61. Camphor soot: A Tunable Light EmitterMohanachandran Nair Sindhu Swapna, SARITHA DEVI H V, Sankararaman S, 2018, original scientific article Abstract: The work in this paper is the first report on the green synthesis of the blue light emitter from waxy, flammable solid collected
from Cinnamomum camphora by controlled combustion for photonic applications. Analysis with field emission scanning
electron microscope and high-resolution transmission electron microscope provides the morphology, whereas the thermo-gravimetric analysis gives the thermal stability of the soot. The optical and structural characterizations are done by recording
UV–Visible, Photoluminescent, and Raman Spectrum. The CIE plot and the power spectrum of the sample show a blue
emission at an excitation of 350 nm at room temperature with a quantum yield of 46.15%. The dependence of luminescent
behavior on temperature and excitation wavelength reveals that the material is a tunable blue emitter. This green synthesis of
the blue light emitter is highly significant, when the world is in search of a simple, phosphor-free, non-toxic, cost-effective
material with good quantum efficiency
Keywords: camphor, soot, blue light emitter
Published in RUNG: 30.06.2022; Views: 1023; Downloads: 0
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62. Photoacoustics - A nondestructive evaluation technique for thermal and optical characterisation of metal mirrorsMohanachandran Nair Sindhu Swapna, NAMPOORI V P N, Sankararaman S, 2018, original scientific article Abstract: Photoacoustic technique has emerged as a powerful tool for nondestructive evaluation and characterization. The high signal to noise ratio, sensitivity, and the least quantity of sample required make the technique suitable for wide range of applications. The intensity modulated laser beam focused on to the sample in the photoacoustic cell generates acoustic waves. Analysis of the acoustic signal enables the measurement of thermal and optical properties of the material. In the present work, the photoacoustic technique has been extended to find the thermal diffusivity and to demonstrate how the technique can be used for measuring optical reflection coefficient of a precious metal mirror—Aranmula mirror. The mirror being metal with high reflection coefficient, it finds application in optical instrumentation. The mirror is subjected to morphological characterization by atomic force microscopy and field emission scanning electron microscopy. The elemental and structural characterizations are done by energy dispersive x-ray spectroscopy, X-ray dot mapping, and X-Ray diffraction analysis. The fractal dimension of the particle distribution over the surface provides information about the surface roughness. The box-counting and power spectral fractal dimensions are found to be around 1.63 and 1.65 respectively.
Keywords: Photoacoustics, Nondestructive evaluation, Aranmula metal mirror, Reflectivity
Published in RUNG: 30.06.2022; Views: 1420; Downloads: 0
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63. Carbon Nanonecklaces with Carbon Nanotubes and Carbon DotsMohanachandran Nair Sindhu Swapna, Sankararaman S, 2017, original scientific article Abstract: Carbon nanoparticles (CNP) have gained significant attention representing
unique carbon-based nanomaterials that find applications in various fields of
science and technology. Carbon nanotubes (CNTs) and carbon dots (CDs)
have now been widely employed as an electrode in super capacitors, as
fluorescent nanomaterials for imaging and for fuel cell applications. In the
present work, we describe a simple, low cost and chemical free method of
synthesizing stable CNPs aligned in the form of a chain popularly known as
carbon necklace with CNTs and CDs. Carbon nanoparticles are synthesized by
controlled combustion of camphor in a single step flame process. The CNPs
synthesized are characterized using X-ray Powder diffraction (XRD), Raman
Spectroscopy, Energy Dispersive X ray diffraction (EDX), Fourier Transform
Infrared Spectroscopy (FTIR), UV-Visible absorption and Photoluminescent
(PL) Spectroscopy. The morphology and size of the CNPs are examined using
Field Emission Scanning Electron Microscope (FESEM) which shows
‘necklace’ structure. The CNPs are collected at two different heights and the
particles formed are found in the range 30 to 60 nm. The UV- Visible and PL
Spectra of the CNPs obtained show the presence CDs. The Raman
Spectroscopic and XRD analysis indicate the presence of CNTs in the sample.
Keywords: Carbon nanoparticles, Combustion, Carbon nanotubes, Carbon
dots, Carbon necklaces
Published in RUNG: 30.06.2022; Views: 1179; Downloads: 0
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64. Investigation of graphene oxide in diesel sootMohanachandran Nair Sindhu Swapna, Sankararaman S, 2017, original scientific article Abstract: Graphene has emerged as a potential material in various scientific disciplines, ranging from material science, engineering, and more
recently biomedicine. The paper describes the investigation of the presence of graphene and graphene oxide (GO) in the carbon soot of
internal combustion diesel engines. The UV-Visible, Fourier transform infrared (FTIR), X- ray diffraction (XRD), Photoluminescent
(PL) and Raman spectroscopic analysis of the sample provided a conclusive evidence of the formation of graphene and GO. The Field
Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive Spectrum (EDX) of the sample show carbon nanoparticles
(CNPs) of size less than 50nm. The High -Resolution Transmission Electron Microscopy (HR-TEM) analysis confirmed the formation
of graphene sheets with carbon nanospheres attached to it. The study reveals the possible exploitation of the diesel soot for potential
applications in science and technology
Keywords: Graphene, Graphene oxide, Carbon nanoparticles, Combustion, Carbon nanotube
Published in RUNG: 30.06.2022; Views: 1218; Downloads: 0
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65. Boron‑rich boron carbide from soot : a low-temperature green synthesis approachMohanachandran Nair Sindhu Swapna, H. V. Saritha Devi, Sankaranarayana Iyer Sankararaman, 2020, original scientific article Abstract: Boron carbide is a promising super-hard semiconducting material for refractory applications ranging from the nuclear industry to spacecraft. The present work is the frst report of not only turning futile soot, containing carbon allotropes in varying
composition, into boron-rich boron carbide (BC), but also developing it by a low-cost, low-temperature, and green synthesis
method. The BC synthesised from gingelly oil soot is subjected to structural, morphological, and optical characterisations.
