Synthesis, Characterization and Properties of Novel Blue Light Emitting Discrete π-Functional Polymer Consisting of Carbazole and Anthracene Units and Their Applications in Polymer Light Emitting Diodes

Ram Gopal,Yi-Chiang Huang,Hsu-Feng Lee,Ming-Sien Chang,Wen-Yao Huang 대한금속·재료학회 2017 ELECTRONIC MATERIALS LETTERS Vol.13 No.3

A new novel blue light emitting polymer containing carbazole andanthracene derivatives has been successfully synthesized via polycondensationchemical reaction of diol and difluoro monomers. An effort has been madeto raise the band gap of blue light emitter by lowering the conjugation extentin the backbone. The synthesized blue polymer exhibits decent solubility,good process ability, high thermal stability, high glass transition temperature(272 °C) and the decomposition temperature of 358 °C. The UV-visabsorption spectra and photoluminescence spectra depict that the lightemission lies in blue region. The solid state photoluminescence (PL) spectraof the polymer (λPL = 456 nm) shows red shift (Δλ = 37 nm) as comparedwith the corresponding solution PL spectra, presumably due to lowerintermolecular distance in solid state. The multi-layered polymer lightemitting diode was fabricated, using blue polymer with ITO/PEDOT: PSS/BP/LiF/Al architecture. The luminance-voltage (L-V) and current densityvoltage(J-V) curves show a maximum luminance of 7544 cd m−2, amaximum emission efficiency of 4.2 cd A−1, a maximum current density of453 mA cm−2 at a turn-on voltage of 4.5 V. Moreover, the PLED instigatepure blue EL emission, stable at 436 nm with outstanding CIE coordinates of(x = 0.15, y = 0.08), which is close to the pure NTSC blue coordinates of(0.14, 0.08).

Single ZnO nanocactus gas sensor formed by etching of ZnO nanorod

Ryong Ryu, Sung,Ram, S. D. Gopal,Cho, Hak-dong,Lee, Dong Jin,Won Kang, Tae,Woo, Yongdeuk The Royal Society of Chemistry 2015 Nanoscale Vol.7 No.25

<P>Etching of materials on the nanoscale is a challenging but necessary process in nanomaterials science. Gas sensing using a single ZnO nanocactus (NC), which was prepared by facile isotropic nanoetching of zinc oxide nanorods (NR) grown by chemical vapor deposition (CVD) using an organic photoresist (PR) by a thermochemical reaction, is reported in this work. PR consists of carboxylic acid groups (COOH) and cyclopentanone (C5H8O), which can react with zinc and oxygen atoms, respectively, on the surface of a ZnO NR. The thermochemical reaction is controllable by varying the concentration of PR and reaction time. A gas sensor was fabricated using a single NC. Gas sensing was tested using different gases such as CH4, NH3 and carbon monoxide (CO). It was estimated that the surface area of a ZnO NC in the case of 50% PR was found to increase four-fold. When compared with a single ZnO NR gas sensor, the sensitivity of a ZnO NC was found to increase four-fold. This increase in sensitivity is attributed to the increase in surface area of the ZnO NC. The formed single ZnO NC gas sensor has good stability, response and recovery time.</P>

Soil Resource Potential of Buraka Micro-Watershed in Mewat District of Haryana, India for Integrated Development

Sk Mahapatra,Cs Walia,Tarsem Lal,Ram Gopal,Gs Sidhu,Jayan Surya 한국토양비료학회 2014 한국토양비료학회 학술발표회 초록집 Vol.2014 No.6

Tumor-like Presentation of Tubercular Brain Abscess: Case Report

Dan B. Karki,Ghanashyam Gurung,Mohan R. Sharma,Ram K. Shrestha,Gita Sayami,Gopal Sedain,Amina Shrestha,Ram K. Ghimire 대한자기공명의과학회 2015 Investigative Magnetic Resonance Imaging Vol.19 No.4

