Microwave-assisted synthesis of carbon dots and its potential as analysis of four heterocyclic aromatic amines

An "on-off-on" Fluorescent Sensor Based on Carbon Dots for the Detection of Au (III) and Creatinine

The present study proposes a new approach for detecting trace amounts of creatinine (Cre) through the utilization of a fluorescence sensor system consisting of nitrogen doped carbon dots (NCDs) and gold ions (Au3+). Yellow fluorescent carbon dots were prepared using a one-step hydrothermal method with o-phenylenediamine and isopropanol as raw materials. First, gold ions are reduced to gold nanoparticles (Au NPs), which bind to NCDs, resulting in electron transfer and fluorescence quenching of NCDs. After adding creatinine, Cre and Au NPs were preferentially combined to form non-fluorescent complexes, and the NCDs fluorescence was restored. The study achieved a detection limit of 1.06 × 10-7 M for Au3+ and 9.29 × 10-9 M for creatinine, indicating a high level of sensitivity. The sensing system has also been successfully utilized for detecting Au3+ in lake water and Cre in human urine, indicating its promising potential and practical applications in the areas of environmental monitoring and biosensing.

Unveiling heterocyclic aromatic amines (HAAs) in thermally processed meat products: Formation, toxicity, and strategies for reduction - A comprehensive review

This comprehensive review focuses on heterocyclic aromatic amines (HAAs), a class of chemicals that commonly form during the cooking or processing of protein-rich foods. The International Agency for Research on Cancer (IARC) has categorized certain HAAs as probable human carcinogens, highlighting the significance of studying their formation and control in food safety research. The main objective of this review is to address the knowledge gaps regarding HAAs formation and propose approaches to reduce their potential toxicity during thermal processing. By summarizing the mechanisms involved in HAAs formation and inhibition, the review encompasses both conventional and recent detection methods. Furthermore, it explores the distribution of HAAs in thermally processed meats prepared through various cooking techniques and examines their relative toxicity. Additionally, considering that the Maillard reaction, responsible for HAAs formation, also contributes to the unique flavors and aromas of cooked meat products, this review investigates the potential effects of inhibiting HAAs formation on flavor substances. A thorough understanding of these complex interactions provides a foundation for developing targeted interventions to minimize the formation of HAAs and other harmful compounds during food processing.

Fabrication of Carbon-Based Quantum Dots via a "Bottom-Up" Approach: Topology, Chirality, and Free Radical Processes in "Building Blocks"

The discovery of carbon-based quantum dots (CQDs) has allowed opportunities for fluorescence bioimaging, tumor diagnosis and treatment, and photo-/electro-catalysis. Nevertheless, in the existing reviews related to the "bottom-up" approaches, attention is mainly paid to the applications of CQDs but not the formation mechanism of CQDs, which mainly derived from the high complexities during the synthesis of CQDs. Among the various synthetic methods, using small molecules as "building blocks", the development of a "bottom-up" approach has promoted the structural design, modulation of the photoluminescence properties, and control of the interfacial properties of CQDs. On the other hand, many works have demonstrated the "building blocks"-dependent properties of CQDs. In this review, from one of the most important variables, the relationships among intrinsic properties of "building blocks" and photoluminescence properties of CQDs are summarized. The topology, chirality, and free radical process are selected as descriptors for the intrinsic properties of "building blocks". This review focuses on the induction and summary of recent research results from the "bottom-up" process. Moreover, several empirical rules pertaining thereto are also proposed.

Facile Synthesis of Carbon Dots from Amido Black 10b for Sensing in Real Samples

Herein, a one-step hydrothermal synthesis method was adopted to fabricate carbon dots (CDs) from amido black 10b in a sodium hydroxide solution. The morphology and composition of the CDs were investigated by XRD, FTIR TEM, XPS, UV-vis, and fluorescence spectroscopy. The obtained CDs (AB-CDs) with an average diameter of 19.4 nm displayed a well-dispersed characteristic in aqueous solutions. The as-prepared CDs showed bright blue fluorescence and good photostability, with a high quantum yield of 24.1%. AB-CDs displayed a selective and noticeable turn-off response to Fe³⁺. Accordingly, the quantitative detection of Fe³⁺ was achieved in the range of 5-200 μmol L^-1 with a detection limit of 1.84 μmol L^-1. The fluorescence response mechanism of Fe³⁺ to AB-CDs was ascribed to static quenching due to the emergence of the ground-state complex. Moreover, ascorbic acid could restore the fluorescence of AB-CDs quenched by Fe³⁺ by reducing Fe³⁺ to Fe²⁺. The developed nanoprobe was used to detect ascorbic acid with a limit of detection of 7.26 μmol L^-1 in the range of 20-300 μmol L^-1. Furthermore, the developed sensing system was successfully applied for an Fe³⁺ assay in a lake water sample and ascorbic acid detection in a human urine sample. The AB-CD-based analytical system showed its latent practical value in the chemical analysis and bioanalytical fields.

