High-performance PANI sensor on silicon nanowire arrays for sub-ppb NH3 detection.

For industrial production and disease diagnosis, real-time detection of low concentrations of NH3 is crucial, necessitating a gas-sensitive sensor compatible with integrated processes and exhibiting excellent performance. Herein, we employed wet etching and rapid in-situ polymerization on silicon nanowire substrates to grow polyaniline fibers, thereby fabricating NH3 gas sensors with p-p heterojunction and three-dimensional network structures. Characterization and gas sensing performance testing were conducted. The results demonstrate the outstanding NH3 detection capabilities of the sensor, providing stable responses down to concentrations as low as 1 ppb, which indicates its LOD is one to two orders of magnitude lower than current similar products. It also exhibits verified selectivity and long-term reliability. The excellent sensing performance is attributed to the high surface area from the silicon nanowire structure and efficient synergy of p-p heterojunction. Additionally, the influence of doping types of the substrates and annealing process were explored. This work serves as a reference for the design of silicon-based gas sensors with high sensitivity, low detection limits, and extended operational lifetimes, suitable for deployment in commercial integrated monitoring systems.

Enhancing the Performance of MoS2 Field-Effect Transistors Using Self-Assembled Monolayers: A Promising Strategy to Alleviate Dielectric Layer Scattering and Improve Device Performance.

Field-effect transistors (FETs) based on two-dimensional molybdenum disulfide (2D-MoS2) have great potential in electronic and optoelectronic applications, but the performances of these devices still face challenges such as scattering at the contact interface, which results in reduced mobility. In this work, we fabricated high-performance MoS2-FETs by inserting self-assembling monolayers (SAMs) between MoS2 and a SiO2 dielectric layer. The interface properties of MoS2/SiO2 were studied after the inductions of three different SAM structures including (perfluorophenyl)methyl phosphonic acid (PFPA), (4-aminobutyl) phosphonic acid (ABPA), and octadecylphosphonic acid (ODPA). The SiO2/ABPA/MoS2-FET exhibited significantly improved performances with the highest mobility of 528.7 cm2 V-1 s-1, which is 7.5 times that of SiO2/MoS2-FET, and an on/off ratio of ~106. Additionally, we investigated the effects of SAM molecular dipole vectors on device performances using density functional theory (DFT). Moreover, the first-principle calculations showed that ABPA SAMs reduced the frequencies of acoustic and optical phonons in the SiO2 dielectric layer, thereby suppressing the phonon scattering to the MoS2 channel and further improving the device's performance. This work provided a strategy for high-performance MoS2-FET fabrication by improving interface properties.

High-performance peptide biosensor based on unified structure of lotus silk.

The sensitive materials of current gas sensors are fabricated on planar substrates, significantly limiting the quantity of sensitive material available on the sensor and the complete exposure of the sensitive material to the target gas. In this work, we harnessed the finest, resilient, naturally degradable, and low-cost lotus silk derived from plant fibers, to fabricate a high-performance bio-sensor for toxic and harmful gas detection, employing peptides with full surface connectivity. The proposed approach to fabricate gas sensors eliminated the need for substrates and electrodes. To ascertain the effectiveness and versatility of the sensors created via this method, sensors for three distinct representative gases (isoamyl alcohol, 4-vinylanisole, and benzene) were prepared and characterized. These sensors surpassed reported detection limits by at least one order of magnitude. The inherent pliancy of lotus silk imparts adaptability to the sensor architecture, facilitating the realization of 1D, 2D, or 3D configurations, all while upholding consistent performance characteristics. This innovative sensor paradigm, grounded in lotus silk, represents great potential toward the advancement of highly proficient bio gas sensors and associated applications.

An Artificial LiSiOx Nociceptor with Neural Blockade and Self-Protection Abilities.

An artificial nociceptor, as a critical and special bionic receptor, plays a key role in a bioelectronic device that detects stimuli and provides warnings. However, fully exploiting bioelectronic applications remains a major challenge due to the lack of the methods of implementing basic nociceptor functions and nociceptive blockade in a single device. In this work, we developed a Pt/LiSiOx/TiN artificial nociceptor. It had excellent stability under the 104 endurance test with pulse stimuli and exhibited a significant threshold current of 1 mA with 1 V pulse stimuli. Other functions such as relaxation, inadaptation, and sensitization were all realized in a single device. Also, the pain blockade function was first achieved in this nociceptor with over a 25% blocking degree, suggesting a self-protection function. More importantly, an obvious depression was activated by a stimulus over 1.6 V due to the cooperative effects of both lithium ions and oxygen ions in LiSiOx and the dramatic accumulation of Joule heat. The conducting channel ruptured partially under sequential potentiation, thus achieving nociceptive blockade, besides basic functions in one single nociceptor, which was rarely reported. These results provided important guidelines for constructing high-performance memristor-based artificial nociceptors and opened up an alternative approach to the realization of bioelectronic systems for artificial intelligence.

