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Thermoelectric Properties of Hot-Pressed Bi-Doped n-Type Polycrystalline SnSe
Nguyen, Van Quang,Nguyen, Thi Huong,Duong, Van Thiet,Lee, Ji Eun,Park, Su-Dong,Song, Jae Yong,Park, Hyun-Min,Duong, Anh Tuan,Cho, Sunglae Springer US 2018 NANOSCALE RESEARCH LETTERS Vol.13 No.1
<P><B>ᅟ</B></P><P>We report on the successful preparation of Bi-doped n-type polycrystalline SnSe by hot-press method. We observed anisotropic transport properties due to the (h00) preferred orientation of grains along the pressing direction. The electrical conductivity perpendicular to the pressing direction is higher than that parallel to the pressing direction, 12.85 and 6.46 S cm<SUP>−1</SUP> at 773 K for SnSe:Bi 8% sample, respectively, while thermal conductivity perpendicular to the pressing direction is higher than that parallel to the pressing direction, 0.81 and 0.60 W m<SUP>−1</SUP> K<SUP>−1</SUP> at 773 K for SnSe:Bi 8% sample, respectively. We observed a bipolar conducting mechanism in our samples leading to n- to p-type transition, whose transition temperature increases with Bi concentration. Our work addressed a possibility to dope polycrystalline SnSe by a hot-pressing process, which may be applied to module applications.</P><P><B>Highlights</B></P><P><P>We have successfully achieved Bi-doped n-type polycrystalline SnSe by the hot-press method.</P><P>We observed anisotropic transport properties due to the [h00] preferred orientation of grains along pressing direction.</P><P>We observed a bipolar conducting mechanism in our samples leading to n- to p-type transition.</P></P><P><B>Electronic supplementary material</B></P><P>The online version of this article (10.1186/s11671-018-2500-y) contains supplementary material, which is available to authorized users.</P>
Nguyen, Huu Tuan,Ryu, Shin Young,Duong, Anh Tuan,Lee, Soonil IOP 2019 Nanotechnology Vol.30 No.50
<P>We report on a substantial increase in luminance and luminous efficiency of green-light emitting devices (LEDs) that use colloidal CdSe@ZnS quantum dots (QDs) as a light-emitting material in response to treatment with 1,2-ethanedithiol (EDT). The maximum luminance increased from 1146 to 8075 cd m<SUP>−2</SUP>, and luminous yield from 0.15 to 1.41 cd A<SUP>−1</SUP> as a result of treating an incomplete device with drops of EDT right after spin-coating QDs onto a ZnO-nanoparticle layer. Based on systematic studies on substrate-dependent change in photoluminescence, and current-voltage and luminance–voltage characteristics, we propose that passivation of intra-gap defect states and relative shifts of energy levels relevant to the operation of QD LEDs are two main results of EDT treatment. In particular, we argue that energy-level shift without emission-color change can be attributed to surface-dipole effects.</P>
Nguyen, Tuan Lam,Pham, Thi Quynh Nga,Hoang, Van Minh,Kim, Bao Giang,Phan, Thi Hai,Doan, Thu Huyen,Nguyen, Thuy Linh,Duong, Khanh Van,Luong, Ngoc Khue Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.no.sup1
Second-hand tobacco smoke (SHS) exposure at home, especially among children, is a serious issue in Viet Nam. During the past decade, much effort has been taken for tobacco control in the country, including various prgorammes aiming to reduce SHS exposure among adults and children. This article analysed trends and factors associated with SHS exposure at home among school children aged 13-15 in Viet Nam, using the Global Youth Tobacco Surveys conducted in 2007 and 2014. Descriptive and inferential statistical methods with logistic regression were applied. Overall, there was a significant reduction in the level of exposure, from 58.5% (95%CI: 57.6-59.3) in 2007 to 47.1% (95%CI: 45.4-48.8) in 2014. Of the associated factors, having one or both parents smoking was significantly associated with the highest odds of SHS exposure at home (OR=5.0; 95%CI: 4.2-6.1). Conversely, having a mother with a college or higher education level was found to be a protective factor (OR=0.5; 95%CI: 0.3-0.8).
