Increase In Relaxation Time Research Articles

The Influence of γ Radiation on the Dielectric Properties of Ferroelectric Langmuir–Blodgett Films

Dielectric relaxation of Debye type has been found for thin vinylidene fluoride‒trifluoroethylene copolymer films of different composition, fabricated by the Langmuir–Blodgett (LB) technique. The influence of γ radiation on the dielectric response of LB films is studied. It is established that the relaxation time increases after the γ irradiation, the phase transition is observed at a lower temperature, and the temperature hysteresis is reduced.

In Ukrainian

An experimental study has beencarried out on the spectral dependence of the relaxation time of surface monopolar photoconductivity in the structures of macroporous silicon, with strong surface absorption of light, while the absorption coefficient varied in the range 2.37∙10 3 –3∙10 5 cm –1 , and the absorption depth from 0.03 μm to 4.22 μm. Visible LEDs 0.38–0.62 µm were used for the studies: ultraviolet, violet, blue, green, yellow, orange and red. Structures of macroporous silicon were formed on n-type silicon with orientation [100] and specific resistivity of 4.5 Ω∙cm using photoelectrochemical etching. The macropores had a diameter of D p = 3.5 μm, a depth of h p = 80 μm and a concentration of N p = 3.5∙10 6 cm –2 . In the structures of macroporous silicon, a "slow" relaxation of monopolar photoconductivity was experimentally observed. It has been found that the relaxation time of monopolar photoconductivity is dependent on the wavelength of the illumination and varieds in the range of 15.5–42 s in the visible range of 0.38–0.62 μm. Moreover, the dependence of the photoconductivity relaxation time on the illumination wavelength had a minimum relaxation time of 15.5 s when illuminated by green light with a wavelength of 0.5215 μm. The reason for the dependence of the relaxation time of the monopolar photoconductivity on the wavelength is the competition of the processes of recombination and trapping of the main charge carriers on the so-called "slow" surface levels. The dominance of the recombination or trapping process is influenced by the characteristics of local centers, the surface conditions, the surface bending of the Y s zones, which determines the surface monopolar photoconductivity and its relaxation. In the long-wavelength region of the spectrum, the decrease in the photoconductivity relaxation time from 42 s to 15.5 s is explained by the dominance of the trapping process of the main charge carriers at "slow" surface levels, which are localized within 1 nm of the silicon surface in the SiO x transition layer. In the short-wavelength region of the spectrum, the slow increase in the photoconductivity relaxation time from 15.5 to 23.7 s is explained by the fact that the trapping of the main charge carriers in the "slow" surface states, which are localized in SiO 2 and have a longer photoconductivity relaxation time, begins to influence the photoconductivity relaxation time. The level of sticking gradually turns into the level of slow recombination with a large absorption coefficient, reaching values of 3∙10 5 cm –1 . The photoconductivity relaxation associated with surface levels changes with a change in the wavelength of illumination, which causes a change in the absorption coefficient, absorption depth, and surface bending of the Y s zones. Due to this, a spectral dependence was observed of the relaxation time of surface photoconductivity in the structure of macroporous silicon.

Charge dynamics on size confined conducting polymers through electron paramagnetic resonance spectroscopy

Abstract A complete understanding of single electron behavior in mesoscopic conjugated polymers is necessary for the development of advanced organic light emitting diodes, spintronics, flexible electronics and bioelectronics. In this study, we investigate the charge dynamics of conjugated polymer nanowires (CPNWs), synthesized using polypyrrole (PPy) and poly (3, 4- ethylenedioxythiophene) (PEDOT) and having diameters of 100 and 200 nm. The electrical properties and magnetic behavior of charges at the localized doping sites are probed using temperature dependent I–V analysis and electron paramagnetic resonance (EPR) spectroscopy. The I–V curves indicate that the applied bias and the diameter of the CPNWs, as well as their crystallinity, are important factors for charge injection and transport along the polymer chain. The EPR experiments show a relative increase in the spin relaxation time of PPy whereas a corresponding decrease is observed for PEDOT, as the diameter decreases. Based on the experimental results, the size effect and the interaction between charge carriers within the one-dimensional conducting polymer are discussed considering the doping states. These results are expected to extend the understanding of electronic behaviors in mesoscopic conjugated polymers.

