Dr. Friedrich Schöppler

• [ 2023 ]
• [ 2022 ]
• [ 2021 ]
• [ 2019 ]
• [ 2017 ]
• [ 2016 ]
• [ 2015 ]
• [ 2014 ]
• [ 2013 ]
• [ 2011 ]
• [ 2009 ]

• Trions, Exciton Dynamics, and Spectral Modifications in Doped Carbon Nanotubes: A Singular Defect-Driven Mechanism. Eckstein, Klaus H.; Kunkel, Pascal; Voelckel, Markus; Schöppler, Friedrich; Hertel, Tobias. In J. Phys. Chem. C, 127(39), pp. 19659–19667. American Chemical Society, 2023.
  • [ BibTeX ]
  • [ URL ]
  • [ DOI ]
  @article{eckstein2023trions, author = {Eckstein, Klaus H. and Kunkel, Pascal and Voelckel, Markus and Schöppler, Friedrich and Hertel, Tobias}, booktitle = {The Journal of Physical Chemistry C}, journal = {J. Phys. Chem. C}, keywords = {}, month = 10, number = 39, pages = {19659–19667}, publisher = {American Chemical Society}, title = {Trions, Exciton Dynamics, and Spectral Modifications in Doped Carbon Nanotubes: A Singular Defect-Driven Mechanism}, volume = 127, year = 2023 }

• Electroluminescence from Single-Walled Carbon Nanotubes with Quantum Defects. Li, Min-Ken; Riaz, Adnan; Wederhake, Martina; Fink, Karin; Saha, Avishek; Dehm, Simone; He, Xiaowei; Schöppler, Friedrich; Kappes, Manfred M.; Htoon, Han; Popov, Valentin N.; Doorn, Stephen K.; Hertel, Tobias; Hennrich, Frank; Krupke, Ralph. In ACS Nano, p. ASAP. 2022.
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  • [ DOI ]
  Individual single-walled carbon nanotubes with covalent sidewall defects have emerged as a class of photon sources whose photoluminescence spectra can be tailored by the carbon nanotube chirality and the attached functional group/molecule. Here we present electroluminescence spectroscopy data from single-tube devices based on (7, 5) carbon nanotubes, functionalized with dichlorobenzene molecules, and wired to graphene electrodes. We observe electrically generated, defect-induced emissions that are controllable by electrostatic gating and strongly red-shifted compared to emissions from pristine nanotubes. The defect-induced emissions are assigned to excitonic and trionic recombination processes by correlating electroluminescence excitation maps with electrical transport and photoluminescence data. At cryogenic conditions, additional gate-dependent emission lines appear, which are assigned to phonon-assisted hot-exciton electroluminescence from quasi-levels. Similar results were obtained with functionalized (6, 5) nanotubes. We also compare functionalized (7, 5) electroluminescence data with photoluminescence of pristine and functionalized (7, 5) nanotubes redox-doped using gold(III) chloride solution. This work shows that electroluminescence excitation is selective toward neutral defect-state configurations with the lowest transition energy, which in combination with gate-control over neutral versus charged defect-state emission leads to high spectral purity.

  @article{doi:10.1021/acsnano.2c03083, abstract = {Individual single-walled carbon nanotubes with covalent sidewall defects have emerged as a class of photon sources whose photoluminescence spectra can be tailored by the carbon nanotube chirality and the attached functional group/molecule. Here we present electroluminescence spectroscopy data from single-tube devices based on (7, 5) carbon nanotubes, functionalized with dichlorobenzene molecules, and wired to graphene electrodes. We observe electrically generated, defect-induced emissions that are controllable by electrostatic gating and strongly red-shifted compared to emissions from pristine nanotubes. The defect-induced emissions are assigned to excitonic and trionic recombination processes by correlating electroluminescence excitation maps with electrical transport and photoluminescence data. At cryogenic conditions, additional gate-dependent emission lines appear, which are assigned to phonon-assisted hot-exciton electroluminescence from quasi-levels. Similar results were obtained with functionalized (6, 5) nanotubes. We also compare functionalized (7, 5) electroluminescence data with photoluminescence of pristine and functionalized (7, 5) nanotubes redox-doped using gold(III) chloride solution. This work shows that electroluminescence excitation is selective toward neutral defect-state configurations with the lowest transition energy, which in combination with gate-control over neutral versus charged defect-state emission leads to high spectral purity.}, author = {Li, Min-Ken and Riaz, Adnan and Wederhake, Martina and Fink, Karin and Saha, Avishek and Dehm, Simone and He, Xiaowei and Schöppler, Friedrich and Kappes, Manfred M. and Htoon, Han and Popov, Valentin N. and Doorn, Stephen K. and Hertel, Tobias and Hennrich, Frank and Krupke, Ralph}, journal = {ACS Nano}, keywords = {}, note = {PMID: 35732039}, pages = {ASAP}, title = {Electroluminescence from Single-Walled Carbon Nanotubes with Quantum Defects}, year = 2022 }

