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Fluorescent Carbon Quantum Dots (CQDs) are being used in medical applications, particularly in theranostics. These Carbon Quantum Dots have been gaining more attention lately due to their potential as an effective replacement for hazardous synthetic organic dyes in a variety of biomedical applications, including live cell imaging and diagnostics. In this study, highly fluorescent Carbon Quantum Dots by one pot microwave based green route with a size of less than 10 nm, was prepared from commercially available almond resin, Prunus dulcis and conjugated with honey as additional reagent for surface functionalization. They exhibit a deep blue emission on excitation at 350 nm with an elevated quantum yield at 61%. They possess atomic nature and basic features such as high photo-stability, varying fluorescence, greater biocompatibility, and better water solubility. These fluorescent labels exhibit faster cellular invagination without disturbing the cell stability. The CQDs present cell imaging capacity with multi-coloration for visualizing the fine architecture of the nucleus naming, the nuclear membrane and nucleolus, which is linked with their varied, surface structures such as amphiphilic property and higher positive charges. These characteristics with minimal invasion have made carbon quantum dots to become the spotlight in theranostics. They can be used as alternatives to synthetic dyes for fluorescence- related cell-imaging. The intriguing fact about this approach is that it opens the possibility of combining therapy and diagnostics into one unit, which can alter how some diseases are handled and, in turn, transform the field of healthcare. [ABSTRACT FROM AUTHOR]

In recent years, near‐infrared quantum dots (NIR QDs) have emerged as a promising candidate for biological imaging owing to their strong fluorescence penetrating into biological tissues and high imaging signal‐to‐noise ratio. Among various materials, InP QDs are environmentally friendly and have a relatively narrow bandgap of 1.35 eV, which provides a possibility for their emission wavelength to extend to the near‐infrared region. However, the strong reactivity of the precursor of phosphorus makes it challenging to synthesize NIR InP QDs, as it leads to rapid nucleation of the InP core. Herein, a method of epitaxial growth is reported to synthesize NIR InP QDs. Through high‐temperature nucleation and low‐temperature epitaxial growth, NIR InP QDs larger than 15 nm in size and with an emission wavelength of 807 nm are successfully synthesized. Furthermore, by removing InPOx defects on the surface of the core through HF etching, the quantum yield (QY) is increased from 6% to 12%. Ligand exchange successfully converted oil‐soluble ligands into water‐soluble ones, leading to excellent performance in cell imaging. The study provides a promising approach to the synthesis of desirable NIR InP QDs for use in biomedical imaging applications. [ABSTRACT FROM AUTHOR]

Using nitrogen-doped graphene quantum dots (N-GQDs) and 3-aminophenylboronic acid (APBA), a novel fluorescence nanosensor was developed. This nanosensor exhibits high selectivity and sensitivity for lysine detection. Its sensing mechanism involves the suppression of electron transfer from APBA to the N-GQDs unit, thereby inhibiting photoinduced electron transfer and initiating internal charge transfer. At an optimal pH of 7, the protonated α-amine and ε-amine groups of lysine interact with the amide and boronic acid moieties, respectively. This interaction results in a redshift of fluorescence, substantially enhancing the response signal. A linear response was observed within a concentration range 0.40–3.01 μM, with the detection limit being 0.005 μM. A similar linear range was also achieved for the determination of lysine in human serum. Density functional theory calculations correlating molecular orbits and geometries support UV–vis and fluorescence findings. Additionally, the nanosensor was successfully applied to detect lysine in living cells and real samples, including milk and honey. For practical application, we construct a lysine-specific sensing platform using a commercial chip (TCS34725) that collects red, blue, and green signals, thereby facilitating the convenient use of the nanosensor. Overall, this study offers new perspectives on the development and application of fluorescent nanosensors for detecting individual amino acids. [ABSTRACT FROM AUTHOR]

In this study, biomass-derived carbon quantum dots (CQDs) were synthesized by an one-step hydrothermal method using folium cycas as a carbon source. By optimizing the reaction conditions, the fluorescence quantum yield of CQDs was obtained to be as high as 8.91%, and strong blue emission light was emitted. The characterization results showed that the CQDs were quasi-spherical with an average particle size of 2.69 ± 0.08 nm and contained a large number of hydrophilic functional groups with excellent water solubility and photostability. The CQDs showed high selectivity and sensitivity for the detection of Fe3+, with a low limit of detection of 0.72 μM and a wide linear range of 0–200 μM. The practical applicability of the CQDs was further established by carrying out Fe3+ detection in environmental sample analysis. Besides, CQDs have been successfully applied to in vitro cell imaging and bioimaging. The final by-product of the hydrothermal reaction, biochar, is used for dye adsorption. This work identifies the importance of using a relatively green process and an inexpensive biomass precursor to produce high-quality CQDs that hold a promising future for use in metal ion detection, bioimaging, and practical sensing applications. [ABSTRACT FROM AUTHOR]

Indocyanine Green (ICG) as an agent for photodynamic therapy (PDT) of melanoma cancer has low quantum yield, short circulation half-life, poor photo-stability, and tendency to aggregation. N-doped carbon quantum dot (CQD) nanoparticle was applied to encapsulate ICG and overcome ICG obstacle in PDT with simultaneous cell imaging property. CQD was prepared using hydrothermal method. Cell culture study and In vivo assessments on C57BL/6 mice containing melanoma cancer cells was performed. Results showed that CQD size slightly enhanced from 24.55 nm to 42.67 nm after ICG loading. Detection of reactive oxygen species (ROS) demonstrated that CQD improved ICG photo-stability and ROS generation capacity upon laser irradiation. Cell culture study illustrated that ICG@CQD could decrease survival rate of melanoma cancer cells of B16F10 cell line from 48% for pure ICG to 28% for ICG@CQD. Confocal microscopy images approved more cellular uptake and more qualified cell imaging ability of ICG@CQD. In vivo assessments displayed obvious inhibitory effect of tumor growth for ICG@CQD in comparison to free ICG on the C57BL/6 mice. In vivo fluorescence images confirmed that ICG@CQD accumulates remarkably more than free ICG in tumor region. Finally, ICG@CQD was proposed as an innovative nanocarrier for PDT and diagnosis. [ABSTRACT FROM AUTHOR]

Research into the anticancer activity of quantum-sized carbon dots (CDs) has emerged as a promising avenue in cancer research. This CDs delves into the opportunities and challenges associated with harnessing the potential of these nanostructures for combating cancer. Quantum-sized carbon dots, owing to their unique physicochemical properties, exhibit distinct advantages as potential therapeutic agents. Opportunities lie in their tunable size, surface functionalization capabilities, and biocompatibility, enabling targeted drug delivery and imaging in cancer cells. However, we include challenges, a comprehensive understanding of the underlying mechanisms, potential toxicity concerns, and the optimization of synthesis methods for enhanced therapeutic efficacy. A succinct summary of the state of the research in this area is given in this review, emphasizing the exciting possibilities and ongoing challenges in utilizing quantum-sized carbon dots as a novel strategy for cancer treatment. [ABSTRACT FROM AUTHOR]

Here, we report a novel kind of protein nanoparticles of 11 nm in size, which have a central protein core surrounded by two layers of lipid. One layer of the lipid was covalently attached to the protein, while the other layer has been physically assembled around the protein core. Particle synthesis is highly modular, while both the size and charge of the protein nanoparticles are controlled in a predictable manner. Circular dichroism studies of the conjugate showed that the protein secondary structure is retained, while biophysical characterizations indicated the particle purity, size, and charge. The conjugate had a high thermal stability to steam sterilization conditions at 121°C (17 psi). After labeling the protein core with few different fluorescent dyes, they were strongly fluorescent with the corresponding colors independent of their size, unlike quantum dots. They are readily digested by proteases, and these water‐soluble, non‐toxic, highly stable, biocompatible, and biodegradable conjugates are suitable for cell imaging and drug delivery applications. [ABSTRACT FROM AUTHOR]

