research article facile method for preparation of silica...

Research ArticleFacile Method for Preparation of Silica Coated MonodisperseSuperparamagnetic Microspheres

Xuan-Hung Pham1 San Kyeong2 Jaein Jang3 Hyung-Mo Kim1 Jaehi Kim2

Seunho Jung1 Yoon-Sik Lee2 Bong-Hyun Jun1 and Woo-Jae Chung3

1Department of Bioscience and Biotechnology Konkuk University Seoul 143-701 Republic of Korea2School of Chemical and Biological Engineering Seoul National University Seoul 151-747 Republic of Korea3Department of Genetic Engineering College of Biotechnology and Bioengineering Sungkyunkwan UniversitySuwon 440-746 Republic of Korea

Correspondence should be addressed to Bong-Hyun Jun bjunkonkukackr and Woo-Jae Chung wjchungskkuedu

Received 15 October 2015 Revised 28 December 2015 Accepted 10 January 2016

Academic Editor Zhisong Lu

Copyright copy 2016 Xuan-Hung Pham 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 paper presents a facile method for preparation of silica coated monodisperse superparamagnetic microsphere Hereinmonodisperse porous polystyrene-divinylbenzenemicrobeadswere prepared by seeded emulsion polymerization and subsequentlysulfonated with acetic acidH

2SO4 The as-prepared sulfonated macroporous beads were magnetized in presence of Fe2+Fe3+

under alkaline condition and were subjected to silica coating by sol-gel process providing water compatibility easily modifiablesurface form and chemical stability FE-SEM TEM FT-IR and TGAwere employed to characterize the silica coatedmonodispersemagnetic beads (sim75120583m) The proposed monodisperse magnetic beads can be used as mobile solid phase particles candidate forprotein and DNA separation

1 Introduction

Manipulation of biological objects at the cellular scale isnecessary for both fundamental studies and the purificationof biological products For example optical tweezers [1 2]allow studying the strength of interactions between singlemolecules with piconewton accuracy such as DNA and pro-tein Due to the advantage of noncontact with biomoleculesor cell during separation the magnetic manipulation hasbeen attracted in bioapplication over the several decades [3ndash9]

The dimension of the magnetic nano-microparticles thekey factor for the successful magnetic separation is usuallyless than 10 120583m to ensure perfect and selective interactionwith biological objectsThese particlesrsquo surface must be mod-ified with biocompatible inorganic or organic materials toboth prevent aggregation caused by hydrophobic ormagneticattraction and facilitate the immobilization of specific ligandssuch as antibody aptamer and DNA [3 10]

The magnetic microparticles have been attracted for usein bioapplication for many years due to the advantages thatthey offer easily scalable time-efficient cost-effective andgentle separation of biological compounds by using externalmagnetic field gradient [11ndash17] The magnetic microspheresoffered many exciting applications in biomedical field as asolid support for protein purification [18ndash20] targeted drugdelivery [21ndash24] cell separation [25ndash27] medical diagnosis[28ndash30] immunoassays [31] DNA sequencing [32] and cellanalysis [33] Various materials have been used for matricesembedding superparamagnetic nanoparticles in the form ofmicrobeads including mesoporous silica polysaccharidespoly(ethylene glycol) and many other synthetic polymers[26 34ndash39] By doing so the resulting microbeads retainsuperparamagnetic property with tunable size

The porous PS-DVB (polystyrene-divinylbenzene) beadsusually give a very rigid structure resulting from their highlycross-linked matrix and thus they had less possibility ofcollapsing in most solvents which allows the solvents and

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2016 Article ID 1730403 9 pageshttpdxdoiorg10115520161730403

2 Journal of Nanomaterials

reagents to freely access the internal reactive sites throughthe interconnected pore networks [40ndash43] The microbeadswith pore networks can act as monodisperse core structuresand provide the space within the beads where in situ formingnanomagnetite resides Recently we reported on the use ofporous PS-DVB based monodisperse magnetic beads withSERS (surface-enhanced Raman scattering) active property(magnetic SERS beads) in protein separation [44 45]

Despite extensive efforts made by many research groupsthe demand formagnetic polymeric particles having uniformsize superparamagnetic property chemical stability user-defined magnetic contents biocompatibility and the readilytailorable surface is still increasing in potential applicationto biochips and bioseparation In this paper we demonstrateour strategy to preparemonodisperse porous PS-based super-paramagnetic beads (sim75 120583m) which on surface were coatedwith silica that can result in improving biocompatibility andcapability for facile surface modification [46ndash48]

2 Experimental

21 Materials Tetraethylorthosilicate (TEOS) ammoniumhydroxide (NH

4OH) styrene 221015840-azobis-isobutyronitrile

(AIBN) dibenzoyl peroxide (BPO including 97 of activecompound) dibutyl phthalate (DBP) sodium silicateFe3Cl3sdot6H2O FeCl

2sdot4H2O ethylene glycol NN-dimethyl-

formamide (DMF) sodium dodecyl sulfate (SDS) polyvi-nylpyrrolidone-40 (PVP-40 Mr 40000) NN-diisopropyl-ethylamine (DIEA) and (3-aminopropyl)triethoxysilane(APTS) were purchased from Sigma-Aldrich (MO USA)

22 Methods

221 Preparation of Monodisperse Macroporous PS-DVBBeads Monodisperse macroporous PS-DVB (polystyrene-divinylbenzene) beads were prepared by seeded polymeriza-tion methods Monodisperse PS seeds (4 120583m) were preparedusing dispersion polymerization method [49] Dispersionmedium was ethanol2-methoxyethanol (3 2) which con-tains 1 g of PVP-40 as a steric stabilizer (90mL) AIBN(150mg) was dissolved in styrene (15mL) in which inhibitorwas removed and then was added to the as-prepared disper-sion medium After sonication for 10min dispersion poly-merization was performed in a cylindrical reaction chamberwith shaking (120 cpm) at 70∘C for 20 h The suspension wascentrifuged and the precipitates were washed intensively withdistilled water by repeating centrifugation and vortexingFinally the PS seeds were washed with ethanol and vacuum-dried overnight affording PS seeds (4 120583m 83 g)

