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Microelectrode glucose biosensor based on three-dimensional hybrid nanoporous platinum/graphene oxide nanostructure was developed for rapid glucose detection of tomato and cucumber fruits. The nanostructure was fabricated by a two-step modification method on microelectrode for loading a larger amount of glucose oxidase. The nanoporous structure was prepared on the surface of the platinum microelectrode by electrochemical etching, and then graphene oxide was deposited on the prepared nanoporous electrode by electrochemical deposition. The nanoprorous platinum/graphene oxide nanostructure had the advantage of improving the effective surface area of the electrode and the loading quantity of glucose oxidase. As a result, the biosensor achieved a wide range of 0.1-20.0 mM in glucose detection, which had the ability to accurately detect the glucose content. It was found that the three-dimensional hybrid nanostructure on the electrode surface realized the rapid direct electrochemistry of glucose oxidase. Therefore, the biosensor achieved high glucose detection sensitivity (11.64 μA mM -1cm -2), low detection limit (13 μM) and rapid response time (reaching 95% steady-state response within 3 seconds), when calibrating in glucose standard solution. In agricultural application, the as-prepared biosensor was employed to detect the glucose concentration of tomato and cucumber samples. The results showed that the relative deviation of this method was less than 5% when compared with that of HPLC, implying high accuracy of the presented biosensor in glucose detection in plants.

Electrochemical sensing is an effective method for trace determination of specific substances. However, there are many active substances in plants, and the pH environment of plant organs varies. These factors directly affect the performance of electrochemical sensors and make it difficult to realize real-time detection accurately. Here, an online intelligent monitoring system for indole-3-acetic acid (IAA) was proposed, including reusable microsensor, portable electrochemical workstation, and online cloud platform. The microsensor was fabricated by depositing nanocomposites of nitrogen-doped carbon nanotubes/core–shell Au@Cu2O nanoparticles on the carbon fiber microelectrode. The IAA microsensor has a wide concentration range of 1–10 000 ng/mL and an ultralow detection limit of 10.8–57.8 pg/mL at a pH range of 4–8. The influence of different pH values on IAA detection was investigated. It is also revealed that the IAA microsensor has good anti-interference ability, repeatability, and stability which are suitable for real-time detection of IAA in living plants. Artificial neural network (ANN) algorithm is employed to establish the relationship between electrochemical signal and IAA concentration, and the ANN model is then configured in the online monitoring system to intelligently obtain the IAA concentration. Based on this system, real-time and online monitoring of the IAA concentration in a living cabbage stem was realized for a long time of 12 h. This study provides a feasible solution based on electrochemical sensing to monitor online the living plant for precision agriculture.

A simple yet effective method based on methanol treatment is proposed to enhance the external quantum efficiency (EQE) of the photomultiplication type organic photodetector with a structure of Glass/ITO/PEDOT:PSS/P3H:PC71BM (100:1, wt./wt.)/Al. By modifying the PEDOT:PSS film surface with methanol, the EQE of photodetector significantly improved within a broad wavelength range of 300–700 nm. The maximum EQE of 25300% occurs at the wavelength of 350 nm in the methanol-treated device under −9 V bias, which more than doubles that (11500%) of the device without treatment. In addition, as a result of the methanol treatment, the detectivity of the device improved from 3.72 × 1012 to 7.24 × 1012 Jones at −9 V under 350 nm light illumination. The large improvement is attributed to the fact that the methanol treatment can improve the electrical performance of the PEDOT:PSS by removing the insulator PSS within the film and also result in PC71BM aggregations in the active layer. The latter can enhance the tunneling hole injection by the intensified energy-level bending, which is induced by both the trapped electrons in these aggregations and accumulated ones near Al electrode. As a result, the modification of both the PEDOT:PSS layer and the active layer increases the response current, resulting in the EQE improvement.

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