Inductive wear debris sensor has been widely used in real time machine lubricant oil condition monitoring and fault forecasting. However, the small sensing zone, which is designed for high sensitivity, of the existing sensors leads to low throughput. In order to improve the throughput, a novel multichannel wear debris sensor that is based on phase division multiplexing is presented. By introducing the phase shift circuit into the system, multiple sensing coils could work at different initial phases. Multiple signals of sensing coils could be combined into one output without information loss. Synchronized sampling is used for data recording, and output signals of multiple sensing coils are extracted from the recorded data. A four-channel wear debris sensor system was designed to demonstrate our method. Subsequently, crosstalk analysis, pseudo-dynamic testing and dynamic testing were conducted to check the sensing system. Results show that signals of four sensing coils could be simultaneously detected and the detection limit for ferrous wear debris is 33 μm. Using the presented method, real time wear debris detection in multiple channels could be achieved without increasing the number of excitation source and data acquisition equipment.

Seawater pollution caused by heavy metal ions is a growing concern among the public. Perovskite quantum dots (PeQDs) are ideal probes for detecting metal ions due to their exceptional sensing characteristics, including remarkable sensitivity, low detection limit, and good selectivity. However, traditional lead-based PeQDs exhibit drawbacks related to lead toxicity and poor water stability. Herein, lead-free halide PeQDs Cs₃Bi₂Br₉ were synthesized using Bi³⁺ instead of Pb²⁺ via the ligand-assisted reprecipitation method. The luminescence performance of the precursor is analyzed with respect to the reaction conditions. The results reveal that the optimal reaction temperature is 80 °C, the ideal octylamine dosage is 35 μL, and the most effective reaction time is 10 min. Photoluminescence spectra of Cs₃Bi₂Br₉ are analyzed at various temperatures and demonstrate that fluorescence intensity decreases as temperature increases. The value of the exciton binding energy (Eb) is determined to be 88.6 meV. Cs₃Bi₂Br₉ PeQDs synthesized under the optimum reaction conditions are utilized as fluorescent probes to detect copper ions in seawater. Results from experiments demonstrate that the presence of copper ions markedly quenched the photoluminescence of Cs₃Bi₂Br₉ owing to the effective transfer of electrons from Cs₃Bi₂Br₉ to Cu²⁺. A strong linear correlation between the degree of quenching and the contents of Cu²⁺ is observed. Cs₃Bi₂Br₉ PeQDs demonstrate a sensitivity and detection limit of 1.21 μM⁻¹ and 98.3 nM, respectively. Furthermore, this probe exhibits good photostability, water stability, and selectivity for copper ions, thereby indicating its potential for detecting marine heavy metal contaminants.

It is urgent that a convenient and sensitive technique of detecting Hg²⁺ be developed because of its toxicity. Conventional fluorescence analysis works with a single fluorescence probe, and it often suffers from signal fluctuations which are influenced by external factors. In this research, a novel dual-emission probe assembled through utilizing CdTe quantum dots (QDs) and rhodamine B was designed to detect Hg²⁺ visually. Only the emission of CdTe QDs was quenched after adding Hg²⁺ in the dual-emission probe, which caused an intensity ratio change of the two different emission wavelengths and hence facilitated the visual detection of Hg²⁺. Compared to single emission QDs-based probe, a better linear relationship was shown between the variation of fluorescence intensity and the concentration of Hg²⁺, and the limit of detection (LOD) was found to be11.4 nM in the range of 0–2.6 μM. Interestingly, the intensity of the probe containing Hg²⁺ could be recovered in presence of glutathione (GSH) due to the stronger binding affinity of Hg²⁺ towards GSH than that towards CdTe QDs. Based on this phenomenon, an IMPLICATION logic gate using Hg²⁺/GSH as inputs and the fluorescence signal of QDs as an output was constructed.

Novel and high-security anti-counterfeiting technology has always been the focus of attention and research. This work proposes a nanocomposite combination of upconversion nanoparticles (UCNPs) and perovskite quantum dots (PeQDs) to achieve color-adjustable dual-mode luminescence anti-counterfeiting. Firstly, a series of NaGdF₄: Yb/Tm UCNPs with different sizes were synthesized, and their thermal-enhanced upconversion luminescence performances were investigated. The upconversion luminescence (UCL) intensity of the samples increases with rising temperature, and the UCL thermal enhancement factor rises as the particle size decreases. This intriguing thermal enhancement phenomenon can be attributed to the mitigation of surface luminescence quenching. Furthermore, CsPbBr₃ PeQDs were well adhered to the surfaces and surroundings of the UCNPs. Leveraging energy transfer and the contrasting temperature responses of UCNPs and PeQDs, this nanocomposite was utilized as a dual-mode thermochromic anti-counterfeiting system. As the temperature increases, the color of the composite changes from green to pink under 980 nm excitation, while it displays green to non-luminescence under 365 nm excitation. This new anti-counterfeiting material, with its high security and convenience, has great potential in anti-counterfeiting applications.