Trap-state-assisted white light emission from a CdSe nanocrystal integrated hybrid light-emitting diode.

Chandramohan, S,Ryu, Beo Deul,Kim, Hyun Kyu,Hong, Chang-Hee,Suh, Eun-Kyung Optical Society of America 2011 Optics letters Vol.36 No.6

<P>This Letter reports on the fabrication of hybrid white-light-emitting diodes made of semiconductor nanocrystals (NCs) integrated on InGaN/GaN LEDs. Using core type and core/shell type CdSe NCs, the white light properties are systematically engineered for white light generation with high color rendering index (CRI). Unlike CdSe/ZnS core/shell NCs, which exhibited a unique narrowband edge emission, core type CdSe NCs offered extended broad emission toward orange/red wavelengths associated with deep trap states. Consequently, the light-emitting properties of the devices showed strong dependence on the type of NCs used, and devices with CdSe NCs offered admirable characteristics, such as Commission Internationale d'Eclairage coordinates of (0.356, 0.330) and a CRI as high as 87.4.</P>

Performance evaluation of GaN light-emitting diodes using transferred graphene as current spreading layer

Chandramohan, S.,Bok Ko, Kang,Han Yang, Jong,Deul Ryu, Beo,Katharria, Y. S.,Yong Kim, Taek,Jin Cho, Byung,Hong, Chang-Hee American Institute of Physics 2014 Journal of Applied Physics Vol.115 No.5

This study elucidates the correlation among conductivity of graphene and interface aspects in GaN light-emitting diodes (LEDs). Using a multilayer graphene of low sheet resistance, it is demonstrated that graphene alone can make ohmic contact with p-GaN without necessitating additional interlayer. Large-area blue LED with relatively low contact resistance in the order of 10(-2) ohm-cm(2) and improved forward voltage of 3.2 +/- 0.1 V was realized irrespective of the use of the interlayer. The results from parallel evaluation experiments performed by varying the layer numbers of graphene with ultrathin NiOx interlayer revealed that the poor lateral conductivity of monolayer or few layer graphene can be well compensated by the interlayer. A combination of three layer graphene and NiOx offered device with enhanced electro-optical performance. But the Schottky barrier associated with the inadequate adhesion of transferred graphene dominates all the benefits and becomes a major bottleneck preventing the formation of low resistance stable ohmic contact. (c) 2014 AIP Publishing LLC.

Impact of Interlayer Processing Conditions on the Performance of GaN Light-Emitting Diode with Specific NiO_<i>x</i>/Graphene Electrode

Chandramohan, S.,Kang, Ji Hye,Ryu, Beo Deul,Yang, Jong Han,Kim, Seongjun,Kim, Hynsoo,Park, Jong Bae,Kim, Taek Yong,Cho, Byung Jin,Suh, Eun-Kyung,Hong, Chang-Hee American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.3

<P>This paper reports on the evaluation of the impact of introducing interlayers and postmetallization annealing on the graphene/p-GaN ohmic contact formation and performance of associated devices. Current–voltage characteristics of the graphene/p-GaN contacts with ultrathin Au, Ni, and NiO<SUB><I>x</I></SUB> interlayers were studied using transmission line model with circular contact geometry. Direct graphene/p-GaN interface was identified to be highly rectifying and postmetallization annealing improved the contact characteristics as a result of improved adhesion between the graphene and the p-GaN. Ohmic contact formation was realized when interlayer is introduced between the graphene and p-GaN followed by postmetallization annealing. Temperature-dependent <I>I</I>–<I>V</I> measurements revealed that the current transport was modified from thermionic field emission for the direct graphene/p-GaN contact to tunneling for the graphene/metal/p-GaN contacts. The tunneling mechanism results from the interfacial reactions that occur between the metal and p-GaN during the postmetallization annealing. InGaN/GaN light-emitting diodes with NiO<SUB><I>x</I></SUB>/graphene current spreading electrode offered a forward voltage of 3.16 V comparable to that of its Ni/Au counterpart, but ended up with relatively low light output power. X-ray photoelectron spectroscopy provided evidence for the occurrence of phase transformation in the graphene-encased NiO<SUB><I>x</I></SUB> during the postmetallization annealing. The observed low light output is therefore correlated to the phase change induced transmittance loss in the NiO<SUB><I>x</I></SUB>/graphene electrode. These findings provide new insights into the behavior of different interlayers under processing conditions that will be useful for the future development of opto-electronic devices with graphene-based electrodes.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-3/am3026079/production/images/medium/am-2012-026079_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am3026079'>ACS Electronic Supporting Info</A></P>

