Polyamine-Functionalized Carbon Quantum Dots as Fluorescent Probes for Selective and Sensitive Detection of Copper Ions

Enhanced chemiluminescence by carbon dots for rapid detection of bisphenol A and nitrite

Herein, a novel chemiluminescence (CL) sensor was successfully developed based on chlorine doped carbon dots (Cl/CDs) for the rapid determination of bisphenol A (BPA) and nitrite. The Cl/CDs were synthesized through a hydrothermal method, using ascorbic acid as the precursor and hydrochloric acid as the dopant. It was found that Cl/CDs significantly enhanced the CL intensity of the acid-KMnO4 system, while BPA and nitrite quenched the CL intensity of the Cl/CDs-sensitized acid-KMnO4 system. Under optimal conditions, BPA exhibited a linear detection range of 0.05-10 μM, with limits of detection (LOD) and quantification (LOQ) of 0.86 nM and 2.8 nM, respectively. Nitrite showed a linear detection range of 0.7-100 μM, with LOD and LOQ of 22.5 nM and 75 nM, respectively. The CL sensor was successfully use to determine BPA in water samples and nitrite in pickles, ham and celery, with spike recovery rates of 96.3 %-104.8 % and 96.0 %-104.9 %, respectively.

Carbon quantum dots for the diagnosis and treatment of ophthalmic diseases

Carbon quantum dots (CQDs), an emerging nanomaterial, are gaining attention in ophthalmological applications due to their distinctive physical, chemical, and biological characteristics. For example, their inherent fluorescent capabilities offer a novel and promising alternative to conventional fluorescent dyes for ocular disease diagnostics. Furthermore, because of the excellent biocompatibility and minimal cytotoxicity, CQDs are well-suited for therapeutic applications. In addition, functionalized CQDs can effectively deliver drugs to the posterior part of the eyeball to inhibit neovascularization. This review details the use of CQDs in the management of ophthalmic diseases, including various retinal diseases, and ocular infections. While still in its initial phases within ophthalmology, the significant potential of CQDs for diagnosing and treating eye conditions is evident.

Synthesis of novel polyethyleneimine-capped silver nanoclusters exhibiting ultraviolet-A fluorescence and their application in multiple sensing

Cupric ions (Cu2+), pyrophosphate (PPi), and alkaline phosphatase (ALP) are involved in a variety of biochemical processes such as DNA replication, cellular metabolism and play an important role in human growth and development. It is of great significance to establish a method for the sensitive detection of Cu2+, PPi and ALP. In this work, polyethyleneimine-capped silver nanoclusters (PEI-AgNCs) were successfully synthesized by a one-pot method using hydrazine sulfate as reductant, exhibiting a unique strong fluorescence emission in the near-ultraviolet region at ∼339 nm. Since the fluorescence of PEI-AgNCs can be quenched by Cu2+ through inner filtering effect (IFE), then recovered by competitive binding of pyrophosphate and Cu2+, and later weakened again by catalytic hydrolysis of alkaline phosphatase, a sensitive and selective strategy based on the changes of fluorescence "ON" or "OFF" was established to detect Cu2+, PPi and ALP. The LODs of these three analytes were 36 nM, 0.2 μM, and 0.14 U L-1 at a S/N ratio of 3, respectively. A series of logic gate circuits for sensing cupric ions, pyrophosphate, and alkaline phosphatase were successfully constructed. The established methods have the potential for biosensing and environmental analysis and the specific UV-A fluorescence property of PEI-AgNCs may be helpful in photonic and optical areas.

Luminous blue carbon quantum dots employing Anisomeles indica (catmint) induce apoptotic signaling pathway in triple negative breast cancer (TNBC) cells

Herein, luminous blue carbon quantum dots (CDs) employing Anisomeles indica (Catmint) were reported with imaging, self-targeting, and therapeutic effects on triple-negative breast cancer (TNBC, MDA-MB-231) cells. The salient features of CDs generated from catmint are as follows: i) optical studies confirm CDs with excitation-dependent emission; ii) high-throughput characterization authenticates the formation of CDs with near-spherical shape with diameter ranging between 5 and 15 nm; iii) CDs induce cytotoxicity (3.22 ± 0.64 μg/ml) in triple-negative breast cancer (TNBC, MDA-MB-231) cells; iv) fluorescence microscopy demonstrates that CDs promote apoptosis by increasing reactive oxygen species (ROS) and decreasing mitochondrial membrane potential; v) CDs significantly up-regulate pro-apoptotic gene expression levels such as caspases-8/9/3. Finally, our work demonstrates that catmint-derived CDs are prospective nanotheranostics that augment cancer targeting and imaging.

A review on green synthesis, biological applications of carbon dots in the field of drug delivery, biosensors, and bioimaging

Since the beginning of nanoscience and nanotechnology, carbon dots (CDs) have been the foundational idea and have dominated the growth of the nano-field. CDs are an intriguing platform for utilization in biology, technology, catalysis, and other fields thanks to their numerous distinctive structural, physicochemical, and photochemical characteristics. Since several carbon dots have already been created, they have been assessed based on their synthesis process, and luminescence characteristics. Due to their biocompatibility, less toxic effects, and most significantly their fluorescent features in contrast to other carbon nanostructures, CDs have several benefits. This review focuses on the most recent advancements in the characterization, applications, and synthesis techniques used for CDs made from natural sources. It will also direct scientists in the creation of a synthesis technique for adjustable carbon dots that is more practical, effective, and environmentally benign. With low toxicity and low cost, CDs are meeting the new era's requirements for more selectivity and sensitivity in the detection and sensing of various things, such as biomaterial sensing, enzymes, chemical contamination, and temperature sensing. Its variety of properties, such as optical properties, chemiluminescence, and morphological analysis, make it a good option to use in bioimaging, drug delivery, biosensors, and cancer diagnosis.

Selective and sensitive CQD-based sensing platform for Cu2+ detection in Wilson's disease

Excessive Cu2+ intake can cause neurological disorders (e.g. Wilson's disease) and adversely affect the gastrointestinal, liver, and kidney organs. The presence of Cu2+ is strongly linked to the emergence and progression of Wilson's disease (WD), and accurately measuring the amount of copper is a crucial step in diagnosing WD at an early stage in a clinical setting. In this work, CQDs were fabricated through a facile technique as a novel fluorescence-based sensing platform for detecting Cu(II) in aqueous solutions, and in the serum samples of healthy and affected individuals by WD. The CQDs interact with Cu(II) ions to produce Turn-on and Turn-off states at nano-molar and micro-molar levels, respectively, with LODs of 0.001 µM and 1 µM. In fact, the Cu2+ ions can act like a bridge between two CQDs by which the charge and electron transfer between the CQDs may increase, possibly can have significant effects on the spectroscopic features of the CQDs. To the best of our knowledge, this is the first reported research that can detect Cu(II) at low levels using two different complexation states, with promising results in testing serum. The potential of the sensor to detect Cu(II) was tested on serum samples from healthy and affected individuals by WD, and compared to results obtained by ICP-OES. Astonishingly, the results showed an excellent correlation between the measured Cu(II) levels using the proposed technique and ICP-OES, indicating the high potential of the fluorimetric CQD-based probe for Cu(II) detection. The accuracy, sensitivity, selectivity, high precision, accuracy, and applicability of the probe toward Cu(II) ions make it a potential diagnostic tool for Wilson's disease in a clinical setting.