Ferric ion (Fe3+) serves as an essential and indispensable inorganic element in various biological process. Excess Fe3+ is harmful for biological systems and human health. Herein, highly sensitive carbon quantum dots (Fe-CQDs) for ferric ions were synthesized by a high-efficiency, one-step hydrothermal route utilizing L-arginine and citric acid. The prepared Fe-CQDs exhibited good water solubility, high photostability, and bright blue florescence with relatively high quantum yields (QYs) over 21.33% and a Stokes shift exceeding 100 nm. The functionalized Fe-CQDs offer rapid, sensitive, and selective recognition of Fe3+ with a linear relationship from 0.6 to 80 μM and a low detection limit of 0.2 μM. Moreover, the synthesized Fe-CQDs illustrated strong anti-interference properties in samples and buffer solutions. The developed sensor demonstrated high biocompatibility and was successfully applied for intracellular Fe3+ determination in SHSY5Y and HT22 cells, illustrating excellent imaging application. The present work provides a promising platform for the early clinical diagnosis of Fe3+-associated diseases. [ABSTRACT FROM AUTHOR]

Bacterial and biofilm infections pose great challenges to clinical treatments. This study reports the application of long-wavelength-emitting silicon quantum dots (SiQDs) as antibacterial and antibiofilm agents, and for multi-colored bacterial imaging. Several SiQDs–protein complexes were prepared and screened to obtain high-efficient antibacterial nanocomplex, and SiQDs–polylysin (SiQDs–PLL) exhibited the best antibacterial behavior with minimum inhibitory concentration values against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) at 10 and 15.62 μg mL−1, respectively, superior to the ability of pure SiQDs. Compared to Cu2+ and Mn2+, Zn2+ combined with SiQDs–PLL also showed enhanced antibacterial activity because of the synergistic effect. Furthermore, compared to SiQDs, SiQDs–PLL showed an excellent inhibitory effect against the S. aureus biofilm, by completely inhibiting its growth and achieving 62.13% biofilm removal rate at the concentrations of 60 and 200 μg mL−1, respectively. The antibacterial mechanisms of SiQDs and SiQDs–PLL were explored: SiQDs and SiQDs–PLL exerted antibacterial effects by destroying the bacterial cell membrane and promoting the leakage of cell content (DNA and RNA), thus exhibiting the potential as ideal candidates as antimicrobial agents in clinical settings. SiQDs and SiQDs–PLL also exhibit potential in bacterial imaging due to their excellent optical properties and low cytotoxicity. [ABSTRACT FROM AUTHOR]

Pyrediyne, a recent addition to the 2D organic nanomaterials family, is known for its improved electrical conductivity, which can have potential applications in the performance of thin film transistors, field effect transistors, and charge storage devices. It has been shown that similar to carbon quantum dots, pyrediyne quantum dots (PDYQDs) can also be generated from 2D pyrediyne nanosheets and can be utilized for imaging cancer cells. In this context, it is highly desirable to enhance the photoluminescence properties of PDYQDs in order to improve the quality of quantum dots‐based cell imaging techniques. Herein, PDYQDs are effectively functionalized using aqueous functionalization agents such as NH3, PEG200, and PEG20000 via a simple and cost‐effective methodology, which resulted in a significant enhancement in the emission quantum yield (QY) (up to 30.2 %) through effectively reducing the non‐radiative recombination centers. After confirming their cytocompatibility using in vitro studies, the amine‐functionalized PDYQDs were utilized for imaging L929 mouse fibroblast cells. The findings in the present study suggest that it is worth exploring various surface functionalization techniques to enhance the applications of novel carbon‐based nano‐structures in various biological and optoelectronic devices. [ABSTRACT FROM AUTHOR]

This study focuses on the use of carbon quantum dots (CQDs) from Syzygium cumini seeds prepared through hydrothermal synthesis for anti-oxidant, bioimaging, and anti-neoplastic activities. Syzygium cumini seeds were incorporated with various biomass-sourced precursors to enhance their physicochemical properties, and doping of folic acid was performed to create surface passivated folate receptors for better anti-neoplastic activity exhibiting minimal toxicity, excellent biocompatibility, outstanding luminosity, and optical features. The concentration of CQDs required to inhibit the proliferation of cells by 50% (at 500 μg mL−1 concentration) was calculated by applying the dose–response curve applied to the HeLa cell line, and the conclusion was computed by means of an augmented mimicking approach, leading to roughly identical inhibition by folic acid doped S. cumini seeds (40.926%) and doxorubicin (DOX) (43.39%) justifying better anti-neoplastic activity. The anti-oxidant potency of the prepared CQDs was assessed to be exceedingly excellent, with an index of up to 98.99%, implying resilient surface passivation. CQDs utilized for in vitro photoluminescence and live cell imaging of S. cerevisiae displayed green and blue fluorescence images with stabilized luminescence with extraordinary quantum yield (50.74%). [ABSTRACT FROM AUTHOR]

Objective: Medical imaging techniques have widely revolutionized the diagnosis and treatment of various health conditions. Among these techniques, magnetic resonance imaging (MRI) has stood out as a noninvasive and versatile tool. Now, a breakthrough innovation called "manganese-carbon dots" is poised to enhance MRI imaging and provide physicians with even greater insight into the human body. Materials and methods: In this study, one-pot hydrothermal method was used to fabricate magneto-fluorescent carbon quantum dots using manganese citrate, urea, and Mn2+. Manganese citrateAQ3 acted as a carbon source and contrast agent. TEM,XPS, FTIR, UV–Vis, fluorescent analysis confirmed the successful synthesis of magneto-fluorescent carbon quantum dots. The MTT assay was used to study its biocompatiblity, Finallay application of itscompound for mri imaging was investigated. Results: Characterization Techniques confirmed the succesful synthesis of product. MTT assay showed no toxicity of this product on HEK-293 cells. In addition, it exhibited high r1 relaxivity (7.4 mM–1 S−1) suggesting excellent potential of magneto-fluorescent carbon quantum dots as MRI T1 contrast agent and enabling specific imaging. Conclusion: Based on the results obtained, the synthesized carbon quantum dots could be used as fluorescence/MRI bimodal platform for in vivo imaging. [ABSTRACT FROM AUTHOR]

Telomerase as a new valuable biomarker for early diagnosis and prognosis evaluation of cancer has attracted much interest in the field of biosensors, cell imaging, and drug screening. In this review, we mainly focus on different optical techniques and various signal amplification strategies for telomerase activity determination. Fluorometric, colorimetry, chemiluminescence, surface-enhanced Raman scattering (SERS), and dual-mode techniques for telomerase sensing and imaging are summarized. Signal amplification strategies include two categories: one is nucleic acid-based amplification, such as rolling circle amplification (RCA), the hybridization chain reaction (HCR), and catalytic hairpin assembly (CHA); the other is nanomaterial-assisted amplification, including metal nanoclusters, quantum dots, transition metal compounds, graphene oxide, and DNA nanomaterials. Challenges and prospects are also discussed to provide new insights for future development of multifunctional strategies and techniques for in situ and in vivo analysis of biomarkers for accurate cancer diagnosis. [ABSTRACT FROM AUTHOR]

