Reactive oxygen species (ROS) are being explored as a potential treatment, but accurate assessment of their efficacy is hindered by the dual roles of therapeutic intervention and diagnostic monitoring. Especially, ROS can alter lysosomal polarity by increasing membrane permeability. Therefore, ROS generation can be evaluated by monitoring the polarity changes of lysosomes. Hence, in this study, we developed a new lysosomal polarity-responsive carbon dot nanozyme (LF-CDs) that exerts peroxidase-like (POD-like) activity under light irradiation for controllable generation of ROS and sensing of ROS levels via lysosomal polarity response. Western blot analysis revealed that LF-CDs induced adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) phosphorylation within cells through the generation of ROS, effectively regulating intracellular glucose metabolism. Importantly, the ROS produced by LF-CDs can cause lysosomal polarity variation and trigger a corresponding fluorescence change in LF-CDs, reflecting the generation of ROS and enabling in situ monitoring of the regulation of glucose metabolism by ROS. By combining photocatalytic property with fluorescence imaging, this work overcomes the limitations of traditional ROS monitoring, offering a new insight into the evaluation of the biological effects of ROS during therapeutic processes.

The obtaining of the localized bioinformation of organelles and multi-dimension dynamic fluctuations in the morphology and microenvironment of organelles is beneficial for gaining a deeper understanding of the relevant physiology/pathology at subcellular level. In recent years, fluorescent carbon dots (CDs) have emerged as outstanding targeted probes for the fluorescence imaging of various organelles or organelle microenvironments, due to their excellent optical property, good biocompatibility, suitable size, as well as abundant surface functional groups. Moreover, these organelle-targeting or microenvironment-responsive CDs have also shown promising application in diagnosis and treatment by integrating them with drug delivery systems or developing their additional photodynamic/photothermal properties. In this review, we summarize the development status of CDs with responsiveness to various organelles and their microenvironment parameters, and highlight their anchoring strategies and responsive mechanisms through associating the structural and surface properties of CDs with unique features of organelles. The typical applications of these organelle-specific CDs in bioimaging, cancer diagnosis and tumor treatment are also outlined to help understanding of their biological significance. Finally, the existing opportunities and challenges of these organelle-specific CDs are discussed, in order to offer some valuable development directions. We hope this review will be conductive to grasping the fundamental design principles of organelle-targeting CDs and inspiring more organelle-responsive mechanisms for CDs.

Harnessing defect emission in CdS quantum dots (QDs) for efficient near-infrared (NIR) emission remains difficult. We report a synergistic strategy combining crystal-phase and defect engineering. High-concentration synthesis stabilizes the metastable wurtzite phase. A sulfur-rich stoichiometry (Cd:S=1:1.25) increases the concentration of sulfur vacancies (V_S), which is electron paramagnetic resonance (EPR)-confirmed and enables broadband NIR emission at 740 nm. Trace Zn2+ incorporation, confirmed as surface-adsorbed, further enhances monodispersity and passivates non-radiative traps, boosting emission intensity. A prototype light-emitting diode (LED) integrated with the Zn2+-modified CdS QDs exhibits broad emission (580-1100 nm), demonstrating dual functionality for visible lighting and NIR night vision.

Synchronous regulation of the photoluminescence and physicochemical characteristics of multicolor carbon dots (CDs) can fully realize their application potential in multicomponent imaging. Herein, by utilizing an acid-regulated synthetic strategy, green-emissive and orange-emissive CDs that target lipid droplets (LDs) and mitochondria (Mito) have been developed for fluorescence visualization of LD-Mito interactions. The finding of different molecular fluorophores reveals that the precursor undergoes different reaction pathways in neutral and acidic conditions, which alters the size of sp2-conjugated domain and surface properties for the successful regulation of photoluminescence properties and organelle-targeting ability. Moreover, the one-step fabrication of these two CDs was also realized by lowering the dosage of acid. Therefore, the multicolor imaging of LDs and Mito has been achieved with one-step staining, disclosing that their interaction frequency decreases during the lipotoxicity process. This work successfully demonstrates the high coupling potential between multicolor CDs and organelle-interaction visualization, which would provide guidance on the correlation between photoluminescence features and other properties of multicolor CDs for extending application space.