Establishing postprandial bio-equivalency and IVIVC for generic metformin sustained release small sized tablets

Chandramohan Eaga,Shivakumar Mantri,Rajkumar Malayandi,Phani Krishna Kondamudi,Sumon Chakraborty,S. V. N. Raju,Deepika Aggarwal 한국약제학회 2014 Journal of Pharmaceutical Investigation Vol.44 No.3

The objective of current study was to developmetformin hydrochloride modified release small sizedtablets, and to evaluate its bioequivalence when comparedwith the reference product (Glucophage SR). The physicochemicalproperties of the formulated and referencetablets were determined and compared. The in vitro dissolutionprofiles of formulated tablets were obtained usingbio-relevant media and IVIVC was established. Bioequivalenceinvestigation was carried out in 32 healthy malevolunteers who received a single dose 1,000 mg of bothtest and reference products in a randomized two-waycrossover design in postprandial conditions. After dosing,serial blood samples were collected for a period of 48 h. Metformin concentration was assayed by using a validatedLC–MS/MS method. The log-transformed Cmax and AUCwere statistically compared by analysis of variance, and the 90 % confidence intervals (CI) of the ratio of the logtransformedCmax and AUC between the most promisingdeveloped formulation and the reference product weredetermined. It was deduced that the dissolution rate profileof the formulated modified release small sized tablets wassimilar to the reference product employed in the study. Their similarity and difference factors were found to bewell within the established limits. In the bioequivalencestudy, the difference in Cmax, AUClast and AUCinf betweenthe test and reference product was not statistically significant,with the 90 % CI of 100.73–116.20, 86.16–97.37 and87.12–96.99 %, respectively. The results suggested that themetformin small tablets formulated with reduced quantityof controlled release polymer were found to be bioequivalentin the postprandial state. For these small tablets,pH 5.5 acetate buffer as a bio-relevant dissolution mediafor the development of IVIVC.

Surface Plasmon Enhanced Photoluminescence of Rhodamine B Confined in SBA15

Dinakaran, K.,Chandramohan, A.,Venkatesan, M.R.,Devaraj, S.,Devi, V.,Alagar, M. Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.11

Rhodamine B dye (RB) has been introduced into the mesoporous silica (SBA15) and Ag anchored mesoporous silica by applying solution impregnation method. Surface treatment of SBA15 with 3-aminopropyltrimethoxysilane (APTMS) facilitates selective anchoring of the RB molecules on SBA15. The photoluminescence spectra of RB confined within SBA15 indicates higher emission intensity, than that of the RB solid, particularly in the presence of Ag nanoparticles. The significant enhancement in photoluminescence intensity is attributed to the local enhancement of the optical fields near the molecules by interactions with silver plasmons.

Fabrication and charge-transfer characteristics of CdS QDs sensitized vertically grown flower-like ZnO solar cells with CdSe cosensitizers

Sudhagar, P.,Chandramohan, S.,Kumar, R. Saravana,Sathyamoorthy, R.,Hong, Chang-Hee,Kang, Yong Soo Wiley Blackwell (John Wiley Sons) 2011 Physica status solidi. PSS. A, Applications and ma Vol.208 No.2

Electrospun and electropolymerized carbon nanofiber–polyaniline–Cu material as a hole transport material for organic solar cells

Esakkimuthu Shanmugasundaram,Chandramohan Govindasamy,Muhammad Ibrar Khan,Vigneshkumar Ganesan,Vimalasruthi Narayanan,Kannan Vellaisamy,Rajaram Rajamohan,Stalin Thambusamy 한국탄소학회 2023 Carbon Letters Vol.33 No.7

Carbon nanofibers (CNFs) are promising materials for the construction of energy devices, particularly organic solar cells. In the electrospinning process, polyacrylonitrile (PAN) has been utilized to generate nanofibers, which is the simplest and most popular method of creating carbon nanofibers (CNFs) followed by carbonization. The CNFs are coated on stainless steel (SS) plates and involve an electropolymerization process. The prepared Cu, CNF, CNF–Cu, PANI, PANI–Cu, CNF–PANI, and CNF–PANI–Cu electrode materials’ electrical conductivity was evaluated using cyclic voltammetry (CV) technique in 1 M H2SO4 electrolyte solution. Compared to others, the CNF–PANI–Cu electrode has higher conductivity that range is 3.0 mA. Moreover, the PANI, CNF–PANI, and CNF–PANI–Cu are coated on FTO plates and characterized for their optical properties (absorbance, transmittance, and emission) and electrical properties (CV and Impedance) for organic solar cell application. The functional groups, and morphology-average roughness of the electrode materials found by FT–IR, XRD, XPS, SEM, and TGA exhibit a strong correlation with each other. Finally, the electrode materials that have been characterized serve to support and act as the nature of the hole transport for organic solar cells.