Pore-size dependence and slow relaxation of hydrogel friction on smooth surfaces

Hydrogels consist of a cross-linked polymer matrix imbibed with a solvent such as water at volume fractions that can exceed 90%. They are important in many scientific and engineering applications due to their tunable physiochemical properties, biocompatibility, and ultralow friction. Their multiphase structure leads to a complex interfacial rheology, yet a detailed, microscopic understanding of hydrogel friction is still emerging. Using a custom-built tribometer, here we identify three distinct regimes of frictional behavior for polyacrylic acid (PAA), polyacrylamide (PAAm), and agarose hydrogel spheres on smooth surfaces. We find that at low velocities, friction is controlled by hydrodynamic flow through the porous hydrogel network and is inversely proportional to the characteristic pore size. At high velocities, a mesoscopic, lubricating liquid film forms between the gel and surface that obeys elastohydrodynamic theory. Between these regimes, the frictional force decreases by an order of magnitude and displays slow relaxation over several minutes. Our results can be interpreted as an interfacial shear thinning of the polymers with an increasing relaxation time due to the confinement of entanglements. This transition can be tuned by varying the solvent salt concentration, solvent viscosity, and sliding geometry at the interface.

Structural Dynamics of An ELM-11 Framework Transformation Accompanied with Double-Step CO2 Gate sorption: An NMR Spin Relaxation Study

[Cu(4,4'-bipyridine)2(BF4)2] (ELM-11), an elastic layer-structured MOF (metal-organic framework), is expected to be a sophisticated CO2 reservoir candidate because of its high capacity and recovery efficiency for CO2 sorption. While ELM-11 shows a unique double-step gate sorption for CO2 gas, the dynamics of the structural transition have not yet been clarified. In this study, the dynamics of the 4,4'-bipyridine linkers and the BF4- anions were studied by determining 1H spin-lattice relaxation times (T1). The ELM-11 structural transition accompanying CO2 sorption was also examined through the CO2 uptake dependence of the 1H spin–spin relaxation time (T2), in addition to T1. In its closed form, the temperature dependence of the 1H T1 of ELM-11 was analyzed by considering the contributions of both paramagnetic and dipolar relaxations, which revealed the isotropic reorientation of BF4- and the torsional flipping of the 4,4'-bipyridine moieties. The resultant activation energy of 32 kJ mol-1 for the isotropic BF4− reorientation is suggestive of strong (B-F...Cu2+) interactions between Cu(II) and the F atoms in BF4−. Furthermore, the CO2 uptake dependence of T1 was found to be dominated by competition between the increase in the longitudinal relaxation time of the electron spins and the decrease in the spin density in the unit cell.

Observation of the hot-phonon effect in monolayer MoS2

Femtosecond transient absorption measurements have been performed to study the pump wavelength- and fluence-dependent hot carrier relaxation dynamics in monolayer MoS2. The relaxation process of the photoinduced carriers monitored within hundreds of femtoseconds after photoexcitation is demonstrated to be achieved through the carrier–phonon scattering mechanism. It is observed that an efficient hot-phonon effect can slow down the relaxation rate by around three times with the injected carrier density changing from 1 × 1012 to 3 × 1013 cm−2. A pronounced increase in the hot carrier relaxation time with decreasing temperature is further detected, which is attributed to the decreased phonon occupancy at lower temperature.

Effect of hydrocolloids on structural and functional properties of wheat/potato (50/50) flour dough

Abstract Physicochemical analyses were performed to study the effect of hydrocolloids on wheat/potato (50/50) flour doughs. Pectin, hydroxypropilmethylcellulose, Arabic gum and konjac glucomannan were tested at 1.5 g/100 g (flour basis). Textural and rheological assays indicated great differences between the control dough (100 % wheat flour) and doughs containing wheat/potato flour (50/50). These differences were reduced when hydrocolloids were added with Arabic gum and hydroxypropilmethylcellulose being the gums that better mimic the control dough properties. The analysed dough showed a bimodal distribution of relaxation times indicating that more than one molecular mechanism was responsible for relaxation. The presence of potato flour led to a marked decrease in relaxation times indicating a faster decay of stress as a function of time. The presence of gums probably increased relaxation times by establishing stronger non-covalent interaction with the dough components, rendering high molecular weight aggregates, which slowed down relaxation behaviour. Differential scanning calorimetry results showed that potato flour did not significantly changed the gelatinization temperature, but the addition of hydrocolloids shifted this parameter to higher values. Samples containing gums broadened the endotherm making the process slower and more energy demanding. The microstructure was studied at different levels (optical, confocal and scanning electron microscopy) and it was observed that potato flour made the microstructure smoother and more uniform. On the other hand, the addition of hydrocolloids led to rougher structures. These observations were confirmed by modelling image texture with different algorithms such as grey level co-occurrence matrix, fractal dimension and lacunarity.

