A new Mo 6 cluster complex and its silica and polyurethane composites have been synthesized and characterized. These materials are highly luminescent with emission above 650 nm, produce singlet oxygen with high efficiency, are photostable, and can be excited up to 580 nm. These proper-[a] Institute of Inorganic Chemistry of the AS CR, v.v.i Husinec-Ř ež 1001, 25068 Ř ež,

The excited-state dynamics, luminescence, and redox properties of a series of hexanuclear molybdenum cluster complexes, (nBu4N)2[Mo6X14] and (nBu4N)2[Mo6X8(CF3COO)6] (X = Cl, Br, or I), were investigated. Substitution of the apical halogen ligands for the trifluoroacetate ligands increased the oxidation potentials and induced a blue shift in the absorption and luminescence bands as well as a considerable increase in the luminescence quantum yields for heavy inner ligands. Time-resolved transient absorption measurements showed that the intersystem crossing from the excited singlet states is ultrafast with time constants ranging between <120 fs and 1.68 ps and leads to hot triplet states. The following cooling occurred at a ps time scale and was assigned to electronic redistribution within the emissive triplet state sublevels. The formation of singlet oxygen, O2((1)Δg), suggested earlier on the basis of photooxidation experiments for some complexes, was revised by direct measurements of O2((1)Δg) phosphorescence. We showed the effects of the attached ligands on key physico-chemical and photophysical parameters of the title complexes. The synthesis and structural characterisation of a new cluster complex, (nBu4N)2[Mo6Br8(CF3COO)6], completed the series. Our results demonstrated that the complexes with heavy inner ligands (Br, I) and apical trifluoroacetate ligands were photochemically and electrochemically stable, highly luminescent, and good sensitisers of O2((1)Δg).

Newly synthesized zinc phthalocyanine bearing sixteen quaternized imidazolyl moieties on the periphery displays high water-solubility, lack of aggregation and high singlet oxygen quantum yield in water (ΦΔ > 0.33). The in vitro tests indicated excellent anticancer photodynamic activity (EC50 = 36.7 nM) and low dark toxicity to non-cancerous cells (TC50 = 395 μM).

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Polystyrene ion-exchange nanofiber materials with large surface areas and adsorption capacities were prepared by electrospinning followed by the sulfonation and adsorption of a cationic 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin (TMPyP) photosensitizer on the nanofiber surfaces. The morphology, structure, and photophysical properties of these nanofiber materials were characterized by microscopic methods and steady-state and time-resolved fluorescence and absorption spectroscopies. The externally bound TMPyP can be excited by visible light to form triplet states and singlet oxygen O2((1)Δg) and singlet oxygen-sensitized delayed fluorescence (SODF). The photophysical properties of the nanofibers were strongly dependent on the amount of bound TMPyP molecules and their organization on the nanofiber surfaces. The nanofibers demonstrated photooxidative activity toward inorganic and organic molecules and antibacterial activity against E. coli due to the sensitized formation of O2((1)Δg) that is an effective oxidation/cytotoxic agent. The nanofiber materials also adsorbed heavy metal cations (Pb(2+)) and removed them from the water environment.

Inimitable properties of carbon quantum dots as well as a cheap production contribute to their possible application in biomedicine especially as antibacterial and antibiofouling coatings. Fluorescent hydrophobic carbon quantum dots are synthesized by bottom-up condensation method and used for deposition of uniform and homogeneous Langmuir−Blodgett thin films on different substrates. It is found that this kind of quantum dots generates singlet oxygen under blue light irradiation. Antibacterial and antibiofouling testing on four different bacteria strains (Escherichia coli, Staphylococcus aureus, Bacillus cereus, and Pseudomonas aeruginosa) reveals enhanced antibacterial and antibiofouling activity of hydrophobic carbon dots thin films under blue light irradiation. Moreover, hydrophobic quantum dots show noncytotoxic effect on mouse fibroblast cell line. These properties enable potential usage of hydrophobic carbon quantum dots thin films as excellent antibacterial and antibiofouling coatings for different biomedical applications.

Newly synthesized octahedral molybdenum cluster compound (n-Bu4N)2[Mo6I8(OOC-1-adamantane)6] revealed uncharted features applicable for the development of X-ray inducible luminescent materials and sensitizers of singlet oxygen, O2((1)Δg). The compound exhibits a red-NIR luminescence in the solid state and in solution (e.g., quantum yield of 0.76 in tetrahydrofuran) upon excitation by UV-vis light. The luminescence originating from the excited triplet states is quenched by molecular oxygen to produce O2((1)Δg) with a high quantum yield. Irradiation of the compound by X-rays generated a radioluminescence with the same emission spectrum as that obtained by UV-vis excitation. It proves the formation of the same excited triplet states regardless of the excitation source. By virtue of the described behavior, the compound is suggested as an efficient sensitizer of O2((1)Δg) upon X-ray excitation. The luminescence and radioluminescence properties were maintained upon embedding the compound in polystyrene films. In addition, polystyrene induced an enhancement of the radioluminescence intensity via energy transfer from the scintillating polymeric matrix. Sulfonated polystyrene nanofibers were used for the preparation of nanoparticles which form stable dispersions in water, while keeping intact the luminescence properties of the embedded compound over a long time period. Due to their small size and high oxygen diffusivity, these nanoparticles are suitable carriers of sensitizers of O2((1)Δg). The presented results define a new class of nanoscintillators with promising properties for X-ray inducible photodynamic therapy.

Polyurethane (PUR) nanofabrics based on nanofibers of average diameters in the range of 250-110 nm with different meso-tetraphenylporphyrin (TPP) loading (0.01-5 wt %) were prepared by an electrospinning process. The oxygen quenching of excited states and singlet oxygen-sensitized delayed fluorescence (SODF) of TPP were studied at different oxygen pressures. We found that TPP in PUR matrix is present in monomeric state, and it is easily accessed by oxygen. Analysis of the kinetics of the TPP triplet, singlet oxygen, and SODF indicates that repopulation of TPP fluorescent state includes reaction of singlet oxygen with TPP triplets. The integrated SODF achieved more than 20% of the prompt fluorescence for nanofabric loaded with 5 wt % TPP. The dependence of SODF intensity on the TPP concentration in nanofibers is nearly quadratic.