When designing sensors for optoelectronic devices, fluorescent materials are always the choice of material chemists. Among the existing fluorescent molecules, the most widely used sensing materials are colloidal nanocrystals, which are classified as quantum dots (QDs). Photoluminescence and tuning of the band gap are the two domains that are explored while engineering optically active crystals. The selection of dopants in a host lattice is the initial step towards achieving the material of choice and designing tailor-made stable materials. Among various QD materials, doped ZnS quantum dots have emerged as a fascinating class, showcasing distinctive characteristics resulting from both transition and non-transition metal doping. This work reviews recent developments in the synthesis, structural characterization, and applications of transition and non-transition metal-doped ZnS quantum dots. Transition metal doping, involving elements such as Mn, Co, and Cu, imparts remarkable photoluminescence properties to QDs, rendering them suitable for optoelectronic devices, such as light-emitting diodes and displays. Non-transition metal doping, involving elements such as Al, Mg, and Ga, facilitates bandgap engineering, paving the way for enhanced light absorption and utilization in photovoltaics and photocatalysis. Transition and non-transition metal-doped ZnS quantum dots exhibit diverse applications across multiple domains. In the field of biomedicine, their biocompatibility, tunable fluorescence, and ability to generate reactive oxygen species under light irradiation present opportunities for cellular imaging and photodynamic therapy. Moreover, their integration into composite materials holds the potential for enhanced electronic and optoelectronic device performance. Challenges in this field include achieving precise control over dopant concentrations, uniformity, and stability, while also addressing scalability issues for large-scale production. Future directions include exploring novel doping strategies, co-doping schemes, and surface functionalization techniques to further enhance the properties of doped ZnS quantum dots. In conclusion, transition and non-transition metal-doped zinc sulphide quantum dots showcase a realm of exciting possibilities for technological innovation. Their unique properties, enabled by judicious dopant incorporation, make them valuable materials for applications spanning optoelectronics, energy conversion, and biomedical sciences. As research in this field advances, these doped quantum dots are poised to significantly contribute to the progression of next-generation technologies. [ABSTRACT FROM AUTHOR]

The exact role of the size and shell thickness of the core–shell nanoparticles on the antifungal property remains marginally known. Herein, a detail study of the antifungal property of the model core–shell quantum dots CdSe@CdS of size 2.4–3.9 nm, where the shell thickness was also varied from 0.2 to 0.7 nm, is presented. The core–shell structure exhibited tenfold enhancement in fluorescence compared to the core-only structure. Further, it was found that the CdSe particles (core-only) were most toxic towards Candida albicans cells, and the antifungal property was observed to be in the order CdSe > CdSe@CdS inferred from their MIC90 values (25 and 150 μg/mL, respectively). Interestingly, larger particles showed a much lower MIC90 value, which could be because of their higher shell thickness. The presence of CdS shell decreased the toxicity of CdSe due to the mitigating property of sulphur on Candida cells. The presence of sulfur decreased the toxic property of cadmium ions allowing for the higher shell thickness particles to be less toxic. While the core-only CdSe nanoparticles of the smallest size showed complete inhibition (100%) of fungus at a low concentration of 50 μg/mL, for the core–shell particles same was noticed at a much higher concentration of 200 μg/mL. Smaller QDs easily penetrated the fungal cells, thereby interacting more effectively with the cellular structure inducing cell damage. Results suggested that the cellular response was a distinct function of the physical size and shell thickness of these nanocrystals. [ABSTRACT FROM AUTHOR]

Graphene quantum dots (GQDs) possess potential properties for the targeted transport and tracking of anticancer medication to tumor cells. For this purpose, the synthesized GQDs were decorated with folic acid (FA) and methoxy polyethylene glycol (mPEG2000), and finally loaded with tamoxifen (TMX) drug. The synthesized nano‐drug was characterized using FTIR, XRD, UV‐Vis, PL, HRTEM, FESEM, and DLS analytical devices. Based on the obtained data, the average hydrodynamic diameter of particles dissolved in water was 294.7 nm and the size of dehydrated particles was between 53 and 210 nm. PL data showed that prepared nanoparticles have an emission wavelength of 438 nm, which is in the blue fluorescent wavelength range, thus making these nanoparticles suitable for cell imaging. The encapsulation efficiency and loading percentage of tamoxifen in nanoparticles were calculated at about 52.5 % and 30 %, respectively, and cumulative drug release reached 89 % within 42 hours. The cytotoxicity effects of nanoparticles were investigated. According to IC50 results, the targeted mPEG‐GQDs‐FA/TMX (TMX‐FPGs) nano‐drug was more toxic than free TMX on MCF‐7 cells and had reduced side effects on healthy HDF cells. TMX‐FPGs induced apoptosis cell death, significantly. The confocal imaging experiments showed that TMX‐FPGs are appropriate for monitoring and targeting MCF‐7 cells. [ABSTRACT FROM AUTHOR]

[Display omitted] The development of quantum dot (QD)-based modular bioprobe that has a compact size and enable a facile conjugation of various biofunctional groups is in high demand. To address this, we surface engineered QDs with zwitterion polymer ligands to have an inherent compact size and derivatized them sequentially with the recombinant proteins SpyCatcher/SpyTag (SC/ST) to use their protein ligation system. SC/ST spontaneously form one complex through the isopeptide bond between them. SC-conjugated QDs (QD–SC) were used as base building blocks. Then, ST–biomolecules were added for modular biofunctionalization. We synthesized compact sized (∼15 nm) QD–SC–ST–affibody (antibody-mimicking small protein for tumor detection) conjugates, which showed successful cell-receptor targeting. The target cell-receptor could be easily tuned by changing the type of ST-affibody. We also demonstrated that anti-human-chorionic-gonadotropin mouse IgG 1 antibodies can be labeled on the QD surface by mixing QD–SC with the ST–MG1Nb (mouse-IgG 1 -specific protein). The immunoassay performance of the antibody-labeled QDs was evaluated using a pregnancy test kit, displaying equivalent detection sensitivity to a commercially available kit. This study proposed an innovative strategy for QD biofunctionalization in a modular manner, which can be expanded to a diverse range of colloidal particle derivatization. [ABSTRACT FROM AUTHOR]

Utilizing carbon quantum dots (CQDs) as biomaterials for delivering small substances has gained significant attention in recent research. However, the interactions and mechanisms of action of CQDs on plants have received relatively little focus. Herein, we investigated the transportation of CQDs into various organs of Arabidopsis thaliana (L.) Heynh. via the vessel system, leading to the epigenetic inheritance of Argonaute family genes. Our findings reveal that CQDs may interact with microRNAs (miRNAs), leading to the repression of post-transcriptional regulation of target genes in the cytoplasm. Transcriptome and quantitative PCR analyses demonstrated consistent gene expression levels in offspring. Moreover, microscopic observations illustrated rapid CQD localization on cell membranes and nuclei, with increased nuclear entry at higher concentrations. Notably, our study identified an alternative regulatory microRNA, microRNA172D, for the Argonaute family genes through methylation analysis, shedding light on the connection between CQDs and microRNAs. [ABSTRACT FROM AUTHOR]

This study synthesized carbon quantum dots (CQDs) with green photoluminescence through a hydrothermal method that utilized mulberry juice as the carbon source. The influence of fruit ripeness on the physical and chemical properties, focusing on the fluorescence spectra, has been explored. Fourier-transform infrared spectroscopy (FT-IR) and energy dispersive X-ray analysis (EDX) showed that there were oxygen-containing groups, and X-ray diffraction (XRD) showed that the carbon quantum dots (CQDs) were graphitic. The results revealed that the CQDs had an average size of around 7.4 nm and 9.7 nm for unripe and ripe mulberry juice, respectively. These CQDs emitted green light at 500 nm and 510 nm in unripe and ripe mulberry juice, respectively, when excited at a wavelength of 400 nm. The prepared CQDs exhibited excitation-dependent photoluminescence (PL) emission behavior, demonstrating their dependence on the excitation light. The impact of fruit ripeness on optical properties was explored by examining fluorescent spectra from different fruits (including tomato and blackberry), demonstrating comparable behaviors observed in mulberry fruit. In addition, the prepared CQDs were utilized as a fluorescent sensor with high specificity to detect Cu2+ ions. The detection limit (DL) for this sensor was determined to be 0.2687 µ M, and the limit of qualification (LOQ) is 0.814 µ M. The linear range for detection lies between 0.1 and 1 µ M. The selectivity of the CQDs towards Cu2+ ions was confirmed by recording the PL response for Cu2+ ions compared to the weak response of other metal ions. According to these results, the CQDs can be applied in various cellular imaging and biology applications, bio-sensing, optoelectronics, and sensors. [ABSTRACT FROM AUTHOR]

In this paper, a novel amino acid surface-functionalized semiconductor CdTe quantum dot fluorescent probe amidated by carboxyl and amide groups was synthesized to detect pyrophosphate ions (P2O74−, PPi). L-Arginine (L-Arg) was grafted onto cysteine modified CdTe quantum dots (Mea-CdTe QDs) to form a new L-Arginine-functionalized quantum dot fluorescent probe (L-Arg@Mea-CdTe). The prepared probe has good optical properties with multiple grafted functional groups on the surface. The guanidine group of the L-Arg@Mea-CdTe fluorescent probe is strongly basic and will be fully protonated under physiological conditions. The resulting hydrogen bonds bound to pyrophosphate lead to significant changes in the fluorescence of CdTe quantum dots. IR and XPS characterization were performed to confirm it. The addition of PPi induces a significant fluorescence quenching of L-Arg@Mea-CdTe in aqueous solution. The fluorescent QDs probe can also detect pyrophosphate with good sensitivity and anti-interference performance. The detection limit of the L-Arg@Mea-CdTe fluorescence probe for PPi is as low as 0.30 μM. In addition, the novel nano-fluorescent probe was successfully applied to detect PPi in water and in cell imaging. [ABSTRACT FROM AUTHOR]

Synthesis of y-SiQDs and their application to image H 2 S in cells and onion tissue. [Display omitted] Yellow fluorescent silicon quantum dots (y-SiQDs) with 22.2% fluorescence quantum yield were synthesized by a simple hydrothermal method using 3-glycidoxypropyl triethoxysilane (GOTS) and m-aminophenol. The excitation wavelength is 550 nm with an emission wavelength of 574 nm, which effectively avoids the interference of biological autofluorescence. Notably, the synthesis approach does not require any post-modification and the y-SiQDs can be directly used for hydrogen sulfide (H 2 S) quantification due to static quenching. It exhibits high sensitivity and excellent selectivity for H 2 S with a 0.2-10 μM (R2 = 0.9953) linear range and detection limit of 54 nM. y-SiQDs have excellent stability and biocompatibility and can be used for H 2 S imaging in living cells and onion tissues. [ABSTRACT FROM AUTHOR]

The analysis of trace Fe(III) ions in water is of vital importance in the fields of biology, environment and health. The fluorescent switch technique based on photoluminescent carbon dots (CDs) is highly favorable due to their bio-adaptability, safety and economy, but it is hindered in the highly specific recognition at the trace level. In this work, oxytetracycline-derived CDs (denoted as OCDs) with a uniform size (ca. 2.04 nm), nitrogen dopant, and rich hydroxyl-/carboxyl- groups have been successfully fabricated via a bottom-up hydrothermal carbonization approach. The as-prepared OCDs have displayed excellent photoluminescence characteristics and fluorescence switch performance for the rapid detection of Fe(III) within 2 min with the limit of detection (LOD) as low as 0.440 μM (24.6 ppb) and the second highest sensitivity of 3.52 × 10−2 μM−1 among reported CDs-based Fe(III) fluorescent switch materials. This detection system is stable in the analysis matrix with many interfering metal ions, at least with the help of the masking agent cysteine, realizing the specific detection of Fe(III) in real water environments. The contributions from the fluorophore concentration and the affinity between fluorophore and quencher have been revealed by the numerical model, providing a roadmap for the design of metal ion fluorescence switch materials based on a complex formation quenching mechanism. Fluorescence cell imaging in plant cells has also been performed successfully with the as-synthesized OCDs. This work presents a high-performing CDs-based Fe(III) fluorescence switch derived from the environmentally-risky oxytetracycline, as well as a feasible strategy for recycling waste antibiotics. [ABSTRACT FROM AUTHOR]

β-Carotene is a natural antioxidant that has an indispensable effect on the growth and immunity of the human body. For intracellular and in vitro detection of β-carotene, N-doped carbon quantum dots (O-CDs) were prepared by co-heating carbonization of 1,5-naphthalenediamine and nitric acid in ethanol solvent for 2 h at 200 °C. O-CDs have longer wavelength orange light emission, with an optimal excitation peak of 470 nm and an optimal emission peak of 590 nm. According to the principle of the internal filtering effect on which the detection system is based, O-CDs present a good linear relationship with β-carotene within a wide range of 0–2000 μM, and the R2 coefficient of the linear regression equation is 0.999. In addition, O-CDs showed targeting of lysosomes in cell imaging and could be used to detect intracellular lysosomal movement. These experiments show that O-CDs can be used for in vivo and in vitro detection of β-carotene and can serve as a potential substitute to commercial lysosome targeting probes. [ABSTRACT FROM AUTHOR]

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Carbon dots (CDs) with red fluorescence emission are highly desirable for use in bioimaging and trace- substance detection, with potential applications in biotherapy, photothermal therapy, and tumor visualization. Most CDs emit green or blue fluorescence, thus limiting their applicability. We report a novel fluorescent detection platform based on high-brightness red fluorescence emission carbon dots (R-CDs) co-doped with nitrogen and bromine, which exhibit pH and oxidized L -glutathione (GSSG) dual-responsive characteristics. The absolute quantum yield of the R-CDs was as high as 11.93%. We discovered that the R-CDs were able to detect acidic pH in live cells and zebrafish owing to protonation and deprotonation. In addition, GSSG was detected in vitro over a broad linear range (8–200 μM) using the R-CDs with excitation-independent emission. Furthermore, cell imaging and bioimaging experiments demonstrated that the R-CDs were highly cytocompatible and could be used as fluorescent probes to target lysosomes and nucleolus. These studies highlight the promising prospects of R-CDs as biosensing tools for bioimaging and trace-substance detection applications. [ABSTRACT FROM AUTHOR]

Background: Norovirus is a common pathogen that causes foodborne outbreaks every year and the increasing number of deaths caused by it has become a substantial concern in both developed and underdeveloped countries. To date, no vaccines or drugs are able to control the outbreak, highlighting the importance of finding specific, and sensitive detection tools for the viral pathogen. Current diagnostic tests are limited to public health laboratories and/or clinical laboratories and are time-consuming. Hence, a rapid and on-site monitoring strategy for this disease is urgently needed to control, prevent and raise awareness among the general public. Results: The present study focuses on a nanohybridization technique to build a higher sensitivity and faster detection response to norovirus-like particles (NLPs). Firstly, the wet chemical-based green synthesis of fluorescent carbon quantum dots and gold nanoparticles (Au NPs) has been reported. Then, a series of characterization studies were conducted on the synthesized carbon dots and Au NPs, for example, high-resolution transmission emission microscopy, fluorescence spectroscopy, fluorescence life-lime measurement, UV–visible spectroscopy, and X-ray diffraction (XRD). The fluorescence emission of the as-synthesized carbon dots and the absorption of Au NPs were located at 440 nm and 590 nm, respectively. Then, the plasmonic properties of Au NPs were utilized to enhance the fluorescence emission of carbon dots in the presence of NLPs in human serum. Here, the enhanced fluorescence response was linearly correlated up to 1 μg mL−1. A limit of detection (LOD) value was calculated to be 80.3 pg mL−1 demonstrating that the sensitivity of the proposed study is 10 times greater than that of the commercial diagnostic kits. Conclusions: The proposed exciton-plasmon interaction-based NLPs-sensing strategy was highly sensitive, specific, and suitable for controlling upcoming outbreaks. Most importantly, the overall finding in the article will take the technology a step further to applicable point-of-care (POC) devices. [ABSTRACT FROM AUTHOR]