Probing Flow-Induced Biomolecular Interactions With Micro-Extensional Rheology: Tau Protein Aggregation.

Biomolecules in solutions subjected to extensional strain can form aggregates, which may be important for our understanding of pathologies involving insoluble protein structures where mechanical forces are thought to be causative (e.g., tau fibers in chronic traumatic encephalopathy (CTE)). To examine the behavior of biomolecules in solution under mechanical strains requires applying rheological methods, often to very small sample volumes. There were two primary objectives in this investigation: (1) To probe flow-induced aggregation of proteins in microliter-sized samples and (2) To test the hypothesis that tau protein aggregates under extensional flow. Tau protein (isoform:3R 0 N; 36.7 kDa) was divided into 10 μl droplets and subjected to extensional strain in a modified tensiometer. Sixteen independent tests were performed where one test on a single droplet comprised three extensional events. To assess the rheological performance of the fluid/tau mixture, the diameter of the filament that formed during extension was tracked as function of time and analyzed for signs of aggregation (i.e., increased relaxation time). The results were compared to two molecules of similar and greater size (Polyethylene Oxide: PEO35, 35 kDa and PEO100, 100 kDa). Analysis showed that the tau protein solution and PEO35 are likely to have formed aggregates, albeit at relatively high extensional strain rates (∼10 kHz). The investigation demonstrates an extensional rheological method capable of determining the properties of protein solutions in μl volumes and that tau protein can aggregate when exposed to a single extensional strain with potentially significant biological implications.

Optical Properties of Titanium in the Regime of the Limited Light Penetration

In this study, the titanium layers from 12 to 1470 nm thick were fabricated by using the method involving dynamically changed working gas pressure (gas injection magnetron sputtering). The influence of the deposition time on the optical and electrical properties of Ti films, as well as on their microstructure, are considered. The samples are investigated by means of spectroscopic ellipsometry, atomic force microscopy, X-ray diffraction, and confocal optical microscopy. Additionally, for the Ti layers, the sheet resistance was determined. The produced coatings exhibit privileged direction of growth (002). The obtained results show a gradual increase in the mean relaxation time of free-carriers with the increase in the thickness of titanium film. However, the plasma energy exhibits maximum for the coating with the thickness of 93 nm. For such thickness, the lowest value of optical resistivity (about 200 cm) was observed. It was found that the dc- and optical resistivity exhibit similar values for titanium films with thickness up to 93 nm. For thicker Ti layers, significant differences in resistivities (dc- and optical) were noticed. The behavior of the Drude parameter (the plasma energy), calculated optical resistivity, and discrepancies between values of optical and dc-resistivities for thicker Ti coatings can be explained as a result of the limited light penetration.

Defining the Progression of Diabetic Cardiomyopathy in a Mouse Model of Type 1 Diabetes.

The incidence of diabetes and its association with increased cardiovascular disease risk represents a major health issue worldwide. Diabetes-induced hyperglycemia is implicated as a central driver of responses in the diabetic heart such as cardiomyocyte hypertrophy, fibrosis, and oxidative stress, termed diabetic cardiomyopathy. The onset of these responses in the setting of diabetes has not been studied to date. This study aimed to determine the time course of development of diabetic cardiomyopathy in a model of type 1 diabetes (T1D) in vivo. Diabetes was induced in 6-week-old male FVB/N mice via streptozotocin (55 mg/kg i.p. for 5 days; controls received citrate vehicle). At 2, 4, 8, 12, and 16 weeks of untreated diabetes, left ventricular (LV) function was assessed by echocardiography before post-mortem quantification of markers of LV cardiomyocyte hypertrophy, collagen deposition, DNA fragmentation, and changes in components of the hexosamine biosynthesis pathway (HBP) were assessed. Blood glucose and HbA1c levels were elevated by 2 weeks of diabetes. LV and muscle (gastrocnemius) weights were reduced from 8 weeks, whereas liver and kidney weights were increased from 2 and 4 weeks of diabetes, respectively. LV diastolic function declined with diabetes progression, demonstrated by a reduction in E/A ratio from 4 weeks of diabetes, and an increase in peak A-wave amplitude, deceleration time, and isovolumic relaxation time (IVRT) from 4–8 weeks of diabetes. Systemic and local inflammation (TNFα, IL-1β, CD68) were increased with diabetes. The cardiomyocyte hypertrophic marker Nppa was increased from 8 weeks of diabetes while β-myosin heavy chain was increased earlier, from 2 weeks of diabetes. LV fibrosis (picrosirius red; Ctgf and Tgf-β gene expression) and DNA fragmentation (a marker of cardiomyocyte apoptosis) increased with diabetes progression. LV Nox2 and Cd36 expression were elevated after 16 weeks of diabetes. Markers of the LV HBP (Ogt, Oga, Gfat1/2 gene expression), and protein abundance of OGT and total O-GlcNAcylation, were increased by 16 weeks of diabetes. This is the first study to define the progression of cardiac markers contributing to the development of diabetic cardiomyopathy in a mouse model of T1D, confirming multiple pathways contribute to disease progression at various time points.