• Diffusive and Unimolecular Nonradiative Decay of Excited States in Doped Carbon Nanotubes. Eckstein, Klaus H.; Kunkel, Pascal; Voelckel, Markus; Schöppler, Friedrich; Abudulimu, Abasi; Lüer, Larry; Hertel, Tobias. 2021.
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Doping can profoundly affect the electronic- and optical-structure of semiconductors. Here we address the effect of surplus charges on non-radiative (NR) exciton and trion decay in doped semiconducting single-wall carbon nanotubes. The dependence of exciton photoluminescence quantum yields and exciton decay on the doping level, with its characteristically stretched-exponential kinetics, is attributed to diffusion-limited NR decay at charged impurity sites. By contrast, trion decay is unimolecular with a rate constant of \($2.0\,\rm ps^-1$\). Our experiments thus show that charged impurities not only trap trions and scavenge mobile excitons but that they also facilitate efficient NR energy dissipation for both.

  @preprint{eckstein2021diffusive, abstract = {Doping can profoundly affect the electronic- and optical-structure of semiconductors. Here we address the effect of surplus charges on non-radiative (NR) exciton and trion decay in doped semiconducting single-wall carbon nanotubes. The dependence of exciton photoluminescence quantum yields and exciton decay on the doping level, with its characteristically stretched-exponential kinetics, is attributed to diffusion-limited NR decay at charged impurity sites. By contrast, trion decay is unimolecular with a rate constant of $2.0\,\rm ps^{-1}$. Our experiments thus show that charged impurities not only trap trions and scavenge mobile excitons but that they also facilitate efficient NR energy dissipation for both.}, author = {Eckstein, Klaus H. and Kunkel, Pascal and Voelckel, Markus and Schöppler, Friedrich and Abudulimu, Abasi and Lüer, Larry and Hertel, Tobias}, keywords = {}, note = {cite arxiv:2103.15477}, title = {Diffusive and Unimolecular Nonradiative Decay of Excited States in Doped Carbon Nanotubes}, year = 2021 }

• Quantifying Doping Levels in Carbon Nanotubes by Optical Spectroscopy. Eckstein, Klaus H.; Oberndorfer, Florian; Achsnich, Melanie M.; Schöppler, Friedrich; Hertel, Tobias. In The Journal of Physical Chemistry C, 123(49), pp. 30001–30006. 2019.
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  • [ DOI ]
  Controlling doping is essential for the successful integration of semiconductor materials into device technologies. However, the assessment of doping levels and the distribution of charge carriers in carbon nanotubes or other nanoscale semiconductor materials is often either limited to a qualitative attribution of being “high” or “low” or entirely absent. Here, we describe efforts toward a quantitative characterization of doping in redox- or electrochemically doped semiconducting single-wall carbon nanotubes (s-SWNTs) using vis–NIR absorption spectroscopy. We discuss how carrier densities up to about 0.5 nm–1 can be quantified with a sensitivity of roughly 1 charge per 104 carbon atoms assuming inhomogeneous or homogeneous carrier distributions.

  @article{doi:10.1021/acs.jpcc.9b08663, abstract = {Controlling doping is essential for the successful integration of semiconductor materials into device technologies. However, the assessment of doping levels and the distribution of charge carriers in carbon nanotubes or other nanoscale semiconductor materials is often either limited to a qualitative attribution of being “high” or “low” or entirely absent. Here, we describe efforts toward a quantitative characterization of doping in redox- or electrochemically doped semiconducting single-wall carbon nanotubes (s-SWNTs) using vis–NIR absorption spectroscopy. We discuss how carrier densities up to about 0.5 nm–1 can be quantified with a sensitivity of roughly 1 charge per 104 carbon atoms assuming inhomogeneous or homogeneous carrier distributions.}, author = {Eckstein, Klaus H. and Oberndorfer, Florian and Achsnich, Melanie M. and Schöppler, Friedrich and Hertel, Tobias}, journal = {The Journal of Physical Chemistry C}, keywords = {}, number = 49, pages = {30001-30006}, title = {Quantifying Doping Levels in Carbon Nanotubes by Optical Spectroscopy}, volume = 123, year = 2019 }

