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Introduction
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March 2018 - present
Education
October 2015 - March 2018
April 2014 - September 2015
April 2010 - March 2014
Publications
Publications (43)
Combining all‐inorganic perovskites (CsPbX 3 ) with metal–organic frameworks (MOFs) offers great promise for efficient optoelectronic applications, but a lack of understanding of the microscopic mechanisms of host‐guest interactions that lead to stability limits their further advancement. Herein, a series of CsPbX 3 ‐MOF composites is studied based...
Photoluminescence blinking in individual semiconducting and perovskite quantum dots reflects reduced emission quantum yield and represents an obstacle towards quantum dot applications. One of the origins of blinking is the presence of surface structural defects that can function as charge traps. To reduce the defects the surface can be modified by,...
Luminescent lanthanide complexes containing effective photosensitizers are promising materials for use in displays and sensors. The photosensitizer design strategy has been studied for developing the lanthanide-based luminophores. Herein, we demonstrate a photosensitizer design using dinuclear luminescent lanthanide complex, which exhibits thermall...
We report the preparation and nanoscale photophysical characterization of mixed cation perovskite films of the composition MA1-xFAxPbI3, with x = 0, 0.3 and 0.5. Films with x = 0.5 and 0.3 prepared in air using ethyl acetate as an antisolvent in a one-step spin-coating process are compositionally stable in ambient air for more than a year, in contr...
Conjugated polymer chains in compact conformations or in films exhibit spectral features that can be attributed to interactions between individual conjugated segments of the chain, including formation of aggregates or excimers. Here, we use atomic force microscopy (AFM) on single chains of the conjugated polymer polyfluorene (PFO) to control the in...
We use fluorescence microscopy to study the nanoscale properties of a series of mixed-cation perovskite MA1−xFAxPbI3 films, an important photovoltaic material. Measuring photoluminescence spectra on submicrometer scales reveals the compositional heterogeneity of the films. The heterogeneity is largest for the FA 50% fraction films which contain pur...
Polyfluorene-based copolymers such as poly(9,9-dioctylfluorene)-alt-5% (bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-1,4-phenylenediamine) (F8-5% BSP) are efficient blue emitting polymers with various electronic phases: F8 blue-emitting glassy phase, F8 ordered more red-emitting β-phase, and F8/BSP charge transfer (CT) state. Polymer light-emitting dev...
Molecular aggregates were discovered in 1930’s, yet, the forces and excitonic coupling energy associated with the aggregate formation have not been detected so far. We directly measure such force and energy on single chains of the conjugated polymer polyfluorene using atomic force and fluorescence microscopes. The polyfluorene chain is attached on...
p>Polymer free volume is a rational concept for interpreting polymer properties connected to the fraction of unoccupied volume. While arbitrary definition of “free volume” often led to controversy, quantitative evaluation of polymer free volume is important for developing membrane materials as well as packing materials for chromatography that adsor...
Poly(9,9-dioctylfluorene) (PFO) is one of the most important conjugated polymer materials, exhibiting outstanding photophysical and electrical properties. PFO is also known for a diversity of morphological phases determined by conformational states of the main chain. Our goal in this work is to address some of the key questions on formation and dyn...
Trivalent lanthanide complexes are an important class of luminescent material characterized by their strong absorption of light by the organic ligands and subsequent energy transfer to the lanthanide ion, realizing intense luminescence from the ion. With this mechanism of luminescence, the total quantum yield of a lanthanide complex is the product...
The spectroscopy of nitrate complexes of Eu(III) and Tb(III) with chiral and racemic imine-based [L1 = (N,N’-bis(2-pyridylmethylidene)-1,2-(R,R + S,S)-cyclohexanediamine) and L3 = N, N’-bis(2-quinolylmethylidene)-1,2-(R,R + S,S)-cyclohexanediamine] and amine-based [L2 = N,N’-bis(2-pyridylmethyl)-1,2-(R,R + S,S)-cyclohexanediamine) and L4 = N,N’-bis...
Perfluorophenyl‐terminated porphyrin self‐assembled into exceptionally large J‐aggregates in methylcyclohexane; a solvophobic effect of methylcyclohexane on perfluoroarene enhanced a self‐complementary quadrupolar interaction between the perfluorophenyl group and the porphyrin ring, and caused nucleation growth of needles. Eventually, the longitudi...
A quadrupolar interaction of porphyrin bearing two pentafluorophenylethynyl terminals (1) drove the formation of a successive one‐dimensional staircase structure, i.e., J‐aggregates, to yield millimeter‐length needles with a single‐crystalline character in methylcyclohexane solution. In contrast, π‐stacked interaction of porphyrin bearing two non‐f...
The use of multidentate chelating ligands enriches the geometric diversity of coordinated gold clusters, offering much knowledge to benefit the understanding of their unique electronic structures and optical properties. Herein we report different behaviors of [core+exo]-type Au6 clusters bearing C3- and C4-bridged diphosphines (1 and 2), highlighti...
