Red Emissive Carbon Research Articles

A biosensor encompassing fusarinine C-magnetic nanoparticles and aptamer-red/green carbon dots for dual-channel fluorescent and RGB discrimination of Campylobacter and Aliarcobacter

The diarrhea pathogens Campylobacter and Aliarcobacter are similar in morphology and their leading symptoms, making them difficult to be differentially diagnosed. Herein, we report a biosensor with two modules to differentiate the genera-representative species of C. jejuni and A. butzleri. Module 1 was fusarinine C-decorated magnetic nanoparticles; module 2 consisted of C. jejuni-specific aptamer modified with red-emitting carbon dots (CDs) and A. butzleri-specific aptamer-modified green-emitting CDs, consisting non-interfering dual-fluorescence detection channels. Module 1 was used to selectively capture C. jejuni and A. butzleri from an un-cultured sample, and the specific CDs in module 2 would then recognize and bind to their counterpart bacteria when subjected to the collected module 1-bacteria complex. By measuring the fluorescence intensities from the CDs-bound bacteria, the abundance of each bacterium could be differentially indicated. This biosensor exhibited a wide detection range of up to 1 × 107 CFU/mL and the lowest limit of detection (LOD) of 1 CFU/mL, for each bacterium. Thus, the biosensor with dual-fluorescent channels facilitated a culture-independent, ultrasensitive and discriminative detection of C. jejuni and A. butzleri. Remarkably, this fluorescent detection could be transformed into RGB color indication to render the visual discrimination. After the biosensor was coupled with microfluidics, a biosensing platform was developed, which could render fluorescent and RGB differentiation of the two bacteria in human stool or chicken broilers, achieving a LOD of 5 CFU/mL and turnaround time of 65 min. This work established the first biosensor-based methodology for the discriminative detection of Campylobacter and Aliarcobacter in real samples.

Lysosome-targeted carbon dots with a light-controlled nitric oxide releasing property for enhanced photodynamic therapy

The reactive oxygen species (ROS) generation efficiency is always limited by the extreme tumor microenvironment (TME), leading to unsatisfactory antitumor effects in photodynamic therapy (PDT). As a promising gas therapy molecule, nitric oxide (NO) is independent of oxygen and could even synergize ROS to enhance the therapeutic effect. However, the short half-life, instability, and uncontrollable release of exogenous NO limited the application of tumor synergistic therapy. Herein, we reported a novel kind of red-emissive carbon dots (CDs) that was capable of lysosome-targeted and light-controlled NO delivery. The CDs were synthesized by using metformin and methylene blue (MB) via a hydrothermal method. The obtained metformin-MB CDs (MMCDs) exhibited a higher 1O2 quantum yield and NO generation efficiency under light emitting diode (LED) light irradiation. Noteworthily, the 1O2 could further in situ oxidize NO into peroxynitrite anions (ONOO−), which own the higher cytotoxicity against cancer cells. Cell experiments indicate that MMCDs could destruct lysosome membrane integrity and kill almost 80% of HepG2 cells under light irradiation while very low cytotoxicity in the dark. Moreover, MMCDs significantly decreased tumor volume and weight after phototherapy in hepatoma HepG2-bearing mice. Our study provides a new strategy for light-controlled NO generation as well as precise lysosome-targeting for enhancement of PDT efficiency.

Red-Emissive Carbon Dots Combined with Ferric Ions for Detection of Total Antioxidant Capacity in Food

Red-Emissive Carbon Dots Combined with Ferric Ions for Detection of Total Antioxidant Capacity in Food

Advancing glioblastoma imaging: Exploring the potential of organic fluorophore-based red emissive carbon dots

Over time, the interest in developing stable photosensitizers (PS) which both absorb and emit light in the red region (650 and 950 nm) has gained noticeable interest. Recently, carbon dots (CDs) have become the material of focus to act as a PS due to their high extinction coefficient, low cytotoxicity, and both high photo and thermal stability. In this work, a Federal and Drug Association (FDA) approved Near Infra-Red (NIR) organic fluorophore used for photo-imaging, indocyanine green (ICG), has been explored as a precursor to develop water-soluble red emissive CDs which possess red emission at 697 nm. Furthermore, our material was found to yield favorable red-imaging capabilities of glioblastoma stem-like cells (GSCs) meanwhile boasting low toxicity. Additionally with post modifications, our CDs have been found to have selectivity towards tumors over healthy tissue as well as crossing the blood-brain barrier (BBB) in zebrafish models.