Analytical control of imatinib in bioanalytical samples using graphene quantum dots sensing

An analytical method for the determination of imatinib (IMA, the primary treatment for chronic myeloid leukemia), based on the fluorescence properties of graphene quantum dots (GQDs), is reported in this work. The method is addressed to the analytical control of IMA in biological and pharmaceutical samples, due to the present interest in the control of the doses of this anticancer drug, as well as the therapeutic monitoring. The whole method involves the use of a solid-phase extraction (SPE) procedure, followed by an evaporation step, for the treatment of biological samples. For that, tC18 sorbent cartridges were used. After the sample treatment, the solution containing the analyte was mixed with an aqueous solution of GQDs at pH 7.2, and the fluorescent quenching of GQDs was measured. IMA was determined in the 10-250 µg L-1 range, with a limit of detection of 21 µg L-1 and a precision of 1.5% as relative standard deviation, measured in terms of reproducibility. The recovery for biological samples was in the 84-113% range.

Ferrocene probe-assisted fluorescence quenching of PEI-carbon dots for NO detection and the logic gates based sensing of NO enabled by trimodal detection

Our research demonstrates the effectiveness of fluorescence quenching between polyethyleneimine functionalised carbon dots (PEI-CDs) and cyclodextrin encapsulated ferrocene for fluorogenic detection of nitric oxide (NO). We confirmed that ferrocene can be used as a NO probe by observing its ability to quench the fluorescence emitted from PEI-CDs, with NO concentrations ranging from 1 × 10-6 M to 5 × 10-4 M. The photoluminescence intensity (PL) of PEI-CDs decreased linearly, with a detection limit of 500 nM. Previous studies have shown that ferrocene is a selective probe for NO detection in biological systems by electrochemical and colorimetric methods. The addition of fluorogenic NO detection using ferrocene as a probe enables the development of a three-way sensor probe for NO. Furthermore, the triple mode NO detection (electrochemical, colorimetric, and fluorogenic) with ferrocene aids in processing sensing data in a controlled manner similar to Boolean logic operations. This work presents key findings on the mechanism of fluorescence quenching between ferrocene hyponitrite intermediate and PEI-CDs, the potential of using ferrocene for triple channel NO detection as a single molecular entity, and the application of logic gates for NO sensing.

Chitosan-initiated gold nanoparticles with enhanced fluorescence for unique Fe3+/PPi sensing and photothermal therapy

The design of surface ligands is crucial for ligand-protected gold nanoparticles (AuNPs). Herein, following the principle of green synthesis, environmentally friendly gold nanoparticles (AuNPs@His@CC, AuHC) were fabricated based on dual ligands of histidine and carboxylated chitosan. AuHC showed the advantages of low toxicity, good photoluminescent stability and ideal biocompatibility. Compared with single histidine-coated gold nanoclusters (AuNCs@His, AuH), AuHC presented enhanced fluorescence attributed to the addition of chitosan. The blue-emitting AuHC has a unique response to Fe3+ with detection limits as low as 9.51 nM. Interestingly, the quenched fluorescence of AuHC-Fe3+ system could be restored through the introduction of PPi with a detection limit of 10.6 μM. So an "on-off-on" fluorescence sensing platform was achieved. Apart from good optical properties and sensing, the designed AuHC demonstrated outstanding photothermal conversion efficiency (27.8 %), which made it ideal material for thermal ablation of tumor. To be specific, after laser irradiation (660 nm, 0.78 W cm-2, 10 min) of AuHC, the survival rate of HeLa cells as a tumor cell model decreased to 12.7 %, indicating that AuHC has a significant tumor inhibition effect in vitro. Besides, AuHC also could be a befitting candidate for overcoming drug-resistant tumor cells such as MCF-7/ADR cells. Notably, AuHC can markedly ablate solid tumors in 4T1 tumor-bearing mice after laser irradiation (660 nm, 0.78 W cm-2, 10 min). Hence this work provides insight into the design of multifunctional AuNPs platform for simultaneously integrating the ion sensing and photothermal therapy of cancer.

AIE fluorogen-based oxidase-like fluorescence nanozyme-integrated smartphone for monitoring the freshness authenticity of soy products

Food safety concerns about the authenticity of soy product freshness have increased due to high demand from public. Developing an accurate and convenient monitoring method for freshness authenticity is crucial for safeguarding food safety. From this motive, this study employed PtPd NPs to encapsulate tetraphenylethylene (TPE) for engineering an AIE-based fluorescent nanozyme (PtPd NPs@TPE) with oxidase-like activity, achieving the ratiometric fluorescence monitoring of putrescine (PUT) to judge the freshness authenticity of soy products. In this design, PUT acted as an antioxidant and inhibited the oxidation process of PtPd NPs@TPE to o-phenylenediamine (OPD), leading to the reduction of oxidative product 2,3-diaminophenothiazine (DAP) alone with the weaken of yellow fluorescence from DAP at 552 nm and bright of bule fluorescence from PtPd NPs@TPE at 442 nm. On this basis, a ratiometric fluorescence strategy integrated with smartphone-based sensor was developed for PUT with acceptable results to combat food freshness fraud of soy products.

Carbon Quantum Dots: Properties, Preparation, and Applications

Carbon quantum dots are a novel form of carbon material. They offer numerous benefits including particle size adjustability, light resistance, ease of functionalization, low toxicity, excellent biocompatibility, and high-water solubility, as well as their easy accessibility of raw materials. Carbon quantum dots have been widely used in various fields. The preparation methods employed are predominantly top-down methods such as arc discharge, laser ablation, electrochemical and chemical oxidation, as well as bottom-up methods such as templates, microwave, and hydrothermal techniques. This article provides an overview of the properties, preparation methods, raw materials for preparation, and the heteroatom doping of carbon quantum dots, and it summarizes the applications in related fields, such as optoelectronics, bioimaging, drug delivery, cancer therapy, sensors, and environmental remediation. Finally, currently encountered issues of carbon quantum dots are presented. The latest research progress in synthesis and application, as well as the challenges outlined in this review, can help and encourage future research on carbon quantum dots.

