ZnO-TiO₂ core-shell nanowires decorated with Au nanoparticles for plasmon-enhanced photoelectrochemical water splitting

Park, Jinse,Deshmukh, P.R.,Sohn, Youngku,Shin, Weon Gyu Elsevier 2019 JOURNAL OF ALLOYS AND COMPOUNDS Vol.787 No.-

<P><B>Abstract</B></P> <P>The present work reports the development of Au-nanoparticle decorated ZnO-TiO<SUB>2</SUB> core-shell nanowires on the Si-wafer. The developed Au-nanoparticle decorated ZnO-TiO<SUB>2</SUB> core-shell nanowires exhibit a unique structure with uniform sensitization of Au-nanoparticles with the diameter in the range of 5–9 nm on the ZnO-TiO<SUB>2</SUB> core-shell heterostructure. This unique structure of Au-nanoparticle decorated ZnO-TiO<SUB>2</SUB> core-shell nanowires demonstrates an enhanced photocurrent density of 1.63 mAcm<SUP>−2</SUP> upon illumination by visible light unveiling high photoelectrochemical water splitting activity. This photocurrent density is higher than the pristine ZnO nanowires (0.51 mAcm<SUP>−2</SUP>) and ZnO-TiO<SUB>2</SUB> core-shell nanowires (1.23 mAcm<SUP>−2</SUP>). Furthermore, photoelectrochemical water splitting efficiency of Au-nanoparticle decorated ZnO-TiO<SUB>2</SUB> core-shell nanowires was found to be 0.70%, which is higher than the ZnO nanowires (0.22%) and ZnO-TiO<SUB>2</SUB> core-shell nanowires (0.53%) at the same applied potential of +0.8 V<SUB>RHE</SUB>. The improved photocurrent density and efficiency is due to the enhanced absorbance in the visible region owing to the surface plasmon resonance effect of Au-nanoparticle, effective withdrawal of hot electron from the Au-nanoparticle at the interface of metal/semiconductor due to Schottky barrier as well as excellent charge-separation and transportation originating from the core-shell nanowires.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Development of Au decorated ZnO-TiO<SUB>2</SUB> core-shell NWs by CVD and photo-deposition. </LI> <LI> Au decorated ZnO-TiO<SUB>2</SUB> core-shell NWs shows the photocurrent density of 1.63 mAcm<SUP>−2</SUP>. </LI> <LI> Au decorated ZnO-TiO<SUB>2</SUB> core-shell NWs shows the fast photoresponse. </LI> <LI> Au decorated ZnO-TiO<SUB>2</SUB> core-shell NWs shows photoconversion efficiency of 0.70%. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Core-shell 구조의 Au/TiO₂ 나노 미립자의 합성 및 특성 평가

유연태,Paul Mulvaney 한국세라믹학회 2003 한국세라믹학회지 Vol.40 No.9

Au/TiO$_2$ core-shell 구조 나노 미립자가 졸-겔법에 의해서 제조되었고, TiO$_2$ shell의 형상과 결정성이 TEM과 UV-Vis. absorption spectrometer에 의해서 조사되었다. Au/TiO$_2$ core-shell 나노 미립자는 Au 콜로이드 에탄올 수용액 중에서 TOAA(Titanium Oxide Acethylacetonate)의 가수분해에 의해 합성될 수 있었다. Au 나노 미립자의 표면에 형성된 TiO$_2$ shell의 두께는 약 1 nm이었다. TiO$_2$ shell의 결정성을 조사하기 위하여. TiO$_2$가 피복된 Au 콜로이드 에탄올 용액에 254 nm의 자외선과 $^{60}$Co의 방사선을 조사하였다. Au 나노 미립자의 surface plasmon 현상은 방사선이 조사되었을 때만 나타났고, 이 결과로부터 TiO$_2$ shell은 비정질 상태임을 알 수 있었으며, Au의 분산성 향상을 위해 표면에 처리된 MUA(Mercaptoundecanoic Acid)층은 전자의 이동을 방해하는 장애물로 작용하지 않음을 확인할 수 있었다. Au/TiO$_2$ core-shell structure nanoparticles were synthesised by sol-gel process, and the morphology and crystallinity of TiO$_2$ shell were investigated by TEM and UV-Vis. absorption spectrometer. Au/TiO$_2$ core-shell structure nanoparticles could be prepared by the hydrolysis of TOAA (Titanium Oxide Acethylacetonate) in Au colloid ethanol solution with $H_2O$. The thickness of TiO$_2$ shell on the surface of Au particles was about 1 nm. To investigate the crystallinity of TiO$_2$ shell, UV light with 254 nm and radioactive lay of $^{60}$ CO were irradiated on the TiO$_2$ coated Au colloid ethanol solution. The surface plasmon phenomenon of Au nanoparticles appeared only when the radioactive lay was irradiated on the TiO$_2$ coated Au colloid ethanol solution. From these results, it was found that the TiO$_2$ shell was amorphous and the MUA (Mercaptoundecanoic Acid) layer on the Au particle for its dispersion didn't act as an obstacle to disturb the movement of electron onto the surface of Au particle.