Engineering excitation-independent turn-on fluorescent probe for mercury: Functionalized dendritic silica doped with red-emissive carbon dots towards simultaneous detection and remediation with biosensing application

The simultaneous detection and remediation of highly toxic mercury-ion are urgently needed for environmental benefits. However, most of the fluorescence probes for mercury-ion exhibit blue luminescence with fluorescence quenching, and the simultaneous functions are scarce. Therefore, a new strategy is adopted to observe turn-on fluorescence with mercury-ion using red-emissive carbon dots (CDs) as a fluorescence tag and alkyl thiol functionalized dendritic fibrous nano-silica (DFNS@SH) as a substrate for specificity. The newly constructed composite material (CD@DFNS@SH) shows excitation-independent selective turn-on red luminescence in the presence of mercury-ion with a LOD (limit of detection) value of 5 nM, which is well below the threshold limit prescribed by the World Health Organization (WHO) in drinking water. In addition, this material also shows a high adsorption capacity toward mercury remediation (695 mg g−1) from the aqueous system. The adsorption parameters are best fitted with the Langmuir model with a pseudo-second-order interaction mechanism. Furthermore, fluorescence imaging used the composite material for biosensing of mercury-ion in living organisms, Artemia Salina (brine shrimp). The material's real sample quantification of mercury-ion and recyclability are other advantages offered by this material.

Red-emitting carbon dots as fluorescent probes for the rapid detection of brilliant blue FCF in foods

Red-emitting carbon dots as fluorescent probes for the rapid detection of brilliant blue FCF in foods

Efficient red-emitting carbon dots for bioimaging and spectral engineering by polyetherimide modification

A novel type of red-emitting carbon dots was synthesized using urea and neutral red via the solvothermal method at a temperature of 200 °C for 4 h. The resulting CDs, named NR-CDs, display a distinct red emission at 620 nm when excited at a wavelength of 470 nm, achieving a quantum yield of 61.11% in acetone. Interestingly, NR-CDs exhibit strict solvent polarity dependence, i.e. the emission wavelength of NR-CDs red-shifts with an increase in solvent polarity. Besides, when incubated with NR-CDs and excited by an excitation wavelength of 470 nm, 4-T1 cells emit a clear red fluorescence. Meanwhile, high-quality in-vivo fluorescent images of zebrafish embryos and larvae were obtained by incubating with NR-CDs. Moreover, by modifying with polyetherimide (PEI), the peak value of PEI-NR-CDs shifts from 620 nm to 596 nm, and the emission is increased by 264 %. Co-localization experiment with commercial dye (Lyso-Tracker Green) shows that PEI-NR-CDs are localized in lysosomes and could be used as a lysosomal tracer for cells. Furthermore, PEI-NR-CDs were prepared into fluorescent ink, which exhibited orange fluorescence under UV light. All results demonstrate that as-obtained NR-CDs and PEI-NR-CDs can be used as reagent for fluorescent-imaging application.

Heating-free synthesis of red emissive carbon dots through separated processes of polymerization and carbonization

Polymerization and carbonization are believed as two basic processes for the bottom-up synthesis of carbon dots (CDs). Since these two processes usually occur simultaneously due to the high reaction temperature and fast reaction rate, it is still a challenge to separate and control these two processes. In the present work, we reported a new room temperature method, which achieved the separated and controlled polymerization and carbonization processes. The polymerization process is realized by dissolving o-phenylenediamine (OPD) in ethanol at room temperature, and finally obtained polymer dots (PDs) without any lattice with a sphere size of 29.6 nm. The carbonization process begins in a manual way by adding concentrated sulfuric acid. After carbonization, CDs (noted as CPDs in this work) with a size of 3.6 nm and a clear lattice can be obtained. Importantly, the separated polymerization and carbonization make us possible to adjust the composition or interactions of intermediate products during the synthesis process. As a prototype, we added acetic acid (AA) additives into OPD precursors during the polymerization stage. Due to the crosslink enhanced emission (CEE) effect via hydrogen bonds which are produced by the amide groups from AA reaction products with H in the –NH3+ or aromatic ring, the resulted CPDs show improved PLQY from an initial 6.87% (without AA) to 16.47%. The current work realized the separated and controllable polymerization and carbonization processes, opening up the door for tuning the composition and interactions of intermediate products before carbonization.

