Acute large-vessel occlusion due to an infected thrombus formation induced by invasive sphenoid sinus aspergillosis: illustrative case.

BACKGROUND: The authors describe a rare case of acute large-vessel occlusion due to an infected thrombus formation that was induced by invasive sphenoid sinus aspergillosis. OBSERVATIONS: An 82-year-old man with a history of immunoglobulin G4-related disease and long-term use of steroids and immunosuppressants was admitted to the authors' hospital with severe right hemiparesis. Cerebral angiography revealed occlusion of the left internal carotid artery (ICA). He underwent thrombectomy, resulting in successful recanalization. However, severe stenosis was evident in the left ICA cavernous segment. Pathological analysis of the retrieved thrombus identified Aspergillus. Postoperative magnetic resonance imaging revealed sinusitis in the left sphenoid sinus as a possible source of the infection. The patient's general condition deteriorated during the course of hospitalization due to refractory aspiration pneumonia, and he died 46 days after thrombectomy. Pathological autopsy and histopathological investigation of the left ICA and the left sphenoid sinus showed that Aspergillus had invaded the wall of the left ICA from the adjacent sphenoid sinus. These findings indicate a diagnosis of acute large-vessel occlusion due to infected thrombus formation induced by invasive sphenoid sinus aspergillosis. LESSONS: Pathological analysis of a retrieved thrombus appears useful for identifying rare stroke etiologies such as fungal infection.

Successful carotid stenting of a carotid arterial dissection after straightening the tortuosity using an inflated balloon guiding catheter and the delivery wire of an anchored stent retriever.

The authors present a patient with carotid dissection in a tortuous arterial segment who successfully underwent carotid artery stenting (CAS) by straightening the tortuosity using an inflated balloon guiding catheter (BGC) and a stent retriever (SR). A 56-year-old man was transferred to our institute with right hemiparesis and a National Institutes of Health Stroke Scale score of 9. Magnetic resonance imaging showed left internal carotid artery (ICA) occlusion and ischemic change in the parietal lobe. Emergent angiography revealed tapered extracranial ICA occlusion sugg carotid artery dissection (CAD). CAS was attempted for CAD due to a mismatch of the motor area on clinical imaging. However, several attempts to navigate the stent delivery system over a guidewire failed. Therefore, we deployed a Trevo NXT ProVue SR (3 × 32 mm) in the middle cerebral artery, inflated a BGC, and then pulled on both to straighten the tortuous carotid artery, which resulted in successful navigation of the stent delivery system. The patient's symptoms improved after the recanalization. This case demonstrates the utility of a technique for navigation of a stent delivery system through a tortuous carotid artery in which the tortuosity is straightened by pulling on an inflated BGC and the delivery wire of the SR.

Understanding the reaction mechanism and kinetics of photocatalytic oxygen evolution on CoOx-loaded bismuth vanadate.

Photocatalytic water splitting for green hydrogen production is hindered by the sluggish kinetics of oxygen evolution reaction (OER). Loading a co-catalyst is essential for accelerating the kinetics, but the detailed reaction mechanism and role of the co-catalyst are still obscure. Here, we focus on cobalt oxide (CoOx) loaded on bismuth vanadate (BiVO4) to investigate the impact of CoOx on the OER mechanism. We employ photoelectrochemical impedance spectroscopy and simultaneous measurements of photoinduced absorption and photocurrent. The reduction of V5+ in BiVO4 promotes the formation of a surface state on CoOx that plays a crucial role in the OER. The third-order reaction rate with respect to photohole charge density indicates that reaction intermediate species accumulate in the surface state through a three-electron oxidation process prior to the rate-determining step. Increasing the excitation light intensity onto the CoOx-loaded anode improves the photoconversion efficiency significantly, suggesting that the OER reaction at dual sites in an amorphous CoOx(OH)y layer dominates over single sites. Therefore, CoOx is directly involved in the OER by providing effective reaction sites, stabilizing reaction intermediates, and improving the charge transfer rate. These insights help advance our understanding of co-catalyst-assisted OER to achieve efficient water splitting.

Endovascular embolization and needle aspiration of a life-threatening cervical hematoma due to a neurofibromatosis type 1-associated arteriovenous fistula: illustrative case.

