Deep Eutectic Solvent-Assisted Preparation of Nitrogen/Chloride-Doped Carbon Dots for Intracellular Biological Sensing and Live Cell Imaging

Nanostructured rhodamine B/aluminosilicate extracted sugarcane bagasse modified with tobacco-derived carbon quantum dot as ratiometric fluorescence probe for determination of tetracycline

Tetracycline (TC), as a widely used antibiotic, is very useful in treating bacterial infections. However, its residues in animal foodstuffs can enter the human body through the food cycle and causes severe and chronic diseases. On the other hand, due to its weak non-biodegradability, it is considered a threat to the environment. In this regard, the development of sensing methods to detect and measure TC is need of the hour. Herein, a dual-emission fluorescence sensor based on porous aluminosilicate structure (ASS) with rough surface hexagonal shape morphology and pore diameter less than 2 nm was prepared. The porous AAS was modified by post-modification method with blue carbon dots (CDT) and rhodamine B (RB) as two fluorophores to develop the ratiometric fluorescence (RF) sensor (CDT-AAS/RB). Nanostructured CDT-AAS/RB emitted two resolved peaks at 445 and 585 nm , which were dramatically quenched in the presence of TC. The RF sensor, with excellent sensitivity, was able to measure TC over the linear range of 0.001-150 μM with a limit of detection of 5.4 nM in the aqueous phosphate buffer. Moreover, the AAS component granted high selectivity and anti-interference ability to the sensor. In addition, the stability of the sensor was greatly improved due to the non-accumulation of CDT nanoparticles and RB molecules in the presence of the AAS. The proposed method was able to determine TC in complex real samples with satisfactory recovery, and the obtained results were validated with standard high-performance liquid chromatography technique.

Fabrication of a ratiometric fluorescent probe based on Tb3+ doped dual-emitting carbon dots for the detection of cytochrome c

Cytochrome c (Cyt-c) was commonly an intrinsic biomarker for a variety of cellular characteristics, such as respiration, energy levels, and apoptosis. Herein, a simple fluorescence sensor was constructed for the detection of Cyt-c in buffer and real serum samples. The carbon dots doped with Tb3+ on the premise of 1-(2-pyridylazo)-2-naphthol (PAN) were fabricated and used as a dual-emission ratiometric fluorescent probe for detecting Cyt-c based on the internal filtering effect (IFE). As a fluorescent probe for ultra-sensitive detection, Cyt-c was quantitatively detected at different concentrations from 1 to 1000 nM. The fluorescent detection method for Cyt-c showed a good linear relationship from 1 to 50 nM, and the limit of detection (LOD) was 0.35 nM. In the recovery range of 101.27-103.39 % in human serum samples, the relative standard deviation (RSD) was less than 3.27 % (n = 3). In the end, the possible structures of CDs were predicted by DFT theoretical simulation calculations. All the results proved the ability of carbon dots as fluorescent probes to detect biomarkers and the application prospects in bioanalysis.

N/Se co-doped porous carbon catalyst derived from a deep eutectic solvent and chitosan as green precursors: Investigation of catalytic activity for metal-free oxidation of alcohols

Heteroatom-doped porous carbon-based materials with high surface area compared to their metal-based homologs are considered environmentally friendly and ideal catalysts for organic reactions. In this paper, a new method for the convenient fabrication, cost-effective, and high efficiency of nitrogen/selenium co-doped porous carbon-based catalysis (marked as N/SePC-T) was designed. The N/SePC-T catalysts were created from the direct pyrolysis of a eutectic solvent containing choline chloride/urea as the nitrogen-rich carbon source, selenium dioxide as a source of heteroatom and chitosan as a secondary carbon source in different temperatures (T). The efficacy of the carbonization temperature on the pore structure, morphology, and catalytic activity of the N/SePC-T materials was investigated and displayed, the N/SePC-900 (having a surface area of 562.01 m2/g and total pore volume of 0.2351 cm3 g-1) has the best performance. The morphology, structure, and physicochemical properties of N/SePC-900 were characterized using various analyses including XRD, TEM, TGA, FE-SEM, EDX, FT-IR, XPS, and Raman. The optimized N/SePC-900 catalyst indicated excellent catalytic performance in the oxidation of benzylalcohols to corresponding aldehydes in very mild conditions.

Nitrogen and Chlorine Co-doped Carbon Dots as a Highly Selective and Sensitive Fluorescent Probe for Sensing of PH, Tetracycline Detection and Cell Imaging

Carbon dots have been widely focused on the field of sensing and detection due to their excellent optical property. Herein, novel orange fluorescent nitrogen and chlorine co-doped carbon dots (N,Cl-CDs) are obtained by one-pot hydrothermal method using o-phenylenediamine and neutral red. Based on the inner filter effect, the prepared N,Cl-CDs can be innovatively developed as an effective "signal-off" multifunctional sensing platform for sensitive determination of tetracycline. The proposed sensor was utilized to realize the determination of tetracycline in Rirver water samples/milk samples (λex = 390 nm, λem = 606 nm) with satisfactory recoveries and relative standard deviations. The linear range of are 0.05 to 45 μM and 45 to135 μM, and detection limit is 3.9 nM (3σ/m). Meanwhile, the luminescent intensity of N,Cl-CDs was reduced gradually when pH changed continuously from 12 to 2, showing a pH-responsive fluorescence property with two linear ranges of pH 3-7 and pH 7-10. In addition, due to the characteristics of low toxicity and excellent biocompatibility, the N, Cl-CDs were also used in the imaging of oocystis cells, which is hopeful to realize the detection of tetracycline in living cells.

Facile Bond Exchanging Strategy for Engineering Wet Adhesion and Antioxidant/Antibacterial Thin Layer over a Dynamic Hydrogel via the Carbon Dots Derived from Tannic Acid/ε-Polylysine

Adhesive hydrogels, playing an essential role in stretchable electronics, soft robotics, tissue engineering, and so forth, upon functioning often need to adhere to various substrates in wet conditions and simultaneously exhibit antibacterial/antioxidant properties while possessing the intrinsic stretchability and elasticity of the hydrogel network intact. Therefore, simple approaches to conveniently access adhesive hydrogels with multifunctional surfaces are being pursued. Herein, a facile strategy has been proposed to construct multifunctional adhesive hydrogels via surface engineering of a multifunctional carbon dot (CD)-decorated polymeric thin layer by dynamic bond exchange. By this strategy, a double cross-linked network hydrogel of polyacrylamide (PAM) and oxidized dextran (ODA) was engineered with a unique dense layer over the Schiff base hydrogel matrix by aqueous solution immersion of PA-120, versatile CDs derived from tannic acid (TA) and ε-polylysine (PL). Without any additional agents, the PA-120 CDs with residual polyphenolic/catechol and amine moieties were incorporated into the surface structure of the hydrogel network by the combined action of the Schiff base and hydrogen bonds to form a dense surface layer that can exhibit high wet adhesive performance via the amine-polyphenol/catechol pair. The armor-like dense architecture also endowed hydrogels with considerably enhanced tensile/compression properties and excellent antioxidant/antibacterial abilities. Besides, the single-sided modified Janus hydrogel and completely surface-modified hydrogel can be flexibly developed through this approach. This strategy will provide new insights into the preparation and application of surface-modified hydrogels featuring multiple functions and tunable interfacial properties.

