Baked pretzels are a popular choice for a quick snack, easily identifiable by their classic twisted shape, glossy exterior, and small salt crystals sprinkled on top, making them a standout snack. However, it is not commonly known that compounds with fluorescent properties can be formed during their production. Carbon nanodots (CNDs) with an average size of 3.5 nm were isolated and identified in bakery products. This study delved into the formation of CNDs in pretzel production using a fractional factorial experimental design. The research revealed that the baking temperature had the most significant impact on the concentration of CNDs, followed by the concentration of NaOH in the immersion solution, and then the baking time. This study highlights the unique role of the NaOH immersion step, which is not typically present in bread-making processes, in facilitating the formation of CNDs. This discovery highlights the strong correlation between the formation of CNDs and the heat treatment process. Monitoring and controlling these factors is crucial for regulating the concentration of CNDs in pretzel production and understanding nanoparticle formation in processed foods for food safety.

Co-N-CDs-based MXene nanocomposites (MXene@PDA/Co-N-CDs) were constructed by decorating Co-N-CDs on polydopamine-functionalized MXene nanosheets. Both Co-N-CDs and MXene nanosheets have peroxidase-like activity; when the two materials are combined to form MXene@PDA/Co-N-CDs nanocomposites, the peroxide-like activity can be further enhanced. MXene@PDA/Co-N-CDs could oxidize the substrate 3,3\'5,5\'-tetramethylbenziline (TMB) to form ox-TMB, as confirmed by detecting the absorption of the blue products. A highly selective colorimetric biosensor was developed for the determination of glutathione (GSH) in the concentration range of 0.3 to 20 µM with a lower detection limit (LOD) of 0.12 µM, which realized the accurate detection of GSH in human serum and urine samples. Moreover, in the tumor microenvironment, MXene@PDA/Co-N-CDs could catalyze hydrogen peroxide to produce hydroxyl free radicals and produce a photothermal effect under the exposure of NIR-I irradiation. The catalytic activity of MXene@PDA/Co-N-CD nanocomposites was fully achieved for the death of cancer cells through photothermal/photodynamic synergistic therapy. The MXene@PDA/Co-N-CDs nanozyme offers multiple applications in GSH detection and tumor therapy.

Using lignin as a raw material to prepare fluorescent nanomaterials represents a significant pathway toward the high-value utilization of waste biomass. In this study, Ni-doped lignin carbon dots (Ni-LCDs) were rapidly synthesized with a yield of 63.22 % and a quantum yield of 8.25 % using a green and simple hydrothermal method. Exploiting the inner filter effect (IFE), Cr(VI) effectively quenched the fluorescence of the Ni-LCDs, while the potent reducing agent ascorbic acid (AA) restored the quenched fluorescence, thus establishing a highly sensitive fluorescence switch sensor platform for the sequential detection of Cr(VI) and AA. Importantly, the integration of a smartphone facilitated the portability of Cr(VI) and AA detection, enabling on-site, in-situ, and real-time monitoring. Ultimately, the developed fluorescence and smartphone-assisted sensing platform was successfully applied to detect Cr(VI) in actual water samples and AA in various fruits. This study not only presents an efficient method for the conversion and utilization of waste lignin but also broadens the application scope of the CDs in the field of smart sensors.

The widespread use of antibiotics often leads to increased bacterial resistance. Herein, we reported silver peroxide-incorporated carbon dots (defined as Ag2O2-CDs) with high photothermal conversion efficiency via in situ oxidation process. The prepared Ag2O2-CDs exhibited ultra-small size of 2.0 nm and hybrid phase structure. Meanwhile, the Ag2O2-CDs were of similar optical performance to traditional carbon dots (CDs). Importantly, the incorporation of Ag2O2 into CDs significantly enhanced photothermal conversion efficiency from 3.8% to 28.5%. By combining silver ion toxicity and photothermal ablation, the Ag2O2-CDs were capable of destroying gram-positive and gram-negative bacterium effectively. These findings demonstrated that the Ag2O2-CDs could be served as a potential antibacterial agent for clinical applications. .

Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor and known for its challenging prognosis. Sonodynamic therapy (SDT) is an innovative therapeutic approach that shows promise in tumor elimination by activating sonosensitizers with low-intensity ultrasound. In this study, a novel sonosensitizer is synthesized using Cu-doped carbon dots (Cu-CDs) for the sonodynamic treatment of GBM. Doping with copper transforms the carbon dots into a p-n type semiconductor having a bandgap of 1.58 eV, a prolonged lifespan of 10.7 µs, and an improved electron- and hole-separation efficiency. The sonodynamic effect is efficiency enhanced. Western blot analysis reveals that the Cu-CDs induces a biological response leading to cell death, termed as cuproptosis. Specifically, Cu-CDs upregulate dihydrosulfanyl transacetylase expression, thereby establishing a synergistic therapeutic effect against tumor cell death when combined with SDT. Furthermore, Cu-CDs exhibit excellent permeability through the blood-brain barrier and potent anti-tumor activity. Importantly, the Cu-CDs effectively impede the growth of glioblastoma tumors and prolong the survival of mice bearing these tumors. This study provides support for the application of carbon-based nanomaterials as sonosensitizers in tumor therapy.

