Formation and Growth of Atomic Scale Seeds of Au Nanoparticle in the Nanospace of an Organic Cage Molecule.

Seed-mediated growth has been widely used to synthesize noble metal nanoparticles with controlled size and shape. Although it is becoming possible to directly observe the nucleation process of metal atoms at the single atom level by using transmission electron microscopy (TEM), it is challenging to control the formation and growth of seeds with only a few metal atoms in homogeneous solution systems. This work reports site-selective formation and growth of atomic scale seeds of the Au nanoparticle in a nanospace of an organic cage molecule. We synthesized a cage molecule with amines and phenols, which were found to both capture and reduce Au(III) ions to spontaneously form the atomic scale seeds containing Au(0) in the nanospace. The growth reaction of the atomic scale seeds afforded Au nanoparticles with an average diameter of 2.0±0.2 nm, which is in good agreement with the inner diameter of the cage molecule.

Calving prediction with continuous measurement of subcutaneous tissue glucose concentration in pregnant cows.

To reduce losses of dams and calves due to unfortunate events, such as dystocia and freezing to death, identifying the onset of calving and providing necessary assistance are crucial. Prepartum increase in blood glucose concentration is a known indicator to detect labor in pregnant cows. However, some issues, including the need for frequent blood sampling and stress on cows, must be resolved before establishing a method for anticipating calving using changes in blood glucose concentrations. Herein, instead of measuring the blood glucose concentrations, subcutaneous tissue glucose concentration (tGLU) was measured in peripartum primiparous (n = 6) and multiparous (n = 8) cows at 15 min intervals using a wearable sensor. A transient increase in tGLU was observed in the peripartum period, with peak individual concentrations occurring between 2.8 h before and 3.5 h after calving. tGLU in primiparous cows was significantly higher than that in multiparous cows. To account for individual variations in basal tGLU, the maximum relative increase in the 3-h moving average of tGLU (Max MA) was used to predict calving. Cutoff points for Max MA were established by parity, with receiver operating characteristic analysis predicting calving within 24, 18, 12, and 6 h. Except for one multiparous cow that showed an increase in tGLU just before calving, all cows reached at least two cutoff points and calving was predicted successfully. The time interval between reaching the tGLU cutoff points that predicted calving within 12 h and actual calving was 12.3 ± 5.6 h. In conclusion, this study demonstrated the potential role of tGLU as a predictive indicator of calving in cows. Advancements in machine learning-based prediction algorithms and bovine-optimized sensors will help in increasing the accuracy of calving prediction using tGLU.

Thermosensitive visible-light-excited visible-/NIR-luminescent complexes with lanthanide sensitized by the π-electronic system through intramolecular H-bonding.

Visible-luminescent lanthanide (LnL) complexes with a highly planar tetradentate ligand were successfully developed for a visible-light solid-state excitation system. L was designed by using two 2-hydroxy-3-(2-pyridinyl)-benzaldehyde molecules bridged by ethylenediamine, which was then coordinated to a series of Ln ions (Ln = Nd, Sm, Eu, Gd, Tb, Dy, and Yb). From the measurement of single-crystal X-ray analysis of EuL, two phenolic O atoms and two imine N atoms in L were coordinated to the Eu ion, and each π-electronic system took coplanar with the edged-pyridine moiety through an intramolecular hydrogen bond. The enol group on the phenolic skeleton changed to the keto form, and the pyridine was protonated. Thus, intramolecular proton transfer occurred in L after the complexation. Other complexes take isostructure. The space group is P-1, and the c-axis shrinks with decreasing temperature without a phase transition in EuL. The yellow color caused by the planar structure of L can sensitize ff emission by visible light, and the luminescence color of each complex depends on central Ln ions. Furthermore, a phosphorescence band also appeared at rt with ff emission in LnL. Drastic temperature dependence of luminescence was clarified quantitatively.

Roadmap on Recent Progress in FINCH Technology.

Fresnel incoherent correlation holography (FINCH) was a milestone in incoherent holography. In this roadmap, two pathways, namely the development of FINCH and applications of FINCH explored by many prominent research groups, are discussed. The current state-of-the-art FINCH technology, challenges, and future perspectives of FINCH technology as recognized by a diverse group of researchers contributing to different facets of research in FINCH have been presented.

Incoherent color digital holography with computational coherent superposition for fluorescence imaging [Invited].