Performance and emission characteristics of biodiesel-blend in diesel engine: A review

Yogesh PALANI,Chandramohan DEVARAJAN,Dhanashekar MANICKAM,Sathish THANIKODI 대한환경공학회 2022 Environmental Engineering Research Vol.27 No.1

Many researchers delve for an alternative fuel to overcome the fossil fuel crisis. Developed countries have embarked focus on renewable energy like wind energy, geothermal, biofuel, ocean energy and solar energy. Biodiesel is considered to be one of the most felicitous one kinds of renewable energy with similar properties of diesel fuel. Biodiesel is gaining prominence due to the global fossil fuel crisis and emission control challenges. Biodiesel blends are formulated in numerous proportion with diesel to run the diesel engine and it has significantly reduced the harmful pollutants from contaminating the environment. This review paper summarizes the outcome of biodiesel blends on properties, performance and emission-quality of a diesel engine under different operating conditions. Results from the literature provide a comparative data between conventional diesel and diesel-biodiesel blend which indicates that the diesel-biodiesel blend provides shorter ignition delay and lesser heat release rate as well as slightly higher efficiency. The emissions like CO, HC and particulate matter are reduced while choosing biodiesel blends. Biodiesel blend with additives such as alcohol can be the appropriate solution for the fuel crisis. Finally, the review concludes the advantages and future scope of biodiesel as a better competent for diesel fuel.

Characterization of Rajath Bhasma and Evaluation of Its Toxicity in Zebrafish Embryos and Its Antimicrobial Activity

Kalishwaralal Kalimuthu,김지민,Chandramohan Subburaman,권우영,황성연,정세한,조민근,김형주,박기수 한국미생물·생명공학회 2020 Journal of microbiology and biotechnology Vol.30 No.6

In India, nanotechnology has been used in therapeutic applications for several millennia. One example of a traditional nanomedicine is Rajath Bhasma (also called calcined silver ash), which is used as an antimicrobial and for the treatment of various ailments and conditions such as memory loss, eye diseases, and dehydration. In this study, we aimed to characterize the physical composition and morphology of Rajath Bhasma and its suitability for use as a non-toxic antimicrobial agent. First, Rajath Bhasma was physically characterized via i) Fourier-transform infrared spectroscopy to analyze the surface functional groups, ii) scanning electron microscopy coupled with energydispersive X-ray spectroscopy to observe the morphology and elemental composition, and iii) X-ray diffraction to determine the crystalline phases. Thereafter, functional characterization was performed through toxicity screening using zebrafish embryos and through antimicrobial activity assessment against gram-positive (Staphylococcus epidermidis) and gram-negative (Escherichia coli) bacteria. Rajath Bhasma was found to harbor alkene, hydroxyl, aldehyde, and amide functional groups originating from biological components on its surface. The main component of Rajath Bhasma is silver, with particle size of 170-210 nm, and existing in the form of spherical aggregates with pure crystalline silver structures. Furthermore, Rajath Bhasma did not exert toxic effects on zebrafish embryos at concentrations below 5 μg/ml and exhibited effective antimicrobial activity against both gram-positive and gram-negative bacteria. The present results indicate that Rajath Bhasma is a potentially effective antimicrobial agent without toxicity when used at concentrations below 5 μg/ml.

Production and characterization of mechanical and microstructural behaviour of friction stir welded Al6063 composites reinforced with Gr/B4C/SiC particles

Suresh Babu B,Chandramohan G,Boopathi C,Pridhar T,Srinivasan R 한양대학교 세라믹연구소 2018 Journal of Ceramic Processing Research Vol.19 No.1

The present study elucidates the influence of reinforcement particles in friction stir welded aluminium (Al 6063) matrixcomposites on mechanical properties of the metal matrix composition. Initially composites were successfully fabricated withdifferent weight percentage and combination of reinforcements (graphite (gr), B4C and SiC) through stir casting technique. All sets of composite specimen were welded through solid state joining process of friction stir welding technique, theparameters such as tool rotational speed (800, 1000 and 1200 rpm), welding speed (20 and 40 mm/min) and axial loading (10and 20 kN) are taken for characterization of fabricated composites. The effects of friction stir welding parameters wereexamined by mechanical and microstructural characterizations. The composites microstructure and dispersion of particlereinforcements were analysed through optical microscope and also the mechanical properties of yield strength, ultimatestrength and elongation were analysed using universal testing machine. The optimized friction stir weld parameters wereidentified for 20% weight fraction reinforced hybrid composites.