Brush Layer Charge Characteristics of a Biomimetic Polyelectrolyte- Modi fi ed Nanoparticle Surface - Zhou et al. - 2020 - Unknown

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pubs.acs.org/LangmuirArticleBrushLayerChargeCharacteristicsofaBiomimeticPolyelectrolyte-ModifiedNanoparticleSurfaceTengZhou,*LuyuDeng,LiuyongShi,TingLi,XiangtaoZhong,andLipingWen*CiteThis:Langmuir2020,36,15220−15229ReadOnlineACCESSMetrics&MoreArticleRecommendationsABSTRACT:Nanoparticlesurfacechargeregulationtechnologyplaysanimportantroleinionrectification,drugdelivery,andcellbiology.Thebiomimeticpolyelectrolytecanbecombinedwithnanoparticlesbynanomodificationtechnologytoformalayerofcoating,whichiscalledthebrushlayerofnanoparticles.Inthisstudy,basedonthePoisson−Nernst−Planck(PNP)equationsystem,atheoreticalmodelconsideringabionicelectrolytebrushlayerwithchargedensityregulatedbyachemicalreactionisconstructed.Thechargepropertiesofbrushednanoparticlesarestudiedbychangingthesizesofnanoparticles,thepHvalueofthesolution,backgroundsaltsolutionconcentration,andbrushlayerthickness.Theresultshowsthatthechargedensityofbrushednanoparticlesincreaseswiththeincreaseofparticlesize.Theisoelectricpoint(IEP)oftheequilibriumreactionagainstthebrushlayerispH=5.5.WhenthepH<5.5,thechargedensityoftheparticlebrushlayersdecreaseswiththeincreaseofpH,andwhenthepH>5.5,thechargedensityoftheparticlebrushlayerincreaseswiththeincreaseofpH.Bycomparingthechargedensityofdifferentbrushthicknesses,itisfoundthatthelargerthebrushthickness,thesmallerthechargedensityofthebrushlayer.Thisresearchprovidestheoreticalsupportforthechangeofthethroughporevelocitywhenmacromolecularorganiccompoundspassthroughnanopores.16DownloadedviaUNIVOFPRINCEEDWARDISLANDonMay16,2021at12:23:38(UTC).■INTRODUCTIONcellmethod.However,thesurfacecharacteristicsofnano-Seehttps://pubs.acs.org/sharingguidelinesforoptionsonhowtolegitimatelysharepublishedarticles.particlesmadeofpurelyinorganicmaterialsaredifferentfromWiththedevelopmentofnanotechnology,thepublicgraduallybegantocombinebionics,organicchemistry,andnano-thoseofcellsormicroorganisms.Forexample,polyelectrolytetechnologytosimulatethebiologicalshellsofvariousorganismslayerswithspecialchargepropertiesarepresentonmost17,18andcellsatthemicroscale,ortomodifynanoparticlesbysurfacebiologicalcellsurfaces.Hence,weemployednanomodifi-1,2modificationtechnology.Greatachievementshavebeenmadecationtechnologytocoatthesurfaceofsilicananoparticleswithinmanyfieldsbyusingsurfacemodificationtechnology,suchasbionicpolyelectrolyte(e.g.,lysine)toformasurfacebrushlayerDNAsequencing,3,4proteintransport,5drugdelivery,6,7andion19,20composedoforganicmaterials.Thiskindofbiomimetic8,9currentrectification.Atpresent,theresearchofsurfacepolyelectrolyte,whichissensitivetopHorsaltconcentration,propertiesismainlyfocusedonthenanoparticlesmadeofhasattractedbroadattentioninmanyscientificandindustrialinorganicmaterials,suchasthestudyofsurfacecharge10propertiesofsiliconoxideparticlesofdissimilarsizes,theinteractionbetweenthesilicananoparticlesandthesilicaplateinReceived:August15,2020electrolytesolution,11,12andtheelectrophoresisofsilicaRevised:November28,2020particlesofsolutionswithdifferentpHs.13,14SomepreviousPublished:December11,2020papersdiscussedthecoatingpropertiesofsteel/siliconsurface15deposition,andtheioncharacteristicsoftheanodelayerionsourceweresimulatedwiththethree-dimensionalparticle-in-©2020AmericanChemicalSocietyhttps://dx.doi.org/10.1021/acs.langmuir.0c0241715220Langmuir2020,36,15220−15229