Red-Emitting Carbon Quantum Dots for Biomedical Applications: Synthesis and Purification Issues of the Hydrothermal Approach.

The possibility of performing the synthesis of red-emitting carbon quantum dots (r-CDs), in a well-controllable, large scale and environmentally sustainable way is undoubtedly of fundamental importance, as it will pave the way to their employment in advanced medical large-scale applications. Knowledge of the difficulties involved in producing r-CDs with reproducible optical, structural, and chemical characteristics, might help in their large-scale production, making the process standardizable. In this work, we present an experimental study, also supported by results reported in the literature, on the issues encountered during the synthesis and post-synthesis purification treatments of r-CDS. We focused on the hydrothermal approach as it was found to be more suitable for future large-scale industrial applications. We propose three synthetic strategies and observed that employing p-phenylenediamine (p-PDA), as a precursor, the synthetic process showed low efficiency with low yields of r-CDs, large amounts of unreacted precursor, and reaction intermediates. Changing reaction parameters does not improve performance. The r-CDs obtained using citric acid (CA) and urea, as precursors, resulted to be sensitive to pH and difficult to separate from the reaction mixture. Furthermore, the proposed synthetic strategies show that the hydrothermal preparation of r-CDS requires approaches that are not fully sustainable.

Red Emissive Carbon Dot Superoxide Dismutase Nanozyme for Bioimaging and Ameliorating Acute Lung Injury (Adv. Funct. Mater. 19/2023)

Carbon Dots In article number 2213856, Qing-Ying Luo, Kelong Fan, Minrong Zhu, and co-workers develop a red emissive carbon dot nanozyme with high superoxide dismutase (SOD)-like activity over 4000 U mg−1. The SOD nanozyme activity is revealed to be relying on their surface functional groups which capture O2•− and then promote the electron transfer between O2•− and π-system of carbon dot. The carbon dot SOD nanozyme shows great potential in bioimaging and ameliorating acute lung injury.

Synthesis and bioimaging application of red-emissive carbon dots

Fluorescent red-emissive carbon dots (RCDs) were synthesized using the solvothermal method with citric acid as a carbon source, N,N-dimethylformamide as a nitrogen source, and formamide as a solvent. The as-synthesized RCDs show red fluorescence in an aqueous solution and have an excellent stability towards photobleaching as well as extremely low cytotoxicity and are successfully used for cell and zebrafish imaging. The results indicate that RCDs have potential applications in both in vitro and in vivo bioimaging.

Portable smartphone platform based on tunable chiral fluorescent carbon dots for visual detection of L-Asp and L-Lys

Amino acids are involved in many physiological processes such as neurotransmitter transmission, protein synthesis and immune regulation, which play an indispensable role in life science. However, accurate monitoring of amino acid metabolism still faces a huge challenging due the lack of robust detection approaches. Herein, three-color emission tunable fluorescent carbon dots (CDs) were successfully synthesized by a simple one-step solvothermal treatment using classical precursors. These multi-color CDs exhibited a bright and steady luminescence shifting from blue to red under UV–vis light excitation. Detailed characterization by various precision instruments demonstrated that the unique structure of the prepared polychromatic emission CDs was composed of sp2 hybrid carbon nucleus and part of sp3 hybrid carbon atom. These CDs displayed low cytotoxicity and excellent multi-color cell imaging ability at single wavelength excitation. Moreover, the chiral structure on the surface of the red emissive carbon dots (R-CDs) was well preserved at temperatures far below the melting point of the chiral precursor. Especially, the chiral red emissive CDs (R-L-CDs) as sensitive and selective fluorescent probe could quickly identify L-Aspartic acid (L-Asp) and L-Lysine (L-Lys) in water and biological samples. Additionally, smart phone color recognizer application could realize more accurate visual detection to compensate the defect that the naked eye did not distinguish subtle colors. Therefore, the multi-excitation mode could be effectively shield background interference from complex samples by introducing a self-calibrating reference signal, ensuring accurate and reliable quantitative information, endowing R-L-CDs as a biosensor with far-reaching prospects for further application by binding target analytes.

