Photocatalytic Bactericidal Efficiency of Ag Doped TiO2/Fe3O4 on Fish Pathogens under Visible Light

Research ArticlePhotocatalytic Bactericidal Efficiency of Ag Doped TiO2Fe3O4on Fish Pathogens under Visible Light

Ekkachai Kanchanatip12 Nurak Grisdanurak3 Naichia Yeh4 and Ta Chih Cheng5

1 International Postgraduate Program in Environmental and Hazardous Waste Management Chulalongkorn UniversityBangkok 10330 Thailand

2National Center of Excellence for Environmental and Hazardous Waste Management Chulalongkorn UniversityBangkok 10330 Thailand

3Department of Chemical Engineering Faculty of Engineering Thammasat University Bangkok 12120 Thailand4Center of General Education MingDao University Changhua 52345 Taiwan5Department of Tropical Agriculture and International Cooperation National Pingtung University of Science and TechnologyPingtung 91201 Taiwan

Correspondence should be addressed to Nurak Grisdanurak gnurakengrtuacth and Ta Chih Cheng chengtachihgmailcom

Received 22 February 2014 Revised 27 April 2014 Accepted 8 May 2014 Published 27 May 2014

Academic Editor Hong Liu

Copyright copy 2014 Ekkachai Kanchanatip et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

This research evaluates photocatalytic bactericidal efficiencies of Ag-TiO2Fe3O4in visible light using target pollutants that include

Aeromonas hydrophila Edwardsiella tarda and Photobacterium damselae subsp piscicida The investigation started with Ag-TiO2Fe3O4synthesis and calcination followed by a series of product tests that include the examination of crystallite phase light

absorption element composition morphology and magnetic properties The results of the experiment indicate that Ag and Fe3O4

significantly enhanced the light absorption capacity of TiO2in the entire visible light range The Ag-TiO

2Fe3O4prepared in

this study displays significantly enhanced visible light absorption and narrowed band gap energy The magnetic property of Ag-TiO2Fe3O4made it easy for retrieval using a permanent magnet bar The photocatalytic activity of Ag-TiO

2Fe3O4remains above

85 after three application cycles which indicates high and favorable efficiency in bactericidal evaluation The experiments haveproved that the Ag-TiO

2Fe3O4magnetic photocatalyst is a promising photocatalyst for antibacterial application under visible light

1 Introduction

Bacterial pathogens are a main cause of fish mortalities incultured fish and occasionally in wild fish As facultativepathogen exists for both fish and human [1 2] humaninfections caused by pathogens transmitted from fish oraquatic environment are quite general Such infection variesby seasons dietary habits and the immune system statusof the exposed individual Traditional methods such aschlorination are chemical intensive and have many disad-vantages For example chlorine used in water treatmentfor disinfection can react with organic material to generatecarcinogenic chloroorganic compounds Moreover certainpathogens bacteria and protozoans have been known to beresistant to chlorine disinfection [3]

Applications of photocatalytic processes are viable solu-tions to environmental problems Heterogeneous photocat-alytic oxidation (PCO) has been proposed as one of theadvanced oxidation techniques for mineralization of hydro-carbon pollutants PCO helps to create strong oxidationagents that breakdown organics to CO

2in the presence of

the photocatalyst H2O and light Heterogeneous systems

also have the advantages of minimal waste generation andreusability of catalysts

TiO2 one of the most promising semiconductor pho-

tocatalysts for removing pollutant and cleaning water is oflow cost nontoxic and physically and chemically stableTiO2particles are both photocatalytic and antimicrobial [4]

Anatase TiO2is superior to rutile and brookite for organic

compound removal However its wide band gap (32 eV)

Hindawi Publishing CorporationInternational Journal of PhotoenergyVolume 2014 Article ID 903612 8 pageshttpdxdoiorg1011552014903612

2 International Journal of Photoenergy

allows it to be activated only by UV Also the high rateof electron-hole (eminus-h+) recombination in TiO

2particles

results in low photocatalytic efficiency Doping TiO2with

various transition metal ions narrows the band gap [5] andexpands the photoresponse of TiO

2into visible spectrum

[6] Also electron transfer between those metal ions andTiO2can alter eminus-h+ recombination as the metal ions are

incorporated into the TiO2lattice Feng et al [7] have studied

the antibacterial mechanism of Ag+ on bacteria and foundthat Ag+ deprives DNA moleculesrsquo replication abilities Inaddition Ag+ increases visible light absorption and holds upthe eminus-h+ recombination of TiO

2

Many of the particles used in the separation technologyare superparamagnetic which can be magnetized with anexternal magnetic field and redispersed upon the removalof magnet [8 9] For example the magnetic property Fe

3O4

helps to enhance the recovery of the catalyst via externalmagnetic fieldMagnetic Fe

3O4particles suspended in carrier

fluids are referred to as magnetic fluids Additionally Fe3O4

also enhances the visible light absorptionwhich resulted fromthe band gap reduction [10]

2 Materials and Methods

21 Materials The chemicals used in this study includetitanium (IV) isopropoxide (98 Acros Organics) isopropylalcohol (999 Carlo Erba) acetylacetone (995 Carlo-Erba) silver nitrate (998 Sigma-Aldrich) ferric chlorideanhydrous (98 Katayama Chemical Inc) ferrous chloride(97 Katayama Chemical Inc) and sodium hydroxide (97Katayama Chemical Inc) These chemicals are analyticalreagent grades and used without further modification