Synthesis of monoclinic Y 2 O 3 remains a challenging task due to complex formation conditions such as high pressure or high temperature environments. Monoclinic yttria exhibits better photoluminescence characteristics compared to the cubic phase and hence can be a better host for nanophosphors. Reports are available predicting the stability of monoclinic phase at low temperature in extremely fine particles. But experimental preparation of this phase at low temperature is not yet reported. Here we report the first-time preparation of monoclinic Y 2 O 3 at 90 °C using simple laboratory hot air oven. The synthesized nanoparticles exhibit intense PL emission in the blue region and hence can find applications in display industry. The band structure calculations were carried out using density functional theory and the excitonic Bohr radius was estimated using the electron as well as hole effective masses determined from band structure. The cytotoxicity studies reveal non-toxic nature the particles. The fluorescence imaging experiments show that the material is capable of emitting blue fluorescence in L6 skeletal cell lines and it ensures the applicability of this material in the biomedical field. [ABSTRACT FROM AUTHOR]

Synthesis of carbon dots from molasses using the microwave method with the addition of EDTA as a passivation agent has been carried out. Addition of EDTA to improve the optical properties of the carbon dots. The resulting carbon dots were characterized by UV, UV-Visible, PL, FTIR, and TEM lamps. A physical test of carbon dots under a UV lamp showed a change in light intensity, carbon dots with the addition of a passivation agent were brighter than those without a passivation agent. Analysis of the optical properties of carbon dots using UV-Vis spectrophotometer and photoluminescence showed a significant increase in absorbance intensity and emission intensity from 500 a.u to 3600 a.u. FTIR analysis shows the formation of carbon dots which are indicated by the presence of C=C, O-H, C-H, C-O-C, and C-N groups at certain wavenumbers. TEM analysis showed that the carbon dots produced had an average diameter of 1.8 nm. From the analysis, it is identified that the addition of EDTA can improve carbon dots' optical properties. [ABSTRACT FROM AUTHOR]

Tyrosinase (TYR), an important biomarker for melanoma, offered significant information early detection of melanoma and may decrease the likelihood of mortality. Therefore, this article constructed a highly sensitive and selective green fluorescent functionalized carbon quantum dots (TYR-CQDs) for tyrosinase (TYR) activity detection by one-step hydrothermal protocol utilizing catechol, citric acid and urea as precursors. The prepared TYR-CQDs illustrated excellent linear relationship and broad linear range with a low detection limit, which exhibited high accuracy and recovery in quantitative determination of TYR in human serum samples. Furthermore, the TYR-CQDs had successfully realized intracellular TYR detection owing to excellent biocompatibility, high anti-interference ability and good cellular imaging capability, suggesting the potential biomedical applications in early diagnosis of melanoma and other tyrosinase-related diseases. [ABSTRACT FROM AUTHOR]

Small molecular dyes are commonly used for bacterial imaging, but they still meet a bottleneck of biological toxicity and fluorescence photobleaching. Carbon dots have shown high potential for bio-imaging due to their low cost and negligible toxicity and anti-photobleaching. However, there is still large space to enhance the quantum yield of the carbon quantum dots and to clarify their mechanisms of bacterial imaging. Using carbon dots for dyeing alive bacteria is difficult because of the thick density and complicated structure of bacterial cell walls. In this work, both dead or alive bacterial cell imaging can be achieved using the primary amine functionalized carbon dots based on their small size, excellent quantum yield and primary amine functional groups. Four types of carbon quantum dots were prepared and estimated for the bacterial imaging. It was found that the spermine as one of precursors can obviously enhance the quantum yield of carbon dots, which showed a high quantum yield of 66.46% and high fluorescence bleaching-resistance (70% can be maintained upon 3-h-irradiation). Furthermore, a mild modifying method was employed to bound ethylenediamine on the surface of the spermine–carbon dots, which is favorable for staining not only the dead bacterial cells but also the alive ones. Investigations of physical structure and chemical groups indicated the existence of primary amine groups on the surface of spermine–carbon quantum dots (which own a much higher quantum yield) which can stain alive bacterial cells visibly. The imaging mechanism was studied in detail, which provides a preliminary reference for exploring efficient and environment-friendly carbon dots for bacterial imaging. [ABSTRACT FROM AUTHOR]

The structure, thermal analysis, optical properties, and emission mechanism of fluorescent carbon dots (CDs) have been improved as a result of a vast quantity of new study. Unlike quantum confinement outcomes in quantum dots, CDs usually suffer from intricate optical characteristics coming from a variety of raw materials and synthesis processes based on thermal treatment. The thermal-treatment-based synthesis of CDs and their application in bioenergy systems are discussed in this review. Heating rate, gas atmosphere, and heating regime are among the parameters used in the thermal study of carbon nanomaterials, allowing researchers to investigate the necessary characteristics for applications such as biomass production, photo-catalysis, biodiesel, optoelectronics, and photo-thermal energy conversion. In general, this review proposes CDs as a unified definition of reported carbon nanomaterials, summarises the thermal properties of CDs derived from the formation process, optical properties, and redox characteristics of CDs, and illustrates energy conversion applications, as well as the related mechanistic framework and relationships. The thermal analysis CDs' unique properties may bring up new opportunities and difficulties in a variety of fields. This review also covers energy conversion applications, including the framework and linkages of the mechanisms involved. It is thought that the use of CDs constitutes an advance in the core capabilities of thermal analysis and may provide new perspectives and difficulties in a broader range of applications. [ABSTRACT FROM AUTHOR]

Fluorescence lifetimes and quantum yields featuring polycyclic aromatic hydrocarbons (PAHs) and other organics constituting pyrogenic carbon particulate matter (PM) are seldom measured. In this work, PM sampled in a fuel-rich ethylene flame was firstly separated in organic carbon (OC), soluble in dichloromethane, and refractory organic carbon (ROC), soluble in N -methyl pyrrolidinone, and then analyzed by size exclusion chromatography (SEC) coupled with online UV and fluorescence detection, and by offline fluorescence spectroscopy and mass spectrometry. It was found that three classes of differently light emitting carbon dots (CDs) could be bottom-up synthesized in the same flame system by selecting appropriately the residence time. Actually, OC presented blue fluorescence regardless the residence time, whereas ROC sampled at low and high residence time emitted fluorescence in the green (green CDs) and in the yellow (yellow CDs) region, respectively. The SEC molecular weight of all CDs presented similar trimodal distributions, centered around 300, 1000 and 10,000 u. For the first time fluorescence lifetimes and quantum yields of pyrogenic CD fractions were measured as additional parameters useful for discriminating the fluorescent components and inferring their structural properties, with the support of mass spectrometry. The different spectroscopic features of CDs could be associated to different compositional characteristics as the polydispersity of molecular components featuring blue CDs, opposed to the oligomer-like nature of green and yellow CDs. Pyrogenic CDs showed different fluorescence emission ranges, quantum yield and lifetimes, appealing for their possible applications in the fields of imaging, electronics and sensors. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon quantum dots (CQDs) with excellent properties have attracted attention owing to wide applications in many fields. In this paper, we report a method to synthesize CQDs at room temperature without any external energy supply and energy-catalyzing reagents. The characterization results indicate that the CQDs have good dispersion and water solubility, the averaged dimension is around 5.37 nm, consisting mainly of C, O, N, and S elements, the fluorescence quantum yield was 8.72%. In addition, the experimental results show that CQDs have excellent optical stability and good biocompatibility, which can be used in the field of cellular imaging. [ABSTRACT FROM AUTHOR]

R-CDAs have been synthesized in a one-pot solvothermal procedure starting from 3,4-diaminobenzoic acid in an acidic medium. Transmission electron microscopy (TEM) revealed that R-CDAs nanoparticles exhibited a much larger diameter of 7.2–28.8 nm than traditional monodisperse carbon dots. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) revealed the presence of polar functional groups (hydroxyl, amino, carboxyl) on the surface of R-CDAs. Upon excitation with visible light (550 nm), R-CDAs emit stable, red fluorescence with a maximum at 610 nm. Under the optimum conditions, Cu2+ ions quench the fluorescence of this probe, and the signal is linear in a concentration range of copper ions between 5 and 600 nM with the detection limit of only 0.4 nM. Recoveries from 98.0 to 105.0% and relative standard deviations (RSD) from 2.8 to 4.5% have been obtained for detection of Cu2+ in real water samples. Furthermore, the R-CDAs fluorescent probe showed negligible cytotoxicity toward HeLa cells and good bioimaging ability, suggesting its potential applicability as a diagnostic tool in biomedicine. [ABSTRACT FROM AUTHOR]

