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Kim, Tae-Gun,Joshi, Bhavana,Park, Chan-Woo,Samuel, Edmund,Kim, Min-Woo,Swihart, Mark T.,Yoon, Sam S. Elsevier 2019 Journal of alloys and compounds Vol.798 No.-
<P><B>Abstract</B></P> <P>We demonstrate a promising Fe<SUB>2</SUB>O<SUB>3</SUB>/ZnO/TiO<SUB>2</SUB> photoanode for photoelectrochemical water splitting. Passivation of the Fe<SUB>2</SUB>O<SUB>3</SUB> surface with thin layers of ZnO and TiO<SUB>2</SUB> enhances the water splitting photocurrent density of Fe<SUB>2</SUB>O<SUB>3</SUB>. The increased photoelectrochemical activity of the hematite-based structure with heterojunctions, compared to that of bare Fe<SUB>2</SUB>O<SUB>3</SUB>, results from improved charge separation during water oxidation. The multilayered Fe<SUB>2</SUB>O<SUB>3</SUB> film exhibits a seven-fold improvement in photocurrent density (to 4.25 mA cm<SUP>−2</SUP>) compared with bare Fe<SUB>2</SUB>O<SUB>3</SUB>, due to suppression of electron–hole recombination. The transient photocurrent density and impedance were evaluated to assess the effect of the passivation layer thickness and achieve a high photocurrent at low potential (0.7 V vs. Ag/AgCl) through improved light harvesting of the Fe<SUB>2</SUB>O<SUB>3</SUB> film with an ultrathin ZnO/TiO<SUB>2</SUB> overlayer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Photocurrent density is 7 times higher due to TiO<SUB>2</SUB> protection layer for Fe<SUB>2</SUB>O<SUB>3</SUB> than pristine Fe<SUB>2</SUB>O<SUB>3</SUB>. </LI> <LI> Excellent photoelectrochemical performance due to high electron-hole separation. </LI> <LI> Large-scale production of an efficient water splitting photoanodes by supersonic cold spray. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Mo-doped BiVO<sub>4</sub> nanotextured pillars as efficient photoanodes for solar water splitting
Kim, Min-Woo,Kim, Karam,Ohm, Tae Yoon,Joshi, Bhavana,Samuel, Edmund,Swihart, Mark T.,Yoon, Hyun,Park, Hyunwoong,Yoon, Sam S. Elsevier 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.726 No.-
<P><B>Abstract</B></P> <P>We present electrospray-deposited nanotextured Mo-doped BiVO<SUB>4</SUB> pillars with improved photoelectrochemical water splitting performance. The three-dimensional nanotextured Mo-BiVO<SUB>4</SUB> pillars exhibit large interstitial spaces, which result in a high photocurrent. The doping of Mo at the optimal concentration (0.15%) results in a two-fold increase in the photocurrent density (PCD) (1.78 mA·cm<SUP>−2</SUP> at 1.2 V versus Ag/AgCl) over that of pristine BiVO<SUB>4</SUB>. We attribute this increase in the PCD to increases in recombination time and in donor (electron) concentration owing to the doping with hexavalent Mo, as confirmed by Bode phase and Mott-Schottky analyses, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mo-doped BiVO<SUB>4</SUB> films are formed by electrospray deposition. </LI> <LI> Films consist of 3D nanotextured pillars, which help increase the photocurrent. </LI> <LI> Optimal Mo doping results in two-fold increase in photocurrent density. </LI> <LI> This is owing to an increase in the time constant for electron recombination. </LI> <LI> Another factor responsible is the increase in donor (electron) concentration. </LI> </UL> </P>
Kim, Tae-Gun,Samuel, Edmund,Joshi, Bhavana,Park, Chan-Woo,Kim, Min-Woo,Swihart, Mark T.,Yoon, Woo Young,Yoon, Sam S. Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.766 No.-
<P><B>Abstract</B></P> <P>Highly flexible, binder-free, scalable, and high-capacity lithium ion battery anodes were fabricated by ball-milling SnO<SUB>2</SUB> and ZnO<SUB>2</SUB> particles to form Zn<SUB>2</SUB>SnO<SUB>4</SUB>/SnO<SUB>2</SUB> ternary oxide particles that were supersonically sprayed over a large area of a flexible copper foil without using any binders. The addition of rGO promoted uniform distribution of the particles and enhanced the overall performance of the composite anodes, which showed excellent long-term stability and a reversible capacity of 1316 mAh·g<SUP>−1</SUP> at a specific current of 100 mA g<SUP>−1</SUP> after 100 cycles. The supersonic deposition promoted inter-particle cohesion as well as adhesion of the coating materials onto the flexible substrate. Without added binder, the potential adverse effects of using binders on the electrical properties of the anodes were eliminated. The morphology and composition of the samples were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. The low-cost and scalable synthesis and deposition methods used here may offer a pathway for achieving commercially viable high-capacity anodes for various flexible electronic devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> SnO<SUB>2</SUB> and ZnO<SUB>2</SUB> were ball-milled to form Zn<SUB>2</SUB>SnO<SUB>4</SUB>/SnO<SUB>2</SUB> ternary oxide particles. </LI> <LI> Reduced graphite oxide (rGO) promoted uniform distribution of the particles. </LI> <LI> The uniform distribution enhanced the overall electrode performance. </LI> <LI> Supersonic deposition promoted interparticle cohesion & particle−substrate adhesion. </LI> </UL> </P>
Kim, Yong Il,Samuel, Edmund,Joshi, Bhavana,Kim, Min-Woo,Kim, Tae Gun,Swihart, Mark T.,Yoon, Sam S. Elsevier 2018 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.353 No.-
