 M queous formldehyde ws diluted to 0.1 M followed y phototlyti degrdtion for 2 hrs under visilelight irrdition. Tle 1 shows the effet of UV pretretment. The photodegrdtion of formldehyde with Ti 2 (P2) is negligile, 2.29%. Photodegrdtion with Ti 2/metl oxide is 11.8% 31.8% higher thn with Ti 2 (P2). Sensitiztion of Ti 2 (P2) with PTCDI inreses phototlyti degrdtion with Ti 2 (P2) from 2.29% (Tle 1) to 20.7% (Tle 2), onfirming the sensitizer effet. The phototlyti tivity of PTCDImodified Ti 2/metl oxide is.73% 30.18% higher thn tht of Ti 2/metl oxide. These results show different tendenies with respet to the deolortion of methylene lue, ut improved phototlyti tivity with CW 4, Gd 2 2 S: T, nd PTCDI is onfirmed. Photoluminesene spetr of sensitizermodified Ti 2 powders. Figure 4 shows the photoluminesene spetr of Ti 2/Gd 2 2S:T nd PTCDImodified Ti 2 under exittion t 24 nm. Definitions nd the orreltion of the phototlyti tivity of Ti 2 /Gd 2 2 S:T with its photoluminesene spetr re given in the previous study. 14 The pek of the photoluminesene spetr of Ti 2 (P2) is loted ner 490 nm; the PTCDI pek, inluding the lower shoulder pek, is loted ner 69 nm. The deteted emission pek in the longer wvelength orresponds to the virtion modes in PTCDI (~ m 1 ). This mens PTCDI modifition ws rried out suessfully nd it enhned phototlyti tivity. 17 The shpe of the photoluminesene spetrum of PTCDI is very similr to the shpe of the UVvis spetrum. The min pek nd lower shoulder pek

5 Phototlyti Ativity of Sensitizer/Ti 2 Bull. Koren Chem. So. 2010, Vol. 31, No PL intensity (. u.) 8.00E E E+0.00E E E E E+0 Ti 2/Gd 2 2S:T Ti E Wvelength (nm) TTi 2 TTi 2/PTCDI TTi 2/Gd 2 2S:T/PTCDI TTi2/Gd22S:T PPTCDI Ti 2/PTCDI Ti2/Gd22S:T/PTCDI PTCDI Figure 4. Photoluminesene spetr of Ti 2 (P2)/3,4,9,10perylenetetrroxyli diimide modified Ti 2/3,4,9,10perylenetetrroxyli diimide nd Gd22S:T modified Ti2/Gd22S:T modified Ti 2/3,4,9,10perylenetetrroxyli diimide (PTCDI) (T = R.T., s.r = 10 se 1 ). of the photoluminesene spetr of PTCDImodified Ti 2 were deteted t 69 nm nd 717 nm y ompring the PTCDI spetr with tht of Ti 2 (P2). This mens tht PTCDImodified Ti 2 sors visile light nd emits light in the longer wvelength of 69 nm. This shows tht its phototlyti tivity s visilelight hrvesting phototlyst improved. In the photoluminesene spetr of PTCDImodified Ti 2/Gd 2 2S:T, the PTCDI pek is high ner 69 nm ompred with tht of Ti 2/Gd 2 2S:T, whih is nerly flt. Furthermore, the photoluminesene spetr of PTCDImodified Ti 2/Gd 2 2S:T inlude pek t 480 nm nd t 4 nm. The highest phototlyti tivity (9.02 ± 0.31%, Tle 2) shows the modifying effet of PTCDI nd Gd 2 2S:T. verll, the results in Tle 2 show tht phototlyti tivity n e gretly inresed y PTCDI nd metl oxide. Conlusions We hve shown here tht Ti 2 sensitized with the dye 3,4, 9,10Perylenetetrroxyli diimide out performs Ti 2 (Deguss, P2) in phototlyti tivity nd lso ts s visilelight hrvesting phototlyst. The se of Ti 2 modified with Gd 2 2S:T nd then further modified with 3,4,9,10Perylenetetrroxyli diimide illustrtes the gins in phototlyti tivity hieved y this proess. This study points the wy to the ommeriliztion of lighthrvesting phototlyst through thin film optimized for phototlyti tivity nd trnsmittne. The UVvis sorption spetr of PTCDI were oserved in the wide visilelight region (400 nm 60 nm). Its min pek nd lower shoulder pek were oserved t 69 nm nd 717 nm in the photoluminesene spetr. These results support our onlusion tht PTCDI improves the phototlyti tivity of semiondutor mterils, resulting in visilelight hrvesting phototlyst. Also, we onfirmed tht UV pretretment enhnes phototlyti tivity. UV pretretment used drsti hnges on the thin film surfe, susequent to whih the thin film exhiited super hydrophiliity, property tht hs lrge positive effet on phototlyti tivity. However, in one se tht devited from the oserved trend, the tivity of the Gd 2 2S: Tmodified Ti 2 deresed fter UV light irrdition. Perhps, this is relted to disturnes reted y the intertion etween hrteristi hnges in the thin film surfe nd the optil properties of Gd 2 2S:T. Further study is needed to explin this pprent nomly. Aknowledgments. The uthor would like to thnk KAST (Kngw Ademy of Siene nd Tehnology) phototlyst lortory reserher for help nd guidne during nd lso muh useful informtion. Referene 1. Fujishim, A.; Ro, T. N.; Tryk, D. A. J. Photohem. Photoiol. C 2000, 1, Mine, T.; Tryk, D. A.; Swunym, P.; Kikuhi, Y.; Hshimoto, K.; Fujishim, A. J. Photohem. Photoiol. A 2000, 137, Nguyen, V. N. H.; Aml, R.; Beydoun, D. Chem. Eng. Si. 2003, 8, Colón, G. et l., J. Photohem. Photoiol. A 2006, 179, 20.. Morikw, T.; Irokw, Y.; hwki, T. Appl. Ctl. A 2006, 314, Try, B. Int. J. Photoenergy. 2008, 2008, Ding, H.; Sun, H.; Shn, Y. J. Photohem. Photoiol. A 200, 169, Ajito, K.; Sukmto, J. P. H.; Nghr, L. A.; Hshimoto, K.; Fujishim, A. J. Eletronl. Chem. 199, 386, Zhng, X.; Udgw, K.; Liu, Z.; Nishimoto, S.; Xu, C.; Liu, Y.; Ski, H.; Ae, M.; Murkmi, T.; Fujishm, A. J. Photohem. Photoiol. A 2009, 202, Li, D.; Hung, H.; Chen, X.; Chen, Z.; Li, W.; Ye, D.; Fu, X. J. Solid Stte Chem. 2007, 180, Irie, H.; Wtne, Y.; Hshimoto, K. J. Phys. Chem. B 2003, 107, Brohsztin, S. et l., Miroporous Mesoporous Mter. 2007, 102, Ko, H. C.; Kim, S.; Choi, W.; Moon, B.; Lee, H. Chem. Commun. 2006, Kim, B. G.; Lee, H. G.; Kim, H. S.; Kim, Y. S. Bull. Koren. Chem. So. 2009, 30, Liu, B.; Wen, L.; Zho, X. Appl. Surf. Si. 2008, 2, Jnssen, R. A. J. et l., J. Phys. Chem. A 2008, 112, Djurisi, A. B. et l., Adv. Funt. Mter. 2008, 18, 66.