The valine-based N-doped carbon dots with high peroxidase-like activity

Developing artificial nanoparticles with peroxidase-like activity are being attracted great interests because their catalytic activity are not easy to lose under harsh conditions compared with natural enzymes. In this work, the N-doped carbon dots (CDs) were prepared, and it was found that the N-doped CDs showed high peroxidase-like catalytic activity towards the reaction system of hydrogen peroxide - 3, 3', 5, 5'-tetramethylbenzidine (TMB). The catalytic mechanism of the N-doped CDs was explored by usingelectron spin resonance (ESR) spectra, cyclic voltammetry (CV) method and simulation of density functional theory calculation. This work can offer a new feasible method for synthesizing N-doped CQDs used as artificial peroxidases in biological and environment applications.

Fluorescent Carbon Dots and their Applications in Sensing of Small Organic Molecules

Background:

Fluorescence-based sensing is considered highly sensitive and fluorescent probes with improved properties are always desired. Fluorescent carbon dots (CDs) are newly emerging quasi-spherical nanoparticles of less than 10 nm in size and belong to the carbon nano-material’s family. CDs have great potential as fluorescent probes and currently are under open deliberation by the researchers due to their striking properties such as low environmental hazard, high selectivity, greater sensitivity, good biocompatibility, tunable fluorescent properties and excitation dependent multicolor emission behavior.

Introduction:

This review demonstrates various available methods for fabrication of fluorescent CDs, capping of CDs and characterization with various techniques including UV-visible, FT-IR, and TEM. Analytical applications using CDs for the sensing of small organic molecules, specifically nitroaromatic compounds in the environmental samples are complied.

Methods:

The review covers literature related to synthesis and characterization of carbon dots. It includes around 171 research articles in this field.

Results:

Carbon dots can be synthesized using numerous routes. In all cases CDs possess spectral properties with little variation in wavelength maxima. Optical properties of CDs can be tuned by compositing these with metallic quantum dots or by modifying their surface with desired functionalities. HR-TEM is needed to see the morphology and size of particles whereas UV-Visible and FTIR are indispensable tools for this kind of research. These particles are successfully applied to sense small molecules in some matrices.

Conclusion:

Carbon dots are bright stars in fluorescent sensing of small molecules. However, more research is needed to determine small organic molecules in diversified areas of analysis.

Detection of heterocyclic amine (PhIP) by fluorescently labelled cucurbit[7]uril

A “host–guest” system for 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) detection was designed. This method might be the first quick measurement technique for HCA and may find wide application in food safety detection.

Selective Impedimetric Chemosensing of Carcinogenic Heterocyclic Aromatic Amine in Pork by dsDNA-Mimicking Molecularly Imprinted Polymer Film-Coated Electrodes

Inspired by the easy intercalation of quinoxaline heterocyclic aromatic amines (HAAs) in double-stranded DNA (dsDNA), we synthesized a nucleobase-functionalized molecularly imprinted polymer (MIP) as the recognition unit of an impedimetric chemosensor for the selective determination of a 2-amino-3,7,8-trimethyl-3H-imidazo[4,5-f]quinoxaline (7,8-DiMeIQx) HAA. HAAs are generated in meat and fish processed at high temperatures. They are considered to be potent hazardous carcinogens. The MIP film was prepared by potentiodynamic electropolymerization of a pre-polymerization complex of two adenine- and one thymine-substituted bis(2,2'-bithien-5-yl)methane functional monomer molecules with one 7,8-DiMeIQx template molecule, in the presence of the 2,4,5,2',4',5'-hexa(thiophene-2-yl)-3,3'-bithiophene cross-linking monomer, in solution. The as-formed MIP chemosensor allowed for the selective impedimetric determination of 7,8-DiMeIQx in the 47 to 400 μM linear dynamic concentration range with a limit of detection of 15.5 μM. The chemosensor was successfully applied for 7,8-DiMeIQx determination in the pork meat extract as a proof of concept.