Novel and safe debranched starch-zinc complexes with endoconcave structure as zinc supplements.

Zinc deficiency is a serious risk to human health and growth, especially in children. The development of zinc supplements can effectively reduce this harm. Here, a series of debranched starch­zinc complexes (DS-Zn) were prepared, whose zinc complexation was inversely proportional to the amylopectin content in the debranched starch (DS). The physicochemical properties of DS-Zn were characterized using the conductivity, XRD, iodine staining and thermogravimetry. Combined with XPS, solid-state 13C NMR and IR, it was elucidated that the structure of DS-Zn is endoconcave structure with 2-O and 3-O of DS on the inner side and 6-O of DS on the outer side, where zinc is located. The DS-Zn exhibits good biosafety including blood, cellular and mutagenicity. In vitro simulations of digestion and zinc-deficient cellular models showed that DS-Zn was more tolerant to the gastrointestinal environment and more effective in zinc supplementation (increased by 33 %) than inorganic zinc supplements. Utilizing the compressibility of starch, DS-Zn was prepared as a more palatable oral cartoon tablet for children. This study will provide important support to advance the development and application of novel starch-based zinc nutritional supplements.

Investigating on sensing mechanism of MoS2-FET biosensors in response to proteins.

Field-effect transistor (FET) biosensors based on two-dimensional materials have gained extensive attention due to their high sensitivity, label-free detection capability, and fast response. Molybdenum disulfide (MoS2), with tunable bandgap, high surface-to-volume ratio, and smooth surface without dangling bonds, is a promising material for FET biosensors. Previous reports have demonstrated the fabrication of MoS2-FET biosensors and their high sensitivity detection of proteins. However, most prior research has focused on the realization of MoS2-FETs for detecting different kinds of proteins or molecules, while comprehensive analysis of the sensing mechanism and dominant device factors of MoS2-FETs in response to proteins is yet to investigate. In this study, we first fabricated MoS2-FET biosensor and detected different types of proteins (immunoglobulin G (IgG),ß-actin, and prostate-specific antigen (PSA)). Secondly, we built the model of the device and analyzed the sensing mechanism of MoS2-FETs in response to proteins. Experimental and modeling results showed that the induced doping effect and gating effect caused by the target protein binding to the device surface were the major influential factors. Specifically, the channel doping concentration and gate voltage (Vg) offset exhibited monotonic change as the concentration of the protein solution increases. For example, the channel doping concentration increased up to ∼37.9% and theVgoffset was ∼-1.3 V with 10-7µgµl-1IgG. The change was less affected by the device size. We also investigated the effects of proteins with opposite acid-base properties (ß-actin and PSA) to IgG on the device sensing mechanism.ß-actin and PSA exhibited behavior opposite to that of IgG. Additionally, we studied the response behavior of MoS2-FETs with different dimensions and dielectric materials (channel length, MoS2thickness, dielectric layer thickness, dielectric layer material) to proteins. The underlying mechanisms were discussed in details. This study provides valuable guidelines for the design and application of MoS2-FET biosensors.

Genomic representation predicts an asymptotic host adaptation of bat coronaviruses using deep learning.

Introduction: Coronaviruses (CoVs) are naturally found in bats and can occasionally cause infection and transmission in humans and other mammals. Our study aimed to build a deep learning (DL) method to predict the adaptation of bat CoVs to other mammals. Methods: The CoV genome was represented with a method of dinucleotide composition representation (DCR) for the two main viral genes, ORF1ab and Spike. DCR features were first analyzed for their distribution among adaptive hosts and then trained with a DL classifier of convolutional neural networks (CNN) to predict the adaptation of bat CoVs. Results and discussion: The results demonstrated inter-host separation and intra-host clustering of DCR-represented CoVs for six host types: Artiodactyla, Carnivora, Chiroptera, Primates, Rodentia/Lagomorpha, and Suiformes. The DCR-based CNN with five host labels (without Chiroptera) predicted a dominant adaptation of bat CoVs to Artiodactyla hosts, then to Carnivora and Rodentia/Lagomorpha mammals, and later to primates. Moreover, a linear asymptotic adaptation of all CoVs (except Suiformes) from Artiodactyla to Carnivora and Rodentia/Lagomorpha and then to Primates indicates an asymptotic bats-other mammals-human adaptation. Conclusion: Genomic dinucleotides represented as DCR indicate a host-specific separation, and clustering predicts a linear asymptotic adaptation shift of bat CoVs from other mammals to humans via deep learning.

