scholarly journals Relaxation Phenomena in Chitosan-Au Nanoparticle Thin Films

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3214
Author(s):  
Elodie Strupiechonski ◽  
Marisa Moreno-Ríos ◽  
Erika O. Ávila-Dávila ◽  
Ramón Román-Doval ◽  
Evgeny Prokhorov ◽  
...  
Keyword(s):  
Thin Films ◽  
Glass Transition ◽  
Relaxation Process ◽  
Disordered Systems ◽  
Chemical Reduction ◽  
Sodium Succinate ◽  
Au Nanoparticle ◽  
Relaxation Processes ◽  
Potential Barriers ◽  
Percolation Effect

Chitosan–gold nanoparticle (CS/AuNP) thin films were synthesized through the chemical reduction of HAuCl4 in sodium citrate/chitosan solutions. The dielectric and dynamic mechanical behaviors of CS/AuNP films have been investigated as a function of moisture and HAuCl4 content. Two relaxation processes in the nanocomposites have been observed. The α-relaxation process is related to a glass transition in wet CS/AuNP films. However, in dry composites (with 0.2 wt% of moisture content), the glass transition vanished. A second relaxation process was observed from 70 °C to the onset of thermal degradation (160 °C) in wet films and from 33 °C to the onset of degradation in dry films. This relaxation is identified as the σ-relaxation and may be related to the local diffusion process of ions between high potential barriers in disordered systems. The α- and σ-relaxation processes are affected by the HAuCl4 content of the solutions from which films were obtained because of the interaction between CS, sodium succinate, and gold nanoparticles. With about 0.6 mM of HAuCl4, the conductivity of both wet and dry films sharply increased by six orders, corresponding to the percolation effect, which may be related to the appearance of a conductivity pathway between AuNPs, HAuCl4, and NaCl.

scholarly journals PACMAN PERCOLATION AND THE GLASS TRANSITION

Fractals ◽  
2013 ◽  
Vol 21 (03n04) ◽  
pp. 1350021 ◽  
Author(s):  
RAFFAELE PASTORE ◽  
MASSIMO PICA CIAMARRA ◽  
ANTONIO CONIGLIO
Keyword(s):  
Monte Carlo ◽  
Relaxation Time ◽  
Glass Transition ◽  
Monte Carlo Simulations ◽  
Relaxation Process ◽  
Time Scales ◽  
Relaxation Processes ◽  
Percolation Transition ◽  
Glass Model ◽  
Different Time Scales

We investigate via Monte Carlo simulations the kinetically constrained Kob-Andersen lattice glass model showing that, contrary to current expectations, the relaxation process and the dynamical heterogeneities seems to be characterized by different time scales. Indeed, we found that the relaxation time is related to a reverse percolation transition, whereas the time of maximum heterogeneity is related to the spatial correlation between particles. This investigation leads to a geometrical interpretation of the relaxation processes and of the different observed time scales.

Insights into the Structural Dynamics of PLGA at Terahertz Frequencies

2018 ◽  
Author(s):  
Talia A. Shmool ◽  
J. Axel Zeitler
Keyword(s):  
Glass Transition ◽  
Relaxation Process ◽  
Free Volume ◽  
Variable Temperature ◽  
Dipole Moments ◽  
Relaxation Processes ◽  
Segmental Motion ◽  
Terahertz Time Domain Spectroscopy ◽  
Free Volume Theory ◽  
Terahertz Frequencies

The mechanical properties of an amorphous copolymer are directly related to the dynamic processes occurring at the molecular level. Poly lactic-co-glycolic acid (PLGA) is a biodegradable co-polymer, and in this work we investigate the dynamics of PLGA and its glass transition behaviour by performing variable temperature terahertz time-domain spectroscopy (THz-TDS) experiments. We correlate PLGA dynamics, as measured at terahertz frequencies, their temperature dependence, molecular weight (MW), lactide to glycolide ratio, and free volume. The THz-TDS data can be used to detect two distinct glass transition processes, T<sub>g,α</sub> and T<sub>g,β</sub>. To complement our analysis, we use dynamic mechanical analysis (DMA) to probe the β- and α-relaxation processes in PLGA, and compare the results obtained from the DMA experiments with those obtained using THz-TDS. We attribute T<sub>g,β</sub> to the change in dipole moments associated with the β-relaxation process, originating from the local rotation of C-O macromolecular chain segments, and T<sub>g,α</sub> to the change in dipole moments due to large segmental motion of the copolymer backbone associated with the α-relaxation process. We connect our experimental results to the free volume theory proposed by Fox and Flory, and demonstrate our results are consistent with the relationship between the experimentally determined T<sub>g,β</sub> and T<sub>g,α</sub> and free volume and PLGA dynamics.