BACKGROUND: In cases of neurofibromatosis in which the bleeding source is considered strongly related to a neurofibroma, an open surgical approach could risk uncontrollable bleeding from the vascular wall infiltration by neurofibroma. The case of a neurofibromatosis type 1 (NF1)-associated arteriovenous fistula presenting with a life-threatening cervical hematoma that was successfully treated with alternative treatment is described. OBSERVATIONS: A 68-year-old woman diagnosed with NF1 presented with sudden onset of a spontaneous right cervical mass. Neck imaging on admission showed a massive subcutaneous hematoma with tracheal deviation and abnormal vascular structure in the hematoma. Digital subtraction angiography showed that an arteriovenous fistula (AVF) fed from a vertebral artery located within the hematoma cavity was the primary source of bleeding and feeding arteries from the occipital artery to the neurofibroma. Embolization of the cervical neurofibroma, as well as the AVF, was performed to reduce the secondary risk of bleeding, and was accomplished. After endovascular treatment, needle aspiration of the cervical hematoma was performed to reduce the mass effect. LESSONS: When performing open surgery via tissues with neurofibromatosis proliferation, uncontrollable bleeding can occur. Therefore, endovascular embolization and needle aspiration of the hematoma should be considered in this setting.

Intracranial aneurysm rupture within three days after receiving mRNA anti-COVID-19 vaccination: Three case reports.

Background: Although neurological adverse events have been reported after receiving coronavirus disease 2019 (COVID-19) vaccines, associations between COVID-19 vaccination and aneurysmal subarachnoid hemorrhage (SAH) have rarely been discussed. We report here the incidence and details of three patients who presented with intracranial aneurysm rupture shortly after receiving messenger ribonucleic acid (mRNA) COVID-19 vaccines. Case Description: We retrospectively reviewed the medical records of individuals who received a first and/ or second dose of mRNA COVID-19 vaccine between March 6, 2021, and June 14, 2021, in a rural district in Japan, and identified the occurrences of aneurysmal SAH within 3 days after mRNA vaccination. We assessed incidence rates (IRs) for aneurysmal SAH within 3 days after vaccination and spontaneous SAH for March 6-June 14, 2021, and for the March 6-June 14 intervals of a 5-year reference period of 2013-2017. We assessed the incidence rate ratio (IRR) of aneurysmal SAH within 3 days after vaccination and spontaneous SAH compared to the crude incidence in the reference period (2013-2017). Among 34,475 individuals vaccinated during the study period, three women presented with aneurysmal SAH (IR: 1058.7/100,000 person-years), compared with 83 SAHs during the reference period (IR: 20.7/100,000 persons-years). IRR was 0.026 (95% confidence interval [CI] 0.0087-0.12; P < 0.001). A total of 28 spontaneous SAHs were verified from the Iwate Stroke Registry database during the same period in 2021 (IR: 34.9/100,000 person-years), and comparison with the reference period showed an IRR of 0.78 (95%CI 0.53-1.18; P = 0.204). All three cases developed SAH within 3 days (range, 0-3 days) of the first or second dose of BNT162b2 mRNA COVID-19 vaccine by Pfizer/BioNTech. The median age at the time of SAH onset was 63.7 years (range, 44- 75 years). Observed locations of ruptured aneurysms in patients were the bifurcations of the middle cerebral artery, internal carotid-posterior communicating artery, and anterior communicating artery, respectively. Favorable outcomes (modified Rankin scale scores, 0-2) were obtained following microsurgical clipping or intra-aneurysm coiling. Conclusion: Although the advantages of COVID-19 vaccination appear to outweigh the risks, pharmacovigilance must be maintained to monitor potentially fatal adverse events and identify possible associations.

Intracranial hemorrhage associated with direct oral anticoagulant after clipping for an unruptured cerebral aneurysm: A report of two cases.

Background: Two cases of patients who developed intracranial hemorrhage associated with direct oral anticoagulant (DOAC) use after clipping of an unruptured cerebral aneurysm (uAN) are presented. These cases will help neurosurgeons assess the risks of patients with atrial fibrillation or deep venous thrombosis receiving DOACs who require craniotomy. Case Description: Case 1 was a 65-year-old man on apixaban 10 mg/day who underwent clipping for a left middle cerebral artery uAN. Apixaban was discontinued 72 h before surgery. During surgery, a thin and pial artery bled slightly at 1 point of the frontal lobe, and hemostasis was easily achieved. Computed tomography (CT) 19 h after surgery showed no evidence of intracranial hemorrhage. He was treated with a heparin-apixaban bridge from 29 h to 41 h after surgery. CT showed a left subarachnoid hematoma 24 h later. Case 2 was a 73-year-old woman on dabigatran 110 mg/day who underwent clipping for a right MCA uAN. Dabigatran was discontinued 48 h before surgery. During surgery, a thin and pial artery bled slightly at 2 points of the temporal lobe, and hemostasis was easily achieved. CT 19 h after surgery showed no evidence of intracranial hemorrhage. Dabigatran (110 mg/day) was restarted 29 h after surgery. CT then showed a right subarachnoid hematoma 94 h later, and dabigatran was discontinued, and it was then restarted 38 h later. However, 31 h later, CT showed an additional slight subarachnoid hemorrhage. Finally, she developed a right chronic subdural hematoma. Conclusion: In patients undergoing neurosurgical procedures, discontinuation of DOACs should be individualized based on neurosurgical bleeding risk and patient renal function. Restarting of DOACs could be considered after at least 48 h when hemostasis has been achieved. Bridging of DOACs cannot be recommended.

