Efficient Hydrogen Production by a Photoredox Cascade Catalyst Comprising Dual Photosensitizers and a Transparent Electron Mediator.

One-directional electron transport between a photocatalyst and redox mediator is crucial for achieving highly active Z-scheme water-splitting photocatalysis. Herein, a photoredox cascade catalyst that artificially mimics the electron transport chain in natural photosynthesis was synthesized from a Pt-TiO2 nanoparticle catalyst, two photosensitizers (RuCP6 and RuP6), and a visible-light-transparent electron mediator (HCRu). During photocatalytic hydrogen evolution in the presence of a redox-reversible electron donor, [Co(bpy)3]2+ (bpy = 2,2'-bipyridine), the HCRu-Zr-RuCP6-Zr-RuP6@Pt-TiO2 (PRCC-1) photocatalyst exhibited the highest reported initial (1 h) apparent quantum yield (iAQY = 2.23%) of dye-sensitized TiO2 photocatalysts to date. Furthermore, PRCC-1 successfully produced hydrogen when using hydroquinone monosulfonate (H2QS-) as the hydrogen source.

Photocatalyst-Mediator Interface Modification by Surface-Metal Cations of a Dye-Sensitized H2 Evolution Photocatalyst.

To develop highly active H2 evolving dye-sensitized photocatalysts (DSPs) applicable for Z-scheme water splitting, we synthesized a series of Ru(II)-dye-double-layered DSPs, X'-RuCP6-Zr-RuP6@Pt-TiO2 (X'-DSP) with different surface-bound metal cations (X' = Fe2+, Y3+, Zr4+, Hf4+, and Bi3+). In 0.5 M KI aqueous solution, the photocatalytic H2 evolution activity under blue light irradiation (λ = 460 ± 15 nm) increased in the following order: nonmetal-modified DSP, H+-DSP (turn over number for 6 h irradiation = 35.2) < Fe2+-DSP (54.9) ≈ Bi3+-DSP (55.2) < Hf4+-DSP (65.5) ≈ Zr4+-DSP (68.3) ≈ Y3+-DSP (71.5), suggesting that the redox-inactive and highly charged metal cations tend to improve the electron donation from the iodide electron mediator. On the other hand, DSPs having heavy metal cations, Hf4+-DSP (18.4) and Bi3+-DSP (16.6), exhibited better activity under green light irradiation (λ = 530 ± 15 nm) than Zr4+-DSP (15.7) and H+-DSP (7.80), implying the contribution of a heavy atom effect of the surface-bound metal cation to partially allow the spin-forbidden metal-to-ligand charge-transfer excitation.

Vapochromic luminescence of a spin-coated copper(I) complex thin film by the direct coordination of vapour molecules.

A homogeneous thin film of a simple and highly luminescent Cu(i) complex, [CuI(PPh3)2(py)] (PPh3 = triphenylphosphine, py = pyridine) (Cu-py), was fabricated via spin coating using polyvinylpyrrolidone (PVP) and pyridine without destroying the complex. The thin film (Cu-py@PVP), with a thickness of 1 µm, exhibited efficient response to vapour, exhibiting reversible luminescence changes between blue-green and yellow upon exposure to vapours of N-heteroaromatic compounds such as py and 2-methylpyrazine (Mepyz). Vapochromic luminescence colour change resulting from ligand substitution was also observed in the crystal state, but the response of the thin film was remarkably faster than that of the crystalline samples. The vapour-induced ligand exchange on the thin film was fully characterised by comparing the luminescence properties of the Cu-py crystal with the newly prepared Cu(i) complex, [CuI(Mepyz)(PPh3)2] (Cu-Mepyz).

Enhancement of Photocatalytic Activity for Hydrogen Production by Surface Modification of Pt-TiO2 Nanoparticles with a Double Layer of Photosensitizers.