An extensive study on enhancing the thermal conductivity of core-shell nanoparticle composites using finite element method

Ngo, I.L.,Byon, C. Pergamon Press 2016 International journal of heat and mass transfer Vol. No.

This paper describes an extensive study on enhancing the thermal conductivity (TC) of core-shell nanoparticle polymer composites under the effects of the TC ratios between core nanoparticles, shell layer and the matrix material, and the volume fractions (VF) of core and shell. Finite element method is used for both numerical simulation and solving the related nonlinear equations. Consequently, the effective thermal conductivity (ETC) of such a polymer composites can be enhanced by adding larger VF and higher TC of core and shell into the matrix. Shell layer plays a more important role in the TC enhancement compared to core nanoparticle. It is revealed that an abrupt increase of ETC exists even at low VF of shell layer under the appropriate conditions, high shell TC and low core one in general. The maximum ETC is due to the synergic effects of core nanoparticle and shell layer filled in the matrix, and it exists when core VF is 0.516 times greater than that of shell. Many other good guidance are provided for enhancing and achieving the maximum ETC of core-shell nanoparticle polymer composites, and they play an important role in producing the advanced polymer composites.

Temperature-induced gel formation of core/shell nanoparticles for the regeneration of ischemic heart

Oh, K.S.,Song, J.Y.,Yoon, S.J.,Park, Y.,Kim, D.,Yuk, S.H. Elsevier Science Publishers 2010 Journal of controlled release Vol.146 No.2

Vascular endothelial growth factor (VEGF)-loaded core/shell nanoparticles were prepared and their gelation behavior in response to temperature was characterized for the regeneration of ischemic heart. The core is composed of lecithin containing VEGF and the shell is composed of Pluronic F-127 (poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer). When Capryol 90 (propylene glycol monocaprylate) was added to an aqueous solution of the core/shell nanoparticles, a temperature-induced gel composed of core/shell nanoparticles was observed to form at body temperature. This phenomenon was utilized for the stable localization of core/shell nanoparticles at the ischemic area. For an in vivo assessment, VEGF-loaded core/shell nanoparticles with and without inducement of the gel formation were applied to a subacute myocardial infarction model in rats and functional analysis of the heart was monitored by means of a PV catheter four weeks later. The results showed that the VEGF-loaded core/shell nanoparticles and their gel improved the heart functions, particularly with regard to the ejection fraction and cardiac output.

Capacitance Evaluation of Inorganic Core–Shell Nanoparticles with Different Shell Layers Using SPM-Combined Impedance Spectroscopy

Lim, Youngjoon,Lee, Sang-Yup The Electrochemical Society 2016 Journal of the Electrochemical Society Vol.163 No.2

<P>Inorganic core-shell nanoparticles have widely been used in engineering, however, the overall effect of the shell layer on the electrical properties has not been intensely investigated. In this study, we examine the electrical properties of inorganic core-shell nanoparticles with different shell layers using AC-impedance spectroscopy combined with a conductive scanning probe microscope (c-SPM). Three model core-shell nanoparticles, Se@MSe (M: Ag, Zn and Cd), were synthesized using the cation exchange method and their impedance signals were evaluated to determine the capacitance of nanoparticles with various shell layers. The capacitance of an inorganic core-shell nanoparticle showed a positive correlation with the dielectric properties of the shell layer. This means that the electrical properties of a core-shell nanoparticle are heavily influenced by the shell layer rather than the particle core. This study demonstrated that impedance spectroscopy can be utilized for the electrical characterization of inorganic core-shell nanoparticles, and accentuated the importance of the layer properties of the shell on the capacitance of nanoparticles. (C) 2015 The Electrochemical Society.</P>