Facile synthesis of efficient red-emissive carbon quantum dots as a multifunctional platform for biosensing and bioimaging

The red-emissive carbon quantum dots (r-CQDs) have gained considerable interest in the field of fluorescence imaging as they can effectively overcome short-wave background interference. However, the development of efficient and simple synthetic pathways for the preparation of r-CQDs with high production yield and fluorescence quantum yield remains a great challenge. Herein, we prepared the intense red-emissive carbon quantum dots (r-CQDs) through one-pot hydrothermal treatment of methylene violet. The morphology and structure of the as-prepared r-CQDs were characterized through transmission electron microscopy, Raman spectra, Fourier transform infrared spectra, and X-ray photoelectron spectroscopy. r-CQDs were well dispersed in water with an average size of 2.39 nm. The surface of r-CQDs was full of oxygen-containing functional groups, which contributed to their high solubility in water. Under ultraviolet light (365 nm) irradiation, both the aqueous solution and powder of r-CQDs emitted intense red luminescence. r-CQDs exhibited the excitation-independent emission property with the maximum fluorescence peak at 596 nm. The fluorescence quantum yield of r-CQDs was calculated to be 26.46% in water using rhodamine B as a reference. Due to the significantly different fluorescence intensity in water and organic solvents, r-CQDs could be applied as the fluorescence sensor to quickly detect the trace amounts of water in various organic solvents. Moreover, the fluorescence of r-CQDs showed selective response to hypochlorite (ClO−) through an “on-off” sensing mechanism. The good biocompatibility of r-CQDs was verified by the cell counting kit-8 (CCK-8) method against mouse hepatocellular carcinoma (Hepa 1–6) cells. Finally, the r-CQDs were successfully used in cellular imaging and they were mainly located in the lysosomes of cancel cells. Thus, r-CQDs could be served as a powerful fluorescence nano-platform for biosensing and bioimaging.

RNA-Targeting Carbon Dots for Live-Cell Imaging of Granule Dynamics.

It is significant to monitor the different RNA granules dynamics and phase separation process inside cells under various stresses, for example, oxidative stress. The current small-molecule RNA probes work well only in fixed cells and usually encounter problems such as insufficient stability and biocompatibility, and thus a specific RNA-targeting fluorescent nanoprobe thatcan be used in the living cells is urgently desired. Here, the de novo design and microwave-assisted synthesis of a novel RNA-targeting, red-emissive carbon dots (named as M-CDs) are reported by choosing neutral red and levofloxacin as precursors. The as-synthesized M-CDs is water-soluble with a high fluorescence quantum yield of 22.83% and can selectively bind to RNA resulting in an enhanced red fluorescence. More interestingly, such an RNA-targeting, red-emissive M-CDs can be fast internalized into cells within 5s and thus used for real-time imaging the dynamic process of intracellular stress granules under oxidative stress, revealing some characteristics of granules that have not been identified by previously reported RNA and protein biomarkers. This research paves a new pathway for visualizing bulk RNA dynamics and studying phase-separation behaviors in living cells by rational design of the fluorescent carbon dots in terms of structure and functionality.

Red emissive carbon dots-based probe for rapid identification and continuous tracking of Gram-positive bacteria in tumor cells

Red fluorescent carbon dots (R-CDs) and blue fluorescent carbon dots (B-CDs) were synthesized, and then coupled with D-alanine (D-Ala) to construct CDs based probes (R-CDs@D-Ala, B-CDs@D-Ala). The two probes can not only rapidly and selectively identify Gram-positive bacteria within 30 s, but also keep continuous tracking for 24 h. Further, R-CDs@D-Ala was successfully used to detect G+ bacteria from Hela cells, showing good identification results. Moreover, the fluorescence superposition of the two probes can display the differences in the growth and division status of different G+ bacteria, providing strong support for bacterial diagnosis and treatment in the tumor microenvironment. Therefore, CDs based nanoprobes provide a rapid and effective method for diagnosis of bacterial infectious diseases and has good practical application value.

Single-chip horticultural LEDs enabled by greenly synthesized red-emitting carbon quantum dots

Light emitting diodes (LEDs) having the emission spectra that match the absorption regions of a target plant are strongly demanded for vertical farming. Herein, we demonstrate the use of red-emitting carbon quantum dots (R-CQDs) as a phosphor to fabricate cost-effective horticultural LEDs. R-CQDs having chlorophyll molecules embedded in a carbogenic matrix were solvothermally synthesized using ethanol extract of bougainvillea leaves as a green carbon source. R-CQDs emit a narrow band maximizing at 670 nm originated from the chlorophyll centers when excited either the carbogenic matrix or embedded chlorophyll. R-CQD phosphor converts partially 410 nm light emitted from a LED chip to red and far red regions, thus offering cheaper, single – chip LEDs for agriculture lighting.