Sex Pheromone Receptor-Derived Peptide Biosensor for Efficient Monitoring of the Cotton Bollworm Helicoverpa armigera.

The cotton bollworm, Helicoverpa armigera (H. armigera), causes damage to a wide range of cultivated crops and is one of the pests with the greatest economic importance for global agriculture. Currently, the detection of H. armigera is based on manual sampling. A low limit of detection (LOD), convenient, and real-time monitoring method is urgently needed for its early warning and efficient management. Here, we characterized the amino acid sequence in the sex pheromone receptors (SPRs) recognizing the pheromone components of H. armigera by three-dimensional (3D) modeling and molecular docking. Next, sex pheromone receptor-derived peptides (SPRPs) were synthesized and conjugated to nanotubes by chemical connection. The modified nanotubes were used to fabricate a sensor capable of real-time monitoring of gaseous sex pheromone compounds with a low LOD (∼10 ppb for Z11-16:Ald) and selectivity, and the sensor was able to detect a single live H. armigera. Furthermore, the developed biosensor allowed direct monitoring of the pheromone release dynamics by female H. armigera and showed that the release was instantly reduced in response to light. Here, we report the first demonstration of a biosensing method for detecting gaseous sex pheromones and live H. armigera. The findings show the great potential of the SPRP sensor for broad applications in insect biology study and infestation monitoring.

Ultrasensitive Flexible Olfactory Receptor-Derived Peptide Sensor for Trimethylamine Detection by the Bending Connection Method.

Trimethylamine (TMA) is a harmful gas that exists ubiquitously in the environment; therefore, the sensitive and specific monitoring of TMA is necessary. In this work, we prepared ultrasensitive flexible sensors for TMA detection based on single-walled carbon nanotubes (SWCNTs) and olfactory receptor-derived peptides (ORPs) on low-cost plastic substrates. A novel bending connection method was developed by intentionally bending the interdigitated electrodes with SWCNTs to form a three-dimensional structure during the ORP-connection process, leading to the exposure of more modification sites. The method showed ∼4.7-fold more effective connection amount of the ORPs to SWCNTs compared to the conventional flat-condition connection method. The flexible ORP-SWCNT sensors could significantly improve the limit of detection for gaseous TMA from the reported lowest limit of 10 parts per quadrillion (ppq) to 0.1 ppq. The flexible ORP sensors also exhibited excellent sensitivity to vaporized TMA standards and TMA generated by different kinds of foods under different bending conditions. The results showed that the bending connection method in this work was effective for ultrasensitive flexible ORP sensors and their associated applications.

Flexible silicon nanowires sensor for acetone detection on plastic substrates.

Acetone commonly exists in daily life and is harmful to human health, therefore the convenient and sensitive monitoring of acetone is highly desired. In addition, flexible sensors have the advantages of light-weight, conformal attachable to irregular shapes, etc. In this study, we fabricated high performance flexible silicon nanowires (SiNWs) sensor for acetone detection by transferring the monocrystalline Si film and metal-assisted chemical etching method on polyethylene terephthalate (PET). The SiNWs sensor enabled detection of gaseous acetone with a concentration as low as 0.1 parts per million (ppm) at flat and bending states. The flexible SiNWs sensor was compatible with the CMOS process and exhibited good sensitivity, selectivity and repeatability for acetone detection at room temperature. The flexible sensor showed performance improvement under mechanical bending condition and the underlying mechanism was discussed. The results demonstrated the good potential of the flexible SiNWs sensor for the applications of wearable devices in environmental safety, food quality, and healthcare.

High-performance olfactory receptor-derived peptide sensor for trimethylamine detection based on Steglich esterification reaction and native chemical ligation connection.

