Natural Carbon Source Research Articles

Green Protocol for the Synthesis of Luminescent Carbon Nanodots Derived from Murraya Koenigii Leaves and Urea: Enhancing Photoluminescence for Advanced Bioimaging.

We have synthesized Murraya Koenigii leaves powder-derived carbon nanodots (CNDs) by hydrothermal method. A tribute to our commitment to environmental sustainability is the unique composition of our CNDs, which are made entirely of natural carbon sources and a green solvent, water. Our further efforts to improve performance led us to start making nitrogen-doped CNDs. By using urea as a non-toxic source of nitrogen, we observed a substantial increase in fluorescence intensity, extending the usefulness and potential of these nanomaterials. We investigated the optical properties using UV-Vis and fluorescence spectroscopy. The other parameters, like structural and size-shape morphology, were analyzed using FTIR, XRD, and HR-TEM, respectively. The fluorescence spectroscopy demonstrated their capability to exhibit wavelength-dependent photoluminescence (PL), highlighting the potential of these CNDs for cell bioimaging applications. The fluorescence properties affirm their suitability for biomedical applications, as they do not involve any inherent risk to cells.

Trans-aconitic acid assimilation system as a widespread bacterial mechanism for environmental adaptation.

The ability of bacteria to use natural carbon sources greatly affects their growth and survival in the environment. Bacteria have evolved versatile abilities to use environmental carbon sources, but their diversity and assimilation pathways remain largely unexplored. Trans-aconitic acid, a geometric isomer of cis-aconitic acid involved in the tricarboxylic acid cycle, has long been considered a natural carbon source metabolizable by bacteria. However, its catabolism and ecological role in linking bacterial interactions with the environments remain unclear. Here, we identify a regulatory system in Bacillus velezensis FZB42 that is capable of sensing and catabolizing trans-aconitic acid. The system consists of a tar operon, an adjacent positive regulatory gene tarR, and a shared promoter. After receiving the trans-aconitic acid signal, the TarR protein interacts directly with the promoter, initiating the expression of the membrane transporter TarB and aconitate isomerase TarA encoded by the operon, which function in importing the trans-aconitic acid and isomerizing it into the central intermediate cis-aconitic acid. Subsequent soil colonization experiments reveal that trans-aconitic acid assimilating ability can give its coding bacteria a growth and competitive advantage. Bioinformatics analyses coupled with bacterial isolation experiments further show that the assimilation system of trans-aconitic acid is widely distributed in the bacterial domain, and its assimilating bacteria also extensively distributed in nature, indicating an important role of trans-aconitic acid metabolism in bacterial carbon acquisition. This work emphasizes the importance of metabolic adaptation to environmental carbon sources for bacterial survival and may provide inspiration for engineering microbes with enhanced environmental competitiveness.

Carbohydrate Derived Value-added Products from Lignocelluloses

Abstract: Chemistry is confronted with the pressing issues of depleting non-renewable fossil resources and the imperative to combat environmental pollution, which is crucial for a sustainable future. Biomass stands out as the sole organic carbon source in nature among the array of sustainable resources available, positioning it as a prime substitute for fossil-derived chemicals and fuels. Extensive research has been conducted on the abundant lignocelluloses as a potential source for biofuels, bioenergy, and various valuable products, wherein, the incorporation of various processes in biomass fractionation to separate biopolymers (such as lignin, cellulose, and hemicellulose) has the potential to enhance the overall value of the process. However, industrial demonstration of biomass utilization for commercial products has been limited due to the challenges posed by the recalcitrance and complexity of biomass. Therefore, there is a need for efficient reaction processes to enable the production of bio-chemicals and fuels from renewable lignocellulose. This review focuses on the latest chemical methods developed for producing value-added chemicals from biomass-derived cellulose as a renewable feedstock.

