Papers by Keyword: Raman Spectroscopy

Abstract: The unsurpassed and exceptional properties of graphene (Gr) have prompted significant progress toward Gr-based applications, and have furthermore unleashed a host of complimentary two-dimensional materials that provide new, and emerging technologies synergistic with an already well-established Gr science. The Raman spectroscopy reveals both basic and advance features. It emerged as an important optical and structural characterization tool, following in the footsteps of related form of carbon. Till date, no comprehensive descriptions of Raman spectroscopy on Gr characterization have been published yet. This is to say that, no review can possibly complete. We have presented an extensive overview of the Raman spectroscopy, filled-up this gap and discussed the theoretical background associated with the Gr and other carbon-based materials, and some thoughts about the future of this field are highlighted. Thus, it would be used as a reference guide for the utilization of Raman spectroscopy to investigate the various features of Gr and carbon-based materials.

Abstract: Carbon nanotubes (CNT) has been synthesized by pyrolysing fermented tapioca liquid using an immersed heater. It was made single-walled carbon nanotubes (SWCNT) through heating at 700, 800 and 900 °C by the chemical vapour deposition (CVD) method and characterized by using Raman spectroscopy, thermogravimetric analysis and field emission scanning electron microscopy (FESEM). The synthesized SWCNT demonstrated larger diameters at 700 °C which decreased at 800 and 900 °C, respectively. The SWCNTs were indicated based on the radial breathing mode (RBM) peak present between 200 - 300 raman shift (cm^-1). The diameters of synthesized CNTs ranged between 54 - 200 nm. Raman spectrum revealed that the G-bands were 1569, 1582 and 1576 cm^-1, respectively, whereas the D-bands were 1346, 1350 and 1358 cm^-1 for SWCNT synthesis at 700, 800 and 900 °C, respectively. The modified CVD method set up in the present study was successfully used for large scale synthesis of CNTs from an aqueous precursor such as fermented tapioca liquid.

Abstract: Over the past few decades, magnetite nanoparticle has been profusely because of their wide range of applications. The co-precipitation method is the simplest and suitable method for the preparation of this nanoparticle. It goes through several reaction steps for the formation of various phases of magnetic nanoparticles. Goethite (FeO(OH)), is one of the intermediates, and it drastically suppressed with the magnetic properties of the Fe oxide phase. In our study, it was shown that at 30°C temperature pure magnetic nanoparticles is formed. But when precipitation temperature is increase to 80°C, goethite is also present with the magnetite nanoparticle. Hence, it is deduced that precipitation temperature plays a significant role in accelerating goethite phase formation when synthesising magnetite nanoparticle by this precipitation method. Data obtained from Raman spectroscopy and XRD supported the above observation.

Abstract: Magnetite (Fe₃O₄) nanoparticles were synthesized in aqueous solutions without any surfactants. The Fe₃O₄ nanoparticles are nearly spherical and have an average diameter of 10.33nm and a narrow size distribution. Bundles of single-walled carbon nanotube (SWCNT) were synthesized using these Fe₃O₄ nanoparticles supported by MgO. Transmission electron microscopy (TEM) images show that tremendous amount of bundles SWCNT with uniform diameters were produced. The average diameter of bundles SWCNT is 1.22nm. Raman spectrum shows that well graphitized SWCNTs were formed based on the low ratio of I_D/I_G. Fe₃O₄ nanoparticles could be an effective active metal to synthesize large quantity bundles of SWCNT.

Abstract: Single crystalline high quality α-Mn₂O₃ nanorods and sea-urchins assembled with pen-type nanoneedles have been successfully synthesized by template-free hydrothermal route. The variation in hydrothermal temperature has affected the morphology of the α-Mn₂O₃ sea-urchin assembled with the nanoneedles noticeably. The influence of temperature change on the thickness, crystallinity, surface morphology and optical properties of α-Mn₂O₃ has been characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) analysis, Transmission Electron Microscopy (TEM), High Resolution Transmission Electron Microscopy (HRTEM), Raman Spectroscopy (RS) and UV-visible Spectroscopy. The results showed that in our experimental conditions, single crystalline nanorods of the α-Mn₂O₃ were obtained at a low temperature of 180 °C, while single crystalline sea-urchin assembled with pen-type nanoneedles were obtained by increasing the temperature to 280 °C. Nanorods and sea-urchin assembled with pen-type nanoneedles obtained had the well defined morphology and crystalline quality. The sea-urchin synthesized at 280 °C exhibited more than 90% absorption in UV-visible spectrum.

