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- 저자 : Bipin Kumar Gupta (검색결과 2 건)
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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.
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Kumar, K. Naveen,Kim, Jong Su,Cho, Migyung,Shim, Jaesool,Gupta, Bipin Kumar,Kang, Misook ELSEVIER SCIENCE 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.721 No.-
<P><B>Abstract</B></P> <P>A bright novel red emission was obtained from Eu<SUP>3+</SUP>: CaLa<SUB>2</SUB>ZnO<SUB>5</SUB> (CLZO) Phosphors under visible excitation. We have successfully synthesized Eu<SUP>3+</SUP>: CLZO Phosphors by the solid state reaction method. The phase formation and surface morphological studies were analyzed by X-ray diffraction and Field emission scanning electron microscopy respectively. Thermal analysis was done by TG/DTA. Photoluminescence spectral profiles reveal that the strong red emission has been noticed at 626 nm (<SUP>5</SUP>D<SUB>0</SUB>→<SUP>7</SUP>F<SUB>2</SUB>) from the Eu<SUP>3+</SUP>: CLZO Phosphors under the excitation of 467 nm. The emission and excitation spectral profiles were systematically analyzed and their bands were assigned with corresponding electronic transitions. Upon increasing the Eu<SUP>3+</SUP> concentration, the photoluminescence performance has also been increased remarkably. The optimized concentration of the Eu<SUP>3+</SUP> was noticed at 14 mol%. Upon co-doping with Dy<SUP>3+</SUP> ions to Eu<SUP>3+</SUP>: CLZO Phosphors, the red emission pertaining to Eu<SUP>3+</SUP> was appreciably enhanced through energy transfer form Dy<SUP>3+</SUP> to Eu<SUP>3+</SUP> ions. The energy transfer mechanism was substantiated by several fluorescent methods. The prominent <I>red</I> emission of the Dy<SUP>3+</SUP>/Eu<SUP>3+</SUP>: CLZO Phosphors under blue excitation which suggests that these phosphor materials could be promising candidates for red luminescent optical devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Dazzling <I>red</I> emission is observed from Eu<SUP>3+</SUP>/Dy<SUP>3+</SUP>:CaLa<SUB>2</SUB>ZnO<SUB>5</SUB> Phosphors. </LI> <LI> Red emission of Eu<SUP>3+</SUP> was significantly enhanced by co-doping with Dy<SUP>3+</SUP>. </LI> <LI> Effective sensitization of Dy<SUP>3+</SUP> ions has been elucidated. </LI> <LI> The energy transfer path way was clearly demonstrated from Dy<SUP>3+</SUP> to Eu<SUP>3+</SUP>. </LI> <LI> CIE coordinates are very close to National Television Standard Committee (NTSC). </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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