Repozitorij Univerze v Novi Gorici

Iskanje po repozitoriju
A+ | A- | Pomoč | SLO | ENG

Iskalni niz: išči po
išči po
išči po
išči po
* po starem in bolonjskem študiju


1 - 10 / 40
Na začetekNa prejšnjo stran1234Na naslednjo stranNa konec
Modulation of charge transfer exciton dynamics in organic semiconductors using different structural arrangements : none
Cristian Soncini, Abhishek Kumar, Federica Bondino, Elena Magnano, Matija Stupar, Barbara Ressel, Giovanni De Ninno, Antonis Papadopoulos, Efthymis Serpetzoglou, Emmanuel Stratakis, Maddalena Pedio, 2023, izvirni znanstveni članek

Opis: In devices based on organic semiconductors, aggregation and inter-molecular interactions play a key role in affecting the photo-physical and dynamical carrier properties of the material, potentially becoming a limiting factor to achieving high efficiency. As a consequence, a detailed understanding of the interplay between the film molecular structure and the material properties is essential to properly design devices with optimized performance. Here we demonstrate how different molecular structural arrangements modulate the charge transfer (CT) dynamics in cobalt phthalocyanine (CoPc) thin films. By transient absorption spectroscopy and time-resolved photoemission spectroscopy, we study the influence of different CoPc structures on the dynamical electronic properties, the CoPc intra and inter- molecular de-excitation pathways up to 7 ns. We rationalize the ultrafast formation of triplet states in the CoPc through an electron exchange process between the single-occupied Co3dz2 orbital and p orbitals of the macrocycle, which obviate for an energetically unfavourable spin-flip. We found enhanced CT exciton lifetime in the case of the herringbone structure with respect to the brickwork one, possibly explainable by a more efficient CT exciton delocalization along the stacking axis.
Ključne besede: Charge transfer, organic molecules, time resolved spectroscopies
Objavljeno v RUNG: 30.06.2023; Ogledov: 367; Prenosov: 2
.pdf Celotno besedilo (1,30 MB)
Gradivo ima več datotek! Več...

Markov chain : a novel tool for electronic ripple analysis
Vijayan Vijesh, K. Satheesh Kumar, Mohanachandran Nair Sindhu Swapna, Sankaranarayana Iyer Sankararaman, 2022, izvirni znanstveni članek

Ključne besede: complex network, Markov chain, rectifier, time series, ripple
Objavljeno v RUNG: 29.11.2022; Ogledov: 580; Prenosov: 0
Gradivo ima več datotek! Več...

Speckle interferometric investigation of argon pressure-induced surface roughness modifications in RF-sputtered MoO[sub]3 film
S. Soumya, R. Arun Kumar, S. Sreejyothi, Vimal Raj, Mohanachandran Nair Sindhu Swapna, Sankaranarayana Iyer Sankararaman, 2021, izvirni znanstveni članek

Opis: Film quality analysis is of more considerable signifcance due to its diversifed applications in various felds of technology. The present work reports the speckle interferometric analysis of the argon pressure-induced surface roughness modifcations of RF sputtered MoO3 flms. The paper suggests a new method of surface quality analysis of thin flms through a parameter δ, which is the diference between the initial and fnal inertia moment values in the study of the thermal-induced dynamic speckle pattern. The limitations of root mean square surface roughness analysis of the atomic force microscopic image of the flms is also exemplifed. The research suggests that argon pressure plays a vital role in the surface property of RF sputtered flms and also that the dynamic speckle analysis can give precise information about the quality of flms. The contour plot of particle displacement vector under thermal stress, suggests the degree of uniformity in the distribution of particles in the flm.
Ključne besede: speckle pattern interferometry, time history of speckle pattern, cross correlation, inertia moment
Objavljeno v RUNG: 04.07.2022; Ogledov: 705; Prenosov: 0
Gradivo ima več datotek! Več...

Weathering induced morphological modification on the thermal diffusivity of natural pyrrhotite : a thermal lens study
Mohanachandran Nair Sindhu Swapna, V. Gokul, Vimal Raj, R. Manu Raj, S. N. Kumar, Sankaranarayana Iyer Sankararaman, 2021, izvirni znanstveni članek