Designing rational and lightweight magnetic-dielectric composites for efficient electromagnetic wave absorption remains a significant challenge. Herein, the FeCoNi metal-induced nitrogen-doped carbon nanotubes (FeCoNi@NCNTs) were synthesized though unique nanoconfinement strategy during carbon thermal reduction reaction. In confined environment, sufficient conditions were provided for the multidimensional growth of nanostructures. The mechanisms of carbon nanotube growth and electromagnetic wave absorption were further investigated. The FeCoNi@NCNTs exhibited a minimum reflection loss of -59.5 dB within the 2-18 GHz frequency range. Moreover, the composite achieved a minimum effective absorption bandwidth of 5.3 GHz at 2.0 mm. This work provides a new insight for preparing various magnetic-dielectric composites with rich absorption effects and broadband microwave absorption.

Targeted fluorescence probes for imaging and differentiation of hepatocellular carcinoma (HCC) are highly desirable from its scientific research and clinical applications. However, most of the current targeted fluorescence probes focus on the variation of intracellular microenvironment caused by the cancerization of hepatocyte, which causes a fluorescence intensity alteration but fails to produce a spatial differentiation due to the lack of robust parameters for further improving accuracy. Herein, the study develops a new fluorescent carbon dot (CTF-CDs) that can target the overexpressed GABA(A) receptor (GABA(A)R) on cell membrane for accurate and high-contrast imaging of HCC and differentiation. The competition response between CTF-CDs and typical receptor-binding ligands reveals their affinity toward the picrotoxin-binding site of GABA(A)R. Based on this GABA(A)R-targeting ability, accurate imaging of HCC cells is realized by lighting their membranes, along with a big difference from the intracellular fluorescence of normal liver cells and other cancer cells. In addition, the CTF-CDs have also been used to visualize the anticancer drug-induced variations on HCC cell membrane and fluorescent imaging in HCC tissue. This work extends the targeting object of fluorescence probes from intracellular microenvironment to membrane protein, adding a new dimension to the imaging and differentiation of HCC.

Physical unclonable functions (PUFs) have emerged as an unprecedented solution for modern information security and anticounterfeiting by virtue of their inherent unclonable nature derived from distinctive, randomly generated physical patterns that defy replication. However, the creation of traceable optical PUF tags remains a formidable challenge. Here, we demonstrate a traceable PUF system whose unclonability arises from the random distribution of diamonds and the random intensity of the narrow emission from germanium vacancies (GeV) within the diamonds. Tamper-resistant PUF labels can be manufactured on diverse and intricate structural surfaces by blending diamond particles into polydimethylsiloxane (PDMS) and strategically depositing them onto the surface of objects. The resulting PUF codes exhibit essentially perfect uniformity, uniqueness, reproducibility, and substantial encoding capacity, making them applicable as a private key to fulfill the customization demands of circulating commodities. Through integration of a digitized "challenge-response" protocol, a traceable and highly secure PUF system can be established, which is seamlessly compatible with contemporary digital information technology. Thus, the GeV-PUF system holds significant promise for applications in data security and blockchain anticounterfeiting, providing robust and adaptive solutions to address the dynamic demands of these domains.

Traffic station can not only ensure the normal operation of urban traffic, but also an important display window of urban culture and image. However, at present, the design of urban traffic station has the sameness and the lack of uniqueness. And in the process of design, there is neglect of regional

As a new type of luminescent material, carbon dots (CDs) have attracted increased attention for their superior optical properties in recent years. However, solid-state fluorescent CDs, especially with red emission, are still a major challenge. Here, CDs with solid-state red emission were synthesized by co-doping of N and B using the one-step microwave method. The CD powder exhibits excitation-independent solid-state red fluorescence without any dispersion matrices, with optimum solid-state fluorescence wavelength of 623 nm. The hydrogen bonding interaction in CDs is helpful for solid-state fluorescence of CDs. The I G / I D value of CDs reaches up to 3.49, suggesting their very high graphitization degree, which is responsible for their red emission. In addition, CDs show the concentration-induced multicolor emission, which is attributed to the decreased energy gap in the high concentrated CD solution. To exploit their concentration-dependent emission, CDs with changing ratio in matrices are applied as a color-converting layer on ultraviolet chip to fabricate multicolor light-emitting diodes with light coordinates of (0.33, 0.38), (0.41, 0.48), (0.49, 0.44), and (0.67, 0.33), which belong to green, yellow, orange, and red light, respectively.