A 17-year-old girl presented with complaints of headache and decreasing vision ofone month’s duration, without any history of fever, weight loss, or any evidence ofan immuno-compromised state. Her neurological examination was normal, exceptfor papilledema. Laboratory investigations were within normal limits, except for aslightly increased Erythrocyte Sedimentation Rate (ESR). Non-contrast computerizedtomography of her head revealed complex mass in left frontal lobe with a concentric,slightly hyperdense, thickened wall, and moderate perilesional edema with masseffect. Differential diagnoses considered in this case were pilocytic astrocytoma,metastasis and abscess. Magnetic resonance imaging (MRI) obtained in 3.0 Tesla(3.0T) scanner revealed a lobulated outline cystic mass in the left frontal lobe withtwo concentric layers of T2 hypointense wall, with T2 hyperintensity between theconcentric ring. Moderate perilesional edema and mass effect were seen. Postgadolinium study showed a markedly enhancing irregular wall with some enhancingnodular solid component. No restricted diffusion was seen in this mass in diffusionweighted imaging (DWI). Magnetic resonance spectroscopy (MRS) showed increasedlactate and lipid peaks in the central part of this mass, although some areas at thewall and perilesional T2 hyperintensity showed an increased choline peak withoutsignificant decrease in N-acetylaspartate (NAA) level. Arterial spin labelling (ASL) anddynamic susceptibility contrast (DSC) enhanced perfusion study showed decrease inrelative cerebral blood volume at this region. These features in MRI were suggestiveof brain abscess. The patient underwent craniotomy with excision of a grayishnodular lesion. Abundant acid fast bacilli (AFB) in acid fast staining, and epithelioidcell granulomas, caseation necrosis and Langhans giant cells in histopathology, wereconclusive of tubercular abscess. Tubercular brain abscess is a rare manifestationthat simulates malignancy and cause diagnostic dilemma. MRI along with MRS andmagnetic resonance perfusion studies, are powerful tools to differentiate lesions insuch equivocal cases.

Tumor-like Presentation of Tubercular Brain Abscess: Case Report

Karki, Dan B.,Gurung, Ghanashyam,Sharma, Mohan R.,Shrestha, Ram K.,Sayami, Gita,Sedain, Gopal,Shrestha, Amina,Ghimire, Ram K. Korean Society of Magnetic Resonance in Medicine 2015 Investigative Magnetic Resonance Imaging Vol.19 No.4

A 17-year-old girl presented with complaints of headache and decreasing vision of one month's duration, without any history of fever, weight loss, or any evidence of an immuno-compromised state. Her neurological examination was normal, except for papilledema. Laboratory investigations were within normal limits, except for a slightly increased Erythrocyte Sedimentation Rate (ESR). Non-contrast computerized tomography of her head revealed complex mass in left frontal lobe with a concentric, slightly hyperdense, thickened wall, and moderate perilesional edema with mass effect. Differential diagnoses considered in this case were pilocytic astrocytoma, metastasis and abscess. Magnetic resonance imaging (MRI) obtained in 3.0 Tesla (3.0T) scanner revealed a lobulated outline cystic mass in the left frontal lobe with two concentric layers of T2 hypointense wall, with T2 hyperintensity between the concentric ring. Moderate perilesional edema and mass effect were seen. Post gadolinium study showed a markedly enhancing irregular wall with some enhancing nodular solid component. No restricted diffusion was seen in this mass in diffusion weighted imaging (DWI). Magnetic resonance spectroscopy (MRS) showed increased lactate and lipid peaks in the central part of this mass, although some areas at the wall and perilesional T2 hyperintensity showed an increased choline peak without significant decrease in N-acetylaspartate (NAA) level. Arterial spin labelling (ASL) and dynamic susceptibility contrast (DSC) enhanced perfusion study showed decrease in relative cerebral blood volume at this region. These features in MRI were suggestive of brain abscess. The patient underwent craniotomy with excision of a grayish nodular lesion. Abundant acid fast bacilli (AFB) in acid fast staining, and epithelioid cell granulomas, caseation necrosis and Langhans giant cells in histopathology, were conclusive of tubercular abscess. Tubercular brain abscess is a rare manifestation that simulates malignancy and cause diagnostic dilemma. MRI along with MRS and magnetic resonance perfusion studies, are powerful tools to differentiate lesions in such equivocal cases.

Photo Physical Studies of PVP Arrested ZnS Quantum Dots

Ashutosh Kumar Shahi,Bishnu Kumar Pandey,Bheeshma Pratap Singh,Bipin Kumar Gupta,Sukhvir Singh,Ram Gopal 대한금속·재료학회 2017 ELECTRONIC MATERIALS LETTERS Vol.13 No.2

Monodispersed polyvinylpyrrolidone (PVP) arrested ZnS quantumdots (QDs) having diameter in range ~2-5 nm are synthesized by acolloidal precipitation method using PVP as the stabilizing agent. X-ray diffraction (XRD), transmission electron microscopy (TEM),high resolution transmission electron microscopy (HRTEM),selective area electron diffraction (SAED) and Fourier transforminfrared (FT-IR) spectroscopy are probed to investigate thestructural information. The optical properties are studied usingdiffuse UV-visible reflectance and photoluminescence (PL)spectroscopy techniques. TEM images as well as XRD reflectionpeak broadening indicate the nanometer size particles formationwith cubic (sphalerite) phase within the polymer matrix. Opticalabsorbance studies reveal an excitonic peak at around ~310 nmdictates the effect of quantum confinement effect in the ZnS QDs. PL emission spectra for ZnS QDs in PVP exhibit four emissionpeaks at ~382 nm, ~414 nm, ~480 nm and ~527 nm are observed. These excitonic emissions from ZnS QDs are caused by theinterstitial sulfur/Zn vacancies and surface states.