Water contamination due to the presence of lead is one of the leading causes of environmental and health hazards because of poor soil and groundwater waste management. Herein we report the synthesis of functionally modified luminescent carbon quantum dots (CQDs) obtained from watermelon juice as potential nanomaterials for the detection of toxic Pb2+ ions in polluted water and cancer cells. By introducing surface passivating ligands such as ethanolamine (EA) and ethylenediamine (ED) in watermelon juice, watermelon-ethanolamine (WMEA)-CQDs and watermelon-ethylenediamine (WMED)-CQDs exhibited a remarkable ~10-fold and ~6-fold increase in fluorescence intensity with respect to non-doped WM-CQDs. The relative fluorescence quantum yields of WMEA-CQDs and WMED-CQDs were found to be 8% and 7%, respectively, in an aqueous medium. Among various functionally-modified CQDs, only WMED-CQDs showed high selectivity towards Pb2+ ions with a remarkably good limit of detection (LoD) of 190 pM, which is less than that of the permissible limit (72 nM) in drinking water. The functionally altered WMED-CQDs detected Pb2+ metal ions in polluted water and in a human cervical cancer cell line (HeLa), thus advocating new vistas for eco-friendly nanomaterials for their use as diagnostic tools in the environment and biomedical research areas. [ABSTRACT FROM AUTHOR]

R-CDAs have been synthesized in a one-pot solvothermal procedure starting from 3,4-diaminobenzoic acid in an acidic medium. Transmission electron microscopy (TEM) revealed that R-CDAs nanoparticles exhibited a much larger diameter of 7.2–28.8 nm than traditional monodisperse carbon dots. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) revealed the presence of polar functional groups (hydroxyl, amino, carboxyl) on the surface of R-CDAs. Upon excitation with visible light (550 nm), R-CDAs emit stable, red fluorescence with a maximum at 610 nm. Under the optimum conditions, Cu2+ ions quench the fluorescence of this probe, and the signal is linear in a concentration range of copper ions between 5 and 600 nM with the detection limit of only 0.4 nM. Recoveries from 98.0 to 105.0% and relative standard deviations (RSD) from 2.8 to 4.5% have been obtained for detection of Cu2+ in real water samples. Furthermore, the R-CDAs fluorescent probe showed negligible cytotoxicity toward HeLa cells and good bioimaging ability, suggesting its potential applicability as a diagnostic tool in biomedicine. [ABSTRACT FROM AUTHOR]

In this work, a simple, continuous and completely green method based on microflow technique is demonstrated for the synthesis of carbon quantum dots (CQDs) from diverse bio‐based precursors. CQDs prepared from milk is illustrated as a case study to show the process feasibility. Crystalline fluorescent CQDs of 12.53% quantum yield and good stability are synthesized by the approach, even at 120°C. Systematic experiments further suggest their optical properties, bandgap energy, and fluorescence lifetime are closely related to the synthesis temperature. The maximum production rate of the CQDs was 51.1 mg/h at 180°C. Cytotoxicity and cellular imaging tests against 3T3 cells reveal the CQDs possess high biocompatibility, and can penetrate cell membranes and display bright fluorescence. The process versatility is investigated by expanding the precursor to watermelon juice, orange juice, and soy milk, indicating successful synthesis of small‐sized CQDs of low cytotoxicity and strong photoluminescence by the technique. [ABSTRACT FROM AUTHOR]

Green and low‐cost photoluminescent graphene quantum dots (GQDs) were prepared by a one‐step hydrothermal method with konjac glucomannan (KGM), a natural polysaccharide, as the precursors. Then, the folic acid (FA)‐functionalized GQDs (FA‐GQDs) was formed by the amidation of GQDs with FA, and the drug carrier named as FA‐GQDs‐DOX was obtained by loading doxorubicin (DOX) on FA‐GQDs. Due to the inherent fluorescence properties of GQDs and DOX in FA‐GQDs‐DOX, the resultant samples could be used to selectively label cancer cells without external dyes, and the cellular uptake and the drug‐releasing behavior could be visualized. The coupling of FA with GQDs and the loading of DOX on FA‐GQDs were confirmed by various means. In addition, the cell imaging showed that the FA‐GQDs could be used as a fluorescent probe to recognize folate receptor (FR)‐positive cancer cells and that the FA‐GQDs‐DOX could selectively deliver DOX to FR‐positive cancer cells. As a result, the FA‐GQDs‐DOX could be applied in early diagnosis and targeted therapy of cancer. [ABSTRACT FROM AUTHOR]

Schematic diagram of the preparation of the NIR-CDs and their application for the detection of ClO− and cell membrane imaging. [Display omitted] • NIR-CDs with emission at 653 nm were prepared by hydrothermal method. • NIR-CDs exhibited excellent selectivity and sensitivity for the detection of ClO−. • NIR-CDs were used for determination of ClO− level in tap water sample with satisfactory results. • NIR-CDs were successfully used for the imaging of cell membrane. Devising carbon dots with long wavelength emission (red light or near infrared), high selectivity and good bio-compatibility is critical in fluorescence detection and imaging, but achieving this goal remains a great challenge. Herein, near-infrared emissive carbon dots (NIR-CDs) with obvious emission characteristic of 653 nm were synthesized through hydrothermally treatment of toluidine bule and gallic acid. Noticeably, the NIR-CDs exhibited excellent selectivity and sensitivity to hypochlorite (ClO−), and the limit of detection is as low as 42.7 nM. The selective recognition reaction between ClO− and the surface functional groups of NIR-CDs inhibits the fluorescence from NIR-CDs. The quenching mechanism was confirmed by fluorescence lifetime decays, FT-IR spectroscopy and UV–vis absorption spectra. More remarkably, the NIR-CDs have rich hydrophilic groups showed lower cytotoxicity, excellent bio-compatibility and specific cell membrane localization ability. The established spectrofluorometric method based on NIR-CDs has been used to determination of ClO− level in tap water sample, the recoveries were 97.7 %–103.3 %. In addition, the NIR-CDs also has been successfully applied for the imaging of cell membrane. The study provides a novel idea for developing NIR ClO− probe as well as cell membrane localization probe based on CDs, which present bright prospects in real water samples monitoring and cell membrane imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • Highly fluorescent phenylboronic acid functionalized quantum dots (P-QDs) were synthesized. • P-QDs can sensitively detect LTL in different real samples. • The combination of P-QDs and LTL had significant growth inhibition and migration blocking effects on HepG2 cells. Luteolin (3′,4′,5,7-tetrahydroxyflavone, LTL) is a kind of hydrophobic flavonoid, which has a number of pharmacological actions. It has a number of pharmacological actions, including anti-inflammatory, antioxidant, anticancer, and antihepatic fibrosis properties. High-dose LTL, on the other hand, can cause oxidative DNA damage and hydroxyl radical generation. It is critical to create easy, sensitive, and dependable LTL detection technologies and delivery methods for LTL quality control, clinical drug monitoring and enhancing drug bioavailability. In this work, a novel phenylboronic acid derived quantum dots (P-QDs) were synthesized for LTL sensitive detection and pH-responsive delivery. It showed remarkable selectivity and a brilliant fluorescence with a quantum yield of 43.62 %. In vitro experiments reveal negligible cytotoxicity. P-QDs and LTL coupling (P-QDs/LTL) showed powerful proliferation inhibition and migration restriction effects on HepG2 cells. In addition, P-QDs/LTL could time-dependently release it to restore fluorescence in the microacidic environment of HepG2 cells, thus demonstrating satisfactory fluorescence imaging capability. This strategy demonstrated a favourable linear relationship between LTL concentration and the fluorescence intensity of P-QDs in the range of 0.02–200 μM (R2 = 0.9952), with a detection limit of 1.16 nM (S/N=3). The recoveries in different real samples were in the range of 85.23 %-108.04 % with RSDs ≤6.1 %. The material is both a new attempt at LTL detection methodology and has significant promise for providing pH-responsive intracellular release of drug monitoring and cancer therapies from naked QDs without the requirement for sophisticated modified grafting. [ABSTRACT FROM AUTHOR]

