Visible-Light-Driven Photoproduction of Hydrogen Using Rhodium Catalysts and Platinum Nanoparticles with Formate

Kim, Soojin,Lee, Ga Ye,Baeg, Jin-Ook,Kim, Youngmee,Kim, Sung-Jin,Kim, Jinheung American Chemical Society 2014 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.118 No.45

<P>Photochemical hydrogen production is carried out using molecular Rh complexes and sodium formate in the presence of platinum nanoparticles (PtNPs) in aqueous buffer solution. Visible-light-driven photocatalytic reactions for hydrogen production with and without nicotinamide adenine dinucleotide (NAD<SUP>+</SUP>) follow two different pathways. Complex [Cp*Rh(bpy)(OH<SUB>2</SUB>)]<SUP>2+</SUP> selectively reduces NAD<SUP>+</SUP> to generate NADH using formate as a proton and electron donor and the chemically generated NADH is sequentially used by PtNPs upon photoactivation of eosin Y to produce hydrogen. However, hydrogen is also produced in photoreactions of the Rh catalyst and PtNPs with formate in the absence of NAD<SUP>+</SUP> and eosin Y. The second pathway for hydrogen production was performed under the conditions without NAD<SUP>+</SUP> and eosin Y and derived from a direct electron transfer from <I>in situ</I> generated rhodium(III)-hydride species to photoexcited PtNPs. The direct electron transfer from the rhodium-hydride species to visible-light-driven PtNPs was first observed in this study. These two pathways for hydrogen production showed different rate-limiting steps based on a Hammett plot using Rh catalysts containing electron-donating and electron-withdrawing groups. Kinetic isotope effects as well as Hammett plot supported the rate-limiting step of the NADH generation for the first pathway of hydrogen production and the Rh–H formation for the second pathway.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2014/jpccck.2014.118.issue-45/jp504876w/production/images/medium/jp-2014-04876w_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp504876w'>ACS Electronic Supporting Info</A></P>

New cyclopentadienyl rhodium catalysts for electrochemical hydrogen production

Kim, Jinheung,Rajkumar, Eswaran,Kim, Soojin,Park, Yu Mi,Kim, Youngmee,Kim, Sung-Jin,Lee, Hye Jin Elsevier 2017 CATALYSIS TODAY - Vol.295 No.-

<P><B>Abstract</B></P> <P>The electrocatalytic activity of two new molecular rhodium catalysts was investigated in a hydrogen evolution system in the presence of a proton source using glassy carbon electrodes in acetonitrile and water. Rhodium complexes supported by pbi and pbt ligands, i.e., [Cp*Rh(pbt)Cl](PF<SUB>6</SUB>) (<B>1</B>) and [Cp*Rh(pbi)Cl] (<B>2</B>) (where Cp* is pentamethylcyclopentadienyl, pbt is 2-(2′-pyridyl)benzothiazole, and pbi is 2-(2′-pyridyl)benzimidazole), were observed to electrocatalytically evolve H<SUB>2</SUB> at potential of −0.90V vs Ag/AgCl in CH<SUB>3</SUB>CN and CH<SUB>3</SUB>CN/H<SUB>2</SUB>O. Cyclic voltammetry of <B>1</B> and <B>2</B> in the presence of acid revealed redox waves consistent with the Rh(III)/Rh(I) couple. Bulk electrolysis were used to confirm the catalytic nature of the process for complexes <B>1</B> and <B>2</B>, with turnover numbers in excess of 100 and essentially quantitative faradaic yields for H<SUB>2</SUB> production. The potentials at which these Rh complexes catalyzed H<SUB>2</SUB> evolution were close to the thermodynamic potentials for the production of H<SUB>2</SUB> from protons in CH<SUB>3</SUB>CN and CH<SUB>3</SUB>CN/H<SUB>2</SUB>O, with the small overpotential being 50mV for <B>1</B> as determined by electrochemistry. The complex <B>1</B> with more positive Rh(III/I) redox potentials exhibited higher activity for H<SUB>2</SUB> production.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Rhodium complexes supported by pbi and pbt ligands to electrocatalytically evolve H<SUB>2</SUB>. </LI> <LI> Rh complexes with turnover numbers over 100 and quantitative faradaic yields for H<SUB>2</SUB>. </LI> <LI> The pbi complex with more positive Rh(III/I) redox potential for higher H<SUB>2</SUB> production. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Two new (pentamethylcyclopentadienyl)Rh(III) complexes containing pyridyl-benzothiazole and pyridyl-benzimidazole were prepared and a systematic study of proton electroreduction catalyzed by the two new rhodium catalysts was performed at glassy carbon electrode. The Rh complex of pyridyl-benzothiazole was more efficient in the electrocatalytic hydrogen production in the presence of trifluoroacetic acid.</P> <P>[DISPLAY OMISSION]</P>

