Air/liquid interfacial formation process of conductive metal-organic framework nanosheets.

The air/liquid interface is a superior platform to create nanosheets of materials by promoting spontaneous two-dimensional growth of components. Metal-organic frameworks (MOFs)-intrinsically porous crystals-with π-conjugated triphenylene-based ligands show high electrical conductivities. Forming nanosheets of such conductive MOFs should enable their use in electronic devices. Although highly conductive MOF nanosheets have been created at the air/liquid interface, direct control of their continuity, morphology, thickness, crystallinity, and orientation directly influencing device performance remains as an issue to be addressed. Here, we present detailed insights into the formation process of electrically conductive MOF nanosheets composed of 2,3,6,7,10,11-hexaiminotriphenylene (HITP) and Ni2+ ions (HITP-Ni-NS) at the air/liquid interface. The morphological and structural features of HITP-Ni-NS strongly depend on the standing time-the time without any external actions involved, but leaving the interface undisturbed after setting the ligand solution onto the metal-ion solution. We find that the fundamental features of HITP-Ni-NS are determined by the standing time with conductivity sensitively influenced by such pre-determined HITP-Ni-NS characteristics. These findings will lead towards the establishment of a rational strategy for creating MOF nanosheets at the air/liquid interface with desired properties, thereby accelerating their use in diverse potential applications.

Assembling Triphenylene-Based Metal-Organic Framework Nanosheets at the Air/Liquid Interface: Modification by Tuning the Spread Solution Concentration.

Metal-organic frameworks (MOFs)─crystalline coordination polymers─with unique characteristics such as structural designability accompanied by tunable electronic properties and intrinsic uniform nanopores have become the platform for applications in diverse scientific areas ranging from nanotechnology to energy/environmental sciences. To utilize the superior features of MOF in potential applications, the fabrication and integration of thin films are of importance and have been actively sought. Especially, downsized MOFs into nanosheets can act as ultimately thin functional components in nanodevices and potentially display unique chemical/physical properties rarely seen in bulk MOFs. Assembling nanosheets by aligning amphiphilic molecules at the air/liquid interface has been known as the Langmuir technique. By utilizing the air/liquid interface as a reaction field between metal ions and organic ligands, MOFs are readily formed into the nanosheet state. The expected features in MOF nanosheets including electrical conduction largely depend on the nanosheet characteristics such as lateral size, thickness, morphology, crystallinity, and orientation. However, their control has not been achieved as yet. Here, we demonstrate how changing the concentration of a ligand spread solution can modify the assembly of MOF nanosheets, composed of 2,3,6,7,10,11-hexaiminotriphenylene (HITP) and Ni2+ ions (HITP-Ni-NS), at the air/liquid interface. A systematic increase in the concentration of the ligand spread solution leads to the enlargement of both the lateral size and the thickness of the nanosheets while retaining their perfect alignment and preferred orientation. On the other hand, at much higher concentrations, we find that unreacted ligand molecules are included in HITP-Ni-NS, introducing disorder in HITP-Ni-NS. These findings can develop further sophisticated control of MOF nanosheet features, accelerating fundamental and applied studies on MOFs.

Uniaxially Oriented Electrically Conductive Metal-Organic Framework Nanosheets Assembled at Air/Liquid Interfaces.

Although most metal-organic frameworks (MOFs)─highly porous crystalline metal complex networks with structural and functional varieties─are electrically insulating, high electrical conduction has been recently demonstrated in MOFs while retaining permanent porosity. Usability of electronically active MOFs effectively emerges when they are created in a thin-film state as required in major potential applications such as chemiresistive sensors, supercapacitors, and electrode catalysts. Thin-film morphology including crystallinity, thickness, density, roughness, and orientation sensitively influences device performance. Fine control of such morphological parameters still remains as a main issue to be addressed. Here, we report a bottom-up procedure of assembling a conductive MOF nanosheet composed of 2,3,6,7,10,11-hexaiminotriphenylene molecules and nickel ions (HITP-Ni-NS). Creation of HITP-Ni-NS is achieved by applying air/liquid (A/L) interfacial bottom-up synthesis. HITP-Ni-NS has a multilayered structure with 14 nm thickness and is endowed with high crystallinity and uniaxial orientation, demonstrated by synchrotron X-ray crystallography. Facile transferability of HITP-Ni-NS assembled at air/liquid interfaces to any desired substrate enables us to measure its electrical conductivity, recorded as 0.6 S cm-1─highest among those of triphenylene-based MOF nanosheets with a thickness lower than 100 nm.

Bolus injection of contrast agents with various iodine concentrations and delivery rates for intracranial three-dimensional CT angiography: evaluation of intracranial arteriovenous contrast using a multidetector-row CT scanner.

