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The existing electrochemical biosensors lack controllable and intelligent merit to modulate the sensing process upon external stimulus, leading to challenges in analyzing a few copies of biomarkers in unamplified samples. Here, we present a self-actuated molecular-electrochemical system that consists of a tentacle and a trunk modification on a graphene microelectrode. The tentacle that contains a probe and an electrochemical label keeps an upright orientation, which increases recognition efficiency while decreasing the pseudosignal. Once the nucleic acids are recognized, the tentacles nearby along with the labels are spontaneously actuated downward, generating electrochemical responses under square wave voltammetry. Thus, it detects unamplified SARS-CoV-2 RNAs within 1 min down to 4 copies in 80 μL, 2-6 orders of magnitude lower than those of other electrochemical assays. Double-blind testing and 10-in-1 pooled testing of nasopharyngeal samples yield high overall agreement with reverse transcription-polymerase chain reaction results. We fabricate a portable prototype based on this system, showing great potential for future applications.

Transition-metal dichalcogenides (TMDs) have been considered potential materials for the next generation of semiconductors. Realizing controllable growth of TMD crystals is a prerequisite for their future applications, which remains challenging. Here, we reveal a new mechanism of self-expanding molten salt-driven growth for a salt-assisted method and achieve the patterned growth of TMD single-crystal arrays with a size of hundreds of micrometers. Time-of-flight secondary ion mass spectroscopy and other spectroscopy characterizations identify the component of the molten salt solution. Microscopic characterizations reveal the existence of salt solution as an interlayer between a TMD monolayer and the silicon substrate as well as particles along the crystal edge. The edged salt solution serves as a self-expanding liquid substrate, which confines the reactive sites to the localized liquid surface, thus avoiding random nucleation. The surface reaction also assures monolayer crystal formation due to self-limiting growth. Besides, the liquid substrate affords sources and spreads itself continuously owing to the nonwetting effect on TMD crystals, thereby facilitating the continuous extension of the TMD monolayer. This work provides novel insights into the controllable synthesis of TMD monolayers and paves the way for the fabrication of TMD-based integrated functional devices.

Though Olefin-linked covalent organic frameworks (oCOFs) possess excellent π-electron delocalization, the barely reversible olefin linkage brings challenges for oCOFs’ synthesis and functionalization. Here, we synthesize new oCOFs with tertiary amine knots which have twisted configuration and electron-donating nature. Investigation into the structural variation and photoelectric performance shows that the twisted configuration of oCOF-TFPA could favor to the intramolecular charge transfer process and reduce the possibility of aggregation-caused quenching. Photoelectrical measurements and electric band structure calculation both verify the superiority of this oCOFs’ structure in photoelectric sensing.

An aptamer-based field-effect transistor (Apta-FET) is a well-developed assay method with high selectivity and sensitivity. Due to the limited information density that natural nucleotide library holds, the Apta-FET faces fundamental restriction in universality to detect various types of analytes. Herein, we demonstrate a type of Apta-FET sensors based on an artificial nucleotide aptamer (AN-Apta-FET). The introduction of an artificial nucleotide increases the diversity of the potential aptamer structure and expands the analyte category of the Apta-FET. The AN-Apta-FET specifically detects hepatoma exosomes, which traditional Apta-FET fails to discriminate from other tumor-derived exosomes, with a limit of detection down to 242 particles mL

Organic single crystals (OSCs) have received increasing interest in the last decades for their potential applications in flexible electronics. Although there are various subtractive manufacturing methods of organic electronics, the subtractive manufacturing of OSCs is still a challenge, since OSCs are assembled via weak van-der-Waals interactions which are vulnerable and cannot afford damages and suffer the degradation of performances after the process. Here, we develop an epitaxial etching strategy which clips the OSCs and keeps high-quality crystalline nature of the resulting materials. As a result, high-quality organic micro-ribbon arrays are fabricated which maintains 89% charge mobility in average compared with original OSCs, showing great potential of this subtractive manufacturing method in future organic electronics.

