Highly photoluminescent and temperature-sensitive P, N, B-co-doped carbon quantum dots and their highly sensitive recognition for curcumin

Biogenic carbon quantum dots from marine endophytic fungi (Aspergillus flavus) to enhance the curcumin production and growth in Curcuma longa L

In this study, we have investigated the effect of carbon quantum dots (FM-CQDs) synthesized from marine fungal extract on Curcuma longa to improve the plant growth and curcumin production. The isolated fungus, Aspergillus flavus has produced a high amount of indole-3-acetic acid (IAA) (0.025 mg g-1), when treated with tryptophan. CQDs were synthesized from the A. flavus extract and it was characterized using ultraviolet visible spectrophotometer (UV-Vis) and high-resolution transmission electron microscopy (HR-TEM). The synthesized CQDs were excited at 365 nm in an UV-Vis and the HR-TEM analysis showed approximately 7.4 nm in size with a spherical shape. Both fungal crude extract (FCE) at 0-100 mg L-1 and FM-CQDs 0-5 mg L-1 concentrations were tested on C. longa. About 80 mg L-1 concentration FCE treated plants has shown a maximum height of 21 cm and FM-CQDs at 4 mg L-1 exhibited a maximum height of 25 cm compared to control. The FM-CQDs significantly increased the photosynthetic pigments such as total chlorophyll (1.08 mg g-1 FW) and carotenoids (17.32 mg g-1 FW) in C. longa. Further, antioxidant enzyme analysis confirmed that the optimum concentrations of both extracts did not have any toxic effects on the plants. FM-CQDs treated plants increased the curcumin content up to 0.060 mg g-1 by HPLC analysis. Semi quantitative analysis revealed that FCE and FM-CQDs significantly upregulated ClCURS1 gene expression in curcumin production.

Unraveling fluorescent mechanism of biomass-sourced carbon dots based on three major components: Cellulose, lignin, and protein

The complexity of biomass components leads to significant variations in the performance of biomass-based carbon dots (CDs). To shed light on this matter, this study presents a comparative analysis of the fluorescence properties of CDs using pure cellulose, lignin, and protein as models. Three CDs showed different fluorescent properties, resulting from the structure difference and carbonization behavior in the hydrothermal. The relatively gentle thermal degradation of proteins allows the macromolecular structure of amino acids to be preserved. This preservation results in a more regular lattice structure, a larger sp2 domain size, and N-doping, which contribute to the highest quantum yield (QY) of 8.7% of the CDs. In contrast, cellulose undergoes more severe thermal degradation with large amounts of small molecules generated, resulting in the CDs with fewer surface defects, more irregular lattice structures, and lower QY. These results provide a guideline for the design of carbon dots from different biomass.

Pyridinic-N-rich carbon dots in IFE-based Turn-off Fluorometric detection of nerve agent Mimic- Diethyl chlorophosphate and multicolor cell imaging

Fluorometric sensors for the detection of nerve agent mimics have received a lot of interest nowadays due to their high sensitivity and selectivity, ease of operation, and real-time monitoring. Pyridinic-N-rich carbon dots (NCDs) prepared through microwave-assisted pyrolysis of l-Malic acid and urea have been explored first time in this work as a novel turn-off fluorescent probe for the sensitive and selective detection of diethyl chlorophosphate (DCP), a nerve agent mimic. The as-prepared carbon dots contained a large amount of pyridinic nitrogen on their surface, which can modulate the photoluminescence properties of the NCDs. The blue emissive NCDs possessed both excitation wavelength-dependent and independent emission behavior. The detection of DCP was premised on quenching of the fluorescence emission intensity of NCDs in the presence of similar chemical reagents (e.g., trimethyl phosphate, triethyl phosphate, triethyl phosphonoacetate, triphenyl phosphate, diphenyl phosphate, tributyl phosphate). Fluorescence quenching of the NCDs in the presence of DCP has been attributed to the inner filter effect (IFE). From the linear Stern-Volmer plot (R² = 0.9992), the limit of detection (LOD) was found to be 84 μM for sensing DCP for the concentration ranging between 3 and 15 mM. The biocompatibility of NCDs was assessed through cytotoxicity assay on MDA-MB-231 breast cancer cells. Fluorescence imaging demonstrated that NCDs have low cytotoxicity and can be employed successfully in cell imaging.