Multiparametric qMTI Assessment and Monitoring of Normal Appearing White Matter and Classified T1 Hypointense Lesions in Relapsing-Remitting Multiple Sclerosis

BackgroundQuantitative magnetization transfer imaging (qMTI)1 is an efficient technique that is sensitive to the density of the macromolecular protons which are found mainly in white matter myelin. ObjectiveThe aim of this study is to investigate the statistical significance of complementary qMTI parameters including magnetization transfer rate (Ksat)2 and longitudinal relaxation time under MT saturation pulse (T1sat)3 compared to magnetization transfer ratio (MTR)4 and longitudinal relaxation time (T1)5 in relapsing remitting multiple sclerosis (RRMS)6 patients. MethodsIn this study, conventional MRI protocols as well as MT-3DSPGR imaging were performed on twelve clinically definite RRMS patients and twelve age-matched controls. Two general methodologies were utilized for qMTI calculations, including global volumetric measurement of MTI-T1 parameters using a pixel-based analysis method throughout the brain white matter and the regional assessments within classified MS lesions with respect to their hypointensities on T1-weighted scans. MTI-T1 parameters of segmented lesions and normal appearing white matter (NAWM)7 in RRMS patients were evaluated in comparison with normal white matter (NWM)8 of control subjects. ResultsSignificant reductions of MTR and Ksat values in isointense (p<0.0001), mild (p<0.0001) and severe hypointense lesions in comparison with NAWM on T1-weighted scans, were associated with considerable increases in both tissue relaxation times with and without MT pulse, T1sat (p<0.0001) and T1 (p<0.0001) respectively. Similar significant changes of quantitative MT imaging parameters and T1 values were also seen in non-lesion areas of NAWM in MS patients compared to those of NWM in healthy volunteers. ConclusionComplementary qMT imaging parameter contributes to the magnetization transfer phenomenon including Ksat and T1sat can provide more reliable information about the magnitudes and mechanisms of myelin destruction in multiple sclerosis compared to the conventional MTR and T1 relaxation time values.

Improving Interaction at Polymer-Filler Interface: The Efficacy of Wrinkle Texture.

One of the main issues in preparing polymer-based nanocomposites with effective properties is to achieve a good dispersion of the nanoparticles into the matrix. Chemical interfacial modifications by specific coupling agents represents a good way to reach this objective. Actually, time consuming compatibilization procedures strongly compromise the sustainability of these strategies. In this study, the role of particles’ architectures in their dispersion into a poly-lactic acid matrix and their subsequent influences on physical-chemical properties of the obtained nanocomposites were investigated. Two kinds of silica nanoparticles, “smooth” and “wrinkled,” with different surface areas (≈30 and ≈600 m2/g respectively) were synthesized through a modified Stöber method and used, without any chemical surface pre-treatments, as fillers to produce poly-lactic acid based nanocomposites. The key role played by wrinkled texture in modifying the physical interaction at the polymer-filler interface and in driving composite properties, was investigated and reflected in the final bulk properties. Detailed investigations revealed the presence of wrinkled nanoparticles, leading to (i) an enormous increase of the chain relaxation time, by almost 30 times compared to the neat PLA matrix; (ii) intensification of the shear-thinning behavior at low shear-rates; and (iii) slightly slower thermal degradation of polylactic acid.

Silica particle deposition in superheated steam in an annular flow: Computational modeling and experimental investigation

The work presents computational modeling and an experimental investigation of silica deposition occurring in geothermal systems with superheated steam flows. An advection diffusion model was implemented for predicting silica particle transport and deposition in turbulent flows. The model includes the effect of Brownian diffusion, turbulent diffusion, turbophoresis, Saffman lift force, and drag force on particle motion. Simulation results for deposition of silica particles in superheated steam flow were validated experimentally. An experimental setup consisting of a superheated steam generating system, silica injection system and test section assembly was designed and constructed. Deposition velocity was measured for silica fume particles ranging from 1 to 20 μm in diameter. The measured data shows agreement with the implemented model simulation results showing an increase in deposition velocity with increase in particle relaxation time in diffusion impaction regime.

