Deposition of Zinc Oxide on Different Polymer Textiles and Their Antibacterial Properties

16 Pages·2017·4.85 MB·English

materials
Article
Deposition of Zinc Oxide on Different Polymer
Textiles and Their Antibacterial Properties
MartaFiedot-Toboła1,* ID,MagdalenaCiesielska2,IrenaMaliszewska2,OlgaRac-Rumijowska1,
PatrycjaSuchorska-Woz´niak1 ID,HelenaTeterycz1andMarekBryjak2
1 FacultyofMicrosystemElectronicsandPhotonics,WrocławUniversityofScienceandTechnology,
Janiszewskiego11/17,50-372Wrocław,Poland;[email protected](O.R.-R.);
[email protected](P.S.-W.);[email protected](H.T.)
2 FacultyofChemistry,WrocławUniversityofScienceandTechnology,Norwida4/6,50-373Wrocław,Poland;
[email protected](M.C.);[email protected](I.M.);
[email protected](M.B.)
* Correspondence:marta.fi[email protected];Tel.:[phone]
(cid:1)(cid:2)(cid:3)(cid:1)(cid:4)(cid:5)(cid:6)(cid:7)(cid:8)(cid:1)
(cid:1)(cid:2)(cid:3)(cid:4)(cid:5)(cid:6)(cid:7)
Received:25March2018;Accepted:26April2018;Published:30April2018
Abstract: A surface modification of polyamide 6 (PA), polyethylene terephthalate (PET) and
polypropylene (PP) textiles was performed using zinc oxide to obtain antibacterial layer. ZnO
microrods were synthesized on ZnO nanoparticles (NPs) as a nucleus centers by chemical bath
deposition(CBD)process.ScanningElectronMicroscopy(SEM)andX-raydiffraction(XRD)indicated
that wurzite ZnO microrods were obtained on every sample. Differential Scanning Calorimetry
(DSC),FourierTransformInfraredSpectroscopy(FTIR),AtomicForceMicroscopy(AFM)andLiquid
AbsorptionCapacity(LAC)analysisindicatethattheamountandstructureofantibacteriallayer
isdependentonroughnessandwettabilityoftextilesurface. Therougherandmorehydrophilic
is the material, the more ZnO were deposited. All studied textiles show significant bactericidal
activityagainstEscherichiacoli(E.coli)andStaphylococcusaureus(S.aureus). Apossiblemechanism
anddifferenceinsensitivitybetweenGram-negativeandGram-positivebacteriatoZnOisdiscussed.
ConsideringthatantibacterialactivityofZnOiscausedbyReactiveOxygenSpecies(ROS)generation,
aninfluenceofsurfacetovolumeratioandcrystallineparametersisalsodiscussed.
Keywords: zinc oxid; polymer textiles; nanoparticles; microrods; wettability; roughness;
antimicrobialproperties
1. Introduction
Thetextileindustry,similartoothersectors,systematicallychangesasaresultofnewproduct
developmentwhichmeetsuserexpectations,aswellastheenrichmentoftextileapplicationsinvarious
fields. Nowadays,therearemanyfunctionaltextilesbutthemostpopularofthemseemtobematerials
withantibacterialproperties[1–3]. Highdemandforthistypeoffabricisrelatedtotheproblemof
increasingresistanceofmicroorganismstodrugs[4,5]. Antimicrobialmaterialscanhelpinpreventing
reproductionandspreadofpathogens. Therefore,theycouldbeusedforobtainingdisposabletextiles
suchasprotectiveaprons,caps,surgicalcurtains,anddressings,aswellasreusablematerialssuchas
bedsheets,towelsorworkclothes. Theycouldalsobeusedineverydayapplications,suchassport
clothestostayfreshlonger.
Onthetextilemarkettherearemanyantibacterialagents. Theydiffernotonlyineffectiveness
anddurabilitybutalsoinimpactonusersandtheenvironment. Themostcommonsubstancesinclude
ammoniumsalts[6,7],chitosan[8,9],triclosan[10,11]andmetalormetaloxidenanoparticles[12–14].
