Catalytic template assisted chemical vapor deposition method for the synthesis of graphitic carbon nanostructures

( Raji Atchudan ),이용록 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0

The graphitic carbon nanostructures (GCNs) were synthesized over the catalytic templates using acetylene as carbon precursor by simple chemical vapor deposition (CVD) method. The catalytic templates such as iron oxide nanoparticles (IONPs) and Mn impregnated MgO (Mn-MgO) were characterized and were used for the production GCNs. The reaction parameters such as temperature and flow of carbon precursor were optimized in order to achieve GCNs with excellent quality and quantity. The interlayer distance of resulted GCNs is match well with the bulk graphite. All the analytical results strongly support that the prepared GCNs to be highly ordered and well graphitic in nature. Further, the results demonstrate that the GMC/g-CNTs synthesized over Mn-MgO/IONPs might be a promising contender for the large-scale process. Moreover, the produced GCNs might be an ideal candidate for nanoelectronic applications.

Hollow mesoporous silica spheres supported Ag and Ag–Au catalyzed reduction of 4-nitrobenzo-15-crown

Raji Vadakkekara,Mousumi Chakraborty,Parimal A. Parikh 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.3

Hollow mesoporous silica (HMS) spheres of size within the range 120–220 nm have been prepared usingpropanol–water solvent as template and cetyltrimethylammonium bromide (CTAB) as stabilizer. HMSsupported silver and silver–gold catalysts were prepared by impregnating metal nanoparticles on HMSand were characterized by ultraviolet–visible spectroscopy (UV–vis), dynamic light scattering (DLS),optical microscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transforminfrared spectroscopy (FTIR), inductive coupled plasma optical emission spectroscopy (ICP-OES) and N2adsorption–desorption. The reduction of 4-nitrobenzo-15-crown (4-NB-15-C) was compared using HMSsupported silver and silver–gold nanocatalysts varying experimental parameters. Bimetallic Ag–Au/HMS nanocatalysts was found to be more active than monometallic Ag/HMS nanocatalyst.

Analysis of Stability and Dynamic Behaviour of Ultra Lift Luo Converter

Raji, J.,Kamaraj, V. The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.5

Ultra Lift Luo Converter (ULC) gained considerable research interest in recent years. The stability analysis of voltage mode and peak current mode controlled ULC in continuous conduction mode is analyzed in this paper. The Eigen value theory is used for the stability analysis of voltage mode controlled ULC. Then to characterize the dynamics of inner current loop, the expressions of closed loop transfer function and loop gain are determined. An algorithm has been developed to analyze the stability of the peak current mode controlled ULC. The theoretical results are correlated with the simulation results obtained using PSIM 9.1(SMARTCTRL 1.0) software. Finally it is proposed to fabricate a prototype and validate the performance by suitable experimental setup.

Synthesis of high-quality carbon nanotubes by using monodisperse spherical mesoporous silica encapsulating iron oxide nanoparticles

Raji Atchudan,차봉근,나스리나론,김재윤,주진 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.1

Well-graphitized carbon nanotubes (CNTs) were grown by using monodisperse spherical mesoporous silica encapsulating single iron oxide (Fe3O4) nanoparticles (MSEINPs) as catalytic templates by chemical vapor deposition (CVD) and using acetylene as carbon source. The catalytic templates were synthesized by a sol-gel method. The MSEINPs exhibited better activity and selectivity in CNT synthesis than bare Fe3O4 catalysts. The synthesized multiwall carbon nanotubes (MWCNTs) were analyzed by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and Raman spectroscopy. The carbon deposits are rich in MWCNTs, as confirmed by FESEM and TGA. The wall thickness of the MWCNTs is controlled primarily by the size of the spherical mesoporous silica layer encapsulating the Fe3O4 NPs, while the inner diameter of the CNTs is determined by the size of the Fe3O4 NPs at the center of the MSEINPs. The average diameter of the MWCNTs increased significantly with increases in the growth temperature and acetylene flow rate. The analytical results show that the CNTs prepared on MSEINPs are well graphitized with a narrow size distribution in thickness, and straight and longer tubes are obtained without major defects as compared to the CNTs grown on bare Fe3O4 NPs.

