Aspect-Ratio Dependence on Formation Process of Gold Nanorods Studied by Time-Resolved Distance Distribution Functions

AbstractMolybdenum dialkyl dithiocarbamate (MoDTC) is a friction reducing additive commonly used in lubricants. MoDTC works by forming a low-friction molybdenum disulphide (MoS2) film (tribofilm) on rubbed surfaces. MoDTC-induced MoS2 tribofilms have been studied extensively ex-situ; however, there is no consensus on the chemical mechanism of its formation process. By combining Raman spectroscopy with a tribometer, effects of temperature and shear stress on MoS2 tribofilm formation in steel-steel contacts were examined. Time-resolved Raman spectra of the tribofilm were acquired, together with the instantaneous friction coefficient. The tribofilm is constantly being formed and removed mechanically during rubbing. Increasing shear stress promotes MoS2 formation. The nature of the tribofilm is temperature-dependent, with high-temperature tribofilms giving a higher friction than lower temperature films. Below a critical temperature Tc, a small amount of MoS2 gives significant friction reduction. Above Tc, a patchy film with more MoS2, together with a substantial amount of amorphous carbon attributed to base oil degradation, forms. The composition of this tribofilm evolves during rubbing and a temporal correlation is found between carbon signal intensity and friction. Our results highlight the mechanochemical nature of tribofilm formation process and the role of oil degradation in the effectiveness of friction modifier MoDTC.

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Probing a two-step channel formation process in injection-type pentacene field-effect transistors by time-resolved electric-field-induced optical second-harmonic generation measurement

Organic Electronics ◽

10.1016/j.orgel.2012.08.030 ◽

2012 ◽

Vol 13 (12) ◽

pp. 2801-2806 ◽

Cited By ~ 4

Author(s):

Dai Taguchi ◽

Hiroshi Masada ◽

Takaaki Manaka ◽

Mitsumasa Iwamoto ◽

Takao Nishiura ◽

...

Keyword(s):

Electric Field ◽

Harmonic Generation ◽

Formation Process ◽

Field Effect ◽

Field Effect Transistors ◽

Second Harmonic ◽

Channel Formation ◽

Time Resolved ◽

Injection Type ◽

Second Harmonic Generation Measurement

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Aspect ratio dependence in magnetorotational instability shearing box simulations

Astronomy and Astrophysics ◽

10.1051/0004-6361:200809730 ◽

2008 ◽

Vol 487 (1) ◽

pp. 1-5 ◽

Cited By ~ 68

Author(s):

G. Bodo ◽

A. Mignone ◽

F. Cattaneo ◽

P. Rossi ◽

A. Ferrari

Keyword(s):

Aspect Ratio ◽

Magnetorotational Instability ◽

Ratio Dependence

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Aspect-ratio Dependence of Optical Nonlinearities on Resonance with Longitudinal Surface Plasmon in Au Nanorods: Unique Character versus Common Behavior

SCIENCE NATURE ◽

10.30598/snvol1iss1pp001-007year2018 ◽

2018 ◽

Vol 1 (1) ◽

pp. 001-007

Author(s):

Science Nature

Keyword(s):

Aspect Ratio ◽

Surface Plasmon ◽

Nonlinear Behavior ◽

Dipole Approximation ◽

Saturable Absorption ◽

Reverse Saturable Absorption ◽

Optical Nonlinearities ◽

Ratio Dependence ◽

Unique Character ◽

Metal Metal

Unique character and common behavior are two distinguished things. In frontier nanoscience and nanotechnology, unique characters were normally obtained in some novel exotics materials such as metal-metal core-shell materials, metallic-semiconducting hybrid nanomaterials, and organic-inorganics complex nano-compounds. On the other hand, normal behavior of natural phenomena including in nano-size objects were obviously predicted based on their exact size related to confinement effect, and capability to interact with another physical system in nature. Here, we report an example of unique character due to evolution nonlinear behavior observed in gold nanorod with their aspect-ratio dependence of optical nonlinearities investigated by femtosecond Z-scan measurements closed to resonance longitudinal surface plasmon peak in gold nanorods (Au NRs). Saturable absorption manifests itself at low excitation (laser irradiances < ~7.0 GW/cm2), while reverse saturable absorption dominates at higher excitation. Both the nonlinear processes are found to increase with the aspect ratio of Au NRs. Based on the discrete dipole approximation, qualitative explanations are presented for the observed nonlinear behavior. While common behavior in metallic quantum dots or other shapes of metallic nanomaterials was not the significant in our observation.

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