Carbon quantum dots in bioimaging and biomedicines

Carbon quantum dots (CQDs) are gaining a lot more attention than traditional semiconductor quantum dots owing to their intrinsic fluorescence property, chemical inertness, biocompatibility, non-toxicity, and simple and inexpensive synthetic route of preparation. These properties allow CQDs to be utilized for a broad range of applications in various fields of scientific research including biomedical sciences, particularly in bioimaging and biomedicines. CQDs are a promising choice for advanced nanomaterials research for bioimaging and biomedicines owing to their unique chemical, physical, and optical properties. CQDs doped with hetero atom, or polymer composite materials are extremely advantageous for biochemical, biological, and biomedical applications since they are easy to prepare, biocompatible, and have beneficial properties. This type of CQD is highly useful in phototherapy, gene therapy, medication delivery, and bioimaging. This review explores the applications of CQDs in bioimaging and biomedicine, highlighting recent advancements and future possibilities to increase interest in their numerous advantages for therapeutic applications.

Nitrogen-doped cyan-emissive carbon quantum dots for fluorescence tetracycline detection and lysosome imaging

Tetracyclines (TCs) prevent the growth of peptide chains and the synthesis of proteins, and they are widely used to inhibit Gram-positive and -negative bacteria. For the detection of tetracyclines in cell and in vitro, a convenient and simple detection system based on nitrogen-doped cyan carbon quantum dots (C-CQDs) was developed. C-CQDs have excellent excitation-independent properties, the best optimal excitation peak is 360 nm and the best emission peak is 480 nm. Based on the inner filter effect (IFE), the fluorescence intensity of C-CQDs in solution decreases with the increase of tetracyclines. In the range of 0-100 μM, C-CQDs present a good linear relationship with three tetracyclines (CTC, TET, OCT), with R ² all greater than 0.999. C-CQDs can detect tetracycline in milk samples with recovery in the range of 98.2-103.6%, which demonstrates their potential and broad application in real samples. Furthermore, C-CQDs exhibit excellent lysosomal targeting, as indicated by a Pearson's coefficient of 0.914 and an overlap of 0.985. The internalisation of C-CQDs was mainly affected by lipid raft-mediated endocytosis in endocytic pathway experiments. These experiments indicate that C-CQDs can be effectively used to detect TC content and target lysosomes as an alternative to commercial dyes.

Preparation of sulphuric acid-mediated N,S-codoped red emissive carbon dots: Applications in food dyes detection, solid-state luminescence and cell imaging

As diseases such as cardiovascular disease and cancer caused by food problems are more and more frequent, food safety has received great attention. Among them, the safety problem caused by food dyes is more prominent. Thus, it is of great value to develop sensitive detection methods for food dyes. In present study, sulphuric acid-mediated N,S-codoped red emissive carbon dots (namely as R-CDs) had been manufactured by using N-phenyl-o-phenylenediamine as precursor, sulfuric acid as additive for the first time. The structural and fluorescence properties of R-CDs had been systematically studied. The results demonstrated that R-CDs showed uniform spherical morphology and had a graphite-like structure, for which the average diameters size was 5.05 nm. Due to the various functional groups such as hydroxyl, pyridinic N, pyrrolic N and -C-SO₄, R-CDs emitted bright red fluorescence. Importantly, because of the interactions between the functional groups of R-CDs with the selected food dyes, three dyes including amaranth, brilliant blue FCF and methylene blue can sensitively quench the fluorescence of R-CDs through IFE and static quenching effects. The linearity ranges of them were separately detected as 0.20 μM -20 μM, 10 nM-1 μM and 60 nM-8 μM. The limits of detection (LODs) of them were 70 nM, 4 nM and 20 nM, respectively. Further, R-CDs was successfully applied to the sensitive detection of three dyes from various food samples. To maximize the fluorescence properties of R-CDs, a R-CDs/PVA composite gel was fabricated to make R-CDs fluoresce in solid state condition. The potential of R-CDs/PVA composite gel for preliminary visualization analysis of three dyes was studied. Finally, ascribed to the low toxicity and good biocompatibility, the potential of R-CDs as probe for cell imaging was explored preliminarily.

Novel β-cyclodextrin doped carbon dots for host-guest recognition-assisted sensing of isoniazid and cell imaging

In the present study, novel β-cyclodextrin doped carbon dots (CCDs) were prepared via a simple one-pot hydrothermal method at a mild temperature (140 °C), using mixtures of β-cyclodextrin and citric acid as precursors. By characterizing the chemical properties of CCDs prepared at 140 °C and 180 °C, the importance of low-temperature reaction for preservation of the specific structure of β-CD was elucidated. The CCDs showed excellent optical properties and were stable to changes in pH, ionic strength and light irradiation. Since the fluorescence of the CCDs could be selectively quenched by isoniazid (INZ) through specific host-guest recognition effects, a convenient isoniazid fluorescence sensor was developed. Under the optimal conditions, the sensor exhibited a relatively low detection limit of 0.140 μg mL^-1 and a wide detection range from 0.2 μg mL^-1 to 50 μg mL^-1 for INZ detection. Furthermore, the sensor was employed successfully for the determination of INZ in urine samples with satisfactory recovery (91.1-109.5%), displaying potential in clinical applications. Finally, low cytotoxicity of the prepared CCDs was confirmed using the CCK-8 method, followed by application in HepG2 cell imaging.

An insight into the potentials of carbon dots for in vitro live-cell imaging: recent progress, challenges, and prospects

Carbon dots (CDs) are a strong alternative to conventional fluorescent probes for cell imaging due to their brightness, photostability, tunable fluorescence emission, low toxicity, inexpensive preparation, and chemical diversity. Improving the targeting efficiency by modulation of the surface functional groups and understanding the mechanisms of targeted imaging are the most challenging issues in cell imaging by CDs. Firstly, we briefly discuss important features of fluorescent CDs for live-cell imaging application in this review. Then, the newest modulated CDs for targeted live-cell imaging of whole-cell, cell organelles, pH, ions, small molecules, and proteins are elaborately discussed, and their challenges in these fields are explained.