A self-powered photodetector through facile processing using polyethyleneimine/carbon quantum dots for highly sensitive UVC detection

Ultraviolet C (UVC) photodetectors have garnered considerable attention recently because the detection of UVC is critical for preventing skin damage in humans, monitoring environmental conditions, detecting power aging in facilities, and military applications. As UVC detectors are "solar-blind", they encounter less interference than other environmental signals, resulting in low disturbance levels. This study employed a natural precursor (glucose) and a one-step ultrasonic reaction procedure to prepare carbon quantum dots (CQDs), which served as a convenient and environmentally friendly material to combine with polyethyleneimine (PEI). The prepared materials were used to develop a self-powered, high-performance UVC photodetector. The thickness of the constitutive film was investigated in detail based on the conditions of the electron transport pathway and trap positions to further improve the performance of the PEI/CQD photodetectors. Under the optimized conditions, the photodetector could generate a strong signal (1.5 mA W-1 at 254 nm) and exhibit high detectability (1.8 × 1010 Jones at 254 nm), an ultrafast response, and long-term stability during the power supply sequence. The developed solar-blind UVC photodetector can be applied in various ways to monitor UVC in an affordable, straightforward, and precise manner.

Highly Efficient Photoswitchable Smart Polymeric Nanovehicle for Gene and Anticancer Drug Delivery in Triple-Negative Breast Cancer

Over the past few decades, there has been significant interest in smart drug delivery systems capable of carrying multiple drugs efficiently, particularly for treating genetic diseases such as cancer. Despite the development of various drug delivery systems, a safe and effective method for delivering both anticancer drugs and therapeutic genes for cancer therapy remains elusive. In this study, we describe the synthesis of a photoswitchable smart polymeric vehicle comprising a photoswitchable spiropyran moiety and an amino-acid-based cationic monomer-based block copolymer using reversible addition-fragmentation chain transfer (RAFT) polymerization. This system aims at diagnosing triple-negative breast cancer and subsequently delivering genes and anticancer agents. Triple-negative breast cancer patients have elevated concentrations of Cu2+ ions, making them excellent targets for diagnosis. The polymer can detect Cu2+ ions with a low limit of detection value of 9.06 nM. In vitro studies on doxorubicin drug release demonstrated sustained delivery at acidic pH level similar to the tumor environment. Furthermore, the polymer exhibited excellent blood compatibility even at the concentration as high as 500 μg/mL. Additionally, it displayed a high transfection efficiency of approximately 82 ± 5% in MDA-MB-231 triple-negative breast cancer cells at an N/P ratio of 50:1. It is observed that mitochondrial membrane depolarization and intracellular reactive oxygen species generation are responsible for apoptosis and the higher number of apoptotic cells, which occurred through the arrest of the G2/M phase of the cell cycle were observed. Therefore, the synthesized light-responsive cationic polymer may be an effective system for diagnosis, with an efficient anticancer drug and gene carrier for the treatment of triple-negative breast cancer in the future.

Rare Earth-Carbon Dots Nanocomposite-Modified Glass Nanopipettes: Electro-Optical Detection of Bacterial ppGpp

As an important alarmone nucleotide, guanosine 3'-diphosphate-5'-diphosphate (ppGpp) can regulate the survival of bacteria under strict environmental conditions. Direct detection of ppGpp in bacteria with high sensitivity and selectivity is crucial for elucidating the role of ppGpp in bacterial stringent response. Herein, the terbium-carbon dots nanocomposite (CDs-Tb) modified glass nanopipet was developed for the recognition of ppGpp. The CDs-Tb in glass nanopipette preserved their fluorescence properties as well as the coordination capacity of Tb3+ toward ppGpp. The addition of ppGpp not only led to the fluorescence response of CDs-Tb but also triggered variations of surface charge inside the glass nanopipet, resulting in the ionic current response. Compared with nucleotides with similar structures, this method displayed good selectivity toward ppGpp. Moreover, the dual signals (fluorescence and ionic current) offered a built-in correction for potential interference. Apart from the high selectivity, the proposed method can determine the concentration of ppGpp from 10-13 to 10-7 M. Taking advantage of the significant analytical performance, we monitored ppGpp in Escherichia coli under different nutritional conditions and studied the relationship between ppGpp and DNA repair, which is helpful for overcoming antibiotic resistance and promoting the development of potential drugs for antibacterial treatment.

Carbon Dots and Their Polymeric Nanocomposites: Insight into Their Synthesis, Photoluminescence Mechanisms, and Recent Trends in Sensing Applications

Carbon dots (CDs), a novel class of carbon-based nanoparticles, have received a lot of interest recently due to their exceptional mechanical, chemical, and fluorescent properties, as well as their excellent photostability and biocompatibility. CDs' emission properties have already found a variety of potential applications, in which bioimaging and sensing are major highlights. It is widely acknowledged that CDs' fluorescence and surface conditions are closely linked. However, due to the structural complexity of CDs, the specific underlying process of their fluorescence is uncertain and yet to be explained. Because of their low toxicity, robust and wide optical absorption, high chemical stability, rapid transfer characteristics, and ease of modification, CDs have been recognized as promising carbon nanomaterials for a variety of sensing applications. Thus, following such outstanding properties of CDs, they have been mixed and imprinted onto different polymeric components to achieve a highly efficient nanocomposite with improved functional groups and properties. Here, in this review, various approaches and techniques for the preparation of polymer/CDs nanocomposites have been elaborated along with the individual characteristics of CDs. CDs/polymer nanocomposites recently have been highly demanded for sensor applications. The insights from this review are detailed sensor applications of polymer/CDs nanocomposites especially for detection of different chemical and biological analytes such as metal ions, small organic molecules, and several contaminants.

Unveiling Carrier Relaxation Mechanism in Protonated/Deprotonated Carbon Dots and Their Solvent Effects via Ultrafast Spectroscopy

The intricate nature of the surface structure of carbon dots (CDs) hinders a comprehensive understanding of their emission behavior. In this study, we employ two types of CDs created through acid-alkali treatments, one with surface protonation and the other with surface deprotonation, with the objective of investigating the impact of these surface modifications on carrier behavior using ultrafast spectroscopy techniques. TEM, XRD, FTIR and Raman spectra demonstrate the CDs' structure, featuring graphitic core and abundant surface functional groups. XPS confirms the successful surface modifications of CDs via protonation and deprotonation. Ultrafast transient absorption (TA) spectroscopy reveals that deprotonation modification may decelerate the relaxation process, thereby increasing the visible PL quantum yields (PLQY). Conversely, protonation may accelerate the relaxation process due to the induced low-energy absorption band, resulting in self-absorption and reduced PLQY. Furthermore, TA analysis of CDs in mixed solvents with different proportions of ethanol shows the beneficial effect of ethanol in decelerating the relaxation process, leading to an increased PLQY of 33.7 % for deprotonated CDs and 22.1 % for protonated CDs. This study illuminates the intricate relationship between surface deprotonation/protonation modifications and carrier behavior in CDs, offering a potential avenue for the design of high-brightness CDs for diverse applications.

