A Methodology of Fabricating Novel Electrodes for Semiconductor Devices: Doping and Van der Waals Integrating Organic Semiconductor Films.

Electrodes are indispensable components in semiconductor devices, and now are mainly made from metals, which are convenient for use but not ideal for emerging technologies such as bioelectronics, flexible electronics, or transparent electronics. Here the methodology of fabricating novel electrodes for semiconductor devices using organic semiconductors (OSCs) is proposed and demonstrated. It is shown that polymer semiconductors can be heavily p- or n-doped to achieve sufficiently high conductivity for electrodes. In contrast with metals, the doped OSC films (DOSCFs) are solution-processable, mechanically flexible, and have interesting optoelectronic properties. By integrating the DOSCFs with semiconductors through van der Waals contacts different kinds of semiconductor devices can be constructed. Importantly, these devices exhibit higher performance than their counterparts with metal electrodes, and/or excellent mechanical or optical properties that are unavailable in metal-electrode devices, suggesting the superiority of DOSCF electrodes. Given the existing large amount of OSCs, the established methodology can provide abundant electrode choices to meet the demand of various emerging devices.

Double [4]Helicene-like Naphthobisbenzothiophene Diimides and Their Thienyl-S,S-dioxidized Derivatives with Attractive Solid-State Fluorescence and High Electron Affinity.

A series of double [4]helicene-like naphthobisbenzothiophene diimides and their thienyl-S,S-dioxidized derivatives are synthesized via MoCl5-catalyzed cyclization and m-CPBA-mediated oxidation reactions. The functional five-membered ring diimides show a helicene-like geometry, strong solid-state fluorescence, and deep LUMO of -4.37 eV.

Body-Ordered Approximations of Atomic Properties.

We show that the local density of states (LDOS) of a wide class of tight-binding models has a weak body-order expansion. Specifically, we prove that the resulting body-order expansion for analytic observables such as the electron density or the energy has an exponential rate of convergence both at finite Fermi-temperature as well as for insulators at zero Fermi-temperature. We discuss potential consequences of this observation for modelling the potential energy landscape, as well as for solving the electronic structure problem.

An Activatable and Reversible Virus-Mimicking NIR-II Nanoprobe for Monitoring the Progression of Viral Encephalitis.

Viral encephalitis is an inflammatory disease of the brain parenchyma and caused by various viral infections. In vivo monitoring of the progression of viral infections can aid accurate diagnosis of viral encephalitis and effective intervention. We developed an activatable and reversible virus-mimicking near-infrared II nanoprobe consisting of an Fe2+ -coordinated, viral protein-decorated vesicle encapsulating PbS quantum dots with a 1300 nm fluorescence emission. The probe can cross the blood-brain barrier and monitor real-time changes in reactive oxygen and nitrogen species concentrations during viral infection by tuning the quenching level of quantum dots and regulating the fusion-fission behavior of vesicles via changes in Fe oxidation state. This switching strategy reduces background noise and improves detection sensitivity, making this nanoprobe a promising imaging agent for dynamic visualization of viral encephalitis and future clinical applications.

H2 O2 -Responsive NIR-II AIE Nanobomb for Carbon Monoxide Boosting Low-Temperature Photothermal Therapy.

Low-temperature photothermal therapy (PTT), which circumvents the limitations of conventional PTT (e.g., thermotolerance and adverse effects), is an emerging therapeutic strategy which shows great potential for future clinical applications. The expression of heat shock proteins (HSPs) can dramatically impair the therapeutic efficacy of PTT. Thus, inhibition of HSPs repair and reducing the damage of nearby normal cells is crucial for improving the efficiency of low-temperature PTT. Herein, we developed a nanobomb based on the self-assembly of NIRII AIE polymer PBPTV and carbon monoxide (CO) carrier polymer mPEG(CO). This smart nanobomb can be exploded in a tumor microenvironment in which hydrogen peroxide is overexpressed and release CO into cancer cells to significantly inhibit the expression of HSPs and hence improve the antitumor efficiency of the low-temperature PTT.