Advances in the Methods for the Synthesis of Carbon Dots and Their Emerging Applications

Cutting-edge technologies are making inroads into new areas and this remarkable progress has been successfully influenced by the tiny level engineering of carbon dots technology, their synthesis advancement and impressive applications in the field of allied sciences. The advances of science and its conjugation with interdisciplinary fields emerged in carbon dots making, their controlled characterization and applications into faster, cheaper as well as more reliable products in various scientific domains. Thus, a new era in nanotechnology has developed into carbon dots technology. The understanding of the generation process, control on making processes and selected applications of carbon dots such as energy storage, environmental monitoring, catalysis, contaminates detections and complex environmental forensics, drug delivery, drug targeting and other biomedical applications, etc., are among the most promising applications of carbon dots and thus it is a prominent area of research today. In this regard, various types of carbon dot nanomaterials such as oxides, their composites and conjugations, etc., have been garnering significant attention due to their remarkable potential in this prominent area of energy, the environment and technology. Thus, the present paper highlights the role and importance of carbon dots, recent advancements in their synthesis methods, properties and emerging applications.

Microwave-Assisted One Pot Three-Component Synthesis of Novel Bioactive Thiazolyl-Pyridazinediones as Potential Antimicrobial Agents against Antibiotic-Resistant Bacteria

Pyridazine and thiazole derivatives have various biological activities such as antimicrobial, analgesic, anticancer, anticonvulsant, antitubercular and other anticipated biological properties. Chitosan can be used as heterogeneous phase transfer basic biocatalyst in heterocyclic syntheses. Novel 1-thiazolyl-pyridazinedione derivatives were prepared via multicomponent synthesis under microwave irradiation as ecofriendly energy source and using the eco-friendly naturally occurring chitosan basic catalyst with high/efficient yields and short reaction time. All the prepared compounds were fully characterized by spectroscopic methods, and their in vitro biological activities were investigated. The obtained results were compared with those of standard antibacterial/antifungal agents. DFT calculations and molecular docking studies were used to investigate the electronic properties and molecular interactions with specific microbial receptors.

Green synthesis of fluorescent N,S-carbon dots from bamboo leaf and the interaction with nitrophenol compounds

A simple and green approach for the synthesis of photoluminescent N,S-carbon dots (N,S-CDs) has been proposed using a single natural source precursor (bamboo leaf) as raw materials. The as-synthesized N,S-CDs exhibited a highly stable, excitation wavelength-dependent emission, excellent photobleaching, alkali, and salt tolerance. Here, the mechanism of N,S-CDs luminescence was studied via the UV-vis absorption spectrum and photoluminescence spectroscopy. Based on the quenching properties of nitrophenol compounds on the fluorescence of N,S-CDs, the interaction between N,S-CDs and nitrophenol compounds was investigated on detail in aqueous solution. More importantly, the study on photophysical properties of the N,S-CDs may provide the basis for the development of the N,S-CDs for the fluorescent probe of nitrophenol compounds.

A Short Report on the Polymerization of Pyrrole and Its Copolymers by Sonochemical Synthesis of Fluorescent Carbon Dots

In polymer chemistry, polymerization constitutes the process of the conversion of monomers into polymers using an initiator to form polymeric chains. There are many polymerization techniques and different systems exist by which the polymers are classified. Recently, our group has reported the synthesis of polymers using both carbon dots (CDs) and UV light as initiators. In these reports, the carbon dots were used with or without UV light. The CDs produce free radicals in the presence of UV light, indicating their role as initiators. The CD surface has many unshared or unpaired electrons, making it negatively charged. The present study focuses on the use of CDs for the formation of polymers from monomers containing various functional group. The properties of the synthesized CDs and the polymers obtained from the various monomers were characterized by various analytical techniques, including Fourier-Transform Infrared (FTIR) spectroscopy, X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and Solid-State NMR spectroscopy. This polymerization technique is of interest both from the scientific aspect and for its applicative potential. The synthesized polymers were investigated for their various applications.