Suppression of back energy transfer is crucial in realizing efficient luminescent lanthanide complexes. However, the only practical method reported to this day is to raise the energy of the triplet excited state so that back energy transfer is energetically unfavorable, which limits the application where the absorbing wavelength of the organic liga...
Spin-orbit coupling is essential in lanthanide complexes for raising the yield of triplet excited state where the energy transfer to lanthanide ion mainly proceeds from, and therefore the sensitization efficiency of the lanthanide ion. However, since spin-orbit coupling mixes states of different multiplicity, strong spin-orbit coupling means that t...
Concentration quenching due to energy transfer between lanthanide ions have long been the shortcoming of lanthanide-based compounds, especially for luminescent functionalities like upconversion and multi-emission where energy transfer is necessary. Concentration quenching in lanthanide coordination polymers, on the other hand, is empirically known...
The upcoming chapters require that the readers have some background in the theory of lanthanide luminescence and the theory of kinetic analysis. The theory of lanthanide luminescence, or the infamous Judd-Ofelt theory, is one of the most critical development in lanthanide physics and chemistry that allowed great advancement in the understanding of...
Photoluminescent materials are used everywhere in our current society from daily lives to industries and research. As simple as it may seem, there are numerous types of photoluminescent materials (each with possibly different luminescence mechanisms), and tremendous amount of effort has been invested in research on these materials, sometimes going...
Energy transfer from organic ligands to a lanthanide ion is the main concept of sensitized luminescence in lanthanide complexes. Back energy transfer is the reverse process, which occur when the energy of the triplet excited state is close to the emitting excited state of the lanthanide ion and can lead to decrease in sensitization efficiency and t...
Throughout this thesis, various aspects of energy transfer processes in polynuclear lanthanide complexes have been explored. The purpose of this chapter is to present the conclusion of each of the chapters and to summarize them so that the core concept of the thesis can be discussed and concluded. An outlook based on the conclusions of this thesis...
This book describes the luminescence mechanism of polynuclear lanthanide complexes, focusing on energy transfer processes using a combination of experimental and theoretical approaches.
Lanthanide complexes show intense luminescence from the lanthanide ion through sensitization by the organic ligands. The high chromaticity of the emission and the l...
![Figure 4. Spectrometric titration of 2 ([2] 0 = 1.4 × 10 −4 M, red...](publication/324738867/figure/fig4/AS:619107892350976@1524618232154/Spectrometric-titration-of-2-2-0-14-10-4-M-red-line-with-pyridine-gray-lines_Q320.jpg)
Expanded π-systems with a narrow highest occupied molecular orbital–lowest unoccupied molecular orbital band gap encounter deactivation of excitons due to the “energy gap law” and undesired aggregation. This dilemma generally thwarts the near-infrared (NIR) luminescence of organic π-systems. A sophisticated cofacially stacked π-system is known to i...
Europium chalcogenide alloys, EuSxSe1-x, have been synthesized in both the solid-state and as colloidal nanoparticles; and the composition, structure, magnetism, and optical band gaps have been characterized. The goal was to observe the consequences of selenium concentration on the electronic structure as evidenced by the optical and magnetic prope...
In luminescent lanthanide (Ln(III)) complexes, the yield and the lifetime of triplet excited state of organic ligands are crucial factors that affect the ligands-to-Ln(III) energy transfer efficiency. Such factors are dependent on spin-orbit coupling induced by the Ln(III) ions that mixes different multiplicity states through heavy atom and paramag...
Photoluminescence of Ce³⁺- and Pr³⁺-activated Sr2GeO4 powders was measured between 17 and 600 K. For both ions strong 4fⁿ⁻¹5dⁿ→4fⁿ (d-f) emission is observed at low temperatures, around 410 nm (Ce³⁺) and 280 nm (Pr³⁺). The Ce³⁺ d-f emission quenches starting at 150 K and disappearing completely just above room temperature. Pr³⁺ d-f luminescence sho...
Invited for the cover of this issue are Takayuki Nakanishi from Hokkaido University, Sapporo, Japan, and co-workers. The cover image shows the YbIII coordination polymer used for the investigation of the concentration quenching mechanism.
The Front Cover shows the YbIII coordination polymer used for the investigation of the concentration quenching mechanism. For this study, a combination of theoretical and experimental techniques was utilized. Experimentally, the YbIII coordination polymer is excited by a photon, depicted as the lightning strike, and its emission behavior is observe...
Phonons are important in energy transfer for compensating the energy mismatch between a donor and an acceptor. In inorganic hosts doped with lanthanides, phonon-assisted energy transfer can lead to quenching by a direct transfer of the energy to the phonon mode of the acceptor lanthanide. We demonstrate that this also applies to lanthanide coordina...
Upon mechanical stimulation, 9-anthryl gold(I) isocyanide complex 3 exhibited a bathochromic shift of its emission color from the visible to the infrared (IR) region, which is unprecedented in its magnitude. Prior to exposure to the mechanical stimulus, the polymorphs 3α and 3β exhibit emission wavelength maxima (λem,max) at 448 nm and 710 nm, resp...