Trimethylamine (TMA) commonly exists in daily life and is harmful to human health, therefore the convenient and sensitive monitoring of TMA is highly desired. In this study, we developed a method to fabricate a high-performance TMA sensor by chemically conjugating olfactory receptor-derived peptides (ORPs) to single-walled carbon nanotubes (SWCNTs) on interdigital electrodes. First, the SWCNTs were modified with thioester by Steglich esterification reaction. Next, the ORPs with a cysteine residue at the N-terminus were connected to the thioester by native chemical ligation and modified to the surface of the SWCNTs. The chemical connection method enabled more effective loading of ORPs to the SWCNTs compared to the previously reported physical connection method. Using this approach, the ORPs-SWCNTs sensor for gaseous TMA was fabricated and enabled detection of TMA with a concentration as low as 0.01 parts per trillion, which was three orders of magnitude lower than the reported lowest detection limit up to date. Furthermore, we tested the performance of the ORP-sensor with vaporized TMA and TMA generated from various spoiled food, and the sensor exhibited excellent sensitivity, selectivity, and stability for TMA detection. The results demonstrated the effectiveness of the proposed chemical connection method for the fabrication of ORP-sensor and the great potential of using these sensors for applications in environmental safety, food quality evaluation, and healthcare.

Highly sensitive detection of multiple proteins from single cells by MoS2-FET biosensors.

Single-cell analysis of proteins is critical to gain precise information regarding the mechanisms that dictate the heterogeneity in cellular phenotypes and their differential response to internal and external stimuli. However, tools that allow sensitive and easy measurement of proteins in individual cells are still limited. The emerging semiconductor-based bioelectronics may provide a new approach to overcome the challenges in this field, however its utility in single-cell protein analysis has not been explored. In this study, we investigated multiple protein detection in single cells by MoS2 field effect transistors (MoS2-FETs) modified with specific biological probes. First, ß-actin antibody was connected to the surface of MoS2-FETs by covalent bonds, and the fabricated device was tested using ß-actin solution with concentrations from 10-9 to 10-3 µg/µL. Next, we examined the application of MoS2-FET for protein analysis in complex biological samples, and the device showed electrical signal response to human embryonic kidney cell line HEK293T in a dose-dependent manner. Furthermore, we applied this method to analyze individual liver cancer MHCC-97L cells, targeting four cellular proteins, including ß-actin, epidermal growth factor receptor, sirtuin-2, and glyceraldehyde-3-phosphate dehydrogenase. The devices modified with corresponding probes could identify the target proteins and showed cell number-dependent responses. As a proof of principle, we demonstrated sensitive and multiplexed detection of proteins in single cells using MoS2-FETs. The biosensor and this detection method are cost-efficient and user-friendly with broad application prospects in biological studies and clinical diagnosis.

2D-MoS2/BMN Ceramic Hybrid Structure Flexible TFTs with Tunable Device Properties.

Two-dimensional (2D) layered semiconductor materials have emerged as prospective channel materials in flexible thin-film field effect transistors (TFTs) recently because of their unique electrical and mechanical characteristics. Meanwhile, high-quality ceramics, with outstanding dielectric property and fabrication process compatible with low-cost flexible substrates, have become one of the best candidates of gate dielectric layers in flexible TFTs. In this work, 2D MoS2 and dielectric ceramic Bi2MgNb2O9 (BMN) were utilized to fabricate flexible TFTs on low-cost polyethylene terephthalate substrates. The MoS2/BMN hybrid structure exhibited good quality by Raman, X-ray photoelectron spectroscopy, and atomic force microscopy characterizations. In addition, the flexible MoS2/BMN TFTs indicated good performances with a small gate voltage. More importantly, with the modulation of gate voltage, the flexible TFTs surprisingly exhibited three different device types, that is, multilayer MoS2/BMN n-type TFT (device type 1), homojunction MoS2/BMN TFT (device type 2), and thick MoS2/BMN p-type TFT (device type 3). In particular, with different bias conditions, the homojunction TFT showed bipolarity of transfer characteristics and forward/backward rectifications of output characteristics similar to p-n/n-n junctions. The high dielectric constant and high quality of the BMN ceramic layer enabled the gate to effectively modulate these different structures of MoS2 channels. The operation mechanisms of these three types of flexible TFTs were investigated. Additionally, the flexible MoS2/BMN TFTs showed good flexibility and performance stability with external strains. The results prove the great potential of integration of 2D materials, high-quality dielectric ceramics, and low-cost plastic substrates for high-performance flexible TFTs and further applications of flexible electronics.

Exploring Spatially Non-Stationary and Scale-Dependent Responses of Ecosystem Services to Urbanization in Wuhan, China.