Materials2018,11,707;doi:10.3390/ma11050707 www.mdpi.com/journal/materials
Materials2018,11,707 2of16
Inthispaper,themodificationofthreedifferenttypesoffabrics(PA,PET,andPP)withzincoxide
microrodsispresented.Thesefabricsarecommonlyusedinthetextileindustryandaremadeofpolymers
ofvaryingsurfacewettability. ZnOhasbeenselectedastheantibacterialagentbecauseitisnon-toxic,
veryeffectiveanddoesnotchangethecoloroftheoutputfabrics[15,16]. Inpreviousstudiesauthors
haveshownthatthemorphologyandcrystallinestructureofZnOiscrucialforthefinalantimicrobial
properties[17,18].Inthiswork,zincoxidemicrorodswerenotgrowndirectlyonthefabricsurface,but
rathercolloidalZnOnanoparticleswereusedascrystallizationnuclei.Theauthorssupposethatthisallows
forasignificantincreaseinbiologicalactivityofthemodifiedfabrics. Obtainedantibacterialmaterials
couldbeusedineverydaylifeapplicationssuchassportclothes,medicaltextilesorbedding.
2. MaterialsandMethods
2.1. AppliedTextileMaterials
Inthesestudies,threedifferenttextileswereusedandmodified: PA,PETandPP.Thefirsttwo
weremadebyWISTILS.A.companyfromKalisz,Poland(productNo5707,5235). ThePPtextile
wasmanufacturedbyŁódz´ UniversityofTechnology(Łódz´,Poland). Theaforementionedmaterials
arecomposedofdifferentpolymergroups: polyesters,polyamidesandpolyolefins. Thesetextiles
havesimilarstructureandhighresistancetodeformations. Theyweremadein1/1plainweavewith
thicknessca. 0.20mm. Theaveragesizeofmacro-poresinthetextilesrangedfrom30to70µm. Textiles
wereinitiallywashedandthermallystabilizedafterproduction(Table1).
Table1.Characteristicfeaturesofusedtextilesuperficiallymodified.
Warp Weft
Textile FabricSurface TheWayof
Yarn Numberof Yarn Numberof Mass(g/m2) FabricPreparation
Character Threads/10cm Character Threads/10cm
84 84
PP 460 330 72 washing
dtexf33 dtexf33
84 150 washing,thermal
PET dtexf48 390 dtexf216 320 79 stabilization(20s,190◦C)
72 160 washing,thermal
PA dtexF17 380 dtexF144 310 81 stabilization(20s,185◦C)
Toanalyzepropertiesofinspectedtextiles,severalmeasurementswereperformed. Thesurface
was studied by a Scanning Electron Microscope Evo LS 15 (Zeiss, Oberkochen, Germany) and an
Atomic Force Microscope. AFM measurements were carried out using a commercial NanoMan V
microscopewithaNanoScopeVController(VeecoInstruments/Bruker,NewYork,NY,USA).Samples
werescannedintappingmodewithspringconstant40N/mandresonantfrequency300kHzusing
RTESP probes (Veeco Instruments/Bruker, New York, NY, USA). Acquired data were processed
usingnon-commercialsoftwareTopoGraf(FacultyofMicrosystemElectronicsandPhotonics,Wrocław
UniversityofScienceandTechnology,Wrocław,Poland).Subsequently,therootmeansquareroughness
(Rq)wascalculated.
DifferentialScanningCalorimetrystudieswereperformedusingDSC6equipment(PerkinElmer,
Waltham,MA,USA).Thesetestswereperformedinnitrogenatmosphere,passingthroughthesystem
atarateof20mL/min. TheanalysisoftheobtainedresultswasperformedusingPyrissoftware(v.3.81,
PerkinElmer,Waltham,MA,USA).Thecrystallinitydegreewasalsocalculated.
ThechemicalstructureofsampleswasexaminedusingFourierTransformInfraredSpectroscopy
intheNicolet380system(ThermoFisherScientific,Waltham,MA,USA).Thespectrumwasrecorded
intherangeof60to4000cm−1witharesolutionof4cm−1.
Thewettabilityoftextileswasmeasuredasanabilitytoabsorbliquid,inaccordancewithISO
9073-6:2003standard“Textiles. Testmethodsfornonwovens. Part6: Absorption”[19]. Materialswere
cutinto10×10cm2samples,andthenweighedbeforeandafterimmersinginwaterfor60s.