1Langmuirpubs.acs.org/LangmuirArticleFigure1.Schematicdiagramofnanoparticlesmodifiedbybiomimeticpolyelectrolyte.21fields.Weexploredvariousphenomenaoforganicmacro-thechangeofthechargedensityoftheparticlebrushlayerwithmoleculesinelectrolytesolutionbystudyingthiskindofbrushbackgroundsaltsolutionconcentrationandsolutionpHunder25layer,andnanoparticleswithbrushlayerpossibilitiesinthedifferentbrushthicknessesindetail.preparationofnovelnanomaterialsandfilmscanalsobeInthisstudy,atheoreticalmodelofbiomimeticpolyelec-explored.trolyte-modifiednanoparticlesisthePNPequationsystem.TheWhennanoparticleswithbrushlayerscontactwithansurfaceofnanoparticlesismodifiedbybiomimeticpolyelec-32,33electrolytesolution,thebrushlayerofparticleswillundergoatrolytetoformanorganicbrushlayer.Herein,thechargedeprotonation/protonationreaction,whichwillchangethepropertiesofbrushlayerscanbechangedbyadjustingthechargepropertiesofthebrushlayerofparticles.22Thechargechemicalreactionofthebiomimeticpolyelectrolytegroupsingeneratedbythebrushlayerwillattractorrepeltheionsinthethebrushlayer.Differentfromthepreviousstudies,whichonlysolution,andfinally,thebrushlayerofparticleswillshowexploredtheinfluenceofparticlesizeandpHofelectrolytepositiveornegativeelectricproperties.Organicmacromolecularsolutiononthesurfacechargeofnanoparticles,thispapersubstancesareaffectedbythechargepropertiesofthebrushinvestigatedthebrushlayerchargepropertiesofnanoparticleslayeroftheparticlesduringvarioustransportprocesses.Forwithabrushfromfouraspects:particlesize,pHofelectrolyteexample,thetransportefficiencyofvirusesinnanoporousmediasolution,backgroundsaltconcentration,andbrushlayerisaffectedbythechargedensityonthesurfaceoftheproteinthickness.Thismodelissuperiortosilicaparticlesinsome34shellandtheporewall.23Theabsorptionofmetalelementsbypracticalnano-biosensorapplications.Insummary,theresultssphericalmicroorganismsisinfluencedbythesizeandchargeprovidetheoreticalsupportfortheresearchonthecurrentdensitydistributionofmicroorganisms.24Thechargedensityofchangedetectionoforganicmacromolecularparticlespassing35−38brushparticlesmodifiedbybiomimeticpolyelectrolyteisthroughnanoporesandproteintransportefficiencyin39,40variablebackgroundsaltenvironments.affectedbymanyfactors,suchasparticlesizes,thethicknessofthebrushlayer,pHofelectrolytesolution,andconcentration25ofthebackgroundsaltsolution.Becauseofthedifferent■MATHEMATICALMODELcurvature,thebrushlayerchargedensitywithdifferentsizeswillAsphericalnanoparticlewithradiusofRpisplacedinanchangedifferently.Forexample,thesizeofporcinecircovirusiselectrolytesolutionincludingXtypesofions,asshowninFigureabout17nm,andthatofmycoplasmacellsisabout100nm;1.ThisstudyselectstheKClsolutionwithaconcentrationoftheirchargepropertiesontheproteinshellandonthecellCKClasthebackgroundsaltsolutionintheelectrolyte;KOHand26,2728membranearedifferent.Inaddition,Luetal.studiedtheHClareusedtoregulatethepHoftheelectrolytesolution.nanoparticleswithdifferentsurfacemodificationsintherangeTherefore,therearefourkindsofionsinsolution:H+,K+,OH−,2−100nmandassumedaconstantparticlechargetoandCl−.Thesurfaceofnanoparticlesismodifiedbybiomimetic29characterizetheparticle−waterinteraction.However,pre-polyelectrolyteP∼NH2andP∼COOH(e.g.,lysine)toformaviousstudiesmostlyconcentrateontheeffectofpolymerbrushlayerwithathicknessofdm.Atthenanoscale,weregardgraftingdensityonthechargedensityofthebrushlayerbythebrushlayerasasinglechainconnectedbymultiplechangingthegraftingdensityofpolymerinthebrushlayer.Inelectrolytegroups,whichisuniformlyandtightlyconnectedtobiomimeticpolyelectrolyte-modifiednanochannels,thegraftingtheparticlesurface.Therefore,theinfluenceofparticlesurfacedensityofpolyelectrolyteinthebrushlayeraffectstheionpropertiesisignored.Thisstudyisbasedonthesteady-state.selectivity,channelconductivity,andthebrushlayerchargeThus,theinfluenceofthefunctionalgroupchaindeformationis30,31density.Unfortunately,thereareafewreportsontheeffectalsoignored.ofthethicknessofthebrushlayeronthechargedensityoftheAtwo-dimensionalaxisymmetricmodelisusedinthisstudy.particlebrushlayer.AfurtherdiscussionhasnotbeenhadaboutTherearemanykindsofionsinthesolution.Thepotentialand15221https://dx.doi.org/10.1021/acs.langmuir.0c02417Langmuir2020,36,15220−15229

2Langmuirpubs.acs.org/LangmuirArticleionmasstransferinsolutionarecontrolledbythesteady-stateρ=[1000(PF∼]NH+−−[P∼]COO)m3PNPequationsystemiKΓKΓ[H+]yjjaabbzz4=−1000Fjj+zz2jK+[]H+1H+[]K+z−∇==εε0fϕρeFz∑icikab{(9)i=1(1)ThenetvolumedensitiesoftheacidelectrolytegroupandalkalineelectrolytegroupareΓ=[P∼COO−]+[P∼COOH]anda=Nσ/1000dnandΓ=[P∼NH+]+[P∼NH]=Nσ/mmab32m∇·=∇ND·−∇−ijjczDiFc∇=ϕyzz0,i=(1,2,3,4)1000dmna,respectively.σmisthegraftingdensityofthebrushiijiiizkRT{layerontheparticlesurface(thenumberofelectrolytegroup(2)chainsconnectedontheparticlesurfaceinunitvolume,242−44whereFistheFaradayconstant;ϕisthepotentialinsidegenerallyfrom0.05to0.6chains/nm),naistheAvogadroconstant,andNisthenumberofelectrolytegroupsonasingleelectrolytesolution;Ni,ci,zi,andDirepresenttheionicfluxes,chaininthebrushlayer.themolarconcentration,valence,anddiffusioncoefficientofthe++−Consideringthechargepropertiesofthebrushlayer,theithionicspecies(i=1forH,i=2forK,i=3forCl,andi=4−averagevolumechargedensityofthebrushlayerisdefinedasforOH),respectively;ρeisthespacechargedensityinsidetheelectrolytesolution;Ristheuniversalgasconstant;ε0isthe1RdPm+absolutedielectricconstant;εfistherelativedielectricconstantρ=∫ρmdydmRP(10)oftheelectrolytesolution;andTistheabsolutetemperatureofelectrolytesolution.Ontheinnersurfacesofthenanoparticle,Aelectricdoublelayer(EDL)withathicknessofλDexiststhenormalionicfluxofeachspeciesiszero,n·Ni=0(i=1,2,3,outsidetheparticlebrushlayer:4).Theelectricpotentialϕatinfinityissetto0.Inthebrush4layerofnanoparticles,thebulkchargedensityofthebrushlayer22boundarycondition,−ε0εf·n·∇ϕ=ρm,isimposed.λD0=εεfRT/∑FzCii0Inordertosolvethecouplingeq1andeq2,appropriatei=1(11)boundaryconditionsarerequired.AxisymmetricboundaryInordertoavoidtheeffectofelectricdoublelayeroverlapconditionsareappliedalongthey-axisforeachionicbetweenparticlesandthesolutiondomain,thefar-fieldconcentrationandforelectricpotential.Inareasfarawayfromboundaryasd=RP+60λDisemployedinthesolutionthechargednanoparticles(e.g.,dottedlineinFigure1),itisprocedure.assumedthattheionicconcentrationofeachkindretainsitsvolumeconcentration,ci=Ci0,i=1,2,3,4.Accordingtothe■EXPERIMENTALSECTIONelectroneutralcondition,thevolumeconcentrationofvarious41Theabove-mentionedtwo-dimensionalaxisymmetricmodelisionsinthesolutionisasfollowssimulatedbyCOMSOLMultiphysics(version4.0).Thisstudyisbasedonthesteady-statePNPequationsystemtocoupleelectricfield−+pH3−−+(14pH)3CC10==10and4010(3)andflowfield.Theeffectsofparticlesize,pHvalueofelectrolytesolution,concentrationofthebackgroundsaltsolution,andthebrushCC20==KClandCCCC30KCl+10−≤40whenpH7layerthicknessonthechargecharacteristicsofthebrushlayerarediscussedthroughthecalculationresultsofthenumericalscheme.Free(4)triangularmeshwithinthemodelisadopted;thetotalnumberofCCCCCC20=−+KCl1040and30=KClwhenpH>7triangularmeshesis28854,andthenumberoftriangularmeshesinthebrushlayeris924.