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Title: Probing structure-induced optical behavior in a new class of self-activated luminescent 0D/1D CaWO₄ metal oxide – CdSe nanocrystal composite heterostructures

In this report, we synthesize and characterize the structural and optical properties of novel heterostructures composed of (i) semiconducting nanocrystalline CdSe quantum dot (QDs) coupled with (ii) both one and zero-dimensional (1D and 0D) motifs of self-activated luminescence CaWO₄ metal oxides. Specifically, ~4 nm CdSe QDs have been anchored onto (i) high-aspect ratio 1D nanowires, measuring ~230 nm in diameter and ~3 μm in length, as well as onto (ii) crystalline 0D nanoparticles (possessing an average diameter of ~ 80 nm) of CaWO₄ through the mediation of 3-mercaptopropionic acid (MPA) as a connecting linker. Composite formation was confirmed by complementary electron microscopy and spectroscopy (i.e. IR and Raman) data. In terms of luminescent properties, our results show that our 1D and 0D heterostructures evince photoluminescence (PL) quenching and shortened PL lifetimes of CaWO₄ as compared with unbound CaWO₄. We propose that a photo-induced electron transfer process occurs from CaWO₄ to CdSe QDs, a scenario which has been confirmed by NEXAFS measurements and which highlights a decrease in the number of unoccupied orbitals in the conduction bands of CdSe QDs. By contrast, the PL signature and lifetimes of MPA-capped CdSe QDs within these heterostructures do not exhibit noticeable changes as comparedmore » with unbound MPA-capped CdSe QDs. The striking difference in optical behavior between CaWO₄ nanostructures and CdSe QDs within our heterostructures can be correlated with the relative positions of their conduction and valence energy band levels. In addition, the PL quenching behaviors for CaWO₄ within the heterostructure configuration were examined by systematically varying (i) the quantities and coverage densities of CdSe QDs as well as (ii) the intrinsic morphology (and by extension, the inherent crystallite size) of CaWO₄ itself.« less
 [1] ;  [2] ;  [2] ;  [2] ;  [3] ;  [2] ;  [2] ;  [1] ;  [3] ;  [2] ;  [1] ;  [4]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States)
  2. State Univ. of New York at Stony Brook, Stony Brook, NY (United States)
  3. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)
  4. Brookhaven National Lab. (BNL), Upton, NY (United States); State Univ. of New York at Stony Brook, Stony Brook, NY (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0897-4756; R&D Project: PM037; KC0201030
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Chemistry of Materials
Additional Journal Information:
Journal Volume: 27; Journal Issue: 3; Journal ID: ISSN 0897-4756
American Chemical Society (ACS)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY nanowire, luminescence, quantum dot, photoinduced charge transfer, synthesis