• Localized Charges Control Exciton Energetics and Energy Dissipation in Doped Carbon Nanotubes. Eckstein, Klaus H.; Hartleb, Holger; Achsnich, Melanie M.; Schöppler, Friedrich; Hertel, Tobias. In ACS Nano, 11(10), pp. 10401–10408. American Chemical Society, 2017.
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  • [ DOI ]
  Doping by chemical or physical means is key for the development of future semiconductor technologies. Ideally, charge carriers should be able to move freely in a homogeneous environment. Here, we report on evidence suggesting that excess carriers in electrochemically p-doped semiconducting single-wall carbon nanotubes (s-SWNTs) become localized, most likely due to poorly screened Coulomb interactions with counterions in the Helmholtz layer. A quantitative analysis of blue-shift, broadening, and asymmetry of the first exciton absorption band also reveals that doping leads to hard segmentation of s-SWNTs with intrinsic undoped segments being separated by randomly distributed charge puddles approximately 4 nm in width. Light absorption in these doped segments is associated with the formation of trions, spatially separated from neutral excitons. Acceleration of exciton decay in doped samples is governed by diffusive excitors transport to, and nonradiative decay at charge puddles within 3.2 ps in moderately doped s-SWNTs. The results suggest that conventional band-filling in s-SWNTs breaks down due to inhomogeneous electrochemical doping.

  @article{Eckstein_2017, abstract = {Doping by chemical or physical means is key for the development of future semiconductor technologies. Ideally, charge carriers should be able to move freely in a homogeneous environment. Here, we report on evidence suggesting that excess carriers in electrochemically p-doped semiconducting single-wall carbon nanotubes (s-SWNTs) become localized, most likely due to poorly screened Coulomb interactions with counterions in the Helmholtz layer. A quantitative analysis of blue-shift, broadening, and asymmetry of the first exciton absorption band also reveals that doping leads to hard segmentation of s-SWNTs with intrinsic undoped segments being separated by randomly distributed charge puddles approximately 4 nm in width. Light absorption in these doped segments is associated with the formation of trions, spatially separated from neutral excitons. Acceleration of exciton decay in doped samples is governed by diffusive excitors transport to, and nonradiative decay at charge puddles within 3.2 ps in moderately doped s-SWNTs. The results suggest that conventional band-filling in s-SWNTs breaks down due to inhomogeneous electrochemical doping.}, author = {Eckstein, Klaus H. and Hartleb, Holger and Achsnich, Melanie M. and Schöppler, Friedrich and Hertel, Tobias}, journal = {ACS Nano}, keywords = {}, month = {09}, number = 10, pages = {10401-10408}, publisher = {American Chemical Society}, title = {Localized Charges Control Exciton Energetics and Energy Dissipation in Doped Carbon Nanotubes}, volume = 11, year = 2017 }

• Substrate-Mediated Cooperative Adsorption of Sodium Cholate on (6,5) Single-Wall Carbon Nanotubes. Bergler, Felix F.; Stahl, Sabine; Goy, Annika; Schöppler, Friedrich; Hertel, Tobias. In Langmuir, 32(37), pp. 9598–9603. American Chemical Society (ACS), 2016.
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  • [ DOI ]
  The interaction of sodium cholate (NaC) with (6,5) single-wall carbon nanotubes (SWNTs) is investigated using photoluminescence spectroscopy. Dilution of SWNT-NaC suspensions is accompanied by changes in the exciton PL quantum yield and peak emission energy. An abrupt change of the exciton emission peak energy at NaC concentrations between 10 and 14 mM indicates strongly cooperative formation of a micellar phase on (6,5) SWNT surfaces with a Hill coefficient of n(H) = 65 +/- 6. This is in contrast to the formation of free NaC micelles with aggregation numbers of only about 4 and suggests that the cooperativity of NaC micelle formation on nanotube surfaces is strongly substrate-enhanced. The temperature dependence of this previously unobserved transition is used for a determination of Delta(mic)(G) over bar (Theta)/(1 + beta) = -(11.4 +/- 0.2) kJ.mol(-1) which, for typical Na+ counterion binding with beta approximate to 0.2, yields a free SWNT-NaC micellization enthalpy Delta(mic)(G) over bar (Theta) of -13.7 kJ.mol(-1).

