Ultra-sensitive detection of pyridine in water using zinc porphyrin incorporated in a transparent hydrophobic film

In this study, we investigated the axial coordination reaction between pyridine and zinc meso-tetra(4-sulfonatophenyl)porphyrin (ZnTPPS) incorporated in a transparent layered double hydroxide (LDH) film modified with 1-decanesulfonate (C10S) in an aqueous solution. The apparent equilibrium constant ([Formula: see text]) of the axial coordination reaction between pyridine and ZnTPPS incorporated in the transparent ZnTPPS/C10S/LDH film was approximately 260 times that of the corresponding reaction in an aqueous solution. The hydrophobisation of the LDH interlayer space by C10S, which led to the elimination of water molecules surrounding ZnTPPS and enabled the accumulation of pyridine molecules, was responsible for such a significant increase in the apparent [Formula: see text] value. The developed film can detect pyridine in aqueous solutions with ultra-high sensitivity in the order of 10^-5 mol/L through changes in the colour tone, which is comparable to the molecular detection ability of insect antennae. The sensing response was also observed at pyridine concentrations as low as 10^-9 mol/L.

Synthesis, photodynamic activities, and cytotoxicity of new water-soluble cationic gallium(III) and zinc(II) phthalocyanines

The cationic Ga(III) and Zn(II) phthalocyanines carrying N-methyl-pyridinium groups at eight peripheral β-positionshave been synthesized. These complexes are highly soluble in dimethyl sulfoxide (DMSO) and moderately soluble in water and phosphate buffered saline (PBS); both Ga(III)Cl and Zn(II) complexes have shown no aggregation in water up to 1.2 × 10^-4 and 1.5 × 10^-5 M, respectively. A higher water-solubility of Ga(III)Cl complex as compared to Zn(II) complex is ascribed to the presence of an axially coordinated chloride. The spectroscopic properties, photogeneration of singlet oxygen (¹O₂), and cytotoxicity of these complexes have been investigated. The absolute quantum yields (ΦΔ_absolute) for the photogeneration of singlet oxygen using Ga(III)Cl and Zn(II) complexes have been determined to be 4.4 and 5.3%, respectively, in DMSO solution. The cytotoxicity and intracellular sites of localization of Ga(III)Cl and Zn(II) complexes have been evaluated in human HEp2 cells. Both complexes, localized intracellularly in multiple organelles, have shown no cytotoxicity in the dark. Upon exposure to a low light dose (1.5 J/cm²), however, Zn(II) complex has exhibited a high photocytotoxicity. The result suggests that Zn(II) complex can be considered as a potential photosensitizer for Photodynamic therapy (PDT).

Optical Humidity Sensing Using Transparent Hybrid Film Composed of Cationic Magnesium Porphyrin and Clay Mineral

A transparent hybrid film composed of cationic magnesium porphyrin and clay mineral was developed, and its chromic behavior depending on relative humidity (RH) was investigated. The hybrid film was obtained via intercalation of magnesium porphyrin into clay film; magnesium porphyrin was intercalated into the interlayer spaces of the clay mineral without aggregation. The absorption spectra of the hybrid film showed red shifts compared to the aqueous solution of magnesium porphyrin because of the π-conjugated system extension with coplanarization of the meso-substituted pyridinium group and porphyrin ring. The absorption maximum of the hybrid film was gradually shifted to a shorter wavelength, and the color of the hybrid film was changed with increasing RH. The X-ray diffraction measurement suggested that the basal space of clay was expanded with increasing RH, indicating that the interlayer space of clay was expanded by water adsorption, and the spectral shift was induced by the change in coplanarization degree between the porphyrin ring and meso-substituted pyridinium groups.

Preparation, photophysical characterization, and modeling of LDS722/Laponite 2D-ordered hybrid films

A novel hybrid material with promising optical properties for nonlinear optical applications is presented, as formed by LDS 722 organic dye confined in Laponite clay. Thin films of the hybrid material with different dye loadings have been prepared. The film thickness, the dye and water content, and the clay swelling due to guest molecule incorporation have been characterized. Then, the photophysical properties of the thin films have been studied in detail using experimental methods and molecular simulation. As the dye load increases, the hybrid films present a hypsochromic shift in absorption and a bathochromic shift in emission. The former is attributed to the increasing strength of solvation of the dye donor group, while the latter is ascribed to a switch from an intramolecular to an intermolecular charge-transfer process as the dye load increases. The LDS 722 molecules are preferentially oriented in the host clay almost in parallel to the platelet surfaces, inducing macroscopic order that makes the material responsive to polarized light.

Hybridization between periodic mesoporous organosilica and a Ru(II) polypyridyl complex with phosphonic acid anchor groups

A new method for the hybridization of a ruthenium(II) polypyridyl complex ([Ru(bpy)2((CH2PO3H2)2-bpy)](2+) (RuP2(2+): bpy =2,2'-bipyridine; (CH2PO3H2)2-bpy =2,2'-bipyridine-4,4'di(metylphosphonic acid)) with biphenylene-bearing periodic mesoporous organosilica (Bp-PMO made from 4,4'bis(triethoxysilyl)biphenyl [(C2H5O)3Si-(C6H4)2-Si(OC2H5)3]) was developed. Efficient and secure fixation of the ruthenium(II) complex with methylphosphonic acid groups (RuP2(2+)) in the mesopores of Bp-PMO occurred. This method introduced up to 660 μmol of RuP2(2+) in 1 g of Bp-PMO. Two modes of adsorption of RuP2(2+) in the mesopores of Bp-PMO were observed: one is caused by the chemical interaction between the methylphosphonic acid groups of RuP2(2+) and the silicate moieties of Bp-PMO and the other is attributed to aggregation of the RuP2(2+) complexes. In the case of the former mode, adsorbed RuP2(2+) (up to 80-100 μmol g(-1)) did not detach from Bp-PMO after washing with acetonitrile, dimethylformamide, or even water. Emission from the excited biphenylene (Bp) units was quantitatively quenched by the adsorbed RuP2(2+) molecules in cases where more than 60 μmol g(-1) of RuP2(2+) was adsorbed, and emission from RuP2(2+) was observed. Quantitative emission measurements indicated that emission from approximately 100 Bp units can be completely quenched by only one RuP2(2+) molecule in the mesopore, and photons absorbed by approximately 400 Bp units are potentially accumulated in one RuP2(2+) molecule.

High density intercalation of porphyrin into transparent clay membrane without aggregation

Cationic porphyrin was successfully intercalated into transparent clay membrane by developing the new strategy for the sample preparation conditions. When water:ethanol = 1:2 (v:v) was used as solvent for porphyrin penetration process, high density intercalation of porphyrin into the clay membrane was achieved. In the interlayer space, porphyrin molecules do not aggregate owing to intercharge distance matching effect (size-matching effect), even at high density condition. Judging from XRD and absorption measurements, the orientations of the porphyrins in the clay layers should be almost parallel to the clay nanosheet as monolayer. Because the fluorescence quantum yield did not depend on its loading level, it is turned out that intercalated TMPyP in the clay film keeps the photoactivity even under the high density conditions.