PURPOSE: We evaluated the difference in computed tomography (CT) attenuation values of the intracranial arterial and venous systems among the various contrast injection protocols (higher iodine delivery rate or higher concentration of the agent) on the source images of intracranial three-dimensional CT angiography (3D-CTA) using a multidetector-row CT (MDCT) scanner. MATERIALS AND METHODS: We used 100 ml of iopamidol 300 at an injection rate of 3.0 ml/s, 100 ml of iopamidol 300 at an injection rate of 3.7 ml/s, and 80 ml of iopamidol 370 at an injection rate of 3.0 ml/s. There were 10 patients in each group. Attenuation values of the bilateral internal carotid arteries (ICAs), basilar artery trunk, bilateral cavernous sinuses (CSs), and Galenic vein were measured quantitatively on the axial CT angiographic source images obtained by four-channel MDCT. RESULTS: Injection of the high-concentration contrast with a higher iodine-delivery rate achieved good arteriovenous contrast at the cavernous portion. With the same rate of iodine delivery, injection of the intermediate concentrate agent increased the CT value of not only the ICAs but also the CSs. CONCLUSION: High-concentration contrast could increase ICA attenuation without intracavernous attenuation gain during the "first-pass" phase.

Resection of a locally advanced hilar tumor and the hepatic artery after stepwise hepatic arterial embolization: a case report.

We herein report a case of a hilar tumor with extensive invasion to the proper hepatic artery, which was successfully treated with a radical resection in a 57-year-old female patient after a stepwise hepatic arterial embolization. She underwent right colectomy and partial hepatectomy for advanced colon cancer two years ago and radiofrequency ablation therapy for a liver metastasis one year ago, respectively. A recurrent tumor was noted around the proper hepatic artery with invasion to the left hepatic duct and right hepatic artery 7 mo previously. We planned a radical resection for the patient 5 mo after the absence of tumor progression was confirmed while he was undergoing chemotherapy. To avoid surgery-related liver failure, we tried to promote the formation of collateral hepatic arteries after stepwise arterial embolization of the posterior and anterior hepatic arteries two weeks apart. Finally, the proper hepatic artery was occluded after formation of collateral flow from the inferior phrenic and superior mesenteric arteries was confirmed. One month later, a left hepatectomy with hepatic arterial resection was successfully performed without any major complications.

[A case of direct carotid cavernous fistula, whom three-dimensional computed tomographic angiography was helpful for decision making of selective coil embolization].

We reported the case of an 84-year-old female suffering from chemosis and exophthalmos. Carotid arteriograms revealed a direct carotid-cavernous fistula (CCF) but could not clearly show the fistula point because of its high-flow nature. We then performed three-dimensional computed tomographic angiography (3D-CTA) using a multi detector-row CT (MDCT) scanner. Multi-planar reformatted CT images distinctly revealed a right carotid aneurysm at the cavernous portion and a shunting point between the aneurysm and the cavernous sinus. Based on this information, we opted to performa transvenous coil embolization to treat this patient. Successful selective coil embolization was performed at the fistulous point was done with a smaller number of coils than ordinarily required in sinus packing. Performing 3D-CTA by using a MDCT was helpful in decision making for the selective coil embolization to treat direct CCF.

Attenuation values of the intracranial arterial and venous vessels by bolus injection of various contrast agents: a study with a single-detector helical CT scanner.

PURPOSE: We evaluated the arteriovenous contrast on the source images of intracranial three-dimensional computed tomography (CT) angiography (3D-CTA) using a high-concentration (370 mg I/ml) contrast agent in comparison with intermediate-concentration (300 mg I/ml) contrast. MATERIALS AND METHODS: With a fixed intravenous injection rate and scanning delay, 3D-CTA was performed using a single-detector helical CT scanner in 30 consecutive patients. We used 100 ml of iohexol 300 for 10 patients, 100 ml of iopamidol 300 for 10 patients, and 80 ml of iopamidol 370 for 10 patients. Attenuation values of the bilateral internal carotid arteries, bilateral middle cerebral arteries, basilar artery trunk, bilateral cavernous sinuses, bilateral basal veins, and Galenic vein were measured quantitatively on the axial CT angiographic source images. RESULTS: High-concentration contrast significantly increased the attenuation values of the intracranial arterial system without increasing the attenuation of the venous system. CONCLUSION: High-concentration contrast is helpful for obtaining valuable arteriovenous contrast on source images with intracranial 3D-CTA.

[An experimental study for tumor detection by indocyanine green with near-infrared topography].

We studied tumor detection by indocyanine green (ICG) with near-infrared topography in rat experimental tumors: hepatoma AH109A and osteosarcoma POB 102. Time-intensity curves and topograms after ICG injection were obtained in tumors and surrounding normal tissues. Intensities in tumors were slowly reduced, and intensities in normal tissues were rapidly reduced, resulting in positive tumor image in topogram. It is concluded that near-infrared topography enhanced by ICG is useful for cancer detection.