Influenceof van der WaalsInteractionsbetweenthe AlkylChainsofSurfaceLigandson the Size and Size Distributionof NanocrystalsPreparedby the DigestiveRipeningProcess

Abstract

Thermalheatingof polydispersednanocrystals(NCs)with surface-activeorganicligandsin a solventleads tothe formationof monodispersedNCs, and this processis known asdigestiveripening(DR). Here, by performingDR on Au NCs usingdifferent-chain-lengthamine and thiol ligands,we evidentlyshowthat ligandswith C12chain length result in the formationof NCswith narrowsize distributionswhen comparedto C8, C16, and C20chain length ligands.Furthermore,our findingsalso show that inthe case of alkyl thiol, the NC size remainsmore or less the same,while the size distributiongets altered significantlywith the chainlength.On the other hand, both size and size distributionareaffectedsignificantlywhen the alkyl amine chain length is varied.Fouriertransforminfrared(FTIR)studies indicatethat the van derWaals (vdW) interactionsare weakestwhen the amine with C12carbon chain is used as the DR agent, while in the case of thiols,moleculeswith C8and C12chain lengths have nearly the same vdW interactions(with C12slightly weaker than C8), which are weakerthan those of C16and C20. Moleculardynamics(MD) simulationresults corroboratethe experimentalobservationsand suggestthatdue to more defects in the alkyl chain, the C8and C12(amine as well as thiol) ligands are disorderedand less stable on Au(111)andAu(100)surfaces.This could result in efficientetchingand redeposition,makingthe ligands with C8and C12chain lengths the betterDR agents.