Curcumin has been used in traditional medicine because of its pharmacological activity, including antioxidant, antibacterial, anticancer, and anticarcinogenic properties. Therefore, sensitive and selective monitoring of curcumin is highly demand for practical application. In this study, we describe the construction of a fluorescence method for curcumin assay based on nitrogen-doped MoS 2 quantum dots (N–MoS 2 QDs). The N–MoS 2 QDs are constructed by a solvothermal method using sodium molybdate and Cys as precursors. With the addition of curcumin, the bright blue fluorescence of N–MoS 2 QDs is quenched by the inner filter effect (IFE). The QDs emitted bright blue fluorescence and could be quenched by the addition of curcumin via IFE. The dynamic range is the range of 0.1–10 μM for curcumin detection, with a detection limit of 59 nM. N–MoS 2 QDs were applied for curcumin assay in real samples with good recovery. In addition, the N–MoS 2 QDs exhibited relative low cytotoxicity and could be applied for fluorescence-based imaging in biological samples. Our study indicates that the sensor possesses good selectivity to monitor curcumin in water samples, human urine samples, ginger powder samples, mustard samples, and curry samples with satisfactory recoveries. The N–MoS 2 QDs possess less cytotoxicity with excellent biocompatibility and were applied for in vitro cell imaging. A new label-free nanosensor for curcumin assay has been developed based on nitrogen-doped MoS 2 quantum dots quenched via inner filter effect. [Display omitted] • Curcumin can quench the fluorescence of the nitrogen-doped MoS 2 quantum dots via inner filter effect (IFE). • The limit of detection of this proposed method is 59 nM. • This proposed method is applicable for the detection of curcumin in real samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • N-BPQD was synthesized through a solvothermal method using formamide as N source and solvent. • The N-BPQD exhibit a bright blue fluorescence with high quantum yield of 73.7%. • N-BPQD on fPAD was used as a visual fluorescent sensing platform for detection of bilirubin. • The fluorescent sensor shows high sensitivity and selectivity to bilirubin. • N-BPQD was a good fluorescent probe for cellular imaging. A facile top down producing approach for synthesis and doping of a nitrogen doped black phosphorus quantum dots (N-BPQD) in one-pot was developed by solvothermal method with formamide as a nitrogen source and solvent. The nitrogen atoms had introduced into BPQD structure and exhibit a bright blue photoluminescent with a high quantum yield of 73.7 %. The morphology and chemical structure of N-BPQD was characterized by transmission electron microscopy, Raman spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. A fluorescent paper analysis device (fPAD) was applied in rapid and cost-effective detection of biomarker bilirubin with naked eyes. The fPAD sensor present a high selectivity, stability and sensitive response to bilirubin in a wide linear range of 10 to 150 µM with a limit of detection limit as 26 nM (S/N = 3) and limit of quantitation as 86 nM (S/N = 10). The principles-based density functional theory, calculations on doping and binding energy of N-BPQD were analyzed via the density functional theory (DFT) simulations. Moreover, N-BPQD showed extremely low cytotoxicity, which is a promising as a good fluorescent probe for stem cell imaging application. This work provide a new platform for diagnosis of jaundice disease. [ABSTRACT FROM AUTHOR]

• Photoluminescent PS-CDs were prepared using pumpkin seeds as a novel carbon source. • The proposed method is simple, economic and environmental friendly. • A strong blue emission with high quantum yield of 12.7 % was obtained by PS-CDs. • PS-CDs are used as potential chemosensor for Cu2+ and Fe3+ ions in aqueous media. • PS-CDs are low toxic and its metal complexes used as cell imaging with HCT-116 cells. A facile and efficient green synthesis of photoluminescent carbon dots (CDs) was achieved using pumpkin seeds (PS) through the hydrothermal-carbonization method. Pumpkin seeds , well-known for their nutrient-rich composition, offer potential health benefits, including heightened fertility, enhanced heart health, and improved blood sugar regulation. The as-synthesized PS-CDs characterization through UV–vis, photoluminescence (PL), FTIR, XRD, and HR(TEM) analysis. The PL PS-CDs exhibited an excitation-dependent behavior, with the peak shifting from 410 nm to 475 nm under excitation wavelengths ranging from 270 nm to 400 nm. Notably, the synthesized PS-CDs displayed outstanding advantages, such as a high fluorescent quantum yield of 12.7 % with bright blue emissions when exposed to UV light at 365 nm. High-resolution TEM images revealed an average size of approximately 4.0 ± 0.2 nm for the synthesized PS-CDs, ranging from 2 to 7 nm with interlayer distance of 0.21 nm. PL spectra of PS-CDs solution, with an excitation wavelength of 338 nm and emission wavelength of 420 nm, were examined in the presence of various metal ions (50 μM). The fluorescence lifetime of the PS-CDs showed an exponential curve, with an average lifetime (τ av) of 8.47 ns for Cu2+and 3.61 ns for Fe3+ ions, respectively, which is strongly indicates that quenching occurs through a static mechanism. The PS-CDs exhibited high sensitivity and selectivity towards Cu2+ and Fe3+ ions, with a linear relationship observed up to a concentration of 50 μM and detection limits of 0.43 and 0.11 μM (S/ N = 3), respectively. Moreover, the low-toxicity and strongly fluorescent PS-CDs were successfully applied for cell imaging. The practical utility of the developed sensor was determined through the analysis of Cu2+ and Fe3+ ions in spiked water samples, highlighting its considerable analytical and bioanalytical applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Sustainable and green natural lignin raw materials are considered as reliable precursors for large-scale production of carbon quantum dots (CQDs). However, extracting CQDs with ultra-low cytotoxicity and favorable fluorescence properties from lignin remains a challenge. Herein, the bio-waste lignin was converted into crude CQDs by an eco-friendly and rapid microwave pyrolysis approach in just 15 min. The as-obtained CQDs modified with nitrogen-atoms (N-CQDs) display a representative graphite-like structure, strong hydrophilicity, tiny particle size of 6.9 nm, and bright green fluorescence with a quantum yield of approximately 22.2% and fluorescence lifetime of 4.29 ns. Moreover, the N-CQDs exhibit high fluorescence stability under the conditions of a range of pH (5–11), continuous UV irradiation (∼2 h), and NaCl presence with concentrations of 0–1.2 mol/L. More importantly, the N-CQDs show negligible cytotoxicity. Even at the higher N-CQD concentration (300 μg/mL), A549 cells still maintain over 90% activity. The N-CQDs could be utilized for fluorescence imaging in living cells based on the above favorable characteristics. The present work paves the way for the value-added utilization of bio-waste lignin and the production of safe cell imaging agents. [Display omitted] • N-CQDs were produced from bio-waste lignin by a microwave pyrolysis approach. • N-CQDs generated in PEI have better fluorescence properties than those in water. • The N-CQDs with low toxicity can be utilized for fluorescence imaging in living cells. • Even at higher N-CQDs concentrations (300 μg/mL), A549 cells maintain 90% activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • We present a simplified fluorescent microscopy-surface plasmon resonance (FM-SPR) system. • Real-time simultaneous observation and acquisition of fluorescent carbon dots labeled silk fibroin kinetic processes using FM-SPR system. • The fluorescence image changes fitted well with the SPR signal changes. • The linear detection range was 2.5 μg/mL–100 μg/mL, and the real lowest detection limit reached 0.5 μg/mL. • The association rate and dissociation rate of N-CDs to SF which were 2.65 × 10−5/s and 1.52 × 10 −5/s, respectively. The use of fluorescent carbon dots (CDs) as highly precise biolabeling probes has been widespread in the fields of live cell imaging and protein labeling due to their small size and excellent photoluminescence ability to accurately target specific molecules with surface chemical properties. However, there was a lack of research on the interaction between CDs and labeled molecules. In this work, we presented a novel investigation strategy, the fluorescence microscopy-surface plasmon resonance (FM-SPR) system, which combined the use of fluorescence microscopy and wavelength modulation surface plasmon resonance to study the interaction between CDs and labeled molecules in real-time. Using this system, simultaneously recorded the SPR signals and the fluorescence images on the surface of the FM-SPR sensor chip. We observed the dynamic curve and fluorescence images of the interaction between green emissive nitrogen-doped carbon dots (N-CDs) and silk fibroin (SF) in real-time. The kinetic parameters, the quantitative analysis, and the investigation of the binding could be achieved. The results showed a strong linear relationship between the change in SPR signals and the concentration of N-CDs, with a linear coefficient of 0.99913. The linear detection range was 2.5 μg/mL–100 μg/mL, and the real lowest detection limit reached 0.5 μg/mL. Additionally, the green fluorescence points in the imaging region on the FM-SPR sensor chip increased with the concentration of N-CDs, which was consistent with the change in SPR signals. Using this system we also acquired the association rate and dissociation rate of N-CDs to SF which were 2.65 × 10−5/s and 1.52 × 10−5/s, respectively. This demonstrated the effectiveness of our method in quantitatively analyzing SF labeled with N-CDs. [ABSTRACT FROM AUTHOR]

