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.

High-performance pyramid-SiNWs biosensor for NH3gas detection.

NH3is widely existed in the environment and is closely associated with various health issues. Additionally, detecting the small amounts of NH3exhaled by patients with liver and kidney diseases offers potential opportunities for painless early disease diagnosis. Therefore, there is an urgent need for a convenient, rapid, and highly sensitive real-time NH3monitoring method. This work presents a high-performance NH3sensor based on olfactory receptor-derived peptides (ORPs) on a pyramid silicon nanowires (SiNWs) structure substrate. First, we successfully fabricated the pyramid-SiNWs structure on a silicon substrate using a chemical etching method. Subsequently, by dehydrative condensation reaction between the amino groups on APTES and the carboxyl groups of ORPs, ORPs were successfully immobilized onto the pyramid-SiNWs structure. This methodology allows the ORPs sensor on the pyramid-SiNWs substrate to detect NH3as low as 1 ppb, which was the reported lowest limit of detection, with a higher response rate compared to ORPs sensors on flat SiNWs substrates. The sensors also exhibit good sensitivity and stability for NH3gas detection. The results show the feasibility and potential applications of ORPs-pyramid-SiNWs structure sensors, in the fields of food safety, disease monitoring, and environmental protection, etc.

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.

Dielectric ceramics/TiO2/single-crystalline silicon nanomembrane heterostructure for high performance flexible thin-film transistors on plastic substrates.

A dielectric ceramics/TiO2/single-crystalline silicon nanomembrane (SiNM) heterostructure is designed and fabricated for high performance flexible thin-film transistors (TFTs). Both the dielectric ceramics (Nb2O3-Bi2O3-MgO) and TiO2 are deposited by radio frequency (RF) magnetron sputtering at room temperature, which is compatible with flexible plastic substrates. And the single-crystalline SiNM is transferred and attached to the dielectric ceramics/TiO2 layers to form the heterostructure. The experimental results demonstrate that the room temperature processed heterostructure has high quality because: (1) the Nb2O3-Bi2O3-MgO/TiO2 heterostructure has a high dielectric constant (∼76.6) and low leakage current. (2) The TiO2/single-crystalline SiNM structure has a relatively low interface trap density. (3) The band gap of the Nb2O3-Bi2O3-MgO/TiO2 heterostructure is wider than TiO2, which increases the conduction band offset between Si and TiO2, lowering the leakage current. Flexible TFTs have been fabricated with the Nb2O3-Bi2O3-MgO/TiO2/SiNM heterostructure on plastic substrates and show a current on/off ratio over 104, threshold voltage of ∼1.2 V, subthreshold swing (SS) as low as ∼0.2 V dec-1, and interface trap density of ∼1012 eV-1 cm-2. The results indicate that the dielectric ceramics/TiO2/SiNM heterostructure has great potential for high performance TFTs.

High-Performance Flexible Single-Crystalline Silicon Nanomembrane Thin-Film Transistors with High- k Nb2O5-Bi2O3-MgO Ceramics as Gate Dielectric on a Plastic Substrate.

A novel method of fabricating flexible thin-film transistor based on single-crystalline Si nanomembrane (SiNM) with high- k Nb2O5-Bi2O3-MgO (BMN) ceramic gate dielectric on a plastic substrate is demonstrated in this paper. SiNMs are successfully transferred to a flexible polyethylene terephthalate substrate, which has been plated with indium-tin-oxide (ITO) conductive layer and high- k BMN ceramic gate dielectric layer by room-temperature magnetron sputtering. The BMN ceramic gate dielectric layer demonstrates as high as ∼109 dielectric constant, with only dozens of pA current leakage. The Si-BMN-ITO heterostructure has only ∼nA leakage current at the applied voltage of 3 V. The transistor is shown to work at a high current on/off ratio of above 104, and the threshold voltage is ∼1.3 V, with over 200 cm2/(V s) effective channel electron mobility. Bending tests have been conducted and show that the flexible transistors have good tolerance on mechanical bending strains. These characteristics indicate that the flexible single-crystalline SiNM transistors with BMN ceramics as gate dielectric have great potential for applications in high-performance integrated flexible circuit.