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Title: Ligand-induced dependence of charge transfer in nanotube–quantum dot heterostructures

Abstract

As a model system to probe ligand-dependent charge transfer in complex composite heterostructures, we fabricated double-walled carbon nanotube (DWNT) – CdSe quantum dot (QD) composites. Whereas the average diameter of the QDs probed was kept fixed at ~4.1 nm and the nanotubes analyzed were similarly oxidatively processed, by contrast, the ligands used to mediate the covalent attachment between the QDs and DWNTs were systematically varied to include p-phenylenediamine (PPD), 2-aminoethanethiol (AET), and 4-aminothiophenol (ATP). Herein, we have put forth a unique compilation of complementary data from experiment and theory, including results from transmission electron microscopy (TEM), near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, Raman spectroscopy, electrical transport measurements, and theoretical modeling studies, in order to fundamentally assess the nature of the charge transfer between CdSe QDs and DWNTs, as a function of the structure of various, intervening bridging ligand molecules. Specifically, we correlated evidence of charge transfer as manifested by changes and shifts associated with NEXAFS intensities, Raman peak positions, and threshold voltages both before and after CdSe QD deposition onto the underlying DWNT surface. Importantly, for the first time ever in these types of nanoscale composite systems, we have sought to use theoretical modeling to justify and account formore » our experimental results. Finally, our overall data suggest that (i) QD coverage density on the DWNTs varies, based upon the different ligand pendant groups used and that (ii) the presence of a π-conjugated carbon framework within the ligands themselves and the electron affinity of the pendant groups collectively play important roles in the resulting charge transfer from QDs to the underlying CNTs.« less

Authors:
 [1];  [2];  [3];  [3];  [4];  [4];  [5];  [1];  [6];  [6];  [5];  [4];  [7];  [8]
  1. Stony Brook Univ., NY (United States). Dept. of Chemistry
  2. Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Sciences Division
  3. State Univ. of New York (SUNY) at Stony Brook, Stony Brook, NY (United States). Inst. of Advanced Computational Science
  4. Purdue Univ., West Lafayette, IN (United States). Birck Nanotechnology Center, Dept. of Electrical and Computer Engineering
  5. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). Material Measurement Lab.
  6. State Univ. of New York (SUNY) at Stony Brook, Stony Brook, NY (United States). School of Marine and Atmospheric Sciences
  7. State Univ. of New York (SUNY) at Stony Brook, Stony Brook, NY (United States). Inst. of Advanced Computational Science; Brookhaven National Lab. (BNL), Upton, NY (United States). Computational Science Center
  8. Stony Brook Univ., NY (United States). Dept. of Chemistry; Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Sciences Division
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1303000
Report Number(s):
BNL-112413-2016-JA
Journal ID: ISSN 2040-3364; NANOHL; R&D Project: PM037; KC0201030
Grant/Contract Number:
SC00112704; ACI-121664; OCE-1336724
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nanoscale
Additional Journal Information:
Journal Name: Nanoscale; Journal ID: ISSN 2040-3364
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; 36 MATERIALS SCIENCE; NEXAFS; theoretical modeling; charge transfer; CdSe QDs; DWNTs; ligands