Materials2018,11,707 3of16
2.2. TextileModificationProcess
To induce antibacterial properties in textiles, zinc oxide microrods were deposited on their
surface by hydrothermal method. Before the process, materials were dipped in colloidal zinc
oxide nanoparticles for 30 s and then dried at 90 ◦C for 15 min. The colloid contained a spherical
ZnO nanoparticles with average radius of ca. 6 nm. Their characterization and synthesis method
were presented in previous work [20]. The nanoparticles adsorbed on the textile surface during
hydrothermal ZnO microrods deposition were nucleation centers. The hydrothermal deposition
was carried in a 100 mM water mixture of hexamethylenetetramine (HMT) and zinc nitrate
(Zn(NO ) ·6H O).Obtainedchemicalbathwasstirredfor24handfiltered. Then, textilesamples
3 2 2
wereaddedandthewholesystemwasheatedto90◦Cfor8h. Afterthedepositionprocess,modified
sampleswerewashedinultrasoundwasherEW-08849-02(Cole-Parmer,VernonHills,IL,USA)and
driedinaroomtemperature.
Thenextstepwastocharacterizeobtainedantibacteriallayer. Masschangesofsampleswere
determined,theirmicrostructureandcrystalstructurewereexaminedusingaccordinglySEMand
X-rayPhilipsMaterialsResearchDiffractometer(Philips,Eindhoven,Netherlands),utilizingCuKα
radiation. Obtainedresultsinclude: interplanardistance,latticeconstantsandthevolumeoftheunit
cell,determinedusingBragg’slawandtheWilliamson–Hall(W-H)method.
Theantibacterialpropertiesofmodifiedtextilesweredeterminedbytheserialdilutionmethod
againsttwodifferentpathogens: Gram-negativeE.coliPCM2057andGram-positiveS.aureusPCM
458. Anamountof1mLofanovernightcultureofthetestedbacteria(grownaerobicallyat37◦C,
withshaking,inMuellerbroth)wascentrifugedat5000gfor5min,andthenthesupernatantwas
discarded. The pellet was re-suspended in 1 mL of saline to give an inoculum of approximately
1.2×106colony-formingunits(CFU/mL)forS.aureusand1.3×107CFU/mLforE.coli. Samplesof
theZnOmodifiedtextiles(1cm×1cm)wereplacedintubescontaining3mLofdistilledwater. Then,
300(or30)µLofpre-preparedbacterialsuspensionwasaddedtothetubes. Tubeswereincubatedfor
2,5and24hat37◦C.Then,serialdilutionswerepreparedand100µLaliquotsofeachdilutionwere
seededinduplicateontoMuellerAgar(Difco)andincubatedfor24–48hat37◦C.Afterincubation,
thenumberofcolonyformingunitspermilliliter(CFU/mL)wasestablished. Bacterialsuspensions
treatedwithunmodifiedPA,PETandPPaswellassuspensionswithouttextilesampleswerepositive
andnegativecontrols,respectively.
Theantibacterialactivityofmodifiedtextileswasalsostudiedonthesolidmediuminaccordance
withtheISO20645:2004standard“Textilefabrics-Determinationofantibacterialactivity.Agardiffusion
platetest”[21].
3. ResultsandDiscussion
3.1. TextileCharacterization
BasedonSEMandAFMobservations,itwasindicatedthatthesurfaceofPETissmoothbutrich
inparticleswhichcouldberesiduesfromtheproductionprocess(Figure1b). PPandPAsurfaceswere
roughandfreeofpollutions(Figure1a,c). Thoseresultswereconfirmedbyarootmeansquaredvalue
whichwas17.98nmforPA,6.57nmforPETand10.50nmforPP.
Materials2018,11,707 4of16
Figure1.SEMandAFMimagesof:(a)PA;(b)PET;and(c)PP.
The composition and degree of crystallinity of the materials were determined based on DSC
analysis. These studies have shown that fabrics consist exclusively of polymers, as declared by
manufacturers. This is indicated by the presence of characteristic exothermic peaks (Figure 2).
The degree of crystallinity was calculated using Formula (1) and summarized in Table 2. It was
observedthatX ofalltextilesissimilar.
c
∆H
X = m (1)
C ∆H
m100
where ∆H is the melting enthalpy of sample and ∆H is the melting enthalpy of 100%
m m100
crystallinepolymer.
Materials2018,11,707 5of16
Figure2.DSCanalysisoftheusedtextiles.
Table2.DSCresultsforanalyzedtextiles.
Sample ∆Hm100(J/g) ∆Hm(J/g) Xc(%)
PA 230.1 116.2 50.5
PET 140.1 70.7 50.5
PP 207.1 106.1 51.2
FTIRanalysisconfirmedDSCresults,showingpeakscharacteristicforfunctionalgroupsofmain
textilepolymers,withoutanyadditives(Figure3)[22–24].