<P><B>Abstract</B></P> <P>Highly flexible freestanding carbon nanofibers were electroplated with silver for use in supercapacitor applications. The brittle carbon nanofibers were encased within bendable silver shells to provide superior flexibility and resilience of the supercapacitors. The enhanced electrical conductivity derived from the silver shell structure dramatically increased the capacitance of the supercapacitor. The silver shell also conferred structural stability to the carbon core, thus furnishing stable, long-term electrode performance. Nearly 100% of the specific capacitance was retained after <I>N</I> = 10,000 galvanostatic charge-discharge cycles. The mechanical endurance or stability of the fabricated electrode was evaluated using 1,000 bending cycles, demonstrating that the electrode performance remained unchanged. Cyclic voltammetry and galvanostatic discharge curves were measured at various scan rates and current densities. The fabricated electrodes were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy, which clearly illustrated the carbon-core and silver-shell structure.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Silver-coated freestanding carbon nanofibers were fabricated for supercapacitors. </LI> <LI> Carbon nanofibers encased with silver shells exhibited superior flexibility. </LI> <LI> Good electrical conductivity of silver shell structure led to superior capacitance. </LI> <LI> The core-shell structure ensured long-term stability of the electrode performance. </LI> <LI> Specific capacitance retention after <I>N</I> = 10,000 charge-discharge cycles was 100%. </LI> </UL> </P>
Kim, Min-Woo,Kim, Karam,Ohm, Tae Yoon,Yoon, Hyun,Joshi, Bhavana,Samuel, Edmund,Swihart, Mark T.,Choi, Sung Kyu,Park, Hyunwoong,Yoon, Sam S. Elsevier 2018 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.333 No.-
<P><B>Abstract</B></P> <P>We report the fabrication and the performance in photoelectrochemical water splitting of thin films of electrostatically sprayed nanotextured bismuth vanadate (BiVO<SUB>4</SUB>) pillars coated with thin ZnO/TiO<SUB>2</SUB> passivation layers formed by atomic layer deposition. The thin ZnO and TiO<SUB>2</SUB> layers deposited on the BiVO<SUB>4</SUB> nanopillars formed a heterostructure that promoted electron–hole separation and the migration of electrons toward the ITO substrate. The photocurrent density (PCD) of the ZnO/TiO<SUB>2</SUB> coated BiVO<SUB>4</SUB> was 2.5 times higher (2.25mA/cm<SUP>2</SUP> at 1.2V (versus Ag/AgCl)) than that of pristine BiVO<SUB>4</SUB> (0.9mA/cm<SUP>2</SUP> at 1.2V (versus Ag/AgCl)). We present incident/absorbed photon-to-current efficiency and electrochemical impedance measurements confirming that this improvement is a result of the heterojunction produced by the conformal ZnO/TiO<SUB>2</SUB> coating and discuss the mechanism of this dramatic enhancement of PCD.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Electrosprayed nanotextured bismuth vanadate (BiVO<SUB>4</SUB>) pillars were covered with ZnO/TiO<SUB>2</SUB> layers via atomic layer deposition. </LI> <LI> ZnO/TiO<SUB>2</SUB>-coated BiVO<SUB>4</SUB> pillars were used in photoelectrochemical water splitting. </LI> <LI> This heterostructure structure promoted electron–hole separation and the migration of electrons. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kim, Yong-il,Yoon, Hai-Jeon,Paeng, Jin Chul,Cheon, Gi Jeong,Lee, Dong Soo,Chung, June-Key,Kim, E. Edmund,Moon, Woo Kyung,Kang, Keon Wook Wolters Kluwer Health, Inc. All rights reserved. 2016 Clinical nuclear medicine Vol.41 No.8
<P>Purpose: We performed pretreatment angiogenesis imaging (Ga-68-NOTA-arginyl-glycyl-aspartic acid [RGD] PET/CT) to compare its prognostic value to dynamic contrast-enhanced (DCE) MRI in breast cancer patients. Methods: Forty-four female patients with stage II or III breast cancer (aged 47.3 +/- 8.1 years) were prospectively enrolled and underwent Ga-68-NOTA-RGD PET/CT and DCE-MRI imaging. All patients received neoadjuvant chemotherapy and underwent surgery. With pretreatment Ga-68-NOTA-RGD PET/CT, SUVmax of the tumor in the torso (-T) and regional (-R) images were measured. With pretreatment DCE-MRI, the largest diameter of the tumor and maximum enhancement index (EImax; EImax = [highest signal / baseline signal] - 1) of the tumor were assessed. Results: Ten patients (22.7%) were found to have breast cancer recurrence after 17.9 +/- 11.2 months. The SUVmax-R (P = 0.017, cutoff >2.79) of Ga-68-NOTA-RGD PET/CT, the largest diameter of tumor (P = 0.017, cutoff >6.3 cm), and the EImax (P = 0.008, cutoff >5.38) of DCE-MRI showed significant results by univariate analysis. The 3-year disease-free survival of SUVmax-R was 91.7% versus 59.1% by Kaplan-Meier analysis (hazard ratio, 5.379). Multivariable analysis demonstrated that SUVmax-R with tumor diameter or EImax were the significant parameters. In addition, the combined parameters of SUVmax-R and EImax revealed better predictive value for prediction of breast cancer recurrence (75.0%) than each parameter of SUVmax-R (64.2%) and EImax (68.7%). Conclusions: Increased angiogenic activity of regional Ga-68-NOTA-RGD PET/CT (SUVmax-R) can be an early prognostic marker for the prediction of breast cancer recurrence.</P>