Impacts of Thermal Radiation and Heat Consumption/Generation on Unsteady MHD Convection Flow of an Oldroyd-B Fluid with Ramped Velocity and Temperature in a Generalized Darcy Medium

This article analyzes the time-dependent magnetohydrodynamic flow of Oldroyed-B fluid in the presence of heat consumption/generation and thermal radiation. The flow is restricted to a vertical infinite plate saturated in porous material along with ramp wall velocity and ramp wall temperature conditions. This flow also incorporates the generalized Darcy’s law. In this paper, accurate equation of velocity field is presented first and then solutions of mass and energy equation are derived in Laplace domain. Real-time domain solutions are obtained by tackling the complexity of Laplace domain expressions through numerical Laplace inversion. Skin friction coefficient and Nusselt number are also calculated. A comparison for ramp wall temperature condition and isothermal temperature condition is also drawn to investigate the difference. A graphical study is conducted to analyze the influence of parameters on fluid flow and heat transfer. It is found that radiation parameter and heat generation elevate the energy profile, while flow is accelerated by increasing the retardation time and porosity parameter and an opposite behavior is noted for increasing relaxation time and magnetic parameter. Furthermore, heat transfer rate is higher for increasing Prandtl number and velocity on plate decreases with increase in relaxation time λ 1 .

Active topological glass

The glass transition in soft matter systems is generally triggered by an increase in packing fraction or a decrease in temperature. It has been conjectured that the internal topology of the constituent particles, such as polymers, can cause glassiness too. However, the conjecture relies on immobilizing a fraction of the particles and is therefore difficult to fulfill experimentally. Here we show that in dense solutions of circular polymers containing (active) segments of increased mobility, the interplay of the activity and the topology of the polymers generates an unprecedented glassy state of matter. The active isotropic driving enhances mutual ring threading to the extent that the rings can relax only in a cooperative way, which dramatically increases relaxation times. Moreover, the observed phenomena feature similarities with the conformation and dynamics of the DNA fibre in living nuclei of higher eukaryotes.

Influence of magnetic dilution on relaxation processes in a solid solution comprising tetrahedral Co/ZnII complexes.

Single ion magnets have long been considered good prospective candidates to record a bit of information. One of the smallest known single ion magnets is CoBr2(pyridine)2. This molecular compound exhibits slow relaxation of magnetization mainly due to the thermally activated Orbach process, [A. M. Majcher et al., Chem. Sci., 2018, 9, 7277-7286]. However, the total relaxation time is dramatically shortened at low temperatures due to the direct, Raman, and quantum tunneling of magnetization processes. At low temperatures, the distribution of the probability of the possible relaxation pathways in this case favours QTM and the direct process over the Orbach process. To prolong the relaxation time, the compound was diluted with diamagnetic ZnII, producing 5 analogues of the general formula: CoxZn1-xBr2(pyridine)2 (x = 0.91, 0.67, 0.43, 0.24, and 0.06), confirmed to be a solid solution by independent experimental techniques (powder X-ray diffraction, infrared spectroscopy). The presence of diamagnetic ZnII ions changes the distribution of the dipolar interactions between the CoII centres in the material, which results in a monotonous change in the relaxation times, which in turn become longer with increasing dilutions, which is explained by the diminishing QTM contribution. The appearance of multiple relaxation processes is also observed for higher x, which is explained as the creation of multiple, separate frequency domains, as a result of the competition between QTM and the direct process contributions. We present a thorough, systematic study of magnetic dilution, which will hopefully be useful to estimate optimal dilutions in similar solid solutions.

