11. Generalized Theory of Thermal Conductivity for Different Media: Solids to NanofluidsSankararaman S, Swapna Mohanachandran Nair Sindhu, 2019, original scientific article Abstract: The advent of nanotechnology in the 21st
century opened a new branch of nanoscience known as
nanofluids, finding a wide range of industrial applications
especially in heat transfer. Though the theory of thermal
conductivity of solids is well established, there is no such
conclusive model to explain the thermal conductivity of
nanofluids. In the present work we propose a generalized
theory for thermal conductivity applicable to materials ranging
from heterogeneous solids, porous materials, nanofluids, and
ferrofluids. The model could explain the effective thermal
conductivity of not only the combination of solids but also
solid−fluid mixtures. The proposed theory could successfully
link the existing models for porous solid materials and
nanofluids as its special cases. The proposed model is verified against experimental data by simulating the theoretical equations
Found in: osebi
Keywords: thermal conductivity, generalised model, Sankar-Loeb model
Published: 05.07.2022; Views: 388; Downloads: 0
 Fulltext (3,99 MB) |
12. Soot as a precursor for the low temperature synthesis of organometallic sodium carbideSankararaman S, SARITHA DEVI H V, Swapna Mohanachandran Nair Sindhu, 2019, original scientific article Abstract: The carbonaceous soot finds a wide range of applications in many fields due to the richness of various allotropes of carbon. The present work explores the possibility of least investigated sodium carbide (Na2C2) as a potential semiconducting material for photonic applications. The soot, formed by the
incomplete combustion of gingelly oil is taken as the carbon precursor for the low-temperature synthesis of the industrially significant organometallic Na2C2. The morphological modifications are analyzed using High-Resolution Transmission Electron Microscope and elemental study is carried out by Energy Dispersive Spectroscopy and x-ray dot mapping. The formation of Na2C2 is primarily identified from x-ray powder diffraction pattern and further confirmed by other structural and
thermal analysis techniques such as Fourier Transform Infrared, Raman spectroscopy, and Thermogravimetry. The region of optical absorption, bandgap, as well as its emission properties are
studied by recording the Ultraviolet-Visible and Photoluminescence spectrum. The Tauc plot analysis
suggests its semiconducting nature with direct bandgap energy of 2.08 eV. The analysis with the help of CIE, and power spectrum reveal a prominent blue emission around 440 nm irrespective of
excitation in the UV region. Thus, the major highlights of this work lie in two factors- firstly, the effective utilization of the soot and secondly, easier low-temperature and cost-effective synthesis of semiconducting Na2C2 for photonic applications.
Found in: osebi
Keywords: carbonaceous soot, sodium carbide, photonic applications
Published: 05.07.2022; Views: 375; Downloads: 0
Fulltext (1,33 MB) |
13. Thermal induced order fluctuations in carbon nanosystem with carbon nanotubesSwapna Mohanachandran Nair Sindhu, Sankararaman S, 2019, original scientific article Abstract: The allotropes of carbon nanomaterials such as carbon nanotubes (CNTs) and nanoparticles (CNPs) have emerged as a thrust area of research during the last decade because of their unique properties.CNTs are widely used in microelectronic, sensor, bio-imaging, supercapacitors, fuel cell, and etc.
applications. In the present work, we report the thermal induced order fluctuations in the CNPs with CNTs synthesized from camphor. The samples annealed to different temperatures are characterized by various spectroscopic techniques such as UV–Visible, Raman, Fourier Transform Infrared, and X-ray Photoelectron Spectroscopy. Samples’ structure and morphology are analyzed by scanning and transmission electron microscopes, and X-ray diffraction. The thermogravimetric analysis indicates
not only the mass variation upon annealing but the thermal stability also. The spectroscopic and thermal analyses reveal the thermal induced oscillations in the carbon system which can be assigned to the dynamics in CNTs through desorption of hydrogen/ thinning or shortening of multi-walled CNTs/sp2 - sp3 conversions and the removal of amorphous carbon (AC). Since the amount of CNTs in the sample decides the electrical behavior, the sample can be tuned to a desired electrical conductivity
by annealing and thus making it a tunable material for electronic applications.