22 Synthesis of Ag-TiO2Fe3O4 The Ag-TiO

2Fe3O4mag-

netic photocatalyst was synthesized in two steps First mag-netite (Fe

3O4) nanoparticles were synthesized via coprecip-

itation method in which FeCl3anhydrous and FeCl

2sdot4H2O

salts in the molar ratio of 2 1 were dissolved and vigorouslystirred in double-distilled water NaOH was then droppedslowly into the solution until a large amount of black precipi-tates formedThe resulting precipitates were collected using amagnet and washed several times with double-distilled waterand ethanol The reaction in this process is as follows

2FeCl3+ FeCl

2+ 8NaOH 997888rarr Fe

3O4+ 8NaCl + 4H

2O (1)

In the second step Ag-TiO2Fe3O4composite particles

were prepared using modified sol-gel method Acetylacetone(Acac) as a chelating agent was added into isopropyl alcoholand stirred magnetically Titanium isopropoxide (TTIP) wasthen added gradually to the mixture with Acac IPA TTIPin molar ratio of 284 2364 1 An appropriate volume ofaqueous silver nitrate was added to the titanium solutionto attain 1 wt of Ag on TiO

2and stirred vigorously for

30 minutes Meanwhile Fe3O4particles were dispersed in

isopropyl alcohol and sonicated in an ultrasonic apparatusfor 10 minutesThereafter slowly add the mixture of Ag-TiO

2

into Fe3O4suspension with TTIP Fe

3O4ratio of 10 (weight

basis) and stir the mixture at room temperature for 3 hours

to ensure uniform compositionThe obtained suspensionwasplaced in a hot air oven at 90∘C for the particles to dry Finallythe composite particleswere calcinated in oxygen at 450∘C for3 hours to form Ag-TiO

2Fe3O4

23 Characterization of Ag-TiO2Fe3O4 The properties of

Ag-TiO2Fe3O4magnetic photocatalyst were characterized

with various instruments The crystal structure of the par-ticles was characterized with X-ray diffraction (XRD) on aBruker AXS diffractometer with CuK120572 radiation The X-raywas generated with a current of 40mA and a potential of40 kV in angular range (2120579) from 10∘ to 80∘ The UV-Visiblediffuse reflectance spectra in the range of 320ndash800 nm wereacquired from a Hitachi U3501UV-visible diffuse reflectancespectrophotometer (UV-Vis DRS) equipped with integratingsphere Pure BaSO

4powder was used as a reflectance stan-

dard Transmission electron microscopy (TEM) observationof the samples was performed on a HITACHI 7500 transmis-sion electron microscope operated at 80 kV The magnetiza-tion of photocatalyst was measured using superconductingquantum interference device (SQUID)

24 Evaluation of Photocatalytic Bactericidal Activities Theresearch team has evaluated photocatalytic bactericidal activ-ities using modified antibacterial drop test In order todifferentiate the effect of TiO

2and silver the experiment was

conducted both under visible light and in dark to block pho-tocatalytic process to assure that the bactericidal activity isexclusively from silver Fish pathogens used in the experimentincluded Aeromonas hydrophila (BCRC13018) Edwardsiellatarda (BCRC10670) and Photobacterium damselae subsppiscicida (BCRC17065) Bacterial cells were collected viacentrifugation at 9500 rpm for 10 minutes to remove super-natants The pellets were then rinsed twice with 15mL phos-phate buffer saline (PBS 137mM sodium chloride 10mMphosphate 27mM potassium chloride pH 74) Ten mLof pathogens in PBS was added to each 6 cm diametersterilized glass Petri dish containing various amounts of Ag-TiO2Fe3O4and irradiated with visible fluorescence light

(FL40SsdotN-EDLsdotNU MitsubishiOsram Japan 120582 gt 420 nm1040 lux) for various time intervals The control groupswere without photocatalyst All control and experimentalgroups had 3 replicates At each time interval 20120583L of suchsolution was transferred from each Petri dish to 96-wellplate containing 180 120583L of 005 235-triphenyl tetrazoliumchloride (TTC) and incubated at 28∘C for 10 hours Theabsorbance of each tube at 540 nmwasmeasured with ELISAreader after adding 50 120583L of isopropanol to the tubes toterminate reaction [11]

The inhibition efficiencies to fish pathogen were calcu-lated as

[Abs]119894 minus [Abs]119905[Abs]119894

times 100 (2)

where [Abs]119894is the absorbance of control group at certain

time interval and [Abs]119905is the absorbance of experimental

group at the same time interval

International Journal of Photoenergy 3

20 25 30 35 40 45 50 55 60 65 70 75 80

Inte

nsity

(au

)

P25 TiO2

Ag nanoparticlesFe3O4

Ag-TiO2Fe3O4

2120579 (deg)

Figure 1 XRD spectra of Ag-TiO2Fe3O4

3 Results and Discussion

Figure 1 displays the XRD patterns of P25 TiO2 Fe3O4

and Ag-TiO2Fe3O4 The main peaks of Ag-TiO

2Fe3O4are

present at 253 38 48 and 54∘ corresponding to (101)(004) (200) and (211) planes of TiO

2 respectively (JCPDS

number 21-1272) With no evidence of its correspondenceto the rutile phase the patterns correspond to the anatasephase exclusively at the calcination temperature of 450∘CThese results help to conclude that the presence of theiron oxide has no accelerating effect on the anatase-rutilephase transformation of the TiO

2 In addition there is no

characteristic peak of Ag presented in the pattern whichimplies that the amount of Ag particles is not adequate topresent their characteristic patterns [12 13] The pattern ofFe3O4does not appear in the XRD which may indicate that

