Preparation Of Graphene Quantum Dots Research Articles

Modification of starch-derived graphene quantum dots as multifunctional nanofillers to produce polymer starch/polyvinyl alcohol composite films for active packaging

Here we reported a facile and green route to prepare graphene quantum dots (GQDs) by using corn starch as a nanofiller for the preparation of starch-based active films. The aqueous solution of GQDs displayed excitation wavelength-independent emission, stable photoluminescence, and good bio-safety. And the results demonstrated that the starch-derived GQDs have good compatibility with the natural polymer starch/polyvinyl alcohol (PVA) matrix. With the addition of GQDs over 50 μg/mL, the composite film has a very satisfactory UV blocking capacity. Moreover, 100 μg/mL of GQDs significantly increases the elongation at break and tensile strength of the obtained film to 1.79 and 2.94 times respectively, while the water solubility is only 53.9% of that of the starch/PVA film. The maximum scavenging rates of 2,2-diphenyl-1-picrylhydrazyl free radical by the starch/PVA film containing 150 μg/mL of GQDs was 83.3%. As the amount of GQDs added increases, the inhibitory effect of the composite film on Staphylococcus aureus and Escherichia coli becomes more and more significant. The starch-sourced composite film's eco-friendly nature and superior performance make it a promising alternative to traditional plastic materials for active packaging.

Alendronate-Functionalized Graphene Quantum Dots as an Effective Fluorescent Sensing Platform for Arsenic Ion Detection.

Alendronate-functionalized graphene quantum dots (ALEN-GQDs) with a quantum yield of 57% were synthesized via a two-step route: preparation of graphene quantum dots (GQDs) by pyrolysis method using citric acid as the carbon source and post functionalization of GQDs via a hydrothermal method with alendronate sodium. After careful characterization of the obtained ALEN-GQDs, they were successfully employed as sensing materials with superior selectivity and sensitivity for the detection of nanomolar levels of arsenic ions (As(III)). According to the mechanistic investigation, arsenic ions can quench the fluorescence intensity of ALEN-GQDs through metal-ligand interaction between the As(III) ions and the surface functional groups of the fluorescent probe. This probe provided a rapid method to monitor As(III) with a wide detection range (44nM-1.30µM) and a low detection limit of 13nM. Finally, to validate the applicability, this novel fluorescent probe was successfully applied for the quantitative determination of As(III) in rice and water samples.

Preparation of Graphene Quantum Dots Decorated Montmorillonite to Reinforce Fire Retardancy of Polystyrene

Preparation of Graphene Quantum Dots Decorated Montmorillonite to Reinforce Fire Retardancy of Polystyrene

Sustainable Preparation of Graphene Quantum Dots from Leaves of Date Palm Tree.

The date palm (Phoenix dactylifera), a subtropical and tropical tree, included in the family Palmae (Arecaceae) is one of the oldest cultivated plants of mankind. Date palm is a major agricultural product in the semi-arid and arid areas of the world, particularly in Arab countries. These trees generate high quantities of agricultural waste in the form of dry leaves, seeds, etc. In this study, dried date palm leaves were used as green precursors for synthesizing graphene quantum dots (GQDs). This work reported the preparation of GQDs using two different sustainable methods. GQD-1 was developed using a simple, hydrothermal technique at 200 °C for 12 h in water, with no requirement of reducing or passivizing agents or organic solvents. GQD-2 was prepared using a hydrothermal technique at 200 °C for 12 h in water, with the usage of just distilled water and absolute ethanol. The compositional analysis of the leaf extract was performed, along with the morphological, compositional, and optical examination of the sustainably developed GQDs. The characterization results confirmed the successful formation of GQDs, with average sizes ranging from 3.5 to 8 nm. This study helps to obtain GQDs in an economical, eco-friendly, and biocompatible manner and can assist in large-scale production and in recycling date palm tree waste products from Middle East countries into value-added products.

