An Artificial Universal Tactile Nociceptor Based on 2D Polymer Film Memristor Arrays with Tunable Resistance Switching Behaviors.

Nociceptor is an important receptor in the organism's sensory system; it can perceive harmful stimuli and send signals to the brain in order to protect the body in time. The injury degree of nociceptor can be divided into three stages: self-healing injury, treatable injury, and permanent injury. However, the current studies on nociceptor simulation are limited to the self-healing stage due to the limitation of the untunable resistance switching behavior of memristors. In this study, we constructed Al/2DPTPAK+TAPB/Ag memristor arrays with adjustable memory behaviors to emulate the nociceptor of biological neural network of all three stages. For this purpose, a PDMS/AgNWs/ITO/PET pressure sensor was assembled to mimic the tactile perception of the skin. The memristor arrays can not only simulate all the response of nociceptor, i.e., the threshold, relaxation, no adaptation, and sensitization with the self-healing injury, but can also simulate the treatable injury and the permanent injury. These behaviors are both demonstrated with a single memristor and in the form of pattern mapping of the memristor array.

Photoelectric Multi-Signal Output Sensor Based on Two-Dimensional Covalent Organic Polymer Film Modified by Novel Aggregation-Induced Emission Probes.

Optical sensors, especially fluorescence sensors, have been widely used because of their advantages in sensing, such as the high sensitivity, good selectivity, no radiation source, and easy operation. Here, we report an example of fluorescence sensing based on two-dimensional (2D) covalent organic polymers and highlight that the material can achieve a fast response and multi-signal output. This 2DPTPAK+TAPB-based sensor can quickly detect aromatic hydrocarbons and Fe3+ by the fluorescence signal or electrical resistance signal.

Functional Covalent Organic Frameworks Microspheres Synthesized by Self-limited Dynamic Linker Exchange for Stationary Phases.

Synthesizing uniform functional covalent organic frameworks (COFs) microspheres is the prerequisite of applying COFs as novel stationary phases for liquid chromatography. However, the synthesis of functionalized COFs microspheres is challenging due to the difficulty in maintaining microspheric morphology when conferring functions. Here, we develop a facile and universal "self-limited dynamic linker exchange" strategy to achieve surface functionalization of uniform COFs microspheres. Six different types of COFs microspheres are constructed, showing the universality and superiority of the strategy. The library of COFs micro-spheres stationary phases can be further enriched on demand by varying different functional building blocks. The "self-limited dynamic linker exchange" is attributed to the result of a delicate balance of reaction thermodynamics and molecular diffusion energy barrier. As a demonstration, the chiral functional COFs microspheres are used as stationary phases of chiral chromatography and realized effective enantioseparation. This article is protected by copyright. All rights reserved.

Overcoming the Unfavorable Effects of "Boltzmann Tyranny:" Ultra-Low Subthreshold Swing in Organic Phototransistors via One-Transistor-One-Memristor Architecture.

Organic phototransistors (OPTs), as photosensitive organic field-effect transistors (OFETs), have gained significant attention due to their pivotal roles in imaging, optical communication, and night vision. However, their performance is fundamentally limited by the Boltzmann distribution of charge carriers, which constrains the average subthreshold swing (SSave) to a minimum of 60 mV/decade at room temperature. In this study, an innovative one-transistor-one-memristor (1T1R) architecture is proposed to overcome the Boltzmann limit in conventional OFETs. By replacing the source electrode in an OFET with a memristor, the 1T1R device exploits the memristor's sharp resistance state transitions to achieve an ultra-low SSave of 18 mV/decade. Consequently, the 1T1R devices demonstrate remarkable sensitivity to photo illumination, with a high specific detectivity of 3.9 × 109 cm W-1Hz1/2, outperforming conventional OPTs (4.9 × 104 cm W-1Hz1/2) by more than four orders of magnitude. The 1T1R architecture presents a potentially universal solution for overcoming the detrimental effects of "Boltzmann tyranny," setting the stage for the development of ultra-low SSave devices in various optoelectronic applications.

Functional Covalent Organic Framework (COF) Nanoparticles for Biomimic Mineralization and Bacteria Inhabitation.

Biomimic mineralization of hard tissues with hierarchical structures is a challenging task, while designing multifunctional materials possessing both the ability of biomimic mineralization and drug delivery is even more difficult. Herein, inspired by the multilevel structure and mineralization ability of amelogenin, a novel carboxyl-functionalized covalent organic framework (COF) nanosphere material was designed and synthesized, which exhibited a significant biomimetic remineralization ability as demonstrated on SiO2 glass, Ti6Al4V, and an acid-etched enamel surface. Furthermore, the nanoporous structure also enables the COF nanospheres to serve as a drug delivery system for the controlled release of antibacterial drugs. This work provides a promising strategy for the design of multifunctional biomimic materials.