High luminescent N,S,P co-doped carbon dots for the fluorescence sensing of extreme acidity and folic acid

Carbon dots are popular luminescent materials because of their excellent fluorescence properties, but the low quantum yield limits their application. Heteroatom doping is a more convenient and popular approach to increase the quantum yield of carbon dots. Here, novel N,S,P heteroatom co-doped carbon dots (N,S,P-CDs) were synthesized by a simple one-step hydrothermal method using m-phenylenediamine, L-cysteine and phosphoric acid as raw materials. The as-prepared N,S,P-CDs showed excellent photoluminescence properties with a fluorescence quantum yield of up to 41%, which greatly encourages their application in fluorescence sensing. The N,S,P-CDs exhibited good fluorescence stability under salt solution, xenon lamp irradiation and ultraviolet lamp irradiation except for a high sensitivity to extreme acidity. The fluorescence intensity of the N,S,P-CDs can be decreased by as much as 85% when the pH of the solution changes from 2.50 to 4.75, that is, a small fluctuation in pH can cause an intense response of the fluorescence of the N,S,P-CDs. Therefore, an excellent fluorescence sensing platform for accurately monitoring the pH of extreme acidity has been constructed. In addition, the N,S,P-CDs can be applied for quantitative detection of folic acid based on the strong quenching effect of folic acid on the fluorescence of the N,S,P-CDs. Good linearity was obtained in the concentration range of 4.85-82.45 μM, with a detection limit of 0.148 μM. The constructed sensing platform was used for the determination of folic acid in actual samples of orange juice, oatmeal and tablets with satisfactory results.

Multiple heteroatom dopant carbon dots as a novel photoluminescent probe for the sensitive detection of Cu2+ and Fe3+ ions in living cells and environmental sample analysis

Heavy metal ion pollution harms human health and the environment and continues to worsen. Here, we report the synthesis of boron (B), phosphorous (P), nitrogen (N), and sulfur (S) co-doped carbon dots (BP/NS-CDs) by a one-step facile hydrothermal process. The optimum synthetic parameters are of 180 °C temperature, 12 h reaction time and 15% of PBA mass. The as-synthesized BP/NS-CDs exhibits excellent water solubility, strong green photoluminescence (PL) at 510 nm, and a high quantum yield of 22.4%. Moreover, BP/NS-CDs presented high monodispersity (7.2 ± 0.45 nm), excitation-dependent emission, PL stability over large pH, and high ionic strength. FTIR, XRD, and XPS are used to confirm the successful B and P doping of BP/NS-CDs. BP/NS-CD photoluminescent probes are selectively quenched by Cu²⁺ and Fe³⁺ ions but showed no response to the presence of other metal cations. The PL emission of BP/NS-CDs exhibited a good linear correlation with Cu²⁺ and Fe³⁺ concentrations with detection limits of 0.18 μM and 0.27 μM for Cu²⁺ and Fe³⁺, respectively. Furthermore, the HCT116 survival cells kept at 99.4 ± 1.3% and cell imaging capability, when the BP/NS-CDs concentration is up to 300 μg/mL by MTT assay. The proposed sensor is potential applications for the detection of Cu²⁺ and Fe³⁺ ions in environmental water samples.

Functional bioactive compounds in ginger, turmeric, and garlic

Nutrition plays a very important role in the health promotion of individuals and brought about a global paradigm shift from pharmaceuticals to nutraceuticals. This is due to the high cost, non-availability, and side effects associated with the unregulated consumption of pharmaceuticals. Over the ages, nutraceuticals from food products were reported to contain bioactive compounds with great health and physiological benefits. This report reviews bioactive compounds in selected foods namely ginger (Zingiber officinale), turmeric (Curcuma longa), and garlic (Allium sativum) as potential natural therapeutics for ailments of cancer and heart-related diseases. Analytical profiles, functional activities, and characterization of these compounds were discussed with possible recommendations for the prospective treatment of diseases using these nutraceuticals.

Nanostructured Carbon Electrocatalysts for Energy Conversions

The growing energy demand worldwide has led to increased use of fossil fuels. This, in turn, is making fossil fuels dwindle faster and cause more negative environmental impacts. Thus, alternative, environmentally friendly energy sources such as fuel cells and electrolyzers are being developed. While significant progress has already been made in this area, such energy systems are still hard to scale up because of their noble metal catalysts. In this concept paper, first, various scalable nanocarbon-based electrocatalysts that are being synthesized for energy conversions in these energy systems are introduced. Next, notable heteroatom-doping and nanostructuring strategies that are applied to produce different nanostructured carbon materials with high electrocatalytic activities for energy conversions are discussed. The concepts used to develop such materials with different structures and large density of dopant-based catalytic functional groups in a sustainable way, and the challenges therein, are emphasized in the discussions. The discussions also include the importance of various analytical, theoretical, and computational methods to probe the relationships between the compositions, structures, dopants, and active catalytic sites in such materials. These studies, coupled with experimental studies, can further guide innovative synthetic routes to efficient nanostructured carbon electrocatalysts for practical, large-scale energy conversion applications.