MXene based saturation organic vertical photoelectric transistors with low subthreshold swing.

Vertical transistors have attracted enormous attention in the next-generation electronic devices due to their high working frequency, low operation voltage and large current density, while a major scientific and technological challenge for high performance vertical transistor is to find suitable source electrode. Herein, an MXene material, Ti3C2Tx, is introduced as source electrode of organic vertical transistors. The porous MXene films take the advantage of both partially shielding effect of graphene and the direct modulation of the Schottky barrier at the mesh electrode, which significantly enhances the ability of gate modulation and reduces the subthreshold swing to 73 mV/dec. More importantly, the saturation of output current which is essential for all transistor-based applications but remains a great challenge for vertical transistors, is easily achieved in our device due to the ultra-thin thickness and native oxidation of MXene, as verified by finite-element simulations. Finally, our device also possesses great potential for being used as wide-spectrum photodetector with fast response speed without complex material and structure design. This work demonstrates that MXene as source electrode offers plenty of opportunities for high performance vertical transistors and photoelectric devices.

Solution-Processed CsPbBr3 Quantum Dots/Organic Semiconductor Planar Heterojunctions for High-Performance Photodetectors.

Planar heterojunctions (PHJs) are fundamental building blocks for construction of semiconductor devices. However, fabricating PHJs with solution-processable semiconductors such as organic semiconductors (OSCs) is a challenge. Herein, utilizing the orthogonal solubility and good wettability between CsPbBr3 perovskite quantum dots (PQDs) and OSCs, fabrication of solution-processed PQD/OSC PHJs are reported. The phototransistors based on bilayer PQD/PDVT-10 PHJs show responsivity up to 1.64 × 104 A W-1 , specific detectivity of 3.17 × 1012 Jones, and photosensitivity of 5.33 × 106 when illuminated by 450 nm light. Such high photodetection performance is attributed to efficient charge dissociation and transport, as well as the photogating effect in the PHJs. Furthermore, the tri-layer PDVT-10/PQD/Y6 PHJs are used to construct photodiodes working in self-powered mode, which exhibit broad range photoresponse from ultraviolet to near-infrared, with responsivity approaching 10-1 A W-1 and detectivity over 106 Jones. These results present a convenient and scalable production processes for solution-processed PHJs and show their great potential for optoelectronic applications.

Construction of Durable Self-Cleaning PDMS Film on Polyester Fabric Surface.

The superhydrophobic surface can be prepared by two methods; one is by reducing the surface energy, and the other is by constructing a micro-nano rough structure. To achieve high superhydrophobic performance in terms of durability, the firm combination of hydrophobic coating and substrate is particularly important. Here, we use polydimethylsiloxane (PDMS) as a low surface energy monomer, water-borne polyurethane (WPU) as a dispersing aid, and use high-power ultrasound to disperse PDMS in water to make emulsion. The polyester matrix is etched by atmospheric plasma, dipped in PDMS emulsion, dried, and finally baked to induce PDMS on the surface of polyester fiber to cross-link into film. A series of tests on the self-cleaning polyester fabric prepared by this method show that when the concentration of PDMS is 8 g/L and the mass ratio of PDMS to WPU is 20:1, the water contact angle (WCA) reaches the maximum value of 148.2°, which decreases to 141.5° after 200 times of washing and 138.6° after 5000 times of rubbing. Before and after PDMS coating, the tensile strength of polyester fabric increases from 489.4 N to 536.4 N, and the water vapor transmission decreases from 13,535.7 g/(m2·d) to 12,224.3 g/(m2·d). This research is helpful to the large-scale production of self-cleaning polyester fabric. In the future, on the basis of this research, we will add functional powder to endow self-cleaning polyester fabric with higher hydrophobicity and other properties.