We present color fluorescence imaging using an incoherent digital holographic technique in which holographic multiplexing of multiple wavelengths is exploited. Self-interference incoherent digital holography with a single-path in-line configuration and the computational coherent superposition scheme are adopted to obtain color holographic three-dimensional information of self-luminous objects with a monochrome image sensor and no mechanical scanning. We perform not only simultaneous color three-dimensional sensing of multiple self-luminous objects but also color fluorescence imaging of stained biological samples. Color fluorescence imaging with an improved point spread function is also demonstrated experimentally by adopting a Fresnel incoherent correlation holography system.

Two-step phase-shifting interferometry for self-interference digital holography.

We propose a phase-shifting interferometry technique using only two in-line phase-shifted self-interference holograms. There is no requirement for additional recording or estimation in the measurement. The proposed technique adopts a mathematical model for self-interference digital holography. The effectiveness of the proposed technique is demonstrated by experiments on incoherent digital holographic microscopy and color-multiplexed fluorescence digital holography with computational coherent superposition. Two-color-multiplexed four-step phase-shifting incoherent digital holography is realized for the first time, to the best of our knowledge, using the proposed technique.

Quantum cutting-induced near-infrared luminescence of Yb3+ and Er3+ in a layer structured perovskite film.

Quantum cutting is an attractive optical phenomenon where one high-energy photon is converted into two low-energy photons, resulting in photoluminescence quantum yields (PLQYs) above 100%. In this report, we demonstrate a novel approach to enhance the quantum cutting energy transfer from an all-inorganic perovskite (CsPbCl3) to ytterbium (Yb3+) and erbium (Er3+) ions as near-infrared (NIR) emitters by using the highly orientated crystalline film. Yb3+ ions are fixed in the neighborhood of the CsPbCl3 lattice by preparing a one-to-one layer arrangement consisting of quasi-2D CsPbCl3 perovskite and Yb3+ layers. The successful preparation of layer arrangements resulted in the highly sensitized luminescence of Yb3+ by CsPbCl3 with NIR PLQYs exceeding 130%, which is attributed to quantum cutting. In addition, Er3+ luminescence at 1540 nm is acquired by the co-existence of Er3+ with Yb3+ in a layer, which is a result of the intralayer metal-to-metal energy transfer from Yb3+ activated by CsPbCl3 via the interlayer quantum cutting process. The PLQY of Er3+ luminescence reaches to 12.6%, which is the highest value ever observed for Er3+ compounds, resulting from the efficient interlayer quantum cutting process over 100% and the following intralayer resonance metal to metal energy transfer with the efficiency over 80%.

Spearmint Extract Containing Rosmarinic Acid Suppresses Amyloid Fibril Formation of Proteins Associated with Dementia.

Neurological dementias such as Alzheimer's disease and Lewy body dementia are thought to be caused in part by the formation and deposition of characteristic insoluble fibrils of polypeptides such as amyloid beta (Aß), Tau, and/or α-synuclein (αSyn). In this context, it is critical to suppress and remove such aggregates in order to prevent and/or delay the progression of dementia in these ailments. In this report, we investigated the effects of spearmint extract (SME) and rosmarinic acid (RA; the major component of SME) on the amyloid fibril formation reactions of αSyn, Aß, and Tau proteins in vitro. SME or RA was added to soluble samples of each protein and the formation of fibrils was monitored by thioflavin T (ThioT) binding assays and transmission electron microscopy (TEM). We also evaluated whether preformed amyloid fibrils could be dissolved by the addition of RA. Our results reveal for the first time that SME and RA both suppress amyloid fibril formation, and that RA could disassemble preformed fibrils of αSyn, Aß, and Tau into non-toxic species. Our results suggest that SME and RA may potentially suppress amyloid fibrils implicated in the progression of Alzheimer's disease and Lewy body dementia in vivo, as well.

Aspects of lanthanide complexes for selectivity, intensity and sharpness in luminescence bands from twenty-four praseodymium, europium and gadolinium complexes with differently distorted-hexadentate ligands.