A designed DNA/amino acid amphiphile-based supramolecular oxidase-mimetic catalyst for colorimetric DNA detection

DNA is self-assembled with Fmoc-amino acids and Cu2+ to construct a supramolecular catechol oxidase-mimetic catalyst, which exhibits remarkable activity in catalyzing colorimetric reactions. This catalytic system is used for the detection of DNA hybridization with a high selectivity and a low detection limit.

Quantum dots: a tool for the detection of explosives/nitro derivatives

Nitro derivatives are considered as major environmental pollutants and issues of health concern. In current times, a variety of methods and techniques have been utilized for the sensing of these nitro derivatives. In view of this, the remarkable fluorescence properties of quantum dots (QDs) provide a great opportunity to detect these nitro derivatives. This review highlighted the recent reports of QDs as the sensing material for these nitro derivative explosives. Different modifications in QDs using physical and chemical approaches can be used to improve their sensing output. Various interaction mechanisms have been discussed between QDs and nitro derivatives to change their fluorescence properties. Finally, the current challenges and the perspective for the forthcoming future are provided in the concluding section. We hope this review will be beneficial in guiding the utilization of QDs in sensing applications.

Greener production of a starch-based nanohybrid material (core-shell) for the simultaneous extraction of persistent organic pollutants in shrimp samples

Here, a novel nanohybrid material (Ag@CD@ANS) based on oat starch was produced, characterized, and applied to extract persistent organic pollutants in a shrimp sample. By the characterization experiments, Ag@CD@ANS was successfully synthesized. The functionalization of the material by 1,2-naphthoquinone-4-sulphonic acid (ANS) was confirmed using the infrared technique and CHN elemental analysis. The isotherm study showed that the material has a high adsorption capacity for the pesticides of interest (flutriafol, atrazine, heptachlor, DDT and bifenthrin) allowing their extraction from shrimp samples. The optimal condition for extraction was obtained using multivariate analysis. The nature of the elution solvent (hexane, methanol, acetonitrile) and the mass ratio between sample:adsorbent (1:1; 1:5 and 1:10) were the evaluated factors for extraction using Ag@CD@ANS and commercial adsorbents (neutral alumina, octadecyl, silica gel). From the multivariate analysis, it was observed that the optimal condition for pesticide extraction using Ag@CD@ANS was reached, using a 1:5 ratio (sample:adsorbent) and acetonitrile (10 mL) as elution solvent. For the commercial adsorbents, the optimal condition for pesticide extraction was reached, using a 1:3 ratio (sample:adsorbent), acetonitrile (10 mL) and neutral alumina as commercial adsorbent. Ag@CD@ANS efficiency was compared with an optimal commercial adsorbent (neutral alumina). No significant difference (p < 0.05) between neutral alumina and Ag@CD@ANS was observed. Recoveries ranging from 75 to 105 % with coefficients of variation ≤ 15 % (n = 3) were obtained using neutral alumina while using Ag@CD@ANS, recoveries ranging from 73 to 102 %, with coefficient of variation ≤ 13 % (n = 3) were obtained for the target pesticides. Limits of detection ranging from 0.5 to 1.0 µg Kg-1 and limits of quantification ranging from 1.6 to 3.3 µg Kg-1 were reached. The results demonstrated that Ag@CD@ANS can alternatively be used as a support for the extraction of persistent organic pollutants, having the advantage of being reusable for up to three cycles.

Low Cu(II) Concentration Detection Based on Fluorescent Detector Made from Citric Acid and Urea

Carbon quantum dots (CQD) are an advanced fluorescent material, which has attracted more and more attention in theoretical research and practical applications. To obtain stable CQDs with high fluorescence characteristics for detecting trace metal ions in water, nitrogen-doped carbon quantum dots (N-CQDs) based fluorescent sensors were synthesized by the hydrothermal method, using citric acid and urea as source. Transmission electron microscopy (TEM) images showed that the synthesized N-CQDs maintained a narrow particle size distribution bellow 10 nm, and its average size was 3.07 nm. Fourier transform infrared spectroscopy (FT-IR) indicated that abundant hydroxyl and carboxyl functional groups existed on N-CQDs surface, which helped N-CQDs highly disperse in water. In addition, UV-vis spectroscopy and photoluminescence demonstrated that the N-CQDs obtained a 10.27% of quantum yield (QY) with relatively high and stable fluorescence performance. As a fluorescent sensor, the N-CQDs showed a fluorescence "ON-OFF" mechanism during the Cu2+ detection, which was induced from the electrons transition in surface functional groups. The final N-CQDs exhibited a wide linear relationship between fluorescence response and concentration of Cu2+ in range of 0.3-0.7 μM with a detection limit of 0.071 μM. Furthermore, the detection of Cu2+ in the simulating surface water (by adding interfering metal ions in purified water) and the tap water (from municipal water in Beijing) were used to verify N-CQDs practical application.

Green Synthesis of Nickel Oxide NPs Incorporating Carbon Dots for Antimicrobial Activities

A biosynthesis composite using the green synthesis of titled metal nanoparticles (nickel oxide nanoparticles, NiO NPs, and carbon dots, C-dots) was produced, characterized, and then applied for antimicrobial activities. NiO NPs were produced using the Croton macrostachyus (Bakkannisa) plant leaf extract and nickel nitrate (III) hexahydrate [Ni(NO3)2·2H2O] as precursors, while C-dots were produced using citric acid and o-phenylenediamine (o-OPD). The distribution of the average particle size of the NiO NPs and NiO NPs@C-dots was 25.34 ± 0.12 and 24.95 ± 0.22 nm, respectively. The antimicrobial effects of the prepared materials were tested against the selected bacterial and fungal strains. Based on the outcomes of the bioassay, it was realized that both the bare and composite materials were effective against all bacterial strains. The composite's high surface area with strong inhibitive effective antimicrobial effects against bacterial and fungal strains were observed. Therefore, strong inhibitive effects of 21-24 and 22-26 mm were observed with NiO NPs and NiO NPs@C-dots, respectively.

