Guizhou University

In this study, a portable photoelectrochemical diagnostic platform based on CuCo₂O₄@ZnIn₂S₄ nanocomposites and a smartphone was developed to detect dopamine (DA). CuCo₂O₄@ZnIn₂S₄ heterojunction was prepared by a simple one-pot method, and it was found that CuCo₂O₄@ZnIn₂S₄ showed significant photoelectrochemical (PEC) activity. DA acts as an electron donor and interacts with the composites. The holes in the composites oxidize DA to produce dopaquinone, reducing the electron-hole recombination rate and increasing the photocurrent signals. These signals can be immediately read using a portable smartphone. The results of this study confirmed that the increase in the photocurrent of the sensor was linked to the interaction between DA and the composites. Under optimized conditions, the linear range was 0.01-2000 μM, and the limit of detection (LOD) was 0.08 μM (S/N = 3). The sensor performs well on human serum samples and demonstrates high long-term stability. Therefore, convenient photoelectrochemical analysis of serum is achievable using a user-friendly, portable smartphone detection device.

The supramolecular fluorescent probe exhibited promising application in the field of detection and analysis, but developing supramolecular fluorescent probes with long wavelength emission and enhancement functions for the detection of phenylethylamines is a challenge. In this work, the guest molecule SPn with a D-π-A structure was designed and synthesized, and supramolecular fluorescent probe (SPn/Q[8]) with long wavelength emission was constructed by the host-guest interaction with cucurbit[8]uril (Q[8]). This probe detects phenethylamines based on an indicator displacement assay, which is a process characterized by a fast effect rate (within 6.24 s), high selectivity, and low detection limit. In addition, a smartphone-based quantitative detection system was developed for trace detection of phenethylamine, with a detection limit of 2.35 μM. This research not only developed a new approach for supramolecular fluorescent probes, but also provided a useful tool for the on-site detection of phenylethylamine.

Spermidine has emerged as a promising biomarker for the early-stage diagnosis of cancer in humans. A novel extractive spectrophotometric analytical method has been developed for the determination of spermidine in urine samples. This technique leverages the selective extraction of spermidine from complex matrices using a cucurbit[7]uril-truxene derivative (Q[7]-Cs-Tr) as a fluorescent extractant. The Q[7]-Cs-Tr forms a stable host-guest complex with spermidine, facilitating its extraction from the aqueous phase to the organic phase. The formation of this complex results in a decrease in the fluorescence intensity of the Q[7]-Cs-Tr in the organic phase. Key factors influencing extraction efficiency, including the type of dispersed organic solvent, extractant concentration, solution pH, extraction times, and equilibrium time, were thoroughly investigated. The method demonstrated minimal interference from various metal ions, anions, amino acids, and other biogenic amines. It also exhibited a low limit of detection (8.6 nM), excellent linearity (R² = 0.9972), and high repeatability (RSD = 2.4 % intra-day, RSD = 3.6 % inter-day). The proposed method was successfully applied to determine spermidine levels in urine samples, yielding satisfactory recoveries ranging from 96.3 % to 103.5 %. Compared to existing methods, this approach is simple, reliable, highly sensitive, and exhibits low interference, making it a potential robust tool for clinical diagnostics.