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Abnormal lysosomal viscosity is closely associated with cancer progression, underscoring the need for bifunctional fluorescent probes and photosensitizers (PSs) that can both monitor viscosity and facilitate imaging‐guided therapy for simultaneous cancer diagnosis and treatment. Despite advances in lysosome‐targeted PSs development, few have demonstrated the ability to generate both Type I and Type II reactive oxygen species (ROS). In this study, we present BTTPA, a lysosome‐targeted fluorescent probe and photosensitizer, designed to integrate cancer diagnosis via viscosity imaging and cancer treatment through photodynamic therapy (PDT). Our findings reveal that BTTPA selectively targets lysosomes, enabling dynamic monitoring of cellular viscosity and distinguishing cancer cells from normal cells. Upon light activation, BTTPA efficiently generates both Type I and Type II ROS. Apoptosis assays further confirm BTTPA's effectiveness in inducing cancer cell apoptosis, highlighting its potential as a powerful tool for cancer diagnosis and therapy. [ABSTRACT FROM AUTHOR]

• The unique physical and chemical properties of CD-based fluorescent probes are discussed. • The six sensing mechanisms of CD-based fluorescent probes are introduced in detail. • The sensing application of CD-based fluorescent probes are elaborated. • The challenges of CD-based fluorescent probes and possible strategies to overcome them are also summarized. Due to the advantages of in situ, real-time, and non-destructive detection of target molecules, fluorescent probes have become an indispensable tool in the fields of disease diagnosis and environmental and food safety monitoring. However, with the development of modern science and technology, sensing techniques have new challenges and requirements, such as increased sensitivity, better selectivity, and high-throughput visual detection in complicated practical samples. Developing effective fluorescent probes is still ongoing research. Fluorescent carbon dots (CDs) are a novel carbon-based nanomaterial that have attracted tremendous attention because of their excellent biocompatibility, tunable fluorescence properties, good photostability, and easy synthesis and surface modification, and they have shown great potential in fluorescent sensing and imaging applications. In this review, we summarize the recent advances in CD-based fluorescent probes, including the design strategies, sensing mechanisms, and their applications in sensitive and selective detection of public safety substances, organic amines, phenols, bioactive molecules, biological enzymes, and inorganic salts. A future perspective is introduced to highlight the existing challenges and possible strategies to overcome the problems in practical application of currently developed CD-based fluorescent probes, which may be instructive to the design of effective fluorescent probes in the future. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) with blue fluorescence were synthesized through hydrothermal treatment of p -dihydroxybenzene and hydrazine hydrate. The fluorescence of the investigated CDs could be selectively quenched by iron ions (Fe3+) because of the strong metal-ligand coordination and electrostatic interactions between the large amount of hydroxyl, amino, and carboxyl groups on CDs' surface and Fe3+. Interestingly, this non-fluorescent CDs + Fe3+ complex displayed a sensitive and selective turn-on fluorescence toward ampicillin with a limit of detection of 0.70 μM. The sensing process could be observed by naked eyes under the 365 nm UV light irradiation. Importantly, CDs + Fe3+ complex had been successfully applied in the detection of ampicillin in river water. • Fluorescent CDs were synthesized through hydrothermal treatment of p -dihydroxybenzene and hydrazine hydrate. • The fluorescence of CDs was quenched significantly and quickly upon addition of Fe3+. • The quenched fluorescence of CDs could be selectively turned on by the addition of ampicillin. • The CDs-Fe3+ system was successfully applied in the ampicillin detection in river water. [ABSTRACT FROM AUTHOR]

[Display omitted] • Using kaempferol as raw material, a new non-pollution yellow fluorescent probe was synthesized by simple hydrothermal method. • The proposed turn-off–on probe was enabled high sensitivity against mercury (Hg2+) ions and cysteine (Cys). • The practicality of CDs was investigated in real water samples for detecting Hg2+. Herein, carbon dots (CDs) with bright yellow fluorescence were synthesized by using kaempferol as a carbon source, through a hydrothermal method in NaOH solution. The as-prepared CDs were highly soluble and spherical with uniform size and mean particle diameter of 3.2 nm. The CDs have unique high selectivity, sensitivity and anti-interference ability to mercury (Hg2+). Under different pH conditions, Hg2+ ions can still quench the fluorescence of CDs effectively and stably. On the other hand, cysteine can re-ignite the fluorescence of CDs as a result of strong chelation interaction that exists between -SH and Hg2+. There are good linear relationships between the concentration of Hg2+ and (F 0 -F)/F 0 , the concentration of cysteine and (F-F 0)/F 0 , and the detection limits are 1.6 μM and 0.8 μM, respectively. In addition, CDs can effectively detect Hg2+ in tap water and lake water and detect cysteine in serum. [ABSTRACT FROM AUTHOR]

Simultaneous detection and reduction of Au3+ in contaminated water is extremely desirable. Herein, we synthesized red fluorescent carbon dots (CDs) for Au3+ detection with dual colorimetric and fluorescent spectral response within 2 min. The CDs showed high sensitivity and selectivity towards Au3+ with a low detection limit of 29 nM. Further, CDs selectively reduce Au3+ to Au0 via redox reaction between the thioether group on the surface of CDs and Au3+. Accordingly, CDs were effectively utilized to detect and extract Au3+ without interference from other metal ions. [Display omitted] • Red fluorescent CDs were synthesized and characterized. • CDs show colorimetric and fluorescent spectral response to Au3+. • CDs can selectively reduce Au3+ to Au0 from environmental water. • The sensing and reduction mechanism of CDs toward Au3+ were demonstrated. [ABSTRACT FROM AUTHOR]