Figure3.FTIRresultsforanalyzedtextiles.
The liquid absorption capacity (LAC) was determined according to polish standard ISO
9073-6:2003 Formula (2) [19]. It was observed that the liquid absorption capacity is significantly
largerforPAsamplethanforothermaterials. Consideringstandarddeviationoftheresults,itcould
Materials2018,11,707 6of16
beseenthatthereissmalldifferencebetweenPETandPP.However,PPischaracterizedbyslightly
smallerLACvalue(Table3),whichisaresultofitschemicalcomposition. Itisbuiltfromnonpolar
groupscontainingcarbon–hydrogenbonds,whereasPEThasoxygengroupsandPAhasadditional
amidegroups,whicharecharacterizedbystrongpolarproperties.
m −m
LAC = n k (2)
m
k
wherem isthemassofwetsample(g)m isthemassofdrysample.
n k
Table3.LACresultsforanalyzedtextiles.
Sample PA PET PP
LAC(%) 185± 169±3 160±5
3.2. DepositionandCharacterizationofAntibacterialMaterial
To form nucleation centers on the textile surface, all fabrics were immersed in a previously
preparedZnONPscolloidandthendried(Figure4a). Further,ahydrothermaldepositionofZnO
microrodswasperformedonsuchmaterials,usingaqueoussolutionsofzincnitrateandurotropine.
The process was carried out at 90 ◦C for 8 h (Figure 4b). After the process, the modified fabrics
wererinsedinanultrasonicscrubbertoremovetheexcessofantibacterialagentandthendriedat
roomtemperature.
Figure4.Aschemeofmodificationprocess.(A)ZnONPsdeposition;(B)CBDsolutionpreparation.
ThemechanismofhydrothermaldepositionofZnOusingHMTandZn(NO ) isverycomplex
3 2
andmultistage.Dependingonthetemperateandtime,differentreactions,whichdeterminateobtaining
products,takeplace. Usedprocesscondition(90◦C,8h)wereselectedbasedonpreviousstudieson
theinfluenceoftemperatureandtimeonzincoxidehydrothermaldeposition[17,18]. Forthisreason,
thesetopicsarenotdiscussedinthisarticle.
Theamountofzincoxidedepositedonthesubstratewasdeterminedbymeasuringtheweight
gain. Thesemeasurementshaveshownthatthemorehydrophilicisthefabric,themorezincoxideis
depositedonthesurface. Weightgainwasaccordingly6.3±0.2mgforPA,5.1±0.1mgforPETand
3.9±0.1mgforPP.
Thecrystalstructureanalysisoftheantibacteriallayerformedonthefibersurfacewasperformed
usingXRD.Characteristicpackswereobservedontheobtaineddiffractogramsatabout2θ =31.6◦,
34.2◦,36.1◦,47.4◦,56.5◦,62.7◦,65.7◦,67.5◦,and69.0◦,whichcorrespondstothecrystalplanes[100],
Materials2018,11,707 7of16
[002],[101],[102],[110],[103],[200],[112],and[201]ofhexagonalwurzitestructurethatwereobserved
(Zincite,JCPDS5-0664). ThatconfirmedthepresenceofZnOonalltextilesurfaces(Figure5).
Figure5.XRDdiffractogramsofmodifiedtextiles.
ToperformathoroughcharacterizationofobtainedZnOcrystals,interplanardistances,lattice
constants, andtheunitcellvolumewerecalculated[25]. Itwasobservedthatthevaluesoflattice
constants and the unit cells volume are similar for all samples and are bigger than the standard
valuesforzincoxidecell(Table4). ThemicrostrainsandaveragecrystallitesizeinZnOwerealso
determined,usingtheWilliamson–Hall(W-H)method[26]. Tocalculatethestraincurveandcrystallite
size,βcosφ=f(4sinφ)wasplottedforpreferreddiffractionpeaks(Figure6).
Figure6.TheW-Hcurvesforsamples.
ItwasobservedthatthecrystallitesizeisincreasingforsamplesinorderPET,PAandPP.These
results,concerningthestrainvaluesinZnOstructureshowthesametendency. Aconclusioncould
bemadethatthebiggeristhecrystallitesize,thebiggeristhestrainobserved. Comparisonbetween
theseresultsandstandarddata(Zincite,JCPDS5-0664)showedthateveryobtainedcrystallitewas
Materials2018,11,707 8of16
characterizedbygreaterunitcellparametersvaluesthandatadeterminedbyJCPDS(Table4). This
couldbeaconsequenceofdefectsembeddedinthestructure,amountofwhichisrelatedtostrain
valuesandcrystallitesize. ThemostirregularcrystalswereobtainedforZnOdepositedonPPsurface.