Luminescence of carbon quantum dots and their application in biochemistry

Similar to fullerenes, carbon nanotubes and graphene, carbon dots (CDs) are causing a lot of research work in their own right. CDs are a type of surface-passivated quantum dot that contain carbon atoms. Their distinctive characteristics, such as luminescent emission that varies with size and wavelength, resistance to photobleaching, easy biological binding, lack of toxicity, and economical production without the need for intricate synthetic processes, have led to a noteworthy surge in attention within the research community. Different techniques can be utilized to create these CDs, spanning from basic candle burning to laser ablation. This review article delves into the principles of fluorescence technology, providing insights into how different synthesis methods of quantum dots impact their luminescent properties. Additionally, it highlights the latest applications of quantum dots in catalysis and biomedical fields, with special emphasis on the current status of luminescent properties in biology and chemistry. Towards the end, the article discusses the limitations of quantum dots in current practical applications, pointing out that CDs hold promising potential for future applications.

Optically active organic and inorganic nanomaterials for biological imaging applications: A review

Recent advancements in the field of nanotechnology have enabled targeted delivery of drug agents in vivo with minimal side effects. The use of nanoparticles for bio-imaging has revolutionized the field of nanomedicine by enabling non-invasive targeting and selective delivery of active drug moieties in vivo. Various inorganic nanomaterials like mesoporous silica nanoparticles, gold nanoparticles, magnetite nanoparticles graphene-based nanomaterials etc., have been created for multimodal therapies with varied multi-imaging modalities. These nanomaterials enable us to overcome the disadvantages of conventional imaging contrast agents (organic dyes) such as lack of stability in vitro and in vivo, high reactivity, low-quantum yield and poor photo stability. Inorganic nanomaterials can be easily fabricated, functionalised and modified as per requirements. Recently, advancements in synthesis techniques, such as the ability to generate molecules and construct supramolecular structures for specific functionalities, have boosted the usage of engineered nanomaterials. Their intrinsic physicochemical properties are unique and they possess excellent biocompatibility. Inorganic nanomaterial research has developed as the most actively booming research fields in biotechnology and biomedicine. Inorganic nanomaterials like gold nanoparticles, magnetic nanoparticles, mesoporous silica nanoparticles, graphene-based nanomaterials and quantum dots have shown excellent use in bioimaging, targeted drug delivery and cancer therapies. Biocompatibility of nanomaterials is an important aspect for the evolution of nanomaterials in the bench to bedside transition. The conduction of thorough and meticulous study for safety and efficacy in well-designed clinical trials is absolutely necessary to determine the functional and structural relationship between the engineered nanomaterial and its toxicity. In this article an attempt is made to throw some light on the current scenario and developments made in the field of nanomaterials in bioimaging.

Histamine Recognition by Carbon Dots from Plastic Waste and Development of Cellular Imaging: Experimental and Theoretical Studies

The present work highlights the sustainable approach for the transformation of plastic waste into fluorescent carbon dots (CDs) through carbonization and then they were functionalized with L-cysteine and o-phenylenediamine. CDs which were characterized by different analytical techniques such as X-ray diffraction (XRD), thermogravimetric analysis (TGA), Scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are employed to recognize Cu2+, Fe2+, and Hg2+ ions. The results show that the fluorescence emission was considerably quenched, and it is consistent with the interference and Jobs plots. The detection limit was found to be 0.35µM for Cu(II), 1.38 µM for Hg(II), and 0.51µM Fe(III). The interaction of CDs with metal ions enhances the fluorescence intensity detecting histamine successfully. It shows that plastic waste-based CDs can be applied clinically to detect toxic metals and biomolecules. Moreover, the system was employed to develop the cellular images using Saccharomyces cerevisiae cells with the support of a confocal microscope. Furthermore, theoretical studies were performed for the naphthalene layer (AR) as a model for C-dots, then optimized its structure and analyzed by using the molecular orbital. The obtained TD-DFT spectra coincided with experimental spectra for CDs/M2+/histamine systems.

Eutectic Media Open a Synthetic Route to Oligocitrazinic Acid Fluorophores of Purple Hue

Under isochoric and solvent-free conditions, the reaction between ammonium formate and citric acid results in a deeply purple reaction product with fluorescent properties. This brings this reaction in the realm of bio-based fluorophores and bottom-up carbon nanodots from citric acid. The reaction conditions are optimized in terms of UV-vis spectroscopic properties and, subsequently, the main reaction product is separated. While the structural analysis does not give any indication for carbon nanodots in a general sense, it points towards the formation of molecular fluorophores that consist of oligomerized citrazinic acid derivatives. Furthermore, EPR spectroscopy reveals the presence of stable free radicals in the product. We hypothesize that such open-shell structures may play a general role in molecular fluorophores from citric acid and are not yet sufficiently explored. Therefore, we believe that analysis of these newly discovered fluorophores may contribute to a better understanding of the properties of fluorophores and CND from citric acid in general.

Recent developments, applications and challenges for carbon quantum dots as a photosynthesis enhancer in agriculture

Since the world's population is expanding, mankind may be faced with a huge dilemma in the future, which is food scarcity. The situation can be mitigated by employing sustainable cutting-edge agricultural methods to maintain the food supply chain. In recent years, carbon quantum dots (CQD), a member of the well-known carbon-based nanomaterials family, have given rise to a new generation of technologies that have the potential to revolutionise horticulture and agriculture research. CQD has drawn much attention from the research community in agriculture owing to their remarkable properties such as good photoluminescence behaviour, high biocompatibility, photo-induced electron transfer, low cost, and low toxicity. These unique properties have led CQD to become a promising material to increase plant growth and yield in the agriculture field. This review paper highlights the recent advances of CQD application in plant growth and photosynthesis rate at different concentrations, with a focus on CQD uptake and translocation, as well as electron transfer mechanism. The toxicity and biocompatibility studies of CQD, as well as industrial scale applications of CQD for agriculture are discussed. Finally, the current challenges of the present and future perspectives in this agriculture research are presented.

Ratiometric and visual determination of copper ions with fluorescent nanohybrids of semiconducting polymer nanoparticles and carbon dots

Developing nanohybrid composition based fluorescent carbon dots (CDs) for ratiometric detection of copper ions is highly appealing. Herein, a ratiometric sensing platform (GCDs@RSPN) for copper ions detection has been developed by loaded green fluorescence carbon dots (GCDs) on the surface of red emission semiconducting polymer nanoparticles (RSPN) through electrostatic adsorption. The GCDs, featuring abundant amino groups, can selectively bind copper ions to induce the photoinduced electron transfer, leading to fluorescence quenching. A good linearity within the range of 0-100 μM is obtained, and the limit of detection (LOD) is 0.577 μM by using obtained GCDs@RSPN as ratiometric probe to detect copper ion. Moreover, the paper-based sensor derived from GCDs@RSPN was successfully applied for the visual detection of Cu²⁺.