  @article{Bergler_2016, abstract = {The interaction of sodium cholate (NaC) with (6,5) single-wall carbon nanotubes (SWNTs) is investigated using photoluminescence spectroscopy. Dilution of SWNT-NaC suspensions is accompanied by changes in the exciton PL quantum yield and peak emission energy. An abrupt change of the exciton emission peak energy at NaC concentrations between 10 and 14 mM indicates strongly cooperative formation of a micellar phase on (6,5) SWNT surfaces with a Hill coefficient of n(H) = 65 +/- 6. This is in contrast to the formation of free NaC micelles with aggregation numbers of only about 4 and suggests that the cooperativity of NaC micelle formation on nanotube surfaces is strongly substrate-enhanced. The temperature dependence of this previously unobserved transition is used for a determination of Delta(mic)(G) over bar (Theta)/(1 + beta) = -(11.4 +/- 0.2) kJ.mol(-1) which, for typical Na+ counterion binding with beta approximate to 0.2, yields a free SWNT-NaC micellization enthalpy Delta(mic)(G) over bar (Theta) of -13.7 kJ.mol(-1).}, author = {Bergler, Felix F. and Stahl, Sabine and Goy, Annika and Schöppler, Friedrich and Hertel, Tobias}, journal = {Langmuir}, keywords = {}, month = {09}, number = 37, pages = {9598-9603}, publisher = {American Chemical Society (ACS)}, title = {Substrate-Mediated Cooperative Adsorption of Sodium Cholate on (6,5) Single-Wall Carbon Nanotubes}, volume = 32, year = 2016 }
• Interaction of Polymers with Single-Wall Carbon Nanotubes. Brunecker, Frank K.; Schöppler, Friedrich; Hertel, Tobias. In The Journal of Physical Chemistry C, 120(18), pp. 10094–10103. American Chemical Society (ACS), 2016.
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  • [ DOI ]
  The interaction of sodium cholate (NaC) with (6,5) single-wall carbon nanotubes (SWNTs) is investigated using photoluminescence spectroscopy. Dilution of SWNT-NaC suspensions is accompanied by changes in the exciton PL quantum yield and peak emission energy. An abrupt change of the exciton emission peak energy at NaC concentrations between 10 and 14 mM indicates strongly cooperative formation of a micellar phase on (6,5) SWNT surfaces with a Hill coefficient of n(H) = 65 +/- 6. This is in contrast to the formation of free NaC micelles with aggregation numbers of only about 4 and suggests that the cooperativity of NaC micelle formation on nanotube surfaces is strongly substrate-enhanced. The temperature dependence of this previously unobserved transition is used for a determination of Delta(mic)(G) over bar (Theta)/(1 + beta) = -(11.4 +/- 0.2) kJ.mol(-1) which, for typical Na+ counterion binding with beta approximate to 0.2, yields a free SWNT-NaC micellization enthalpy Delta(mic)(G) over bar (Theta) of -13.7 kJ.mol(-1).

  @article{Brunecker_2016, abstract = {The interaction of sodium cholate (NaC) with (6,5) single-wall carbon nanotubes (SWNTs) is investigated using photoluminescence spectroscopy. Dilution of SWNT-NaC suspensions is accompanied by changes in the exciton PL quantum yield and peak emission energy. An abrupt change of the exciton emission peak energy at NaC concentrations between 10 and 14 mM indicates strongly cooperative formation of a micellar phase on (6,5) SWNT surfaces with a Hill coefficient of n(H) = 65 +/- 6. This is in contrast to the formation of free NaC micelles with aggregation numbers of only about 4 and suggests that the cooperativity of NaC micelle formation on nanotube surfaces is strongly substrate-enhanced. The temperature dependence of this previously unobserved transition is used for a determination of Delta(mic)(G) over bar (Theta)/(1 + beta) = -(11.4 +/- 0.2) kJ.mol(-1) which, for typical Na+ counterion binding with beta approximate to 0.2, yields a free SWNT-NaC micellization enthalpy Delta(mic)(G) over bar (Theta) of -13.7 kJ.mol(-1).}, author = {Brunecker, Frank K. and Schöppler, Friedrich and Hertel, Tobias}, journal = {The Journal of Physical Chemistry C}, keywords = {}, month = {05}, number = 18, pages = {10094-10103}, publisher = {American Chemical Society (ACS)}, title = {Interaction of Polymers with Single-Wall Carbon Nanotubes}, volume = 120, year = 2016 }