Fe3O4is encapsulated by Ag-TiO

2 However the broadened

patterns suggest that Ag+ doping suppresses the growth ofTiO2crystals

The average crystallite size (119863) of catalyst is estimatedusing Scherrerrsquos equation

119863 =

119896120582

120573 cos 120579 (3)

where 119863 is crystallite size (nm) 119896 is crystallite shape factor(090) 120582 is X-ray wavelength for CuK120572 (015418 nm) 120573 isthe full-width-half-maximum (FWHM) of the peak and 120579 isBragg angle

The crystallite size can be measured via the diffractiondata in Figure 1 according to the Scherrer equation for thepeak at 253∘ The estimated size is about 1253 nm

Figure 2 shows the influence of Ag and Fe3O4on the

UV-Visible light absorption Fe3O4slightly enhances the

visible light absorption of TiO2 With the modification of

Ag the shifting of Ag-TiO2absorption spectrum to longer

wavelengths is noticeable which is due to the interactionbetween Ag and TiO

2matrix In addition Ag-TiO

2Fe3O4

demonstrates significantly higher absorption in the 400ndash800 nm range

0

02

04

06

08

1

12

14

16

325 375 425 475 525 575 625 675 725 775

Abso

rban

ce

Wavelength (nm)

P25 TiO2

TiO2Fe3O4

Ag-TiO2

2Fe3O4Ag-TiO

Figure 2 UV-Vis diffuse reflectance spectra for the as-synthesizedsamples

Table 1 Estimated band gap energy of as-synthesized samples

Sample Band gap energy(eV) Band edge wavelength (nm)a

TiO2Fe3O4 29 428Ag-TiO2 27 460Ag-TiO2Fe3O4 235 528a119864bg = ℎ119888120582

As shown in Figure 3 UV-Vis absorption spectra areconverted to the Tauc plot of (120572h])12 and photon energy andthe linear extrapolations are made by drawing a tangent linethrough the maximum slope and taking its intersection withX-axis at (120572h])12 = 0 [14]

The calculated energy band gaps of TiO2Fe3O4 Ag-TiO

2

and Ag-TiO2Fe3O4are 29 27 and 235 eV respectively

(Figure 3) Compared to the original anatase TiO2band

gap of 32 eV Fe3O4and Ag dopants have improved the

photocatalytic activity under visible light via narrowing theband gap and enhancing the visible light absorption of TiO

2

(Table 1)Figure 4 shows the XPS spectra for Ag3d region of Ag-

TiO2Fe3O4 The spectra consist of two peaks at around

367 and 373 eV which correspond to Ag3d52

and Ag3d32

respectively The peaks are slightly broadened and can beconsidered as the sum of multiple overlapping peaks Asthe XPS infers the silver species on the Ag-TiO

2Fe3O4

photocatalyst are metallic silver and silver ions coexisting interms of the bonding energy corresponding to Ag3d

52of

metallic Ag (Ag0 368 eV) Ag2O (Ag+ 3675 eV) and AgO

(Ag2+ 367 eV) respectively [15 16]Figure 5 shows the morphology of the sample under

TEM The Ag-TiO2Fe3O4particle connects tightly to one

another The diameter of the particles is in the range of 14ndash40 nm

Figure 6 displays the energy dispersive X-ray (EDX)spectra analysis of Ag-TiO

2Fe3O4and Table 2 lists the


0

05

1

15

2

25

15 2 25 3 35

Photon energy (eV)

Ag-TiO2Fe3O4

Ag-TiO2

TiO2Fe3O4

(120572h)12

Figure 3 Tauc plot for the determination of band gap for the as-synthesized samples

365366367368369370371372373374375

Inte

nsity

(au

)

Binding energy (eV)

Ag3d52

Ag3d32

Figure 4 X-ray photoelectron spectra (XPS) of the as-synthesizedAg-TiO

2Fe3O4in the Ag3d region

composition of the prepared photocatalyst Among the fourelements (Ti Fe O and Ag) presented higher Ti contentcompared tomagnetite could be resulting from the formationof TiO

2layer coated on Fe

3O4particles The Ag signals

are around 28 keV which may indicate the existence of Agparticles in catalyst

Figure 7 displays the magnetic property of Ag-TiO2Fe3O4measured at 25∘CThe absence of hysteresis loop

of the sample indicates the superparamagnetic characterof the material [17] Figure 8 shows the synthesized Ag-TiO2Fe3O4(with a saturation magnetization of 27 emug)

being recollected from the solution with a magnetFigure 9 shows the indigo carmine decolorization effi-

ciency of TiO2 Ag-TiO

2 TiO2Fe3O4 and Ag-TiO

2Fe3O4

in visible light Ag-TiO2exhibits the highest photocatalytic

189nm

180nm

100nm

HV = 800 kV

Direct mag 200000x

Figure 5 TEM photograph for the as-synthesized Ag-TiO2Fe3O4

Spectrum 1

(keV)

FeFe

Fe

Ti

Ti

Ti

Ag

O

Full scale 1149 cts cursor 0000 keV

109876543210

Figure 6 Energy dispersiveX-ray spectra for the as-synthesizedAg-TiO2Fe3O4

Table 2 Characterization data of EDX for Ag-TiO2Fe3O4

Element Weight () Atomic ()O K 2655 5412Ti K 3385 2305Fe K 3859 2253Ag L 101 03Total 10000

activity (near 100 indigo carmine degradation within 2hours) No decolorization has been found in undopedTiO2 The decolorization efficiencies of TiO

2Fe3O4and Ag-

TiO2Fe3O4are sim68 and sim85 respectively after 5 hours

The results suggest that Ag deposition has enhanced thevisible light photocatalytic activity of TiO

