'Giant'CdSe/CdScore/shellnanocrystals(NCs)weresynthesizedwiththickCdSshell(15monolayers),andthex-raydiffraction(XRD)measurementindicatesthereisazincblendephaseinthethickCdSshell,whereasittransformedintowurtzitephaseunder5minradiationwitha400nm,594μJ∕cm2femtosecond(fs)laserbeam.TheevolutionoftheNCs’spontaneousemissionunderthefslaserradiationwasrecordedwithaHamamatsustreakcamera.Theas-synthesizedNCsexhibitanamplifiedspontaneousemission(ASE)at530nm,whichcomesfromabulk-likeCdSshellduetotheinterfacialpotentialbarrier,whichcouldslowdowntherelaxationofholesfromtheshelltothecore.Afterbeingannealedbyanfslaser,theASEoftheg-NCsistransferredfromabulk-likeCdSshelltoaquantum-confinedCdSecorebecausethephasetransformationdeterminedwiththeXRDmeasurementcouldremovetheinterfacialbarrier.BesidestheASEat643nm,twoshorter-wavelengthASEpeaksat589and541nm,correspondingtoopticaltransitionsofthesecond(1P)andthird(1D)electronquantizationshellsoftheCdSecore,alsoappear,thusindicatingthatAugerrecombinationiseffectivelysuppressed.