(5)Thefollowingphysicalparametersareusedinthesimulations:ε0=8.854×10−12CV−1m−1,ε=80,R=8.31Jmol−1K−1,F=96490CWhenthepHofthesolutionchanges,thebiomimeticfmol−1,andT=298K,respectively.Theuniformnanoparticlebrushpolyelectrolytegroups’,P∼COOHandP∼NH2,layerinthestructureandthedeformationofthebrushlayerareignored,protonation/deprotonationreactionswilloccurinsidethewhichiseffectiveiftherepeatedunitNofthebiomimeticbrushlayer43polyelectrolytegroupsisinarelativelylowrange(e.g.,N≤20).−+(6)Thegraftingdensityofbiomimeticelectrolyteinthebrushlayerisσm=P∼↔COOHP∼+COOH−20.15chainsnm;thenumberofelectrolytegroupsonasingle-chainis++N=20,pKa=−logKa=2.2(α-carboxyl),pKb=−logKb=−8.8(α-P∼+↔NH23HP∼NH(7)amino).25,45Therelativepermittivityεandthediffusivityoftheionicfspeciesi,Di,insidethenanoparticlebrushlayersarethesameasthoseAssumingtheequilibriumconstantsofthetworeactionsareKaoutsidethem.ThediffusioncoefficientsofH+,K+,OH−,andCl−areDiandKb,respectively(i=1,2,3,4)=9.31×10−9,1.96×10−9,5.30×10−9,and2.03×10−9,respectively.−+[∼PNH+][∼PCOOH][]3Inordertoverifythecorrectnessofournumericalcalculationresult,KKab=and=+thecodeofthismodelisvalidatedbycomparingwiththeresultofrefs[∼PCOOH][∼PNHH2][](8)31and25,whichderivedthechangecurveofthechargedensityofthewhere[H+]isthelocalconcentrationofH+inthebrushlayer,brushlayeronthechannelwallwhenthegatevoltageiszero.Forthe[H+]=10−pHexp(−ϕ/ϕ),andϕ=RT/Fdenotestheconvenienceofverification,wedesignedaplatemodifiedby00biomimeticpolyelectrolyte(particleswithinfiniteradiuscanbereferencethermalpotential.[P∼COO−],[P∼COOH],[P∼regardedasaplate),whichisplacedinthesolutiondomainwithaNH],and[P∼NH+]denotethebulkdensityofeach23backgroundsaltconcentrationof1mM.Bynumericalsimulationandelectrolytegroupinthebrushlayer,respectively.Itcanbeshowncalculation,thecurveofthebrushlayerchargedensitywithpHisdrawnthatthevolumechargedensityofthebrushlayercanbeandcomparedwiththeresultsinrefs31and25.Itisclearlyillustratedexpressedasthatoursimulationresult(blackcurve)isfullyconsistentwiththe15222https://dx.doi.org/10.1021/acs.langmuir.0c02417Langmuir2020,36,15220−15229

3Langmuirpubs.acs.org/LangmuirArticleanalysisresult(reddot)ofrefs31and25,asshowninFigure2.Thus,modelcalculationandcomparedwiththeresultsinthetheaccuracyandreliabilityofthepresentmodelhavebeenverified.literature,25,46,47whenpH=5.5,thechargedensityofthebrushlayerisclosetozero;thus,pH=5.5istheisoelectricpoint(IEP)oftheparticlebrushlayer.ThisshowsthatwhenpH=5.5,thenumberofP−COO−groupsandP−NH+groupsinthe3brushlayerstaysequal,whichmakesthebrushlayerinanelectricallyneutralstate.Fromtheabovephenomena,itfollowsthatthenanoparticlebrushlayercanmaintainanelectricallyneutralstatebyadjustingthepHvalue,sothattheeffectofelectricfieldontheparticlescanbeneglectedtosomeextentwhenmodelsaredevelopedorexperimentsarecarriedout.Fromtheabovediscussion,itcanbeseenthatwhenpH<5.5,thechargedensityoftheparticlebrushlayerdecreaseswiththeincreaseofpHfromFigure3.WhenpH>5.5(thechargedensityisnegativeatthistime),thechargedensityoftheparticlebrushlayerincreaseswiththeincreaseofpH.BecausewhenpH<5.5,P∼NH+H+↔P∼NH+isthedominantreactioninthe23brushlayer,andalargenumberofthegroupsofP∼NH2unitewithH+toformthegroupsofP∼NH+inthebrushlayer.Asa3result,thechargedensityofthebrushlayerisofpositivepolarity,andtheconcentrationofH+inthebrushlayerdecreaseswiththeFigure2.FluctuatingcurveofthebrushlayerchargedensitydependingincreaseofpH,whichleadstothedecreaseofthechargedensityonpHoftheplate,asshownasthesolidblackline;thereddotofthebrushlayerasthereactionproceedstothereverse.Whenrepresentstheanalysisresultinrefs31and25.CKCl=1mM.pH>5.5,thedominantreactioninthebrushlayertransformintoP∼COOH↔P∼COO−+H+.Atthistime,alarge■numberofthegroupsofP∼COOHinthebrushlayerdissociateRESULTSANDDISCUSSION+−HandthegroupsofP∼COO,whichresultsinnegativeChargeDensityoftheBrushLayer:pHEffect.Throughpolarityofbrushchargedensity.Atthesametime,withthetheanalysisofthecalculationresults,itcanbeconcludedthat+increaseofpH,theconcentrationofHinthebrushlayerthechangeofbulkchargedensityinthebrushlayerwillbedecreases,whichmakethereactionproceedtotheforwardandaffectedbythechangeofparticlesizeandpHvalueintheultimatelyleadstoanincreaseofnegativebrushchargedensity.solution.Figure3depictsthebrushchargedensityofFromFigure3,itcanbeseenthatthechargedensityofthebrushlayerdependsonnanoparticlesize.Theabsolutevalueofbrushchargedensity|ρ|decreaseswiththeincreaseofparticlesizeatacertainpH.Withtheincreaseofparticlesize,thecontactareabetweentheparticlesandthesolutionincreases,andthelocalconcentrationofH+inthebrushlayerincreases,whichleadtothedecreaseofthechargedensityofthebrushlayer.Foraclearerdescriptionoftheeffectofparticlesizeonthechargedensityoftheparticlebrushlayer,wenormalizethechargedensityoftheparticlebrushlayerandthatoftheplatebrushlayeratdifferentpHs.Figure4depictsthefunctionalrelationshipbetweenthenormalizedbrushchargedensityofnanoparticlesandpHwhentheconcentrationoftheback-groundsaltsolutionis1mM.Whentheparticlesizeis80nm,thenormalizedcurveoftheparticleiscloseto1,whichindicatesthatthechargedensityoftheparticlebrushlayerislessaffectedbythesizewhentheparticleradiusincreasestoacertain10extent.ThechangeofchargedensitywithpHcanbeexplainedbychangingtheconcentrationofH+inthebrushlayer.AsFigure3.BrushlayerchargedensityofnanoparticleswithdifferentsizesasafunctionofpHwhentheconcentrationofthebackgroundsaltshowninFigure5,whenpH<5.5,thechargedensityofthesolutionequals1mM.brushlayerisofpositivepolarity,andthenormalizedtheconcentrationofH+inthebrushlayerincreasesatfirstandthendecreaseswiththechangeofpH,reachingthemaximumwhennanoparticleswithdifferentsizesvaryingwithpHwhenthepHis3.5.Similarly,whenpH<5.5,thechargedensityoftheconcentrationofthebackgroundsaltsolutionis1mM(CKCl=1brushlayerinFigure4increasesatfirst,thendecreases,andmM).Meanwhile,thebrushchargedensityofthebrushplatereachesthemaximumwhenpHis3.5.WhenpH>5.5,thecanbetreatedasarulertodealwiththebrushchargedensityofchargedensityofthebrushlayerisofnegativepolarity,andthenormalizedconcentrationofH+inthebrushlayerdecreasesatparticlesinadimensionlessway.AscanbeseenfromFigure3,thebrushchargedensityofparticlesisofpositivepolaritywhenfirstandthenincreaseswiththechangeofpH,reachingthethesolutionpHislessthanafixedvalue.WhenthesolutionpHmaximumwhenpHis7.5,asshowninFigure5.Atthesameisgreaterthanafixedvalue,thebrushchargedensityofparticlestime,thechargedensityofthebrushlayerinFigure4increasesatshowsnegativepolarity.Asaconsequenceofthetheoreticalfirst,thendecreases,andreachesthemaximumwhenpHis7.5.15223https://dx.doi.org/10.1021/acs.langmuir.0c02417Langmuir2020,36,15220−15229