One Spatio-Temporal Sharpening Attention Mechanism for Light-Weight YOLO Models Based on Sharpening Spatial Attention.

Attention mechanisms have demonstrated great potential in improving the performance of deep convolutional neural networks (CNNs). However, many existing methods dedicate to developing channel or spatial attention modules for CNNs with lots of parameters, and complex attention modules inevitably affect the performance of CNNs. During our experiments of embedding Convolutional Block Attention Module (CBAM) in light-weight model YOLOv5s, CBAM does influence the speed and increase model complexity while reduce the average precision, but Squeeze-and-Excitation (SE) has a positive impact in the model as part of CBAM. To replace the spatial attention module in CBAM and offer a suitable scheme of channel and spatial attention modules, this paper proposes one Spatio-temporal Sharpening Attention Mechanism (SSAM), which sequentially infers intermediate maps along channel attention module and Sharpening Spatial Attention (SSA) module. By introducing sharpening filter in spatial attention module, we propose SSA module with low complexity. We try to find a scheme to combine our SSA module with SE module or Efficient Channel Attention (ECA) module and show best improvement in models such as YOLOv5s and YOLOv3-tiny. Therefore, we perform various replacement experiments and offer one best scheme that is to embed channel attention modules in backbone and neck of the model and integrate SSAM into YOLO head. We verify the positive effect of our SSAM on two general object detection datasets VOC2012 and MS COCO2017. One for obtaining a suitable scheme and the other for proving the versatility of our method in complex scenes. Experimental results on the two datasets show obvious promotion in terms of average precision and detection performance, which demonstrates the usefulness of our SSAM in light-weight YOLO models. Furthermore, visualization results also show the advantage of enhancing positioning ability with our SSAM.

Doped Vertical Organic Field-Effect Transistors Demonstrating Superior Bias-Stress Stability.

Bias-stress stability is essential to the practical applications of organic field-effect transistors (OFETs), yet it remains a challenge issue in conventional planar OFETs. Here, the feasibility of achieving high bias-stress stability in vertical structured OFETs (VOFETs) in combination with doping techniques is demonstrated. VOFETs with silver nanowires as source electrodes are fabricated and the device performance is optimized by understanding the influence of device parameters on performance. Then, the bias-stress stability of the optimized PDVT-10 VOFETs is investigated and found to be superior to the corresponding planar OFETs, which is attributed to reduced trapping effects of gate dielectrics in the VOFETs. Moreover, the bias-stress stability can be further improved by doping PDVT-10 to passivate bulk traps. Consequently, the characteristic time of doped PDVT-10 VOFETs extracted from stretched exponential equation is found to be over four times larger than that of the planar PDVT-10 OFETs under the same bias-stress conditions. These results present the promising applications of VOFETs as well as an effective strategy to achieve highly bias-stress stable OFETs.

Bis-acenaphthoquinone diimides with high electron deficiency and good coplanar conformation.

A series of novel bis-acenaphthoquinone diimides featuring a highly electron-deficient bis-acenaphthoquinone core are facilely synthesized via Knoevenagel condensation reaction. The diimides show high electron deficiency and good coplanar conformation, together with one of them having a maximum electron mobility up to 0.038 cm2 V-1 s-1.

Accurate and Efficient Lipoprotein Detection Based on the HCR-DNAzyme Platform.

Cardiovascular disease is one of the main causes of death in the world, which is closely associated with dyslipidemia. Dyslipidaemia is usually manifested as a relatively higher level of low-density lipoprotein (LDL) and lower level of high-density lipoprotein (HDL). Thus, the quantitative detection of the LDL and HDL particles is of great importance to predict the risk of cardiovascular diseases. However, the traditional methods can only indirectly reflect the HDL/LDL particle concentrations by detecting the cholesterol or proteins in HDL/LDL particles and are always laborious and time-consuming. Thus, the accurate and efficient approach for the detection of intact HDL and LDL particles is still lacking so far. We developed an enzyme- and isolation-free method to measure the concentration of HDL and LDL based on DNAzyme and hybridization chain reaction (HCR)-based signal amplification. This method can be used to directly and accurately detect the concentration of "actual" HDL and LDL particles instead of the cholesterol in HDL and LDL, with limits of detection of 10 and 30 mg/dL, respectively, which also satisfied the lipoprotein analysis in clinical samples. Therefore, this HCR-DNAzyme platform has great potential in clinical applications and health management.