Dynamic Visualization of Endoplasmic Reticulum Stress in Living Cells via a Two-Stage Cascade Recognition Process

The endoplasmic reticulum (ER) is crucial for the regulation of multiple cellular processes, such as cellular responses to stress and protein synthesis, folding, and posttranslational modification. Nevertheless, monitoring ER physiological activity remains challenging due to the lack of powerful detection methods. Herein, we built a two-stage cascade recognition process to achieve dynamic visualization of ER stress in living cells based on a fluorescent carbon dot (CD) probe, which is synthesized by a facile one-pot hydrothermal method without additional modification. The fluorescent CD probe enables two-stage cascade ER recognition by first accumulating in the ER as the positively charged and lipophilic surface of the CD probe allows its fast crossing of multiple membrane barriers. Next, the CD probe can specifically anchor on the ER membrane via recognition between boronic acids and o-dihydroxy groups of mannose in the ER lumen. The two-stage cascade recognition process significantly increases the ER affinity of the CD probe, thus allowing the following evaluation of ER stress by tracking autophagy-induced mannose transfer from the ER to the cytoplasm. Thus, the boronic acid-functionalized cationic CD probe represents an attractive tool for targeted ER imaging and dynamic tracking of ER stress in living cells.

A label-free fluorescence nanosensor based on nitrogen and phosphorus co-doped carbon quantum dots for ultra-sensitive detection of new coccine in food samples

In this paper, an innovative method for the sensitive detection of new coccine using N, P-doped carbon quantum dots (N,P-CQDs) as fluorescent nanosensor is reported for the first time. The sensing mechanism is based on the fluorescence quenching of N,P-CQDs by new coccine through inner filter effect (IFE). N,P-CQDs were prepared by simple hydrothermal treatment of citric acid, phosphoric acid and ethylenediamine. Under the optimal conditions, the new coccine has two good linear responses in the concentration range of 0.2-100 and 100-200 μM, and the detection limits are as low as 24.8 and 9.4 nM, respectively. Our developed nanosensor has been successfully used for the determination of new coccine in food samples with good precision and high accuracy. This work highlights the economic, rapid, simple, selective and ultra-sensitive for new coccine detection, and opens up a new way for the monitoring of new coccine in actual food samples.

Ultra-bright carbon quantum dots for rapid cell staining

A schematic illustration of the synthesis of G-CDs and cell imaging under one-photon and two-photon conditions.

The improvement of biocompatibility by incorporating porphyrins into carbon dots with photodynamic effects and pH sensitivities

Photodynamic therapy (PDT) is a promising new treatment for cancer; however, the hydrophobic interactions and poor solubility in water of photosensitizers limit the use in clinic. Nanoparticles especially carbon dots have attracted the attention of the world^'s scientists because of their unique properties such as good solubility and biocompatibility. In this paper, we integrated carbon dots with different porphyrins to improve the properties of porphyrins and evaluated their efficacy as PDT drugs. The spectroscopic characteristics of porphyrins nano-conjugates were studied. Singlet oxygen generation rate and the light- and dark-induced toxicity of the conjugates were studied. Our results showed that the covalent interaction between CDs and porphyrins has improved the biocompatibility. The synthesized conjugates also inherit the pH sensitivity of the carbon dots, while the conjugation also decreases the hemolysis ratio making them a promising candidate for PDT. The incorporation of carbon dots into porphyrins improved their biocompatibility by reducing toxicity.

A ratiometric fluorescence sensor based on carbon quantum dots realized the quantitative and visual detection of Hg2

In this paper, based on the fluorescence of carbon quantum dots (CQDs) quenched by mercury ions (Hg²⁺ ) and the nonresponse of Hg²⁺ to rhodamine B fluorescence, a dual emission ratio fluorescence sensor was constructed to realize the quantitative detection of Hg²⁺ . Under excitation at 365 nm, the fluorescence spectrum showed double emission peaks at 437 nm and 590 nm, corresponding to the fluorescence emissions of CQDs and rhodamine B, respectively. This method quantitatively detected Hg²⁺ based on the linear relationship between the ratio of the intensities of the two emission peaks F₄₃₇ /F₅₉₀ and the concentration of Hg²⁺ . The detection range was 10-70 nM, and the limit of detection (S/N = 3) was 3.3 nM. In addition, this method could also realize the qualitative and semiquantitative detection of Hg²⁺ according to the fluorescence colour change of the probe under ultraviolet light. After various evaluations, the method could be successfully applied to the quantitative and visual detection of Hg²⁺ in tap water, and demonstrated excellent selectivity, anti-interference performance, and repeatability of the method.

N,Cl-Codoped Carbon Dots from Impatiens balsamina L. Stems and a Deep Eutectic Solvent and Their Applications for Gram-Positive Bacteria Identification, Antibacterial Activity, Cell Imaging, and ClO- Sensing

In this study, we first synthesized metal-free N,Cl-doped carbon dots (N,Cl-CDs) using Impatiens balsamina L. stems as green precursors in a deep eutectic solvent (DES). The obtained N,Cl-CDs were characterized through transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, fluorescence (FL) spectroscopy, and ultraviolet (UV) spectroscopy. In addition to the common features of carbon dots (CDs), such as high light stability, small size, low toxicity, good aqueous solubility, and favorable biocompatibility, these N,Cl-CDs exhibited excellent recognition and selectivity for Gram-positive bacteria by doping with N and Cl elements using DES. The N,Cl-CDs with positive charge cannot only differentiate Gram-positive bacteria by selective fluorescence imaging but also have antibacterial effects on Gram-positive bacteria. Through potential, ROS, and morphological analyses of bacteria before and after treatment with N,Cl-CDs, the antibacterial mechanisms of bacteriostasis, Enterococcus faecium, Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Salmonella were explored. In addition, N,Cl-CDs demonstrated low cytotoxicity and good cell imaging ability in cancer and normal cells. Moreover, they can be used as a fluorescence sensor for the detection of ClO- with a detection range from 100 nM to 40 μM and a limit of detection (LOD) of 30 nM. In summary, the prepared N,Cl-CDs could be applied as environmentally friendly Gram-positive bacterial identification and antibacterial agents. Additionally, their cell imaging and ClO- detection abilities were outstanding.

