The environmental problems of global warming and fossil fuel depletion are increasingly severe, and the demand for energy conversion and storage is increasing. Ecological issues such as global warming and fossil fuel depletion are increasingly stringent, increasing energy conversion and storage needs. The rapid development of clean energy, such as solar energy, wind energy and hydrogen energy, is expected to be the key to solve the energy problem. Several excellent literature works have highlighted quantum dots in supercapacitors, lithium-sulfur batteries, and photocatalytic hydrogen production. Here, we outline the latest achievements of quantum dots and their composites materials in those energy storage applications. Moreover, we rationally analyze the shortcomings of quantum dots in energy storage and conversion, and predict the future development trend, challenges, and opportunities of quantum dots research.

The pH/redox dual-sensitive fluorescent carbon dots (pHRCDs) with the fluorescence quantum yield of 16.97% were synthesized by the pyrolysis of L-glutamic acid (L-glu) and dopamine (DA). Compared with the quantum dot (QD)−dopamine conjugate, when the pH value of the solution was changed from neutral to alkaline, the pHRCDs exhibited unique optical phenomenon including red-shift of fluorescence peak and the fluorescence intensity first decreasing from pH 7 to 10 and then increasing from pH 10 to 13. The pHRCDs could be developed for a discriminative and highly sensitive dual-response fluorescent probe for the detection of oxidized glutathione (GSSG) and ascorbic acid (AA) activity in human blood. Under the optimized experimental conditions, the dual-response fluorescent probe can detect GSSG and AA in the linear range of 1.2−3.6 and 27−35 μM with the detection limits of 0.1 and 3.1 μM, respectively. In addition, the pHRCDs demonstrated low cytotoxicity and good biocompatibility, which can be well applied to in vitro cell imaging, and the pHRCDs/GSH fluorescence system has been successfully developed for the detection of AA in real samples.

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Despite the rapid development of science and technology, the effective treatment of cancer still threatens human life and health. However, the success of cancer treatment is closely related to early diagnosis, identification, and effective treatment. In recent years, with the strengthening of the development and research of nanomaterials for cancer diagnosis and treatment, researchers have found that carbon dots (CDs) have the advantages of wide absorption, excellent biocompatibility, diverse imaging characteristics, and photostability and are widely used in various fields, such as sensing, imaging, and drug/gene transportation. Recently, researchers also discovered that CDs could be used as an effective photosensitizer to generate active oxygen or convert light energy into heat under the stimulation of the external lasers, making them have the effects of photothermal and photodynamic therapy for cancer. In this review, we first outline the single-modal and multimodal imaging analysis of CDs in cancer cells. After introducing diversified imaging functions, we focused on the design and the latest research progress of CDs in phototherapy and introduced in detail the strategies of CDs in phototherapy treatment and the challenges faced by clinical applications. We hope that this overview can provide important insights for researchers and accelerate the pace of research on CDs in imaging-guided phototherapy treatment.