P-doped carbon nano-powders for fingerprint imaging

A simple, fast, and laboratory efficient doped P carbon nanoparticles synthesis is developed for fingerprint imaging, using 1,3-dihydroxyacetone and di-phosphorous pentoxide. Fluorescence nanoparticles, with an average size of 230 nm were obtained, without additional energy input or external heating. ATR, solid NMR, XPS and fluorescence spectroscopy revealed their surface functionalization; a reaction mechanism is proposed. Fluorescence measurements exhibited a maximum emission band at ca. 495 nm, when excited at 385 nm. The images obtained, on different surfaces such as mobile telephone screen, magnetic band and metallic surface of a credit card and a Euro banknote treated with the obtained nano-powders allows us to record positive matches, confirming that the experimental results illustrate the effectiveness of proposed method.

One-step synthesis of S,B co-doped carbon dots and their application for selective and sensitive fluorescence detection of diethylstilbestrol

S,B co-doped carbon dots were synthesized, and their application in the detection of diethylstilbestrol.

Novel polymerization of aniline and pyrrole by carbon dots

This work reports on the synthesis of polymers (polyaniline, polypyrrole, and co-polymerization of polyaniline and polypyrrole) from monomers using carbon dots and UV light as initiators.

Fluorescent Nanoparticles with Tissue-Dependent Affinity for Live Zebrafish Imaging

Carbon quantum dots (CDs) are widely investigated because of their low toxicity, outstanding water solubility, and high biocompatibility. Specifically, fluorescent CDs have attracted ever-increasing interest. However, so far, only a few studies have focused on assessing the fluorescence of nitrogen-doped CDs (N@CDs) during in vivo exposure. Here, we describe a strategy for low-cost, one-pot synthesis of N@CDs. The low toxicity and suitability of the N@CDs for fluorescence imaging are validated using zebrafish (ZF) as a model. Strong fluorescence emission from ZF embryos and larvae confirms the distribution of N@CDs in ZF. The retention of N@CDs is very stable, long lasting, and with no detectable toxicity. The presence of a strong fluorescence at the yolk sac, especially in the vicinity of the intestine, suggests that a high content of N@CDs entered the digestive system. This indicates that N@CDs may have potential imaging applications in elucidating different aspects of lipoprotein and nutritional biology, in a ZF yolk lipid transport and metabolism model. On the other hand, the presence of a strong selective fluorescence at the eyes and melanophore strips at the trunk and tail region of ZF larvae suggests that N@CDs has a high melanin-binding affinity. These observations support a novel and revolutionary use of N@CDs as highly specific bioagents for eye and skin imaging and diagnosis of defects in them. N@CDs are known for their multifunctional applications as highly specific bioagents for various biomedical applications because of their exceptional biocompatibility, photostability, and selective affinity. These characteristics were validated in the developmental ZF model.

Microwave-assisted one pot three-component synthesis of some novel pyrazole scaffolds as potent anticancer agents

Background

Pyrazoles, thiazoles and 1,3,4-thiadiazoles have been reported to possess various pharmacological activities.

Results

An efficient and a novel approach for the synthesis of some novel pyrazole based-azoles are described via multi-component reaction under controlled microwave heating conditions. The structures of the synthesized compounds were assigned on the basis of elemental analysis, IR, ¹H NMR and mass spectral data. All the synthesized compounds were tested for in vitro activities against two antitumor cell lines, human lung cancer and human hepatocellular carcinoma compared with the employed standard antitumor drug (cisplatin).

Conclusions

All the newly synthesized compounds were evaluated for their anticancer activity against human lung cancer and human hepatocellular carcinoma cell lines using MTT assay. The results obtained exploring the high potency of six of the tested compounds compared with cisplatin. Graphical abstract

Thermo-responsive microgels based on encapsulated carbon quantum dots

In this work carbon quantum dots (CQDs) nanoparticles are synthesized from d-lactose using a hydrothermal method and then they are coated with polyethylene glycol (CQDs@PEG).