Swelling and polymerization processes were performedin a glass reactor equipped with overhead stirrer and areflux condenser in an oil bath equipped with a temperaturecontroller The two-step seeded polymerization method wasemployed for preparation of monodisperse macroporouspoly(styrene-co-DVB) (PS-DVB) beads The PS seeds (4 120583m700mg) were dispersed in DBP (07mL) emulsified aque-ous medium (100mL) containing 025 (ww) SDS Theresultant dispersion medium was stirred (400 rpm) at roomtemperature for 20 h for swelling the PS seeds with DBP

Mixture of styrene (46mL) and DVB (23mL) in whichBPO (240mg) was dissolved was emulsified in an aqueousmedium (100mL) containing 025 (ww) SDS by usinghomogenizer for 1min The emulsified monomer solutionwas added to the DBP-swollen PS seeds dispersion mediumbeing stirred Monomer swelling was performed for 20 h atroom temperature with continuous stirring (400 rpm) Afterswelling process an aqueous solution of 10 (wv) PVA indeionizedwater (10mL) was added to the dispersionmediumand themediumwas purged with nitrogen stream for 30minThe seeded polymerization was performed at 70∘C for 20 hwith continuous stirring (200 rpm) to obtain monodispersePS-DVB beads The polymer beads were intensively washedwith warm deionized water (50∘C) by repeating washingand centrifugation Subsequently the collected beads werewashedwith ethanol andTHF intensively to removeDBP andlinear polymer Finally the beads were dried in vacuum at30∘C for 24 h to obtain macroporous PS-DVB beads (75 120583m25 g)

222 Sulfonation of Macroporous PS-DVB Beads Sulfona-tion of the PS-DVB beads was performed with reference tothe reported method [50] Briefly monodisperse PS-DVBbeads (1 g) were added to 5mL of acetic acid in an ice bathSulfuric acid (50mL) was then slowly added to the beadsat room temperature and the temperature was increased upto 90∘C and the resin mixture was stirred for 30min to2 hr The dispersion was poured into iced water (400mL)to quench the reaction and the sulfonated PS-DVB beadswere collected by centrifugation The beads were extensivelywashed with deionized water by repeating centrifugation-decantation Subsequently the sulfonated microspheres werewashed three times with ethanol and dried under vacuum(11 g)

223 Magnetization of Sulfonated Macroporous PS-DVBBeads Thesulfonatedmacroporous PS-DVBbeads (500mg)were dispersed in deionized water (10mL) at room tem-perature with mechanical stirring (200 rpm) and purgingwith nitrogen A freshly prepared mixture of FeCl

3sdot6H2O

(618mg 226mmol) and FeCl2sdot4H2O (257mg 128mmol)

in deionized water (10mL) was added to the dispersionfor adsorption After 2 h with continuous stirring 28ammonium hydroxide (50mL) was added dropwise to thebeads suspension for 40min The magnetized microsphereswere isolated from the mixture by centrifugation and brieflywashed with 25 TFA and then extensively with deionizedwater and ethanol Finally the magnetized microsphereswere dried under vacuum (magnetizedmicrospheres 75 120583m653mg)

224 Preparation of Silica Coated Magnetic Beads APTSsolution (1 (vv) 100mL) was added to 100mg of magneticsulfonated PS-DVB beads and was shaken for 10min atroom temperature Thereafter ammonium hydroxide (282mL) was added to the bead dispersion and was shakenfor 20min at room temperature To the dispersion TEOS(2mL) was added and vigorously shaken for 12 h at room

Journal of Nanomaterials 3

DVBStyrene Acetic acid Base

TEOS

PS seed Macroporous PS-DVB

microbead

Sulfonated PS-DVBmicrobead

Magnetic microbead

Silica coated monodisperse magnetic bead

H2SO4 FeCl3 + FeCl2NH3

Scheme 1 Synthetic scheme of silica coated superparamagnetic microbead

temperature The resulting beads (silica coated magneticbeads)were collected bymagnet andwashedwith ethanol fivetimes

225 Streptavidin Separation of Silica CoatedMagnetic BeadsAPTS (240120583L) and ammonium hydroxide (40120583L) wereadded to 4mL absolute ethanol containing 200mg of silicacoated magnetic beads and incubated for 6 h at room tem-perature The resulting beads (amine-silica coated magneticbeads) were collected by magnet washed with ethanol fivetimes and dispersed into PBS pH 72 to obtain 10mgml ofamine-silica coated magnetic beads

Biotin (5mg) was activated with EDC (40mg) and NHS(20mg) in PBS pH 72 for 1 h at room temperature Thenthis solution was added into amine-silica coated magneticbeads (1mg 100 120583L) to modify biotin on its surface Thebiotinylated silica coated magnetic beads were collected bymagnet washed with ethanol five times and dispersed into100 120583L PBS pH 90 The biotinylated silica coated magneticbeads were passivated with 5 BSA in PBS pH 90 forpreventing nonspecific binding

Streptavidin-FITC (100 120583g) in PBS pH 90 was added intothe biotinylated silica coated magnetic beads and incubatedfor 30mins at room temperature The biotinylated silicacoated magnetic beads after incubation with streptavidin-FITC were collected by magnet washed with PBS pH 90containing 01 Tween 20 for five times and dispersed into100 120583L PBS pH 90 The fluorescent images were collectedby the Olympus BX-UCB at room temperature with 200msexposure

226 Characterization Cross-sectional images of the beadswere obtained using transmission electron microscopy(TEM Jeol Inc JEM 1010) The slices for the TEM analysiswere prepared by means of an ultramicrotome (RCMMTX)The surface and cross-sectional images of the beads wereobtained using field emission scanning electron microscopy(FE-SEM Carl Zeiss SUPRA 55VP) The existence of themagnetic NP particles was confirmed by means of anenergy dispersive X-ray spectrometer (EDX Bruker EDX)The amount of magnetic particles embedded in the beadswas measured by a thermogravimetric analyzer (TGAPerkinElmer Pyris 6)

3 Results and Discussion

For preparing magnetic beads we employed a method usingmagnetization of uniform porous microbeads As shownin Scheme 1 monodisperse superparamagnetic microbeadhas a spherical core-shell structure with silica layer overmagnetized core PS-DVB bead