Rapid screening of infected individuals from a large population is an effective means in epidemiology, especially to contain outbreaks such as COVID-19. The gold standard assays for COVID-19 diagnostics are mainly based on the reverse transcription polymerase chain reaction, which mismatches the requirements for wide-population screening due to time-consuming nucleic acid extraction and amplification procedures. Here, we report a direct nucleic acid assay by using a graphene field-effect transistor (g-FET) with Y-shaped DNA dual probes (Y-dual probes). The assay relies on Y-dual probes modified on g-FET simultaneously targeting ORF1ab and N genes of SARS-CoV-2 nucleic acid, enabling high a recognition ratio and a limit of detection (0.03 copy μL–1) 1–2 orders of magnitude lower than existing nucleic acid assays. The assay realizes the fastest nucleic acid testing (∼1 min) and achieves direct 5-in-1 pooled testing for the first time. Owing to its rapid, ultrasensitive, easily operated features as well as capability in pooled testing, it holds great promise as a comprehensive tool for population-wide screening of COVID-19 and other epidemics.

In principle, polymerization tends to produce amorphous or poorly crystalline materials. Efficiently producing high-quality single crystals by polymerization in solvent remains as an unsolved issue in chemistry, especially for covalent organic frameworks (COFs) with highly complex structures. To produce μm-sized single crystals, the growth time is prolonged to >15 days, far away from the requirements in practical applications. Here, we find supercritical CO2 (sc-CO2) accelerates single-crystal polymerization by 10,000,000 folds, and produces two-dimensional (2D) COF single crystals with size up to 0.2 mm within 2~5 min. Although it is the fastest single-crystal polymerization, the growth in sc-CO2 leads to not only the largest crystal size of 2D COFs, but also higher quality with improved photoconductivity performance. This work overcomes traditional concept on low efficiency of single-crystal polymerization, and holds great promise for future applications owing to its efficiency, industrial compatibility, environmental friendliness and universality for different crystalline structures and linkage bonds., Rapid growth of highly crystalline Covalent organic framework (COF) materials remains challenging. Here, the authors accelerate single-crystal polymerization using supercritical CO2 and realize the fabrication of two-dimensional COF single crystals within several minutes.

Effective detection of methamphetamine (Met) requires a fast, sensitive, and cheap testing assay. However, commercially available methods require expensive instruments and highly trained operators, which are time-consuming and labor-intensive. Herein, an antibody-modified graphene transistor assay is developed for sensitive and minute-level detection of Met in complex environments. The anti-Met probe captured charged targets within 120 s, leading to a p-doping effect near the graphene channel. The limit of detection reaches 50 aM (5.0 × 10−17 M) Met in solution. The graphene transistor would be a valuable tool for Met detection effective prevention of drug abuse.

Accurate and population-scale screening technology is crucial in the control and prevention of COVID-19, such as pooled testing with high overall testing efficiency. Nevertheless, pooled testing faces challenges in sensitivity and specificity due to diluted targets and increased contaminations. Here, we develop a graphene field-effect transistor sensor modified with triple-probe tetrahedral DNA framework (TDF) dimers for 10-in-1 pooled testing of SARS-CoV-2 RNA. The synergy effect of triple probes as well as the special nanostructure achieve a higher binding affinity, faster response, and better specificity. The detectable concentration reaches 0.025-0.05 copy μL

The evolutionary success in information technology has been sustained by the rapid growth of sensor technology. Recently, advances in sensor technology have promoted the ambitious requirement to build intelligent systems that can be controlled by external stimuli along with independent operation, adaptivity, and low energy expenditure. Among various sensing techniques, field-effect transistors (FETs) with channels made of two-dimensional (2D) materials attract increasing attention for advantages such as label-free detection, fast response, easy operation, and capability of integration. With atomic thickness, 2D materials restrict the carrier flow within the material surface and expose it directly to the external environment, leading to efficient signal acquisition and conversion. This review summarizes the latest advances of 2D-materials-based FET (2D FET) sensors in a comprehensive manner that contains the material, operating principles, fabrication technologies, proof-of-concept applications, and prototypes. First, a brief description of the background and fundamentals is provided. The subsequent contents summarize physical, chemical, and biological 2D FET sensors and their applications. Then, we highlight the challenges of their commercialization and discuss corresponding solution techniques. The following section presents a systematic survey of recent progress in developing commercial prototypes. Lastly, we summarize the long-standing efforts and prospective future development of 2D FET-based sensing systems toward commercialization.