2 Such enhance-

ment may be attributed to the electron interaction at thecontact between the metal deposits and the semiconductorsurface The Ag deposits act as eminus traps that immobilizethe photogenerated electrons The trapped electrons are thentransferred to oxygen to form highly oxidative species suchas O2

minus The Fe3O4in the photocatalyst helps to enhance the

visible light activity of TiO2 As TiO

2is the active site of

the catalyst substituting Ag-TiO2with Fe

3O4may decrease

the photocatalytic activity Although Ag-TiO2demonstrates

higher decolorization efficiency thanAg-TiO2Fe3O4 yet Ag-

TiO2is not recollectable with magnet after dispersing in


0

1

2

3

0 5000 10000

Mag

netiz

atio

n M

g (e

mu

g)

Magnetic field

minus3

minus2

minus1

minus10000 minus5000

298k

Ag-TiO2Fe3O4

Mass 10184mg

Figure 7 Magnetization curves of Ag-TiO2Fe3O4at room temperature

(a) (b)

(c) (d)

Figure 8 Photographs of Ag-TiO2Fe3O4dispersed in water after sonication (a) along with its response to the presence of magnet at 10

seconds (b) 1 minute (c) and 5 minutes (d)


0

20

40

60

80

100

0 1 2 3 4 5

Dec

olor

izat

ion

()

Time (h)

Ag-TiO2

TiO2

Ag-TiO2Fe3O4

TiO2Fe3O4

Figure 9 Photocatalytic activity in decolorization of indigo carmine(OD620 = 01) under visible light irradiation at room temperature

water As a result onlyAg-TiO2Fe3O4is used for bactericidal

efficiency evaluationThe catalyst reusability is an important parameter for

practical applications The repetitive use of as-synthesizedAg-TiO

2Fe3O4was studied for different cycles of indigo

carmine decolorization under visible light irradiation Thecatalyst was recovered using a permanent magnet bar andused for three cycles with all other parameters kept constantThe results demonstrate that Ag-TiO

2Fe3O4maintains good

activity in three runs with only a small loss The drop indecolorization might be due to the loss or aggregation ofthe particles during the recycling processThe decolorizationafter 6 h irradiation at the third run (Figure 10) was around85 which indicates that Ag-TiO

2Fe3O4sustains well from

recycling and has good potential for practical applicationsThe research team tested three Ag-TiO

2Fe3O4loadings

(ie 35mg 27mg and 18mg) to select its suitable onein 10mL of phosphate buffer saline (PBS) containing fishpathogens As displayed in Figure 11 the antibacterial effi-ciencies are less than 10 in all loadings for all catalystswithin the first 30 minutes After that the specimen of 35mgAg-TiO

2Fe3O4load demonstrates sharp efficiency increase

to reach sim100 after 90 minutes The specimen of 27mgload demonstrates increased antibacterial efficiency after 60minutes to reach 95 after 120 minutes The specimen of18mg load demonstrates very low antibacterial efficiencyonly 18 fish pathogens degradation Therefore 27mg loadwas chosen for further study

The experiment uses Aeromonas hydrophila (BCRC-13018)Edwardsiella tarda (BCRC10670) andPhotobacteriumdamselae subsp piscicida (BCRC17065) as target bacteriaThese bacteria which cause losses in wild and farmed fishstocks are gram negative fish pathogens that inhabit infreshwater as well as seawater As shown in Figure 12 theeffects have been slow in the first 30 minutes and thenstart to increase more significantly Almost all bacteria were

0

20

40

60

80

100

0 1 2 3 4 5 6

Dec

olor

izat

ion

()

Time (h)

Cycle 1Cycle 2Cycle 3

0

20

40

60

80

100

1 2 3

Dec

olor

izat

ion

()

Cycle

Figure 10 The reusability of Ag-TiO2Fe3O4as demonstrated in

decolorization of indigo carmine under visible light irradiation

destroyed by Ag-TiO2Fe3O4after 120 minutes irradiation

The bactericidal efficiency is about 20 for both BCRC13018and BCRC17065 after 60 minutes of visible light irradiationNo significant difference has been found between these twopathogens After 120 minutes the bactericidal efficienciesincrease to 93 for BCRC13018 and 81 for BCRC17065The results suggest that Photobacterium damselae subsppiscicida is more resistant to Ag-TiO

2Fe3O4among these

three pathogensFigure 13 shows that in the dark where no photocatalysis

process occurs Aeromonas hydrophila and Photobacteriumdamselae subsp piscicida degrade sim15 after 120 minuteswhile Edwardsiella tarda degrades more quickly and reach100 within 120 minutes The bactericide effect seems to beexclusive due to the presence of Ag+ Such findings indicatethat Edwardsiella tarda is a very sensitive microorganism andmore susceptible to silver particle These results suggest thatAg-TiO

2Fe3O4rsquos photocatalytic bactericidal effect is species

dependent

4 Conclusions

Ag-TiO2Fe3O4magnetic photocatalyst has demonstrated

strong antimicrobial properties through amechanism includ-ing photocatalytic production of reactive oxygen species


0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)

35mg27mg18mg

Figure 11 Photocatalytic bactericidal efficiency for Aeromonashydrophila (BCRC13018) at different loadings of Ag-TiO

2Fe3O4

under visible light irradiation

0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)