4Langmuirpubs.acs.org/LangmuirArticleFigure4.Normalizedcurveofthebrushlayerchargedensityofnanoparticleswithdifferentsizesat1mMsaltsolutionconcentration[(a)pH<5.5,(b)pH>5.5].layerturnsintonegativepolarity.AtthesamepH,thechargedensityoftheparticlebrushlayerincreaseswiththeincreaseofbackgroundsaltconcentration,andthecurvetendstobeflatwhenthebackgroundsaltsolutionconcentrationincreasestoacertainextent.ThechargedensityofthenanoparticlebrushlayerismainlyaffectedbytheconcentrationofH+inthebrushlayer.Figure7depictstheconcentrationvariationofH+inthebrushlayerwiththeconcentrationofthebackgroundsaltsolutionatdifferentpHs.TheconcentrationvariationofH+intheparticlebrushlayerisinfluencedbytheconcentrationofK+inthebrushlayer,whichisnotonlyrelatedtotheconcentrationofthebackgroundsaltsolutionbutalsoaffectedbythepositiveandnegativepropertiesofbrushchargeatdifferentpHs.Figure8depictstheconcentrationvariationofK+intheparticlebrushlayerdependingontheconcentrationofthebackgroundsaltsolutionatdifferentpHs.WhenpH<5.5,theconcentrationofK+inthebrushlayerislessthanthatinthebackgroundsaltsolution.With+Figure5.NormalizationcurveoftheconcentrationofHinthebrushtheaidoftheconcentrationofK+inthebackgroundsaltsolutionlayerofnanoparticleswithdifferentsizesat1mMsaltsolution+subtractedfromtheconcentrationofKinthebrushlayer,theconcentration.+changeratesoftheconcentrationofKinthebrushlayerareobtained,asshownFigure8a,b.WhenpH>5.5,theChargeDensityoftheBrushLayer:BackgroundSalt+concentrationofKinthebrushlayerishigherthanthatinConcentrationEffect.ItcanbeobservedinFigure3thatthethebackgroundsaltsolution.Withtheaidoftheconcentrationcurveoftheparticleradiusat80nmcoincideswiththatat100++ofKinthebrushlayersubtractedfromtheconcentrationofKnm,whichshowsthatwhentheradiusofnanoparticlesincreasesinbackgroundsaltsolution,thechangeratesoftheto80nm,theparticlesizehaslittleeffectonthechargedensityofconcentrationofK+inthebrushlayerarethusobtained,asthebrushlayer.SincethesizeofmostDNAmoleculesisshownFigure8c,d.SoitcanbeseenfromFigure8,whenpH5.5,thechargedensityinthebrushlayerisofitisfoundthatwhenpH>5.5,thechargedensityinthebrushnegativepolarity.AsshowninFigure8c,d,thecationinthe15224https://dx.doi.org/10.1021/acs.langmuir.0c02417Langmuir2020,36,15220−15229

5Langmuirpubs.acs.org/LangmuirArticleFigure6.ChargedensityofnanoparticlebrushlayerdependingontheconcentrationofthebackgroundsaltsolutionatdifferentpHs:(a)pH=3,3.5,4;(b)pH=4.5,5,5.5;(c)pH=6,6.5,7;(d)pH=7.5,8,8.5.Figure7.CurvesofH+intheparticlebrushlayerwithbackgroundsaltsolutionconcentrationatdifferentpHs:(a)pH=3,3.5,4;(b)pH=4.5,5,5.5;(c)pH=6,6.5,7;(d)pH=7.5,8,8.5.brushlayerisattracted,whichmakestheK+concentrationinthedensityofthebrushlayer.Classically,thesizeofbiomimeticbrushlayerlargerthanthatinthesolution.Withtheincreaseofpolyelectrolytechainsisabout1−3nminanα-helicalstructuretheconcentrationofthebackgroundsaltsolution,thedifferenceandabout6nminaβ-foldedstructurewhenthenumberofbetweentheconcentrationofK+inthebrushlayerandthegroupsN=20.45WehavemadeanexplorationbyestablishingaconcentrationofK+inthesolutionincreases.Asaresult,themathematicalmodelforthecalculationandanalysisand+comparingwiththeresultsintheliterature.21,25UndertheconcentrationofKinthebrushlayerincreasesrelativetothatinsolution,andtheH+exclusioneffectsareincreased.Theconditionofafixednanoparticleradiusof10nm,theeffectofconcentrationofH+inthebrushlayerdecreaseswiththechangingthethicknessofthebrushlayeronthechargeincreaseofbackgroundsaltsolutionconcentration,asshowninpropertiesofthebrushlayerisdiscussedbycomparingtheFigure7c,d.changesofthechargedensityofthebrushlayeratdifferentChargeDensityoftheBrushLayer:BrushThicknessbackgroundsaltconcentrationsandsolutionpHs.TheeffectofEffect.Thethicknessofthebrushlayeralsoaffectsthechargechangingthethicknessofthebrushlayeronthecharge15225https://dx.doi.org/10.1021/acs.langmuir.0c02417Langmuir2020,36,15220−15229

6Langmuirpubs.acs.org/LangmuirArticleFigure8.CurveofK+intheparticlebrushlayerwithbackgroundsaltsolutionconcentrationatdifferentpH:(a)pH=3,3.5,4;(b)pH=4.5,5,5.5;(c)pH=6,6.5,7;(d)pH=7.5,8,8.5.Figure9.ChangecurveofchargedensitywithbackgroundsaltsolutionconcentrationandpHunderdifferentbrushthicknesses:(a)atCKCl=1mM;(b)atpH=7.propertiesofthebrushlayerisdiscussed.ThecharacterdensityUndertheconditionofpH=7,thechargedensityofthebrushcurvesoftheparticlebrushlayerwithbackgroundsaltsolutionlayerisnegative,andthechargedensityofthebrushlayerconcentrationandpHunderdifferentbrushthicknessesareincreaseswiththeincreaseoftheconcentrationoftheshowninFigure9a,b,respectively.FromFigure9a,b,wecanseebackgroundsaltsolution,asshowninFigure9a.TheconcentrationofH+inthebrushlayerdecreaseswiththethatthechargedensityoftheparticlebrushlayerincreaseswithincreaseofbackgroundsaltsolutionconcentration,asshowninthedecreaseofthebrushlayerthicknessattheuniformFigure10a.TheconcentrationofH+inthebrushlayerisaffectedbackgroundsaltconcentrationorpH.ReducingthethicknessofbytherelativeconcentrationofK+inthebrushlayer(thethebrushlayerisequivalenttoincreasingthedensityof+differencebetweentheconcentrationofKinthebrushlayerbiomimeticpolyelectrolyteinthebrushlayer,whichmakesthe+andtheconcentrationofKinsolution),asshowninFigure10b.densityofvariousgroupsinvolvedinchemicalreactionsandFromFigure10a,b,itcanbeseenthatwhenthethicknessofthechemicalreactionsinthebrushlayerincrease,resultinginabrushlayerdecreases,theconcentrationofH+andK+inthesignificantincreaseinthepositive(ornegative)chargedensityinbrushlayerincreasesinthesamebackgroundsaltsolutionthebrushlayer.ComparingFigures3and9b,wecanseethattheconcentration.Byvirtueofthedecreaseofthebrushlayerchangeprocessandtrendofchargedensityoftheparticlebrushthickness,thenegativechargedensityoftheparticlebrushlayerlayeratdifferentpHsremaininvariableregardlessofthechangeincreases,andthecationattractionincreases.FromFigure10a,b,ofparticlesizeorbrushthickness.thesmallerthethicknessofthebrushlayer,themoreobviousthe15226https://dx.doi.org/10.1021/acs.langmuir.0c02417Langmuir2020,36,15220−15229

7Langmuirpubs.acs.org/LangmuirArticleFigure10.VariationcurveofionconcentrationwithbackgroundsaltsolutionconcentrationunderdifferentbrushthicknessesatpH=7.(a)ConcentrationofH+.