Effective screening of infectious diseases requires a fast, cheap, and population-scale testing. Antigen pool testing can increase the test rate and shorten the screening time, thus being a valuable approach for epidemic prevention and control. However, the overall percent agreement (OPA) with polymerase chain reaction (PCR) is one-half to three-quarters, hampering it from being a comprehensive method, especially pool testing, beyond the gold-standard PCR. Here, a multiantibodies transistor assay is developed for sensitive and highly precise antigen pool testing. The multiantibodies capture SARS-CoV-2 spike S1 proteins with different configurations, resulting in an antigen-binding affinity down to 0.34 fM. The limit of detection reaches 3.5 × 10-17 g mL-1SARS-CoV-2 spike S1 protein in artificial saliva, 4-5 orders of magnitude lower than existing transistor sensors. The testing of 60 nasopharyngeal swabs exhibits ∼100% OPA with PCR within an average diagnoses time of 38.9 s. Owing to its highly precise feature, a portable integrated platform is fabricated, which achieves 10-in-1 pooled screening for high testing throughput. This work solves the long-standing problem of antigen pool testing, enabling it to be a valuable tool in precise diagnoses and population-wide screening of COVID-19 or other epidemics in the future.

Direct SARS-CoV-2 nucleic acid testing with fast speed and high frequency is crucial for controlling the COVID-19 pandemic. Here, direct testing of SARS-CoV-2 nucleic acid is realized by field-effect transistors (FETs) with an electro-enrichable liquid gate (LG) anchored by tetrahedral DNA nanostructures (TDNs). The applied gate bias electrostatically preconcentrates nucleic acids, while the liquid gate with TDNs provides efficient analyte recognition and signal transduction. The average diagnosis time is ∼80 s, and the limit of detection approaches 1-2 copies in 100 µL of clinical samples without nucleic acid extraction and amplification. As such, TDN-LG FETs solve the dilemma of COVID-19 testing on mass scale that diagnosis accuracy and speed undergo trade-off. In addition, TDN-LG FETs achieve unamplified 10-in-1 pooled nucleic acid testing for the first time, and the results are consistent with PCR. Thus, this technology promises on-site and wide population COVID-19 screening and ensures safe world-reopening.

Metal-air batteries in fiber shape, which are theoretically endowed with high energy densities, have emerged as a versatile platform for the advance of next-generation flexible electronics. The past decade has witnessed the booming development of fiber-shaped metal-air batteries including flexible lithium-air (oxygen) batteries, zinc-air batteries, aluminum-air batteries and lithium-CO2 batteries. Here the recent advances of fiber-shaped metal-air batteries are briefly summarized, with particular emphasis on the fabrication of flexible electrodes, the electrolyte exploitation and encapsulating material optimization. The remaining challenges and promising directions are highlighted to provide clues for the practical implementation of fiber-shaped metal-air batteries.

The growth of covalent organic frameworks (COFs) normally goes through a fast polymerization process, which quickly forms amorphous powder and then slowly crystallizes to obtain nanometer-sized cry...

Recent development of self-healing material has attracted tremendous attention, owing to its biomimetic ability to restore structure and functionality when encountering damages. Here, we develop a three-dimensional (3D) printable self-healing composite conductive polymer by mixing hydrogen-bond-based supramolecular polymer with low-cost carbon black. It has a room-temperature self-healing capability in both conductivity and mechanical property, while its shear-thinning behavior enables fabrication of a self-healable circuit by 3D printing technology. As an application, the circuit shows an excellent temperature-dependent behavior of the resistance, indicating its great potential for practical application in the artificial intelligence field.

The fast spread of SARS-CoV-2 has severely threatened the public health. Establishing a sensitive method for SARS-CoV-2 detection is of great significance to contain the worldwide pandemic. Here, we develop a graphene field-effect transistor (g-FET) biosensor and realize ultrasensitive SARS-CoV-2 antibody detection with a limit of detection (LoD) down to 10-18 M (equivalent to 10-16 g mL-1) level. The g-FETs are modified with spike S1 proteins, and the SARS-CoV-2 antibody biorecognition events occur in the vicinity of the graphene surface, yielding an LoD of ∼150 antibodies in 100 μL full serum, which is the lowest LoD value of antibody detection. The diagnoses time is down to 2 min for detecting clinical serum samples. As such, the g-FETs leverage rapid and precise SARS-CoV-2 screening and also hold great promise in prevention and control of other epidemic outbreaks in the future.