Effects of Annealing Sequences on Ferroelectric Properties of Nb-Doped Bismuth Titanate Thin Films

Jong Kuk Kim,Jinheung Kim,Eun Kyung Choi,Jong-Hwa Kim,Sang Su Kim,Tae Kwon Song 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV

Nb-doped Bi4Ti3O12 (Nb-BIT) ferroelectric thin lms were prepared on Pt/Ti/SiO2/Si substrates by metalorganic solution deposition (MOSD) method. A nonionic block copolymer was used in the preparation of the precursor solutions in order to give a random orientation of crystal grains. Two annealing methods of conventional furnace annealing (CFA) and rapid thermal annealing (RTA) were compared to investigate dierences in microstructures, phase formations and ferroelectric properties of the crystallized Nb-BIT thin lms. Also, the eects of pre-heating at 500 C by RTA before the nal annealing steps at 700 C were studied. The lm crystallized at 700 C by CFA with pre-heating at 500 C by RTA showed good ferroelectric properties with random orientation and remanent polarization Pr = 26 C/cm2 at a maximum applied eld of 200 kV/cm. The pulse polarizations (P = P .. P^) decreased about 30 % of initial value after being subjected to 1.51010 read/write cycles at a frequency of 1 MHz.

Effects of Surfactant on Surface Morphology and Orientation of Nb-Doped Bi$_4$Ti$_3$O$_{12}$ Thin Films

Sang Su Kim,Eun Kyung Choi,Jin Soo Kim,Jinheung Kim,Jong Kuk Kim,Tae Kwon Song 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV

We have tried to use surfactants in order to tune the shape and orientation of Nb-doped Bi4Ti3O12 (BITNb) thin lms. BITNb thin lms were prepared on Pt(111)/Ti/SiO2/Si(100) substrates by a metalorganic solution deposition method. The precursor solution for the BITNb thin lms was modied with adding surfactant cetyltrimethylammonium bromide in acid or basic atmospheres. The measured XRD patterns revealed that the BITNb thin lm prepared with a surfactant in acid atmosphere showed only a Bi4Ti3O12-type phase with highly c-axis orientation. However, for the BITNb thin lm prepared without surfactant showed random orientation. The remanent polarization (2Pr) and the coercive eld (2Ec) of BITNb thin lms with c-axis and random orientation were 2.0 C/cm2 and 14.9 kV/cm, and 12.3 C/cm2 and 113.9 kV/cm, respectively.샀琴

Enhancing the Wound Healing Effect of Conditioned Medium Collected from Mesenchymal Stem Cells with High Passage Number Using Bioreducible Nanoparticles

Im, Gwang-Bum,Kim, Yeong Hwan,Kim, Yu-Jin,Kim, Sung-Won,Jung, Euiyoung,Jeong, Gun-Jae,Wang, Ke,Kim, Jinheung,Kim, Dong-Ik,Kim, Tae-Hyung,Yi, Gi-Ra,Yu, Taekyung,Bhang, Suk Ho MDPI AG 2019 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.20 No.19

<P>Injecting human mesenchymal stem cells (hMSCs) at wound sites is known to have a therapeutic effect; however, hMSCs have several limitations, such as low viability and poor engraftment after injection, as well as a potential risk of oncogenesis. The use of a conditioned medium (CM) was suggested as an alternative method for treating various wounds instead of direct hMSC administration. In addition to not having the adverse effects associated with hMSCs, a CM can be easily mass produced and can be stored for long-term, thereby making it useful for clinical applications. In general, a CM is collected from hMSCs with low passage number; whereas, the hMSCs with high passage number are usually discarded because of their low therapeutic efficacy as a result of reduced angiogenic factor secretion. Herein, we used a CM collected from high passage number (passage 12, P12) hMSCs treated with gold-iron nanoparticles (AuFe NPs). Our AuFe NPs were designed to release the iron ion intracellularly via endocytosis. Endosomes with low pH can dissolve iron from AuFe NPs, and thus, the intracellularly released iron ions up-regulate the hypoxia-inducible factor 1α and vascular endothelial growth factor (VEGF) expression. Through this mechanism, AuFe NPs improve the amount of VEGF expression from P12 hMSCs so that it is comparable to the amount of VEGF expression from low passage number (passage 6, P6), without treatment. Furthermore, we injected the CM retrieved from P12 MSCs treated with AuFe NPs in the mouse skin wound model (AuFe P12 group). AuFe P12 group revealed significantly enhanced angiogenesis in the mouse skin wound model compared to the high passage hMSC CM-injected group. Moreover, the result from the AuFe P12 group was similar to that of the low passage hMSC CM-injected group. Both the AuFe P12 group and low passage hMSC CM-injected group presented significantly enhanced re-epithelization, angiogenesis, and tissue remodeling compared to the high passage hMSC CM-injected group. This study reveals a new strategy for tissue regeneration based on CM injection without considering the high cell passage count.</P>