Monodisperse polystyrene-divinylbenzene (PS-DVB)beads (75 120583m cross-linked with 33 DVB) were preparedusing the seeded polymerization method that was previouslyreported by Ugelstad [49] The seeded polymerization is auseful method for preparation of monodisperse microbeadswhich is essential for bioapplications including relativequantitative flow cytometry and biochip applicationsThe PSseeds were prepared in the range of 40sim42 120583m (61 solidyield) (Figure 1(a)) and the molecular weight was 29000(determined by GPC analysis) The final PS-DVB beadswere prepared with repolymerization of the seeds (4120583m25 g 47 solid yield) using DBP as a porogen and activatedswelling agent

The prepared PS-DVB microbeads showed a macrop-orous surface (Figure 1(b)) which enables the magnetiteparticles to form easily inside the microbeads upon magne-tization from iron salts adsorbed in the porous structuresHowever the PS-DVB microbead itself was not compatiblein aqueous solution to adsorb the ferrous and ferric saltsThus we introduced sulfonate groups onto the PS-DVBmicrobeads to make them compatible in aqueous solutionand the sulfonate group might have the effect that the ironsalt is drawn into the microbeads and is considerably boundtherein

Sulfonated PS-DVB polymers have been used for manyyears in cationic exchange chromatography as well as otheranalytes [51ndash53] Recently Chambers and Fritz have reportedon the simple preparation of sulfonated PS-DVB with the-SO3H loading range of 027sim263mmolg using sulfonic

acid and acetic acid [50] To demonstrate the effect ofsulfonation loading level of beads to magnetization variousloading levels of sulfonate groupwere prepared by controllingtemperature and reaction time (data not shown) As a resultfrom applying Chamberrsquos method to the as-prepared PS-DVB microbeads we obtained high loaded sulfonated PS-DVB (PS-DVB-SO

3H) of 41mmolg by elemental analysis

FT-IR analysis showed that the sulfonation of the phenylgroups of the PS-DVB was successfully achieved (Figure 2)In the FT-IR spectra of PS-DVB before (Figure 2(a)) and


5120583m

(a)

5120583m 5120583m

(b)

Figure 1 SEM images of (a) PS seeds and (b) PS-DVB microbeads prepared by seeded emulsion polymerization at low magnification (left)and high magnification (right)

(a)

(b)

3000 2500 2000 1500 1000 5003500Wavenumber (cmminus1)

60

80

100

120

140

160

180

Tran

smitt

ance

(au

)

Figure 2 FT-IR spectra of PS-DVB microbeads (a) before and (b)after sulfonation Shaded area represents the characteristic peak ofsulfonate groups Resolution setting 4 cmminus1 16 scans

after sulfonation (Figure 2(b)) the changes in the combina-tion vibrations (finger bands) between 1950 and 1650 cmminus1particularly characterize the phenyl group in themicrobeadsThe band centered around 1200 cmminus1 (Figure 2(b)) representsthe characteristic peak of the OySyO asymmetric stretchingvibration The absorbance peaks at 1005 and 1126 cmminus1 resultfrom the vibrations of phenyl ring substitutedwith a sulfonategroup and sulfonate anion respectively that are attached tophenyl ring [54] A broad band centered around 3450 cmminus1 isassociated with OH stretching vibration of the sulfonic acidgroup (Figure 2(b))

Direct polymerization of ion-binding monomers duringthe seeded emulsion polymerization process can be analternative method of preparing functional macroporousmicrobeads However formation of uniformly macroporousstructures using the ionic monomers is often challenging Incontrast the postmodification of highly cross-linked macro-porous beads as described above can preserve the structureof monodisperse microbeads

After magnetization of sulfonated PS-DVB microbeadswith a mixture of ferrous ions and ferric ions (2 1 molarratio) in the excess basic solution of ammonium hydroxideprecipitates of magnetite were observed in the solution aswell as in the beads as they turned blackish The surface

morphology of microbeads was not significantly changedafter magnetization meaning that the magnetite was formedand precipitated mostly inside the porous structure of themicrobeads (Figures 3(a) and 3(b)) After purifying themagnetized beads from the mixture by centrifugation weconfirmed that the precipitate is indeed iron oxide fromenergy dispersive X-ray spectroscopy (Figure 3(c)) Thesemagnetized microbeads indeed responded to external mag-netic field (Figure 3(d) inset) The magnetic property wasmaintained even after keeping the beads for 4 h in 100 TFA

The saturation magnetization value of the resulting beadswas 76 emug (Figure 3(d)) which is relatively lower thanthat of commercial magnetites (sim70 emug) However themagnetized beads showed strong magnetic property enoughin that they can be separated from the solvent by 4000gauss magnet in 4 sec The magnetized sulfonated PS-DVBmicrobeads consist of many isolated around a few tens nmiron oxide grains that are embedded in a polymer matrixwhich can lead to their superparamagnetic behavior Thesulfonation of the beads and the subsequent magnetiza-tion successfully provided a means for preparing magneticmicrobeads in straightforward and cost-effective way

Iron oxide contents of the magnetized beads were mea-sured by TGA (Figure 4) Iron oxide content was in the rangeof 18ndash26 whose value was suitable for further applicationof the magnetic beads comparing with the conventionalmagnetic beads In the magnetization process we attemptedto simplify the purification by washing the beads after ironsalts adsorption to prevent the formation of the magnetite inthe solution after precipitation of iron salts using ammoniumhydroxide (MAG 1)The iron oxide content of themagnetizedbeads was lower than that of beads prepared by in situprecipitationmethod without additional washing step (MAG2)

Finally the magnetic beads were coated with a silica shellusing APTS and tetraethoxyorthosilicate (TEOS) for theirsurface to be water-compatible and amenable to chemicalmodification using various types of functional silane com-pounds The amino silane compound APTS is prone to pro-mote the adhesion of silane layer on the negatively chargedsulfonated beads thereby facilitating the further base-catalyzed condensation of TEOS from the surface We found


5120583m

(a)

5120583m

(b)

Spectrum 1ClC

OFe

Cl Fe Fe

Full scale 782 cts cursor 0000 keV

1 2 3 4 5 6 7 8 9 100(keV)

Element Weight () Atomic composition ()C KO KCl KFe KTotal

7463

1040

251

1246

10000

8681

908

099

312

(c)

0 6000 12000minus6000minus12000

H (Oe)

minus8

minus4

0

4

8

M (e

mu

g)

(d)