Citation Formats

Wang, Lei, Han, Jinkyu, Sundahl, Bryan, Thornton, Scott, Zhu, Yuqi, Zhou, Ruiping, Jaye, Cherno, Liu, Haiqing, Li, Zhuo-Qun, Taylor, Gordon T., Fischer, Daniel A., Appenzeller, Joerg, Harrison, Robert J., and Wong, Stanislaus S. Ligand-induced dependence of charge transfer in nanotube–quantum dot heterostructures. United States: N. p., 2016. Web. doi:10.1039/C6NR03091B.
Wang, Lei, Han, Jinkyu, Sundahl, Bryan, Thornton, Scott, Zhu, Yuqi, Zhou, Ruiping, Jaye, Cherno, Liu, Haiqing, Li, Zhuo-Qun, Taylor, Gordon T., Fischer, Daniel A., Appenzeller, Joerg, Harrison, Robert J., & Wong, Stanislaus S. Ligand-induced dependence of charge transfer in nanotube–quantum dot heterostructures. United States. doi:10.1039/C6NR03091B.
Wang, Lei, Han, Jinkyu, Sundahl, Bryan, Thornton, Scott, Zhu, Yuqi, Zhou, Ruiping, Jaye, Cherno, Liu, Haiqing, Li, Zhuo-Qun, Taylor, Gordon T., Fischer, Daniel A., Appenzeller, Joerg, Harrison, Robert J., and Wong, Stanislaus S. 2016. "Ligand-induced dependence of charge transfer in nanotube–quantum dot heterostructures". United States. doi:10.1039/C6NR03091B. https://www.osti.gov/servlets/purl/1303000.
@article{osti_1303000,
title = {Ligand-induced dependence of charge transfer in nanotube–quantum dot heterostructures},
author = {Wang, Lei and Han, Jinkyu and Sundahl, Bryan and Thornton, Scott and Zhu, Yuqi and Zhou, Ruiping and Jaye, Cherno and Liu, Haiqing and Li, Zhuo-Qun and Taylor, Gordon T. and Fischer, Daniel A. and Appenzeller, Joerg and Harrison, Robert J. and Wong, Stanislaus S.},
abstractNote = {As a model system to probe ligand-dependent charge transfer in complex composite heterostructures, we fabricated double-walled carbon nanotube (DWNT) – CdSe quantum dot (QD) composites. Whereas the average diameter of the QDs probed was kept fixed at ~4.1 nm and the nanotubes analyzed were similarly oxidatively processed, by contrast, the ligands used to mediate the covalent attachment between the QDs and DWNTs were systematically varied to include p-phenylenediamine (PPD), 2-aminoethanethiol (AET), and 4-aminothiophenol (ATP). Herein, we have put forth a unique compilation of complementary data from experiment and theory, including results from transmission electron microscopy (TEM), near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, Raman spectroscopy, electrical transport measurements, and theoretical modeling studies, in order to fundamentally assess the nature of the charge transfer between CdSe QDs and DWNTs, as a function of the structure of various, intervening bridging ligand molecules. Specifically, we correlated evidence of charge transfer as manifested by changes and shifts associated with NEXAFS intensities, Raman peak positions, and threshold voltages both before and after CdSe QD deposition onto the underlying DWNT surface. Importantly, for the first time ever in these types of nanoscale composite systems, we have sought to use theoretical modeling to justify and account for our experimental results. Finally, our overall data suggest that (i) QD coverage density on the DWNTs varies, based upon the different ligand pendant groups used and that (ii) the presence of a π-conjugated carbon framework within the ligands themselves and the electron affinity of the pendant groups collectively play important roles in the resulting charge transfer from QDs to the underlying CNTs.},
doi = {10.1039/C6NR03091B},
journal = {Nanoscale},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 7
}