• Ultrafast Spectral Exciton Diffusion in Single-Wall Carbon Nanotubes Studied by Time-Resolved Hole Burning. Schilling, Daniel; Mann, Christoph; Kunkel, Pascal; Schöppler, Friedrich; Hertel, Tobias. In The Journal of Physical Chemistry C, 119(42), pp. 24116–24123. American Chemical Society (ACS), 2015.
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  • [ DOI ]
  We have studied ultrafast spectral diffusion (SD) within exciton bands of semiconducting single-wall carbon nanotubes (s-SWNTs) using one- and two-dimensional, near-infrared transient hole burning spectroscopy and time-resolved fluorescence spectroscopy at temperatures between 15 and 293 K. We find that inhomogeneous spectral broadening of 60 meV for s-SWNTs embedded in gelatin exceeds the homogeneous line width of 3.3 meV by over an order of magnitude. The experiments show that ultrafast spectral diffusion of excitons in gel-immobilized s-SWNTs on the 250 fs time scale can be attributed to axial intratube exciton diffusion. Comparison with kinetic Monte Carlo simulations suggests that the length-scale characteristic of the granularity of the axial potential energy landscape is about 24 nm.

  @article{Schilling_2015, abstract = {We have studied ultrafast spectral diffusion (SD) within exciton bands of semiconducting single-wall carbon nanotubes (s-SWNTs) using one- and two-dimensional, near-infrared transient hole burning spectroscopy and time-resolved fluorescence spectroscopy at temperatures between 15 and 293 K. We find that inhomogeneous spectral broadening of 60 meV for s-SWNTs embedded in gelatin exceeds the homogeneous line width of 3.3 meV by over an order of magnitude. The experiments show that ultrafast spectral diffusion of excitons in gel-immobilized s-SWNTs on the 250 fs time scale can be attributed to axial intratube exciton diffusion. Comparison with kinetic Monte Carlo simulations suggests that the length-scale characteristic of the granularity of the axial potential energy landscape is about 24 nm.}, author = {Schilling, Daniel and Mann, Christoph and Kunkel, Pascal and Schöppler, Friedrich and Hertel, Tobias}, journal = {The Journal of Physical Chemistry C}, keywords = {}, month = 10, number = 42, pages = {24116-24123}, publisher = {American Chemical Society (ACS)}, title = {Ultrafast Spectral Exciton Diffusion in Single-Wall Carbon Nanotubes Studied by Time-Resolved Hole Burning}, volume = 119, year = 2015 }
• A comparison of Raman and photoluminescence spectra for the assessment of single-wall carbon nanotube sample quality. Kastner, Matthias; Stahl, Sabine; Vollert, Ivonne; Loi, Christian; Rühl, Nicolas; Hertel, Tobias; Schöppler, Friedrich. In Chemical Physics Letters, 635, pp. 245–249. Elsevier BV, 2015.
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  • [ DOI ]
  We compare mass-yields, Raman band intensity ratios and photoluminescence quantum yields (PLQY) of (6,5) single-wall carbon nanotubes (SWNT), produced by alcohol catalytic chemical vapor deposition at reaction temperatures ranging from 600 degrees C to 850 degrees C. The highest PLQYs for suspensions of unprocessed raw material and for density gradient ultracentrifuged (DGU) samples are obtained if SWNTs were grown at 850 degrees C. Accordingly, the Raman defect band intensity ratios of DGU samples decrease toward the highest CVD growth temperatures. In contrast, PLQYs of non-DGU processed, polydisperse raw material suspensions, do not correlate with commonly used Raman D/G defect band intensity ratios.

  @article{Kastner_2015, abstract = {We compare mass-yields, Raman band intensity ratios and photoluminescence quantum yields (PLQY) of (6,5) single-wall carbon nanotubes (SWNT), produced by alcohol catalytic chemical vapor deposition at reaction temperatures ranging from 600 degrees C to 850 degrees C. The highest PLQYs for suspensions of unprocessed raw material and for density gradient ultracentrifuged (DGU) samples are obtained if SWNTs were grown at 850 degrees C. Accordingly, the Raman defect band intensity ratios of DGU samples decrease toward the highest CVD growth temperatures. In contrast, PLQYs of non-DGU processed, polydisperse raw material suspensions, do not correlate with commonly used Raman D/G defect band intensity ratios.}, author = {Kastner, Matthias and Stahl, Sabine and Vollert, Ivonne and Loi, Christian and Rühl, Nicolas and Hertel, Tobias and Schöppler, Friedrich}, journal = {Chemical Physics Letters}, keywords = {}, month = {08}, pages = {245-249}, publisher = {Elsevier BV}, title = {A comparison of Raman and photoluminescence spectra for the assessment of single-wall carbon nanotube sample quality}, volume = 635, year = 2015 }

