TY - JOUR
T1 - Nonlinear Viscoelasticity of Highly Ordered, Two-Dimensional Assemblies of Metal Nanoparticles Confined at the Air/Water Interface
AU - Masuda, Shihomi
AU - Mielke, Salomé
AU - Amadei, Federico
AU - Yamamoto, Akihisa
AU - Wang, Pangpang
AU - Taniguchi, Takashi
AU - Yoshikawa, Kenichi
AU - Tamada, Kaoru
AU - Tanaka, Motomu
N1 - Funding Information:
M.T. thanks W. Abuillan for helpful discussions and acknowledges the INTERREG V Upper Rhine Program (NANO-TRANSMED), the German Science Foundation (DFG Ta253/12), and Nakatani Foundation for supports. S.M. (Masuda) is grateful to Advanced Graduate Course on Molecular Systems for Devices (Leading Graduate Schools) and S.M. (Mielke) to Konrad Adenauer Foundation for the fellowships.
Publisher Copyright:
© 2018 American Chemical Society.
PY - 2018/10/30
Y1 - 2018/10/30
N2 - In this study, we investigated the viscoelastic properties of metal nanoparticle monolayers at the air/water interface by dilational rheology under periodic oscillation of surface area. Au nanoparticles capped with oleylamine form a stable, dense monolayer on a Langmuir film balance. The stress response function of a nanoparticle monolayer was first analyzed using the classical Kelvin-Voigt model, yielding the spring constant and viscosity. The obtained results suggest that the monolayer of nanoparticles is predominantly elastic, forming a two-dimensional physical gel. As the global shape of the signal exhibited a clear nonlinearity, we further analyzed the data with the higher modes in the Fourier series expansion. The imaginary part of the higher mode signal was stronger than the real part, suggesting that the dissipative term mainly causes the nonlinearity. Intriguingly, the response function measured at larger strain amplitude became asymmetric, accompanied by the emergence of even modes. The significance of interactions between nanoparticles was quantitatively assessed by calculating the potential of mean force, indicating that the lateral correlation could reach up to the distance much larger than the particle diameter. The influence of surface chemical functions and core metal has also been examined by using Au nanoparticles capped with partially fluorinated alkanethiolate and Ag nanoparticles capped with myristic acid. The combination of dilational rheology and correlation analyses can help us precisely control two-dimensional colloidal assembly of metal nanoparticles with fine-adjustable localized surface plasmon resonance.
AB - In this study, we investigated the viscoelastic properties of metal nanoparticle monolayers at the air/water interface by dilational rheology under periodic oscillation of surface area. Au nanoparticles capped with oleylamine form a stable, dense monolayer on a Langmuir film balance. The stress response function of a nanoparticle monolayer was first analyzed using the classical Kelvin-Voigt model, yielding the spring constant and viscosity. The obtained results suggest that the monolayer of nanoparticles is predominantly elastic, forming a two-dimensional physical gel. As the global shape of the signal exhibited a clear nonlinearity, we further analyzed the data with the higher modes in the Fourier series expansion. The imaginary part of the higher mode signal was stronger than the real part, suggesting that the dissipative term mainly causes the nonlinearity. Intriguingly, the response function measured at larger strain amplitude became asymmetric, accompanied by the emergence of even modes. The significance of interactions between nanoparticles was quantitatively assessed by calculating the potential of mean force, indicating that the lateral correlation could reach up to the distance much larger than the particle diameter. The influence of surface chemical functions and core metal has also been examined by using Au nanoparticles capped with partially fluorinated alkanethiolate and Ag nanoparticles capped with myristic acid. The combination of dilational rheology and correlation analyses can help us precisely control two-dimensional colloidal assembly of metal nanoparticles with fine-adjustable localized surface plasmon resonance.
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U2 - 10.1021/acs.langmuir.8b02713
DO - 10.1021/acs.langmuir.8b02713
M3 - Article
C2 - 30265009
AN - SCOPUS:85055617863
VL - 34
SP - 13025
EP - 13034
JO - Langmuir
JF - Langmuir
SN - 0743-7463
IS - 43
ER -