We structurally and spectroscopically investigated a series of praseodymium (Pr) complexes with eight ligands that form helicate molecular structures. The mother ligand skeleton (L) has two bipyridine moieties bridged with ethylenediamine. The bridged skeleton of PrL was changed to diamines 1-methyl-ethylenediamine, trimethylenediamine and 2,2'-dimethyl-trimethylenediamine, and the corresponding ligands were designated as Lme, Lpr and Ldmpr, for each Pr in these complexes upon UV-excitation. The luminescence quantum yields of PrL and PrLpr in the visible and near infrared (NIR) regions indicate that PrL is excited by both the electronic state of the ligand and the ff absorption band, whereas PrLpr is excited through the ligand. The addition of a methyl group to PrL and PrLpr has a different effect on the Pr emission intensity with the intensity of PrLme decreasing more than that of PrL and PrLdmpr and increasing more than that of PrLpr. Thus, the coordination of Pr and the increased rigidity of the ligand upon methylation enhance luminescence. The azomethine moieties on Lme, Lpr and Ldmpr were reduced and formed the corresponding PrLH, PrLmeH, PrLprH and PrLdmprH complexes. The luminescence of the non-methylated series is due to transitions related to the 1D2 level and thus the methylated series luminesces due to high energy levels such as 3PJ arising from the shortened π electronic systems. We also discuss the strong red emission of a series of Eu complexes with eight ligands from the viewpoint of their molecular structures and luminescence efficiencies and evaluate the Judd-Ofelt parameters from the luminescence spectra of Eu complexes.

Cesium Acetate-Induced Interfacial Compositional Change and Graded Band Level in MAPbI3 Perovskite Solar Cells.

Compositional engineering and interfacial modifications have played pivotal roles in the accomplishment of high-efficiency perovskite solar cells (PSCs). Different interfaces in the PSCs influence the performance remarkably either by altering the crystallization of the active material or shifting the energy levels or improving the electrical contact. This work reports how a thin layer of cesium acetate on the TiO2 electron transport layer (ETL) induces generation of a PbI2-rich methylammonium lead iodide (MAPbI3) composition at the ETL/MAPbI3 interface, which downshifts the conduction band level of MAPbI3 to create an energy level gradient favorable for carrier collection, resulting in higher photocurrent, fill factor, and overall power conversion efficiency.

VOC Over 1.4 V for Amorphous Tin-Oxide-Based Dopant-Free CsPbI2Br Perovskite Solar Cells.

CsPbI2Br perovskite solar cells have attracted much attention because of the rapid development in their efficiency and their great potential as a top cell of tandem solar cells. However, the VOC outputs observed so far in most cases are far from that desired for a top cell. Up to now, with various kinds of treatments, the reported champion VOC is only 1.32 V, with a VOC deficit of 0.60 V. In this work, we found that aging of the SnCl2 precursor solution for the electron-transporting layer can promote the VOC of CsPbI2Br solar cells by employing a dopant-free-polymer hole transport material (HTM) over 1.40 V and efficiency over 15.5% with high reproducibility. With the champion VOC of 1.43 V, the VOC deficit was reduced to <0.50 V, which is achieved for the first time. This simple technique of SnCl2 solution aging forms a uniform and smooth amorphous SnOx film with pure Sn4+, elevates the conduction band of SnOx, and reduces the interfacial gaps and the trap state density of the device, resulting in enhancement in average VOC from ∼1.2 V in the nonaged case to ∼1.4 V in the aged case. Furthermore, the device using an aged SnCl2 solution also exhibits a much better long-term stability than that made of the fresh solution. These achievements in dopant/additive-free CsPbI2Br solar cells can be useful for future research on CsPbI2Br and tandem solar cells.

Sensitized Yb3+ Luminescence in CsPbCl3 Film for Highly Efficient Near-Infrared Light-Emitting Diodes.

Near-infrared (NIR) light emitting diodes (LEDs) with the emission wavelength over 900 nm are useful in a wide range of optical applications. Narrow bandgap NIR emitters have been widely investigated using organic compounds and colloidal quantum dots. However, intrinsically low charge mobility and luminescence efficiency of these materials limit improvement of the external quantum efficiency (EQE) of NIR LEDs, which is far from practical applications. Herein, a highly efficient NIR LED is demonstrated, which is based on an energy transfer from wide bandgap all inorganic perovskite (CsPbCl3) to ytterbium ions (Yb3+) as an NIR emitter doped in the perovskite crystalline film. High mobility of electrically excited carriers in the perovskite crystalline film provides a long carrier diffusion and enhances radiative recombination of an emission center due to minimized charge trapping losses, resulting in high EQE value in LEDs. The NIR emission of Yb3+ at around 1000 nm is found to be sensitized by CsPbCl3 thin film with a photoluminescence quantum yield over 60%. The LED based on Yb3+-doped CsPbCl3 film exhibits a high EQE of 5.9% with a peak wavelength of 984 nm, achieved by high carrier transporting ability and effective sensitized emission property in the solid-film structure.