Stepwise versus Concerted: Theoretical Insights into the Stereoselectivity in Aryl Imine Formation Assisted by Acid and Water.

The wide applications of the aryl Schiff base require extensive understanding of the mechanism of its formation, which remains unclear. In this work, the detailed formation mechanisms between benzaldehyde and aniline or 4-(9-anthryl) ethynyl aniline were investigated at the CCSD(T)//B3LYP level, and the influence of water molecules and acid catalysis and the stereoselectivity were addressed. The results show that the participation of explicit water molecules greatly accelerates the reactions by alleviating the ring tension of the transition states, and acid catalysis strongly favors the imine formation and provides driving force for the forward reaction. In acidic conditions, both N-protonated carbinolamine formations and imine formations are achieved under mild conditions with the assistance of water molecules, and the proton transfer is more advanced than the C-N and C═N bond formation, which is in good agreement with the experimental observations. In contrast, under neutral conditions, even with the assistance of two water molecules, the reaction is hard to take place at room temperature owing to the high Gibbs free energy barriers with the proton transfer and the C-N or C═N bond formation concerted. The analysis of stereoselectivity shows that the formation of trans imine is both kinetically and thermodynamically more favorable than the cis one under the acidic condition with the assistance of water molecules, and the presence of conjugated substituent 4-(9-anthryl) ethynyl of aniline marginally raises the energy barriers. This work provides a systematic view of the mechanism for the formation of aryl imine and is expected to offer insights for the control of the dynamic covalent chemistry and the synthesis of covalent organic frameworks.

Synthesis of a covalent organic framework with hetero-environmental pores and its medicine co-delivery application.

The topology type and the functionalization of pores play an important role in regulating the performance of covalent organic frameworks. Herein, we designed and synthesized the covalent organic framework with hetero-environmental pores using predesigned asymmetrical dialdehyde monomer. According to the results of structural characterization, crystallinity investigation, and theoretical calculation, the hetero-environmental pores of the obtained framework are regarded as the alternant arrangement. The distinctive hetero pore structure leads the designed material to show more advantages as compared with control materials in loading both hydrophobic and hydrophilic antibiotics for wound healing. This dual-antibiotic strategy can expand the antibacterial range as compared with the single antibiotic one, and reduce the generation of drug resistance. In summary, this strategy for designing covalent organic frameworks with hetero-environmental pores can extend the structural variety and provide a pathway for improving the practical application performance of these materials.

Recent Advances in Field Effect Transistor Biosensors: Designing Strategies and Applications for Sensitive Assay.

In comparison with traditional clinical diagnosis methods, field-effect transistor (FET)-based biosensors have the advantages of fast response, easy miniaturization and integration for high-throughput screening, which demonstrates their great technical potential in the biomarker detection platform. This mini review mainly summarizes recent advances in FET biosensors. Firstly, the review gives an overview of the design strategies of biosensors for sensitive assay, including the structures of devices, functionalization methods and semiconductor materials used. Having established this background, the review then focuses on the following aspects: immunoassay based on a single biosensor for disease diagnosis; the efficient integration of FET biosensors into a large-area array, where multiplexing provides valuable insights for high-throughput testing options; and the integration of FET biosensors into microfluidics, which contributes to the rapid development of lab-on-chip (LOC) sensing platforms and the integration of biosensors with other types of sensors for multifunctional applications. Finally, we summarize the long-term prospects for the commercialization of FET sensing systems.

Regulating the Synergistic Effect in Bimetallic Two-Dimensional Polymer Oxygen Evolution Reaction Catalysts by Adjusting the Coupling Strength Between Metal Centers.

Bimetallic electrocatalysts with its superior performance has a broad application prospect in oxygen evolution reaction (OER), but the fundamental understanding of the mechanism of synergistic effect is still limited since there lacks a practical way to decouple the influence factors on the intrinsic activity of active sites from others. Herein, a series of bimetallic Co-Ni two-dimensional polymer (2DP) model OER catalysts with well-defined architecture, monolayer characteristic, were designed and synthesized to explore the influence of the coupling strength between metal centers on OER performance. The coupling strength was regulated by adjusting the spacing between metal centers or the conjugation degree of bridge skeleton. Among the examined 2DPs, CoTAPP-Ni-MF-2DP, which has the strongest coupling strength between metal centers exhibited the best OER performance. These model systems can help to explore the precise structure-performance relationships, which is important for the rational catalyst design at the atomic/molecular levels.