Preparation of aldehyde-graphene quantum dots from glucose for controlled release of anticancer drug

In this study, we prepared graphene quantum dots (GQDs) via a green process using rice straw as a carbon source. The non-toxic nature of GQDs is suitable for application in human body-related research. Furthermore, GQDs possess biodegradability and biocompatibility characteristics, indicating high suitability for applications in the field of drug delivery. Based on the fact that acid-sensitive bonds between GQDs and the drug doxorubicin are formed by aldehyde groups on GQD surfaces, we adopted a semi-modified TEMPO method to partially oxidize the surface functional groups of GQDs without destroying the structure. This enabled an increase in the surface aldehyde group content, which in turn enhanced the drug loading capacity of GQDs. The aldehyde group content of the GQDs was measured via Fourier transform infrared (FTIR) spectroscopy, titration based on the Cannizzaro reaction, and X-ray photoelectron spectroscopy (XPS). The drug loading effect of the GQDs was determined via absorbance measurements at 485 nm on a UV-Vis spectrophotometer. The results indicated that the semi-modified TEMPO method significantly affected the introduction of surface aldehyde groups and the enhancement of the drug loading efficiency in GQDs. Finally, the polymeric material cationic poly (vinylcyclohexene carbonates) (CPVCHCs) was used for the encapsulation of GQDs and regulation of drug release. Under the premise that the total amount of drugs released remains unaffected, the initial burst release of the drug is effectively delayed, which aids in reducing harmful effects of the drug on the human body.

Saccharide-Passivated Graphene Quantum Dots from Graphite for Iron(III) Sensing and Bioimaging

So far, it is difficult to prepare graphene quantum dots (GQDs) with high quantum yield (QY), high biocompatibility, and high yield by conventional top-down methods. We describe here a facile strategy to synthesize GQDs in NaOH/N-methylpyrrolidone (NMP) under sonication, which was subsequently passivated by saccharide to improve their stability. In the synthesis process, the GQDs were predominantly generated through exfoliation of graphite sheets. NaOH boosted the formation of GQDs by intercalation into the layer of graphite sheets, and the yield could be effectively increased to 7.54% with a prolonged sonication time and enhanced power, which was different from traditional methods. Due to the structure of the GQDs being similar to that of pristine graphene, GQDs possessed relatively high QYs, up to 19.12%. With further functionalization by hydrophilic saccharide, xylan-passivated GQDs with better stability and QY were applied for the detection of Fe3+ in the range of 0–75 μM with a limit of detection of 92.8 nM. Furthermore, chitosan-oligosaccharide (COS)-passivated GQDs showed good performance in cell imaging. Therefore, this work provides an efficient method to prepare GQDs and presents their promising application in ferroptosis after passivation.

Sustainable Preparation of Graphene Quantum Dots for Metal Ion Sensing Application

Over the past several years, graphene quantum dots (GQDs) have been extensively studied in water treatment and sensing applications because of their exceptional structure-related properties, intrinsic inert carbon property, eco-friendly nature, etc. This work reported on the preparation of GQDs from the ethanolic extracts of eucalyptus tree leaves by a hydrothermal treatment technique. Different heat treatment times and temperatures were used during the hydrothermal treatment technique. The optical, morphological, and compositional analyses of the green-synthesized GQDs were carried out. It can be noted that the product yield of GQDs showed the maximum yield at a reaction temperature of 300 °C. Further, it was noted that at a treatment period of 480 min, the greatest product yield of about 44.34% was attained. The quantum yields of prepared GQDs obtained after 480 min of treatment at 300 °C (named as GQD/300) were noted to be 0.069. Moreover, the D/G ratio of GQD/300 was noted to be 0.532 and this suggested that the GQD/300 developed has a nano-crystalline graphite structure. The TEM images demonstrated the development of GQD/300 with sizes between 2.0 to 5.0 nm. Furthermore, it was noted that the GQD/300 can detect Fe3+ in a very selective manner, and hence the developed GQD/300 was successfully used for the metal ion sensing application.

Boron-Doped Graphene Quantum Dots (BGQDs) from Spent Coffee Ground for Glucose Sensor

We have prepared graphene quantum dots (GQDs) and boron-doped GQDs (BGQDs) utilizing spent coffee grounds (SCGs) via a simple one-step hydrothermal process for glucose sensor application. FTIR and XPS characterizations reveal that the boron atoms have been successfully doped into graphene structures. BGQDs on glassy carbon electrode (GCE) in PBS were found to be two times as active compared to GCE/GQDs electrodes. The significant difference in electrochemical activity shown by BGQDs is evidence that boron from boric acid was doped into the graphene dominion. The generation of boronic acid groups on the boron-doped graphene quantum dots (BGQDs) surfaces facilitates the application of GQDs as a new photoluminescence (PL) probe for label-free glucose sensing. The photoluminescence of developed GQDs showed a linear response to glucose over a concentration range of 5–45 mM with a limit of detection of 12.45 mM whereas BGQDs biosensor was found to exhibit a higher sensitivity over the same concentration range with limit of detection of 3.23 mM towards glucose sensing. These results demonstrate that the synthesized BGQD has a promising potential in electrochemical activity and efficient to the PL enhancement mechanism determination of glucose.

