Takashi Hayashita

A thiourea-based chromoionophore for selective binding and sensing of acetate

Abstract Highly selective binding and sensing of acetate over various monovalent inorganic anions (MeCO 2 − ≫H 2 PO 4 − >Cl − , Br − , I − , SCN − , NO 3 − , HSO 4 − , ClO 4 − ) are achieved by N , N ′-bis( p -nitrophenyl)thiourea as a hydrogen-bonding chromoionophore in 1% water–99% MeCN (v/v), and acetic acid in vinegar is successfully determined by the complexation-induced chromogenic response of this chromoionophore.

Highly selective recognition of lead ion in water by a podand fluoroionophore/γ-cyclodextrin complex sensor

We report herein a novel podand fluoroionophore/gamma-cyclodextrin (gamma-CyD) complex sensor that shows markedly high selectivity for lead (Pb2+) ion in water.

Selective Liquid Membrane Transport of Lead(II) by an Acyclic Polyether Dicarboxylic Acid Ionophore.

The effects of the chain structure and substitutents in six acyclic polyether dicarboxylic acids and one acyclic polyether carboxylic acid upon the efficiency and selectivity of pH-driven Pb(2+) transport in a bulk chloroform membrane system have been assessed. Among the carriers, 1,2-bis[2-(o-carboxyphenoxy)ethoxy]-4-tert-butylbenzene (1) is found to exhibit high selectivity for transport of Pb(2+) compared with alkali metal cations and a variety of other divalent metal ion species. Ionophore 1 also extracts Pb(2+) from aqueous solution into chloroform with the loss of two protons. A 1:1 complex of Pb(2+) with di-ionized 1 was isolated.

Chromoionophores Based on Crown Ethers and Related Structures for Alkali Metal Ion Sensing in Aqueous Media

Recent progress in chromoionophores based on (1) spherand and hemispherand, (2) cryptand, and (3) dibenzo-16-crown-5 and calix[4]crown which selectively respond to alkali metal ions in aqueous media is reviewed in relation to their molecular structure and photometric function. The design concept of the chromoionophores for colorimetry in aqueous media is discussed in the light of their acid dissociation and metal complex formation equilibria.

Positioning dependent anion recognition by thiourea-based chromoionophores via hydrogen bonding in aqueous vesicle solutions

A cationic vesicle interface exhibited a filter function for less hydrophobic anions, and highly selective anion recognition via hydrogen bonding was achieved by thiourea-based chromoionophores (Cn-TU) located deep inside the vesicle.

Design and Function of Supramolecular Recognition Systems Based on Guest-Targeting Probe-Modified Cyclodextrin Receptors for ATP

In this study, we have developed a rational design strategy to obtain highly selective supramolecular recognition systems of cyclodextrins (CyDs) on the basis of the lock and key principle. We designed and synthesized dipicolylamine (dpa)-modified γ-CyD-Cu2+ complexes possessing an azobenzene unit (Cu·1-γ-CyD) and examined how they recognized phosphoric acid derivatives in water. The results revealed that Cu·1-γ-CyD recognized ATP with high selectivity over other phosphoric acid derivatives. The significant blue shift in the UV-vis spectra and 1H NMR analysis suggested that the selective ATP recognition was based on the multipoint interactions between the adenine moiety of ATP and both the CyD cavity and the azobenzene unit in addition to the recognition of phosphoric moieties by the Cu-dpa complex site. Our unique receptor made it capable of distinguishing ATP from AMP and ADP, revealing the discrimination of even a length of one phosphoric group. This study demonstrates that, compared to conventional recognition systems of CyDs, this multipoint recognition system confers a higher degree of selectivity for certain organic molecules, such as ATP, over their similar derivatives.

The design of phenylboronic acid azoprobe–polyamidoamine dendrimer complexes as supramolecular sensors for saccharide recognition in water

The selective molecular recognition event by physical or chemical signals is a key concept for the design of novel supramolecular sensors. In this study, we designed a novel saccharide recognition system based on the self-assembly of phenylboronic acid azoprobes (1-BAzo-NPs) on the surface of the polyamidoamine (PAMAM) dendrimer in water. The two sulfonic acid moieties in 1-BAzo-NP enhanced the binding affinity of the azoprobe for the PAMAM dendrimer surface. UV-Vis spectral measurements indicated that 1-BAzo-NP showed poor saccharide recognition at pH 7.0, whereas the 1-BAzo-NP–PAMAM complex well recognized the saccharides, particularly glucose. The complexation with glucose yielded aggregates having diameters of 100–200 nm as determined by dynamic light scattering (DLS) measurements and transmission electron microscopy (TEM). The sensitivity to and selectivity for the saccharides were controlled by the density of the assembled phenylboronic acid azoprobes and PAMAM generation. Together, the results revealed that the selective saccharide recognition at pH 7.0 was feasible by boronic acid assembly on the PAMAM dendrimer surface.

Lead Ion Selective Signal Amplification by a Supramolecular Podand Fluoroionophore/Surfactant Complex Sensor in Water

Below the critical micelle concentration (cmc) of Triton X-100, a PD-18C6/Triton X-100 complex was found to exhibit an amplified fluorescence response for Pb2 +  in water. No such signal amplification was noted above the cmc. Dynamic light scattering and dark-field microscope analyses revealed that the PD-18C6/Triton X-100 complex formed micron-size aggregates (1.24±0.39 μm) triggered by selective Pb2 +  binding, resulting in the enhancement of fluorescence intensity with a distinct blue shift of the fluorescence emission at pH 5.70. This is a novel supramolecular function of a PD-18C6/Triton X-100 complex sensor for selective Pb2 +  recognition in water.

Photocurrent enhancement of porphyrin molecules over a wide-wavelength region based on combined use of silver nanoprisms with different aspect ratios

We succeeded in controlling the wavelength range in which the photocurrent of porphyrin is enhanced by tuning as well as expanding the wavelength ranges in which the localized surface plasmon resonance (LSPR) occurs. We fabricated photoelectric conversion systems consisting of 5,10,15,20-tetrakis(p-carboxyphenyl)porphyrin (TCPP) and silver nanoprisms with small (SAgPRs) and large (LAgPRs) aspect ratios as plasmonic nano-antennae. Their photocurrents were much larger than those from TCPP-modified Ag planar electrodes at the specific wavelengths corresponding to their LSPR bands (SAgPRs: 460–610 nm; LAgPRs: 610–690 nm). The maximum enhancement factors (EFs) for the SAgPRs and the LAgPRs were 37 and 35, respectively. In order to enhance the photocurrents, we expanded the LSPR bands by the combined use of SAgPRs and LAgPRs. The system consisting of the mixture (MAgPRs) showed enhancement of the photocurrent over the entire Q-band region (480–690 nm). Finally, the total EFs of the photocurrents were evaluated by irradiation with AM1.5G sunlight through a long-pass filter of 480 nm and the results revealed that the EFs were in the order of MAgPRs > SAgPRs > LAgPRs. Furthermore, the system showed stability without loss of the enhancement property for at least 10 min under the solar irradiation.

An acyclic polyether dicarboxylic acid ionophore with high selectivity for pH-driven uphill transport of lead(II) ion

1,2-Bis[2-(o-carboxyphenyloxy)ethoxy]-4-tert-butylbenzene transports PbII ion against its concentration gradient in a liquid membrane system with high selectivity over a variety of monovalent and divalent metal ions.