Polyamine-functionalized carbon quantum dots (CQDs) with high fluorescence quantum yield (42.5%) have been synthesized by the low temperature (<200 °C) carbonization of citric acid with branched polyethylenimine (BPEI) in one simple step. The obtained BPEI–CQDs are spherical graphite nanocrystals (average 6.2 nm in size) capped with abundant BPEI at their surfaces. It is the first report that CQDs are both amino-functionalized and highly fluorescent, which suggests their promising applications in chemical sensing.
Herein, a novel bright-green and highly fluorescent polyethyleneimine capped copper nanoclusters (CuNCs@PEI) has been hydrothermally synthesized, which is employed as a fluorescence probe to determine rifampicin. Under optimum synthetic conditions, the morphology, surface chemistry and optical features of resulting CuNCs@PEI are well characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, UV–Vis absorption spectra, transient and steady-state fluorescence. In comparison to previous reports, the new species with a larger diameter of approximately 3 nm exhibit higher fluorescence quantum yield (QY) up to nearly 10.7%, and demonstrate tolerability to extreme pH, high ionic strengths as well as long-term UV irradiation. These excellent optical properties ascribe to unique grain size and surface chemical features of products, which are further discussed in this work. In addition, we employed as-prepared CuNCs@PEI to detect rifampicin based on fluorescence quenching phenomenon. The fluorescence intensity of probe is linearly proportional to rifampicin over the concentration rage from 0 to 20 μM, where the limit of detection (LOD) is 50 nM. Besides, this probe can be also used to assay rifampicin in serum samples with satisfactory recoveries.
Fluorescent carbon quantum dots are emerging as a new class of fluorescent probes due to their unique optical properties . Herein, we presented a simple, one-pot and effective preparation strategy for copper-functionalized carbon quantum dots (Cu-CDs). The Cu-CDs demonstrated excitation-independent emissions, high fluorescent quantum yield (~ 24.4%) and excellent fluorescent stability. The fluorescence of Cu-CDs could be quenched efficiently in the presence of histidine (His) due to the coordination occurring between surface Cu and imidazole side chains of His. Thus, the Cu-CDs could be used as an efficient fluorescent probe for His detection. Under optimal conditions, the fluorescent signals of Cu-CDs decreased linearly with the concentrations of His over a range of 0.1–15 µM. The detection limit was 30 nM. The proposed method provided obvious advantages of rapid response, convenience, simplicity, high selectivity and sensitivity. Moreover, good results also have been obtained for His detection in real biological fluid samples.
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