Real-Time Dissecting the Dynamics of Drug Transportation in the Live Brain.

Brain diseases are becoming a more and more serious threat to human health. Many critical properties of the transport mechanisms of drugs in live brains remain poorly understood. In this work, single-particle tracking was used to dissect the transport dynamics of wheat germ agglutinin (WGA) in live brain and characterize the geometry and rheology of the extracellular space (ECS). The results revealed that the movements of WGA were influenced by the specific-binding molecules and the nature of the ECS. We further analyzed the mobility behaviors of WGA globally and quantitatively and found that movement of WGA in brain cells of acute slices was an active transport process associated with actin filaments and microtubules. This work paves the way for studies aiming at characterizing the biophysics of drug transport in the context of live brains, which may contribute to developing potential new therapeutic applications for brain diseases.

Natural-Killer-Cell-Inspired Nanorobots with Aggregation-Induced Emission Characteristics for Near-Infrared-II Fluorescence-Guided Glioma Theranostics.

Nature has always inspired robotic designs and concepts. It is conceivable that biomimic nanorobots will soon play a prominent role in medicine. The "Terminator" in the science fiction film is a cybernetic organism with living tissue over a metal endoskeleton, which inspired us to develop natural-killer-cell-mimic nanorobots with aggregation-induced emission (AIE) characteristics (NK@AIEdots) by coating a natural kill cell membrane on an AIE-active polymeric endoskeleton, PBPTV, a highly bright NIR-II AIE-active conjugated polymer. Owing to the AIE and soft-matter characteristics of PBPTV, as-prepared NK@AIEdots maintained a superior NIR-II brightness (quantum yield ∼7.9% in water) and good biocompatibility. Besides, they can serve as a tight junction (TJ) modulator to trigger an intracellular signaling cascade, causing TJ disruption and actin cytoskeleton reorganization to form an intercellular "green channel" to help them to cross the blood-brain barrier (BBB) silently. Furthermore, they can initiatively accumulate in glioblastoma cells in the complex brain matrix for high-contrast and through-skull tumor imaging. The tumor growth was also greatly inhibited by these NK@AIEdots under the NIR light illumination. As far as we know, the quantum yield of PBPTV is the highest among the existing NIR-II luminescent conjugated polymers. Besides, the NK-cell biomimetic nanorobots showed great potential for BBB-crossing active delivery.

Low Bandgap Donor-Acceptor π-Conjugated Polymers From Diarylcyclopentadienone-Fused Naphthalimides.

Two novel aromatic imides, diarylcyclopentadienone-fused naphthalimides (BCPONI-2Br and TCPONI-2Br), are designed and synthesized by condensation coupling cyclopentadienone derivatives at the lateral position of naphthalimide skeleton. It has been found that BCPONI-2Br and TCPONI-2Br are highly electron-withdrawing acceptor moieties, which possess broad absorption bands and very low-lying LUMO energy levels, as low as -4.02 eV. On the basis of both building blocks, six low bandgap D-A copolymers (P1-P6) are prepared via Suzuki or Stille coupling reactions. The optical and electrochemical properties of the polymers are fine-tuned by the variations of donors (carbazole, benzodithiophene, and dithienopyrrole) and π-conjugation linkers (thiophene and benzene). All polymers exhibit several attractive photophysical and electrochemical properties, i.e., broad near-infrared (NIR) absorption, deep-lying LUMO levels (between -3.88 and -3.76 eV), and a very small optical bandgap ( E g opt ) as low as 0.81 eV, which represents the first aromatic diimide-based polymer with an E g opt of <1.0 eV. An investigation of charge carrier transport properties shows that P5 exhibits a moderately high hole mobility of 0.02 cm2 V-1 s-1 in bottom-gate field-effect transistors (FETs) and a typical ambipolar transport behavior in top-gate FETs. The findings suggest that BCPONI-2Br, TCPONI-2Br, and the other similar acceptor units are promising building blocks for novel organic semiconductors with outstanding NIR activity, high electron affinity, and low bandgap, which can be extended to various next-generation optoelectronic devices.

