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Photo-Bleaching Eect in Divalent Samarium-Doped Alkaline-Earth Fluorohalides
Weiping Qin,Kiwan Jang,Changdae Kim,Hynngab Cho,Seongtae Park,Yonghwa Chung,Yong-ill Lee 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.2
When a CW laser was focused on a sample of divalent samarium-doped alkaline-earth uorohalides (Mg0:5Sr0:5FCl0:5Br0:5 : Sm2+ or BaFCl0:5Br0:5 : Sm2+), the uorescence intensity of Sm2+ ions decreased rapidly. Under irradiation from a 488-nm laser with a power density of 10 W/cm2, the intensity of the 5D0 ! 7F0 (Sm2+) emission decreased as much as 96 % of its initial intensity in 30 minutes (for an X-ray-reduced sample). The so-called photo-bleaching eect can be in uenced by the processes used for sample synthesis, such as the reduction method, the grinding process or X-ray irradiation. The decreasing curves obtained in the photo-bleaching experiments were tted, a biexponential decreasing mode was found, which included a fast decrease (time constant tens of seconds) and a slow decrease (time constant hundreds of seconds). There was no evidence to support the divalent samarium ions being photo-ionized into trivalent samarium ions in the photobleaching process. The most probable mechanism for the photo-bleaching eect involves structural defects and color centers in the samples.
Zhang, Weiping,Li, Guiying,Wang, Wanjun,Qin, Yaxin,An, Taicheng,Xiao, Xinyan,Choi, Wonyong Elsevier 2018 Applied Catalysis B Vol.232 No.-
<P><B>Abstract</B></P> <P>A chemically modified Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>(M = Mo, W)/rGO composite was firstly synthesized via a liquid-exfoliation solvothermal method. The structure, morphology, optical properties and composition were characterized by X-ray diffraction, FT-IR spectroscopy, scanning electron microscopy, UV–vis diffuse reflectance spectra and X-ray photoelectron spectroscopy, respectively. The characterization results indicated that compact structure could be obtained by using this typical method due to in-situ chemical modification, which could also control the sizes of Ag<SUB>3</SUB>PO<SUB>4</SUB> nano-sheets by adding MS<SUB>2</SUB>/rGO hybrids. More importantly, the resultant Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO composite exhibited higher photocatalytic activity and stability toward the degradation of 4-nitrophenol than pure Ag<SUB>3</SUB>PO<SUB>4</SUB> under sunlight irradiation. The stable structure of Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO was closely related with Z-scheme electronic structure and electrical conductivity of MS<SUB>2</SUB>/rGO hybrids, leading to a higher consumption and transfer of photogenerated electrons. However, by controlling the amounts of MS<SUB>2</SUB>/rGO hybrids, more stable but lower photocatalytic activity composites could be obtained. Further analysis found that the holes and O<SUB>2</SUB> <SUP>−</SUP> were the main reactive species involved in the photocatalytic degradation of 4-nitrophenol. In addition, possible photocatalytic degradation pathways of 4-nitrophenol were also proposed based on the identified intermediates. The findings of this work may provide a new method to design efficient composites for photocatalytic degradation of organic pollutants.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO catalyst was fabricated via a liquid-exfoliation solvothermal method. </LI> <LI> Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO has high photocatalytic activity and stability under sunlight. </LI> <LI> The stability of Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO was due to its rapid transfer of photogenerated e<SUP>−</SUP>. </LI> <LI> h<SUP>+</SUP> and O<SUB>2</SUB> <SUP>−</SUP> were the main RSs in photocatalytic degradation of 4-nitrophenol. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Synthesis of well dispersed uniform sub-4 nm Y2O3:Eu3+ colloidal nanocrystals.
Zhao, Dan,Seo, Seokjun,Zhang, Haibo,Bae, Byeong-Soo,Qin, Weiping American Scientific Publishers 2010 Journal of nanoscience and nanotechnology Vol.10 No.3
<P>Well dispersed uniform sub-4 nm Y2O3:Eu colloidal nanocrystals have been synthesized through the non-hydrolytic high-temperature thermal decomposition technique. The as-synthesized nanocrystals can be stably dispersed in nonpolar solvents due to the capping organic ligands on their surface. Compared with bulk materials, the nanocrystals exhibited different luminescence features, including the intensity enhancement of the 5D0 --> 7F4 transition observed in the emission spectrum.</P>
Fabrications and photoluminescence of Sm2+ -doped aluminosilicate thin films
Yonghwa Chung,Kiwan Jang,Eunjin Cho,HyoJin Seo,Ilgon Kim,Sangsu Kim,Seongtae Park,Weiping Qin,Yong-Ill Lee 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.43 No.I
Sm2+-doped 10Al2O390SiO2 thin lms were prepared by coating on Al-deposited Si(100) wafers with a sol solution and heating in air, as well as in a H2 atmosphere. The prepared thin films were examined with a scanning electron microscope for observing their morphologies, and the photoluminescence spectra of Sm2+ ions were measured. The morphologies of the thin lms were found to be highly dependent upon the samarium precursors and the emission peaks due to the 5D0 ! 7F0 transitions of Sm2+ ions were highly dependent on the reduction processes of the Sm3+ ions and the samarium precursors.