Carbon dots on based folic acid coated with PAMAM dendrimer as platform for Pt(IV) detection

Carbon quantum dots (CQDs) coated with poly(amidoamine) (PAMAM-NH2) dendrimer are prepared from folic acid and phosphoric acid under a hydrothermal procedure. The obtained nanoparticles are successfully used as fluorescent sensor for Pt(IV) (in the form of chloroplatinate ion). CQDs possess many attractive features including uniform dispersion with average size about 13nm for unmodified particles and, ∼30nm when they are coated with PAMAM-NH2 dendrimer. The synthesized nanoparticles have been characterized by elemental analysis, attenuated total reflectance (ATR), X-ray photoelectron (XPS) and Raman spectroscopies, transmission electron microscopy (TEM), dynamic light scattering (DLS), and steady-state and life-time fluorescence. CQDs are used as fluorescent sensor of Pt(IV) ion in aqueous media showing linear quenching effect of their fluorescence. The results obtained demonstrated a limit of detection of 657nM with an accuracy of the method of 0.13% (as RSD, n=10) and sensitivity of 78nM. Moreover, with the presence of other interference species, good results are obtained when applied in real samples from platinum nanoparticles synthesis. The dissolved platinum ions can be quantified in the range 6-96μM with an accuracy of 2.5%.

Perylenetetracarboxylic anhydride as a precursor of fluorescent carbon nanoonion rings

Thermal annealing at 400 °C of perylenetetracarboxylic anhydride in low molecular mass PEG gives rise to the formation of well defined nanoobjects of 2.5 nm height and size distribution from 10 to 65 nm (average 40 nm) after purification of the raw mixture with silicagel chromatography. TEM reveals that the flat nanoobjects are constituted of concentric graphenic rings (0.34 nm interlayer distance). The morphology of the nanoparticles resembles onion rings of nanometric dimensions (nanoonion rings C-NOR). C-NOR particles have an excitation dependent emission with λem from 430 to 570 nm and a maximum emission quantum yield of 0.49. C-NOR particles can be internalized into Hep3B human hepatoma cells as determined by confocal fluorescence microscopy and are remarkably biocompatible affecting slightly cell viability according to the MTT test.

Novel 4-heteroaryl-antipyrines as DPP-IV inhibitors

Type 2 diabetes mellitus is a vast growing progressive disease that almost affects one person among every twelve globally. Regardless the availability of wide variety of oral hypoglycemics, only one-third of patients achieves proper glycemic control. With the advantage of the low risk of hypoglycemia, DPP-IV attracted the attention of medicinal chemists as a new target for oral hypoglycemics. In this report, a lead compound 1, with antipyrine scaffold, was obtained, and its binding mode was calculated. Several derivatives with bridged nitrogenous heterocycles have been synthesized via multicomponent reaction under controlled microwave heating conditions. The antidiabetic activity versus DPP-IV protein was evaluated and compared with sitagliptin. Compounds with smaller- or medium-sized nitrogenous bridges were comparable with sitagliptin in terms of DPP-IV inhibitory activity, potentially via targeting Glu203 and Glu204. The oral hypoglycemic activities of compounds with submicromolar IC50 values were further evaluated using diabetic mouse model.

Synthesis of highly fluorescent nitrogen and phosphorus doped carbon dots for the detection of Fe(3+) ions in cancer cells

Highly fluorescent nitrogen and phosphorus-doped carbon dots with a quantum yield 59% have been successfully synthesized from citric acid and di-ammonium hydrogen phosphate by single step hydrothermal method. The synthesized carbon dots have high solubility as well as stability in aqueous medium. The as-obtained carbon dots are well monodispersed with particle sizes 1.5-4 nm. Owing to a good tunable fluorescence property and biocompatibility, the carbon dots were applied for intercellular sensing of Fe(3+) ions as well as cancer cell imaging.

Single step synthesis of carbon dot embedded chitosan nanoparticles for cell imaging and hydrophobic drug delivery

The florescent carbon dot conjugated chitosan nanoparticles are developed for the cellular imaging and delivery of poorly water soluble drug telmisartan (TEL).

A ratiometric nanosensor based on fluorescent carbon dots for label-free and highly selective recognition of DNA

A ratiometric nanosensor based on fluorescent carbon dots for label-free and highly selective recognition of DNA.

P-doped carbon dots act as a nanosensor for trace 2,4,6-trinitrophenol detection and a fluorescent reagent for biological imaging

A simple and rapid method for sensitive and selective detection of 2,4,6-trinitrophenol (TNP) was developed with the use of water-soluble carbon dots (CDs) as a nanosensor.