• Dynamical Contact Line Pinning and Zipping during Carbon Nanotube Coffee Stain Formation. Li, Han; Hain, Tilman C.; Muzha, Andreas; Schöppler, Friedrich; Hertel, Tobias. In ACS Nano, 8(6), pp. 6417–6424. American Chemical Society (ACS), 2014.
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  • [ DOI ]
  Thin films of single-wall carbon nanotubes (SWNTs) can be deposited onto solid substrates by evaporation-induced self-assembly. However, for this process to become more accessible to thin-film-based device fabrication requires optimization and a better understanding of the parameters and mechanisms governing nanoparticle film growth. Here, we focus on the role of contact-line (CL) dynamics at the edge of a receding meniscus for the deposition of thin nanoparticle films from colloidal suspensions. We find that film deposition rates can be increased by up to 2 orders of magnitude over earlier reports if parameters such as SWNT concentration, surfactant concentration, and height of the capillary bridge from which particles are deposited are properly adjusted. Most importantly we have also discovered that CL dynamics leading to the formation of striped films (coffee stains) are best described by dynamical pinning and kink-induced zipping. The existence of critical SWNT and surfactant concentrations as well as their role in determining stripe characteristics can be well accounted for by the proposed dynamical pinning and zipping model.

  @article{Li_2014, abstract = {Thin films of single-wall carbon nanotubes (SWNTs) can be deposited onto solid substrates by evaporation-induced self-assembly. However, for this process to become more accessible to thin-film-based device fabrication requires optimization and a better understanding of the parameters and mechanisms governing nanoparticle film growth. Here, we focus on the role of contact-line (CL) dynamics at the edge of a receding meniscus for the deposition of thin nanoparticle films from colloidal suspensions. We find that film deposition rates can be increased by up to 2 orders of magnitude over earlier reports if parameters such as SWNT concentration, surfactant concentration, and height of the capillary bridge from which particles are deposited are properly adjusted. Most importantly we have also discovered that CL dynamics leading to the formation of striped films (coffee stains) are best described by dynamical pinning and kink-induced zipping. The existence of critical SWNT and surfactant concentrations as well as their role in determining stripe characteristics can be well accounted for by the proposed dynamical pinning and zipping model.}, author = {Li, Han and Hain, Tilman C. and Muzha, Andreas and Schöppler, Friedrich and Hertel, Tobias}, journal = {ACS Nano}, keywords = {}, month = {05}, number = 6, pages = {6417-6424}, publisher = {American Chemical Society (ACS)}, title = {Dynamical Contact Line Pinning and Zipping during Carbon Nanotube Coffee Stain Formation}, volume = 8, year = 2014 }

• Fluorescence Spectroscopy of Gel-Immobilized Single-Wall Carbon Nanotubes with Microfluidic Control of the Surfactant Environment. Bergler, Felix F.; Schöppler, Friedrich; Brunecker, Frank K.; Hailman, Michael; Hertel, Tobias. In The Journal of Physical Chemistry C, 117(25), pp. 13318–13323. American Chemical Society (ACS), 2013.
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  • [ DOI ]
  We describe the design and use of a microfluidic fluorescence cell for nanoparticle spectroscopy. The cell allows for microfluidic control of solvent and surfactant environments to study interfacial processes of nanoscale systems. We present a spectroscopic investigation on the effect of surfactant type and concentrations on the first subband exciton transition of (6,5) single-wall carbon nanotubes (SWNTs). SWNT fluorescence here serves as a surface-sensitive probe of changes at the surfactantnanotube interface. The experiments show that a displacement of H2O or of adsorbed DNA by sodium cholate from solution leads to a pronounced blue-shift of exciton emission features and a roughly 5-fold increase of photoluminescence (PL) intensities. This is due to a combination of physical and chemical interactions. The major contribution to changes in PL quantum yield and exciton peak position can be attributed to changes in dielectric screening and its effect on exciton oscillator strengths.