A hydrophilaP damselae subsp piscicidaE tarda

Figure 12 Bactericidal efficiency of 27mg Ag-TiO2Fe3O4to

Aeromonas hydrophila (⧫) Edwardsiella tarda (998771) and Photobac-terium damselae subsp piscicida (◼) under visible light

that damage cell components and viruses [18] The holeson the valence band of TiO

2can react with either H

2O or

OHminus absorbed on the surface to produce hydroxyl radicalsand with the electrons on the conduction band to reduceO2to produce superoxide anion The detection of other

reactive oxygen species such as H2O2and singlet oxygen

has also been reported Hydroxyl radical and superoxideanions both known to be highly reactive with biologicalsamples are considered the main species generated in theanodic and cathodic pathways respectively of photocatalyticprocesses in the presence of oxygen The XPS data indicateddifferent silver species coexisting in the Ag3d

52region of

0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)

P damselae subsp piscicidaA hydrophilaE tarda


Aeromonas hydrophila (◼) Edwardsiella tarda (998771) and Photobac-terium damselae subsp piscicida (⧫) in the dark

photocatalyst with binding energies at around 367 eV and368 eV assigned to silver ion (Ag+ andor Ag2+) and metallicsilver (Ag0) respectively Ag+ can cause severe alterationsto bacteria via binding to bacterial denatured DNA andRNA so as to inhibit the replication The modifications ofmembrane structure that include changes in membrane-bound enzyme activities metabolic pathways transport sys-tems and permeability alterations lead to cell death Ag+fromAg-TiO

2inactivatesmembrane proteins and respiratory

enzymes Reactive oxygen species damage cell membranewhen cell comes into contact with catalyst surface Ag alsoacts as the trap of photogenerated electrons to prevent the eminus-h+ pairs from recombining rapidly after photoexcitation

As a final remark the research team intend to use lightemitting diodes (LEDs) of different colors as the light sourceto identify the most responsive spectrum of Ag-TiO

2Fe3O4

for the future study since high intensity LEDs have becomeprominent light sources for scientific research [19ndash21]

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors thank the National Science Council Taiwan forsponsoring this research under Project no NSC 102-2313-B-020-004 They also thank the Office of International AffairsNational Pingtung University of Science and TechnologyTaiwan for part of the financial support The advice onthe experiment provided by The Faculty of EngineeringThammasat University Thailand is also appreciated


References

[1] V S Blazer ldquoBacterial fish pathogensrdquo Environmental Biology ofFishes vol 21 no 1 pp 77ndash79 1988

[2] L Novotny L Dvorska A Lorencova V Beran and I PavlikldquoFish a potential source of bacterial pathogens for humanbeingsrdquo Veterinarni Medicina vol 49 no 9 pp 343ndash358 2004

[3] Z Zhang and J Gamage ldquoApplications of photocatalytic disin-fectionrdquo International Journal of Photoenergy vol 2010 ArticleID 764870 11 pages 2010

[4] K S Yao T C Cheng S J Li et al ldquoComparison of photocat-alytic activities of various dye-modified TiO

2thin films under

visible lightrdquo Surface and Coatings Technology vol 203 no 5ndash7pp 922ndash924 2008

[5] W Choi A Termin and M R Hoffmann ldquoThe role ofmetal ion dopants in quantum-sized TiO

2 correlation between

photoreactivity and charge carrier recombination dynamicsrdquoJournal of Physical Chemistry vol 98 no 51 pp 13669ndash136791994

[6] M Maeda and T Yamada ldquoPhotocatalytic activity of metal-doped titaniumoxide films prepared by sol-gel processrdquo Journalof Physics Conference Series vol 61 no 1 article 151 pp 755ndash759 2007

[7] Q L Feng JWu G Q Chen F Z Cui T N Kim and J O KimldquoAmechanistic study of the anti-bacterial effect of silver ions onEsherichia coli and Staphylococcus aureusrdquo Journal of BiomedicalMaterials Research vol 52 pp 662ndash668 2000

[8] WWuQHe andC Jiang ldquoMagnetic iron oxide nanoparticlessynthesis and surface functionalization strategiesrdquo NanoscaleResearch Letter vol 3 no 11 pp 397ndash415 2008

[9] B Tural N Ozkan and M Volkan ldquoPreparation and char-acterization of polymer coated superparamagnetic magnetitenanoparticle agglomeratesrdquo Journal of Physics and Chemistry ofSolids vol 70 no 5 pp 860ndash866 2009

[10] Q He Z Zhang J Xiong Y Xiong and H Xiao ldquoA novelbiomaterialmdashFe

3O4TiO2core-shell nano particle with mag-

netic performance and high visible light photocatalytic activityrdquoOptical Materials vol 31 no 2 pp 380ndash384 2008

[11] T C Cheng K S Yao N Yeh et al ldquoBactericidal effect of blueLED light irradiated TiO

2Fe3O4particles on fish pathogen in

seawaterrdquoThin Solid Films vol 519 no 15 pp 5002ndash5006 2011[12] S A Amin M Pazouki and A Hosseinnia ldquoSynthesis of TiO

2-

Ag nanocomposite with sol-gel method and investigation of itsantibacterial activity against E colirdquo Powder Technology vol196 no 3 pp 241ndash245 2009

[13] K Loganathan P Bommusamy P Muthaiahpillai and MVelayutham ldquoThe syntheses characterizations and photo-catalytic activities of silver platinum and gold doped TiO

2

nanoparticlesrdquo Environmental Engineering Research vol 16 no2 pp 81ndash90 2011

[14] E Kanchanatip N Grisdanurak R Thongruang and ANeramittagapong ldquoDegradation of paraquat under visible lightover fullerenemodifiedV-TiO

2rdquoReactionKineticsMechanisms

and Catalysis vol 103 no 1 pp 227ndash237 2011[15] I M Arabatzis T Stergiopoulos M C Bernard D Labou S G