To investigate the effect of the surface structure of dye-sensitized photocatalyst nanoparticles, we prepared three types of RuII -photosensitizer (PS)-double-layered Pt-cocatalyst-loaded TiO2 nanoparticles with different surface structures, Zr-RuCP6 -Zr-RuP6 @N wt %Pt-TiO2 , RuCP6 -Zr-RuP6 @N wt %Pt-TiO2 , and RuCP2 -Zr-RuP6 @N wt %Pt-TiO2 (N=0.2, 1, and 5), and evaluated their photocatalytic H2 evolution activity in the presence of redox-reversible iodide as the electron donor. Although the driving force of the electron injection from I- to the photo-oxidized RuIII PS is comparable, the activity increased in the following order: RuCP2 -Zr-RuP6 @1 wt %Pt-TiO2 < RuCP6 -Zr-RuP6 @1 wt %Pt-TiO2 < Zr-RuCP6 -Zr-RuP6 @1 wt %Pt-TiO2 . The apparent quantum yield of Zr-RuCP6 -Zr-RuP6 @1 wt %Pt-TiO2 in the first hour reached 1 %. Zeta-potential measurements suggest that the surface Zr4+ -phosphate groups attracted I- anions to the nanoparticle-solution interface. Our results indicate that the surface modification of dye-sensitized photocatalysts is a promising approach to enhance photocatalytic activity with various redox mediators.

Two-Step Vapochromic Luminescence of Proton-Conductive Coordination Polymers Composed of Ru(II)-Metalloligands and Lanthanide Cations.

Two proton-conductive and phosphorescent porous coordination polymers, La3-[H5.5RuP]2 and Pr3-[H5.5RuP]2 (H12RuP = [Ru(H4dpbpy)3]2+, H4dpbpy = 2,2'-bipyridine-4,4'-bis(phosphonic acid), composed of Ru(bpy)3-type metalloligands (bpy = 2,2'-bipyridine) functionalized with six phosphonate groups and lanthanide cations (Ln3+ = La3+ or Pr3+) were successfully synthesized. X-ray diffraction studies revealed that six to seven protons of the H12RuP metalloligand were removed in the coordination polymerization reaction to form the porous coordination framework (Ln3-[H5.5RuP]2) with Ln3+ cations (Ln3+ = La3+ or Pr3+). Although their porous structures collapsed on the removal of water molecules from the porous channels, the original porous structures were reconstructed by water adsorption. Interestingly, the triplet metal-to-ligand charge-transfer (3MLCT) emission of Ln3-[H5.5RuP]2 was blue-shifted on increasing the relative humidity (RH) in the low RH region, whereas the inverse red shift was observed in the high RH region, resulting in the highest-energy 3MLCT emission at medium RH. The origin of this two-step vapochromic luminescence (that is, the blue and red shifts of the 3MLCT emission) is ascribable to the water-adsorption-triggered reconstruction of the porous structure and the proton release from the H5.5RuP metalloligand to the water filled channels, respectively. The proton conductivity of Ln3-[H5.5RuP]2 is about 1000-times higher at 20% RH and 10-times higher at 95% RH than that of the carboxylate analog, La7-[RuC]4 (H6RuC = [Ru(H2dcbpy)3]2+; H2dcbpy = 2,2'-bipyridine-4,4'-bis(carboxylic acid)), probably because of the highly acidic phosphonic acid groups.

Distinguishing liver haemangiomas from metastatic tumours using gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid-enhanced diffusion-weighted imaging at 1.5T MRI.