A Highly Crystalline Single Layer 2D Polymer for Low Variability and Excellent Scalability Molecular Memristors.

Large-scale growth of highly crystalline single layer 2D polymers (SL-2DPs) and their subsequent integration into memristors is key to advancing the development of high-density data storage devices. However, leakage problems resulting from the porous structure of 2DPs continue to make such advances extremely challenging. Herein, we overcome this issue by incorporating long alkoxy chains into key molecular building blocks to obtain a highly crystalline 2DP, as visualized by scanning tunneling microscopy, and prevent metal permeation in the subsequent device fabrication process. SL-2DP memristors constructed via direct evaporation of the top electrodes exhibit low variability (σVset  = 0.14) due to the single-monomer-thick feature together with the high regular structure and coordination ability which minimizes the stochastic spatial distribution of conductive filaments (CFs) in both vertical and lateral dimensions. The variability is further decreased to 0.04 by confining the formation and fracture of CFs to the interface through the utilization of bilayer junctions. Using peak force tunneling atomic force microscopy, the nanometer scalability (< 50 nm2 ) and low power consumption of these molecular memristor devices are demonstrated.

Spatial Well-defined Bimetallic Two-Dimensional Polymers with Single-Layer Thickness for Electrocatalytic Oxygen Evolution Reaction.

Innovative bimetallic materials provide more possibilities for further improving the performance of oxygen evolution reaction (OER) electrocatalysts. However, it is still a great challenge to rationally design bimetallic catalysts because there is not a practical way to decouple the factors influencing the intrinsic activity of active sites from others, thus hindering in-depth understanding of the mechanism. Herein, we provide a rational design of bimetallic Ni, Co two-dimensional polymer model OER catalyst. The well-defined architecture, identical density of active sites and monolayer characteristic allow us to decouple the intrinsic activity of active sites from other factors. The results confirmed that the relative position and local coordination environment has significant effect on the synergistic effect of the bimetallic centres. The highest electrocatalytic activity with the turnover frequency value up to 26.19 s-1 was achieved at the overpotential of 500 mV.

Mineralization of calcium phosphate on two-dimensional polymer films with controllable density of carboxyl groups.

Two-dimensional polymers functionalized with controllable density of carboxyl groups were constructed with the Langmuir-Blodgett method. Mineralization of calcium phosphate shows significantly different characteristics on these films, which clearly indicates that the density of carboxy groups plays a determining role in controlling the nucleation and orientated growth of calcium phosphate.

Single Molecule Level and Label-Free Determination of Multibiomarkers with an Organic Field-Effect Transistor Platform in Early Cancer Diagnosis.

The single molecule level determination with a transistor (SiMoT) platform has attracted considerable attention in the recognition of various ultralow abundance biomolecules, while complicated labeling and testing processes limit its further applications. Recently, organic field-effect transistor (OFET)-based biosensors are good candidates for constructing an advanced label-free SiMoT platform due to their facile fabrication process, rapid response time, and low sample volume with a wide range of detection. However, the sensitivity of most OFET-based biosensors is in the order of nM and pM, which cannot meet the detection requirements of ultralow abundance protein. Herein, a label-free SiMoT platform is demonstrated by integrating pillar[n]arene as a signal amplifier, and the detection limit can reach 4.75 aM. Besides, by simultaneous determination of α-fetoprotein, carcinoembryonic antigen, and prostate antigen, the proposed multiplexed OFET-based SiMoT platform provides a key step in reliable early cancer diagnosis.

Red Phosphorescent Carbon Quantum Dot Organic Framework-Based Electroluminescent Light-Emitting Diodes Exceeding 5% External Quantum Efficiency.

Carbon quantum dots (CQDs) have developed into prospective nanomaterials for next-generation lighting and displays due to their intrinsic advantages of high stability, low cost, and environmental friendliness. However, confined by the spin-forbidden nature of triplet state transitions, the highest theoretical value of external quantum efficiency (EQE) of fluorescent CQDs is merely 5%, which fundamentally limits their further application in electroluminescent light-emitting diodes (LEDs). Soluble phosphorescent CQDs offer a means of breaking the shackle to achieve efficient monochromatic electroluminescence, especially red emission, which is a pivotal constituent in full-color displays. Here, the synthesis of red (625 nm) phosphorescent carbon quantum dot organic frameworks (CDOFs) with a quantum yield of up to 42.3% and realization of high-efficiency red phosphorescent electroluminescent LEDs are reported. The LEDs based on the CDOFs exhibited a red emission with a maximum luminance of 1818 cd m-2 and an EQE of 5.6%. This work explores the possibility of a new perspective for developing high-performance CQD-based electroluminescent LEDs.

