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Single molecule fluorescent probes have attracted considerable attention due to their ultimate sensitivity, fast response, low sample consumption, and high signal-to-noise ratio. Nanoparticles with outstanding optical properties make them perfect candidates for probes in the application of single molecule detection. In this review, we focus on various kinds of nanoparticles acting as single molecule fluorescent probes, including quantum dots, upconverting fluorescent nanoparticles, carbon dots, single-wall carbon nanotubes, fluorescent nanodiamonds, polymeric nanoparticles, nanoclusters, and metallic nanoparticles. Optical properties of various nanoparticles and their recent application in single molecule fluorescent probes are explored. How nanoparticles boost the sensitivity of detection is emphasized in combination with different sensing strategies. Future trends of nanoparticles in single molecule detection are also discussed. We hope that this review can provide practical guidance for researchers who work on nanoparticle-based single molecule fluorescent probes., (© 2022 John Wiley & Sons Ltd.)

Carbon dots (CDs) have excellent optical properties, low toxicity and easy preparation, which have led to them being widely used in biomedicine, sensing and optical devices. However, although great progress has been made in the preparation of CDs, the detailed exploration of their photoluminescence (PL) mechanism is still under debate due to their complex structures and surface functionalities. Here, we proposed a single change in the pH of the synthesis condition, which had no effect on the CDs intrinsic core states and avoided the mutual influence of multiple PL origins. The m-phenylenediamine (m-PD) served as a carbon source, whose protonation degree determined the surface state of the resulting CDs and the accompanying fluorescence characteristics. The as-obtained CDs materials can be applied in the chemical sensor and anti-counterfeiting fields in a targeted manner. Therefore, our work not only contributes to the explanation of the CDs PL mechanism, but also obtains a series of CDs materials with controllable PL properties.

In common advanced oxidation processes, excess reagents and energy are often added to the reaction system to maintain the continuity of the reaction. These additions result in a large waste of resources and energy, which has become a bottleneck in the development of water treatment technology. In this study, we propose a new strategy to solve this problem based on a novel dual-reaction-center (DRC) Fe-ZnS quantum dots (Fe-ZnS QDs) catalyst that forms a non-equilibrium surface with an electron-polarized distribution. Through experimental and theoretical studies, it was verified that the activation of trace amounts of H 2 O 2 could break the energy barrier for pollutants to transfer electrons. The dissolved oxygen (DO) in the reaction system could be activated by gaining energy on the surface of the Fe-ZnS QDs catalyst, and was converted to 1 O 2 to attack organic pollution. In addition, the pollutants themselves supplied electrons to H 2 O 2 through the surface of the Fe-ZnS QDs catalyst to generate more •OH radicals for pollutant degradation, thus providing two fast paths for pollutant degradation. The system could drive the reaction through a trace amount of H 2 O 2 , thereby activating DO to generate 1 O 2 while effectively using the energy of pollutants. Therefore, the proposed system offers a new direction for the development of environmentally-friendly catalysts and greatly reduces the consumption of resources and energy., (Copyright © 2021 Elsevier B.V. All rights reserved.)

[Display omitted] Semiconductor quantum dots, as promising solid-state platform, have exhibited deterministic photon pair generation with high polarization entanglement fidelity for quantum information applications. However, due to temporal correlation from inherently cascaded emission, photon indistinguishability is limited, which restricts their potential scalability to multi-photon experiments. Here, by utilizing quantum interferences to decouple polarization entanglement from temporal correlation, we improve four-photon Greenberger–Horne–Zeilinger (GHZ) state entanglement fidelity from (58.7 ± 2.2) % to (75.5 ± 2.0) %. Our work paves the way to realize scalable and high-quality multi-photon states from quantum dots. [ABSTRACT FROM AUTHOR]