Figure 3 Characteristics of magnetized sulfonated microbeads SEM images of sulfonated PS-DVB microbeads (a) before and (b) aftermagnetization (c) Representative EDS analysis result of magnetized microbeads (d) Hysteresis loops of magnetic beads Inset the beadswere attracted to one side of the tube using a magnet

MAG 1 MAG 2

PS-DVB-SO3H

200 400 600 8000Temperature (∘C)

0

20

40

60

80

100

120

Wei

ght (

)

Figure 4 TGA thermograms of sulfonated PS-DVB microbeads(PS-DVB-SO

3H) before and after magnetization (MAG 1) mag-

netization after washing the iron salt adsorbed beads (MAG 2)magnetization without washing (in situ magnetization) iron oxidecontent 18 (MAG 1) and 26 (MAG 2)

that this pretreatment greatly enhanced the silica coatingefficiency as compared to no pretreatment (data not shown)and pretreatment with (3-mercaptopropyl)triethoxysilanesolution [44] The surface morphology of the beads sig-nificantly changed after the sol-gel process (Figures 5(a)ndash5(d)) revealing formation of silica grains on the surface(Figures 5(b) and 5(d)) From the cross-sectional analysisthe silica shell of 200ndash300 nm was observed around the coremagnetic beads The silica coated magnetic beads were alsohomogeneous in size and could be obtained in gram scale

To support the presence of silica coating on the magneticbeads we carried out EDX analysis of the sulfonated PS-DVB magnetic PS-DVB and silica coatedmagnetic PS-DVBbeads The result was shown in Figure 6 The sulfonatedPS-DVB beads contained C O and S elements with theatomic composition of 865 91 and 44 respectivelyin Figure 6(a) After magnetic nanoparticles were depositedon the sulfonated PS-DVB beads C element decreaseddramatically to 672while O element increased up to 203Particularly the presence of Fe element with 57 confirmedthe successful deposition of magnetic nanoparticles on thesulfonated PS-DVB beads When the silica shell was coated


50kV times10000 2120583m

Magnetized PS-DVB-SO3H

(a)

100 kV times10000 2120583m

Silica coated magnetized PS-DVB-SO3H

(b)

50kV times50000 200nm


(c)

100 kV times40000 200nm


(d)

200nm


(e)

200nm


(f)

Figure 5 Silica coating of magnetized PS-DVB-SO3Hmicrobeads SEM images of magnetized PS-DVB-SO

3Hmicrobeads (a c) before and

(b d) after silica coating at low magnification and high magnification Cross-sectioned TEM images of (e) magnetized PS-DVB-SO3H and

(f) silica coated magnetized PS-DVB-SO3Hmicrobeads

on the magnetic PS-DVB beads the silica coated magneticPS-DVB beads contained C (503) O (333) S (59)Fe (38) and Si (67) element as shown in Figure 6(c)Comparing to that of themagnetic PS-DVB beads O elementof the silica coated magnetic beads increased by 13 whichis about two times Si element that demonstrated the presenceof SiO

2on the surface of magnetic PS-DVB beadsTherefore

EDXdata was consistent with TEM images and evidenced thesuccessful deposition of silica shell on the magnetic PS-DVBbeads surface

To demonstrate the application of the silica coatedmagnetic beads we used streptavidin-FITC as modelbiomolecules for bioseparation Briefly the silica coatedmagnetic beads surface was modified with amine group andconjugated with biotin through EDCNHS The fluorescentimages were shown in Figures 6(d)ndash6(f) The fluorescenceof the biotinylated silica coated magnetic beads withoutreaction with streptavidin-FITC was negligible comparingto the biotinylated silica coated magnetic beads treated withstreptavidin-FITC as shown in Figure 6(e) Also we carried


4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

S S

Pt Pt

Pt

S

(a)

4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

S S

Fe Fe Pt Pt

Pt

FeS

(b)

4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

Si S S

Fe Fe Pt Pt

Pt

Si FeS

(c)

(d) (e) (f)

Figure 6 Chemical composition and bioapplication of silica coatedmagnetized PS-DVB-SO3Hmicrobeads EDX data of (a) PS-DVB-SO

3H

(b) magnetized PS-DVB-SO3H and (c) silica coated magnetized PS-DVB-SO

3Hmicrobeads Fluorescent images of silica coated magnetized

PS-DVB-SO3H microbeads without (d) and with (e) streptavidin-FITC (f) Nonspecific adsorption of streptavidin-FITC to silica coated

magnetized PS-DVB-SO3H beads

out the nonspecific binding test of silica coated magneticbeads without biotinylation and BSA blocking in Figure 6(f)Streptavidin-FITC easily adsorbed into the silica coatedmagnetic beads Therefore BSA blocking step played animportant role in our protocol

4 Conclusions

In conclusion we successfully prepared monodisperse silicacoated superparamagnetic magnetic beads using the macro-porous polystyrene microbeads as template materials Thesulfonation of the porous PS-based beads and the subsequentmagnetization successfully provided a means for preparingmagnetic microbeads in straightforward and cost-effectiveway which can be readilymodifiedwith silica shell as a water-compatible protective layer and surface modification site forvarious functional silane compounds When used with flowcytometry or in a microfluidic system the monodispersemagnetic microbeads may have great potentials for drugscreening medical diagnostics and combinatorial chemicalsynthesis in more simple convenient and cost-effective way

Abbreviations

FE-SEM Field emission scanning electron microscopyTEM Transmission electron microscopyFT-IR Fourier transform infrared spectroscopyTGA Thermogravimetric analysis

Conflict of Interests

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

Acknowledgments

This work was supported by the National Research Foun-dation of Korea Grant funded by the Korean Government(NRF-2014S1A2A2027641) and by the Ministry of ScienceICTampFuture Planning (2014-A002-0065) and by the 2015KUBrain Pool of Konkuk University

References

[1] C-H Chiou Y-Y Huang M-H Chiang H-H Lee and G-BLee ldquoNew magnetic tweezers for investigation of the mechan-ical properties of single DNA moleculesrdquo Nanotechnology vol17 no 5 pp 1217ndash1224 2006

[2] C-H Chiou and G-B Lee ldquoA micromachined DNA manipu-lation platform for the stretching and rotation of a single DNAmoleculerdquo Journal ofMicromechanics andMicroengineering vol15 no 1 p 109 2005

