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Optical emission diagnosis of carbon nanoparticle incorporated chlorophyll for sensing applications
Mohanachandran Nair Sindhu Swapna, RAJ VIMAL, SARITHA DEVI H V, Sankararaman S, 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.
Keywords: carbon nanoparticle, optical emission, fluorescence
Published in RUNG: 05.07.2022; Views: 1127; Downloads: 0
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8.
Soot as a precursor for the low temperature synthesis of organometallic sodium carbide
Mohanachandran Nair Sindhu Swapna, SARITHA DEVI H V, Sankararaman S, 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.
Keywords: carbonaceous soot, sodium carbide, photonic applications
Published in RUNG: 05.07.2022; Views: 1216; Downloads: 0
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9.
Concentration-dependent thermal duality of hafnium carbide nanofluid for heat transfer applications : a mode mismatched thermal lens study
Vijayakumar Gokul, Mohanachandran Nair Sindhu Swapna, Vimal Raj, H. V. Saritha Devi, Sankaranarayana Iyer Sankararaman, 2021, original scientific article

Abstract: he mode mismatch dual-beam thermal lens technique is a sensitive tool for studying the nanofuids’ thermal difusivity in thermal engineering. The work reports the low-temperature green synthesis of hafnium carbide (HfC) using rice four as a natural carbon precursor and its potential in heat transfer nanofuids by studying the concentration-dependent thermal difusivity. The structure characterisations confirm the formation of HfC, whose refractory nature is revealed through the high thermal stability observed in the thermogravimetric analysis. The Tauc plot analysis shows direct bandgap energy of 2.92 eV. The fuorescence study suggests bluish-pink emission with CIE coordinates (0.271, 0.263). The existence of the critical concentration of HfC in the nanofuid decides its suitability for heat transfer or heat trap applications indicating a concentration-dependent thermal duality. Thus, the study is signifcant as it overcomes the major drawbacks of the existing methods of the synthesis of refractory HfC, using toxic chemical and costly equipment for heat transfer applications.
Keywords: hafnium carbide, hydrothermal synthesis, rice flour, thermal lens spectroscopy
Published in RUNG: 04.07.2022; Views: 1157; Downloads: 0
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10.
Tunable fluorescence from natural carbon source- Pandanus
Mohanachandran Nair Sindhu Swapna, SARITHA DEVI H V, AMBADAS G, Sankararaman S, 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.
Keywords: Fluorescence, Pandanus, natural carbon, cellulose
Published in RUNG: 04.07.2022; Views: 1037; Downloads: 0
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