Dynamic membrane contacts between lipid droplets (LDs) and mitochondria play key roles in lipid metabolism and energy homeostasis. Understanding the dynamics of LDs under energy stimulation is thereby crucial to disclosing the metabolic mechanism. Here, the reversible interactions between LDs and mitochondria are tracked in real-time using a robust LDs-specific fluorescent probe (LDs-Tags). Through tracking the dynamics of LDs at the single-particle level, spatiotemporal heterogeneity is revealed. LDs in starved cells communicate and integrate their activities (i.e., lipid exchange) through a membrane contact site-mediated mechanism. Thus the diffusion is intermittently alternated between active and confined states. Statistical analysis shows that the translocation of LDs in response to starvation stress is non-Gaussian, and obeys nonergodic-like behavior. These results provide deep understanding of the anomalous diffusion of LDs in living cells, and also afford guidance for rationally designing efficient transporter.

Hepatocellular carcinoma (HCC) is a metabolic disease with high mortality caused by abnormal deposition of lipid droplets (LDs). The number and distribution of LDs can effectively reflect the severity of HCC. Additionally, polarity change is also an important indicator for monitoring HCC. Therefore, using fluorescence imaging technology to accurately identify LDs is helpful for HCC diagnosis and treatment evaluation. To date, the study that can simultaneously monitor the polarity and spatiotemporal characteristics of LDs to diagnose HCC has not been reported yet. Herein, a novel LD-targeting near-infrared carbon dots (CDs) with dual-report function of determining the LDs polarity as well as presenting their spatial characteristics was developed. The high lipophilicity and solvatochromic effect of CDs endows it with the ability to image LDs with high-fidelity, so it can not only report the spatiotemporal characteristics of LDs including the number, size, and aggregation degree, but also determine their polarity variations. Therefore, the high-contrast fluorescence diagnosis of HCC was successfully realized by using dual-function CDs. Meanwhile, the CDs were further utilized to evaluate the efficacy of anticancer drugs with satisfactory performance. Overall, this CD-based LDs probe may provide a new perspective for the diagnosing of LDs-related diseases and screening of anticancer drugs.

Polarity is an integral microenvironment parameter in biological systems closely associated with a multitude of cellular processes. Abnormal polarity variations accompany the initiation and development of pathophysiological processes. Thus, monitoring the abnormal polarity is of scientific and practical importance. Current state-of-the-art monitoring techniques are primarily based on fluorescence imaging which relies on a single emission intensity and may cause inaccurate detection due to heterogeneous accumulation of the probes. Herein, we report carbon dots (CDs) with ultra-sensitive responses to polarity. The CDs exhibit two linear relationships: one between fluorescence intensity and polarity and the other between polarity and the maximum emission wavelength. The emission spectrum is an intrinsic property of the probes, independent of the excitation intensity or probe concentration. These features enable two-color imaging/quantitation of polarity changes in lipid droplets (LDs) and in the cytoplasm via in situ emission spectroscopy. The probes reveal the polarity heterogeneity in LDs which can be applied to make a distinction between cancer and normal cells, and reveal the polarity homogeneity in cytoplasm.

Carbon dots (CDs) as a class of new fluorescent materials have attracted numerous interests. However, there remains a significant challenge to prepare CDs with full-color solid-state photoluminescence (PL). In this work, CDs with tunable full-color solid-state PL are prepared via one-step microwave method using phloroglucinol and urea as sources by regulating reactant ratio and microwave power. The maximum emission of CDs gradually shifts from 445 to 643 nm, and quantum yield of five typical CDs with blue (B), green (G), yellow (Y), orange (O) and red (R) emission reaches up 48.2%, 26.0%, 18.5%, 13.7% and 5.7%, respectively. It is the first time, as far as we know, to realize full-color solid-state CDs without additional disperse matrices. The G-, Y-, O-, R-CDs show aggregation-induced red-shift behavior, while B-CDs exhibit unique crystallization-induced emission enhancement property. Finally, CDs are utilized as phosphors combing with ultraviolet chip to fabricate multicolor and white light emitting diodes (LED). The obtained white LED exhibits an adjustable correlated temperature (3937−8588 K) and high color rendering index (80−88). This study provides a novel guidance for developing self-quenching resistant CDs with multicolor emission.

In vivo imaging has become a key tool in biomedical studies because it provides a large amount of information about biological stimuli. Owing to the excellent biocompatibility and optical properties, carbon dots (CDs) have been widely used for fluorescence bioimaging. Whereas strong background autofluorescence from tissues is one of the largest concerns with CDs-based in vivo imaging, the development of CDs with large Stokes shifts is becoming critical for reducing the background autofluorescence. Herein, a novel design strategy to increase the Stokes shift of CDs was developed. By breaking the symmetry of the electronic structure of the precursor, the Stokes shift was significantly increased from 75 nm in p-phenylenediamine-derived CDs to 161 nm in 2-nitro-4-aminodiphenylamine (NAP)-derived CDs. In addition, the asymmetric electronic structure also enhanced the intramolecular charge transfer effect, which endowed NAP-CDs with a sensitive response to micro-environment polarity. As cancer cells possess lower polarity than normal cells, NAP-CDs would be effectively applied for cancer imaging with remarkably reduced background fluorescence from cell, tissue, organ to in vivo levels. The asymmetric electronic structure strategy reported here provides an important theoretical basis for the rational design and effective synthesis of CDs with large Stokes shift for practical biomedical applications.

