Noncontact optical nanothermometers operating within the biological transparency windows are required to study temperature-sensitive biological phenomena at the nanoscale. Nanoparticles containing rare-earth ions such as Nd3+ have been reported to be efficient luminescence-based ratiometric thermometers, however often limited by poor water solubility and concentration-related quenching effects. Herein, we introduce a new type of nanothermometer, obtained by employing low-dimensional carbon nanodots (CNDs) as matrices to host Nd3+ ions (NdCNDs). By means of a one-pot procedure, small (∼7-12 nm), water-soluble nanoparticles were obtained, with high (15 wt %) Nd3+ loading. This stable metal-CND system features temperature-dependent photoluminescence in the second biological window (BW II) upon irradiation at 808 nm, thereby allowing accurate and reversible (heating/cooling) temperature measurements with good sensitivity and thermal resolution. The system possesses remarkable biocompatibility in vitro and promising performance at a high penetration depth in tissue models.

This study investigates the remarkable attributes of sulfur-doped carbon nanodots (CDs) synthesized in high yield and a narrow size distribution (4.8 nm). These CDs exhibit notable features, including potential bioelimination through renal clearance and efficient photothermal conversion in the near-infrared region with multicolor photoluminescence across the visible spectrum. Our research demonstrates high biocompatibility and effective near-infrared (NIR)-triggered photothermal toxicity when targeting mammospheres and patient-derived tumor organoids. Moreover, the study delves into the intricate cellular responses induced by CD-mediated hyperthermia. This involves efficient tumor mass death, activation of the p38-mitogen-activated protein kinase (MAPK) pathway, and upregulation of genes associated with apoptosis, hypoxia, and autophagy. The interaction of CDs with mammospheres reveals their ability to penetrate the complex microenvironment, impeded at 4 °C, indicating an energy-dependent endocytosis mechanism. This observation underscores the CDs\' potential for targeted drug delivery, particularly in anticancer therapeutics. This investigation contributes to understanding the multifunctional properties of sulfur-doped CDs and highlights their promising applications in cancer therapeutics. Utilizing 3-D tumor-in-a-dish patients\' organoids enhances translational potential, providing a clinically relevant platform for assessing therapeutic efficacy in a context mirroring the physiological conditions of cancerous tissues.

A ratiometric fluorescent and colorimetric detecting assay for NO2- was realized by a hybrid nanosensor (Co2+-CDs@R-CDs) utilizing firstly through the redox reaction of nitrite (NO2-) with Co2+, of which the hybrid nanosensor Co2+-CDs@R-CDs was fabricated by Co2+-doped carbon dots (Co2+-CDs) and a reference of red-emitting carbon dots (R-CDs). The ratiometric fluorescent linear detection range of NO2- was 2.5-45 μM and the limit of detection (LOD) was 0.068 μM with the response time of 120 s. While, the colorimetric linear detection range of NO2- was 2.5-60 μM and the LOD was 0.075 μM. In addition, a portable smartphone system which could measure the R (red), G (green), and B (blue) values of the fluorescence and the visible color of the coated Co2+-CDs@R-CDs paper strip-based sensor had also been developed and successfully applied to detect NO2- in sausage, pickles and tap water samples.

In this study, we present an economical and efficient synthesis method for carbon nanodots (CNDs) derived from cinnamon bark wood powder, with the incorporation of L-arginine as a dopant at varying ratios (Cinnamon : L-Arginine - 1:0.25, 1:0.5) via a hydrothermal reaction. Extensive structural and optical characterization was conducted through techniques such as FTIR, XRD, HR-TEM, DLS, UV-Vis, and PL spectra, providing a comprehensive understanding of the properties of CNDs and doped-CNDs. Quantum yields (QY) were quantified for synthesized materials, contributing to the assessment of their fluorescence efficiency. The synthesized CNDs were successfully applied for bioimaging of yeast cells, employing fluorescence microscopy to visualize their interaction. Remarkably, L-arginine-doped CNDs exhibited enhanced fluorescence, showcasing the influence of the dopant. The nature of these CNDs was rigorously investigated, confirming their biocompatibility. Notably, this work presents a novel approach to synthesizing CNDs from a renewable and sustainable source, cinnamon bark wood powder, while exploring the effects of L-arginine doping on their optical and biological properties. This work not only contributes to the synthesis and characterization of CNDs but also highlights their potential for diverse applications, emphasizing their structural, optical, and biological attributes. The findings underscore the versatility of CNDs derived from cinnamon bark wood powder and their potential for advancing biotechnological and imaging applications.

Due to the broadband response and low selectivity of external light, negative photoconductivity (NPC) effect holds great potential applications in photoelectric devices. Herein, different photoresponsive carbon nanodots (CDs) are prepared from diverse precursors and the broadband response from the NPC CDs are utilized to achieve the optoelectronic logic gates and optical imaging for the first time. In detail, the mcu-CDs which are prepared by the microwave-assisted polymerization of citric acid and urea possess the large specific surface area and abundant hydrophilic groups as sites for the adsorption of H2O molecules and thereby present a high conductivity in dark. Meanwhile, the low affinity of mcu-CDs to H2O molecules permits the light-induced desorption of H2O molecules by heat effect and thus endow the mcu-CDs with a low conductivity under illumination. The easy absorption and desorption of H2O molecules contribute to the extraordinary NPC of mcu-CDs. With the broadband NPC response in CDs, the optoelectronic logic gates and flexible optical imaging system are established, achieving the applications of \"NOR\" or \"NAND\" logic operations and high-quality optical images. These findings unveil the unique optoelectronic properties of CDs, and have the potential to advance the applications of CDs in optoelectronic devices.