Hit Multiple Targets with One Arrow: Pb2+ and ClO- Detection by Edge Functionalized Graphene Quantum Dots and Their Applications in Living Cells

Recently, multimodal detection of analytes through a single nanoprobe has become an eminent approach for researchers. Herein a fluorescent nanoprobe, functionalized-GQD (F-GQD), has been designed through edge functionalization of graphene quantum dots (GQDs) by 2,6-diaminopyridine molecules. The fluorescence of F-GQD is quite sensitive to medium pH, making it a suitable pH sensor within the pH range 2-6. Interestingly, F-GQD shows dual sensing of Pb²⁺ and ClO^- by entirely different pathways; Pb²⁺ exhibits fluorescence turn-on performance while ClO^- triggers turn-off fluorescence quenching. The fluorescence enhancement may originate from the Pb²⁺-induced aggregation of the nanodots. The limit of detection (LOD) was also impressive, 1.2 μM and 12.6 nM for Pb²⁺ and ClO^-, respectively. The detailed mechanistic investigations reveal that both dynamic and static quenching effects operate together in the F-GQD-ClO^- system. The dynamic quenching was attributed to the energy migration from F-GQD to ClO^- through hydrogen bonding interaction (static quenching) between the amine group at the F-GQD surface and ClO^-. The F-GQD nanodot reveals excellent sensitivity toward the detection of ClO^- in real samples. Moreover, the F-GQDs also serve as multicolor fluorescent probes for cell imaging; the probe can easily penetrate the cell membrane and successfully detect intracellular ClO^-.

State of the Art and Perspectives on the Biofunctionalization of Fluorescent Metal Nanoclusters and Carbon Quantum Dots for Targeted Imaging and Drug Delivery

The interface of nanobio science and cancer nanomedicine is one of the most important current frontiers in research, being full of opportunities and challenges. Ultrasmall fluorescent metal nanoclusters (MNCs) and carbon quantum dots (CQDs) have emerged as promising fluorescent nanomaterials due to their unique physicochemical and optical properties, facile surface functionalization, good photostability, biocompatibility, and aqueous dispersity. These characteristics make them advantageous over conventional fluorophores such as organic dye molecules and semiconductor quantum dots (QDs) for the detection, diagnosis, and treatment of various diseases including cancer. Recently, researchers have focused on the biofunctionalization strategy of the MNCs and CQDs which can tailor their physicochemical and biological properties and, in turn, can empower these biofunctionalized nanoprobes for diverse applications including imaging, drug delivery, theranostics, and other biomedical applications. In this invited feature article, we first discuss some fundamental structural and physicochemical characteristics of the fluorescent biocompatible quantum-sized nanomaterials which have some outstanding features for the development of multiplexed imaging probes, delivery vehicles, and cancer nanomedicine. We then demonstrate the diverse surface engineering of these fluorescent nanomaterials with reactive target specific functional groups which can help to construct multifunctional nanoprobes with improved targeting capabilities having minimal toxicity. The promising future of the biofunctionalized fluorescent quantum-sized nanomaterials in the field of bioanalytical and biomedical research is elaborately demonstrated, showing selected recent works with relevant applications. This invited feature article finally ends with a short discussion of the current challenges and future prospects of the development of these bioconjugated/biofunctionalized nanomaterials to provide insight into this burgeoning field of MNC- and CQD-based diagnostics and therapeutic applications.

Enhancing Light Absorption and Prolonging Charge Separation in Carbon Quantum Dots via Cl-Doping for Visible-Light-Driven Photocharge-Transfer Reactions

Limited light absorption beyond the UV region and rapid photocarrier recombination are critical impediments for the improved photocatalytic performance of carbon quantum dots (CQDs) under visible-light irradiation. Herein, we demonstrate single-step microwave-assisted syntheses of O-CQDs (typical CQDs terminated by carboxylic and hydroxyl functional groups) from a sucrose precursor and Cl-doped CQDs (Cl-CQDs) from a sucralose precursor in short reaction times and without using obligatory strong acids for Cl doping. The doping of Cl into the CQDs is observed to widen the absorption range and facilitate an enhanced separation of photoexcited charge carriers, which is confirmed by the results of optical absorption, photothermal response, and pump-probe ultrafast transient absorption spectroscopy measurements of the O-CQDs and Cl-CQDs. The photoexcited charge carriers with their longer lifetimes in Cl-CQDs enabled the quick degradation of methylene blue dye, rapid conversion of Ag⁺ ions to metallic Ag nanoparticles on the CQD surfaces, and reduction of GO to a well-dispersed rGO through the photoelectron transfer reactions under visible-light irradiation. The facile Cl doping strategy, hybridization of Ag nanoparticles or rGO to CQDs, and the elevated charge separation mechanism would open up new avenues in designing CQD-based materials for futuristic applications.

Surface chemistry in calcium capped carbon quantum dots

Colloidal carbon quantum dots (C-dots) have attracted a lot of attention because of their excellent optical properties for various types of applications. Due to the complicated structure of C-dots, the photoluminescence (PL) mechanism of C-dots is still unclear. In particular, it is still a big challenge to understand well the surface chemistry of C-dots. In this work, we used a vacuum-heating approach to produce high-quality C-dots. With different purification procedures, the surface chemistry of C-dots can be well-controlled. Removal of Ca²⁺ by Na₂CO₃ led to the disappearance of the absorption at 405 nm and a decrease of the quantum yield. In addition, the Na₂CO₃ treated C-dots exhibited an excitation-dependent PL behavior. These results confirmed that Ca²⁺ can interact with the surface functional group of C[double bond, length as m-dash]O of the C-dots, forming a stable structure surrounding the C-dot core, which contributed to a high quantum yield (QY) of 65%, excitation-independent PL behavior and absorption at 405 nm. Furthermore, the PL of the C-dots is strongly dependent on the pH, indicating that the Ca²⁺ capped C-dots could be used as pH indicators. Our finding provides clear evidence for the surface-chemistry dependent PL behavior of C-dots.

Photoluminescence with an unusual open-loop and rigid delocalized conjugated structure in quantum dots

It is well known that almost all photoluminescent molecules are aromatic or heterocyclic ring compounds for bioimaging analysis. A question remains as to whether a breakthrough can be achieved regarding a novel photoluminescent molecule without a ring structure, and in a what manner. In this study, we explored the photoelectric conversion and structure of photoluminescent compounds, and constructed an intra-molecular coupling positive-negative-junction (PNJ) with an open-loop and rigid Π₅⁶ delocalized conjugated structure of the coupling p-π conjugate system. This was performed to enable strong absorption of the R/tail-end band for the high probability of an n → π*/n → σ* electron transition for photoluminescence production. Subsequently, the Π₅⁶ structure was formed in a short-chain aliphatic molecule as a hydrolytic product of citric acid and urea, and computational methodology was employed to estimate the feasibility of the molecule photoluminescence. Finally, a quantum dot material was fabricated from the aliphatic molecule, the optical properties of the quantum dots were investigated, and the biocompatibility and bioimaging ability of quantum dots were assessed. This work presents not only a theoretical exploration but also practical application of a new strategy to obtain molecules, compounds, and materials with bioimaging.

