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As the use of triboelectric nanogenerators (TENGs) increases, the generation of related electronic waste has been a major challenge. Therefore, the development of environmentally friendly, biodegradable, and low-cost TENGs must be prioritized. Having discovered that plant proteins, by-products of grain processing, possess excellent triboelectric properties, we explore these properties by evaluating the protein structure. The proteins are recycled to fabricate triboelectric layers, and the triboelectric series according to electrical properties is determined for the first time. Using a special structure design, we construct a plant-protein-enabled biodegradable TENG by integrating a polylactic acid film, which is used as a new type of mulch film to construct a growth-promoting system that generates space electric fields for agriculture. Thus, from the plant protein to the crop, a sustainable recycling loop is implemented. Using bean seedlings as a model to confirm the feasibility of the mulch film, we further use it in the cultivation of greenhouse vegetables. Experimental results demonstrate the applicability of the proposed plant-protein-enabled biodegradable TENG in sustainable agriculture.

The growing demand of intelligent wearable devices has triggered rapid development of highly stretchable strain sensors and power sources. Here, we fabricated a sandwich-structured stretchable device, where a composite film is encapsulated in two layers of polydimethylsiloxane (PDMS). The highly conductive composite film is composed of one-dimensional (1D) silver nanowires (AgNWs) network wrapped with two-dimensional (2D) metallic MoS2 nanosheets. The combination of 1D AgNWs and 2D metallic MoS2 nanosheets endows the composite film with excellent flexibility and conductivity, which enables their use as high-performance skin-mountable strain sensor with the maximum gauge factor of 215.4 and high stretchability up to 70%. Furthermore, the sandwich-structured device can serve as a stretchable triboelectric nanogenerator (STENG). Results show that the STENG with an area of 1 × 2.5 cm2 could produce an average power density of 0.16 W/m2. In addition, the STENG could retain stable output performance even under a stretching ratio of 50%. With the outstanding stretchability, it can be fully conformal on nonplanar irregular object such as plant leaves. Moreover, we demonstrated that the fabricated STENG could harvest wind energy and serve as a self-powered wind speed sensor when attached to plant leaves. This work provides new prospects for stretchable power sources and shows potential applications in wearable electronics.

In this work, a fully stretchable triboelectric nanogenerator (FSTENG) composed of an electrospun electrode and a porous PDMS friction layer with anti-nickel foam structure was fabricated. This FSTENG can deliver an optimal output voltage of 92 V, which is ten times greater than that of the TENG based on flat PDMS film. The superior performance is attributed to the use of anti-nickel foam structure-based porous PDMS film in FSTENG, which enhances the surface-to-volume ratio and surface roughness. Importantly, the FSTENG could maintain stable output performance even under a stretching ratio of 50%. With these excellent features, the developed FSTENG was designed as a self-driven sensor for finger bending and walking status monitoring. Furthermore, to expand the driving mode of FSTENG, FSTENG was successfully attached to the leaf for monitoring the wind speed in the natural environment without external power supply. The excellent flexibility, stretchability, and versatility of FSTENG make it as a promising self-driven sensor for human behavior and environmental monitoring.

The increasing potential of wearable electronics has been motivating the development of self-powered devices to overcome the restriction imposed by conventional power supply. Herein, a kind of highly electronegative and conducting material of MXene nanosheet has been innovatively integrated with poly(vinyl alcohol) (PVA) for electrospinning nanofibers film to fabricate flexible all-electrospun triboelectric nanogenerator (TENG). Silk fibroin (SF) was chosen for electrospinning nanofibers film to serve as electron donor for TENG with great triboelectricity and biocompatible nature. The MXene-based all-electrospun nanogenerator shows excellent stability and durability as well as extraordinary electrical performance, which supports an instantaneously maximum peak power density of 1087.6 mW/m2 as the load resistance is 5.0 MΩ. Moreover, beyond harvesting electrical power, the fabricated TENG was utilized for real-time monitoring various types of body motion. Lastly, we used the developed TENG to power electrowetting on dielectric (EWOD) chip to actuate droplet transport. Considering the excellent triboelectric performance, ease of large-scale manufacturing, and environmental friendliness, this MXene-based all-electrospun TENG provides a promising solution for developing practical, flexible, and self-powered electronic devices.