Synthesis of Au Nanoclusters by Reduction of Bovine Serum Albumin: The Role of Sodium Hydroxide

Using bovine serum albumin (BSA) as both a reductant and ligand had been developed as one of the most used approaches for synthesis of fluorescent Au nanoclusters (NCs), in which first HAuCl₄ and BSA were mixed together and then NaOH was added to the mixture after a certain time to obtain the Au NCs. In this work, the role of sodium hydroxide in the formation and emission properties of the Au NCs was investigated systematically. It was revealed, for the first time, that activity of the gold precursor and, thus, emission properties of the resulting Au NCs are dependent upon the addition time of sodium hydroxide. Meanwhile, the reducing ability of BSA is dependent upon the concentration of sodium hydroxide added to the reaction solution. By optimization of the addition time and concentration of sodium hydroxide used, Au NCs with improved emission properties were successfully synthesized under relatively low BSA concentrations, which showed improved performance toward the sensing of Cu²⁺ ions.

Diethylenetriamine-β-CD-modified carbon quantum dots for selective fluorescence sensing of Hg2+ and Fe3+ and cellular imaging

Diethylenetriamine-β-cyclodextrin-modified carbon quantum dots (3 N-CQDs) were synthesized via a one-step hydrothermal method using citric acid as the carbon source and diethylenetriamine-β-cyclodextrin (3 N-β-CD) as the nitrogen source. The successful preparation of 3 N-CQDs were revealed by infrared absorption spectroscopy, ultraviolet (UV)-visible absorption spectroscopy, fluorescence spectroscopy, XRD, XPS, TEM, and TG. Further spectroscopic studies showed that the synthesized carbon quantum dots offered good anti-interference capability. The relative fluorescence quantum yield was 67.2 %. The limits of detection for Hg²⁺ and Fe³⁺ were 0.25 µM and 0.57 μM, respectively. Cytotoxicity and imaging studies showed that the prepared carbon quantum dots had low cytotoxicity, good biocompatibility, and good cellular imaging capability for HeLa cells. They offered fluorescent sensing of Hg²⁺ and Fe³⁺ in live cells. Therefore, 3 N-CQDs were ideal fluorescent probes for the detection of Hg²⁺ and Fe³⁺ in water.

Lanthanide ternary complex as a fluorescent probe for highly sensitive and selective detection of copper ions based on selective recognition and photoinduced electron transfer

Copper ions have a very important role in human health, industrial and agricultural production. Herein, lanthanide ternary complex of 2,6-pyridinedicarboxylic acid (DPA)-Eu³⁺-polyethyleneimine (PEI) as a fluorescent probe was thus fabricated for highly sensitive and selective detection of copper ions. PEI itself is non-fluorescent, the PEI-Eu³⁺complex is also non-fluorescent, and PEI has specific recognition to copper ions due to its higher affinity ability to copper ion than other metal ions. It was found that Cu²⁺ ions cannot quench the characteristic fluorescence of Eu³⁺ in the DPA-Eu³⁺ system, while in the DPA-Eu³⁺-PEI system, Cu²⁺ ions can greatly quench the characteristic fluorescence of Eu³⁺ due to photoinduced electron transfer (PET). The luminescent and quenching mechanism was also discussed in detail. The DPA-Eu³⁺-PEI probe not only has high sensitivity and selectivity, but also has very rapid fluorescence response and the response time is only 1 min. A good linear relationship between the fluorescence ratios of F₀/F and the concentrations of Cu²⁺ was obtained in the range of 0.02 ∼ 10.0 μM (R² = 0.998), and the limit of detection (LOD) is 8.0 nM. The probe was successfully applied for the detection of Cu²⁺ ions in the lake and river water samples, wastewater and urine samples. This work may provide a new strategy for fabricating simple and effective fluorescence probe and a promising application for the rapid and on-site detection in environmental monitoring and biological fluids.

Wavelength-Dependent Metal-Enhanced Fluorescence Biosensors via Resonance Energy Transfer Modulation

Fluorescence can be enhanced or quenched depending on the distance between the surface of a metal nanoparticle and the fluorophore molecule. Fluorescence enhancement by nearby metal particles is called metal-enhanced fluorescence (MEF). MEF shows promising potential in the field of fluorescence-based biological sensing. MEF-based biosensor systems generally fall into two platform categories: (1) a two/three-dimensional scaffold, or (2) a colloidal suspension. This review briefly summarizes the application studies using wavelength-dependent carbon dots (UV-VIS), noble metals (VIS), and upconversion nanoparticles (NIR to VIS), representative nanomaterials that contribute to the enhancement of fluorescence through the resonance energy transfer modulation and then presents a perspective on this topic.

Metal organic frameworks as promising sensing tools for electrochemical detection of persistent heavy metal ions from water matrices: A concise review

Water bodies are being polluted rapidly by disposal of toxic chemicals with their huge entrance into drinking water supply chain. Among these pollutants, heavy metal ions (HMIs) are the most challenging one due to their non-biodegradability, toxicity, and ability to biologically hoard in ecological systems, thus posing a foremost danger to human health. This can be addressed by robust, sensitive, selective, and reliable sensing of metal ions which can be achieved by Metal organic frameworks (MOF) based electrochemical sensors. In the present era, MOFs have caught greater interest in a variety of applications including sensing of hazardous pollutants such as heavy metal ions. So, in this review article, types, synthesis and working mechanism of MOF based sensors is explained to give general overview with updated literature. First time, detailed study is done for sensing of metal ions such as chromium, mercury, zinc, copper, manganese, palladium, lead, iron, cadmium and lanthanide by MOFs based electrochemical sensors. The use of MOFs as electrochemical sensors has attractive success story along with some challenges of the area. Considering these challenges, we attempted to highlight the milestone achieved and shortcomings along with future prospective of the MOFs for employing it in electrochemical sensing devices for HMIs. Finally, challenges and future prospects have been discussed to promote the development of MOFs-based sensors in future.

Recyclable fluorescence sensing based on copper clusters for simultaneous determination of copper ions and ammonia

A one-step strategy for synthesizing fluorescent copper clusters stabilized by L-cysteine has been successfully established in aqueous solutions. The direct determination of copper ions was realized by the fluorescence enhancement phenomenon caused by the preparation and aggregation process. At the same time, ammonia treatment can lead to rapid fluorescence quenching, resulting from the influence on the aggregation behavior of Cu clusters, while the fluorescence can be recovered by the continuous addition of copper ions. Therefore, a recyclable fluorescence sensing system is constructed for the simultaneous determination of copper ions and ammonia. This method is simple, anti-interference and has been successfully applied to the determination of environmental samples.