Insights into the Structural Dynamics of PLGA at Terahertz Frequencies

2018 ◽  
Author(s):  
Talia A. Shmool ◽  
J. Axel Zeitler
Keyword(s):  
Glass Transition ◽  
Relaxation Process ◽  
Free Volume ◽  
Variable Temperature ◽  
Dipole Moments ◽  
Relaxation Processes ◽  
Segmental Motion ◽  
Terahertz Time Domain Spectroscopy ◽  
Free Volume Theory ◽  
Terahertz Frequencies

The mechanical properties of an amorphous copolymer are directly related to the dynamic processes occurring at the molecular level. Poly lactic-co-glycolic acid (PLGA) is a biodegradable co-polymer, and in this work we investigate the dynamics of PLGA and its glass transition behaviour by performing variable temperature terahertz time-domain spectroscopy (THz-TDS) experiments. We correlate PLGA dynamics, as measured at terahertz frequencies, their temperature dependence, molecular weight (MW), lactide to glycolide ratio, and free volume. The THz-TDS data can be used to detect two distinct glass transition processes, T<sub>g,α</sub> and T<sub>g,β</sub>. To complement our analysis, we use dynamic mechanical analysis (DMA) to probe the β- and α-relaxation processes in PLGA, and compare the results obtained from the DMA experiments with those obtained using THz-TDS. We attribute T<sub>g,β</sub> to the change in dipole moments associated with the β-relaxation process, originating from the local rotation of C-O macromolecular chain segments, and T<sub>g,α</sub> to the change in dipole moments due to large segmental motion of the copolymer backbone associated with the α-relaxation process. We connect our experimental results to the free volume theory proposed by Fox and Flory, and demonstrate our results are consistent with the relationship between the experimentally determined T<sub>g,β</sub> and T<sub>g,α</sub> and free volume and PLGA dynamics.

Stress Relaxation during Isothermal Annealing at Elevated Temperatures in Electroplated Cu Films

2003 ◽  
Vol 795 ◽  
Author(s):  
Soo-Jung Hwang ◽  
Young-Chang Joo ◽  
Junichi Koike
Keyword(s):  
Thin Films ◽  
Stress Relaxation ◽  
Relaxation Process ◽  
Surface Diffusion ◽  
Elevated Temperatures ◽  
Isothermal Annealing ◽  
Slow Relaxation ◽  
Diffusion Creep ◽  
Relaxation Processes ◽  
Fast Relaxation

ABSTRACTDeformation mechanisms of electroplated Cu thin films on TaN/SiO2/Si were investigated by performing isothermal annealing above 200 °C. Stress relaxation behavior during isothermal annealing was analyzed by curve fitting using exponential decay equations. During heating, fast relaxation and subsequent slow relaxation processes were observed. In contrast, during cooling, only slow relaxation process was observed. Among possible mechanisms for stress relaxation, diffusion creep was found to be the most plausible mechanism based on the obtained values of the activation energy. It was suggested that the slow relaxation process observed both in the heating and in the cooling processes was attributed to a grain-boundary diffusion creep. On the other hand, the fast relaxation process observed during heating was attributed to a surface-diffusion controlled mechanism. The surface diffusion mechanism was considered to be characteristic to Cu thin films that did not form stable surface oxide.

scholarly journals Structural, Optical and Electrical Properties of Al+MoO3 and Au+MoO3 Thin Films Prepared by Magnetron Codeposition

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 766
Author(s):  
Tihomir Car ◽  
Ivan Jakovac ◽  
Ivana Šarić ◽  
Sigrid Bernstorff ◽  
Maja Micetic
Keyword(s):  
Thin Films ◽  
Electrical Properties ◽  
Au Nanoparticle ◽  
Content Increase ◽  
Optical And Electrical Properties ◽  
Volume Percentage ◽  
Sputtering Deposition ◽  
Nanoparticle Formation ◽  
Al Content ◽  
Sputtering Power