Formation of SiO_x shell on Si nanoparticles and its effects on electrochemical properties as a Li-ion battery's anode

Jang, Boyun,Koo, Jeongboon,Choi, Sunho,Kim, Joonsoo Elsevier 2018 Materials chemistry and physics Vol.215 No.-

<P><B>Abstract</B></P> <P>Crystalline Si core–amorphous SiO<SUB>x</SUB> shell nanoparticles were synthesized from SiCl<SUB>4</SUB> using an atmospheric microwave plasma process and their microstructures were investigated. It was found that the amorphous SiO<SUB>x</SUB> shell thickness was determined by varying the applied microwave power. The increase of applied power directly increased the length of the flame at the end of the plasma. Through observation of the microstructures with varying lengths of the flame, it was found that a highly crystalline Si phase was formed in the plasma and amorphous SiO<SUB>x</SUB> phase was formed in the flame. The longer flame resulted in the thicker SiO<SUB>x</SUB> shell around the Si core. The electrochemical properties of the varying SiO<SUB>x</SUB> shell thicknesses were also investigated in that the synthesized Si-SiO<SUB>x</SUB> nanoparticles were used as anode materials in a lithium-ion battery (LIB). Thin shells such as native oxide did not influence the electrochemical behaviour of the Si core, whilst some shells were too thick to allow Li-ions to react with the Si core. Using Si-SiO<SUB>x</SUB> nanoparticles with the optimum SiO<SUB>x</SUB>:Si ratio of 18:82, the following electrochemical properties were obtained: a first reversible capacity of 932 mAh/g, an initial columbic efficiency (ICE) of 52.5%, and a capacity retention of 83.7% at the 100<SUP>th</SUP> cycle.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Si nanoparticles with amorphous SiO<SUB>x</SUB> shells with various thicknesses are synthesized. </LI> <LI> The formation of SiO<SUB>x</SUB> shell and its effect on the Si nanoparticle is studied. </LI> <LI> The Si/SiO<SUB>x</SUB> ratios are varied by controlling flame length at the end of plasma. </LI> <LI> The relations between microstructures and electrochemical properties are analyzed. </LI> <LI> The Si-SiO<SUB>x</SUB> core-shell nanoparticle exhibits improved electrochemical performance. </LI> </UL> </P>

Effects of shell thickness on Ag-Cu₂O core-shell nanoparticles with bumpy structures for enhancing photocatalytic activity and stability

Lee, Changsoo,Shin, Kihyun,Lee, Yung Jong,Jung, Chanwon,Lee, Hyuck Mo Elsevier 2018 CATALYSIS TODAY - Vol.303 No.-

<P><B>Abstract</B></P> <P>Here we examine Ag-Cu<SUB>2</SUB>O core-shell nanoparticles with bumpy structures for use in plasmonic photocatalysts. We synthesized the nanoparticles using a very simple co-reduction process. The shell thickness of the nanoparticles was controlled in order to investigate the effects of shell thickness on photocatalytic activity and stability. With increasing shell thickness, it was be observed that the activity and the stability were simultaneously improved. A thin shell lead to de-wetting of Cu<SUB>2</SUB>O from the Ag core and considerable oxidation of Cu<SUB>2</SUB>O to CuO. The high activity could be due to the unique structure of Ag-Cu<SUB>2</SUB>O, which has a high surface area and plasmonic charge transfer from the Ag core. In addition, we elucidated the stability tendency using conducted density functional theory (DFT) calculation. Strain induced between the Ag core and shell is critical to the stability, leading to de-wetting and oxidation of Cu<SUB>2</SUB>O.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We synthesized Ag-Cu<SUB>2</SUB>O core-shell NPs with bumpy structure. </LI> <LI> The Ag-Cu<SUB>2</SUB>O core-shell NPs have high surface area and broad range of UV–vis absorption. </LI> <LI> Shell thickness of Ag-Cu<SUB>2</SUB>O NPs play a key role for activity and stability of the photocatalysts. </LI> <LI> Combined experimental and theoretical study was conducted. </LI> <LI> High strain between core and shell of thin core-shell NPs induce de-wetting and oxidation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Hollow PdCu₂@Pt core@shell nanoparticles with ordered intermetallic cores as efficient and durable oxygen reduction reaction electrocatalysts