Antibacterial Carbon Dots-Based Composites

The emergence and global spread of bacterial resistance to conventionally used antibiotics have highlighted the urgent need for new antimicrobial agents that might replace antibiotics. Currently, nanomaterials hold considerable promise as antimicrobial agents in anti-inflammatory therapy. Due to their distinctive functional physicochemical characteristics and exceptional biocompatibility, carbon dots (CDs)-based composites have attracted a lot of attention in the context of these antimicrobial nanomaterials. Here, a thorough assessment of current developments in the field of antimicrobial CDs-based composites is provided, starting with a brief explanation of the general synthesis procedures, categorization, and physicochemical characteristics of CDs-based composites. The many processes driving the antibacterial action of these composites are then thoroughly described, including physical destruction, oxidative stress, and the incorporation of antimicrobial agents. Finally, the obstacles that CDs-based composites now suffer in combating infectious diseases are outlined and investigated, along with the potential applications of antimicrobial CDs-based composites.

A novel and ultrasensitive fluorescent probe derived from labeled carbon dots for recognitions of copper ions and glyphosate

Labeling materials with special functional groups are very valuable for the creation of novel probes. Hence, a novel fluorescent probe was constructed by conjugating 4-butyl-3-thiosemicarbazide (BTSC) with carbon dots (CDs). The CDs labeled by BTSC (BTSC-CDs) displayed a strong capability for recognition of Cu²⁺ and Cu²⁺ could quench the emission of BTSC-CDs significantly. The fluorescence quenching was proved to be a static quenching which was resulted from the interaction between BTSC-CDs and Cu²⁺ to form a ground-state BTSC-CDs/Cu²⁺complex, and the fluorescence intensities showed a good linear correlation with Cu²⁺ concentrations in the range of 0.20-30 μM. What is more important, by adding glyphosate into the sensor system of BTSC-CDs/Cu²⁺ the fluorescence of the probe turned on again owing to the stronger chelating between glyphosate and Cu²⁺ than between BTSC-CDs and Cu²⁺. This could realize the specific detection of glyphosate and the limit of detection was low to 0.27 μM. Detecting glyphosate using the complex BTSC-CDs/Cu²⁺ system in actual samples with satisfactory outcomes indicated that a novel fluorescent probe for Cu²⁺ and subsequent glyphosate detections has been provided.

Porphyrin Functionalized Carbon Quantum Dots for Enhanced Electrochemiluminescence and Sensitive Detection of Cu2

Porphyrin (TMPyP) functionalized carbon quantum dots (CQDs-TMPyP), a novel and efficient carbon nanocomposite material, were developed as a novel luminescent material, which could be very useful for the sensitive detection of copper ions in the Cu²⁺ quenching luminescence of functionalized carbon quantum dots. Therefore, we constructed a sensitive "signal off" ECL biosensor for the detection of Cu²⁺. This sensor can sensitively respond to copper ions in the range of 10 nM to 10 μM, and the detection limit is 2.78 nM. At the same time, it has good selectivity and stability and a benign response in complex systems. With excellent properties, this proposed ECL biosensor provides an efficient and ultrasensitive method for Cu²⁺ detection.

The Formation Process and Mechanism of Carbon Dots Prepared from Aromatic Compounds as Precursors: A Review

Fluorescent carbon dots are a novel type of nanomaterial. Due to their excellent optical properties, they have extensive application prospects in many fields. Studying the formation process and fluorescence mechanism of CDs will assist scientists in understanding the synthesis of CDs and guide more profound applications. Due to their conjugated structures, aromatic compounds have been continuously used to synthesize CDs, with emissions ranging from blue to NIR. There is a lack of a systematic summary of the formation process and fluorescence mechanism of aromatic precursors to form CDs. In this review, the formation process of CDs is first categorized into three main classes according to the precursor types of aromatic compounds: amines, phenols, and polycyclics. And then, the fluorescence mechanism of CDs synthesized from aromatic compounds is summarized. The challenges and prospects are proposed in the last section.

Green Synthesis of Carbon Nanoparticles (CNPs) from Biomass for Biomedical Applications

In this review, we summarize recent work on the "green synthesis" of carbon nanoparticles (CNPs) and their application with a focus on biomedical applications. Recent developments in the green synthesis of carbon nanoparticles, from renewable precursors and their application for environmental, energy-storage and medicinal applications are discussed. CNPs, especially carbon nanotubes (CNTs), carbon quantum dots (CQDs) and graphene, have demonstrated utility as high-density energy storage media, environmental remediation materials and in biomedical applications. Conventional fabrication of CNPs can entail the use of toxic catalysts; therefore, we discuss low-toxicity manufacturing as well as sustainable and environmentally friendly methodology with a focus on utilizing readily available biomass as the precursor for generating CNPs.

Glucose determination in human serum by applying inner filter effect quenching mechanism of upconversion nanoparticles

Accurate blood glucose determination is essential to the clinical diagnosis and management of diabetes. This work establishes an inner filter effect (IFE) strategy between upconversion nanoparticles (UCNPs) and quinone-imine complex for glucose monitoring in human serum simply and efficiently. In this system, the enzyme glucose oxidase (GOx) catalyzes the reaction of glucose into hydrogen peroxide (H₂O₂) and gluconic acid when compulsion by oxygen. In the presence of horseradish peroxidase (HRP), the produced H₂O₂ can catalytically oxidize phenol and 4-amino antipyrine (4-AAP) to generate quinone-imine products. The purple-colored quinone-imine complex effectively absorbed the fluorescence of NaYF₄:Yb³⁺, Er³⁺ UCNPs, leading to the strong fluorescence quenching of UCNPs through IFE. Thus, a new approach was established for glucose monitoring by determining the fluorescence intensity. Under the optimal condition, this approach shows better linearity to glucose from 2-240 μmol/L with a low detection limit at 1.0 μmol/L. Owing to the excellent fluorescence property and background-free interference of the UCNPs, the biosensor was applied for glucose measurements in human serum and got a satisfactory result. Furthermore, this sensitive and selective biosensor revealed great potential for the quantitative analysis of blood glucose or different kinds of H₂O₂-involved biomolecules for the application of clinical diagnosis.

Chiral Carbon Dots: Synthesis and Applications in Circularly Polarized Luminescence, Biosensing and Biology

Chiral carbon dots (CDs) are a novel luminescent zero-dimensional carbon-based nanomaterial with chirality. They not only have the advantages of good biocompatibility, multi-color-emission, easy functionalization, but also exhibits highly symmetrical chiral optical characteristics, which broadens their applicability to enantioselectivity of some chiral amino acids like cysteine and lysine, asymmetric catalysis as well as biomedicine in gene expression and antibiosis. In addition, the exploration of the excited state chirality of CDs has developed its excellent circularly polarized luminescence (CPL) properties, opening up a new application scenario like recognition of chiral light sources and anti-counterfeit printing with information encryption. This review mainly focuses on the mature synthesis approaches of chiral CDs, including chiral ligand method and supramolecular self-assembly method, then we consider emerging applications of chiral CDs in CPL, biosensing and biological effect. Finally, we concluded with a perspective on the potential challenges and future opportunities of such fascinating chiral CDs.