Biologically inspired transport of solid spherical nanoparticles in an electrically-conducting viscoelastic fluid with heat transfer

Bio-inspired pumping systems exploit a variety of mechanisms including peristalsis to achieve more efficient propulsion. Non-conducting, uniformly dispersed, spherical nanosized solid particles suspended in viscoelastic medium forms a complex working matrix. Electromagnetic pumping systems often employ complex working fluids. A simulation of combined electromagnetic bio-inspired propulsion is observed in the present article. Currents formation has increasingly more applications in mechanical and medical industry. A mathematical study is conducted for MHD pumping of a bi-phase nanofluid coupled with heat transfer in a planar channel. Two-phase model is employed to separately identity the effects of solid nanoparticles. Base fluid employs Jeffery?s model to address viscoelastic characteristics. The model is simplified using long wavelength and creeping flow approximations. The formulation is taken to wave frame and non-dimensionalise the equations. The resulting boundary value problem is solved analytically, and exact expressions are derived for the fluid velocity, particulate velocity, fluid-particle temperature, fluid and particulate volumetric flow rates, axial pressure gradient and pressure rise. The influence of volume fraction density, Prandtl number, Hartmann number, Eckert number, and relaxation time on flow and thermal characteristics is evaluated in detail. The axial flow is accelerated with increasing relaxation time and greater volume fraction whereas it is decelerated with greater Hartmann number. Both fluid and particulate temperature are increased with increment in Eckert and Prandtl numbers, whereas it is reduced when the volume fraction density increases. With increasing Hartmann number pressure rise is reduced

Strain effect on phonon transport in open framework Si24: A first-principles study

Strain engineering is one of the most efficient methods to modulate the thermal transport property due to its flexibility and easy realization in experiments. In this paper, taking the newly synthesized open framework Si24 as an example, we systematically investigated the strain effect on phonon transport by means of the first-principles study. The phonon thermal conductivity (κ) of bulk material usually increases under compression and decreases under tension. However, our calculations show that the κ of Si24 decreases abnormally in the range of ε = −4% (compression, P = 4 GPa) to ε = 5% (tension, P = -4 GPa). When the tensile strain increases further, the κ begins to decrease and finally reaches the value (31.6 W/mK at ε = 19%) below the pristine κ (45.3 W/mK). By analyzing the key factors of κ at the phonon mode level, we find that this abnormal variation on κ of Si24 is mainly depending on the competition between the phonon relaxation time (τ) and other phonon parameters which include volume, specific heat capacity, and phonon group velocity. The abnormally increased κ in the strain range of ε = −4% to ε = 5% is mainly attributed to the increase of phonon relaxation time (τ), which can be further explained by phonon scattering intensity. However, as for tension ε > 5%, the reduction of κ under tensile strain mainly comes from the negative effect of phonon group velocity, specific heat capacity, and crystal volume on κ. The findings presented in this work are expected to deepen our understanding of phonon transport in the open framework Si24 and uncovers the underlying mechanism behind the anomalous strain-dependent κ of Si24, which is helpful for further research of Si allotropes, such as improve the thermoelectric performance.

Phase Space Analysis of Relaxation Dynamics of Isoscalar Giant Monopole Resonances

A classical model based on the independent particle approach to the nuclear dynamics is used to study the influence of the phase space structures on the onebody dissipation of isoscalar Giant Monopole Resonances. The model consists of a harmonic oscillator describing the collective excitation coupled with a nonlinear (Woods-Saxon) oscillator representing the motion of each nucléon. We are particulary interested in the dependence of relaxation on the energy of the system. We have found that in a rather broad region of parameter space, contrary to the common expectation, both Lyapunov exponent and relaxation time increase as a function of the total energy. We examine the conditions required for this effect to occur and demonstrate the key role of the dispersion relation of the nonlinear oscillator.

Distinct changes of Debye relaxation in primary and secondary monoalcohols by carbon nano-dots

The origin of the dielectric Debye relaxation in monoalcohols has kept interests for decades. In this work, we explored the Debye relaxation in a primary alcohol, 2-ethyl-1-hexanol, and a secondary one, 4-methyl-3-heptanol, by doping with carbon nano-dots. Dielectric and infrared spectra of the pure and doped samples were measured. We found that doping in 2-ethyl-1-hexanol decreases slightly the Debye relaxation strength together with a subtle decrease in the relaxation time, while, strikingly, the Debye relaxation strength in 4-methyl-3-heptanol is enhanced significantly, accompanied by increased relaxation time. Differently, the relaxation strength of the structural α-relaxation is both enhanced in the two monoalcohols. The infrared measurements reveal an evident increase in the fraction of associated hydrogen bonds for the doped 4-methyl-3-heptanol when compared to the pure sample. In contrast, only trivial difference is exhibited for the case of 2-ethyl-1-hexanol and its doped one. The remarkable effects of the carbon nano-dots on the Debye relaxation in the tested 4-methyl-3-heptanol sample could suggest the preferential transition from H-bond rings to chains.