Solid-State Fluorescent Selenium Quantum Dots by a Solvothermal-Assisted Sol-Gel Route for Curcumin Sensing

Toward the need for solid-state fluorescent quantum dots, resistant to self-quenching, we describe a solvothermal-assisted sol-gel method to synthesize Se quantum dots. Morphological and crystalline characterizations reveal that Se quantum dots (average size 3-8 nm) have a trigonal crystal structure. The presence of planar defects (dislocations, stacking faults, twins, and grain boundaries) suggests formation of Se nanocrystallites through aggregation-based crystal growth mechanisms. Under ultraviolet excitation, the quantum dots exhibit an excitation wavelength-dependent solid-state blue emission with an average lifetime of 1.96 ns. Depending on fluorescence quenching by curcumin, selenium quantum dots act as ideal candidates for inner filter effect-based curcumin sensing.

Nitrogen-doped fluorescence carbon dots as multi-mechanism detection for iodide and curcumin in biological and food samples

Iodine ion is one of the most indispensable anions in living organisms, particularly being an important substance for the synthesis of thyroid hormones. Curcumin is a yellow-orange polyphenol compound derived from the rhizome of Curcuma longa L., which has been commonly used as a spice and natural coloring agent, food additives, cosmetics as well as Chinese medicine. However, excess curcumin may cause DNA inactivation, lead to a decrease in intracellular ATP levels, and trigger the tissue necrosis. Therefore, quantitative detection of iodine and curcumin is of great significance in the fields of food and life sciences. Herein, we develop nitrogen-doped fluorescent carbon dots (NCDs) as a multi-mechanism detection for iodide and curcumin in actual complex biological and food samples, which was prepared by a one-step solid-phase synthesis using tartaric acid and urea as precursors without adding any other reagents. An assembled NCDs-Hg2+ fluorescence-enhanced sensor for the quantitative detection of I- was established based on a fluorescence "turn-off-on" mechanism in a linear range of 0.3-15 μM with a detection limit of 69.4 nM and successfully quantified trace amounts of I- in water samples and urine sample. Meanwhile, the as-synthesized NCDs also can be used as a fluorescent quenched sensor for curcumin detection based on the synergistic internal filtration effect (IFE) and static quenching, achieving a good linear range of 0.1-20 μM with a satisfactory detection limit of 29.8 nM. These results indicate that carbon dots are potential sensing materials for iodine and curcumin detection for the good of our health.

One-step synthesis of red emission multifunctional carbon dots for label-free detection of berberine and curcumin and cell imaging

In this work, the red emission multifunctional carbon dots (R-CDs) were prepared via one-pot hydrothermal strategy of neutral red (NR) and ethylenediamine (EDA) for the label-free detection of berberine and curcumin, cell imaging, and fluorescent flexible film. The as-fabricated R-CDs not only possess good water dispersibility and excellent fluorescence stability, but also were successfully employed as a photoluminescent nanoprobe for label-free monitoring of berberine (BRH) and curcumin (Cur) based on dynamic quenching and internal filter effect (IFE), respectively. More importantly, as-proposed R-CDs displayed outstanding cellular permeability and lower cytotoxicity for cellular applications, which was consistent with the results of confocal fluorescence imaging and cell viability measurement of SMMC7721 cells. Thus, the multifunctional R-CDs may provide a rich tool library for biosensing and cellular imaging reagent applications. Interestingly, R-CDs were also used to manufacture R-CDs/PVA composites as fluorescent flexible films. To the best of our knowledge, this is the first demonstration of a label-free multifunctional fluorescent nanoprobe for berberine and curcumin based on red emission CDs.

Doped-carbon dots: Recent advances in their biosensing, bioimaging and therapy applications

As a fascinating class of fluorescent carbon dots (CDs), doped-CDs are now sparked intense research interest, particularly in the diverse fields of biomedical applications due to their unique advantages, including low toxicity, physicochemical, photostability, excellent biocompatibility, and so on. In this review, we have summarized the most recent developments in the literature regarding the employment of doped-CDs for pharmaceutical and medical applications, which are published over approximately the past five years. Accordingly, we discuss the toxicity and optical properties of these nanomaterials. Beyond the presentation of successful examples of the application of these multifunctional nanoparticles in photothermal therapy, photodynamic therapy, and antibacterial activity, we further highlight their application in the cellular labeling, dual imaging, and in vitro and in vivo bioimaging by use of fluorescent-, photoacoustic-, magnetic-, and computed tomography (CT)-imaging. The potency of doped-CDs was also described in the biosensing of ions, small molecules, and drugs in biological samples or inside the cells. Finally, the advantages, disadvantages, and common limitations of doped-CD technologies are reviewed, along with the future prospects in biomedical research. Therefore, this review provides a concise insight into the current developments and challenges in the field of doped-CDs, especially for biological and biomedical researchers.