[3] L Yi G Yu and X Chenjie ldquoUsing magnetic nanoparticles tomanipulate biological objectsrdquo Chinese Physics B vol 22 no 9Article ID 097503 2013

[4] E Cho M N Tahir J M Choi H Kim J H Yu and SJung ldquoNovel magnetic nanoparticles coated by benzene- and120573-cyclodextrin-bearing dextran and the sorption of polycyclic


aromatic hydrocarbonrdquo Carbohydrate Polymers vol 133 pp221ndash228 2015

[5] Y S Park C Shin H S Hwang et al ldquoIn vitro generationof functional dendritic cells differentiated from CD34 negativecells isolated from human umbilical cord bloodrdquo Cell BiologyInternational vol 39 no 9 pp 1080ndash1086 2015

[6] S Kyeong C Jeong H Kang et al ldquoDouble-layer mag-netic nanoparticle-embedded silica particles for efficient bio-separationrdquo PLoS ONE vol 10 no 11 Article ID e0143727 2015

[7] M Lee Y L Kang W Y Rho et al ldquoPreparation of plasmonicmagnetic nanoparticles and their light scattering propertiesrdquoRSC Advances vol 5 no 27 pp 21050ndash21053 2015

[8] S Kyeong C Jeong H Y Kim et al ldquoFabrication of mono-dispersed silica-coated quantum dot-assembled magneticnanoparticlesrdquo RSC Advances vol 5 no 41 pp 32072ndash320772015

[9] H Mok and M Q Zhang ldquoSuperparamagnetic iron oxidenanoparticle-based delivery systems for biotherapeuticsrdquoExpert Opinion on Drug Delivery vol 10 no 1 pp 73ndash87 2013

[10] J-Y Hyeon J-W Chon I-S Choi C Park D-E Kim andK-H Seo ldquoDevelopment of RNA aptamers for detection ofSalmonella Enteritidisrdquo Journal of Microbiological Methods vol89 no 1 pp 79ndash82 2012

[11] V N Morozov and T Y Morozova ldquoActive bead-linkedimmunoassay on proteinmicroarraysrdquoAnalytica Chimica Actavol 564 no 1 pp 40ndash52 2006

[12] Z Jiang J Llandro T Mitrelias and J A C Bland ldquoAnintegrated microfluidic cell for detection manipulation andsorting of single micron-sized magnetic beadsrdquo Journal ofApplied Physics vol 99 no 8 Article ID 08S105 2006

[13] Y Sun Y Bai D Song X Li L Wang and H Zhang ldquoDesignand performances of immunoassay based on SPR biosensorwith magnetic microbeadsrdquo Biosensors and Bioelectronics vol23 no 4 pp 473ndash478 2007

[14] J Broomberg S Gelinas J A Finch and Z Xu ldquoReview ofmagnetic carrier technologies for metal ion removalrdquoMagneticand Electrical Separation vol 9 no 3 pp 169ndash188 1999

[15] T R Sathe A Agrawal and S Nie ldquoMesoporous silica beadsembedded with semiconductor quantum dots and iron oxidenanocrystals dual-function microcarriers for optical encodingand magnetic separationrdquo Analytical Chemistry vol 78 no 16pp 5627ndash5632 2006

[16] R F H Dekker ldquoImmobilization of a lactase onto a mag-netic support by covalent attachment to polyethyleneimine-glutaraldehyde- activated magnetiterdquo Applied Biochemistry andBiotechnology vol 22 no 3 pp 289ndash310 1989

[17] C H Lochmuller and L S Wigman ldquoAffinity separations inmagnetically stabilized fluidized beds synthesis and perfor-mance of packingmaterialsrdquo Separation Science andTechnologyvol 22 no 11 pp 2111ndash2125 1987

[18] Y Pan X Du F Zhao and B Xu ldquoMagnetic nanoparticlesfor the manipulation of proteins and cellsrdquo Chemical SocietyReviews vol 41 no 7 pp 2912ndash2942 2012

[19] J BaoW Chen T Liu et al ldquoBifunctional Au-Fe3O4nanoparti-

cles for protein separationrdquoACSNano vol 1 no 4 pp 293ndash2982007

[20] Y Zhang W Ma D Li M Yu J Guo and C WangldquoBenzoboroxole-functionalized magnetic coreshell micros-pheres for highly specific enrichment of glycoproteins underphysiological conditionsrdquo Small vol 10 no 7 pp 1379ndash13862014

[21] J Kim H S Kim N Lee et al ldquoMultifunctional uniformnanoparticles composed of a magnetite nanocrystal core anda mesoporous silica shell for magnetic resonance and fluores-cence imaging and for drug deliveryrdquo Angewandte ChemiemdashInternational Edition vol 47 no 44 pp 8438ndash8441 2008

[22] B Luo S Xu A Luo et al ldquoMesoporous biocompatibleand acid-degradable magnetic colloidal nanocrystal clusterswith sustainable stability and high hydrophobic drug loadingcapacityrdquo ACS Nano vol 5 no 2 pp 1428ndash1435 2011

[23] D Li J Tang C Wei et al ldquoDoxorubicin-conjugated meso-porous magnetic colloidal nanocrystal clusters stabilized bypolysaccharide as a smart anticancer drug vehiclerdquo Small vol8 no 17 pp 2690ndash2697 2012

[24] A Chandna D Batra S Kakar and R Singh ldquoA review ontarget drug delivery magnetic microspheresrdquo Journal of AcuteDisease vol 2 no 3 pp 189ndash195 2013

[25] D Wang J He N Rosenzweig and Z Rosenzweig ldquoSuper-paramagnetic Fe

2O3beads-CdSeZnS quantum dots core-shell

nanocomposite particles for cell separationrdquo Nano Letters vol4 no 3 pp 409ndash413 2004

[26] B-H Jun M S Noh J Kim et al ldquoMultifunctional silver-embedded magnetic nanoparticles as SERS nanoprobes andtheir applicationsrdquo Small vol 6 no 1 pp 119ndash125 2010

[27] J Gao W Zhang P Huang B Zhang X Zhang and B XuldquoIntracellular spatial control of fluorescent magnetic nanopar-ticlesrdquo Journal of the American Chemical Society vol 130 no 12pp 3710ndash3711 2008