Systematic Investigationon the Central Metal IonDependent Binding Geometry of M-<i>meso</i>-Tetrakis(<i>N</i>-methylpyridinium-4-yl)porphyrin to DNA and Their Efficiencyas an Acceptor in DNA-Mediated Energy Transfer

Kim, YoungRhan,Gong, Lindan,Park, Jongjin,Jang, Yoon Jung,Kim, Jinheung,Kim, Seog K. AmericanChemical Society 2012 The journal of physical chemistry. B, Condensed ma Vol.116 No.7

<P>Binding geometry to DNA and the efficiency as a donor for energy transfer of various metallo- and nonmetallo-porphyrins were investigated mainly by polarized light spectrscopy and fluorescence measurements. Planar porphyrins including nonmetallo meso-tetrakis(N-methylpyridinium-4-yl)porphyrin (TMPyP), CuTMPyP, and NiTMPyP produced large red-shift and hypochromism in absorption spectrum and a negative circular dichroism (CD) in the Soret band suggesting that these porphyrins intercalate between DNA base-pairs as expected. In the intercalation pocket, the molecular plane of these porphyrins tilts to a large extent. From a linear dichroism (LD) study, the angle between the two electric transition moments in the Soret band were 16 degrees, 12 degrees, and 11 degrees for TMPyP, NiTMPyP, and CuTMPyP, respectively. On the other hand, porphyrins with axial ligands namely, VOTMPyP, TiOTMPyP, and CoTMPyP, produced a positive CD signal in the Soret band. Hyperchromism and less red-shift were apparent in the absorption spectrum. These observations indicated that the porphyrins with an axial ligand bind outside of the DNA. The angles of both the B-x and B-y transition with respect to the local DNA helix were 39 degrees similar to 46 degrees for all porphyrins. From these results, the conceivable binding site of porphyrins with axial ligands is suggested to be the minor groove. All porphyrins were able to quench the fluorescence of intercalated ethidium. Strong overlap between emission spectrum of ethidium and the absorption spectrum of porphyrins when they simultaneously bound to DNA was found suggesting the mechanism behind energy transfer is, at least in part, the Forster type resonance energy transfer (FRET). The minimum distance in base pairs between ethidium and porphyrin required to permit the excited ethidium to emit a photon was the longest for CoTMPyP being 17.6 base pairs and was the shortest for CuTMPyP and NiTMPyP at 8.0 base pairs. The variation in the distance was almost proportional to the extent of the spectral overlap, the common area under emission spectrum of ethidium and absorption spectrum of porphyrin, supporting the FRET mechanism, whereas the effect of the orientation factor which was considered by relative binding geometry was limited.</P>

Photochemical Production of NADH Using Cobaloxime Catalysts and Visible-Light Energy

Kim, Jin Ah,Kim, Soojin,Lee, Jungha,Baeg, Jin-Oog,Kim, Jinheung American Chemical Society 2012 Inorganic Chemistry Vol.51 No.15

<P>In this study, a visible-light-driven photocatalytic system for the generation of dihydronicotinamide adenine dinucleotide (NADH) from aqueous protons was examined using cobaloxime as a catalyst, eosin as a photosensitizer, and triethanolamine as a sacrificial electron donor. Irradiation of a reaction solution containing cobaloxime, eosin, and triethanolamine (TEOA) converted NAD<SUP>+</SUP> to NADH with a yield of 36% in a phosphate buffer. The reaction rates for the production of NADH were dependent on the concentrations of the catalyst, NAD<SUP>+</SUP>, and TEOA. Introduction of an electron-donating or -withdrawing substituent in the para position of the pyridine changed the rate constant and affected the conversion efficiency. The rates obtained by the different substituents were linearly correlated with the Hammett coefficients of the introduced substituents. Last, reduction of CO<SUB>2</SUB> was carried out in the presence of formate dehydrogenase using NADH photochemically generated using the cobaloxime/eosin/TEOA system.</P><P>Photocatalytic reduction and protonation of nucleotide cofactor NAD<SUP>+</SUP> driven by visible light is demonstrated, using cobaloxime complexes as a hydride-transfer mediator and eosin as a photosensitizer. The in situ generated NADH is used for reduction of CO<SUB>2</SUB> catalyzed by formate dehydrogenase.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/inocaj/2012/inocaj.2012.51.issue-15/ic300185n/production/images/medium/ic-2012-00185n_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ic300185n'>ACS Electronic Supporting Info</A></P>

Fabrication and electrochemical application of monolayers of well-ordered macroporous silica.