Peptoid Nanosheet-Based Sensing System for the Diagnosis and Surveillance of Amnestic Mild Cognitive Impairment and Alzheimer's Disease.

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases characterized by progressive cognitive decline. Early diagnosis and dynamic monitoring are essential to the treatment and care of AD but challenging. Here we develop a noninvasive, blood-based AD detection method based on surface plasmonic resonance imaging (SPRi) technique. The functionalized sensing SPRi chips were constructed with self-assembled loop-displaying peptoid nanosheets to improve the detection sensitivity of plasma amyloid ß42 (Aß42). We analyze the plasma from 30 clinically diagnosed AD patients, 29 amnestic cognitive impairment (aMCI) patients, and 30 control individuals and demonstrate that this sensing system can significantly distinguish the three groups with high sensitivity and specificity. In the follow-up studies of the aMCI patients, we find that decrease in the binding signals in the patients correlates with the disease progression into AD whereas the almost unchanged signals correlate with stable disease remaining at aMCI status. These results show the capability of the peptoid-nanosheet-based SRPi sensing system for the early diagnosis and dynamic monitoring of AD.

Dual-functional porous MOFs with hierarchical guest encapsulation for room-temperature phosphorescence and white-light-emission.

The development of optical materials with room temperature phosphorescence (RTP) and white light emission (WLEDs) is highly desirable and remains a challenging task. Herein, a porous metal-organic framework PCN-921 with a high quantum yield (ΦF = 93.6%) was achieved. To make full use of the advantages of the high porosity of PCN-921, we hierarchically encapsulated different guest molecules coronene and rhodamine B (RhB) into the framework. Unsurprisingly, the hybrid material coronene@PCN-921 was obtained after in situ encapsulation of the guest coronene into the framework, and it exhibits obvious RTP behavior with a long phosphorescence lifetime of 62.5 ns. Subsequently, second guest RhB molecules were introduced after soaking in RhB solution and the material RhB@coronene@PCN-921 was achieved. Interestingly, it exhibits white light emission with the CIE coordinates of (0.29, 0.34), and can be used as a high performance WLED lamp. This is the first work on dual-functional hybrid dyes@MOFs with hierarchical guest encapsulation for RTP and white light emission, which suggests the potential applications of MOFs in multifunctional optical devices.

Ternary Conductance Switching Realized by a Pillar[5]arene-Functionalized Two-Dimensional Imine Polymer Film.

Nowadays, most manufacturing memory devices are based on materials with electrical bistability (i. e., "0" and "1") in response to an applied electric field. Memory devices with multilevel states are highly desired so as to produce high-density and efficient memory devices. Herein, we report the first multichannel strategy to realize a ternary-state memristor. We make use of the intrinsic sub-nanometer channel of pillar[5]arene and nanometer channel of a two-dimensional imine polymer to construct an active layer with multilevel channels for ternary memory devices. Low threshold voltage, long retention time, clearly distinguishable resistance states, high ON/OFF ratio (OFF/ON1/ON2=1 : 10 : 103 ), and high ternary yield (75 %) were obtained. In addition, the flexible memory device based on 2DPTPAZ+TAPB can maintain its stable ternary memory performance after being bent 500 times. The device also exhibits excellent thermal stability and can tolerate a temperature as high as 300 °C. It is envisioned that the results of this work will open up possibilities for multistate, flexible resistive memories with good thermal stability and low energy consumption, and broaden the application of pillar[n]arene.

An intermolecular hydrogen bond plays a determining role in product selection of a surface confined Schiff-base reaction.

Herein, we illustrate how the cooperation of intermolecular hydrogen bonds and conformation flexibility leads to the formation of diverse complex covalent nanostructures on the surface, while the relative abundance of the final products can be further tuned by adjusting the molar ratio and concentration of monomers.

Ultra-thin two-dimensional molecular crystals grown on a liquid surface for high-performance phototransistors.

A novel strategy for the growth of molecularly thin two-dimensional molecular crystals (2DMCs) of organic semiconductors with poor solubility was developed. Large-area bilayer 2DMCs were grown on a liquid surface at elevated temperatures, with record mobility and superior photoresponse.

Boronic ester Sierpinski triangle fractals: from precursor design to on-surface synthesis and self-assembling superstructures.

Herein, we designed and synthesized a precursor with a three-fold node and successfully constructed covalent Sierpinski triangle (ST) fractals with boronic ester linkages both at the liquid/solid interface at room temperature and by thermal annealing in a water atmosphere under ambient conditions. Remarkably, large-scale ordered superstructures of covalent STs are constructed by thermal annealing, which paves the way for property investigation of STs.