Preparation of Graphene Quantum Dots by Visible-Fenton Reaction and Ultrasensitive Label-Free Immunosensor for Detecting Lipovitellin of Paralichthys Olivaceus.

The increasing levels of environmental estrogens are causing negative effects on water, soil, wildlife, and human beings; label-free immunosensors with high specificities and sensitivities are being developed to test estrogeneous chemicals in complex environmental conditions. For the first time, highly fluorescent graphene quantum dots (GQDs) were prepared using a visible-Fenton catalysis reaction with graphene oxide (GO) as a precursor. Different microscopy and spectroscopy techniques were employed to characterize the physical and chemical properties of the GQDs. Based on the fluorescence resonance energy transfer (FRET) between amino-functionalized GQDs conjugated with anti-lipovitellin monoclonal antibodies (Anti-Lv-mAb) and reduced graphene oxide (rGO), an ultrasensitive fluorescent “ON-OFF” label-free immunosensor for the detection of lipovitellin (Lv), a sensitive biomarker derived from Paralichthys olivaceus for environmental estrogen, has been established. The immunosensor has a wide linear test range (0.001–1500 ng/mL), a lower limit of detection (LOD, 0.9 pg/mL), excellent sensitivity (26,407.8 CPS/(ng/mL)), and high selectivity and reproducibility for Lv quantification. The results demonstrated that the visible-Fenton is a simple, mild, green, efficient, and general approach to fabricating GQDs, and the fluorescent “ON-OFF” immunosensor is an easy-to-use, time-saving, ultrasensitive, and accurate detection method for weak estrogenic activity.

Effective removal of Pb(II)/4-nitroaniline/E. faecalis and E. coli pollutants from water by a novel unique graphene quantum dots@gemifloxacin@ double-layered Fe/Al nanocomposite

Design and assembly of a novel sustainable unique nanocomposite with multi-purpose activities with efficient adsorptive removal behavior toward different organic, inorganic and biological pollutants is a challenging aspect. Therefore, the current work is directed to prepare graphene quantum dots (GQDs) from mango peels via a facile method. GQDs were coupled with FeAl double layered hydroxide (FA-DLH) and intercalated via co-precipitation with gemifloxacin antibiotic (Gem) for the formation of a 3D structure with multiple functional nanocomposite (GQDs@Gem@FA-DLH). This was utilized for various pollutants removal including lead (Pb(II)), 4-nitroaniline (4NA), Enterococcus faecalis (E. faecalis) and Escherichia coli (E. coli)). GQDs@Gem@FA-DLH was characterized from FT-IR, EDX, HR-TEM, BET, XRD and TGA techniques. The maximum removal of 4NA and Pb(II) were established as 90.7% (pH 2.0) and 98.8% (pH 6.0), respectively. The adsorption performance by GQDs@Gem@FA-DLH was favored according to Langmuir and pseudo-second order. Furthermore, the antibacterial removal activity against gram-positive (E. faecalis) and gram-negative (E. coli) by GQDs@Gem@FA-DLH was assessed using two different methods, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) and the removal percentages reached to 91.3% and 82.9%, respectively. Moreover, the removal of bacteria from wastewater based on the total plate count was established as 80%.

Water resistance, thermal stability, luminescence enhancement of core-double shell structure K2TiF6:Mn4+ phosphor

In order to improve fluorescent thermal stability and water-proof of Mn4+-doped red emitting fluoride phosphors applied for white light emitting diodes (WLEDs), in this work, a coating strategy is explored to prepare graphene quantum dots (GQDs) and K2TiF6 double coated Mn4+ doped K2TiF6 red emitting phosphor with high efficiency, fluorescent thermal stability and water-proof. After coating with double shell of GQDs and K2TiF6, fluorescent intensity, fluorescent thermal stability and water-proof are remarkably improved. The mechanism of the above improvements is explained and suggested. The results implied that double coating by GQDs and matrix is an effectively way to obtain Mn4+-doped fluoride phosphors with high emission, fluorescent thermal stability and water-proof at the same time.