An efficient synthesis of graphenated carbon nanotubes over the tailored mesoporous molecular sieves by chemical vapour deposition method

( Raji Atchudan ),주진,( Arumugam Pandurangan ),( Kyungpook National University ),( Anna University ) 한국공업화학회 2014 한국공업화학회 연구논문 초록집 Vol.2014 No.0

Investigation of ultra-lift Luo-converter with peak, average and hysteresis current-mode control

Raji, J.,Kamaraj, V. The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.6

The Renewable energy system, electric vehicle, and telecommunication applications require relatively stable power converters with a high gain and enhanced noise immunity. A study of three different types of current-mode controllers for high-gain ultra-lift Luo-converter (ULC) is discussed in this paper. The stability of a constant frequency peak current-mode controller (PCM), an average current-mode controller (ACM) and a variable frequency hysteresis current-mode controller (HCM) are analyzed based on small-signal characteristics. Using mathematical modeling of the controllers, the closed-loop transfer functions such as control voltage to output voltage, current loop gain, inductor current to control voltage, and audio susceptibility are obtained. These transfer functions along with MATLAB simulation results for PCM, ACM and HCM controllers are compared. Then, the component losses of the ULC converter using PCM, ACM and HCM controllers are calculated and an efficiency comparison of different control techniques is done. Investigations of the voltage and current stresses of the switch and diodes are also carried out. Finally, a prototype is fabricated to validate the performance of the converter.

Semiconductor coupled solar photo-Fenton's treatment of dyes and textile effluent

Raji, Jeevitha R.,Palanivelu, Kandasamy Techno-Press 2016 Advances in environmental research Vol.5 No.1

$NanoTiO_2$ was synthesized by ultrasonication assisted sol-gel process and subjected to iron doping and carbon-iron codoping. The synthesized catalysts were characterized by XRD, HR-SEM, EDX, UV-Vis absorption spectroscopy and BET specific surface area analysis. The average crystallite size of pure $TiO_2$ was in the range of 30 - 33 nm, and that of Fe-$TiO_2$ and C-Fe $TiO_2$ was in the range of 7 - 13 nm respectively. The specific surface area of the iron doped and carbon-iron codoped nanoparticles was around $105m^2/g$ and $91m^2/g$ respectively. The coupled semiconductor photo-Fenton's activity of the synthesized catalysts was evaluated by the degradation of a cationic dye (C.I. Basic blue 9) and an anionic dye (C.I. Acid orange 52) with concurrent investigation on the operating variables such as pH, catalyst dosage, oxidant concentration and initial pollutant concentration. The most efficient C-Fe codoped catalyst was found to effectively destruct synthetic dyes and potentially treat real textile effluent achieving 93.4% of COD removal under minimal solar intensity (35-40 kiloLUX). This reveals the practical applicability of the process for the treatment of real wastewater in both high and low insolation regimes.

Robust decentralized control of structures using the LMI H_∞controller with uncertainties

Raji, Roya,Hadidi, Ali,Ghaffarzadeh, Hosein,Safari, Amin Techno-Press 2018 Smart Structures and Systems, An International Jou Vol.22 No.5

This paper investigates the operation of the $H_{\infty}$ static output-feedback controller to reduce dynamic responses under seismic excitation on the five-story and benchmark 20 story building with parametric uncertainties. Linear matrix inequality (LMI) control theory is applied in this system and then to achieve the desired LMI formulations, some transformations of the LMI variables is used. Conversely uncertainties due to material properties, environmental loads such as earthquake and wind hazards make the uncertain system. This problem and its effects are studied in this research. Also to decrease the transition of large amount of data between sensors and controller, avoiding the disruption of whole control system and economy problems, the operation of the decentralized controllers is investigated in this paper. For this purpose the comparison between the performance of the centralized, fully decentralized and partial decentralized controllers in uncoupled and coupled cases is performed. Also, the effect of the changing the number of stories in substructures is considered. Based on the numerical results, the used control algorithm is very robust against the parametric uncertainties and structural responses are decreased considerably in all the control cases but partial decentralized controller in coupled form gets the closest results to the centralized case. The results indicate the high applicability of the used control algorithm in the tall shear buildings to reduce the structural responses and its robustness against the uncertainties.

Electrocatalytic and energy storage performance of bio-derived sulphur-nitrogen-doped carbon

Atchudan, Raji,Edison, Thomas Nesakumar Jebakumar Immanuel,Perumal, Suguna,Parveen, Asrafali Shakila,Lee, Yong Rok Elsevier 2019 Journal of Electroanalytical Chemistry Vol.833 No.-

