The use of metal ions to bridge the fluorescent materials to target analytes has been demonstrated to be a promising way to sensor design. Herein, the effect of rare-earth ions on the fluorescence of L-methioninestabilized gold nanoclusters (Met-AuNCs) was investigated. It was found that europium (Eu 3+ ) can significantly suppress the emission of Met-AuNCs, while other rare-earth ions showed a negligible impact. The mechanism on the observed fluorescence quenching of Met-AuNCs triggered by Eu 3+ was systematically explored, with results revealing the dominant role of photoinduced electron transfer (PET). Eu 3+ can bind to the surface of Met-AuNCs by the coordination effect and accepts the electron from the excited Met-AuNCs, which results in Met-AuNC fluorescence suppression. After introducing dipicolinic acid (DPA), an excellent biomarker for spore-forming pathogens, Eu 3+ was removed from the surface of Met-AuNCs owing to the higher binding affinity between Eu 3+ and DPA. Consequently, an immediate fluorescence recovery occurred when DPA was present in the system. Based on the Met-AuNC/Eu 3+ ensemble, we then established a simple and sensitive fluorescence strategy for turn-on determination of biomarker DPA, with a linear range of 0.2−4 μM and a low limit of detection of 110 nM. The feasibility of the proposed method was further validated by the quantitative detection of DPA in the soil samples. We believe that this study would significantly facilitate the construction of metal-ion-mediated PET sensors for the measurement of various interested analytes by applying fluorescent AuNCs as detection probes.

Injecting Al–Si-based sorbents, typically kaolin, to capture alkali vapors is an effective technology to mitigate alkali-related operation problems of pulverized fuel (PF)-fired boilers. Aimed at evaluating the sorbent performance with a numerical approach, a transient one-dimensional single-particle model was developed for kaolin particle capturing KOH vapor under the conditions prevailing in PF-fired boilers, which fully addresses the intraparticle vapor diffusion and reactions and the reactivity change as a result of the sorbent deactivation. The model was validated with literature data from the experiments on an isothermal entrained flow reactor and proven to reasonably describe kaolin capturing KOH vapor covering a wide range of reaction conditions. The model was employed to numerically investigate the effects of the temperature and sorbent deactivation, particle size, and K/(Al + Si) molar ratio on the K-capture performance. It was found that the reactions of sorbent particles of around 3.5–5.5 μm are kinetics−diffusion-controlled at temperatures below ca. 1100 °C and the diffusion effects are enhanced with an increasing particle size. Sorbent deactivation at higher temperatures reduces K capture but looses the diffusion limitation on K capture for larger particles. The Arrhenius increase of reaction reactivity and sorbent deactivation together with the diffusion effects determine the optimal temperature window for kaolin capturing KOH vapor, which shifts from around 1200 °C for 3.5–5.5 μm particles to around 1350 °C for 13.5–20 μm particles. The modeling study suggests using smaller particle sorbents for achieving high K-capture performance but also supports using larger size sorbents because of the fitness of their temperature windows with high-temperature conditions of PF-fired boilers.

Although metal nanoclusters (MNCs) have shown great promise for the further development of photochemical techniques to be applied in diverse areas (e.g., photoelectronic devices, photochemical sensors, photocatalysts, and energy storage and conversion systems), the fundamental problem of their electron transfer behavior still remains unsolved. Herein, a driving force-dependent photoinduced electron transfer process of gold nanoclusters (AuNCs) is clarified for the first time from a rational-designed opposite-charged system. It was found that the electron transfer dynamic of carboxylated chitosan and dithiothreitol-commodified AuNCs (CC/DTT-AuNCs) can be satisfactorily described by the Marcus electron transfer theory. This proved model was applied to estimate the ultrafast charge separation process between CC/DTT-AuNCs and mitoxantrone, which was confirmed by fluorescence quenching and femtosecond transient absorption spectroscopy measurements. We envision that this work will open a new door for understanding the electron transfer behavior of MNCs and facilitate the design of advanced optoelectronic devices.

Monitoring nicotine concentrations in human fluids is extremely crucial owing to the harmful effect of nicotine on human health. Herein, it is shown that nicotine could quench the cathodic electrochemiluminescence (ECL) of gold nanoclusters (AuNCs) with high efficiency. The ECL quenching mechanism of nicotine was studied in detail using various experimental tools and theoretical calculations. It was concluded that the strongly oxidizing intermediate SO4 •–, produced from K2S2O8, could oxidized nicotine, resulting in ECL emission quenching. On the basis of this high-efficiency ECL quenching of the AuNCs/K2S2O8 system, a recyclable, ultrasensitive, and selective ECL sensing platform for nicotine detection was proposed. Even in the absence of any complex signal amplification techniques, the ECL sensor for nicotine detection showed an unprecedentedly low detection limit of 7.0 × 10–13 M (S/N = 3) and a wide linear range over 8 orders of magnitude. Most remarkably, it could be successfully used for nicotine detection in human urine samples. This is expected to promote the investigations and applications on nicotine-related diseases. We believe that the proposed ECL platform can hold great prospects for commercialization in biomedical fields and tobacco industries.

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