  @article{Bergler_2013, abstract = {We describe the design and use of a microfluidic fluorescence cell for nanoparticle spectroscopy. The cell allows for microfluidic control of solvent and surfactant environments to study interfacial processes of nanoscale systems. We present a spectroscopic investigation on the effect of surfactant type and concentrations on the first subband exciton transition of (6,5) single-wall carbon nanotubes (SWNTs). SWNT fluorescence here serves as a surface-sensitive probe of changes at the surfactantnanotube interface. The experiments show that a displacement of H2O or of adsorbed DNA by sodium cholate from solution leads to a pronounced blue-shift of exciton emission features and a roughly 5-fold increase of photoluminescence (PL) intensities. This is due to a combination of physical and chemical interactions. The major contribution to changes in PL quantum yield and exciton peak position can be attributed to changes in dielectric screening and its effect on exciton oscillator strengths.}, author = {Bergler, Felix F. and Schöppler, Friedrich and Brunecker, Frank K. and Hailman, Michael and Hertel, Tobias}, journal = {The Journal of Physical Chemistry C}, keywords = {}, month = {06}, number = 25, pages = {13318-13323}, publisher = {American Chemical Society (ACS)}, title = {Fluorescence Spectroscopy of Gel-Immobilized Single-Wall Carbon Nanotubes with Microfluidic Control of the Surfactant Environment}, volume = 117, year = 2013 }
• Photoluminescence microscopy and spectroscopy of individualized and aggregated single-wall carbon nanotubes. Schöppler, Friedrich; Rühl, Nicolas; Hertel, Tobias. In Chemical Physics, 413, pp. 112–115. Elsevier BV, 2013.
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  • [ DOI ]
  We have studied photophysical properties of individual single-wall carbon nanotubes (SWNTs) and SWNT aggregates in colloidal suspensions using fluorescence microscopy, -spectroscopy and time-correlated single photon counting. The results suggest that SWNT aggregates, formed by addition of a divalent salt to a monomer SWNT suspension, have an open structure with a density of approximate to 12 SWNTs mu m (3). We also find a sizable spectral red-shift of 16 nm, line-broadening of 23 nm and reduced PL lifetimes in coagulated structures, independent of aggregate size for the range of structures studied here. Such changes may be used as fingerprint of SWNT aggregate formation in similar environments.

  @article{Sch_ppler_2013, abstract = {We have studied photophysical properties of individual single-wall carbon nanotubes (SWNTs) and SWNT aggregates in colloidal suspensions using fluorescence microscopy, -spectroscopy and time-correlated single photon counting. The results suggest that SWNT aggregates, formed by addition of a divalent salt to a monomer SWNT suspension, have an open structure with a density of approximate to 12 SWNTs mu m (3). We also find a sizable spectral red-shift of 16 nm, line-broadening of 23 nm and reduced PL lifetimes in coagulated structures, independent of aggregate size for the range of structures studied here. Such changes may be used as fingerprint of SWNT aggregate formation in similar environments.}, author = {Schöppler, Friedrich and Rühl, Nicolas and Hertel, Tobias}, journal = {Chemical Physics}, keywords = {}, month = {02}, pages = {112-115}, publisher = {Elsevier BV}, title = {Photoluminescence microscopy and spectroscopy of individualized and aggregated single-wall carbon nanotubes}, volume = 413, year = 2013 }
• Fluorescence Spectroscopy of Gel-Immobilized Single-Wall Carbon Nanotubes with Microfluidic Control of the Surfactant Environment. Bergler, Felix F.; Schoeppler, Friedrich; Brunecker, Frank K.; Hailman, Michael; Hertel, Tobias. In JOURNAL OF PHYSICAL CHEMISTRY C, 117(25), pp. 13318–13323. AMER CHEMICAL SOC, 2013.
  • [ Abstract ]
  • [ BibTeX ]
  We describe the design and use of a microfluidic fluorescence cell for nanoparticle spectroscopy. The cell allows for microfluidic control of solvent and surfactant environments to study interfacial processes of nanoscale systems. We present a spectroscopic investigation on the effect of surfactant type and concentrations on the first subband exciton transition of (6,5) single-wall carbon nanotubes (SWNTs). SWNT fluorescence here serves as a surface-sensitive probe of changes at the surfactantnanotube interface. The experiments show that a displacement of H2O or of adsorbed DNA by sodium cholate from solution leads to a pronounced blue-shift of exciton emission features and a roughly 5-fold increase of photoluminescence (PL) intensities. This is due to a combination of physical and chemical interactions. The major contribution to changes in PL quantum yield and exciton peak position can be attributed to changes in dielectric screening and its effect on exciton oscillator strengths.