Found in: osebi
Keywords: Carbon nanotubes, Camphor, Thermal induced oscillations
Published: 05.07.2022; Views: 301; Downloads: 0
Fulltext (2,75 MB) |
14. Carbon nanoparticles assisted energy transport mechanism in leaves: A thermal lens studySwapna Mohanachandran Nair Sindhu, 2019, original scientific article Abstract: In the world of increasing population and pollution due to carbon emissions, the research for effective utilization of futile diesel soot for fruitful applications has become a necessity for a sustainable development. The contribution to pollution from vehicles and industries due to the aging of engines has caused a crisis. Carbon nanoparticles (CNPs) have been the subject of interest because of their good physical, chemical, and biological properties. The present work investigates the role of CNPs produced by internal combustion engines on the energy transport mechanism among leaf pigments using the sensitive and nondestructive single beam thermal lens technique. The studies reveal the absorption changes by various chlorophyll pigments with the concentration of CNPs sprayed on the leaves. Though for low concentrations CNPs lower the photon absorbance by chlorophyll pigments, the effect gets reversed at higher concentrations. The variation of thermal diffusivity with CNP concentration and its role in the energy transport mechanism among chlorophyll pigments are also studied. It is found that CNP concentrations of 625-2500mg/l are good for better intra-pigment energy transport leading to increased rate of photosynthesis and plant yield and thereby helping in attaining food security. The variation of CNP assisted energy transport among leaf pigments on the production of nicotinamide adenine dinucleotide phosphate (NADPH) and carbohydrates is also studied with ultraviolet (UV) and near-infrared (NIR) spectroscopy.
Found in: osebi
Keywords: carbon nanoparticle, soot, energy transport, thermal lens, photosynthesis
Published: 05.07.2022; Views: 381; Downloads: 0
Fulltext (1,84 MB) |
15. Order fluctuation induced tunable light emission from carbon nano systemSankararaman S, Swapna Mohanachandran Nair Sindhu, 2019, original scientific article Abstract: The paper reports the thermal-induced order fuctuations, in a carbon nanosystem with carbon nanotubes (CNTs) synthesized
by the incomplete combustion of gingelly oil. The sample annealed at diferent temperatures (30–400 °C) is subjected to
various morphological and spectroscopic characterizations. The ultraviolet–visible spectroscopic and thermogravimetric
analyses reveal the CNTs in the sample. The high-resolution transmission electron microscopy (HR-TEM) also confrms the
formation of CNTs in the sample. The Raman spectrum and X-ray difraction pattern show the signature of multi-walled
to single-walled CNT transformation and thus an order fuctuation on annealing. The quantum yield of the sample, measured by integrating sphere method, yields 46.15% at an emission wavelength of 575 nm. When the excitation wavelength
is varied from 350 to 510 nm, the CIE coordinate moves from the white region to the yellowish-green region. The varying
amount of CNTs in the soot, upon annealing is found to vary the luminescence emission from the sample. The study reveals
the thermal-induced oscillatory order in carbon nanosystem with carbon nanotubes (CNTs) leading to tunable excitation/
thermal-dependent luminescence emission and thereby suggesting the possibility of converting the futile soot for fruitful
applications in photonics and nanoelectronics.
Found in: osebi
Keywords: Carbon nanosystem, Single-walled carbon nanotubes, Multi-walled carbon nanotubes, Raman spectroscopy, Thermogravimetric analysis, CIE plot, Quantum yield, gingelly oil
Published: 05.07.2022; Views: 334; Downloads: 0
Fulltext (1,82 MB) |
16. Optical emission diagnosis of carbon nanoparticle incorporated chlorophyll for sensing applicationsSankararaman S, SARITHA DEVI H V, RAJ VIMAL, Swapna Mohanachandran Nair Sindhu, 2019, original scientific article Abstract: Chlorophyll fluorescence (Chl F) is widely used in sensing applications to understand terrestrial vegetation
and environmental and climatic variations. The increasing rates of industrialization and carbon emission
from internal combustion engines (ICEs) pose a threat to sustainable development. This study analyses
the impact of carbon nanoparticles (CNPs) from ICEs on the optical absorption and fluorescence emission of leaf pigments. Leaf pigments without and with CNPs were subjected to UV-visible and photo-luminescence (PL) spectroscopy analyses. The field emission scanning electron microscopy and high-resolution transmission electron microscopy images of CNPs showed their morphology. The Jablonski diagram of the CNP-incorporated chlorophyll system helped in understanding the fluorescence emission,internal conversion, and the exchange of energy between them. The variations in (i) total chlorophyll, (ii)
optical absorbance by total chlorophyll, (iii) PL emission peak (at 675 nm and 718 nm) intensities for different excitation wavelengths, and (iv) normalized absorbance at the PL emission peaks with different CNP concentrations were analysed by dividing into three regions. In Region I (0–0.625 mg ml−1 ), the
radiative component dominated the nonradiative component as a result of energy transfer from CNPs to chlorophyll. In Region II (0.625–1.2 mg ml−1 ), the increase in CNP concentration initiated diffusion into chloroplasts, resulting in the increase in the nonradiative part of total energy and decrease in PL peak
intensity. In Region III (1.2–2.5 mg ml−1
), the energy absorbed by the CNPs dissipated more nonradiatively, leading to a slow rate of increase in the radiative part. The visual response of PL emission, color purity,
and the distribution of the emitted energy over the spectrum studied with the help of CIE plots, power spectrum, and confocal fluorescence microscopy revealed the fluorescence emission in the red region. This study suggests the possibility of employing Chl F in agricultural, environmental, and biological fields
for sensing applications.