Opis: Natural pyrrhotites have gained significant attention due to their interesting electronic, antimicrobial, and chemical properties. The present work attempts to explore the morphology-induced modifications in the thermal characteristics of natural pyrrhotite due to ageing. The morphological, elemental, structure, optical, and thermal characterisations help in understanding the effect of ageing. The effects of five years of ageing of the sample are (i) Field Emission Scanning Electron Microscopic analysis reveals a morphological transformation from flakes to agglomerated powder, (ii) elemental analyses suggest the ageing induced compositional modification (iii) the Tauc plot analysis shows a bandgap energy modification from 1.46 eV to 1.92 eV, (iv) X-ray Diffraction (XRD), Fourier Transform Infrared, and X-ray photoelectron spectroscopic studies affirm the formation of oxy-hydroxides (v) the XRD data indicates an increase of dislocation density, and (vi) Photoluminescence study shows a deep violet emission evidenced through the CIE plot. The study by the thermal lens technique shows a lowering of thermal diffusivity study by 23%, due to the morphological modifications, adsorbed/chemisorbed hydroxyl groups, and the formation of secondary compounds due to oxidation and weathering. The phonon boundary scattering, weathering induced smaller grain size, reduced phonon mean free path, and point defects also account for the lowering of the thermal diffusivity value and thereby influencing its properties.
Ključne besede: pyrrhotite, thermal diffusivity, thermal lens, ageing, morphology
Objavljeno v RUNG: 30.06.2022; Ogledov: 709; Prenosov: 5
URL Povezava na celotno besedilo
Gradivo ima več datotek! Več...

Downscaling of sample entropy of nanofluids by carbon allotropes : a thermal lens study
Mohanachandran Nair Sindhu Swapna, Vimal Raj, S. Sreejyothi, K. Satheesh Kumar, Sankaranarayana Iyer Sankararaman, 2020, izvirni znanstveni članek

Opis: The work reported in this paper is the first attempt to delineate the molecular or particle dynamics from the thermal lens signal of carbon allotropic nanofluids (CANs), employing time series and fractal analyses. The nanofluids of multi-walled carbon nanotubes and graphene are prepared in base fluid, coconut oil, at low volume fraction and are subjected to thermal lens study. We have studied the thermal diffusivity and refractive index variations of the medium by analyzing the thermal lens (TL) signal. By segmenting the TL signal, the complex dynamics involved during its evolution is investigated through the phase portrait, fractal dimension, Hurst exponent, and sample entropy using time series and fractal analyses. The study also explains how the increase of the photothermal energy turns a system into stochastic and anti-persistent. The sample entropy (S) and refractive index analyses of the TL signal by segmenting into five regions reveal the evolution of S with the increase of enthalpy. The lowering of S in CAN along with its thermal diffusivity (50%–57% below) as a result of heat-trapping suggests the technique of downscaling sample entropy of the base fluid using carbon allotropes and thereby opening a novel method of improving the efficiency of thermal systems.
Ključne besede: carbon allotropic nanofluids, time series, entropy, MWCNT, thermal lens signal
Objavljeno v RUNG: 30.06.2022; Ogledov: 750; Prenosov: 0
Gradivo ima več datotek! Več...

Soot effected sample entropy minimization in nanofluid for thermal system design : a thermal lens study
Mohanachandran Nair Sindhu Swapna, Vimal Raj, K. Satheesh Kumar, Sankaranarayana Iyer Sankararaman, 2020, izvirni znanstveni članek

Opis: The present work suggests a method of improving the thermal system efficiency, through entropy minimisation, and unveils the mechanism involved by analysing the molecular/particle dynamics in soot nanofluids (SNFs) using the time series, power spectrum, and wavelet analyses of the thermal lens signal (TLS). The photothermal energy deposition in the SNF lowers the refractive index due to the temperature rise. It triggers the particle dynamics that are investigated by segmenting the TLS and analysing the refractive index, phase portrait, fractal dimension (D), Hurst exponent (H), and sample entropy (SampEn). The wavelet analysis gives information about the relation between the entropy and the frequency components. When the phase portrait analysis reflects the complex dynamics from region 1 to 2 for all the samples, the SampEn analysis supports it. The decreasing value of D (from 1.59 of the base fluid to 1.55 and 1.52) and the SampEn (from 1.11 of the base fluid to 0.385 and 0.699) with the incorporation of diesel and camphor soot, indicate its ability to lower the complexity, randomness, and entropy. The increase of SampEn with photothermal energy deposition suggests its relation to the thermodynamic entropy (S). The lowering of thermal diffusivity value of the base fluid from 1.4 × 10−7 m2/s to 1.1 × 10−7 and 0.5 × 10−7 m2 /s upon diesel and camphor soot incorporation suggests the heat-trapping and reduced molecular dynamics in heat dissipation.
Ključne besede: soot, entropy, thermal system, photothermal, time series, nanofluid, fractal
Objavljeno v RUNG: 30.06.2022; Ogledov: 747; Prenosov: 0
Gradivo ima več datotek! Več...

Iskanje izvedeno v 0.06 sek.
Na vrh