The results for PA and PET were very similar. Therefore, authors suppose that, in the substrate,
hydrophobicityplaysthemostimportantrolethecrystallizationprocess.
Table4.ChangesinZnOunitcellparametersandcrystallites.
Sample d (Å) d (Å) a(Å) c(Å) V(Å3) ε D(nm)
(100) (002)
PA 2.83 2.62 3.27 5.24 48.52 0.00069 23.3
PET 2.83 2.61 3.27 5.23 48.43 0.00061 22.8
PP 2.83 2.61 3.27 5.23 48.43 0.00099 24.6
Standard 2.81 2.60 3.25 5.21 47.60 - -
ThemicrostructureofZnOdepositedonthesurfaceofpolymermaterialswasdeterminedbySEM
observation. Theelongatedzincoxidestructuresformedbyflower-likeagglomerateswerecreated
(Figure7). TheagglomeratesonthesurfaceofthePAaremadeofsharp-endedsinglerods,whilethose
onPPandPETaremadeofmicrorods. TheaveragelengthoftheZnOmicrorodsgrownonthesurface
ofPA,PET,andPPmaterialswasaccordingly3.9±0.4,5.6±0.2,and4.1±0.6µm,respectively. Their
diametersare252±5,398±8,and313±2nm,respectively. Basedonthesevalues,calculatedaverage
shaperatio(A )[17]was15.6,14.3,and13.2,respectively.
R
Figure7.SEMimagesofZnOdepositedon:(a)PA;(b)PET;and(c)PP.
The shape, location and crystalline structure of ZnO rods are significantly different from the
resultsoftheauthors’previouswork[17]. Inthisstudy,arelativelyevendistributionofzincoxiderods
onthesurfaceofthefabric,withoutagglomerates,wasobserved.Thesestructureshaveasimilarlength
Materials2018,11,707 9of16
butaremuchthicker(1.6µmindiameter). AuthorsbelievethatthisisbecauseZnOnanoparticlesare
usedinthepresentstudyasheterogeneousnucleationcenters. Theheterogeneousnucleationoccurs
much more easily on the surface of the solid-state nanoparticles in contact with the solution than
homogeneousnucleationdirectlyfromsolution. Ifthecrystallizationnucleusispresentedasasphere,
the equation describing the equilibrium of surface energy at the triple point follows Equation (3)
(Figure8). BecausecrystallizationnucleusismadeofZnONPs,onwhichZnOcrystalsaregrowing,
thesurfaceenergybetweenZnOnucleusandliquid(γ )isequaltosurfaceenergybetweenliquid
NL
andZnOcrystal(γ )(4–6).
LC
Therefore, the reduction of the energy required for the crystallization of the material in the
heterogeneousprocesscomparedtothehomogeneousdependsonthecontactangleofthematerial
andisexpressedbytheVolmercoefficientf(θ)inEquation(7). Thus,thesmalleristhecontactangleof
thematerialatwhichcrystallizationoccurs,theloweristheenergyrequiredforthisprocess[27].
γ = γ +γ cosθ (3)
NL NC LC
γ = γ (4)
NL LC
γ −γ cosθ = γ (5)
NL LC NC
γ (1−cosθ) = γ (6)
NL NC
(2+cosθ)·(1−cosθ)2
f(θ) = (7)
4
whereγ isthesurfaceenergybetweennucleusandliquid(J/m2);γ isthesurfaceenergybetween
NL NC
nucleusandcrystal[J/m2];γ isthesurfaceenergybetweenliquidandcrystal(J/m2);andθisthe
LC
contactangle(o).
Figure8.Aschemeofaofcontactangledetermination.
Inthepresentstudies,crystallizationwascarriedoutonnanoparticlesofZnOappliedonthe
fabricsurface.Consequently,theZnOcrystallizationenergyonthesurfaceofallthreefabricsshouldbe
comparable. However,itshouldbesignificantlysmallerthaninthecaseofusingtextilesnotcovered
byZnOnanoparticles(withoutcrystallizationnucleus). Therefore,thefirststageoftheprocess(the
depositionofZnOnanoparticlesonthetextilesurface)hasadecisiveinfluenceontheformationof
zincoxiderods.