Linewidth Narrowing with Ultimate Confinement of an Alkali Multipole Plasmon by Modifying Surface Electronic Wave Functions with Two-Dimensional Materials.

This work demonstrates significant line narrowing of a surface multipole plasmon (MP) by modifying the surface electronic wave function with two-dimensional materials (2DMs): graphene and hexagonal boron nitride. This is found in an optical reflectivity of alkali atoms (Cs or K) on an Ir(111) surface covered with the 2DMs. The reduction in reflectivity induced by deposition of the alkali atoms becomes as large as 20% at ∼2 eV, which is ascribed to a MP of a composite of alkali/2DM/alkali/Ir multilayer structure. The linewidth of the MP band becomes as narrow as 0.2 eV by the presence of the 2DM between the two alkali layers. A numerical simulation by time-dependent density functional theory with a jellium model reveals that the density of states of the surface localized state is sharpened remarkably by the 2DMs that decouple the outermost alkali layer from the Ir bulk. Consequently, a local field enhancement of an order of 10^{5} is achieved by ultimate confinement of the MP within the outermost alkali layer. This work leads to a novel strategy for reducing plasmon dissipation in an atomically thin layer via atomic scale modification of surface structure.

Long-Term Outcomes of Cerebral Blood Flow and Neurotransmitter Receptor Function on Iodine-123-Iomazenil Single-Photon Emission Computed Tomography and Cognitive Assessments After Parent Artery Occlusion Combined with Cerebral Revascularization for Internal Carotid Artery Aneurysms.

OBJECTIVE: Many studies of external-internal carotid artery (EC-IC) bypass as cerebral revascularization for unclippable internal carotid artery (ICA) aneurysms have reported surgical outcomes, including bypass patency and aneurysm resolution. However, no previous studies have assessed the long-term outcomes of cerebral blood flow (CBF), brain neural density, and cognition. The purpose of the present study was to evaluate the long-term outcomes of CBF and neurotransmitter receptor function using early and late images of iodine-123 (123I)-iomazenil (IMZ) single-photon emission computed tomography (SPECT) and the cognitive function of patients who had undergone EC-IC bypass for symptomatic aneurysms in the cavernous portion of the ICA. METHODS: We performed a prospective observational study of 11 patients who had undergone superficial temporal artery-middle cerebral artery bypass or bypass using a saphenous vein graft for symptomatic aneurysms in the cavernous portion of the ICA. One patient experienced extensive infarction and, therefore, did not undergo postoperative testing. 123I-IMZ SPECT was performed with scanning at 23 minutes (early) and 180 minutes (late) after tracer administration before and after surgery. The preoperative and follow-up neuropsychological test scores from 6 patients were also analyzed. RESULTS: None of 10 patients who had undergone EC-IC bypass showed reductions in CBF and brain neural density. In addition, the neuropsychological test scores had not changed significantly from preoperatively to postoperatively. CONCLUSION: Using early and late 123I-IMZ SPECT, the present study has demonstrated that patients undergoing uncomplicated cerebral revascularization for unclippable ICA aneurysms will not experience reductions in CBF or neurotransmitter receptor function, and their cognitive function was not impaired.

Orientational ordering in heteroepitaxial water ice on metal surfaces.