Chiroptical Spectroscopic Studies on Lanthanide Complexes with Valinamide Derivatives in Solution.

Ligands based on 2,2'-bipyridine and valinamide moieties induce circularly polarized luminescence in their europium complexes. Both the R and S enantiomers of the complexes were successfully obtained. Single-crystal X-ray analysis of the racemic crystal confirmed that the ligand is coordinated to the europium ion in a tetradentate fashion. The π-electronic system of the ligand is co-planar with the valinamide moiety, and acts as an efficient photoantenna to sensitize europium luminescence by UV excitation. The luminescence quantum yield (QY) of europium in the valinamide-containing complex was 44 % in acetonitrile. The glum value to evaluate the circularly polarized luminescence was relatively high at |0.13| estimated from their magnetic dipole transitions around 593 nm. For comparison, we prepared hexadentate europium complexes in the S- and R-forms derived from two bipyridine moieties linked by ethylenediamines. The determined QYs were 18 % (S) and 16 % (R), and the glum value |0.12| for the hexadentate complexes. The photophysical properties of the gadolinium complexes of the ligands were also evaluated.

Lanthanide Luminescence Enhancement of Core-Shell Magnetite-SiO2 Nanoparticles Covered with Chain-Structured Helical Eu/Tb Complexes.

Oligomeric-brush chains of helical lanthanide (Ln) complexes retain their structural and luminescent behavior after coating onto magnetic nanoparticles (MNPs) consisting of Fe3O4 covered with silicate. It is one of the type of bifunctional NPs exhibiting luminescence of Ln and superparamagnetism of Fe3O4. In comparison to a simple monolayer of complexes adsorbed on a modified surface, a layer made of luminescent chains allowed us to obtain a more intensive red/green luminescence originating from Eu3+/Tb3+ ions, and at the same time, no visible increase in particle size (compared to Fe3O4@silica particles) was observed. The luminescent properties of the Tb3+ complex were altered by MNPs; the decrease of the luminescence was not as large as expected, the excitation spectrum changed significantly, and the average luminescence lifetime was much longer at room temperature. Surprisingly, this phenomenon was not observed at 77 K and also did not occur for the Eu3+ complexes. The possibility to stack building blocks in a chain using complexes of different lanthanide ions can be used to design novel multifunctional nanosystems.

Lanthanide-Oligomeric Brush Films: From Luminescence Properties to Structure Resolution.

Lanthanide (Ln) based luminescent materials are experiencing an increasing interest in their applications in several fields. In this study, we report a series of new lanthanide-oligomeric brush films, supported on quartz substrates and prepared using a layer-by-layer method (LbL). Oligomeric brush films are composed of small oligomers from our previously reported coordination polymers [x-EuL] and [x-TbL] (with x = 1, 3, and 5 generations of Ln complexes), which are grown perpendicularly from a carboxylate self-assembled monolayer. Oligomers composed of our previously described helical lanthanide complex LnL (Ln: Eu and Tb) as a luminescent moiety and benzene-1,4-dicarboxylate acid (bdc) used as a linker. Mixed films having the fifth-generation Ln complexes composed of equimolar mixture of Eu and Tb ions were prepared. Oligomeric brush films are highly transparent and exhibited a colored emission under UV irradiation. Pure Ln (Eu or Tb) films showed a strong luminescence from the Ln ions. Their luminescent properties depended on the number of lanthanide layers in the films composed of the first to third generations of lanthanide complexes. Then, the increase of the complex layers induced no difference in the luminescent properties. An energy transfer from Tb to Eu ions in the mixed films indicated a short distance between lanthanide ions of a fifth layer. The structural analysis together with the observed luminescent properties and some previous studies allowed to clarify the disposition of the oligomers in the films.

Photomultiplying Visible Light Detection by Halide Perovskite Nanoparticles Hybridized with an Organo Eu Complex.