The Photodynamic Anti-Tumor Effects of New PPa-CDs Conjugate with pH Sensitivity and Improved Biocompatibility

BACKGROUND

Photodynamic therapy has been increasingly used to cope with the alarming problem of cancer. Porphyrins and its derivatives are widely used as potent photosensitizers (PS) for PDT. However, hydrophobicity of porphyrins poses a challenge for their use in clinics, while most of the carbon dots (CDs) are known for good biocompatibility, solubility, and pH sensitivity.

OBJECTIVE

To improve the properties/biocompatibility of the pyropheophorbide-α for PDT.

METHODS

PPa-CD conjugate was synthesized through covalent interaction using amide condensation. The structure of synthesized conjugate was confirmed by TEM, 1HNMR, and FTIR. The absorption and emission spectra were studied. In vitro, cytotoxicity of the conjugate was examined in the Human esophageal cancer cell line (Eca-109).

RESULTS

The results showed that the fluorescence of the drug was increased from its precursor. CD based conjugate could generate ROS as well as enhanced the biocompatibility by decreasing the cytotoxicity. The conjugated drug also showed pH sensitivity in different solutions.

CONCLUSION

The dark toxicity, as well as hemocompatibility, were improved.

Kilogram-Scale Synthesis and Functionalization of Carbon Dots for Superior Electrochemical Potassium Storage

Carbon dot is a type of carbon material with an ultrasmall size of less than 10 nm for all three dimensions, which has attracted more and more attention due to its useful merits. Unfortunately, the complicated synthesis method and low yield largely limit its wide large-scale application. Herein, an inexpensive and high-efficiency aldol condensation method under ambient temperature and pressure was proposed for the large-scale synthesis of CDs, which can obtain products with 1.083 kg in 2 h and realize the functionalization of carbon dots doped with nitrogen (NCDs) and sulfur/nitrogen doubly (NSCDs), and then the mechanism and structure of CDs formation were explained. Moreover, utilizing the feature of controllable assembly of carbon dots, and combined with theoretical calculations, we have designed functionalized 1D carbon fibers (CF) to construct high-performance potassium storage anode materials through the assembly of carbon dots induced by a Zn compound. Benefitting from the microstructure and surface functional groups derived from CDs, the N-doped CF (NCF700) exhibits superior electrochemical energy storage performance for potassium ion batteries (PIBs). This study provides a low-cost and high-yield method to produce CDs and promotes the practical application of CDs in electrochemical energy storage.

Carbon Nanomaterials: Synthesis, Functionalization and Sensing Applications

Recent advances in nanomaterial design and synthesis has resulted in robust sensing systems that display superior analytical performance. The use of nanomaterials within sensors has accelerated new routes and opportunities for the detection of analytes or target molecules. Among others, carbon-based sensors have reported biocompatibility, better sensitivity, better selectivity and lower limits of detection to reveal a wide range of organic and inorganic molecules. Carbon nanomaterials are among the most extensively studied materials because of their unique properties spanning from the high specific surface area, high carrier mobility, high electrical conductivity, flexibility, and optical transparency fostering their use in sensing applications. In this paper, a comprehensive review has been made to cover recent developments in the field of carbon-based nanomaterials for sensing applications. The review describes nanomaterials like fullerenes, carbon onions, carbon quantum dots, nanodiamonds, carbon nanotubes, and graphene. Synthesis of these nanostructures has been discussed along with their functionalization methods. The recent application of all these nanomaterials in sensing applications has been highlighted for the principal applicative field and the future prospects and possibilities have been outlined.

On-off-on nanosensors of carbon quantum dots derived from coal tar pitch for the detection of Cu2+, Fe3+, and L-ascorbic acid

Novel nitrogen-doped carbon quantum dots (N-CQDs) were synthesized by a chemical oxidation method using medium-low temperature coal tar pitch as the raw material. Such quantum dots were developed as a highly sensitive fluorescent "on-off-on" switch sensor for the selective and simultaneous sensing of Cu²⁺ and Fe³⁺. The as-prepared N-CQDs, which emit blue light, were characterized by TEM images, FT-IR spectra, Raman spectroscopy, XPS analysis, fluorescence spectra, and UV-vis absorption spectra. The results showed that the N-CQDs exhibit outstanding optical properties and high optical stability within the pH range of 4-10, with a quantum yield of approximately 7%. Additionally, the material performed as an "on-off" sensor which can be dramatically extinguished by Cu²⁺ and Fe³⁺. A linear relationship between Cu²⁺ and Fe³⁺ ion concentration and fluorescence intensity was observed in the range from 0 to 50 μM. The limits of detection of the fluorescent sensor toward Cu²⁺ and Fe³⁺ were 0.16 μM and 0.173 μM, respectively. The Fe³⁺-quenched N-CQDs were restored after adding L-ascorbic acid, due to the redox reaction between Fe³⁺ and L-ascorbic acid, which resulted in the detachment of Fe³⁺ from the surface of the N-CQDs. The linear range for the detection of L-ascorbic acid was 0-28 μM. Therefore, the amount of L-ascorbic acid can be measured by using the sensing system consisting of Fe³⁺ and N-CQDs. In consequence, N-CQDs are considered an important material for the detection of Cu²⁺ and Fe³⁺ in water samples or L-ascorbic acid in drugs.

Nitrogen and fluorine co-doped green fluorescence carbon dots as a label-free probe for determination of cytochrome c in serum and temperature sensing

As an important biomarker, the analysis of cytochrome c (Cyt c) plays a crucial role in cell-apoptosis or even cancer diagnosis. This work develops a label-free probe for Cyt c using the nitrogen and fluorine co-doped carbon dots (N, F-CDs) which were facile prepared through solvothermal method with 3, 4-difluorophenylhydrazine as precursor. The N, F-CDs have an average diameter of 3.4 nm, and can form a quite stable colloidal solution. The N, F-CDs show bright yellow-green fluorescence, excitation/emission wavelengths 475/530 nm, and a relatively high fluorescence quantum yield of 16.9%. Interestingly, the N, F-CDs indicate a linear and reversible variation of emission intensity with a sensitivity of -1.11% per ℃ in the temperature range from 25 to 60 ℃. Inner filter effect (IFE) between N, F-CDs and Cyt c turns the fluorescence of N, F-CDs from "on" to "off". The sensor possesses the excellent anti-interference ability towards the main components of plasma. Under optimum conditions, there is a linear relationship between fluorescence intensity function (F₀-F) and the concentration of Cyt c in the range of 0.5-25 μΜ with a limit of detection (LOD) (S/N = 3) of 0.25 μM. Finally, the developed method has been successfully used to detect Cyt c in human serum sample with satisfactory recoveries in a range of 93.14-110.40%.