INTRODUCTION: The aim of this study to evaluate the effectiveness of enhanced diffusion-weighted imaging (DWI) for distinguishing liver haemangiomas from metastatic tumours (mets). METHODS: This study included 23 patients with 27 haemangiomas and 26 patients with 46 mets. Breath-holding diffusion-weighted imaging (DWI) (b-values of 0, 50, 100, 150, 200, 400 and 800 s/mm2 ) were obtained before and 20 min after injection of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA). Lesion contrast-to-noise ratios (CNRs) were calculated. The data were processed using the bi-exponential model of intravoxel incoherent motion (IVIM). Receiver operating characteristic analysis was performed to compare the diagnostic performance when distinguishing haemangioma from mets. RESULTS: The CNRs of haemangioma and mets at post-contrast enhancement increased. All IVIM parameters for liver haemangioma and mets showed no significant differences between pre- and post-contrast enhancement. The highest Az value of CNR and IVIM parameters occurred at a post-contrast b-value of 0 s/mm2 and true diffusion (D). The highest qualitative evaluation occurred at a b-value of 800 s/mm2 . The sensitivity and specificity, with a CNR of 100 or higher at a post-contrast b-value of 0 s/mm2 and considered to be haemangioma, were 89% and 67% (<10 mm, 91%, 77%) respectively. The sensitivity and specificity, when D was higher than 1.4 × 10-3 mm2 /s, were 74% and 83% (<10 mm, 64%, 77%) respectively. The sensitivity and specificity of qualitative evaluation by enhanced DWI were 74% and 76% (<10 mm, 64%, 80%) respectively. CONCLUSIONS: The accuracy of the CNR was highest with b = 0; however, examination at high b-values had advantages in the qualitative evaluation of some small-size lesions.

Ureteral intussusception associated with a fibroepithelial polyp: a case report.

We present a case of a 67-year-old man with intussusception of the right ureter associated with a fibroepithelial polyp. The concentric sign and line sign are characteristic radiological findings in intussusception, and these findings could be seen in the present case. Although this entity is rare, its radiological findings are specific. Multidetector row computed tomography and its multiplanar reconstruction make the diagnosis feasible, although the qualitative diagnosis of the tumor was difficult.

Two cases of sclerosing angiomatoid nodular transformation of the spleen with gradual growth: usefulness of diffusion-weighted imaging.

Sclerosing angiomatoid nodular transformation (SANT) is a recently recognized and rare, nonneoplastic lesion of the spleen. Some papers have reported an increased SANT diameter during the follow-up period. We present two cases of SANT whose size increased during the follow-up period. Diffusion-weighted magnetic resonance imaging (DWI) findings correlated well with the pathological findings of SANT, the multinodular high-intensity area as the angiomatoid nodules and the peripheral low-intensity area as fibrous tissues. Therefore, DWI may be a useful imaging tool.

Distinguishing hepatic hemangiomas from metastatic tumors using T1 mapping on gadoxetic-acid-enhanced MRI.

OBJECTIVE: The objective was to evaluate the usefulness of T1 mapping in distinguishing hepatic hemangiomas from metastatic tumors on gadoxetic-acid-enhanced magnetic resonance imaging. METHODS: We examined 20 hemangiomas in 14 patients and 21 metastatic tumors in 11 patients. We performed T1 mapping using the double-flip angle method before and after the injection of gadoxetic acid. Quantitative evaluation was carried out using the pre- and post-contrast enhancement ratios (CERs), and qualitative evaluation was conducted to evaluate the added value of T1 mapping using receiver operating characteristics analysis. RESULTS: The mean CERs of metastatic tumors at 70 s, 240 s and 20 min after the injection of gadoxetic acid were 1.54 (95% confidence interval: 1.37-1.71), 1.47 (1.34-1.6) and 1.30 (1.19-1.41); those of hemangiomas were 3.36 (2.41-4.31), 3.06 (2.44-3.68) and 2.20 (2.02-2.38), respectively. The mean CERs of hemangiomas were significantly higher than those of metastatic tumors (P<.05). When the mean CER cutoff value 20 min after the injection was set at 1.6, the diagnostic sensitivity of hepatic hemangiomas was 100%. There was no added value observed statistically in the qualitative evaluation of T1 mapping (P>.05). CONCLUSION: It is valuable to evaluate quantitatively T1 mapping 20 min after hepatobiliary phase acquisition in the case of difficulty in distinguishing hepatic hemangiomas from metastatic tumors qualitatively.