Heteroepitaxial growth of crystalline ice thin films of water on metal substrates under ultrahigh vacuum provides an excellent opportunity to investigate the interior and surface structures of crystalline ice that are closely related to their physicochemical properties. Here we present the spectroscopic studies of the orientational ordering and the surface relaxation of crystalline ice films grown on two representative metal surfaces: Pt(111) and Rh(111). A versatile tool for exploring these structures is sum frequency generation (SFG) vibrational spectroscopy; homodyne detection of SFG signals serves as a good measure of orientational ordering in the interior of crystalline ice films while heterodyne detection enables us to determine the direction of water molecules at the interface with metal substrates, in the interior of crystalline ice films, and at their surfaces. Water molecules on the wetting layer of Pt(111) are preferentially oriented in H-down configuration, and the configuration is passed along into the interior of crystalline ice films. In contrast, water molecules on Rh(111) are adsorbed in a mixture of H-down and H-up configurations, leading to orientationally disordered crystalline ice films. The inter-layer distance at the top of the surface is modulated alternately in accordance with the orientation of molecules hydrogen bonded to the bilayer underneath. Therefore, the molecular orientation also plays an important role in their surface relaxation.

A case of paroxysmal homonymous hemianopsia: Uncommon presentation of nonconvulsive status epilepticus.

Paroxysmal homonymous hemianopsia (HH) is uncommon presentation of epilepsy. We demonstrate a rare case of paroxysmal HH that was diagnosed by magnetic resonance (MR) arterial spin-labeling (ASL). A 82-year-old woman presented with abrupt onset of isolated visual field abnormality without convulsive epilepsy at 16 days after a traumatic head injury. Diffusion weighted and MR-ASL obtained on admission revealed hyperintensity and hyperperfusion in the right temporo-occipital cortex. Nonconvulsive status epilepticus was suspected. The patient was treated with oral levetiracetam and the symptoms resolved in 3 days. Paroxysmal HH should be considered in patients who present with simple partial epilepsy, and MR-ASL imaging may assist in the differential diagnosis of these patients.

Direct Experimental Evidence for Markedly Enhanced Surface Proton Activity Inherent to Water Ice.

Autoionization and subsequent proton transfer processes determine the proton activity inherent to water molecular systems. In this study, we provide direct experimental evidence that the proton activity is markedly enhanced at the surface of crystalline ice, on the basis of the simultaneous observation of H/D exchange of water molecules at the surface and in the interior of well-defined double-layer ice films composed of H2O and D2O. Thermal desorption mass spectrometry showed clear signatures derived from the surface H/D exchange equilibrium, whereas infrared absorption spectroscopy indicated no appreciable H/D exchange progress in the interior. Detailed kinetic analyses revealed that the rate of H/D exchange at the surface is at least 3 orders of magnitude higher than in the interior. This drastic enhancement of the proton activity suggests an extremely high concentration of surface-hydrated protons in comparison with those in the bulk. Our results also highlight the impact of the local hydrogen-bond structure on the autoionization of water molecules.

Thickness dependent homogeneous crystallization of ultrathin amorphous solid water films.

The crystallization mechanism and kinetics of amorphous materials are of paramount importance not only in basic science but also in the application field because they are closely related to their thermal stability. In the case of amorphous nanomaterials, thermal stability distinctively different from that of bulk materials often emerges. Despite intensive studies in the past, a thorough understanding of the stability at the molecular level has not been reached particularly on how crystallization processes depend on size and are influenced by their surface and interface. In this article, we report the film-size-dependent crystallization of thermally relaxed nonporous ASW ultrathin films on a Pt(111) surface as a benchmark system of amorphous molecular films. The crystallization processes at the surface and interior of the ASW ultrathin films are monitored simultaneously with thermal desorption and infrared reflection absorption, respectively, as a function of the film thickness. Here, we demonstrate that the crystallization is initiated solely by "homogeneous nucleation" irrespective of the film thickness while the crystallization rate remarkably depends on the thickness; the rate of 5-layer (∼1.5 nm) ASW films is one order of magnitude higher than that of 20-layer (∼6 nm) films. Moreover, we found a clear correlation between the film-thickness-dependent crystallization kinetics and microscopic structural disorder associated with the broad distribution of hydrogen-bond lengths between water molecules.

Enhanced structural disorder at a nanocrystalline ice surface.

