Spacer Engineering Enables Fine-Tuned Thin Film Microstructure and Efficient Charge Transport for Ultrasensitive 2D Perovskite-Based Heterojunction Phototransistors and Optoelectronic Synapses.

2D Ruddlesden-Popper phase layered perovskites (RPLPs) hold great promise for optoelectronic applications. In this study, a series of high-performance heterojunction phototransistors (HPTs) based on RPLPs with different organic spacer cations (namely butylammonium (BA+), cyclohexylammonium (CyHA+), phenethylammonium (PEA+), p-fluorophenylethylammonium (p-F-PEA+), and 2-thiophenethylammonium (2-ThEA+)) are fabricated successfully, in which high-mobility organic semiconductor 2,7-dioctyl[1]benzothieno[3,2-b]benzothiophene is adopted to form type II heterojunction channels with RPLPs. The 2-ThEA+-RPLP-based HPTs show the highest photosensitivity of 3.18 × 107 and the best detectivity of 9.00 × 1018 Jones, while the p-F-PEA+-RPLP-based ones exhibit the highest photoresponsivity of 5.51 × 106 A W-1 and external quantum efficiency of 1.32 × 109%, all of which are among the highest reported values to date. These heterojunction systems also mimicked several optically controllable fundamental characteristics of biological synapses, including excitatory postsynaptic current, paired-pulse facilitation, and the transition from short-term memory to long-term memory states. The device based on 2-ThEA+-RPLP film shows an ultra-high PPF index of 234%. Moreover, spacer engineering brought fine-tuned thin film microstructures and efficient charge transport/transfer, which contributes to the superior photodetection performance and synaptic functions of these RPLP-based HPTs. In-depth structure-property correlations between the organic spacer cations/RPLPs and thin film microstructure/device performance are systematically investigated.

[Clinical features of children with Guillain-Barré syndrome and the significance of Brighton criteria].

OBJECTIVE: To study the clinical features of children with Guillain-Barré syndrome (GBS) and the significance of Brighton criteria in childhood GBS. METHODS: A retrospective analysis was performed on the medical data of 72 children with GBS. Brighton criteria were used for the grading of diagnostic certainty (level 1 as the highest level, and level 4 as the lowest level). A Spearman's rank correlation analysis was used to evaluate the correlation of auxiliary examinations with the level of diagnostic certainty of Brighton criteria. RESULTS: A total of 72 children with GBS were enrolled, with a mean age of onset of (98±32) months. All children (100%, 72/72) had weakness of bilateral limbs and disappearance or reduction of tendon reflex, and limb weakness reached the highest level of severity within 4 weeks. Of all the 72 children, 68 (94%) had positive results of neural electrophysiological examination and 51 (71%) had positive results of cerebrospinal fluid (CSF) examination, and the positive rate of neural electrophysiological examination was significantly higher than that of CSF examination (P < 0.01). The median interval time from disease onset to neural electrophysiological examination was significantly shorter than from disease onset to CSF examination (11 days vs 14 days, P < 0.01). Of all the 72 children, 49 (68%) met Brighton criteria level 1 and 21 (29%) met Brighton criteria level 2. Neural electrophysiological examination and CSF examination were positively correlated with the level of diagnostic certainty of Brighton criteria (rs=0.953 and 0.420 respectively, P < 0.01). CONCLUSIONS: Most of the children with GBS meet Brighton criteria level 1, and the positive results of CSF examination and neural electrophysiological examination play an important role in improving the level of diagnostic certainty of Brighton criteria. Neural electrophysiological examination has a higher positive rate than CSF examination in the early stage of the disease.