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34. The role of hydroxyl ions in the evolution of optical nonlinearity of CuO : a Z scan studyRiya Sebastian, Mohanachandran Nair Sindhu Swapna, H. V. Saritha Devi, Vimal Raj, Misha Hari, Sankaranarayana Iyer Sankararaman, 2019, izvirni znanstveni članek Ključne besede: hydroxyl ions, optical nonlinearity, Z scan, copper oxide
Objavljeno v RUNG: 05.07.2022; Ogledov: 1058; Prenosov: 58
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38. Optical emission diagnosis of carbon nanoparticle incorporated chlorophyll for sensing applicationsMohanachandran Nair Sindhu Swapna, RAJ VIMAL, SARITHA DEVI H V, Sankararaman S, 2019, izvirni znanstveni članek Opis: 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.
Ključne besede: carbon nanoparticle, optical emission, fluorescence
Objavljeno v RUNG: 05.07.2022; Ogledov: 1099; Prenosov: 0
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39. Order fluctuation induced tunable light emission from carbon nano systemMohanachandran Nair Sindhu Swapna, Sankararaman S, 2019, izvirni znanstveni članek Opis: 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.
Ključne besede: Carbon nanosystem, Single-walled carbon nanotubes, Multi-walled carbon nanotubes, Raman spectroscopy, Thermogravimetric analysis, CIE plot, Quantum yield, gingelly oil
Objavljeno v RUNG: 05.07.2022; Ogledov: 1216; Prenosov: 0
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40. Thermal induced order fluctuations in carbon nanosystem with carbon nanotubesMohanachandran Nair Sindhu Swapna, Sankararaman S, 2019, izvirni znanstveni članek Opis: 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.
Ključne besede: Carbon nanotubes, Camphor, Thermal induced oscillations
Objavljeno v RUNG: 05.07.2022; Ogledov: 955; Prenosov: 0
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