MR characterization of focal nodular hyperplasia: gadoxetic acid versus superparamagnetic iron oxide imaging.

PURPOSE: We evaluated the diagnostic efficacy of gadoxetic acid- and superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging for focal nodular hyperplasia (FNH). MATERIALS AND METHODS: We retrospectively evaluated 11 patients with 11 FNHs. Both gadoxetic acid- and SPIO-enhanced MR imaging were performed. A 3-dimensional (3D) volumetric interpolated breath-hold examination was used with the gadoxetic acid dynamic study. SPIO-enhanced MR imaging included T2- and T2*-weighted images. We quantitatively and qualitatively compared lesion-specific enhancement of both contrast media. RESULTS: The mean signal-to-noise (S/N) ratio of the FNH lesions differed significantly on pre- and postenhanced imaging of each contrast medium (P<0.05); mean contrast-to-noise (C/N) ratio did not (P>0.05). All observers described all lesions as hyperintense in the arterial phase on gadoxetic acid-enhanced MR imaging and observed the presence of central scar, fibrous septa, and rim most clearly in gadoxetic acid-enhanced hepatobiliary phase images. CONCLUSION: Gadoxetic acid-enhanced MR imaging was more useful than SPIO-enhanced MR imaging in characterizing FNH.

Comparison of Kupffer-phase Sonazoid-enhanced sonography and hepatobiliary-phase gadoxetic acid-enhanced magnetic resonance imaging of hepatocellular carcinoma and correlation with histologic grading.

OBJECTIVES: To determine the relative wash-out of hepatocellular carcinomas and dysplastic nodules using Kupffer-phase sonography with Sonazoid (Daiichi-Sankyo, Tokyo, Japan) enhancement and hepatobiliary-phase gadoxetic acid-enhanced magnetic resonance imaging (MRI) in the evaluation of the histopathologic grades of individual nodules. METHODS: This retrospective study included 66 consecutive patients with 78 histologically confirmed hepatocellular carcinomas and dysplastic nodules. In patients with carcinomas, 33 were well differentiated; 29 were moderately differentiated; and 11 were poorly differentiated; and there were 5 dysplastic nodules. All patients underwent both gadoxetic acid-enhanced MRI and Sonazoid-enhanced sonography. The interval between the two imaging examinations was less than 30 days. Six radiologists independently reviewed both images and rated the degree of relative wash-out between the tumorous and nontumorous areas on Kupffer- and hepatobiliary-phase images using a continuous rating scale. We compared these results with the histopathologic grade of each nodule, and the results were then analyzed with multireader multicase receiver operating characteristic analysis. RESULTS: The average Kupffer-phase (P < .001) and hepatobiliary-phase (P = .004) rating scores increased as the carcinomas became less differentiated (Kruskal-Wallis test). The diagnostic accuracies of the average area under the receiver operating characteristic curve, which were estimated using the confidence levels of the relative wash-out of the Kupffer- and hepatobiliary-phase images, were 0.705 and 0.785 for dysplastic nodules versus well-, moderately, and poorly differentiated carcinomas (P = .517), 0.791 and 0.687 for dysplastic nodules and well-differentiated carcinomas versus moderately and poorly differentiated carcinomas (P = .093), and 0.871 and 0.716 for dysplastic nodules and well-and moderately differentiated carcinomas versus poorly differentiated carcinomas (P = .005), respectively. CONCLUSIONS: Kupffer-phase Sonazoid-enhanced sonography and hepatobiliary-phase gadoxetic acid-enhanced MRI may be useful in estimating the histologic grade, although Kupffer-phase Sonazoid-enhanced sonography may be more accurate in distinguishing hepatocellular carcinomas, especially moderately and poorly differentiated types.