TheLAC,R ,SEMandAFManalysesprovidethemostimportantsurfaceparametersforthe
q
evaluationofnanoparticleinfluenceonthefibersurface. LACvaluedemonstratestheabilitytoabsorb
solvent and is therefore connected with both surface chemistry and roughness. R is a numerical
q
indicator of surface roughness. Comparison of those two parameters can provide all necessary
informationabouttextilesurface. Basedonobtainedresults,theLACandR valuesforPAarethe
q
highest. PETandPPhavesimilarLACvaluebutmuchsmallerthanPA.TheR valuewasbiggerfor
q
PPthanforPET.ThoseresultswereconfirmedbySEMandAFMimages. ThePETsurfaceisflat,but
thePAandPPsurfacehave“orangepeel”structure. Thoseobservations,incombinationwithDSC
andFTIRspectra,leadtoconclusionthatPAsurfaceistheroughestandmosthydrophilic. Surfaceof
thePETfibersareflatandhydrophilic,whilethePPsurfaceisroughandhydrophobic.
Duringimmersionofsubstratesinzincoxidecolloid,nanoparticlescanbindwiththetextileby
chemisorptions,physisorptionand/orhydrogenbondonthesurface. Theeffectivenessofthisbond
Materials2018,11,707 10of16
dependsonwettabilityandsurfaceroughness. Inthecaseofroughhydrophobicsurfaces(Figure9a)
oronflathydrophobicsurfaces(Figure9b),thecrystallizationcenterscanbecreatedonlyinsome
placeswithlimitedarea. Ontheotherhand,onthehydrophilicandroughfibers,nanoparticlescould
beeasilyadsorbed(Figure9c).
Figure9.Ashapeofcolloiddropondifferenttextilesurfaces:(a)PP;(b)PET;and(c)PA.
TheamountofZnOdepositedonthetextilesurfaceisdecreasinginfollowingorder:PA,PET,and
PP.ThecrystallitesizeandstrainvaluesofZnOareincreasingintheorder:PET,PAandPP.Inaddition,
somedifferenceswereobservedonSEMimages(Figure7). OnPA,textileneedlelikestructureswere
observedwiththehighestA value(3.9µmlength,252nmdiameter). OnPET,thelongestrodswere
R
depositedwithhigherA (5.6µmlength,398nmdiameter)thanonPPsample(4.1µmlength,313nm
R
diameter). Inaddition,thezincoxidemicrocrystalsformedflower-likeagglomeratesonthefabric
surface. AgglomeratesformedonthesurfaceofthePAaremadeofsharp-endedrods. Incontrast,the
agglomeratesformedonthePPandPETsurfacesareconstructedofmicrorodsbecausethefabrics
afterimmersioninthecolloidalsolutionweredried. Nanoparticlestendtoagglomerateduringdrying
processastheconsequenceofincreaseinconcentration. Thiseffectismosteasilyachievedonsmooth
and/orhydrophobicsurfaces(Figure10).
Figure10.AschemeoftheZnONPson:(a)hydrophilic;and(b)hydrophobicsurfaceafterdrying.
Aforementioned nanoparticle agglomerates are base for ZnO microrods growth. As a result,
the biggest amount of ZnO nanoparticles is present on PA surface, then on PET and the least on
PP. It has to be noticed that the difference between PET and PP is not significant, which is due to
the balance between roughness and wettability of their surfaces. After shape, crystallite size and
structurestrainsanalysesaconclusioncouldbemadethatonPAnucleationispreferredtothegrowth
process,incontrasttoPET.ThisargumentisaffirmedbyneedlelikecrystalsobservedinsampleofPA
(Figure7a)whicharetheconsequenceofZn2+ deficiency. OnPP,nanoparticleswerelooselyattached
tothesurface,duetoitshydrophobiccharacterandthefactthatthesizeofcolloiddropsisdetermined
onlybysurfaceroughness. ThisisprovenbythebiggeststrainvaluesinZnOmicrorodsonPPtextile.
3.3. AntibacterialCharacterization
ThebactericidalactivityofthetextileandcontrolsampleswasassessedusingEscherichiacoliand
Staphylococcusaureus. ThedecreaseinthenumberofE.coliafter2hofincubationinsaline(datanot
shown)andinthepresenceoftheunmodifiedtextiles(Figure11)wassimilarandranged2×104–5×