Detailed knowledge of the structure and dynamics of the surface of ice particles is of considerable importance for understanding catalytic reactions in the upper atmosphere. Here we report the enhanced structural disorder specific at a nanoscale ice island studied by using heterodyne-detected vibrational sum-frequency generation spectroscopy under ultrahigh vacuum. Ultrathin films of isotopically diluted HOD crystalline ice are grown on Rh(111), whose average height (≥1.4 nm) is controlled by varying the nominal film thickness. The Im χ(2) spectrum of the hydrogen-bonded O-H stretching band shows a bipolar line shape reflecting the orientation-dependent hydrogen bond length alternation in the subsurface of the ice island. The peak splitting and the bandwidth of the bipolar spectrum increase with a decrease in the nominal film thickness. This is ascribed to the significant enhancement of structural disorder at the surface of the ice island as the terrace size is decreased. Temperature dependence of the Im χ(2) spectra of the hydrogen bonded O-H stretching band indicates that the thermal expansivity of the top layer increases upon decreasing the island size. In addition, the stretching frequency of the dangling OD band at the island surface with the average height less than 18 nm shows a systematic blue shift with increasing temperature from 100 to 145 K: this is in stark contrast to thick ice films and bulk ice showing a negligible peak shift at a temperature lower than 180 K. These findings indicate that the anharmonicity of the intermolecular potential at the top layer of the ice island is strongly enhanced upon decreasing its terrace size, providing valuable insights for understanding the properties of ice particles in the outer atmosphere including polar mesospheric clouds.

Singlet fission of amorphous rubrene modulated by polariton formation.

The excited-state dynamics of molecular aggregates are governed by their potential energy landscape that can hardly be controlled artificially. However, it is possible to alter the excited state dynamics by a strong coupling between light and molecules (polariton formation) because it can decouple the electronic and vibrational degrees of freedom. Here, we demonstrate this polaron decoupling effect on the photochemical dynamics in singlet fission (SF) of amorphous rubrene thin films embedded in optical microcavities. The vibronic feature of polariton states in this system is characterized through the analysis of steady state absorption spectra by using the Holstein-Tavis-Cummings model. On the basis of this analysis, we show with time-resolved spectroscopy that the SF rate following a resonant excitation of the lowest energy polariton state is indeed modulated when the cavity photon energy is changed. A numerical simulation by using Fermi's golden rule formula with the vibronic polariton feature successfully accounts for the observed modulation of the SF rate, indicating that the polaron decoupling plays a decisive role in the nonadiabatic dynamics.

A case of chronic subdural hematoma demonstrating the epileptic focus at the area with sulcal hyperintensity on fluid-attenuated inversion recovery image.

Although the sulcal hyperintensity on fluid-attenuated inversion recovery (FLAIR) images is detected in some chronic subdural hematoma (CSDH) cases, its clinical significance remains determined. A 77-year-old man with symptomatic CSDH presented with generalized tonic-clonic seizures at 9 days after surgery. 123I-iomazenil -single photon emission computed tomography revealed transient reduction in cortical benzodiazepine receptors binding potential at the region corresponding to that of the sulcal hyperintensity on FLAIR images. Findings of sulcal hyperintensity on FLAIR imaging under the CSDH may have a relation with the cause of epileptic seizure.

Microsurgical clipping for anterior communicating artery aneurysm associated with the accessory anterior cerebral artery via the pterional approach.

BACKGROUND: Accessory anterior cerebral artery (ACA), a type of median artery of anomalous triplicate ACA, is not rare, but aneurysms of the anterior communicating artery (ACoA) associated with accessory ACA can be a considerable challenge to treat surgically based on the morphological features of the ACoA complex. CASE DESCRIPTION: A 35-year-old man was admitted to our hospital with severe headache and subsequent loss of consciousness. Initial computed tomography (CT) showed typical findings of subarachnoid hemorrhage in the basal cistern and three-dimensional CT angiography revealed an ACoA aneurysm arising from the trifurcation of the accessory ACA, the branching point of the ACoA, and the right A1 or A2 segment of the ACA. The aneurysmal fundus projected superolaterally to the right, and was treated via a right-sided pterional approach. The aneurysm was behind the ipsilateral A2 segment of the ACA and the accessory ACA was hidden behind the aneurysm. The aneurysm was successfully obliterated with clipping using a straight fenestrated Yasargil titanium clip. Complete aneurysm occlusion and patency of both the A2 segment of the ACA and the accessory ACA were confirmed intraoperatively by indocyanine green angiography. CONCLUSION: In treating this aneurysm via the pterional approach, selection of approach side it is critical to preserve prevent the patency of the accessory ACA and to simultaneously perform aneurysm clipping without leaving a neck remnant. Selecting the optimal approach based on preoperative neuroimaging of which side will allow both these actions is important.

Fenestrated T-bar Clips in Surgical Management of Internal Carotid Artery Aneurysms: Technical Note.

