Fluorescence detection has always suffered from high background fluorescence from real samples such as milk. Therefore, cumbersome pretreatments of samples were necessary to remove the fluorescent substances but led to long processing times and low efficiency. Time-resolved luminescence detection is a powerful technique for eliminating short-lived background fluorescence without additional pretreatments. However, the related instruments are usually equipped with high-speed excitation sources and detectors, which are always bulky and expensive. Herein, we developed a low-cost and miniaturized imaging system for high-throughput time-gated luminescence detection. An UV LED array was used to excite multiple samples, the luminescence of which could be detected by a smartphone simultaneously. An analog circuit was designed to synchronize the LED to the mechanical chopper to eliminate the background signals resulting from scattering and short-lived autofluorescence. Compared to other synchronous circuits based on FPGAs and microcontrollers, this analog circuit required no programming and memory. For the first time, high-throughput time-resolved luminescence detection of tetracycline in milk without any separation or enrichment was achieved by utilizing a smartphone as a camera, and the scattered signals and the background fluorescence were eliminated efficiently. The limit of detection reached as low as 53 nM (∼0.024 ppm), lower than the residue limit set by the European Union. This high-throughput time-gated luminescence detection method can be used for quantitative analysis of many real samples with high background fluorescence.
Latent fingerprint visualization is usually interfered by background fluorescence of substrates. The room temperature phosphorescent carbon dots (CDs) can effectively eliminate background fluorescence interference through their afterglow properties. However, developing CDs with multicolor room temperature phosphorescence (RTP) as fingerprint reagents remains a significant challenge. In this study, multicolor RTP CDs were synthesized via a facile one-step pyrolysis using benzamide and boric acid as precursors. The tunable phosphorescence color was achieved via regulating the amount of benzamide and reaction temperature. The prepared CDs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), fourier transform infrared (FT-IR) spectra, X-ray photoelectron spectroscopy (XPS), ultraviolet-visible absorption spectra, and photoluminescence spectra. The results indicated that synthesized CDs were amorphous structures, sphere-like in shape with good dispersibility, and rich in functional groups on the surface. The three CDs exhibited blue, cyan, and green phosphorescence emission after UV lamp cessation. Based on the multicolor phosphorescence properties, the prepared CDs were successfully applied to interference-free development of latent fingerprints (LFPs) on various fluorescent substrate surfaces. All three CDs achieved high-quality fingerprint imaging on the selected substrates with well-defined details. Compared to single-color CDs, multicolor CDs could provide flexible selection for achieving high-contrast imaging on complex fluorescent substrates.
The two sensitive fluorescence quantitative immunochromatographic assays (FQICAs), background fluorescence quenching immunochromatographic assay (bFQICA) and time-resolved fluorescent immunochromatographic assay (TRFICA), play an important role increasingly in rapid detection technology for food safety. Amantadine (AMD), used extensively in virus infections in livestock and poultry, has been prohibited due to hazard concerns over public human health. Therefore, AMD was used as a model molecule in the FQICAs establishment and comparison based on the same bioreagents. The outstanding performance in technical parameters of the two FQICAs indicated that they could provide rapid, precise, reliable technical support for large-scale on-site screening for AMD detection. What’s more, the systematic and comprehensive comparison of the two FQICAs would give useful suggestions for scientists and users in monitoring the harmful compounds.
危险品化学品经营许可证（带存储）