Graphene Quantum Dots from Natural Carbon Sources for Drug and Gene Delivery in Cancer Treatment

Cancer therapy is constantly evolving, with a growing emphasis on targeted and efficient treatment options. In this context, graphene quantum dots (GQDs) have emerged as promising agents for precise drug and gene delivery due to their unique attributes, such as high surface area, photoluminescence, up-conversion photoluminescence, and biocompatibility. GQDs can damage cancer cells and exhibit intrinsic photothermal conversion and singlet oxygen generation efficiency under specific light irradiation, enhancing their effectiveness. They serve as direct therapeutic agents and versatile drug delivery platforms capable of being easily functionalized with various targeting molecules and therapeutic agents. However, challenges such as achieving uniform size and morphology, precise bandgap engineering, and scalability, along with minimizing cytotoxicity and the environmental impact of their production, must be addressed. Additionally, there is a need for a more comprehensive understanding of cellular mechanisms and drug release processes, as well as improved purification methods. Integrating GQDs into existing drug delivery systems enhances the efficacy of traditional treatments, offering more efficient and less invasive options for cancer patients. This review highlights the transformative potential of GQDs in cancer therapy while acknowledging the challenges that researchers must overcome for broader application.

Tri-site Synergistic Cu(I)/Cu(II)─N Single-Atom Catalysts for Additive-Free CO2 Conversion.

As the highly stable and abundant carbon source in nature, the activation and conversion of CO2 into high-value chemicals is highly desirable yet challenging. The development of Cu(I)/Cu(II)─N tri-site synergistic single-atom catalysts (TS-SACs) with remarkable CO2 activation and conversion performance is presented, eliminating the need for external additives in cascade reactions. Under mild conditions (40°C, atmospheric CO2), the catalyst achieves high yields (up to 99%) of valuable 2-oxazolidinones from CO2 and propargylamine. Notably, the catalyst demonstrates easy recovery, short reaction times, and excellent tolerance toward various functional groups. Supported by operando techniques and density functional theory calculations, it is elucidated that the spatially proximal Cu(I)/Cu(II)─N sites facilitate the coupling of multiple chemical transformations. This surpasses the performance of supported isolated Cu(I) or Cu(II) catalysts and traditional organic base-assisted cascade processes. These Cu(I)/Cu(II)─N tri-site synergistic atom active sites not only enable the co-activation of CO2 at the Cu(II)─N pair and alkyne at the Cu(I) site but also induce a di-metal locking geometric effect that accelerates the ring closure of cyclic carbamate intermediates. The work overcomes the limitations of single metal sites and paves the way for designing multisite catalysts for CO2 activation, especially for consecutive activation, tandem, or cascade reactions.

Fluorescent sensing of rutin by carbon dots derived from the heart of cumin seeds

Carbon dots (CDs) prepared from biomass usually produce poor quantum yield and reproducibility. A fine separation of raw materials may enhance the fluorescence performance. In this work, embryos of cumin seeds were precisely chosen as the carbon source to prepare (CDs) through hydrothermal method. The obtained product (CDs-E) possessed a higher quantum yield of 10.60 % than those synthesized with testas or whole seeds, which may be due to the relatively smaller particle size and more C-N functional groups. Rutin, as a common natural active component, could quench the fluorescence of CDs-E notably through internal filtering effect. Herein, a highly selective fluorescent sensor based on CDs-E for detecting rutin was proposed with a linearity range of 0.05 ∼ 30 μM and a detection limit of 0.015 μM obtained. Additionally, the developed method was successfully applied for the detection of rutin in Flos Sophorae, rutin tablets and capsules. This work showed the significance of fine classification for natural carbon source in preparation of CDs and provided a feasible method for quality monitoring of rutin-related pharmaceuticals, health care products and traditional Chinese medicinal materials.

An investigation on the photocatalytic and antibacterial response of green fluorescent carbon dots synthesized from corn flour

Abstract The present work elucidates on a facile hydrothermal synthesis method for producing highly fluorescent carbon dots using corn flour as a natural carbon source. The structural confirmation was validated through XRD (X-ray Diffraction), HR-TEM (High-Resolution Transmission Electron Microscope), and FTIR (Fourier Transform Infra-Red) studies. The synthesized carbon dots exhibited an excitation-dependent photoluminescence (PL) emission. The optical band gap of as-synthesized carbon dots was estimated using UV-absorption spectral analysis. The variation in optical and luminescent response of the carbon dot suspension with the rate of centrifugation was also monitored. Furthermore, investigations on the photocatalytic response of as-synthesized carbon dots towards degradation of methylene blue and its activity as a potential antimicrobial agent against Escherichia coli are also presented.