<P><B>Abstract</B></P> <P>Sulphur and nitrogen-rich carbon layers (S/N-CLs) have been derived successfully <I>via</I> a simple calcination for high energy applications including supercapacitor and electrocatalytic hydrogen evolution reaction (HER). The flexible working electrode was fabricated using thoroughly analyzed S/N-CLs composite as an active electrode energy material for supercapacitor and HER. The S/N-CLs composite shows a higher specific capacitance of 266Fg<SUP>−1</SUP> at a current density of 0.5Ag<SUP>−1</SUP> and a satisfied cycling stability with 84% capacitance retention even after 5000cycles of galvanostatic charge-discharge. On the other hand, the synthesized S/N-CLs composite was used as an electrocatalyst for HER and it exhibits an excellent HER performance with an onset overpotential of −75mV, and a Tafel slope of 73mVdec<SUP>−1</SUP> in 0.5M H<SUB>2</SUB>SO<SUB>4</SUB> aqueous electrolyte. Also, the S/N-CLs composite displayed good stability and strong durability. The high electrocatalytic activity and stability of S/N-CLs composite toward HER due to the active site of a compound which may originate from the heteroatom-functional groups including N and S in the carbon structure. Overall, the high-performance supercapacitors and enhancing HER based on heteroatom-doped carbon structures could be promising in replacing traditional supercapacitors for many electronic devices and electrocatalyst for HER.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Conversion of <I>Magnolia liliiflora</I> into S/N-CLs composite by a simple carbonization </LI> <LI> S/N-CLs delivered a higher C<SUB>s</SUB> of 266Fg<SUP>−1</SUP> at 0.5Ag<SUP>−1</SUP> with a satisfied stability. </LI> <LI> S/N-CLs exhibits an excellent HER performance with a Tafel slope of 73mVdec<SUP>−1</SUP>. </LI> <LI> This is the first attempt in synthesis of S/N-CLs using <I>Magnolia liliiflora</I> flower. </LI> <LI> S/N-CLs will be an alternative for traditional energy storage material and electrocatalyst. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Facile green synthesis of nitrogen-doped carbon dots using <i>Chionanthus retusus</i> fruit extract and investigation of their suitability for metal ion sensing and biological applications

Atchudan, Raji,Edison, Thomas Nesakumar Jebakumar Immanuel,Chakradhar, Dasagrandhi,Perumal, Suguna,Shim, Jae-Jin,Lee, Yong Rok Elsevier 2017 Sensors and actuators. B, Chemical Vol.246 No.-

<P><B>Abstract</B></P> <P>Nitrogen-doped carbon dots (N-CDs) were synthesized from <I>Chionanthus retusus (C. retusus)</I> fruit extract using a simple hydrothermal-carbonization method. Their ability to sense metal ions, and their biological activity in terms of cell viability and bioimaging applications were evaluated. The resulting N-CDs were characterized by various physicochemical techniques such as high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy. The optical properties were characterized by ultraviolet visible (UV-vis) fluorescence spectroscopy techniques. The average size of the N-CDs was approximately 5±2nm with an interlayer distance of 0.21nm, as calculated from the HRTEM images. The presence of phytoconstituent functionalities and the percentages of components in the N–CDs were confirmed by XPS studies, and a nitrogen content of 5.3% was detected. The N–CDs demonstrated highly durable fluorescence properties and low cytotoxicity with a quantum yield of 9%. The synthesized N–CDs were then used as probes for the detection of metal ions. The N–CDs exhibited high sensitivity and selectivity towards Fe<SUP>3+</SUP>, with a linear relationship between 0 and 2μM and a detection limit of 70μM. The synthesized N–CDs are anticipated to have diverse biomedical applications, particularly for bioimaging, given their high fluorescence, excellent water solubility, good cell permeability, and negligible cytotoxicity. Finally, the potential of N–CDs as biological probes was investigated using fungal (<I>Candida albicans</I> and <I>Cryptococcus neoformans</I>) strains via fluorescent microscopy. We found that N–CDs were suitable candidates for differential staining applications in yeast cells with good cell permeability, localization with negligible cytotoxicity. Hence, N–CDs may find dual utility as probes for the detection of cellular pools of metal ions (Fe<SUP>3+</SUP>) and also for early detection of opportunistic yeast infections in biological samples.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Durable fluorescent N-CDs prepared using <I>C. Retusus</I> via hydrothermal-carbonization. </LI> <LI> This method of synthesis and N-CDs is an ideal for sensing of Fe<SUP>3+</SUP> and bio-imaging. </LI> <LI> N-CDs was used as a promising fluorescent probe for the direct detection of Fe<SUP>3+</SUP>. </LI> <LI> N-CDs were used as selective probes for yeast <I>C. albicans</I> and <I>C. neoformans</I>. </LI> <LI> N-CDs exhibits selective uptake, good biocompatibility and negligible cytotoxicity. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>