A semiconducting photoresist contributes to precise and reliable manufacture of highly integrated organic electronics., Owing to high resolution, reliability, and industrial compatibility, all-photolithography is a promising strategy for industrial manufacture of organic electronics. However, it receives limited success due to the absence of a semiconducting photoresist with high patterning resolution, mobility, and performance stability against photolithography solution processes. Here, we develop a comprehensive semiconducting photoresist with nano-interpenetrating structure. After photolithography, nanostructured cross-linking networks interpenetrate with continuous phases of semiconducting polymers, enabling submicrometer patterning accuracy and compact molecular stacking with high thermodynamic stability. The mobility reaches the highest values of photocrosslinkable organic semiconductors and maintains almost 100% after soaking in developer and stripper for 1000 min. Owing to the comprehensive performance, all-photolithography is achieved, which fabricates organic inverters and high-density transistor arrays with densities up to 1.1 × 105 units cm−2 and 1 to 4 orders larger than conventional printing processes, opening up a new approach toward manufacturing highly integrated organic circuits and systems.

The detection of samples at ultralow concentrations (one to ten copies in 100 μl) in biofluids is hampered by the orders-of-magnitude higher amounts of 'background' biomolecules. Here we report a molecular system, immobilized on a liquid-gated graphene field-effect transistor and consisting of an aptamer probe bound to a flexible single-stranded DNA cantilever linked to a self-assembled stiff tetrahedral double-stranded DNA structure, for the rapid and ultrasensitive electromechanical detection (down to one to two copies in 100 μl) of unamplified nucleic acids in biofluids, and also of ions, small molecules and proteins, as we show for Hg

Direct and sensitive short-wavelength ultraviolet (UVC) dosimeters could provide a safer disinfection environment against viruses. We developed direct, quantitative, specific and highly sensitive UVC dosimeters based on DNA nanostructure-modified graphene field-effect transistors. Detectable doses of the dosimeters range from 0.005 to 6 kJ m−2 and such dosimeters have at least 5 times better sensitivity than the current direct UV dosimeters.

ConspectusSince the rise of two-dimensional (2D) materials, synthetic methods including mechanical exfoliation, solution synthesis, and chemical vapor deposition (CVD) have been developed. Mechanical exfoliation prepares randomly shaped materials with small size. Solution synthesis introduces impurities that degrade the performances. CVD is the most successful one for low-cost scalable preparation. However, when it comes to practical applications, disadvantages such as high operating temperature (∼1000 °C), probable usage of metal catalysts, contamination, defects, and interstices introduced by postgrowth transfer are not negligible. These are the reasons why plasma-enhanced CVD (PECVD), a method that enables catalyst-free in situ preparation at low temperature, is imperatively desirable.In this Account, we summarize our recent progress on controllable preparation of 2D materials by PECVD and their applications. We found that there was a competition between etching and nucleation and deposition in PECVD, making it highly controllable to obtain desired materials. Under different equilibrium states of the competition, various 2D materials with diverse morphologies and properties were prepared including pristine or nitrogen-doped graphene crystals, graphene quantum dots, graphene nanowalls, hexagonal boron nitride (h-BN), B-C-N ternary materials (BCxN), etc. We also used mild plasma to modify or treat 2D materials (e.g., WSe2) for desired properties.PECVD has advantages such as low temperature, transfer-free process, and industrial compatibility, which enable facile, scalable, and low-cost preparation of 2D materials with clean surfaces and interfaces directly on noncatalytic substrates. These merits significantly benefit the as-prepared materials in the applications. Field-effect transistors with high motilities were directly fabricated on graphene and nitrogen-doped graphene. By use of h-BN as the dielectric interfacial layer, both mobilities and saturated power densities of the devices were improved owing to the clean, closely contacted interface and enhanced interfacial thermal dissipation. High-quality materials and interfaces also enabled promising applications of these materials in photodetectors, pressure sensors, biochemical sensors, electronic skins, Raman enhancement, etc. To demonstrate the commercial applications, several prototypical devices were studied such as distributed pressure sensor arrays, touching module on a robot hand for braille recognition, and smart gloves for recording sign language. Finally, we discuss opportunities and challenges of PECVD as a comprehensive preparation methodology of 2D materials for future applications beyond traditional CVD.

Self-healing materials have been developed over the past decade with the recovery ability after damage. However, most researches focused on the self-healing process at three-dimension. Herein, we prepare monolayer self-healing hydrogen-bond-based supramolecular polymer film and explore the self-healing process at the two-dimensional limit. The healing process, which can be reversibly repeated for at least three times, is influenced by the temperature, the molecule-substrate interaction and the substrate roughness. In the application, the monolayer self-healing polymer film can be used to modify the SiO2 dielectric for copper phthalocyanine field effect transistor with improved mobility. This work will be valuable for developing two-dimensional functional self-healing materials in the future.