Actin-binding carbon dots selectively target glioblastoma cells while sparing normal cells

Curcumin, a pleiotropic signalling molecule from Curcuma longa, is reported to be effective against multiple cancers. Despite its promising effect, curcumin had failed in clinical trials due to its low aqueous solubility, stability and poor bioavailability. While several approaches are being attempted to overcome the limitations, the improved solubility observed with curcumin-derived carbon dots appeared to be a strategy worth exploring. To assess if the carbon dots possess bio-activity similar to curcumin, we synthesized carbon dots (CurCD) from curcumin and ethylenediamine. Unlike curcumin, the as-synthesized curcumin carbon dots exhibited excellent solubility, excitation-dependent emission and photostability. The anti-cancer activity evaluated with glioblastoma cells using the well-established in vitro models indicated its comparable/enhanced activity over curcumin. Besides, the selective affinity of CurCD to the actin filament, indicated it's prospective to serve as a marker of actin filaments. In addition, the non-toxic effects observed in normal cells and fish embryos indicated CurCD was more biocompatible than curcumin. While this work reveals the superior properties of CurCD over curcumin, it provides a new approach to explore other plant derived molecules with similar limitations like curcumin.

Preparation of species-specific monoclonal antibody and development of fluorescence immunoassay based on fluorescence resonance energy transfer of carbon dots for accurate and sensitive detection of Alicyclobacillus acidoterrestris in apple juice

The growth and metabolism of Alicyclobacillus acidoterrestris can lead to the spoilage of commercial fruit juice. Existing methods have some drawbacks such as complex sample pretreatment, skilled technician requirement, reduced sensitivity and specificity. Herein, a novel fluorescence immunoassay was developed using a monoclonal antibody (mAb) against A. acidoterrestris as the sensing element and carbon dots (CDs) as the signal response unit. The CDs can be quenched via fluorescence resonance energy transfer (FRET) by the oxidization product of p-phenylenediamine (PPD), a chromogenic substrate of horseradish peroxidase (HRP). This approach showed enhanced accuracy and sensitivity with relatively low limit of detection (LOD) of 6.16 × 10² CFU mL^-1. Moreover, apple juice contaminated with 1 CFU mL^-1 of A. acidoterrestris can be identified after 24 h enrichment. This fluorescence immunoassay could serve as a powerful tool for laboratory identification and on-site inspection of A. acidoterrestris, reducing the adverse effect on the quality of fruit juice.

Deep eutectic solvent assisted synthesis of carbon dots using Sophora flavescens Aiton modified with polyethyleneimine: Application in myricetin sensing and cell imaging

Here, an efficient method for synthesizing carbon dots (CDs) using a deep eutectic solvent (DES) was developed. To investigate the influence of different DESs on the quantum yield of CDs, different hydrogen-bonding acceptors (HBAs) and hydrogen-bonding donors (HBDs) were used to synthesize the DES and prepare CDs. Using Sophora flavescens Aiton as precursor, CDs were prepared using choline chloride (ChCl)/urea based DES as reaction media and doping agent in the presence of water. The CDs showed strong blue fluorescence and were further modified with polyethyleneimine (CDs@PEI). The fluorescence intensity of CDs@PEI was selectively quenched by myricetin with a limit of detection (LOD) of 10 nM. Furthermore, CDs@PEI was used to analyze myricetin in the extracts that were fluorescent by DES with satisfactory performance of Abelmoschus manihot (Linn.) Medicus flowers, vine teas and blueberries. Finally, the bio-imaging application of CDs@PEI was tested and the results confirmed its potential application in bio-imaging.

Optical Sensing and Imaging of pH Values: Spectroscopies, Materials, and Applications

This is the first comprehensive review on methods and materials for use in optical sensing of pH values and on applications of such sensors. The Review starts with an introduction that contains subsections on the definition of the pH value, a brief look back on optical methods for sensing of pH, on the effects of ionic strength on pH values and pKa values, on the selectivity, sensitivity, precision, dynamic ranges, and temperature dependence of such sensors. Commonly used optical sensing schemes are covered in a next main chapter, with subsections on methods based on absorptiometry, reflectometry, luminescence, refractive index, surface plasmon resonance, photonic crystals, turbidity, mechanical displacement, interferometry, and solvatochromism. This is followed by sections on absorptiometric and luminescent molecular probes for use pH in sensors. Further large sections cover polymeric hosts and supports, and methods for immobilization of indicator dyes. Further and more specific sections summarize the state of the art in materials with dual functionality (indicator and host), nanomaterials, sensors based on upconversion and 2-photon absorption, multiparameter sensors, imaging, and sensors for extreme pH values. A chapter on the many sensing formats has subsections on planar, fiber optic, evanescent wave, refractive index, surface plasmon resonance and holography based sensor designs, and on distributed sensing. Another section summarizes selected applications in areas, such as medicine, biology, oceanography, bioprocess monitoring, corrosion studies, on the use of pH sensors as transducers in biosensors and chemical sensors, and their integration into flow-injection analyzers, microfluidic devices, and lab-on-a-chip systems. An extra section is devoted to current challenges, with subsections on challenges of general nature and those of specific nature. A concluding section gives an outlook on potential future trends and perspectives.

Sensitive fluorescence detection of atorvastatin by doped carbon dots synthesized in deep eutectic media

Fluorescence properties of nanoparticles can be influenced by solvent. In this work, carbon dots (CDs) were synthesized in deep eutectic solvent by microwave assisted method. Quantum yield (QY) and size of the synthesized CDs were 41.3% and 2 nm, respectively. N/Cl -doped CDs had excellent sensitivity and selectivity for atorvastatin and detection limit was 0.8 nM. Simple and low-cost synthesis method and excellent sensitivity are advantages of this detection method for atorvastatin. The as-synthesized N/Cl-doped CDs were successfully used to determine atorvastatin in blood serum.