Neophytides and P Falaras ldquoSilver-modified titanium dioxidethin films for efficient photodegradation of methyl orangerdquoApplied Catalysis B Environmental vol 42 no 2 pp 187ndash2012003

[16] P Prieto V Nistor K Nouneh M Oyama M Abd-Lefdil andR Dıaz ldquoXPS study of silver nickel and bimetallic silver-nickel

nanoparticles prepared by seed-mediated growthrdquo Applied Sur-face Science vol 258 no 22 pp 8807ndash8813 2012

[17] Z Teng X Su G Chen et al ldquoSuperparamagnetic high-magnetization composite microspheres with Fe

3O4SiO

2core

and highly crystallized mesoporous TiO2shellrdquo Colloids and

Surfaces A Physicochemical and Engineering Aspects vol 402pp 60ndash65 2012

[18] Q Li S Mahendra D Y Lyon et al ldquoAntimicrobial nanoma-terials for water disinfection and microbial control potentialapplications and implicationsrdquo Water Research vol 42 no 18pp 4591ndash4602 2008

[19] N Yeh and J-P Chung ldquoHigh-brightness LEDs-Energy efficientlighting sources and their potential in indoor plant cultivationrdquoRenewable and Sustainable Energy Reviews vol 13 no 8 pp2175ndash2180 2009

[20] N G Yeh C-HWu and T C Cheng ldquoLight-emitting diodesmdashtheir potential in biomedical applicationsrdquo Renewable andSustainable Energy Reviews vol 14 no 8 pp 2161ndash2166 2010

[21] N Yeh P Yeh N Shih O Byadgi and T C ChengldquoApplications of light-emitting diodes in researches conductedin aquatic environmentrdquo Renewable and Sustainable EnergyReviews vol 32 pp 611ndash618 2014

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allows it to be activated only by UV Also the high rateof electron-hole (eminus-h+) recombination in TiO

2particles

results in low photocatalytic efficiency Doping TiO2with

various transition metal ions narrows the band gap [5] andexpands the photoresponse of TiO

2into visible spectrum

[6] Also electron transfer between those metal ions andTiO2can alter eminus-h+ recombination as the metal ions are

incorporated into the TiO2lattice Feng et al [7] have studied

the antibacterial mechanism of Ag+ on bacteria and foundthat Ag+ deprives DNA moleculesrsquo replication abilities Inaddition Ag+ increases visible light absorption and holds upthe eminus-h+ recombination of TiO

2

Many of the particles used in the separation technologyare superparamagnetic which can be magnetized with anexternal magnetic field and redispersed upon the removalof magnet [8 9] For example the magnetic property Fe

3O4

helps to enhance the recovery of the catalyst via externalmagnetic fieldMagnetic Fe

3O4particles suspended in carrier

fluids are referred to as magnetic fluids Additionally Fe3O4

also enhances the visible light absorptionwhich resulted fromthe band gap reduction [10]

2 Materials and Methods

21 Materials The chemicals used in this study includetitanium (IV) isopropoxide (98 Acros Organics) isopropylalcohol (999 Carlo Erba) acetylacetone (995 Carlo-Erba) silver nitrate (998 Sigma-Aldrich) ferric chlorideanhydrous (98 Katayama Chemical Inc) ferrous chloride(97 Katayama Chemical Inc) and sodium hydroxide (97Katayama Chemical Inc) These chemicals are analyticalreagent grades and used without further modification

22 Synthesis of Ag-TiO2Fe3O4 The Ag-TiO

2Fe3O4mag-

netic photocatalyst was synthesized in two steps First mag-netite (Fe

3O4) nanoparticles were synthesized via coprecip-

itation method in which FeCl3anhydrous and FeCl

2sdot4H2O

salts in the molar ratio of 2 1 were dissolved and vigorouslystirred in double-distilled water NaOH was then droppedslowly into the solution until a large amount of black precipi-tates formedThe resulting precipitates were collected using amagnet and washed several times with double-distilled waterand ethanol The reaction in this process is as follows

2FeCl3+ FeCl

2+ 8NaOH 997888rarr Fe

3O4+ 8NaCl + 4H

2O (1)

In the second step Ag-TiO2Fe3O4composite particles

were prepared using modified sol-gel method Acetylacetone(Acac) as a chelating agent was added into isopropyl alcoholand stirred magnetically Titanium isopropoxide (TTIP) wasthen added gradually to the mixture with Acac IPA TTIPin molar ratio of 284 2364 1 An appropriate volume ofaqueous silver nitrate was added to the titanium solutionto attain 1 wt of Ag on TiO

2and stirred vigorously for

30 minutes Meanwhile Fe3O4particles were dispersed in

isopropyl alcohol and sonicated in an ultrasonic apparatusfor 10 minutesThereafter slowly add the mixture of Ag-TiO

2

into Fe3O4suspension with TTIP Fe

3O4ratio of 10 (weight

basis) and stir the mixture at room temperature for 3 hours

to ensure uniform compositionThe obtained suspensionwasplaced in a hot air oven at 90∘C for the particles to dry Finallythe composite particleswere calcinated in oxygen at 450∘C for3 hours to form Ag-TiO

2Fe3O4

23 Characterization of Ag-TiO2Fe3O4 The properties of

Ag-TiO2Fe3O4magnetic photocatalyst were characterized

with various instruments The crystal structure of the par-ticles was characterized with X-ray diffraction (XRD) on aBruker AXS diffractometer with CuK120572 radiation The X-raywas generated with a current of 40mA and a potential of40 kV in angular range (2120579) from 10∘ to 80∘ The UV-Visiblediffuse reflectance spectra in the range of 320ndash800 nm wereacquired from a Hitachi U3501UV-visible diffuse reflectancespectrophotometer (UV-Vis DRS) equipped with integratingsphere Pure BaSO