Due to ultra-high reactivity, direct determination of free radicals, especially hydroxyl radical (•OH) with ultra-short lifetime, by field-effect transistor (FET) sensors remains a challenge, which hampers evaluating the role that free radical plays in physiological and pathological processes. Here, we develop a •OH FET sensor with a graphene channel functionalized by metal ion indicators. At the electrolyte/graphene interface, highly reactive •OH cuts the cysteamine to release the metal ions, resulting in surface charge de-doping and a current response. By this inner-cutting strategy, the •OH is selectively detected with a concentration down to 10−9 M. Quantitative metal ion doping enables modulation of the device sensitivity and a quasi-quantitative detection of •OH generated in aqueous solution or from living cells. Owing to its high sensitivity, selectivity, real-time label-free response, capability for quasi-quantitative detection and user-friendly portable feature, it is valuable in biological research, human health, environmental monitoring, etc., Field effect transistors based on graphene hold promise for future sensing applications. Here, the authors report a free radical sensor in which the •OH radical cuts cysteamine to release Cd2+ from the electrolyte/graphene interface and selectively detects •OH with a concentration down to 10−9 M.

With the development of wireless technology and flexible electronics, flexible frequency reconfigurable antennas have been directly used as sensors to detect mechanical signals. As an important frequency reconfigurable antenna, microstrip antenna has been widely studied in the field of flexible and flexible electronics in recent years. However, the stretchability of microstrip antennas usually comes at the cost of reducing the conductivity of the radiated conductor. Here, we report a flexible force sensitive frequency reconfigurable microstrip antenna, which fabricated by silver fiber conductive fabric with a double-wire braided structure. In order to increase the detection of pressure, an elastic dielectric layer with a microhemispheric array was introduced into the microstrip antenna to extend the frequency band width of the reconfigurable antenna. The relative frequency of the antenna varied from 0% to −12.9%, and the sensing sensitivity was −1.9 kPa−1. As potential applications, we demonstrate the use of a flexible frequency reconfigurable antenna base on stretchable conductive fabric as a strain sensor capable of measuring bending angle and movements of a human finger. The change in the resonance frequency with the externally applied tensile strain in this antenna design has a sensitivity of 3.448, manifesting a 4.19- and a 13.79-fold increase of sensitivity when compared to those in previous reports that used arched or both-planes serpentine rectangular microstrip antenna. This is of great significance for the application of wearable antenna in wireless mechanical sensing technology.

PdTe2-based photodetectors reveal anisotropic and highly efficient intraband photocurrents at long wavelength., Emergent topological Dirac semimetals afford fresh pathways for optoelectronics, although device implementation has been elusive to date. Specifically, palladium ditelluride (PdTe2) combines the capabilities provided by its peculiar band structure, with topologically protected electronic states, with advantages related to the occurrence of high-mobility charge carriers and ambient stability. Here, we demonstrate large photogalvanic effects with high anisotropy at terahertz frequency in PdTe2-based devices. A responsivity of 10 A/W and a noise-equivalent power lower than 2 pW/Hz0.5 are achieved at room temperature, validating the suitability of PdTe2-based devices for applications in photosensing, polarization-sensitive detection, and large-area fast imaging. Our findings open opportunities for exploring uncooled and sensitive photoelectronic devices based on topological semimetals, especially in the highly pursuit terahertz band.

Traditional methods to prepare two-dimensional (2D) B-C-N ternary materials (BC

Two-dimensional (2D) p-n junctions are basic components of various functional devices. However, the shortage of natural p-type 2D semiconductors makes it difficult to achieve both p-type and n-type transport in high-performance multifunctional devices. Here, continuous and uniform p-type Si2Te3 thin films are grown on SiO2/Si substrates, which are simultaneously used as an in situ Si source. Large-size 2D films with dimensions of ∼8 × 2 cm2 are prepared for the first time using a reliable and simple chemical vapor deposition (CVD) technique. Film growth occurs via the vapor-liquid-solid mechanism, allowing the film thickness to be controlled by the substrate temperature. As the Si2Te3 film thickness increases from 3 to 8 nm, the bandgap decreases from 2.07 to 1.65 eV. Moreover, the directly grown thin films possess high crystallinity, showing electronic properties that are comparable to those of MoTe2 crystals and MoS2 films. Therefore, this large-area growth of p-type Si2Te3 enriches the 2D semiconductor library and opens up a new platform for the study of p-type Si2Te3, which has potential for application in p-n junctions.