A red-emitting Europium(III) complex as a luminescent probe with large Stokes shift for the sequential determination of Cu2+ and biothiols in real samples

In this work, a novel Eu³⁺-DTPA-bis(AMC) complex with red luminescence was designed and synthesized for sequential detection of Cu²⁺ and biothiols (Cys/Hcy/GSH) based on the displacement strategy with the good selectivity, high sensitivity, and large Stokes shift (288 nm). The possible detection mechanism was verified by UV-vis, the high-resolution mass spectrometry, and the fluorescence decay curve. The experimental parameters, including the solution pH, the incubation time, the concentration ratio of Eu³⁺-DTPA-bis(AMC) to Cu²⁺ and biothiols concentration, were optimized. Under the optimal conditions, it shows a good linear relationship between the concentration (0-10 μM) of Cu²⁺ and the fluorescence intensity of Eu³⁺-DTPA-bis(AMC), with a low detection limit of 0.065 μM. The linear range and the limit of detection of the Eu³⁺-DTPA-bis(AMC)/Cu²⁺ system for Cys/Hcy/GSH were 2.5-22.5/5-45/5-50 μM and 0.11/0.07/0.05 μM, respectively. Surprisingly, the high or low concentration of Eu³⁺-DTPA-bis(AMC)/Cu²⁺ can significantly affect the selectivity of the sensing system to biothiols (Cys/GSH/Hcy). When the concentration of the Eu³⁺-DTPA-bis(AMC)/Cu²⁺ system is 10.0 μΜ, it could recognize biothiols (Cys/GSH/Hcy) from other substances, but when the concentration is as low as 3.3 μM, it could further specifically distinguished Cys from Hcy/GSH. Owing to the high anti-interference characteristics, accuracy and specificity, the sensing system was well applied to the cascade detection of Cu²⁺ in actual environmental samples and Cys in biological and food samples, including FBS, urine, milk, beverage, fresh juice with the satisfactory recoveries from 96.20 to 106.80 %.

Amide salt pyrolysis fabrication of graphene nanosheets with multi-excitation single color emission

A novel and simple approach of using amide salt pyrolysis to produce photoluminescent (multi-excitation and single color emission) graphene nanosheets (GNs) with a thickness of <1 nm and a diameter of about 100-200 nm is described herein. It has characteristics of high water solubility, low toxicity, easy manufacturing, etc., and has potential application prospects in analytical chemistry and biomedicine.

Applications of carbon dots and its modified carbon dots in bone defect repair

Bone defect repair is a continual and complicated process driven by a variety of variables. Because of its bright multicolor luminescence, superior biocompatibility, water dispersibility, and simplicity of synthesis from diverse carbon sources, carbon dots (CDs) have received a lot of interest. It has a broad variety of potential biological uses, including bone defect repair, spinal cord injury, and wound healing. Materials including CDs as the matrix or major component have shown considerable benefits in enabling bone defect healing in recent years. By altering the carbon dots or mixing them with other wound healing-promoting agents or materials, the repair effect may be boosted even further. The report also shows and discusses the use of CDs to heal bone abnormalities. The study first presents the fundamental features of CDs in bone defect healing, then provides CDs manufacturing techniques that should be employed in bone defect repair, and lastly examines their development in the area of bioengineering, particularly in bone defect repair. In this work, we look at how carbon dots and their alteration products may help with bone defect healing by being antibacterial, anti-infective, osteogenic differentiation-promoting, and gene-regulating.

Preparation of Fluorescent Carbon Dots Composites and Their Potential Applications in Biomedicine and Drug Delivery-A Review

Carbon dots (CDs), a new member of carbon nanostructures, rely on surface modification and functionalization for their good fluorescence phosphorescence and excellent physical and chemical properties, including small size (<10 nm), high chemical stability, biocompatibility, non-toxicity, low cost, and easy synthesis. In the field of medical research on cancer (IARC), CDs, a new material with unique optical properties as a photosensitizer, are being applied to heating local apoptosis induction of cancer cells. In addition, imaging tools can also be combined with a drug to form the nanometer complex compound, the imaging guidance for multi-function dosage, so as to improve the efficiency of drug delivery, which also plays a big role in genetic diagnosis. This paper mainly includes three parts: The first part briefly introduces the synthesis and preparation of carbon dots, and summarizes the advantages and disadvantages of different preparation methods; The second part introduces the preparation methods of carbon dot composites. Finally, the application status of carbon dot composites in biomedicine, cancer theranostics, drug delivery, electrochemistry, and photocatalysis is summarized.

A fluorescent and scattering dual-mode probe based on a carbon dot@cerium-guanosine monophosphate coordination polymer network for tetracycline detection

Dual-mode sensing with a two-signal read-out is conducive to the improvement of detection accuracy. Herein, a fluorescent and scattering dual-mode chemosensor for tetracycline (TC) is proposed based on a carbon dot@cerium-guanosine monophosphate (CD@GMP-Ce) coordination polymer network. The inexpensive CD@GMP-Ce was prepared by exploiting the adaptive inclusion capability of coordination polymers and possessed remarkable fluorescence and strong Rayleigh scattering. The functional CD@GMP-Ce demonstrated fluorescence and scattering, the two optical-signal responses to TC simultaneously. Based on TC-specific fluorescence and scattering decline, the dual-mode detection of TC was established and the probe's detection limits were 43 nM in the fluorescence mode and 77 nM in the scattering mode, respectively. Furthermore, the potential application of the dual-mode sensor was verified by measuring TC in milk and tap-water samples. The study not only provides a new perspective for the development of assay methods for TC but also expands the applications of cerium coordination polymers.

An up-conversion test paper based on "switch-off" of fluorescence is constructed to sensitively and selectively detect cancer-causing dye Sudan III in lipstick

Cancer-causing dye Sudan III is banned adding to cosmetics, so a method for detecting trace Sudan III in cosmetics is established. A single dispersed up-conversion molecularly imprinted fluorescent nanoprobe is constructed and coated on the filter paper. The mechanism for detecting Sudan III by this composite fluorescent nanoprobes-paper is systematically analyzed. The fluorescent response (max emission peak is at 541 nm) is linearly related to 10-1000 nM Sudan III, and Sudan III can be selectively recognized (imprinting factor increased to 4.1). The limit of detection and quantitation are further reduced to 2.89 nM and 9.63 nM, respectively. The recoveries of Sudan III in lipstick samples are between 93.18 and 108.3%, and relative standard deviation is less than or equal to 4.6%. Trace Sudan III in cosmetics are detected accurately and sensitively by this method due to up-conversion nanoparticles with little interference of background fluorescence and molecularly imprinted polymers with selective enrichment.