Single-walled carbon nanohorns (SWCNHs) was utilized as an ion-to-electron transducer to fabricate all-solid-state ion-selective electrodes (ISE) for the first time. To evaluate the performance of developed SWCNHs-based calcium ISE, various electrochemical experiments were carried out. A Nernstian response (29.69 ± 0.24 mV/decade, R2 = 0.9996) was acquired across a broad linear range between 10−6 and 10−2 M, and the detection limit of 10−6.1 M was achieved in the meantime. Additionally, water layer test and reversed chronopotentiometry were used to estimate the long-term and short-term stability of SWCNHs-based ISE, respectively, indicating SWCNHs is capable of enhancing potential stability on account of its hydrophobicity. Furthermore, a SWCNHs-based reference electrode (RE) was fabricated by directly coating a photo-polymerised reference membrane (RM) onto a SWCNHs modified electrode. Results demonstrated that the SWCNHs-based RE exhibited slight potential fluctuation for common ions with different charges over a wide concentration range of calibration. Based on these superior results, an integrated all-solid-state SWCNHs-based potentiometric sensing device combined SWCNHs-based ISE and SWCNHs-based RE was constructed for detecting calcium, which shows a Nernstian response with a slope of 27.14 mV/decade. This developed electrode in the aid of SWCNHs exhibits fast response as well as outstanding potential stability, making it extreme promising for routine sensing application.

Flexible sensing devices have drawn tremendous attention in the past decades due to their potential applications in future hand-held, potable consumer, and wearable electronics. Here, we firstly developed an ultrasensitive wireless potentiometric aptasensor based on flexible freestanding graphene paper for kanamycin detection. Flexible graphene paper made from a simple vacuum filtration method was used as a biocompatible platform for effective immobilization of aptamer. A nuclease-assisted amplification strategy was introduced into this potentiometric biosensing system in order to significantly improve the detection sensitivity through a classic catalytic recycling reaction of target induced by the nuclease (DNase I). As expected, an ultra-low detection limit of 30.0 fg/mL for kanamycin was achieved. Furthermore, the developed potentiometric enzymatic aptasensor exhibits high selectivity, favorable flexibility, excellent stability and reproducibility, which holds great promising for its routine sensing application.

Real-time monitoring of the wind vector, including wind speed and direction, is significant for crop management and production in agricultural environment. However, traditional wind vector sensors are difficult to meet the needs of modern sustainable agriculture due to their considerable size, low accuracy, and lack of energy supply. Hence, there is a great need for wind vector sensors that can respond super-sensitively to environmental stimuli without external power supply. Herein, a transparent and degradable hydroxyethyl cellulose film was introduced to fabricate a triboelectric nanogenerator (TENG) based on the slit effect for wind energy harvesting and self-powered wind vector monitoring. The maximum output voltage of slit-effect-enabled TENG (SE-TENG) is up to ~ 600 V under a wind speed of 7 m/s, and various agricultural sensors can be continuously driven. Furthermore, an omnidirectional wind energy harvester (OWEH) composed of eight SE-TENGs and an electrometer data-acquisition board was assembled to monitor the wind directions and speed ranging from 0.5 to 10 m/s accurately. This work poses an effective and green method for wind vector monitoring in agricultural environment and demonstrates the potential of TENG technology in intelligent agriculture.

Agro-product safety is one of the most important topics in our daily lives, making it particularly critical to assure the quality of all consumed agro-products. Therefore, it is highly desirable to develop sensitive and stable methods to detect the contaminants in agro-products. Meanwhile, nanomaterials with outstanding properties have received widespread attention. A variety of nanomaterials have been incorporated into biosensors to realize highly sensitive, stable, and rapid detection of contaminants in agro-products, such as mycotoxins, pesticides, antibiotics, heavy metals, and microorganisms. During the past years, more potential nanomaterials with more variety of structures have been applied to develop new kinds of biosensors, and show ultra-higher sensitivity in the field of agro-product contaminant detection. This review summarizes the latest researches in the field of nanomaterial-based biosensors for agro-product contaminant detection in the past four years (2017–2020). Furthermore, the limitations analysis and research trends in this field are also provided.

Fibers with high stretchability and conductivity are considered as essential building blocks for next-generation fiber-based electronics. Herein, we presented a facile, scalable, and environmentally-friendly approach for the fabrication of multifunctional fibers. The fiber obtained by wet-spinning technology is composed of MXene and carbon nanotube (CNT) embedded in polyurethane (PU), with a cobblestone-shaped gold nanostructure (namely, AuCNS) on its surface formed by spontaneous reduction between AuCl4¯ and MXene. The fiber exhibits high conductivity and excellent durability under mechanical deformations, which makes it promising for constructing wearable fiber-based devices. The formation of AuCNS significantly enhances the surface roughness and catalytic behavior of the fiber. An ultra-sensitive pressure sensor with high sensitivity, fast response time, and excellent durability was fabricated using the fiber as sensing units. Besides, a three-electrode fiber-based flexible electrochemical sensor for highly sensitive detection of H2O2 can be designed due to the excellent electrocatalytic activity of AuCNS. The fiber can also be used as an electrode for constructing a fiber-based triboelectric nanogenerator for water energy harvesting. All these indicate that this multifunctional fiber would hold great promise in next-generation fiber-based wearable sensors as well as self-powered systems.

