No abstract

Despite the emerging interest in research and development of Ti 3 CN MXene nanosheet (NS)-based optoelectronic devices, there is still a lack of in-depth studies of the underlying photophysical processes, like carrier relaxation dynamics and nonlinear photon absorption, operating in such devices, hindering their further and precise design. In this paper, we attempt to remedy the situation by fabricating fewlayer Ti 3 CN NSs via combining selective etching and molecular intercalation and by investigating the carrier relaxation possesses and broadband nonlinear optical responses via transient absorption and Z-scan techniques. These results are complemented by first-principle theoretical analyses of the optical properties. Both saturable absorption and reverse saturable absorption phenomena are observed due to multiphoton absorption effects. The analysis of these results adds to the understanding of the basic photophysical processes, which is anticipated to be beneficial for the further design of MXenebased devices.

Neurological sequelae after COVID-19 vaccination are rare. We investigated the possible pathogenesis behind the development of neurological complications within a short period after Saudi residents received a COVID-19 vaccine. Patients and Methods: We evaluated 18 patients who recently received a COVID-19 vaccine (Comirnaty and Vaxzevria vaccines) and presented with neurological complications to the Saudi German Hospitals in Jeddah, Saudi Arabia. Neurologists assessed the patients' clinical presentation, radiological investigations, and laboratory findings. Results: Three patients who received the first dose of the Vaxzevria vaccine experienced severe cerebral venous thrombosis, two of them were complicated by intracranial hemorrhage. Their laboratory investigations showed very high d-dimers and severe thrombocytopenia, which have been linked to higher mortality and poor outcome. Ischemic stroke occurred in eight cases (44.4%) with a predominance in older male patients. Three patients presented with seizures, two had optic neuritis. Guillain-Barré syndrome (GBS) and Miller Fisher syndrome (MFS) occurred in two male patients following vaccination with Comirnaty. Conclusion: Neurological complications after COVID-19 vaccinations are very rare, and only a few cases have been reported worldwide. The shared pathophysiological basis between COVID-19 viral infection and COVID-19 vaccines stands behind the very rare neurological complications resulting from the hypercoagulable state triggered by the general inflammatory condition. We suspect some differences in the pathogenesis of ischemic stroke caused by COVID-19 infection and COVID-19 vaccines, which render COVID-19 vaccine-associated ischemic stroke more responsive to treatment. To date, no definitive association between the vaccine and GBS has been proven by any strong evidence, but it has recently been added as a very rare side effect of the Janssen COVID-19 vaccine. No possible links of Miller Fisher syndrome to COVID-19 vaccines have been reported before the one reported in this study.

Step-scheme heterojunctions formed between two firmly bound photocatalysts facilitate charge separation due to interfacial charge transfer, which is usually illustrated by the gain or loss of electrons in the constituent photocatalysts characterized by in situ irradiated X-ray photoelectron spectroscopy. This technique provides a steady-state view of charge distribution but overlooks the transient and complex dynamics of charge transfer, trapping, and recombination. To provide a molecular-level and dynamic view of these processes, we investigated the behaviors of photogenerated charge carriers within an inorganic/organic TiO 2 / polydopamine S-scheme heterojunction using ultrafast transient absorption spectroscopy and time-resolved photoluminescence spectroscopy. We found the interfacial charge transfer within the step-scheme heterojunction occurred at a smaller shorter time scale than recombination, leading to efficient charge separation. Moreover, the charge−discharge property of polydopamine induces electron backflow, which should be avoided in practical photocatalytic applications. The composite showed higher photocatalytic H 2 O 2 -production activities due to faster H 2 O 2 formation and suppressed H 2 O 2 decomposition.

No abstract