"Quantized" Doping of Individual Colloidal Nanocrystals Using Size-Focused Metal Quantum Clusters

Beatriz Santiago-González, Angelo Monguzzi, Valerio Pinchetti, Alberto Casu, Mirko Prato, Roberto Lorenzi, Marcello Campione, Norberto Chiodini, Carlo Santambrogio, Francesco Meinardi, Liberato Manna, Sergio Brovelli*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


The insertion of intentional impurities, commonly referred to as doping, into colloidal semiconductor quantum dots (QDs) is a powerful paradigm for tailoring their electronic, optical, and magnetic behaviors beyond what is obtained with size-control and heterostructuring motifs. Advancements in colloidal chemistry have led to nearly atomic precision of the doping level in both lightly and heavily doped QDs. The doping strategies currently available, however, operate at the ensemble level, resulting in a Poisson distribution of impurities across the QD population. To date, the synthesis of monodisperse ensembles of QDs individually doped with an identical number of impurity atoms is still an open challenge, and its achievement would enable the realization of advanced QD devices, such as optically/electrically controlled magnetic memories and intragap state transistors and solar cells, that rely on the precise tuning of the impurity states (i.e., number of unpaired spins, energy and width of impurity levels) within the QD host. The only approach reported to date relies on QD seeding with organometallic precursors that are intrinsically unstable and strongly affected by chemical or environmental degradation, which prevents the concept from reaching its full potential and makes the method unsuitable for aqueous synthesis routes. Here, we overcome these issues by demonstrating a doping strategy that bridges two traditionally orthogonal nanostructured material systems, namely, QDs and metal quantum clusters composed of a "magic number" of atoms held together by stable metal-to-metal bonds. Specifically, we use clusters composed of four copper atoms (Cu4) capped with d-penicillamine to seed the growth of CdS QDs in water at room temperature. The elemental analysis, performed by electrospray ionization mass spectrometry, X-ray fluorescence, and inductively coupled plasma mass spectrometry, side by side with optical spectroscopy and transmission electron microscopy measurements, indicates that each Cu:CdS QD in the ensemble incorporates four Cu atoms originating from one Cu4 cluster, which acts as a "quantized" source of dopant impurities.

Original languageEnglish (US)
Pages (from-to)6233-6242
Number of pages10
JournalACS Nano
Issue number6
StatePublished - Jun 27 2017

Bibliographical note

Publisher Copyright:
© 2017 American Chemical Society.


  • aqueous synthesis
  • colloidal nanocrystal quantum dots
  • elemental analysis
  • metal quantum clusters
  • photoluminescence
  • quantized doping
  • seeded growth

ASJC Scopus subject areas

  • General Materials Science
  • General Engineering
  • General Physics and Astronomy


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