[28] J Kim Y Piao and T Hyeon ldquoMultifunctional nanostructuredmaterials for multimodal imaging and simultaneous imagingand therapyrdquo Chemical Society Reviews vol 38 no 2 pp 372ndash390 2009

[29] H-S Cho Z Dong G M Pauletti et al ldquoFluorescentsuperparamagnetic nanospheres for drug storage targetingand imaging a multifunctional nanocarrier system for cancerdiagnosis and treatmentrdquo ACS Nano vol 4 no 9 pp 5398ndash5404 2010

[30] E-Q Song J Hu C-Y Wen et al ldquoFluorescent-magnetic-biotargeting multifunctional nanobioprobes for detecting andisolating multiple types of tumor cellsrdquo ACS Nano vol 5 no 2pp 761ndash770 2011

[31] T Alefantis P Grewal J Ashton A S Khan J J Valdes andV G Del Vecchio ldquoA rapid and sensitive magnetic bead-basedimmunoassay for the detection of staphylococcal enterotoxin Bfor high-through put screeningrdquoMolecular and Cellular Probesvol 18 no 6 pp 379ndash382 2004

[32] J Lundeberg B Pettersson and M Uhlen ldquoDirect DNAsequencing of PCR products using magnetic beadsrdquo in PCRSequencing Protocols R Rapley Ed pp 57ndash66 Springer NewYork NY USA 1996

[33] S-Q Gu Y-X Zhang Y Zhu W-B Du B Yao and Q FangldquoMultifunctional picoliter droplet manipulation platform andits application in single cell analysisrdquo Analytical chemistry vol83 no 19 pp 7570ndash7576 2011

[34] T-J Yoon K N Yu E Kim et al ldquoSpecific targeting cellsorting and bioimaging with smart magnetic silica core-shellnanomaterialsrdquo Small vol 2 no 2 pp 209ndash215 2006

[35] J-S Choi Y-W Jun S-I Yeon H C Kim J-S Shin andJ Cheon ldquoBiocompatible heterostructured nanoparticles formultimodal biological detectionrdquo Journal of the AmericanChemical Society vol 128 no 50 pp 15982ndash15983 2006


[36] C-W Lu Y Hung J-K Hsiao et al ldquoBifunctional magnetic sil-ica nanoparticles for highly efficient human stem cell labelingrdquoNano Letters vol 7 no 1 pp 149ndash154 2007

[37] J Kim S Park J E Lee et al ldquoDesigned fabrication ofmultifunctional magnetic gold nanoshells and their applicationto magnetic resonance imaging and photothermal therapyrdquoAngewandte ChemiemdashInternational Edition vol 45 no 46 pp7754ndash7758 2006

[38] G L Liu Y Lu J Kim J C Doll and L P Lee ldquoMagneticnanocrescents as controllable surface-enhanced raman scatter-ing nanoprobes for biomolecular imagingrdquoAdvancedMaterialsvol 17 no 22 pp 2683ndash2688 2005

[39] P A Mosier-Boss and S H Lieberman ldquoSurface-enhancedraman spectroscopy substrate composed of chemically modi-fied gold colloid particles immobilized on magnetic micropar-ticlesrdquo Analytical Chemistry vol 77 no 4 pp 1031ndash1037 2005

[40] S H Choi Y N Ko K Y Jung and Y C Kang ldquoMacrop-orous Fe

3O4carbon composite microspheres with a short Li+

diffusion pathway for the fast chargedischarge of lithium ionbatteriesrdquo ChemistrymdashA European Journal vol 20 no 35 pp11078ndash11083 2014

[41] K Deepankumar S P Nadarajan S Mathew et al ldquoEngineer-ing transaminase for stability enhancement and site-specificimmobilization through multiple noncanonical amino acidsincorporationrdquo ChemCatChem vol 7 no 3 pp 417ndash421 2015

[42] M S Ramasamy S S Mahapatra and J W Cho ldquoFunctional-ization of graphene with self-doped conducting polypyrrole byclick couplingrdquo Journal of Colloid and Interface Science vol 455pp 63ndash70 2015

[43] M Luqman J-W Lee K-K Moon and Y-T Yoo ldquoSulfonatedpolystyrene-based ionic polymer-metal composite (IPMC)actuatorrdquo Journal of Industrial and Engineering Chemistry vol17 no 1 pp 49ndash55 2011

[44] B-H Jun M S Noh G Kim et al ldquoProtein separation andidentification using magnetic beads encoded with surface-enhanced Raman spectroscopyrdquo Analytical Biochemistry vol391 no 1 pp 24ndash30 2009

[45] B H Jun G Kim S Jeong et al ldquoSilica core-based Surface-Enhanced Raman Scattering (SERS) tag advances in multi-functional SERS nanoprobes for bioimaging and targeting ofbiomarkersrdquo Bulletin of the Korean Chemical Society vol 36 no3 pp 963ndash978 2015

[46] W Zhao J Gu L Zhang H Chen and J Shi ldquoFabricationof uniform magnetic nanocomposite spheres with a magneticcoremesoporous silica shell structurerdquo Journal of the AmericanChemical Society vol 127 no 25 pp 8916ndash8917 2005

[47] M S Noh B-H Jun S Kim et al ldquoMagnetic surface-enhancedRaman spectroscopic (M-SERS) dots for the identification ofbronchioalveolar stem cells in normal and lung cancer micerdquoBiomaterials vol 30 no 23-24 pp 3915ndash3925 2009

[48] J-H Kim J-S Kim H Choi et al ldquoNanoparticle probes withsurface enhanced Raman spectroscopic tags for cellular cancertargetingrdquo Analytical Chemistry vol 78 no 19 pp 6967ndash69732006

[49] J Ugelstad ldquoSwelling capacity of aqueous dispersions ofoligomer and polymer substances and mixtures thereofrdquo DieMakromolekulare Chemie vol 179 no 3 pp 815ndash817 1978

[50] T K Chambers and J S Fritz ldquoEffect of polystyrene-divinylbenzene resin sulfonation on solute retention in high-performance liquid chromatographyrdquo Journal of Chromatogra-phy A vol 797 no 1-2 pp 139ndash147 1998