A new methodological design is proposed for carbon dots (CDs)-based crystallization-induced phosphorescence (CIP) materials via one-step self-assembled packaging controlled by NH4 +. O-phenylenediamine (o-PD) as a nitrogen/carbon source and the ammonium salts as oxidants are used to obtain CDs supramolecular crystals with a well-defined staircase-like morphology, pink fluorescence and ultralong green room-temperature phosphorescence (RTP) (733.56 ms) that is the first highest value for CDs-based CIP materials using pure nitrogen/carbon source by one-step packaging. Wherein, NH4 + and o-PD-derived oxidative polymers are prerequisites for self-assembled crystallization so as to receive the ultralong RTP. Density functional theory calculation indicates that NH4 + tends to anchor to the dimer on the surface state of CDs and guides CDs to cross-arrange in an X-type stacking mode, leading to the spatially separated frontier orbitals and the through-space charge transfer (TSCT) excited state in turn. Such a self-assembled mode contributes to both the small singlet-triplet energy gap (ΔEST) and the fast inter-system crossing (ISC) process that is directly related to ultralong RTP. This work not only proposes a new strategy to prepare CDs-based CIP materials in one step but also reveals the potential for the self-assembled behavior controlled by NH4 +.

Quasi-2D perovskites based blue light-emitting diodes (LEDs) suffer from its poor electroluminescence performance, mainly caused by the nonradiative recombination in in defect-rich low-n phases and the unbalanced hole-electron injection in the device. Here, we developed a highly efficient quasi-2D perovskite based sky-blue LEDs behaving recorded external quantum efficiency (EQE) of 21.07% by employing carbon dots (CDs) as additives in the hole transport layer (HTL). We ascribe the high EQE to the effective engineering of CDs: (1) The CDs at the interface of HTLs can suppress the formation of low-efficient n = 1 phase, resulting a high luminescence quantum yield and energy transfer efficiency of the mixed n-phase quasi-2D perovskites. (2) The CDs additives can reduce the conductivity of HTL, partially blocking the hole injection, and thus making more balanced hole-electron injection. The CDs-treated devices have excellent Spectral stability and enhanced operational stability and could be a new alternative additive in the perovskite optoelectronic devices.

Water pollution, significantly influenced by the discharge of synthetic dyes from industries, such as textiles, poses a persistent global threat to human health. Among these dyes, methylene blue, particularly prevalent in the textile sector, exacerbates this issue. This study introduces an innovative approach to mitigate water pollution through the synthesis of nanomaterials using biomass-derived carbon quantum dots (CQDs) from grape pomace and watermelon peel. Utilizing the hydrothermal method at temperatures between 80 and 160 °C over periods ranging from 1 to 24 h, CQDs were successfully synthesized. A comprehensive characterization of the CQDs was performed using UV-visible spectroscopy, Fourier-transform infrared spectroscopy, dynamic light scattering, Raman spectroscopy, and luminescence spectroscopy, confirming their high quality. The photocatalytic activity of the CQDs in degrading methylene blue was evaluated under both sunlight and incandescent light irradiation, with measurements taken at 20 min intervals over a 2 h period. The CQDs, with sizes ranging from 1-10 nm, demonstrated notable optical properties, including upconversion and down-conversion luminescence. The results revealed effective photocatalytic degradation of methylene blue under sunlight, highlighting the potential for scalable production of these cost-effective catalytic nanomaterials for synthetic dye degradation.

The blood-brain barrier (BBB) prevents the use of many drugs for the treatment of neurological disorders. Recently, nitrogen-doped carbon dots (NCDs) have emerged as promising nanocarriers to cross BBB. The primary focus of our study was to evaluate the effectiveness of NCDs for the symptomatic treatment of Alzheimer\'s disease (AD). In this study, we developed and characterized NCDs bound to rutin, a flavonoid with known benefits for AD. Despite its benefits, the transportation of rutin via NCDs for AD therapy has not been explored previously. We characterized the particles using FTIR and UV-visible spectroscopy followed by atomic force microscopy. Once the design was optimized and validated, we performed in vivo testing via a hemolytic assay to optimize the dosage. Preliminary in vitro testing was performed in AlCl3-induced rat models of AD whereby a single dose of 10 mg/kg NCDs-rutin was administered intraperitoneally. Interestingly, this single dose of 10 mg/kg NCDs-rutin produced the same behavioral effects as 50 mg/kg rutin administered intraperitoneally for 1 month. Similarly, histological and biomarker profiles (SOD2 and TLR4) also presented significant protective effects of NCDs-rutin against neuronal loss, inflammation, and oxidative stress. Hence, NCDs-rutin are a promising approach for the treatment of neurological diseases.

In this work, the B, N co-doped carbon dots (B, N-CDs) were synthesized via facile hydrothermal approach with 6-aminopyridine boronic acid as precursor. In addition to emitting intense blue luminescence when exposed to ultraviolet light, the prepared B, N-CDs displayed remarkable peroxidase-like activity, which could efficiently catalyze the oxidation of 3, 3\', 5, 5\' -tetramethylbenzidine (TMB) to blue ox-TMB in the presence of hydrogen peroxide (H2O2). Furthermore, the fluorescence intensity of B, N-CDs increased gradually upon the addition of H2O2. Since cholesterol oxidase (ChOx) can catalyze the oxidation of cholesterol to form H2O2, the as-prepared B, N-CDs was then used as both colorimetric and fluorometric sensors for the detection of cholesterol with detection limit of 0.87 and 2.31 μM, respectively. Finally, the dual-mode approach based on B, N-CDs was effectively utilized for detecting cholesterol levels in serum samples, proving the potential application of B, N-CDs in the field of biological assay.