Enhanced in situ bioremediation of chlorinated ethenes: from in situ microcosms to full-scale application

Concentrations greater than 20 mg/L of chlorinated volatile organic compounds (cVOCs) including tetrachloroethene (PCE), trichloroethene (TCE), and cis-1,2-dichloroethene (cDCE) have been present in site groundwater for more than four decades. To promote a faster clean-up time, an in situ bioremediation approach was evaluated using In-Situ Microcosms® (ISMs) followed by a full-scale in situ bioremediation approach. The ISM study evaluated slow-release versus quick-release carbon substrates with and without bioaugmentation using the chlorinated ethene degrading culture, SDC-9™. After a three-month incubation period, the ISMs were retrieved. The ISMs amended with a carbon source with or without bioaugmentation displayed greater than a 93% reduction in TCE, which corresponded to an increase in cDCE in all the ISMs. The Dehalococcoides population and gene abundances associated with chlorinated ethene biodegradation (tceA, bvcA, vcrA) increased three orders of magnitude in the bioaugmented ISMs over the natural attenuation ISM and carbon source only amended ISMs. Additionally, the SDC-9™ and AquaBupH®, an enhanced emulsified oil substrate (EOS®) and buffer, amended ISM unit showed the highest level of vinyl chloride and similar level of ethene to the SDC-9™ and EHC®, a controlled-release, organo-iron substrate, ISM. However, the AquaBupH and SDC-9™ ISM displayed the highest level of acetate, demonstrating active fermentation processes. The results of the ISM study indicated that a combined approach of biostimulation along with bioaugmentation effectively promoted conditions conducive to reductive dechlorination. The full-scale in situ bioremediation system coupled biostimulation with bioaugmentation using SDC-9™ to successfully reduce chlorinated ethenes in groundwater. The slow-release carbon substrate, EOS-100® served as a sustained carbon source along with CoBupH (buffering agent similar to AquaBupH), facilitating the production of hydrogen, through volatile fatty acid fermentation. This led to the reduction of chlorinated ethenes over the subsequent three years, showcasing minimal rebound in contaminant levels. Two rounds of bioaugmentation notably increased the Dehalococcoides population, accelerating the biodegradation processes, which is setting up the site for monitored natural attenuation. This study shows that using ISMs to guide full-scale bioremediation design resulted in an effective cVOC biodegradation system that led to quicker and more sustainable clean-up.

Green Synthesis of Highly Fluorescent NCQDs: A Comprehensive Study on Synthesis, Characterization, Photophysical Properties, pH Sensing, Heavy Metal Detection, and Solvatochromic Behavior through Hydrothermal Method.

Solvatochromic studies in conjunction with NCQDs and analysis of material at different pH levels provide valuable insights about the process of metal ion sensing. Metal ion sensing holds significant importance in various fields like environment monitoring, biomedical diagnostics and various industrial purpose. The detection of metal ions by mixing the nitrogen-doped quantum dots (NCQDs) in the solvent at different pH levels for the analysis of the photoluminescence spectra is the unique property to achieve selective metal ion detection.In present study, the synthesis of NCQDs was performed by the use of flowers of Tecoma stans. The synthesis of NCQDs to best of our knowledge using flowers of Tecoma stans as natural carbon source via hydrothermal process has been done for the first time. The NCQDs exhibit absorption bands ranging from 190 to 450nm, with the energy band gap varying from 3.55 to 5.42eV when mixed with different solvent such as, 1-4 dioxane, acetone, acetonitrile, ethyl- acetate, ethanol, methanol and toluene. The fluorescence spectra exhibited highly intense range from approximately 390 to 680nm across various solvents. XRD analysis further confirmed the crystalline nature of the particles with an average size of 6.96nm. Different peak positions of the FTIR spectra support functional groups having C-H stretching, C = O (carbonyl) stretching, and C = C stretching vibrations.In the study a notable solvatochromic shift was observed, indicating sensitivity to change in solvent polarity. Additionally, the investigation of the ratio of ground to excited state dipole moment based on solvatochromic shift yielded a value of 3.30. This provide valuable information about optical and electronic properties of NCQDs. Overall, our study sheds light on the unique properties of NCQDs synthesized from Tecoma stans flowers and their potential applications in metal ion sensing, pH probing, and solvent polarity studies.