Abstract: A new carbon material called graphene has been attracting an increasing research interest owing to its unique electrical and mechanical properties that is useful for the various device applications. The synthesis of graphene from graphene oxide usually involves harmful chemical reducing agents that are toxic and undesirable to human and the environment. By avoiding the use of toxic and environmentally harmful reductants, we report a green approach for the reduction of graphene oxide by using reducing sugars to synthesis graphene. Graphite oxide was synthesized from graphite powder using modified Hummers method. Graphite oxide then further exfoliated to graphene oxide by using ultrasonic irradiation. Graphene then was obtained by the mild reduction of graphene oxide with reducing sugars (glucose, lactose and maltose). The structural study of the as-prepared graphene is characterized by Raman spectroscopy and fourier infra red spectroscopy. Raman and FTIR spectra indicates the partial removal of oxygen functional groups from the surface of GO. Characterizations indicate that graphene oxide is successfully reduced to graphene by sugar.

Abstract: Polymer gel is a kind of radiation dosimetry system that has been applied widely in radiotherapy treatment. In this study, the samples of NIPAM-based polymer gel which posses a good potential as 3D radiation dosimetry are synthesized. The samples of polymer gel were irradiated up to 20 Gy by using gamma cell instrument with ⁶⁰Co sources at a constant dose rate. Upon irradiation, then the chemical changes in polymer gel were characterized by using Raman spectroscopy. The polymerization was referred to an increment in Raman intensity at 815 cm^-1, assigned for C-C stretching mode of NIPAM polymer gel, as the dose increased. The consumptions of the co-monomers were referred to a decrement in Raman intensities at 1025 cm^-1 and 2353 cm^-1 assigned for C=C stretching modes of NIPAM and BIS respectively, as the dose increased. Result shows that the amount of carbon single bonds increases while the amount of carbon covalent bonds decreases following irradiation.

Abstract: Hexahedral nanocrystals of L-Alanine [CH₃CH(NH₂)COOH] doped LaF₃:Ce (ALFC) of assorted sizes have been synthesized in deionized water using water soluble chlorides of lanthanides with subsequent microwave irradiation to reduce agglomeration. The average particle sizes obtained by XRD, SEM, and TEM have been 22nm, 37nm and 23nm respectively. The surface modification by functional groups of L-Alanine is observed in the FTIR and FT-RAMAN spectra and their decomposition is studied in TGA/DTA spectrum .The electron-phonon interaction of A_1g phonon mode and fundamental E_g phonon mode have been observed in far infra-red region by FT-RAMAN spectra. The UV-Vis spectrum shows multiple absorption edges corresponding to energies at E₁ = 5.11eV, E₂ = 4.47eV, and E₃=5.781eV which indicates the quantum dot nature of the nanocrystals and its application in optoelectronic devices. ALFC nanocrystals showed green color emission peak centered at 554 nm with their potential application in bio imaging and bio tagging.Keywords: nanostructures, fluorides, Transmission electron microscopy, Raman spectroscopy, Thermogravimetric analysis (TGA).

Abstract: NiO nanoparticles are successfully prepared by sol-gel technique. A systematic change in preparation parameters like calcination temperature, calcination time and pH value has been done in order to study the influence on crystallite size. The prepared samples are characterized by X-ray diffractometer, Transmission electron microscopy, Energy dispersive x-rays analysis and Raman spectroscopy. It is shown that crystallite size mainly depends on the calcination temperature rather than pH value or calcination time.

Abstract: In cermet coating such as WC-based coating, the coexisting of ceramic and metal results in micro-galvanic corrosion due to different corrosion potential of each element. In this study, WC-17wt%Co was used. The corrosion behaviour of the coating was evaluated by potentiodynamic test in two different electrolyte which are 0.5 M sulphuric acid and 3% by weight alkaline drilling fluid. This coating shows higher corrosion potential in acid electrolyte compares to in alkaline electrolyte. Clear passivation is seen for both cases. Raman shift is able to detect WO₃ and WO₃H₂O as a corrosion product after corrosion test. Keywords: corrosion, WC, Raman shift