[51] F Schoebrechts E Merciny and G Duyckaerts ldquoContributionde la chromatographie en phase liquide a haute performance ala separation des lanthanides trivalents sur resine cationique enpresence drsquoedta I Synthese et proprietes generales des resinespelliculaires polystyrene-divinylbenzne sulfonatesrdquo Journal ofChromatography A vol 174 no 2 pp 351ndash360 1979

[52] A Klingenberg and A Seubert ldquoComparison of silica-basedand polymer-based cation exchangers for the ion chromato-graphic separation of transition metalsrdquo Journal of Chromatog-raphy A vol 640 no 1-2 pp 167ndash178 1993

[53] T Hargitai P Reinholdsson B Tornell and R Isaksson ldquoFunc-tionalized polymer particles for chiral separationrdquo Journal ofChromatography A vol 630 no 1-2 pp 79ndash94 1993

[54] R A Weiss A Sen C L Willis and L A Pottick ldquoBlockcopolymer ionomers 1 Synthesis and physical propertiesof sulphonated poly(styrene-ethylenebutylene-styrene)rdquo Poly-mer vol 32 no 10 pp 1867ndash1874 1991

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

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The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


reagents to freely access the internal reactive sites throughthe interconnected pore networks [40ndash43] The microbeadswith pore networks can act as monodisperse core structuresand provide the space within the beads where in situ formingnanomagnetite resides Recently we reported on the use ofporous PS-DVB based monodisperse magnetic beads withSERS (surface-enhanced Raman scattering) active property(magnetic SERS beads) in protein separation [44 45]

Despite extensive efforts made by many research groupsthe demand formagnetic polymeric particles having uniformsize superparamagnetic property chemical stability user-defined magnetic contents biocompatibility and the readilytailorable surface is still increasing in potential applicationto biochips and bioseparation In this paper we demonstrateour strategy to preparemonodisperse porous PS-based super-paramagnetic beads (sim75 120583m) which on surface were coatedwith silica that can result in improving biocompatibility andcapability for facile surface modification [46ndash48]

2 Experimental

21 Materials Tetraethylorthosilicate (TEOS) ammoniumhydroxide (NH

4OH) styrene 221015840-azobis-isobutyronitrile

(AIBN) dibenzoyl peroxide (BPO including 97 of activecompound) dibutyl phthalate (DBP) sodium silicateFe3Cl3sdot6H2O FeCl

2sdot4H2O ethylene glycol NN-dimethyl-

formamide (DMF) sodium dodecyl sulfate (SDS) polyvi-nylpyrrolidone-40 (PVP-40 Mr 40000) NN-diisopropyl-ethylamine (DIEA) and (3-aminopropyl)triethoxysilane(APTS) were purchased from Sigma-Aldrich (MO USA)

22 Methods

221 Preparation of Monodisperse Macroporous PS-DVBBeads Monodisperse macroporous PS-DVB (polystyrene-divinylbenzene) beads were prepared by seeded polymeriza-tion methods Monodisperse PS seeds (4 120583m) were preparedusing dispersion polymerization method [49] Dispersionmedium was ethanol2-methoxyethanol (3 2) which con-tains 1 g of PVP-40 as a steric stabilizer (90mL) AIBN(150mg) was dissolved in styrene (15mL) in which inhibitorwas removed and then was added to the as-prepared disper-sion medium After sonication for 10min dispersion poly-merization was performed in a cylindrical reaction chamberwith shaking (120 cpm) at 70∘C for 20 h The suspension wascentrifuged and the precipitates were washed intensively withdistilled water by repeating centrifugation and vortexingFinally the PS seeds were washed with ethanol and vacuum-dried overnight affording PS seeds (4 120583m 83 g)

Swelling and polymerization processes were performedin a glass reactor equipped with overhead stirrer and areflux condenser in an oil bath equipped with a temperaturecontroller The two-step seeded polymerization method wasemployed for preparation of monodisperse macroporouspoly(styrene-co-DVB) (PS-DVB) beads The PS seeds (4 120583m700mg) were dispersed in DBP (07mL) emulsified aque-ous medium (100mL) containing 025 (ww) SDS Theresultant dispersion medium was stirred (400 rpm) at roomtemperature for 20 h for swelling the PS seeds with DBP

Mixture of styrene (46mL) and DVB (23mL) in whichBPO (240mg) was dissolved was emulsified in an aqueousmedium (100mL) containing 025 (ww) SDS by usinghomogenizer for 1min The emulsified monomer solutionwas added to the DBP-swollen PS seeds dispersion mediumbeing stirred Monomer swelling was performed for 20 h atroom temperature with continuous stirring (400 rpm) Afterswelling process an aqueous solution of 10 (wv) PVA indeionizedwater (10mL) was added to the dispersionmediumand themediumwas purged with nitrogen stream for 30minThe seeded polymerization was performed at 70∘C for 20 hwith continuous stirring (200 rpm) to obtain monodispersePS-DVB beads The polymer beads were intensively washedwith warm deionized water (50∘C) by repeating washingand centrifugation Subsequently the collected beads werewashedwith ethanol andTHF intensively to removeDBP andlinear polymer Finally the beads were dried in vacuum at30∘C for 24 h to obtain macroporous PS-DVB beads (75 120583m25 g)

222 Sulfonation of Macroporous PS-DVB Beads Sulfona-tion of the PS-DVB beads was performed with reference tothe reported method [50] Briefly monodisperse PS-DVBbeads (1 g) were added to 5mL of acetic acid in an ice bathSulfuric acid (50mL) was then slowly added to the beadsat room temperature and the temperature was increased upto 90∘C and the resin mixture was stirred for 30min to2 hr The dispersion was poured into iced water (400mL)to quench the reaction and the sulfonated PS-DVB beadswere collected by centrifugation The beads were extensivelywashed with deionized water by repeating centrifugation-decantation Subsequently the sulfonated microspheres werewashed three times with ethanol and dried under vacuum(11 g)

223 Magnetization of Sulfonated Macroporous PS-DVBBeads Thesulfonatedmacroporous PS-DVBbeads (500mg)were dispersed in deionized water (10mL) at room tem-perature with mechanical stirring (200 rpm) and purgingwith nitrogen A freshly prepared mixture of FeCl