Production of alkaline protease by Aspergillus niger in a new combinational paper waste culture medium

Enzymes derived from microbial sources have gained increasing popularity in industrial applications over the past decades. Despite the high production cost, alkaline proteases have wide applications in industries such as tanneries, food production, and detergents. In recent years, there has been a shift towards utilizing natural carbon sources for cultivating microorganisms and extracting proteases in order to reduce production costs. This study aimed to investigate the biochemical and kinetic properties of protease enzymes obtained from Aspergillus niger cultivated in a paper waste medium and compare with the enzyme produced in a basal medium. Glucose is a more favorable carbon source compared to cellulose, so paper waste was pretreated with cellulose-degrading bacteria to convert cellulose into smaller carbohydrates. After the growth of A.niger in basal and combinational media, the enzymatic properties were compared between the extracted enzymes by using casein as substrate. The results demonstrated that A.niger could produce protease enzymes in the paper waste medium similar to the basal medium with more than 5-fold cost saving. The specific activity of the enzymes isolated from the basal and paper waste media was calculated to be 184.95 ± 10.56 Uml-1 and 169.88 ± 11.05 Uml-1, respectively. Carbon sources did not affect the optimum pH and temperature of the protease enzyme, which were found to be 8 and 37 °C, respectively. This study provides valuable insights into the production of alkaline protease from A.niger using a combinational medium (paper waste pretreated by cellulose-degrading bacteria), offering a cost-effective approach for industrial applications.

Synthesis of carbon quantum dots from Trigonella foenum-graecum L seeds and their biodistribution in mice as an inorganic isotope label

Nowadays, researchers are paying significant attention to the processing of natural carbon sources in order to improve human safety and reduce environmental pollution by means of green synthesis methods. Based on this, the present study has been investigated the green synthesis of carbon quantum dots (CQDs) with unique properties, by a natural carbon source called Trigonella foenum-graecum L (TF), through one- pot hydrothermal strategy. The results of different analysis methods (FTIR, FESEM, EDAX, TEM, UV–Vis, and PL) provided the necessary confirmations for the synthesized CQDs. Synthesized CQDs with spherical morphology and an average size of ∼ 5 nm have been a quantum efficiency of 18.9 % and optimal fluorescence under the excitation wavelength of 410 nm. Subsequently, the biological effects of CQDs (MTT assay) on CT26 cancer cell line was confirmed to be cytotoxic by observing an increase in the concentration of CQDs along with the IC50 value (∼826 μg/ml). Also, the two factors of colloidal stability and cytotoxicity, which depend on the concentration of CQDs, were considered to investigate the biological distribution of labeled 99mTc-CQDs that were intravenously injected into rats. Taken together, this work has been succeeded in providing data on the potential of CQDs for diagnostic and imaging fields in broader research.

Rational hydrothermal-assisted green synthesis of blueish emitting carbon dots as an optical sensing platform for antibiotic detection in the milk sample

Carbon dots (CDs) derived from biological entities significantly play a major part in environmental and biomedical applications, comprising electrocatalytic oxidations, antibiotics detection, biosensing, and bioimaging. In the present work, facile green synthesis of blue-emitting CDs has been done using one-step hydrothermal treatment of pulp extract of Ziziphus mauritiana, acting as a natural source of carbon for optical determination of ciprofloxacin (CIP) antibiotics. The process is easy, safe for the environment, and doesn't require any specialized equipment or chemicals. The structural and optical characteristics of the synthesized CDs are done using XRD, FTIR, UV–visible spectroscopies, SEM-EDX, PL, and TEM. CDs were found to have a quasi-spherical shape with an average size of 2.54 nm. Nitrogen (1.2 wt.%), oxygen (41.8 wt.%), and carbon (40.7 wt.%) are the main component found in CDs, as observed by EDX. These CDs showed blue emission under UV light, excitation-dependent emission, and wide excitation-emission spectra. These prepared CDs were used to selectively detect CIP and exhibit a high quantum yield of 30% at the excitation wavelength of 340 nm. After the optimal parameters, the sensor gave the linear detection range from 10 to 100 µM along with a detection limit of 0.56 µM. Moreover, the practical applicability of the developed sensor was confirmed in real milk samples to test the consistency and accuracy of the sensor. In conclusion, the proposed method is a green, rapid, highly sensitive, and selective method for the detection of CIP in real milk samples, demonstrating the potential application of CDs in food detection.