Preparation of Functionalized Carbon Nanomaterials and Their Applications in Polymer Solar Cells

With the rapid development of society, energy consumption is increasing, and renewable clean energy is an important way to solve the problem of increasing energy consumption and how to protect the environment. Solar energy is a kind of sustainable development of clean energy. In the development of solar energy, polymer solar cells have attracted much attention due to low cost and good performance. With the deepening of research, the efficiency of polymer solar cells continues to increase, but there is still a problem of short service life, and how to improve the service life and efficiency of polymer solar cells has become a research hot spot. Since functionalized carbon nanomaterials have the advantages of good electrical conductivity, mechanical properties and strong chemical properties, this paper aims to improve the photoelectric conversion efficiency of polymer solar cells by applying functionalized carbon nanomaterials to polymer solar cells. Firstly, the working principle of solar cells was introduced. Secondly, graphene quantum dots functionalized carbon nanomaterials were prepared by hydrothermal method. Finally, graphene quantum dots are applied to polymer solar cells as acceptor materials and interface modification, and the photoelectric conversion efficiency of polymer solar cells is improved successfully. Simulation analysis shows that the prepared graphene quantum dots can improve the stability and efficiency of polymer solar cells, and play an active role in polymer solar cells.

Passivated graphene quantum dots for carbaryl determination in juices.

This paper reports a simple method for the preparation of suitable graphene quantum dots after surface passivation, to be used for the determination of carbaryl in juice samples. A comparison of synthetic conditions for the preparation of graphene quantum dots following the top-down approach is described. In the one-step route selected, evaluation of diverse reaction time for cutting and modulating the oxidizing sites in the broken pieces of the initial graphene layer is conducted with a mixture of concentrated acids. Exploring the passivation effect on the purified graphene quantum dots, we demonstrated the suitability of the selected graphene quantum dots for practical application in the detection of carbaryl using fluorometric detection. Higher sensitivity was achieved after 8min of contact, in which graphene quantum dots promotes the degradation of carbaryl into naphthol, being the latter responsible for the analytical signal. The detection and quantification limits were 0.36 and 1.21μg/L, respectively, being the response linear up to 26μg/L with excellent precision (better than 3.2% at the limit of detection). The recovery of the analyte from commercial juice samples (91.4-96.7%) testifies to the applicability of the proposal for the analytical problem selected.

Preparation of Graphene Quantum Dots and Their Sensing Properties in Quartz Crystal Microbalance Acetone Sensor

Preparation of Graphene Quantum Dots and Their Sensing Properties in Quartz Crystal Microbalance Acetone Sensor

Preparation of graphene quantum dots with glycine as nitrogen source and its interaction with human serum albumin.

Graphene quantum dots (GQDs) could be regarded as graphene with a lateral dimension less than 100 nm. Compared with graphene, GQDs not only possess the excellent properties of graphene but also have been proven to have low toxicity, high fluorescence stability, strong water solubility, as well as better biocompatibility. In this work, an amide bond-based, N-doped graphene quantum dot was synthesized using a simple hydrothermal method. When the reaction time was 4 h and the temperature was 180°C, fluorescence excitation and emission peaks of the product were 340 nm and 450 nm, respectively. Its interaction with human serum albumin (HSA) was investigated using spectroscopy, gel electrophoresis, and molecular simulation. Gel electrophoresis showed that the product did not cause complete scission of the peptide chain in HSA, indicating good biocompatibility. The results of molecular docking showed that the product tended to bind to site III of HSA. This paper provides a meaningful reference for design and development in nanomedicine.

Preparation of Graphene Quantum Dots by Laser-induced Polydimethylsiloxane

Preparation of Graphene Quantum Dots by Laser-induced Polydimethylsiloxane

Preparation of graphene quantum dots modified hydrogenated carboxylated nitrile rubber interpenetrating cross-linked film

In this paper, an amino-rich graphene quantum dots (GQDs) were efficiently prepared. Hydrogenated carboxylated nitrile latex (HXNBR) was prepared by hydrogenation of carboxylated nitrile latex (XNBR) by residual hydrazine hydrate during the preparation of GQDs, and a large amount of amino groups on the GQDs were reacted with carboxyl groups on the XNBR. Hence, a novel-interpenetrating network HXNBR film containing GQDs was successfully prepared. The physical properties and aging resistance of the films were investigated. The composite films have ultraviolet-visible excited fluorescence. By comparing the fluorescence of the films, it was confirmed that HXNBR grafting of GQDs to form an interpenetrating network enables GQDs to be well dispersed in the matrix.