(b)ConcentrationofK+.changeoftheconcentrationofK+curve;thelargerthethicknessorcid.org/0000-0002-8744-9083;Email:zhouteng@ofthebrushlayer,themoreobviousthechangeofthehainanu.edu.cnconcentrationofH+curve.Therefore,whenweneedtoobserveLipingWen−CASKeyLaboratoryofBio-InspiredMaterialsthetrendoftheconcentrationofK+change,wecanchooseaandInterfacialScience,TechnicalInstituteofPhysicsandsmallerbrushthickness.WhenweneedtodiscusstheeffectofChemistry,ChineseAcademyofSciences,Beijing100190,theconcentrationofH+onchargedensity,wecanchoosetheChina;Email:wen@mail.ipc.ac.cnlargerbrushthickness.Authors■LuyuDeng−MechanicalandElectricalEngineeringCollege,CONCLUSIONSHainanUniversity,Haikou570228,Hainan,ChinaInthisstudy,abiomimeticpolyelectrolyteisusedtomodifyLiuyongShi−MechanicalandElectricalEngineeringCollege,nanoparticlestoformanorganicbrushlayeronthesurfaceofHainanUniversity,Haikou570228,Hainan,Chinananoparticles.ThechargepropertiesofbrushednanoparticlesTingLi−InstituteofBiomedicalEngineering,ChineseAcademyareexploredfromfouraspects:thesizeofnanoparticles,thepHofMedicalScienceandPekingUnionMedicalCollage,Tianjinvalueofelectrolytesolution,theconcentrationoftheback-100730,Chinagroundsaltsolution,andthethicknessofthebrushlayer.TheXiangtaoZhong−MechanicalandElectricalEngineeringresultsshowthatthechargedensityofthebrushlayerdependsCollege,HainanUniversity,Haikou570228,Hainan,ChinauponthelocalconcentrationofH+inthebrushlayer.Thesize+Completecontactinformationisavailableat:changeofnanoparticleswiththebrushleadstothelocalHhttps://pubs.acs.org/10.1021/acs.langmuir.0c02417changeofbrushlayer,whichmakesthechargedensityofthebrushlayerdecreasewiththeincreaseofparticlesize.NotesNevertheless,whentheparticlesizeincreasesto80nm,theTheauthorsdeclarenocompetingfinancialinterest.chargedensitywillnotchangeinthebrushlayerwiththeparticleradius.Thesimulationresultsshowthatthepolarityofbrush■layerchargeisreversedatpH=5.5(IEP),andthebrushlayerACKNOWLEDGMENTSchargedensitydecreasesatfirstandthenincreases.TheionThisworkisfundedbyNationalNaturalScienceFoundationofconcentrationinthebrushlayerisaffectedbythechangeofH+China(Grant52075138,61964006,andU1830118)andandK+concentrationgradientinthesolution.TheabsoluteHainanProvincialNaturalScienceFoundation(Grantvalueofbrushlayerchargedensityincreaseswiththeincreaseof2019RC032and519MS021).backgroundsaltconcentration.ThechargedensityofthebrushlayerislargeratthesamebackgroundsaltconcentrationorpH■REFERENCESwhenthethicknessofthebrushlayerissmaller.Theseresults(1)Huang,G.;Xiong,Z.;Qin,H.;Zhu,J.;Sun,Z.;Zhang,Y.;Peng,X.;canbeusedtoexplainwhythetransportefficiencyofvariousou,J.;Zou,H.Synthesisofzwitterionicpolymerbrusheshybridsilicaproteinsisdifferentindifferentinternalenvironments.Thesenanoparticlesviacontrolledpolymerizationforhighlyefficientresultsprovidetheoreticalsupportforthetechniqueofchangingenrichmentofglycopeptides.Anal.Chim.Acta2014,809,61−8.thevelocityofmacromolecularorganiccompoundswitha(2)Lu,Y.;Ballauff,M.Sphericalpolyelectrolytebrushesasnanoreactorsforthegenerationofmetallicandoxidicnanoparticles:certainsizethroughnanoporesbycontrollingthebackgroundSynthesisandapplicationincatalysis.Prog.Polym.Sci.2016,59,86−saltsolution.104.(3)Zhao,H.;Hu,W.;Ma,H.;Jiang,R.;Tang,Y.;Ji,Y.;Lu,X.;Hou,■AUTHORINFORMATIONB.;Deng,W.;Huang,W.;Fan,Q.Photo-InducedCharge-VariableConjugatedPolyelectrolyteBrushesEncapsulatingUpconversionCorrespondingAuthorsNanoparticlesforPromotedsiRNAReleaseandCollaborativeTengZhou−MechanicalandElectricalEngineeringCollege,PhotodynamicTherapyunderNIRLightIrradiation.Adv.Funct.HainanUniversity,Haikou570228,Hainan,China;Mater.2017,27,1702592.15227https://dx.doi.org/10.1021/acs.langmuir.0c02417Langmuir2020,36,15220−15229

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