Label-free chlorine and nitrogen-doped fluorescent carbon dots for target imaging of lysosomes in living cells

Lysosomes with a single-layered membrane structure are mainly involved in the scavenging of foreign substances and play an important role in maintaining normal physiological functions of living cells. In this work, near-neutrally charged fluorescent carbon dots (CDs) were prepared with lipophilicity through a facile one-pot hydrothermal carbonization of chloranil and triethylenetetramine at 160 °C for 3 h. The as-obtained CDs are proved to have good photostability, low cost, and excellent biocompatibility. Importantly, the as-prepared CDs with high quantum yield of 30.8% show excitation-dependent emission with great stability, and thus, they can be well used for the long-term target imaging of lysosomes in living cells without further modification. Meanwhile, the CDs can quickly enter into the lysosomes within 30 min, and the green fluorescence (FL) of CDs reaches the plateau when incubated for 60 min. By comparing the fluorescent intensity, the information about distribution and amount of lysosomes in different cells can be obtained. The proposed CD-based strategy demonstrates great promise for label-free target imaging of lysosomes in living cells. Graphical abstract The near-neutral carbon dots (CDs) with lipophilicity are used as label-free fluorescent nanoprobes for the long-term imaging of lysosomes in living cells.

A dual-functional probe for sensing pH change and ratiometric detection of Cu2

A series of benzothiazole-based compounds were synthesized and characterized. Among them, probe Z showed significant dual-functional performance which was capable of sensing pH change and Cu²⁺. Probe Z displayed fluorescent turn-on under alkaline conditions due to deprotonation of the hydroxyl group along with the obviously color change from colorless to mint green. Interestingly, it further achieved in ratiometric detection of Cu²⁺ through absorbance or fluorescence signals in strong alkaline condition. The limit of detection was calculated correspondingly as 0.37 μM and 1.35 μM, respectively. Especially, the combination of the XNOR and INHIBIT logic gates could be used to confirm that one medium was in neutrality or alkalinity condition. Moreover, Z was successfully used in real water samples and test paper for fast identification of Cu²⁺, respectively.

Design of long-wavelength emission carbon dots for hypochlorous detection and cellular imaging

A facile strategy for the preparation of nitrogen and phosphorus co-doped carbon dots (N, P-CDs) with long-wavelength emission is attractively proposed in one-pot hydrothermal strategy. The resulting N, P-CDs hold exceptional optical features and display excitation wavelength-independent properties with the emission wavelength at 590 nm, which enable it with the satisfactory relative quantum yield (QY) of 15.6% in long-wavelength region. In addition, the proposed N, P-CDs demonstrates specific selectivity towards ClO^- over other competitive reactive oxygen species and exhibits rapid fluorescence response time to ClO^-. Moreover, the N, P-CDs exhibits low-cytotoxicity and excellent cell membrane permeability for recognizing ClO^- in SMMC-7721 cells, which demonstrates their enormous potential in biological system.

A review: recent advances in preparations and applications of heteroatom-doped carbon quantum dots

Carbon quantum dots (CQDs) are widely used in optoelectronic catalysis, biological imaging, and ion probes owing to their low toxicity, stable photoluminescence, and ease of chemical modification. However, the low fluorescence yield and monochromatic fluorescence of CQDs limit their practical applications. This review summarizes the commonly used approaches for improving the fluorescence efficiency of CQDs doped with non-metallic (heteroatom) elements. Herein, three types of heteroatom-doped CQDs have been investigated: (1) CQDs doped with a single heteroatom; (2) CQDs doped with two heteroatoms; and (3) CQDs doped with three heteroatoms. The limitations and future perspectives of doped CQDs from the viewpoint of producing CQDs for specific applications, especially for bioimaging and light emitting diodes, have also been discussed herein.

One Stone, Two Birds: pH- and Temperature-Sensitive Nitrogen-Doped Carbon Dots for Multiple Anticounterfeiting and Multiple Cell Imaging

Carbon dots (CDs) as new fluorescent materials with excellent fluorescence properties have shown enormous potential applications, especially in anticounterfeiting and cell imaging. Herein, nitrogen-doped CDs (NCDs) with excellent biocompatibility were prepared by a simple thermal sintering method. An extremely large red shift (∼130 nm) of the emission peak was observed when the excitation wavelength changes from 355 to 550 nm, indicating that NCDs are excellent fluorescent labeling materials for multiple cell imaging. On the other hand, NCDs showed obvious changes of emission intensity and peak position when the temperature increased from 223 to 323 K and the pH values changed from 1 to 13, respectively, which has been demonstrated by the "horse" pattern printed with NCD water-soluble fluorescent inks. The nontoxic NCDs dispersed in a multiple matrix are highly sensitive to excitation wavelength, temperature, and pH, indicating their great potential application in multiple anticounterfeiting and multiple cell imaging.

Atomically dispersed Eu(III) sites in natural deep eutectic solvents based fluorescent probe efficient identification of Fe3+ and Cu2+ in wastewater

Heavy metal ions in wastewater have brought serious environmental pollution. To improve the detection efficiency, it is important to find useful fluorescent probes. The emerging green natural deep eutectic solvents (NADESs) offer attractive option for "green" detection for its good biocompatibility, easy preparation, and high sensitivity. In this study, a multi-functionalized fluorescent probe with atomically dispersed EuCl₃·6H₂O in amino acid-based NADESs (l-Glutamic acid/Glycerol, l-Glu/Gly) was synthesized by metal-ligand coordination interactions with a mass ratio of 15:1. Combined with the NADESs and rare earth metal, the l-Glu/Gly/EuCl₃·6H₂O could form the amino site and Eu²⁺ site fluorescent centers. Under the excitation wavelength of 370 nm, it had dual emission peaks at 425 nm and 470 nm with efficient resonance energy transfer. The stable optoelectronic properties of l-Glu/Gly/EuCl₃·6H₂O under external factors, such as mass ratio (13,1 to 18:1), temperature (30-50 °C), pH (1 to 14) and storage time ( >42 days), approved l-Glu/Gly/EuCl₃·6H₂O an excellent fluorescence probe. In the application of water-quality monitoring, Fe³⁺ and Cu²⁺ could react with l-Glu/Gly/EuCl₃·6H₂O in different reactive patterns. The blue fluorescence was quenched by Fe³⁺ and enhanced by Cu²⁺, thus metal ions could be distinguished with high sensitivity. The detective process was determined and the fluorescent mechanism was also proposed. l-Glu/Gly/EuCl₃·6H₂O fluorescent probe was demonstrated to be an efficient fluorescent probe for metal detection avoiding the hydrothermal process, and the cumbersome of ilter, dialysis, freeze drying.

