Understanding the Dielectric Properties of Heat-Treated Carbon Nanofibers at Terahertz Frequencies: a New Perspective on the Catalytic Activity of Structured Carbonaceous Materials

Download
2009-06-18
Parrott, Edward P. J.
Zeitler, J. Axel
McGregor, James
Oei, Shu-Pei
Ünalan, Hüsnü Emrah
Tan, Swee-Ching
Milne, William I.
Tessonnier, Jean-Philippe
Schloegl, Robert
Gladden, Lynn F.
Terahertz time domain spectroscopy (THz-TDS) has been used to study the electrical and optical properties of a series of carbon nanofibers (CNFs) that have undergone different heat treatments. The high-temperature heat-treated (HHT) sample displayed increased absorption and real refractive indices across the range 0.3-3.5 THz when compared to the low-temperature heat-treated (LHT) and pyrolitically stripped (PS) samples. The experimental results were fitted by using a Drude-Lorentz model and an effective medium approximation to yield the electrical parameters of the sample such as the plasma frequency, phonon mode frequency, and oscillator strength. These parameters were used to rationalize the differences as being due to an increase in graphitic order in the HHT sample when compared to the LHT sample and to an even greater extent the PS sample. HHT, LHT, and PS CNFs can be used as catalysts for the oxidative dehydrogenation of ethylbenzene to styrene. They exhibit different catalytic yield and selectivity which can be correlated with their dielectric properties at terahertz frequencies. The results suggest that THz-TDS is a useful tool for characterizing the graphiticity of CNFs in terms of electon density and mobility which, in turn, correlate with the catalytic performance of these materials.
JOURNAL OF PHYSICAL CHEMISTRY C

Suggestions

Study on the Effect of Chemically Different Substrates on Nucleation and Growth Mechanism of Perfluoropentacene Thin Films
Yavuz, Adem; Danışman, Mehmet Fatih (American Chemical Society (ACS), 2019-08-15)
We studied the effect of chemical properties of substrates on the structural properties of perfluoropentacene (PFP) thin films grown by the supersonic molecular beam deposition technique. To this end, we have used m-carborane-1-thiol, template-stripped gold, and mica substrate surfaces and investigated the PFP film properties as a function of film thickness and molecular flux (deposition rate). On all three substrates, the PFP molecules adsorb in standing-up orientation in the first layer and overlayers. Ho...
Revealing Laser Crystallization Mechanism of Silicon Thin Films via Pulsed IR Lasers
Çlnar, Kamil; Yeşil, Cihan; Bek, Alpan (American Chemical Society (ACS), 2020-01-01)
Pulsed laser absorption-mediated explosive crystallization of silicon films has extensively been studied using microscopy techniques on single laser pulse-irradiated regions in the literature. In this work, we experimentally demonstrate and theoretically explain in detail the use of slow quenching regime for laser crystallization mediated by highly overlapping pulses. Increasing the use of Si in thin film transistors and photovoltaic applications drives researchers to find cost-effective and efficient ways ...
Relative Photon-to-Carrier Efficiencies of Alternating Nanolayers of Zinc Phthalocyanine and C-60 Films Assessed by Time-Resolved Terahertz Spectroscopy
Esentürk, Okan; Lane, Paul A.; Heilweil, Edwin J. (American Chemical Society (ACS), 2009-10-29)
Multilayer and 1:1 blended films of zinc phthalocyanine (ZnPc) and buckminsterfullerene (C-60) were investigated as model active layers for solar cells by time-resolved terahertz spectroscopy (TRTS). Relative photon-to-carrier efficiencies were determined from ultrafast decay dynamics of photogenerated carriers using 400 and 800 nm excitation for delay times up to 0.5 ns. The findings are in good agreement with reported solar-cell device measurements, and the results exhibit a near linear increase of the re...
Effect of molecular and electronic structure on the light-harvesting properties of dye sensitizers
Mete, E.; Üner, Deniz; Cakmak, M.; Gulseren, O.; Ellialtoglu, S. (American Chemical Society (ACS), 2007-05-24)
The systematic trends in structural and electronic properties of perylenediimide (PDI)-derived dye molecules have been investigated by DFT calculations based on the projector-augmented wave (PAW) method including gradient-corrected exchange-correlation effects. Time-dependent density functional theory (TDDFT) calculations have been performed to study the visible absorbance activity of these complexes. The effect of different ligands and halogen atoms attached to PDI were studied to characterize the light-ha...
Balancing hydrophobic and hydrophilic forces at the Water/Vapor interface: Surface structure of soluble alcohol monolayers
Can, Suleyman Z.; Mago, Deesha D.; Esentürk, Okan; Walker, Robert A. (American Chemical Society (ACS), 2007-06-28)
Surface tension and surface specific vibrational techniques were used to study the structure of soluble alcohol monolayers adsorbed to the air/water interface. Surface tension measurements were used to determine terminal monolayer coverages of different alcohol isomers whereas the surface specific vibrational sum frequency generation probed the interfacial structure and organization. The alcohols studied ranged from heptanols to dodecanols with constitutional isomers having the -OH group in the 1, 2, 3, and...
Citation Formats
E. P. J. Parrott et al., “Understanding the Dielectric Properties of Heat-Treated Carbon Nanofibers at Terahertz Frequencies: a New Perspective on the Catalytic Activity of Structured Carbonaceous Materials,” JOURNAL OF PHYSICAL CHEMISTRY C, pp. 10554–10559, 2009, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/37049.