BACKGROUND: Using a conventional right-angled fenestrated clip for an internal carotid artery (ICA) aneurysm is potentially disadvantageous because of the worse surgical visibility during and after clip application, especially in tight surgical fields. METHODS: We report a case of ruptured posteromedially projecting ICA aneurysm treated using a right-angled fenestrated T-bar clip (Yasargil titanium clip, Aesculap AG & Co, Tuttlingen, Germany). A 52-year-old woman was admitted to our hospital with severe headache. Three-dimensional computed tomography angiography showed a saccular aneurysm arising from the left, unusually short ICA, located proximal to the anterior choroidal artery. The right-angled fenestrated T-bar clip (blade length, 5 mm) was applied across the ICA, followed by reconstruction of the ICA wall with preservation of the anterior choroidal artery and simultaneous obliteration of the aneurysm. RESULTS: The key characteristic of the fenestrated T-bar clip is that the fenestrated portion of the clip is connected to the center of the blades. The tips of the blades on both sides are thus clearly visible during clip application. CONCLUSIONS: Application of the T-bar clip allows the surgeon to perform clip ligation of a posteromedially projecting ICA aneurysm while preserving the adjacent perforating artery.

Primary Central Nervous System Lymphoma Presenting as Growing Intracerebral Hemorrhage.

BACKGROUND: Hemorrhage at presentation in primary central nervous system (CNS) lymphoma is rare. We encountered a case of primary CNS lymphoma presenting as a growing intracerebral hemorrhage. CASE DESCRIPTION: An 80-year-old man presented with mild dysarthria. Computed tomography demonstrated a round, high-density mass with surrounding vasogenic edema in the left frontal lobe. Although the patient was placed on antihypertensive therapy for suspected subacute subcortical hemorrhage, neurologic symptoms gradually worsened. Computed tomography after 2 weeks revealed that the high-density lesion and surrounding edema had increased in size compared with previous images. The patient had been transferred to our hospital 14 days after admission to another institution. Magnetic resonance imaging demonstrated a mass lesion comprising hemorrhage of different phases in the left frontal lobe. Contrast-enhanced T1-weighted imaging demonstrated a mass lesion with heterogeneous enhancement in the left frontal lobe. The patient underwent craniotomy with gross total removal of the hemorrhagic lesion. The histopathologic diagnosis was diffuse large-cell non-Hodgkin lymphoma, and immunohistochemistry showed high immunoreactivity for vascular endothelial growth factor. CONCLUSION: Although exceedingly rare, primary central nervous system lymphoma can present as growing intracerebral hemorrhage due to repeated intratumoral hemorrhages. High expression of vascular endothelial growth factor and the mass effects of hemorrhage could be associated with the onset and growth of intracerebral hemorrhage. Early evaluation and meticulous observation are important to avoid progressive, life-threatening situations in such cases.

Conformational Planarization versus Singlet Fission: Distinct Excited-State Dynamics of Cyclooctatetraene-Fused Acene Dimers.

A set of flapping acene dimers fused with an 8π cyclooctatetraene (COT) ring showed distinct excited-state dynamics in solution. While the anthracene dimer showed a fast V-shaped-to-planar conformational change within 10 ps in the lowest excited singlet state, reminding us of extended Baird aromaticity, the tetracene dimer and the pentacene dimer underwent intramolecular singlet fission (SF) in different manners: A fast and reversible SF with a characteristic delayed fluorescence (FL), and a fast and quantitative SF, respectively. Conformational flexibility of the fused COT linkage plays an important role in these ultrafast dynamics, demonstrating the utility of the flapping molecular series as a versatile platform for designing photofunctional systems.

Water-Assisted Hole Trapping at the Highly Curved Surface of Nano-TiO2 Photocatalyst.

Heterogeneous photocatalysis is vital in solving energy and environmental issues that this society is confronted with. Although photocatalysts are often operated in the presence of water, it has not been yet clarified how the interaction with water itself affects charge dynamics in photocatalysts. Using water-coverage-controlled steady and transient infrared absorption spectroscopy and large-model (∼800 atoms) ab initio calculations, we clarify that water enhances hole trapping at the surface of TiO2 nanospheres but not of well-faceted nanoparticles. This water-assisted effect unique to the nanospheres originates from water adsorption as a ligand at a low-coordinated Ti-OH site or through robust hydrogen bonding directly to the terminal OH at the highly curved nanosphere surface. Thus, the interaction with water at the surface of nanospheres can promote photocatalytic reactions of both oxidation and reduction by elongating photogenerated carrier lifetimes. This morphology-dependent water-assisted effect provides a novel and rational basis for designing and engineering nanophotocatalyst morphology to improve photocatalytic performances.