3sdot6H2O

(618mg 226mmol) and FeCl2sdot4H2O (257mg 128mmol)

in deionized water (10mL) was added to the dispersionfor adsorption After 2 h with continuous stirring 28ammonium hydroxide (50mL) was added dropwise to thebeads suspension for 40min The magnetized microsphereswere isolated from the mixture by centrifugation and brieflywashed with 25 TFA and then extensively with deionizedwater and ethanol Finally the magnetized microsphereswere dried under vacuum (magnetizedmicrospheres 75 120583m653mg)

224 Preparation of Silica Coated Magnetic Beads APTSsolution (1 (vv) 100mL) was added to 100mg of magneticsulfonated PS-DVB beads and was shaken for 10min atroom temperature Thereafter ammonium hydroxide (282mL) was added to the bead dispersion and was shakenfor 20min at room temperature To the dispersion TEOS(2mL) was added and vigorously shaken for 12 h at room



TEOS


microbead


Magnetic microbead


















5120583m

(a)

5120583m 5120583m

(b)


(a)

(b)


60

80

100

120

140

160

180

Tran

smitt

ance

(au

)










5120583m

(a)

5120583m

(b)

Spectrum 1ClC

OFe

Cl Fe Fe


1 2 3 4 5 6 7 8 9 100(keV)


7463

1040

251

1246

10000

8681

908

099

312

(c)

0 6000 12000minus6000minus12000

H (Oe)

minus8

minus4

0

4

8

M (e

mu

g)

(d)


MAG 1 MAG 2

PS-DVB-SO3H

200 400 600 8000Temperature (∘C)

0

20

40

60

80

100

120

Wei

ght (

)







50kV times10000 2120583m


(a)

100 kV times10000 2120583m


(b)



(c)

100 kV times40000 200nm


(d)

200nm


(e)

200nm


(f)










4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

S S

Pt Pt

Pt

S

(a)

4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

S S

Fe Fe Pt Pt

Pt

FeS

(b)

4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

Si S S

Fe Fe Pt Pt

Pt

Si FeS

(c)

(d) (e) (f)


3H






4 Conclusions


Abbreviations




Acknowledgments


References






































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





TEOS


microbead


Magnetic microbead


















5120583m

(a)

5120583m 5120583m

(b)


(a)

(b)


60

80

100

120

140

160

180

Tran

smitt

ance

(au

)










5120583m

(a)

5120583m

(b)

Spectrum 1ClC

OFe

Cl Fe Fe


1 2 3 4 5 6 7 8 9 100(keV)


7463

1040

251

1246

10000

8681

908

099

312

(c)

0 6000 12000minus6000minus12000

H (Oe)

minus8

minus4

0

4

8

M (e

mu

g)

(d)


MAG 1 MAG 2

PS-DVB-SO3H

200 400 600 8000Temperature (∘C)

0

20

40

60

80

100

120

Wei

ght (

)







50kV times10000 2120583m


(a)

100 kV times10000 2120583m


(b)



(c)

100 kV times40000 200nm


(d)

200nm


(e)

200nm


(f)










4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

S S

Pt Pt

Pt

S

(a)

4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

S S

Fe Fe Pt Pt

Pt

FeS

(b)

4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

Si S S

Fe Fe Pt Pt

Pt

Si FeS

(c)

(d) (e) (f)


3H






4 Conclusions


Abbreviations




Acknowledgments


References






































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




5120583m

(a)

5120583m 5120583m

(b)


(a)

(b)


60

80

100

120

140

160

180

Tran

smitt

ance

(au

)










5120583m

(a)

5120583m

(b)

Spectrum 1ClC

OFe

Cl Fe Fe


1 2 3 4 5 6 7 8 9 100(keV)


7463

1040

251

1246

10000

8681

908

099

312

(c)

0 6000 12000minus6000minus12000

H (Oe)

minus8

minus4

0

4

8

M (e

mu

g)

(d)


MAG 1 MAG 2

PS-DVB-SO3H

200 400 600 8000Temperature (∘C)

0

20

40

60

80

100

120

Wei

ght (

)







50kV times10000 2120583m


(a)

100 kV times10000 2120583m


(b)



(c)

100 kV times40000 200nm


(d)

200nm


(e)

200nm


(f)










4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

S S

Pt Pt

Pt

S

(a)

4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

S S

Fe Fe Pt Pt

Pt

FeS

(b)

4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

Si S S

Fe Fe Pt Pt

Pt

Si FeS

(c)

(d) (e) (f)


3H






4 Conclusions


Abbreviations




Acknowledgments


References






































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




5120583m

(a)

5120583m

(b)

Spectrum 1ClC

OFe

Cl Fe Fe


1 2 3 4 5 6 7 8 9 100(keV)


7463

1040

251

1246

10000

8681

908

099

312

(c)

0 6000 12000minus6000minus12000

H (Oe)

minus8

minus4

0

4

8

M (e

mu

g)

(d)


MAG 1 MAG 2

PS-DVB-SO3H

200 400 600 8000Temperature (∘C)

0

20

40

60

80

100

120

Wei

ght (

)







50kV times10000 2120583m


(a)

100 kV times10000 2120583m


(b)



(c)

100 kV times40000 200nm


(d)

200nm


(e)

200nm


(f)










4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

S S

Pt Pt

Pt

S

(a)

4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

S S

Fe Fe Pt Pt

Pt

FeS

(b)

4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

Si S S

Fe Fe Pt Pt

Pt

Si FeS

(c)

(d) (e) (f)


3H






4 Conclusions


Abbreviations




Acknowledgments


References






































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




50kV times10000 2120583m


(a)

100 kV times10000 2120583m


(b)



(c)

100 kV times40000 200nm


(d)

200nm


(e)

200nm


(f)










4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

S S

Pt Pt

Pt

S

(a)

4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

S S

Fe Fe Pt Pt

Pt

FeS

(b)

4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

Si S S

Fe Fe Pt Pt

Pt

Si FeS

(c)

(d) (e) (f)


3H






4 Conclusions


Abbreviations




Acknowledgments


References






































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

S S

Pt Pt

Pt

S

(a)

4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

S S

Fe Fe Pt Pt

Pt

FeS

(b)

4 6 8 10 12 142(keV)

02468

10121416

cps (

eV)

C O

Si S S

Fe Fe Pt Pt

Pt

Si FeS

(c)

(d) (e) (f)


3H






4 Conclusions


Abbreviations




Acknowledgments


References






































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



research article facile method for preparation of silica...

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