One-step synthesis of yellow-emissive carbon dots with a large Stokes shift and their application in fluorimetric imaging of intracellular pH

A new nanoprobe based on yellow-emissive carbon dots (Y-CDs) was developed for sensing full-range intracellular pH values. By using o-phenylenediamine as the raw material, Y-CDs with a quantum yield of 31% were prepared through a one-pot solvothermal carbonization method. The Y-CDs exhibited a distinctive fluorescence emission peak at 570 nm with excitation at 450 nm, showing a very large Stokes shift (120 nm). Notably, the nanoprobe revealed a linear relationship between fluorescence intensity and pH value within the range of pH 4.0 to 8.2, exhibiting the ability of this probe to monitor full-range intracellular pH variations. In addition, the nanosensor possessed excellent photostability and fluorescence reversibility in pH measurements and showed excellent selective detection of the influences of other biological species. The CD-based nanoprobe was successfully used to perform quantitative fluorescence imaging of intracellular pH variation, demonstrating its promise for application in cellular systems.

CdSe quantum dots capped with a deep eutectic solvent as a fluorescent probe for copper(II) determination in various drinks

The present study shows that copper(II) ions can be determined with a new fluorescent probe that is based on the use of CdSe quantum dots capped with deep eutectic solvent (DES-CdSe QDs). The capped QDs were prepared in aqueous phase by a one-step procedure under ambient atmosphere using selenium dioxide as a stable precursor for selenium, and ascorbic acid as non-toxic reducing agent. The deep eutectic solvent is composed of choline chloride and thioglycolic acid and acts as stabilizing and functionalizing agent. The fluorescent probe undergoes an increase in the fluorescence intensity (with excitation/emission wavelengths at 380/560 nm) in the presence of Cu(II). Other ions display no significant effect on fluorescence. The effects of sample pH value, concentration of buffer, and volume of QDs solution were optimized by response surface methodology using a Box-Behnken statistical design. Under the optimal conditions, the response of the probe is linear in the 10-600 nM Cu(II) concentration range, with a 5.3 nM limit of detection. This is lower than the allowable maximum Cu(II) concentration in drinking water. The relative standard deviation of the method for five replicate measurements of Cu(II) at a 100 nM concentration level is 2.0%. The probe was successfully applied to the determination of Cu(II) in various drinks. Graphical abstractSchematic representation of a fluorometric method for the determination of Cu(II) at nanomolar concentration levels. The fluorescent system consists of deep eutectic solvent-capped cadmium selenide quantum dots (DES-CdSe QDs). Fluorescence is strongly enhanced by copper(II).

A composite prepared from MnO2 nanosheets and a deep eutectic solvent as an oxidase mimic for the colorimetric determination of DNA

A composite was fabricated from deep eutectic solvent and MnO₂ nanosheets (DES/MnO₂) and is shown to be a viable oxidase mimic. The property, morphology and composition of DES/MnO₂ was characterized. DES/MnO₂ displays oxidase-like activity and can oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to form a blue product (oxTMB) with an absorption maximum at 652 nm. Due to the presence of the DES, the polyanionic and negatively charged DNA is easily adsorbed on the surface of the composite by hydrogen bonding and electrostatic interactions. This leads to the inhibition of the oxidase-mimicking activity of DES/MnO₂. This finding was used to design a colorimetric method for the determination of DNA. The assay work in the 10-100 μg mL^-1 DNA concentration range and has a detection limit of 0.37 μg mL^-1. The inhibiting mechanism was further studied by zeta potential measurements, dynamic light scattering and transmission electron microscopy. The selectivity study shows the DES/MnO₂-TMB system to be highly selective for DNA when compared with many proteins, carbohydrates, salts and amino acid. RNA, on the other hand, interferes. The real sample analysis result illustrates that the new method can be used for the detection of DNA in bovine whole blood. Graphical abstractA novel oxidase mimic based on deep eutectic solvent-functionalized MnO₂ nanosheets was synthesized, which can directly catalyze oxidation of 3,3',5,5'-tetramethylbenzidine (TMB, colorless) to oxTMB (blue). A sensitive and convenient colorimetric strategy for visual detection of DNA was established through DES/MnO₂-TMB sensing system.

Deep eutectic solvents-derived carbon dots for detection of mercury (II), photocatalytic antifungal activity and fluorescent labeling for C. albicans

A novel nitrogen and chloride co-doped carbon dots (N/Cl-CDs) based choline chloride-urea deep eutectic solvents (DESs) were synthesized by one-step hydrothermal method with high quantum yield of 37% and excellent photoluminescent properties. This N/Cl-CDs fluorescent probe had been successfully applied to sensitively and selectively detect the concentration of Hg²⁺ with a linear range of 0.2-40 μM and a detection limit of 0.05 μM. Moreover, the N/Cl-CDs displayed a strong photocatalytic antifungal activity against C. albicans and their photoinduced antifungal functions were evaluated under conditions of varying other experimental parameters. The antifungal efficiency of N/Cl-CDs (7 mg/mL) against C. albicans is upon 100% when extending the visible light irradiation time to 80 min. In addition, the excellent luminescence properties of N/Cl-CDs can also label C. albicans and displayed multicolour fluorescence imaging at different excitation wavelengths. Based on their functions of fluorescence probe, antifungal and fluorescence imaging, N/Cl-CDs would provide potentials for a wide range of applications in the detection and microbe in the near future.

Magnetic carbon nanotube modified with polymeric deep eutectic solvent for the solid phase extraction of bovine serum albumin

This article described the fabrication of novel magnetic carbon nanotube modified with polymeric deep eutectic solvent (M-CNT@PDES) and its application as extractant for the magnetic solid phase extraction (MSPE) of bovine serum albumin (BSA). The physicochemical properties and morphology of M-CNT@PDES were characterized by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), thermo-gravimetric analysis (TGA), zeta potentials, fourier transform infrared spectrometry (FT-IR) and transmission electron microscope (TEM). Afterwards, several parameters such as pH value, initial concentration of BSA, extraction time, ionic strength and extraction temperature were optimized. The results indicated that the modification of PDES significantly improved the extraction performance for BSA, and the maximum extraction capacity was 225.15 mg/g under the optimized conditions. In addition, 0.20 mol/L NaCl-PBS solution was chosen as the appropriate eluent, and favourable elution rate (81.22%) was obtained. Circular dichroism spectroscopy (CD) indicated that the secondary structure of BSA has not changed during extraction and elution. The regenerative experiment and application in real calf serum confirmed the outstanding durability and practical application ability of M-CNT@PDES. All of above verified that the proposed M-CNT@PDES coupled with MSPE method has great application potential for the pre-concentration of biomolecules.