We synthesized two new porous coordination polymers (PCPs) {Ln7(OH)5[Ru(dcbpy)3]4·4nH2O} (Ln7-Ru4; Ln = Ce, Nd) composed of the luminescent ruthenium(II) metalloligand [Ru(4,4'-dcbpy)3](4-) ([4Ru]; 4,4'-dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) and lanthanide ions Ln(3+) (Ln = Ce, Nd). These two PCPs Ln7-Ru4 are isomorphous with the previously report...
Lanthanide (Ln(III)) complexes form an important class of highly efficient luminescent materials showing characteristic line emission after efficient light absorption by the surrounding ligands. The efficiency is however lowered by back energy transfer from Ln(III) ion to the ligands, especially at higher temperatures. Here we report a new strategy...
The reaction of diphenyldipyridinogermole with Cu2I2(PPh3)3 in THF afforded a complex with high thermal stability. Crystals whose linear polymeric structures were determined by single-crystal X-ray diffraction study emitted orange phosphorescence with the quantum yield of 25%. The sufficient solubility of the complex permitted the fabrication of a...
Remarkable improvements of environmental durability and energy conversion efficiency in silicon solar cells were achieved using ethylene vinyl acetate (EVA) protection film containing polymethylmethacrylate (PMMA) polymer beads (PB), which includes hyper-stable luminescent lanthanide coordination polymer [Eu(hfa)3(dpbp)]n (hfa: hexafluoroacetylacet...
UV durability of luminescent Eu(III) complexes for future solar cell application is estimated using Fourier transform infrared spectroscopy (FT-IR). Sandwich-typed glass cells containing Eu(III) complexes powders under UV irradiation are used for the carbonyl index analysis (calculation of decomposition percentage of organic ligands) using FT-IR me...
Series of nonanuclear Tb(III) clusters with ligands of different length of alkyl chain groups and their photophysical properties are demonstrated. The nonanuclear Tb(III) clusters (Tb9 clusters) are composed of nine oxygen-bridged Tb(III) ions and sixteen alkyl salicylate ligands, where alkyl chain are ethyl (Tb9-Et), propyl (Tb9-Pr), butyl (Tb9-Bu...
The photophysical properties of novel nonanuclear Tb(III) clusters with 5-methyl-methylsalicylate (Tb-L1) and 4-methyl-methylsalicylate (Tb-L2) ligands are reported. The position of the methyl group has affected on their photophysical properties. The prepared nonanuclear Tb(III) clusters were identified by FAB-Mass spectrometry and powder X-ray dif...
Luminescent beads composed of Eu(hfa)3(TPPO)2 (hfa: hexafluoroacetylacetonate, TPPO: triphenylphosphine oxide) in PMMA copolymer (polymethylmethacrylate- styrene and polymethylmethacrylate-trifluoromethylmethacrylate copolymers), PMMA-St-Eu and PMMA-TF-Eu have been reported for improvement of energy conversion efficiency on silicon solar cell. The...
Questions
Questions (3)
Just like the question states, I'm looking for a monochromator (or more precisely a polychromator) that is meant to be attached to an EM-CCD camera for use in fluorescence microscopes. The way it works is that there's a knob that inserts a slit, and another knobs that switches between a mirror (imaging) and grating (spectrograph), allowing switching between a spectrograph and imaging observed by the CCD camera.
It's something like this:
My lab owns this one, but it has a very small field of view in the imaging mode for a wide-field fluorescence microscopy. It also has a freely variable slit, which becomes problematic when I want to measure single-molecule fluorescence spectrum with the same spectral resolution between different positions. Their older models were better in that sense (it had large field of view, and there were several preset slit sizes) but they are no longer manufactured.
I'm wondering if your lab happen to use one, what manufacturer+model are you using?
Note: Yes, I have considered using a transmitting grating to split an image into real space image (zeroth order) and spectral image (first order). However, it obviously sacrifices spectral resolution and intensity. Also, it's inapplicable for relatively larger samples (samples larger than diffraction limit). I am not planning to use a confocal microscopy neither, which omits the option of using adedicated spectrometer.
(edited for terrible grammar)
I've sometimes encountered this phenomenon where I get an opposite arrow for transition between MOs when I do excited state calculation in Gaussian16.
I get something like :
56 -> 58
57 -> 58
57 <- 58
(57 is HOMO and 58 is LUMO)
What does this mean? It seems strange that I am seeing a transition from LUMO to HOMO.
I am looking for several ways to determine the crystallographic axes on the crystal.
I have a crystal on a quartz slip, and I want to know which lattice plane I am looking at when I look at one plane of the crystal. I do have CIF data for the crystal.
I know one way is to see the x-ray diffraction pattern of the one particular crystal with the incident x-ray propagating to the direction I want to determine the plane for. However, this is not possible when I have it on a quartz slip.
Is there any other way I can determine this?