Ecosystem services (ESs) are facing challenges from urbanization processes globally. Exploring how ESs respond to urbanization provides valuable information for ecological protection and urban landscape planning. Previous studies mainly focused on the global and single-scaled responses of ESs but ignored the spatially heterogenous and scale-dependent characteristics of these responses. This study chose Wuhan City in China as the study area to explore the spatially varying and scale-dependent responses of ESs, i.e., grain productivity, carbon sequestration, biodiversity potential and erosion prevention, to urbanization using geographically weighted regression (GWR). The results showed that the responses of ESs were spatially nonstationary evidenced by a set of local parameter estimates in GWR models, and scale-dependent indicated by two kinds of scale effects: effect of different bandwidths and effect of grid scales. The stationary index of GWR declined rapidly as the bandwidth increased until reaching to a distance threshold. Moreover, GWR outperformed ordinary least square at both grid scales (i.e., 5 km and 10 km scales) and behaved better at finer scale. The spatially non-stationary and scale-dependent responses of ESs to urbanization are expected to provide beneficial guidance for ecologically friendly urban planning.

Monitoring Land Subsidence in Wuhan City (China) using the SBAS-InSAR Method with Radarsat-2 Imagery Data.

Wuhan city is the biggest city in central China and has suffered subsidence problems in recent years because of its rapid urban construction. However, longtime and wide range monitoring of land subsidence is lacking. The causes of subsidence also require further study, such as natural conditions and human activities. We use small baseline subset (SBAS) interferometric synthetic aperture radar (InSAR) method and high-resolution RADARSAT-2 images acquired between 2015 and 2018 to derive subsidence. The SBAS-InSAR results are validated by 56 leveling benchmarks where two readings of elevation were recorded. Two natural factors (carbonate rock and soft soils) and three human factors (groundwater exploitation, subway excavation and urban construction) are investigated for their relationships with land subsidence. Results show that four major areas of subsidence are detected and the subsidence rate varies from -51.56 to 27.80 millimeters per year (mm/yr) with an average of -0.03 mm/yr. More than 83.81% of persistent scattered (PS) points obtain a standard deviation of less than -6 mm/yr, and the difference between SBAS-InSAR method and leveling data is less than 5 mm/yr. Thus, we conclude that SBAS-InSAR method with Radarsat-2 data is reliable for longtime monitoring of land subsidence covering a large area in Wuhan city. In addition, land subsidence is caused by a combination of natural conditions and human activities. Natural conditions provide a basis for subsidence and make subsidence possible. Human activities are driving factors and make subsidence happen. Moreover, subsidence information could be used in disaster prevention, urban planning, and hydrological modeling.

Tunable interlayer coupling and Schottky barrier in graphene and Janus MoSSe heterostructures by applying an external field.

A Janus MoSSe monolayer, synthesized recently though the chemical vapor deposition method [A. Y. Lu, H. Zhu, J. Xiao, C. P. Chuu, Y. Han, M. H. Chiu, C. C. Cheng, C. W. Yang, K. H. Wei Y. Yang, Y. Wang, D. Sokaras, D. Nordlund, P. Yang, D. A. Muller, M. Y. Chou, X. Zhang and L. J. Li, Nat. Nanotechnol., 2017, 12, 744-749], has drawn considerable attention as a new two-dimensional (2D) material owing to its fascinating electronic and optical properties. In this study, based on first-principles calculations, we systematically explore for the first time the performance of Janus MoSSe monolayers as a channel material contacting with graphene to form van der Waals (vdW) heterostructures. Our calculations show that the intrinsic electronic properties of both the graphene and MoSSe monolayer are preserved well in our proposed two graphene/MoSSe heterostructures (i.e. G/SMoSe and G/SeMoS heterostructures), and n-type Schottky contacts with a small Schottky barrier height (SBH) are formed at their respective interfaces. An analytical model is presented for the barrier heights. Moreover, the n-type Schottky barrier at the G/SMoSe heterostructure interface can be reduced by increasing the interlayer distance and can even be changed to an Ohmic contact by applying a negative electric field. More interestingly, varying the interlayer distance or applying an external electric field can effectively modulate the Schottky barrier and the Schottky contact (n-type and p-type) of the G/SeMoS heterostructure interface. These theoretical findings not only provide insights into the fundamental properties of the graphene/MoSSe interfaces but also open the possibility of designing high-performance field-effect transistors (FETs) based on the graphene/MoSSe heterostructures.