Biosensors and Sensing Systems for Rapid Analysis of Phenolic Compounds from Plants: A Comprehensive Review

Phenolic compounds are secondary metabolites frequently found in plants that exhibit many different effects on human health. Because of the relevant bioactivity, their identification and quantification in agro-food matrices as well as in biological samples are a fundamental issue in the field of quality control of food and food supplements, and clinical analysis. In this review, a critical selection of sensors and biosensors for rapid and selective detection of phenolic compounds is discussed. Sensors based on electrochemistry, photoelectrochemistry, fluorescence, and colorimetry are discussed including devices with or without specific recognition elements, such as biomolecules, enzymes and molecularly imprinted materials. Systems that have been tested on real matrices are prevalently considered but also techniques that show potential development in the field.

Recent Advancement in Bio-precursor derived graphene quantum dots: Synthesis, Characterization and Toxicological Perspective

Graphene quantum dots (GQDs), impressive materials with enormous future potential, are reviewed from their inception, including different precursors. Considering the increasing burden of industrial and ecological bio-waste, there is an urgency to develop techniques which will convert biowaste into active moieties of interest. Amongst the various materials explored, we selectively highlight the use of potential carbon containing bioprecursors (e.g. plant-based, amino acids, carbohydrates), and industrial waste and its conversion into GQDs with negligible use of chemicals. This review focuses on the effects of different processing parameters that affect the properties of GQDs, including the surface functionalization, paradigmatic characterization, toxicity and biocompatibility issues of bioprecursor derived GQDs. This review also examines current challenges and s the ongoing exploration of potential bioprecursors for ecofriendly GQD synthesis for future applications. This review sheds further light on the electronic and optical properties of GQDs along with the effects of doping on the same. This review may aid in future design approaches and applications of GQDs in the biomedical and materials design fields.

Synthesis of green-emitting carbon quantum dots with double carbon sources and their application as a fluorescent probe for selective detection of Cu2+ ions

Green-emitting carbon quantum dots (G-CQDs) were prepared using tartaric acid and bran by one-pot solvothermal treatment and had photoluminescence quantum yields (PL QY) as high as 46%. The morphology of the G-CQDs is characterized by TEM, which shows the average diameter of G-CQDs is approximately ∼4.85 nm. The FT-IR spectra display the presence of -OH, C-N, N-H and -COOH on the surface of the G-CQDs. The emission wavelength of the G-CQDs was ∼539 nm in the case of ∼450 nm excitation wavelength, which corresponds to the green fluorescence. Furthermore, the G-CQDs were used as a fluorescent probe for detection Cu2+ ions, and demonstrated a linear distribution between ln(F/F 0) and the Cu2+ ions concentration. Specifically, the Cu2+ ion concentration should fall in the G-CQD concentration range of 0-0.5 mM and the detection limit is 0.0507 μM. Thus, due to the excellent chemical stability and good luminescence performance, these G-CQDs could be excellent probes widely used in detection fields.

A monocomponent bifunctional benzophenone–carbazole type II photoinitiator for LED photoinitiating systems

A bifunctional benzophenone–carbazole-based photoinitiator (BPC) was designed from its molecular structure viewpoint.

A simple, cost-effective and selective analysis of glucose via electrochemical impedance sensing based on copper and nitrogen co-doped carbon quantum dots

Cu,N co-doped CQDs were prepared and employed as electrode modification materials for improving the efficiency of electron transfer. The Cu and N co-doped CQDs exhibited high electrocatalytic activity for glucose sensing in alkaline medium.

Recent Advancements in Doped/Co-Doped Carbon Quantum Dots for Multi-Potential Applications

Carbon quantum dots (CQDs)/carbon nanodots are a new class of fluorescent carbon nanomaterials having an approximate size in the range of 2–10 nm. The majority of the reported review articles have discussed about the development of the CQDs (via simple and cost-effective synthesis methods) for use in bio-imaging and chemical-/biological-sensing applications. However, there is a severe lack of consolidated studies on the recently developed CQDs (especially doped/co-doped) that are utilized in different areas of application. Hence, in this review, we have extensively discussed about the recent development in doped and co-doped CQDs (using elements/heteroatoms—e.g., boron (B), fluorine (F), nitrogen (N), sulphur (S), and phosphorous (P)), along with their synthesis method, reaction conditions, and/or quantum yield (QY), and their emerging multi-potential applications including electrical/electronics (such as light emitting diode (LED) and solar cells), fluorescent ink for anti-counterfeiting, optical sensors (for detection of metal ions, drugs, and pesticides/fungicides), gene delivery, and temperature probing.