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Characterization of surface chemistry of PtFe bimetallic nanoparticles
Omelianovych, Oleksii,Larina, Liudmila L.,Dao, Van-Duong,Choi, Ho-Suk Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.457 No.-
<P><B>Abstract</B></P> <P>The aim of this study is to find optimal Ar plasma etching conditions without significantly altering the surface of PtFe bimetallic nanoparticles (BNPs). Various treatment parameters such as acceleration voltage, ion beam current, and etching time are considered in this study. Studies have shown that severe alteration of surface chemical composition is closely related to the energy of Ar ions. High energy (3 keV) Ar cleaning, leads to partial reduction of alloy particles along with decontamination. However, the use of ion energies of 1 keV or lower leads to preferential cleaning with minor alteration of surface chemistry and subsequently allows us to acquire reliable XPS data of PtFe BNPs. Profiling of the NPs revealed that both metal oxides and elemental metals are simultaneously synthesized during dry plasma reduction. PtO is formed at the level of 30 atomic percent in the synthesis procedure, which is due to the influence of oxygen radicals in atmospheric plasma.</P> <P><B>Highlights</B></P> <P> <UL> <LI> High energy (3 keV) Ar<SUP>+</SUP> cleaning leads to serious alteration of surface chemistry of PtFe nanoparticles. </LI> <LI> For PtFe NPs Ar<SUP>+</SUP> cleaning should be conducted using ion energies of 1 keV or less. </LI> <LI> Reasonable amount of metal nanoparticles can be oxidized due to synthesis operation conditions. </LI> <LI> Significant amount of metallic iron is present in a bulk of PtFe nanoparticles synthesized via dry plasma reduction. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Omelianovych, O.,Dao, V.D.,Larina, L.L.,Choi, H.S. Pergamon Press 2016 Electrochimica Acta Vol. No.
This research develops an efficient catalyst material for counter electrodes (CEs) in dye-sensitized solar cells (DSCs) using an inexpensive and ecologically sustainable manufacturing method. In order to achieve this, bimetallic PtFe nanoparticles are synthesized on an FTO substrate using dry plasma reduction (DPR) under atmospheric pressure. The chemical composition of the Pt<SUB>x</SUB>Fe<SUB>1-x</SUB> (0@?x@?1) alloy was optimized in order to achieve high catalytic activity and excellent electrical properties in the developed material. It is found that the Pt<SUB>0.75</SUB>Fe<SUB>0.25</SUB> alloy exhibits the largest value of |I<SUB>red</SUB>|=1.440mA and the lowest value of R<SUB>ct</SUB>=0.88Ω. As a result, an efficiency of 8.94% with J<SUB>sc</SUB>=15.03mAcm<SUP>-2</SUP>,V<SUB>oc</SUB>=805mV, and FF=74.32% is achieved. The obtained efficiency is higher than that of 8.24% for a device using a Pt<SUB>1</SUB>Fe<SUB>0</SUB> CE. The obtained results indicate that the PtFe alloy fabricated using DPR is an alternative CE material for highly efficient DSCs.
Andrii Omelianovych,김지혜,Larina Liudmila,안병태 한국물리학회 2015 Current Applied Physics Vol.15 No.12
In2S3 as an alternative Cd-free buffer in Cu(In,Ga)Se2 (CIGS) solar cells was deposited on CIGS substrate by a chemical bath deposition and characterized after post annealing to optimize film properties for CIGS solar cells. A uniform and pinhole-free In2S3 film was deposited on a CIGS substrate by H2O2 treatment prior to chemical bath deposition. The In2S3 layer was an amorphous state due to the co-existence of In eS, IneO, and IneOH bonds. Annealing at 200 ℃ induced copper diffusion from CIGS into In2S3 layer and lowered the band gap from 3.3 to 1.9 eV, leading to phase change from amorphous state to crystalline state. The conduction band alignment at the In2S3/CIGS interface can be controlled by the post annealing. The shunt current through In2S3 film was prevented down to the thickness of 30 nm and a 1.15 eV shallow defect was eliminated by the annealing. The results indicated that post annealing in air is a critical to fabricate CIGS solar cells with a sub-30 nm CBD-In2S3 buffer layer.
Oh, Hyo-Jun,Umapathi, Reddicherla,Omelianovych, Oleksii,Dao, Van-Duong,Jeong, Jun-Kyo,Lee, Ga-Won,Choi, Ho-Suk Elsevier S.A. 2019 Thin Solid Films Vol.676 No.-
<P><B>Abstract</B></P> <P>Dry plasma reduction under atmospheric pressure is a unique approach for stably, continuously, easily, and uniformly fabricating Ag layer on the metal seeds-polyethylene terephthalate (PET) substrate. In this study, effects of particle size, surface uniformity, surface coverage, and film thickness of metal seeds such as Ag, Cu, Fe and Ni on the formation of uniform Ag layer were studied on the basis of their surface free energies and critical radius, which further leads to variations in the sheet resistance levels of the silver layers. The root mean square roughness and sheet resistance of the Ag layer PET substrate were decreased with the deposition of metal seeds. Among the added seed metals, Ni seed has shown best uniformity. Furthermore, the fabricated films were applied for electromagnetic interference (EMI) shielding. Among the added seed metals, Ni has shown the highest electromagnetic interference shielding effectiveness. The present study will be useful for the development of various low-cost metal films in the field of EMI shielding.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Uniform silver layer successfully fabricated with the aid of dry plasma reduction. </LI> <LI> Fabricated films were applied as electromagnetic interference shielding materials. </LI> <LI> Surface of silver layer formed more smoothly and uniformly by applying metal seeds. </LI> <LI> The findings may be useful for the development of various low-cost metal films. </LI> </UL> </P>