Evolutions of helical edge states in disordered HgTe/CdTe quantum wells

We study the evolutions of the nonmagnetic disorder-induced edge states with the disorder strength in the HgTe/CdTe quantum wells. From the supercell band structures and wave-functions, it is clearly shown that the conducting helical edge states, which are responsible for the reported quantized conductance plateau, appear above a critical disorder strength after a gap-closing phase transition. These edge states are then found to decline with the increase of disorder strength in a stepwise pattern due to the finite-width effect, where the opposite edges couple with each other through the localized states in the bulk. This is in sharp contrast with the localization of the edge states themselves if magnetic disorders are doped which breaks the time-reversal symmetry. The size-independent boundary of the topological phase is obtained by scaling analysis, and an Anderson transition to an Anderson insulator at even stronger disorder is identified, in-between of which, a metallic phase is found to separate the two topologically distinct phases.Comment: 7 pages, 5 figure

Construction of Electrostatic Self-Assembled 2D/2D CdIn2S4/g-C3N4 Heterojunctions for Efficient Visible-Light-Responsive Molecular Oxygen Activation

Molecular oxygen activated by visible light to generate radicals with high oxidation ability exhibits great potential in environmental remediation The efficacy of molecular oxygen activation mainly depends on the separation and migration efficiency of the photoinduced charge carriers. In this work, 2D/2D CdIn2S4/g-C3N4 heterojunctions with different weight ratios were successfully fabricated by a simple electrostatic self-assembled route. The optimized sample with a weight ratio of 5:2 between CdIn2S4 and g-C3N4 showed the highest photocatalytic activity for tetracycline hydrochloride (TCH) degradation, which also displayed good photostability. The enhancement of the photocatalytic performance could be ascribed to the 2D/2D heterostructure; this unique 2D/2D structure could promote the separation and migration of the photoinduced charge carriers, which was beneficial for molecular oxygen activation, leading to an enhancement in photocatalytic activity. This work may possibly provide a scalable way for molecular oxygen activation in photocatalysis

Enhanced Z-LDA for Small Sample Size Training in Brain-Computer Interface Systems

Background. Usually the training set of online brain-computer interface (BCI) experiment is small. For the small training set, it lacks enough information to deeply train the classifier, resulting in the poor classification performance during online testing. Methods. In this paper, on the basis of Z-LDA, we further calculate the classification probability of Z-LDA and then use it to select the reliable samples from the testing set to enlarge the training set, aiming to mine the additional information from testing set to adjust the biased classification boundary obtained from the small training set. The proposed approach is an extension of previous Z-LDA and is named enhanced Z-LDA (EZ-LDA). Results. We evaluated the classification performance of LDA, Z-LDA, and EZ-LDA on simulation and real BCI datasets with different sizes of training samples, and classification results showed EZ-LDA achieved the best classification performance. Conclusions. EZ-LDA is promising to deal with the small sample size training problem usually existing in online BCI system

In Situ Electrochemical Sensing and Real-Time Monitoring Live Cells Based on Freestanding Nanohybrid Paper Electrode Assembled from 3D Functionalized Graphene Framework

In this work, we develop a new type of freestanding nanohybrid paper electrode assembled from 3D ionic liquid (IL) functionalized graphene framework (GF) decorated by gold nanoflowers (AuNFs), and explore its practical application in in situ electrochemical sensing of live breast cell samples by real-time tracking biomarker H₂O₂ released from cells. The AuNFs modified IL functionalized GF (AuNFs/IL–GF) was synthesized via a facile and efficient dopamine-assisted one-pot self-assembly strategy. The as-obtained nanohybrid assembly exhibits a typical 3D hierarchical porous structure, where the highly active electrocatalyst AuNFs are well dispersed on IL–GF scaffold. And the graft of hydrophilic IL molecules (i.e., 1-butyl-3-methylimidazolium tetrafluoroborate, BMIMBF₄) on graphene nanosheets not only avoids their agglomeration and disorder stacking during the self-assembly but also endows the integrated IL–GF monolithic material with unique hydrophilic properties, which enables it to be readily dispersed in aqueous solution and processed into freestanding paperlike material. Because of the unique structural properties and the combinational advantages of different components in the AuNFs/IL–GF composite, the resultant nanohybrid paper electrode exhibits good nonenzymatic electrochemical sensing performance toward H₂O₂. When used in real-time tracking H₂O₂ secreted from different breast cells attached to the paper electrode without or with radiotherapy treatment, the proposed electrochemical sensor based on freestanding AuNFs/IL–GF paper electrode can distinguish the normal breast cell HBL-100 from the cancer breast cells MDA-MB-231 and MCF-7 cells, and assess the radiotherapy effects to different breast cancer cells, which opens a new horizon in real-time monitoring cancer cells by electrochemical sensing platform