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  • As a model system for understanding charge transfer in novel architectural designs for solar cells, double-walled carbon nanotube (DWNT)–CdSe quantum dot (QD) (QDs with average diameters of 2.3, 3.0, and 4.1 nm) heterostructures have been fabricated. The individual nanoscale building blocks were successfully attached and combined using a hole-trapping thiol linker molecule, i.e., 4-mercaptophenol (MTH), through a facile, noncovalent π–π stacking attachment strategy. Transmission electron microscopy confirmed the attachment of QDs onto the external surfaces of the DWNTs. We herein demonstrate a meaningful and unique combination of near-edge X-ray absorption fine structure (NEXAFS) and Raman spectroscopies bolstered by complementary electricalmore » transport measurements in order to elucidate the synergistic interactions between CdSe QDs and DWNTs, which are facilitated by the bridging MTH molecules that can scavenge photoinduced holes and potentially mediate electron redistribution between the conduction bands in CdSe QDs and the C 2p-derived states of the DWNTs. Specifically, we correlated evidence of charge transfer as manifested by (i) changes in the NEXAFS intensities of π* resonance in the C K-edge and Cd M3-edge spectra, (ii) a perceptible outer tube G-band downshift in frequency in Raman spectra, as well as (iii) alterations in the threshold characteristics present in transport data as a function of CdSe QD deposition onto the DWNT surface. Furthermore, the separate effects of (i) varying QD sizes and (ii) QD coverage densities on the electron transfer were independently studied.« less
  • As a model system for understanding charge transfer in novel architectural designs for solar cells, double-walled carbon nanotube (DWNT)–CdSe quantum dot (QD) (QDs with average diameters of 2.3, 3.0, and 4.1 nm) heterostructures have been fabricated. The individual nanoscale building blocks were successfully attached and combined using a hole-trapping thiol linker molecule, i.e., 4-mercaptophenol (MTH), through a facile, noncovalent π–π stacking attachment strategy. Transmission electron microscopy confirmed the attachment of QDs onto the external surfaces of the DWNTs. We herein demonstrate a meaningful and unique combination of near-edge X-ray absorption fine structure (NEXAFS) and Raman spectroscopies bolstered by complementary electricalmore » transport measurements in order to elucidate the synergistic interactions between CdSe QDs and DWNTs, which are facilitated by the bridging MTH molecules that can scavenge photoinduced holes and potentially mediate electron redistribution between the conduction bands in CdSe QDs and the C 2p-derived states of the DWNTs. Specifically, we correlated evidence of charge transfer as manifested by (i) changes in the NEXAFS intensities of π* resonance in the C K-edge and Cd M3-edge spectra, (ii) a perceptible outer tube G-band downshift in frequency in Raman spectra, as well as (iii) alterations in the threshold characteristics present in transport data as a function of CdSe QD deposition onto the DWNT surface. Furthermore, the separate effects of (i) varying QD sizes and (ii) QD coverage densities on the electron transfer were independently studied.« less
    Cited by 2
  • To study the charge transfer between cadmium selenide (CdSe) quantum dots (QDs) and double-walled nanotubes (DWNTs), various sizes of CdSe-ligand-DWNT structures are synthesized, and field-effect transistors (FETs) from individual functionalized DWNTs rather than networks of the same are fabricated. From the electrical measurements, two distinct electron transfer mechanisms from the QD system to the nanotube are identified. By the formation of the CdSe-ligand-DWNT heterostructure, an effectively n-doped nanotube is created due to the smaller work function of CdSe as compared with the nanotube. In addition, once the QD-DWNT system is exposed to laser light, further electron transfer from the QDmore » through the ligand, i.e. 4-mercaptophenol (MTH), to the nanotube occurs and a clear QD-size dependent tunneling process is observed. Furthermore, the detailed analysis of a large set of devices and the particular methodology employed here for the first time allowed for extracting a wavelength and quantum dot size dependent charge transfer efficiency – a quantity that is evaluated for the first time through electrical measurement.« less
  • To study the charge transfer between cadmium selenide (CdSe) quantum dots (QDs) and double-walled nanotubes (DWNTs), various sizes of CdSe-ligand-DWNT structures are synthesized, and field-effect transistors (FETs) from individual functionalized DWNTs rather than networks of the same are fabricated. From the electrical measurements, two distinct electron transfer mechanisms from the QD system to the nanotube are identified. By the formation of the CdSe-ligand-DWNT heterostructure, an effectively n-doped nanotube is created due to the smaller work function of CdSe as compared with the nanotube. In addition, once the QD-DWNT system is exposed to laser light, further electron transfer from the QDmore » through the ligand, i.e. 4-mercaptophenol (MTH), to the nanotube occurs and a clear QD size-dependent tunneling process is observed. Lastly, the detailed analysis of a large set of devices and the particular methodology employed here for the first time allowed for extracting a wavelength and quantum dot size dependent charge transfer efficiency – a quantity that is evaluated for the first time through electrical measurement.« less
  • Metal-to-ligand charge-transfer (MLCT) absorption bands for the complexes Ru(bpy)/sub 3//sup 2 +/, Os(bpy)/sub 3//sup 2 +/, Os(bpy)/sub 2/(py)/sub 2//sup 2 +/, Os(bpy)/sub 2/(CH/sub 3/CN)/sub 2//sup 2 +/, and Os(bpy)/sub 2/(1,2-(Ph/sub 2/P)/sub 2/C/sub 6/H/sub 4/)/sup 2 +/ (bpy is 2,2'-bipyridiene;py is pyridine) are solvent dependent. The dependence can be interpreted with use of dielectric continuum theory but the D/sub 3/ ions Ru(bpy)/sub 3//sup 2 +/ and Os(bpy)/sub 3//sup 2 +/ only if in the excited state the excited electron is localized on a single ligand rather than delocalized over all three. 37 references, 4 figures, 2 tables.