Red-emissive carbon dots based fluorescent and smartphone-integrated paper sensors for sensitive detection of carbendazim

Trace detection of carbendazim (CBZ), a worldwide used pesticide, in crops and foods is important and urgent to reduce risks to human health. Herein, newly red-emissive carbon dots (R-CDs) based fluorescent and smartphone-integrated paper sensors were developed for highly-selective, and -sensitive rapid sensing of CBZ. R-CDs were synthesized from citric acid and urea via a DMF solvothermal method, which showed excellent analytical performance due to abundant carboxyl groups on the surface and long emission wavelength to avoid autofluorescence interference of matrix. According to the red fluorescence quenching by CBZ via π-π interaction and photoinduced electron-transfer effect, the newly fluorescent nano sensor could realize CBZ sensing within 3 min with high selectivity out of the other six interfering pesticides, as well as fascinating sensitivity with an ultralow detection limit of 3.5 ng/mL. The practicable application in the spiked medicinal Lotus seeds samples exhibited satisfactory recoveries of 95.5%-108.3%. The portable paper-based sensor fabricated by depositing R-CDs on the filter paper enabled quantitative readout of test strip results assisted with a smartphone, providing a rapid on-site tool for CBZ detection in medicinal foods. This is the first report of a novel, sensitive, and portable R-CDs based sensing platform for simple, cost-effective, and rapid on-site detection of CBZ in the field of food safety with great application potential.

Red emission carbon dots for mitoxantrone detection

Red-emitting carbon dots were designed for the first time as the fluorescent probe for the determination of mitoxantrone (MITX) anticancer drug in human serum based on the inner filter effect (IFE). With the increase of MITX concentration, the single emission fluorescence intensity of the red carbon dots (R-CDs) at 655 nm gradually decreased and the emission peak position red-shifted to 661 nm. The developed R-CDs detection probe was sensitive to MITX with a wide linear detection range of 0.096–30 µM and a low limit of detection (LOD) of 0.032 µM. Moreover, the proposed method had been successfully applied to the determination of MITX in human serum samples, showing exhibited good operability, low cost, and high accuracy.

Investigation into Red Emission and Its Applications: Solvatochromic N-Doped Red Emissive Carbon Dots with Solvent Polarity Sensing and Solid-State Fluorescent Nanocomposite Thin Films.

In this work, a NIR emitting dye, p-toluenesulfonate (IR-813) was explored as a model precursor to develop red emissive carbon dots (813-CD) with solvatochromic behavior with a red-shift observed with increasing solvent polarity. The 813-CDs produced had emission peaks at 610 and 698 nm, respectively, in water with blue shifts of emission as solvent polarity decreased. Subsequently, 813-CD was synthesized with increasing nitrogen content with polyethyleneimine (PEI) to elucidate the change in band gap energy. With increased nitrogen content, the CDs produced emissions as far as 776 nm. Additionally, a CD nanocomposite polyvinylpyrrolidone (PVP) film was synthesized to assess the phenomenon of solid-state fluorescence. Furthermore, the CDs were found to have electrochemical properties to be used as an additive doping agent for PVP film coatings.

Red emissive N-doped carbon dots encapsulated within molecularly imprinted polymers for optosensing of pyrraline in fatty foods.

A novel and facile method was proposed for preparation of red emissive N-doped carbon dots encapsulated within molecularly imprinted polymers (RNCDs@MIPs) using a one-pot room-temperature reverse microemulsion polymerization. RNCDs used citric acid and urea as carbon and nitrogen sources by one-step solvothermal synthesis with the optimum emission of 620nm. Unique optical properties of RNCDs coupled with high selective MIPs make the RNCDs@MIPs conjugate capable to adsorb specific targets of pyrraline (PRL), such a binding event was then transduced to quench fluorescence response signal of the RNCDs. RNCDs@MIPs for PRL showed linearity from 0.1 to 40μg/L, with a detection limit of 65ng/L. The RNCDs@MIPs exhibited a good reproducibility of 4.67% obtained from four times of rebinding for PRL. The optosensing probe was successfully applied to thedetection of PRL in fatty foods with the spiked recovery of 85.93-106.96%.