CQD/PEDOT:PSS composites were prepared via the hydrothermal method from glucose carbon quantum dots (CQDs) and an aqueous solution of PEDOT:PSS conducting polymer and their electrical and optical properties were investigated. The morphology and structure of these samples were investigated by AFM, SEM, EDX, and EBSD. It was found that the CQDs and CQD/PEDOT:PSS composites had a globular structure with globule sizes of ~50–300 nm depending on the concentration of PEDOT:PSS in these composites. The temperature dependence of the resistivity was obtained for the CQD/PEDOT:PSS (3%, 5%, 50%) composites, which had a weak activation character. The charge transport mechanism was discussed. The dependence of the resistivity on the storage time of the CQD/PEDOT:PSS (3%, 5%, 50%) composites and pure PEDOT:PSS was obtained. It was noted that mixing CQDs with PEDOT:PSS allowed us to obtain better electrical and optical properties than pure CQDs. CQD/PEDOT:PSS (3%, 5%, 50%) composites are more conductive composites than pure CQDs, and the absorbance spectra of CQD/PEDOT:PSS composites are a synergistic effect of interaction between CQDs and PEDOT:PSS. We also note the better stability of the CQD/PEDOT:PSS (50%) composite than the pure PEDOT:PSS film. CQD/PEDOT:PSS (50%) composite is promising for use as stable hole transport layers in devices of flexible organic electronics. [ABSTRACT FROM AUTHOR]

Biomass materials have abundant natural resources, renewability and good biochemical compatibility, so biomass-based fluorescent materials prepared from biomass materials have gradually become a research hotspot. In particular, the low cost and environmentally friendly properties of chitosan have been widely used in the field of functional materials. Chitosan-based functional materials have attracted extensive attention in the detection and removal of organic and inorganic pollutants. They have been widely used in biological imaging, environmental detection, drug carriers and other fields. This paper reviews the preparation and application of chitosan-based fluorescent probes, including chitosan-derived fluorescent probe materials and chitosan-based carbon quantum dots. At the same time, it focuses on the application research of chitosan-based carbon quantum dots in the fields of environmental detection, cell imaging, drug carriers, photocatalysis, etc. In addition, it provides new ideas and application prospects for the development and application of chitosan-based fluorescent materials in the future. [ABSTRACT FROM AUTHOR]

Selenite (SeO32−), as the most toxic form of selenium in water, is a great threat to water quality and human health, which also has been closely associated with various physiological and pathological processes. The sensitive detection and quantification of SeO32− are imperative for the early diagnosis and prevention of selenite-associated disease. Herein, we constructed novel o-phenylenediamine functionalized carbon quantum dots (OPD-CQDs) by a one-step hydrothermal method. The OPD-CQDs exhibited good water solubility, high quantum yield, strong photostability, excellent biocompatibility and cell imaging capabilities, and also displayed high selectivity and sensitivity to SeO32− with an excellent linear relationship and a low limit of detection (86 nM). Moreover, the OPD-CQDs were successfully employed for the quantitative determination of SeO32− in tap water and human serum with high accuracy and recovery rate. In particular, the designed OPD-CQDs were successfully applied for intracellular SeO32− detection with excellent biocompatibility and cellular imaging capability. The present research demonstrated that OPD-CQDs provided a novel approach for imaging and detecting SeO32− in live cells and in vivo. Based on these excellent properties and comprehensive applications, OPD-CQDs illustrated great potential to offer a scientific and effective method for SeO32− detection in complex environments and clinical early diagnosis of SeO32− related diseases. [ABSTRACT FROM AUTHOR]

Ammonium citrate dibasic，trometamol and neodymium nitrate are employed as raw materials to effectively synthesize blue fluorescent neodymium and nitrogen co-doped carbon dots(Nd，N-CDs)with a fluorescence quantum yield of up to 93. 05% via hydrothermal method. The morphology and surface structure of Nd，N-CDs are characterized in detail by several techniques including transmission electron microscopy (TEM)， powder X-ray diffraction (XRD)， infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy(XPS). In addition，ultraviolet visible absorption spectroscopy and fluorescence spectroscopy are used to investigate its optical properties and optical stability. Results show that drug molecule sulfasalazine(SSZ)could dramatic decrease the fluorescence of Nd，N-CDs ，but other four drug molecules and metal ions have no significant influence. Thus，a fluorescence detection method for selective detection of SSZ is established. The linear detection range is between 0. 1 μmol/L and 50 μmol/L，and the detection limit is 0. 05 μmol/L. Further investigation shows that the fluorescence quenching mainly involves two mechanisms that are dynamic quenching and fluorescence resonance energy transfer. The as-established analytical method could be used to determine the content of SSZ in actual tablets with recovery ranging from 98. 1%~104. 2%. Furthermore，the synthesized Nd，N-CDs present good biocompatibility and could be used as a fluorescent probe to penetrate the cell wall to stain the cytoplasm，however，it could not enter the cell nucleus，which effectively avoids further cell damage. [ABSTRACT FROM AUTHOR]

Carbon quantum dots (CQDs) are carbon nanomaterials with fluorescent properties. Due to their unique structure and optical properties, CQDs have become a research hotspot in recent years. In this paper, iodine-doped CQDs (I-CQDs) with high photoluminescence (PL) (fluorescence quantum yield ∼ 36.2%) were innovatively prepared using a self-doping method with p-iodobenzoic acid as the only precursor. The average particle size of the I-CQDs is 6.42 nm, the maximum excitation wavelength is 330 nm, and the maximum emission wavelength is 408 nm. Fluorescence-sensing experiments showed that the I-CQDs could be used as a 'turn-off' fluorescence sensor for Fe3+, with a detection limit of 0.47 μM. The cause of the fluorescence quenching can be attributed to dynamic quenching and the inner filter effect. When the sensor detects ferric ions in actual water samples, the spiked recoveries are 99.2% to 107.5%, with good reproducibility and high accuracy. Moreover, I-CQDs with their lower cytotoxicity could be used for the imaging of HeLa cells over longer times and as a new type of fluorescent labeling material for environment monitoring, cell labeling, and cellular imaging. [ABSTRACT FROM AUTHOR]