Raining as a common phenomenon in agricultural environment sometimes may bring adverse effects on agricultural production, to remedy this, agrotextiles are extensively utilized. In this study, the technology of triboelectric nanogenerator (TENG) is firstly integrated into agrotextiles. To construct a robust TENG yarn, a facile and effective method for the fabrication of stretchable electrode is developed, i.e. coating an elastic fibre with MXene ink, followed by spontaneous growth of Ag nanoparticles (AgNPs). By consecutively coating the conductive fibre with PDMS, the final developed triboelectric yarn (diameter of ~400 μm) is demonstrated to possess extraordinary output performance, generating a voltage of 7.7 V with a effective contact length of 3 cm. Moreover, the excellent mechanical property, highly stretchability, outstanding robustness, and considerable hydrophobicity of the TENG yarn also make it be capable of being woven into net or integrated into agrotextile. Thus, in the meantime of providing protection for crop plantation and animal husbandry to improve the quality and yield of agricultural products, the raindrop energy can also be harvested. Moreover, it can also act as a self-powered sensor to monitor dynamic force, which provide a basic information of weather condition. All in all, this developed TENG yarn enables many promising advantages such as being easily engineered and scaled up, therefore possessing great potential to apply in agrotextile for building intelligent agriculture.

In recent years, the agricultural Internet of Things (IoT) has been developing rapidly, but the corresponding long-term sustainable and efficient power source for sensors in IoT is still under researching. In this work, an integrated self-cleaning and self-charging device capable of harvesting energy from the swinging crop leaves and raindrops was developed based on laser-induced graphene (LIG) technology, which consists of a multi-operating mode triboelectric nanogenerator (MTENG) and a micro-supercapacitor (MSC). Moreover, the lotus leaf-like bionic structure formed on the device surface based on the template method gives the device the characteristics of waterproof and self-cleaning, so that the device can maintain stable output in a humid environment. Outstanding flexibility, strong self-cleaning effect, stable electrical output, and high integration make this self-charging device possess the potential to replace traditional energy sources for agricultural IoT sensors.

Two-dimensional (2D) transition metal carbides and nitrides, named MXene, appear promising application prospects in sensor filed. Metal nanoparticles, especially bimetallic nanoparticles, are the superior nanocatalyst, which process excellent features due to the high specific surface area and synergistic catalytic capacity. Using ultrathin MXene nanosheets as the natural reducing agent and support, we prepare the shape-controlled Au-Pd bimetallic nanoparticles via a self-reduction process at room temperature in a short time, which can well enhance the catalytic performance and are benefit for the acetylcholinesterase immobilization. Based on their desired properties, we propose a disposable electrochemical biosensor for the detection of organophosphorus pesticide using the multi-dimensional nanocomposites (MXene/Au-Pd) as the functional platform. Under the optimized conditions, our fabricated biosensor exhibits a favorable linear relationship with the concentration of paraoxon from 0.1 to 1000¿¿g¿L¿1, with a low detection limit of 1.75¿ng L¿1. Furthermore, the biosensor can be applied for paraoxon detection in pear and cucumber samples, providing an effective and useful avenue for the applicability of novel 2D nanomaterials in biosensing field., This work was supported by the National Science Fund for Excellent Young Scholars of China (Grant No. 31922063).

The ambient dissipated energy such as the vast scale of mechanical energy in the agricultural system (e.g., leaf swing energy) and the writing motion existing extensively in our daily life are underutilized. Herein, to address these issues and overcome the limitations of conventional batteries, we fabricated a highly flexible and effective triboelectric nanogenerator (TENG) based on MXene and polydimethylsiloxane (PDMS) composite (PDMS/MXene) film and laser-induced graphene (LIG) electrode. The introduction of conductive and electronegative MXene into PDMS to fabricate porous film, not only enhances the electrical conductivity but also increases the triboelectronegativity. As a result, the output performance is significantly improved, 7-fold greater than the pure flat PDMS-based TENG. The developed TENG with excellent performance, considerable adhesion, and outstanding flexibility was successfully applied for harvesting leaf swing energy and being used as a writing board to collect writing energy. Furthermore, we developed a MXene-based TENG array acting as a self-powered sensor for handwriting recognition. In this regard, MXene-enabled TENG possesses a great promising in harvesting mechanical energy from the agricultural field (e.g., leaf swing energy) and human activities (e.g., writing), moreover, it can further be applied in writing or tactile sensing for pad, robotics, and man-machine interaction field.