Electrochemical Sensor Based on N–Doped Carbon Nanodots Derived from the Agro-Waste Cotton Boll Peel Extracts for Nano Molar Determination of an Anti-Cancer Drug, Pemetrexed

A green and facile one-step synthetic route was proposed for the synthesis of nitrogen-doped carbon nanodots (N-CDs) from agro-waste cotton boll peel extract as a natural carbon source and glycine as a nitrogen source. The prepared N-CDs were utilized further in the fabrication of an electrochemical sensor for the nanomolar determination of an anti-cancer drug, pemetrexed (PMT). The electrode material was characterized by XRD, FTIR, TEM, Raman, EDX, UV–vis, fluorescence, cyclic voltammetric and electrochemical impedance spectroscopic studies. The N-CDs drop-casted on the surface of glassy carbon electrode (GCE) served as a good sensing material and exhibited electrocatalytic activity as evident from ∼20-fold enhancement in the oxidation peak current of PMT at N-CDs/GCE with 130 mV lesser positive oxidation peak potential than that at bare GCE. This was attributed to excellent conductivity, higher electroactive surface area, graphitic cores of N-CDs besides the interactions between PMT and N-CDs via hydrogen bonding and π–π stacking. The sensing performance of the demonstrated electrode was optimized by varying the peak current dependant parameters and also by investigating the influence of interfering substances in the determination of PMT. The electrochemical behaviour of PMT at different pH revealed the adsorption controlled electrode process with the involvement of protons. Under optimized conditions, differential pulse voltammetric (DPV), square wave voltammetric (SWV) and adsorptive differential pulse voltammetric (AdSDPV) methods were developed for sensitive determination of PMT at nano molar level. Further, these developed analytical methods were applied successfully for the determination of PMT in analyte fortified human urine samples and pharmaceutical formulations.

Management of Agri-Food Waste Based on Thermochemical Processes towards a Circular Bioeconomy Concept: The Case Study of the Portuguese Industry

Sustainable biomass production has a significant potential for mitigating greenhouse gas emissions, providing an alternative to produce eco-friendly biofuels, biochemicals, and carbonaceous materials for biological, energetic, and environmental applications. Biomass from agroforestry and agricultural wastes is the richest natural carbon source and a sustainable option for woody biomass from a circular economic perspective. The European Union (EU) is estimated to produce 1.3 billion tons of agri-food waste annually. Portugal has a large supply of residual biomass, as well as other byproducts and wastes from forestry, agriculture, and the food industry, and has a high availability of residual biomass. By using biomass waste to create high-value products, Portugal envisages an improvement in its economic performance, while reducing its dependence on energy imports and fossil fuel use. This review explores the potential of agri-food waste obtained from Portuguese industries through thermochemical conversion technologies as a promising sustainable substitute for wood-based biomass for the development of eco-friendly biofuels, biochemicals, and high-value carbonaceous materials, and their applications. This strategy, based on the circular bioeconomy concept, can help reduce reliance on fossil fuels, reduce greenhouse gas emissions, fulfil the needs of the growing population, and offer a sustainable waste management solution.