Kim, In Young,Jeong, Byeongmoon,Yoon, Moon Young,Kim, Jinheung American Scientific Publishers 2010 Journal of nanoscience and nanotechnology Vol.10 No.1

<P>Highly ordered macroporous silica films with a monolayer thickness and regular array of spherical pores with diameters of about 305 nm are prepared using templates self-assembled by polymethylmethacrylate (PMMA) spheres on solid surfaces by spin coating. The macropores are uniform in size and completely exposed on the bottom surface of the film after the PMMA spheres are etched out. Based on electrochemical experiments, the film allows for easy mass transport of Ru(bpy)3(2+) to the ITO surface. Electrochemical detection of DNA hybridization was also carried out in model oligonucleotide hybrids immobilized on the macroporous silica film.</P>

Artificial Photocatalytic System Using Polydiacetylene-(−NH-phen)Ru(bpy)₂ for Cofactor Regeneration and CO₂ Reduction

Kim, Soojin,Lee, Songyi,Anjong, Tikum Florence,Jang, Ha Yoon,Kim, Ji-Yeong,Lee, Chiho,Park, Sungnam,Lee, Hye Jin,Yoon, Juyoung,Kim, Jinheung American Chemical Society 2016 The Journal of Physical Chemistry Part C Vol.120 No.50

<P>For the practical use of a photobioreactor for artificial photosynthesis, efficient visible light-absorbing materials have to link reduction and oxidation catalysts for an efficient energy flow. As a step toward this goal of an NADH regeneration system and enzymatic production of solar fuels from CO2, we report the synthesis of a new polydiacetylene compound that is covalently connected with [Ru(phen-NH2) (bpy)(2)](2+) (bpy =2,2'-bipyridine, phen =1,10-phenonthroline-5-amine). The [(bpy)(2)Ru(phen-NH-)]-polydiacetylene absorbed a wide range of visible light because of the presence of two chromophores, the Ru complex and polydiacetylene. The polyacetylene backbone was converted from blue to red by conformational changes under the catalytic reaction conditions in a buffer solution. The electron transfer from the photoexcited [ku(phen)(bpy)(2)](2+) to the polydiacetylene backbone was observed. In a visible light-driven photocatalytic NAD+ reduction by (cyclopentadienyl)Rh(bpy)(H2O)(2+) With [(bpy),Ru(phen-NH)]-polydiacetylene, NADH was regenerated, and the reactivity using Ru(bpy),(phen-NH)-polydiacetyleue was enhanced relative to control experiments using only [Ru(phen)(bpy)(2)](2+) or polydiacetylene. The consecutive carbon dioxide reduction coupled with formate dehydrogenase was carried out to utilize the in situ photoregenerated NADH catalytically. The catalytic condition using [(bpy),Ru(phen-NH)]-polydiacetylene also showed much higher reactivity than the controls.</P>

Photocatalytic Systems of Pt Nanoparticles and Molecular Co Complexes for NADH Regeneration and Enzyme-coupled CO₂ Conversion

Kim, Ellen,Jeon, Minkyung,Kim, Soojin,Yadav, Paras Nath,Jeong, Kwang-Duk,Kim, Jinheung Korean Society of Photoscience 2013 Rapid communication in photoscience Vol.2 No.2

Natural photosynthesis utilizes solar energy to convert carbon dioxide and water to energy-rich carbohydrates. Substantial use of sunlight to meet world energy demands requires energy storage in useful fuels via chemical bonds because sunlight is intermittent. Artificial photosynthesis research focuses the fundamental natural process to design solar energy conversion systems. Nicotinamide adenine dinucleotide ($NAD^+$) and $NADP^+$ are ubiquitous as electron transporters in biological systems. Enzymatic, chemical, and electrochemical methods have been reported for NADH regeneration. As photochemical systems, visible light-driven catalytic activity of NADH regeneration was carried out using platinum nanoparticles, molecular rhodium and cobalt complexes in the presence of triethanolamine as a sacrificial electron donor. Pt nanoparticles showed photochemical NADH regeneration activity without additional visible light collector molecules, demonstrating that both photoactivating and catalytic activities exist together in Pt nanoparticles. The NADH regeneration of the Pt nanoparticle system was not interfered with the reduction of $O_2$. Molecular cobalt complexes containing dimethylglyoxime ligands also transfer their hydrides to $NAD^+$ with photoactivation of eosin Y in the presence of TEOA. In this photocatalytic reaction, the $NAD^+$ reduction process competed with a proton reduction.