Xiaojuan Zhao,Qimei Zhang,Haiguang Chen,Gongliang Liu,Weidong Bai
A highly sensitive and selective electrochemical biomimetic sensor was fabricated for fast detection of chloramphenicol (CAP) in honey and milk samples. Platinum thin-film microelectrode (Pt TFME), which could provide unique electrochemical properties and achieve measurement using very limited solution volumes, was surface-modified by electropolymerizing o -phenylenediamine. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the preparation process of CAP-imprinted poly( o -phenylenediamine) film and rebinding ability of CAP into the imprinted cavities. The electrochemical properties of the sensor were further investigated with square wave voltammetry (SWV) by using K 3 Fe(CN) 6 as an electroactive probe. The current difference of oxidation peaks of K 3 Fe(CN) 6 had a good linear relationship with the concentration of CAP in the range of 0.9–10 nM. The detection limit was 0.39 nM based on the signal to noise ratio of 3. The developed sensor was successfully applied to determine CAP in honey and milk samples, and the result was in good agreement with that obtained by high performance liquid chromatography-mass spectrometry (HPLC-MS). The sensor showed high sensitivity and excellent selectivity to CAP in comparison to other structurally related and/or normally existing antibiotics, and demonstrated great promise for the rapid quantification of CAP in real food samples and field analysis.
Platinum (Pt) resistance temperature detectors (RTDs) are extensively employed as thin-film temperature sensors. However, agglomeration of Pt thin films occurs above 800 °C due to grain boundary grooving on the free surface, ultimately limiting its application at high temperatures. In this work, a Pt RTD was prepared by depositing multilayer Al2O3 protective layer on Pt thin films using electrodynamic jet printing (EJP) technology. The surface morphology and energy-dispersive spectroscopy spectrum of Pt thin films indicated that the voids on the surface are reduced, the grains’ growth is inhibited, and the movement and grooving of grain boundaries are limited. The test results indicate that the Pt RTD has not failed after six cycles of repeated warming and cooling from 800 °C to 1300 °C. After repeated cycles, the initial resistance of the Pt RTD is with a rate of change of less than 0.5%. In addition, the maximum relative deviation of the resistance in a single cycle is less than 1.6%. The Pt RTD with an 18-layer Al2O3 protective layer has undergone 12 cycles without failure, indicating a cycle life exceeding 10 h. Pt RTDs are stable over the range of 25 °C–1400 °C with correlation coefficients R2 greater than 0.999, showing good linear correlation. It can withstand temperatures up to 1440 °C when printed with 18 protective layers. Compared to a Pt RTD without protective layers, the operating temperature is increased by 40%. This advancement provides a viable solution for the high-temperature monitoring of hot-end components in aerospace applications.
Tunable microwave absorbers have gained significant interest due to their capability to actively control microwaves. However, the existing architecture-change-based approach lacks flexibility, and the active-element-based approach is constrained by a narrowband operation or small dynamic modulation range. Here, a novel electrically tunable microwave absorbing device (TMAD) is demonstrated that can achieve dynamic tuning of the average reflection amplitude between −13.0 and −1.2 dB over a broadband range of 8–18 GHz enabled by reversible metal electrodeposition. This reversible tunability is achieved by electrodepositing silver (Ag) layers with controlled morphology on nanoscopic platinum (Pt) films in a device structure similar to a tunable Salisbury screen, employing Ag electrodeposited on Pt films as the modifiable resistive layer. Furthermore, this TMAD possesses a simple device architecture, excellent bistability, and multispectral compatibility. Our approach offers a new strategy for dynamically manipulating microwaves, which has potential utility in intelligent camouflage and communication systems.
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