Tunable broadband terahertz absorption and shielding of bioderived graphitic carbon microspheres

The rapid advancement of Terahertz (THz) science and technology has led to a growing interest in electromagnetic interference (EMI) shielding in the THz frequency region. There is an urgent need for broadband and tunable devices capable of absorbing terahertz (THz) waves to effectively eliminate undesired THz interference. In this regard, this work demonstrates the facile synthesis of graphitic carbon microspheres from turpentine oil (a natural carbon source) and its broadband absorption and shielding properties in the THz frequency region from 0.2 THz to 1.6 THz. Advanced characterization techniques like XRD, FESEM, RAMAN, and XPS have been employed to explore the structural, microstructural, and elemental properties of graphitic carbon microspheres (GCMs). Herein, an effort has been made to discuss the underlying mechanism for THz absorption by GCMs. The minimum shielding efficacy reaches −27.5 dB covering the broad frequency region from 0.2 to 1.6 THz with a matching thickness of ∼3.75 μm, signifying that more than 99% of the THz radiations can be shielded. Also, GCMs are exhibiting exceptional terahertz absorption (∼86%) spanning from 0.2 to 1.6 THz for the same sample thickness. Our findings reveal valuable insights into the THz shielding properties of graphitic carbon thin films without any complex element doping or functionalization, shedding light on their suitability for future THz-based devices.

An effective and simple strategy for highly selective and anti-interference detection of dopamine based on the carbon quantum dots-molecularly imprinted polymers modified electrode

Dopamine (DA) dysfunction is known to cause neurological and physiological disorders, such as schizophrenia, Parkinson's disease, and addictive behavior. Therefore, dopamine detection is essential for both diagnosis and disease prevention. In this study, a novel and effective electrochemical sensor was fabricated based on a carbon quantum dots (CQDs)@molecularly imprinted polymers (MIPs) modified electrode for dopamine detection. The CQDs were obtained by an eco-friendly hydrothermal carbonization method, using sycamore leaves as a natural carbon source. The structure of the prepared CQDs@MIPs composite was confirmed through techniques including Ultraviolet–visible absorption spectroscopy, dynamic light scattering technique, scanning electron microscopy, and transmission electron microscopy. By combining the rapid electron transfer rate of the CQDs with the selective activity of the MIPs, the prepared CQDs@MIPs composite-modified electrode demonstrated greatly enhanced electrochemical performance. The developed sensor exhibited a good response towards dopamine detection, with a considerably lower detection limit (5 × 10−9M) and a wider linear range (5 × 10−9–5 × 10−4M) compared to current publications. In addition to the outstanding reproducibility and anti-interference ability, this ‘green sourced’ sensor showed great potential for practical applications, as validated by the satisfactory recovery analysis of dopamine from goat blood serum.

Synthesis of Photoluminescent Carbon Dots Using Hibiscus Tea Waste and Heteroatom Doping for Multi-Metal Ion Sensing: Applications in Cell imaging and Environmental Samples

Novel photoluminescent carbon dots (CDs) were synthesized through a facile hydrothermal method using Hibiscus tea extract as a natural carbon source and boric acid as a boron source. The optical and physicochemical properties of the as-synthesized nitrogen- and boron-doped CDs (NB-CDs) were characterized using UV–Visible (UV–Vis), photoluminescence (PL) spectroscopy, Fourier-transform infrared (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The as-synthesized NB-CDs showed spherical morphology of approximately 6.2 ± 0.5 nm with quantum yield (9.2%), high aqueous solubility, strong photo-stability, and excitation-dependent PL behavior. The obtained NB-CDs exhibited high stability over a wide pH range and high ionic strength. Additionally, NB-CDs exhibited PL enhancement response with excellent sensitivity toward multi-metal ions, including Ag+, Cd2+, and Cr3+ ions, with very low detection limits of 44.5, 164.4, and 54.6 nM, respectively, with a wide concentration range of 0–10 μM. Upon testing the cytotoxicity of the NB-CDs at a concentration of 20 μg/mL for 24 h, we found no obvious inhibition of cell viability. Therefore, the proposed sensor method can be successfully applied to detect Ag+, Cd2+, and Cr3+ ions in cell imaging as well as in real water environmental samples.

Detection and Environmental Optimization of dextran produced from Lactobacillus spp.