A molecular layer of an organo europium (Eu) complex was hybridized with the surface of halide perovskite (MAPbI3) nanocrystals to control charge transport between photoexcited perovskites and a metal electrode. A thin hybridized nanocrystalline film was found to cause an efficient photomultiplication reaction based on hole accumulation at photoexcited perovskite nanoparticles and charge tunneling across the Eu complex molecules under application of a low external bias (-0.5 V). A photodetecting device based on the Eu complex and perovskite absorber demonstrated photoinduced current generation at extremely high quantum conversion efficiency of 290 000% for weak monochromatic light (<1 mW cm-2), yielding a power responsivity value up to 1289 A W-1. High sensitivity of photodetection was enabled by using nanosized particles (<5 nm) of perovskite having a high surface area in contact with the Eu complex, while sensitivity was reduced by use of thick and large particle perovskite layers.

Multicolor upconversion luminescence of dye-coordinated Er3+ at the interface of Er2O3 and CaF2 nanoparticles.

Multicolor upconversion luminescence of Er3+ was successfully enhanced by optimizing the interface in dye-coordinated nanoparticles with a core/shell structure. Red and green upconversion emissions of Er3+ were obtained at the interface of oxide nanoparticles via the intramolecular energy transfer from the coordinating squaraine dye with high light-absorption ability, which was more efficient than emissions through the energy transfer from metal ions such as Yb3+. Additionally, CaF2 nanoparticles as a core material minimized the energy loss with nonradiative downward relaxations in Er3+, resulting in the observation of unusual blue upconversion emissions from the upper energy level of Er3+ by nonlaser excitation using a continuous-wave (CW) Xe lamp at an excitation power of 1.2 mW/cm2.

Gelation and luminescence of lanthanide hydrogels formed with deuterium oxide.

Gel formations and efficient lanthanide luminescence appeared in deuterium oxide (D2O) medium instead of light water (H2O), and their solvation possibilities by using luminescence lifetimes were discussed. The lanthanide ions in the hydrogel of 1 obtained by H2O (abbreviated as H2O-Ln1; Ln = Eu, Tb, and Gd) in our previous report act as the coupling part between neighbor molecules for the bundle structure. Here, D2O also acts as a medium to form the lanthanide-hydrogel of 1, and increases intensities of luminescence for Tb, because a soft crystalline state reducing resonance thermal relaxation is realized. The gel-formation and luminescence band positions of Ln1 in D2O corresponded to those in H2O. From the observation of luminescence lifetimes in H2O and D2O, the number of coordinating water molecules on Eu and Tb were estimated to be around 3 or 4 for both. The luminescence intensity of Eu1 did not increase even in D2O, due to a blue shift of the excited triplet state of 1, as compared to that in H2O.

Phosphorescence Resulting from Interaction between Two Non-equivalent Metals on a Helical π-Conjugated Surface.

A [7]helicene bis-ruthenium complex, with one ruthenium atom bound to the cyclopentadienyl (Cp) ring and the other coordinated to the arene ring at the edge of the helicene, was synthesized. This complex showed phosphorescence both in butyronitrile (Φ=31 %, 77 K) and in the solid state (Φ=18 %, 77 K). The two non-equivalent ruthenium metal atoms, attached to the helicene ligand, interact with each other upon photoabsorption and emission.

Alkyl chain elongation and acyl group effects in a series of Eu/Tb complexes with hexadentate π-electronic skeletons and their enhanced luminescence in solutions.

Five Eu complexes with long alkyl chain groups, abbreviated as EuLCx ("x" indicates the number of methylene groups: x = 8, 12, 14, 18, and 22), were synthesized to evaluate their structural and luminescence properties in chloroform. The mother helicate Eu complex, EuL, which has two bipyridine moieties bridged by an ethylenediamine, has been previously reported. A reduced form in which the azomethine groups of L also coordinated to the Eu ion, EuLH, was newly prepared. EuLH also adopts a helicate molecular structure based on single crystal X-ray structural analysis. The amine hydrogens of the bridging ethylenediamine of LH are active sites for substitution and were exchanged with five different alkyl chains to form EuLCx. Luminescence band positions and shapes of EuLCx in chloroform were completely identical, with a quantum yield of 37.1 ± 1.2 and a lifetime of around 1.25 ms. This indicates that the environments surrounding the Eu ion in the various complexes are all similar. Luminescence quantum yields of TbLH and TbLC18 are also strengthened, 48.7% in acetonitrile and 55% in chloroform, respectively. Potential energy surfaces were also described by using density functional theory, suggesting the possibility of a 1 : 2 complex of Eu and the ligand as a main luminescent species in solutions. This 1 : 2 complexation forms Eu-oxygen coordination using acyl groups. It indicates that the acyl group modification results in a different structure from the mother complexes.