  @article{bergler2013fluorescence, abstract = {We describe the design and use of a microfluidic fluorescence cell for nanoparticle spectroscopy. The cell allows for microfluidic control of solvent and surfactant environments to study interfacial processes of nanoscale systems. We present a spectroscopic investigation on the effect of surfactant type and concentrations on the first subband exciton transition of (6,5) single-wall carbon nanotubes (SWNTs). SWNT fluorescence here serves as a surface-sensitive probe of changes at the surfactantnanotube interface. The experiments show that a displacement of H2O or of adsorbed DNA by sodium cholate from solution leads to a pronounced blue-shift of exciton emission features and a roughly 5-fold increase of photoluminescence (PL) intensities. This is due to a combination of physical and chemical interactions. The major contribution to changes in PL quantum yield and exciton peak position can be attributed to changes in dielectric screening and its effect on exciton oscillator strengths.}, author = {Bergler, Felix F. and Schoeppler, Friedrich and Brunecker, Frank K. and Hailman, Michael and Hertel, Tobias}, journal = {JOURNAL OF PHYSICAL CHEMISTRY C}, keywords = {}, number = 25, pages = {13318–13323}, publisher = {AMER CHEMICAL SOC}, title = {Fluorescence Spectroscopy of Gel-Immobilized Single-Wall Carbon Nanotubes with Microfluidic Control of the Surfactant Environment}, volume = 117, year = 2013 }

• Molar Extinction Coefficient of Single-Wall Carbon Nanotubes. Schöppler, Friedrich; Mann, Christoph; Hain, Tilman C.; Neubauer, Felix M.; Privitera, Giulia; Bonaccorso, Francesco; Chu, Daping; Ferrari, Andrea C.; Hertel, Tobias. In The Journal of Physical Chemistry C, 115(30), pp. 14682–14686. American Chemical Society (ACS), 2011.
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  • [ DOI ]
  The molar extinction coefficient of single-wall carbon nanotubes (SWNTs) is determined using fluorescence tagging, as well as atomic force microscopy (AFM) imaging, which facilitate the correlation of nanotube concentrations with absorption spectra. Tagging of SWNTs is achieved using fluorescence-labeled single-strand DNA oligomers as the dispersion additive, while AFM imaging is used to determine the mass of SWNTs in the retentate of vacuum-filtered colloidal SWNT suspensions. The resulting absorption cross section for the first exciton transition of (6,5) nanotubes of 1.7 x 10(-17) cm(2) per C-atom corresponds to an extinction coefficient of (4400 +/- 1000) M(-1).cm(-1), which is equivalent to an oscillator strength of 0.010 per carbon atom.

  @article{Sch_ppler_2011, abstract = {The molar extinction coefficient of single-wall carbon nanotubes (SWNTs) is determined using fluorescence tagging, as well as atomic force microscopy (AFM) imaging, which facilitate the correlation of nanotube concentrations with absorption spectra. Tagging of SWNTs is achieved using fluorescence-labeled single-strand DNA oligomers as the dispersion additive, while AFM imaging is used to determine the mass of SWNTs in the retentate of vacuum-filtered colloidal SWNT suspensions. The resulting absorption cross section for the first exciton transition of (6,5) nanotubes of 1.7 x 10(-17) cm(2) per C-atom corresponds to an extinction coefficient of (4400 +/- 1000) M(-1).cm(-1), which is equivalent to an oscillator strength of 0.010 per carbon atom.}, author = {Schöppler, Friedrich and Mann, Christoph and Hain, Tilman C. and Neubauer, Felix M. and Privitera, Giulia and Bonaccorso, Francesco and Chu, Daping and Ferrari, Andrea C. and Hertel, Tobias}, journal = {The Journal of Physical Chemistry C}, keywords = {}, month = {07}, number = 30, pages = {14682-14686}, publisher = {American Chemical Society (ACS)}, title = {Molar Extinction Coefficient of Single-Wall Carbon Nanotubes}, volume = 115, year = 2011 }

• SERS Labels for Red Laser Excitation: Silica-Encapsulated SAMs on Tunable Gold/Silver Nanoshells. Kuestner, Bernd; Gellner, Magdalena; Schuetz, Max; Schoeppler, Friedrich; Marx, Alexander; Stroebel, Philipp; Adam, Patrick; Schmuck, Carsten; Schluecker, Sebastian. In ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 48(11), pp. 1950–1953. WILEY-V C H VERLAG GMBH, 2009.
  • [ BibTeX ]
  @article{kuestner2009labels, author = {Kuestner, Bernd and Gellner, Magdalena and Schuetz, Max and Schoeppler, Friedrich and Marx, Alexander and Stroebel, Philipp and Adam, Patrick and Schmuck, Carsten and Schluecker, Sebastian}, journal = {ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, keywords = {}, number = 11, pages = {1950–1953}, publisher = {WILEY-V C H VERLAG GMBH}, title = {SERS Labels for Red Laser Excitation: Silica-Encapsulated SAMs on Tunable Gold/Silver Nanoshells}, volume = 48, year = 2009 }