Found in: osebi
Keywords: carbon nanoparticle, optical emission, fluorescence
Published: 05.07.2022; Views: 314; Downloads: 0
Fulltext (1,92 MB) |
17. Tunable fluorescence from natural carbon source- PandanusSankararaman S, AMBADAS G, SARITHA DEVI H V, Swapna Mohanachandran Nair Sindhu, 2019, original scientific article Abstract: Carbon materials possessing photoluminescence properties are considered as potential candidates in a
wide range of photonic and optoelectronic applications. In this work, the cellulose derived from the natural source,
Pandanus, is autoclave-treated for the synthesis of fluorescent carbon. The natural fibres are greatly preferred
over synthetic ones due to their cost-effectiveness, easy processability, non-abrasivity, non-toxic and environment-friendly characteristics along with high mechanical strength and damage tolerance. These properties enable them
to be used as templates for synthesis, as important reinforcement materials for commercial thermoplastics and
for making value-added products. In this study, the synthesised sample is subjected to structural, morphological,
elemental and optical characterisations. These studies reveal that the sample can be used as a low-cost tunable
light-emitting source for photonic, biomedical and biosensing applications.
Found in: osebi
Keywords: Fluorescence, Pandanus, natural carbon, cellulose
Published: 04.07.2022; Views: 313; Downloads: 0
Fulltext (1,58 MB) |
18. Fractal Applications in Bio-NanosystemsSankararaman S, Swapna Mohanachandran Nair Sindhu, 2019, review article Abstract: We live in a world of high complexity in all means. The present article is an attempt to elucidate the potential of fractal analysis in understanding and quantifying the complexity. Of several methods of fractal analysis, we have used only the box counting and power spectral methods for explaining the potential of the technique. The application of fractal analysis in bio-nanosystems, thin films, are forensic science are
exemplified though our own work.
Found in: osebi
Keywords: fractal application, bionanosystem
Published: 04.07.2022; Views: 352; Downloads: 0
Fulltext (508,87 KB) |
19. Fluorescent emission from a natural carbon matrix incorporating sodiumSwapna Mohanachandran Nair Sindhu, 2019, original scientific article Abstract: The process of functionalization of metals in natural carbon matrices has become an important area of research due to its improved properties and applications. Carbon materials possessing photoluminescence (PL) properties find a wide range of applications in photonics. Among the various carbon materials available in nature, cellulose has critical importance since it is the most abundant and wide-spread biopolymer on Earth, and also, the important component in plants’ skeleton. In the present work, the functionalized carbonaceous material is prepared by the hydrothermal treatment of natural cellulosic source Aloe Vera and the metallic element sodium is properly incorporated into it by adding sodium borohydride to observe the fluorescence emission changes. The incorporation of metal ions in the carbon matrix leads to structural modifications and properties as evidenced by field emission scanning electron microscopy, Energy dispersive spectroscopy, X-ray dot mapping, X-ray Photoelectron spectroscopy, and X-ray diffraction analysis. The optical emission characteristics are studied using Photoluminescence spectroscopy, CIE plot, power spectrum, color purity, and quantum yield. The excitation wavelength dependent photoluminescence emission mechanism shown by the carbon–metal incorporated products obtained from the cellulosic raw materials makes them suitable for biomedical and biosensing applications because of the non-toxic and eco-friendly nature.
Found in: osebi
Keywords: Fluorescent emission, sodium carbide, cellulose, carbon matrix
Published: 30.06.2022; Views: 395; Downloads: 0
Fulltext (3,09 MB) |
20. Pharmacological application of thermal Lens technique - A thermal diffusivity studySwapna Mohanachandran Nair Sindhu, 2018, original scientific article Abstract: The photothermal phenomenon has emerged as a potential tool for the nondestructive evaluation of thermal and optical properties of materials. Thermal analysis of drugs is an unavoidable part of preformulation study, as temperature variations can induce structural changes of the constituents of drugs. Techniques based on photothermal phenomena are highly sensitive, as only the absorbed radiation contributes to the signal. Periodic illumination and subsequent nonradiative de-excitation generate thermal lens signals of various types within and around the sample. Variation of thermal diffusivity with a concentration of the commonly used drug terbutaline is studied through the single-beam thermal lens technique. The ultraviolet–visible spectrum of the drug shows strong absorption around 500 nm, which suggests the possible wavelengths that can be used for the study. It is found that concentration of the drug in liquid form decides its thermal stability, as its thermal diffusivity varies with concentration. The study gives information about the optimum value for the concentration of the drug noted above for which the chance of thermal stability is high.
Found in: osebi
Keywords: thermal lens, thermal diffusivity, pharmacology, drug
Published: 30.06.2022; Views: 385; Downloads: 0
Fulltext (1,47 MB) |