The feld emission scanning electron microscope shows beautiful fower-like morphology, and the thermogravimetric analysis reveals the high-temperature stability of the sample synthesised. The Tauc plot of the sample indicates a 2.38 eV direct
bandgap. The formation of BC and boron-rich carbide evidenced by X-ray difraction studies is confrmed through Raman
and Fourier transform infrared spectroscopic signatures of B–C and C–B–C bonds. The fuorescence, power spectrum, and
CIE analyses carried out suggest the blue light emission for excitation at 350 nm
Keywords: boron carbide, soot, carbon nanoparticle, refractory, allotropes, green synthesis
Published in RUNG: 30.06.2022; Views: 1244; Downloads: 0
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66. Bioacoustic signal analysis through complex network featuresMohanachandran Nair Sindhu Swapna, RAJ VIMAL, Sankararaman S, 2022, original scientific article Abstract: The paper proposes a graph-theoretical approach to auscultation, bringing out the potential of graph features in
classifying the bioacoustics signals. The complex network analysis of the bioacoustics signals - vesicular (VE) and
bronchial (BR) breath sound - of 48 healthy persons are carried out for understanding the airflow dynamics
during respiration. The VE and BR are classified by the machine learning techniques extracting the graph features
– the number of edges (E), graph density (D), transitivity (T), degree centrality (Dcg) and eigenvector centrality
(Ecg). The higher value of E, D, and T in BR indicates the temporally correlated airflow through the wider
tracheobronchial tract resulting in sustained high-intense low-frequencies. The frequency spread and high-frequencies in VE, arising due to the less correlated airflow through the narrow segmental bronchi and lobar,
appears as a lower value for E, D, and T. The lower values of Dcg and Ecg justify the inferences from the spectral
and other graph parameters. The study proposes a methodology in remote auscultation that can be employed in
the current scenario of COVID-19.
Keywords: Bioacoustic signal, Graph theory, Complex network, Lung auscultation
Published in RUNG: 30.06.2022; Views: 1211; Downloads: 0
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67. Is SARS CoV-2 a multifractal? : unveiling the fractality and fractal structureMohanachandran Nair Sindhu Swapna, S. Sreejyothi, Vimal Raj, Sankaranarayana Iyer Sankararaman, 2021, original scientific article Abstract: A first report of unveiling the fractality and fractal nature of severe acute respiratory syndrome coronavirus (SARS CoV-2)
responsible for the pandemic disease widely known as coronavirus disease 2019 (COVID 19) is presented. The fractal analysis of
the electron microscopic and atomic force microscopic images of 40 coronaviruses (CoV), by the normal and differential box-counting method, reveals its fractal structure. The generalised dimension indicates the multifractal nature of the CoV. The higher
value of fractal dimension and lower value of Hurst exponent (H) suggest higher complexity and greater roughness. The
statistical analysis of generalised dimension and H is understood through the notched box plot. The study on CoV clusters also
confirms its fractal nature. The scale-invariant value of the box-counting fractal dimension of CoV yields a value of 1.820. The study opens the possibility of exploring the potential of fractal analysis in the medical diagnosis of SARS CoV-2.
Keywords: Fractality, SARS CoV, Coronavirus, Fractal dimension, Multifractal
Published in RUNG: 30.06.2022; Views: 1127; Downloads: 0
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69. Weathering induced morphological modification on the thermal diffusivity of natural pyrrhotite : a thermal lens studyMohanachandran Nair Sindhu Swapna, Vijayakumar Gokul, Vimal Raj, R. Manu Raj, S. N. Kumar, Sankaranarayana Iyer Sankararaman, 2021, original scientific article Abstract: 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.
Keywords: pyrrhotite, thermal diffusivity, thermal lens, ageing, morphology
Published in RUNG: 30.06.2022; Views: 1134; Downloads: 6
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70. Time series and fractal analyses of wheezing : a novel approachMohanachandran Nair Sindhu Swapna, Ammini Renjini, Vimal Raj, S. Sreejyothi, Sankaranarayana Iyer Sankararaman, 2020, original scientific article Abstract: Since the outbreak of the pandemic Coronavirus Disease 2019, the world is in search of novel non-invasive methods for safer
and early detection of lung diseases. The pulmonary pathological symptoms refected through the lung sound opens a possibility of detection through auscultation and of employing spectral, fractal, nonlinear time series and principal component
analyses. Thirty-fve signals of vesicular and expiratory wheezing breath sound, subjected to spectral analyses shows a clear
distinction in terms of time duration, intensity, and the number of frequency components. An investigation of the dynamics
of air molecules during respiration using phase portrait, Lyapunov exponent, sample entropy, fractal dimension, and Hurst
exponent helps in understanding the degree of complexity arising due to the presence of mucus secretions and constrictions
in the respiratory airways. The feature extraction of the power spectral density data and the application of principal component analysis helps in distinguishing vesicular and expiratory wheezing and thereby, giving a ray of hope in accomplishing
an early detection of pulmonary diseases through sound signal analysis.
Keywords: auscultation, wheeze, fractals, nonlinear time series analysis, sample entropy
Published in RUNG: 30.06.2022; Views: 1262; Downloads: 0
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