Nanocrystalscalledquantumdotshavepromisedtorevolutionizedisplaytech-nologies,solarpowerandbiologicalimagingformorethanadecade.Yetthequan-tum-dotmarkethasremainedsmall,withahandfulofcompaniessellingdotsdirectlytoresearchers,usingtheparticlestodeveloptheirownproductsorlicensingtheirtechnologiestopartners.“Quantumdotshavebeenaroundforquiteawhile,butthey’retakingareallylongtimetomature,”saysDavidHwangofthemarket-analysiscompanyLuxResearchinNewYork.Akeybarrierisprice:quantumdotscancostanywherefromUS$3,000to$10,000pergram,restrictingtheirusetohighlyspecializedapplications.Butindustryanalystsarenowpredictingextremelyrapidgrowthforthemarketoverthenextfewyears,drivenbydemandforenergy-efficientdisplaysandlighting,andenabledbycheaper,moreefficientmanufac-turingprocesses.InSeptember2008,market-researchcompanyBCCResearchofWellesley,Massachusetts,predictedthatthemarketforproductsrelyingonquantumdotswouldgrowfrom$28.6millionin2008to$721millionby2013,withparticularlyrapidgrowthintheoptoelectronicssectorfrom2010(seegraph).DotsbythekiloMostcommerciallyavailablequantumdotshaveasemiconductorcore,oftenamixtureofcadmiumandselenium,measuringabout2–10nanometresindiameter.Thiscoreissurroundedbyashell,usuallyofanothersemi-conductormaterial,andanouterpolymerorinorganiclayer.Thesmallsizeofthedotsgivesthemuniqueproperties.Photonshittingadotexciteanelec-tronfromthesemiconductormaterial,leavingapositivelycharged‘hole’:thiselectron–holepairiscalledanexciton.Inabulksemiconduc-tor,excitonscanhavearangeofenergieswithinacontinuousband.Butinthenanoscaledots,excitonsoccupydistinct,quantizedenergystates.Thismeansthataseachexcitedelectronrecombineswithahole,itemitsaphotonwithaspecific,predictablewavelength.Smallerdotsgiveoffbluelight,whereaslargerdotsofthesamematerialappearred.Althoughquantumdotswereinitiallymadeusingexpensivetechniquesborrowedfromthecomputer-chipindustry,mostdotsarecur-rentlymadeby