Lipid droplets (LDs) play indispensable roles in numerous physiological processes; hence, the visualization of the dynamic behavior of LDs in living cells is of great importance in physiological and pathological research. In this article, the quantitative structure-activity relationship (QSAR) theory was employed as an effective design strategy for the development of organelle-targeting carbon dots (CDs). The lipid-water partition coefficient (Log P) of the QSAR was adopted as a key parameter to predict the cellular uptake and subcellular localization of CDs in live cells. By carefully adjusting the molecular structure and lipophilicity of the precursors, p-phenylenediamine-derivatized nucleolus-targeting hydrophilic CDs were converted to lipophilic CDs [4-piperidinoaniline (PA) CDs] with inherent LD-targeting performance. The PA CDs were able to indicate the dynamic behavior of LDs and visualize the changes of bisphenol A-induced nonalcoholic fatty liver disease-like changes in a cellular model. The QSAR strategy of CDs demonstrated here is expected to be increasingly exploited as a powerful design tool for developing various organelle-targeting CDs.

Carbon dots (CDs) have attracted a lot of attention because of their tunable emission wavelength, high photobleaching resistance, and environmental friendliness. However, they suffer from aggregation-induced quenching in the solid state, which limits their application in solid-state fields. In this work, yellow- and orange-emissive N, B-codoped CDs (y-NB-CDs and o-NB-CDs) with highly efficient solid-state fluorescence and dual emission were achieved by a facile one-step microwave method. The obtained y-NB-CDs in the powder state show bright yellow fluorescence with a high solid-state QY of 39.0% and typical dual emission peaks at 484 and 565 nm. The as-synthesized o-NB-CDs in the powder state exhibit bright orange fluorescence with a high solid-state QY of 31.1% and dual emission at 484 and 585 nm. After systematically studying the effect of N, B-codoping on the solid-state fluorescence of NB-CDs, we demonstrate that the hydrogen bond between B-OH on the surface of the NB-CDs can inhibit the direct contact of nanoparticles, and a high content of graphitic N in NB-CDs can increase the probability of the radiative process of the aromatic domains, both of which trigger high-efficiency solid-state fluorescence of NB-CDs. This finding provides a general and efficient method for highly emissive solid-state CDs. In addition, N, B-codoping can also give NB-CDs dual emission in the short-wavelength and long-wavelength regions, ascribed to the carbon core and surface defect state, respectively. Finally, y-NB-CDs were demonstrated as a phosphor to prepare a near white light-emitting diode with a color rendering index of 84 by combining them with an ultraviolet chip.

Carbon dots(CDs) have attracted extensive attention of researchers because of their excellent fluorescence performance, low toxicity, extensive raw materials and good biocompatibility. However, the emission wavelengths of most CDs are in short-wavelength region of blue and green light,limiting their widespread application. The synthesis of multicolor CDs can guide the realization of long wavelength CDs and broaden the application of CDs. Therefore, the multicolor emitting mechanism of CDs from sizes, inner structures and surface states of CDs was reviewed, the adjusting measures of achieving multicolor CDs were presented, including raw materials, reaction conditions, surface modification, and separation and purification. Furthermore, the application of multicolor CDs in light emitting diode and bioimaging was also summarized.

Aggregation-caused quenching (ACQ) effect, known as the main cause to restrain solid-state luminescence of carbon quantum dots (CQDs), hinders further application of CQDs in white light-emitting diodes (WLED). Here, a complex of CQDs and phthalimide crystals (CQDs/PC) was prepared through a one-step solvothermal method. CQDs/PC prevented CQDs from touching directly by embedding the CQDs in phthalimide crystal matrix in situ, which effectively reduced the ACQ effect. Furthermore, CQDs/PC exhibited multi-peak fluorescence spectra that span the green, yellow and orange spectral regions. Finally, a WLED fabricated based on CQDs/PC achieved a color-rendering index of 82 and a correlated color temperature of 5430 K. This work provides a quick and effective strategy to apply CQDs to WLED.