4powder was used as a reflectance stan-

dard Transmission electron microscopy (TEM) observationof the samples was performed on a HITACHI 7500 transmis-sion electron microscope operated at 80 kV The magnetiza-tion of photocatalyst was measured using superconductingquantum interference device (SQUID)

24 Evaluation of Photocatalytic Bactericidal Activities Theresearch team has evaluated photocatalytic bactericidal activ-ities using modified antibacterial drop test In order todifferentiate the effect of TiO

2and silver the experiment was

conducted both under visible light and in dark to block pho-tocatalytic process to assure that the bactericidal activity isexclusively from silver Fish pathogens used in the experimentincluded Aeromonas hydrophila (BCRC13018) Edwardsiellatarda (BCRC10670) and Photobacterium damselae subsppiscicida (BCRC17065) Bacterial cells were collected viacentrifugation at 9500 rpm for 10 minutes to remove super-natants The pellets were then rinsed twice with 15mL phos-phate buffer saline (PBS 137mM sodium chloride 10mMphosphate 27mM potassium chloride pH 74) Ten mLof pathogens in PBS was added to each 6 cm diametersterilized glass Petri dish containing various amounts of Ag-TiO2Fe3O4and irradiated with visible fluorescence light

(FL40SsdotN-EDLsdotNU MitsubishiOsram Japan 120582 gt 420 nm1040 lux) for various time intervals The control groupswere without photocatalyst All control and experimentalgroups had 3 replicates At each time interval 20120583L of suchsolution was transferred from each Petri dish to 96-wellplate containing 180 120583L of 005 235-triphenyl tetrazoliumchloride (TTC) and incubated at 28∘C for 10 hours Theabsorbance of each tube at 540 nmwasmeasured with ELISAreader after adding 50 120583L of isopropanol to the tubes toterminate reaction [11]

The inhibition efficiencies to fish pathogen were calcu-lated as

[Abs]119894 minus [Abs]119905[Abs]119894

times 100 (2)

where [Abs]119894is the absorbance of control group at certain

time interval and [Abs]119905is the absorbance of experimental

group at the same time interval


20 25 30 35 40 45 50 55 60 65 70 75 80

Inte

nsity

(au

)

P25 TiO2


Ag-TiO2Fe3O4

2120579 (deg)





2Fe3O4are










119863 =

119896120582

120573 cos 120579 (3)









2Fe3O4


0

02

04

06

08

1

12

14

16

325 375 425 475 525 575 625 675 725 775

Abso

rban

ce

Wavelength (nm)

P25 TiO2

TiO2Fe3O4

Ag-TiO2

2Fe3O4Ag-TiO







2





2




and Ag3d32


2Fe3O4


52of








0

05

1

15

2

25

15 2 25 3 35

Photon energy (eV)

Ag-TiO2Fe3O4

Ag-TiO2

TiO2Fe3O4

(120572h)12


365366367368369370371372373374375

Inte

nsity

(au

)

Binding energy (eV)

Ag3d52

Ag3d32




2layer coated on Fe








2Fe3O4


189nm

180nm

100nm

HV = 800 kV

Direct mag 200000x


Spectrum 1

(keV)

FeFe

Fe

Ti

Ti

Ti

Ag

O


109876543210





2Fe3O4and Ag-



2 Such enhance-






3O4may decrease





0

1

2

3

0 5000 10000

Mag

netiz

atio

n M

g (e

mu

g)

Magnetic field

minus3

minus2

minus1


298k

Ag-TiO2Fe3O4

Mass 10184mg


(a) (b)

(c) (d)




0

20

40

60

80

100

0 1 2 3 4 5

Dec

olor

izat

ion

()

Time (h)

Ag-TiO2

TiO2

Ag-TiO2Fe3O4

TiO2Fe3O4











2Fe3O4loadings





0

20

40

60

80

100

0 1 2 3 4 5 6

Dec

olor

izat

ion

()

Time (h)


0

20

40

60

80

100

1 2 3

Dec

olor

izat

ion

()

Cycle





2Fe3O4among these




dependent

4 Conclusions




0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)

35mg27mg18mg


2Fe3O4


0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)






2O or




52region of

0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)








2Fe3O4




Acknowledgments



References





2thin films under















2-



2









3O4SiO

2core
















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy




Journal of


Quantum Chemistry




CatalystsJournal of




20 25 30 35 40 45 50 55 60 65 70 75 80

Inte

nsity

(au

)

P25 TiO2


Ag-TiO2Fe3O4

2120579 (deg)





2Fe3O4are










119863 =

119896120582

120573 cos 120579 (3)









2Fe3O4


0

02

04

06

08

1

12

14

16

325 375 425 475 525 575 625 675 725 775

Abso

rban

ce

Wavelength (nm)

P25 TiO2

TiO2Fe3O4

Ag-TiO2

2Fe3O4Ag-TiO







2





2




and Ag3d32


2Fe3O4


52of








0

05

1

15

2

25

15 2 25 3 35

Photon energy (eV)

Ag-TiO2Fe3O4

Ag-TiO2

TiO2Fe3O4

(120572h)12


365366367368369370371372373374375

Inte

nsity

(au

)

Binding energy (eV)