Structural, optical and electrical properties of Al+MoO3 and Au+MoO3 thin films prepared by simultaneous magnetron sputtering deposition were investigated. The influence of MoO3 sputtering power on the Al and Au nanoparticle formation and spatial distribution was explored. We demonstrated the formation of spatially arranged Au nanoparticles in the MoO3 matrix, while Al incorporates in the MoO3 matrix without nanoparticle formation. The dependence of the Au nanoparticle size and arrangement on the MoO3 sputtering power was established. The Al-based films show a decrease of overall absorption with an Al content increase, while the Au-based films have the opposite trend. The transport properties of the investigated films also are completely different. The resistivity of the Al-based films increases with the Al content, while it decreases with the Au content increase. The reason is a different transport mechanism that occurs in the films due to their different structural properties. The choice of the incorporated material (Al or Au) and its volume percentage in the MoO3 matrix enables the design of materials with desirable optical and electrical characteristics for a variety of applications.

Impact of Surface-Modified Nanoparticles on Glass Transition Temperature and Elastic Modulus of Polymer Thin Films

2007 ◽  
Vol 40 (22) ◽  
pp. 7755-7757 ◽  
Author(s):  
Jong-Young Lee ◽  
Kristin E. Su ◽  
Edwin P. Chan ◽  
Qingling Zhang ◽  
Todd Emrick ◽  
...  
Keyword(s):  
Thin Films ◽  
Glass Transition ◽  
Elastic Modulus ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Polymer Thin Films ◽  
Surface Modified ◽  
Surface Modified Nanoparticles

Synthesis and Fabrication of PVA-Ag-Cu and PANI-Ag-Cu Nanocomposite Thin Film Sensor for Detection of E. coli in Water

2014 ◽  
Vol 911 ◽  
pp. 131-135 ◽  
Author(s):  
H. Abdullah ◽  
Noor Azwen Noor Azmy ◽  
Norshafadzila Mohammad Naim ◽  
Aisyah Bolhan ◽  
Aidil Abdul Hamid ◽  
...  
Keyword(s):  
Thin Films ◽  
Chemical Reduction ◽  
Oxidative Polymerization ◽  
Face Centered Cubic ◽  
High Concentration ◽  
Film Sensor ◽  
E Coli ◽  
Host Materials ◽  
Face Centered ◽  
Xrd Patterns

Polymers are excellent host materials for nanoparticles of metals and semiconductors. PVAAgCu nanocomposite was synthesized from chemical reduction, whereas PANIAgCu nanocomposite was synthesized by chemical oxidative polymerization. PVAAgCu and PANIAgCu thin films were deposited on the glass substrate by spin coating technique. The films were characterized by using XRD and AFM. The sensitivity of the samples was analyzed by IV measurement. The peaks in XRD patterns confirm the presence of Ag-Cu nanoparticles in face centered cubic structure. AFM images show the roughness of PVAAgCu and PANIAgCu increased as Ag concentration decreased and Cu concentration increased. I-V measurements indicate that the change in the current of the films increases with the presence of E. coli. The sensitivity on E. coli increases for PVAAgCu and PANIAgCu thin films with high concentration of Cu.

MAGNETIC RESISTIVITY IN Bi2Sr2Ca(Cu1-xCox)2Od EPITAXIAL THIN FILMS

2007 ◽  
Vol 21 (01) ◽  
pp. 127-132
Author(s):  
T. R. YANG ◽  
G. ILONCA ◽  
V. TOMA ◽  
P. BALINT ◽  
M. BODEA
Keyword(s):  
Magnetic Field ◽  
Thin Films ◽  
Activation Energy ◽  
Glass Transition ◽  
Effective Activation Energy ◽  
Epitaxial Thin Films ◽  
Effective Activation ◽  
High Quality ◽  
Plastic Deformations ◽  
Magnetic Resistivity

The scaling behavior of the effective activation energy of high-quality epitaxial c-oriented Bi 2 Sr 2 Ca ( Cu 1-x Co x)2 O d thin films with 0≤x ≤0.025 has been studied as a function of temperature and magnetic field. For all samples, the effective activation energy scales as U(T, μoH)=Uo(1-T/T c )mHn with exponent m=1.25±0.03, n=-1/2 and the field scaling 1/μoH and -UμoH for thick films and ultra thin films, respectively. The results are discussed taking into account of the influence of the Co substitution with a model in which U(T, H) arises from plastic deformations of the viscous flux liquid above the vortex-glass transition temperature.

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