Introduction: Dextrans are D-glucose homopolysaccharides made by bacteria. There are several different bacterial species that produce these polysaccharides. Dextran is used as an adjuvant, drug carrier emulsifier, carrier, and stabiliser in the food, pharmaceutical, and chemical sectors, Nano gel. The aim of the study is to isolate Lactobacillus spp. from clinical sources, to identify the dextran production yield in Lactobacillus spp, and to reach the optimal growing parameters to discover the optimal dextran growth conditions. Methodology: 50 isolates of Lactobacillus spp. were gathered from different medical facilities in Baghdad City, 21 isolates came from healthy women's vagina (16 Lactobacillus plantarum, 5 Lactobacillus acidophilus), and 29 isolates came from samples of infant stool (15 Lactobacillus plantarum, 4 Lactobacillus acidophilus, and 10 Lactobacillus gasseri). All isolates were examined for dextran production using mucoid and spectrophotometric methods. Results: Lactobacillus acidophilus that was isolated from the genital tract of healthy women produced greater dextran. The results shows that the optimum conditions for dextran production that were investigated, there are several parameters play important roles to reach the optimal conditions, including, different natural carbon sources, nitrogen source, temperature, sucrose concentration, incubation time, pH, inoculum size. Conclusions: he optimum conditions for production were at 37 ºC for 48h at pH 5.5 with 4 % inoculum size and 6 g/ 100ml sucrose concentration with 6% best nitrogen source beef extract and the best natural carbon source for dextran production was dates.

Electrolyte performance of green synthesized carbon quantum dots from fermented tea for high-speed capacitors

In recent years, obtaining carbon nanomaterials from natural products by natural methods has been among the most popular topics. The materials synthesized by this way have beneficial properties such as biocompatible, photostable and less harmful for environment. In this study, carbon quantum dots (CQDs) were synthesized by using fermented tea as a natural material and carbon source. The capacitor performance as an electrolyte was investigated with high-speed charge-discharge method as unusual in the literature. The characterizations of the CQDs were realized by HRTEM, XRD, XPS, UV–Vis absorption, and fluorescence spectroscopy techniques. The resulting particles have a size of about 10 nm according to HRTEM image. While the structural properties of the CQDs were confirmed by XRD and XPS, and optical behaviors were confirmed by UV–Vis and fluorescence spectroscopies. The electrochemical behavior of the obtained CQDs was tested as electrolyte material for capacitor applications. Experiments were carried out in three different operating potential windows in the 0–2 V range, and CQDs electrolytes exhibited high capacitive effect in symmetrical capacitors. However, the cyclic voltammetry (CV) analyses revealed that the CQDs electrolytes displayed a full supercapacitor electrolyte feature in the 0–0.5 V range. The CQDs electrolytes have a promising material for technological and industrial applications with their unique redox performance and high capacitive effect.

One-Pot Synthesis of Nitrogen-Doped Graphene Quantum Dots and Their Applications in Bioimaging and Detecting Copper Ions in Living Cells.

Two natural carbon sources, glutamic acid and tyrosine, were used to fabricate strong green emission nitrogen-doped graphene quantum dots (N-GQDs) with the one-pot pyrolysis method. The morphology of the prepared GQDs has been characterized by high-resolution transmission electron microscopy, showing a well-displayed crystalline structure with a lattice spacing of 0.262 nm. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were used to analyze the surface functional groups and elemental composition, suggesting that the N-GQDs have active carboxylic and amino functional groups. Meanwhile, photoluminescence and ultraviolet-visible (UV-vis) spectroscopy were used to evaluate the optical properties of GQDs; the prepared N-GQDs show an excitation-dependent fluorescence behavior with a maximum excitation/emission wavelength at 460/522 nm, respectively. N-GQDs showed good photostability and the fluorescence intensity quenched about 10% after irradiating 2800 s in the experiment of time kinetic analysis. The MTT assay was utilized to assess the viability of N-GQDs; good biocompatibility with a relatively high quantum yield of 12% demonstrated the potential for serving as bioimaging agents. Besides, the selectivity study on metal ions indicates that the N-GQDs could be used in Cu2+ detection. The linear range is from 0.1 to 10 μM with a limit of detection of 0.06 μM. Overall, these proposed N-GQDs with one-pot synthesis showed their promising potential in cell imaging and Cu2+ monitoring applications involved in the biological environment.