Ag3d52

Ag3d32




2layer coated on Fe








2Fe3O4


189nm

180nm

100nm

HV = 800 kV

Direct mag 200000x


Spectrum 1

(keV)

FeFe

Fe

Ti

Ti

Ti

Ag

O


109876543210





2Fe3O4and Ag-



2 Such enhance-






3O4may decrease





0

1

2

3

0 5000 10000

Mag

netiz

atio

n M

g (e

mu

g)

Magnetic field

minus3

minus2

minus1


298k

Ag-TiO2Fe3O4

Mass 10184mg


(a) (b)

(c) (d)




0

20

40

60

80

100

0 1 2 3 4 5

Dec

olor

izat

ion

()

Time (h)

Ag-TiO2

TiO2

Ag-TiO2Fe3O4

TiO2Fe3O4











2Fe3O4loadings





0

20

40

60

80

100

0 1 2 3 4 5 6

Dec

olor

izat

ion

()

Time (h)


0

20

40

60

80

100

1 2 3

Dec

olor

izat

ion

()

Cycle





2Fe3O4among these




dependent

4 Conclusions




0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)

35mg27mg18mg


2Fe3O4


0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)






2O or




52region of

0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)








2Fe3O4




Acknowledgments



References





2thin films under















2-



2









3O4SiO

2core
















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy




Journal of


Quantum Chemistry




CatalystsJournal of




0

05

1

15

2

25

15 2 25 3 35

Photon energy (eV)

Ag-TiO2Fe3O4

Ag-TiO2

TiO2Fe3O4

(120572h)12


365366367368369370371372373374375

Inte

nsity

(au

)

Binding energy (eV)

Ag3d52

Ag3d32




2layer coated on Fe








2Fe3O4


189nm

180nm

100nm

HV = 800 kV

Direct mag 200000x


Spectrum 1

(keV)

FeFe

Fe

Ti

Ti

Ti

Ag

O


109876543210





2Fe3O4and Ag-



2 Such enhance-






3O4may decrease





0

1

2

3

0 5000 10000

Mag

netiz

atio

n M

g (e

mu

g)

Magnetic field

minus3

minus2

minus1


298k

Ag-TiO2Fe3O4

Mass 10184mg


(a) (b)

(c) (d)




0

20

40

60

80

100

0 1 2 3 4 5

Dec

olor

izat

ion

()

Time (h)

Ag-TiO2

TiO2

Ag-TiO2Fe3O4

TiO2Fe3O4











2Fe3O4loadings





0

20

40

60

80

100

0 1 2 3 4 5 6

Dec

olor

izat

ion

()

Time (h)


0

20

40

60

80

100

1 2 3

Dec

olor

izat

ion

()

Cycle





2Fe3O4among these




dependent

4 Conclusions




0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)

35mg27mg18mg


2Fe3O4


0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)






2O or




52region of

0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)








2Fe3O4




Acknowledgments



References





2thin films under















2-



2









3O4SiO

2core
















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy




Journal of


Quantum Chemistry




CatalystsJournal of




0

1

2

3

0 5000 10000

Mag

netiz

atio

n M

g (e

mu

g)

Magnetic field

minus3

minus2

minus1


298k

Ag-TiO2Fe3O4

Mass 10184mg


(a) (b)

(c) (d)




0

20

40

60

80

100

0 1 2 3 4 5

Dec

olor

izat

ion

()

Time (h)

Ag-TiO2

TiO2

Ag-TiO2Fe3O4

TiO2Fe3O4











2Fe3O4loadings





0

20

40

60

80

100

0 1 2 3 4 5 6

Dec

olor

izat

ion

()

Time (h)


0

20

40

60

80

100

1 2 3

Dec

olor

izat

ion

()

Cycle





2Fe3O4among these




dependent

4 Conclusions




0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)

35mg27mg18mg


2Fe3O4


0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)






2O or




52region of

0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)








2Fe3O4




Acknowledgments



References





2thin films under















2-



2









3O4SiO

2core
















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy




Journal of


Quantum Chemistry




CatalystsJournal of




0

20

40

60

80

100

0 1 2 3 4 5

Dec

olor

izat

ion

()

Time (h)

Ag-TiO2

TiO2

Ag-TiO2Fe3O4

TiO2Fe3O4











2Fe3O4loadings





0

20

40

60

80

100

0 1 2 3 4 5 6

Dec

olor

izat

ion

()

Time (h)


0

20

40

60

80

100

1 2 3

Dec

olor

izat

ion

()

Cycle





2Fe3O4among these




dependent

4 Conclusions




0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)

35mg27mg18mg


2Fe3O4


0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)






2O or




52region of

0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)








2Fe3O4




Acknowledgments



References





2thin films under















2-



2









3O4SiO

2core
















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy




Journal of


Quantum Chemistry




CatalystsJournal of




0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)

35mg27mg18mg


2Fe3O4


0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)






2O or




52region of

0

20

40

60

80

100

0 30 60 90 120

Bact

eric

idal

effici

ency

()

Time (min)








2Fe3O4




Acknowledgments



References





2thin films under















2-



2









3O4SiO

2core
















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy




Journal of


Quantum Chemistry




CatalystsJournal of




References





2thin films under















2-



2









3O4SiO

2core
















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy




Journal of


Quantum Chemistry




CatalystsJournal of












Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy




Journal of


Quantum Chemistry




CatalystsJournal of



Photocatalytic Bactericidal Efficiency of Ag Doped TiO2/Fe3O4 on Fish Pathogens under Visible Light

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Transcript of Photocatalytic Bactericidal Efficiency of Ag Doped TiO2/Fe3O4 on Fish Pathogens under Visible Light