Duong Van Thiet,NGUYENVAN QUANG,Nguyen Thi Minh Hai,Nguyen Thi Huong,조성래,Duong Anh Tuan,Dang Duc Dung,트란반탐 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.8
In this work, we report on the structural and thermoelectric properties of Sb2Te3 films deposited on GaSb(111) substrates by using molecular beam epitaxy. The effects of the growth temperature on the microstructure and thermoelectric properties of the films were investigated. The results show that Sb2Te3 films grow on GaSb(111) along (00l) axis normal to the substrate and have a hexagonal structure with a layer-by-layer growth mode in growth temperature range from 200 to 250 °C while at 175 and 300 °C, the films show an island growth mode. Te and Sb2Te3 phases coexist at a growth temperature of 175 °C. The films exhibit a metallic behavior for growth temperatures below 250 °C and a semiconductor behavior at 300 °C. By changing growth temperature, we were able to vary the carrier density from 9.96×1018 to 4.55×1019 cm −3. At room temperature, the Seebeck coefficients are 110, 146, and 138 μV/K for growth temperatures of 175, 200 and 250 °C, respectively, and a large value of the power factor 61.67 μW/cm-K2 is achieved for the film grown at 250 °C.
Hien, Nguyen Khoa,Bao, Nguyen Chi,Ai Nhung, Nguyen Thi,Trung, Nguyen Tien,Nam, Pham Cam,Duong, Tran,Kim, Jong Seung,Quang, Duong Tuan Elsevier 2015 Dyes and pigments Vol.116 No.-
<P><B>Abstract</B></P> <P>A fluorescent chemosensor based on dimethylaminocinnamaldehyde-aminothiourea (DA) has been designed, synthesized, and applied with a combined theoretical and experimental study. The synthetic path, optimized molecular structure and characteristics of DA were carried out using the calculations at the B3LYP/LanL2DZ level of theory. The experimental investigations have a good agreement with the theoretical results. DA can be used as a chemosensor for simultaneous quantification of silver, copper, and mercury ions in aqueous solution at the ppb level. The stable geometric structures of the complexes between DA and Ag<SUP>+</SUP>, Hg<SUP>2+</SUP>, Cu<SUP>2+</SUP> with stoichiometry of 1:1, 2:1, and 2:1, have been found and investigated for electronic properties and fluorescence quenching phenomena by using Atoms in Molecules (AIM) and Natural Bond Orbitals (NBO) analyses.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A chemosensor has been studied with a combined theoretical and experimental study. </LI> <LI> Suitable for detecting trace amounts of Ag(I), Hg(II), Cu(II) ions at the ppb concentration level. </LI> <LI> High water solubility, simplicity, rapid analysis time, wide range of pH. </LI> <LI> The stable geometric structures of the complexes have been found and investigated. </LI> <LI> The fluorescence quenching of complexes is studied by using AIM and NBO analyses. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Hang Nguyen Thai Phung,Van Nguyen Khanh Tran,Phuong Ai Duong,Hung Vu Tuan Le,Nguyen Duc Truong 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.70 No.11
Mono, co- and tri-doped TiO2 thin films with the transition metals (vanadium and/or chrominium) and a nonmetal (nitrogen) have been fabricated by sol-gel method. X-ray diffraction results clearly reveal anatase crystal structure for all obtained samples and doping with any dopants doesn’t change the anatase phase of TiO2. Compared to TiO2, three types of doped TiO2 thin films exhibit a red-shift in the absorption edge and have much better photocatalytic properties for methylene blue degradation in visible light region. The maximum visible-photocatalytic performance was achieved for tri-doped TiO2 sample. The mechanism for enhancing visible-photocatalytic activity of co-doped and tri-doped TiO2 thin films was also examined.