Park, Hee-Young,Park, Jin Hoo,Kim, Pil,Yoo, Sung Jong Elsevier 2018 Applied Catalysis B Vol.225 No.-

<P><B>Abstract</B></P> <P>Carbon-supported hollow PdCu<SUB>2</SUB>@Pt core@shell nanoparticles with ordered intermetallic cores were prepared as an efficient and durable oxygen reduction reaction (ORR) electrocatalyst for polymer electrolyte membrane fuel cells (PEMFCs). PdCu<SUB>2</SUB> cores prepared using a chemical reduction method were thermally treated to produce ordered intermetallic structures. A Pt shell was then deposited via a galvanic displacement process. The effect of the galvanic displacement conditions on the properties and structure of the obtained core–shell nanoparticles was investigated by varying the solution pH and anion concentration. Acidic conditions and low Cl<SUP>−</SUP> concentrations were found to provide a uniform Pt layer with a hollow core, while maintaining the ordered intermetallic core structure. These hollow PdCu<SUB>2</SUB>@Pt core@shell nanoparticles showed high activity and stability for ORR electrocatalysis in PEMFCs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pt shell was deposited on ordered intermetallic PdCu<SUB>2</SUB> nanoparticles (PdCu<SUB>2</SUB>@Pt-H). </LI> <LI> Pt shell was fabricated by galvanic replacement reaction of Cu and Pd by Pt. </LI> <LI> Low pH and low Cl<SUP>−</SUP> concentration gave Pt shell with hollow and ordered PdCo<SUB>2</SUB> core. </LI> <LI> PdCu<SUB>2</SUB>@Pt-H showed high oxygen reduction reaction activity and durability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Preparation and Reconstitution of Core-shell Type Nanoparticles of Poly(ε -caprolactone)/Poly(ethyleneglycol)/Poly(ε -caprolactone) Triblock Copolymers

Jeong, Young-Il,Ryu, Jae-Gon,Kim, Young-Hoon,Kim, Sung-Ho Korean Chemical Society 2002 Bulletin of the Korean Chemical Society Vol.23 No.6

One of the improtant characteristics of core-shell type nanoparticles is the long-term storage and reuse as an aqueous injection solution when required. For this reason, reconstruction of lyophilized core-shell type nanoparticles is considered to be essential . BAB type triblock copolymers differ from AB type diblock copolymers, which contain the A block as a hydrophilic part and the B block as a hydrophobic part. by not being easily redistributed into phosphate-buffered saline (PBS, pH 7.4, 0.1 M). Therefore, lyophilized core-shell type nanoparticles of CEC triblock copolymer were reconstituted using a somication process with a bar-type sonicator in combination with a freezing-thawing process. Soncation for 30s only resuspended CEC nanoparticles in PBS; their particle size distribution showed a monomodal pattern with narrow size distribution. The bimodal size distribution pattern and the aggregates were reduced by further sonication for 120 s but these nanoparticles showed a wide size distribution. The initial burst of drug release was increased by reconstitution process. The reconstitution of CEC core-shell type nanoparticles by freezing-thawing resulted in trimodal distribution pattern and formed aggregates, although freezing-thawing process was easier than sonication . Drug release form CEC nanoparticles prepared by freezing-thawing was slower than from the original dialysis solution. Although core-shell typenanoparticles of CEC triblock copolymers were not easily performed. Cytotoxicity testing of core-shell type nanoparticles of CEC-2 triblock copolymers containing clonazepam (CNZ) was performed using L929 cells. Cytotoxicity of CNZ was decreased by incorporation into nanoparticles.

Enhanced UV Emission in ZnO/ZnS Core Shell Nanoparticles Prepared by Epitaxial Growth in Solution

Simmi Sharma,Santa Chawla 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.3

Co-precipitation in highly alkaline environment resulted in well crystalline ZnO nanoparticles over which ZnS shell was grown in situ in solution at room temperature. Formation of epitaxial hexagonal ZnS over wurtzite ZnO core particles have been confirmed by x-ray diffraction and transmission electron microscopy studies. The core ZnO nanoparticles show prominent UV emission which enhances appreciably due to ZnS shell formation in ZnO/ZnS core/shell particles. Experimental evidence indicates the quenching of non radiative recombination pathways due to shell formation. The results suggest that synthesized epitaxial core/shell particles have charge confinement mainly in the core region with type I characteristics of band alignment and can be useful for device applications.