A scene that contains both old and instant events with a clear motion trail is visually intriguing and dynamic, which can convey a sense of change, transition, or evolution. Developing an eco-friendly delay display system offers a powerful tool for fusing old and instant events, which can be used for visualizing motion trails. Herein, we brighten triplet excitons of carbon nanodots (CNDs) and increase their emission yield by a multidimensional confinement strategy, and the CND-based delay display array is demonstrated. The intense confinement effects via multidimensional confinement strategy suppress nonradiative transitions, and 240% enhancement in the phosphorescence efficiency and 260% enhancement in the lifetime of the CNDs are thus realized. Considering their distinctive phosphorescence performances, a delay display array containing a 4 × 4 CND-based delay lighting device is demonstrated, which can provide ultralong phosphorescence over 7 s, and the motion that occurred in different timelines is recorded clearly. This finding will motivate the investigation of phosphorescent CNDs in motion trail recognition.

Room-temperature phosphorescent materials, renowned for their long luminescence lifetimes, have garnered significant attention in the field of optical materials. However, the challenges posed by thermally induced quenching have significantly hindered the advancement of luminescence efficiency and stability. In this study, thermally enhanced phosphorescent carbon nanodots (CND) are developed by incorporating them into fiber matrices. Remarkably, the phosphorescence lifetime of the thermally enhanced CND exhibits a twofold enhancement, increasing from 326 to 753 ms, while the phosphorescence intensity experienced a tenfold enhancement, increasing from 25 to 245 as the temperature increased to 373 K. Rigid fiber matrices can effectively suppress the non-radiative transition rate of triplet excitons, while high temperatures can desorb oxygen adsorbed on the surface of the CND, disrupting the interaction between the CND and oxygen. Consequently, a thermally enhanced phosphorescence is obtained. In addition, benefiting from the thermally enhanced phosphorescence property of CND, a warning indicator with an anti-counterfeiting function for monitoring cold-chain logistics is demonstrated based on CND.

Sleep deprivation (SD) is highly prevalent in the modern technological world. Emerging evidence shows that sleep deprivation is associated with oxidative stress. At the organelle level, the Golgi apparatus actively participates in the stress response. In this study, to determine whether SD and Golgi apparatus stress are correlated, we rationally designed and fabricated a novel Golgi apparatus-targeted ratiometric nanoprobe called Golgi dots for O2·- detection. This probe exhibits high sensitivity and selectivity in cells and brain slices of sleep-deprived mice. Golgi dots can be readily synthesized by coprecipitation of Golgi-F127, an amphiphilic polymer F127 modified with a Golgi apparatus targeting moiety, caffeic acid (CA), the responsive unit for O2·-, and red emissive carbon nanodots (CDs), which act as the reference signal. The fluorescence emission spectrum of the developed nanoprobe showed an intense peak at 674 nm, accompanied by a shoulder peak at 485 nm. As O2·- was gradually added, the fluorescence at 485 nm continuously increased; in contrast, the emission intensity at 674 nm assigned to the CDs remained constant, resulting in the ratiometric sensing of O2·-. The present ratiometric nanoprobe showed high selectivity for O2·- monitoring due to the specific recognition of O2·- by CA. Moreover, the Golgi dots exhibited good linearity with respect to the O2·- concentration within 5 to 40 μM, and the limit of detection (LOD) was ~ 0.13 μM. Additionally, the Golgi dots showed low cytotoxicity and an ability to target the Golgi apparatus. Inspired by these excellent properties, we then applied the Golgi dots to successfully monitor exogenous and endogenous O2·- levels within the Golgi apparatus. Importantly, with the help of Golgi dots, we determined that SD substantially elevated O2·- levels in the brain.

Carbon nanodots (CNDs) produced in pure water by the ablation of graphite with a nanosecond laser pulse exhibit weak photoluminescence. A small addition of polyethyleneimine (PEI) to the aqueous suspension of CNDs causes a significant increase in emissions. This paper presents experimental and theoretical studies of the emission properties of CND/PEI systems. The obtained CNDs responded to even trace amounts of PEI in solution (~0.014% v/v), resulting in a significant increase in the initial weak blue emission of CNDs and PEI taken separately. Morphology and size measurements showed that particle aggregation occurred in the presence of the polymer. A decrease in the calculated Stokes shift values was observed with increasing PEI content in the solution. This indicates a reduction in the number of non-radiative transitions, which explains the increase in the emission intensity of the CND/PEI systems. These results therefore confirmed that the increase in the emission of CND/PEI systems is caused by particle aggregation. Kinetic studies proved that the process is controlled mainly by diffusion, the initial stage of which has a dominant influence on determining the optical properties of the system.

Carbon nanodots (CNDs), a fascinating carbon-based nanomaterial (typical size 2-10 nm) owing to their superior optical properties, high biocompatibility, and cell penetrability, have tremendous applications in different interdisciplinary fields. Here, in this Review, we first explore the superiority of CNDs over other nanomaterials in the biomedical, optoelectronics, analytical sensing, and photocatalysis domains. Beginning with synthesis, characterization, and purification techniques, we even address fundamental questions surrounding CNDs such as emission origin and excitation-dependent behavior. Then we explore recent advancements in their applications, focusing on biological/biomedical uses like specific organelle bioimaging, drug/gene delivery, biosensing, and photothermal therapy. In optoelectronics, we cover CND-based solar cells, perovskite solar cells, and their role in LEDs and WLEDs. Analytical sensing applications include the detection of metals, hazardous chemicals, and proteins. In catalysis, we examine roles in photocatalysis, CO2 reduction, water splitting, stereospecific synthesis, and pollutant degradation. With this Review, we intend to further spark interest in CNDs and CND-based composites by highlighting their many benefits across a wide range of applications.