Protein-modified conjugated polymer nanoparticles with strong near-infrared absorption: a novel nanoplatform to design multifunctional nanoprobes for dual-modal photoacoustic and fluorescence imaging.

Engineering conjugated polymer nanoparticles (CPNs) with an easily-modified surface is essential to construct multifunctional nanoprobes as contrast agents for dual-modal photoacoustic (PA) and fluorescence imaging, which can take advantages of the complementary information from a single modality. In this study, an abundant protein with plenty of functional groups was introduced for the first time to produce easily-modified CPNs, leading to a robust nanoplatform to engineer PA-based multifunctional nanoprobes due to their strong optical absorption in the near-infrared region. Meanwhile, the bovine serum albumin (BSA)-modified CPNs were further engineered by introducing gold clusters in situ, which can serve as fluorescent nanoprobes for dual-modal molecular imaging. In particular, the developed nanoplatform exhibited superior stability and excellent biocompatibility, making it an ideal candidate for various cancer-theranostics applications. More importantly, our imaging results demonstrated that the BSA-modified CPNs were excellent candidates to design PA-based contrast agents for multimodal imaging using the function of the protein. In addition, other functional blocks can also be added to the nanoplatform based on its easily-modified surface, making it a general method for the construction of multifunctional nanoprobes for disease theranostics.

Recombinant-fully-human-antibody decorated highly-stable far-red AIEdots for in vivo HER-2 receptor-targeted imaging.

We developed highly bright and stable far-red emissive AIEdots by using a new kind of click-functional PEG grafted amphiphilic polymer to coat hydrophobic AIE-active polymers (PDFDP). Furthermore, an anti-HER2 recombinant fully human antibody was produced and conjugated on the AIEdots via metal-free click chemistry to fabricate in vivo tumor-targeting nanoprobes.

Regioregular Bis-Pyridal[2,1,3]thiadiazole-Based Semiconducting Polymer for High-Performance Ambipolar Transistors.

We report a regioregular bis-pyridal[2,1,3]-thiadiazole (BPT) acceptor strategy to construct the first ambipolar pyridal[2,1,3]thiadiazole-based semiconducting polymer (PBPTV). The use of BPT unit enables PBPTV to achieve high electron affinity, low LUMO level, and extended π-conjugation. All these factors provide PBPTV with encouraging hole and electron mobilities up to 6.87 and 8.49 cm2 V-1 s-1, respectively. Our work demonstrates that the BPT unit is a promising building block for designing high-performance electron-transporting semiconductors in organic electronics.

High-Performance, Air-Stable Field-Effect Transistors Based on Heteroatom-Substituted Naphthalenediimide-Benzothiadiazole Copolymers Exhibiting Ultrahigh Electron Mobility up to 8.5 cm V-1 s-1.

Rational heteroatom engineering is applied to develop high-performance electron-transporting naphthalenediimide copolymers. Top-gate field-effect transistors fabricated from selenophene-containing polymers achieve an ultrahigh electron mobility of 8.5 cm2 V-1 s-1 and excellent air-stability. The results demonstrate that the incorporation of selenophene heterocycles into the polymers can improve the film-forming ability, intermolecular interaction, and carrier transport significantly.