Preparation of graphene quantum dots with high quantum yield by a facile one-step method and applications for cell imaging

The preparation and biological applications of graphene quantum dots (GQDs) have attracted much attention. Here, a one-step hydrothermal method for synthesizing nitrogen-doped GQDs (N-GQDs) using graphene oxide (GO), ethylenediamine and hydrogen peroxide, simultaneously achieved oxidative cleavage and chemical reduction of GO. The average size of the synthesized N-GQDs was about 1.84 ± 0.28 nm and their quantum yield of the N-GQDs reached about 0.46, which was higher than that of other GQDs synthesized by top-down methods. The cytotoxicity of these N-GQDs on Hela cells was evaluated using a cell counting Kit-8 assay. The effects of N-GQDs on different cell lines and fluorescence imaging were also observed by confocal laser scanning microscopy. The results suggested that these N-GQDs penetrated into cells by endocytosis and were promising fluorescent probes for biological imaging.

Graphene quantum dot decorated magnetic graphene oxide filled polyvinyl alcohol hybrid hydrogel for removal of dye pollutants

Herein, a novel and simple coagulation route is adopted for quick preparation of graphene quantum dots (GQDs) integrated magnetic graphene oxide (GO/Fe3O4/GQD) by using ethanol-HCl as destabilizing agent. The ultra-high surface area of GQDs with layered graphene like structure makes them more sensitive to environmental changes as well as eco-friendly (cell viability ~ 86.7%) candidate for dye removal application. The as-prepared nanohybrid filler is then in situ incorporated within PEG-1500 induced macroporous polyvinyl alcohol/carboxymethyl cellulose hydrogel beads. The prepared PVA/CMC-B@GO/Fe3O4/GQD (L) nanocomposite hydrogel is characterized with SEM, TEM, XRD and FTIR. Surface topography and roughness of the nanocomposite hydrogel is evaluated through AFM microscopy, while pore distribution in the nanocomposite hydrogel is explored through BET adsorption isotherm and mercury porosimetry. Moreover, pH responsive swelling behavior of the nanocomposite hydrogel is well studied along with detail investigation towards removal of cationic pollutants (MB/RhB) with respect to contact time and solution temperature.

Human mesenchymal stem cells encapsulated-coacervated photoluminescent nanodots layered bioactive chitosan/collagen hydrogel matrices to indorse cardiac healing after acute myocardial infarction

Acute Myocardial Infarction (MI) is one of the foremost causes of human death worldwide and it leads to mass death of cardiomyocytes, interchanges of unfavorable biological environment and affecting electrical communications by fibrosis scar formations, and specifically deficiency of blood supply to heart which leads to heart damage and heart failure. Recently, numerous appropriate strategies have been applied to base on solve these problems wound be provide prominent therapeutic potential to cardiac regeneration after acute MI. In the present study, a combined biopolymeric conductive hydrogel was fabricated with conductive ultra-small graphene quantum dots as a soft injectable hydrogel for cardiac regenerations. The resultant hydrogel was combined with human Mesenchymal stem cells (hMSCs) to improved angiogenesis in cardiovascular tissues and decreasing cardiomyocyte necrosis of hydrogel treated acute-infarcted region has been greatly associated with the development of cardiac functions in MI models. The prepared graphene quantum dots and hydrogel groups was physico-chemically analyzed and confirmed the suitability of the materials for cardiac regeneration applications. The in vitro analyzes of hydrogels with hMSCs have established that enhanced cell survival rate, increased expressions of pro-inflammatory factors, pro-angiogenic factors and early cardiogenic markers. The results of in vivo myocardial observations and electrocardiography data demonstrated a favorable outcome of ejection fraction, fibrosis area, vessel density with reduced infarction size, implying that significant development of heart regenerative function after MI. This novel strategy of injectable hydrogel with hMSCs could be appropriate for the effective treatment of cardiac therapies after acute MI.